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Listen-Before-Talk (LBT) is the clear channel assessment (CCA) check method of Licensed-Assisted Access (LAA) framework. A flexible LBT strategy is important when LAA devices coexist with WiFi system in unlicensed spectrum. The existing adaptive LBT methods modify the LAA contention window (CW) size according to information exchanged between the coexisting two systems. This work proposes an adaptive LAA-LBT scheme, without the need of special inter-system coordinations and information exchange, for the fair coexist of downlink LAA and WiFi devices. This strategy includes a flexible Initial Clear-Channel Assessment (ICCA) procedure and a dynamic CW adjustment scheme, where the ICCA duration and the CW size varies according to the detection results by LAA system. All the LAA detection needed in this work is non-threatening and transparent to WiFi system. Simulation results show that this strategy is valid for adjusting the successful-airtime-ratio for the two coexisting systems.
Wang et al. (Sun,) studied this question.