Femtocell关键技术及组网应用

本文对femtocell 概念及技术特点进行了阐述;针对femtocell 关键技术进行了分析;分析了femtocell 系统组网架构,并对相关架构进行分析,提出了网络建设及演进方向;对比了femtocell 与Wi-Fi 之间的发展关系、功能定位.     

Femtocell网络干扰抑制技术综述

femtocell是一种室内微型基站,能以较低的功率为室内用户提供高速率的宽带服务,极大地解决了都市生活中室内信号覆盖困难的问题,是未来室内通信服务的主要手段之一。然而femtocell和其他通信设备一样面临着通信干扰管理的巨大挑战,首先在femtocell采用MIMO、OFDM、OFDMA等系统时,对其干扰抑制技术进行分析,然后介绍了femtocell的设备部署以及干扰类型,最后针对femtocell的部署特点以及适用的通信系统进行了比较和总结。     

LTE中femtocell间的功率控制算法

3GPP长期演进(LTE)系统中femtocell密集部署时,femtocell之间会存在较强干扰,针对femtocell的下行干扰,提出了一种基于干扰级别的功率控制算法。根据设定的信干噪比(SINR)门限值,给femtocell用户设置相邻干扰标志,通过上行信道发送给femtocell,再转发给相邻femtocell,femtocell由收到的干扰标志数量划分级别,根据干扰级别进行不同的功率调整。仿真结果表明,该算法很好地提升了femtocell用户的低SINR,femtocell用户吞吐量比无功率控制情况下至少提高了2.1Mbps,达到了降低femtocell间干扰的目的。同时表明,femtocell部署越密集,控制效果更加明显。     

LTE系统中femtocell的动态频谱接入方法

针对LTE系统中femtocell的通信需求,给出一种基于认知无线电技术的动态频谱接入方案,提出一种上行频谱的感知方法,femtocell可发现周围被macrocell用户占用的频谱,还能进一步对这些频谱承载的业务类型进行识别,并根据不同的业务类型,选择不同的接入方法。如果femtocell检测到一段频谱承载的是话音业务,femtocell采用跳频的方法接入这段频谱;如果承载的是数据业务,femtocell就采用功率控制的方法接入频谱。仿真结果表明,该方法使femtocell实现对周围频谱承载业务的智能化识别和接入,从而在满足macrocell用户不同业务类型信干噪比要求的前提下,提高了femtocell小区的吞吐量。     

基于改进的SFR算法家庭基站干扰协调方案研究

在LTE-A通信系统中采用家庭基站(femtocell)与宏基站组成异构网络来满足网络无缝覆盖的需求。然而,当家庭基站与宏基站采用相同的频率资源时就会产生严重的小区间干扰问题。为此,针对已改进的SFR算法的不足,进行进一步改进,提出一种新的改进的SFR算法。首先,根据已改进的SFR算法对宏基站与femtocell进行频率资源分配。然后,通过自适应频率选择为femtocell选择合适频率资源。最后,对femtocell进行功率控制。仿真结果表明,该方案不仅能够很好地解决宏基站小区与femtocell以及femtocell小区间的同频干扰问题,而且对于系统总吞吐量以及边缘小区吞吐量均有很好的提高。     

一种基于femtocell群的缓存切换策略的研究

为了提高局部室内无线通信质量,家庭基站正逐步应用于各类室内无线通信场景。在密集部署femtocell场景中,当用户设备由宏小区层切换至femto层时,密集的femtocell信号会影响用户设备切换的准确性,增加用户设备切换开销和不必要切换概率。针对上述问题,在密集部署femtocell环境下针对切换提出一个femtocell分集理念,在提高切换准确性的同时,降低不必要切换次数,并在此基础上提出了一种缓存切换策略,以提高设备由宏小区层切换至femto层的效率,通过仿真对所提机制的性能进行了验证。     

Inter-femtocell interference coordination in 3D in-building scenario

With rapid development of femtocell,dense deployment of femtocells in buildings will become an important study scenario.In this scenario,there exists severe inter-femtocell interference in the same building,which is revealed by our simulations in the 3-dimention(3D) scenario.If this type of interference is not well controlled,services to indoor users are bound to be deteriorated,especially for the femtocell edge users.Motivated by this problem,femto users’ received interference model is constructed based on the scenario of 3D femtocell deployment.Then,a graph theory based in-building inter-femtocell coordination scheme is proposed,which includes three phases:establishment of femtocell interference graph,femtocell clustering and frequency resources allocation based on the proposed cluster influence circle.Finally,the simulation results confirm that the proposed scheme improves the femtocell average throughput by 22.4% and 26.2% in comparison with frequency universal reuse scheme and frequency hopping scheme respectively,and ensures the channel demodulation reliability of cell edge femto users.     

2011中国femtocell高峰会议9月召开

市场调研机构Informa在201O年12月下旬发布的最新市场研究报告中表示，经过2009、2010两年的市场预热，2011年将成为femtocell高速发展的元年。2011中国femtocell高峰会议（http：／／www．conference．cn／femto）将于9月7～8日在北京召开，自2009年首届举办，此次为第3届会议。     

Femtocell发展势头正好需统一标准完善生态系统

毫微微小区（femtocell）是2007年上半年露出水蕊的一项新技术，笔者曾著文（《现代电信科技》2007年第10期）详尽介绍过。虽然femtocell的优势和潜在好处已被众多移动运营商所认同，但是任何一项新技术的成功需要有统一的标准，需要完整的生态系统来支持，否则就不可能把市场做大。     

AWB7125／7225：蜂窝功率放大器

ANADIGICS推出AWB7125和AWB7225两款小型蜂窝功率放大器（PA）。AWB7125和AWB7225功率放大器针对频段5的WCDMA和LTE应用而优化，包括picocell、企业级femtocell和高性能用户端设备（CPE）。     

家庭基站技术挑战和研究现状

家庭基站作为一种提高室内信号覆盖的新技术,受到了业界的广泛关注.它能以较低的功率为室内用户提供高速率高带宽的服务.本文首先介绍了家庭基站的概念,并分析了在已有的宏蜂窝网络中引入家庭基站带来的好处,然后对家庭基站面临的技术挑战和研究方向进行了说明和分析,最后介绍了家庭基站标准化和商用的现状.     

Interference Management and Six-Sector Macrocells for Performance Improvement in Femto–Macro Cellular Networks

Femtocells are considered as a solution for indoor high data rate demands. Interference mitigation is a fundamental challenge in two-tier femto–macrocell networks. In this paper, we consider six-sector macrocell layout for reducing the co-tier interference in the macrocell network and cross-tier interferences from macrocell to femtocell network. As interference reduces, the whole of available spectrum can be used in each macrocell which increases the spectrum efficiency. We also consider interference-level algorithm to allocate resource for femtocell in which macrocell uses the whole of spectrum. In the coverage area of each sector, femtocell uses a portion of the spectrum that is not used by the macrocell users. This approach ignores the high co-channel interference from the macrocell network to the femtocell network and vice versa in each sector. Simulation results show that the proposed layout and interference management scheme reduce the downlink interference and increase the efficiency of the orthogonal frequency division multiple access (OFDMA)-based femtocell and macrocell. Consequently, system throughput and outage probability are improved significantly.     

Analytical evaluation of downlink interference mitigation in multi‐macrocell/femtocell networks with frequency & cell partitioning

In this paper, we propose an interference mitigation method to suppress the downlink interference in multi‐macrocell/femtocell networks, and analytically evaluate the interference mitigation and average rate performances. Specifically, the proposed interference mitigation method consists of three steps: frequency partitioning, cell partitioning, and sub‐band allocation. In the frequency partitioning step, the whole downlink frequency band is divided into nine non‐overlapping sub‐bands. In the cell partitioning step, each macrocell is divided into four macrocell regions and three femtocell regions for macrocells' and femtocells' communications, respectively. In the sub‐band allocation step, each macrocell or femtocell region is allocated a sub‐band to guarantee that any two neighboring macrocell/femtocell regions use different sub‐bands. Conducted simulation results show that the proposed method is effective in mitigating the downlink interference and improving the average downlink per‐channel rate in multi‐macrocell/femtocell networks. In summary, the major contribution of the proposed interference mitigation method is that the downlink interference can be mitigated without cooperation between macrocells and femtocells, while the full frequency utilization of the macrocell is achieved. Copyright © 2016 John Wiley & Sons, Ltd.     

UMTS Multi-Service Uplink Capacity and Interference Statistics of Femtocells

In this work, the multiservice uplink capacity of single and multiple femtocells is given. The COST231 multiwall and multifloor indoor propagation model has been used to calculate the indoor propagation loss. Results show that the uplink capacity of a deployed femtocell will reduce by 2 % if two extra femtocells are deployed in the same building higher and lower of it. Results also show that the uplink capacity is slightly affected if there are several femtocells deployed in the buildings around the one at which the femtocell under study is already exists. It is demonstrated that uplink capacity is interference limited if the femtocell is deployed to serve the users in three floors. Results show that the uplink capacity will be interference and noise limited if the femtocell is deployed to serve the users in five floors. Finally, it is found that the effect of the interference due to the uniformly distributed users within the macrocell around the femtocell is insignificant.     

基于移动宏用户距离估计的家庭基站功率控制

家庭基站是一种可在室内灵活配置、低功率的无线接入点,能够以较低功率为用户提供大带宽、高速率的服务.而家庭基站的密集部署产生了干扰问题,如何有效地管理干扰是当前家庭基站研究的关键问题.在一个移动宏用户穿越家庭基站覆盖范围的场景中,以保障其SINR为目的,设计了一种估计其与家庭基站距离来控制功率的方案,并通过仿真证明其有效性.     

双层分级蜂窝网最优频谱分配与定价

针对异频组网的双层分级蜂窝网,提出了一种基于纳什谈判解法的最优频谱分配与定价策略,该策略能激励家庭基站采用开放用户组模式,最大化频谱效益。通过Stackelberg博弈建模,分析了频谱定价与用户需求的关系。通过纳什谈判解法,获得了最佳的频谱分配与定价策略,按需地为宏基站与家庭基站分配了带宽资源,定量地分析了家庭基站所提高的频谱效益。仿真结果表明,该策略相比非合作博弈方法,可有效提高运营商以及家庭基站拥有者所能获得的频谱效益,部署家庭基站将提高蜂窝网络的总效益。      

认知型飞蜂窝网络中的子信道分配与功率控制

为了解决宏蜂窝与飞蜂窝构成的两层异构网络上行干扰与资源分配问题,提出了一种在认知型飞蜂窝的双层异构网中结合子信道分配和功率控制进行资源分配的框架。通过对异构网中跨层干扰问题进行分析与建模,将求解最优子信道分配矩阵和用户发射功率矩阵作为干扰管理问题的解决方法。模型中认知型飞蜂窝网络子信道和飞蜂窝网络用户构成非合作博弈,双方利用效用函数最优值进行匹配,构成初始信道分配矩阵;再由接入控制器根据接入条件从初始信道分配矩阵中筛选用户,并优化接入用户的发射功率矩阵,得到最优子信道分配矩阵和功率矩阵。仿真结果表明,优化框架提高了双层异构网络中飞蜂窝网络用户的吞吐量和接入率,降低了异构网中跨层干扰。