Joint Optimization of User Association, Subchannel Allocation, and Power Allocation in Multi-Cell Multi-Association OFDMA Heterogeneous Networks

Abstract

Heterogeneous network is a novel network architecture proposed in Long-Term-Evolution (LTE), which highly increases the capacity and coverage compared with the conventional networks. However, in order to provide the best services, appropriate resource management must be applied. In this paper, we consider the joint optimization problem of user association, subchannel allocation, and power allocation for downlink transmission in Multi-cell Multi-association Orthogonal Frequency Division Multiple Access (OFDMA) heterogeneous networks. To solve the optimization problem, we first divide it into two subproblems: 1) user association and subchannel allocation for fixed power allocation; 2) power allocation for fixed user association and subchannel allocation. Subsequently, we obtain a locally optimal solution for the joint optimization problem by solving these two subproblems alternately. For the first subproblem, we derive the globally optimal solution based on graph theory. For the second subproblem, we obtain a Karush-Kuhn-Tucker (KKT) optimal solution by a low complexity algorithm based on the difference of two convex functions approximation (DCA) method. In addition, the multi-antenna receiver case and the proportional fairness case are also discussed. Simulation results demonstrate that the proposed algorithms can significantly enhance the overall network throughput.

Network utility optimization-based joint user association and content placement in heterogeneous networks

“…In the past few years, user association or cell selection have been studied for HetNets [2][3][4][5][6][7]. In [2], the authors address the user association problem in the downlink transmissions of a multi-tier HetNet and propose a unified distributed algorithm, which aims at maximizing the sum utility of long-term rate and minimizing global outage probability at the same time.…”

“…In [6], the authors consider the joint optimization problem of user association, subchannel allocation, and power allocation for downlink transmission in multi-cell multi-association orthogonal frequency division multiple access (OFDMA) HetNets with the objective of maximizing the weighted sumrate and propose an alternating optimization method to solve the joint optimization problem. The authors in [7] deal with the problem of user association in HetNets and propose a novel collaborative filtering (CF)-based wireless network recommendation system, which involves social interactions among UEs.…”

“…Different user association or cell selection strategies may result in different network transmission performance and quality of service (QoS) to users due to the heterogeneity of RANs. While various user association schemes have been proposed for HetNets [2][3][4][5][6][7] and effectively enhanced the transmission performance of the RANs, the backhaul links may still cause challenges and difficulties in offering QoS guaranteed services to UEs. In particular, the demanding requirements of user services, such as multimedia streaming, web browsing applications, and socially interconnected networks, may cause network congestion and long transmission delay in backhaul links [8].…”

“…• The problem of user association or content placement in HetNets has been studied separately in previous works [2][3][4][5][6][7] and [11][12][13][14][15][16]. In this paper, we jointly consider the user association and content placement problem in cache-enabled HetNets and design jointly optimal strategies so that the overall performance of the networks can be maximized.…”

Joint User Association and Resource Allocation in the Uplink of Heterogeneous Networks

“…Furthermore, a plethora of research studies considered user association (UA), sub-channel and power allocation problems in downlink heterogeneous networks (HetNets) [3]- [6]. In [3], joint resource allocation and UA was solved for downlink HetNets to maximize the weighted sumrate. The authors decomposed the original problem into a series of sub-problems.…”