| With the explosive growth of mobile data services and intelligent terminals,the spectrum resources of authorized frequency bands are increasingly scarce,which can cause network congestion in indoor and public hotspots and reduce the performance of LTE networks.Compared with the authorized band,the non-authorized band has a rich spectrum resources.In September 2014,3GPP launched the Licensed-Assisted Access using LTE(LAA)research project,which aims to enhance the capacity of LTE networks by using LTE technology on non-authorized bands and improve user experience.According to the provisions of Japan and Europe,transmission mechanism in the non-authorized channel should be LBT.However,the mechanism may lead to hidden terminal problems between LAA and Wi-Fi.In addition to interference from outside the system,the LAA receiver may also suffer interference from other LAA senders within the system.To avoid intra-system interference,the LAA network uses a scheduling based radio access,That is,the LAA-UE needs to transmit a radio resource,and the LAA-eNB allocates a radio resource to the user.The LAA-UE needs to execute the CCA before using the radio resource.If it is detected that the radio resource is occupied by the Wi-Fi network,the transmission of the LAA-UE on the radio resource is stopped.When the probability of interference is small,the performance of LAA based on scheduling wireless access is better.When the probability of interference is relatively large,the performance of LAA based on scheduling wireless access is low and the user experience is poor.In order to improve the performance of LAA when the probability of interference is large,this thesis verifies the uplink "best" access theory proposed by Lien,and then gives a simulation of the relationship between the number of users,the number of resources,the optimal number of users and the utilization of each resource batch.On this basis,the access algorithm based on partioned interference probability is proposed,and the implementation steps of proposed algorithm are given.The algorithm is suitable for the situation that the probability of interference is changed slowly.It got the balance between the success rate of user access and the utilization of each resource batch.The simulation results show that the proposed algorithm can improve the utilization of each resource batch and the success rate of user access compared with the existing algorithms. |
