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Your search keyword '"Chen, Youjia"' showing total 3 results
Start Over Author "Chen, Youjia" Topic user association
3 results on '"Chen, Youjia"'

1. Distributed Resource Allocation And Spectrum Sharing In Future Heterogeneous Wireless Cellular Networks

Author

Chen, Youjia

Subjects
unlicensed spectrum, resource allocation, Small-cell caching, user association, optimization, heterogeneous networks
Abstract

This thesis focuses on the study of Heterogeneous Networks (HetNets), analyzing the system performance and the allocation of available resources, such as serving BSs, spectrum, power supply and storage. Specifically, four main research focuses are included. The first focus is load balancing problem in HetNets. First, a factor graph model is developed to represent the user association problem and decompose the network-wide objective into local utility functions. Then, a distributed belief propagation (BP) algorithm is proposed to find out the optimal user association. Furthermore, several properties of the factor graph relevant to the performance of the BP algorithm are analyzed using stochastic geometry. The second focus is inter-cell interference in HetNets. To mitigate the inter-cell interference and maximizing the system sum rate, a BP algorithm to jointly optimize the user association, sub-channel assignment and power allocation is proposed. Importantly, a novel factor graph model is developed that not only decomposes the network-wide objective but also transforms the constraints into local functions. The third focus is probabilistic small-cell caching in HetNets, where each SBS caches a subset of the popular content with a specific caching probability. The theoretical results of the successful download probability (SDP) are derived using stochastic geometry theory, i.e., the probability that users can successfully download required content from SBSs. Importantly, I optimize the caching probabilities in two network architectures by maximizing the SDP. The fourth focus is cooperative inter-working of LTE and wireless fidelity (Wi-Fi). A new framework is proposed that considers both systems, downlink and uplink transmissions, and interference in both time and spatial domains. Based on this framework, I theoretically study the performance of a large-scale Wi-Fi network, and the network performance of several inter-working strategies.

Published
2017

2. User Association With Unequal User Priorities in Heterogeneous Cellular Networks.

Author

Chen, Youjia, Li, Jun, Lin, Zihuai, Mao, Guoqiang, and Vucetic, Branka

Subjects
*WIRELESS communications, *DATA transmission systems, *LOAD balancing (Computer networks), *ALGORITHMS, *TOPOLOGY
Abstract

In heterogeneous networks (HetNets), the load between macrocell base stations (MBSs) and small-cell base stations (SBSs) is imbalanced due to their different transmission powers and locations. This load imbalance significantly impacts system performance and affects the experience of mobile users (MUs) with different priorities. In this paper, we aim to distributively optimize the user association in HetNets with various user priorities to solve the load balancing problem. Since the user association is a binary matching problem, which is NP-hard, we propose a distributed belief propagation (BP) algorithm to approach the optimal solution. We first develop a factor graph model, using the network topology, to represent this user association problem. With this factor graph, we propose a novel distributed BP algorithm by adopting the proportional fairness as the objective. Next, we theoretically prove the existence of the fixed point in our BP algorithm. To be more practical, we develop an approximation method to significantly reduce the computational and communication complexity of the BP algorithm. Furthermore, we analyze some properties of the factor graph relevant to the performance of the BP algorithm using the stochastic geometry. Simulation results show that 1) the proposed BP algorithm well approaches the optimal system performance and achieves a much better performance compared with other association schemes and that 2) the analytical results on the average degree distribution and sparsity of the factor graph match with those obtained from the Monte Carlo simulations. [ABSTRACT FROM PUBLISHER]

Published
2016
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3. Joint User Association and Resource Allocation in the Downlink of Heterogeneous Networks.

Author

Chen, Youjia, Li, Jun, Chen, Wen, Lin, Zihuai, and Vucetic, Branka

Subjects
*INTERFERENCE channels (Telecommunications), *RESOURCE allocation, *COMPUTER networks, *COMPUTATIONAL complexity, *COMPUTER simulation
Abstract

In this paper, we consider the intercell interference coordination (ICIC) problem in heterogeneous cellular networks with randomly deployed small-cell base stations (BSs). Current research on ICIC mainly focuses on optimizing the spectrum and power allocations at BSs, whereas the user–BS association is treated as a separate issue. Nevertheless, the user–BS association problem is an important issue in ICIC and should be jointly optimized with resource allocations to achieve global optimality. In this paper, with the objective of maximizing the system sum rate in a distributed manner, we propose a novel belief propagation (BP) algorithm to jointly optimize user association, subchannel assignment, and power allocation. We first develop a factor graph model to decompose the network-wide objective and constraints into multiple local utilities. Then, we transform the maximization of local utilities into the estimations of marginal distributions and propose a distributed BP algorithm to solve the estimations. Simulations show that our distributed BP algorithm dramatically improves the performance compared with the benchmark scheme. [ABSTRACT FROM AUTHOR]

Published
2016
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