Binhong Dong

Detect-and-Forward Relaying Aided Cooperative Spatial Modulation for Wireless Networks

A novel detect-and-forward (DeF) relaying aided cooperative SM scheme is proposed, which is capable of striking a flexible tradeoff in terms of the achievable bit error ratio (BER), complexity and unequal error protection (UEP). More specifically, SM is invoked at the source node (SN) and the information bit stream is divided into two different sets: the antenna index-bits (AI-bits) as well as the amplitude and phase modulation-bits (APM-bits). By exploiting the different importance of the AI-bits and the APM-bits in SM detection, we propose three low-complexity, yet powerful relay protocols, namely the partial, the hybrid and the hierarchical modulation (HM) based DeF relaying schemes. These schemes determine the most appropriate number of bits to be re-modulated by carefully considering their potential benefits and then assigning a specific modulation scheme for relaying the message. As a further benefit, the employment of multiple radio frequency (RF) chains and the requirement of tight inter-relay synchronization (IRS) can be avoided. Moreover, by exploiting the benefits of our low-complexity relaying protocols and our inter-element interference (IEI) model, a low-complexity maximum-likelihood (ML) detector is proposed for jointly detecting the signal received both via the source-destination (SD) and relay-destination (RD) links. Additionally, an upper bound of the BER is derived for our DeF-SM scheme. Our numerical results show that the bound is asymptotically tight in the high-SNR region and the proposed schemes provide beneficial system performance improvements compared to the conventional MIMO schemes in an identical cooperative scenario.

Shuffled Multiuser Detection Schemes for Uplink Sparse Code Multiple Access Systems

The existing multiuser detection schemes for uplink (UP) sparse code multiple access (SCMA) systems are based on a parallel message update for message passing algorithm (MPA). In this letter, a shuffled MPA (S-MPA) scheme for UP SCMA systems is proposed, based on a serial message update strategy. Since the updated messages can join the message propagation immediately in current iteration, the convergence rate is accelerated, so that the complexity of the proposed S-MPA scheme can be substantially reduced with negligible bit error rate (BER) degradation. Simulations show that the proposed S-MPA scheme with two iterations provides similar BER performance to the original MPA scheme with six iterations. Furthermore, a parallel form of the proposed S-MPA scheme, termed group S-MPA, is developed to decrease the detection delay of the proposed S-MPA scheme, which offers a good BER-latency tradeoff.

Low-Complexity Detector in Sparse Code Multiple Access Systems

One of the challenges in the design of sparse code multiple access systems is developing low-complexity detectors. To achieve this goal, we propose a novel low-complexity detector based on an edge selection approach, which remarkably reduces the computational complexity. First, the proposed detector applies adaptive Gaussian approximation to the unselected edges that have smaller modulus of the channel coefficients, on the basis of the different channel qualities. As a result, the original factor graph can be simplified. In addition, a mean and variance feedback mechanism is employed to further compensate the information loss brought by unselected edges. Simulations show that, compared with the original message passing algorithm-based detector, the computational complexity is reduced substantially with negligible bit error rate performance degradation.

A Fast Convergence Multiuser Detection Scheme for Uplink SCMA Systems

Sparse code multiple access (SCMA) is a competitive non-orthogonal multiple access technique for fifth generation wireless communication networks which can accommodate massive connectivity. Among the existing multiuser detection schemes for uplink (UP) SCMA systems, the asynchronous message passing algorithm (ASYN-MPA) scheme, where messages are updated sequentially, generally converges faster than the synchronous variant, where all messages are updated in parallel manner. Nevertheless, the specific pre-defined order of the ASYN-MPA scheme is not always the best option. In this letter, we tackle the problem of how to schedule message for the ASYN-MPA scheme that results in the best convergence rate. Specifically, a novel residual-aided message propagation approach for scheduling messages in the ASYN-MPA scheme, termed residual-aided MPA, is proposed for UP SCMA systems, which exploits the dynamic selection of the message which has the largest residual. Simulations show that the proposed scheme with two iterations provides very similar bit error rate performance to the existing multiuser detection schemes with six iterations (only less than 0.05 dB degradation), whose complexity is reduced substantially.

An Improved Soft-Input Soft-Output Detector for Generalized Spatial Modulation

Generalized spatial modulation (GSM) is a recently proposed appealing multi-input multi-output (MIMO) transmission technique, which is capable of striking a tradeoff between the achievable transmission rate and the cost of radio frequency (RF) chains. In this letter, a novel low-complexity near-optimal soft decision (SoD)-aided detector is proposed for GSM, which considerably reduces the search space by employing a block minimum mean-squared error (B-MMSE) algorithm. Our simulation results show that the proposed detector is capable of achieving a better tradeoff between bit-error-rate (BER) performance and computational complexity compared with the existing matched filter (MF)-based SoD algorithms.

A Subset-Based Coherent FFH System

Fast frequency hopping (FFH) is a powerful antijamming method. Nevertheless, channel estimation in FFH is a difficult issue and even once was deemed impractical. FFH over fading channels usually adopts noncoherent schemes that suffer from combination loss and low spectral efficiency. To address these issues, in this letter, we propose a subset-based coherent FFH (S-CFFH) scheme. The proposed scheme partitions the hopping frequency set into a number of subsets. By controlling the size of hopping frequency subset, we ensure that each hopped frequency recurs within the channel coherence time, which thus enables efficient channel estimation and coherent schemes. We analyze the bit error ratio (BER) of S-CFFH/quaternary phase-shift keying in the presence of partial band noise jamming, highly frequency-selective Rayleigh fading, and channel estimation errors. We further study how to optimize the S-CFFH parameters. Closed-form expressions are provided for the BER and optimum pilot parameter. Simulation results are presented to corroborate our theoretical analysis. It is shown that S-CFFH significantly outperforms conventional noncoherent FFH in both BER and spectral efficiency.

An Improved Frequency Domain Turbo Equalizer for Single-Carrier Spatial Modulation Systems

In this paper, a new time-domain soft-decision feedback (TDSDF) aided frequency domain turbo equalizer (FDTE) is proposed for broadband single-carrier (SC) spatial modulation (SM) systems. Specifically, the proposed equalizer operates on a frame-by-frame basis and is designed based on the minimum block-averaged mean-square error (MBMSE) criterion. To tackle the error propagation problem, a metric in consideration of the reliability of the feedback information is considered. The optimal coefficients of the forward and feedback filters involved in the TDSDF-FDTE design are derived analytically. Simulation results show that the proposed nonlinear TDSDF-FDTE detector is capable of offering a better tradeoff between the bit-error-rate (BER) performance and the imposed computational complexity than the conventional linear frequency domain turbo demapper (FDTD) conceived for SC-SM systems. Furthermore, a 4 dB improvement is observed for the unbalanced channel.

Performance analysis of a subset-based coherent FFH system with spatial modulation in Rayleigh fading channels with multitone jamming

Conventionally, fast frequency hopping (FFH) is regarded as a non-coherent system, which has inevitable shortcomings in low spectral efficiency. To achieve a high spectral efficiency while maintaining a favourable bit error ratio (BER) performance in FFH systems, in this study, the authors extend their previously proposed subset-based coherent FFH (S-CFFH) scheme with the aid of spatial modulation (SM). Furthermore, they derive the closed-form expressions of the pairwise error probability and asymptotically BER bound for the S-CFFH/SM maximum-likelihood receivers in the presence of multitone jamming and highly frequency-selective Rayleigh fading channels, where the perfect and imperfect channel state information are both considered. The authors’ analysis and simulation results show that, the proposed S-CFFH/SM scheme outperforms both the conventional non-coherent FFH and the S-CFFH schemes, in terms of spectral efficiency and BER, respectively.

Generalized Approximate Message Passing Aided Frequency Domain Turbo Equalizer for Single-Carrier Spatial Modulation

In this paper, a pair of novel frequency domain equalizers for broadband single-carrier (SC) spatial modulation (SM) systems over dispersive channels are proposed by integrating with the concept of generalized approximate message passing (GAMP). Specifically, we first propose a GAMP-aided frequency domain turbo equalizer (FDTE-GAMP) operating on a vector-by-vector basis, which exploits the linear mixing channel structure composed of channel matrix and fast Fourier transforms. In the design of this novel detector, the non-Gaussian property of the transmitted SM symbol is fully investigated, in order to provide a more reliable belief of the channel symbols, leading to an accurate extrinsic information. For the sake of simplification, we propose a low-complexity version of FDTE-GAMP by forcing the variance components of transmitted symbols to be the same scalar, and thus avoiding the matrix inversion operation and maintaining a sequence of scalar operations. Simulation results show that the proposed equalizers are capable of providing a better tradeoff between the attainable bit error rate and the imposed computational complexity than the conventional FDTEs conceived for SC-SM systems.

Joint Sparse Graph-Detector Design for Downlink MIMO-SCMA Systems

The application of multiple-input multiple-output (MIMO) technique to sparse code multiple access (SCMA) systems is important to enhance the system performance of future fifth generation wireless networks. However, one of the challenges in design of downlink MIMO-SCMA systems is developing near-optimum bit error rate (BER) performance detectors with affordable computational costs. To achieve this goal, we construct a joint sparse graph combining the single graph of MIMO channels and SCMA codewords, and then design the corresponding virtual SCMA codebooks for the detector. To utilize them, a novel joint processing approach based on message passing algorithm is proposed. Furthermore, two strategies for message update on the joint sparse graph, i.e., parallel and serial schedules, are, respectively, presented. Simulations show that, the proposed detector can achieve the optimal BER performance with significantly reduced complexity, compared to the maximum likelihood detector.