Uplink performance enhancement for LTE licensed-assisted access to unlicensed spectrum

Licensed-assisted access (LAA) is a new operation mode of carrier aggregation for the Long Term Evolution Advanced systems to transmit data on both licensed and unlicensed spectrum. To deal with the issue of co-existence with WiFi systems, LAA is required to perform listen-before-talk, which can significantly impact its resource utilization. In this paper, the concept called multi-subframe scheduling (MSS) which can enhance the performance of uplink LAA data transmission is presented. MSS allows a user equipment to have multiple channel sensing opportunities and/or to transmit data continuously for multiple subframes. Both scheduling-based and random access schemes are evaluated and compared. The optimum configuration of MSS which maximizes resource utilization of LAA is also provided. Numerical results show that MSS improves resource utilization on the unlicensed spectrum significantly.