A Novel Distributed QoS Scheduling to Reduce Spatial Contention in Wireless Ad hoc Networks

• Main Authors: Cheng-Feng Xie, 謝承峰
• Other Authors: Jung-Shian Li
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/23221155353603427459

碩士 === 國立成功大學 === 電機工程學系碩博士班 === 92 === 　　In the recent years, more and more attention has been attracted to providing quality of service (QoS) for real-time traffic in wireless ad hoc networks as the increase of real-time applications. However, the Distributed Coordination Function (DCF), the popular communication protocol in IEEE 802.11 standard, fails to provide QoS guarantee for real-time applications. On the other hand, some characteristics in wireless network, such as fully distributed nature, spatial contention, and multi-hop environment, make QoS-supporting considerably a challenging job. 　　In this thesis, we propose a novel distributed traffic scheduling scheme by considering some special characteristics of wireless ad hoc networks mentioned above. In our scheme, we take advantage of a piggyback in data packets and the promiscuous mode in wireless networks to spread the timing information of head-of-line (HOL) packets among several nodes who share a common channel in a standpoint of spatial contention. A backoff time adjustment policy is developed to coordinate the transmission orders of these contending nodes in accordance with the urgency of their packets. Besides, we address a special phenomenon in wireless ad hoc network called self-coupling problem and design an effective solution to eliminate the blind contentions within a flow. By well-coordination of spatial contention with consideration of priority of each packet, both average end-to-end delay and the packet delivery ratio can be significantly improved so that the QoS condition can be satisfied as far as possible