Femtocell——新兴3G室内覆盖技术的探究

Femtocell是用于增强室内覆盖的一项新兴技术,它的发展推动了固网和移动网的融合（FMC）。相对于同类业务,它具有低成本,高服务质量的优点,并且不需要改变核心网,受到了标准化组织和业界的密切关注。本文对Femtocell进行了解释,阐述了Femtocell技术的基本要素,对比了Femtocell相对其他室内覆盖方案的技术优点,指出了商业化实现的现状及需要解决的问题。     

应用Femtocell快速解决室内3G信号弱覆盖问题

应用Femtocell技术，能有效解决用户室内3G信号深度覆盖问题，为快速改善室内的3G弱覆盖积累实践经验。本文在简要归纳Femtocell特点和优势的基础上，探讨Femtocell的应用经验及面临的问题，进而提出新的建议。     

Femtocell：3G带来的发展契机

众所周知,Femtocell技术是一种扩展移动通信室内覆盖的解决方案,能帮助运营商实现室内,包括家庭场景和企业场景的完全覆盖。在2G时代,由于信号的覆盖基本能满足用户话音业务的需求,因此运营商对Femtocell的需求并不是特别强烈。进入3G时代,由于信号覆盖、数据业务以及FMC（固移融合）需求的提升,Femtocell受到了全球众多运营商的青睐。     

Femtocell技术的由来、优势和市场前景

Femtocell是用于增强室内无线覆盖的一项新技术,近年来受到了业界的广泛注意,发展十分迅速。本文叙述了Femtocell技术的由来和发展;讨论了Femtocell系统的优越性和需解决的关键技术;介绍了国外业界对Femtocell市场的预测。     

Femto技术跟踪研究

Femtocell是毫瓦微蜂窝基站,提供高质量低成本的室内网络解决方案,将会比宏单元实现方式更加有效地使用功率和频率资源的优势。目前,Femtocell通过采用新技术和设计有效的Femtocell架构,解决资源分配、时钟同步和回程、语音服务,干扰管理,基站接入、切换和移动性以及网络运营安全等一系列关键技术问题。上海电信的实验表明:Femtocell室内覆盖技术可以提供高质量低成本的室内无线网络解决方案,是提供差异化业务的最好途径,也是部署下一代移动数据业务必不可少的手段。对各家网络综合运营商提高无线室内覆盖的范围和服务质量有非常重要的意义。     

Femto技术跟踪研究

Femtocell是毫瓦微蜂窝基站,提供高质量低成本的室内网络解决方案,将会比宏单元实现方式更加有效地使用功率和频率资源的优势。目前,Femtocell通过采用新技术和设计有效的Femtocell架构,解决资源分配、时钟同步和回程、语音服务,干扰管理,基站接入、切换和移动性以及网络运营安全等一系列关键技术问题。上海电信的实验表明：Femtocell室内覆盖技术可以提供高质量低成本的室内无线网络解决方案,是提供差异化业务的最好途径,也是部署下一代移动数据业务必不可少的手段。对各家网络综合运营商提高无线室内覆盖的范围和服务质量有非常重要的意义。     

Femtocell系统中认知无线电频谱感知技术

Femtocell技术是为解决3G网络的室内覆盖问题而提出,应用此技术可较好地改善室内信号质量。由于Femtocell同3G系统应用同样的频谱资源,因此可以应用认知无线电频谱感知技术解决频谱资源的复用问题。文中的研究背景为TD-SCDMA系统,分析了频谱感知的原理,给出了感知步骤,并提出了提高频谱感知精度的方法。     

引入Femtocell对CDMA网络的影响

Femtocell是极具竞争力的FMC实现手段之一,可以帮助运营商快速解决室内深度覆盖问题。主要从Femtocell系统结构入手,对引入Femtocell系统对CDMA网络的影响及其网络规划进行分析。     

固定移动网络融合解决方案:Femtocell

Femtocell是市场驱动下的产物,旨在解决家庭及中小企业的室内覆盖问题,近年备受综合运营商的追捧。文章简单介绍了Femtocell设备、接口、网络结构及其对现有移动通信网络的影响,分析了Femtocell的诸多优点,最后预测了Femtocell将会有良好的发展前景。     

Femto典型场景应用和业务策略探讨

Femtocell是业界针对全业务运营商提出的一种室内覆盖、容量解决方案,它利用已有固定宽带提供回程,实现移动通信网络的有效延伸。作为固定移动融合的新技术,个人移动通信市场和家庭宽带通信市场的结合点,Femtocell将是全业务运营商提供差异化业务的重要技术手段。本文主要介绍了Femtocell的技术方案以及国内外运营商的运营现状和策略,同时分析了基于Femtocell的典型场景应用和业务策略。     

毫微微小区技术浮出水面

毫微微小区是一种旨在改善室内覆盖的小型低成本基站，能够在网络最边缘提供高质量的覆盖，适用于家庭及办公室环境。与现有的微小区技术相比．毫微微小区具有设备单元小、网络效率高和成本低的优点。目前，毫微微小区技术仍处在初期阶段，在广泛商用之前还有许多技术、商用和监管方面的问题有待解决。但一旦该技术被用户广泛接受，实现规模商用。必将对移动产业产生不小的影响。     

TD-LTE中家庭基站的干扰管理

据预测在LTE网络中将有超过80%的数据业务发生在室内,因此室内覆盖对LTE通信网来说很重要。家庭基站是近年来新兴的室内覆盖技术。针对引入家庭基站的TD-LTE系统,文中分析了其存在的干扰场景,之后针对各种干扰场景给出相应的干扰管理策略,并详细介绍了3GPP R10中开发的毫微微小区（femtocell）增强型小区间干扰协调（eICIC,enhanced Inter-Cell Interference Coordination）技术,最后给出今后的研究方向。     

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.     

OFDMA毫微微小区网络中基于效用公平的功率控制策略

毫微微小区(Femtocell)网络能够增强室内覆盖,提高系统容量,但是在频谱共享正交频分多址(OFDMA) Femtocell网络中,同频干扰严重限制了网络的性能。针对频谱共享Femtocell网络中的上行链路,基于网络效率和毫微微小区用户间的公平性,该文提出合作纳什议价功率控制博弈模型,该博弈模型不仅考虑了对宏基站的干扰,而且考虑了毫微微小区用户最小信干噪比(SINR)需求。根据该博弈模型,进一步分析了具有帕累托(Pareto)最优的Kalai-Smorodingsky(KS)议价解。仿真结果表明,该策略既能保证用户公平性、最小SINR需求,又能够有效提高网络频谱利用率。     

Dense femtocell networks power self‐optimization: an exact potential game approach

Femtocell is regarded as a promising technology to enhance indoor coverage and improve network capacity. However, highly dense and self‐organized femtocells in urban environment will result in serious inter‐femtocell interference. To solve this problem, this paper proposes a distributed power self‐optimization scheme for the downlink operation of dense femtocell networks. First, a novel convex pricing mechanism is presented to price the transmit power of femtocells and construct the utility function of femtocells. Then, a noncooperative game framework for power self‐optimization of femtocells in dense femtocell networks is established on the basis of the exact potential game theory, which is demonstrated to converge to a pure and unique Nash equilibrium. Finally, combined with firefly algorithm, an effective power self‐optimization algorithm with guaranteed convergence is proposed to achieve the Nash equilibrium of the proposed game. With practical LTE parameters and a 3GPP dual‐strip femtocell model, simulation results show that the proposed game with convex pricing mechanism increases the femtocell network throughput by 7% and reduces the average transmit power of femtocells by 50% in dense femtocell networks, with respect to the compared schemes. Copyright © 2014 John Wiley & Sons, Ltd.     

Auction–Stackelberg game framework for access permission in femtocell networks with multiple network operators

With the explosive growth of indoor data traffic in forthcoming fifth generation cellular networks, it is imperative for mobile network operators to improve network coverage and capacity. Femtocells are widely recognized as a promising technology to address these demands. As femtocells are sold or loaned by a mobile network operator (MNO) to its residential or enterprise customers, MNOs usually employ refunding scheme to compensate the femtocell holders (FHs) providing indoor access to other subscribers by configuring the femtocell to operate in open or hybrid access mode. Due to the selfishness nature, competition between network operators as well as femtocell holders makes it challenging for operators to select appropriate FHs for trading access resources. This inspires us to develop an effective refunding framework, with aim to improve overall network resource utilization, through promoting FHs to make reasonable access permission for well-matched macro users. In this paper, we develop a two-stage auction–Stackelberg game (ASGF) framework for access permission in femtocell networks, where MNO and mobile virtual network operator lease access resources from multiple FHs. We first design an auction mechanism to determine the winner femtocell that fulfils the access request of macro users. We next formulate the access permission problem between the winner femtocell and operators as a Stackelberg game, and theoretically prove the existence of unique equilibrium. As a higher system payoff can be gained by improving individual players’ payoff in the game, each player can choose the best response to others’ action by implementing access permission, while avoiding solving a complicated optimization problem. Numerical results validate the effectiveness of our proposed ASGF based refunding framework and the overall network efficiency can be improved significantly.     

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。      

Power control for data load balancing with coverage in dynamic femtocell networks

We consider the load balancing and coverage problem of femtocell networks in indoor environment. We propose a novel framework exploiting the Voronoi diagram with respect to the radio propagation distance. Our initial power assignment scheme achieves maximal indoor coverage with minimized maximum required transmit power, which results in reduced interference. Our approach can adopt any radio propagation model to achieve more accurate coverage for an indoor environment with various obstacles. Time varying data traffic may cause unbalanced data load of base stations producing traffic overload. Our dynamic power control algorithm redistributes the data load by automatically adjusting transmit power levels according to data traffic estimation while preserving coverage. Moreover, we present an algorithm to cope with the dynamic deletion and insertion of femto base stations. Simulations show that the proposed scheme achieves better coverage, reduced interference, and good load balance compared to previous algorithms.     

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.     

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。