Performance of mobility support mechanisms in a heterogeneous UMTS and IEEE 802.11 network offered under the IEEE 802.21 standard

Wireless networks are becoming increasingly popular. These wireless solutions range from personal networks (e.g. Bluetooth), through local (e.g. WiFi) and metropolitan area networks (e.g. WiMax) up to the cellular networks that offer the coverage almost everywhere. As the number of different wireless technologies grows, a unified and standardized mobility support algorithm for heterogeneous networks is needed. The paper evaluates the performance of mobility support mechanisms and algorithms offered by a new IEEE 802.21 standard. The heterogeneous scenario with UMTS and IEEE 802.11 networks is modeled and investigated. The handover in both directions is discussed, taking into account implementation of MIH Link Going Down event for IEEE 802.11 networks, proposed by the authors. This event is used to optimize handover from IEEE 802.11 network to UMTS networks. The new, proposed in the paper solution, makes it possible to support multimedia services during the heterogenous handovers. To verify the proposed algorithm the simulation environment has been defined, based on ns-2 simulator. The number of experiments was performed to evaluate the packets lost ratio and the delays introduced by heterogenous handover.