Wi-Fi-LAA coexistence: Design and evaluation of Listen Before Talk for LAA

With licensed spectrum at a premium, recent interest has shifted to investigating the possibility of utilizing unlicensed bands as a means of providing additional bandwidth. License assisted access (LAA) and Long Term Evolution-Unlicensed (LTE-U) are radio access technologies (RATs) aimed at providing carrier-grade wireless service in the 5 GHz unlicensed spectrum. Since Wi-Fi devices are widespread in the unlicensed space, it is important to ensure that any new technology deployed coexists fairly with Wi-Fi and other preexisting technologies that already occupy this space. At the heart of the Wi-Fi-LAA coexistence problem is the difference in channel access mechanisms for these two technologies; Wi-Fi is a contention based channel access scheme, while Long Term Evolution (LTE) is schedule-based. As a result, introducing an LTE system as is into the Wi-Fi space would likely result in LAA gradually taking over the channel and starving Wi-Fi of access. In this paper we focus on schemes to address this very issue. In particular, we will focus on various design aspects of Listen Before Talk (LBT) schemes for LAA that aim to emulate the contention based scheme in Wi-Fi as a means of providing equal opportunity channel access for both of these technologies. We consider and evaluate the impact of various design aspects on fairness through several key performance metrics. Our simulation results demonstrate that LBT when applied to LTE can ensure good Wi-Fi-LAA coexistence.