【作者】 常征；

【导师】 张英海； 王卫东；

【作者基本信息】 北京邮电大学 ， 微电子学与固体电子学， 2008， 硕士

【摘要】 4G系统支持多种业务类型,存在多种业务的覆盖,一般业务速率越高,其覆盖范围越小。高速业务的覆盖范围比较小,很难保证覆盖的连续性,致使承载该业务的用户往往还没有到达小区的切换区域就产生掉话。OFDMA系统是典型的4G系统,本文首先介绍了OFDMA系统的原理、多址方式及其无线资源管理技术。对于OFDMA系统,高速率业务通常占用系统资源较多,会对系统的动态特性造成很大影响,造成切换期间和切换之后的一段时间内系统传输性能的下降。目前在多业务共存的环境下,关于多业务切换算法的文章主要关注不同QoS业务的等级划分和切换排队算法,并没有关注未来多业务、多QoS共存的条件下,高速业务用户由于覆盖不连续而造成切换失败的问题。其次,本文针对以上切换算法的不足提出了新型的切换算法:基于覆盖延展的高速业务新型切换算法。该算法在降低信源编码速率的同时结合弱子载波去除策略(Faint Sub-carrier Elimination Strategy,FSES),动态的调整用户子载波的分配,使资源利用更加灵活,延展了高速业务的覆盖面积,形成“暂态覆盖”;采用“暂态切换QoS”,减少切换对目标小区的影响,使高速业务用户能够平滑切换。最后本文设计并实现了OFDMA的系统级仿真平台,并在此仿真平台的基础上,通过仿真分析对本文提出的基于覆盖延展的高速业务新型切换算法性能进行了评估。仿真结果表明,新型的切换算法能够维持高速业务用户通话连续性,降低切换掉话率和接入阻塞率,提高资源利用率,优化了OFDMA系统的整体性能。更多还原

【Abstract】 4G supports various types of services. Different services have different coverage. The coverage of high-speed data service is smaller than that of low-speed data service, which can not guarantee continuous coverage and usually makes the high-speed data service users occur dropping before reaching the handover area.OFDMA is typical 4G system. First, this paper introduces OFDMA system theory, multiple access schemes and radio resource management (RRM) technologies; High-speed data service usually occupies more system resource in 4G system, which will bring greatly impact on dynamic characteristics of system, cause system performance to decline during and after handover process. Existing handover algorithms for multiple services are mainly concerned on classification of services of different QoS and handover with queuing, ignoring the problem of handover failure caused by the discontinuous coverage of high-speed data service in the condition of the coexistence of multiple services and QoS classes.Second, considering the disadvantages of present handover algorithms, this paper proposes a new OFDMA handover algorithm: A Coverage-based Handover Algorithm for High-speed Data Service. The new handover algorithm reduces source rate and adopts FSES (Faint Sub-carrier Elimination Strategy) to adjust the sub-carrier allocation and make the resource allocation more flexible, which extends the coverage of high-speed data service and makes users acquire "transient coverage". Meanwhile, the new algorithm utilizes the "transient handover QoS" to reduce the handover effect to target cell for high-speed data service users and make these users acquire smooth handover. Last, this paper designs and completes the OFDMA system level simulation platform. Based on the platform, the new handover algorithm performance is evaluated by simulation analysis. The simulation results shows that the new algorithm can improve the whole system performance, reduce the handover dropping probability and new call blocking probability, enhance the resource utilization ratio.更多还原