蜂窝通信系统中天线选择在虚拟MIMO的应用

天线选择技术(AS)和虚拟MIMO(Virtual MIMO,VMIMO)技术都被广泛应用于只有一个无线射频(RF)模块的上行通信传输中。为了使两者的优势都得以发挥,该文提出将天线选择技术应用在虚拟MIMO系统中,该文中称作VMIMO-AS系统。然而,仅从被调度用户设备(User Equipment,UE)中选择最好的天线组成虚拟MIMO并不能确保系统获得最佳的性能。该文提出了VMIMO-AS系统中几种不同用户设备配对算法,并对这些算法就吞吐量性能和用户间公平度进行了比较。仿真结果表明第1个用户的选择需要应用AS原则,而考虑到复杂度和性能的折中,配对用户的选择则不需要应用AS原则。     

虚拟MIMO技术

介绍了无线资源管理上行链路中的虚拟MIMO技术,重点分析了该技术各种用户配对方案的优缺点和经典的资源调度算法,最后介绍了虚拟MIMO技术国内外研究成果及虚拟MIMO技术在无线传感器网络领域的广泛应用前景.     

LTE多天线系统资源分配算法与性能分析

在给出LTE（Long Term Evolution）下行多天线传输系统模型的基础上,通过理论分析得出了各多天线模式下用户接收信号信噪比（SINR）的计算公式,提出了含预编码的多用户MIMO（MU—MIMO—Pre）的调度算法。通过系统级仿真得到了不同多天线模式（包括其对应调度算法）以及不同站距下的吞吐量结果和用户公平性曲线,并对各种多天线模式的优缺点进行分析和比较。     

一种基于SNR门限的上行虚拟MIMO配对算法

虚拟多输入多输出（VMIMO）系统由多个单天线的移动终端配成一组,占用相同的时频资源传输信息,关键技术之一是用户配对算法。基于传统的配对算法无法兼顾到配对用户间远近效应与系统吞吐量问题,提出了一种基于信噪比（SNR）门限融合调度的上行VMIMO配对算法。仿真结果表明,所提算法在保证低信噪比用户服务质量的基础上提高了系统吞吐量,同时可以降低对相邻小区的干扰,减小系统丢包率,更适合实际系统的应用。     

协同信道空时优化MIMO无线传输系统

该文提出一种基于虚拟信道的空时优化多输入多输出(MIMO)无线传输系统。通过在发射端产生不同的空时虚拟信道,与实际空间无线信道级联,构成系统的整体传输信道即协同空分信道。系统可以根据接收端的反馈信息采用模拟退火算法来优化虚拟信道,改善误码率(BER)性能。利用虚拟信道方法,可以使一根MIMO发射天线在同一时间、同一频段传输多路叠加合并后的数据信号,从而可以使发射的不同数据信号的总路数超过发射天线的数量,突破了现有MIMO系统在同一时间、同一频段最多只能发射与发射天线数量相等的不同数据信号的传统方式,可以显著提高系统的频谱效率。仿真结果和基于ZC706和AD9361硬件平台的微波暗室实际测试结果充分验证了新MIMO系统的有效性。     

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。     

基于虚拟MIMO的TD-LTE终端省电机制

介绍了无线资源管理上行链路中的虚拟MIMO技术,分析了该技术几种常用的用户配对方案的优缺点,最后重点分析了虚拟MIMO技术在TD-LTE系统中用来提高能量有效性的可能,并提出了基于虚拟MIMO的TDLTE终端省电机制的构想。     

基于块空时分组编码虚拟MIMO中继传输方案

以LTE TDD系统上行链路为研究对象,提出了一种基于块空时分组编码的虚拟MIMO中继传输方案,并推导给出基站低复杂度的虚拟MIMO系统接收机检测算法。研究表明:本传输方案具有提高小区边缘及网络覆盖盲区用户链路传输可靠性的特性,同时可克服传统中继方案频谱效率降低的缺点。     

大规模MIMO系统中收发联合阈值天线选择算法

在大规模多输入多输出(massive MIMO)系统中使用天线选择算法可提高能效和系统吞吐量,然而适用于传统MIMO系统的天线选择算法具有高复杂度,很难用于massive MIMO系统。为优化天线选择算法,以算法复杂度和系统容量为优化目标,提出了收发联合阈值天线选择算法。该算法在发射端使用最大范数双向天线选择算法进行天线选择,在接收端使用分组maxvol算法并通过仿真实验结果的预设阈值进行天线选择。仿真实验表明,收发联合阈值天线选择算法在降低复杂度的同时可以提高系统容量,与递增天线选择算法相比,系统容量最多可提高52.2 bit/s/Hz。提出的天线选择算法可以满足不同天线相关度和信噪比的传输环境。     

基于块空时分组编码DFT-S-OFDM虚拟MIMO传输方案

该文提出了一种基于块空时分组编码的DFT-S-OFDM上行链路虚拟MIMO传输方案,并给出一种低复杂度的虚拟MIMO系统接收机检测算法。仿真研究表明：基于块空时分组编码的DFT-S-OFDM虚拟MIMO传输方案可保持原DFT-S-OFDM系统低峰均比的特性,显著降低虚拟MIMO系统接收机检测门限,提高上行链路虚拟MIMO系统传输可靠性。     

Group-based user pairing for virtual MIMO in LTE

A user pairing method is proposed to improve the throughput gain of virtual multiple input multiple output (virtual MIMO) in 3G long-term evolution (LTE).The approach taken in this study separated the user pairing into four steps 1) the users are divided into two groups according to their signal-to-noise ratio (SNR), and different user pairing metrics are proposed for each group; 2) the scheduler chooses a user for transmitting by a given rule; 3) the scheduler searches the pairing candidate for the selected user in each group; 4) the scheduler chooses the final pairing user from the co-group and crossover-group candidates by using a marginal utility function, to balance fairness and efficiency.The method can improve the throughput of users with high SNR, and guarantee fairness for users with low SNR, so it can be used in 3G LTE systems.The article provides both theoretical analysis and simulation results to support the idea.     

3D-MIMO codebook aided multiple user pairing scheme in LTE-Advanced systems简

Two-dimensional（2D） multiple-input multiple-output（MIMO） is currently concentrated on propagation in horizontal plane, but the impact of elevation angle is not considered. However, due to the three-dimensional（3D） character of the real MIMO channel, 2D MIMO cannot achieve the optimal system throughput. A multiple-user MIMO（MU-MIMO） user pairing scheme was proposed, in which the vertical dimension was taken into consideration. In the proposed scheme, a 3D codebook based on full dimension MIMO channel was designed; then two 3D MU-MIMO user＇s pairing schemes are proposed combining the proposed joint and separate 3D codebook. Simulation evaluates the proposed 3D codebook aided user pairing scheme and compares with the previous 2D MU-MIMO user pairing technology. Owing to the additional spatial degree of freedom in vertical dimension, the proposed 3D MU-MIMO user pairing schemes can effectively improve the overall system performance.     

Space‐time block coding in millimeter wave large‐scale MIMO‐NOMA transmission scheme

In this paper, we introduce a new wireless system architecture using space‐time block coding schemes (STBC) and non‐orthogonal multiple access (NOMA) in millimeter wave (mmWave) large‐scale MIMO systems. The proposed STBC mmWave large‐scale MIMO‐NOMA system utilizes two MIMO subarrays, transmitting data over two channel vectors to mobile users. To reduce the communication overhead and latency in the system, we utilize random beamforming with optimal coefficients at the base station and random‐near random‐far user pairing in implementing the NOMA scheme. Our results show that the proposed STBC mmWave large‐scale MIMO‐NOMA technique significantly outperforms the previous counterparts.     

上行多用户MIMO系统中的用户与天线联合选择方案

在多用户MIMO系统中,基站所能同时进行通信的用户数受到基站和用户端天线数的限制,随着用户数的增加,系统的性能反而会降低,因此,用户选择技术就成为一种改善系统性能的有效技术.在本文中,针对上行多用户MIMO系统提出了一种低复杂度的用户选择算法.为获得更大的系统性能,在用户选择的基础上,进一步提出了一种用户与天线联合选择算法.这两种算法在极大地简化计算复杂度的条件下,提供了与最优算法几乎相同的性能.     

Achievable sum‐rate analysis of correlated two‐antenna MIMO uplink channels

This paper analyzes the achievable sum‐rate of correlated two‐antenna multiple‐input multiple‐output (MIMO) uplink channels. Most of previous works have considered the case when a single user has multiple transmit antennas (i.e. multi‐antenna single‐user scenario). This paper considers the case when two‐antenna MIMO uplink channels comprise two users with a single transmit antenna (i.e. single‐antenna two‐user scenario). The analytic and simulation results show that the achievable sum‐rate of correlated single‐antenna two‐user MIMO uplink channels highly depends on the angle difference between the receive correlation coefficients of two users. It is also shown that the achievable sum‐rate of correlated single‐antenna two‐user MIMO uplink channels is larger than that of correlated two‐antenna single‐user MIMO uplink channels and can even be larger than that of independent and identically distributed Rayleigh two‐antenna MIMO uplink channels. Copyright © 2009 John Wiley & Sons, Ltd.     

Low complexity MIMO scheduling with channel decomposition using capacity upperbound

In multiuser MIMO systems, the base station schedules transmissions to a group of users simultaneously. Since the data transmitted to each user are different, in order to avoid the inter-user interference, a transmit preprocessing technique which decomposes the multiuser MIMO downlink channel into multiple parallel independent single-user MIMO channels can be used. When the number of users is larger than the maximum that the system can support simultaneously, the base station selects a subset of users who have the best instantaneous channel quality to maximize the system throughput. Since the exhaustive search for the optimal user set is computationally prohibitive, a low complexity scheduling algorithm which aims to maximize the capacity upper bound is proposed. Simulation results show that the proposed scheduling algorithm achieves comparable total throughput as the optimal algorithm with much lower complexity.     

5G双小区协作流动热点补偿研究

在通信用户数密集用户业务总量较多的UMi场景下,无线网络节点较多小区覆盖半径较小,用户在小区间移动导致小区间用户分布不均匀,原有用户数及业务量标准部署的5G异构网络相对稀疏,无法满足用户流动产生热点热时容量需求时,双小区协作流动热点补偿采用异构网络多点协作传输技术对小区进行补热,将处于相同移动状态的多个用户虚拟成一个以中心用户为中心的用户簇,建立3D MIMO流动热点模型,提出在两小区以用户最小传输速率为约束条件,最小化小区基站总功率的优化算法,得出高容量、高速率用户体验的"潮汐效应"解决方案。     

Multiuser Pairing-up Schemes under Power Constraints for Uplink Virtual MIMO Networks

Orthogonal user pairing (OUP) was proposed for virtual multiple-input multiple-output (V-MIMO) in uplink 3G LTE system. However, its complexity is too high for practical implementation, especially when user population is large. To improve on this, semi-orthogonal user pairing (SUP) was suggested as an alternative. In this paper, two novel SUP algorithms, namely correlative angle-based SUP (CA-SUP) and Frobenius norm-based SUP (FN-SUP) algorithms are proposed. In view of the fact that ideal power control is difficult to implement, fixed power allocation (FPA) and adaptive power allocation (APA) constraints for the user pairing algorithms are introduced. Ergodic capacities for CA-SUP and FN-SUP algorithms with APA and FPA constraints, in terms of the numbers of users and antennas at Node-B, are evaluated and their capacity upper bounds are derived. Analysis and simulation results show that FN-SUP and CA-SUP algorithms requiring only limited channel state information (CSI) perform well and suit in particular for virtual V-MIMO systems.