Optimum Multi-Subframe Scheduling for LTE Licensed-Assisted Access to Unlicensed Spectrum

Abstract

Licensed-Assisted Access (LAA) is a new operation mode for the Long Term Evolution Advanced systems to transmit data via both licensed spectrum and unlicensed spectrum based on the framework of carrier aggregation. For LAA uplink (UL) transmission, there is a mismatch between resource allocation and actual data transmission due to the requirement of listen-before-talk (LBT). Such a mismatch may cause severe throughput degradation and, therefore, is an important issue to be addressed. In Release 14, two different ideas of multi-subframe scheduling (MSS) were proposed to improve UL throughput by allowing user equipments to either transmit data continuously for multiple subframes or have multiple opportunities to perform LBT. In this paper, we present a family of scheduling schemes which combines the two MSS ideas and evaluate its performance. The optimum one in the proposed family of schemes which maximizes throughput is determined.