低复杂度的满速率和部分分集多天线空时块码及性能

在现有几种满分集空时码的基础上,提出两种满速率和复正交的多天线空时块码方案。一种是基于时分双工(TDD)模式下最大信道增益而设计的;另一种则不再限于TDD方式,具有普遍适用性。同时利用Turbo码良好的抗衰落信道的突发错误能力,来进一步提高所提方案性能。与满分集多天线空时块码相比,该方案可实现满速率、低复杂度和部分分集,具有相对多的空间冗余信息,从而级联Turbo码后可有效弥补部分分集所带来的性能损失。仿真结果也表明在相同系统容量和级联码的情况下,所提方案比其它相应的满分集空时码有着更低的误比特率。     

一种满速率空时分组编码CDMA系统及多用户接收方案

通过引入满速率空时分组码方案, 该文给出一种满速率空时分组编码CDMA系统模型, 并针对现有空时编码CDMA系统过高的译码复杂度, 提出一种低复杂度的多用户接收方案。该方案在通过类似多用户检测方法有效抑制多用户干扰后, 充分利用空时分组码的复正交性来简化原有方案高译码复杂度。与原有指数性译码复杂度相比, 该方案有着线性复杂度, 而且与满分集空时分组编码CDMA系统相比, 可实现满速率、低复杂度和部分分集, 有着相对多的空间冗余信息, 从而级联信道编码后可有效弥补部分分集所带来的性能损失。仿真结果表明在相同系统容量和级联码的情况下, 所给系统比相应的满分集空时编码CDMA系统有着低的误比特率。     

Full-Rate Complex Orthogonal Space-Time Block Code for Multiple Antennas

In this paper, full-rate and complex orthogonal space-time block code (STBC) schemes for multiple antennas are proposed, and turbo code is employed as channel coding to improve the proposed STBC schemes performance further. Compared with full-diversity multiple antennas STBC schemes, the proposed schemes can implement full data rate, partial diversity and a smaller complexity. On the condition of the same system throughput and concatenation of turbo code, the proposed schemes have lower bit error rate (BER) than those low-rate and full-diversity code schemes.This work is supported by China Postdoctoral Science Foundation under grant No. 2005038242 and Chinese Jiangsu Planned Projects for Postdoctoral Research Funds. Xiangbin Yu received the M.S degrees in Communication and Information Systems from Hohai University, Nanjing, China, in 2001; and his Ph.D. in Communication and Information Systems in 2004 from National Mobile Communications Research Laboratory at Southeast University, China. Now he is working as a Postdoctoral Researcher in Information and Communication Engineering Postdoctoral Research Station at Nanjing University of Aeronautics and Astronautics, Nanjing, China. His research interests include multi-carrier digital communication, space-time coding, adaptive modulation and digital signal processing in communications. DaZhuan Xu received the M.S degrees and Ph.D. in Communication and Information Systems from Nanjing University of Aeronautics and Astronautics in 1986 and 2001, respectively. He is now a full professor in College of Information Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, China. Prof. Xu is a Senior Member of China Institute of Electronics (CIE). His research interests include digital communications, soft radio, coding theory, medical signal processing. Guangguo Bi was graduated from Nanjing Institute of Technology, Nanjing, China, in 1960. He is now a professor in the Department of Radio Engineering of Southeast University, Nanjing, China. Prof. Bi is a fellow and a member of the board of Director of the China Institute of Communications, and a senior member of IEEE. His research interests include digital communications, personal communications network, spread spectrum communications, and intelligent information processing. He has published more than 200 papers in above areas.     

High-Rate STBC Communication System Using Imperfect CSI Under Time-Selective Flat-Fading Environment

In this paper, a high-rate space-time block-coded (STBC) mobile communication system using imperfect channel-state-information (CSI) is presented, which is working over the time-selective flat-fading wireless channels. In the work, a flat-fading channel is modelled as a first-order Markov-process, taking into account Doppler shifts and carrier frequency offsets. The STBC data-rate 5/4 with two-transmitter antennas is attained by maximizing the coding gain and by minimizing the transmitted signal peak-to-minimum-power-ratio, while using the selective power scaling in combination with quadrature-phase-shift-keying digital modulation technique. The time-selective nature of underlying channel leads to reduction in the diversity gain, though optimum power scaling factor is incorporated. However, imperfect CSI usually arises due to the availability of noisy channel estimates at the receiver, which causes system performance degradation. Simulation results are presented to illustrate that the effective throughput in terms of frame-error-rate or symbol-error-rate of the presented data-rate \({5 \mathord{\left/ {\vphantom {5 4}} \right. \kern-0pt} 4}\) STBC system is adversely affected because of the noisy channel estimates. But, an efficient channel estimator helps in combating the time-selectivity of channel, and in turn results in effective throughput improvement under the high signal-to-noise-ratio (SNR) conditions only. Subsequently, the data-rate \({9 \mathord{\left/ {\vphantom {9 8}} \right. \kern-0pt} 8}\) STBC system with four-transmitter antennas is explored using similar strategy working over the time-nonselective (time-varying) flat-fading channels, which performs well under the high SNR and low channel estimation noise/error conditions.     

浅析频率选择性信道中的微分空时编码

本文介绍了两种空-时传输机制,通过在频率选择性衰落信道上使用两根传输天线,来得到全速率和全分集非相干性.第一种机制结合了频域的OFDM微分空-时分组编码;第二种机制采用微分反时空-时分组编码,这样可以保证在不需要当前过采样或多根接收天线的情况下保证盲信道估计.     

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.     

Differential space-time coding for frequency-selective channels

We introduce two space-time transmission schemes which allow full-rate and full-diversity noncoherent communications using two transmit antennas over fading frequency-selective channels. The first scheme operates in the frequency domain where it combines differential Alamouti (seeIEEE J. Select. Areas Commun., vol.16, p.1451-58, Nov. 1998) space-time block-coding (STBC) with OFDM. The second scheme operates in the time domain and employs differential time-reversal STBC to guarantee blind channel identifiability without the need for temporal oversampling or multiple receive antennas     

RS与STBC级联编码的可见光MIMO系统

针对采用空时分组编码(Space-Time Block Coding, STBC)的多输入多输出(Multiple-Input Multiple-Output, MIMO)可见光通信(Visible Light Communications, VLC)系统复杂度和天线数难以平衡的问题,为了在一定天线数的条件下获得更多的编码增益,结合正交设计的思路,设计了适合于多阵列协同信息传输的STBC编解码方案,并将RS(Reed-Solomon)码作为外码,STBC编码作为内码,设计了RS-STBC串行级联编码的VLC-MIMO通信系统。仿真和分析表明,该级联系统在天线数较小的条件下能够弥补STBC编码在编码增益上的损失,系统的误码率性能得到了进一步提升,且系统具有较高的可靠性。     

Space–Time Block Codes Achieving Full Diversity With Linear Receivers

In most of the existing space–time code designs, achieving full diversity is based on maximum-likelihood (ML) decoding at the receiver that is usually computationally expensive and may not have soft outputs. Recently, Zhang–Liu–Wong introduced Toeplitz codes and showed that Toeplitz codes achieve full diversity when a linear receiver, zero-forcing (ZF) or minimum mean square error (MMSE) receiver, is used. Motivated from Zhang–Liu–Wong's results on Toeplitz codes, in this paper, we propose a design criterion for space–time block codes (STBC), in which information symbols and their complex conjugates are linearly embedded, to achieve full diversity when ZF or MMSE receiver is used. The (complex) orthogonal STBC (OSTBC) satisfy the criterion as one may expect. We also show that the symbol rates of STBC under this criterion are upper bounded by 1. Subsequently, we propose a novel family of STBC that satisfy the criterion and thus achieve full diversity with ZF or MMSE receiver. Our newly proposed STBC are constructed by overlapping the $2,times,2$ Alamouti code and hence named overlapped Alamouti codes in this paper. The new codes are close to orthogonal and their symbol rates can approach 1 for any number of transmit antennas. Simulation results show that overlapped Alamouti codes significantly outperform Toeplitz codes for all numbers of transmit antennas and also outperform OSTBC when the number of transmit antennas is above $4$.      

Information-Lossless Space–Time Block Codes From Crossed-Product Algebras

It is known that the Alamouti code is the only complex orthogonal design (COD) which achieves capacity and that too for the case of two transmit and one receive antenna only. Damen proposed a design for two transmit antennas, which achieves capacity for any number of receive antennas, calling the resulting space-time block code (STBC) when used with a signal set an information-lossless STBC. In this paper, using crossed-product central simple algebras, we construct STBCs for arbitrary number of transmit antennas over an a priori specified signal set. Alamouti code and quasi-orthogonal designs are the simplest special cases of our constructions. We obtain a condition under which these STBCs from crossed-product algebras are information-lossless. We give some classes of crossed-product algebras, from which the STBCs obtained are information-lossless and also of full rank. We present some simulation results for two, three, and four transmit antennas to show that our STBCs perform better than some of the best known STBCs and also that these STBCs are approximately 1 dB away from the capacity of the channel with quadrature amplitude modulation (QAM) symbols as input     

Some Designs of Full Rate Space–Time Codes With Nonvanishing Determinant

In this correspondence, we first present a transformation technique to improve the normalized diversity product for a full rate algebraic space-time block code (STBC) by balancing the signal mean powers at different transmit antennas. After rewriting a cyclic division algebra structure into a multilayer structure for a full rate code, we show that the normalized diversity product of the transformed code with the multilayer structure is better than the one of the transformed code with the cyclic division algebra structure. We then present a new full rate algebraic STBC with multilayer structure with nonvanishing determinant (NVD) for three transmit antennas when signal constellation is carved from QAM. We show that the new code has larger normalized diversity product than the existing 3 times 3 NVD full rate STBC for quadrature amplitude modulation (QAM) signals, and we also show that it has the largest normalized diversity product in a family of full rate STBC.     

Full-diversity design criterion for multi-user STBC based on integer-forcing detection

Multi-user space time block code systems have the problem of high decoding complexity.To ensure good system performance with low decoding complexity at the same time,low complexity integer-forcing (IF) detection algorithm was applied to multi-user space time block code.Then the upper bound of error probability for IF detection was derived by minimizing the equivalent noise power.To obtain good multi-user space time block code when decoded with IF detection,a full-diversity design criterion was proposed.It was proved that full diversity could be achieved if every user’s space time block code had property of non-vanishing singular value.Simulation result shows that the code gain is found related to the minimum singular value.     

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.     

Improved error performance of a 3/4‐Sezginer space‐time block codes

The Alamouti space‐time block code (STBC) achieves full diversity gain at a rate of 1/2. However, the Alamouti scheme does not provide multiplexing gain. The Silver code offers both diversity and multiplexing gain. It has a minimum normalization determinant of . The Golden code is another STBC that offers both diversity and multiplexing gain. The Golden code is ranked higher than the Silver code because of its lower minimum normalization determinant of , however, the golden code suffers from a high detection complexity in the modulation order of M⁴. The 3/4‐Sezginer code is another STBC, which compromises between the Alamouti scheme and the Golden code in terms of diversity gain and multiplexing gain. The 3/4‐Sezginer code achieves full diversity and half of multiplexing gain. The uncoded space‐time labeling diversity (USTLD) is a recent scheme that improves the error performance when applied to the STBC in multiple‐input multiple‐output (MIMO) systems and will be applied to the 3/4‐Sezginer STBC to improve the error performance in this paper. The theoretical error probability for both the 3/4‐Sezginer STBC and the improved system is formulated using the union bound in this paper. The theoretical error probabilities of both 16‐QAM and 64‐QAM are validated through Monte Carlo simulation. The simulation and theoretical results show that the proposed system with 4 N_R can achieve an SNR gain of 1 dB for 16‐QAM and 1.2 dB 64‐QAM at a bit error rate (BER) of 10^?6.     

Linear Decoupled and Quasi-Decoupled Space–Time Codes

Space-time transmit diversity results in coupling of transmitted symbols across different antennas, which increases the complexity of maximum-likelihood decoding. Symbol coupling can be completely or partially avoided if the space-time code (STC) satisfies specific decoupling conditions; examples of such codes are orthogonal space-time block codes and quasi-orthogonal codes. In this letter, we study decoupling conditions for a linear full-diversity STC. Quasi-decoupled codes are proposed as a partially decoupled full-diversity STC of any rate for any number of transmit antennas with minimum decoding delay. By optimizing the coding gain of quasi-decoupled codes, it is shown that quasi-orthogonal codes have competitive performance with respect to the Alamouti code, and the more-recent threaded algebraic space-time (TAST) codes and ABBA codes. A general full-diversity decoupling condition is considered, and the general solution to this case, which also encompasses previously known orthogonal STCs, is derived     

基于协方差反馈的多天线系统优化发送研究

为了克服多天线信道相关性的影响，提出一种新的自适应发送方案。应用空时分组码特征波束成型技术和格形编码调制（TCM）来获得分集增益和编码增益。针对采用和不采用交织器两种情况，基于成对差错概率（PEP）准则。分析了系统的统计性能，分别得到了使系统编码增益和分集增益最大化的TCM设计准则。根据注水法则和Lagrange乘子法求得波束间功率分配算法最优解。此外，码距作为优化功率加载算法中的权重因子，有效降低了获取波束成形分集的信噪比门限。分析和实验结果表明此方案复杂度低。能有效克服相关衰落。     

MIMO GS OVSF/OFDM Based Underwater Acoustic Multimedia Communication Scheme

An underwater acoustic multimedia communication (UWAMC) system is proposed with 2400 transmission modes according to time-varying multipath underwater acoustic (UWA) channel conditions. The orthogonal variable spreading factor (OVSF) scheme and Gold sequence (GS) scramble code are integrated into multi-input multi-output UWAMC system based on orthogonal frequency-division multiplexing to achieve the quality of service of multimedia transmission in the UWA channel. Binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) adaptive modulation, direct mapping (DM) or space–time block code (STBC) transmission strategies, convolution channel code with rate 1/2 and 1/3, and a power assignment mechanism were adopted in the proposed system. Simulation results show that the bit error rate (BER) and power saving ratio (PSR) performance of the STBC strategy with transmission diversity is superior to that of the DM strategy without transmission diversity, and the performance of the BERs and PSRs of the transmission scheme with the GS scramble code surpasses that of the scheme without the code. The performance of the BERs and PSRs of BPSK modulation with a channel code rate of 1/3 is better than that of BPSK modulation with a channel code rate of 1/2, and the performances of BERs and PSRs of BPSK modulation with a channel code rate of 1/3 are better than that of QPSK modulation with a channel code rate of 1/3. As the length of the OVSF codes increases, the UWAMC system’s BERs decrease, and its PSRs increase. The UWAMC system can achieve either maximum transmission speed or maximum transmission power efficiency.     

Unit-rate complex orthogonal space-time block code concatenated with turbo coding

Space-Time Block （STB） code has been an effective transmit diversity technique for combating fading due to its orthogonal design, simple decoding and high diversity gains. In this paper, a unit-rate complex orthogonal STB code for multiple antennas in Time Division Duplex （TDD） mode is proposed. Meanwhile, Turbo Coding （TC） is employed to improve the performance of proposed STB code further by utilizing its good ability to combat the burst error of fading channel. Compared with full-diversity multiple antennas STB codes, the proposed code can implement unit rate and partial diversity; and it has much smaller computational complexity under the same system throughput. Moreover, the application of TC can effectively make up for the performance loss due to partial diversity. Simulation results show that on the condition of same system throughput and concatenation of TC, the proposed code has lower Bit Error Rate （BER） than those full-diversity codes.     

空间相关信道下分布式MIMO系统中的STBC-VBLAST组合方案

在空间相关信道下分布式多输入多输出(D-MIMO)系统中,提出了一种新的空时分组编码(STBC)和垂直分层空时编码(VBLAST)组合方案.为充分利用D-MIMO系统的拓扑结构和空间相关信道的特性,在下行D-MI-MO系统的每个分布式天线(DA)簇内采用STBC,而在不同DA簇之间采用VBLAST.同时,为了降低系统复杂度并节省总发射功率,采用了基于最小传播路径衰落准则的天线选择方案.仿真结果证明,对比于传统VBLAST方式,所提出的STBC-VBLAST组合方案能显著降低系统误比特率(BER)并提高空间相关信道下BER性能的鲁棒性.因此,该组合方案是实现空间相关信道下D-MIMO系统下行分集与复用的折衷的一种有效方案.     

A 20-Gb/s CMOS multichannel transmitter and receiver chip set forultra-high-resolution digital displays

A multichannel transmitter (TX) and receiver (RX) chip set operating at 20 Gb/s (5 Gb/s×4 ch) has been developed by using 0.25-μm CMOS technology. To achieve multichannel data transmission and high-speed operation, the chip set features: (1) circuits for compensating the phase difference between multiple RX chips, which is due to data skew resulting from different lengths of transmission cables, and for compensating the frequency difference between the system clocks of the TX and RX chips; (2) a self-alignment phase detector with parallel output for a high-speed data-recovery circuit; and (3) a fully pipelined 8B10B encoder. At a 2.5-V power supply, the power consumption of the TX chip during 5-Gb/s operation is 500 mW and that of the RX chip is 750 mW. Four of these TX/RX chip sets can provide an aggregate bandwidth of 20 Gb/s