A multi-CRC selective HARQ scheme for MIMO systems

A multi-Cyclic Redundancy Check （CRC） selective Hybrid Automatic-Repeat-reQuest （HARQ） scheme for improving the throughput efficiency of Multiple Input Multiple Output （MIMO） systems is proposed in this paper. According to different feedback information from the receiver, the proposed HARQ scheme employs two strategies, referred to as retransmission frame selection and space diversity. These two strategies decrease the successive frame errors upon retransmission. Theoretic analysis and computer simulation results show that this HARQ scheme achieves higher throughput than the existing HARQ schemes even in poor conditions of low Signal-to-Noise Ratio （SNR）.     

基于MIMO-OFDM的高速水声通信技术研究

OFDM技术可以对抗水声信道中的多径传播并能实现高的频谱效率,空时编码技术则能够获得空间增益并对抗信道衰落。文中在分析OFDM同步误差和空时分组编码原理的基础上,将这两种无线新技术应用于高速水声通信中,设计实现了一个基于MIMO-OFDM技术的高速水声通信系统,并着重讨论了系统同步的实现方法。湖上实验证明了方案的有效性。     

Wimax (IEEE 802.16 m) system based on space time block code and discrete multiwavelet transform and implementation in FPGA

MIMO (Multiple Input Multiple Output) scheme uses transmit diversity technique which results in high throughput with increased channel capacity. The complexity of MIMO system increases the area and power requirements of the system. The proposed work is to achieve good spectral efficiency and reduction of interference by introducing multiwavelet with MIMO technology. The improvements directly results in reduction of BER (Bit Error Rate) for a given SNR (Signal to Noise Ratio). Implementation of the proposed scheme in FPGA (Field Programmable Gate Array)—virtex5 (xcvlx30t-1f665) shows a considerable improvement in speed and area when compared with the existing methods.     

MIMO广播信道中联合多用户速率和延迟约束调度的研究

该文给出了一种多入多出高斯广播信道中具有延迟约束的多用户无线数据包的传输方案。首先,在信道的QR分解及脏纸编码基础上,通过贪婪算法获取多用户分集与包延迟约束之间的有效结合。其次,将包到达速率、可达服务速率、用户数以及传输天线数构成一优化问题,得到最佳的用户组合及调度周期。最后,在不同用户数及发射天线数情况下对该方案进行了性能仿真,仿真结果表明:在满足包传递最小延迟等待要求的同时,得到了传输容量的最大化。     

几种接收机在MIMO信道下的性能比较

多入多出（MIMO）无线信道具有空间复用增益和分集增益特性,因此MIMO系统和单入单出（SISO）无线系统相比能够获得更高的频谱效率。本文在不同天线组合下分析了几种MIMO空时信号处理算法的性能,仿真结果和理论分析表明：空间复用增益和分集增益不能同时获得最大,因此在设计MIMO通信系统时可根据实际情况选择天线数,即不仅考虑系统抵抗信道衰落的分集增益,还要考虑能够提供更高的数据传输速率,通过折衷考虑空间复杂增益和分集增益,从更全面的观点评估系统的性能。     

MIMO技术及其在无线通信系统中的应用

多输入多输出（Multiple Input Multiple Output，MIMO）技术是无线通信领域的一大重要突破。介绍了MIMO技术的理论基础，研究了无线通信中MIMO技术的应用，包括空间分集、空时编码等。结果表明，MIMO技术能够极大地提高通信系统的容量和频谱利用率。     

Regularized MIMO Equalization for SC-FDMA Systems

In this paper, we propose an efficient frequency domain equalization scheme for Multiple Input Multiple Output (MIMO) Single-Carrier Frequency-Division Multiple Access (SC-FDMA) systems. The proposed scheme avoids the complexity problem associated with the conventional MIMO Zero-Forcing (ZF) equalizer as well as the noise enhancement problem. The matrix inversion process associated with the proposed equalization scheme is performed in two steps to reduce complexity. A regularization term is added in the second step of the matrix inversion to avoid the noise enhancement. Simulation experiments on uplink MIMO SC-FDMA systems show that the proposed equalization scheme provides better performance than that of the ZF equalizer and its complexity is far less than that of the ZF equalizer.     

Variable-rate multiuser diversity in correlated MIMO channel via virtual channel representation

This paper studies the multiuser diversity with constellation selection based on a virtual representation of realistic Multiple Input Multiple Output （MIMO） correlated channels. To realize multiuser diversity in slow fading channels, random beamforming is adopted. Random beamforming matrix exploiting virtual channel representation is constructed, which can match the channel matrix of the desired user better. Sirnultaneously, adaptive coded modulation is applied to each sub-channel of the selected user to improve the system performance further.     

多入单出正交空时分组码系统的调制识别

在现代无线通信系统中,采用正交空时分组码(STBC)的多天线发射技术是提高通信速率和可靠性,并且能够实现简单译码的关键技术。该文针对瑞利信道系统模型,提出一种适用于多入单出正交空时分组码(OSTBC)的调制识别算法。该算法通过对接收到的数据进行重排,将多入单出的系统模型转化为类似多入多出的系统模型,并且根据信源的特殊性用最大似然的思想实现调制类型的识别。仿真结果验证了所提算法的有效性。     

一种基于准正交空时码的低复杂度MIMO差分检测方法

针对可实现全速率传输的准正交空时码,提出了一种低复杂度的准正交MIMO差分检测方法.该方法在发射端对数据比特进行联合星座映射,构造准正交空时码进行差分编码;接收端采用最大似然准则对两组星座符号对(symbol pair)并行差分检测.本文提出的星座集合及联合星座映射方法简化了接收端检测算法,降低了检测计算复杂度.     

Signal constellations design for differential unitary space-time in MIMO-OFDM system over frequency-selective fading channels

In this paper, the design of signal constellations parameters is studied for Differential Unitary Space-Time Modulation （DUSTM） based on the design criterion of maximizing the diversity product. Further, noninteger searching method for the signal constellation parameters design is proposed in order to get better codes. Experimental results show that under the different Doppler spread and data transmission rate, the proposed design performs better than the previous design using integer parameters in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing （MIMO-OFDM） system over frequency-selective fading channels.     

MIMO信号检测中软信息计算的简化方法

编码的多入多出（MIMO）迭代接收技术,是一种高频谱利用率、高性能的接收技术。本文对这种迭代接收机进行了分析。为便于硬件实现,利用QAM调制的特性,对MIMO信号检测中的软信息计算提出了简化方法。仿真结果表明,简化方法对系统性能影响很小。     

A Novel Circulant Approximation Method for Frequency Domain LMMSE Equalization

The coefficients of a Linear Minimum Mean Square Error (LMMSE) equalizer for a stationary random signal are defined by a Toeplitz system. The Toeplitz structure can be exploited to reduce computational complexity. In this paper we investigate the Levinson and Schur algorithm, as well as circulant embedding and circulant approximation methods applied to the Preconditioned Conjugate Gradient (PCG) method and Frequency Domain Equalization (FDE). We develop a novel circulant approximation method which improves the performance/complexity tradeoff. We show that the optimal choice of algorithms largely depends on the antenna configuration. Investigated configurations are Single Input Single Output (SISO), Single Input Multiple Output (SIMO) and Multiple Input Multiple Output (MIMO). All considered algorithms are benchmarked in terms of implementation complexity and capacity achieved by a High Speed Downlink Packet Access (HSDPA) receiver in a multipath fading scenario.     

分布式MIMO-OFDM系统的同步捕获算法

该文提出了一种分布式多输入多输出正交频分复用(MIMO-OFDM)系统初始信号检测和同步捕获算法。该算法设计了导频符号,采用谱分析方法实现可靠的初始信号检测、粗定时和粗频偏估计,并在快速傅里叶变换(FFT)之后进行精确地频偏和定时估计。仿真结果表明,该算法在低信噪比多径瑞利信道条件下具有很好的性能。     

Reduced Complexity Decoding of Space Time Trellis Codes in the Frequency Selective Channel

An iterative approach is developed for decoding Space Time Trellis Codes (STTCs) in frequency selective Multiple Input Multiple Output (MIMO) channels. The method uses the Partitioned Viterbi Algorithm (PVA) as an equaliser for the MIMO system. It is used iteratively with a STTC decoder that provides soft outputs using the Soft Output Viterbi Algorithm (SOVA). It is shown through simulation that the iterative procedure achieves a performance within 2.0dB of Maximum Likelihood (ML) decoding, at a FER of 10^?2, but suffers a small diversity loss. It is also shown that the complexity of the iterative approach is lower than that of ML decoding.     

CFAR Detectors for MIMO Radars

CFAR (Constant False-Alarm Rate) processors are useful for detecting radar targets in a background for which the parameters in the statistical distribution are not known. A variety of CFAR techniques such as CA (Cell Averaging), Go (Greatest Of), SO (Smallest Of), OS (Ordered Statistics) and ACMLD (Automatic Censored Mean-Level Detector) processors have been proposed for SISO (Single Input–Single Output) radars in a non-homogeneous background. In this paper, conventional CFAR algorithms including CA, SO, OS and ACMLD processors are generalized for MIMO (Multiple Input–Multiple Output) radars. The exact expressions for false-alarm probabilities of the proposed algorithms in a homogeneous background are presented. In addition, the detection performance of the proposed detectors is studied by means of simulation in the presence of interfering targets and also colored Gaussian clutter. Besides, the proposed CFAR processors are compared, and it is shown that the ACML-based algorithm is superior to the other investigated methods.     

Constrained Waveform Designing for MIMO RADAR Using Jaya Optimization

Wireless Personal Communications - Multiple Input Multiple Output RADAR system is proficient in forming desired beampattern by designing transmit waveforms. In this paper, Poly Phase coded...     

MIMO衰落信道上MR-MQAM性能分析

使用矩生成函数方法分别推导了Nakagami衰落信道上多分辨率M进制正交幅度调制(MR-MQAM)的平均误比特率(BER)闭合表达式,发送和接收分别采用选择合并/最大比合并(SC/MRC)和正交空时分组编码(OSTBC).数值计算结果表明在相同的天线设置条件下,SC/MRC方案的平均误比特率性能要优于OSTBC.     

Performance analysis of space time block coding techniques for indoor optical wireless systems

Indoor optical wireless systems provide an attractive alternative for realizing next generation Wireless Local Area Networks (WLANs). In this paper, the performance of diffuse optical wireless systems, employing Space Time Block Coding (STBC) techniques, is numerically investigated, accurately taking into account, the indoor channel impulse response and the characteristics of ambient light and thermal noises at the receiver. Discrete Multitone modulation (DMT) is used to mitigate the effect of intersymbol interference due to the channel?s impulse response. The performance of STBC systems, employing two transmit elements, is compared against Single Input/ Single Output (SISO) and Maximum Ratio Combining (MRC) systems operating with the same total optical transmitter power. It is shown that STBC techniques can be used to increase the capacity of diffuse optical wireless systems, improve their coverage and decrease the required optical power at the transmitter. These results demonstrate the usefulness of Multiple Input Multiple Output (MIMO) techniques in the realization of optical WLANs.     

短波MIMO通信的研究进展

短波通信中的天波传播信道因为多径和多模式传播而具有充分散射的特征,因而非常适合多输入多输出技术的应用。总结了短波多输入多输出技术通信的研究现状,归纳并分析了短波多输入多输出技术本身以及间隔式同构天线阵和同位置异构天线阵在短波多输入多输出通信中应用的可行性,并指出了需要进一步解决的问题。