并行分离的高速空时分组码设计方法

为了提高空时分组码的编码速率,文中提出了一种基于发射端编码符号混淆、接收端多天线并行分离的高速空时分组码的设计方法.该方法可以提供很高的编码速率,适用于任意数量的发射天线.仿真分析结果表明文中提出的方法在相同有效吞吐容量下比1/2编码速率的空时分组码有6dB的性能增益.     

OFDM中结合延迟分集与空频编码的下行发射方案

正交空时／空频编码只有在发射天线数为2时才能进行满速率发射。当天线数大于2时,将循环延迟分集和空时编码相结合可在保持满速率发射的同时提高系统的性能,但是循环延迟分集和空频编码相结合却不能较好地提高系统性能。为此本文对循环延迟分集进行改进,将其和空频编码相结合在满速率发射的前提下仍能提高系统的频率分集增益。仿真结果表明,发射天线数大于2时,该方法提高了系统的分集增益,同时降低了误码率。     

MIMO CDMA系统中一种新的循环空时分组编译码方法

该文提出了MIMO CDMA系统中一种新的空时分组编译码方法,称为循环空时分组码(Cyclic Space-Time Block Code,C-STBC),它是将输入信息进行分组循环编码,然后对循环编码后的码字通过不同的天线分别采用不同的扩频码扩频后发射出去。这种CDMA系统下的循环空时分组码对任意的发射天线数都能达到满编码速率和满分集度,且其译码与传统的空时分组码一样简单。仿真结果验证了这种循环空时分组码优于传统的空时分组码。     

OFDM空时发射分集系统信道盲估计

本文研究了OFDM空时发射分集系统的子空间信道盲估计方法。该方法仅利用空时编码及OFDM调制引入的冗余,在接收天线小于发射天线时,也可以对信道进行盲估计。对盲估计方法所共有的估计模糊性问题进行了详细的论述,证明估计仅存在两个标量不确定因子。这种方法不需要对信号进行冗余预编码,系统将有更高的速率;同时也不需要对系统输出进行过采样或采用多天线接收。由于不需要确切知道信道的阶数,算法对信道阶数过估计有较好的鲁棒性。     

STBC—OFDM系统的性能分析及仿真

提出了空时分集的正交频分复用系统(STBC-OFDM)的模型,完成了计算机仿真。结果表明,采用QPSK调制方式,双天线发射,单天线接收STBC与OFDM调制相结合,可以在1MH z带宽下得到1.73M b it/s的码速率,在瑞利信道下,该系统相对于无编码的OFDM系统,在误码率为1-0 3时,可获得3dB的信噪比增益。     

MIMO系统中简单的扩展空时块编码分集技术研究

本文提出一种多输入多输出（MIMO）天线系统中简单的扩展空时块编码（SSTBC）分集技术，采用沃尔什码来区分各天线发送数据子流。采用这种方法，在系统带宽一定时，不降低发送信息速率，同时接收机简单。不同天线的发送信息经过了所有收一发天线对之间的空间子信道，获得了所有路径的部分空间分集增益，仿真结果表明，这种增益的获得不受限于接收分集阶数，并且随发射天线的增加以一定的线性关系增加。     

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.     

衰落信道上TAS/MRC的错误指数

使用梅哲-G 函数,推导了Nakagami-m 衰落发射天线选择（TAS）/最大比合并（MRC）系统的随机编码错误指数（RCEE）、遍历容量、截止速率、删改指数的精确表达式。计算结果表明,Nakagami-m衰落TAS/MRC系统的错误指数与信道衰落参数、信道编码速率、收发天线数目、信道相干时间等因素有关。信道衰落系数越大、编码速率越大、收发天线数目越多,通信系统的RCEE越大,相应的译码错误概率越小,系统的通信可靠性越高。对于给定译码错误概率的MIMO无线通信系统,可以通过计算系统的RCEE来估计信道所需的编码长度、收发天线数目、信道相干时间和空间衰落相关时的编码需求。     

多速率超宽带通信系统中天线传输性能的研究

利用实验测量结合数值仿真的方法,研究了特定室内环境中,不同形状超宽带单极子天线对不同速率多带正交频分(MB-OFDM)超宽带通信系统传输性能的影响.仿真与实验中,MB-OFDM平台采用MATLAB的simulink工具实现,天线与传播环境构成的广义信道特性则通过矢量网络分析仪进行测量.结果表明,单极子天线形状对不同速率MB-OFDM系统的传输误比特率性能有显著影响,文章的方法可用于多速率超宽带通信系统收发天线的优选和性能评价.     

HSDPA领域的四大关键技术

HSDPA(高速下行分组接叭)用于实现WCDMA网络高速下行数据业务，可以使下行的数据速率达到14Mbps的峰值速率。对采用多入多出(MIMO)技术的HSDPA系统，数据速率可以达到20Mbps。在HSDPA技术方案中，涉及到的关键技术主要包括四种，即自适应编码调制(AMC)、H-ASQ、快速蜂窝选择(FCS)和多入多出天线处理(MIMO)。     

A Simple Space-Time-Frequency Block Code Scheme for Four Transmit Antennas

It is well known that the full rate and full diversity complex space-time block code (STBC) is not existed for four transmit antennas. In this letter, we propose a simple quasi-orthogonal space-time-frequency block code (QO-STFBC) scheme with four transmit antennas and n _R receive antennas, where every two transmit antennas constitute one group and each group transmits signals over different subcarriers. The receiver can separate the received signals from each group via odd/even index FFT operation. After recombining the separated received signals with received antennas, an equivalent half rate orthogonal STFBC (O-STFBC) can be used for decoding. Thus, the full rate and full diversity are achieved at the transmitter and receiver, respectively. Simulation result shows that the proposed QO-STFBC scheme has better performance than the other schemes, in rate 2 layered Alamouti scheme is about 4 dB, full rate QO-STBC scheme is about 5 dB and half rate O-STBC scheme is about 7 dB at 10^?3 BER for the transmission of 2 bits/s/Hz.     

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.     

Group transmit antenna selection based on GIS technology for V-BLAST system

The conventional transmit antenna selection for Vertical Bell Laboratories Layered Space Time （V-BLAST） system is very complex because it needs to compute the inverse of channel matrices time after time. In this paper, a new group transmit antenna selection scheme for V-BLAST system is proposed. The 1st group transmit antennas are decided according to a certain selection criterion among the available antennas. Then, with Group Interference Suppression （GIS） technology, the interferences of the transmit symbols from the selected antennas can be suppressed. Finally, the 2nd group transmit antennas are decided among the residual available antennas. Simulations show that its performance is lower than that of the conventional selection scheme. However, the new selection scheme has lower complexity than the conventional one.     

一种降低接收机复杂度的差分空时调制方案

基于对角信号的差分酉空时调制技术不需要信道估计并能实现满天线分集,但接收机的计算复杂度与发射天线数和数据率成指数关系。该文针对发射天线数为偶数的系统,提出了一种降低接收机计算复杂度的差分空时调制方案。该方案将发射天线分成相等数目的两组并在每一组天线上分别进行对角酉空时调制,接着构造差分编码矩阵使得两个对角信号的最大似然检测可以分开进行,从而大大降低了接收机的计算复杂度。理论分析和仿真表明,该方案仍实现了满天线分集,并且对于某些应用环境能提供比对角信号更好的误比特率性能。     

Information-guided channel-hopping for high data rate wireless communication

In this letter, we introduce information-guided channel-hopping, a new scheme for high data rate communication over Rayleigh fading channel using multiple transmit antennas. This scheme is proposed based on the fact that the independence character of multi-channel can be used as an additional information transmitting channel, and the maximum likelihood decoding can be achieved in a simple way by decoupling of the signals conveyed by different methods. The analysis results prove that the capacity behavior of this scheme is better than that of the space-time block coding for more than two transmit antennas.     

Stacked OSTBC: Error Performance and Rate Analysis

It is well known that the Alamouti scheme is the only space-time code from orthogonal designs achieving the capacity of a multiple-input multiple-output (MIMO) wireless communication system with n_T=2 transmit antennas and n_R=1 receive antenna. In this paper, we propose the n-times stacked Alamouti scheme for n_T=2n transmit antennas and show that this scheme achieves the capacity in the case of n_R=1 receive antenna. This result may regarded as an extension of the Alamouti case. For the more general case of more than one receive antenna, we show that if the number of transmit antennas is higher than the number of receive antennas, we achieve a high portion of the capacity with this scheme. Further, we show that the MIMO capacity is at most twice the rate achieved with the proposed scheme for all signal-to-noise ratio (SNR). We derive lower and upper bounds for the rate achieved with this scheme and compare it with upper and lower bounds for the capacity. In addition to the capacity analysis based on the assumption of a coherent channel, we analyze the error rate performance of the stacked orthogonal space-time block code (OSTBC) with the optimal maximum-likelihood (ML) detector and with the suboptimal lattice-reduction (LR)-aided zero-forcing detector. We compare the error rate performance of the stacked OSTBC with spatial multiplexing (SM) and full-diversity achieving schemes. Finally, we illustrate the theoretical results by numerical simulations.     

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.     

Robust Transmit Antenna Selection with Phase Feedback Over Correlated Fading Channels

A new transmit antenna selection (TAS) scheme with phase feedback for multiple-input multiple-output systems is proposed in this paper. This scheme allows two or more transmit antennas to simultaneously use one radio frequency chain. By grouping the transmit antennas according to their similarities in instantaneous channel coefficients into two subsets and treating each subset as a single antenna, both hardware complexity reduction and antenna array gain can be achieved. Compared with the transmit antenna selection combined with space-time block code (TAS/STBC) scheme, the proposed TAS scheme provides excellent robustness, in terms of symbol error rate performance, against spatially correlated fading channels. Moreover, the proposed TAS scheme need not use STBC encoder and decoder which used in the TAS/STBC schemes. Therefore, the proposed TAS scheme is simpler than the TAS/STBC schemes in practical hardware implementation.     

Mitigation of Antenna Displacement with Array Antenna for Data Transmission in Wireless Power Transfer System

Magnetic resonance wireless power transfer is expected to be one of the prevalent schemes because of its high efficiency and long transmission range. However, in this scheme, there is a problem that the characteristics of a transmission channel changes in according with the distance between coil antennas. This paper investigates the performance of data transmission with an array antenna in a wireless power transfer system. In the assumed system, the same antennas for wireless power transfer are used for data transmission. The assumed system uses multiple transmit antennas and beamforming is realized by shifting the phases of signals in a transmitter. Numerical results obtained through computer simulation show that the proposed scheme can mitigate the dependently of a bit error rate (BER) to the distance between the antenna coils. The variation of the performance is suppressed within 1–3 dB at the BER of \(10^{-5}\) in the case of two transmit antennas. In addition, the system with two transmit antennas achieves 2 dB or more improvement in term of the BER performance than that with a single antenna at specific antenna distances.     

A Differential Modulation Scheme for MIMO Links with Distributed Transmit Antennas

This letter proposes a differential en/decoding scheme for multiple-input multiple-output (MIMO) communication links with distributed transmit antennas, in which neither the transmitter nor the receiver knows channel knowledge. The proposed scheme is based on the layered differential space-time codes we present. Simulation results show that the bit error rate (BER) performance is nonidentical in different channel propagation delay cases. The optimum delay time for two transmit antennas system, for example, is about 0.6T_s (where T_s denotes symbol period) when the links achieve better performance.