MIMO-OFDM低延迟信道估计改进算法

为了克服多输入多输出正交频分复用(MIMO-OFDM)移动系统中采用空间复用技术的下行链路性能出现衰退现象,提出一种信道估计改进算法。它根据信道状态并通过一个决策指导方案为4×4 MIMO系统提供大约4bit/s/Hz的数据。通过使用LDPC短码,在LDPC译码器输出端采用MIMO-OFDM符号重建方法,达到提高估计精度的目的。在3GPP MIMO空间信道模型下进行了仿真验证,结果表明指定速率下的估计精度得到改善。     

MIMO—OFDM系统信道估计算法研究

正交频分复用（OFDM）技术能有效克服多径带来的不利影响,提高频谱利用率;多输入多输出（MIMO）技术,可以在不增加系统带宽和发射功率的前提下,成倍提高系统容量和带宽利用率。将两者结合的MIMO—OFDM系统是近年来的研究热点,信道估计在提高该系统性能方面发挥着重要作用。本文主要介绍MIMO—OFDM系统结构,在此基础上介绍基于导频的信道估计,半盲信道估计和盲信道估计。     

基于预编码的MIMO—OFDM系统信道盲估计

本文提出了一种冗余线性预编码应用于多输入／多输出—正交频分复用（MIMO—OFDM）系统，根据编码结构，重构接收信号，使其中表示信道衰落的部分具有旋转不变性性质，结合子空间方法中的TLS—ESPRIT法，实现MIMO—OFDM信道的盲估计。与基于训练序列的信道估计方法相比，本文的信道估计方法不需要训练序列，因而能够节约带宽、提高频谱效率。文章最后进行了Monte Carlo仿真，仿真结果证明了该方法的有效性。     

一种基于EM算法的MIMO-OFDM系统信道估计技术

从提高多输入多输出正交频分复用（MIMO—OFDM）系统频谱利用率的目的出发,提出了一种改进型的基于EM（Expectation Maximization）算法的信道估计技术。仿真结果表明,改进后的算法可以显著提高频谱利用率,同时保持原算法的精度。     

MIMO—OFDM信道估计新方法

利用小波变换思想,提出一种基于小波去噪的多输入多输出正交频分复用（MIMO—OFDM）系统信道估计方法,以提高信道估计性能。该方法首先利用最小二乘（LS）方法进行信道估计,然后对估计后的结果进行小波去噪处理。该方法不需要预先知道信道的统计特性,与传统最小二乘信道估计方法相比,性能有明显提高。     

MIMO—OFDM系统的盲信道估计算法综述

本文首先介绍了MIMO—OFDM系统模型，然后讨论了研究MIMO—OFDM移动通信系统信道估计的意义．紧接着对MIMO—OFDM系统目前存在的几种典型盲信道估计算法进行分析和讨论，最后总结和展望了MIMO—OFDM系统信道估计算法的研究方向和关键问题。     

一种FDD大规模MIMO系统下行信道估计算法

信道估计是大规模多输入多输出(MIMO)系统的关键技术之一。本文针对频分双工(FDD)大规模MIMO正交频分复用(OFDM)系统,研究了下行信道估计问题。通过利用大规模MIMO-OFDM信道在角度-频域中的块稀疏特性,提出了基于块匹配追踪的低复杂度估计算法。另外,针对采用时域正交导频存在估计周期过长,有可能超过系统相干时间的问题,提出了天线分组发送方案,通过牺牲观测数据长度来换取信道估计周期的减少。仿真结果表明,所提算法具有良好的抗噪性能,可以准确找出稀疏向量的非零值位置,并可自适应确定稀疏度。     

4G中MIMO-OFDM系统的研究

本文介绍了第四代移动通信（4G）系统中的OFDM和MIMO技术，叙述了MIMO—OFDM系统模型及其相应的关键技术，包括同步技术、空时处理技术、自适应调制和编码技术、信道估计技术。     

GF(2p)LDPC编码的相位调制OFDM系统在瑞利衰落信道的性能

OFDM是一项能有效对抗高速无线通信中多径衰落的关键技术，为了进一步提高OFDM系统的误码性能，许多信道编码技术已被应用于OFDM系统中，二元域LDPC码以其近香农限的误码性能和较低的译码复杂度成为研究的热点。在AWGN信道下，多元域LDPC码比等效码长的二元域LDPC码有更好的纠错性能。本文提出了一种将多元域LDPC码经过MPSK调制后用于OFDM系统的新方法。仿真结果表明，在多径衰落信道下，通过合理选择多元LDPC码域的阶数和调制的方法，多元域LDPC编码的高阶调制OFDM系统比等效码长的二元域LDPC编码OFDM系统具有更好的性能，并且由于采用了多元域LDPC的快速BP译码，译码复杂度只是稍有增加。     

MIMO-OFDM的通信系统模型设计

为了达到更高的信息传输速率,提出了一种基于MIMO-OFDM的通信系统的实际模型。主要利用正交频分复用(OFDM)各子载波的频谱可以重叠、技术频带利用率高的特点,再配合多输入多输出(MIMO)系统,在通信速率上相比普通单输入单输出(SISO)系统有大幅提升。具体表现为对MIMO信道的估计方案进行改良,主要针对稳定环境下的MIMO信道进行估计,避免了快速时变环境下信道估计性能低劣的缺点。并在符号误差(STO)估计技术的基础上,针对性地找到一般条件下的系统偏差,由此可以得到更为精确的STO估计值。相对于常规方案,该方案性能更为稳定和优异。     

协作空分复用CSM系统中的信道估计算法研究

文章就当前MIMO应用过程中终端多天线受限制问题,阐述了单天线终端协作与基站组成虚拟MIMO多天线阵列——基于OFDMA的CSM协作空分复用系统结构。同时,提出对OFDMA系统中时频二维的资源进行分“块”独立进行信道估计,简化了OFDMA系统信道估计模型的复杂度。然后从应用的角度对比分析了基于OFDMA的CSM系统的信道估计算法LS和MMSE两种算法性能与优缺点。通过在PB3信道模型中仿真,得出适用于慢变信道的平滑滤波后的LS信道估计算法。     

MIMO-OFDM系统中信道盲估计与检测

针对MIMO-OFDM系统,提出了一种基于子空间的盲信道估计与检测方案,该算法将阵列信号处理的思想应用到MIMO-OFDM系统中,通过发送端信号的冗余编码,利用一种类ESPRIT算法进行盲信号检测和信道估计。仿真结果表明该算法的有效性及其信道盲估计方法的性能。     

一种MIMO-OFDM系统信道估计简化方法

提出了一种基于MMSE准则的MIMO-OFDM系统信道估计简化方法。该方法将信道估计问题转化为TBT线性方程求解问题,然后利用快速求解算法避免了复杂的矩阵求逆和矩阵相乘,大大降低了实现复杂度。仿真结果表明,相比于传统MMSE算法,该简化算法在降低复杂度的同时仅带来微弱的性能损失。     

Joint pre-processing co-channel interference cancellation for single user MIMO

In general, multiplexing and diversity gains of single user MIMO systems are restricted by min(M,N) where M, N denote the number of antenna elements at a transmitter and receiver, respectively. In order to increase the multiplexing/diversity gains and improve the performance of single user MIMO systems, a joint pre-processing co-channel interference cancellation (JPCIC) method is proposed. The JPCIC is analyzed in both the perfect and the imperfect channel state information. The dependence of channel capacity on the number of antenna elements in every subset, the number of subsets, transmit powers and channel estimation errors is discussed. As theoretical calculation result, the channel capacity increases when the multiplexing/diversity gains and/or the transmit power increase in a certain channel model whether the channel estimation error is absent or present. Compared to the conventional zero-forcing method, the channel capacity of JPCIC is considerably higher because of higher multiplexing/diversity gains, however, it is less robust and decreased more rapidly due to incomplete cancellation of interference terms when the channel estimation error increases. There is a trade-off between the channel capacity and the complexity of system, however, according to quick development in circuit techniques and miniaturization of devices, the JPCIC is expected to be an attractive technology for MIMO system.     

Channel estimation using spatial partitioning with coalitional game theory (SPCGT) in wireless communication

Wireless Networks - In 5G wireless communication estimation, of downlink channel with orthogonal frequency division multiplexing (OFDM) integrated with multiple input multiple output (MIMO) is a...     

MIMO-FSK non-coherent detection with spatial multiplexing infast-fading environment

Accurate estimationand real-time compensation for phase offset and Doppler shift are essential for coherent multi-input multi-output (MIMO) systems. Here, a spatial multiplexing MIMO scheme with non-coherent frequency-shiftkeying (FSK) detection is proposed. It is immune to random phase interference and Doppler shift while increasingcapacity. It is valuable that the proposed spatial multiplexing MIMO based on energy detection (ED) is equivalentto a linear system, and there is no mutual interference caused by the product of simultaneous signals in square-lawprocessing. The equivalent MIMO channel model is derived as a real matrix, which remains maximal multiplexingcapacity and reduces the channel estimation complexity. Simulation results show that the proposed scheme hasoutstanding performance over Rician flat fading channel, and experimental system obtains four times the capacitythrough 4 antennas on both transmitter and receiver.     

Iterative Joint Channel Estimation and Multi-User Detection for Multiple-Antenna Aided OFDM Systems

Multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems have recently attracted substantial research interest. However, compared to single-input-single-output (SISO) systems, channel estimation in the MIMO scenario becomes more challenging, owing to the increased number of independent transmitter-receiver links to be estimated. In the context of the Bell layered space-time architecture (BLAST) or space division multiple access (SDMA) multi-user MIMO OFDM systems, none of the known channel estimation techniques allows the number of users to be higher than the number of receiver antennas, which is often referred to as a "rank-deficient" scenario, owing to the constraint imposed by the rank of the MIMO channel matrix. Against this background, in this paper we propose a new genetic algorithm (GA) assisted iterative joint channel estimation and multi-user detection (GA-JCEMUD) approach for multi-user MIMO SDMA-OFDM systems, which provides an effective solution to the multi-user MIMO channel estimation problem in the above-mentioned rank-deficient scenario. Furthermore, the GAs invoked in the data detection literature can only provide a hard-decision output for the forward error correction (FEC) or channel decoder, which inevitably limits the system's achievable performance. By contrast, our proposed GA is capable of providing "soft" outputs and hence it becomes capable of achieving an improved performance with the aid of FEC decoders. A range of simulation results are provided to demonstrate the superiority of the proposed scheme.     

有信道估计误差MIMO MRC系统性能研究

利用维希特随机矩阵理论和矩生成函数方法,推导了有信道估计误差的独立瑞利衰落信道上采用多输入多输出（MIMO）最大比合并（MRC）天线分集方案的矩形M进制正交幅度调制（MQAM）的平均误符号率（SER）解析表达式。数值计算结果阐明了信道估计误差和收发天线数对矩形MQAM调制MIMO MRC系统误码性能的影响。     

Performance Evaluation of Adaptive MIMO-OFDM Systems with Limited Feedback Using Measurement Based Channel Models

Performance evaluation of enhanced link adaptation method for MIMO-OFDM systems with limited feedback using measurement based channels and a stochastic channel model is presented in this paper. In particular, impact of practical channel estimation and feedback errors on link performance is analyzed. An adaptive spatial and modulation scheme selection process is based on the effective signal-to-interference-plus-noise ratio (ESINR). Mutual information effective SINR mapping method is applied for calculating ESINR values due to its capability of accurate estimation of the error rate performance of large variety of MIMO channels. Numerical results show that simple adaptive systems that switch between diversity/multiplexing or beamforming/multiplexing schemes obtain relatively good performance in realistic 2 × 2 MIMO channels. It is also shown that the imperfect channel estimation and feedback errors can have significant impact on the link performance. Furthermore, it is noticed that using the stochastic channel model in performance simulations can give rather pessimistic results compared to true measurement data.     

基于迭代的FH-OFDM小数倍频偏估计算法

为了提高跳频正交频分复用（FH—OFDM）系统载波同步估计精度,提出了一种使用信道估计结果辅助,3次迭代的载波和定时估计算法。通过对接收信道噪声的估计确定门限逻辑,实现了高精度小数倍频偏估计。仿真结果表明,20dB信噪比时,在高斯白噪声下,新算法的估计精度高于基于循环前缀的算法10倍;在多径信道下,新算法的估计精度高于基于循环前缀的算法100倍;实验表明,使用该算法接收机性能优于基于循环前缀的算法。实验结果表明,该算法星座收敛较好。