Research On Joint DCA TD-SCDMA/WLAN Network Admission Control Algorithm

TD-SCDMA wireless communication system serves as TDD standard, which isresearched and developed independently by China, and it synthesizes all of thetechnical advantages of TDD and CDMA. The successful deployment of TD-SCDMAnetwork in major cities in China stands for China comes into the3G era formally.However, the spectrum resource of TD-SCDMA is extremely valuable andTD-SCDMA is a serious code resources constrained system, it is hard to meet theusers needs of high-speed data services nowadays. WLAN has the characteristicsof providing high-speed transmission for data services. But WLAN is limited in APtransmit power with limited network coverage, and as its unique competitivetransport mechanism, WLAN fails to contain too many users simultaneously. As thecomplementary characteristics of TD-SCDMA and WLAN network, the research ofTD-SCDMA/WLAN heterogeneous network becomes a hotspot.Channel allocation is one of important tasks during the TD-SCDMA/WLANheterogeneous network access control process. Dynamic channel allocation (DCA)serves as one of the TD-SCDMA unique technology characteristics, and it effectivelymakes useful of the asymmetric transmission characteristics of uplink and downlinkin TDD operation mode in order to achieve the dynamic allocation of the timedomain channel resources. The performance of DCA algorithm directly affects theaccess success rate of new users and handover users, thus it affects the performanceof Call Admission Control in the network system.This paper based on the in-depth analysis of the TD-SCDMA DCA algorithm,joint dynamic channel allocation algorithm was proposed. First, slow DCA based onhot cell was applied in order to effectively reduce the cross slot interference betweenadjacent cells in TDD mode, and the network capacity of overall system wasimproved evidently. Then the queuing theory was applied to model the fast DCAbased on channel reservation mechanism. The blocking rate and dropping rate theoryformula is derived. Finally, making use of WLAN high-speed data servicescharacteristics, which can effectively triage TD-SCDMA packet data services, jointDCA algorithm was proposed.As users could not obtain much network status information, it is hard for them toindependently make the service network selection. According to this problem,network end TD-SCDMA/WLAN network selection algorithm based on game modelwas proposed. Analytic Hierarchy Process (AHP) was applied to obtain the networkmembership value of TD-SCDMA and WLAN, respectively. Then model the network selection problem as users-game, and the solution of this game was applied as thejudgment of the service network conditions.Referred to the network side, TD-SCDMA/WLAN heterogeneous network CACproblem was studied. First both the channel conditions and network conditions ofTD-SCDMA and WLAN were studied, respectively. Reasonable channel model andsurplus network bandwidth model were proposed. Then the CAC selection of newusers and handover users were made based on the proposed effectiveness model.Finally, it is verified by simulation that the proposed model could get more networkoverall effectiveness.