Resource Management of LTE-U Systems for Channel Utilization and User Satisfaction

Deploying long term evolution (LTE) system into unlicensed spectrum for offloading faces two challenges: 1) the metrics of instantaneous performance to characterize user satisfaction are no longer applicable due to non-contiguously available channel and 2) in a light traffic scenario, the channel utilization is low due to the added padding bits of simultaneously scheduled users. To tackle these two issues, dynamically configuring channel occupancy duration (COD) and flexibly allocating subcarriers are needed to design for the LTE system operating in unlicensed spectrum (LTE-U system). In this paper, the channel utilization in the COD and a unified user satisfaction are first defined to characterize the performance of LTE-U system. Then, a time–frequency two-dimention optimization problem is formulated to maximize the weighted sum of the two defined performance indexes. To achieve the tradeoff between the two performance indexes, a control factor is introduced. By using Lyapunov optimization and Dinkelback theory, an optimal time–frequency resource management algorithm is developed. The results show that the proposed algorithm outperforms the baselines, as the algorithm can flexibly balance the two performance indexes of the LTE-U system for diverse applications.