A New TDD Scheme and Interference-Aware Precoding for Device-to-Device Underlay Massive MIMO

In device-to-device(D2D)underlay cellular networks with downlink spectrum sharing,massive MIMO seems promising as the large number of antennas at the base station(BS) can be utilized to suppress interference.However,the channel state information(CSI) from the BS to D2D receivers is required to obtain this advantage.In this paper,we first propose a novel time division duplex(TDD) scheme for D2D users to acquire this CSI,without additional pilot overhead.Moreover,we propose an interference-aware MMSE precoder utilizing the acquired CSI from the BS to not only cellular users but also D2D users to suppress the cellular-to-D2D interference.Simulation results show that our proposed TDD scheme and precoder can significantly improve the achievable sum spectral efficiency(SE) and D2D SE,compared to the classical MMSE precoder.Compared with the interferenceaware ZF precoder,whose performance severely degrades for large user numbers,our proposed interference-aware MMSE precoder can always guarantees a high and stable performance in terms of achievable SE.

Multi-criteria user selection scheme for learning-based multiuser MIMO cognitive radio networks

For multiuser multiple-input-multiple-output （MIMO） cognitive radio （CR） networks a four-stage transmiision structure is proposed. In learning stage, the learning-based algorithm with low overhead and high flexibility is exploited to estimate the channel state information （ CSI ） between primary （PR） terminals and CR terminals. By using channel training in the second stage of CR frame, the channels between CR terminals can be achieved. In the third stage, a multi-criteria user selection scheme is proposed to choose the best user set for service. In data transmission stage, the total capacity maximization problem is solved with the interference constraint of PR terminals. Finally, simulation results show that the multi-criteria user selection scheme, which has the ability of changing the weights of criterions, is more flexible than the other three traditional schemes and achieves a tradeoff between user fairness and system performance.

User Fairness Scheme with Proportional Fair Scheduling in Multi-user MIMO Limited Feedback System

In Multi-user MIMO (MU-MIMO) downlink system, suitable user selection schemes can improve spatial diversity gain. In most of previous studies, it is always assumed that the base station (BS) knows full channel state information (CSI) of each user, which does not consider the reality. However, there are only limited feedback bits in real system. Besides, user fairness is often ignored in most of current user selection schemes. To discuss the user fairness and limited feedback, in this paper, the user selection scheme with limited feedback bits is proposed. The BS utilizes codebook precoding transmitting strategy with LTE codebook. Furthermore, this paper analyzes the influence of the number of feedback bits and the number of users on user fairness and system sum capacity. Simulation results show that in order to achieve better user fairness, we can use fewer bits for feedback CSI when the number of user is small, and more feedback bits when the number of users is large.

Iteration-stopping scheme of turbo receiver in turbo-MIMO systems

The iteration-stopping scheme of turbo receiver, consisting of an inner multiple-input multiple-output （MIMO） detector and an outer turbo decoder, was studied in this paper. In the inner MIMO detector, only the reliabilities of bits in those channel slots which included unreliable information bits were updated when the outer turbo code was a systematical one. In conjunction with the trigger events for stopping the turbo decoding, an iteration-stopping scheme of turbo receiver was proposed. Simulation results show that the proposed scheme has lower complexity, but almost the same error performance compared to the scheme with predetermined maximum iterations.

Evaluation of Linear Precoding Schemes for Cooperative Multi-Cell MU MIMO in Future Mobile Communication Systems

In Mobile Communication Systems, inter-cell interference becomes one of the challenges that degrade the system’s performance, especially in the region with massive mobile users. The linear precoding schemes were proposed to mitigate interferences between the base stations (inter-cell). These schemes are categorized into linear and non-linear;this study focused on linear precoding schemes, which are grounded into three types, namely Zero Forcing (ZF), Block Diagonalization (BD), and Signal Leakage Noise Ratio (SLNR). The study included the Cooperative Multi-cell Multi Input Multi Output (MIMO) System, whereby each Base Station serves more than one mobile station and all Base Stations on the system are assisted by each other by shared the Channel State Information (CSI). Based on the Multi-Cell Multiuser MIMO system, each Base Station on the cell is intended to maximize the data transmission rate by its mobile users by increasing the Signal Interference to Noise Ratio after the interference has been mitigated due to the usefully of linear precoding schemes on the transmitter. Moreover, these schemes used different approaches to mitigate interference. This study mainly concentrates on evaluating the performance of these schemes through the channel distribution models such as Ray-leigh and Rician included in the presence of noise errors. The results show that the SLNR scheme outperforms ZF and BD schemes overall scenario. This implied that when the value of SNR increased the performance of SLNR increased by 21.4% and 45.7% for ZF and BD respectively.

Performance Analysis of ZF and RZF in Low-Resolution ADC/DAC Massive MIMO Systems

Large number of antennas and higher bandwidth usage in massive multiple-input-multipleoutput(MIMO)systems create immense burden on receiver in terms of higher power consumption.The power consumption at the receiver radio frequency(RF)circuits can be significantly reduced by the application of analog-to-digital converter(ADC)of low resolution.In this paper we investigate bandwidth efficiency(BE)of massive MIMO with perfect channel state information(CSI)by applying low resolution ADCs with Rician fadings.We start our analysis by deriving the additive quantization noise model,which helps to understand the effects of ADC resolution on BE by keeping the power constraint at the receiver in radar.We also investigate deeply the effects of using higher bit rates and the number of BS antennas on bandwidth efficiency(BE)of the system.We emphasize that good bandwidth efficiency can be achieved by even using low resolution ADC by using regularized zero-forcing(RZF)combining algorithm.We also provide a generic analysis of energy efficiency(EE)with different options of bits by calculating the energy efficiencies(EE)using the achievable rates.We emphasize that satisfactory BE can be achieved by even using low-resolution ADC/DAC in massive MIMO.

基于MIMO模式的无线传感器网络数据传输协议

在对分簇无线传感器网络在簇群内和簇群之间数据传输能耗进行分析的基础上,提出了一种在簇群间采用M IMO模式进行数据传输的方法。该方法以HEED协议为基础,将MIMO模式引入到簇群间的数据传输过程中,极大地降低了传输能耗,并且创建了一种基于MIMO技术的分簇传感器网络能耗模型,推导出实现网络能耗最小化时系统参数的最优值。实验结果显示,与HEED协议相比,该方法更显著地降低了网络的总体能耗,使网络具有更长的生存期。

MU-MIMO用户调度和预编码跨层联合优化

针对多用户多输入多输出(Multi-User Multiple Input Multiple Output,MU-MIMO)系统中用户调度和预编码传统算法性能不佳和分层设计导致系统复杂度高的问题,利用最大信漏噪比(Signal to Leakage plus Noise Ratio,SLNR)算法的优越性,提出一种基于SLNR算法的用户调度和预编码的跨层联合优化策略,利用迭代搜索最优用户组,并在预编码中加入功率分配。仿真结果表明,新策略比传统算法能够提升系统吞吐量,并改善误码率性能,同时使系统具有较低的复杂度。

LTE系统中混合MIMO传输模式的MMSE均衡器设计及其性能仿真

本文在介绍LTE系统支持的各种MIMO传输模式基础上得出下行混合MIMO传输模式的接收信号模型，并且设计出了基于MMSE准则的均衡器来抑制这种混合干扰；为了提高系统仿真效率，本文还推导出了实际信道估计中，基于信道响应矩阵随机扰动的信千噪比修正公式，并通过链路仿真和系统仿真对比给出修正因子曲线。最后的仿真还给出了混合MIIV10传输模式环境下，不同传输模式用户的误码率和吞吐量变化曲线，结果对实际LTE系统的性能分析有很大的参考价值。

MIMO-OFDM系统ICI自消除改进算法

现有的ICI自消除算法在提高系统载干比(CIR)的同时会降低系统的抗噪声性能。针对这一问题,提出一种在发送端对数据进行复数加权共轭运算的ICI自消除改进算法,这种算法造成的相位旋转最小,可以有效减少接收信号因相位旋转而导致的相位误差,从而提高系统的抗噪声性能。仿真结果表明,所提算法具有与已有算法相近的ICI抑制能力,但比现有算法具有更好的抗噪声性能。

CoMP-MU-MIMO上行用户配对方案性能比较

协作多点传输(CoMP)是3GPP长期演进(LTE)的一个重要技术点,并将在上行采用多用户MIMO技术。分析了上行构成多用户MIMO的用户配对选择方法,并提出了一种在物理层进行用户传输速率公平性的调度方法,使系统在单个用户性能与整个系统的频率效率间取得较好的折衷。用系统仿真的方法对系统性能进行了仿真,证明了所提出算法的有效性。

临近空间通信高仰角区MIMO分集和抗雨衰方案性能研究

基于MIMO分集技术,提出了一种有效对抗雨衰的临近空间协作通信方案。理论分析并推导了该方案的系统容量。在着重对临近空间通信高仰角区雨衰信道的相关特性进行分析的基础上,仿真研究了该方案的抗雨衰性能。研究结果表明:与VBLAST系统相比,方案虽然损失了部分复用增益,但在10-3误码情况下得到近15 dB的增益。与此同时,方案在不同相关特性的信道下产生的误码性能波动小于同等条件下,VBLAST系统产生的性能波动。

基于酉阵的MIMO系统空频编码方案

针对多输入多输出系统发射分集方案中正交性与全速率之间的矛盾,在传统空频编码的基础上,提出了一种基于酉阵的空频块编码多天线系统发射分集方案。利用酉矩阵特性和块正交思想,给出了方案具体实施策略,并借助Givens变化生成典型固定酉阵,推导分析了所提方案全速率性能和准正交特性,证明了与空频块编码方案相比,该方案能更加充分地利用4根发射天线来增大空间分集的性能。最后通过不同场景下的仿真对比,也进一步验证了在不增加复杂度的情况下该分集方案的性能优势。

低分辨率ADCs大规模MIMOAF中继系统性能分析

在全双工大规模多入多出(massive MIMO)中继系统中,大量基站天线的数模转换给系统带来的硬件损伤和能量消耗,并且系统的性能可能会受到环路干扰的影响。为此,基于最大比传输/合并预处理方案,对多用户全双工massive MIMO放大转发中继系统进行研究,该系统由massive MIMO基站和多对单天线用户组成,massive M IM O基站采用低分辨数模转换且工作在全双工模式。通过随机矩阵理论,获得任一用户对各态历经速率的闭式解,并分别研究3种不同功率分配方案下的系统渐近特性。性能分析结果表明,当信源发射功率为常量且基站的发射功率与基站传输天线成反比时,系统能同时有效地遏制环路干扰和低分辨率ADCs的影响,而当信源和基站的发射功率同时与天线数成反比时,系统可抑制环路干扰的影响,但不能抑制量化噪声的影响。

基于多跳协作MIMO的WSN节能策略研究

针对WSN中高效节能的问题,引入了协作MIMO技术的基础上,提出一种多跳协作传输策略。采取实际应用更为广泛的多跳协作传输模型。仿真结果表明,相比现有的基于LEACH的多跳协作MIMO传输策略,提出的传输策略极大地延长网络生存时间达56.16%。

大规模MIMO系统传输关键技术研究进展

随着物联网的兴起和移动互联网业务种类的日渐丰富,人们对蜂窝移动通信数据传输速率以及服务质量提出了更高的要求。由于能够充分挖掘空间维的自由度,在提高频谱效率的同时获得较好的功率利用率,大规模MIMO系统引起了国内外的广泛关注。大规模MIMO系统配置的大规模天线阵列在带来性能增益的同时也带来了前所未有的挑战,如大规模天线阵列系统下传输方案的设计、急剧增加的系统硬件复杂度和计算复杂度等。首先对大规模MIMO系统下的几种传输方案,如联合空分复用(JSDM)传输方案和大规模多波束空分多址(MB-SDMA)传输方案进行了概述,简略描述了不同传输方案的原理和传输过程,进一步简要介绍了目前正在构建的大规模MIMO原型验证系统Argos和Lu Ma Mi,并展示了不同原型验证系统的整体架构与组件。

频控阵MIMO雷达中基于稀疏迭代的多维信息联合估计方法

传统MIMO雷达为了获得准确的距离信息不仅需要引入转移矩阵,而且需要积累更多的快拍数。针对该问题,该文提出了基于稀疏迭代的频控阵MIMO雷达多维信息(距离、角度和幅度)估计方法,该方法利用频控阵MIMO的发射导向矢量不仅与目标的方位角有关,同时也与目标的距离有关这一特性,通过优化加权lq范数(0<q≤1)的目标函数,采用稀疏迭代优化获取目标的距离、角度和幅度信息。该方法仅需单次快拍,并在每次迭代中求解到了目标的多维信息,故不需借助优化工具获得目标信息。仿真显示,相比DAS,IAA和IAA-R,该方法在有效减少快拍数和处理数据的同时,获得了高分辨率的目标距离、角度和幅度估计性能。

窄带干扰下MIMO系统的特征域传输方案

该文提出一种特征域的传输方案(ETS),用以提高窄带干扰下MIMO系统的容量。首先,发射端在特征域产生N路发射信息,然后根据窄带干扰信号的统计特征,通过预编码将发射信息从特征域变换至时域进行传输。在接收端,时域的接收信号再次被变换为N路特征域信号。据此,期望信道被划分为N路并行子信道,根据各子信道的干扰分布采用相对应的传输方案,以最大化干扰场景下信道的利用率。由计算机仿真可得,当系统容量为15 bit/(s·Hz)时,该文所提特征域传输方案相对于传统干扰抑制算法在2×2 MIMO系统中取得了约10 d B的性能增益。

Spectral Efficiency and Power Allocation for Mixed-ADC Massive MIMO System

This paper investigates the achievable uplink spectral efficiency(SE) of a massive multi-input multi-output(MIMO) system with a mixed analog-to-digital converter(ADC) receiver architecture, in which some antennas are equipped with full-resolution ADCs while others are deployed with low-resolution ADCs. We derive the theoretical results and corresponding approximate expressions of the achievable SE in multi-cell systems with maximum ratio combining(MRC) detector and in single-cell systems with zero-forcing(ZF) detector. Based on approximated results, the effects of physical parameters, including the transmit power, the number of antennas, the proportion of full-resolution ADCs and the quantization precision of the low-resolution ADCs on the achievable SE are revealed. Furthermore, we propose the power allocation algorithms based on the lower bound and upper bound of approximate achievable SE. Our results show that the total achievable SE improves by increasing the number of BS antennas, the signal-to-noise ratio(SNR), and the quantization precision. Results showcase that proposed power allocation algorithms remarkably improve the total achievable SE comparing to the equal power allocation algorithm, which verifies the effectiveness of our proposed schemes.

LTE-Advanced上行虚拟MIMO系统用户配对算法研究

LTE引入了虚拟MIMO技术来解决终端天线数目较少的问题。用户配对是进行虚拟MIMO传输的重要环节,传统的配对算法只进行两用户配对,但在LTE-Advanced中,由于基站端最多支持8根发送天线,因此可以进行多用户虚拟MI-MO传输。文章提出了根据传输速率进行自适应用户配对数量选择的算法,并提出最低配对调制编码方案的概念,从而能在保证边缘用户吞吐量的基础上提升系统平均性能。