Research On Multiple Access Control Technology For Maximizing Multi-user Joint Carrying Capacity In Unlicensed Band

With the development of wireless network communication,the wireless network working in the unlicensed band will play an important service carrying and shunting role,especially the wireless local area network(WLAN)in the unlicensed band has become an important carrying means for wireless network services.In recent years,the Institute of Electrical and Electronic Engineers(IEEE)has been standardizing the upcoming next generation WLAN standard,IEEE 802.11 ax.IEEE 802.11 ax introduces the hybrid multi-user access mode of scheduling access and random access.How to measure and optimize the joint multi-user carrying capacity is one important and challenging direction of the next generation WLAN.Therefore,this thesis focuses on the most representative network operated in unlicensed band-i.e.,the next generation WLAN,and adopts a measurement method that can consider the coexistence of scheduling access and random access in the network,to maximize the joint multi-user carrying capacity of the next-generation WLAN.Specifically,the innovations of this thesis are summarized as follows:1.To solve the problem that the joint multi-user carrying capacity of IEEE 802.11 ax network can hardly be measured,a concept and model of multi-user access capacity is proposed.It efficiently measures the joint multi-user carrying capacity of scheduling access and random access.The core idea of multi-user access capacity is to measure the joint multi-user carrying capacity with scheduling access and random access through accurate calculation of scheduling access carrying capacity and statistical prediction of random access carrying capacity.The enhanced multi-layer Markov chain is used to model and analyze the uplink orthogonal frequency division multiple access based random access(UORA)protocol of IEEE 802.11 ax,and the analytic expression of multi-user carrying capacity of IEEE802.11 ax is obtained.A greedy based hybrid access(GBHA)algorithm is proposed,which conforms to the IEEE 802.11 ax draft framework.The accuracy of the proposed model and the effectiveness of the proposed algorithm is verified by simulations.2.For the problem that the UORA mechanism of IEEE 802.11 ax in single-cell scenario is difficult to improve the quality of experience(Qo E)of users and the multi-user carrying capacity of the network,a grouping-based UORA(G-UORA)method based on utility optimization is proposed.It enables users to obtain greater satisfaction and improves the multi-user carrying capacity of the network with the UORA mechanism.Access resources and users are divided into different groups,and users in the same group can only access the resources in the same group.By combining the multi-user access capacity and the utility function reflecting the Qo E of users,the theoretical model of G-UORA method is established.The user group clustering and resource allocation algorithm based on utility is designed.The principle of the algorithm is to maximize the sum of utility of all groups.Finally,the simulation results show that the proposed algorithm can improve the Qo E of users and the multi-user carrying capacity of the network with the UORA mechanism.3.For the problem that the lack of the efficient resource allocation methods for the hybrid access mode with scheduling and random access in the single-cell scenario of IEEE802.11 ax,a utility optimization algorithm based on resource transfer(UORT)is proposed,which improves the joint multi-user carrying capacity of the network with scheduling and random access.The UORT algorithm maximizes the utility of scheduling access users by Lagrange multiplier method,and optimizes the overall utility of scheduling access and random access users by means of resource transfer.In order to reduce the complexity of UORT algorithm,a fast UORT(F-UORT)algorithm is proposed.The allocation ratio of resources between scheduling access users and random access users in UORT algorithm is given and proved.The performance gains of UORT and F-UORT and the proposed resource allocation ratio are verified by simulations.4.For the problem that the joint multi-user carrying capacity of IEEE 802.11 ax network in dense multi-cell scenario is difficult to optimize,a utility optimization algorithm based on interference characteristics(UOIC)is proposed,which improves the Qo E of users in dense multi-cell scenario of IEEE 802.11 ax.The utility model of multi-user access capacity is extended to multi-cell scenario,and the model with interference from multi-cell is introduced.The probability density curve and distribution rule of multi-cell interference random variables under different conditions are obtained by using simulation assistant method.The random variables of inter-cell interference are generated by the accpetance-rejection method,which are superimposed on the utility model of multi-user access capacity to adapt to the multi-cell scenarios.After that,the UOIC algorithm is designed.Finally,the simulation results show that the proposed algorithm can improve the overall satisfaction of scheduling access and random access users in multi-cell scenario.