The primary obstacle in full-duplex (FD) communications lies in self-interference cancellation (SIC). Traditional FD systems often retain residual self-interference (SI) even after employing SIC techniques such as antenna isolation, spatial beam-forming, or the SI reconstruction and subtraction. In contrast, this work introduces an innovative FD transceiver design for SIC, grounded in the mathematical modeling of pseudo-Doppler (PD) shift systems. Our PD-aided transceiver design emerges as a highly effective SIC solution, capable of entirely eliminating SI from the center frequency of the transceiver’s desired signal. By employing a low-pass filter, the desired signal can be extracted without any residual SI contamination. Comparative analyses of SIC performance demonstrate that our transceiver design surpasses traditional FD systems, even when the latter achieve exceptionally high SI suppression levels.

The performance of full-duplex (FD) communications relying on antenna isolation, spatial beamforming, and/or self-interference (SI) reconstruction and subtraction, is limited by residual SI. For degrading the residual SI, we propose a novel FD transceiver design for SI cancellation (SIC), based on the mathematical modelling of pseudo-Doppler shift systems. Our pseudo-Doppler aided transceiver design manifests itself as an endogenous SIC mechanism, which removes SI from the center frequency of a transceiver’s desired signal. A low-pass filter can then be applied to pass on the clean desired signal. Since our design is essentially different from conventional SIC approaches, the SIC capability is defined as the improvement in the output signal-to-SI-plus-noise power ratio, which is taken as a metric for evaluating the intrinsic SIC performance. In terms of the SIC capability and operational complexity, our design outperforms conventional FD systems, even if the latter have managed very high SI suppression factors. To promote the practical application of our design in cellular networking, four main challenges are addressed, including the impact of synchronisation errors, the equivalence of SI suppression, the principles of resource allocation, and the investigation of diversity gain.

As a promising candidate for ultrareliable and low-latency communications, the recent permutation-based transmission concept substantially improves the resource utilization efficiency in the Internet of Things (IoT). In this context, the Age of Information (AoI) experienced in permutation-based short-packet transmissions is characterized in a wiretap channel, where eavesdroppers are wiretapping the status updates delivered over the legitimate link. The AoI of the legitimate link and the secrecy margin of the wiretap channel are formulated in closed forms within the regime of finite-blocklength information theory to quantify the data freshness and security of status updates in the IoT. The optimal packet structure to be delivered over the network interface is found by solving the optimization problems of minimizing the legitimate link’s AoI and maximizing the secrecy margin. Illustrative numerical results are provided for our permutation-based transmission to quantify its performance gains over the conventional encapsulation, specifically in short-packet communications.

High mobility of vehicles causes time-frequency selective fading over physical channels within the Internet of Vehicles (IoV). To improve the resource utilization efficiency, a novel transmission strategy, based on dynamic pilot design, is proposed, in this article, to reduce the pilot consumption in doubly selective channel estimation for the multicast to vehicles running at different speeds. As the channel coherence time is mainly influenced by the receiver mobility in the multicast from a base station to vehicles, we define a multicast block as the channel coherence time of the slowest vehicle in the multicast group, where common pilot symbols are shared. Then, the multicast data destined for different vehicles are loaded into the block according to their own channel coherence times. To evaluate the performance and resource utilization of our dynamic pilot design, the metrics of overhead rate, spectral efficiency, and energy efficiency are formulated for the IoV multicast using multiple-input–multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) transmissions. In terms of these three metrics, illustrative numerical results on the comparisons between our dynamic pilot design and the conventional counterpart are provided, which not only substantiate that the former outperforms the latter but also present useful tools and specifications for the pilot design in the IoV multicast using MIMO–OFDM transmissions over doubly selective channels.

To promote energy and spectrum efficient communications in multiantenna channels, broadcast can provide a substantial gain in system throughput. However, the hardware constraints and strong Line of Sight (LoS) limit the implementation and performance of multiantenna broadcast in the Internet of unmanned aerial vehicles (UAVs). Based on the pseudo-Doppler principle, we propose a joint precoding and antenna array design to reduce the number of radio frequency (RF) chains required by the broadcast and free the LoS path from the interstream interference. The reduction of RF chains is realized by designing the precoding matrix that makes at least one of the transmit antennas have null inputs during any broadcast and, moreover, the LoS path is formed to match the obtained precoding matrix through antenna array design at the broadcasting UAV. The algorithms with low computational complexity for optimizing this design are developed to minimize the transmit power within the UAV broadcast paradigms. Theoretical formulation and numerical results in the metrics of sum data rate and bit error rate substantiate the validity of our proposed design, specifically in the Internet of UAVs with strong LoS.

In this paper, the concept of permutation-based transmissions is developed at the transport layer of short-packet communications, where the application-layer data is divided into two parts: one is conveyed by the permutation of various lengths in a group of packets, and the other is encapsulated into these various-length packets. The former part, referred to as permutation-conveyed data unit (PCDU), improves the goodput and reduces the latency. From a finite blocklength perspective, the maximal payload rate of permutation-based transmissions is formulated, based on which the goodput and latency are derived and obtained in analytical forms. Moreover, the spectral efficiency and energy efficiency are analysed. Illustrative numerical results on the performance and resource utilisation comparisons not only substantiate the advantages of our permutation-based transmissions over conventional transport-layer encapsulation schemes, but also provide useful tools and specifications for the PCDU design in short-packet communications.

In this paper, a novel transmission scheme, referred to as difference-based spatial modulation (DBSM), is proposed to improve the performance of spatial modulation (SM) within multi-antenna systems. The DBSM delivers two adjacent symbols in an arbitrary transmission, where one of the two symbols is radiated from a single transmit antenna. Different from conventional SM, the DBSM selects the active transmit antenna based on the difference between the two adjacent symbols. Although the other symbol is not physically radiated, the information carried by it is conveyed not only through the radiated symbol but also through the selection of active transmit antenna. For the purpose of performance evaluation, the proposed DBSM is compared with conventional SM in terms of bit error rate for the same system settings and the same multi-antenna configurations. Illustrative simulation results substantiates that our DBSM outperforms conventional SM while achieving the same data rate, specifically in the systems with low-order modulation.

In this paper, a novel design named security-oriented polar coding (SOPC) is proposed to enhance the physical layer security (PLS), where the active pattern of frozen bits in a transmission is determined by random channel gain of the legitimate link. Since the channel gain value is not exchanged between the legitimate transmitter and the desired receiver, eavesdroppers cannot ascertain the frozen bit pattern engaged in the legitimate polar coding. When the signal-to-noise ratio (SNR) is low, eavesdroppers are unable to appropriately decode the confidential information delivered over the legitimate link. As the SNR increases, eavesdroppers may have chance to sort out the correct frozen bit pattern through a brute-force search. However, this chance is significantly reduced by our SOPC. We design the SOPC for both single-input-single-output single-antenna eavesdropper (SISOSE) and multiple-input-multiple-output multi-antenna eavesdropper (MIMOME) channels. Its PLS functioning is assessed in terms of the error rate difference between the legitimate receiver and the eavesdropper. Illustrative simulation results substantiate that the SOPC design guarantees degraded decoding performance at eavesdroppers, for both SISOSE and MIMOME channels, even in the presence of a powerful eavesdropper possessing infinite computational resources.

To circumvent the degraded goodput, high latency and low resource utilization efficiency of conventional transport-layer protocols in the Internet of Things, a novel permutation-based encapsulation scheme is proposed for seamless delivery of packets to achieve high goodput and low latency. In this scheme, extra application-layer data is delivered by our permutation-based data unit (PBDU), which is mapped onto the permutation associated with a legitimate tuple of various packet lengths in a group. Therefore, the network interface throughput is substantially improved for a given number of resource units in the physical channel. The optimal design of this encapsulation is expressed in closed form to maximize the PBDU size, allowing us to quantify the attainable improvements of goodput and latency. In addition, the proposed scheme achieves higher physical-layer throughput and secrecy rate than conventional encapsulation.

Solar insecticidal lamps (SILs) play a vital role in green prevention and control of pests. By embedding SILs in wireless sensor networks (WSNs), we establish a novel agricultural Internet of Things (IoT), referred to as the SIL-IoTs. In practice, the deployment of SIL nodes is determined by the geographical characteristics of an actual farmland, the constraints on the locations of SIL nodes, and the radio-wave propagation in a complex agricultural environment. In this article, we mainly focus on the constrained SIL deployment problem (cSILDP) in a mixed-crop farmland, where the locations used to deploy SIL nodes are a limited set of candidates located on the ridges. We formulate the cSILDP in this Scenario as a connected set cover (CSC) problem and propose a hole-aware node deployment method (HANDM) based on the greedy algorithm to solve the constrained optimization problem. The HANDM is a two-phase method. In the first phase, a novel deployment strategy is utilized to guarantee only a single coverage hole in each iteration, based on which a set of suboptimal locations is found for the deployment of SIL nodes. In the second phase, according to the operations of deletion and fusion, the optimal locations are obtained to meet the requirements on complete coverage and connectivity. Experimental results show that our proposed method achieves better performance than the peer algorithms, specifically in terms of deployment cost.

As an important physical control technology, solar insecticidal lamp (SIL) can effectively prevent and control the occurrence of pests. The combination of SILs and wireless sensor networks (WSNs) initiates a novel agricultural Internet of Things (IoT), i.e., SIL-IoTs, to simultaneously kill pests and transmit pest information. In this article, we study the weighted SIL deployment problem (wSILDP) in SIL-IoTs, where weighted locations on ridges are prespecified and some of them are selected to deploy SILs. Different from the existing studies whose optimization objective is to minimize the deployment cost, we consider the deployment cost and the total weight of selected locations jointly. We formulate the wSILDP as the weighted set cover (WSC) problem and propose a layered deployment method based on greedy algorithm (LDMGA) to solve the defined optimization problem. The LDMGA is composed of two phases. First, SILs are deployed layer by layer from the boundary to the center until the entire farmland is completely covered. Second, on the basis of three design operations, i.e., substitution, deletion and fusion, the suboptimal locations obtained in the first phase are fine-tuned to achieve the minimum deployment cost together with the maximum total weight for meeting the coverage and connectivity requirements. Simulation results clearly demonstrate that the proposed method outperforms three peer algorithms in terms of deployment cost and total weight.

As the digital version of a continuous-time delay, the concept of fractional delay (FD) is exploited to approximate a desired delay that is not a multiple of the sampling interval. However, in FD filters, there is always a severe distortion at the beginning of delayed signals, referred to as head distortion. This letter identifies the cause of head distortion and proposes a solution to this problem for reducing the overall distortion in FD filters. For the purpose of performance evaluation, relative root-mean-square (RMS) error is formulated as a metric to quantify the overall difference between the frequency-domain response of an FD filter and the ideal one. Moreover, illustrative numerical results on the proposed scheme applied in FD filters with classical sinc, Farrow and Lagrange interpolation substantiate the validity and feasibility of our solution.

In this paper, the concept of opportunistic bits (OBs) is developed in short-packet communications and investigated from a finite blocklength perspective. In the OB-based transmission, the data unit of a packet is divided into two parts: OBs and conventional bits (CBs). The OBs are not physically transmitted but used to indicate the index of the time slot (TS) when the packet containing CBs is transmitted. The loading of a bulk of OB-based packets into multiple TSs can be modelled as a Repeated Balls-into-Bins process with a multi-queue storage. If the bulk is not large enough, certain combination(s) of OBs will not appear, which leaves certain TS(s) empty and hence reduces the TS load efficiency. To evaluate the OB-based transmission performance, we formulate its maximal payload rate and TS load efficiency. With the aid of these two formulations, the energy gain, the goodput, and the latency of OB-based short-packet communications are derived and obtained in analytical forms. For achieving further insights, illustrative numerical results on the resource utilisation efficiency and the performance not only substantiate the advantages of the OB-based transmission over the conventional but also provide useful tools and specifications for its design in massive short-packet communications.

Providing security guarantee is a critical concern in the ad-hoc networks relying on multi-hop channels, since their flexible topology is vulnerable to security attacks. To enhance the security of a spatial modulation (SM) assisted wireless network, various SM mapping patterns are activated by random channel quality indicator (CQI) patterns over the legitimate link, as a physical-layer secret key. The SM signals are encrypted by random mapping patterns to prevent eavesdroppers from correctly demapping their detections. This secret key is developed for multi-hop wiretap ad-hoc networks, where eavesdroppers might monitor all the transmitting nodes of a legitimate link. We substantially characterise the multi-hop wiretap model with receiver diversity techniques adopted by eavesdroppers. The security performance of the conceived scheme is evaluated in the scenarios where eavesdroppers attempt to detect their received signals using maximal-ratio combining or maximum-gain selection. The achievable data rates of both legitimate and wiretapper links are formulated with the objective of quantifying the secrecy rates for both Gaussian-distributed and finite-alphabet inputs. Illustrative numerical results are provided for the metrics of ergodic secrecy rate and secrecy outage probability, which substantiate the compelling benefits of the physical-layer secret key generation via CQI-mapped SM.

To achieve physical layer security (PLS) with a flexible implementation, a novel design named security-oriented trellis coded spatial-modulation (SO-TCSM) is proposed in this article, where the transmitter does not know the channel state information (CSI) of wiretapping channels and relies on the legitimate CSI to vary the mapping patterns for the antenna information and the radiated information, aiming at the optimisation of free Euclidean distances between the resultant SO-TCSM symbols. Eavesdroppers cannot decode the confidential information delivered in the legitimate link, as they do not know the legitimate CSI and, hence, have no basis to acquire the transmitter's mapping pattern of the moment. Moreover, the SO-TCSM symbols are then compensated to maximise their Euclidean distances, which further improves the legitimate receiver's decoding performance while enhancing the PLS. However, the compensation results in high transmit power when the legitimate channels are in deep fades. To boost the energy efficiency, a constraint is set to limit the transmit power. Under this constraint, the SO-TCSM performance is investigated in terms of bit error rate and transmit power consumption. The outcome of these investigations substantiates that, compared to conventional TCSM designs, our SO-TCSM achieves better performance in the legitimate link with lower decoding complexity.

In this paper, a decode-and-forward (DF) short-packet relaying model is developed to achieve timely status updates for intelligent monitoring within the Internet of Things (IoT), where the status updates generated at an IoT device are delivered to a remote server with the aid of a relay in both half-duplex (HD) and full-duplex (FD) modes. To characterise the data freshness of status updates, we exploit the age of information (AoI) as a metric, which is defined as the time elapsed since the generation of the latest successfully decoded status update. The average AoI is formulated and minimised for both HD-DF and FD-DF relaying IoT networks in finite blocklength regime. For the HD-DF relaying, we introduce a perfect approximation of the average AoI to solve the problem of average AoI minimisation with the optimal blocklengths in two phases. For the FD-DF relaying, we propose an iterative algorithm to solve the problem of average AoI minimisation by optimising the relay’s transmit power and the blocklength. Illustrative numerical results not only substantiate the validity of our proposed algorithms, but also provide useful references for the IoT monitoring network design, specifically for the transmit power thresholds at the IoT device and the relay.

In this paper, a novel transmission strategy, referred to as mapping-varied spatial modulation, is proposed for physical layer security, where the transmitter varies mapping patterns for the radiated information and the antenna information of spatial modulation, based on the instantaneous pattern of legitimate channel quality information that is unknown to eavesdroppers. Therefore, eavesdroppers cannot successfully decode the confidential information and the transmission over the legitimate link is secured from the wire-tap of eavesdroppers, without relying on higher-layer encryption. An important virtue of the proposed transmission strategy is that the transmitter does not need to know eavesdroppers' channels states at all. To further demonstrate the advantage of this scheme, its secrecy rate was formulated for the purpose of facilitating the performance evaluation. Moreover, illustrative numerical results pertaining to the metrics of ergodic secrecy rate and secrecy outage probability not only substantiate the validity of the proposed transmission strategy, but also provide useful references for the system design with the mapping-varied spatial modulation, from the view of physical layer security.

In spatial modulation (SM) systems, when channel state information is available at the transmitter, adaptive power allocation can be exploited to enhance the SM performance. In this paper, optimal power allocation in SM systems is considered from an information-theoretical view. First, as there is no closed-form expression of the SM capacity, the instantaneous mutual information is formulated in an analytic form for SM systems with two transmit antennas. Then, two power-allocation algorithms are proposed to maximize the SM mutual information. One is a sub-optimal power-allocation algorithm that is established in closed form to maximize the upper bound of SM mutual information. The other is an iterative algorithm for optimal power allocation that is proposed to achieve the maximum mutual information of SM systems while dramatically reducing the operational complexity compared with global computer searching. To evaluate the performance of the proposed power-allocation algorithms, numerical and simulation results are reported in terms of outage capacity and ergodic capacity, which demonstrates that the proposed power-allocation algorithms significantly improve the SM performance, compared with conventional equal-power allocation.

In this paper, the concept of spatial modulation is exploited in two-way relay channels, where two single-antenna source terminals exchange information through an assisting multi-antenna relay node, and thereby two novel transmission strategies are proposed based on the decode-and-forward protocol, aiming to achieve high throughput. One strategy is to simply engage spatial modulation in the transmissions of the relay node, whereas the other is to develop transmit diversity with spatial modulation for further benefiting from the feature of two-way relaying. Neither of the strategies requires channel state information at the transmitter and, therefore, the assumption of channel reciprocity that is commonly used in two-way relay channels can be released herein. To evaluate the performance of both proposed strategies, their capacity behaviors are analyzed and numerical comparisons are established in the metrics of achievable rate region and sum-rate. Subsequently, the first strategy, simple spatial modulation, is generalized into the two-way relaying with multi-antenna source terminals to improve the flexibility in system design and demonstrate the tractability of spatial modulation. Illustrative discussions on bit error rate not only substantiate the validity of the proposed strategies but also provide useful tools for the two-way relaying layout without the restriction of channel reciprocity.

In this paper, a novel artificial-noise strategy is proposed for single-antenna point-to-point systems over multi-path fading channels. Unlike existing artificial-noise schemes that are used in multi-antenna systems for the only purpose of confusing eavesdroppers, the main objectives of the artificial noise generated in the proposed strategy are not only to guarantee secure communications, but also to compensate inter-symbol interference induced by multi-path propagation while achieving full multi-path diversity in the desired link between source and legitimate destination. Based on maximal-ratio combining at the destination, the artificial noise herein is specified by the channel state information (CSI) of the desired link. Specifically for the time-division duplex mode, thanks to channel reciprocity, the CSI is available at the source to generate the artificial noise. However, third-party eavesdroppers that are blind to the CSI are not able to decode the source information injected with the artificial noise. Illustrative discussions on the performance not only substantiate the validity of the proposed strategy both in overcoming multi-path effects and for physical layer security, but also provide a useful tool for the frame design with the proposed strategy.

Abstract Information‐guided channel hopping (IGCH) is a promising technique for high‐data‐rate communications using multiple antennas for information mapping at the transmitter and optional antenna diversity at the receiver. Compared with some popular multi‐antenna techniques, the advantage of this scheme is proven in ideal channel conditions, where the channel is spatially white and the perfect channel state information is assumed available at the receiver. The main objective of this paper is to present an information theoretical study on IGCH in realistic propagation environments with channel degeneracy due to spatial correlation and keyhole phenomena as well as imperfect channel estimation. It is proven that good performance promised by IGCH can be achieved in a variety of non‐ideal channel conditions. Moreover, the analysis in this paper provides a convenient tool for the corresponding system design in practical operating environments. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper, a hierarchical cell structure is considered, where public safety broadcasting is fulfilled in a femtocell located within a macrocell. In the femtocell, also known as local cell, an access point broadcasts to each local node (LN) over an orthogonal frequency sub-band independently. Since the local cell shares the spectrum licensed to the macrocell, a given LN is interfered by transmissions of the macrocell user (MU) in the same sub-band. To improve the broadcast performance in the local cell, a novel scheme is proposed to mitigate the interference from the MU to the LN while achieving diversity gain. For the sake of performance evaluation, ergodic capacity of the proposed scheme is quantified and a corresponding closed-form expression is obtained. By comparing with the traditional scheme that suffers from the MU's interference, numerical results substantiate the advantage of the proposed scheme and provide a useful tool for the broadcast design in hierarchical cell systems.

In this study, the authors develop a transmission protocol for cognitive radio networks, whereby fountain codes are exploited in the broadcast channels and secondary users help with the broadcast from the base station (BS) to primary users (PUs). With fountain codes, the BS broadcasts to the secondary transmitter (ST) as well as PUs simultaneously, and stops broadcasting once the ST has received sufficient codeword to decode the original information reliably. Then, the ST will resume the broadcasting to PUs until all of them can decode the original information successfully. While broadcasting, the ST transmits information over its own link, that is, to the secondary receiver, based on dirty paper coding technique. As such, the energy expenditure at the BS is reduced and, moreover, secondary links have more opportunities to access the licensed spectrum band. To evaluate the performance of the developed scheme, they analyse its energy expenditure, broadcast time as well as the throughput over secondary links, and achieve the corresponding closed‐form expressions. Compared with the traditional broadcast protocol without the secondary's help, illustrative numerical results substantiate the validity of the author's derivations, which also demonstrate the efficiency of the developed scheme both on the energy savings and on the spectrum utilisation.

In this paper, we consider a broadcast channel in spectrum-sharing networks, where the base station schedules licensed primary users (PUs) and cognitive secondary users (SUs) simultaneously. Based on such a framework, we present a transmission strategy in the light of dirty paper coding. In order to promise the PUs' quality of service (QoS) in the broadcasting, the base station chooses codewords for the users by taking into account that the codewords pertaining to SUs can be pre-subtracted from those pertaining to PUs as if there were no interference from the secondary's data to the primary's data. For the purpose of performance evaluation, by taking capacity behavior and bit error rate (BER) as metrics, we study the achievable data rate regions for both types of users with the introduced design, and analyze the BER performance in corresponding systems implemented with hierarchical modulation. Numerical results substantiate that with flexible management of the spectrum resources, our proposed scheme provides more communication opportunities for SUs while maintaining PUs' QoS at an acceptable level.

In this work, we consider a cooperative network where multiple relay nodes having different modulation capabilities assist the end-to-end communication between a source and its destination. Firstly, we evaluate the effective capacity (EC) performance of the network under study. According to the analysis, an EC-based relay selection criterion is proposed. Based on the proposed selection rule and half-duplex decode-and-forward protocol, the activated relays cooperatively help with the packet transmission from the source. At the destination, packet combining is taken into account to improve the quality of service. Compared to the popular scheme, opportunistic relay selection, numerical results are provided to prove the validity and advantages of our proposed scheme in certain scenarios. Moreover, the analysis presented herein offers a convenient tool to the relaying transmission design, specifically on which relay selection scheme should be used as well as how to choose the receiving strategy between with and without packet combining at the destination.

In this paper, we focus on a cognitive radio network where adaptive modulation is adopted in primary links. The gap between the primary user (PU)'s received signal-to-noise ratio (SNR) and the lower SNR boundary of the modulation mode that is being used, provides an interference-tolerable zone. Based on this gap, a secondary user (SU) has an increased opportunity to access the licensed spectrum and to determine the transmit power it should use to keep the PU's quality-of-service (QoS) unaffected. However, since the SU cannot obtain perfect information on the PU's received SNR, it has to choose an SNR point between the lower and upper boundaries of the PU's current modulation mode as if this point were the real SNR received by the PU. Considering this issue, in order to quantify the effect of the SU's transmissions on the PU's QoS, we define the PU's service outage probability and obtain its closed-form expressions by taking into account whether the peak transmit power constraint is imposed on the secondary's transmission or not. Subsequently, we derive the SU's achievable data rate in closed form for counterpart scenarios. Numerical results provided here quantify the relation between the PU's service outage probability and the SU's achievable data rate, which further demonstrate that the higher the peak transmit power a secondary transmitter can support, the better performance the cognitive radio network can achieve.

In this paper, a design for the multiple-input-multiple-output~(MIMO) multiuser transmission in the cognitive radio network is developed and its end-to-end performance is investigated under spectrum-sharing constraints. Firstly, the overall average packet error rate is analyzed by considering the channel state information feedback delay and the multiuser scheduling. Then, we provide corresponding numerical results to measure the performance evaluation for several separate scenarios, which presents a convenient tool for the cognitive radio network design with multiple secondary MIMO users.

In this paper, we consider an underlay cognitive relaying network consisting of multiple secondary users and introduce a cooperative transmission protocol using a common relay to help with the communications between all secondary source-destination pairs for higher throughput and lower realization complexity. A whole relay-assisted transmission procedure is composed of multiple access phase and broadcast phase, where the relay is equipped with multiple antennas, and the secondary sources and destinations are single-antenna nodes. Considering the spectrum-sharing constraints on the secondary sources and the relay, we analyze the capacity behaviors of the underlay cognitive relaying network under study. The corresponding numerical results provide a convenient tool for the presented network design and substantiate a distinguishing feature of introduced design in that multiple secondary users' communications do not rely on multiple relays, hence allowing for a more efficient use of the radio resources.

In addressing the issue of achieving high throughput in half-duplex relay channels, we exploit a concept of information-guided transmission for the network consisting of a source node, a destination node, and multiple half-duplex relay nodes. For further benefiting from multiple relay nodes, the relay-selection patterns are defined as the arbitrary combinations of given relay nodes. By exploiting the difference among the spatial channels states, in each relay-help transmission additional information to be forwarded is mapped onto the index of the active relay-selection pattern besides the basic information mapped onto the traditional constellation, which is forwarded by the relay node(s) in the active relay-selection pattern, so as to enhance the relay throughput. With iterative decoding, the destination node can achieve a robust detection by decoupling the signals forwarded in different ways. We investigate the proposed scheme considering "decode-and-forward" protocol and establish its achievable transmission rate. The analytical results on capacity behaviors prove the efficiency of the proposed scheme by showing that it achieves better capacity performance than the conventional scheme.

Information-guided channel-hopping technique employing multiple transmit antennas was previously proposed for supporting high data rate transmission over fading channels. This scheme achieves higher data rates than some mature schemes, such as the well-known cyclic transmit antenna selection and space-time block coding, by exploiting the independence character of multiple channels, which effectively results in having an additional information transmitting channel. Moreover, maximum likelihood decoding may be performed by simply decoupling the signals conveyed by the different mapping methods. In this paper, we investigate the achievable spectral efficiency of this scheme in the case of having channel estimation errors, with optimum pilot overhead for minimum mean-square error channel estimation, when transmitting over block-fading channels. Our numerical results further substantiate the robustness of the presented scheme, even with imperfect channel state information.

In this paper, we consider the relay selection problem for the cooperative transmission in wireless networks with multiple half-duplex relay nodes. In the existing scheme, by using multiple relay nodes, spatial diversity is exploited to improve the transmission reliability. However, only one relay node is active in each relay-help transmission. We propose a novel relay selection scheme to improve relay throughput by selecting more than one relay nodes in the relay-help transmission and using the selection of active relay nodes to map a portion of information to be relayed. In the proposed scheme, extra relayed information can be forwarded besides the basic relayed information transmitted traditionally, and moreover, iterative decoding can be used to achieve robust detection. Especially, we show the efficiency of the proposed scheme by analyzing its capacity performance and comparing with that of the existing scheme.

Machines are becoming the important part of the communication network, from industry to smart homes. The machine-to-machine (M2M) communication is the main mode of these machines, which automatically serves the human in the various ways. More and more M2M applications are based on the cellular networks, taking the advantages of better coverage and lower network deployment cost. However, the current cellular network is designed for the communication between human beings, which targets the voice/media transportation, low access delay and high throughput. Currently, the machine terminals connected in cellular networks are more like mobile phones, implying the complex protocol stack, power consuming and high cost, which are the main obstacles of the deployment of machines. The paper discusses the new cellular based M2M architecture which provides better support of M2M communication with much less complexity and thus lower development cost.

In this paper, we consider a half-duplex relay channel where the relay node cannot transmit and receive simultaneously. The information to be transmitted at the source node is composed of relayed information and non-relayed information. They interfere with each other in the existing scheme when the relay node forwards the relayed information and simultaneously the source node transmits the non-relayed information. In order to improve the transmission reliability, we propose two schemes where the source node chooses the non-relayed information codeword in terms of dirty paper coding (DPC). In Scheme 1, DPC technique is applied during the listening phase; and in Scheme 2, DPC technique is applied during the cooperative phase. Specially, we discuss the capacity behaviors of the proposed schemes and compare them with the baseline, namely the capacity behaviors of the existing scheme without the application of DPC technique. The corresponding numerical results prove that both proposed schemes outperform the existing scheme in the sense of capacity performance.

In this paper, a novel relay selection scheme is proposed for the wireless network with multiple half-duplex relay nodes, which improves relay throughput by selecting more than one relay nodes in each relay-help transmission and using the selection of active relay nodes to map a portion of information to be relayed. Compared with the existing relay selection scheme with only one active relay node in each relay-help transmission, the proposed scheme allows extra relayed information to be forwarded besides the basic relayed information transmitted traditionally. And, the efficiency of the proposed scheme is shown by the analysis of capacity behaviors.

In the conventional pilot symbol assisted modulation design, a data block is composed of a pilot set and an information data set. For improving the quality of the channel estimates, some iteration methods use the detected information symbols as the additional pilots. We work on orthogonal frequency division multiplexing (OFDM) system to divide the information data set into several segments and assign them with different data rates for exploiting the potential of the iterative channel estimation. The averaged data rate can be increased by the proposed scheme with the minimum mean-square error channel estimator. The simulation results confirm this approach.

In this paper, we consider the capacity behaviors of MC-CDMA and CP-CDMA systems by the uses of MMSE receivers. The averaged capacities are derived for the two systems, having a finite spreading factor, in Rayleigh fading environment. The closed-form solutions have been obtained, which show that the capacity of the MC-CDMA is slightly larger than that of the CP-CDMA. The theoretical predictions are confirmed by the simulation results.