Access Performance Analysis And Optimization On LAA-WiFi Coexistence System

In recent years,with the rapid development of Internet applications,the demand for high data rates in wireless communication systems has continued to increase,which has led to a sharp increase in the pressure of licensed spectrum load.However,due to the limited physical range of the available licensed spectrum,new licensed bands have become scarce and expensive.Therefore,deploying LTE on unlicensed bands has become a new solution to meet the demand of limited licensed spectrum.For this reason,the 3rd Generation Partnership Project organization(3GPP)proposed the License Assisted Access(LAA)technology as a solution.However,a large number of WiFi systems have been deployed on unlicensed bands,directly deploying LAA on unlicensed bands will inevitably conflict with WiFi.Thus,under the premise of ensuring fairness,this paper models,analyzes,and optimizes the channel access mechanism of the LAA-WiFi coexistence system in the unlicensed band to improve the throughput performance of the system.Firstly,for the unlicensed band LAA-WiFi coexistence scenario,this paper proposes the LAA-WiFi channel access mechanism in unsaturated scenarios,combines queuing theory and Markov process,constructs the corresponding unsaturated channel access mathematical model of the two systems,analyze the relationship between the throughput and delay performance of the coexistence system and network parameters,protocol parameters,and service parameters.The simulation results verify the validity and correctness of the proposed mathematical model,and show that the coexistence system has better throughput gains in sparse scenarios.At the same time,the simulation results also show that the LAA system has better throughput performance and lower transmission delay under high service intensity,high initial backoff window and high maximum backoff stage.Secondly,based on the channel access mechanism model in the above-mentioned unsaturated scenario,this paper aims to maximize the throughput of the coexistence system under the constraints of WiFi system throughput,and derives the best combination of protocol parameters under different network scenarios and business scenarios,and propose the best protocol parameter(initial backoff window and maximum backoff stage)search method based on traversal and the best protocol parameter search method based on neighborhood to search for the best combination.The simulation results verify the correctness of the two proposed methods,and show that in the case of high WiFi throughput threshold,there is a higher optimal protocol parameter value.At the same time,the results also show that the total throughput of the coexistence system can be greatly improved when the optimal protocol parameter combination is used,and shows more significant improvement in sparse scenarios.