more complex. Two different kinds of wireless networks normally have incomparable signal strength metrics, for example, WLAN compared to UMTS. In, WLAN and UMTS networks both cover an area at the same time. The handover metrics in this situation should include RSS, user preference, network conditions, application types, cost etc. Handover decision algorithm Based on the handover metrics mentioned above, the decision about how and when to switch the interface to which network will be made. Many papers have given reasonable flow charts based on the better service and lower cost, etc. while some others, using fuzzy logic, neuron network or MADM methods to solve the problem. Mobility management When a mobile station transfers a user's session from one network to another, the IP address will change. In order to allow the Corresponding Node that the MS is communicating with to find it correctly and allow the session to continue, Mobility Management is used. The Mobility Management problem can be solved in different layers, such as the Application Layer, Transport Layer, IP Layer, etc. The most common method is to use SIP (Session Initiation Protocol) and Mobile IP. Handoff procedure The handover procedure specifies the control signalling used to perform the handover and is invoked by the handover decision algorithm. See also Load balancing (computing) Media-independent handover Multihoming Access Network Discovery and Selection Function Related standards 3GPP TS 23.234 “3GPP system to WLAN interworking; System description 3GPP TS 23.228 IP Multimedia Subsystem 3GPP TS 23.237 IP Multimedia Subsystem (IMS) Service Continuity; Stage 2 802.21 Media independent handover IEEE 802.21 Mobile IP Wireless networking Mobile telecommunications standards