Analytical study of license-assisted access in 5G networks

The volume of traffic transmitted over cellular networks is growing significantly every year. To improve LTE network throughput, 3GPP has proposed License-Assisted Access (LTE-LAA), which allows utilizing the unlicensed 5GHz spectrum already used by Wi-Fi and other technologies. To enable fair resource sharing, LTE-LAA adopts CSMA/CA-based channel access with binary exponential backoff similar to Wi-Fi. However, because of the LTE-LAA technology constraints, the LTE-LAA base station may start data transmission only at rather rare licensed carrier slot boundaries. The essential question, what the base station should do between the end of the backoff procedure and the closest licensed slot boundary, is left implementation dependent. In the paper, we have developed analytical models to study the performance of different LTE-LAA implementations and analyze channel sharing fairness between LTE-LAA and Wi-Fi networks in the coexistence scenario. Moreover, we investigate how the performance of LTE-LAA channel access can be improved using New Radio flexible numerology, which is one of the main features of currently developed 5G systems.