Handover Strategies in Cellular System

Mobility is the most important feature of a wireless cellular communication system. This continuous service is achieved by Handoff (or Handover) from one cell to another cell. Handoff (also called Handover) is the mechanism that transfers an ongoing call from one cell to another cell as a user moves through the coverage area of a wireless cellular system. The main objective of handover is to maintain the ongoing calls. Many times it is initiated by crossing a cell boundary or by deterioration in quality of the signal in the current channel. Handovers are used to prevent an ongoing call to be disconnected. If handovers are not used then whenever a user leaves the area of a particular cell then its ongoing call is immediately disconnected. The handover process requires a number of parameters e.g. which handover scheme we are using, how many channels are free for call. In the handover process the QoS should be kept up to the standard. Handoff schemes which are poorly designed tend to generate very heavy signaling traffic and, therefore, there is a dramatic decrease in the quality of service (Qos). The reason for the critical handoffs in cellular communication systems is that in neighboring cells always a disjoint subset of frequency bands is used, so negotiations must take place between the current serving base station (BS), the mobile station (MS) and the next potential BS.