Tensor space-time (TST) coding for MIMO wireless communication systems

In this paper, we propose a tensor space-time (TST) coding for multiple-input multiple-output (MIMO) wireless communication systems. The originality of TST coding is that it allows spreading and multiplexing the transmitted symbols, belonging to R data streams, in both space (antennas) and time (chips and blocks) domains, owing the use of two (stream- and antenna-to-block) allocation matrices. This TST coding is defined in terms of a third-order code tensor admitting transmit antenna, data stream and chip as modes. Assuming flat Rayleigh fading propagation channels, the signals received by K receive antennas during P time blocks, composed of N symbol periods each, with J chips per symbol, form a fourth-order tensor that satisfies a new constrained tensor model, called a PARATUCK-(2,4) model. Conditions for identifiability and uniqueness of this model are established, and a performance analysis of TST coding is made, before presenting a blind receiver for joint channel estimation and symbol recovery. Finally, some simulation results are provided to evaluate the performance of this receiver.     

MIMO技术在超宽带通信中的应用

多带UWB通信技术是目前超宽带通信技术中较为热的研究领域,本文引入了一种基于干扰抑制OFDM系统的UWB系统[4],在此基础至上和MIMO技术结合起来,引入一种实际可行的自适应调制算法,算法通过建立各子信道的能量增量表,来实现信息比特和功率的最优分配[1].通过仿真试验可以发现,这种MIMO系统的结合可以改善系统的BER.     

Space-time coding for MIMO systems with co-channel interference

We consider the design of space-time codes for multiple-input multiple-output (MIMO) systems operated in the presence of co-channel interference (CCI). Based on the pairwise probability of error analysis, we develop a new design criterion that determines the code robustness to CCI (CCI diversity gain). We further develop an algebraic framework for constructing space-time codes that jointly optimize the fading and CCI diversity gains. The proposed framework is general for arbitrary numbers of transmit antennas and quadrature amplitude modulation constellations. Numerical results that quantify the performance gains offered by the proposed techniques are also presented.     

一种适用多种空时编码方案的MIMO自编码器通信系统

为提升现有端到端通信系统的适应性与信道估计的准确性,提出了一种适用于多种空时编码方案的多输入多输出(Multiple-Input Multiple-Output,MIMO)自编码器通信系统.该系统将基于卷积神经网络的自编码器引入到MIMO系统中,并结合信道估计网络实现信道均衡,通过端到端的学习方式实现各种空时编码方案下...     

UWB通信系统简介

UWB(Ultra Wide Band)即超宽带通信,它使用大于0.5GHz或大于中心频率20%的带宽、通过微弱的脉冲信号进行通信,最大数据传输速率可以达到几十Mb/s～几百Mb/s。UWB与现有的无线技术的显著不同是不需要使用载波,而是通过发送纳秒级脉冲来传输数据,而且信号传输时的功耗只有几十μW。UWB在保证了高数据速率传输的同时解决了移动终端的功耗问题。因此它被认为是对目前被炒得沸沸扬扬的无线互联(Wi-Fi)技术最具竞争性的技术。UWB简介UWB技术多年来一直是美国军方使用的作战技术之一,如它可以实现穿墙视物等功能。这项技术在通信领域所具…     

Hybrid channel coding scheme for blind space-time coded MIMO systems

This letter proposes a hybrid use of channel codes in wireless systems employing multiple transmit/multiple receive antennas. We concatenate space-time codes (STCs) serially with low-density parity check (LDPC) codes and turbo codes. We show that by using these powerful coding schemes effectively, substantial performance improvements can be achieved. This is motivated by the need for a scheme that gives promising performance even when no training is available. The proposed scheme results in a desirable trade-off between performance and complexity.     

Line coding plan for fiber optic communication systems

Problems in fiber optic digital communication systems are enumerated and a line coding plan that solves these problems is investigated. This plan utilizes a two-level pulse train that has the same features as the conventional three-level alternate mark inversion sequence. An efficient repeater powering scheme is discussed in connection with the coding plans.     

Channel characterization of time reversal UWB communication systems

An ultra wideband (UWB) communications system that applies time reversal to transmit the desired signal is investigated. Exact expressions for the first- and second-order moments, cross-correlation, intersymbol interference metric, and correlation coefficient of time reversal (TR) UWB equivalent channel are derived in terms of the physical channel parameters such as delay spread and mean excess delay. These expressions are verified by simulated and experimental results. It is shown that TR-UWB excess delay is very smaller than UWB and its delay spread decreases as signaling bandwidth increases. Semi-analytical results show that the time reversal UWB delay spread is approximately the same as UWB. Furthermore, an ISI metric is derived for TR-UWB channel based on transmitted signal and UWB channel parameters. Moreover, correlation coefficient of two TR-UWB received signals with different power delay profile is computed analytically. Simulation and analytical results show that for τ?>?0.3T _w correlation coefficient is below 0.25 and for τ?>?T _w correlation coefficient is zero, where T _w is the transmitted pulse width. Finally, theoretical performance of a receiver with one tap matched filter is computed and compared with measured and simulated result.     

Fading correlations in wireless MIMO communication systems

We investigate the effects of fading correlations on wireless communication systems employing multiple antennas at both the receiver and the transmitter side of the link, so called multiple-input multiple-output (MIMO) systems. It turns out that the amount of transmitter sided channel knowledge plays an important part when dealing with fading correlations. Furthermore, the possible availability of time diversity in a time-selective channel can have essential influence on performance. To study the influence of time-selectivity, the concept of sample-mean outage is introduced and applied to information theoretic measures, like capacity or cutoff rate. It will be shown, that in some cases correlated fading may offer better performance than uncorrelated fading permits, which is due to exploitable antenna gain, that will also be defined in a general form for MIMO systems.     

Hardware-accelerated design space exploration framework for communication systems

The efficient hardware implementation of signal processing algorithms requires a rigid characterization of the interdependencies between system parameters and hardware costs. Pure software simulation of bit-true implementations of algorithms with high computational complexity is prohibitive because of the excessive runtime. Therefore, we present a field-programmable gate array (FPGA) based hybrid hardware-in-the-loop design space exploration (DSE) framework combining high-level tools (e.g. MATLAB, C++) with a System-on-Chip (SoC) template mapped on FPGA-based emulation systems. This combination significantly accelerates the design process and characterization of highly optimized hardware modules. Furthermore, the approach helps to quantify the interdependencies between system parameters and hardware costs. The achievable emulation speedup using bit-true hardware modules is a key enabling the optimization of complex signal processing systems using Monte Carlo approaches which are infeasible for pure software simulation due to the large required stimuli sets. The framework supports a divide-and-conquer approach through a flexible partitioning of complex algorithms across the system resources on different layers of abstraction. This facilitates to efficiently split the design process among different teams. The presented framework comprises a generic state of the art SoC infrastructure template, a transparent communication layer including MATLAB and hardware interfaces, module wrappers and DSE facilities. The hardware template is synthesizable for a variety of FPGA-based platforms. Implementation and DSE results for two case studies from the different application fields of synthetic aperture radar image processing and interference alignment in communication systems are presented.     

Source coding theory for cascade and branching communication systems

A source coding problem is considered for cascade and branching communication systems. The achievable rate region is established for the cascade systems and bounds are obtained for the branching systems. Some examples are also included.     

Design of tracking loop with dirty templates for UWB communication systems

Maintaining satisfactory synchronization between transmitter and receiver is one of the major challenges in carrying out highly efficient ultra-wideband (UWB) communications. For tracking purposes, the delay-locked loop (DLL) concept is applied. The DLL could be considered as a fundamental tracking technique for UWB devices. In this paper, the reference signal is generated at the receiver based on an approach called timing with dirty template. This approach promises to improve tracking performance while reducing receiver structure complexity. After the reference template is generated, we derive first-order and second-order DLL designs for UWB systems. Furthermore, we utilize the benefits of time-hopping codes to enhance noise handling ability of the DLL. Finally, the parameters of the proposed DLL will be selected to optimize tracking behavior in the presence of the ambient noise and Doppler effects. Simulation results show tracking performance across various DLL parameter values.     

Adaptive antennas for MIMO OFDM‐CDMA communication systems

In this paper, we propose symbol‐based receivers for orthogonal frequency division multiplexing (OFDM) code‐division multiple‐access (CDMA) multiple‐input‐multiple‐output (MIMO) communications in multipath fading channels. For multiuser and multipath fading environments, both intersymbol interference and multiple‐access interference must be considered. We propose narrowband and wideband antennas and Wiener code filter for MIMO OFDM‐CDMA systems. The proposed receivers are updated symbol‐by‐symbol to achieve low computational complexity. Simulation results show that the proposed Wiener code filter can improve the system performance for the proposed adaptive antennas. The wideband antenna can achieve better error‐rate performance than that of the narrowband antenna when multipath effect exists. The convergence rate of the recursive least squares antennas is faster than that of the least mean square antennas. Copyright © 2013 John Wiley & Sons, Ltd.     

Deep learning-based channel estimation for wireless ultraviolet MIMO communication systems

To solve the problems of pulse broadening and channel fading caused by atmospheric scattering and turbulence, multiple-input multiple-output(MIMO) technology is a valid way. A wireless ultraviolet(UV) MIMO channel estimation approach based on deep learning is provided in this paper. The deep learning is used to convert the channel estimation into the image processing. By combining convolutional neural network(CNN) and attention mechanism(AM), the learning model is designed to extract the depth f...     

A resource allocation strategy for distributed MIMO multi-hop communication systems

An extended form of multi-hop communication systems is introduced which allows the application of multiple-input-multiple-output (MIMO) capacity enhancement techniques over spatially separated relaying mobile terminals to drastically increase end-to-end capacity. An explicit resource allocation strategy is deduced in terms of fractional bandwidth and power allocations to each relaying hop over ergodic Rayleigh flat fading channels employing orthogonal frequency-division multiple-access (FDMA)-based relaying.     

UWB卫星通信系统与窄带系统互扰分析

UWB技术在卫星通信领域推广应用的瓶颈是UWB卫星通信系统与窄带系统的互扰问题。研究了正弦调制高斯脉冲在卫星信道应用的时频域特性,提出了Ka频段UWB卫星通信信道模型,建立UWB卫星通信仿真系统,研究了UWB卫星通信系统和窄带系统在互扰条件下的误码特性,得到了影响互扰的关键因素,提出了适合卫星通信信道传输的UWB信号设计参数,论证了UWB卫星通信系统与窄带系统共享频谱的可行性。     

A design framework for limited feedback MIMO systems with zero-forcing DFE

We consider the design of multiple-input multiple-output communication systems with a linear precoder at the transmitter, zero-forcing decision feedback equalization (ZFDFE) at the receiver, and a low-rate feedback channel that enables communication from the receiver to the transmitter. The channel state information (CSI) available at the receiver is assumed to be perfect, and based on this information the receiver selects a suitable precoder from a codebook and feeds back the index of this precoder to the transmitter. Our approach to the design of the components of this limited feedback scheme is based on the development, herein, of a unified framework for the joint design of the precoder and the ZF-DFE under the assumption that perfect CSI is available at both the transmitter and the receiver. The framework is general and embraces a wide range of design criteria. This framework enables us to characterize the statistical distribution of the optimal precoder in a standard Rayleigh fading environment. Using this distribution, we show that codebooks constructed from Grassmann packings minimize an upper bound on an average distortion measure, and hence are natural candidates for the codebook in limited feedback systems. Our simulation studies show that the proposed limited feedback scheme can provide significantly better performance at a lower feedback rate than existing schemes in which the detection order is fed back to the transmitter.     

An intuitive electromagnetic approach to MIMO communication systems

The aim of this paper is to introduce MIMO propagation in a simple and intuitive way, which exalts the role of the laws of electromagnetism in the channel capacity of space-time communication systems. The approach takes advantage of mode expansions in waveguides and spherical-harmonics expansions in free space to clarify the physical limitations in the channel capacity of MIMO systems.     

Performance enhancement of multiuser MIMO wireless communication systems

This paper describes a new approach to the problem of enhancing the performance of a multiuser multiple-input-multiple-output (MIMO) system for communication from one base station to many mobile stations in both frequency-flat and frequency-selective fading channels. This problem arises in space-division multiplexing systems with multiple users where many independent signal streams can be transmitted in the same frequency and time slot through the exploitation of multiple antennas at both the base and mobile stations. Our new approach is based on maximizing a lower bound for the product of signal-to-interference plus noise ratio (SINR) of a multiuser MIMO system. This provides a closed-form (noniterative) solution for the antenna weights for all the users, under the constraint of fixed transmit power. Our solution is shown by simulation to have better performance than previously proposed iterative or noniterative solutions. In addition, our solution requires significantly reduced complexity over a gradient search-based method that directly optimizes the product SINRs while still maintaining similar performance. Our solution assumes channel state information is present at the base station or transmitter.