A new full-rate full-diversity orthogonal space-time block coding scheme

In this work, we present a new space-time orthogonal coding scheme with full-rate and full-diversity. The proposed space-time coding scheme can be used on quaternary phase-shift keyed (QPSK) transceiver systems with four transmit antennas and any number of receivers. An additional feature is that the coded signals transmitted through all four transmit antennas do not experience any constellation expansion. The performance of the proposed coding scheme is studied in comparison with that of 1/2-rate full-diversity orthogonal space-time code, quasi-orthogonal code, as well as constellation-rotated quasi-orthogonal code. Our study shows that the proposed coding scheme offers full rate and outperforms the 1/2-rate orthogonal codes as well as full-rate quasi-orthogonal codes when the signal-to-noise increases. Compared to the constellation-rotated quasi-orthogonal codes (the improved QO scheme), the newly proposed code has the advantage of not expanding the signal constellation at each transmit antenna. The performance of the newly proposed code is comparable to that of the improved QO scheme.     

A Kind of Quasi-Orthogonal Space-Time Block Codes and its Decoding Methods

1IntroductionSpace-Ti me Coding(STC)technology has been stud-ied extensively in recent years as a method to combatdetri mental effects in wireless fading channel and in-crease the transmission capacity in an open-loop way.Therein,a special class of space-…     

A Kind of Quasi-Orthogonal Space-Time Block Code and its Decoding Methods

It is well known that it is impossible for complex orthogonal space-time block codes with full diversity and full rate to have more than two transmit antennas while non-orthogonal designs will lose the simplicity of maximum likelihood decoding at receivers. In this paper, we propose a new quasi-orthogonal space-time block code. The code is quasi-orthogonal and can reduce the decoding complexity significantly by employing zero-forced and minimum mean squared error criteria. This paper also presents simulation results of two examples with three and four transmit antennas respectively.     

Robust full-diversity full-rate quasi-orthogonal STBC for four transmit antennas

A novel quasi-orthogonal space-time block code (QSTBC) with full-diversity full-rate transmission and double-symbol decoding is proposed for a system with four transmit antennas, which is constructed by linearly combining two optimally power-scaled component Alamouti codes. Compared with the existing QSTBC with optimal constellation rotation, the proposed code provides excellent robustness, in terms of bit error rate performance, against spatially correlated and/or time-selective fading channels.     

Novel full-diversity high-rate STBC for 2 and 4 transmit antennas

We design a new rate-5/4 full-diversity orthogonal space-time block code (STBC) for QPSK and 2 transmit antennas (TX) by enlarging the signalling set from the set of quaternions used in the Alamouti code. Selective power scaling of information symbols is used to guarantee full-diversity while maximizing the coding gain (CG) and minimizing the transmitted signal peak-to-minimum power ratio (PMPR). The optimum power scaling factor is derived analytically and shown to outperform schemes based only on constellation rotation while still enjoying a low-complexity maximum likelihood (ML) decoding algorithm. Finally, we extend our designs to the case of 4 TX by enlarging the set of quasi-orthogonal STBC with power scaling. Extensions to general M-PSK constellations are straightforward.     

Full-rate full-diversity space-time code for four-transmit-antenna systems

This paper introduces a low-complexity full-rate full-diversity space-time (ST) code for wireless communication systems with four transmit antennas. This novel code is designed by combining delay-diversity transmission with Alamouti's orthogonal ST block code. Analytical and computer simulation results show that this code yields significant frame-error-rate (FER) performance gains over some previously reported full-rate full-diversity codes for four transmit antennas.     

一种新的准正交空时分组码的设计

根据正交设计理论,当发送天线数大于2时,不存在可以获得完全分集增益和全速率的复正交空时分组码.对空时分组码采用准正交设计,能够保证数据以全速率传输,但是会使其误码性能降低.文章在对准正交空时分组码(QOSTBC)结构研究的基础上,提出了一种全速率的四发射天线准正交空时分组码,并给出了基于最大似然译码方法.仿真结果表明,文章方案与已有典型的Jafarkhani准正交空时分组码相比,在高信噪比时有更好的误码性能.     

Using Orthogonal and Quasi-Orthogonal Designs in Wireless Relay Networks

Distributed space-time coding was proposed to achieve cooperative diversity in wireless relay networks without channel information at the relays. Using this scheme, antennas of the distributive relays work as transmit antennas of the sender and generate a space-time code at the receiver. It achieves the maximal diversity when the transmit power is infinitely large. This paper is on the design of practical distributed space-time codes (DSTCs). We use orthogonal and quasi-orthogonal designs which are originally used in the design of space-time codes for multiple-antenna systems. It is well known that orthogonal space-time codes have full diversity and linear decoding complexity. They are particularly suitable for transmissions in the network setting using distributed space-time coding since their ldquoscale-freerdquo property leads to good performance. Our simulations show that they achieve lower error rates than the random code. We also compare distributed space-time coding to selection decode-and-forward using the same orthogonal designs. Simulations show that distributed space-time coding achieves higher diversity than selection decode-and-forward (DF) when there is more than one relay. We also generalize the distributed space-time coding scheme to wireless relay networks with channel information at the relays. Although our analysis and simulations show that there is no improvement in the diversity, in some networks, having channel information at the relays saves both the transmission power and the transmission time.     

Efficiently decoded full-rate space-time block codes

Space-time block codes with orthogonal structures typically provide full-diversity reception and simple receiver processing. However, rate-1 orthogonal codes for complex constellations have not been found for more than two transmit antennas. By using a genetic algorithm, rate-1 space-time block codes that accommodate very simple receiver processing at the cost of reduced diversity are designed in this paper for more than two transmit antennas. Simulation results show that evolved codes combined with efficient outer codes provide better performance over fading channels than minimum-decoding-complexity quasiorthogonal codes at typical operating signal-to-noise ratios. When the fading is more severe than Rayleigh fading, the spectral efficiency is specified, and an efficient outer code is used, evolved codes outperform orthogonal space-time block codes.     

Quasi-orthogonal STBC with minimum decoding complexity

In this paper, we consider a quasi-orthogonal (QO) space-time block code (STBC) with minimum decoding complexity (MDC-QO-STBC). We formulate its algebraic structure and propose a systematic method for its construction. We show that a maximum-likelihood (ML) decoder for this MDC-QO-STBC, for any number of transmit antennas, only requires the joint detection of two real symbols. Assuming the use of a square or rectangular quadratic-amplitude modulation (QAM) or multiple phase-shift keying (MPSK) modulation for this MDC-QO-STBC, we also obtain the optimum constellation rotation angle, in order to achieve full diversity and optimum coding gain. We show that the maximum achievable code rate of these MDC-QO-STBC is 1 for three and four antennas and 3/4 for five to eight antennas. We also show that the proposed MDC-QO-STBC has several desirable properties, such as a more even power distribution among antennas and better scalability in adjusting the number of transmit antennas, compared with the coordinate interleaved orthogonal design (CIOD) and asymmetric CIOD (ACIOD) codes. For the case of an odd number of transmit antennas, MDC-QO-STBC also has better decoding performance than CIOD.     

Extending orthogonal block codes with partial feedback

During the last few years a number of space-time block codes have been proposed for use in multiple transmit antennas systems. We propose a method to extend any space-time code constructed for m transmit antennas to m p transmit antennas through group-coherent codes (GCCs). GCCs make use of very limited feedback from the receiver (as low as 1 bit). In particular the scheme can be used to extend any orthogonal code (e.g., Alamouti code) to more than two antennas while preserving low decoding complexity, full diversity benefits, and full data rate.     

空时分组码在CDMA下行链路应用的研究

提出了准正交空时分组码在CDMA系统下行链路的两种应用方法，一种是在发射端对用户信号先扩频后空时编码送至发射天线，另一种是先空时编码后扩频送至发射天线，相应给出了两种方法接收端的译码方法。数据仿真结果表明在CDMA系统下行链路的应用时，准正交空时分组码的误码率低于正交空时分组码的误码率，并且第一种方法的误码率低于第二种方法的误码率。     

Space-time block coding for wireless communications: performanceresults

We document the performance of space-time block codes, which provide a new paradigm for transmission over Rayleigh fading channels using multiple transmit antennas. Data is encoded using a space-time block code, and the encoded data is split into n streams which are simultaneously transmitted using n transmit antennas. The received signal at each receive antenna is a linear superposition of the n transmitted signals perturbed by noise. Maximum likelihood decoding is achieved in a simple way through decoupling of the signals transmitted from different antennas rather than joint detection. This uses the orthogonal structure of the space-time block code and gives a maximum likelihood decoding algorithm which is based only on linear processing at the receiver. We review the encoding and decoding algorithms for various codes and provide simulation results demonstrating their performance. It is shown that using multiple transmit antennas and space-time block coding provides remarkable performance at the expense of almost no extra processing     

On channel orthogonalization using space-time block coding with partial feedback

Orthogonal space-time block codes (OSTBCs) yield full diversity gain even while requiring only a linear receiver. Such full-rate (rate-one) orthogonal designs are available for complex symbol constellations only for N=2 transmit antennas. In this paper, we propose a new family of full-rate space-time block codes (STBCs) using a single parameter feedback for communication over Rayleigh fading channels for N=3,4 transmit antennas and M receive antennas. The proposed rate-one codes achieve full diversity, and the performance is similar to maximum receiver ratio combining. The decoding complexity of these codes are only linear even while performing maximum-likelihood decoding. The partial channel information is a real phase parameter that is a function of all the channel gains, and has a simple closed-form expression for N=3,4. This feedback information enables us to derive (channel) orthogonal designs starting from quasi-orthogonal STBCs. The feedback complexity is significantly lower than conventional closed-loop transmit beamforming. We compare the proposed codes with the open-loop OSTBCs and also with the closed-loop equal gain transmission (EGT) scheme which uses equal power loading on all antennas. Simulated error-rate performances indicate that the proposed channel orthogonalized STBCs significantly outperform the open-loop orthogonal designs, for the same spectral efficiency. Moreover, even with significantly lower feedback and computational complexity, the proposed scheme outperforms the EGT technique for M>N.     

Space-Time Trellis Code Design Based on Super Quasi-Orthogonal Block Codes With Minimum Decoding Complexity

In this letter, we propose a new family of space-time trellis codes, which are constructed by combining a super set of quasi-orthogonal space-time block codes with minimum decoding complexity with an outer multiple trellis coded modulation encoder. A systematic set-partitioning method for quadratic amplitude modulation constellations is given. The proposed scheme can be used for systems with four or more than four transmit antennas. Furthermore, its decoding complexity is low because its branch metric calculation can be implemented in a symbolwise way. Simulation results demonstrate that the proposed scheme has a comparable performance as super quasi-orthogonal space-time trellis codes proposed by Jafarkhani and Hassanpour while providing a lower decoding complexity.     

基于Grassmann流形的非相干空时码设计

本文研究在Grassmann流形上构造非相干酉空时码的代数方法.首先提出一类发射天线数和相干时间都为任意大小的满速率满分集相干空时码,然后采用非线性指数映射方式,将该相干空时码映射到Grassmann流形上,生成Grassmann非相干酉空时码.新构造的Grassmann酉空时码比其它相同发射天线的酉空时码具有更高的频...     

Space-time block codes based on coordinate symmetric orthogonal designs

Space-time block codes based on coordinate symmetric orthogonal designs are proposed. Compared with space-time block codes from complex orthogonal design when the code rate is the same and the transmission rate is fixed, space-time block codes from coordinate symmetric orthogonal design with more transmit antennas can reduce the bit error rate and symbol error rate. Also these new codes have the same low decoding complexity as space-time block codes from complex orthogonal designs.     

Single-block coded modulation for MINO systems

This paper introduces a new class of space-time codes that achieve coding gain without a trellis or any form of inter-block dependency. The construction of the new codes starts from an existing (parent) space-time block code (STBC). Then by increasing the constellation size followed by expurgation of the expanded codebook, a better code is obtained at the original transmission rate. This method can be applied to a wide variety of space-time block codes, including orthogonal codes and quasi-orthogonal codes. A multi-stage design algorithm is presented, and for orthogonal parent codes, an efficient decoding algorithm is developed, and its decoding complexity is analyzed. Despite altering the regular structure of the orthogonal code, the decoding complexity is only affected by a constant factor.     

全速率满分集准正交空时分组码的设计

在未来的第四代移动通信中,基于多输入多输出（MIMO）天线系统的空时编码技术是改善无线通信性能,提高带限系统数据传输速率的一种理想选择,但由于正交空时分组编码不能保证满分集和数据全速率传输,提出了一种利用星座图旋转可获得全速率满分集传输的旋转准正交空时分组码的设计方法。仿真结果表明,这种方法在不增加译码复杂度的情况下,其误比特率无论在低信噪比还是在高信噪比条件下都要优于已有的准正交空时分组码。     

Single-symbol maximum likelihood decodable linear STBCs

Space-time block codes (STBCs) from orthogonal designs (ODs) and coordinate interleaved orthogonal designs (CIOD) 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, these codes are instances of single-symbol decodable codes and it is natural to ask, if there exist codes other than STBCs form ODs and CIODs that allow single-symbol decoding? In this paper, the above question is answered in the affirmative by characterizing all linear STBCs, that allow single-symbol ML decoding (not necessarily full-diversity) over quasi-static fading channels-calling them single-symbol decodable designs (SDD). The class SDD includes ODs and CIODs as proper subclasses. Further, among the SDD, a class of those that offer full-diversity, called Full-rank SDD (FSDD) are characterized and classified. We then concentrate on square designs and derive the maximal rate for square FSDDs using a constructional proof. It follows that 1) except for N=2, square complex ODs are not maximal rate and 2) a rate one square FSDD exist only for two and four transmit antennas. For nonsquare designs, generalized coordinate-interleaved orthogonal designs (a superset of CIODs) are presented and analyzed. Finally, for rapid-fading channels an equivalent matrix channel representation is developed, which allows the results of quasi-static fading channels to be applied to rapid-fading channels. Using this representation we show that for rapid-fading channels the rate of single-symbol decodable STBCs are independent of the number of transmit antennas and inversely proportional to the block-length of the code. Significantly, the CIOD for two transmit antennas is the only STBC that is single-symbol decodable over both quasi-static and rapid-fading channels.