A large-capacity CDMA transmission system that can realize communication with
a
moving unit such as an automobile, transmitting more quantity of information than
the conventional system without increasing the occupied band width, using the same
or narrower frequency band width.
This system assumes the code division multiple access (CDMA) transmission system
for simultaneous multiple communication, which performs phase modulation on a carrier
signal while maintaining a phase of the carrier signal in a predetermined period
at a predetermined value, so as to generate a primary modulated wave, and then,
multiplies the obtained primary modulated wave by a spread code sequence. On the
transmitting side, a differential coding phase modulation (DPSK) is employed to
generate a primary modulated wave. On the other hand, on the receiving side, a
quasi-synchronous detection and difference operation are utilized to detect the
phase difference between the last symbol interval and the current symbol interval,
and the detected phase difference is given as the information of the current symbol interval.
