一种基于矩阵旋转的正交空时分组码

Tarokh等人(1999)运用正交设计理论证明了当发射天线数大于2时,不存在可以获得最大分集增益和最大传输速率的复正交空时分组码。而以牺牲正交性和部分分集增益为代价来获得更高传输速率的非正交空时分组码又会使误码性能降低。该文通过对非正交空时分组码信道相关矩阵采用矩阵旋转的方法,提出了一种可以获得最大传输速率、部分分集增益以及接收端线性解码的正交空时分组码。仿真结果表明,该方案与已有典型的空时分组码相比,具有较好的误码性能。     

无线通信中的空时分组码

空时分组码技术结合信道编码、调制和天线分集技术,当发送天线一定时,他的解码复杂度正比于发送速率,在3G标准中,该技术有着重要的地位。对空时分组码及相关知识进行了介绍,并对可变速率的空时分组码设计进行了探讨,最后展望了空时分组码技术的应用前景。     

MIMO系统中的空时分组码(STBC)的性能分析

通过对MIMO系统的信道模型和分集技术的分析,详细讨论了基于发送分集的空时分组码(STBC,Space-time block coding).对STBC的编码、译码以及传输性能进行了详细的研究;并对它在RayMgh衰落信道上的性能进行了仿真分析.     

一种新的MIMO无线通信空时分组码方案

从MIMO(多入多出)引出空时分组码背景;针对实际MIMO应用提出了一种利用广义复正交方法新设计的满分集的码率为1/2的6个发射天线4个接收天线(6×4)和8个发射天线4个接收天线(8×4)结构的空时分组码系统,仿真结果表明该系统具有良好性能。     

无线通信中的空时编码

空时编码是最近提出的使用多个天线应用于瑞利衰落信道的编码技术。结合分集技术对空时编码进行了综述,包括系统模型、编译码方法、设计准则,在此基础上介绍了空时编码与外码的级联。     

最优天线选择空时分组码的性能分析

空时分组码(Spce—Time Block Coding)是目前研究发送分集(Transmit Diversity)技术的一个热点。针对TD—SCDMA系统的MIMO(Multiple-Input Multiple-Output)信道，将天线子集选择技术与空时分组码(Spce—Time Block Coding)相结合，进一步提升了发送分集的误码率性能。通过理论分析对此方案的进行了性能评估，表明天线选择技术对空时分组码(STBC)的性能有较大的改善。     

正交空时分组码在瑞利衰落信道中的性能估计

根据Alamouti最大似然译码方法，给出了在正交空时分组码传输的衰落信道条件下接收机输出瞬时信噪比的一般表达式，分析了瑞利衰落信道条件下引入正交空时分组码的多天线系统的符号差错性能，研究表明采用正交空时码传输信号，增加发送天线数量和接收天线数量都可以得到更大的分集增益；在接受天线数量一定的情况下，增加发送天线的数量可以带来更大的分集增益，但当发送天线数量增加到一定程度后，再增加发送天线数量就不能带来明显的分集改善了。     

Rician衰落信道下空时分组码的性能分析

基于Alamouti提出的BPSK调制下空时分组码在Rayleigh衰落信道中的码性能原理,推导出高阶(M ary)调制下Rician衰落信道中空时分组码的符号差错率的最小距离球界,并进行计算机仿真分析了两信道下引入空时分组码的多天线系统中发射和接收天线的分集增益,发射天线数量的“地板效应”以及Rician因子K对符号差错性能的影响。     

一种新颖而简单的空时分组码设计方法

引入了准正交方阵嵌入码的概念,提出了一种新颖而简单的方阵嵌入空时分组码的设计方法。在生成同样性能码矩阵的情况下,本文提出的构造公式与已有设计方法相比要简单得多。文章还给出了准正交方阵嵌入码的特性,并结合仿真结果对其性能进行了分析。     

莱斯衰落信道中的正交空时分组码的性能分析

在得到莱斯衰落下正交空时分组码接收信噪比的基础上,分析了在莱斯衰落信道条件下引入正交空时分组码的多天线系统的符号差错性能。理论分析及仿真结果表明在接收天线数量一定的情况下,增加发送天线的数量可以带来更大的分集增益,莱斯系数均值对系统的影响是一致的。     

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     

Extended balanced space-time block coding for wireless communications

Diversity techniques are very effective tools to increase signal reception quality in Rayleigh fading channels. A well-known method to increase diversity in multi-input multi-output (MIMO) communication is transmit antenna selection (TAS). However, TAS is very sensitive to feedback errors. One of the alternative techniques to TAS is balanced space-time block coding (BSTBC) which guarantees full diversity for any number of transmit antennas, provided that few bits of feedback from the destination to the source are available. The main drawback of the BSTBC is limited coding gain since few numbers of code matrices can be generated in the originally proposed scheme. In this work, the authors extend the balanced space-time block code family to improve its coding performance. In our proposed scheme, larger number of codes can be generated for improved coding gain. The performance of the proposed scheme is investigated for both multi-input singleoutput (MISO) and cooperative communication cases. Relay selection (RS) algorithm - the TAS equivalent in the cooperative communications - is also considered. Simulation results show that near optimal (infinite feedback) performance can be achieved with four bit extension of the BSTBC and better signal-to-noise ratio can be obtained compared to TAS or RS schemes. The difference in performance becomes more prevalent in the presence of feedback errors.     

Space-time processing for wireless communications

Space-time processing can improve network capacity, coverage, and quality by reducing co-channel interference (CCI) while enhancing diversity and array gain. This article focuses largely on the receive (mobile-to-base station) time-division multiple access (TDMA) (nonspread modulation) application for high-mobility networks. We describe a large (macro) cell propagation channel and discuss different physical effects such as path loss, fading delay spread, angle spread, and Doppler spread. We also develop a signal model incorporating channel effects. Both forward-link (transmit) and reverse-link (receive) channels are considered and the relationship between the two is discussed. Single- and multiuser models are treated for four important space-time processing problems, and the underlying spatial and temporal structure are discussed as are different algorithmic approaches to reverse link space-time professing with blind and nonblind methods for single- and multiple-user cases. We cover forward-link space-time algorithms and we outline methods for estimation of multipath parameters. We also discuss applications of space-time processing to CDMA, applications of space-time techniques to current cellular systems, and industry trends     

Space-time block coding for single-carrier block transmission DS-CDMA downlink

The combination of space-time block coding (STBC) and direct-sequence code-division multiple access (DS-CDMA) has the potential to increase the performance of multiple users in a cellular network. However, if not carefully designed, the resulting transmission scheme suffers from increased multiuser interference (MUI), which dramatically deteriorates the performance. To tackle this MUI problem in the downlink, we combine two specific DS-CDMA and STBC techniques, namely single-carrier block transmission (SCBT) DS-CDMA and time-reversal STBC. The resulting transmission scheme allows for deterministic maximum-likelihood (ML) user separation through low-complexity code-matched filtering, as well as deterministic ML transmit stream separation through linear processing. Moreover, it can achieve maximum diversity gains of N/sub T/N/sub R/(L+1) for every user in the system, irrespective of the system load, where N/sub T/ is the number of transmit antennas, N/sub R/ the number of receive antennas, and L the order of the underlying multipath channels. In addition, it turns out that a low-complexity linear receiver based on frequency-domain equalization comes close to extracting the full diversity in reduced, as well as full load settings. In this perspective, we also develop two (recursive) least squares methods for direct equalizer design. Simulation results demonstrate the outstanding performance of the proposed transceiver compared to competing alternatives.     

Improved space-time coding for MIMO-OFDM wireless communications

Improved space-time coding for multiple-input multiple-output orthogonal frequency division multiplexing is studied for wireless systems using QPSK modulation for four transmit and four receive antennas. A 256-state code is shown to perform within 3 dB of outage capacity (and within 2 dB with perfect channel estimation), which is better than any other published result without using iterative decoding     

Space-time coding in mobile Satellite communications using dual-polarized channels

The use of dual-orthogonal polarization (horizontal/vertical or circular right-hand/left-hand polarizations) can increase the rate of transmission of satellite communication systems by a factor of two. However, the cross polar discriminations (XPDs) of the satellite and earth station antennas may be large enough to severely interfere between the two polarizations. In this paper, we investigate the use of space-time coding techniques in satellite-land mobile systems using dual-polarized transmit and receive antennas. In particular, we show that we can achieve significant gains by using layered space-time coding concepts and iterative detection and decoding receivers in communications systems employing polarization diversity channels in the presence of line-of-sight components.     

IrLAP protocol performance analysis of IrDA wireless communications

The IRDA IrLAP protocol is analytically modelled. Throughput performance is examined with bit error rate, window size, and turnaround times. It is shown that for the proposed 16 Mbit/s and 127 frame maximum window size extension the link BER quality becomes critical if maximum throughput is to be achieved. A window size of 60 is less sensitive to bit error rate variations. Reducing the minimum turnaround time is always beneficial     

Relaying methods with high coding rate for wireless communications

A cooperative wireless relaying communication system usually consists of a source node, a destination node and one or more relay nodes. In this work Amplify-and-Forward/Decode-and-Forward relaying techniques are discussed in order to improve the performance of a wireless relaying communication system under the case of high code rate. As a performance metric, the outage probability of the proposed Amplify- and-Forward/Decode-and-Forward relaying structure is compared with and without coding issue. Results from the proposed modeling and simulations illustrate that our Amplify-and-Forward/Decode-and-Forward relaying method with high code rating enables robust cooperative wireless communication.     

A new MAC protocol for broadband wireless communications and its performance evaluation

This paper presents a new Time Division Multiple Access/Frequency Division Duplexing (TDMA/FDD) based Medium Access Control (MAC) protocol for broadband wireless networks, supporting Quality of Service (QoS) for real-time multimedia applications. It also gives the Call Blocking Probability (CBP), packet end-to-end delay and utilization analysis of different service classes, as they are most essential performance criterions in broadband wireless network assessment. The Connection Admission Control (CAC) mechanism in the proposed MAC efficiently organizes the bandwidth allocation for different service classes by means of a fairness based scheduling algorithm. In addition, the simulation model of the proposed MAC scheme is realized by using OPNET Modeler network simulator. The results of the analytical calculations for the CBPs are compared to those of the simulation of the proposed MAC, thus validity of the MAC protocol is proved.