Xuan Nam Tran

Spatially Modulated Orthogonal Space-Time Block Codes with Non-Vanishing Determinants

This paper proposes a multiple-input multiple-output (MIMO) transmission scheme for M-ary modulations, called Spatially Modulated Orthogonal Space-Time Block Coding (SM-OSTBC), based on the concept of Spatial Constellation (SC) codewords introduced by Le at el. . In the proposed scheme, transmit codeword matrices are generated by multiplying SC matrices with codewords constructed from Orthogonal Space-time Block Codes (O-STBC). The maximum spectral efficiency of the proposed scheme is equal to (n_T-2+ log_2 M) bpcu, where n_T is the number of transmit antennas and M is the modulation order. The SC matrices provide a means of carrying information bits together with the O-STBC codewords and allow the SM-OSTBC scheme to achieve second-order transmit diversity by satisfying the non-vanishing determinant property. A systematic method to design the SC codewords for an even number of transmit antennas greater than 3 is presented. A single-stream maximum-likelihood (ML) decoder, which requires a low computational complexity thanks to the structure of the SM-OSTBC codewords and to the orthogonality of the O-STBCs, and a sphere decoder with further reduced signal processing complexity are developed. The bit error rate (BER) performance of the proposed scheme is studied by using both theoretical union bound analysis and computer simulations. Finally, simulation results are presented in order to compare BER performance, energy efficiency and decoding complexity of the proposed scheme with those of several existing MIMO transmission schemes.

Spatial Modulation for High-Rate Transmission Systems

This paper proposes a high rate spatial modulation transmission scheme based on the concept of Spatial Constellation (SC) and SC codewords introduced in [1]. In the proposed scheme, transmitted signal vectors are generated by multiplying spatial SC codewords with constellation symbols drawn from a conventional QAM or PSK constellation. The entries of SC codewords will determine how the constellation symbols are weighted and which transmit antennas among a total of nT transmit antennas are activated to transmit the signals. Different SC codewords allow us to have different ways to transmit the constellation symbols. Thus, information bits are born not only by constellation symbols but also by SC codewords. The additional spectral efficiency offered by SC codewords is proportional to the number of SC codewords which can be designed for each antenna configuration. A new low-complexity maximum-likelihood (ML) decoder is also devised for signal recovery. In addition, a theoretical union bound on the bit error probability is derived. Simulation results, supported by the theoretical upper bound, are given to compare bit error rate (BER) performance of the proposed scheme with those of existing MIMO transmission counterparts in the literature for various antenna configurations.

Physical network coding for bidirectional relay MIMO-SDM system

Physical-layer network coding (PNC) is a promising technique to increase transmission throughput over bidirectional relay wireless networks. In this paper, based on the work by Zhang and Liew, we propose a new scheme called multiple input multiple output spatial division multiplexing PNC (MIMO-SDM-PNC). By using MIMO-SDM, the proposed scheme achieves double multiplexing gain and also does not require that the end nodes know the information about the forward channel from the source nodes to the relay. Compared with the system by Zhang and Liew the proposed system achieves the same diversity order. The MMSE based detection was shown to have equivalent BER performance with that of the MIMO-PNC while the ZF based suffers about 2.4 dB power loss due to noise amplification problem.

Design of Two Way Relay Network Using Space-Time Block Coded Network Coding and Linear Detection

This paper presents a design of two-way two-hop relay network using physical layer network coding (PNC) in which multiple antennas are used at all nodes. For transmission over the multiple-input multiple-output channels, the Alamoutis space-time block code (STBC) is used for transmission while linear detection is used for signal estimation at all nodes. In order to facilitate linear detection, we develop an equivalent multiuser STBC model for the proposed network and design the sum-and-difference matrix which is suitable for signal estimation. Simulation results show that the proposed network achieves diversity order 2 with polynomial complexity.

Channel quantization-based physical-layer network coding for two-way relay STBC system

Wireless multiple-input multiple-output (MIMO) two-way relay systems have received increasing attention recently. In a simple two-hop relay system, physical-layer network coding (PNC) is an effective scheme for relay to map the transmitted symbols from two terminal nodes into the network coded symbol. This paper considers a two-hop two-way relay system which uses the Alamouti space-time code for signaling between all nodes and channel quantization for PNC mapping at the relay. Specifically, based on the concept of CQ-PNC we derive a PNC mapping rule for two pairs of network coded symbols. An adaptive mapping scheme based on minimum residual interference power is introduced to reduce the effect of quantization error. Finally, a relay selection method based on minimum residual interference power is proposed as a means to increase the system performance.

Channel quantization based physical-layer network coding for MIMO two-way relay networks

In this paper, a new physical-layer network coding (PNC) scheme is proposed for multiple-input multiple-output two-way relay networks where all network nodes, including two terminal nodes and the relay node, are equipped with multiple antennas. Spatial division multiplexing (SDM) technique is used at the two source nodes to increase transmission rate while the physical-layer network coding based on channel quantization (CQ-PNC) is used at the relay node to achieve diversity gain. The simulation results show that the proposed scheme outperforms significantly both of the previous channel quantization based PNC (CQ-PNC) and SDM-PNC schemes.

A spatial modulation scheme with full diversity for four transmit antennas

In this paper, we propose a Spatial Modulation (SM) with full diversity for 4 transmit antennas, called DS-SM, by designing SC codewords and incorporating them with a Diagonal Space Time Block Code. Similar to the conventional SM scheme, the proposed scheme only activates an antenna element at a time for signal transmission. However, it is different from the conventional SM in that it is able to achieve full diversity. In order to attain low detection complexity, an ML detector based on sphere decoding is presented. Computer simulation shows that the proposed DS-SM scheme outperforms some existing STBC-SM techniques in terms of both bit error rate (BER) performance and effective throughput.

Low-Complexity Estimation for Spatially Modulated Physical-Layer Network Coding Systems

This paper proposes a low-complexity signal estimator at the relay node for a spatially modulated physical-layer network coding system. In the considered system, the two terminal nodes use spatial modulation to transmit their signals to the relay node during the multiple access phase. Based on the channel quantization method, we propose a low-complexity estimator which can detect both antenna indices and -QAM symbols using successive interference cancellation (SIC). Moreover, we design signal constellations for a combined signal component at the relay for arbitrary -QAM modulation. The obtained constellations allow further reduction of the computational complexity of the estimator. Performance evaluations show that the proposed estimator can achieve near-optimal error performance while requiring significantly less computational complexity compared with the maximum-likelihood detector, particularly with high-order modulation.

Repeated index modulation for OFDM with space and frequency diversity

In this paper, an enhanced scheme of Index Modulation for Orthogonal Frequency Division Multiplexing (IM-OFDM), called Repeated IM-OFDM with Diversity Reception (ReIM-OFDM) is proposed. ReIM-OFDM achieves performance improvement over the convetional IM-OFDM at the same spectral efficiency by providing additional space and frequency diversity. Similar to IM-OFDM, the proposed ReIM-OFDM also activates K out of total N subcarriers to convey information bits using both the active sub-carriers and their indices. However, it differs from IM-OFDM in that all activated sub-carriers are modulated by the same M-ary data symbol. For signal combining, either Maximal Ratio Combining (MRC) or Selection Combining (SC) can be used in the spatial and sub-carriers domain to help ReIM-OFDM achieve both space and frequency diversity gain. In order to analyze performance of the system, the Moment Generating Function (MGF) is used to obtain the closed-form expressions for the pairwise index error probability (PEP) and the symbol error probability (SEP) in both cases: ReIM-OFDM-MRC and ReIM-OFDM-SC. Effects of various system parameters on the SEP are analyzed to select the best ReIM-OFDM configuration with minimum error probability. Our analysis proves the effectiveness of ReIM-OFDM over IM-OFDM at the same spectral efficiency.

New upper bound for high-rate spatial modulation systems using QAM modulation

In this paper, we present a new upper bound for the bit error probability (BEP) of the so-called High-Rate Spatial Modulation (HR-SM) system using QAM modulation introduced by Thu Phuong Nguyen et al. in [1], over a quasi-static Rayleigh fading channel. Our approach based on the Verdus theorem [2], the concept of the spatial constellation (SC) codewords and maximum likelihood (ML) decoder in [1] results in the new upper bound which is tighter than the union bound due to eliminating a number of redundant pairwise error probabilities (PEPs). Therefore, by using the new upper bound rather than the union bound, we can evaluate the bit-error performance of HR-SM systems more exactly, especially when the signal-to-noise power ratio (SNR) is sufficiently high.