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).

Abstract: Transmitting and receiving apparatus for transmitting data which includes a purged extended Golay (22,7) code encoder at the transmitter for encoding digital data into constant weight unbalanced codewords representative of the digital data. The constant weight unbalanced codewords contain error correction bits and are preferably transmitted as balanced codewords. When the receiver decodes the original digital data, improved tracking and acquisition of the transmitted data is achieved.

Abstract: Data bits are decoded from a composite signal that is formed by coding multiple bit sequences with respective spreading codes, and transmitting the coded bit sequences simultaneously and asynchronously over a single channel in which the bit sequences are added. This decoding involves a metric in combination with a repetitive decision process which is only linearly dependent on the number of bit sequences in the composite signal.

Abstract: A novel maximum likeihood decoder for the Golay (24,12) code is provided. Instead of decoding the received dimensional vector (X) is a systolic array, the vector is mapped into a (24,5) subcode with an index 128 which is easily decoded. The decoder employs a plurality of precomputational circuits cooperating with a similar plurality of inner product circuits which compute the 128 inner product values and select the maximum inner product value from each inner product circuit. The maximum inner product value from each circuit is loaded into a select logic circuit for selecting the maximum inner product value and its corresponding code word closest to the received vector (X).

Abstract: The present invention provides a high-speed decoder for decoding signals encoded into Nordstrom-Robinson 16,256,6 non-linear code. The novel decoder receives a transmitted encoded signal in the form of a multi-dimensional vector to be decoded. The decoder comprises a plurality of computing elements coupled to the input encoded signals and produces modified multi-dimensional vectors and subcode values which are decoded in a plurality of subcode decoders to produce intermediate inner product values and information words associated with the intermediate inner product values. The intermediate inner product values are compared in comparator means to provide the maximum intermediate inner product value and its associated information which is indicative of the best mathematical estimate of the encoded signal being decoded.

Abstract: Transmitting and receiving apparatus for transmitting data includes a purged code encoder at the transmitter for encoding digital data into constant weight unbalanced codewords representative of the digital data. The constant weight unbalanced codewords containing error correction bits are preferably transmitted as balanced codewords and are decoded at the receiver employing Golay decoders or algebraic decoders to recover the original digital data without the requirement of a large number of matched filter previously employed for decoding.