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Journal of Applied Mathematics
Volume 2013 (2013), Article ID 517846, 19 pages
Research Article

Minimum-Cost QoS-Constrained Deployment and Routing Policies for Wireless Relay Networks

1Department of Information Management, National Taiwan University, No. 1 Section 4, Roosevelt Road, Taipei 106, Taiwan
2Department of Information Management, National Taipei University of Nursing & Health Sciences, No. 365, Ming Te Road, Taipei 112, Taiwan

Received 13 April 2013; Accepted 7 July 2013

Academic Editor: Chih-Hao Lin

Copyright © 2013 Frank Yeong-Sung Lin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


With the continued evolution of wireless communication technology, relaying is one of the features proposed for the 4G LTE Advanced (LTE-A) system. The aim of relaying is to enhance both coverage and capacity. The idea of relays is not new, but relaying is being considered to ensure that the optimum performance is achieved to enable the expectations or good quality of service (QoS) of the users to be met while still keeping capital expenditure (CAPEX) within the budgeted bounds of operators. In this paper, we try to stand for an operator to propose a solution that determines where and how many relays should be deployed in the planning stages to minimize the development cost. In the planning stages, we not only derive a multicast tree routing algorithm to both determine and fulfill the QoS requirements to enhance throughput, but we also utilize the Lagrangian relaxation (LR) method in conjunction with optimization-based heuristics and conduct computational experiments to evaluate the performance. Our contribution is utilizing the LR method to propose an optimal solution to minimize the CAPEX of operators to build up a relay network with more efficiency and effectiveness and the QoS can be guaranteed by service level agreement.