Research On Wireless Link Scheduling Algorithm Based On Fading Channel

In the past decades, Wireless Sensor Networks(WSNs) have gained rapid progress and a series of achievements, which improved the life style and quality of people greatly. As one of the new and high technology which has wide application prospects, WSNs have a series of problems need to be solved as well. Link scheduling is one of fundamental problems in wireless network that can directly impact on some performances such as throughput capacity, transmission delay, lifetime and so on.However, most existing results in this area have always been under the assumption of simple graph-based model or Signal to Interference plus Noise Ratio(SINR) model for wireless interference, which lead to a not realistic or a not accurate result due to the essentially fading characteristic of signals. Rayleigh fading model take into full account the accumulation of interferences and slow fading in the link scheduling process. Therefore, we study link scheduling problem under Rayleigh Fading Model.Another issue should be considered when designing link scheduling algorithms for wireless networks is power assignment. In this thesis, we utilize the oblivious power assignment, which can decrease the energy consumption efficiently. Besides, the oblivious power control will improve the capacity of a wireless network with the decrease of the sum interferences according the reduction of the transmission power.The successful rate of link scheduling and system throughput are both essential indicators to evaluate a scheduling algorithm. If the number of links scheduled simultaneously is too few, the throughput of the system will be low as a result. However, if the number of communication links are excessive, accumulative interference between links will increases. As a result, the successful probability of link transmission will be bring down. In this thesis, we firstly set up the side length of the regular polygon to ensure the successful scheduling of communication links with an appropriate probability, while increasing the number of communication links scheduled concurrently as much as possible. Furthermore, we increase the success rate of communication with the help of error retransmission mechanism. Actually, in spite of considering link scheduling problem under fading model, we could still guarantee to achieve a similar or a higher success probability as in the SINR model. Meanwhile, the throughput of the system is maintained at a higher level.Five schedule algorithms under Rayleigh fading model with oblivious power control, i.e., Regular Triangle Schedule Algorithm(RTSA), Square Schedule Algorithm(SSA), Regular Hexagon Schedule Algorithm(RHSA), 3-Colour Schedule Algorithm based Regular Hexagon(3-CSARH), 4-Colour Schedule Algorithm based Regular Hexagon(4-CSARH) are proposed. We discuss and compare the performance of link capacity, sum capacity of the system and the average time delay of sending nodes. Theoretical analysis and simulation show that our algorithms not only can avoid conflict effectively, improve the channel utilization rate, but also can ensure the quality of communication links and obtain a high system capacity. Meanwhile, the average time delay of sending node is perfectly acceptable.