| Summary: | 碩士 === 國立政治大學 === 資訊科學學系 === 96 === IEEE 802.16 mesh network is a new environment of wireless network. It was designed as a self-organized, distributed scheduling, and multi-hop network. However, it is not robust enough to handle a heavy loading environment for lacking of QoS support. Our research is trying to reduce its media access delay, which comes from both TO (transmission opportunity) competition and improper minislot allocation. TO competition will extend the MSH-DSCH (mesh distributed scheduling) interval and slow down the exchanging speed of control message. Improper minislot allocation comes from the distributed scheduling of minislot. When a subscriber station (SS) allocates too much minislot for low-level traffic, it will defer the allocation of other neighbors’ high-level traffic.
We use Bayer’s [4] dynamic exponent to reduce holdoff time of SS, and speed up the exchange of control message. On the other hand, we design an “importance factor” (IM-factor) to score the importance of request. Through the exchange of IM-factor, SS and its neighbors will produce a threshold of IM-factor to filter the unimportant requests, and prevent minislot from being assigned too late.
In our experiments, the proposed methods can reduce 85% delay and 20% jitter, and increase bandwidth utility by 7%. It shows that our method in reducing transmission delay is pratical and effective.
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