This paper deals with cyclic redundancy check (CRC) decoding when used in the context of non forward error correction (FEC)-encoded IoT systems: CRC decoding remains challenging when combined to continuous phase modulation (CPM). In this paper, a proposed algorithm relying on the candidate diversity principle through a candidate list generation from soft CPM demodulation output combined with CPM-tailored syndrome decoding is evaluated. Applied with Bahl Cocke Jelinek Raviv (BCJR) algorithm for Gaussian minimum shift keying (GMSK) demodulation, it outperforms all existing complexity-affordable methods and performs close to the best evaluated Parallel-List Viterbi Algorithm with usual CRC validation.

We consider the transmission of a continuous phase modulated (CPM) signal through a Gaussian channel affected by Doppler shifts. We propose a receiver robust to the Doppler shifts derived from a non-coherent detection criterion. We compare its performance to another non-coherent receiver based on a linear approximation of the CPM signal (Laurent decomposition) on which we add a Doppler compensation. Simulation results show that the first algorithm is robust to low-moderate Doppler shifts, while the second is robust to any one. We finally compare these two algorithms to delay-optimized differential detectors which do not require any Doppler shift estimation. We also provide complexity estimations to guide the possible complexity-performance trade-offs.

In this paper, we investigate downlink interference management schemes for future railway communications that avoid channel state information (CSI) knowledge at the transmitter side. Assuming reconfigurable antennas at both ends of each train, we apply the dark-blind interference alignment principle. Simulations show that compared to considered orthogonal multiple access techniques, the proposed scheme achieves an efficient trade-off between maximum achievable throughput and error rate.

In this paper, we consider the uplink of a railway communication system with onboard mobile relays. Each onboard relay communicates with two cooperating base stations at the ends of the section along which the train is moving. Each carriage is equipped with two distinct antenna arrays. We design transmit coding schemes distributed between the antenna arrays and we apply receive macrodiversity. Simulations show that the proposed schemes enable to maintain transmission quality and throughput as the carriage moves along the section.

The expansion of wireless applications in dense environments raises many technical issues. The 802 standards need to adapt and enhance the network quality by developing new technologies. The block acknowledgment (BA) mechanism was introduced in the IEEE 802.11e standard to improve medium access control (MAC) efficiency. It requires the exchange of many control frames to establish a session with each user, which turns into an issue for networks in dense environments as it causes increased overhead and latency. This paper deals with the optimization of the BA session management procedure. We propose a modified block acknowledgment session control mechanism which reduces the overhead and latency compared to the original one.

This paper considers the problem of source coding with side information at the decoder, also called Slepian-Wolf source coding scheme. In practical applications of this coding scheme, the statistical relation between the source and the side information can vary from one data transmission to another, and there is a need to adapt the coding rate depending on the current statistical relation. In this paper, we propose a novel rate-adaptive code construction based on LDPC codes for the Slepian-Wolf source coding scheme. The proposed code design method allows to optimize the code degree distributions at all the considered rates, while minimizing the amount of short cycles in the parity check matrices at all rates. Simulation results show that the proposed method greatly reduces the source coding rate compared to the standard low density parity check accumulated (LDPCA) solution.

In this paper, we address the problem of large MIMO detection assuming QAM constellations. We show that the QAM signal becomes a simple signal (that is to say a bounded signal with extreme elements equal to the inferior and superior bounds [1]) after a real transformation. Based on this property, we present a low complexity detection algorithm which significantly outperforms classic algorithms such as zero forcing (ZF) and minimum mean square error (MMSE) algorithms. The proposed detection technique is based on a quadratic programming criterion whose constraints ensure that the detected vector is simple. We implement it successfully in an underdetermined MIMO system (the number of observations is less than the number of sources) and we show the necessary conditions of success detection. Then we consider an outer forward error correcting (FEC) code and we propose a turbo detection scheme. Based on the investigation of the output detector statistics in [2], we propose a symbol to binary converter (SBC) which can feed the FEC decoder with reliable output. On the other side, from the second iteration, the detection scheme resorts to a regularized quadratic criterion so that the searched vector draws near to the estimate resulting from the FEC decoder output. Simulation results show the efficiency of the proposed scheme.

The concatenation of the multiple-input multiple-output (MIMO) linear precoder with an outer forward error correction (FEC) code at the transmitter is investigated in this paper. At the receiver side, the turbo detection is taken into account. It iteratively exchanges the extrinsic information between a soft-demapper and a FEC soft-decoder. We firstly propose a new precoder named FI1designed from an extrinsic information transfer (EXIT) chart analysis. The proposed precoder aims to optimize the iterative receiver convergence by maximizing the ending point I1of the soft-demapper EXIT function. For the sake of low-complexity, FI1is designed for two data streams MIMO transmission with 4-QAM only. Secondly, to cope with the higher data streams transmission, a global b = 2K data streams system is split into K two data streams subsystems. FI1is then applied at each subsystem. Finally, we propose a new algorithm to optimize the inter-subsystems power allocation by maximizing the I1of the global system.

Precoder optimization with full channel state information for finite alphabet signals over multiple-input multiple-output random channels is investigated in this paper. The precoder is represented by a product of power allocation matrix and constellation-forming matrix. There was an optimal algorithm introduced in the literature to globally maximize the channel mutual information by iteratively optimizing these two matrices. However, the computational complexity of the optimal algorithm is painfully high, especially when it is used with the high-order modulation and the high-data stream number. In this paper, we propose a novel sub-optimal low-complexity precoding algorithm and compare it with the optimal one. The new algorithm proceeds in two steps. First, the constellation-forming matrix is fixed in order to maximize the minimum Euclidean distance between the received symbols, which ensures high channel mutual information. Then, given the constellation-forming matrix, an iterative algorithm searches for the power allocation matrix that maximizes the channel mutual information. Since optimizing only one matrix instead of two, the new algorithm not only achieves a lower computational complexity but also avoids the use of initial values, which must be carefully selected for each channel and signal-to-noise ratio for fast convergence. Another advantage of the new algorithm is that the resulting precoder has a fixed form of received constellation thanks to the fixed constellation-forming matrix. This allows us to optimize the symbol mapping on the received constellation. Simulation results show that the proposed low-complexity precoder achieves error-rate performance that is close to performance of the optimal one when the conventional mapping is used. In addition, the new precoder used with optimized mapping at received constellation shows significant error-rate performance improvement.

This paper deals with a reduced-complexity per survivor processing-based CPM demodulation. It relies on a trellis with reduced state number and defined from a rational modulation index possibly different from the transmit modulation index and referred to as virtual receiver modulation index. The virtual receiver modulation index should be chosen so as to achieve a tradeoff between error-rate performance and complexity reduction. The main purpose of this paper is the choice of the virtual receiver modulation index. It gives guidelines to discard the values of the virtual receiver modulation index, that degrade the error-rate performance. Two criteria are used. The first one considers the uncoded CPM case and is based on an approximation of the minimal Euclidean distance. The second one is related to the bit interleaved coded CPM case and resorts to an EXIT chart to analyze the convergence of the iterative receiver.

In this paper, we investigate the concatenation of the multiple input multiple output (MIMO) max-dminlinear precoder with an outer forward error correction (FEC) code at the transmitter. At the receiver side, the turbo equalization is taken into account, which iteratively exchanges the extrinsic information between a minimum mean square error interference canceller (MMSE IC) and a FEC decoder. The analysis done by extrinsic information transfer (EXIT) chart shows that a higher mutual information (MI) at the convergence state of the turbo equalization is observed thanks to the linear precoder. In addition, we exploit this property to propose a new precoder named max-dmin-mod. Numerical simulations are in accordance with the theoretical analysis, which exhibits a significant improvement of the error-rate of the turbo equalization as well as a significant gain of max-dmin-mod compared to original max-dminprecoder.

We consider binary continuous phase modulation (CPM) signals used in some recent low-cost and low-power consumption telecommunications standard. When these signals are generated through a low-cost transmitter, the real modulation index can end up being quite different from the nominal value employed at the receiver and a significant performance degradation is observed unless proper techniques for the estimation and compensation are employed. For this reason, we design new binary schemes with a much higher robustness. They are based on the concatenation of a suitable precoder with binary input and a ternary CPM format. The result is a family of CPM formats whose phase state is constrained to follow a specific evolution. Two of these precoders are considered. We will discuss many aspects related to these schemes, such as the power spectral density, the spectral efficiency, simplified detection, the minimum distance, and the uncoded performance. The adopted precoders do not change the recursive nature of CPM schemes. So these schemes are still suited for serial concatenation, through a pseudo-random interleaver, with an outer channel encoder.

This paper considers bit-loading algorithms to maximize throughput under total power and spectral mask constraints in interference-free OFDM systems. The contribution is twofold. First, we propose a simple criterion to switch between two well-known algorithms from the literature: the conventional Greedy and Greedy-based bit-removing (with maximum allowable bit loading initialization) algorithms. Second, we present a new low-complexity loading algorithm that exploits the bit vector obtained by rounding the water-filling algorithm solution to the associated continuous-input rate maximization problem as an efficient initial bit vector of the Greedy algorithm. We theoretically prove that this bit vector has two interesting properties. The first one states that it is an efficient bit vector, i.e., there is no movement of a bit from one subcarrier to another that reduces the total used power. The second one states that the optimized throughput, starting from this initial bit vector, is achieved by adding or removing bits on each subcarrier at most once. Simulation results show the efficiency of the proposed algorithm, i.e., the achievable throughput is maximized with significant reduction of computation cost as compared to many algorithms in the literature.

The aim of this paper is to study the bit-loading and power allocation problem in the presence of interference (Inter-carrier Interference (ICI) and Inter-Symbol Interference (ISI)) in Orthogonal Frequency Division Multiplexing (OFDM) systems. ISI and ICI significantly degrade the performance of OFDM systems and make the resource management optimized without the assumption of interference less efficient. To solve this problem, an initial solution based on the greedy approach is proposed in this paper. Then, several reduced complexity approaches, which yield a little degradation compared to the initial solution, have been developed. Simulation results presented in the context of Power Line Communication (PLC) show that the performance of proposed algorithms is tight with their upper bound. Moreover, these algorithms efficiently improve the system performance as compared to the constant power water-filling allocation algorithm as well as maximum power allocation algorithm.

This paper deals with distributed coding for sensor networks. We consider energy-and-complexity-constrained sensors that communicate with a distant sink at a relatively low data rate with the help of a relay with higher-power and better-processing capabilities. We assume an orthogonal multiple access to the resources. Sources transmit independently and use simple short block codes to limit delay and complexity. The relay performs network encoding of the detected codewords and forwards either partial or complete coded information. The sink jointly decodes observations coming both from sources and relay to simultaneously estimate the information sent by the source nodes. We first analyse the cooperative scheme from an information theoretical point of view in order to determine the resource allocation strategy between the sources and the relay, which maximizes the overall network sum-rate. When a single relay is used and the source-to-relay link is not error-free, occasional detection errors introduce additional errors at the relay output, which, in turn, critically affect decoding performance and yield error-floors at the destination. In the case of a distributed coding scheme based on product codes, we obtain a closed-form asymptotically-tight approximation of the error probability under a minimum-distance decoding of the product code at the destination. The proposed analysis takes explicitly into account the error propagation at the relay output and may be extended to other forms of distributed coding schemes.

This paper addresses the problem of decoding and precoding in the K-user MIMO interference channels. At the receiver side, a joint decoding of the interference and the desired signal is able to improve the receive diversity order. At the transmitter side, we introduce a joint linear precoding design that maximizes the joint cut-off rate, known as a tight lower bound on the joint mutual information for high signal-to-noise ratio (SNR). We also derive a closed-form solution of the precoding matrices that maximizes the mutual information when the SNR is close to zero. This solution is characterized by its low computational complexity, and only requires a local channel state information knowledge at the transmitters. Our simulation results show that decoding interference jointly with the desired signal results in a significant improvement of the receive diversity order. Also a substantial bit error rate and sum-rate improvements are illustrated using the proposed precoding designs.

This paper adresses the problem of cooperation application in an existing non-cooperative wireless sensor network. Sensors are low-energy and low-data rate devices. They transmit small independent individually-encoded information packets to the same destination. The cooperation scheme is based on a product code distributed among sources and relays and turbodecoded at the destination. We propose a system where a relay code division multiple access-based transmission is superposed with the sources time division multiple access-scheduled transmissions. A relay interference cancelation algorithm is defined and the whole system is simulated considering source-destination and relaydestination AWGN channels. The source-relay channel is assumed error-free. An optimized energy allocation between the sources and the relay is extracted from simulations.

The degree of freedom of the Single Input Single Output (SISO) fading interference channel is asymptotically upperbounded by K/2. This upperbound can be achieved using the Interference Alignment approach (IA), proposed by Cadambe et al., In this work, a new optimized design of the IA scheme is presented. It involves introducing, for each user, a combination matrix so as to maximize the sum rate of the network. The optimal design is obtained via an iterative algorithm proposed in the K-user IA network, and a convergence to a local optimum is achieved. Numerical results enable us to evaluate the performance of the new algorithm and to compare it with other designs.

Non-orthogonal space-time block (STB) code structures used to be optimised considering a maximum-likelihood detection, but depending on the modulation order and/or the antenna number, the prohibitive complexity of such a receiver makes it infeasible in practice. Suboptimal low-complexity receiver structures like linear detectors can be applied instead, yielding degradation of performance compared with the predictions. When a forward error correction (FEC) code is used upstream of the STB code, an iterative receiver consisting of a FEC decoder and an interference canceller (IC) co-operating according to the turbo equalisation principle, can achieve near-optimal performance. This study aims to define the construction of full-rate full-diversity linear dispersion codes with reduced peak-to-average power ratio (PAPR), taking into account the serial concatenation with a FEC at the transmitter and a minimum mean square error (MMSE) turbo equaliser at the receiver. Optimisation criteria are mutual information maximisation, symbol error rate minimisation at the MMSE–IC output, full-diversity thanks to the threaded algebraic space time concept and PAPR minimisation. Explicit constructions are given and the resulting code efficiency is analysed through comparison with equivalent perfect STB codes.

In the absence of the orthogonal design and a very low coding rate channel code, a new bandwidth-efficient multi-user scheme is proposed, which considers random interleavers for different users and multiple antennas at the receiver. Turbo processing is exploited based on the minimum mean square error (MMSE) soft-input soft-output (SISO) detector with interference cancellation (IC) to obtain the receive diversity. The simulation results show that when the number of users K is no more than the product of the number of receive antennas and the reciprocal of the coding rate, the proposed scheme can achieve the single-user performance, which indicates that the uplink user capacity of wireless networks can be dramatically increased with the proposed scheme when more antennas are implemented at the receiver. Meanwhile, it provides a solution to dealing with underdetermined multiple input multiple output (MIMO) systems.

This paper presents iterative decoding structures for concatenated space-time error correcting codes (STECCs), based on the turbo product code decoding algorithm. Thanks to linear combinations of forward error correcting (FEC) codewords, established to create a space-time redundancy, a product code is reconstructed from concatenated STECC ensuring at the receiver an iterative turbo product code decoding scheme that outperforms the existing turbo-like receiver with an interference canceller optimized according to the minimum mean square error (MMSE) criterion.

A new space-time block code family for two transmitters, called the space-time error correcting codes (STECCs), is presented. As it is built from any linear forward error correcting code (FEC), a STECC is able to correct errors while achieving high spectral efficiencies. The key principle is the FEC linearity which is exploited to transmit linear combinations of FEC codewords to create a space-time redundancy. The proposed code exhibits interesting performance on an ISI-free block fading channel. This result is all the more true as the number of FEC codewords considered in the combination is high.

In this paper, performance comparison of frequency-domain (FD) minimum mean square error (MMSE) turbo equalization for OFDM and single-carrier (SC) transmission in ST-BICM systems is investigated. In particular, we propose a joint formulation of the frequency- domain OFDM and SC MMSE turbo equalizer which enable to bring out similarities and differences between the two transmission schemes. This provides a new view on the topic. The relevance of the proposed approach is confirmed by comparing the lower bound of the iterative equalizing process with the corresponding analytical results. Simulation results over multipath Rayleigh block fading channels for various MIMO configurations show the benefits provided by each scheme.

This paper deals with multiple-input multiple-output communication system with single-carrier modulation and frequency domain equalization. Space-time coding schemes adapted to frequency-selective channels namely space-time block codes per block are used. An efficient generalized receiver based on space-time frequency domain detector is investigated. We propose the frequency domain derivation of a generalized minimum mean square error turbo equalizer for orthogonal space-time block code per block. The main advantage of our proposed scheme is that it can be applied to any orthogonal space-time block code per block. Simulation results show that the scheme performs efficiently over frequency-selective block fading channels.

Most of multiple-input multiple-output (MIMO) coding schemes can be sorted into two families. The first one includes the space-time block codes (STBCs) and in particular, the orthogonal STBCs (OSTBCs) as they can be optimally decoded with a low complexity. They improve the transmission quality, the communication range or the receiver robustness. The second family is based on the layered space-time (LST) architecture and aims at increasing the data rate without bandwidth nor power extra cost. To guarantee a given transmission quality, the use of a forward error correcting code (FEC) is mandatory like in the space-time bit interleaved coded modulation (ST-BICM) case. The space-time error correcting codes (STECCs) we introduced, which are based on any linear FEC, appear to be a good compromise between both families. They achieve better performance than the usual Alamouti code associated with the same FEC and propose higher data-rate with space-time puncturing techniques. However, the bottleneck of these codes is the detection stage which complexity grows exponentially with the number of FEC codewords involved in the creation of one STECC codeword. By applying the turbo equalization principle, we can significantly reduce this complexity, while achieving equivalent level of performance.

Since the introduction of the block turbo code (BTC) except, several soft-input/soft-output (SISO) algorithms have been used in order to softly decode product codes. The classical Chase-Pyndiah algorithm seems to be one with the best trade-off between complexity and performance, especially for low error correction capability t (typically 1 or 2) where it is nearly optimal. However, as an algebraic decoding-based algorithm, the lack of codeword diversity is one of its weakness for BTCs with higher error correction capability and/or non binary BTCs. In this paper, we propose an improved iterative decoding algorithm for BTCs. We present a simple sliding encoding-window (SEW) based decoding algorithm which exploits the cyclic and systematic properties of RS and BCH codes. By adding the SEW algorithm to a classical algebraic decoding method, the proposed decoder can easily generate a list of codewords that are close to the decoded codeword. With the codeword diversity, we can compute more reliable soft output necessary in the turbo decoding process, Monte-Carlo simulations of binary and non-binary BTCs are carried out on Gaussian channels. The results show that the algorithm can improve the error performance up to 1.5 dB relative to the conventional Chase-Pyndiah decoder, while the increase in complexity due to the encoding is minor since it is a low-cost process compared to that of algebraic decoding. Compared to the other encoder-based decoding algorithms in the literature, the proposed algorithm has the advantage that there is no requirement to recompute the generator of parity-check matrix by using Gaussian elimination operations, thus a lower computational complexity

In this paper, we propose a set of design criteria of constructing shortened turbo product codes. Based on the criteria, we design two families of rate-compatible turbo product codes. The performance of rate-compatible turbo product codes is evaluated on the Gaussian channels using Monte Carlo simulations. We also propose a modified Gallager bounding technique to the rate-compatible turbo product codes. We show that the performance bound has a good match with the simulation results.

This paper presents a simple approach to assess performance that can be achieved by the MMSE turbo equalizer in ST-BICM systems over multipaths Rayleigh block fading channels with i.i.d fading statistics. By considering perfect information exchange between the SISO decoder and the linear MMSE equalizer, the performance reaches the matched filter bound, and a closed form expression of the corresponding probability of bit error can be derived at the output of the equalizer. In particular, we emphasize that the suggested approach provides an attractive and reliable tool for performance validation consistently with the proposed expression of the probability of bit error. Simulations for 4-PSK and 8-PSK modulated signals show the relevance of the proposed approach and the full benefit provided by the MMSE turbo equalizer. In addition some clarification of the signal-to- noise ratio definition is pointed out.

We generalize the space time code structure and define new space time block codes per block. Compared to space time block codes they are well adapted to selective frequency channels. We thus propose an efficient receiver consisting of first a space time code frequency domain detector followed by a predictive decision feedback equalizer with frequency domain feedforward filter and time domain feedback filter. Simulations show the efficiency of the whole structure

In this paper, we present an original use of Reed-Solomon (RS) codes as Space-Time Block Codes (STBCs) and compare them to orthogonal STBCs (OSTBCs). Due to their symbol structure, they can have a representation close to that of an STBC. RS codes are admittedly more complex to decode as they have no orthogonal properties. However, they offer much higher coding rates. In addition, a wide range of these codes can be easily generated. To decode them, we have developed a new algorithm using a sliding encoding-window (SEW), which is combined with the decoding-based Chase algorithm. We compare the RS(15,7) code to the Alamouti one, both having an equivalent coding rate. Its performance compared to Alamouti gets better as the receive diversity increases. Moreover, RS codes do not require the channel to remain constant over the code duration. In fact, they offer better results if the channel changes rapidly, which can be obtained virtually by introducing interleaving.

In this paper we propose an image coding scheme based on Block Turbo Codes (BTC) for protecting SPIHT coded images transmitted over wireless channels. An Unequal Error Protection (UEP) scheme using different product codes is also presented. The optimization of the UEP scheme under a transmission budget constraint is investigated. Performance of the proposed system are first evaluated over Gilbert-Elliott (GE) channels. They are then compared to the well-known system of Sherwood and Zeger, through numerical simulations over a single path Rayleigh fading channel. Then, we present an optimized mobile image transmission framework involving a multiuser asynchronous DS-CDMA transmission system over Rayleigh multipath channels. Simulation results for the 512x512 Lena image, transmitted over the ITU Vehicular A channel, show that a significant gain in PSNR is obtained by using the SIC/RAKE multiuser detector in comparison with a conventional detection by the RAKE receiver. Furthermore, performance are also improved when introducing the UEP scheme.

Product codes were introduced in 1954 by Elias and consist of a serial concatenation of two linear block codes with an uniform interleaver. The coding process only uses two linear block codes and creates a matrix in which both columns and rows are codewords. The decoding process can use different algorithms. After first implementing the Chase algorithm, we present another decoding process including the Hartmann-Nazarov (1976, 1998) algorithm and the fast Hadamard transform (FHT). This algorithm uses a symbol-by-symbol decoding rather than a whole word decoding. The decoding process is implemented on the fixed point DSP TMS320C6201. It communicates, via the RTDX link, with the coder, written in C++ language and running on the PC. The Hartmann-Nazarov algorithm exhibits better performance on the Rayleigh channel. A first evaluation of the bit rates gives us a value close to 500 kbits/s on the DSP clocked at 250 MHz.

Advances in the field of information theory have shown that wireless systems using multiple transmitters and multiple receivers can significantly improve the spectral efficiency. Systems using transmit and receive diversity associated with coding such as space time trellis codes have since been developed. A scheme using convolutional turbo codes (CTC) with two transmitters and two receivers has been proposed previously. It exhibits significant gains over space time trellis codes (up to 6 dB at a BER of 10/sup -5/). Our purpose is to extend that study to block turbo codes (BTC). We use the (32, 26, 4) extended BCH product code with two kinds of modulation (QPSK and 16-QAM). Simulations show that BTC associated with transmit and receive diversity perform as well as CTC in terms of the coding gains while achieving higher spectral efficiencies.