Today we find a large number of wireless networks based on different radio access technologies (RATs) and standards. Furthermore, new RATs will be developed to complement those that exist already today. Each RAT will have its strengths and weaknesses with respect to capacity, cost, achievable data rates, and support for end user mobility. As no single RAT will be able to fully support all service and user requirements, B3G networks will integrate multiple RATs in a common network. It can be anticipated that within a few years’ time, a user terminal (UT) will have a choice of access technologies via which it can connect to the fixed communication infrastructure.