Improving Handoff Efficiency over VANET by QualityScan

• Main Authors: Hung-Lin Chan, 詹弘麟
• Other Authors: Tin-Yu Wu
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/52895721721652681708

碩士 === 淡江大學 === 電機工程學系碩士班 === 98 === Vehicular ad hoc network (VANET) is an emerging intelligent transportation system (ITS) that integrates wireless communications with vehicles. ITS applications currently include driving safety, transportation efficiency, information and entertainment-related applications. Compared with handheld devices, the mobility of vehicles, the main terminals in VANETs, is obviously higher and the handoff procedure consequently occurs frequently. Too long handoff latency works upon the transmission quality, especially on some real-time network services. Since traditional mobility management mechanisms no longer meet the needs of VANETs, many fast handoff schemes were proposed. However, without considering the loading status of different APs, most handoff mechanisms choose the AP with the optimal signal strength as the handoff location. In such a manner, the network bandwidth cannot be utilized efficiently and the overload of some APs may degrade service quality. In VANETs, APs can be established in advance. According to different traffic flow, the number of APs can be adjusted in order to distribute network traffic and improve service quality. For example, the network traffic is undoubtedly high in a crowded road section. If only one AP provides service, the network traffic is bound to be congested. Therefore, we proposed QualityScan, a fast handoff scheme for VANETs to reduce the handoff latency and keep the APs load-balanced by deploying AP controller (APC) that periodically collect the status of the APs in the subnet and predict the network traffic at the next moment. Based on the result parameter broadcasted in beacon frames, the neighboring MNs can determine the best AP for the service. Thus, the APs in the area can be load-balanced, the service quality can be improved, and the handoff efficiency over VANETs can be further enhanced.