Optimal Generation of Space-Time Trellis Codes via Coset Partitioning

International audienceCriteria to design good space-time trellis codes (STTCs) have been already developed in previous publications. However, the computation of the best STTCs is time-consuming because a long exhaustive or systematic computing search is required, especially for a high number of states and/or transmit antennas. In order to reduce the search time, an efficient method must be employed to generate the STTCs with the best performance. In this paper, a technique called coset partitioning is proposed to design easily and efficiently optimal 2^n-PSK STTCs with any number of transmit antennas. The coset partitioning is an improved extension to multiple input multiple output (MIMO) systems of the set partitioning proposed by Ungerboeck. This extension is based on the lattice and coset Calderbank's approach. With this method, optimal blocks of the generator matrix are obtained for 4-PSK and 8-PSK codes. These optimal blocks lead to the generation of the STTCs with the best Euclidean distances between the codewords. Thus, new codes are proposed with 3 to 6 transmit antennas for 4-PSK modulation and with 3 and 4 transmit antennas for 8-PSK modulation. These new codes outperform the corresponding best known codes. Besides, the first 4-PSK STTCs with 7 and 8 transmit antennas and the first 8-PSK STTCs with 5 and 6 transmit antennas are given and their performance is evaluated by simulation

An improved method to design QPSK Balanced Space-Time Trellis Codes

International audienceRecently, a new class of Space-Time Trellis Codes was proposed as having the best performance. These codes are 'balanced' because they use the points of the constellation with the same probability. In this correspondence, we propose a new and simpler method than exisiting method to design these class for QPSK modulation and several transmit antennas. New and better balanced codes for 3 and 4 transmit antennas are also proposed

New Method to Generate Balanced 2n-PSK STTCs

The first theoretical bases of the space-time trellis codes (STTCs) have been established by Tarokh (1998). Many STTCs have been published using several criteria proposed by Tarokh (1998) and Chen (2001) for slow and fast Rayleigh fading channels. More recently, a new class of codes called balanced codes, which contains all the best STTCs has been presented by Ngo (2007, 2008). These balanced codes have the same property: if the data are generated by a binary memoryless source with equally probable symbols, the used points of the MIMO constellation are generated with the same probability. Therefore, the systematic search for the best codes can be reduced to this class. Thus, the time to find the best codes is reduced. The new and general method is proposed to design balanced 2^n-PSK STTCs for several transmit antennas. This new method is simpler and faster than the previous one presented by Ngo 2007 in particular when the number of transmit antennas and n increase

EM-Based iterative channel estimation and sequence detection for space-time coded modulation

Reliable detection of signals transmitted over a wireless communication channel requires knowledge of the channel estimate. In this work, the application of expectationmaximization (EM) algorithm to estimation of unknown channel and detection of space-time coded modulation (STCM) signals is investigated. An STCM communication system is presented which includes symbol interleaving at the transmitter and iterative EM-based soft-output decoding at the receiver. The channel and signal model are introduced with a quasi-static and time-varying Rayleigh fading channels considered to evaluate the performance of the communication system. Performance of the system employing Kalman filter with per-survivor processing to do the channel estimation and Viterbi algorithm for sequence detection is used as a reference. The first approach to apply the EM algorithm to channel estimation presents a design of an online receiver with sliding data window. Next, a block-processing EM-based iterative receiver is presented which utilizes soft values of a posteriori probabilities (APP) with maximum a posteriori probability (MAP) as the criterion of optimality in both: detection and channel estimation stages (APP-EM receiver). In addition, a symbol interleaver is introduced at the transmitter which has a great desirable impact on system performance. First, it eliminates error propagation between the detection and channel estimation stages in the receiver EM loop. Second, the interleaver increases the diversity advantage to combat deep fades of a fast fading channel. In the first basic version of the APP-EM iterative receiver, it is assumed that noise variance at the receiver input is known. Then a modified version of the receiver is presented where such assumption is not made. In addition to sequence detection and channel estimation, the EM iteration loop includes the estimation of unknown additive white Gaussian noise variance. Finally, different properties of the APP-EM iterative receiver are investigated including the effects of training sequence length on system performance, interleaver and channel correlation length effects and the performance of the system at different Rayleigh channel fading rates

Coherent and Non-coherent Techniques for Cooperative Communications

Future wireless network may consist of a cluster of low-complexity battery-powered nodes or mobile stations (MS). Information is propagated from one location in the network to another by cooperation and relaying. Due to the channel fading or node failure, one or more relaying links could become unreliable during multiple-hop relaying. Inspired by conventional multiple-input multiple-output (MIMO) techniques exploiting multiple co-located transmit antennas to introduce temporal and spatial diversity, the error performance and robustness against channel fading of a multiple-hop cooperative network could be significantly improved by creating a virtual antenna array (VAA) with various distributed MIMO techniques. In this thesis, we concentrate on the low-complexity distributed MIMO designed for both coherent and non-coherent diversity signal reception at the destination node. Further improvement on the network throughput as well as spectral efficiency could be achieved by extending the concept of unidirectional relaying to bidirectional cooperative communication. Physical-layer network coding (PLNC) assisted distributed space-time block coding (STBC) scheme as well as non-coherent PLNC aided distributed differential STBC system are proposed. It is confirmed by the theoretical analysis that both approaches have the potential for offering full spatial diversity gain. 　　 Furthermore, differential encoding and non-coherent detection techniques are generally associated with performance degradation due to the doubled noise variance. More importantly, conventional differential schemes suffer from the incapability of recovering the source information in time-varying channels owing to the assumption of static channel model used in the derivation of non-coherent detection algorithm. Several low-complexity solutions are proposed and studied in this thesis, which are able to compensate the performance loss caused by non-coherent detection and guarantee the reliable recovery of information in applications with high mobility. A substantial amount of iteration gain is achieved by combining the differential encoding with error-correction code and sufficient interleaving, which allows iterative possessing at the receiver

Improved Balanced 2n-PSK STTCs for Any Number of Transmit Antennas from a New and General Design Method

ISBN: 978-1-4244-2517-4International audienceRecently, it has been established that the best space- time trellis codes (STTCs) belong to a specific class of codes. The codes of this class are called "balanced STTCs" because they use the points of the MIMO constellation with the same probability. Therefore, the search of the best codes can be reduced to this class. This paper presents a new and general method to design 2n-PSK balanced STTCs for any number of transmit antennas. This method is simpler than the first method, which was described only for 4-PSK modulation and can be generalized for any configuration of the space-time trellis encoder. Simulation results of new 4-PSK and 8-PSK balanced codes prove the importance of this class

Building Space Time Block Codes with set partitioning for three transmit antennas: application to STTC Codes

Publication in the conference proceedings of EUSIPCO, Florence, Italy, 200

Error Performance Of Super-Orthogonal Space-Time Trellis Codes with Transmit Antenna Selection

Publication in the conference proceedings of EUSIPCO, Florence, Italy, 200

Space-time block coding with imperfect channel estimates

Space-time block coding (STBC) is a method that combines diversity and coding without a corresponding increase in bandwidth and with minimal complexity in the receiver. The performance of STBC with perfect channel state information (CSI) being available at the receiver has been shown to provide approximately 10 dB of improvement over uncoded transmission in Rayleigh fading when using Quadrature Phase Shift Keying (QPSK) at a bit error rate of 10 -3. In this thesis, the performance of space-time block codes is analyzed when the receiver must rely on noisy, or imperfect, estimates of the channel. It is shown that for a QPSK signal constellation the system is robust to errors introduced into the amplitude of the channel estimate, but exhibits extreme performance degradation with errors in the phase of the estimate. In fact, as phase error approaches 0.5 radians the performance breaks down completely. A pilot sequence estimation scheme will be shown that provides performance within 2 dB of the case of perfect CSI at half the data rate