Achieving Optimum Throughput for LTE and WiFi Coexistence

In this paper, we consider how to achieve optimum throughput when LTE with listen before talk (LBT) shares the unlicensed spectrum with WiFi. Basically, we aim to address two problems: 1) How can WiFi access point (AP) and WiFi station (STN) configure the access parameters to maximize the throughput of their own networks when they have knowledge of the access parameter of LTE? 2) How to jointly tune the access parameters of both networks towards the maximum throughput of the whole network? It is found that even when the WiFi network optimally configures the access parameters, the throughput gain is marginal when LTE accesses the unlicensed spectrum with a fixed backoff window size, which necessitates a joint tuning of the access parameters of both parties. With joint tuning, nevertheless, the throughput of the whole network is maximized when only the LTE uses the unlicensed spectrum. To provide a fair coexistence to the WiFi network, the throughput optimization problem is considered under the constraint that the WiFi network share a given portion of the throughput of the whole network. Explicit expressions of optimal access parameters are obtained for both LTE and WiFi networks, which provide direct guidance for harmonious coexistence of the two systems.