Optimal distributed allocation of almost blank subframes for LTE/WiFi coexistence

Since LTE in unlicensed spectrum (LTE-U) was proposed by Qualcomm, it has drawn considerable interest because of its potential to increase the capacity of existing LTE networks by utilizing existing infrastructure in the unlicensed band. But, Wi-Fi technology, already operating in the unlicensed 5 GHz band, creates several potential challenges for managing the activities of these two different technologies in the same band. In this context, we propose an adaptive coexistence scheme between LTE and WiFi by utilizing almost blank subframes (ABS). An ABS is an LTE subframe of duration 1 ms (containing two time slots of 0.5 ms duration) with reduced downlink activity. LTE allocates ABSs over 20 MHz channels in 5 GHz band to allow WiFi to access the spectrum. In the proposed coexistence scheme, each LTE cell optimally distributes ABSs over the frame to provide certain quality of service (QoS) guarantees for WiFi traffic while ensuring the performance of its own users.