# Q-Learning Based Fair and Efficient Coexistence of LTE in Unlicensed Band
## 1 Introduction
Thus, fairness and efficiency are the two critical and conflicting criteria in spectrum resource management under a Wi-Fi and LTE-U coexistence scenario. Figure 1: CableLabs experiment on LTE-U [7]. Figure 2: Preliminary simulation results of duty cycle LTE-U. The present study attempted to reduce the above-mentioned conflicts by taking advantage of the existence of multiple channels in the 5-GHz unlicensed spectrum. The 5-GHz band offers multiple non-overlapping 20/40/80/160 MHz channels. Because all Wi-Fi APs are provisioned to operate in different channels based on the received power measurement, the traffic load on each available channel will be diverse. Therefore, to increase their throughput performance, choosing the least congested channel for the operation of LTE-U with Wi-Fi will be highly advantageous for LTE-U and Wi-Fi individually. The best channel selection approaches are greatly subsidized to increase the effectiveness of the network but not the fairness. Hence, we designed a combination of adaptive duty cycling (ADC) and dynamic channel switch (DCS) mechanisms for the network to access a channel under a dynamic traffic load scenario. The ADC mechanism supports a fair channel access opportunity by reserving a certain number of subframes for the operation of Wi-Fi Stations (STAs). In contrast, the DCS mechanism offers more access opportunities for LTE-U users by avoiding most crowed channels for their operation. When considering futuristic wireless applications, the user-demand will vary across a wider spectrum. Such requirements cannot be satisfied by assigning fixed resources. Hence, the realization of LTE-U collocated with Wi-Fi under a dynamic environment is a prerequisite. Thus, LTE-U is enhanced using Q-learning techniques for an autonomous selection of the appropriate combination of best duty cycles in various channels through iterations of the learning process. This process escalates the spectrum efficiency of the network while assuring the fairness among these LTE and Wi-Fi systems. Meanwhile, to simulate the proposed scenario, a system-level simulation program for a Wi-Fi and LTE-U system was built and utilized. The analysis of the simulation results demonstrates that the proposed algorithm enhances the network performance while sustaining the fairness among Wi-Fi and LTE-U systems. The main contributions of this study are as follows:  
* Description and analysis of collocated LTE-U and Wi-Fi system;
* A Q-learning mechanism used for an ideal and autonomous selection of an LTE-U operational channel muting duration toward fair and efficient spectrum sharing under a dynamic environment;
* A performance evaluation of the proposed Wi-Fi and LTE-U coexistence mechanism with pre-existing coexistence solutions, i.e., duty cycle (DC) only and channel occupancy time (COT) based channel selection. The remainder of this paper is organized as follows. Section 2 details and reviews some recent related studies. Section 3 discusses the proposed LTE and Wi-Fi coexistence mechanism. Section 4 describes the simulation results and provides a detailed evaluation of its performance. Section 5 provides some concluding remarks.