Research On Mobile Terminal Mobility Supporting Within Wireless Lan

The wireless local area network (WLAN) has been widely deployed by households, businesses and neighborhood cafes. With the rapid growth of WLAN, the constraint of roaming domain resulted by single access point becomes one focus of the WLAN customer's dissatisfaction. Consequently it constitutes one of the most interesting research subjects in WLAN as to how to enlarge roaming domain without communication interrruption. Terminal mobility within WLAN is discussed in this paper.Firstly,the main operational principles of wireless LAN are explained in details, such as 802.11 MAC layer,802.11PHY layer, 802.11 LLC layer and two basic topology structure of WLAN etc. Furthermore,several programs of the Inter-Access Point Protocol to solve link layer mobility problems are discussed. The functions and procedures of IAPP are analyzed,and the IAPP main functions has been realized on the Microsoft windows operating system.Secondly, an effective solution of distributed location management is proposed to eliminate those problems such as huge signaling load and long registration latency existing in current Mobile IP application with the WLAN in this paper. Thus the signaling burden is evenly distributed and each traffic load by a foreign agent at specific level located in hierarchical structure of regional network undertakes below infinite threshold with DLM-MIPRR solution. Numerical analysis results indicate that,this scheme can reduce at least 10% singaling cost compared with Mobile IP Regional Registration. And the effective traffic can be distributed to several Gateway Foreign Agents, thus the failure of one Gateway Foreign Agent will not affect the others. Therefore,it improve the network robustness.Finally,based on the principles stated above, an integrated scheme is proposed to solve the mobility of WLAN terminal entirely, which intergerates IAPP with mobile IP for macro-mobility and cellular IP for micro-mobility. Whenever the mobile terminal is moving among different AP or macro roaming, it can select appropriate handover mechanism according to the level of mobility. Consequently it can achieve better mobility supporting under various roaming conditions.