Hybrid Adaptive Channel Access for LTE-U Systems

Abstract

To alleviate the shortage of spectrum resource on licensed bands, long-term evolution in unlicensed bands (LTE-U) has been proposed. To facilitate the fair coexistence between LTE-U and the legacy WiFi networks on unlicensed bands, two well-known channel access mechanisms named as duty-cycle muting (DCM) and listen-before-talk (LBT) have been proposed and studied extensively. Accordingly, in this paper, a unified hybrid adaptive channel access scheme is proposed, which takes advantages of both the DCM and LBT mechanisms. Our proposal can realize the flexible handoff between the DCM and LBT mechanisms to meet the requirements of different markets. It can also adaptively adjust the important parameters, such as the back-off window size and the duty-cycle time fraction based on the WiFi traffic and the available licensed spectrum resource while guaranteeing the fair coexistence between the WiFi and LTE-U systems. Moreover, joint spectrum and transmission power allocation is also studied to improve the spectra efficiency (SE) on both licensed and unlicensed bands. Finally, analytical and numerical results are demonstrated to verify the effectiveness of the proposed scheme.