Capacity of co-existent cellular CDMA and GSM with shadowing and imperfect sectorization, power control and notch filtering

Overlay of existing narrowband mobile communication systems with future wideband systems may improve spectrum efficiency and create the possibility for high-rate data services. This paper presents a generic capacity analysis applied to a GSM-CDMA overlay. The effects of shadowing and imperfect implementation of sectorization, power control and notch filtering are modeled for both uplink and downlink. Based on maximum allowable levels of mutual interference, the total system capacity is modeled and evaluated. Under moderate shadowing and perfect implementation of sectorization, power control and notch filtering, the results match those obtained in previous analyses by other authors, i.e., a capacity gain factor between 3 and 4. However, for low GSM margins in addition to imperfect sectorization, power control and notch filtering, the capacity gain is shown to reduce significantly. Particularly under heavy shadowing conditions, the overlay does not lead to capacity gain. The propagation loss factor and notch filtering are shown to have a large influence on the results. Provided almost perfect notch filtering and power control, the downlink performs slightly better than the uplink.