同信道干扰对多载波CDMA蜂窝系统下行信道的影响

该文主要讨论多载波CDMA蜂窝系统在下行信道中的同信道干扰问题,理论分析了同信道干扰的解析表达式,并通过计算机仿真得出了在一定的传播损耗下多载波CDMA蜂窝系统下行信道的性能。通过仿真发现,即使在有小区间同信道干扰情况下,通过简单的小区布置,多载波CDMA蜂窝系统下行信道就可以有很大的信道容量。     

LTE中频率复用改进算法研究

下一代蜂窝系统中通过频谱复用来克服小区间干扰已成为当前研究热点.针对LTE小区间干扰协调问题,重点讨论比较了几种频率复用方案,并提出一种自适应的部分频率复用优化方案和具体实现算法,仿真表明该算法能显著改善小区边缘用户的吞吐量性能和公平性参数.     

一种消除TD-SCDMA系统小区间干扰的方法

时分-同步码分多址(TD-SCDMA)系统采用的扩频码码长最大为16,当邻小区用户处于2小区边缘时会对本小区造成较大的干扰。针对上行链路提出了一种新的干扰消除方法:串行干扰消除-联合检测(SIC-JD)。该方法采用复杂低的SIC对上行链路中的小区间干扰进行消除,对于小区内干扰和残留的小区间干扰采用联合检测进行消除。3GPP case1信道下的仿真结果显示了此方法能够有效消除小区间和小区内干扰,提高接收机性能。     

多跳蜂窝网络中小区间干扰变化及对多小区网络性能的影响

对蜂窝网络中加入多跳模式后小区间干扰的变化进行了分析,通过分析和仿真给出了不同的无线传输环境下和不同的多跳模式配置(路径损耗、多跳平均跳距、多跳区域内环半径)多跳模式对小区间干扰的降低比例;根据分析结果给出了多跳模式下网络整体性能提高需要的场景和系统配置,使通过多跳模式提高多小区网络系统性能成为可能.     

LTE系统基于IDMA的干扰消除

针对LTE系统小区间干扰不可避免的问题,重点介绍基于交织多址接入(IDMA)的干扰消除,阐述了小区间干扰消除系统模型结构与原理,并给出了LTE系统基于IDMA的干扰消除仿真以及数据分析。     

TD-LTE小区间干扰抑制技术分析

TD-LTE移动通讯是一种能够有效保障移动端信息传输效率的技术,非常适用于现代4G网络,其性能高于2G或3G系统,给现代移动通讯行业的发展提供了巨大的推动作用。但是这种技术在实际的使用过程中会出现小区间干扰问题,尤其是在同频条件的小区间内干扰问题更加严重,因此必须采取有效的干扰抑制技术,提升该系统的应用效果。本文即是对TD-LTE小区间干扰抑制技术进行研究,探讨了TD-LTE的通讯原理和小区间干扰的产生原理,并说明了其干扰抑制技术,以期能为相关工作提供参考。     

多址干扰对CDMA系统的影响及干扰抑制措施

对CDMA通信系统的容量进行了理论分析,并使用SPW(Signal Processing Worksystem)软件对CDMA系统的多址性能进行了仿真,表明了多址干扰对CDMA通信系统的影响。然后,分析了几种现有抑制多址干扰的方法的性能。     

基于大系统方法的上行CDMA蜂窝系统性能分析

结合大尺度和小尺度衰落,采用大系统分析方法对CDMA蜂窝系统上行链路的性能进行分析。首先分析了小区内多址干扰和小区间干扰的情况;其次推导出了通过匹配滤波器后的信干噪比值,该值只与小区负载、用户功率、信道增益有关;最后分析了系统的误码率、吞吐量和频谱效率,并通过仿真验证了分析的准确性。仿真结果发现,随着小区负载的增大,系统的误码率增大,吞吐量下降,但频谱效率有所提高。     

TD—SCDMA智能天线与联合检测的结合仿真

智能天线波束赋形技术能很好地抑制小区间干扰,联合检测只能抑制小区内的多址干扰。在TD-SCDMA系统上行链路实现了智能天线波束赋形与联合检测的算法结合,并按照标准3GPP25．996的信道环境做了仿真,加入小区间干扰,仿真结果表明,智能天线与联合检测的结合能同时抑制小区内多址干扰和小区间干扰。     

LTE-A系统时域小区间干扰协诟技术标准化研究

异构网络被LTE-A系统视为一种提升单位区域频谱效率的关键技术而得到广泛关注。然而,异构网络会带来严重的小区间干扰,小区间干扰协调因此成为3GPP标准化进程研究的重点。首先总结了异构网络及小区间干扰协调技术,然后介绍了目前3GPP中讨论的小区覆盖扩展（CRE：CellRange Extension）和基于几乎空白子帧（ABS：Almost Blank Subframe）的时域小区间干扰协调技术。最后,基于动态系统级仿真平台,评估了CRE和ABS技术方案系统性能。     

TD-SCDMA HSUPA基于系统RoT调度的干扰控制策略

该文提出了系统RoT的概念,以及利用系统RoT进行资源调度的策略,从而控制TD-SCDMA HSUPA(High-Speed Uplink Packet Access)技术中小区间干扰水平。在该策略中,系统RoT充分考虑了用户位置信息,因此在TD-SCDMA HSUPA这种分散调度模式下也能很好地控制小区间的干扰。由系统仿真表明,该策略显著改善了系统性能。     

基于遗传算法的TD-SCDMA多小区联合检测优化技术

TD-SCDMA作为具有我国自主知识产权的3G技术标准,在商用初期阶段,来自邻区的同频干扰一直是其组网过程中主要挑战之一,多小区联合检测是有效解决邻区同频干扰的重要手段,但是由于其计算量庞大,一般实施较复杂。基于遗传算法的研究能够有效的对于TD-SCDMA中多小区联合检测中庞大的计算复杂度予以收敛,同时能够保证有效的检测精度。本文首先对TD-SCDMA同频干扰问题进行简要介绍并分别对遗传算法以及优化后的遗传算法予以阐述,同时,通过仿真结果对基于优化的遗传算法的多小区联合检测性能进行验证。     

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.     

TD-SCDMA系统空域滤波和联合检测的结合技术

在CDMA系统中,同信道干扰(CCI)是决定系统容量的重要指标,CCI包括同小区内的多址干扰(MAI)和相邻小区干扰。在TD-SCDMA系统中,多址干扰可以通过联合检测技术来消除。这里提出一种联合检测和空域滤波的结合技术,其可以同时消除同小区的多址干扰和相邻小区干扰。而且由于这种方法具有较小的运算量,已经可以被工程实现。算法分析和仿真表明TD-SCDMA系统采用这种方法比使用联合检测加天线分集的方法具有较大性能提高。     

Multi‐group linear turbo equalization with intercell interference cancellation for MC‐CDMA cellular systems

In this paper, we investigate multi‐group linear turbo equalization using single antenna interference cancellation (SAIC) techniques to mitigate the intercell interference for multi‐carrier code division multiple access (MC‐CDMA) cellular systems. It is important for the mobile station to mitigate the intercell interference as the performance of the users close to cell edge is mainly degraded by the intercell interference. The complexity of the proposed iterative detector and receiver is low as the one‐tap minimum mean square error (MMSE) equalizer is employed for mitigating the intracell interference, while a simple group interference canceller is used for suppressing the intercell interference. Simulation results show that the proposed iterative detector and receiver can mitigate the intercell interference effectively through iterations for both uncoded and coded signals. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of ANFIS Power Control for Downlink CDMA‐Based LMDS Systems

Rain attenuation and intercell interference are two crucial factors in the performance of broadband wireless access networks such as local multipoint distribution systems (LMDS) operating at frequencies above 20 GHz. Power control can enhance the performance of downlink CDMA‐based LMDS systems by reducing intercell interference under clear sky conditions; however, it may damage system performance under rainy conditions. To ensure robust operation under both clear sky and rainy conditions, we propose a novel power‐control scheme which applies an adaptive neuro‐fuzzy inference system (ANFIS) for downlink CDMA‐based LMDS systems. In the proposed system, the rain rate and the number of users are two inputs of the fuzzy inference system, and output is defined as channel quality, which is applied in the power control scheme to adjust the power control region. Moreover, ITU‐R P.530 is employed to estimate the rain attenuation. The influence of the rain rate and the number of users on the distance‐based power control (DBPC) scheme is included in the simulation model as the training database. Simulation results indicate that the proposed scheme improves the throughput of the DBPC scheme.     

A lower bound on achievable rate of MRT precoding in multicell multiuser massive MIMO networks with Rician flat fading

A multicell multiuser massive multiple‐input‐multiple‐output (MIMO) network with Rician flat fading is considered. Given channel reciprocity, non‐orthogonal uplink channel training in conjunction with minimum mean square error channel estimation at the base stations are used to acquire channel state information. In the forward link, using maximal ratio transmission precoding, base stations send data to corresponding users. In this paper, first, a closed‐form expression for signal to interference and noise ratio and a lower bound on achievable rate are obtained for arbitrary number of base station antennas. Then, using random matrix theory, a simplified approximate expression for large number of base station antennas (i.e., massive MIMO scenario) are calculated. This simplified expression shows that in a multicell multiuser massive MIMO network with Rician flat fading, like Rayleigh fading, as the number of base station antennas goes to infinity, the effects of uncorrelated noise and intercell and intracell interferences tend to zero. The only factor limiting the performance of system is the correlated intercell interference, that is, pilot contamination, due to non‐orthogonality of channel training sequences in adjacent cells. Numerical results show that our obtained closed‐form expression is a good lower bound on sum‐rate for various system parameters. Copyright © 2016 John Wiley & Sons, Ltd.     

A Coordinated Location-dependent Downlink Scheduling Scheme in Cellular TD-CDMA Networks with Partitioned Cells: A Two-Cell Two-Partition Case

A downlink networkwide opportunity scheduling scheme, called coordinated location-dependent downlink scheduling scheme (CLDSS), that combines the intracell power allocation and intercell transmission coordination is proposed for cellular TD-CDMA networks. Each cell in the network is partitioned into co-centric areas based on the load distribution, and the transmission from base stations is controlled based on the intracell load as well as coordinated to minimize intercell interference. The performance in terms of average throughput employing the CLDSS is analyzed for a 2-cell system in shadow fading environment with two partitioned areas in each cell—which provides an upper bound on the cellular system performance. Monte Carlo simulation study is also done to validate the numerical results obtained from the analytical study. It is shown that CLDSS scheme can provide soft throughput, i.e., the average throughput remains relatively invariant with the number of users and also can provide better performance in the non-uniform user distribution within a cell when compared to non-CLDSS schemes.     

区间C／I平衡多区蜂窝CDMA系统的性能

本文研究多区蜂窝ＣＤＭＡ系统的性能。采用区间载扰比（Ｃ／Ｉ）平衡技术控制移动台和基台的发射功率以补偿路径损失和对数阴影的综合影响，用蒙特卡诺模拟方法计算了区间Ｃ／Ｉ平衡蜂窝ＣＤＭＡ系统的中断概率，研究了相邻小区数和不同标准偏差的对数阴影对系统性能的影响以及微蜂窝ＣＤＭＡ系统的总用户数和小区数的关系，并同区内Ｃ／Ｉ平衡蜂窝ＣＤＭＡ系统的性能进行了比较。