An Overview on Decision Techniques for Vertical Handoffs across Wireless Heterogeneous Networks

Wireless communication of the future w ill comprise of several heterogeneous networks whose access technologies will vary to a large extent on the network capacity, data rates, bandwidth, power consumption, Received Signal Strength and coverage areas. With their complementary characteristics, integration of these networks to offer overlapping coverage to mobile users pose many interesting research challenges to bring about anytime, anywhere connectivity. The best of these networks with their varying characteristics can be brought about through a process called vertical handoff. Vertical handoff is the seamless transfer of an ongoing user session between these networks and requires accurate and precise decisions about the availability of the networks and their resources for connection. A good handoff decision should avoid unwanted handoffs which leads to an increased computational load or should not miss making a handoff leading to an ongoing service being dropped causing packet loss. Many techniques for vertical handoffs have been proposed in literature which are based on several parameters, but there still exists some ambiguity as to which of these parameters give an optimum performance. This paper aims at providing an account on the various policies developed in the decision phase of the vertical handoff.