The Research Based On Load Balance Of Access Point Handoff Algorithms

In recent years, with the development of WLAN technology, the application area has been continuously expanded, with increasing number of users and enlarging service varieties. The contradiction between limited wireless bandwidth resource and ever-growing demand of various network services is becoming more and more remarkable, while the unbalanced load distribution among APs waste a mass of wireless bandwidth resource. How to balance the load among APs, enhance the utilization of wireless bandwidth, and improve the performance of the whole system become one of the most important and popular research in WLAN.First, we elaborated association service, handoff service and load balancing service of IEEE 802.11 protocol, using mathematic analysis to point out the limitation of load balancing service in IEEE 802.11 protocol. Then, based on who choose the new AP, we divided the existing load balanced scheme into base structure and center structure; Moreover, according to handoff trigger condition, divided the existing load balanced scheme into lost number of beacon startup and integrating SNR and AP's load startup. We also carried a comprehensive and integrated analysis and evaluation to the above-mentioned.Aiming at high density and large traffic WLAN environment, we put forward a new AP handoff mechanism based on load balance, using center structure: When an AP's load is exceeding the load threshold, it will trigger a handoff. AP is used to collect the load message of neighboring APs, using mobile host to collect the SNR of APs that visible to them, then calculating as per function ISL, flexibly combining load with SNR to choose the mobile host that need to handoff and the target AP. Furthermore, by employing advance authentication, we effectively minimized the delay of handoff.At last, on the OPNET simulation platform, a network testing environment was well set up to compare new mechanism with IEEE 802.11 protocol. The test result showed that the load balance capability between APs in the new AP handoff mechanism has been greatly improved compared to IEEE 802.11 protocol under the high density and large load environment, the throughput of the whole system has been increased by around 50%, and that in parts of mobile host has been enhanced over twice more than before. The new mechanism has greatly improved the utilization of wireless bandwidth resource and performance of the whole system.