Oki Electric Industry Co., Ltd.

Akiyoshi Kawahashi

Manabu Kawabe

Atsushi Fukasawa

Takuro Sato

Toshio Kato

In a block-spreading code-division multiple-access communication system a demodulator stores received chip data in a separate memory area for each transmitting station. Each area has a capacity of at least two blocks. When a complete block is received from a transmitting station, all blocks of data stored in the corresponding memory area are correlated against a set of product codewords, which are obtained by spreading a set of orthogonal codewords by the transmitting station's spreading code, to find the codeword that gives the maximum correlation value. For the oldest block, this correlation value and information identifying the codeword are output. For all blocks, the maximum correlation value and corresponding product codeword are used to calculate interference correction data, which are subtracted from the data in other memory areas.

Block-spreading code-division multiple-access demodulator with improved

A code-division multiple-access spread-spectrum communication system uses pairs of spreading codes with rates of N/2 chips per data symbol to provide a capacity equivalent to that obtained in a conventional system with N chips per symbol. In the transmitter, identical input data are spread in parallel by both spreading codes, then used to modulate two orthogonal carrier signals, and the resulting radio-frequency signals are combined for transmission from an antenna. In the receiver, the received signal is demodulated by parallel multiplication with the two carrier signals, the resulting baseband signals are correlated with the two spreading codes, and the results are added.

Code-division multiple-access communication system providing enhanced

A demodulator for code-division multiple-access spread-spectrum communications stores received chip data in a separate memory area for each transmitting station. Each area has a capacity of at least two symbols. When a complete symbol is received from a transmitting station, all chip data stored in the corresponding memory area are correlated with the corresponding spreading code, and estimated symbol values are derived from the correlated values. The correlated or estimated value of the oldest symbol is output as a demodulated value. The difference between each estimated symbol value and the previous estimate for the same symbol is multiplied by the spreading code to generate remaining interference values, which are subtracted from all chip data stored in memory areas for other transmitting stations, thereby updating those data.

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Tokyo, Japan

Akiyoshi Kawahashi