Inter-System Handover and Coverage Detection for 3G/WLAN Cooperation

Future wireless communication systems will feature by a high degree of interoperability for which system integration is commonly regarded as an important aspect. To allow for smooth network migration, Vertical Handover (VHO) thereby is one of the key enabling technologies. Within this paper, VHO simulations are presented and analytically verified to demonstrate maintenance of services in a patchy WLAN environment. To allow for optimized VHO triggering, an intelligent concept referred to as Hybrid Information System is presented. Anyway, prior to taking sophisticated handover decisions, knowledge on alternatively available systems needs to be present. This entails the initial detection of complementary systems, which directs the system integration aspect to the problem of coverage detection. The present paper copes with this problem by proposing a new algorithm, referred to as Centre of Gravity. The algorithm evaluates densities of location related measurement reports whereby special attention is put on inherent positioning errors.