Research On Multiple Link In The Next Generation WLAN

With the rapid development of the mobile Internet,wireless local area networks and cellular networks form the basis of the Internet of Everything in the world.Wireless local area network is widely used in people's daily life by virtue of its flexibility,scalability and low economic cost.In recent years,Applications such as VR/AR and high-definition video have continuously emerged,which has put forward higher requirements for the throughput of wireless local area networks.Therefore,the 802.11 standard organization established the next-generation wireless LAN working group in 2019 to formulate the EHT standard,which aims at 30 Gbps peak throughput to meet the needs of emerging applications.One of the key technologies for the EHT standard to improve throughput is multi-link technology.Multilink technology breaks through the limitation of single physical link in the traditional wireless local area network,and aggregates multiple links in the 2.4GHz,5GHz and 6GHz frequency bands to transmit data frames,so that the system can achieve better performance.This thesis closely follows the research direction of next-generation wireless local area network,takes multi-link technology as the research focus,and deeply studies the multi-link access scheme and load balancing scheme.The specific research content of the thesis is as follows:The thesis summarizes the key technologies of the physical layer and media control link layer enhancement in the EHT standard,introduces the multi-link protocol framework,access mechanism and transmission mechanism,and focuses on the synchronous transmission mechanism and asynchronous transmission mechanism.This thesis discusses in depth the limitations of the existing single-user access scheme in the synchronous mode:once the user obtains the right to use media resources on a certain link,all the synchronous links are aggregated for transmission.As the payload is distributed across multiple links,the proportion of inherent system overhead on each link increases,resulting in a decrease in link efficiency.In order to break through the limitations of the single-user multi-link access scheme and increase system throughput,this thesis proposes a single-user and multi-user hybrid access scheme.In this solution,both the user terminals and access points can compete for link resources.When the user terminals compete for link resources,they aggregate synchronous link transmission,and when access points compete for channel resources,multi-user synchronous transmission is triggered.Using this strategy can improve the link efficiency by increasing the proportion of valid data in the channel.At the same time,a theoretical analysis of the single-user and multi-user hybrid access scheme is carried out,and the synchronous access mechanism is modeled using a three-dimensional Markov chain,and the influence of terminal user density,competition window size and data frame length on system throughput is analyzed.The single-user access scheme was compared through simulation,and the advantages of the hybrid access scheme were verified.In order to further improve the throughput of the system,this thesis analyzes the transmission capabilities of multi-link devices in different frequency band links.Aiming at the problems of different frequency band link transmission capacity and different interference status,a multi-link load balancing strategy is proposed.It explains in detail how users obtain link status information,how to select links,and how to switch links.And through theoretical analysis of link switching conditions,it provides support for multi-link load balancing strategies.