CONSTRUCTIONS OF UNITARY SPACE-TIME CODES WITH FULL DIVERSITY

The problem of constructing unitary space-time codes with high diversity product has been studied in many prior works.Recently,constructions of parametric fully diverse unitary space-time codes for prime number antennas system have been introduced.In this paper,the authors propose new construction methods based on these constructions.And fully diverse codes of any number antennas are obtained from these constructions.Unitary space-time codes from present constructions are found to have better error performance than many best known ones.

A novel rate-2 full diversity algebraic space-time code

Orthogonal space-time block codes(OSTBCs)have attracted considerable attention due to their low complexity linear decoding and full diversity in Rayleigh fading channels.However,OSTBCs exist only for certain numbers of transmit antennas and do not provide full code rate when more than two transmit antennas are used.In this paper,a novel rate-2 algebraic space-time code that combines coordinate-interleaving and group precoding is proposed.By properly choosing the designed parameters,the coding scheme can achieve full diversity order and high coding gain.The receiver adopts polynomial complexity sphere decoding algorithm to get maximum likelihood(ML)performance.Analysis and simulations illustrate that the new code exhibits significant performance gain over the conventional OSTBCs and diagonal algebraic space-time code.

A Method for Improving Power Distribution Characteristics of Space Time Block Codes

Improving power distribution characteristics of space time block codes(STBCs),namely peak to average power ratio(PAPR),average to minimum power ratio(Ave/min),and probability of transmitting"zero"by antenna,makes easier their practical implementation.To this end,this study proposes to multiply full diversity STB C with a non-singular matrix in multiple input multiple output(MIMO)or multiple input single output(MISO)systems with linear or maximum likelihood(ML)receivers.It is proved that the obtained code achieves full diversity and the order of detection complexity does not change.The proposed method is applied to different types of STBCs.The bit error rate(BER)and power distribution characteristics of the new codes demonstrate the superiority of the introduced method.Further,lower and upper bounds on the BER of the obtained STBCs are derived for all receivers.The proposed method provides trade-off among PAPR,spectral efficiency,energy efficiency,and BER.

An Improved Group Space-Time Block Code Through Constellation Rotation

A new improved group space-time block code (G-STBC) based on constellation rotation for four transmit antennas was proposed. In comparison with the traditional G-STBC coding scheme, the proposed space-time code has longer code length and adopts proper rotation-based symbols, which can increase the minimum distance of space-time codes and thereby improve code gain and achieve full diversity performance. The simulation results verify that the proposed group space-time code can achieve better bit error performance than both the traditional group space-time code and other quasi-orthogonal space-time codes. Compared with Ma’s full diversity full rate (FDFR) codes, the proposed space-time code also can achieve the same excellent error performance. Furthermore, the design of the new space-time code gives another new and simple method to construct space-time codes with full diversity and high rate in case that it is not easy to design the traditional FDFR space-time codes.

Performance of multiuser CDMA system with space-time block coding in MIMO Rayleigh fading channels

In this paper, by introducing orthogonal space-time coding scheme, the multiuser CDMA systems with different space time codes are given, and corresponding system performance is investigated over Rayleigh fading channel. A low-complexity multiuser receiver scheme is developed for space-time coded CDMA systems. The scheme can make full use of the complex orthogonality of space-time coding to simplify the high decoding complexity of the existing scheme. Compared to the existing scheme with exponential decoding complexity, it has linear decoding complexity. Based on the performance analysis and mathematical calculation, average bit error rate （BER） of the system is derived in detail, and tight closed-form approximation expressions of BER are attained. Simulation results on average BER are in agreement with the theory analysis. The results show that the proposed scheme can achieve almost the same performance as the existing scheme. Moreover, on the condition of same system throughput and concatenation of channel code, the given full-rate space-time coded CDMA system has lower BER than the full-diversity space-time coded CDMA systems.

New design of single-symbol decodable STBCs for MIMO communication system

Single-symbol maximum-likelihood （ML） decodable space-time block codes （SSDCs） can achieve a maximal symbol rate of 6/7 for multiple-input multiple-output （MIMO） communication system with five or six transmit antennas by using rate-efficient generalized coordinate interleaved orthogonal designs （RE-GCIODs）. Unfortunately, there are many zero entries in the eodeword matrix of RE-GCIODs. The zero entries result in high peak-to-average power ratio （PAPR） and also impose a severe constraint on hardware implementation. In this paper, for MIMO communication systems with five or six transmit antennas and one receive antenna, a new SSDC is proposed. By combining Alamouti code and orthogonal space-time block code （OSTBC）, desirable properties like RE-GCIODs can be achieved and are derived, including maximal symbol rate up to 6/7, full diversity and single-symbol ML decodability. Moreover, by reducing the number of zero entries in the codeword matrix, the peak-to-average power ratio （PAPR） of our proposed code is lower than RE-GCIODs. Simulation results show that the proposed codes outperform RE-GCIODs under peak power constraint while performing almost same under average power constraint.

New design of no-zero-entry single symbol ML decodable STBCs based on group precoding

In multiple-input multiple-output （MIMO） systems, space-time block codes （STBCs） from orthogonal designs （ODs） and coordinate interleaved orthogonal designs （CLOD） have been attracting wider attention due to their amenability for fast （single symbol） maximum-likelihood （ML） decoding, and full-rate with full-rank over quasi-static fading channels. However, most of these codes, for transmitting antennas more than 4, have large number of zero entries in their codeword matrix. Due to the zero entries in the design, the transmitting antennas need to be switched on and off imposing severe hardware constraints. To solve this problem, we propose a method to generate a new class of no-zero-entry single symbol maximum likelihood decodable STBCs （NZESSDCs）, which is based on coordinate interleaving and group precoding technique. The ability of the proposed group precoding based NZESSDCs （called G-NZESSDCs） on single symbol ML Decoding and full diversity are analyzed and derived. The performance evaluation is accomplished by numerical simulation and is compared with recently reported NZESSDCs （called C-NZESSDCs）. Compared with C-NZESSDCs, the proposed G-NZESSDCs have same bit-error-rate （BER） performance and better peak-to-average ratio （PAPR） performance.