Methods for the Allocation of Almost Blank Subframes with Fixed Duty Cycle for Improved LTE-U/Wi-Fi Coexistence

In order to cope with the increased demand of wireless services and applications, LTE over unlicensed spectrum has been proposed to extend the operation of LTE to operate also over unlicensed bands. However, this extension faces various challenges regarding the coexistence between LTE-U and different technologies that use these unlicensed spectrum bands such as Wi-Fi technology. The first scenario of LTE allowing LTE to operate over unlicensed bands is LTE-Unlicensed duty cycling (LTE-U). Specifically, LTE-U can coexist with Wi-Fi by allowing LTE-U devices to transmit only in predetermined duty cycles (DCs) or to use adaptive DCs for LTE based on the activity measurements. In this paper, we investigate the downlink performance of LTE-U and Wi-Fi under different traffic loads. The main novelty of this work is to exploit the knowledge of the existing Wi-Fi traffic activity to select a fixed DC for LTE. Moreover, two proposed methods to allocate the blank subframes within LTE frames are provided. Simulation results using NS-3 simulator for LTE-U and Wi-Fi coexistence mechanism under different traffic loads are provided. In particular, the results show that the coexistence mechanism between LTE-U and Wi-Fi in the 5 GHz band achieves better total aggregated throughputs for the coexisting technologies using the proposed approach. Moreover, the location of the blank subframes plays a key role in this coexistence in terms of the total aggreaated throughputs.