Enabling Backoff and Eliminating Redundant Idle Period for Medium Access in LTE-U

To address the burgeoning demand for mobile data, 3GPP is actively studying the capability of operating LTE in the unlicensed band, referred to as LTE-U. One of the main challenges of this approach is to maintain better coexistence between WiFi and LTE-U devices. To enable the coexistence, the listen before talk (LBT) principle has been adopted for LTE-U medium access with two flavors of mechanisms, i.e., load based equipment (LBE) and frame based equipment (FBE) access. In this paper, we consider the FBE mechanism and enhance its performance by introducing a backoff procedure for LTE devices. We investigate the original FBE mechanism defined by 3GPP and the enhanced FBE (E- FBE) mechanism from our earlier work. Then we propose a novel FBE mechanism by both enabling a backoff approach for access contention and eliminating the unnecessary waiting time for nodes which failed in previous transmission contention. Furthermore, we compare the performance of these three mechanisms with respect to four parameters. Numerical results based on simulations demonstrate that the proposed mechanism outperforms the other two in terms offairnessindex,transmissionopportunities,collisio nprobability, as well as transmission delay.