Research Of Key QoS Problems For Wireless Access Network

Nowadays mobile communication has become a hot research issue. Because the QoS of mobile network directly decides the usability and practicability of network, QoS-related problems in mobile network have been in dire need of a solution. Currently the QoS of Internet has made a big leap, but that of mobile network a small step. There are a lot of QoS solutions for wired network, but there are sharp diffirence between wired network and wireless network, thus these solutions cannot apply to wireless network without modification. For wireless access network the QoS problems are just became to be spotted, and there are a lot of issues.Some key QoS problems in wireless access network are focused in this thesis, esp. the following three problems: 1. Research of terminal-based schedule policy and decreasing the energy-comsumption of wireless terminals; 2. Research of adaptive admission control policy and providing guranteed QoS measures, such as the rate of handoff calls; 3. Research of the performance problems of TCP on wireless links and focusing on performance/thoughput effection caused by link model and wireless link delay.The main contribution of the thesis as follows:1. A new delay-sending schedule policy is classified and testified. Moble terminal has limited energy and how to decrease the energy consumption of wireless terminals is a great challenge for wireless terminals. Most of the energy is consumed by sending data. According to information theory, the time to complete sending one bit is inverse proportional to the energy to send one bit. So at proper time and at proper rate to send data is a core problem. All the theoretical analysis and simulation result has been done, and two papers are submitted. One is accepted by ICCC 2003, which is indexed by El.2. A probability-based call admission control scheme is contrived. Adaptive call admission control plays a vital role for wireless access network. There are a lot of call admission control shcemes for wireless access network. But these are quite difficult and not adaptive to diffirent traffic. We adopt a method similar to RED(Random Early Detection) and device a probability-based call admission control scheme. Simulation results show that this scheme works. And we also divece a multimedia access controlscheme and verify the result.3. The analytical model for TCP on wireless links is formulated. The relationship between thoughput and burst errors is analyzed; and random process and Markov process are used to formulate the relationship. The analytical results are obtained and simulation results are verified.