Joint Channel Access Mechanism and Scheduling Design and for Licensed Assisted Access System
We consider an Uplink License Assisted Access (LAA) system in which LTE systems compete transmission resources with WiFi systems. Before sending any signals, a listen-before-talk (LBT) process is mandated for LAA system: users are required to sense the environment and can only transmit if the channel is considered idle. To guarantee that all users are aligned for transmission, a designation period of time, referred as the LBT gap is designed at the beginning of each subframe. We proposed a mechanism to calculate the optimal length of this LBT gap based on the condition of the environment, the payload size and the LBT process counter size for each individual user. The proposed mechanism can achieve a balance between the probability of successful transmission and the efficiency of using the resource. With an optimized LBT gap, we further incorporate the probability of successful transmission into the multi-user scheduling algorithm design. Our simulation results show that the mechanism of deciding the optimal LBT gap and the corresponding scheduling algorithm can significantly improve the throughput of LTE system and reduce the delay of end-to-end transmission delay.