Performance analysis of vertical handover in a UMTS-WLAN integrated network

The 4G wireless communication system is envisioned to integrate cellular network (e.g. UMTS) and wireless LAN (WLAN), in virtue of the individual coverage and capacity complementary characteristics. This paper describes a possible architecture integrating UMTS and 802.11 WLAN at SGSN. A functional entity, network interwork unit (NIU), is placed between the SGSN and WLAN access network side to hide the WLAN particularities. In this integrated architecture, mobile IP based vertical handover management increases the heterogeneous system signaling cost as well as handover latency, so one major task in the handover design is to reduce the unnecessary handover probability. This paper presents an analytical vertical handover initiation model based on the criteria of received signal strength (RSS) and distance. The handover performance evaluation criterion of interest is the handover probability. The numerical results show that our model is in line with the real cases when the distance between the base station (BS) of UMTS cell and the access point (AP) of WLAN is long or not.