A Hybrid-LBT MAC with Adaptive Sleep for LTE LAA Coexisting with Wi-Fi over Unlicensed Band

In this paper, we investigate the access mechanisms of LTE Licensed Assisted Access (LAA) co-existing with Wi-Fi over the unlicensed band. To this end, we first develop an analytical model to study the performance of existing Load Based Equipment (LBE) MAC for Unlicensed Long Term Evolution (U-LTE), identify the fairness issues, and quantify the reservation overhead of the protocol. To maximize the network throughput and ensure fair spectrum sharing of U- LTE and Wi-Fi, we propose a hybrid MAC protocol that combines the best features of LBE MAC and Frame Based Equipment (FBE) MAC. A two-level renewal process-based model is also developed to analyze the throughput performance of the proposed MAC. By jointly optimizing the sleep period and the contention window size of U-LTE, the best co-existing performance in terms of the total network throughput and throughput fairness of U-LTE and Wi-Fi can be achieved, with minimal reservation overhead. Extensive simulations using NS-3 validate the analysis and demonstrate the efficiency of the proposed MAC protocol.