Reconfigurable holographic surfaces (RHS) have emerged as a promising enablers for Integrated Sensing and Communication (ISAC) owing to their ultra-dense electromagnetic control capability. In this work, we consider near-field multi-user localization as a key ISAC function. However, hardware-induced phase-shift constraints and complex-plane coupling effects severely degrade the performance of classical subspace-based estimators such as multiple signal classification (MUSIC). In this work, we analytically characterize the impact of practical phase-shift constraints on the MUSIC spectrum and reveal the resulting pseudo-peak and angular bias phenomena. To address these challenges, we propose a hierarchical sensing framework that integrates subspace estimation with sparsity-aware recovery. Specifically, we introduce a regularized orthogonal matching pursuit (ROMP)-assisted multi-sector sensing mechanism that exploits directional sparsity and sector-level structural partitioning of RHS, enabling robust multi-user angle-of-arrival (AoA) estimation under limited-resolution hardware. Furthermore, to alleviate near-field distance estimation bias, we design a nonlinear fusion estimator that aggregates angle observations from multiple local far-field sectors using confidence-weighted integration based on sector-specific priors. A confidence-aware sector selection scheme is also developed to suppress unreliable observations without relying on data-driven learning models. Extensive Monte Carlo simulations demonstrate that our method achieves over 80% reduction in root mean square error (RMSE) localization compared to conventional MUSIC and least-squares schemes, and maintains meter-level accuracy even under severe hardware distortions and sector limitations.

The recent advances in quantum information processing, sensing, and communications are surveyed with the objective of identifying the associated knowledge gaps and formulating a roadmap for their future evolution. Since the operation of quantum systems is prone to the deleterious effects of decoherence, which manifests itself in terms of bit-flips, phase-flips, or both, the pivotal subject of quantum error mitigation is reviewed both in the presence and absence of quantum coding. The state of the art, knowledge gaps, and future evolution of quantum machine learning (QML) are also discussed, followed by a discourse on quantum radar systems and briefly hypothesizing about the feasibility of integrated sensing and communications (ISAC) in the quantum domain (QD). Finally, we conclude with a set of promising future research ideas in the field of ultimately secure quantum communications with the objective of harnessing ideas from the classical communications field.

Reconfigurable holographic surfaces (RHS) are expected to play a key role in future mobile networks. However, the substantial increase in antenna aperture and operating frequency brings new challenges for near-field communication. We propose a near-field multi-user 3D hierarchical beam training scheme tailored for RHS-based multi-input multi-output (MIMO) systems, supporting both near-field and far-field user deployment, while considering hardware constraints. Since the hierarchical beam training scheme involves activating varying numbers of transmitting elements at each search layer, and RHS elements are densely packed, significant mutual coupling effects may arise. To mitigate this, we propose two element activation strategies: centered activation and sparse activation based on different RHS element positioning patterns within the hierarchical beam training framework. Furthermore, we design a practical beam training approach tailored to a hybrid digital–holographic architecture, optimized through an alternating algorithm that accounts for both binary and coupled amplitude-phase hardware constraints on RHS meta-elements. Simulation results demonstrate strong robustness under various hardware and channel state information (CSI) imperfections, achieving performance close to that of fully digital systems. Finally, we further analyse the asymptotic orthogonality of near-field beam focusing vectors under different RHS surface geometries. The results show that rectangular surfaces offer superior beam orthogonality for beams steered in the same direction but located at different distances.

The feasibility of continuous variable quantum key distribution (CV-QKD) is considered in the Terahertz (THz) band, experiencing time-varying and frequency-selective fading. Advanced multi-carrier modulation is required for improving the secret key rate (SKR). However, the hostile quantum channel requires powerful classical channel coding schemes for maintaining an adequate reconciliation performance. Against this background, for the first time in the open literature, we propose a multi-carrier quantum transmission regime that incorporates both orthogonal frequency division multiplexing (OFDM) and orthogonal time frequency space (OTFS) transmission over doubly selective fading THz channels. Furthermore, we propose a modified multi-dimensional reconciliation algorithm for CV-QKD, facilitating the integration of OFDM/OTFS quantum transmission with low-density parity check (LDPC) coded key reconciliation. Moreover, we harness multiple-input multiple-output (MIMO) beamforming for mitigating the severe THz path loss. Our SKR analysis results demonstrate that the proposed OTFS-based and LDPC-assisted CV-QKD system is capable of outperforming its OFDM counterpart in mobile wireless scenarios. Moreover, we also demonstrate that increasing the MIMO dimension reduces the transmission power required for achieving the secure transmission distance target.

Continuous-variable quantum key distribution (CV-QKD) maps information onto the quadrature components of electromagnetic waves, so that off-the-shelf wireless transceivers can be utilized. This motivates the move from optical to Terahertz (THz) bands. However, wireless THz channels suffer from severe path loss, while the mobility of wireless users imposes doubly selective fading. Against this background, we propose a new CV-QKD regime that relies on hybrid beamforming (HBF) assisted multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) and orthogonal time frequency space (OTFS) system, where the channel’s transmissivity and robustness against double selectivity are overcome by HBF and OTFS, respectively. Secondly, in order to provide channel state information (CSI) for both the transmitter (CSI-T) and receiver (CSI-R), practical channel estimation methods are conceived. They operate in the time-frequency domain for OFDM and in the delay-Doppler domain for OTFS. Thirdly, soft-decision detection is devised for our MIMO OFDM/OTFS aided multi-dimensional reconciliation (MDR) scheme. Low-density parity-check (LDPC) coding is invoked for further improving secure CV-QKD transmission distance in the THz band. Our simulation results demonstrate that the proposed HBF MIMO OTFS-based CV-QKD system relying on realistic estimated CSI is capable of achieving an adequate secret key rate (SKR) and secure transmission distance in hostile doubly selective THz channels.

The paper proposes multiple dual-function UAVs hybrid enabled mobile edge computing systems scheme, where UAVs serving ground users (GUs) are allowed to dynamically switch their roles to act as edge servers or aerial relays. Due to the limited battery or fuel of UAVs and GUs, a deep reinforcement learning (DRL) and successive convex approximation (SCA) combined algorithm is proposed to minimize the system energy consumption by jointly optimizing service assignment, task splitting, trajectory of UAVs and resource of both UAVs and GUs. Numerical results demonstrate that the proposed algorithm can be fast converged with limited iterations and outperform the single-function UAV schemes and binary task splitting strategies with a better system performance. Meanwhile, the average energy consumption (AEC) can be greatly reduced with the kinetic limitation of UAVs, while maintaining the average task latency (ATL) within an acceptable range.

Abstract This paper proposes a novel machine learning (ML) assisted low‐latency low density parity check (LDPC) coded adaptive modulation (AM) system, where short block‐length LDPC codes are used. Conventional adaptive modulation and coding (AMC) system includes fixed look‐up table method, which is also called inner loop link adaptation (ILLA) and outer loop link adaptation (OLLA). For ILLA, the adaptive capability is achieved by switching the modulation and coding modes based on a look‐up table using signal‐to‐noise ratio (SNR) thresholds at the target bit error rate (BER), while OLLA builds upon the ILLA method by dynamically adjusting the SNR thresholds to further optimize the system performance. Although both improve the system overall throughput by switching between different transmission modes, there is still a gap to optimal performance as the BER is comparatively far away from the target BER. Machine learning (ML) is a promising solution in solving various classification problems. In this work, the supervised learning based k‐nearest neighbours (KNN) algorithm is invoked for choosing the optimum transmission mode based on the training data and the instantaneous SNR. This work focuses on the low‐latency communications scenarios, where short block‐length LDPC codes are utilized. On the other hand, given the short block‐length constraint, we propose to artificially generate the training data to train our ML assisted AMC scheme. The simulation results show that the proposed ML‐LDPC‐AMC scheme can achieve a higher throughput than the ILLA system while maintaining the target BER. Compared with OLLA, the proposed scheme can maintain the target BER while the OLLA fails to maintain the target BER when the block length is short. In addition, when considering the channel estimation errors, the performance of the proposed ML‐LDPC‐AMC maintains the target BER, while the ILLA system's BER performance can be higher than the target BER.

In this paper, a novel power auctioneers network (PAN) is proposed to enable the sharing of resources from licensed users in exchange for performance gains using the Cooperative Non-Orthogonal Multiple Access (C-NOMA) protocol. This system exploits a matching-based algorithm based on game theory, namely Pragmatic Distributed Algorithm (PDA), to handle the challenge of user pairing and power allocation in C-NOMA. PDA is a cooperative game that allows for the sharing of potential relays within a network through a round-robin approach, allowing for fairer resource distribution. This approach uses distributed methods to perform tasks on user devices to remove the strain on the base station’s resources. Monte Carlo simulations demonstrate that the addition of these games to a wireless network provides a significant performance increase compared to traditional orthogonal multiple access methods, the unoptimised C-NOMA and the Distributed Matching Algorithm (DMA) method. Lastly, the idea of instability in matching algorithms in the context of wireless communications is explored by altering the number of users within a network.

Symbiotic radio (SR) is a key technique to solve the energy shortage and spectrum limitation of the future Internet of Things (IoT). In the SR-aided IoT networks supporting energy harvesting (EH), we study the cooperation schemes and offloading strategy between the primary users (PUs), IoT devices, and the base station (BS) for reasonably allocating the spectrum, power, and time resources. Considering the monetary transactions between the PUs and IoT devices, two cooperation schemes, namely, the “Preferential Scenario” and the “No-Preferential Scenario,” are proposed. In the Preferential Scenario, based on the final strategy, the IoT devices use the purchased spectrum and power to offload their own tasks to the BS after assisting the cooperative PUs to offload during a certain time slot. Due to the assistance of IoT devices for the PUs, IoT devices enjoy a discount when paying for the purchased spectrum and power. In the No-Preferential Scenario, the IoT devices and the cooperative PUs offload tasks to the BS together in a certain time slot according to the offloading strategy. The spectrum and power used by the IoT devices are purchased at the original price without a discount. For each scenario, we study the utility maximization problem of the PUs, where the utility of PUs includes the transmission rates and income. The utility-based resource-sharing algorithm is proposed to obtain an approximately optimal resource allocation scheme. Our simulation results indicate that the proposed algorithm provides good performances for both scenarios, while each scenario applying the proposed algorithm has its own advantages.

To alleviate the explosive growth of data traffic caused by the increased use of smart devices, new transmission techniques are needed to increase the utilization of limited bandwidth resources and for providing high transmission rates in future wireless networks. On the other hand, due to their flexibility and autonomy, unmanned aerial vehicles (UAVs) are considered as a potential candidate to support ubiquitous connectivity and operate as flying base stations, where the deployment of UAVs can affect the quality of experience (QoE) of users. Hence, in this paper, we employ UAVs as aerial base stations to transmit data to ground users (GUs) via air to ground (A2G) communication links, where we show how content awareness can help improve the data rate. Specifically, we design two content-sharing (CS) data transmission schemes to improve the average data rate of the GUs. Additionally, two UAV deployment strategies, namely the fixed-point deployment scheme and traverse-search deployment scheme, are proposed based on the proposed CS transmission schemes. The simulation results demonstrate that our proposed data transmission schemes combined with their proposed deployment schemes outperform the traditional transmission scheme by 26 bits/s/Hz and 51 bits/s/Hz, respectively.

Data packet routing in aeronauticalad hocnetworks (AANETs) is challenging due to their high-dynamic topology. In this article, we invoke deep learning (DL) to assist routing in AANETs. We set out from the single objective of minimizing the end-to-end (E2E) delay. Specifically, a deep neural network (DNN) is conceived for mapping the local geographic information observed by the forwarding node into the information required for determining the optimal next hop. The DNN is trained by exploiting the regular mobility pattern of commercial passenger airplanes from historical flight data. After training, the DNN is stored by each airplane for assisting their routing decisions during flight relying solely on local geographic information. Furthermore, we extend the DL-aided routing algorithm to a multiobjective scenario, where we aim for simultaneously minimizing the delay, maximizing the path capacity, and maximizing the path lifetime. Our simulation results based on real flight data show that the proposed DL-aided routing outperforms existing position-based routing protocols in terms of its E2E delay, path capacity, as well as path lifetime, and it is capable of approaching the Pareto front that is obtained using global link information.

Quantum phase estimation is an important component in diverse quantum algorithms. However, it suffers from spectral leakage, when the reciprocal of the record length is not an integer multiple of the unknown phase, which incurs an accuracy degradation. For the existing single-sample estimation scheme, window-based methods have been proposed for spectral leakage mitigation. As a further advance, we propose a dual-frequency estimator, which asymptotically approaches the Cramér-Rao bound, when multiple samples are available. Numerical results show that the proposed estimator outperforms the existing window-based methods, when the number of samples is sufficiently high.

Recent advances in quantum technologies pave the way for noisy intermediate-scale quantum (NISQ) devices, where the quantum approximation optimization algorithm (QAOA) constitutes a promising candidate for demonstrating tangible quantum advantages based on NISQ devices. In this paper, we consider the maximum likelihood (ML) detection problem of binary symbols transmitted over a multiple-input and multiple-output (MIMO) channel, where finding the optimal solution is exponentially hard using classical computers. Here, we apply the QAOA for the ML detection by encoding the problem of interest into a level-$p$QAOA circuit having$2p$variational parameters, which can be optimized by classical optimizers. This level-$p$QAOA circuit is constructed by applying the prepared Hamiltonian to our problem and the initial Hamiltonian alternately in$p$consecutive rounds. More explicitly, we first encode the optimal solution of the ML detection problem into the ground state of a problem Hamiltonian. Using the quantum adiabatic evolution technique, we provide both analytical and numerical results for characterizing the evolution of the eigenvalues of the quantum system used for ML detection. Then, for level-1 QAOA circuits, we derive the analytical expressions of the expectation values of the QAOA and discuss the complexity of the QAOA based ML detector. Explicitly, we evaluate the computational complexity of the classical optimizer used and the storage requirement of simulating the QAOA. Finally, we evaluate the bit error rate (BER) of the QAOA based ML detector and compare it both to the classical ML detector and to the classical minimum mean squared error (MMSE) detector, demonstrating that the QAOA based ML detector is capable of approaching the performance of the classical ML detector.

Quantum error mitigation (QEM) is a class of promising techniques capable of reducing the computational error of variational quantum algorithms tailored for current noisy intermediate-scale quantum computers. The recently proposed permutation-based methods are practically attractive, since they do not rely on anya prioriinformation concerning the quantum channels. In this treatise, we propose a general framework termed as permutation filters, which includes the existing permutation-based methods as special cases. In particular, we show that the proposed filter design algorithm always converge to the global optimum, and that the optimal filters can provide substantial improvements over the existing permutation-based methods in the presence of narrowband quantum noise, corresponding to large-depth, high-error-rate quantum circuits.

Quantum error mitigation (QEM) is a class of promising techniques for reducing the computational error of variational quantum algorithms. In general, the computational error reduction comes at the cost of a sampling overhead due to the variance-boosting effect caused by the channel inversion operation, which ultimately limits the applicability of QEM. Existing sampling overhead analysis of QEM typically assumes exact channel inversion, which is unrealistic in practical scenarios. In this treatise, we consider a practical channel inversion strategy based on Monte Carlo sampling, which introduces additional computational error that in turn may be eliminated at the cost of an extra sampling overhead. In particular, we show that when the computational error is small compared to the dynamic range of the error-free results, it scales with the square root of the number of gates. By contrast, the error exhibits a linear scaling with the number of gates in the absence of QEM under the same assumptions. Hence, the error scaling of QEM remains to be preferable even without the extra sampling overhead. Our analytical results are accompanied by numerical examples.

Sensors can be interconnected to form a wireless sensor network (WSN) for monitoring the environment. However, there is an increasing demand for innovative automation systems and hence the industrial wireless protocols are suffering from spectrum inefficiency and interference issues. Cognitive radio provides a promising solution to spectrum scarcity problem in dense WSNs. However, cognitive nodes are very vulnerable to adversaries such as jamming. In this contribution, we propose a game-theoretic anti-jamming technique for cognitive radio enabled sensor nodes, based on the Markov game framework. Both random and intelligent jammers are considered and our simulation results show that the proposed approach outperforms the existing benchmark scheme.

The secrecy capacity based on the assumption of having continuous distributions for the input signals constitutes one of the fundamental metrics for the existing physical layer security (PHYS) solutions. However, the input signals of real-world communication systems obey discrete distributions. Furthermore, apart from the capacity, another ultimate performance metric of a communication system is its symbol error ratio (SER). In this article, we pursue a radically new approach to PHYS by considering rigorous direct SER optimization exploiting the discrete nature of practical modulated signals. Specifically, we propose a secure precoding technique based on a multi-objective SER criterion, which aims for minimizing the confidential messages' SER at their legitimate user, while maximizing the SER of the confidential messages leaked to the illegitimate user. The key to this challenging multi-objective optimization problem is to introduce a priority factor that controls the priority of directly minimizing the SER of the legitimate user against directly maximizing the SER of the leaked confidential messages. Furthermore, we define a new metric termed as the security-level, which is related to the conditional symbol error probability of the confidential messages leaked to the illegitimate user. Additionally, we also introduce the secure discrete-input continuous-output memoryless channel (DCMC) capacity referred to as secure-DCMC-capacity, which serves as a classical security metric of the confidential messages, given a specific discrete modulation scheme. The impacts of both the channel's Rician factor and the correlation factor of antennas on the security-level and the secure-DCMC-capacity are investigated. Our simulation results demonstrate that the proposed priority-aware secure precoding based on the direct SER metric is capable of securing transmissions, even in the challenging scenario, where the eavesdropper has three receive antennas, while the legitimate user only has a single one.

Hybrid Transmit Precoding (TPC) is one of the most compelling solutions for millimeter wave (mmWave) multiple-input multiple output (MIMO) systems. However, most attention has been focused on narrow-band scenarios. Hence, we dedicate our efforts to the design of hybrid TPC for wideband mmWave MIMO systems, where the beam squint dramatically affects the system performance. We firstly show that the channel matrices of the different subcarriers possess distinct subspaces in case of high bandwidths, hence traditional hybrid TPC schemes suffer from an eroded performance. Therefore, we propose novel hybrid TPC schemes exploiting the full channel state information (CSI), which project all frequencies to the central frequency and construct the common analog TPC matrix for all subcarriers. Moreover, we propose several low-complexity array-vector based hybrid TPC schemes. The high-complexity manifold optimization based hybrid TPC method and the fully digital TPC operating with and without considering beam squint are provided as benchmarks. Our extensive numerical simulations show that the proposed hybrid TPC schemes are capable of achieving similar performance to the excessive-complexity fully digital TPC, when the bandwidth tends to 0.5 GHz and always outperform the traditional hybrid TPC schemes.

As the enabling technologies move up to the mmWave and even to the TeraHertz bands for the next-generation wireless systems, the signal processing of high-bandwidth orthogonal frequency division multiplexing (OFDM) becomes increasingly power-thirsty, owing to the following OFDM deficiencies: (1) the high peak-to-average power ratio (PAPR); (2) the bandwidth efficiency loss due to the cyclic prefix (CP) overhead; (3) the sensitivity to carrier frequency offset; (4) the complex out-of-band (OOB) filtering. Over the past six decades, a variety of waveforms have been developed in order to mitigate these deficiencies, which are generally achieved at the cost of compromising some of OFDM’s beneficial properties, such as its subcarrier (SC) orthogonality, its high throughput and its straighforward adoption to multiple-input multiple-output (MIMO) systems. Against this background, we propose a new waveform termed as multi-band discrete Fourier transform spread-OFDM with index modulation (MB-DFT-S-OFDM-IM), where the component multi-carrier techniques are conceived to constructively function together in order to mitigate the OFDM deficiencieswithout compromising the beneficial OFDM properties. More explicitly, first of all, the PAPR is reduced by the DFT-precoding. Secondly, thanks to the IM design, MB-DFT-S-OFDM-IM is capable of achieving a high throughput that is strictly equal to or higher than the OFDM throughput. Thirdly, MB-DFT-S-OFDM-IM achieves a beneficial frequency diversity gain, which leads to a higher tolerance to carrier frequency offset. Fourthly, the OOB filters are placed in each sub-band before DFT, so that the SC orthogonality remains intact, which is unique to the proposed MB-DFT-S-OFDM-IM structure. Last but not least, we extend the proposed MB-DFT-S-OFDM-IM to support a variety of MIMO schemes, where the IM philosophy is integrated with the space-, time- and frequency-domains within a singleunifiedplatform.

Seven decades after the foundation of classical information theory and the invention of the transistor that launched the digital communication and computing revolutions, we are entering a new era of quantum information science and engineering (QISE). Despite holding its impressive sway for nearly 60 years, the celebrated Moore’s law is beginning to hit physical limits, as the ever-shrinking transistor size is making it necessary to account for quantum effects. Concurrently, the growing demand for high-rate processing is imposing unsustainable power and heat dissipation requirements. Thus, there is an urgent need to develop quantum information processing systems that can circumvent the limitations of existing technology.

Multi-hop communication with the aid of large-scale antenna arrays will play a vital role in future emergence communication systems. In this paper, we investigate amplify-and-forward based and multiple-input multiple-output assisted multi-hop communication, in which all nodes employ hybrid transceivers. Moreover, channel errors are taken into account in our hybrid transceiver design. Based on the matrix-monotonic optimization framework, the optimal structures of the robust hybrid transceivers are derived. By utilizing these optimal structures, the optimizations of analog transceivers and digital transceivers can be separated without loss of optimality. This fact greatly simplifies the joint optimization of analog and digital transceivers. Since the optimization of analog transceivers under unit-modulus constraints is nonconvex, a projection type algorithm is proposed for analog transceiver optimization to overcome this difficulty. Based on the derived analog transceivers, the optimal digital transceivers can then be derived using matrix-monotonic optimization. Numerical results obtained demonstrate the performance advantages of the proposed hybrid transceiver designs over other existing solutions.

For the multiple-input multiple-output (MIMO) uplink employing high-order quadrature amplitude modulation (QAM) signaling and with nonlinear high power amplifiers (HPAs) at mobile users' transmitters, the existing multiuser detection methods can no longer be applied. We propose a novel nonlinear multiuser detection scheme for the nonlinear MIMO uplink. Specifically, we adopt an effective B-spline parameterization of the nonlinear transmit HPAs and derive an efficient and accurate algorithm to identify the nonlinear MIMO uplink channel, including the nonlinear B-spline model of the nonlinear transmit HPAs and the estimate of the linear MIMO channel matrix. Moreover, as the direct result of this nonlinear MIMO channel identification, the B-spline inverse model of nonlinear transmit HPAs can readily be identified. The nonlinear multiuser detection can be effectively implemented by the zero-forcing linear detection based on the estimated linear MIMO channel and followed by compensating the nonlinear distortion of the nonlinear transmit HPAs based on the estimated B-spline inverse model. An extensive simulation investigation is performed to demonstrate the effectiveness of our proposed nonlinear multiuser detection scheme for nonlinear MIMO uplink with high-order QAM signaling.

Radio frequency (RF) signals have been relied upon for both wireless information delivery and wireless charging to the massively deployed low-power Internet of Things (IoT) devices. Extensive efforts have been invested in physical layer and medium-access-control layer design for coordinating simultaneous wireless information and power transfer (SWIPT) in RF bands. Different from the existing works, we study the coding controlled SWIPT from the information theoretical perspective with practical transceiver. Due to its practical decoding implementation and its flexibility on the codeword structure, unary code is chosen for joint information and energy encoding. Wireless power transfer (WPT) performance in terms of energy harvested per binary sign and of battery overflow/underflow probability is maximised by optimising the codeword distribution of coded information source, while satisfying required wireless information transfer (WIT) performance in terms of mutual information. Furthermore, a Genetic Algorithm (GA) aided coding design is proposed to reduce the computational complexity. Numerical results characterise the SWIPT performance and validate the optimality of our proposed GA aided unary coding design.

Quantum Key Distribution (QKD) has been regarded as a novel approach to establish a secure communication between two legitimate partners. With the recent success of space based experimental QKD systems, researchers are now focussing on implementing more practical and efficient QKD systems that meet the challenges faced in space-based implementations. One pressing problem is the need for efficient and easy to implement reconciliation schemes for practical QKD systems. Rate-adaptive schemes based on LDPC codes constitute an appealing implementation of the key reconciliation process since they cover the entire range of the channel parameter space with a limited set of pre-defined Mother codes. In this paper, we investigate in detail some rate- adaptive reconciliation schemes based on LDPC codes, illustrating how their performance compares to other set-ups in which fixed-rate non- adaptive LDPC codes optimised for different channel conditions are adopted. In particular, the impact rate-adaptive codes have on decoding complexity, and subsequently the overall secure key throughput, is quantified through full blown simulations of an entanglement-based version of the QKD protocol within the context of an entanglement source onboard a satellite. Our work highlights that even though rate adaptive schemes schemes for QKD reconciliation appear ideal for future space-based implementations of single- photon QKD, identification of ideal Mother codes for such schemes remains to be resolved.

In this paper we present a novel secure quantum turbo coded (QTC) superdense (SD) coding scheme. We have integrated SD with QTC to benefit from the inherent near optimum performance of turbo codes. We have further incorporated the quantum secure direct communication (QSDC) protocol within the proposed QTC-SD system for the sake of ensuring absolute security. Explicitly, the QSDC protocol exploits dummy entangled pairs for detecting the presence of eavesdropper. Hence, the proposed scheme ensures absolute security, detects the presence of an eavesdropper and considers practical issues when error is induced in a quantum depolarizing channel. Furthermore, we have experimentally determined the noise threshold levels for the proposed QTC-SD system to detect the presence of an eavesdropper.

Wireless multihop networks (WMHNs) have to strike a trade-off among diverse and often conflicting quality-of-service requirements. The resultant solutions may be included by the Pareto front under the concept of Pareto optimality. However, the problem of finding all the Pareto-optimal routes in WMHNs is classified as non-deterministic polynomial-hard, since the number of legitimate routes increases exponentially, as the nodes proliferate. Quantum computing offers an attractive framework of rendering the Pareto-optimal routing problem tractable. In this context, a pair of quantum-assisted algorithms has been proposed, namely the non-dominated quantum optimization and the non-dominated quantum iterative optimization. However, their complexity is proportional to √N, where N corresponds to the total number of legitimate routes, thus still failing to find the solutions in “polynomial time.” As a remedy, we devise a dynamic programming framework and propose the so-called evolutionary quantum pareto optimization (EQPO) algorithm. We analytically characterize the complexity imposed by the EQPO algorithm and demonstrate that it succeeds in solving the Pareto-optimal routing problem in polynomial time. Finally, we demonstrate by simulations that the EQPO algorithm achieves a complexity reduction, which is at least an order of magnitude when compared to its predecessors, albeit at the cost of a modest heuristic accuracy reduction.

An ideal visible light communication (VLC) system should facilitate reliable data transmission at high throughputs, while also providing flicker-free illumination at the user-defined dimming level. In this spirit, we conceive a unary code aided dimming scheme for ON-OFF keying (OOK) modulated VLC systems. The proposed unary-coded scheme facilitates joint dimming and throughput control, while relying on iterative decoding. It is demonstrated that the proposed unary-coded dimming scheme provides attractive throughput gains over its contemporaries and it is also capable of approaching the theoretical throughput limit. Furthermore, we design novel joint dimming-forward error correction coding schemes, which significantly outperform their compensation time dimming-based counterparts in terms of the attainable bit error rate performance as well as the throughput. Finally, in the quest for approaching the capacity, we also optimize our system using EXTRINSIC information transfer charts and demonstrate an SNR-gain of upto 6 dB over the compensation time dimming-based classic benchmarker.

In this contribution, the performance of a Distributed Self-Concatenated Convolutional Coding (DSECCC) scheme is analyzed by using Iterative Decoding (ID) for cooperative communications (CC) with the aid of relay selection (RS) and power allocation (PA). In the RS based DSECCC-ID scheme, where the transmit Signal to Noise power Ratio (SNR) is equal for both source and relay, we can achieve the minimum value of the required SNR at both destination and relay simultaneously by choosing a relay at an appropriate geographical location. By contrast, in the PA based DSECCC-ID scheme, where the position of the relay is in the middle, minimum required transmit SNRs are used both at the source and the relay. These schemes are analyzed with the help of binary Extrinsic Information Transfer (EXIT) charts. From our simulation results, we found that the RS based DSECCC-ID scheme outperforms the PA based DSECCC-ID scheme.

Hierarchical modulation (HM) is a layered modulation scheme, which is widely employed by the telecommunication industry. The higher flexibility and lower complexity of the HM scheme has its dramatic benefits for wireless communications, hence the achievable performance of cooperation‐aided coded HM has drawn substantial research interests. In this study, a triple‐layer HM‐aided four‐node cooperative communication system is proposed, and its discrete‐input continuous‐output memoryless channel capacity is derived, which is used for finding the optimal position of the relay nodes as well as to design appropriate HM constellations. The authors’ simulation results show that if a rate‐1/2 ‘perfect’ channel code is assumed, the four‐node network becomes capable of conveying a coded HM‐64QAM signal in three time slots at an average signal‐to‐noise ratio of −0.71 dB.

Turbo detection performed by exchanging extrinsic information between the soft-decision QAM detector and the channel decoder is beneficial for the sake of exploring the bit dependency imposed both by modulation and by channel coding. However, when the soft-decision coherent QAM detectors are provided with imperfect channel estimates in rapidly fading channels, they tend to produce potentially unreliable LLRs that deviate from the true probabilities, which degrades the turbo detection performance. Against this background, in this paper, we propose a range of new soft-decision multiple-symbol differential sphere detection (MSDSD) and decision-feedback differential detection (DFDD) solutions for differential QAM (DQAM), which dispense with channel estimation in the face of rapidly fading channels. Our proposed design aims for solving the two inherent problems in soft-decision DQAM detection design, which have also been the most substantial obstacle in the way of offering a solution for turbo detected MSDSD aided differential MIMO schemes using QAM: 1) how to facilitate the soft-decision detection of the DQAM's amplitudes, which-in contrast to the DPSK phases-do not form a unitary matrix, and 2) how to separate and streamline the DQAM's soft-decision amplitude and phase detectors. Our simulation results demonstrate that our proposed MSDSD aided DQAM solution is capable of substantially outperforming its MSDSD aided DPSK counterpart in coded systems without imposing a higher complexity. Moreover, our proposed DFDD aided DQAM solution is shown to outperform the conventional solutions in literature. Our discussions on the important subject of coherent versus noncoherent schemes suggest that compared to coherent square QAM relying on realistic imperfect channel estimation, MSDSD aided DQAM may be deemed as a better candidate for turbo detection assisted coded systems operating at high Doppler frequencies.

An uplink transmission for Adaptive Dynamic Network Coding(ADNC) assisted Cooperative Cognitive Radio(CCR) system is proposed for facilitating the recovery of the source information received from the Primary Users (PUs) at the BS. The Cognitive Users (CUs) acting as Relay Nodes invoke the ADNC technique, where the CCR- based control information is exchanged between the CUs and the BS. % The network encoder may be activated in its adaptive mode for the sake of supporting the CUs, depending on the Boolean value of the feedback flags generated by the receiver based on the success/failure of the Adaptive Turbo Trellis Coded Modulation (ATTCM) channel decoder and of the network decoder. As a result, our novel ATTCM-ADNC-CCR system constructed based on a holistic approach is capable of providing an increased throughput, despite reducing the transmission-period of the PU. This reduced transmission-period can also be directly translated into an increased time-duration for the secondary communications of the CUs.

Unlike a generic PSK/QAM detector, which may visit a constellation diagram only once, a depth-first Sphere Decoder (SD) has to re-visit the same constellation diagram multiple times. Therefore, in order to prevent the SD from repeating the detection operations, the Schnorr-Euchner search strategy of Schnorr and Euchner may be invoked for optimizing the nodes' search-order, where the ideal case is for the SD to visit the constellation nodes in a zigzag fashion. However, when the hard-decision Multiple-Symbol Differential Sphere Detection (MSDSD) of Lampe et al. is invoked for using multiple receive antennas NR≥ 1, the Schnorr-Euchner search strategy has to visit and sort all the MPSK constellation points. A similar situation is encountered for the soft-decision MSDSD of Pauli et al., when the a priori LLRs gleaned from the channel decoder are taken into account. In order to tackle these open problems, in this paper, we propose a correlation process for the hard-decision MSDSD of Lampe et al. and a reduced-complexity design for the soft-decision MSDSD of Pauli et al., so that the Schnorr-Euchner search strategy always opts for visiting the MPSK constellation points in a zigzag fashion. Our simulation results demonstrate that a substantial complexity reduction is achieved by our reduced-complexity design without imposing any performance loss. Explicitly, up to 88.7% complexity reduction is attained for MSDSD (Nw= 4) aided D16PSK. This complexity reduction is quite substantial, especially when the MSDSD is invoked several times during turbo detection. Furthermore, in order to offer an improved solution and a comprehensive study for the soft-decision MSDSD, we also propose to modify the output of the SD to harmonize its operation with the near-optimum Approx-Log-MAP. Then the important subject of coherent versus noncoherent is discussed in the context of coded systems, which suggests that MSDSD aided DPSK is an eminently suitable candidate for turbo detection assisted coded systems operating at high Doppler frequencies.

With the proliferation of smart-phones and tablet PCs, the data rates of wireless communications have been soaring. Hence, the need for power-efficient communications relying on low-complexity multiple-stream detectors has become more pressing than ever. As a remedy, in this paper we design low-complexity soft-input soft-output quantum-assisted multi-user detectors (QMUD), which may be conveniently incorporated into state-of-the-art iterative receivers. Our design relies on extrinsic information transfer charts. Our QMUDs are then employed in multi-carrier interleave-division multiple-access (MC-IDMA) systems, which are investigated in the context of different channel code rate and spreading factor pairs, whilst fixing the total bandwidth requirement. One of our QMUDs is found to operate within 0.5 dB of the classical maximum a posteriori probability MUD after three iterations between the MUD and the decoders, while requiring only half its complexity, at a BER of 10-5in the uplink of a rank-deficient MC-IDMA system relying on realistic imperfect channel estimation at the receiver, while supporting 14 users transmitting QPSK symbols.

In this contribution, we propose and study a bufferaided opportunistic routing (BOR) scheme, which combines the benefits of both opportunistic routing and multihop diversity (MHD) aided transmissions. It was conceived for a buffer-aided three-node network (B3NN) composed of a source node (SN), a buffer-aided relay node (RN) and a destination node (DN). In this network, there are three channels namely the SN-RN, RN-DN and SN-DN channels. The key motivation is that we are aiming for activating the specific channels requiring a recuded energy dissipation. In order to study this problem, a three-dimensional (3D) transmission activation probability space (TAPS) is proposed, which is divided into four regions representing each of the three channels plus an outage region. In a specific time slot (TS), the instantaneous channel fading values may be directly mapped to a specific point in this 3D channel space. The BOR scheme then relies on the position of this point to select the most appropriate channel for its transmission. Both the energy dissipation and the outage probability (OP) are investigated for transmission in this network. The results show that when the system is operated at a normalized throughput of 0.4 packet/TS, the energy dissipation was reduced by 24.8% to 77.6% compared to three different benchmark schemes. Alternatively, our technique is capable of reducing the OP by 89.6% when compared to conventional opportunistic routing. As in all buffer-aided system, the performance improved with the cost of higher packet delay, which is also studied.

Hierarchical modulation (HM) is widely employed across the telecommunication industry. The potential application of the coded HM scheme in cooperative communications has drawn much interest. In this paper, a twin-relay-aided triple-layer cooperative communication system is proposed. The system amalgamates rate-1/2 TTCM, triple-layer HM-64QAM, and twin-layer SPM-16QAM schemes in the context of cooperative communications. We have optimized the entire system based on the HM ratio pair (R1, R2), the superposition modulation (SPM) weighting pair (α, β), and the positions of the two relays. The simulation results show that our optimized system is capable of reliably transmitting a triple-layer HM-64QAM signal with the aid of two time slots at an average signal-to-noise ratio of 6.94 dB per time slot.

The potentially excessive complexity of the Maximum Likelihood Multi-User Detector (ML MUD) in large-scale Spatial Division Multiple Access (SDMA) systems dictates the employment of low-complexity sub-optimal MUDs in the context of conventional systems. However, this limitation was circumvented by the recently proposed Dürr-Høyer Algorithm (DHA)-aided Quantum Weighted Sum Algorithm (QWSA)-based Quantum Multi-User Detector (QMUD) employed for performing optimal ML iterative detection in SDMA systems. Focusing our attention on the QWSA, we analyse the QMUD and the evolution of the quantum system with the aid of a simple SDMA uplink scenario. We characterize the performance of the DHA-QWSA QMUD advocated, which is capable of matching the performance of the ML MUD both in terms of its EXIT charts and BER curves.

In multihop diversity aided multihop links, the number of bits transmitted in each Time Slot (TS) is affected by both the Channel Quality (CQ) and the Buffer Fullness (BF), when adaptive modulation is employed. We assume that every node has buffers for temporarily storing its received packets for further transmission at instances of good CQ. For the sake of improving the throughput, a Maximum Throughput Adaptive Rate Transmission (MTART) scheme was proposed, where the specific hop having the capability of transmitting the highest number of bits (packets) will be activated. If more than one hops are capable of transmitting the same number of bits, the particular hop having the highest CQ (reliability) is activated. We demonstrate that the MTART scheme has 8 dB gain at the Outage Probability (OP) of 10-3and has 3 dB gain in terms of the throughput attained in comparison to the conventional adaptive modulation aided scheme.

Asymmetric Distributed Source-Channel coding (DSC) is considered, where a pair of correlated sources are transmitting to a central node. The distributed scheme is based on Turbo Trellis Coded Modulation (TTCM), where the first source will be channel encoded and then compressed before it is sent over Nakagami-m fading channels. The second source signal, however, is assumed to be available flawlessly at the destination for exploitation as side information for improving the decoding performance of the first source. A wide range of fading scenarios were considered, where reliable communications approaching the Slepian-Wolf Shannon (SW/S) limit were exhibited. Finally, the scheme is capable of adapting to the time-variant short-term correlation between the two sources.

Quantum-based transmission is an attractive solution conceived for achieving absolute security. In this quest, we have conceived an EXtrinsic Information Transfer (EXIT) chart aided channel code design for symbol-based entanglement-assisted classical communication over quantum depolarizing channels. Our proposed concatenated code design incorporates a Convolutional Code (CC), a symbol-based Unity Rate Code (URC) and a soft-decision aided 2-qubit Superdense Code (2SD), which is hence referred to as a CC-URC-2SD arrangement. We have optimized our design with the aid of non-binary EXIT charts. Our proposed design operates within 1 dB of the achievable capacity, providing attractive performance gains over its bit-based counterpart. Quantitatively, the bit-based scheme requires 60% more iterations than our symbol-based scheme for the sake of achieving perfect decoding convergence. Furthermore, we demonstrate that the decoding complexity can be reduced by using memory-2 and memory-3 convolutional codes, while still outperforming the bit-based approach.

In this paper buffer-aided Opportunistic Routing (OR) was designed with the aid of the novel concept of linear Transmission Activation Probability Space (TAPS) partitioning invoked for relay-assisted networks, which combines the benefits of both OR [1] and of buffer-aided transmissions [2]. More specifically, a packet may be transmitted from the Source Node (SN) to the Destination Node (DN) either directly or indirectly via one of theMRelay Nodes (RNs), depending on the instantaneous channel qualities. The above-mentioned linear multi-dimensional TAPS partitioning concept is proposed for partitioning the transmission space into (2M+1) transmission regions plus an outage region, while ensuring that the number of input packets is equal to the number of output packets at each RN's buffer. The benefit of having a buffer and tolerating the associated delay is that the best channel is activated for transmission based on our linear TAPS partitioning method.

A pragmatic distributed algorithm (PDA) is proposed for supporting the efficient spectral access of multiple Primary Users (PUs) and Cognitive Users (CUs) in cooperative Cognitive Radio (CR) networks. The CUs may serve as relay nodes for relaying the signal received from the PUs to their destinations, while both the PUs' and the CUs' minimum rate requirements are satisfied. The key idea of our PDA is that the PUs negotiate with the CUs concerning the specific amount of relaying and transmission time, whilst reducing the required transmission power or increasing the transmission rate of the PU. Our results show that the cooperative spectral access based on our PDA reaches an equilibrium, when it is repeated for a sufficiently long duration. These benefits are achieved, because the PUs are motivated to cooperate by the incentive of achieving a higher PU rate, whilst non-cooperation can be discouraged with the aid of a limited-duration punishment.

A novel adaptive turbo-coded soft-decision aided differential detection (ATSDD) scheme is proposed for cooperative uplink wireless and Radio-over-fiber (ROF) transmission in a Fractional Frequency Reuse (FFR) based multicell, multiuser system. More specifically, the ATSDD scheme is employed by the Mobile Station (MS) for reliably conveying the source bits to a pair of Remote Antennas (RAs) by appropriately adjusting the modulation mode according to the near-instantaneous wireless and ROF channel conditions. The ATSDD switching thresholds are specifically adjusted for ensuring that the Bit Error Ratio (BER) remains below 10^(-5). We also investigated the effect of phase-rotations, which is routinely inflicted by practical imperfect ROF links. We demonstrate that our ATSDD scheme increases the overall throughput.

A buffer-aided two hop link is studied, where the RN is capable of temporarily storing the received packets. We commerce by defining the concept of a two-dimensional Channel Probability Space (CPS) based on the source-relay and relay-destination channel. Specifically, a non-linear CPS division method is proposed, which partitions the CPS into several regions representing the quality of the specific channels plus an outage region. Then the best channel is activated for the sake of minimizing the system's energy dissipation. Finally, the proposed buffer-aided transmission scheme relying on our non-linear CPS division regime is investigated and the results show that at given average end-to-end energy dissipation, the outage probability was reduced by 33.5% compared to the benchmark scheme.

In a system supporting numerous users the complexity of the optimal Maximum Likelihood Multi-User Detector (ML MUD) becomes excessive. Based on the superimposed constellations of K users, the ML MUD outputs the specific multi-level K-user symbol that minimizes the Euclidean distance with respect to the faded and noise-contaminated received multi-level symbol. Explicitly, the Euclidean distance is considered as the Cost Function (CF). In a system supporting K users employing M-ary modulation, the ML MUD uses M^K CF evaluations (CFE) per time slot. In this contribution we propose an Early Stopping-aided Durr-H\o yer algorithm-based Quantum-assisted MUD (ES-DHA QMUD) based on two techniques for achieving optimal ML detection at a low complexity. Our solution is also capable of flexibly adjusting the QMUD's performance and complexity trade-off, depending on the computing power available at the base station. We conclude by proposing a general design methodology for the ES-DHA QMUD in the context of both CDMA and SDMA systems.

A pragmatic distributed algorithm (PDA) is proposed for supporting the efficient spectral access of multiple Primary Users (PUs) and Cognitive Users (CUs) in cooperative Cognitive Radio (CR) networks. The novelty of our PDA is that the PUs negotiate with the CUs concerning the specific amount of relaying and transmission time, the CU is granted, which the CU will either accept or decline. The CUs may serve as relay nodes for relaying the signal received from the PUs to their destinations, while both the PUs' and the CUs' minimum rate requirements are satisfied. This will reduce the required transmission power and/or increase the transmission rate of the PU. Our results show that the proposed scheme performs better than the benchmarker, despite its significantly lower overhead and complexity. Moreover, we show that the cooperative spectral access based on our PDA reaches an equilibrium, when it is repeated for a sufficiently long duration. These benefits are achieved, because the PUs are motivated to cooperate by the incentive of achieving a higher PU rate, whilst non-cooperation can be discouraged with the aid of a limited-duration punishment. Furthermore, we invoke an attractive practical adaptive Turbo Trellis Coded Modulation (ATTCM) scheme, which appropriately adjusts the code rate and the modulation mode according to the near-instantaneous channel conditions. It was found that the joint design of coding, modulation and user-cooperation may lead to significant mutual benefits for all the PUs and the CUs.

Most of the nodes in ad hoc networks rely on batteries, which requires energy saving. Hence, numerous energy-efficient routing algorithms have been proposed for solving this problem. In this paper, we exploit the benefits of cross-layer information exchange, such as the knowledge of the Frame Error Rate (FER) in the physical layer, the maximum number of retransmissions in the Medium Access Control (MAC) layer and the number of relays in the network layer. Energy-consumption-based Objective Functions (OF) are invoked for calculating the end-to-end energy consumption of each potentially available route for both Traditional Routing (TR) and for our novel Opportunistic Routing (OR), respectively. We also improve the TR and the OR with the aid of efficient Power Allocation (PA) for further reducing the energy consumption. For the TR, we take into account the dependencies amongst the links of a multi-hop route, which facilitates a more accurate performance evaluation than upon assuming the links that are independent. Moreover, two energy-efficient routing algorithms are designed based on Dijkstra's algorithm. The algorithms based on the energy OF provide the theoretical bounds, which are shown to be close to the bound found from exhaustive search, despite the significantly reduced complexity of the former. Finally, the end-to-end throughput and the end-to-end delay of this system are analyzed theoretically and a new technique of characterizing the delay distribution of OR is proposed. The simulation results show that our energy-efficient OR outperforms the TR and that their theoretical analysis accurately matches the simulation results.

An iterative Joint Source and Turbo Trellis Coded Hierarchical Modulation is introduced for robust context-aware medical image transmission. Lossless source compression as well as Quality of Service (QoS) might be considered as the main constraints in the telemedicine field. Our proposed scheme advocated was design to exploit both the joint source-and-channel iterative decoding and the cooperative structure in order for tackling these requirements. The Source Node (SN) is constituted by a lossless Variable Length Code (VLC) and Turbo Trellis-Coded Modulation (TTCM) which relies on Hierarchical Modulation (HM). The Relay Node (RN) is used to support the transmission of the most important content of the image. Our proposed scheme exhibits a robustness performance over a realistic uncorrelated Rayleigh fading channel, while it outperforms the non-cooperative scheme by 3 dB at asymptotic (error-free) Peak Signal to Noise Ratio (PSNR) value.

An iterative Joint Source and Channel Coded Modulation (JSCCM) scheme is proposed for robust video transmission over two-way relaying channels. The system advocated was designed for improving the throughput, reliability and coverage area compared to that of conventional one-way relaying schemes. We consider a two-user communication system, where the users exchange their information with the aid of a twin-antenna Relay Node (RN). For each user the proposed lossless video scheme is comprised of a Variable Length Code (VLC) encoder and two Turbo Trellis Coded Modulation (TTCM) encoders one at the Source Node (SN) and one at the RN. The spatio-temporal redundancy of the video sequence is exploited for reducing the iterative decoding complexity. The decoding convergence behaviour of the decoder as well as the power sharing ratio between the two SNs and the RN are characterized with the aid of EXtrinsic Information Transfer (EXIT) charts. Our proposed scheme exhibits an SNR gain of 9 dB compared to the non-cooperative scheme, when communicating over Rayleigh fading channels.

A cooperative communication system assisted by Turbo Trellis-Coded Modulation (TTCM) relying on Hierarchical Modulation (HM) is proposed, which invokes iterative soft decoding. Our results demonstrated that the performance of the single-relay aided cooperative system can be improved by at least 4 dB at a BER of 10−5.

The active cooperation between a primary user (PU) and a cognitive user (CU) has the potential of leading to a transmission power reduction and transmission rate increase for both the PU and the CU. Alternatively, the required bandwidth may be reduced and the freed bandwidth may be leased to a group of CUs for their secondary communications. More explicitly, our cooperative protocol allows a CU to serve as a relay node (RN) for relaying the signal of the first PU, which is a source node (SN), to the second PU, which is a destination node (DN). Furthermore, we conceived adaptive turbo trellis coded modulation (ATTCM) for appropriately adjusting both the code rate and the modulation mode according I to the near‐instantaneous channel conditions. More specifically, we propose an ATTCM aided two‐way relaying cooperative CR scheme that maximises the CU's own data rate and improves the exploitation of the bandwidth released by the PUs. Our numerical and simulation results show that the bandwidth reduction attained by the proposed two‐way relay based CR scheme is more than 80% of the PU's bandwidth.

We have conceived a near-capacity code design for entanglement-assisted classical communication over the quantum depolarizing channel. The proposed system relies on efficient near-capacity classical code designs for approaching the entanglement-assisted classical capacity of a quantum depolarizing channel. It incorporates an Irregular Convolutional Code (IRCC), a Unity Rate Code (URC) and a soft-decision aided Superdense Code (SD), which is hence referred to as an IRCC-URC-SD arrangement. Furthermore, the entanglement-assisted classical capacity of an N-qubit superdense code transmitted over a depolarizing channel is invoked for benchmarking. It is demonstrated that the proposed system operates within 0.4 dB of the achievable noise limit for both 2-qubit as well as 3-qubit SD schemes. More specifically, our design exhibits a deviation of only 0.062 and 0.031 classical bits per channel use from the corresponding 2-qubit and 3-qubit capacity limits, respectively. The proposed system is also benchmarked against the classical convolutional and turbo codes.

In this paper, we propose a new distributed coding structure with a soft input soft output (SISO) relay encoder for error-prone parallel relay channels. We refer to it as the distributed soft coding (DISC). In the proposed scheme, each relay first uses the received noisy signals to calculate the soft bit estimate (SBE) of the source symbols. A simple SISO encoder is developed to encode the SBEs of source symbols based on a constituent code generator matrix. The SISO encoder outputs at different relays are then forwarded to the destination and form a distributed codeword. The performance of the proposed scheme is analyzed. It is shown that its performance is determined by the generator sequence weight (GSW) of the relay constituent codes, where the GSW of a constituent code is defined as the number of ones in its generator sequence. A new coding design criterion for optimally assigning the constituent codes to all the relays is proposed based on the analysis. Results show that the proposed DISC can effectively circumvent the error propagation due to the decoding errors in the conventional detect and forward (DF) with relay re-encoding and bring considerable coding gains, compared to the conventional soft information relaying.

Multilevel Differential Amplitude and Phase-Shift Keying (DAPSK) schemes do not require any channel estimation, which results in low complexity. In this treatise we derive the soft-output probability formulas required for a soft-decision based demodulation of high-order DAPSK, in order to facilitate iterative detection by exchanging extrinsic information with an outer Turbo Code (TC). Furthermore, when the TC block size is increased, the system operates closer to the channel capacity. Compared to the identical-throughput TC assisted 64-ary Differential Phase-Shift Keying (64-DPSK) scheme, the 4-ring based TC assisted 64-ary DAPSK arrangement has a power-efficiency improvement of 2.3 dB at a bit error rate (BER) of 10-5. Furthermore, when the TC block size is increased, the system operates closer to the channel capacity. More specifically, when using a TC block length of 400 modulated symbols, the 64 DAPSK (4, 16) scheme is 7.56 dB away from its capacity curve, while it had a reduced gap as low as 2.25 dB, when using a longer TC block length of 40 000 modulated symbols. Finally, as a novel application example, the soft-decision M-DAPSK scheme was incorporated into an Amplify-and-Forward (AF) based cooperative communication system, which attains another 4.5 dB SNR improvement for a TC block length of 40 000 modulated symbols.

In this paper, we propose to reduce the complexity of both the Approx-Log-MAP algorithm as well as of the Max-Log-MAP algorithm conceived for generalized PSK/QAM detection, where only a reduced-size subset of the PSK/QAM constellation points is taken into account for producing a single soft-bit output. Although the detectors of Gray-labelled low-order PSK/QAM schemes generally produce near-horizontal EXIT curves, our proposed detectors exploit the a priori LLRs gleaned from a channel decoder in order to retain the optimum detection capability for all PSK/QAM constellations. Furthermore, we demonstrate in this paper that the widely applied MIMO schemes including V-BLAST and STBC, which invoke the proposed soft PSK/QAM detectors may also benefit from our reduced-complexity design. Our simulation results confirm that a near-capacity performance may be achieved by the proposed detectors at a substantially reduced detection complexity.

In this paper, we propose a comprehensive reduced-complexity detector both for hard-decision-aided as well as for the soft-decision-assisted Spatial Modulation (SM)/Space-Time Shift Keying (STSK). More explicitly, the detection of the SM scheme, which activates a single one out of M antennas to transmit a single LPSK/QAM symbol, may be carried out by detecting the antenna activation index m and the LPSK/QAM symbol stseparately, so that the detection complexity may be reduced from the order of O(M · L) to the lower bound of O(M + log2L). However, the QAM aided STSK hard detection proposed in [1] results in a performance loss. Furthermore, the Max-Log-MAP algorithm proposed for soft STSK detection in [2] only takes into account the maximum a posteriori probabilities, which also imposed a performance degradation. Therefore, in this paper, we propose a novel solution for hard-decision-aided SM/STSK detection, which retains its optimal performance, despite its reduced detection complexity, when either LPSK or LQAM is employed. Furthermore, we propose the reduced-complexity Approx-Log-MAP algorithm conceived for the soft-decision-aided SM/STSK detector, in order to replace the suboptimal Max-Log-MAP algorithm.

Near-Capacity Multi-user Network-coding (NCMN) based systems operating in multiple modes and relying on an amalgamated Irregular Convolutional Code, a Unity-Rate Code and M-ary Phase-Shift Keying are proposed. We consider a multiuser network in which the users cooperatively transmit their independent information to a common base station (BS). Extrinsic Information Transfer (EXIT) charts were used for designing the proposed NCMN scheme for the sake of approaching the Discrete-input Continuous-output Memoryless Channel's (DCMC) capacity. The NCMN systems are capable of simultaneously exploiting the advantages of all the new modes we designed for our system and those of the conventional mode. The design principles presented in this contribution can be extended to a vast range of NCMN based systems using arbitrary channel coding schemes.

In this paper, we propose to reduce the complexity of both the Approx-Log-MAP algorithm as well as of the Max-Log-MAP algorithm, which were designed for soft-decision-aided Space-Time Block Code (STBC) detectors. First of all, we review the STBC design, which enables regular L-PSK/QAM detectors to be invoked in order to detect STBCs on a symbol-by-symbol basis. Secondly, we propose to operate the L-PSK/QAM aided STBC detection on a bit-by-bit basis, so that the complexity may be reduced from the order of O(L) to O(BPS = log2L). Our simulation results demonstrate that a near-capacity performance may be achieved by the proposed detectors at a substantially reduced detection complexity. For example, a factor six complexity reduction was achieved by the proposed algorithms, when they were invoked for detecting Alamouti's Square 16QAM aided G2 scheme.

In this contribution, we derive the Discrete-input Continuous-output Memoryless Channel (DCMC) capacity of the non-regenerative Multiple-Input Multiple-Output (MIMO) relay channel, when the source-to-destination link is inferior and hence considered absent. We design near-capacity Forward Error Correction (FEC) codes for approaching this capacity limit. It is shown that our design is capable of approaching the DCMC capacity within 0.4dB, when communicating over uncorrelated Raleigh fading channels, where the source node, relay node and destination node are equipped with two antennas each.

A Turbo Trellis-Coded Modulation (TTCM) aided superposition modulation scheme is conceived for a Decode-and-Forward (DAF) based cooperative communication system. More specifically, two source nodes communicate simultaneously with the same destination node via a relay node. Superposition modulation is invoked at the relay node in order to combine and simultaneously transmit the two source signals to the destination node. Hence two timeslots are used to transmit two source signals. Extrinsic Information Transfer (EXIT) charts and power sharing techniques are employed in our design. The performance of the proposed scheme is investigated for transmission over uncorrelated Rayleigh fading channels, which is within about 2 dB of the corresponding capacity.

In this paper, we propose to reduce the complexity of both the Approx-Log-MAP algorithm as well as of the Max-Log-MAP algorithm, which were designed for soft-decision aided PSK detectors. First of all, we extend the shown a posteriori PSK symbol probability formula and streamline it by eliminating its unnecessary calculations in the context of the Approx-Log-MAP algorithm. Secondly, we reduce the complexity of the Max-Log-MAP algorithm, where the maximum a posteriori symbol probability may be obtained without evaluating and comparing all the candidate symbol probabilities. Furthermore, we apply our new soft detection arrangement to a variety of coded systems. Our simulation results demonstrate that a significant detection complexity reduction was achieved by our design without any performance loss. For example, a factor two complexity reduction was achieved by the proposed Max-Log-MAP algorithm, when it was invoked for detecting QPSK symbols, which is expected to be significantly higher, when invoked for 16QAM.

An adaptive Turbo Trellis Coded Modulation (ATTCM) aided Cognitive Radio (CR) scheme is proposed for cooperative communication among Primary Users (PUs) and Cognitive Users (CUs). The new cooperative protocol allows a CU to serve as a Relay Node (RN) for relaying the signal of the first PU, which is a Source Node (SN) to the second PU, which is a Destination Node (DN). More specifically, an active cooperation between the PU and the CU would lead to a reduction of the transmission power and/or to an increased transmission rate for the PU. These benefits may be translated into a reduced transmission bandwidth and the freed bandwidth may be leased to a group of CUs for their secondary communications. Furthermore, our ATTCM scheme appropriately adjusts the code rate and the modulation mode according to the near-instantaneous channel conditions. The ATTCM switching thresholds are chosen to ensure that the Bit Error Ratio (BER) is below 10-6in order to minimize the potential error propagation from the RN to the DN. It was found that the joint design of coding, modulation, user-cooperation and CR techniques may lead to significant mutual benefits for both the PUs and the CUs.

Near-capacity Non-coherent Cooperative Network-coding aided Multi-user (NNCNM) systems are designed with the aid of Extrinsic Information Transfer (EXIT) charts for the sake of approaching the Differential Discrete-input Continuous-output Memoryless Channel's (D-DCMC) system capacity1. The upper and lower Frame Error Ratio (FER) performance bounds are derived for aiding our network coding design. The outage capacity of the D-DCMC channel is also calculated and used for computing the best-case performance bounds of both the corresponding single-link scheme and of the proposed NNCNM system. Moreover, a new technique referred to as the Pragmatic Algebraic Linear Equation Method (PALEM) was proposed for determining the exact number of information sources that may be recovered from the composite NNCNM stream, which constitutes a lower-complexity evaluation of the attainable FER performance of the NNCNM systems without resorting to high-complexity Monte-Carlo simulations. The NNCNM systems advocated are capable of operating within 0.3-0.5 dB from the corresponding D-DCMC capacity. A joint treatment of channel and network coding is considered in our system2. The design principles presented in this contribution may be extended to a vast range of NNCNM based systems using arbitrary channel coding schemes.

Star Quadrature Amplitude Modulation (Star-QAM) is a non-coherent detection aided scheme ideal for low-complexity wireless transceivers. In this contribution, we first derive soft-decision aided StQAM symbol-to-bit demapping combined with iterative detection aided Turbo Coding (TC). Then we combine this physical layer design with network coding (NC) and quantify the attainable coding gain. It is shown that the proposed 16-level Star-QAM (16-StQAM) based TC scheme is capable of achieving a coding gain of about 1.5~dB over the TC aided 16-level Differential Phase-Shift Keying (16DPSK) benchmark scheme at a BER of 10-5. The 16-StQAM based TC assisted scheme is capable of offering another 1.2 dB coding gain, when it is employed in a 'butterfly' topology network arrangement. When the source and relay nodes are allowed to transmit at different power levels, the two-hop 16-StQAM based TC aided NC scheme outperforms the single-hop 16-StQAM based TC scheme by approximately 2.2 dB.

In this paper, we propose a Cooperative Differential Space-Time Spreading (CDSTS) scheme employing multiple relays, which eliminates the demanding requirement of channel estimation both at the relays and at the destination. More explicitly, the source node employs differential encoding during the first transmission interval, and the multiple relays perform Differential Space-Time Spreading (DSTS) based Amplify-and-Forward (AF) relaying in the second transmission interval. Eliminating high-complexity channel estimation is particularly important at the light-weight shirt-pocket-sized mobile handset based relays, since it is unrealistic to estimate the associated mobile-to-mobile channels, which would also pose a security threat and impose a Doppler-dependent pilot overhead. Finally, it would be prone to a channel-estimation-induced performance degradation, which might be close to the 3 dB non-coherent performance penalty. Loosely Synchronized (LS) CDMA spreading codes were adopted for the asynchronous CDMA uplink for the sake of achieving a near-single-user performance using a low-complexity single-user matched-filter detector. The potential performance degradation of the noncoherent receiver experienced in fast fading channels is mitigated by the proposed Multiple-Symbol Differential Sphere Decoding (MSDSD).

We propose a novel near-capacity Multiple-Symbol Differential Decoding (MSDD) aided cooperative Differential Linear Dispersion Code (DLDC), which exhibits a high grade of system design flexibility in terms of the choice of activated relays and the DLDC's rate allocation. More specifically, the system has the freedom to activate a range of DLDCs depending on both the number of relays available in the network, as well as on their position, throughput and complexity considerations.

A novel power- and bandwidth-efficient Turbo Trellis Coded Modulation (TTCM) assisted Space Division Multiple Access (SDMA) based two-way relaying scheme is proposed. The scheme advocated was designed for enhancing the throughput, reliability and coverage area in a cooperative communication system. A twin-antenna Relay Node (RN) is employed for assisting a pair of users, where each user is equipped with a single-antenna mobile unit. During the first transmission period, both users transmit their TTCM-encoded signals to the RN. The twin-antenna RN then detects these signals using various SDMA-based detection algorithms. Iterative SDMA and TTCM detection is invoked at the RN, which then broadcasts the re-encoded TTCM signals to both users during the second transmission period. Finally, each user retrieves the opposite user's signals received from the RN. Our proposed scheme outperforms the non-cooperative TTCM scheme by approximately 5.3 dBs at a BER of 10-6, when communicating over uncorrelated Rayleigh fading channels.

Low-complexity non-coherently detected Differential Amplitude and Phase-Shift Keying (DAPSK) schemes constitute an ideal candidate for wireless communications. In this paper, we derive the soft- output probability formulas required for the soft- decision based demodulation of DAPSK, which are then invoked for Turbo Coded (TC) transmissions. Furthermore, the achievable throughput characteristics of the family of M-ary DAPSK schemes are provided. It is shown that the proposed 4-ring based TC assisted 64-ary DAPSK scheme achieves a coding gain of about 4.2 dBs in comparison to the identical-throughput TC assisted 64-ary Differential Phase-Shift Keying (64-DPSK) scheme at a bit error ratio of 10-5.

Robust video transmission using iteratively detected Self-Concatenated Coding (SCC), multi-dimensional Sphere Packing (SP) modulation and Layered Steered Space-Time Coding (LSSTC) is proposed for H.264 coded video transmission over correlated Rayleigh fading channels. The self-concatenated convolutional coding (SECCC) scheme is composed of a Recursive Systematic Convolutional (RSC) code and an interleaver, which is used to randomise the extrinsic information exchanged between the self-concatenated constituent RSC codes. Additionally, a puncturer is employed for improving the achievable bandwidth efficiency. The convergence behaviour of the MIMO transceiver advocated is investigated with the aid of Extrinsic Information Transfer (EXIT) charts. The proposed system exhibits an $E_b/N_0$ gain of about $9~dB$ at the PSNR degradation point of $1~dB$ in comparison to the identical-rate benchmarker scheme.

In this contribution, we investigate Near-Capacity Multi-user Network-coding (NCMN) based systems using an Irregular Convolutional Code, a Unity-Rate Code and M-ary Phase-Shift Keying. In the NCMN based systems, we consider a multiuser network in which the users cooperatively transmit independent information to a common base station (BS). Extrinsic Information Transfer (EXIT) charts were used for designing the proposed NCMN scheme. The design principles presented in this contribution can be extended to a vast range of NCMN based systems using arbitrary channel coding schemes.

In this contribution, Near-capacity Non-coherent Cooperative Network-coding aided Multi-user (NNCNM) systems are designed with the aid of Extrinsic Information Transfer (EXIT) charts for the sake of approaching the Differential Discrete-input Continuous-output Memoryless Channel (D-DCMC)-based capacity. The proposed sub-frame-based network coding solution allows the system to significantly mitigate the effects of large-scale fading on each frame. Hence, NNCNM systems operating in large-scale fading environments are capable of approaching the D-DCMC capacity of the less hostile single link channel incurring the small-scale fading, but no shadow fading.

Differential Space-Time Modulation (DSTM) employing multiple antennas provides a diversity advantage in rich scattering environments, whilst the excessive complexity of MIMO channel estimation is avoided. However, due to size, cost or other hardware limitations, the multiple antennas may be in deep fade simultaneously and hence experience spatially correlated fading, which leads to a loss of diversity gain. Hence in this paper, we design an Amplify-and-Forward (AF) relaying aided DSTM scheme, which is capable of attaining a diversity gain even when the source node is in deep fade. Furthermore, Multiple-Symbol Differential Sphere Decoding (MSDSD) is developed for the proposed scheme to avoid the potential performance degradation of the noncoherent receiver in fast fading channels.

In ad hoc networks the nodes actively and voluntarily participate in constructing a network and act as relays for other nodes. As a result of node-mobility, the Channel State Information (CSI) varies and hence a substantial amount of control messages have to be exchanged across the network to maintain reliable communications between certain pairs of nodes, which potentially imposes a high energy-consumption. Therefore, minimizing the energy consumption and maximizing the throughput of ad hoc nodes is extremely important. This paper analyzes both the energy consumption and the achievable throughput of a multihop route by exploiting both the CSI quantified, for example in terms of the Frame Error Ratio (FER), as well as the number of Medium Access Control (MAC) retransmissions and the number of hops. Since using limited number of MAC retransmissions in a hop-by-hop retransmission mode imposes dependencies amongst the links of a multi-hop route, a more accurate objective function may be formulated than that which assumes the availability of an infinite number of retransmissions and which considers the links to be independent. Our simulations confirm the improved accuracy of the proposed Objective Function (OF), especially when the FER and the number of hops are high and the number of MAC retransmissions is low. Additionally, a low-complexity routing algorithm is designed, which carries out routing decisions based on the energy consumption predicted by the OF, and strikes a compromise between having 'few long-distance hops' and 'many short-distance hops' for the sake of energy minimization and throughput maximization.

In this paper, we design an energy-efficient cooperative Medium Access Control (MAC) protocol combined with physical layer power / rate control in order to minimize the energy consumption. Based on the Channel State Information (CSI) and relay-to-destination distance, the potential candidate relays carry out autonomous decisions for minimizing the transmission power required for forwarding their data, when relying on their cooperation. Simulation results demonstrate that our scheme is capable of providing considerable energy savings, while maintaining the target Frame Error Ratio (FER), which is achieved at the cost of introducing a modest additional MAC overhead.

Motivated by the recent development of Spatial Modulation (SM) and Differential Space-Time Shift Keying (DSTSK), we propose a reduced-complexity Conventional Differential Detector (CDD) as well as a reduced-complexity Multiple-Symbol Differential Sphere Detector (MSDSD) for DSTSK. Both schemes operate on a symbol-by-symbol basis in order to reduce the complexity of the classic block-by-block-based CDD and MSDSD, whilst still approaching the optimum performance of the full-search-based Maximum Likelihood (ML) detector.

The nodes of ad hoc networks are typically battery-powered, hence requiring the employment of energy-efficient schemes. Near-capacity coding schemes allow a single link to communicate using the lowest possible transmit power, while achieving a low Frame Error Ratio (FER). With the same motivation of conserving battery energy, numerous power-aware routing algorithms have been proposed for improving the overall multiuser network's energy-efficiency instead of improving a single link. Taking both these design factors into consideration, we employ Multi-Antenna aided Relays (MA-Rs) in the context of ad hoc networks, which use a three-stage concatenated transceiver constituted by an Irregular Convolutional Code, Unity-Rate Code and Space-Time Trellis Code (IrCC-URC-STTC) equipped with two antennas. All other mobiles are single-antenna assisted nodes and refrain from relaying, hence they dispense with STTC schemes and use a two-stage concatenated IrCC-URC coding scheme. It is confirmed that as expected, in a high-node-density scenario the average energy consumption per information bit and per node becomes about a factor two lower than that in the equivalent Single-Antenna Relay (SA-R) aided networks.

Differentially detected noncoherent Star Quadrature Amplitude Modulation (Star-QAM) is ideal for low-complexity wireless communications, since it dispenses with high-complexity channel estimation. We conceive soft-decision based demodulation for 16-level Star-QAM (16-StQAM), which is then invoked for iterative detection aided Iteratively-Detected Bit-Interleaved Coded Modulation (BICM-ID). It is shown that the proposed 16-StQAM based BICM-ID scheme achieves a coding gain of approximately 14 dBs in comparison to the 16-level identical-throughput Differential Phase-Shift Keying (16DPSK) assisted BICM scheme at a bit error ratio of 10-6.

In this contribution, we derive the upper and lower Frame Error Ratio (FER) performance bounds of cooperative multiuser communications systems using network coding. Our Monte Carlo simulation based results confirm the accuracy of our derivation.

We propose a novel near-capacity Multiple-Symbol Differential Decoding (MSDD) aided cooperative Differential Linear Dispersion Code (DLDC) scheme, which exhibits a high grade of system design flexibility in terms of the choice of activated relays and the DLDC's rate allocation. More specifically, the system has the freedom to activate a range of DLDCs depending on both the number of relays available in the network, as well as on their position, throughput and complexity considerations.

Motivated by the recent development of spatial modulation (SM) and differential space-time shift keying (DSTSK), we propose a reduced-complexity conventional differential detector (CDD) as well as its reduced-complexity multiple-symbol differential sphere detector (MSDSD) counterpart for DSTSK. Both schemes operate on a symbol-by-symbol basis in order to reduce the complexity of the classic block-by-block-based CDD and MSDSD, whilst still attaining the optimum performance of the full-search-based ML detector.

In this letter, we propose to reduce the detection complexity of soft-decision aided Space-Time Shift Keying (STSK). More explicitly, we propose a vector-by-vector based STSK detector, which exhibits a lower complexity compared to the classic block-by-block based Space-Time Modulation (STM) detector. We further operate the STSK detector on a symbol-by-symbol basis, so that a near-capacity performance may be achieved with the aid of channel coding at a reduced complexity.

We propose Multiple-Symbol Differential Detection (MSDD) aided Differential Space-Time Block Codes (DSTBCs) using QAM. Our solution eliminates the requirement of high-complexity MIMO channel estimation and its pilot overhead, while mitigating the potential performance degradation of noncoherent receivers in fast fading channels. Additionally, we develop Multiple-Symbol Differential Sphere Detection (MSDSD) for the QAM aided DSTBC schemes advocated, in order to circumvent their potentially excessive complexity.

A novel reduced-complexity near-optimal detection algorithm is proposed for enhancing the recent Coherently-detected Space-Time Shift Keying (CSTSK) scheme employing arbitrary constellations, such as {\cal L}-point Phase-Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM). The proposed detector relies on a modified Matched Filter (MF) concept. More specifically, we exploit both the constellation diagram of the modulation scheme employed as well as the Inter-Element-Interference (IEI)-free STSK architecture. Furthermore, we generalize the Pulse Amplitude Modulation (PAM)- or PSK-aided Differentially-encoded STSK (DSTSK) concept and conceive its more bandwidth-efficient QAM-aided counterpart. Then, the proposed reduced-complexity CSTSK detector is applied to the QAM-aided DSTSK scheme, which enables us to carry out low-complexity non-coherent detection, while dispensing with channel estimation. It is revealed that the proposed detector is capable of approaching the optimal Maximum Likelihood (ML) detector's performance, while avoiding the exhaustive ML search. Interestingly, our simulation results also demonstrate that the reduced-complexity detector advocated may achieve the same performance as that of the optimal ML detector for the specific STSK scheme's parameters. Another novelty of this paper is that the star-QAM STSK scheme tends to outperform its square-QAM counterpart, especially for high number of dispersion matrices. Furthermore, we provided both the theoretical analysis and the simulations, in order to support this unexpected fact.

It is widely recognized that half-duplex-relay-aided differential decode-and-forward (DDF) cooperative transmission schemes are capable of achieving a cooperative diversity gain, while circumventing the potentially excessive-complexity and yet inaccurate channel estimation, especially in mobile environments. However, when a cooperative wireless communication system is designed to approach the maximum achievable spectral efficiency by taking the cooperation-induced multiplexing loss into account, it is not obvious whether or not the relay-aided system becomes superior to its direct-transmission based counterpart, especially, when advanced channel coding techniques are employed. Furthermore, the optimization of the transmit-interval durations required by the source and relay is an open issue, which has not been well understood in the context of half-duplex relaying schemes. Hence, we first find the optimum transmission duration, which is proportional to the adaptive channel-code rate of the source and relay in the context of Code-Rate-Optimized (CRO) TDMA-based DDF-aided half-duplex systems for the sake of maximizing the achievable network throughput. Then, we investigate the benefits of introducing cooperative mechanisms into wireless networks, which may be approached in the context of the proposed CRO cooperative system both from a pure capacity perspective and from the practical perspective of approaching the Discrete-input Continuous-output Memoryless Channel (DCMC) capacity with the aid of the proposed Irregular Distributed Differential (IrDD) coding aided scheme. In order to achieve a near-capacity performance at a low-complexity, an adaptive-window-duration based Multiple-Symbol Differential Sphere Detection (MSDSD) scheme is employed in the iterative detection aided receiver. Specifically, upon using the proposed near-capacity system design, the IrDD coding scheme devised becomes capable of performing within about 1.8 dB from the corresponding single-relay-aided DDF cooperative system's DCMC capacity.

An attractive hybrid method of mitigating the effects of error propagation that may be imposed by the relay node (RN) on the destination node (DN) is proposed. We selected the most appropriate relay location for achieving a specific target Bit Error Ratio (BER) at the relay and signalled the RN-BER to the DN. The knowledge of this BER was then exploited by the decoder at the destination. Our simulation results show that when the BER at the RN is low, we do not have to activate the RN-BER aided decoder at the DN. However, when the RN-BER is high, significant system performance improvements may be achieved by activating the proposed RN-BER based decoding technique at the DN. For example, a power-reduction of up to about 19dB was recorded at a DN BER of 10-4.

It is widely recognised that the choice of a specific bit-to-symbol mapping scheme or a beneficial constellation labelling is an influential factor, when designing bit-interleaved coded modulation using iterative decoding (BICM-ID) for the sake of achieving a high iteration gain. Generally, a larger constellation size of a higher-dimensional space renders the bit-to-symbol mapping design more flexible. In this paper, we first define a flexibility measure based on the extrinsic information transfer (EXIT) characteristics of bit-to-symbol mapping schemes. Secondly, we investigate the effect of expanding the constellation to a higher-dimensional space on our proposed EXIT characteristic flexibility index, when transmitting diverse numbers of bits per joint symbol.

In this paper, we consider coding schemes designed for two nodes communicating with each other with the aid of a relay node, which receives information from the two nodes in the first time slot. At the relay node we combine a powerful Superposition Coding (SPC) scheme with Iteratively-Decoded Self-Concatenated Convolutional Codes (SECCC-ID), which exchange mutual information between each other. It is assumed that decoding errors may be encountered at the relay node. The relay node then broadcasts this information in the second time slot after re-encoding it, again, using a SECCC encoder. At the destination, an amalgamated SPC-SECCC block then detects and decodes the signal either with or without the aid of a priori information. Our simulation results demonstrate that the proposed scheme is capable of reliably operating at a low BER for transmission over both AWGN and uncorrelated Rayleigh fading channels. We compare the proposed scheme's performance to a direct transmission link between the two sources having the same throughput. Additionally, the SPC-SECCC system achieves a low BER even for realistic error-infested relaying.

In this contribution we propose a robust H.264 coded wireless video transmission scheme using iteratively decoded self-concatenated convolutional coding (SECCC). The proposed SECCC scheme is composed of constituent recursive systematic convolutional (RSC) codes and an interleaver is used to randomise the extrinsic information exchanged between the constituent RSC codes. Additionally, a puncturer is used to increase the achievable bandwidth efficiency. At the receiver self-iterative decoding is invoked between the hypothetical decoder components. The performance of the system was evaluated using the H.264/AVC source codec for interactive video telephony. Furthermore, EXIT charts were utilised in order to analyse the convergence behaviour of the SECCC scheme advocated. We demonstrate the efficiency of this approach by showing that the video quality is significantly improved, when using the binary SECCC scheme. More explicitly, the proposed system exhibits an Eb/N0gain of 6 dB at the PSNR degradation point of 2 dB in comparison to the identical-rate benchmarker carrying out RSC coding and puncturing, while communicating over correlated Rayleigh fading channels.

Abstract-In this contribution, we propose an adaptive Turbo Trellis Coded Modulation (TTCM) aided Distributed Space-Time Trellis Coding (STTC) scheme for cooperative communication over quasi-static Rayleigh fading channels. An adaptive TTCM (ATTCM) scheme is employed by the source node during the first transmission period for reliably conveying the source bits to N number of relay nodes by appropriately adjusting the code-rate and modulation mode according to the near-instantaneous channel condition. The TTCM switching thresholds are chosen to ensure that the Bit Error Ratio (BER) at each relay node becomes lower than 10-6in order to minimise the potential error propagation imposed by the relay nodes. During the second transmission period, an N-antenna assisted Distributed STTC (DSTTC) scheme is created with the aid of the aforementioned N single-antenna relay nodes. More specifically, the N relay nodes are utilised to form STTC codewords based on the re-encoded TTCM symbols of the relays for transmission to the destination node. At the destination node, iterative extrinsic information exchange is performed between the STTC and TTCM decoders for recovering the original source bits. It is shown that the proposed ATTCM-DSTTC scheme requires 12 dBs less transmission power in comparison to a standard TTCM scheme when aiming for a frame error ratio of 10-3.

A low complexity distributed coding scheme is proposed for communications over Rayleigh fading channels. Convolutional Coding (CC) assisted Differential Phase-Shift Keying (DPSK) modulation is employed at the source node for conveying the source signals to two relay nodes as well as to the destination node during the first transmission period. Iterative detection exchanging extrinsic information between the DPSK demapper and CC decoder is carried out at each relay node in order to recover the source signals. Then, the CC-encoded bits are re-encoded by the two relays to generate Differential Space-Time Block Coding (DSTBC) symbols for transmission to the destination node during the second transmission period. At the destination node, iterative decoding exchanging extrinsic information is invoked between the DPSK demapper and the concatenated CC-DSTBC decoder, where the later is viewed as a single amalgamated decoder. The relay and destination nodes do not have to estimate the channel's fading coefficients due to the employment of DPSK and DSTBC schemes. Our design requires only two decoding iterations between the DPSK and CC decoders at each relay in order to further reduce the complexity of the relay nodes. Our distributed coding scheme assisted by two low-complexity relay nodes outperforms the non-cooperative benchmarker scheme by about 8 dBs, when aiming for a bit error ratio of 10-5.

In this contribution, we propose a novel Distributed Source-coding, Channel-coding and Modulation (DSCM) scheme for cooperative communications. The proposed DSCM scheme is designed for ensuring the decoding convergence of its constituent component codes, namely, the Variable Length Code (VLC) and two Coded Modulation (CM) schemes. The source node encodes the source symbols with the aid of a serially-concatenated VLC and a Turbo Trellis Coded Modulation (TTCM) scheme. The TTCM-VLC encoded symbols are transmitted to both a relay node and to the destination node during the first transmission period. The relay node employs a powerful iterative TTCM-VLC decoder for estimating the VLC-encoded bit sequence. This decoded bit sequence is then re-encoded with the aid of a simple Trellis Coded Modulation (TCM) scheme before it is transmitted to the destination node. At the destination node, a novel four-component iterative decoding arrangement is invoked for recovering the original source symbols. It is shown that the DSCM scheme significantly outperforms the TTCM-VLC benchmarker scheme dispensing with relaying. The proposed power- and bandwidth-efficient DSCM scheme is an ideal candidate for next-generation mobile multimedia systems.

In this contribution, we propose a Distributed Concatenated Irregular Convolutional Coded Unity Rate Coded and Space Time Trellis Coded (DC-IrCC-URC-STTC) scheme for cooperative communications employing multiple single-antenna relays. Each coding arrangement is designed for efficient decoding convergence by employing non-binary Extrinsic Information Transfer (EXIT) charts. The source node transmits two-stage IrCC-URC encoded symbols to two relays during the first transmission period. Then each relay performs two-stage URC-IrCC decoding and re-encodes the information bits using the three-stage concatenated coding scheme IrCC-URC-STTC. However, only the signals of one predefined STTC output are transmitted from each relay to the destination node during the second transmission period. At the destination, the received signals are treated as if they arrived from one transmitter employing STTC using two co-located transmit antennas. The simulation results show that the Monte-Carlo based performance of the DC-IrCC-URC-STTC scheme exactly matches the EXIT-chart analysis. It also performs closely to its idealised counterpart that assumes perfect decoding at the relays when an EXIT-chart based optimal algorithm is applied for selecting relays.

The achievable performance of a jointly optimised iterative source and channel decoding (ISCD) arrangement invoking the Adaptive MultiRate Wideband (AMR-WB) speech codec is characterized, which exploits the intentional redundancy imposed by the proposed Over-Complete source-Mapping (OCM) scheme. The resultant OCM-aided AMR-WB bitstream is protected by a Recursive Systematic Convolutional (RSC) code and mapped to a Differential Space-Time Spreading (DSTS) arrangement using Sphere Packing (SP) modulation for transmission over narrowband temporally correlated Rayleigh fading channels. The effect of appropriately apportioning the total amount of redundancy between the source and channel codecs on the attainable system performance is demonstrated, while keeping the overall coding rate constant. The decoding convergence of the proposed scheme is studied with the aid of Extrinsic Information Transfer (EXIT) charts. Explicitly, our experimental results show that the specific scheme using a 2/3-rate channel encoder and a 3/4-rate OCM scheme exhibits an Eb/N0gain of 0.7 dB at the SegSNR degradation point of 1 dB, when compared to the system that assigns all the redundancy to the OCM scheme. By contrast, the scheme using a 3/4-rate channel encoder and a 8/9-rate OCM results in an Eb/N0gain of 1.0 dB.

This paper proposes a cooperative space-time coding (STC) protocol, amalgamating the concepts of asynchronous cooperation, non-coherent detection as well as Distributed Turbo Coding (DTC), where neither symbol-level time synchronization nor CSI estimation is required at any of the cooperating nodes, while attaining a high performance even at low SNRs. More specifically, a practical cooperative differential space-time spreading (CDSTS) scheme is designed with the aid of interference rejection spreading codes, in order to eliminate the effect of synchronization errors between the relay nodes without the assistance of channel estimation or equalization. Furthermore, a set of space-time codewords are constructed based on Differential Linear Dispersion Codes (DLDC), which allows our CDSTS system to support an arbitrary number of relay nodes operating at a high transmission rate due to its flexible design. Rather than using conventional single-relay-assisted DTCs, novel multi-relay-assisted DTCs and a three-stage iteratively-decoded destination receiver structure are developed. In our simulations the system parameters are designed with the aid of EXIT chart analysis, followed by the characterization of the achievable BER performance for various synchronization delay values as well as for various diversity-multiplexing relationships in frequency-selective fast and/or quasi-static Rayleigh fading environments.

It is widely recognized that differential decode-and-forward (DDF) cooperative transmission scheme is capable of providing a superior performance compared to classic direct transmissions employing differential detection, where no channel coding is used. However, the diversity gains achieved by the cooperative system become modest in practical channel coded scenarios, where the interleaving and channel coding gains dominate. Therefore, when a cooperative wireless communication system is designed to approach the maximum achievable spectral efficiency by taking the cooperation-induced multiplexing loss into account, it is not obvious, whether or not the relay-aided system becomes superior to its direct-transmission based counterpart, especially, when advanced channel coding techniques are employed. Hence in this paper the capacity of the single-relay-assisted DDF based cooperative system was studied in comparison to that of its direct-transmission based counterpart in order to answer the above-mentioned dilemma.

This paper presents an Irregular Distributed Hybrid Concatenated Differential (Ir-DHCD) coding scheme contrived for the relay-aided differential decode-and-forward (DDF) cooperative system using multiple-symbol differential sphere detection (MSDSD), where no channel estimation is required. We proposed a practical design framework for a cooperative system, which is capable of performing close to the network's corresponding non-coherent Discrete-input Continuous-output Memoryless Channel (DCMC) capacity. An adaptive-window-duration based MSDSD scheme is employed to further reduce the iterative detection complexity. Specifically, upon using the proposed near-capacity system design, the Ir-DHCD coding scheme devised becomes capable of performing within about 1.8 dB from the corresponding single-relay-aided DDF cooperative system's DCMC capacity.

The classic Dynamic Source Routing (DSR) protocol opts for the route requiring the lowest number of hops for transmitting data from the source to the destination. However, owing to node mobility in dynamic self-organizing ad hoc networks, the route containing a low number of potentially long-range hops does not always perform well. Furthermore, the currently used route may break owing to node-mobility and the routing information gathered during route discovery may become invalid. In order to circumvent the potentially inaccurate nature of the routing information, a fuzzy logic aided technique is incorporated into the routing algorithm for mitigating the influence of imprecise routing information. As a further benefit, fuzzy logic aided techniques are capable of processing multiple inputs, hence we use both the expected route lifetime and the number of hops as its input parameters, which allows us to integrate the physical layer and network layer into a jointly designed routing protocol. The route life-time is typically reduced with the increased mobility of the nodes. The specific route having the highest route 'stability' is finally selected for data transmission, and based on the route life-time the route-cache expiration time is adjusted adaptively. We will demonstrate that the proposed fuzzy logic based DSR outperforms the conventional DSR in terms of the attainable network throughput, despite having a lower network control load. Finally, we quantify the impact of the physical layer on the achievable performance of the network layer for different physical layer schemes by using the OMNeT++ simulator.

In this paper, we develop a capacity-approaching Cooperative Space-Time Coding CSTC scheme employing irregular design for a twin-relay aided network as an extension of our previous work cast in the context of a half-duplex single-relay-aided network. For the sake of recovering the multiplexing loss imposed by a half-duplex three-terminal network, we employ a successive relaying protocol in this paper, where an additional relay node is activated. Hence, in order to design a near-capacity coding system, first the capacity and the achievable information-rate of a specific space-time coding aided scheme are quantified for the successive relaying aided channel. More specifically, the cooperative space-time codes employed at the source and the relays are jointly designed with the aid of EXtrinsic Information Transfer EXIT charts for the sake of high-integrity operation at Signal-to-Noise Ratios SNRs close to the corresponding successive relaying channel's capacity. Furthermore, unlike in the half-duplex single-relay based system, the destination node performs frame-by-frame Successive Interference Cancellation SIC aided iterative detection, in order to mitigate the efforts of multiple-access interference. Finally, our numerical results demonstrate that our proposed Irregular Cooperative Space-Time Coding Ir-CSTC scheme is capable of near-capacity operation in the successive relaying aided network, which is an explicit benefit of our joint source-and-relay transceiver design.

In this paper 3-D Extrinsic Information Transfer (EXIT) charts are used to design binary Self-Concatenated Convolutional Codes employing Iterative Decoding (SECCC-ID), exchanging extrinsic information with the soft-decision demapper to approach the channel capacity. Recursive Systematic Convolutional (RSC) codes are selected as constituent codes, an interleaver is used for randomising the extrinsic information exchange of the constituent codes, while a puncturer helps to increase the achievable bandwidth efficiency. The convergence behaviour of the decoder is analysed with the aid of bit-based 3-D EXIT charts, for accurately calculating the operating EbN0threshold, especially when SP based soft demapper is employed. Finally, we propose an attractive system configuration, which is capable of operating within about 1 dB from the channel capacity.

This paper presents a low complexity iteratively detected space-time transmission architecture based on Generalized Multi-Layer Space-Time (GMLST) codes and Irregular Convolutional Codes (IRCCs). The GMLST combines the benefits of the Vertical Bell-Labs LAyered Space-Time (VBLAST) scheme and Space-Time Coding (STC). The GMLST is serially concatenated with a Unity-Rate Code (URC) and an IRCC which are used to facilitate near-capacity operation with the aid of an EXtrinsic Information Transfer (EXIT) chart based design. Reduced-complexity iterative multistage Successive Interference Cancellation (SIC) is employed in the GMLST decoder, instead of the significantly more complex Maximum Likelihood (ML) detection. For the sake of approaching the maximum attainable rate, iterative decoding is invoked to achieve decoding convergence by exchanging extrinsic information across the three serial component decoders. Finally, it is shown that the SIC-based iteratively detected IRCC-URC-GMLST system is capable of providing a feasible trade-off between the affordable computational complexity and the achievable system throughput.

In this paper, an Irregular Distributed Space-Time (Ir-DST) coding scheme is studied in the context of a twin-relay aided network in which the successive relaying protocol is employed. A tight upperbound of the successive relaying aided network's capacity is given. The distributed codes at the source and relays are jointly designed with the aid of Extrinsic Information Transfer (EXIT) charts for the sake of high-integrity operation at Signal-to-Noise Ratios (SNRs) close to the corresponding network's capacity. Finally, it is shown that our proposed Ir-DST coding scheme is capable of near-capacity cooperative communications in the successive relaying aided network, which is an explicit benefit of our joint source-and-relay mode design.

In this treatise, we propose an iteratively decoded Bell-labs LAyered Space-Time (BLAST) scheme, which serially concatenates an IRregular Convolutional Code (IRCC), a UnityRate Code (URC) and a BLAST transmitter. The proposed scheme is capable of achieving a near capacity performance with the aid of our Extrinsic Information Transfer (EXIT) chart assisted design procedure. Furthermore, a Markov Chain Monte Carlo (MCMC) based BLAST scheme is employed, which is capable of significantly reducing the complexity imposed. For the sake of approaching the maximum achievable rate, iterative decoding is invoked to attain decoding convergence by exchanging extrinsic information among the three serial component decoders. Our simulation results show that the proposed MCMC-based iteratively detected IRCC-URC-BLAST scheme is capable of approaching the system capacity.

In this contribution, we propose a distributed turbo trellis coded modulation (DTTCM) scheme for cooperative communications. The DTTCM scheme is designed based on its decoding convergence with the aid of non-binary extrinsic information transfer (EXIT) charts. The source node transmits TTCM symbols to both the relay and the destination nodes during the first transmission period. The relay performs TTCM decoding and re-encodes the information bits using a recursive systematic convolutional (RSC) code regardless whether the relay can decode correctly or not. Only the parity bits are transmitted from the relay node to the destination node during the second transmission period. The resultant symbols transmitted from the source and relay nodes can be viewed as the coded symbols of a three-component parallel-concatenated TTCM scheme. At the destination node, a novel three-component TTCM decoding is performed. It is shown that the performance of the DTTCM matches exactly the EXIT chart analysis. It also performs very closely to its idealised counterpart that assumes perfect decoding at the relay.

The powerful tool of EXtrinsic Information Transfer (EXIT) charts is used to design a new serially concatenated Irregular Variable Length Coded (IrVLC) and unity-rate precoded Time-Hopping (TH) Pulse Position Modulation (PPM) aided Ultra-Wide Bandwidth (UWB) Spread-Spectrum (SS) impulse radio for near-capacity operation in Nakagami-m fading channels contaminated by Partial Band Noise Jamming (PBNJ). The benefits of the 3-stage concatenation of the TH-UWB detector, the unity-rate decoder and the outer IrVLC decoder are quantified. A number of novel Variable Length Coding (VLC) codebooks having different coding rates are utilized by the IrVLC scheme for encoding specific fractions of the input source symbol stream. More explicitly, EXIT charts are employed to appropriately select these input stream fractions to shape the inverted EXIT curve of the IrVLC in order to match that of the inner decoder and hence to achieve an infinitesimally low Bit Error Ratio (BER) at near-capacity SNR values.

In this contribution, we propose a distributed binary self-concatenated coding scheme using iterative decoding (DSECCC-ID) for cooperative communications. The DSECCC-ID scheme is designed with the aid of binary extrinsic information transfer (EXIT) charts. The source node transmits SECCC symbols to both the relay and the destination nodes during the first transmission period. The relay performs SECCC-ID decoding. It then re-encodes the information bits using a recursive systematic convolutional (RSC) code during the second transmission period. The resultant symbols transmitted from the source and relay nodes can be viewed as the coded symbols of a three-component parallel-concatenated SEC CC-ID encoder. At the destination node, three component DSECCC-ID decoding is performed. It is shown that the performance of the DSECCC-ID exactly matches the EXIT chart analysis. The EXIT chart gives us an insight into operation of the distributed coding scheme which enables us to significantly reduce the transmit power of the system.

This paper presents an Irregular Distributed SpaceTime (Ir-DST) coding scheme designed for near-capacity cooperative communications. A serial concatenated scheme comprising an IRregular Convolutional Code (IRCC), a recursive Unity-Rate Code (URC) and a Space-Time Block Code (STBC) was designed for the sake of approaching the corresponding source-to-relay link capacity, where the IRCC was optimized with the aid of Extrinsic Information Transfer (EXIT) charts which was used at the source node. At the relay node, another IRCC is concatenated serially with an identical STBC. The relay's IRCC is re-optimized based on EXIT chart analysis for the sake of approaching the relay network's capacity, before transmitting the relayed information. We will demonstrate that the topology of the Ir-DST system coincides with that of a Distributed Turbo Code (DTC). At the destination node, a novel three-stage iterative decoding scheme is constructed in order to achieve decoding convergence to an infinitesimally low Bit Error Ratio (BER). Finally, it is shown that our joint source-and-relay mode design based on EXIT chart analysis is capable of near-capacity cooperative communications.

In this treatise, we investigated the application of singular value decomposion (SVD) assisted multiuser transmission in a multicell scenario. The SVD based scheme is capable of completely removing the cochannel interference, similarly to the classic zero forcing (ZF) based and block diagonalization (BD) aided schemes. Two different power allocation schemes are investigated for both SVD, ZF and BD based multicell transmission. The SVD scheme achieves a suboptimal performance, but at a reduced complexity. Nonetheless, it always outperforms the ZF based scheme due to the joint reception of the transmitted symbols.

A jointly optimised iterative source and channel decoding (ISCD) scheme invoking the Adaptive Multi Rate Wideband (AMR-WB) speech codec is proposed. More explicitly, the transceiver investigated consists of serially concatenated Recursive Convolutional (RSC) codes, a Unity Rate Code (URC) referred to as a precoder and the AMRWB speech codec, where the resultant bitstream is transmitted using Differential Space-Time Spreading (DSTS) and Sphere Packing (SP) modulation over narrowband temporally correlated Rayleigh fading channels. The convergence behaviour of the advocated scheme is investigated with the aid of Extrinsic Information Transfer (EXIT) charts, which suggests that potential performance improvements can be achieved by combining a serially concatenated precoder with the AMR-WB speech codec. The proposed system exhibits an Ef,/No gain of about 1.5 dB in comparison to the benchmark scheme carrying out iterative sourceand channel-decoding as well as DSTS aided SP-demodulation, but dispensing with the precoder, when using Isystem= 4 system iterations.

Irregular Variable Length Coding Design for serial concatenated and iteratively decoded Time-Hopping (TH) Pulse Position Modulation (PPM) UltraWideBand (UWB) Spread-Spectrum (SS) Impulse radio system is considered. The proposed design is capable of low Signal-to-Noise Ratio (SNR) operation in Nakagami-m fading channel amalgamated with joint source and channel coding schemes. A number of component Variable Length Coding (VLC) codebooks with different coding rates are being utilized by IVLC scheme for encoding specific fractions of the input source symbol stream. The EXtrinsic Information Transfer (EXIT) charts are used to select these fractions in order to shape inverted EXIT curve of IVLC according to EXIT curve of the inner decoder match. The proposed scheme can achieve near-zero bit error ratio at low SNR values. This IVLC based scheme provides a gain of up to 0.45 dB over the identical-rate single class VLC based scheme.

A near-capacity time hopping (TH) pulse position modulation (PPM) based ultrawideband (UWB) impulse radio (IR) system is proposed, which invokes iteratively detected self-concatenated convolutional codes (SeCCC) and employs powerful design technique of extrinsic information transfer (EXIT) charts. Orthogonal prolate spheroidal wave function (OPSWF) based signalling pulse shapes are used for the sake of minimizing the multi-user interference (MUI) and intersymbol interference (ISI). Recursive systematic convolutional (RSC) codes are employed as constituent codes combined with an interleaver for randomising the extrinsic information exchange between the constituent codes. Furthermore, a puncturer assists us in increasing the achievable bandwidth efficiency. Iterative decoding is invoked for exchanging extrinsic information between the hypothetical decoder components at the receiver end. The convergence behaviour of the decoder is analysed with the aid of bit-based EXIT charts. Finally, we propose a novel THPPM-UWB-IR-SeCCC system configuration, which is capable of operating within about 0.9 dB of the information-theoretic limits.

In this contribution, the union bounds of self-concatenated convolutional codes (SECCCs) are derived for communications over both additive white Gaussian noise (AWGN) and uncorrelated Rayleigh fading channels. The truncated union bounds of SECCCs are very useful for studying the corresponding bit error ratio (BER) floors. Based on the truncated union bounds, various SECCCs can be designed for a desired BER floor without the need of time-consuming Monte Carlo simulations.

Conventional two-stage turbo-detected schemes typically suffer from a Bit Error Rate (BER) floor, preventing them from achieving infinitesimally low BER values, especially, when the inner coding stage is of non-recursive nature. We circumvent this deficiency by proposing a three-stage turbo-detected Sphere Packing (SP) aided Space-Time Block Coding (STBC) STBC-SP scheme, where a rate-1 recursive inner precoder is employed to avoid having a BER floor. The convergence behaviour of this serially concatenated scheme is investigated with the aid of 3D Extrinsic Information Transfer (EXIT) Charts. Furthermore, the capacity of the STBC-SP scheme is determined and an algorithm is proposed for calculating a tighter upper bound on the maximum achievable bandwidth efficiency, based on the EXIT charts of the STBC-SP demapper. The proposed three-stage turbo-detected scheme operates within about 1.0 dB of the capacity and within 0.5 dB of the maximum achievable bandwidth efficiency limit.

In this treatise extrinsic information transfer (EXIT) charts are used to design binary self-concatenated convolutional codes employing iterative decoding (SECCC-ID) for communicating over both uncorrelated Rayleigh fading and additive white Gaussian noise (AWGN) channels. Recursive Systematic Convolutional (RSC) codes are selected as constituent codes, an interleaver is used for randomising the extrinsic information exchange of the constituent codes, while a puncturer assists us in increasing the achievable bandwidth efficiency. At the receiver, self-iterative decoding is invoked for exchanging extrinsic information between the hypothetical decoder components. The convergence behaviour of the decoder is analysed with the aid of bit-based EXIT charts. Finally, we propose an attractive system configuration, which is capable of operating within about 1 dB of the information-theoretic limits.

This paper presents a low complexity iteratively detected space-time transmission architecture based on generalized layered space-time (GLST) codes and irregular convolutional codes (IRCCs). The GLST combines the benefits of the vertical Bell-labs layered space-time (V-BLAST) scheme and space-time coding (STC). The GLST is serially concatenated with a unity-rate code (URC) and an IRCC which are used to facilitate near-capacity operation with the aid of an extrinsic information transfer (EXIT) chart based design. Reduced- complexity iterative successive interference cancellation (SIC) is employed in the GLST decoder, instead of the significantly more complex maximum likelihood (ML) detection. For the sake of approaching the maximum achievable rate, iterative decoding is invoked to achieve decoding convergence by exchanging extrinsic information across the three serial component decoders. Finally, it is shown that the SIC-based iteratively detected IRCC-URC-GLST system is capable of providing a trade-off between the affordable computational complexity and the system throughput.

In this contribution we show how Shannon's coding theory could be realized for multiple-input multiple-output (MIMO) channels with the aid of Extrinsic Information Transfer (EXIT) charts and the Maximum-Aposteriori Probability (MAP) algorithm. We review the relationship between the channel capacity, EXIT charts and the MAP algorithm, outlining the principles of designing near MIMO-channel capacity coding schemes. Both serial and parallel concatenated coding schemes are designed based on these principles and near MIMO-channel capacity performance is achieved.

In this paper we propose an iteratively detected Sphere Packing (SP) aided Differential Space-Time Spreading (DSTS) scheme using a Recursive Systematic Convolutional (RSC) code, for protecting the soft-bit assisted Adaptive Multi Rate Wideband (AMR-WB) decoder's bitstream, which is also protected by a novel over-complete source-mapping scheme. The convergence behaviour of the Multiple-Input Multiple-Output (MIMO) transceiver advocated is investigated with the aid of both three- dimensional (3D) and two-dimensional (2D) Extrinsic Information Transfer (EXIT) charts. The proposed system exhibits an Eb/Nogain of about 2.5 dB in comparison to the benchmark scheme carrying out iterative source- and channel-decoding as well as DSTS aided SP-demodulation, but dispensing with the over-complete source-mapping, when using Isystem= 3 system iterations.

In this contribution we design the Iteratively Decoded Self-Concatenated Convolutional Codes (SECCC-ID) using extrinsic information transfer (EXIT) charts. Good constituent Trellis Coded Modulation (TCM) codes are selected for communicating over both uncorrelated Rayleigh fading and Additive White Gaussian Noise (AWGN) channels. At the receiver iterative decoding is invoked for exchanging extrinsic information between the hypothetical decoder components. The convergence behaviour of the decoder is analysed with the aid of symbol-based EXIT charts. Similarly, the search for the best TCM constituent codes is also based on EXIT chart analysis. Finally, we demonstrate that the selected codes are capable of operating within 1 dB from the maximum achievable rate.

(STBC) schemes are designed. Recursive unity-rate codes and IRregular Convolutional Codes (IRCCs) are employed for assisting the conventional non-recursive STBC schemes in achieving decoding convergence to an infinitesimally low bit error ratio at near-capacity signal-to-noise ratios. IRregular Convolutional Codes (IRCCs) are used as the outer codes for achieving a near-capacity performance. It was shown that the resultant iteratively decoded STBC schemes are capable of approaching the corresponding channel capacity within 0.4 dB, when communicating over uncorrelated, flat Rayleigh fading channels. I.

This paper presents a novel ultrawideband (UWB), direct sequence code division multiple access (DS-CDMA) aided system designed for the IEEE 802.15.3a UWB channel specifications. Substantial performance improvements can be attained by serially concatenated channel encoding combined with a unity rate code (URC). We compare the performance of the iterative aided decoding correlation (Corr) and minimum mean square error (MMSE) detectors exchanging extrinsic information between the URC's decoder as well as the outer recursive systematic convolutional (RSC) code's decoder. Moreover, the iterative decoding convergence analysis of the proposed system is carried out with the aid of extrinsic information transfer (EXIT) charts. As expected, the iteratively decoded fully-loaded system employing MMSE detection outperforms its counterpart employing the equivalent Corr detection. Explicitly, UWB DS-CDMA using the MMSE detector attains a BER of 10-5at Eb/No=2 dB when supporting U=32 users employing i=12 decoding iterations, while the same system using the Corr detector operates at BER-10-1.

This paper presents a novel analysis on the decoding convergence of Time Hopping (TH) and Direct Sequence (DS) Code-Division Multiple-Access (CDMA) Ultrawide Bandwidth (UWB) systems when communicating over multipath Nakagami channels. The analysis is based on the Extrinsic Information Transfer (EXIT) chart where the UWB systems are serially concatenated pulse-position modulated TH and code-synchronous DS-CDMA. It is shown from an EXIT chart analysis that the multipath diversity can yield a larger area under the EXIT curve of the inner detector. This area is related to the achievable rate of the system and it can be exploited with the aid of iterative detection. Simulation results of the iteratively detected TH and DS-CDMA UWB schemes verify the EXIT chart analysis.

A recently proposed space-time block coding (STBC) signal construction method that combines orthogonal design with sphere packing, referred to here as (STBC-SP), has shown useful performance improvements over Alamouti's conventional orthogonal design. In this contribution, we propose a purely symbol-based LDPC-coded scheme, demonstrating that the performance of STBC-SP systems can be further improved by concatenating sphere packing aided modulation with non-binary LDPC and by performing symbol-based turbo detection between the non-binary LDPC decoder and a rate-1 non-binary inner precoder. We also investigate the convergence behaviour of this symbol-based concatenated scheme with the aid of novel non-binary extrinsic information transfer (EXIT) charts. Finally, we demonstrate that in the investigated scenarios it requires 1-2 dB lower power in comparison to equivalent effective-throughput 0.5, 0.75 and 1 bit/symbol systems employing bit-based turbo detection.

Recently, the authors of this paper proposed systematic Luby transform (SLT) codes and their soft decoding using the classic loglikelihood message passing algorithm for transmission over hostile Wireless Internet channels, where the transmitted data is affected by both packet loss events and random Gaussian noise. This scheme is further improved here with the aid of a new degree distribution and a novel random integer generator, which are termed as the truncated degree distribution and the conditional random integer generator. The SLT code using the new design is capable of achieving BER les 10-5at low Eb/N0values. For example, the SLT(1200,3600) code attains BER < lCT5 in excess of an Eb/No value of 1.5 dB for transmission over the AWGN channel and above 3.5 dB over the uncorrelated Rayleigh channel if additionally a packet erasure probability Pe of 0.1 is inflicted, an Eb/No value above 2 dB is required for transmission over the AWGN channel and in excess of 4 dB over the uncorrelated Rayleigh channel, when using a maximum of Iter = 20 iterations and quadrature phase- shift keying.

Bandwidth efficient parallel-concatenated Turbo Trellis Coded Modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of In-phase (I) and Quadrature-phase (Q) interleavers were employed for interleaving the I and Q components of the TTCM coded symbols, in order to attain an increased diversity gain. The decoding convergence of the IQ-TTCM schemes was analysed using symbol-based EXtrinsic Information Transfer (EXIT) charts. The best TTCM component codes were selected with the aid of both the symbolbased union bound and non-binary EXIT charts, for designing capacity-approaching IQ-TTCM schemes in the context of 8 PSK, 16 QAM, 32 QAM and 64 QAM modulation schemes.

This paper presents a novel turbo-detected multidimensional sphere packing (SP) modulation scheme using four transmit antennas combined with differentially encoded space-time spreading (DSTS). The DSTS scheme can be readily combined with PSK, QAM as well as SP modulation schemes. The SP-aided DSTS system advocated has low-complexity encoding and decoding algorithms that require no channel knowledge and it is capable of outperforming the DSTS system dispensing with sphere packing. Further system performance improvements can be attained by serially concatenated convolutional encoding combined with a unity-rate code (URC) referred to as a precoder. Then, at the receiver side, iterative decoding is invoked by exchanging extrinsic information between the precoder's decoder as well as the outer recursive systematic convolutional (RSC) code's decoder. Moreover, the convergence behaviour of the proposed system is evaluated with the aid of extrinsic information transfer (EXIT) charts. Explicitly, the turbo-detected precoded DSTS-SP system performs within 1.6 dB of the achievable multiple-input multiple output (MIMO) capacity. Finally, in contrast to an equivalent 0.5 bit/symbol throughput turbo- detected DSTS-SP scheme using no preceding, the turbo-detected precoded DSTS-SP scheme exhibits no error floor.

In this paper we propose a novel irregular variable length coding (IrVLC) scheme for near-capacity joint source and channel coding. We employ a number of component variable length coding (VLC) codebooks having different coding rates for encoding particular fractions of the input source symbol stream. These fractions may be chosen with the aid of extrinsic information transfer (EXIT) charts in order to shape the inverted EXIT curve of the IrVLC codec for ensuring that it does not cross the EXIT curve of a serially concatenated channel codec. In this way, an open EXIT chart tunnel may be created even at low Eb/N0values that are close to the capacity bound of the channel. We propose iteratively decoded serially concatenated IrVLC designs amalgamated with Trellis coded modulation (TCM). These schemes are shown to be capable of operating within 0.6 dB of the uncorrelated narrowband Rayleigh fading channel's capacity bound using an average interleaver length of 217,500 bits and an effective bandwidth efficiency of 1.56 bit/s/Hz, assuming ideal Nyquist filtering. By contrast, the equivalent-rate regular VLC-based bench-marker schemes were found to be capable of operating at a higher distance of 1.1 dB from the capacity bound, which is nearly twice that of the proposed IrVLC-TCM scheme. Additionally, an irregular convolutional coiling (IrCC) based bench-marker was found to be capable of operating at 0.8 dB from the capacity bound, owing to its slightly eroded performance when operating with the considered interleaver length.

Conventional two-stage turbo-detected schemes typically suffer from a bit error rate (BER) floor, preventing them from achieving infinitesimally low BER values, especially, when the inner coding stage is of non-recursive nature. We circumvent this deficiency by proposing a three-stage turbo-detected sphere packing (SP) aided space-time block coding (STBC) STBC-SP scheme, where a rate-1 recursive inner precoder is employed to avoid having a BER floor. The convergence behaviour of this serially concatenated scheme is investigated with the aid of 3D extrinsic information transfer (EXIT) charts. Furthermore, the capacity of the STBC-SP scheme is shown and an algorithm is proposed for calculating a tighter upper bound on the maximum achievable bandwidth efficiency. The proposed three-stage turbo-detected scheme operates within about 1.0 dB of the capacity and within 0.5 dB of the maximum achievable bandwidth efficiency limit.

It is demonstrated that iteratively decoded variable length space time coded modulation (VL-STCM-ID) schemes are capable of simultaneously providing both coding gain as well as multiplexing and diversity gain. The VL-STCM-ID arrangement is a jointly designed iteratively decoded scheme combining source coding, channel coding, modulation as well as spatial diversity/multiplexing. In this contribution, we analyse the iterative decoding convergence of the VL-STCM-ID scheme using symbol-based three-dimensional EXIT charts. The performance of the VL-STCM-ID scheme is shown to be about 14.6 dB better than that of the fixed length STCM (FL-STCM) benchmarker at a source symbol error ratio of 10-4, when communicating over uncorrelated Rayleigh fading channels. The performance of the VL-STCM-ID scheme when communicating over correlated Rayleigh fading channels using imperfect channel state information is also studied.

A multilevel coding (MLC) scheme invoking sphere packing (SP) modulation combined with space time block coding (STBC) is designed. The coding rates of each of the MLC component codes are determined using the so-called equivalent capacity based constituent-code rate-calculation procedure invoking a 4-dimensional (4D) sphere packing bit-to-symbol mapping scheme. Four different-rate Low-Density Parity Check (LDPC) constituent-codes are used by the MLC scheme. The performance of the resultant equivalent capacity based design is characterized using simulation results. Our results demonstrate an approximately 3.5 dB gain over an identical scheme dispensing with SP modulation. Furthermore although a similar performance gain is attained by both the proposed MLC scheme and its benchmarker, which uses a single-class LDPC code, the MLC scheme is preferred, since it benefits from the new classic philosophy of using low-memory, low-complexity component codes as well as providing an unequal error protection capability.

Serially concatenated and iteratively decoded irregular variable length coding (IrVLC) combined with preceded fast frequency hopping (FFH) M-ary frequency shift keying (MFSK) is considered. The proposed joint source and channel coding scheme is capable of low signal-to-noise ratio (SNR) operation in Rayleigh fading channels contaminated by partial band noise jamming (PBNJ). The IrVLC scheme is comprised of a number of component variable length coding (VLC) codebooks employing different coding rates for encoding particular fractions of the input source symbol stream. These fractions may be chosen with the aid of extrinsic information transfer (EXIT) charts in order to shape the inverted EXIT curve of the IrVLC codec so that it can be matched with the EXIT curve of the inner decoder. We demonstrate that using the proposed scheme near-zero bit error ratio may be achieved at low SNR values and the IrVLC based scheme yields a further gain of up to 0.3 dB over the identical-rate single-class VLC based benchmarker scheme

In this paper we consider serially concatenated and iteratively decoded irregular variable length coding (IrVLC) combined with preceded differential space-time spreading (DSTS) aided multidimensional sphere packing (SP) modulation designed for near-capacity joint source and channel coding. The IrVLC scheme comprises a number of component variable length coding (VLC) codebooks having different coding rates for the sake of encoding particular fractions of the input source symbol stream. The relative length of these source-stream fractions can be chosen with the aid of extrinsic information transfer (EXIT) charts in order to shape the EXIT curve of the IrVLC codec, so that an open EXIT chart tunnel may be created even at low Eb/N0values that are close to the capacity bound of the channel. These schemes are shown to be capable of operating within 0.9 dB of the DSTS-SP channel's capacity bound using an average interleaver length of 113,100 bits and an effective bandwidth efficiency of 1 bit/s/Hz, assuming ideal Nyquist filtering. By contrast, the equivalent-rate regular VLC-based bench- marker scheme was found to be capable of operating at 1.4 dB from the capacity bound, which is about 1.56 times the corresponding discrepancy of the proposed IrVLC-aided scheme.

Bandwidth efficient parallel-concatenated turbo trellis coded modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of in-phase (I) and quadrature-phase (Q) interleavers were employed for interleaving the I and Q components of the TTCM coded symbols, in order to attain an increased diversity gain. The decoding convergence of the IQ-TTCM schemes was analysed using symbol-based extrinsic information transfer (EXIT) charts. The best TTCM component codes were selected with the aid of both the symbol-based union bound and non-binary EXIT charts for the sake of designing capacity-approaching IQ-TTCM schemes in the context of 8 PSK, 16 QAM and 32 QAM signal sets. It will be shown that our TTCM design is capable of approaching the channel capacity within 0.5 dB at a throughput of 4 bit/s/Hz, when communicating over uncorrelated Rayleigh fading channels using 32 QAM.

Eigen-beamforming is capable of attaining attractive performance gains in the context of multiple-input multiple-output (MIMO) systems, provided that accurate channel state information (CSI) is available. However, when a realistic pilot-based channel predictor is used for acquiring the CSI, a significant performance degradation may be imposed by the phase-ambiguity inherent in the estimated eigen-vectors. In this contribution, both higher-complexity coherently detected coded modulation (CM) schemes requiring channel information as well as their lower-complexity differentially encoded counterparts are employed for assisting the operation of the eigen-beamformer, when using a minimum mean square error based pilot-assisted channel predictor. It is shown that differentially encoded CM schemes are capable of assisting the eigen-beamformer in attaining a coding gain of about 6.5 dBs, when communicating over correlated Rayleigh fading channels.

Bit-Interleaved Coded Modulation using Iterative Decoding (BICM-ID) is amalgamated with Luby Transform (LT) coding. The resultant joint design of the physical and data link layer substantially improves the attainable Bit Error Rate (BER) performance. A Cyclic Redundancy Check (CRC) combined with a novel Log-Likelihood Ratio (LLR) based packet reliability estimation method is proposed for the sake of detecting and disposing of erroneous packets. Subsequently, bit-by-bit LT decoding is proposed, which facilitates a further BER improvement at a lower number of BICM-ID iterations. Finally, we revisit the pseudo random generator function used for designing the LT generator matrix.

Iterative decoding (ID) aided fast frequency hopping (FFH), M-ary frequency shift keying (MFSK) using clipped combining in multiple access (MA) channels is investigated. All users' data are convolutionally encoded and the encoded bits are interleaved and converted to M-ary symbols, which are transmitted using FFH-MFSK modulation. The soft metrics to be passed from the demodulator to the decoder are derived assuming a Rayleigh fading channel. We also propose a novel multiuser detection (MUD) scheme which employs joint soft decoding as well as successive interference cancellation (SIC), the receiver exploiting the soft information fed back by the decoder to the demodulator in order to cancel the interference imposed by reliable symbols. Our simulation results show that the proposed scheme is capable of combatting multiuser interference and outperforms the conventional ID by about 3dB.

A joint video and channel coded system employing an iteratively decoded serial concatenation of a vector quantization (VQ) based video codec and a trellis-coded modulation (TCM) scheme is proposed. The video codec imposes VQ-induced code constraints, which may be completely described by a trellis structure, which is employed as the basis for optimal minimum mean-squared-error VQ-encoding and -decoding. In the latter case, the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is employed to facilitate the iterative exchange of soft information between the VQ and TCM decoder. An error-free video reconstruction quality is supported using 16-Ievel quadrature amplitude modulation (16QAM) based TCM for transmission over Rayleigh-fading channels at a signal-to-noise ratio (SNR) per bit of 5.25 dB. This value is within 1.29 dB of the Rayleigh channel's capacity at our system's effective bandwidth-efficiency of 2 bits/s/Hz. Owing to its ability to exploit the VQ-induced code constraints during iterative decoding, the joint video and channel coding approach is found to consistently outperform the Shannonian source and channel separation philosophy. This is achieved at the cost of a 1.6 times higher computational complexity. Finally, the convergence of the iterative decoder is investigated with the aid of a novel so-called extrinsic information transfer (EXIT) chart

An iteratively decoded variable length space time coded modulation (VL-STCM-ID) scheme capable of simultaneously providing both coding and iteration gain as well as multiplexing and diversity gain is proposed. Non-binary unity-rate precoders are employed for assisting the iterative decoding of the VL-STCM-ID scheme. The discrete-valued source symbols are first encoded into variable-length codewords that are mapped to the spatial and temporal domains. Then the variable-length codewords are interleaved and fed to the precoder assisted modulator. More explicitly, the proposed VL-STCM-ID arrangement is a jointly designed iteratively decoded scheme combining source coding, channel coding, modulation as well as spatial diversity/multiplexing. As expected, the higher the source correlation, the higher the achievable performance gain of the scheme becomes. Furthermore, the performance of the VL-STCM-ID scheme is about 14.6 dB better than that of the fixed length STCM (FL-STCM) benchmarker at a source symbol error ratio of 10-4

In this paper we design bandwidth efficient parallel-concatenated turbo trellis coded modulation (TTCM) schemes for communicating over AWGN and uncorrelated Rayleigh fading channels. The convergence properties of the symbol-based TTCM schemes employing various constituent codes, were analysed using symbol-based extrinsic information transfer (EXIT) charts. The traditional method used of generating EXIT charts is based on computationally complex multidimensional histogram measurements, which is only feasible for analysing TTCM schemes employing low-order modulation schemes, such as 4PSK and 8PSK. Hence, a novel low-complexity technique was employed in this paper for computing the symbol-based EXIT charts. Capacity-approaching TTCM schemes were designed based on the best constituent codes found when employing 8PSK, 16QAM, 32QAM and 64QAM modulation schemes.

The iterative convergence of iteratively detected coded modulation schemes having different block lengths, decoding complexity and an unequal error protection capability is studied, when communicating over AWGN channels using 8PSK modulation. More specifically, the coded modulation schemes investigated include multilevel coding (MLC), trellis coded modulation (TCM), turbo trellis coded modulation (TTCM), bit-interleaved coded modulation (BICM) as well as bit-interleaved coded modulation employing iterative decoding (BICM-ID). A novel three dimensional EXIT chart was introduced for studying the iterative convergence behaviour of the multistage decoding (MSD) scheme used in MLC

Iterative minimum mean square error (MMSE) equalization and channel decoding is appealing, since it exhibits a lower complexity than maximum a posteriori (MAP) turbo equalization. However, the MMSE equalizer's attainable performance is upper-bounded by that recorded for transmission over the coded AWGN channel, a phenomenon usually referred to as "error shoulder". In order to circumvent this performance limitation, we propose a three-stage concatenated transceiver constituted by inner and outer coding as well as MMSE equalization, which achieves significant iteration gains, despite using low-complexity serially concatenated memory-1 convolutional codes. It is demonstrated that this three-stage scheme outperforms the traditional two-stage MMSE turbo equalization scheme above a certain Eb/N0threshold. Furthermore, the convergence behavior of the proposed scheme is analyzed with the aid of 3D extrinsic information transfer (EXIT) charts and their 2D projections, leading to a number of practical iterative receiver design guidelines.

In this contribution, we propose a purely symbol-based LDPC-coded scheme based on a space-time block coding (STBC) signal construction method that combines orthogonal design with sphere packing, referred to here as (STBC-SP). We demonstrate that useful performance improvements may be attained when sphere packing aided modulation is concatenated with non-binary LDPC especially, when performing purely symbol-based turbo detection by exchanging extrinsic information between the non-binary LDPC decoder and a rate-1 non-binary inner precoder. We also investigate the convergence behaviour of this symbol-based concatenated scheme with the aid of novel non-binary extrinsic information transfer (EXIT) charts. The proposed symbol-based turbo-detected STBC-SP scheme exhibits a 'turbo-cliff' at Eb/N0= 5.0 dB and achieves an Eb/N0gain of 19.2 dB at a BER of 10-5over Alamouti's scheme

A novel three-dimensional (3D) EXIT chart is developed for investigating the iterative behaviour of multilevel coding (MLC) invoking multistage decoding (MSD). The extrinsic information transfer characteristics of both the symbol-to-bit demapper used and those of the different protection constituent decoders suggest that potential improvements can be achieved by appropriately designing the demapper. The proposed 3D EXIT chart is then invoked for studying the precoder-aided multilevel coding scheme employing both MSD and parallel independent decoding (PID) for communicating over AWGN and uncorrelated Rayleigh fading channels with the aid of 8PSK modulation. At BER=10-5, the precoder was capable of enhancing the achievable Eb/N0performance by 0.5 dB to 2.5 dB over AWGN and Rayleigh channels, respectively

The calculation of nonbinary extrinsic information transfer charts for the iterative decoding of concatenated index-based codes is addressed. We show that the extrinsic information at the output of a constituent a posteriori probability decoder can be calculated with very low complexity, where expensive histogram measurements are not required any more. An example for turbo trellis-coded modulation demonstrates the capabilities of the proposed approach

Decision feedback equalizer-aided wide-band burst-by-burst adaptive trellis-coded modulation, turbo trellis-coded modulation (TTCM), and bit-interleaved-coded modulation-assisted H.263-based video transceivers are proposed and characterized in performance terms when communicating over the COST 207 typical urban wide-band fading channel. Specifically, four different modulation modes, namely 4QAM, 8PSK, 16QAM, and 64QAM are invoked and protected by the above-mentioned coded modulation schemes. The TTCM assisted scheme was found to provide the best video performance, although at the cost of the highest complexity. A range of lower-complexity arrangements will also be characterized. Finally, in order to confirm these findings in an important practical environment, we have also investigated the adaptive TTCM scheme in the CDMA-based universal mobile telecommunications systems terrestrial radio access (UTRA) scenario and the good performance of adaptive TTCM scheme recorded when communicating over the COST 207 channels was retained in the UTRA environment.

In this contribution a range of coded modulation (CM)-assisted radial basis function (RBF)-based turbo equalization (TEQ) schemes are investigated when communicating over dispersive Rayleigh-fading channels. Specifically, 16 quadrature amplitude modulation-based trellis coded modulation (TCM), turbo TCM (TTCM), bit-interleaved coded modulation (BICM), and iteratively decoded BICM (BICM-ID) are evaluated in the context of an RBF-based TEQ scheme and a reduced-complexity RBF based in-phase/quadrature-phase (I/Q) TEQ scheme. The least mean square (LMS) algorithm was employed for channel estimation, where the initial estimation step-size used was 0.05, which was reduced to 0.01 for the second and the subsequent TEQ iterations. The achievable coding gain of the various CM schemes was significantly increased, when employing the proposed RBF-TEQ or RBF-I/Q-TEQ rather than the conventional noniterative decision feedback equalizer (DFE). Explicitly, the reduced-complexity RBF-I/Q-TEQ-CM achieved a similar performance to the full-complexity RBF-TEQ-CM, while attaining a significant complexity reduction. The best overall performer was the RBF-I/Q-TEQ-TTCM scheme, requiring only 1.88 dB higher signal-to-noise ratio at BER=10/sup -5/, than the identical throughput 3 b/symbol uncoded 8 PSK scheme communicating over an additive white Gaussian noise channel. The coding gain of the scheme was 16.78 dB.

In this contribution we propose a novel M-ary coded modulation assisted genetic algorithm based multiuser detection (CM-GA-MUD) scheme for synchronous CDMA systems. The performance of the proposed scheme was investigated using quadrature-phase-shift-keying (QPSK), 8-level PSK and 16-level quadrature amplitude modulation (16QAM) when communicating over AWGN and narrowband Rayleigh fading channels. When compared with the optimum MUD scheme, the GA-MUD subsystem is capable or reducing the computational complexity significantly. On the other hand, the CM subsystem is capable of obtaining considerable coding gains despite being fed with sub-optimal information provided by the GA-MUD output.

A burst-by-burst adaptive coded modulation-aided joint detection-based CDMA (ACM-JD-CDMA) scheme is proposed for wireless video telephony and we characterise its performance when communicating over the UTRA wideband vehicular fading channels. The coded modulation schemes invoked in our fixed modulation mode based systems are trellis coded modulation (TCM), turbo TCM (TTCM), bit-interleaved coded modulation (BICM) and iterative-decoding assisted BICM (BICM-ID). When comparing the four schemes at a given complexity, TTCM was found to be the best scheme and the performance of the TTCM-assisted ACM-JD-CDMA system was evaluated using a practical modem mode switching regime.

We propose a novel space-time coding-assisted double-spread RAKE receiver (STC-DS-RR) based CDMA scheme for downlink (base to mobile) transmissions over dispersive Rayleigh fading channels. The STC-DS-RR scheme invokes turbo convolutional (TC) channel coding and space-time block coding (STBC) for achieving both time and space diversity gains in addition to the path diversity gain provided by the dispersive Rayleigh fading environments. The double-spreading mechanism of the STC-DS-RR scheme is capable of detecting the wanted user's channel-impaired wideband signals with the aid of a low-complexity RAKE receiver, without resorting to complex multi-user detection. The performance of the proposed scheme was investigated using quadrature-phase-shift-keying (QPSK), when communicating over dispersive channels. It was shown that the wideband scheme advocated is capable of achieving E/sub b//N/sub 0/ gains up to 35 dB in comparison to an uncoded narrowband single-transmitter scheme.

A radial basis function (RBF) assisted turbo equaliser (TEQ) scheme, applied to various coded modulation schemes, is investigated. Specifically, trellis coded modulation (TCM), turbo trellis coded modulation (TTCM), bit-interleaved coded modulation (BICM) and BICM with iterative decoding (BICM-ID) are studied, when communicating over frequency selective fading channels. At a given complexity, the TTCM RBF-TEQ provides the best bit error ratio (BER) and frame error ratio (FER) performance. The RBF-TEQ structure is shown to provide an SNR performance improvement of about 5.5 dB at a BER of 10/sup -4/ in comparison to the conventional non-iterative DFE scheme.

Decision feedback equalizer (DFE) aided wideband burst-by-burst (BbB) adaptive trellis coded modulation (TCM), turbo trellis coded modulation (TTCM), bit-interleaved coded modulation (BICM) and BICM with iterative decoding (BICM-ID) are proposed and characterised in performance terms over the COST 207 typical urban (TU) wideband fading channel. These schemes are evaluated using a practical modem mode switching regime. System I represents schemes without channel interleaving, while System II invokes channel interleaving over four transmission bursts. A substantially improved bit per symbol (BPS) and bit error rate (BER) performance was achieved by System II in comparison to System I. BbB-adaptive TTCM was found to give the best performance, when aiming for a target BER of below 0.01%.