呼叫准入约束下Macro-Femto小区选择GSPN模型研究

Cell Selection GSPN Model Constrained by Call Admission in Macro-Femto Networks

随着数据业务快速增长,仅靠宏蜂窝网络已无法满足流量需求;飞蜂窝网络可以有效分流宏蜂窝流量,近年来所构成的Macro-Femto架构得到了较广泛的部署。Macro-Femto网络部署的关键问题之一是小区选择,由于飞蜂窝网络频谱资源有限,进行小区选择时仍需考虑呼叫准入控制(Call Admission Control,CAC)。图形化的广义随机Petri网(Generalized Stochastic Petri Nets,GSPN)具有并行性、不确定性和异步特性以及强大的分析复杂系统的功能。针对Macro-Femto网络的呼叫准入约束机制,通过分析呼叫对信道的占用情形,在改进呼叫重审机制的基础上,建立了呼叫准入控制策略GSPN模型。利用建立的GSPN模型,分析了不同呼叫准入控制策略对新呼叫和切换呼叫阻塞率的影响,给出了部分重审机制的呼叫准入控制策略。在分析飞蜂窝的高速服务特性和宏蜂窝的高负载能力的基础上,结合部分重审呼叫准入策略和GSPN方法,提出了基于负载的飞蜂窝优先选择方案(Load-Based Femto-Priority Selection Scheme,LFP)。仿真结果表明,较典型的飞蜂窝优先选择方案,所提出的LFP方案对新呼叫的阻塞率和切换呼叫的掉线率分别降低了2.7%和4.6%。

Alone with the increase of data service,it can not meet the traffic demand only by using macrocell deployment.As an efficient means to offload macrocell traffic,femtocell networks are introduced and formed the Macro-Femto architecture.Cell selection will be an open challenge when Macro-Femto network is deployed.As for channel resource scarcity in femto-base station,putting call admission on femtocell network may also be of great concern.Graphical generalized stochastic Petri net（GSPN）characters parallelism,uncertainty and asynchrony,and is suitable to analyze complicated system.For call admission constrains in Macro-Femto networks,the occupancy of calls to channels was first studied and GSPN model was built on call admission by advancing call retrials.Based on GSPN approach,the modified part-retrial-based call admission control strategy was introduced after analyzing the influence of call admission control strategy on call blocking rate.Concerning high-speed service characteristic in femtocell and high capability in macrocell,load-based femto-priority（LFP）selection scheme was proposed with adoption of part-retrial call admission control strategy and GSPN.Simulation results show that,compared with femto-priority selection scheme.The proposed LFP scheme can achieve lower new and handover calls blocking probability by 2.7% and 4.6%.