In recent years, LTE system with unlicensed bands is proposed. It can achieve not only to boost the capacity of cellular networks but also to use unlicensed bands effectively since LTE can achieve better spectrum efficiency than Wi-Fi. However, when LTE is introduced into an environment where Wi-Fi access points are already deployed, significant interference may be caused to Wi-Fi, Therefore, the coexistence of LTE and Wi-Fi with unlicensed bands is the problem. In this paper, we assume an environment where LTE base stations and Wi-Fi access points are deployed high-densely with unlicensed bands and co-channel interference frequently is caused. Then, we aim to enhance the average user throughput and its fairness through a centralized control of LTE and Wi-Fi, Specifically, we propose a channel assignment method and a users' access system selection method using GA. The proposed method enhances both the average user throughput and the fairness of user throughput compared with conventional static channel assignment methods.