Some Improvements On QDSR Protocol In Wireless Ad Hoc Network

Along with the continuing research on the wireless Ad Hoc network and bandwidth increasing of wireless network card, research on multimedia transmission over Ad Hoc network is becoming a new hotspot. Real time video transmission requires a routing protocol to find a path, which can transmit video traffics steadily and provide enough bandwidth. Based on estimation of node's available bandwidth, a real time video transmission testbed has been implemented by our group[7], which makes a series extension to standard DSR protocol. The extended DSR, which will be refered to as QDSR in the following, can support real time video transmission in small scale network.But only means of controlling video transmission, used in QDSR, is admission control. Although the admission control can guarantte enough bandwidth in every nodes for total admitted flows passed the nodes, the bandwidth requested by every flow is not guarantted. Because some flows may have advantage of access of channel sometimes, or have some traffic burst in short time scale, these flow may obtain more bandwidth ; on the other hand, other flows are not able to obtain their requested bandwidth. To overcome this shortage of QDSR, the author estended the flow control capability to our QDSR: every node monitor the bandwidth usage of every flow passed the node in real time, the used bandwidth by a flow will be adjusted according to its requested bandwidth, under the condition of providing video transmission quality. The flow control mechanism can improve the QDSR in video transmission quality.During the transmission of multihop flow, because there exists interferences within the flow, the situation may qccurs, in which some subsequal nodes would not have packet to transmit and waiting for previous node's packets. This will lead low bandwidth utilization. To overcome this problem,a flow schedule mechanism was proposed in the paper. By deferring the packet transmission at source node, the interferences within the flow will be reduced and the way of the transmission of multihop flow is optimazied, the throughput of multihop path will be raised.At the end, the author implemented the QSDR and above mentioned improvements to QDSR in NS simulation environment. The simulation experiments showed that the improvements proposed in this paper refine the perfomances of QDSR, and delievery rate are promoted and end-to-end delay is reduced, which is more appropriate for multimedia transmission in Ad Hoc networks.