一种下行多用户MIMO系统中的鲁棒波束形成算法

提出了一种下行多用户MIMO系统中的鲁棒性线性处理算法.该算法利用了信道均值和天线相关矩阵等信道统计信息,在总发射功率不大于目标值的约束条件下,能够使所有用户的均方误差(total mean square error,TMSE)在随机信道上的平均值最小.该算法不明显依赖瞬时信道信息(channel state information,CSI),当信道估计得到的CSI不准确时,它能够有效降低由CSI偏差带来的性能损失.仿真结果表明提出的算法能够有效地降低由于不准确CSI带来的误码率和平均MSE的损失.     

多用户下行链路使用广义空间调制的方案

针对多用户多输入多输出系统,讨论了一种多用户下行链路使用广义空间调制传输多用户信号的方案。该方案利用广义空间调制(GSM, generalized spatial modulation)技术,发送端和接收端均不需要知道信道状态信息,系统结构比较简单。同时,能有效消除信道间干扰,获得较优的系统性能。仿真分析表明,该方案在克服传统多用户MIMO系统缺点的同时,能获得较低的系统误码率。     

多用户MIMO下行链路线性收发机设计

该文提出一种以最小化系统总均方误差(Sum MSE)为准则,迭代设计线性收发机的方案。该方案通过对接收机的改进设计,能够有效地避免传统MMSE设计过程中出现的拉格朗日乘子不易计算的缺点,大大降低设计复杂度。由于拉格朗日乘子有解析解,发射预编码矩阵也有闭式解,并且可以通过定点迭代算法有效解出。收端的接收机也不用基站下发,只要各自采用MMSE均衡即可。仿真结果证明该方法的有效性。     

下行链路多用户MIMO线性收发机设计

针对多用户多天线(MIMO)下行链路系统中的信干噪比(SINR)平衡问题和功率最小化问题,本文基于上下行链路对偶性提出一种新的收发机设计策略.该策略通过首先优化功率和接收滤波器、然后优化预编码器的交互迭代方式,避开传统算法中的复杂特征向量问题,从而极大的降低算法复杂度.仿真结果显示,本文算法具备更好的收敛性,相同性能下所需的计算精度远小于传统算法.     

多用户STBC下行链路预处理优化算法

给出了一种基于天线选择的多用户STBC下行链路预处理优化算法.该方法对发送端天线进行组合,即从所有发送天线中选出部分天线组成多个天线集合,每个天线集合中发送天线个数为能够获得空间分集增益的最小数目,从这些天线集合中选出最大化多用户STBC系统分集增益的一个集合作为最终发送天线.对基于天线选择的算法进行了仿真分析,结果表明,该算法比未采用选择的算法可以获得更高的分集增益,还与基于特征模式选择的算法进行了比较,结果表明:该方法比基于特征模式选择的算法使系统获得了更高的性价比.     

多小区多用户TDD MIMO下行链路干扰抑制预编码算法

针对多小区多用户TDD MIMO下行链路,提出了一种基于预编码的联合干扰抑制算法。首先,利用广义MMSE信道逆的QR分解设计预编码矩阵抑制下行链路的多用户干扰(MUI)。然后,从信号能量泄露的角度设计第二个预编码矩阵抑制小区间干扰(ICI)和残留的多用户干扰。该算法能够利用TDD MIMO信道的互易性,不需要用户端的反馈。在市区微小区组成的多用户TDD MIMO系统中的仿真结果表明,该算法能有效地提高系统容量和用户端平均信干噪比(SINR)。     

MIMO下行链路联合波束成形稳健性设计

针对MIMO下行链路中的发射/接收波束成行器,提出了一种对非精确CSI稳健的联合设计方案。方案采用的设计准则是在总发射功率受限的条件下最小化系统和MSE。根据此非凸和非线性优化问题的最优解条件,通过交替地计算每个用户的最优解来近似地获得原问题最优解。仿真结果表明,与非稳健性方法相比,该方案能有效地减少非精确CSI引起的性能损失。     

下行链路干扰分析

WCDMA系统属于干扰受限系统，这使得干扰分析在3G网络规划中显得尤为重要，本文重点分析了下行链路的小区内干扰和小区间干扰。     

TD-SCDMA下行链路算法研究

传统联合检测技术算法复杂度高,不利于TD-SCDMA下行链路基带接收芯片的设计。本文提出了一种新的分决联合检测算法,将需要运算的矩阵进行分决处理,以降低运算量。在理论分析的基础上,建立下行链路仿真模型,通过分析分决数目对系统性能以及运算复杂度的影响,可以证明分决技术显著降低了下行链路接收机的运算复杂度。     

LTE无线网络下行链路动态资源分配算法研究

本文采用李雅普诺夫最优化的方法设计了一种资源分配算法,理论分析和仿真结果表明,该方法不但提高了系统的吞吐量,同时还在在吞吐量和延迟之间实现了较好的均衡。     

Robust Transceiver Design for Multicell MIMO Downlink Systems

The robust linear transceiver design for the more general model of multicell MIMO downlink system with imperfect channel state information is discussed in this paper. Our aim is to minimize the total power of the network while the quality of service (QoS) in terms of mean-square error (MSE) for every user should be strictly guaranteed for every channel realization in the uncertain region. Unfortunately, this problem may be infeasible due to the MSE constraints. Therefore, we provide a complete analysis of this problem by dividing the solutions into two phases. In phase I, a novel approach is devised to check the feasibility of this problem by considering one alternative problem which is always feasible. This alternative problem is troublesome due to infinite nonconvex MSE constraints. To handle this, we propose an iterative algorithm that performs optimization alternatively by switching between the precoders and decoders. The two subproblems in the algorithm can be recast as semidefinite programming problems which can be efficiently solved. In phase II, one novel iterative algorithm is proposed to solve the original robust problem. Finally, simulation results show that our proposed algorithms converge rapidly and can provide guaranteed QoS for all users. Moreover, we also show that, the more antennas at the users, the more power savings it can provide.     

时空编码WCDMA下行链路MMSE接收机

ＷＣＤＭＡ下行链路的性能受到信道衰落和多址干扰的影响。本文提出一种带时空编码的ＷＣＤＭＡ下行链路ＭＭＳＥ接收机,可以在减小信道衰落的同时达到抑制多址干扰的目的。应用高斯近似法对接收机性能进行了分析。仿真结果表明,该接收机能使系统性能得以较大提高。     

基于上下行对偶性的多用户MIMO下行链路鲁棒收发机设计

针对多用户多天线(MIMO)下行链路信道状态信息(CSI)非理想的条件,该文研究SINR平衡问题及功率最小化问题的收发机设计。在信道误差受限情况下,该文建立worst-case SINR上下行链路对偶性,并基于该对偶性,为两种鲁棒收发机提出新的设计策略。该策略避免了凸优化内点迭代算法,从而大大降低复杂度。仿真结果显示,所提算法与现有的凸优化算法性能一致。     

Robust Transceiver Optimization in Downlink Multiuser MIMO Systems

We study robust transceiver optimization in a downlink, multiuser, wireless system, where the transmitter and the receivers are equipped with antenna arrays. The robustness is defined with respect to imperfect knowledge of the channel at the transmitter. The errors in the channel state information are assumed to be bounded, and certain quality-of-service targets in terms of mean-square errors (MSEs) are guaranteed for all channels from the uncertainty regions. Iterative algorithms are proposed for the transceiver design. The iterations perform alternating optimization of the transmitter and the receivers and have equivalent semidefinite programming representations with efficient numerical solutions. The framework supports robust counterparts of several MSE-optimization problems, including transmit power minimization with per-user or per-stream MSE constraints, sum MSE minimization, min-max fairness, etc. Although the convergence to the global optimum cannot be claimed due to the intricacy of the problems, numerical examples show good practical performance of the presented methods. We also provide various possibilities for extensions in order to accommodate a broader set of scenarios regarding the precoder structure, the uncertainty modeling, and a multicellular setup.      

Loading Schemes for Downlink OFDMA Systems

In this paper we study the subcarrier and bit allocation strategies for downlink OFDMA system.Our opti-mization objective is to find optimum subcarrier and bit assignment minimizing the total transmitted power with the con-straints on BER and data rate for all users.We divide this problem into three steps:resource allocation,subcarrier assign-ment and single-user power and bit allocation.For the first two steps we propose new algorithms.Various loading schemesconstitute by combining these algorithms as well as algorithms proposed in Ref.[6].Simulation results demonstrate thatour proposed suboptimal loading scheme can achieve performance closer to the near optimal algorithm in Ref.[8]withmuch lower complexity than schemes in Ref.[6].     

用于WCDMA系统的MMSE接收机的功率与数据速率相结合的分配算法

该文针对3GPP WCDMA系统的反向链路,提出了一种基于MMSE接收机的功率和数据速率相结合的控制算法。该算法可以保证用户在达到目标信干比的同时,减小平均发射功率、加快收敛速度,从而提高系统的整体性能。仿真结果验证了所提出方案的正确性和优化算法的有效性。采用该文提出的算法,与MMSE功率控制算法比较,系统容量可增加近10％,而收敛速度可提高30％左右。     

OFDM系统的联合收发机设计

Orthogonal Frequency Division Multiplexing (OFDM) is an effective technique to deal with a frequency selective channel since it can convert the channel into some flat fading subchannels. However, very different output SNR values of the sub-channels will lead to poor bit error performance when a linear equalizer and Equal Bit Allocation (EBA) are adopted in OFDM systems. So, we proposed three novel nonlinear Joint Transceiver (JT) schemes based on Zero-Forcing (ZF) criterion and Minimum Mean Square Error (MMSE) criterion respectively, which can transform all subchannels of an OFDM system into subchannels with identical channel gain. Thus, EBA is equivalent to the Optimum Bit Allocation (OBA) for these subchannels. Numerical analysis helps us to obtain the theoretical approximate BER values of the JT scheme. Simulation results verify the numerical analysis and confirm that the performance of our proposed JT scheme greatly outperforms the traditional linear equalizer with EBA at moderate and high SNR values.     

视距相关信道下考虑非理想CSI的多用户MIMO收发联合设计

在FDD模式多用户MIMO(Multi-input Multi-output)系统下行链路中,由于信道估计、反馈信道等存在误差,使得发送端获取理想信道状态信息(CSI,channel state information)十分困难。针对获得非理想CSI的多用户MIMO系统,考虑在基站和各用户的天线分别具有相关性并引入视距分量的信道条件下,提出了一种新的基于块对角化的MMSE准则收发联合设计算法。该算法首先通过块对角化消除用户间的共信道干扰,然后针对存在信道估计误差的用户信道依据MMSE准则分别迭代求解每个用户预编码和解码矩阵。论文设计出一种基于训练序列的信道估计误差算法,并获得等效信道模型,使得收发端获得的信道状态信息更有实际意义。本文假设反馈信道理想,发射端可以完整得到信道估计矩阵。在MMSE准则下,推导获得了Lagrange乘子的解析解,避免了求解非线性方程的复杂过程,显著降低了计算复杂度。和已有算法相比,该算法不仅可以获得良好的误码性能还可以对各用户进行独立优化,处理更加灵活。仿真分析了视距分量、信道相关性以及信道估计误差对算法性能的影响。仿真结果表明,该算法误码性能良好,算法收敛快,并且对信道估计误差带来的影响有较好的抑制作用。