Performance Analysis And Optimization Of LAA And Wi-Fi Coexistence Network

Long Term Evolution(LTE)in unlicensed spectrum(LTE-Unlicensed)is considered an effective solution to the challenge of exponential growth in data traffic in the coming years.Licensed Assisted Access(LAA)is a promising variant of LTE-Unlicensed that has been standardized by the 3rd Generation Partnership Project(3GPP)in Release 13.Bianchi's model is widely applied for performance analysis of LAA and Wi-Fi coexistence networks.It should be noted that the Bianchi's model is only applicable to the case of synchronous channel access,namely the corresponding key timing parameters for channel access of the LAA and Wi-Fi,such as the duration of an idle time slot and the deferment before resuming counting down the backoff timer,are respectively identical.The LAA in 3GPP Release 15 has flexible Clear Channel Assessment(CCA)durations that are not aligned with the Distributed Interframe Space(DIFS)and backoff slots in the Wi-Fi.Therefore,the coexistence network of LAA and Wi-Fi has the features of asynchronous channel access.Based on the features of LAA and Wi-Fi coexistence networks with asynchronous channel access,Superframe model is proposed in this paper for accurate performance analysis of that coexistence network.The performance evaluation is conducted by comparing the simulation results with the theoretical calculations using the Superframe model.How to ensure the friendly and fair coexistence with the existing Wi-Fi networks has aroused considerable attention.In view of this,this paper proposes an adaptive p-persistent LAA scheme,known as p-LAA,to balance the tradeoff between the throughput and fairness of the p-LAA/Wi-Fi coexistent system in a saturated scenario.The throughput and fairness of the p-LAA/Wi-Fi coexistent system are firstly theoretically derived from the perspective of asynchronous channel access.Based on the Superframe model,we then derive the throughput of the p-LAA/Wi-Fi coexistent system.Further,the channel access probability of the p-LAA protocol is optimized to achieve the balance between the throughput and fairness.Finally,the accuracy of our theoretical analysis is verified by sufficient Monte Carlo simulations.The numerical results show that p-LAA can significantly improve the fairness and throughput of the coexistence network,especially in the LAA defer period shorter than the Wi-Fi defer period and more LAA evolved NodeBs(eNBs)scenarios.