Journal of Communications and Networks

The Korean Institute of Commucations and Information Sciences (한국통신학회)
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Traffic Asymmetry Balancing in OFDMA-TDD Cellular Networks

  • Foutekova, Ellina (Institute for Digital Communications at the School of Engineering & Electronics, The University of Edinburgh) ;
  • Sinanovic, Sinan (Institute for Digital Communications at the School of Engineering & Electronics, The University of Edinburgh) ;
  • Haas, Harald (Institute for Digital Communications at the School of Engineering & Electronics, The University of Edinburgh)
  • Published : 2008.06.30
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Abstract

This paper proposes a novel approach to interference avoidance via inter-cell relaying in cellular OFDMA-TDD (orthogonal frequency division multiple access - time division duplex) systems. The proposed scheme, termed asymmetry balancing, is targeted towards next-generation cellular wireless systems which are envisaged to have ad hoc and multi-hop capabilities. Asymmetry balancing resolves the detrimental base station (BS)-to-BS interference problem inherent to TDD networks by synchronizing the TDD switching points (SPs) across cells. In order to maintain the flexibility of TDD in serving the asymmetry demands of individual cells, inter-cell relaying is employed. Mobile stations (MSs) in a cell which has a shortage of uplink (UL) resources and spare downlink (DL) resources use free DL resources to off-load UL traffic to cooperating MSs in a neighboring cell using ad hoc communication. In an analogous fashion DL traffic can be balanced. The purpose of this paper is to introduce the asymmetry balancing concept by considering a seven-cell cluster and a single overloaded cell in the center. A mathematical model is developed to quantify the envisaged gains in using asymmetry balancing and is verified via Monte Carlo simulations. It is demonstrated that asymmetry balancing offers great flexibility in UL-DL resource allocation. In addition, results show that a spectral efficiency improvement of more than 100% can be obtained with respect to a case where the TDD SPs are adapted to the cell-specific demands.

Keywords

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