DBASE: a distributed bandwidth allocation/sharing/extension protocol for multimedia over IEEE 802.11 ad hoc wireless LAN

In ad hoc networks, carrier sense multiple access (CSMA) is one of the most pervasive medium access control (MAC) schemes for asynchronous data traffic. However, CSMA could not guarantee the quality of real-time traffic. In this paper, we will propose a distributed bandwidth allocation/sharing/extension (DBASE) protocol to support multimedia traffics with the characteristics of variable bit rate (VBR) and constant bit rate (CBR) over ad hoc WLAN. Overall quality of service (QoS) will be guaranteed in DBASE. Such a bandwidth allocation procedure is based on a contention process that only occurs before the first successful access and a reservation process after the successful contention. If any real-time station leaves, the reserved bandwidth will be released by DBASE immediately. The designed DBASE protocol will not only allocate sufficient bandwidth for real-time stations but also permit them to extend bandwidth requirements on demand if there is any excess bandwidth left. Moreover, the proposed DBASE is still compliant with the IEEE 802.11 standard. In this paper, the system capacity of DBASE is analyzed and the performance of DBASE is evaluated by simulations. Simulations show that the DBASE is able to provide high channel utilization, low access delay and small delay variation for real-time services.