Handoff control method and communication system in a multiple frequency environment

摘要

A handoff control method and communication system is provided that uses a virtual cell boundary in a multiple frequency environment. The handoff control method includes forming a virtual cell boundary using a frequency coexisting between a terminal base station on a boundary area of multiple frequency environment and an adjacent base station. Pre-determining a likelihood of handoff possibilities is then based on distance or round trip delay between the virtual cell boundary when establishing calls in the terminal base station to thereby assign different frequencies to the calls. When a call assigned as a frequency group having small handoff possibilities transitions to an object base station, a handoff time point is determined as the call approaches the virtual cell during movement to the object base station to control a hard handoff processing procedure between frequencies. Thus, the frequencies are assigned using information already in CDMA protocol messaging to accurately determine which and when established calls are to be handed-off to adjacent base stations. Accordingly, the percentage of successful handoffs is improved.