- Research Article
- Open Access
Low-Complexity Banded Equalizers for OFDM Systems in Doppler Spread Channels
EURASIP Journal on Advances in Signal Processingvolume 2006, Article number: 067404 (2006)
Recently, several approaches have been proposed for the equalization of orthogonal frequency-division multiplexing (OFDM) signals in challenging high-mobility scenarios. Among them, a minimum mean-squared error (MMSE) block linear equalizer (BLE), based on a band LDL factorization, is particularly attractive for its good tradeoff between performance and complexity. This paper extends this approach towards two directions. First, we boost the BER performance of the BLE by designing a receiver window specially tailored to the band LDL factorization. Second, we design an MMSE block decision-feedback equalizer (BDFE) that can be modified to support receiver windowing. All the proposed banded equalizers share a similar computational complexity, which is linear in the number of subcarriers. Simulation results show that the proposed receiver architectures are effective in reducing the BER performance degradation caused by the intercarrier interference (ICI) generated by time-varying channels. We also consider a basis expansion model (BEM) channel estimation approach, to establish its impact on the BER performance of the proposed banded equalizers.
Wang Z, Giannakis GB: Wireless multicarrier communications: where Fourier meets Shannon. IEEE Signal Processing Magazine 2000, 17(3):29–48. 10.1109/79.841722
Robertson P, Kaiser S: The effects of Doppler spreads on OFDM(A) mobile radio systems. Proceedings of the 49th IEEE Vehicular Technology Conference (VTC '99), September 1999, Amsterdam, The Netherlands 329–333.
Russell M, Stüber GL: Interchannel interference analysis of OFDM in a mobile environment. Proceedings of the 45th IEEE Vehicular Technology Conference (VTC '95), July 1995, Chicago, Ill, USA 820–824.
Barhumi I, Leus G, Moonen M: Time-domain and frequency-domain per-tone equalization for OFDM over doubly selective channels. Signal Processing 2004, 84(11):2055–2066. 10.1016/j.sigpro.2004.07.016
Cai X, Giannakis GB: Bounding performance and suppressing intercarrier interference in wireless mobile OFDM. IEEE Transactions on Communications 2003, 51(12):2047–2056. 10.1109/TCOMM.2003.820752
Choi Y-S, Voltz PJ, Cassara FA: On channel estimation and detection for multicarrier signals in fast and selective Rayleigh fading channels. IEEE Transactions on Communications 2001, 49(8):1375–1387. 10.1109/26.939860
Gorokhov A, Linnartz J-P: Robust OFDM receivers for dispersive time-varying channels: equalization and channel acquisition. IEEE Transactions on Communications 2004, 52(4):572–583. 10.1109/TCOMM.2004.826354
Jeon WG, Chang KH, Cho YS: An equalization technique for orthogonal frequency-division multiplexing systems in time-variant multipath channels. IEEE Transactions on Communications 1999, 47: 27–32. 10.1109/26.747810
Rugini L, Banelli P, Leus G: Simple equalization of time-varying channels for OFDM. IEEE Communications Letters 2005, 9(7):619–621. 10.1109/LCOMM.2005.1461683
Schniter P: Low-complexity equalization of OFDM in doubly selective channels. IEEE Transactions on Signal Processing 2004, 52: 1002–1011. 10.1109/TSP.2004.823503
Harris FJ: On the use of windows for harmonic analysis with the discrete Fourier transform. Proceedings of the IEEE 1978, 66(1):51–83.
Al-Dhahir N, Sayed AH: The finite-length multi-input multi-output MMSE-DFE. IEEE Transactions on Signal Processing 2000, 48(10):2921–2936. 10.1109/78.869048
Stamoulis A, Giannakis GB, Scaglione A: Block FIR decision-feedback equalizers for filterbank precoded transmissions with blind channel estimation capabilities. IEEE Transactions on Communications 2001, 49(1):69–83. 10.1109/26.898252
Kannu AP, Schniter P: MSE-optimal training for linear time-varying channels. Proceedings IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP '05), March 2005, Philadelphia, Pa, USA 3(1):789–792.
Ma X, Giannakis GB, Ohno S: Optimal training for block transmissions over doubly-selective wireless fading channels. IEEE Transactions on Signal Processing 2003, 51(5):1351–1366. 10.1109/TSP.2003.810304
Stamoulis A, Diggavi SN, Al-Dhahir N: Intercarrier interference in MIMO OFDM. IEEE Transactions on Signal Processing 2002, 50(10):2451–2464. 10.1109/TSP.2002.803347
Golub GH, Van Loan CF: Matrix Computations. 3rd edition. Johns Hopkins University Press, Baltimore, Md, USA; 1996.
Tong L, Sadler BM, Dong M: Pilot-assisted wireless transmissions. IEEE Signal Processing Magazine 2004, 21(6):12–25. 10.1109/MSP.2004.1359139
Negi R, Cioffi J: Pilot tone selection for channel estimation in a mobile OFDM system. IEEE Transactions on Consumer Electronics 1998, 44(3):1122–1128. 10.1109/30.713244
Giannakis GB, Tepedelenlioglu C: Basis expansion models and diversity techniques for blind identification and equalization of time-varying channels. Proceedings of the IEEE 1998, 86(10):1969–1986. 10.1109/5.720248
Leus G, Moonen M: Equalization techniques for fading channels. In Handbook on Signal Processing for Communications. Edited by: Ibnkahla M. CRC Press, Boca Raton, Fla, USA; 2004. chapter 16
Kay SM: Fundamentals of Statistical Signal Processing: Estimation Theory. Volume 1. Prentice Hall, Englewood Cliffs, NJ, USA; 1993.
Zemen T, Mecklenbraäuker CF: Time-variant channel equalization via discrete prolate spheroidal sequences. Proceedings of the IEEE Asilomar Conference on Signals, Systems and Computers, November 2003, Pacific Grove, Calif, USA 2: 1288–1292.
Borah DK, Hart BD: Frequency-selective fading channel estimation with a polynomial time-varying channel model. IEEE Transactions on Communications 1999, 47(6):862–873. 10.1109/26.771343
Leus G: On the estimation of rapidly time-varying channels. Proceedings of European Signal Processing Conference (EUSIPCO '04), September 2004, Vienna, Austria 2227–2230.
Kannu AP, Schniter P: Capacity analysis of MMSE pilot patterns for doubly-selective channels. Proceedings of 6th IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC '05), June 2005, New York, NY, USA