Robust power allocation in two-tier heterogeneous networks
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RESEARCH
Open Access
Robust power allocation in two-tier heterogeneous networks Peng Liu, Jiandong Li* , Hongyan Li and Kan Wang
Abstract This paper focuses on a robust distributed power allocation scheme for downlink two-tier heterogeneous networks (HetNets). The objective is to maximize the network aggregate utility of femtocell users (FUEs) which factors the fairness between users under the constraint of not causing serious interference to existing macrocell users (MUEs). Being impractical for different nodes to cooperate in HetNets to obtain precise estimated values of the channel gains between them, it is a challenge to guarantee the performance of the power allocation algorithm by using existing methods. This work makes a step forward in the direction of conquering this challenge by taking into account channel uncertainty, and the robust counterpart of nominal problem, without channel uncertainty, is framed by using worst-case robust optimization theory. To make the robust counterpart computationally tractable, we exploit its convexity and derive that the channel uncertainties between a FUE and nearby femtocell base stations (FBSs) fall into water-filling form being related to the received power from interference sources. Based on the inherent relationship between channel uncertainty and received power, we design a distributed algorithm which merely needs to solve a deterministic problem. The algorithm is devised based on alternating direction method of multipliers (ADMM) with a fast convergence speed. The simulation results demonstrate the robustness of our proposed approach, and the corresponding cost of robustness is investigated. 1 Introduction Femtocell base stations (FBSs) are low-power nodes to provide high throughput and customized services to users, and together with macrocells, they form heterogeneous networks (HetNets). Deploying femtocells is an effective and efficient way to increase wireless network capacity, and it provides great benefits to network operators by producing new services. Along with their small size, low cost, and plug-and-play features [1,2], femtocells are considered as a big thing [3] in both existing and future mobile communications. On the other hand, with their marked development, femtocells tend to be largescale and self-organized [4], which brings a big challenge for interference management. More specially, to satisfy femtocell occupants’ self-interests, most of them prefer to configure their networks as Closed Subscriber Group (CSG) mode, i.e., users cannot access a specific femtocell without authorization and hence will cause interference *Correspondence: [email protected] The State Key Lab of ISN & Information Science Institute, Xidian University, Xi’an, Shaanxi 710071, China
to nearby macrocell users (MUEs). Moreover, nearby femtocells would interfere with each other as they become denser, thereby deteriorating network performance. Some analyses of typical interference scenarios have been made by [5,6]. In general, there are two types of interference issues,
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