Performance analysis of multi-carrier LAA and Wi-Fi coexistence in unlicensed spectrum

Licensed-Assisted Access (LAA) to unlicensed spectrum has been regarded as a promising technology to meet the exponential growth of traffic demands. Based on listen-before-talk (LBT), LAA can allow mobile operators to utilize unlicensed spectrum as supplementary carriers for data offloading and also can guarantee fair coexistence with other access technologies (e.g., Wi-Fi) in unlicensed band. To obtain more available bandwidth and achieve higher data transmission rate, multiple unlicensed carriers could be aggregated by using multi-carrier LBT. However, multi-carrier LBT mechanism cannot always enhance system performance when the stations including Wi-Fi APs and LAA stations are densely deployed. This is because that the dense deployment of stations will lead to increasing the collision probability and decreasing the probability of successful transmission. To reveal the fundamental characteristics of multi-carrier LAA mechanism, in this paper, we first analyze the performance of multi-carrier LBT mechanism. Then, we propose a low-complexity algorithm for multi-carrier LBT operations to provide better system performance under saturation traffic scenario. Furthermore, the simulation results verifies our theoretical analysis, and the proposed algorithm can further enhance the system performance.