Analysis on forward link pilot ratio for DS-CDMA under correlated Rician fading

In the forward link of many CDMA systems, a common pilot channel (shared by all users) is employed to provide the reference for coherent demodulation. A higher pilot ratio yields a good channel estimate but takes away some capacity from traffic users while a lower pilot ratio results in a higher traffic power need per user. This paper analyzes this trade-off by deriving the analytical error performance which includes (1) the imperfect channel estimation by pilot channel and (2) a very general channel model where correlation between paths as well as Rician fading (ranges from Rayleigh to AWGN) is considered. The effect of the interference pattern from different base stations is also evaluated.

[1]  M. Pursley,et al.  Analysis of Direct-Sequence Spread-Spectrum Multiple-Access Communication Over Rician Fading Channels , 1979, IEEE Trans. Commun..

[2]  James K. Cavers,et al.  Analysis of the error performance of trellis-coded modulations in Rayleigh-fading channels , 1992, IEEE Trans. Commun..

[3]  J. E. Mazo,et al.  Probability of error for quadratic detectors , 1965 .

[4]  J. Cavers.  An analysis of pilot symbol assisted modulation for Rayleigh fading channels (mobile radio) , 1991 .

[5]  M. P. Fitz,et al.  Design and analysis of transmitter diversity using intentional frequency offset for wireless communications , 1997 .

[6]  C. Helstrom,et al.  Approximate Evaluation of Detection Probabilities in Radar and Optical Communications , 1978, IEEE Transactions on Aerospace and Electronic Systems.

[7]  John G. Proakis,et al.  Digital Communications , 1983 .

[8]  Andrew J. Viterbi,et al.  Erlang Capacity of a Power Controlled CDMA System , 1993, IEEE J. Sel. Areas Commun..

[9]  Laurence B. Milstein,et al.  Coherent DS-CDMA performance in Nakagami multipath fading , 1995, IEEE Trans. Commun..

[10]  Valentine A. Aalo,et al.  Performance analysis of coherent DS-CDMA systems in a Nakagami fading channel with arbitrary parameters , 1997 .

[11]  Stephen O. Rice,et al.  Uniform asymptotic expansions for saddle point integrals — Application to a probability distribution occurring in noise theory , 1968 .

[12]  Andrew J. Viterbi,et al.  On the capacity of a cellular CDMA system , 1991 .

[13]  G. Turin.  The characteristic function of Hermitian quadratic forms in complex normal variables , 1960 .

[14]  M. Benthin,et al.  Influence of channel estimation on the performance of a coherent DS-CDMA system , 1997 .

[15]  M. P. Fitz.  A dual-tone reference digital demodulator for mobile digital communication , 1993 .