| In wireless ubiquitous environment, various wireless access technologies coexist and overlap each other, which are connected by a wired backbone network or wireless mesh networks.Meanwhile, ad-hoc connections among user terminals are achieved by using bluetooth or IEEE802.11 technologies. Thus, such environment provides ubiquitous access for ubiquitous services.The way of accessing single network can not meet user demand for multimedia services.Multi-homing ability of terminals provides the possibility of multi-flow transmission of multimedia services, which can fully extend resource space, so as to meet user service requirements. The main works of this thesis are as follows:Firstly, the challenges of each protocol layer caused by multi-flow transmission are introduced.Then the resource optimization allocation algorithms of multi-flow transmission for multimedia services are surveyed.Secondly, a resource optimization allocation algorithm of multi-flow transmission based on network cooperation for load balancing is proposed. In this algorithm, the price metric based on load ratio is introduced to achieve load balancing. In addition, this algorithm can be applied to various networks by using the concept of equivalent channel resource. At last, a log distance path loss model is utilized to describe the real wireless channel conditions accurately. Moreover, the performance of this algorithm is verified by simulations.Thirdly, by using multi-attribute decision making, a multi-flow rate distribution algorithm based on terminal cooperation is proposed. In this algorithm, the slave terminal and its access network are selected and put in candidate terminal set first. Then cooperative terminals are selected according to the system utility function. And, the best multi-flow rate distribution is achieved based on the fairness principle. Simulation results verify the performance of this algorithm.Finally, the conclusions are summarized, and the future research directions are given. |
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