Soft interference cancellation in multiuser communications
Tóm tắt
In this paper the performance of soft interference cancellation in synchronous multiuser channels is investigated. Two-stage detection with decorrelator in the first stage is considered. Soft first stage tentative decisions are formed by means of a multilevel quantizer or linear clipper. The asymptotic multiuser efficiency (AME) is used as a performance measured for optimization of the nonlinearity. It is shown, for the two-user case, that soft interference cancellation by means of an optimized linear clipper achieves the AME of the maximum likelihood detector if the crosscorrelation of the signature waveforms is less than
$$1/\sqrt 2 $$
. For the K-user case, novel upper bounds on the AME for two-stage detectors with feedback interference cancellation, with both hard and soft tentative decisions, are obtained. The derived bounds are used to examine the performance of two-stage detectors in a cellular scenario.
Từ khóa
Tài liệu tham khảo
S. Verdu, “Optimum multiuser asymptotic efficiency,” IEEE Trans. Commun., Vol. COM-34, 1986.
S. Verdu, “Optimum multiuser signal detection,” Ph.D. dissertation, Dep. Elec. Comput. Eng., University of Illinois, Urbana-Champaign, IL, 1984.
M. K. Varanasi and B. Aazhang, “Near-optimum detection in synchronous CDMA systems,” IEEE Trans. Commun., Vol. COM-39, 1991.
R. Lupas, “Near-far resistant linear multiuser detectors,” Ph.D. Dissertation, Dep. Elec. Eng., Princeton University, NJ, 1989.
R. Lupas and S. Verdu, “Linear multiuser detectors for synchronous CDMA channels,” IEEE Trans. on Information Theory, Vol. IT-35, 1989.
X. Zhang and D. Brady, “Soft-decision multistage detection for asynchronous AWGN channels,” Proc. of the 31 Annual Allerton Conference on Communications, Control and Computing, Allerton House, Urbana-Champaign, IL, 1993.
L. B. Nelson and H. V. Poor, “Soft-decision interference cancellation for AWGN multiuser channels,” Proc. of the Inter. Symp. on Information Theory, Trondheim, Norway, 1994.
A. Duel-Hallen, “Decorrelating decision feedback multiuser detector for synchronous code-division multipleaccess channel,” IEEE Trans. Commun., Vol. COM-41, 1993.