多小区Massive MIMO系统中低复杂度MMSE线性检测算法研究

文章针对多小区Massive MIMO上行链路系统中MMSE线性检测中涉及大矩阵求逆具有高复杂度的问题,提出了一种低复杂度的MMSE检测算法。首先考虑已知目标小区的信道状态信息而其他小区信道状态信息未知条件下,通过求解干扰项与噪声之和的均值与方差,将多小区信道模型转化为单小区信道模型,再利用MMSE算法进行检测。为了降低求逆矩阵的复杂度,将大矩阵分解为对角矩阵和空心矩阵之和,再利用诺依洛曼级数近似将其展开,并优化展开项因子来增加算法收敛速度。仿真结果表明,所提出的改进算法在性能损失很少的情况下复杂度从O(K~3)降低到O(K~2),其中K为本小区中的用户数。     

基于干扰感知的上行调度算法研究

针对LTE系统中上行小区间干扰特性,提出了一种基于干扰感知的LTE上行比例公平调度算法改进方案。该方案通过小区协作方式计算协作簇内的小区调度优先级和基于干扰感知的用户调度优先级并以此进行资源调度。仿真结果表明,相对于未采用干扰感知的比例公平调度算法,该方案的两种形式都能够在保障系统吞吐量性能的前提下,有效地提高小区边缘用户性能,同时证明了干扰感知的越精确,小区边缘用户的性能越好。     

一种LTE多小区干扰环境下的信道估计方法

随着无线通信的发展,小区密度与频谱利用率不断增加,高频率复用度使得处于小区边缘的用户受到严重的来自邻小区的同频干扰。提出一种长期演进(LTE)多小区干扰环境下的信道估计算法,当服务小区与强干扰小区使用相同的导频位置,且两小区之间存在时偏与频偏时,联合估计服务小区与干扰小区的信道频域响应(CFR);根据导频位置、导频序列、时偏和频偏大小信息建模,通过求解方程组得到服务小区与强干扰小区的信道时域响应(CTR),对服务小区与强干扰小区CTR分别进行傅里叶变换得到CFR。仿真结果表明,在服务小区信干噪比(SINR)较小时,与传统信道估计算法相比,所提方法在归一化均方误差(NMSE)、误比特率(BER)性能上均有明显提升。     

移动通信网小区选择无干扰信道组的一种算法

本文提出了一种在小区内选择无干扰信道组的算法。文中介绍了这种算法的基木原理及计算流程;因此,可根据所要求的不同小区数N和每个小区的信道数m,计算出无同频干扰、区内邻道干扰和无三阶互调干扰的信道组,并可求出最大的相容信道组数,从而达到了在满足无干扰的条件下,频谱的高度利用。     

非理想信道环境下的多小区干扰对齐技术研究

由于普遍采用频率复用因子为1的方式组网,多小区干扰已成为限制无线通信系统容量的主要因素。为了有效抑制小区间干扰提高小区边缘吞吐量,近年提出了干扰对齐技术,其优势在于可以获得干扰信道的最高自由度。一般的干扰对齐研究仅限于理想信道,研究通过非理想信道环境下的多小区干扰对齐技术,分析了时延信道信息对干扰系统容量的影响。结果表明,信道状态信息的时延大大降低了系统容量,特别是在高信噪比条件下对系统性能的影响更大。     

异构网络特征子信道干扰对准算法优化

包含多种低功率发射节点的异构网络因其在系统容量提升和解决室内及热点场景覆盖上的优势,正成为新一代无线通信系统组网的趋势。但异构网络干扰问题也因小区数目的增加而复杂化。近年提出的干扰对准技术因能实现系统自由度的最大化而成为解决异构网络干扰问题的有效手段。文章在对经典干扰对准算法进行分析的基础上,对特征子信道干扰对准方案进行了改进,优化了发送预编码矩阵和接收滤波矩阵算法,并提出算法在宏蜂窝——毫微微蜂窝异构网络场景下的应用方案。     

干扰距离最远的多用户多天线干扰对齐算法

针对多用户多天线中小区边缘用户同频干扰问题,提出了一种基于干扰距离最远准则的多用户MIMO干扰对齐优化算法,通过对等效干扰信道进行SVD分解,选择与等效干扰信道矩阵距离最大的特征子信道作为传输预编码矩阵,并分析了算法复杂度以及空间相关性对性能的影响,仿真结果显示系统频谱效率较原始算法在8天线下有31.57％的提高.     

一种加权均方误差最小化的鲁棒性干扰对齐算法

线性干扰对齐的一个常见优化目标是总传输速率最大化,但因为和速率函数的非凸特性而难以直接求解。加权均方误差最小化算法借助均方误差与和速率之间的等价关系解决了这一问题。这一方法需要获得准确的信道状态信息,在实际应用中,通道估计误差的存在会导致算法性能的下降。该文提出一种改进算法,在干扰对齐预编码矩阵与接收矩阵的优化求解过程中将通道估计误差的统计特性考虑在内。仿真结果表明,相比以往的加权均方误差最小化算法,该文算法对信道估计误差具有较高的鲁棒性,可以有效提高总的传输速率。     

三小区多用户MIMO系统中干扰对齐优化算法

针对三小区多用户MIMO干扰信道系统,通过一个启发性例子,联合设计发射预编码矩阵和接收赋形矩阵,给出基于特征向量闭式解的干扰对齐优化算法,相比已有干扰对齐算法,用户端可使用更少的天线资源获得相同的自由度性能,且只需本小区内用户协作共享信道信息;并归纳出普适场景下系统配置与可达自由度之间的关系：设定每个小区中的基站配置M根天线和K个用户,用户配置N根天线,各个基站对本小区中每个用户都发送d个数据流,当M=N≥2 Kd时,所提算法总共可获得3 Kd个自由度。所提算法可以完全消除小区间干扰和用户间干扰,相比传统的正交化干扰抑制算法,系统容量得到了明显地提升。     

基于压缩感知的同频干扰下LTE系统信道估计算法

本文提出一种基于压缩感知的同频干扰下长期演进系统信道估计方法。与现有方法不同,本文将干扰和噪声区别对待,利用干扰信号结构建立该系统下多小区信道估计模型(MCCE)。由于无线信道在宽带系统下表现出较为明显的稀疏特性,本文将压缩感知技术应用于上述模型,通过求解新的感知矩阵,并利用多输入多输出信道共有非零支撑集的特性,提出了适用于长期演进系统的联合改进子空间追踪算法(J-MSP),解决了上述模型下字典矩阵列相关度较高的问题;由于所提模型中含有未知的干扰符号,因此还需解决信道和干扰符号的联合估计。仿真结果和分析表明,本文方法在干扰与本小区同步时相比单小区信道估计方法性能显著提升,异步时与最大似然算法性能相当,同时也适用于无干扰场景。      

基于LTE上行的随机接入前导信号与SRS信号间干扰研究

为最大程度提高系统容量,3GPP成立了长期演进（Long Term.Evolution）计划。LTE上行随机接入信道（RACH）前导信号和参考信号的传输均通过映射到子帧内SC-FDMA符号的形式来实现,两者在时间和频率上可能出现重叠,此时将产生相互干扰。本论文讨论了3G LTE随机接入前导信号和参考信号中的SRS信号（Sounding Reference Signal）间相互干扰产生的原理,并通过多终端链路仿真,分析两种信号在相互干扰影响下的性能变化,总结影响性能的因素,并提出通过选择特定SC-FDMA符号传输SRS信号的方式来减小干扰的方法。     

An Iterative Interference Alignment Scheme for the SISO Interference Channel

In this paper, we propose a novel iterative interference alignment (IA) scheme for the single-input single-output (SISO) interference channel system using minimum total mean square error criterion under the individual transmitter power constraints. We show that interference alignment under such criterion could be realized through an iterative algorithm. The convergence of the proposed algorithm is discussed. We also proposed a robust MMSE-based iterative design with imperfect channel state information. Simulation results, compared with several existing IA schemes, have shown that the proposed method could effectively improve the BER performance of the SISO interference channel system while maintaining the same degree of freedom as Cadambe?CJafar scheme. The proposed robust MMSE-based iterative interference alignment scheme is shown to be less sensitive to channel estimation error.     

LTE系统中基于压缩感知的信道反馈方案研究

针对基于完全信道状态信息预编码的长期演进(LTE)多输入多输出-正交频分复用(MIMO-OFDM)系统面临反馈开销很大的问题,提出了基于压缩感知的反馈方案,该方案利用压缩感知技术在接收端对信道估计得到的信道信息进行观测,并将观测值反馈到发送端,在发送端通过梯度投影算法重构信道状态信息。通过仿真证明,该反馈方案在大幅减小反馈开销的同时达到了与完全信道状态信息反馈时非常接近的性能。     

基于软频率复用规划的LTE小区间干扰抑制

主要分析了LTE系统的小区间干扰（ICI）协调技术和ICI消除技术。针对传统软频率复用规划的不足提出了改进方案,并且通过迭代ICI消除技术,达到更好的干扰抑制效果。     

Quasi‐distributed Interference Coordination for HSPA HetNet

The heterogeneous network (HetNet) has been discussed in detail in the Long‐Term Evolution (LTE) and LTE Advanced standards. However, the standardization of High‐Speed Packet Access HetNet (HSPA HetNet) launched by 3GPP is pushing at full steam. Interference coordination (IC), which is responsible for dealing with the interference in the system, remains a subject worthy of investigation in regard to HSPA HetNet. In this paper, considering the network framework of HSPA HetNet, we propose a quasi‐distributed IC (QDIC) scheme to lower the interference level in the co‐channel HSPA HetNet. Our QDIC scheme is constructed as slightly different energy‐efficient non‐cooperative games in the downlink (DL) and uplink (UL) scenarios, respectively. The existence and uniqueness of the equilibrium for these games are first revealed. Then, we derive the closed‐form best responses of these games. A feasible implementation is finally developed to achieve our QDIC scheme in the practical DL and UL. Simulation results show the notable benefits of our scheme, which can indeed control the interference level and enhance the system performance.     

3GPP LTE中Femtocell数据信道干扰管理策略

对3GPP LTE中针对家庭基站引入后的干扰场景进行了介绍,之后从频率资源和功率资源2个资源分配自由度对数据信道的干扰管理算法进行了分析,最后,对家庭基站在3GPP LTE版本10中的标准化方向进行分析。     

Network Performance Analysis of TCP-Based 3GPP LTE Time Division Duplex Systems

This paper deals with the determination of downlink (DL) and uplink (UL) channel split ratio for time division duplex (TDD) based long term evolution (LTE) networks. In a TDD system, UL and DL transmissions are carried out at different time intervals, but share the same frequency band. The TDD framing in LTE is adaptive in the sense that the DL to UL bandwidth ratio may vary with time. This paper proposes an adaptive split ratio (ASR) scheme for LTE networks to automatically adjust the bandwidth ratio of DL to UL, according to the current traffic profile, wireless interference, and transport layer parameters. This provides the maximum aggregate throughput in LTE systems. The performance analysis shows that ASR scheme outperforms static allocation in terms of higher aggregate throughput and better adaptively to network dynamics. Further, it is also observed that the ASR scheme performs well for LTE, compared to worldwide interoperability for microwave access (WiMAX) system.     

移动卫星系统与LTE网络间干扰共存性能的研究

The interference coexistence performance between the systems of a Long Term Evolution (LTE) network and Mobile Satellite Service (MSS) system, both of which work around the frequency of approximately 2 GHz according to the bandwidth allocation in China, is proposed in this article. The related background of an MSS system and the common terminologies are introduced. Further, the coexistence scenarios of different coverage situations shared by the two systems are discussed. The interference impact of an MSS transmission on an LTE system is evaluated using a specific Monte Carlo method. Finally, simulation results show that although no crucial issues for the coexistence of an LTE downlink and the MSS are observed, the LTE uplink suffers a considerable amount of interference from the MSS transmission. Given the insufficient isolation between LTE and MSS existing networks, and the rapid advance in the field of LTE, problems may emerge in the near future. Further, this article can be of sig-nificance in providing reference for frequency spectrum planning in the existing LTE net-works.     

Intercell Interference Coordination Using Threshold-Based Region Decisions

IMT-Advanced mobile communication systems make it possible for any devices to access high-speed networks anytime and anywhere. To meet the needs of IMT-Advanced systems, cellular systems must solve the problem of intercell interference caused by frequency reuse. Intercell interference problems become severe when orthogonal frequency division multiplexing (OFDM) transmission, which is a key technology for 4G communication systems, is used in a cellular system. In this paper, a zone-based intercell interference coordination (ICIC) scheme with high flexibility and low cost is proposed, and its performance is evaluated through multicell system-level simulations carried out according to the simplified 3GPP (3rd Generation Partnership Project) Long Term Evolution (LTE) system parameters. In the proposed algorithm, each cell is divided into several regions based on threshold values. Each region reuses frequencies in different ways, and the regions have different maximum transmit (TX) powers according to the interference environment. Even though the proposed scheme can be implemented with low complexity by using only the existing user equipment (UE) measurement, simulation results have confirmed that it provides significant improvements in geometry distribution.