Skip to main content

Robust Adaptive OFDM with Diversity for Time-Varying Channels

Abstract

The performance of an orthogonal frequency-division multiplexing (OFDM) system can be significantly increased by using adaptive modulation and transmit diversity. An accurate estimate of the channel, however, is required at the transmitter to realize this benefit. Due to the time-varying nature of the channel, this estimate may be outdated by the time it is used for detection. This results in a mismatch between the actual channel and its estimate as seen by the transmitter. In this paper, we investigate adaptive OFDM with transmit and receive diversities, and evaluate the detrimental effects of this channel mismatch. We also describe a robust scheme based on using past estimates of the channel. We show that the effects of the mismatch can be significantly reduced with a combination of diversity and multiple channel estimates. In addition, to reduce the amount of feedback, the subband approach is introduced where a common channel estimate for a number of subcarriers is fedback to the transmitter, and the effect of this method on the achievable rate is analyzed.

[1234567891011121314151617181920212223242526272829303132333435]

References

  1. Goldsmith AJ, Chua S-G: Variable-rate variable-power MQAM for fading channels. IEEE Transactions on Communications 1997,45(10):1218-1230. 10.1109/26.634685

    Article  Google Scholar 

  2. Keller T, Hanzo L: Adaptive multicarrier modulation: a convenient framework for time-frequency processing in wireless communication. Proceedings of the IEEE 2000,88(5):611-640. 10.1109/5.849157

    Article  Google Scholar 

  3. Alouini M-S, Goldsmith AJ: Adaptive modulation over Nakagami fading channels. Wireless Personal Communications 2000,13(1):119-143. 10.1023/A:1008979107539

    Article  Google Scholar 

  4. Leke A, Cioffi JM: A maximum rate loading algorithm for discrete multitone modulation systems. Proceedings of the IEEE Global Telecommunications Conference (GLOBECOM '97), November 1997, Phoenix, Ariz, USA 3: 1514-1518.

    Article  Google Scholar 

  5. Chow PS, Cioffi JM, Bingham JAC: A practical discrete multitone transceiver loading algorithm for data transmission over spectrally shaped channels. IEEE Transactions on Communications 1995,43(2–4):773-775.

    Article  Google Scholar 

  6. Fischer RFH, Huber JB: A new loading algorithm for discrete multitone transmission. Proceedings of IEEE Global Telecommunications Conference (GLOBECOM '96), November 1996, London, UK 1: 724-728.

    Google Scholar 

  7. Leke A, Cioffi JM: Impact of imperfect channel knowledge on the performance of multicarrier systems. Proceedings of IEEE Global Telecommunications Conference (GLOBECOM '98), November 1998, Sydney, NSW, Australia 2: 951-955.

    Google Scholar 

  8. Su Q, Schwartz S: Effects of imperfect channel information on adaptive loading gain of OFDM. Proceedings of the 54th IEEE Vehicular Technology Conference (VTC '01), October 2001, Atlantic City, NJ, USA 1: 475-478.

    Google Scholar 

  9. Wyglinski AM, Labeau F, Kabal P: Effects of imperfect subcarrier SNR information on adaptive bit loading algorithms for multicarrier systems. Proceedings of IEEE Global Telecommunications Conference (GLOBECOM '04), November-December 2004, Dallas, Tex, USA 6: 3835-3839.

    Article  Google Scholar 

  10. Onggosanusi EN, Gatherer A, Dabak AG, Hosur S: Performance analysis of closed-loop transmit diversity in the presence of feedback delay. IEEE Transactions on Communications 2001,49(9):1618-1630. 10.1109/26.950348

    Article  MATH  Google Scholar 

  11. Hanzo L, Webb W, Keller T: Single and Multi-Carrier Quadrature Amplitude Modulation. IEEE Press, New York, NY, USA; 2000.

    Google Scholar 

  12. Ye S, Blum RS, Cimini LJ Jr.: Adaptive modulation for variable-rate OFDM systems with imperfect channel information. IEEE Transactions on Wireless Communications 2006,5(11):3255-3265.

    Article  Google Scholar 

  13. Narula A, Lopez MJ, Trott MD, Wornell GW: Efficient use of side information in multiple-antenna data transmission over fading channels. IEEE Journal on Selected Areas in Communications 1998,16(8):1423-1436. 10.1109/49.730451

    Article  Google Scholar 

  14. Visotsky E, Madhow U: Space-time transmit precoding with imperfect feedback. IEEE Transactions on Information Theory 2001,47(6):2632-2639. 10.1109/18.945281

    Article  MathSciNet  MATH  Google Scholar 

  15. Zhou S, Giannakis GB: Optimal transmitter eigen-beamforming and space-time block coding based on channel mean feedback. IEEE Transactions on Signal Processing 2002,50(10):2599-2613. 10.1109/TSP.2002.803355

    Article  Google Scholar 

  16. Zhou S, Giannakis GB: How accurate channel prediction needs to be for transmit-beamforming with adaptive modulation over Rayleigh MIMO channels? IEEE Transactions on Wireless Communications 2004,3(4):1285-1294. 10.1109/TWC.2004.830842

    Article  Google Scholar 

  17. Yao Y, Giannakis GB: Rate-maximizing power allocation in OFDM based on partial channel knowledge. IEEE Transactions on Wireless Communications 2005,4(3):1073-1083.

    Article  Google Scholar 

  18. Xia P, Zhou S, Giannakis GB: Adaptive MIMO-OFDM based on partial channel state information. IEEE Transactions on Signal Processing 2004,52(1):202-213. 10.1109/TSP.2003.819986

    Article  MathSciNet  Google Scholar 

  19. Ben-Tal A, Nemirovski A: Robust convex optimization. Mathematics of Operations Research 1998,23(4):769-805. 10.1287/moor.23.4.769

    Article  MATH  MathSciNet  Google Scholar 

  20. Boyd S, Vandenberghe L: Convex Optimization. Cambridge University Press, Cambridge, UK; 2004.

    Book  MATH  Google Scholar 

  21. Goeckel DL: Adaptive coding for time-varying channels using outdated fading estimates. IEEE Transactions on Communications 1999,47(6):844-855. 10.1109/26.771341

    Article  Google Scholar 

  22. Pascual-Iserte A, Palomar DP, Pérez-Neira AI, Lagunas MÁ: A robust maximin approach for MIMO communications with imperfect channel state information based on convex optimization. IEEE Transactions on Signal Processing 2006,54(1):346-360.

    Article  Google Scholar 

  23. Kassam SA, Poor HV: Robust techniques for signal processing: a survey. Proceedings of the IEEE 1985,73(3):433-481.

    Article  MATH  Google Scholar 

  24. Verdu S, Poor HV: On minimax robustness: a general approach and applications. IEEE Transactions on Information Theory 1984,30(2, part 2):328-340. 10.1109/TIT.1984.1056876

    Article  MATH  MathSciNet  Google Scholar 

  25. Guo Y, Levy BC: Worst-case MSE precoder design for imperfectly known MIMO communications channels. IEEE Transactions on Signal Processing 2005,53(8, part 1):2918-2930.

    Article  MathSciNet  Google Scholar 

  26. Vorobyov SA, Gershman AB, Luo Z-Q: Robust adaptive beamforming using worst-case performance optimization: a solution to the signal mismatch problem. IEEE Transactions on Signal Processing 2003,51(2):313-324. 10.1109/TSP.2002.806865

    Article  Google Scholar 

  27. Shahbazpanahi S, Gershman AB, Lou Z-Q, Wong KM: Robust adaptive beamforming for general-rank signal models. IEEE Transactions on Signal Processing 2003,51(9):2257-2269. 10.1109/TSP.2003.815395

    Article  Google Scholar 

  28. Lorenz RG, Boyd SP: Robust minimum variance beamforming. IEEE Transactions on Signal Processing 2005,53(5):1684-1696.

    Article  MathSciNet  Google Scholar 

  29. Chung ST, Goldsmith AJ: Degrees of freedom in adaptive modulation: a unified view. IEEE Transactions on Communications 2001,49(9):1561-1571. 10.1109/26.950343

    Article  MATH  Google Scholar 

  30. Jakes WC: Microwave Mobile Communications. John Wiley & Sons, New York, NY, USA; 1974.

    Google Scholar 

  31. Matlab optimziation toolbox http://www.mathworks.com/products/optimization/.

  32. Johnson RA, Wichern DW: Applied Multivariate Analysis. Prentice-Hall, Englewood Cliffs, NJ, USA; 1982.

    MATH  Google Scholar 

  33. Horn RA, Johnson CR: Matrix Analysis. Cambridge University Press, Cambridge, UK; 1999.

    Google Scholar 

  34. Taricco G, Biglieri E: Exact pairwise error probability of space-time codes. IEEE Transactions on Information Theory 2002,48(2):510-513. 10.1109/18.979326

    Article  MATH  MathSciNet  Google Scholar 

  35. Goldsmith A: Wireless Communications. Cambridge University Press, Cambridge, UK; 2005.

    Book  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Erdem Bala.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and permissions

About this article

Cite this article

Bala, E., Cimini, L.J. Robust Adaptive OFDM with Diversity for Time-Varying Channels. J Wireless Com Network 2007, 078156 (2007). https://doi.org/10.1155/2007/78156

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1155/2007/78156

Keywords