Throughput Analysis of LAA and Wi-Fi Coexistence Network With Asynchronous Channel Access

The licensed-assisted access (LAA) technology has been proposed as a promising solution to increase the network capability by extending the frequency bands for long term evolution networks. The performance evaluation of the LAA systems has been extensively studied in recent years. However, most existing works did not consider the fact that Wi-Fi stations and LAA equipments are typically not synchronized in such a heterogeneous network. They are not aligned in time domain because of different time-slot durations, channel access back off, and contention window sizes. Therefore, in this paper, we investigate the throughput performance of the LAA and Wi-Fi coexisting networks with asynchronous channel access. To deal with the asynchronism, we first introduce the concept of the heterogeneous network superframe based on the fact that the timing relation between LAA and Wi-Fi systems will be restored to a fixed pattern after a busy slot. Thereafter, we model the LAA and Wi-Fi channel access behaviors in superframes as 2-D Markov chains, respectively. Based on the Markov chains and the structure of the superframe, we analyze the throughput performance by fully considering the asynchronism of the heterogeneous channel access. The accuracy of our theoretical analysis is validated by numerical results. Meanwhile, we have also investigated the effects of the number of LAA equipments, Wi-Fi stations, and the maximum contention window size upon the system throughput.