Contention Window Size Adaptation Algorithm for LAA-LTE in Unlicensed Band

Fair coexistence between Licensed-Assisted Access using LTE (LAA-LTE) and Wi-Fi in the unlicensed spectrum of 5 GHz is a primary challenge. Listen-Before-Talk (LBT) scheme is required to ensure the fairness among different operators in unlicensed band. In this paper, we focus on the downlink performance of LAA and Wi-Fi with different load intensity. To achieve not only channel access fairness but also higher throughput gain, a contention window (CW) size adaptation algorithm based on LBT Category 4 channel access scheme is proposed. In the analysis, the behavior of LAA eNodeB (eNB) is modeled as a Markov chain to depict the procedure of LBT Category 4 and the throughput can be calculated. Compared with the fixed contention window size mechanism, simulation results show that our algorithm can achieve at least 5% LAA-LTE performance gain in average user throughput with different load intensity.