Modeling And Analysis Of Service Differentiation For Data Transmission Over Wireless Multimedia Networks

With the rapid development of personal digital communication and social network, and the increasing of powerful data terminals and various network applications, which push the network technology forward from wired to wireless, from fixed to mobile, from text data to multimedia transmission, and the Quality of Service (QoS) is also promoted from be ignored to be supported, from single priority to multi-priority service differentiation. Under this condition, Wireless Multimedia Network (WMN), i.e. a network can communicate with anyone using anymode at anytime and anywhere, have been widely researched and employed in military, commercial and daily lives. WMNs can not only make up the deficiencies of tranditional wired networks, also support the transmission of multimedia applications, such as voice, video and images, etc.Based on the fundings of National Natural Science Foundation of China (Grant No.61070043,61379123) and National Science&Technology Pillar Program during the Twelfth Five-year Plan Period (Grant No.2012BAD10B01), oriented to the service differentiaon mechanism of IEEE802.11e EDCA protocol in WMN, this thesis had conducted in-depth investigation in terms of service differentiation and its performance for multimedia transmission, and has acquired considerable achievements, where the major contributions of this thesis were listed as follows:(1) According to the binary backoff mechanism of IEEE802.11e EDCA protocol, two analytical models based on Markov Chain were proposed for EDCA protocol working in saturated and unsaturated cases, respectively. The probabilities of data collision, state distribution, state transfer and access the channel of each priority queue can be derived from the proposed model. Since all the video frames are allocated to queue AC(2) according to the default rules of EDCA protocol, we built a packet loss model for video transmission by integrating the collision probability of AC(2) and wireless channel error rate. At the same time, a delay model for video transmission was also proposed by considering the effect of time delay on video transmission quality. Relying on the above packet loss model and time delay model, with the structure of MPEG-4coding, we proposed a video transmission model and introduced the Decoded Frame Rate (DFR) to evaluate the video transmission quality. Due to the characteristics of bursty data flows and dynamic network conditions, we investigated the more practical and complicated video transmission quality in unsaturated case than in saturated case. Through an in-depth study of EDCA protocol and its post backoff mechanism, an analytical model based on Markov Chain in unsaturated case was proposed by introducing a special backoff state "idle state". The corresponding packet loss model and delay model for video transmission in unsaturated case were also presented. Similarly, based on the above packet loss model and time delay model, with the structure of MPEG-4coding, we proposed a novel video transmission model for video transmission in unsaturated case.(2) Although EDCA protocol achieves service differentiation by introducing four Access Categories (ACs), its performance is deteriorated seriously due to high collision probability among ACs and underutilization of channel resources. In order to overcome these deficiencies, a novel Hybrid Slot Allocation Mechanism (HSAM) was proposed by assembling three time slots into a super slot. The main idea of HSAM is to stagger the transmission slots of different ACs to reduce their collisions. Based on the extended Markov Chain model, two comprehensive analytical models were presented to evaluate the performance of HSAM both in unsaturated case and saturated case. Extensive results from simulations have demonstrated the superior performance of HSAM than EDCA protocol in terms of throughput, packet loss and MAC delay. Moreover, the simulation results are matched very well by the derived analytical models.(3) In order to deal with the mapping problem of video frames in EDCA protocol, a Parameter Adaptive Bi-directional Mapping (PABM-EDCA) mechanism was proposed to assign each video frame with appropriate priority. This mechanism takes the structure of hierarchical video coding and the importance of each video frame into consideration, and utilizes the information of Application Layer and MAC Layer through cross-layer optimization. According to the importance of different video frames and network condition, we proposed the adaptive forward mapping mechanism and double backward mapping mechanism, respectively. Both of the above mechanisms had been equipped with congestion awareness ability. From the comparison of PABM-EDCA with other three mapping mechanisms, the experiment results showed the superior performance of PABM-EDCA under dynamic network contidions.(4) Based on the extended Lotka-Volterra (LV) biological competitive model, a bio-inspired self-adaptive rate control approach for multi-priority data transmission was proposed. This approach calculated the optimum sending rate of each flow by taking the system stability, limited available network resources and competitions from other flows into consideration. Then the proposed approach was applied to four categories of data flows defined in EDCA protocl, the allocated bandwidth of each data flow was optimized through model parameter optimization. Under the recommended parameter values, the total bandwidth utilization was maximized up to93%compared with60%-70%achieved by the EDCA protocol, whilst maintaining the service differentiation of multi-priority flows. Extensive simulation studies had been conducted to show the superior performance of the proposed approach.