Multiplex communications – Wide area network – Packet switching
Patent
1989-08-15
1991-07-09
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
375 1, 375115, 375 96, 375 39, 445101, H04J 1300
Patent
active
050311735
ABSTRACT:
A composite signal is formed by simultaneously transmitting multiple asynchronous data bit sequences, that are coded with respective spreading codes, in a single channel; and a circuit is provided which decodes any bit b(x) in that composite signal. This circuit includes a set of filters which are matched to all of the spreading codes and which obtain (a) a matched filter output signal y(x) for the x-th data bit b(x) and (b) matched filter output signals y(x+1) thru y(x+k-1) for the k-1 data bits that immediately follow data bit b(x); K is the number of bit sequences in the composite signal. An arithmetic unit combines the matched filter output signals via the expression: ##EQU1## where H(x,x.+-.i) is the cross correlation of the spreading codes for data bits b(x) and b(x.+-.i) over the time period that those data bits overlap (and thus add) in the composite signal, and ESTb(x-i) is an estimate of data bit b(x-i) which precedes bit b(x). An output unit decodes the data bit b(x) as a "1" if the above expression is positive, and as a "0" if the above expression is negative. In one embodiment, ESTb(x-i) is the SIGN of a matched filter output y(x-i) for data bit b(x-i). In another embodiment, ESTb(x-i) is the result from the output unit which decoded data bit b(x-i).
REFERENCES:
patent: 4455665 (1984-06-01), Kromer, III
patent: 4475186 (1984-10-01), Gutleber
patent: 4651327 (1987-03-01), Fujita
patent: 4791653 (1988-12-01), McFarland et al.
patent: 4805189 (1989-02-01), Mahoney
patent: 4882737 (1989-11-01), Dzung
patent: 4908836 (1990-03-01), Rushforth et al.
Rushforth Craig K.
Short Robert T.
Xie Zhenhua
Fassbender Charles J.
Olms Douglas W.
Starr Mark T.
Ton Dang
Unisys Corporation
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