WiMAX relay networks: opportunistic scheduling to exploit multiuser diversity and frequency selectivity

ABSTRACT

We study the problem of scheduling in OFDMA-based relay networks with emphasis on IEEE 802.16j based WiMAX relay networks. In such networks, in addition to a base station, multiple relay stations are used for enhancing the throughput, and/or improving the range of the base station. We solve the problem of MAC scheduling in such networks so as to serve the mobiles in a fair manner while exploiting the multiuser diversity, as well as the frequency selectivity of the wireless channel. The scheduling resources consist of tiles in a two-dimensional scheduling frame with time slots along one axis, and frequency bands or sub-channels along the other axis. The resource allocation problem has to be solved once every scheduling frame which is about 5 - 10 ms long. While the original scheduling problem is computationally complex, we provide an easy-to-compute upper bound on the optimum. We also propose three fast heuristic algorithms that perform close to the optimum (within 99.5%), and outperform other algorithms such as OFDM²A proposed in the past. Through extensive simulation results, we demonstrate the benefits of relaying in throughput enhancement (an improvement in the median throughput of about 25%), and feasibility of range extension (for e.g., 7 relays can be used to extend the cell-radius by 60% but mean throughput reduces by 36%). Our algorithms are easy to implement, and have an average running time of less than 0.05 ms making them appropriate for WiMAX relay networks.

References

1. GLPK (GNU Linear Programming Kit), version 4.22.
2. M. Andrews. A survey of scheduling theory in wireless data networks. In Proceedings of the 2005 IMA summer workshop on wireless communications, 2005.
3. M. Andrews and L. Zhang. Scheduling algorithms for multi-carrier wireless data systems. In ACM Mobicom 2007, September 2007.
4. M. Charafeddine, O. Oymant, and S. Sandhu. System-level performance of cellular multihop relaying with multiuser scheduling. In CISS, March 2007.
5. Y. W. Cheong, R. S. Cheng, K. B. Latief, and R. D. Murch. Multiuser ofdm with adaptive subcarrier, bit and power allocation. IEEE Journal on Selected Areas in Communications, October 1999.
6. S. Deb, V. Mhatre, and V. Ramaiyan. WiMAX relay networks: Opportunistic scheduling to exploit multiuser diversity and frequency selectivity. Bell Labs Technical Report, Feb 2008.
7. M. Ergen, S. Coleri, and P. Varaiya. QoS aware adaptive resource allocation techniques for fair scheduling in ofdma based broadband wireless access systems. IEEE Tran. on Broadcasting, Dec 2003.
8. IEEE 802.16 task group. Channel Models for Fixed Wireless Applications, ieee 802.16.3c-01/29r4 edition, July 2001.
9. IEEE 802.16e task group. Air Interface for Fixed and Mobile Broadband Wireless Access Systems. Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands, 802.16e-2005 edition, February 2006.
10. IEEE 802.16j task group. Air Interface for Fixed and Mobile Broadband Wireless Access Systems: Multihop Relay Specification, 802.16j-06/026r4 edition, June 2007.
11. O. Jo and D. Cho. Traffic adaptive uplink scheduling scheme for relay station in ieee 802.16 based multihop system. In IEEE VTC, 2004.
12. R. Cohen L. Katzir. Computational analysis and efficient algorithms for micro and macro ofdma scheduling. In IEEE Infocom 2008.
13. F. P. Kelly, A.K. Maulloo, and D.K.H. Tan. Rate control in communication networks: shadow prices, proportional fairness and stability. Journal of the Operational Research Society, (49):237--252.
14. D. Kivanc, G. Li, and H. Liu. Computationally efficient bandwidth allocation and power control for ofdma. IEEE Transactions on Wireless Communications, 2(6):1150--1158, November 2003.
15. H. J. Kushner and P. A. Whiting. Convergence of proportional-fair sharing algorithms under general conditions. IEEE Transactions on Wireless Communication, 3(4):1250--1259, July 2004.
16. G. Narlikar, G. Wilfong, and L. Zhang. Designing multihop wireless backhaul networks with delay guarantees. In IEEE Infocom 2006.
17. K. Navaie and Halim Yanikomeroglu. Multi-route and multi-user diversity in infrastructure-based multi-hop networks. Cooperation in Wireless Networks: Principles and Applications, Editors: Frank H.P. Fitzek and Marcos D. Katz, 2006.
18. O. Oyman. OFDMA2A: A centralized resource allocation policy for cellular multi-hop networks. In IEEE Asilomar Conference on Signals, Systems and Computers, Nov 2006.
19. J. Padhye R. Draves and B. Zill. Routing in multi-radio, multi-hop wireless mesh network. In ACM Mobicom, September 2004.
20. T. S. Rappaport. Wireless Communications: Principles and Practice. Prentice Hall, 2001.
21. W. Rhee and J. M. Cioffi. Increase in capacity of multiuser ofdm system using dynamic subchannel allocation. In IEEE VTC, 2000.
22. Wimax forum. Mobile WiMAX Part I: A Technical Overview and Performance Evaluation, August 2006.
23. Q. Wu and E. Esteves. The CDMA2000 high rate packet data system. Chapter 4 of Advances in 3G Enhanced Technologies for Wireless Communications. Editors: Jiangzhou Wang and Tung-Sang Ng.
24. Y. Yu, S. Murphy, and L. Murphy. A clustering approach to planning base station and relay station locations in ieee 802.16j multi-hop relay networks. In IEEE ICC, 2008.

Index Terms

• Hardware

  • Communication hardware, interfaces and storage

• Networks

  • Network types

    • Mobile networks

    • Wireless access networks