Low complexity adaptive equalizer radio receiver employing direc

Details Low complexity adaptive equalizer radio receiver employing direc Low complexity adaptive equalizer radio receiver employing direc

1993-10-29

1994-12-06

Grimm, Siegfried H.

Demodulators

Phase shift keying or quadrature amplitude demodulator

375 14, 375 80, 375 84, 375101, H04L 2712

Patent

active

053714717

ABSTRACT:
A low complexity adaptive equalizer for use in U.S. digital cellular radios demodulates .pi./4-shifted differentially encoded quadrature phase shift keyed (DQPSK) encoding in the presence of intersymbol interference (ISI) with reduced decoding complexity by employing an estimated received constellation which takes into account channel changes over time and ISI. The decoding complexity is reduced by tracking a reduced number of estimated reference symbol constellation points and taking advantage of the geometry to estimate the remaining symbol constellation points. Reference symbol constellation points are updated directly to compensate for changes in the channel, instead of determining channel impulse response (CIR) coefficients, and convolving the CIR coefficients with received symbols to determine new reference symbol constellation points.

REFERENCES:
patent: 4603393 (1986-07-01), Laurent et al.
patent: 4656648 (1987-04-01), Vallet
patent: 5263026 (1993-11-01), Parr et al.
patent: 5285480 (1994-02-01), Chennakeshu et al.
"Receiver Performance for the North American Digital Cellular System" by G. Larsson, B. Gudmundson, K. Raith, 41st Vehicular Technology Society Conference Proceedings, pp. 1-6, St. Louis, Mo. May 1991.
Forney, Jr., "The Viterbi Algorithm", Proceedings of the IEEE, vol. 61, pp. 268-278, Mar. 1973.
"An Adaptive MLSE Receiver for TDMA Digital Mobile Radio" by R. D'Avella, et al, IEEE Jorunal on Selected Areas in Communications, vol. 7, No. 1, Jan. 1989, pp. 122-129.

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