Improved performance of a CDMA cellular system with macrocell diversity

In order to deal with the service demand of a mixture of high and low mobility users a system with overlapped macrocells and microcells has been proposed. In this paper we present architectures for code division multiple access (CDMA) based hybrid macrocell/microcell systems. These architectures are based on the principle of reducing the interference to macrocell users in a highly dense environment. This is accomplished by replacing the macrocell antenna with many microcell antennas, which are connected to a macrocell processor. The functions of this processor is to configure the proper connections between users and antennas. The characteristics of microcell propagation are used to justify the proposed antenna connection protocols which include 2-antenna and 3-antenna protocols. System architectures for both linear and two-dimensional service areas are discussed. System performance is evaluated in terms of carrier-to-interference ratio (CIR). The analysis procedure models the number of users in each cell as a Poisson distributed random variable. The CIR expressions for both the conventional and hybrid systems are reformulated. It is shown that the proposed architecture can lead to a dramatic increase in capacity as compared to conventional CDMA cellular systems