Maximizing the throughput of duty-cycle based licensed-assisted access in the unlicensed band

Abstract

Long Term Evolution (LTE) boasts several throughput enhancing techniques like optimized MAC layer protocols, better modulation schemes, spatial multiplexing, carrier aggregation, etc. Although these techniques allow LTE to offer data rates as high as 300 Mbps, LTE is expected to fall short of consumer expectations due to the exponentially increasing user data demands. In a bid to cope with the increasing data demands, the mobile network operators and the research community, alongside 3GPP, are working towards standardizing the operation of LTE in the 5 GHz unlicensed band by opportunistically supplementing the licensed LTE carrier with a carrier in the unlicensed band — a feature named Licensed-Assisted Access (LAA). Since this unlicensed band already hosts well-established technologies like Wi-Fi, a need arises for a fair coexistence mechanism between LAA and Wi-Fi users. In this regard, we propose a novel duty-cycle based fair coexistence condition that not only facilitates Wi-Fi and LAA to be fair neighbours, but also maximizes the LAA throughput in the unlicensed band. To the best of our knowledge, this condition is the first to provide a fairness bound which gives a fair duty-cycle for LAA and Wi-Fi transmissions in the unlicensed band. The simulation results obtained validate our analytical model. Furthermore, the derived condition shows that the LAA throughput in the unlicensed band can be improved by around 65 to 1350 Kbps, when there are ten or fewer active users in a Wi-Fi cell of 20 MHz bandwidth, over the current state of the art coexistence scheme that facilitates proportional fairness between LAA and Wi-Fi in the unlicensed band.