On the feasibility of spectrum sharing between GSM and IS-95

This paper addresses the feasibility of spectrum overlay of IS-95 over the GSM system. A simulation methodology has been adopted to ascertain the behaviour of the narrow band IS-95 and GSM system when using the same frequency spectrum, geographic region and time. This study is exploratory in nature and the IS-95 and GSM systems that are modelled, are based on the specifications provided in the GSM and IS-95. A hybrid model is developed to assist in writing a simulation program, taking into account the cellular parameters such as fading, path loss etc. and system specific parameters such as frame structure, channel allocation, sectorisation, discontinuous transmission, power control etc. The depth of the frame structure for each system is selected, that is enough for the power control and slow frequency hopping (for GSM) to work properly. The performance is computed in terms of received interference energies at a burst level. A burst corresponds to a transmission, on a time slot for GSM, and on a power control group for IS-95. Threshold erasure rates are defined for the IS-95 and GSM system and are compared with recorded erasure rates obtained via simulation. Constant receiver power control for GSM and E_b/I_o, balancing control for IS-95 were used. It is then shown that due to the behaviour of the power control schemes, the systems can not co-exist fruitfully