MAI cancellation in long-sequence DS-CDMA systems

The main objective of this research is to design receiving structures capable of rejecting multiple-access interference (MAI), which is the major channel imperfection in DS-CDMA systems with very long signature sequences. The use of long sequences, albeit more practical, presents some difficulties over the periodic sequence assumption usually made in the design of MAI rejection receivers. To circumvent these difficulties, a decentralized linear coherent receiver, which consists of the conventional sequence-matched filter followed by a tapped delay line, is proposed to achieve the desired MAI rejection capability. The proposed receiver is capable of utilizing the diversities provided by oversampling and electronically steerable antenna arrays to achieve MAI rejection by suitably choosing the weights in the tapped delay line. In addition to MAI, the receiver can also combat imperfections caused by fading channel environments and narrowband interference.

The second objective concerns the implementability of the proposed receiver. To this end, both adaptive and non-adaptive algorithms are developed to obtain the weights in the tapped delay line of the receiver.

Publications

  1. Y. N. Rao, J. C. Principe, and T. F. Wong, "Fast RLS-like algorithm for generalized eigendecomposition and its applications," Journal of VLSI Signal Processing, vol. 37, no. 2, pp. 333-344, June 2004.
  2. T. F. Wong and T. M. Lok, "Doubly spread DS-CDMA for efficient blind interference cancellation," IEE Proceedings - Communications, vol. 147, no. 5, pp. 299-304, Oct. 2000.
  3. T. F. Wong, T. M. Lok, and J. S. Lehnert, "Asynchronous Multiple Access Interference Suppression and Chip Waveform Selection with Aperiodic Random Sequences," IEEE Transactions on Communications, vol. 47, no. 1, pp. 103-114, Jan. 1999.
  4. T. F. Wong, T. M. Lok, J. S. Lehnert, and M. D. Zoltowski, "A Linear Receiver for Direct-Sequence Spread-Spectrum Multiple-Access Systems with Antenna Arrays and Blind Adaptation," IEEE Transactions on Information Theory, vol 44, no. 2, pp. 659-676, Mar. 1998.
  5. B. Hombs, J. S. Lehnert, and T. F. Wong, "CDMA for Air Traffic Control," in Proceedings of the 21st Digital Avionics Systems Conference, vol. 1, pp. 3C3-1 - 3C3-8, Irvine, CA, Oct. 2002.
  6. T. F. Wong and T. M. Lok, "Doubly spread DS-CDMA for efficient interference cancellation," in Proceedings of the IEEE Military Communications Conference (MILCOM '99), vol. 1, pp. 177-181 Atlantic City, NJ, Nov. 1999.
  7. R. T. Derryberry, T. F. Wong, and J. S. Lehnert, "An Iterative Blind Adaptive Receiver for DS-SSMA Systems," in Proceedings of the IEEE Military Communications Conference (MILCOM '98), pp. 160-164, Boston, MA, Oct. 1998.
  8. T. F. Wong, T. M. Lok, and J. S. Lehnert, "Chip Waveform Selection in Asynchronous DS-CDMA Systems with Interference Suppression," in Proceeding of the IEEE International Conference on Universal Personal Communications (ICUPC '97), vol. 1, pp. 208-212, San Diego, CA, Oct. 1997.
  9. T. F. Wong, T. M. Lok, and J. S. Lehnert, "Performance evaluation of a blind adaptive linear receiver for cellular DS/CDMA systems," in Proceedings of the 34th Annual Allerton Conference on Communications, Control, and Computing, Allerton House, Monticello, IL, Oct. 1996.
  10. T. F. Wong, T. M. Lok, J. S. Lehnert, and M. D. Zoltowski, "Spread-Spectrum Signaling Techniques with Antenna Arrays and Blind Adaptation," in Proceedings of the IEEE Military Communications Conference (MILCOM '96), vol. 1, pp. 194-198, McLean, VA, Oct. 1996.

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Last modified: 11/9/05