Patent ID: 6351498
Filing Date: 2002-02-26
Classification: H04J,H04L

Abstract:
A digital modulation and demodulation system for radio communications, comprising:a transmitting side device having: a division unit for dividing transmission data in advance, into blocks of LN bits length each, where L and N are natural number greater than one, and dividing each block into N sets of L bits data sequences; an encoding unit for generating orthogonal codes of M bits length each, where M is a natural number, which are uniquely defined with respect to L bits codes given by the L bits data sequences obtained by the division unit; a multiplexing unit for multiplexing N sets of orthogonal codes generated by the encoding unit for each block into a multiplexed signal, such that M bits constituting each orthogonal code are dispersed in time in the multiplexed signal; and a modulation unit for applying a digital modulation to a carrier using the multiplexed signal obtained by the multiplexing unit; and a receiving side device having: a detection unit for obtaining a detection output of signals received from the transmitting side; a separation unit for setting the detection output obtained by the detection unit into reception data-units of NM bits length each in synchronization with multiplexing applied at the transmitting side, and separating each reception data-unit into N sets of M bits sequences; a decoder for obtaining a correlation between each M bits sequence obtained by the separation unit and every possible orthogonal code defined at the transmitting side device, selecting one orthogonal code with a highest correlation, and outputting an L bits data sequence corresponding to each selected orthogonal code; and a composition unit for recovering an original LN bits signal by applying an inverse operation of an operation applied at the transmitting side device, with respect to N sets of L bits data sequences outputted by the decoder for each reception data-unit.