New channel assignment methods for hot-spot overlaying CDMA cellular systems

The CDMA cellular system can provide more capacity than AMPS systems. To deploy microcells overlaying in macrocells to provide more capacity is also attractive. However, system performance and capacity degrade due to the co-channel interference among microcells and macrocells if a single channel is used. Based on a hot-spot overlaying environment, we propose three multi-channel schemes where different channels can be assigned for hot spot and macrocell. Performance measures in terms of capacity, service hole, blocking probability and blocking ratio in uplink and downlink are evaluated. It shows that the schemes with channel selection based on SIR and active users gain more benefits than the scheme with separate channels assigned for macrocells and hot-spot. Using the proposed multi-channel access schemes, we can avoid the co-channel interference among macrocells and hot-spot and provide more capacities than Baier's suggestion [1]. In addition, the proposed schemes make soft handoff workable and improve the system performance.