Channel segregation method in a two-tier CDMA system

The CDMA system can provide more capacity than other systems and the hierar chical layer of cells is required for system design to provide a balance be tween maximizing the number of users perfrequency band and minimizing the n etwork control associated with handoff. However, the co-channel interferenc e from microcell to macrocell and vice versa in such a two-tier structure i s different from that in a homogeneous structure. In order to avoid the ser ious interference, different RF channels should be used in microcell and ma crocell in hierarchical structure. The efficient usage of multi-channels fo r macrocell and microcell is of primary concern herein. In this study, we i nvestigate the channel segregation in a two-tier cellular system. Moreover, we intentionally arrange the procedures for the MS in macrocell and microc ell to choose the channel. The macrocell's (resp., microcell's ) channels t o be accessed are sorted into three priority groups. In order to justify th e merits of the proposed channel segregation method, we define the followin g three performance measures including capacity gain, response to the varia tion of traffic loading and system stability. Under the condition of steady -state traffic load, capacity gain is 10% on the average. If the traffic lo ad vary, the system can respond quickly and retrieve the borrowed channels with 2tp time interval as long as appropriate system parameters are chosen.