Digital communication method and digital communication device

Abstract

A digital communication device includes: a modulator having encoding means for converting two-dimensional digital information signal into a three-dimensional signal and phase modulation means for modifying the carrier phase in according to the three-dimensional signal; and a demodulator having phase demodulation means for detecting information on the three-dimensional signal from the received phase-modulated wave and demodulation means for deciding the two-dimensional digital information from the information on the three-dimensional signal. The digital communication device has a bit error ratio and an occupied radio band width equivalent to a digital communication device using the conventional QPSK or pi / 4 shift QPSK and the error correction method and greatly improves the amplitude fluctuation. Moreover, the digital communication device can transmit a signal with a narrower occupied frequency band width while maintaining the same constant envelope characteristic as the GMSK using the conventional error correction code.

Description

technical field [0001] The present invention relates to digital communication methods and devices used in digital wireless systems and the like. Background technique [0002] The digital modulation method is to convert the digitized information into a frequency other than the baseband and then transmit it, which is an indispensable technology in the digital wireless system. The digital modulation methods used in mobile communications include the PSK (Phase Shift Keying) method in which the carrier phase corresponds to digital information, the FSK (Frequency Shift Keying) method in which the frequency corresponds to digital information, and one of the FSK methods but without GMSK (Gaussian Minimum Shift Keying) method of carrier amplitude variation. [0003] The desired performance of a digital modulation method includes the following three elements: an excellent bit error rate relative to Eb / No, a narrow occupied frequency band of a radio frequency, and a small amplitude fl...

AI Technical Summary

Problems solved by technology

[0024] As explained above, in existing digital communication devices using QPSK or QPSK shifted by π / 4, there is a large fluctuation in the amplitude of the modulated wave, so when the waveform passes through a nonlinear amplifier, the waveform is greatly distorted and a side lobe spectrum is generated. The problem

As a result, degradation of the noise characteristics and an increase in the bit error rate of the received signal

Moreover, when using GMSK and error correction as a fixed-envelope modulation method, there is a problem of low frequency utilization efficiency because the occupied frequency bandwidth is large.

In addition, there is also the problem that the 8-phase phase modulation with the fixed envelope of the trellis encoding cannot obtain such a good bit error rate characteristic relative to Eb / No

Images