The Performance of Relay-Enhanced Cellular OFDMA-TDD Network for Mobile Broadband Wireless Services
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Research Article The Performance of Relay-Enhanced Cellular OFDMA-TDD Network for Mobile Broadband Wireless Services Kyungmi Park,1 Hyun S. Ryu,1 Chung G. Kang,1 Daeyoung Chang,2 Seungho Song,2 Jongguk Ahn,2 and Jongtae Ihm2 1 School 2 SK
of Electrical Engineering, Korea University, Seoul 136-701, South Korea Telecom Access Network R&D Center, Seoul 100-999, South Korea
Correspondence should be addressed to Chung G. Kang, [email protected] Received 7 January 2009; Revised 20 April 2009; Accepted 20 May 2009 Recommended by Dmitri Moltchanov A multihop relay (MR) and repeater are useful means for improving system throughput and coverage in a cellular mobile packet access system, as the carrier-to-interference ratio can be improved when deploying them in a heavily shadowed region. In this paper, we report on our investigation of bandwidth efficiency and the associated service outage performance for different relay scenarios, using system level simulation for a cellular Orthogonal Frequency Division Multiple Access-Time Division Duplexing (OFDMA-TDD) system. We have demonstrated that network throughput gain by typical optical repeaters, which have a simple amplify-and-forwarding capability in a full-duplexing mode, could be minimal in open space subject to cochannel interference from all repeaters in the neighboring cells. This is true, even though they are generally useful for warranting the outage performance with a multiple order of combining gain, especially in the destructive area, for example, basements or indoors with heavy wall attenuation, that naturally shields interference. Meanwhile, we show that multihop relays increase the average system capacity (almost doubling the system throughput) by fully reusing the frequency in every relay station, while improving the per-user data rate in the cell edges or improving the outage performance in the heavily shadowed areas. Copyright © 2009 Kyungmi Park 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.
1. Introduction MultiHop relay systems are considered as a useful means to enhance coverage, throughput, and capacity of mobile wireless broadband, for example, IEEE 802.16e mobile wireless MAN (also known as Mobile WiMAX) [1]. The gains in coverage and throughput can be leveraged to reduce the total deployment costs for a given system performance requirement and thereby improve the economic viability of those systems. The IEEE 802.16j MultiHop relay (MR) task group is one example of standardization activities toward relayenhance cellular system (RECS). This group enables exploitation of such advantages, specifying an OFDMA physical layer and medium access control layer enhancements to the IEEE 802.16 standard for licensed bands to facilitate the operation of relay stations [2]. Furthermore, the MultiHop relay is considered an essential system element in the emerging IMTAdvanced standard of ITU-R fo
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