Modulationsverfahren, Demodulationsverfahren, Modulator und Demodulator sowie Verwendung von Modulator und Demodulator

摘要

Disclosed is a link access apparatus of a CDMA system using a DS/SS communication method, and more particularly an up-link access apparatus which overcomes a near/far problem occurring when mobile stations and a base station perform multiple access communication using code division. An up-link access apparatus in a DS/SS-CDMA system has a transmitter for mixing data to be transmitted to a base station with a PN code unique to that mobile station to thereby PN code modulate the data. The transmitter then mixes the PN code modulated data with a carrier having a frequency that is shifted by an identification frequency to thereby output a spread spectrum signal. The apparatus further includes a receiver for mixing a demodulation carrier made up of the PN code and the identification frequency with the spread spectrum signal from the transmitter to thereby output a mixed signal. The mixed signal is then integrated according to a period having a reciprocal corresponding to the identification frequency, demodulated and output as a digital signal.