R Re es so ou ur rc ce e A Al ll lo oc ca at ti io on n a an nd d U Us se er r A As ss so oc ci ia at ti io on ns s i in n D De en ns se e H He et te er ro og ge en ne eo ou us s W Wi ir re el le es ss s N Ne et tw wo or rk ks s S .M Ahsan Kazmi , Tai Manh Ho, Oanh Tran Thi Kim and Choong Seon Hong * Department of Computer Engineering, Kyung Hee University, 446-701, Republic of Korea Email: { ahsankazmi, hmtai, ttkoanh, cshong} @khu.ac.kr A Ab bs st tr ra ac ct t The proliferation of novel network access devices and demand for high quality of service by the end users are proving to be insufficient for existing wireless cellular networks. These bandwidth hungry access devices and novel applications are straining the network capacity. Heterogeneous access networks are a promising solution for solving this network capacity issues. This motivates a very dense small cell network. To this end, solving user association and resource allocation will be very challenging. Therefore, we formulate the resource allocation and user association problem as an optimization problem and present a scheme which solves the resource allocation and user association in a dense settings. Simulation results reveal the convergence of our proposal in terms of rate, interference protection and we provide comparison with the currently deployed received signal strength indicator association scheme. I I. . I In nt tr ro od du uc ct ti io on n The explosion of cellular devices and bandwidth hungry modern applications over the cellular network has raised the cellular network requirement. The existing cellular system in order to provide this high data rate requirement installs low power small cells along the currently deployed macro cell. This paradigm also known as Heterogeneous Network (HetNets) is the dominating and promising approach used by the network operators to meet the Quality of Service (QoS) for end users. However, this installation of SC poses some new challenges which needs to be handled in order to maximize the benefit of deploying the SCs in the network. In dense setting Hetnets user association and resource allocation will play a vital role and are considered as one of the biggest challenge [1]. First we discuss the user association problem in which users receiveing multiple signals for associating to different base-stations (BSs) from different tiers (i.e., macro/pico/femto) as shown in figure 1. It is well known that associating to a heavily loaded tier can cause degradation in the performance and wastage of resources (for lightly loaded tier) from network point of view. Therefore, associating to the optimal tier among the available can significantly improve the overall network utility. In current practice, user are associated based on the received signal strength indicator (RSSI) values from base stations (BS) only which may result in associating to an overloaded BSs. We therefore, We Femto-BS FUEs FUEs FUEs Cellular BS CUE CUE CUE CUE CUE CUE CUE CUE CUE Femto-BS Femto-BS Femto-BS Fig.1. System model propose a user association scheme in which a user is associated to a cell tier depending on the highest achievable data rate thus maximizing the user throughput and network throughput. The second problem is the interference problem which also can create significant degradation if not handled efficiently. In fact, enabling small cell communication poses significant challenges pertaining to the interference management because of reuse of resources as shown in figure 1[2]. In this paper we address the downlink user association and resource allocation problem for HetNets from an optimization prospective. Our aim is to maximize the utility for the complete network. User equipment (UE) will be associated to the respective macro base station (MBS) or any small cell base station (SC-BS) depending upon the highest achievable data rate instead of currently practiced RSSI values. After 2015년 동계학술발표회 논문집 1050