An Optimal LTE-U Access Method for Throughput Maximization and Fairness Assurance

To solve the issue of scarce spectrum resources of the existing cellular network, LTE-U that expands LTE service to the unlicensed 5GHz spectrum is proposed. However, the centralized medium access control protocol of LTE largely decreases the performance of Wi-Fi networks operating in the same unlicensed spectrum. In the paper, to solve the problem, we propose a new mechanism based on the duty-cycle method. It can adaptively adjust the percentage of the airtime used by a LTE Small cell Base Station (SBS) according to the bandwidth of the licensed spectrum of the SBS and downlink data rate demands of the SBS users to maximize throughput of the SBS network on the unlicensed spectrum while ensuring fairness between the Wi-Fi and SBS network. The fairness is based on 3GPP proposed fairness coexistence criterion. To ensure the fairness, we propose a method to construct a W-Fi network offering the same level of the SBS traffic load, and throughput maximization of the SBS is formulated as a constrained non-linear optimization problem solved by an optimal algorithm. We evaluate the proposed mechanism from two aspects. The first is to prove the proposed Wi-Fi network construction method is valid. The second is to evaluate the performance of our proposed method. Simulation results show that our approach is valid and it can maximize the throughput of the SBS network and ensure the fairness criterion.