Optimization Research Of The Access Strategy In The LAA System

In recent years,the business volume carried by the cellular network is increasing day by day.The increasing network load undoubtedly raises more challenges for the existing wireless communication technologies.One of the most serious problems is how to apply more available frequency resources to the communication network for expanding the frequency resources of the network and increasing the throughput of the communication network to meet the growing business demands.Both Wireless Fidelity(WiFi)and radar technology are wireless communication technologies deployed in the 5 GHz band.The rapid spread and widespread use of WiFi networks can fully confirm the availability of the unlicensed band.As a result,the 3rd Generation Partnership Project(3 GPP)organizers starts to explore a new type of technology to deploy the existing Long Term Evolution(LTE)technology in the unlicensed band,which is 5 GHz band.However,LAA technology is not the only wireless communication technology deployed in the unlicensed band.WiFi networks is bound to interfere with the data transmission of LAA networks.Conversely,the introduction of LAA networks in the unlicensed band can also influence the performance of the WiFi technology which is already deployed in the 5 GHz band.Therefore,how to reduce the mutual interference between the two wireless technologies and make them coexist in a fair and effective manner is the key issue for improving the overall performance of LAA and WiFi networks.In order to solve this problem,the 3 GPP organization has decided to design a set of access mechanisms similar to the WiFi channel detection mechanism through multiple investigations and discussions to reduce the negative impact on WiFi.After several discussions with several well-known companies,an energy detection mechanism named listen-before-talk(LBT)was designed by 3 GPP.In this way,LAA can largely avoid the collision with WiFi during the data transmission.It can be seen from the above analysis that,since the unlicensed band where the LAA network is located in is also occupied by other wireless communication technologies,the competition of the same frequency resources is inevitably existing between different networks,which is also a key problem that restricts the performance of the LAA system.Therefore,the LAA system needs to introduce a reasonable channel access mechanism to ensure that the system can make full use of channel resources in the unlicensed band to maintain the system throughput in a high level and meet the demands of users.Optimization research of the LAA access technology is the focus of this thesis.The thesis is specifically divided into the following three points:First,this thesis summarizes the access technology framework in LAA networks systematically.In order to deploy LTE technology in the unlicensed band and maintain the fair coexistence with the WiFi technology,LAA networks introduce the LBT technology as the channel monitoring mechanism.At the same time,due to the uncertainty of data transmission in LAA networks,relevant standards such as the start and end positions of uplink and downlink data transmission and control signal transmission need to be reformulated.Based on the above contents,this thesis optimizes the access technology of LAA networks.This thesis analyzes the proposals from major companies and represents the formation of access-related technologies.Secondly,the existing channel access method in the LAA system is the scheduling based access strategy.The base station sends the control signaling to inform the user equipment(UE)on which unlicensed channel to perform the data transmission.Since in LAA networks,a user needs to execute the LBT process before sending the data,the transmission opportunity will be wasted when the LBT fails.In order to solve this problem,this thesis proposes a hybrid access mechanism from the aspect of the access strategy.The access strategy can dynamically select the access methods,so that users can use the optimum access method on different load situations in the LAA system to ensure the access success rate of their own,which improves the performance of LAA networks as well.Thirdly,the random access method is used in the hybrid access strategy and it requires all the users to perform the LBT process on all the random channels.This causes users to consume a lot of power because of excessive execution of the LBT process.In order to solve this problem,this thesis designs a joint access strategy in LAA networks.This strategy improves the user access success rate by combining the random access method and the scheduling-based access method in each subframe.When the channel condition is poor,this strategy can effectively reduce the power of users consumed by performing LBT.