Cross-layer design for cooperative MIMO systems with relay selection and imperfect CSI

Based on imperfect channel state information (CSI) and relay selection, a cross-layer optimization scheme is developed for cooperative MIMO system, and the corresponding system performance is investigated in Rayleigh fading channel. By the theoretical analysis and mathematical manipulation, the average spectral efficiency (SE), packet error rate (PER) and packet loss rate (PLR) are derived. As a result, closed-form expressions of the average SE, PER and PLR are obtained, respectively. According to these, a cross-layer design (CLD) scheme subject to the average PER constraints is proposed to avoid the SE performance loss caused by the conventional instantaneous PER constraints. The scheme optimizes the adaptive thresholds by maximizing the average SE of the system, and an iteration method joint the Lagrange multiplier and Newton methods is presented to solve the above optimization problem. Simulation results verify the validity of the theoretical analysis. The results show that the proposed CLD scheme can improve the SE while target PLR is maintained. The CLD scheme under average PER constraints has higher SE than the conventional CLD scheme under instantaneous PER constraints.     

MIMO系统中发射天线选择算法研究

无线信道中由于存在多径衰落,通信系统的可靠性会因此大大降低。增加收发两端的射频链路能够有效地解决这个问题,但射频链增加的同时又会提高成本。为此,提出一种基于发送端的递增改进算法,在不增加射频链路的前提下,完成对天线性能的鉴别,选择出对系统性能贡献最大的天线。仿真结果表明,该算法可有效地提高系统性能,减少系统检测时延。     

Low-complexity joint transmit and receive antenna selection for MIMO systems

In this paper, we present a low-complexity algorithm for real-time joint transmit and receive antenna selection in MIMO systems. The computational complexity of exhaustive search in this problem grows exponentially with the number of transmit and receive antennas. We apply Binary Particle Swarm Optimization (BPSO) to the joint transmit and receive antenna selection problem. In addition, applying the general BPSO to joint antenna selection, we also present a specific improvement to this population-based heuristic algorithm, namely, we feed cyclically shifted initial population so that the average convergence time (the number of iterations until reaching an acceptable solution) is reduced. The proposed BPSO for joint antenna selection problem has a low computational complexity, and its effectiveness is verified through simulation results.     

发射天线选择正交空时码系统的性能分析

分别针对瑞利衰落信道和Nakagami衰落信道,研究了使用发射天线选择(TAS)和正交空时分组码(STBC)的多输入多输出系统的平均符号误码率(ASEP)性能。基于标量加性高斯白噪声(AWGN)信道的方法,推导出了采用脉冲幅度调制(PAM)、相移键控(PSK)和正交幅度调制(QAM)的精确和近似的ASEP闭合表达式。然后对不同条件下的系统性能做了数值仿真,验证了分析结果的正确性。     

Performance analysis for M2M video transmission cooperative networks using transmit antenna selection

Multimedia Tools and Applications - Due to mobile-to-mobile (M2M) communication unpredictability and difficulty in securing reliable channels, transmission of video over M2M networks is...     

Particle swarm optimization assisted joint transmit/receive antenna combining for multiple relays in cooperative MIMO systems

This paper presents a novel relay resource utilization scheme that uses the particle swarm optimization (PSO) algorithm to jointly search the antenna combining (AC) matrices of multiple relays in cooperative MIMO systems. The relays use the AC matrices to weight and combine signals transmitted by the source node, and then forward the weighted signal to the destination node. As a result, the relays can reduce the number of radio frequency (RF) chains used by the transmit/receive antenna elements, and thereby lower the hardware costs of deploying RF chains. Furthermore, because there are fewer RF chains, the relays require less power than relays that use all the RF chains The results of computer simulations demonstrate that the proposed scheme outperforms the full RF-chain relay method and existing approaches in some scenarios.     

Alamouti编码方案在联合天线选择下的BER精确解

提出了一种基于最大瞬时信噪比在瑞利衰落信道中的多发多收(MIMO)天线系统的简单联合收发天线算法.在选定两个发送天线和一个接收天线情况下,利用Alamouti编码可以获得二进制相移键控(BPSK)的误码率(BER)精确解,该分析结果通过仿真得到确切验证.     

Per-layer transmit and receive filters design for Tomlinson-Harashima precoding in multiuser MIMO systems

In this paper,the per-layer design for Tomlinson-Harashima precoding (THP) in the downlink of multiuser multiple-input multiple-output (MIMO) systems is investigated.In these systems,the number of the receivers is equal to that of the transmit antennas.Based on the criterion of maximum system sum-capacity,we study two per-layer joint transmit and receive filters design schemes with receive antenna beamforming (RAB) and receive antenna selection (RAS),respectively.Moreover,the differences of the equivalent channel gains and capacities between these two schemes are analyzed theoretically.Simulation results show that by these per-layer schemes,the system sum-rate is improved significantly with respect to the per-user processing scheme.     

Energy- and spectral-efficiency of zero-forcing beamforming in massive MIMO systems with imperfect reciprocity calibration: bound and optimization

In a time-division duplex (TDD) system with massive multiple input multiple output (MIMO), channel reciprocity calibration (RC) is generally required in order to cope with the reciprocity mismatch between the uplink and downlink channel state information. Currently, evaluating the achievable spectral efficiency (SE) and energy efficiency (EE) of TDD massive MIMO systems with imperfect RC (IRC) mainly relies on exhausting Monte Carlo simulations and it is infeasible to precisely and concisely quantify the achievable SE and EE with IRC. In this study, a novel method is presented for tightly bounding the achievable SE of massive MIMO systems with zero-forcing beamforming under IRC. On the basis of the analytical results, we demonstrate key insights for practical system design with IRC in three aspects: the scaling rule for interference power, saturation region of the SE, and the bound on the SE loss. Finally, the trade-off between spectral and energy efficiencies in the presence of IRC is determined with algorithms developed to optimize SE (EE) under a constrained EE (SE) value. The loss of optimal total SE and EE due to IRC is also quantified, which shows that the loss of optimal EE is more sensitive to IRC in a typical range of transmit power values.     

基于拉普拉斯分布天线阵列下MIMO性能研究

多天线系统是可以克服多径干扰的影响并增加频谱使用效率的系统.MIMO系统的容量增加主要取决于无线电信道的空间相关性性能.主要研究了MIMO天线阵列系统的性能,包括MIMO空间时间相关性和天线阵列配置,推导了当角能量遵循拉普拉斯分布时均匀线性阵列、均匀圆阵的衰落相关性解析公式,并分析了两种天线阵列下的系统信道容量.通过计算机程序模拟仿真验证了分析结果,验证结果表明当阵元间距增大或者衰减因子减小(角度扩展增大)时,空间衰落相关性减小,系统信道容量增大,提升了系统性能.     

Performance analysis of prioritized Automatic Repeat-request systems in the presence of self-similar traffic

Automatic Repeat reQuest (ARQ) is a promising forward error control mechanism for improving the reliability of data transmission over wireless channels. Traffic self-similarity has been discovered to be a ubiquitous phenomenon in communication networks with a significant impact on the network performance and user-perceived Quality-of-Service (QoS). However, due to the high complexity and challenges of modelling traffic self-similarity, there has not been any analytical model reported for ARQ under self-similar traffic. To fill this gap, we develop a novel analytical model of multi-buffer ARQ systems in the presence of prioritized self-similar traffic for reliable data transmission and QoS differentiation. This model can be used to investigate the probabilities of queueing loss and transmission loss in the multi-buffer ARQ systems. The validity of the analytical model is demonstrated via extensive comparison between analytical and simulation results. The model is further adopted to investigate the effects of service capacity and delay bound of ARQ on the system performance.     

自适应MIMO系统在反馈延时下的性能分析

为了提高无线通信系统的频谱利用率,提出一种简单而实用的开环自适应MIMO系统,利用最优贪婪调度算法,在多用户分集和多天线分集的作用下,有效地改善系统的性能.推导了在反馈存在延时的信道条件下频谱效率和中断概率的闭合表达式、分析了发射天线数、重传、用户数以及延时对系统整体性能的影响.     

Performance analysis of uplink MIMO MC-CDMA systems based on linear zero-forcing V-BLAST algorithm

A structure was proposed for multiple-input-multiple-output multicarrier code divi- sion multiple access （MIMO MC-CDMA） uplink transmission system. Linear zero- forcing V-BLAST （ZF V-BLAST） algorithm and maximum ratio combining （MRC） scheme was applied to the receivers. The average bit error rate （BER） expression was derived on condition that the number of receive antennas was larger than that of transmit antennas and it was verified by simulations. Numerical results show that the number of transmit and receive antennas, as well as the number of sub- carriers, all exert significant effects on the BER performance. The space diversity and frequency diversity show different abilities to improve the BER performance. The MIMO MC-CDMA system based on linear ZF V-BLAST algorithm is capable of achieving better BER performance than that of the conventional MC-CDMA system by reducing the number of transmit antennas or increasing the number of receive antennas.     

Performance bounds in linear control of unstable MIMO systems with pole location constraint

This paper proposes a methodology to compute quadratic performance bounds when the closed loop poles of a discrete-time multivariable control loop are confined to a disk, centred at the origin, and with radius less than one. The underlying philosophy in this constraint is to avoid certain undesirable dynamic features which arise in quadratic optimal designs. An expression for the performance loss due to the pole location constraint is also provided. Using numerical examples, we show that the performance loss is compensated by an improved transient performance, specially visible in the control signals.     

Performance analysis of R*-trees with arbitrary node extents

Existing analysis for R-trees is inadequate for several traditional and emerging applications including, for example, temporal, spatio-temporal, and multimedia databases because it is based on the assumption that the extents of a node are identical on all dimensions, which is not satisfied in these domains. We propose analytical models that can accurately predict R*-tree performance without this assumption. Our derivation is based on the novel concept of extent regression function, which computes the node extents as a function of the number of node splits. Detailed experimental evaluation reveals that the proposed models are accurate, even in cases where previous methods fail completely.     

Response time analysis of multiframe mixed-criticality systems with arbitrary deadlines

Real-Time Systems - The well-known model of Vestal aims to avoid excessive pessimism in the quantification of the processing requirements of mixed-criticality systems, while still guaranteeing the...     

Sensitivity analysis of arbitrary deadline real-time systems with EDF scheduling

The correctness of a real-time system depends on not only the system’s output but also on the time at which results are produced. A hard real-time system is required to complete its operations before all its timing deadlines. For a given task set it is useful to know what changes can be made to a task that will result in a system that is borderline schedulable. It is also beneficial in an engineering context to know the minimum speed of a processor that will deliver a schedulable system. We address the following sensitivity analysis (parameter computations) for EDF-scheduled systems on a uniprocessor: task execution times, speed of the processor, task periods and task relative deadlines. We prove that an optimal (minimum or maximum) system parameter can be determined by a single run of the Quick convergence Processor demand Analysis (QPA) algorithm. This algorithm provides efficient and exact sensitivity analysis for arbitrary deadline real-time systems. We also improve the implementation of this sensitivity analysis by using various starting values for the algorithms. The approaches developed for task parameter computations are therefore as efficient as QPA, and are easily incorporated into a system design support tool.