Channel Asymmetry in Cellular OFDMA-TDD Networks

  • Ellina Foutekova1Email author,

    Affiliated with

    • Patrick Agyapong2, 3 and

      Affiliated with

      • Harald Haas1

        Affiliated with

        EURASIP Journal on Wireless Communications and Networking20082008:121546

        DOI: 10.1155/2008/121546

        Received: 17 January 2008

        Accepted: 28 October 2008

        Published: 10 November 2008


        This paper studies time division duplex- (TDD-) specific interference issues in orthogonal frequency division multiple access- (OFDMA-) TDD cellular networks arising from various uplink (UL)/downlink (DL) traffic asymmetries, considering both line-of-sight (LOS) and non-LOS (NLOS) conditions among base stations (BSs). The study explores aspects both of channel allocation and user scheduling. In particular, a comparison is drawn between the fixed slot allocation (FSA) technique and a dynamic channel allocation (DCA) technique for different UL/DL loads. For the latter, random time slot opposing (RTSO) is assumed due to its simplicity and its low signaling overhead. Both channel allocation techniques do not obviate the need for user scheduling algorithms, therefore, a greedy and a fair scheduling approach are applied to both the RTSO and the FSA. The systems are evaluated based on spectral efficiency, subcarrier utilization, and user outage. The results show that RTSO networks with DL-favored traffic asymmetries outperform FSA networks for all considered metrics and are robust to LOS between BSs. In addition, it is demonstrated that the greedy scheduling algorithm only offers a marginal increase in spectral efficiency as compared to the fair scheduling algorithm, while the latter exhibits up to 20% lower outage.

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        Authors’ Affiliations

        Institute for Digital Communications, School of Engineering & Electronics, The University of Edinburgh
        School of Engineering and Science, Jacobs University Bremen
        Department of Engineering and Public Policy, College of Engineering, Carnegie Mellon University


        © Ellina Foutekova et al. 2008

        This article is published under license to BioMed Central Ltd. 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.