一种准动态ICIC干扰协调方案

在新一代宽带无线通信系统中,小区边缘用户的性能需求是主要的需求指标之一。为提高小区边缘的数据速率,必须有效减轻小区间干扰,而干扰协调是一种有效减轻小区间干扰的有效方法。小区间干扰协调技术可分为静态协调、动态协调两种方案,但两种方案在特定情况下都有一定的缺陷。文章提出一种准动态ICIC干扰协调方案,以减轻小区间干扰,提高小区边缘用户的性能。     

一种适用于SC-FDMA多小区系统的协作调度和功率控制算法

该文针对长期演进(LTE)上行单载波频分多址(SC-FDMA)多小区系统的性能受限于小区间干扰的问题,提出一种综合考虑协作调度和功率控制的方案。该方法分步执行小区间的协作调度和功率控制,首先调度各小区中的用户,在此基础上优化用户的发射功率。调度时首先估计小区间的干扰信息并分配频率资源块给每个小区内的用户,在优化用户的发射功率时,同时考虑由于用户功率改变所造成的目标小区和其他干扰小区性能的变化。进一步提出一种低复杂度功率控制方案,在优化目标小区用户的功率时,只考虑受目标小区干扰影响最大的几个小区性能的变化,其他干扰小区性能的变化则通过引入补偿因子来估计。计算机仿真验证了该文所提方法在系统吞吐量和小区边缘吞吐量方面的性能优势显著。     

5G系统中基于小区分群的干扰管理

为了降低5G系统中超密度小区网络的小区间干扰（ICI）,提出了一种基于小区分群的干扰管理方案,其核心思想是将宏小区覆盖下的小小区分群,对群内干扰和群间干扰分别采用基于多小区协作和频域或时域的干扰避免。针对小区分群的关键即干扰权值的计算,提出了一种基于用户的信干噪比（SINR）和干扰泄露（SOIR）计算连续干扰权值的方案,该权值不仅反映用户间的干扰关系,而且自适应地调整干扰用户之间对资源的争夺策略;同时,把距离调和平均数作为小区分群的附加准则。仿真结果表明,与传统的小区分群方案相比,新方案的吞吐量增加20%~30%,小区性能和系统整体性能都有提升。     

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。     

多小区多用户MIMO系统干扰对齐的优化

多小区多用户MIMO系统中存在小区间以及小区内的干扰,传统方法提出的干扰对齐只针对2个小区或者小区内的干扰进行对齐,缺乏对小区间的干扰进行对齐处理.针对这一问题,提出了一种多小区多用户的干扰对齐优化方案,采用基于机会调制算法进行干扰对齐模式优化,不仅能够简化计算、提高量效率,而且能够消除多小区间和小区内的干扰,获得最佳的容量和多用户分集增益.     

基于部分频率复用的多小区协作方案及容量分析

针对无线蜂窝网中的小区间干扰问题,给出一种基于部分频率复用的多小区协作传输方案.该方案将小区用户划分为中心用户和边缘用户,中心用户采用频率复用因子为1的本地基站通信,边缘用户采用频率复用因子为3的多基站协作通信,并通过对多个小区的基站进行功率控制,达到抑制小区间干扰、提高系统容量的目的.数值分析表明,相对于传统多小区蜂窝系统(Traditional Multi-Cell System,TMCS)和广义分布式天线系统(Generalized Distributed Antenna System,GDAS),所提多小区协作蜂窝系统(Multi-Cell Cooperative System,MCCS)可以有效地克服小区间干扰,提高系统容量.     

基于空间分集增益的分布式快速空频编码算法

针对多点协作(Co MP)无线通信系统的下行传输问题,提出一种分布式快速空频编码(DF-SFC)的方案。通过将小区边缘用户分组和分享相邻小区间的子载波获得空间分集增益,有效缓解了载波间干扰(ICI),基于此设计分布式解码器,将用户的解码复杂度降低到相同的非分布式空频编码最佳解码器的50%。通过将所提方案与Alamouti多点协作和非多点协作方案做比较,对用户与其基站之间相对距离对比研究了可实现的传输速率,并且推断出它的性能上限和下限,用于确立小区边缘用户的阈值,实现在提出的多点协作和非多点协作模式之间切换,以提高整体性能。仿真结果表明,在服务小区边缘用户方面提出的方案均优于Alamouti多点协作和非多点协作方案。     

多天线两小区蜂窝系统的低开销线性干扰对齐算法

在蜂窝系统中,由于干扰的存在,用户性能受到影响,特别是对于小区边缘用户,其通信质量较差。干扰对齐作为一种能够消除干扰、提高系统容量的技术,近年来受到广泛关注。针对多天线两小区蜂窝系统的边缘用户,本文给出了一种系统开销小、需要天线数少的线性干扰对齐算法。该算法利用发送端预编码矢量消除小区内干扰,利用接收端干扰抑制矢量消除小区间干扰。采用本文算法后,在每个小区有 个用户、基站有 根发送天线、用户有 根接收天线的情况下,只需 和 就可以实现上下行的干扰对齐,整个系统可以达到 的自由度,并且在下行链路中不需要小区间反馈,而在上行链路中只需要较小的小区间反馈。仿真结果表明,本文提出的算法能够以较小的开销实现比以往的算法更好的性能。      

基于干扰和功率控制的多小区分布式波束成形

在多小区干扰信道中,基于分布式竞争设计,提出两种优化基站发射波束成形矩阵的设计,使每个小区的最差信干噪比最大.一种是基于干扰控制的设计,利用差异化的干扰系数,抑制小区间的干扰,提高系统性能.另一种是基于功率控制的设计,通过调整各基站的发射功率,提高系统性能.这两种设计,都能保持算法的分布式特性,又能有效地提高用户信干噪比.仿真分析表明,基于功率控制的设计在功率大的情况下,性能优于基于干扰控制的设计.     

TD-LTE网络上行CoMP方案研究与外场试验

TD-LTE采用同频组网,使得小区间干扰成为限制网络容量提升的主要瓶颈之一。TD-LTE规模试验的测试数据表明,终端有超过70%的概率会同时检测到多个小区的信号。多小区协作(CoMP)技术通过相邻多个小区对信号进行联合处理,可有效降低小区间干扰。介绍了几种上行CoMP的实现方案及仿真性能,并重点介绍在TD-LTE试验网络中开展上行CoMP外场试验的情况。测试结果表明,通过上行CoMP可将小区边缘用户上行吞吐率提升50%~100%,显著改善了用户体验。     

A new technique for multi-cell joint channel estimation in time division code division multiple access based on reduced rank singular value decomposition

A new technique for multi-cell joint channel estimation (MCJCE) in time division code division multiple access based on singular value decomposition (SVD) reduced rank technique is proposed in this paper. MCJCE is one of the effective solutions to improve the mobile system performance throughout mitigate the inter-cell interference form the neighboring cells. The increasing complexity of multi-cell system model due to the additional processing of the interferer users will be solved by using SVD reduced rank technique, where a limited number of parameter that really need it to describe the channel matrix will be estimated. Two models of multi-cell approaches are discussed, the first one depended on reconstruct the convolutional midamble matrix of inactive users in serving cell by the strongest interferer users from the neighboring cells. The second one will be more inclusive to user traffic scenarios in mobile systems and will be expanding to contain all detected users. The simulation results prove the validity of the proposed reduced rank technique for precision channel estimation (6.4 and 5 dB) and (9 and 7 dB) for case 1 and 2 respectively; BER performance improvements over the conventional estimators.     

一种抑制小区间干扰的比例公平调度算法

针对LTE-Advanced系统中小区间干扰及用户公平性问题,提出了基于多小区联合预编码和静态功率控制的比例公平(MCPPC-PF)调度算法。通过干扰空间迫零和静态控制发射功率的方法抑制小区间干扰,并结合比例公平(PF)调度算法,提高用户的公平性。仿真结果表明,与传统算法相比,MCPPC-PF算法提升系统容量的同时还提高了用户的公平性;与基于多小区联合预编码和静态功率控制的最大化吞吐量调度算法相比,MCPPC-PF算法在系统容量损失了4.6%的情况下,边缘用户容量提高了约45%。     

Analysis of resource allocation with macroscopic diversity for uplink OFDMA systems

This paper describes a framework of link capacity analysis for interference mitigation of uplink Orthogonal Frequency Division Multiple Access systems. A Macroscopic Diversity Oriented Resource Allocation (MDORA) is performed via inter-cell coordination based on the location of Mobile Stations (MSs) by exploiting macroscopic diversity in the uplink transmission. In the numerical analysis, the Inter-Cell Interference is derived as a closed form over a multi-cell environment. Subsequent numerical results demonstrate that MDORA offers an efficient inter-cell interference mitigation and a throughput expansion. Moreover, when up-link sectorization is adopted, the MDORA scheme presents a lower inter-cell interference, a reduced outage probability and an improved throughput.     

Data rate optimization in inter-cell interference environment of visible light communication

This paper investigates the higher-order modulation using Hadamard matrix to improve the data rate performance, particularly in the interference regions of a multi-cell environment in visible light communication. It presents a novel scheme which utilizes Hadamard matrix to produce orthogonal pulses (OPs) that mitigate the inter-cell interference, and covers the interference areas of the room for mobile receivers. The minimum power requirements is examined to achieve optimum data rate in whole area of the room. Moreover, the signal-to-noise ratio is derived to provide the similar capacity distribution between cells. Theoretical analysis and simulation experiments of bit error rate (BER) and capacity performances are conducted and three arrangements of signals in cells are compared, which are defined as all cells use different sets of OPs (DSOPs), all cells use the same set of OPs (SSOPs) and reuse OPs in diagonal (ROPD) cells of the room. The results show that the BER performance of DSOPs is \(10^{-2.7}\) at the high interference area, which is the best performance compared to ROPD and SSOPs. Moreover, DSOPs requires less power to achieve 2, 3 and 4 bits/symbol compared to ROPD and SSOPs.     

多小区OFDMA解码转发中继通信系统的分布式资源分配算法

现有的多小区OFDMA中继通信系统资源分配的研究主要集中在单个小区的场景下,而不考虑由相邻小区引起的共信道干扰的影响。然而,实际系统中更高的频率复用因子和较小的小区半径,会导致严重的小区间干扰。该文考虑了多小区OFDMA解码转发中继通信系统的资源分配,它是一个混合离散型优化问题,即使在单小区场景下也是NP-hard难解的。由于全局最优求解的复杂性,该文提出一种分布式的次优的资源分配算法。算法分成两步:首先基于较低的信道反馈系统开销,分配子载波以满足用户的QoS要求;然后,将功率控制问题进一步简化并分解为多个凸优化的子问题,由椭球算法不断收敛的对偶变量迭代调整各个子问题的最优求解。仿真结果表明,与参考算法相比,所提算法的系统容量和边缘用户的吞吐量性能都有很大的提升。     

Biorthogonal Frequency Division Multiple Access Cellular System with Angle Division Reuse Scheme

In conventional OFDMA cellular systems, mobile stations (MSs) suffer from large ICI in fully loaded cellular environments with full cell frequency reuse, especially at the cell-edge. The fundamental cause is that the signals from serving Base Station (BS) and interference BSs, are modulated by same exponential bases, at same subcarrier. In this paper, a generalized low-complexity fractional Fourier transform (FrFT) based biorthogonal frequency division multiple access (B-OFDMA) cellular system with multiple angle division reuse scheme (MADR) scheme for inter-cell interference (ICI) cancellation is proposed. FrFT angle is regarded as a kind of time-frequency combination resource (TFCR), and it can be optimally allocated to each BS of the cellular system, based on simplified minimal base correlation coefficient (MBCC) criteria, which confirms the inner-cell mutual orthogonality between modulating bases at different subcarriers, and inter-cell mutual approximate orthogonality between modulating bases at same subcarriers. Therefore, at the receiver, ICI can be dramatically suppressed by MMSE equalization and correlative detection in respective optimal FrFT domain. Extensive system simulations are conducted for various practical scenarios to demonstrate the superior performance of the proposed FrFT MADR scheme in bit error rate (BER) and system throughput, especially for cell-edge MSs, compared with conventional OFDMA cellular with different ICI cancellation schemes and scheduling schemes.     

A novel zero-forcing precoding method for multi-cell MIMO systems

Precoding methods at the Base Station (BS) can be used to deal with the inter-cell interference and improve the signal quality of the user especially at the cell edge. In this paper, a novel Zero-Forcing (ZF) precoding method is proposed and investigated for multi-cell Multi-Input Multi-Output (MIMO) systems. We propose a relaxed ZF precoding method by relaxing the ZF criterion to some degree so that the inter-cell interference may not be zero. Complexity analysis shows that compared with the conventional ZF method, the additional computation complexity for the proposed method is trivial. Simulation results show that the proposed relaxed ZF method has better performance than the conventional ZF method in terms of the sum-rate, especially at low Signal to Noise Ratio (SNR).     

Research on uplink coordinated transmission schemes in LTE-advanced systems

The investigation of inter-cell interference mitigation techniques is a key area in wireless communications.Coordinated multiple points(CoMP) transmission/reception is a candidate technique for interference cancellation in 3GPP LTE-Advanced system.However,the coordination scheme in CoMP remains a key research problem to be solved,which will have a strong influence on the performance of CoMP.In this paper,a novel coordinated transmission scheme is proposed for the uplink LTE-Advanced system.In our scheme,several base transceiver stations(BTS) and users are selected as coordination partners which form a CoMP cluster.Joint processing is used at the receiver to mitigate interference.From the perspective of coordinated partner selection,our scheme can be divided into static and dynamic coordination which are both considered to fully exploit the throughput gain of CoMP.The proposed schemes are evaluated by system level simulation and compared with the conventional LTE system based upon single cell processing.Our simulation results demonstrate that the proposed schemes attain superior performance as opposed to the conventional system in terms of cell average and cell edge throughput.