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Interference Cancellation
Interference Avoidance
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Interference Cancellation - Multi-user
Detection
Multi-User Detection
A CDMA system is interference limited, that is,
performance on the uplink (mobile to base station) degrades with the
increase in the number of users. In the case of matched filter
receivers, signals from other users are treated as background noise
and are decoded independently. Therefore, the increase in the number of
users results in the increase of the error floor. However, since
signals from other users are also required to be decoded at the base
station, estimates of signals from other users can be used to estimate
the interference and cancel it from the desired signal. This leads to
the concept of multi-user detection, where signals from different
users are not decoded independently of one another, but jointly, in
order to utilize information about signals from interfering users.
Multi-user detectors provide more immunity to the near-far problem (or
power control errors) and thus provide uplink capacity improvements.
It has been shown [Verdu] that for a large number
of users, the optimal multi-user detector is extremely complex,
especially in the case of asynchronous users. Thus, sub-optimal
multi-user detectors have been explored. Multi-user detectors, in
general can be classified into the following categories:
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Journal Publications
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R.M. Buehrer, "Equal BER Performance in Linear Successive Interference
Cancellation for CDMA Systems," IEEE Transactions on Communications,
vol. 49, no. 7, July 2001.
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R.M. Buehrer, S.P. Nicoloso, and S. Gollamudi, "Linear Versus Non-linear
Interference Cancellation," IEEE/IEICE Journal on Communications
Networks, vol. 1, no. 2, pp. 118-133, June 1999.
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R.M. Buehrer, N.S. Correal, and B.D. Woerner, A Simulation Comparison of Multiuser Receivers for Cellular CDMA,” IEEE Transactions on Vehicular
Technology, vol. 49, no. 4, July 2000.
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R.M. Buehrer and S.P. Nicoloso, "Comments on Partial Parallel Interference
Cancellation," IEEE Transactions on Communications, vol. 47, no. 5,
pp. 658-661, May 1999.
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N.
Correal, R.M. Buehrer and B.D. Woerner, A DSP Based DS-CDMA Multiuser
Receiver Based on Partial Parallel Interference Cancellation,” IEEE
Journal on Selected Areas in Communications, vol. 17, no. 4, pp.
613-630, April 1999.
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R.M. Buehrer and B.D. Woerner, "Analysis of Adaptive Multistage
Interference Cancellation for CDMA Using an Improved Gaussian
Approximation, " IEEE Transactions on Communications, vol. 44, no.
10, pp. 1308-1321, October, 1996.
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R.M.
Buehrer and B.D. Woerner, "Analysis of CDMA Multistage Interference
Cancellation with Phase and Timing Errors," IEEE Journal on Selected
Areas in Communications, vol. 14, no. 8, pp. 1522-1535,
October 1996.
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Conference Publications:
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V.
Bharadwaj and R. M. Buehrer, "Acquisition in CDMA systems using
Parallel Interference Cancellation," 2004 IEEE 58th Vehicular Technology
Conference, 2004. VTC 2004-Spring Milan, Italy May 17-19, 2004
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R.M.
Buehrer, "On the Convergence of Multistage Interference Cancellation,"
Proceedings of the 1999 Asilomar Conference on Signals, Systems and Computers,
October 1999.
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N.S.
Correal, R.M. Buehrer, and B.D. Woerner, “Real-Time DSP Implementation of a
Coherent Partial Interference Cancellation Multiuser Receiver for DS-CDMA,”
Proceedings of the International Conference on Communications, pp.
1536-1540, June 1998.
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R.M.
Buehrer and B.D. Woerner, The Asymptotic Multiuser Efficiency of M-Stage
Interference Cancellation Receivers,” Proceedings of the Personal, Mobile,
and Indoor Radio Conference, pp. 570-574, September 1997, Helsinki,
Finland.
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Mobile & Portable Radio Research Group
Virginia Tech
Tel: (540) 231-2971
FAX: (540) 231-2968
Email: mprg@vt.edu
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