Research On Qos Optimization For Multimedia Conferencing

Multimedia conferencing is one of the most popular media applications over the Internet. Video communication is a key research issue in the QoS guarantee for multimedia conferencing due to the stringent requirements in throughput, de-lay, and reliability. With the rapid advancements in wireless infrastructures with complementary characteristics, the bandwidth aggregation for video delivery over heterogeneous wireless networks has attracted considerable research attentions. It is challenging to effectively integrate the limited channel resources available for providing adequate QoS. This dissertation studies the QoS optimization for mo-bile video delivery in heterogeneous wireless networks and the contributions can be summarized in the following.1. In the context of heterogeneous wireless networks with multihomed cli-ents, the effectiveness of bandwidth aggregation may be significantly impacted by the burst channel losses and frequent bandwidth fluctuations. Previous studies mainly address the problem by reactively increasing the FEC (Forward Error Correction) redundancy. To address the critical problem, we propose a Robust Bandwidth Aggregation (ROBBIA) scheme that includes three phases:1) FEC redundancy estimation,2) transmission rate assignment, and3) packet interleav-ing.2. To optimize the delay performance of high definition video streaming over heterogeneous wireless networks, this paper proposes a novel sub-frame level (SFL) scheduling approach. We analytically formulate the video streaming allocation based on the network calculus and derive the solution based on the water-filling algorithm. The proposed SFL is able to improve the frame-level de-lay performance for optimizing the streaming video quality. Experimental results show that SFL outperforms existing models in reducing the end-to-end delay as well as in improving the video PSNR (Peak Signal-to-Noise Ratio).3. One major problem of the existing Joint Source Channel Coding (JSCC) schemes is that they consider the network between the transmission ends as a single transport link. Challenges arise in the context of multiple available links because involving an unreliable access network in the transmission will only de-grade the video quality. To address the critical problem, we propose a novel Flow Rate Assignment based Joint Source Channel Coding (FRA-JSCC) scheme that includes three phases:1) source rate adaption under delay constraint,2) FEC re-dundancy estimation under delay constraint, and3) flow rate assignment to min-imize the end-to-end video distortion.4. To reduce the total packet delay of real-time multimedia traffic over mul-tipath networks, we propose a Sub-Packet based Multipath Load Distribution (SPMLD) model. The existing load distribution models take insufficient accout of the diversity in multipath networks. We propose to effectively aggregate the multiple communication paths between end devices as a single virtual path. We formulate the packet splitting over multiple paths as a constrained optimization problem and derive its solution based on successive approximation method. Then, we analyze the queueing delay based on D/M/1model and obtain the packet splitting ratio. The proposed SPMLD is able to reduce the end-to-end delay wihle alleviating the packet reordering.The above solutions have been evaluated through extensive simulations us-ing H.264video streaming. Thus, we recommend the above methods for the QoS guarantee of mobile video delivery in heterogeneous wireless networks.