| Abstract With the cost decline of wireless equipment manufacturing and the mature application of wireless communication technology, wireless mesh networks(WMNs), as one important next generation of broadband wireless access technologies, has been widely applied in wireless broadband city, wireless campus (enterprise) and disaster rescue, etc. Meanwhile, various business applications of audio, video and high real-time data services (e.g. VoIP, video conference, etc.) based on WMNs are developing rapidly so that they give higher requests to the QoS indicators (e.g. average delay, delay jitter and bandwidth allocation, etc.) of WMNs. However, some inherent features, such as model of distributed free competition at MAC layer, incompleteness entire networks information, will make QoS over WMNs very difficult compared to existed wireless(wired) networks QoS technology for multimedia transmission. So how to guarantee the QoS of multimedia transmission service is still a hotspot and difficult problem in WMNs open research.Aimed at the network architecture, characteristics and QoS problem in multimedia application of WMNs, this paper analyse some QoS schemes designed from different perspectives of MAC layer, route layer and cross-layer. Then some solutions and analyses are discussed. The main research work in this paper includes:(1) On the issues of performance lacking of quality of service (QoS) in EDCA mechanism and single-path routing protocol, an adaptive priority-based QoS routing scheme is proposed from the perspective of closs-layer design. This scheme configures some threshold values of the QoS parameters for each multimedia flow in the upper layer, then monitors the real-time information of the AC queues at MAC layer to dynamicly adjust the priority of each multimedia data suited to different AC queues. At the same time, it estimates the transmission delay of the different multimedia data to get the average transmission delay of each AC queues when the data is successfully transferred. With these information above, the scheme can balance the chances of channel occupation between different multimedia flows and make sure that they can be fairly transmitted to promote the whole performance of the networks.(2) To address the related QoS problem caused by the links' interference in multi-path data transmission,this paper analyses the EDCA mechanism in the IEEE802.11e standard and mulit-path routing technology, then defines some jointed routing metrics based on cross-layer design.By these jointed routing metrics, routing selection scheme can choose the effective forward routing to meet the different multimedia flows' QoS requirements. The scheme also adopts an improved adaptive parameter assignment method used to channel competition in EDCA and make it can fit the environment of multi-hop transmission.This method can effectively reduce the confliction of data transmission and promote the quality and fairness service of different multimedia transmission.(3) For the lack of QoS supporting in differentiated service of EDCA mechanism in802.11e, a margin delay-bounded based CFB data forwarding scheme is proposed. Aimed at the throughput and fairness problem of the long time occupation of data flow with a longer delay bound, which causes a lot of packet loss and retransmission of data flow with a shorter delay bound value, this scheme estimates the magrin delay bound of data packets and dynamicly adjust the TXOP values and the CFB block values to meet the changes of different multimedia flows and effectivley promote the throughput performance of these flows. |
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