Research On Multi-AP Spectrum Sharing Mechanism Of The Next Generaion WIFI

The next generation Wireless Fidelity (WiFi) aims to greatly improve the spectrum efficiency and throughput through the use of innovative technologies. The physical layer transmission technologies and the Media Access Control (MAC) layer enhancement technologies include adaptive sub-carrier modulation technology, super frame in physical layer, a new frame structure, cognitive radio, channel aggregation technology, single channel/multiple transmission technology, downlink multi-user Multiple Input Multiple Output (MIMO) technology, Orthogonal Frequency Division Multiple Access (OFDMA) technology, Quality of Service(QoS) guarantee technology, enhanced Low Density Parity Check Code (LDPC) technology, link adaptation technique, beamforming etc. The research topic of this thesis is mainly about multi-Access Point (AP) spectrum sharing mechanism in the next-generation WiFi from the aspects of radio resource management and QoS guarantee. First, it needs to determine the multi-AP spectrum sharing strategy, and then design optimizational resource allocation algorithm combined with QoS constraint conditions to complete the wireless resource allocation, including spectrum allocation and power allocation.The main work of this paper is as follows:(1)A possible cell structure and configuration mode of the next generation WiFi is discussed in detail. The higher frequency band and microcell structure can be used to provide flawless coverage and optimizational network capacity. Using AP+Access Controller (AC) mode, APs’ configuration management, communication data processing and network intelligence are centrally controlled by AC, which can provide more efficient and stable network.(2) A multi-AP spectrum sharing strategy is proposed. Users in the same cell use different channels, while users in different cells can use the same channel, as inter-cell spectrum sharing can ensure the maximum degree of spectrum sharing. Under this strategy, the optimal resource allocation problem is analysised under two QoS constraints-the minimum rate constraint and the maximum delay constraint, so as to reduce the inter-cell interference, balance the network load, ensure users’satisfaction, and improve the network capacity and communication performance.(3) A simplified multi-AP spectrum sharing strategy with lower complexity is proposed. As the optimizational resource allocation under the proposed strategy involves the entire system resources, the optimization problem becomes extremely large and complex. Therefore, a rational design of interference suppression strategy is added to simplify the problem, spectrum reallocation strategy is added to improve the spectrum efficiency.(4) Design and analysis of multi-AP spectrum sharing mechanism under the minimum rate constraint is proposed. In the basis of (3), the target of system resource optimization problem is specified combined with user minimum rate constraints, system model, user information and channel information, then the probem is analysised and processed with mathematical method. A resource allocation algorithm is designed to meet the performance requirements with lower complexity. Finally, some factors which affect the algorithm are analyzed, and the performance analysis of the algorithm is given.(5) Design and analysis of multi-AP spectrum sharing mechanism under the maximum delay constraint is proposed. In the basis of (3), using the method of the equivalent bandwidth and the equivalent capacity, the user maximum delay constraint of the upper layer is transferred into the equivalent minimum rate constraint which is only related to the channel state, then the problem is transformed into the multi-AP spectrum sharing mechanism under the minimum rate constraint. Some factors which affect the algorithm are analyzed, and the performance of the algorithm is evaluated by simulation.(6) The research work in this paper is summarized, and the prospects of future research work are given.