Intercell Radio Interference Studies in CDMA-Based LMDS Networks

Among the various alternatives investigated for enhancing the capacity of the millimeter wave segment of broadband wireless access (BWA) networks is the use of orthogonal direct sequence code division multiple access (DS-CDMA) instead of time division multiple access (TDMA), the dominant multiple access scheme to date. This paper aims at contributing to the ongoing research on the feasibility of CDMA-based Local Multipoint Distribution Service (LMDS) by presenting an analytical study of intercell interference, which is the major factor limiting capacity. The study is focused on the statistical properties of the carrier-to-interference ratio (CIR) in both the downstream and the upstream channel. Since the propagation phenomena affecting LMDS are quite different than those affecting narrowband wireless networks, emphasis is placed on incorporating the spatial inhomogeneity of rain attenuation in the interference analysis and on estimating the additional CIR degradation not taken into account in the conventional clear sky approach. The proposed model is accompanied by illustrative simulations identifying worst case interference scenarios and clarifying various aspects of the system.