Direct sequence code division multiple access (DS-CDMA) communic

Details Direct sequence code division multiple access (DS-CDMA) communic Direct sequence code division multiple access (DS-CDMA) communic

1994-08-24

1996-08-27

Marcelo, Melvin

Multiplex communications

Wide area network

Packet switching

375210, 375348, H04J 1304

Patent

active

055508103

ABSTRACT:
A DS-CDMA system comprises at least one transmitter and at least one receiver operating on a dedicated signal channel which is used by other DS-CDMA operators in a non-synchronous way. A receiver for use in such a DS-CDMA system includes a data aided multiuser interference canceller (38) comprising a feedforward filter (48) connected to a subtracting stage (50). A decision stage (52) is connected to an output of the subtracting stage (50). Decisions from the decision stage (52) are stored in a memory which also stores preliminary decisions made on the signal applied to the feedforward filter (48) by a simple receiver (46). These decisions are applied to a feedback filter (58) the output of which is connected to the subtracting stage (50) thereby removing the effects of pre-cursive and post-cursive interference. The input to, and output from, the decision stage 52 are compared and the difference is used for adjusting the tap weights of the feedforward and feedback filters (48,58). In the case of a single input, single output, the feedforward filter (48) comprises a fractionally spaced equalizer which despreads and filters the DS-CDMA signal. In the case of multiple input, multiple output, the received signal is despread in a bank of code matched filters and the output is applied to the canceller (38) in which the feedforward filter (48) comprises a linear synchronous equalizer.

REFERENCES:
patent: 4621355 (1986-11-01), Hirosaki et al.
patent: 5341395 (1994-08-01), Bi
"Adaptive Cancellation of Nonlinear Intersymbol Interference for Voiceband Data Transmission" E. Biglieri et al, IEEE Journal on Selected Areas in Communications, vol. SAC2, No. 5, Sep. 1984, pp. 765-777.
"Equalization, Detection and Channel Coding for Digital Transmission and Recording Systems" J. W. M. Bergmans, Proc. of Sixth Symposium on Information Theory in the Benelux May 23-24 1985.
"Equalizers for Multiple Input/Multiple Output Channels and Pam Systems with Cyclostationary Input Sequences" A. Duel-Hallen, IEEE Journal on Selected Areas in Communications, vol. 10, No. 3, Apr. 1992, pp. 630-639.
"Very Low Rate Convolutional Codes for Maximum Theoretical Performance of Spread Spectrum Multiple Access Channels" A. Viterbi, IEEE Journal on Selected Areas in Communications, vol. 8, No. 4, May 1990, pp. 641-649.

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