Research On Handoff Algorithm In Mobile Communication System

Market promotion of the third generation mobile communication (3G) provides strong support to China's economic construction services, but also have brought new challenges to handoff between different cells and between the different systems, soft handoff system is one of the key technologies of UMTS ,but also the focus of wireless resource management and optimization. Handoff algorithms and related parameters have direct impacts on the system's capacity and quality of service (QoS). This thesis emphasis on study of handoff technology, handoff algorithm, UMTS and B3G handoff. The work can be summarized in following point:(1) On the study and analysis and research of handoff technology, the handoff control mode function presents multi-state properties. There are differences between different 3G technologies on using environment, channels distribution, modulation and Congestion control modulation on basis of RNC access control, and there are also big differences between the service type, air interface, and network layer, we need to achieve a smooth handoff with FMIPv6, achieve rapid successful rate of the handoff with algorithm.(2) In UMTS system, because the real-time services of high data continue to increase, bandwidth will be insufficient, due to the increased precision of positioning systems and the advances of mobile IP technology, while the traditional algorithm response to handoff calls slowly and can not achieve the best match between system performance and capacity, the high packet loss rate of channel leads to data retransmission of wireless network. According to geographical location services (LBS) information and the vector of mobile terminal speed changes, judge the coming data handoff call and reserve channels quickly and accurately, change bandwidth adaptively and dynamically, author have designed A new kind of wireless network dynamic data rated handoff algorithm based on LBS information(3) World Interoperability for Microwave Access (WiMAX), complete wireless broadband access can be resolved "last mile" problem. Because of complex QoS definitions of IEEE802.16 .Handoff strategy play a key role in the wireless resource management, the traditional access handoff control strategy is difficult to solve a variety of services handoff. Author establish a new Markov model, and put up with call access handoff control scheme(AR-CAC) referring from UMTS call access control which adaptively reserve channels through channel utility probability and the load of Unsolicited Grant Service and Real Time Polling Service(4) In future, handoff between the next UMTS network and the WiMAX network is particularly frequent, as the huge differences between bandwidth, air interface, core network and the coupling of the network have greatly affected the handoff successful rate. It is presented that a mixed network hardware handoff mechanism which aims at considering receive signal strength (RSS), hysteresis level and hysteresis time as judging standard of handoff.