关于LTE切换成功率优化的探讨

文章通过对LTE切换流程中的分析,针对提升切换成功率提出了一系列的优化措施,通过这些措施的实施,使得LTE切换成功率得到明显提升。     

关于动态软切换参数优化分析及实践

本文主要对CDMA网络中的动态软切换算法原理进行探讨分析,计算出相关动态软切换的启控点,并通过实例阐述了动态软切换开启能有效降低了软切换因子比例,提高资源利用率。     

LTE中基于移动特性的切换优化

LTE系统对3G系统的多方面进行了全面的改进和演化,使系统性能得到了全面的提升。为了降低基础设施建设费用以及网络运营费用,运营商提出了自组织网络（SON）技术。针对移动鲁棒性优化（MRO）问题,根据该系统下用户移动性对切换优化的影响,提出了对不同移动速度用户设置不同的小区迟滞参数值,即US-MRO优化算法。分析和仿真结果表明,该切换优化算法有效地提高了用户切换成功率,使用户满意度得到提升。     

LTE系统中切换优化算法的研究

3GPP提出了一种自组织,自配置,自愈合网络,即SON(Self-organizing Network)。SON的一个重要方面就是移动健壮性优化(Mobility Robust Optimization,MRO),其主要目的是通过基站自配置合适的切换参数,提高基站的切换性能。本文提出了一种基于SON的切换参数优化(Handover Parameter Optimization,HPO)算法,并且考虑了不同移动速度的UE对切换性能的影响,设置不同的迟滞参数,通过检测不同的场景动态调整切换参数。最后搭建了仿真平台,仿真结果表明,经过该算法优化后,切换性能大幅提高。     

基于SON的LTE HeNB切换参数优化算法研究

针对家庭基站覆盖面小的特点,分析得出家庭基站最大允许的速度、触发时间以及基于A3事件的判决门限是影响家庭基站切换的主要参数,提出了一种基于自组织网络切换优化算法。该算法通过统计切换结果中的乒乓切换、过早切换和过晚切换的数目来动态地调整切换参数,仿真结果表明该算法可以通过动态的调整参数,使由切换导致的无线链路失败达到最低。     

LTE切换问题的分析与优化

在LTE系统中,切换技术是LTE的关键技术之一,如果切换失败则无法保证用户业务的连续性,影响用户的使用体验。本文针对LTE网络中可能出现的切换问题进行分析,并说明导致各种切换问题的原因,最后通过实际案例,对切换参数进行优化,提高切换的成功率,优化网络性能。     

LTE切换优化方法的研究概况

本文对LTE进行研究,其作为通信技术新一代技术代名词之一,在节约运营成本等反面发挥了巨大的优势.如今,经过优化,LTE技术已经在切换流程等方面拥有了更加强大的功能.本文从LTE目前的发展现状入手,对LTE切换流程、切换优化方法等及加以叙述、比较,目的是得到更加优化后的动态调整切换控制参数、中断时间的降低结果.同时使得LTE切换优化,成为未来通信体制下的热门课题,进行更加持续的深入的研究.     

LTE切换优化方法的研究概况

在3G普及的今天,LTE(Long Term Evolution)已成为新一代通信技术的代名词,运营商如何节约运营成本已成为重要研究方向。针对LTE目前的发展状况,详细介绍了LTE的切换流程,并比较了几种关于LTE切换自优化的方法,主要包括降低UE(User Equipment)中断时间和动态调整切换控制参数等。分析表明,针对不同通信体制下的切换自优化必将成为新热门课题之一。     

LTE切换自优化算法进展综述

LTE是新一代通信技术的代名词,它对现有3G系统的网络结构和无线接入方式都有较大改进.在简要介绍LTE系统的网络架构及切换功能的基础上,重点介绍并比较了2种LTE切换自优化算法：常见的用户速度的负载均衡算法有效地降低了系统的掉话率,使系统的整体性能得到提高,但没有考虑到目标小区资源变化的情况;基于RSRP/RSRQ负载均衡算法综合考虑了源小区和目标小区的RSRP（参考信号接收功率）和RSRQ（参考信号接收质量）,降低了系统的切换失败率,同时减少了不必要的切换,但没有考虑用户运动方向的影响.综合加权考虑多种因素,如用户的移动方向以及小区资源的变化等对切换的影响等方面均有待深入开展研究.     

基于SideLink的LTE-V2X联合切换方案设计

在LTE-V2X系统中,针对车载用户切换过程中蜂窝链路及SideLink(SL)链路质量不高以及SL辅助切换过程中SL链路易中断的问题,该文提出一种基于SL的联合切换方案,主要包含：联合切换流程设计、联合切换信令流程设计以及联合切换判决算法设计。首先,在联合切换流程中利用SL技术实现联合切换,并对执行联合切换的SL链路质量进行筛选,以保证联合切换的可靠性;其次,对联合切换信令流程进行了完善,以优化SL辅助切换过程中SL链路易中断问题;最后,在联合切换判决算法中将车载用户的移动方向纳入切换判决条件,从而减少不必要的切换。仿真结果显示,该文所提方案能有效提升切换成功率,与此同时还能有效减少执行LTE切换的次数。

     

On the need for dynamic downlink intercell interference coordination for realistic Long Term Evolution deployments

Intercell interference is the main issue limiting the capacity of modern orthogonal frequency‐division multiple access based cellular networks. Recently, extensive research work has been carried out in this field, and intercell interference coordination techniques have been recognized as key enablers of current (and future) cellular technologies. In this article, (i) a comprehensive survey of the most representative contributions is provided together with (ii) a generic methodology to measure their actual merit. The performance of several interference avoidance strategies has been evaluated both from system and user point of view in the context of a Long Term Evolution (LTE)‐based network considering not only synthetic cellular scenarios but also realistic deployments. Our literature review indicates that there is a need for adaptive/operator‐customizable low‐complex intercell interference coordination (ICIC) schemes suitable for realistic LTE deployments. Results obtained by means of a comprehensive set of simulations corroborate and support this premise. In this article, it is shown that simultaneous gains in terms of spectral/energy efficiency and fairness can be achieved through dynamic mechanisms with respect to both classic hard reuse schemes and static ICIC techniques. Besides numerical results, a novel merit assessment methodology based on several weighted performance metrics is proposed. Our findings show that dynamic schemes outperform static techniques by around 20–35% in realistic deployments. Copyright © 2012 John Wiley & Sons, Ltd.     

LTE上行链路中基于探测参考信号的信噪比估计

信噪比是衡量信道质量的一个重要参数,该文主要研究LTE(Long Term Evolution)系统中基于探测参考信号(Sounding Reference Signal, SRS)的信噪比估计方法。针对DASS(Difference of Adjacent Subcarrier Signal)算法在高信噪比下噪声估计误差较大的这一缺点,该文提出一种适用于SRS的改进DASS方法。该方法通过重新定义子载波的差分方式,减小了噪声估计的误差,并且由于对连续的3个SRS频点,仅需要估计一次噪声,使得该文方法的复杂度仅为原DASS方法的1/3。仿真结果表明,所提方法的估计性能优于其余的方法,特别是在低时延和中等时延信道下,高信噪比时的估计精度提高了约10倍。     

LTE位置管理中信令开销的分析

为了克服2G和3G移动通信网络位置管理方案的缺陷,4G长期演进(Long Term Evolution,LTE)采用了基于跟踪区列表(Tracking Area List,TAL)的位置管理方案。基于TAL的位置管理方案的性能取决于TAL分配方案。考虑到本地移动设备(User Equipment,UE)的活动区域相对固定,该文提出一种嵌入式马尔科夫链模型,用于分析本地UE的基于TAL的位置管理方案的信令开销。推导得到位置更新开销和寻呼开销的数学公式。利用这些公式,可搜索得到能使信令开销最低化的最佳TAL分配方案。     

Dynamic Resource Adjustment for Coexistence of LAA and Wi‐Fi in 5 GHz Unlicensed Bands

To enable the coexistence of Licensed Assisted Access (LAA) and Wi‐Fi in 5 GHz unlicensed bands, a new channel access mechanism is proposed. Accounting for the fairness between LAA and Wi‐Fi, the proposed mechanism finds the optimal transmission time ratio by adaptively adjusting the transmission durations for LAA and Wi‐Fi. In addition, we propose a new analytical model for the distributed coordination function of IEEE 802.11 through some modifications of conventional analytical models for saturation and non‐saturation loads. By computing the activity ratio of Wi‐Fi, the proposed analytical model is able to control the time ratio between LAA and Wi‐Fi, which is required for practical implementation of the proposed access mechanism. Through numerical simulations, the proposed channel access mechanism is compared with conventional methods in terms of throughput and utility.     

LTE网络中多目标优化的动态负载均衡算法

小区间动态负载均衡算法的优劣对网络性能有很大的影响,现有算法大都顾此失彼,难以保证网络关键性能指标(如呼叫阻塞率等)达到最佳。为解决这个问题,该文将负载均衡问题建模为多目标优化问题,分别对不同服务质量要求用户建模其相应目标优化函数,对有服务质量要求用户的目标函数是负载均衡指示函数和网络平均负载函数的联合优化函数,而对没有服务质量要求用户(BE用户)的目标函数是所有BE用户吞吐量的总效用函数,并将小区可用资源数和用户服务质量要求作为约束条件。另外,考虑到在实际系统中运行的计算复杂度问题,提出一种复杂度较低的分布式负载均衡算法。包括资源调度策略,用户切换条件和呼叫接入控制。仿真结果表明,该文算法可达到较好的负载均衡效果,能有效降低有服务质量要求用户的呼叫阻塞率,提高网络资源利用率。     

Optimization of Handover Parameters for Traffic Sharing in GERAN

Cellular network traffic is unevenly distributed both in time and space, which greatly complicates network dimensioning. As a result, some cells in the network are permanently congested, while others are underutilized. In a previous paper, the authors showed that this problem can be effectively solved in GSM/EDGE Radio Access Networks (GERAN) by modifying handover boundaries. However, several drawbacks prevent operators from fully exploiting the potential of this technique. This paper investigates the limitations of current traffic-sharing approaches with tight frequency reuses in GERAN. To deal with such limitations, an algorithm is proposed to jointly optimize handover margins and signal-level constraints based on network statistics for traffic sharing in GERAN. A complementary algorithm is proposed to adjust cell (re)selection offsets to minimize the number of handovers. Simulation results show that the proposed method achieves a significant reduction in call blocking without excessive call quality impairment or increase of network signaling load when compared to the current approaches. More traffic can thus be handled without the need for any hardware upgrades, providing a cost-effective means to increase network capacity.