Skip to main content

Multipass Channel Estimation and Joint Multiuser Detection and Equalization for MIMO Long-Code DS/CDMA Systems


The problem of joint channel estimation, equalization, and multiuser detection for a multiantenna DS/CDMA system operating over a frequency-selective fading channel and adopting long aperiodic spreading codes is considered in this paper. First of all, we present several channel estimation and multiuser data detection schemes suited for multiantenna long-code DS/CDMA systems. Then, a multipass strategy, wherein the data detection and the channel estimation procedures exchange information in a recursive fashion, is introduced and analyzed for the proposed scenario. Remarkably, this strategy provides, at the price of some attendant computational complexity increase, excellent performance even when very short training sequences are transmitted, and thus couples together the conflicting advantages of both trained and blind systems, that is, good performance and no wasted bandwidth, respectively. Space-time coded systems are also considered, and it is shown that the multipass strategy provides excellent results for such systems also. Likewise, it is also shown that excellent performance is achieved also when each user adopts the same spreading code for all of its transmit antennas. The validity of the proposed procedure is corroborated by both simulation results and analytical findings. In particular, it is shown that adopting the multipass strategy results in a remarkable reduction of the channel estimation mean-square error and of the optimal length of the training sequence.



  1. 1.

    Dahlman E, Beming P, Knutsson J, Ovesjo F, Persson M, Roobol C: WCDMA-the radio interface for future mobile multimedia communications. IEEE Transactions on Vehicular Technology 1998,47(4):1105–1118. 10.1109/25.728481

    Article  Google Scholar 

  2. 2.

    Madhow U: Blind adaptive interference suppression for direct-sequence CDMA. Proceedings of the IEEE 1998,86(10):2049–2069. 10.1109/5.720252

    Article  Google Scholar 

  3. 3.

    Wang X, Poor HV: Blind multiuser detection: a subspace approach. IEEE Transactions on Information Theory 1998,44(2):677–690. 10.1109/18.661512

    MATH  MathSciNet  Article  Google Scholar 

  4. 4.

    Weiss AJ, Friedlander B: Channel estimation for DS-CDMA downlink with aperiodic spreading codes. IEEE Transactions on Communications 1999,47(10):1561–1569. 10.1109/26.795824

    Article  Google Scholar 

  5. 5.

    Xu ZD, Tsatsanis MK: Blind channel estimation for long code multiuser CDMA systems. IEEE Transactions on Signal Processing 2000,48(4):988–1001. 10.1109/78.827533

    Article  Google Scholar 

  6. 6.

    Escudero CJ, Mitra U, Slock DTM: A Toeplitz displacement method for blind multipath estimation for long code DS/CDMA signals. IEEE Transactions on Signal Processing 2001,49(3):654–665. 10.1109/78.905897

    Article  Google Scholar 

  7. 7.

    Tripathi V, Mantravadi A, Veeravalli VV: Channel acquisition for wideband CDMA signals. IEEE Journal on Selected Areas in Communications 2000,18(8):1483–1494. Special issue on Wideband CDMA 10.1109/49.864012

    Article  Google Scholar 

  8. 8.

    Buzzi S, Poor HV: Channel estimation and multiuser detection in long-code DS/CDMA systems. IEEE Journal on Selected Areas in Communications 2001,19(8):1476–1487. 10.1109/49.942510

    Article  Google Scholar 

  9. 9.

    Buzzi S, Poor HV: A multipass approach to joint data and channel estimation in long-code CDMA systems. IEEE Transactions on Wireless Communications 2004,3(2):612–626. 10.1109/TWC.2003.821125

    Article  Google Scholar 

  10. 10.

    Telatar IE: Capacity of multi-antenna Gaussian channels. European Transactions on Telecommunications 1999,10(6):585–595. 10.1002/ett.4460100604

    Article  Google Scholar 

  11. 11.

    Foschini GJ, Gans MJ: On limits of wireless communications in a fading environment when using multiple antennas. Wireless Personal Communications 1998,6(3):311–335. 10.1023/A:1008889222784

    Article  Google Scholar 

  12. 12.

    Marzetta TL, Hochwald BM: Capacity of a mobile multiple-antenna communication link in Rayleigh flat fading. IEEE Transactions on Information Theory 1999,45(1):139–157. 10.1109/18.746779

    MATH  MathSciNet  Article  Google Scholar 

  13. 13.

    Foschini GJ: Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas. Bell Labs Technical Journal 1996,1(2):41–59.

    Article  Google Scholar 

  14. 14.

    Foschini GJ, Golden GD, Valenzuela RA, Wolniansky PW: Simplified processing for high spectral efficiency wireless communication employing multi-element arrays. IEEE Journal on Selected Areas in Communications 1999,17(11):1841–1852. 10.1109/49.806815

    Article  Google Scholar 

  15. 15.

    Hochwald BM, Marzetta TL, Papadias CB: A transmitter diversity scheme for wideband CDMA systems based on space-time spreading. IEEE Journal on Selected Areas in Communications 2001,19(1):48–60. 10.1109/49.909608

    Article  Google Scholar 

  16. 16.

    Reynolds D, Wang X, Poor HV: Blind adaptive space-time multiuser detection with multiple transmitter and receiver antennas. IEEE Transactions on Signal Processing 2002,50(6):1261–1276. 10.1109/TSP.2002.1003052

    Article  Google Scholar 

  17. 17.

    Alamouti SM: A simple transmit diversity technique for wireless communications. IEEE Journal on Selected Areas in Communications 1998,16(8):1451–1458. 10.1109/49.730453

    Article  Google Scholar 

  18. 18.

    Golub GH, Van Loan CF: Matrix Computations. 3rd edition. The Johns Hopkins University Press, Baltimore, Md, USA; 1996.

    Google Scholar 

  19. 19.

    Mailaender L: Capacity bound for linear MIMO systems with channel estimation. Proceedings of IEEE 6th Workshop on Signal Processing Advances in Wireless Communications (SPAWC '05), June 2005, New York, NY, USA 1048–1052.

    Google Scholar 

  20. 20.

    Yoo T, Goldsmith A: Capacity of fading MIMO channels with channel estimation error. Proceedings of IEEE International Conference on Communications (ICC '04), June 2004, Paris, France 2: 808–813.

    Google Scholar 

Download references

Author information



Corresponding author

Correspondence to Stefano Buzzi.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Buzzi, S. Multipass Channel Estimation and Joint Multiuser Detection and Equalization for MIMO Long-Code DS/CDMA Systems. J Wireless Com Network 2006, 024132 (2006).

Download citation


  • Channel Estimation
  • Training Sequence
  • Data Detection
  • Multiuser Detection
  • Spreading Code