Patent ID: 6731611
Filing Date: 2004-05-04
Classification: H04L

Abstract:
A method for duplex data transmission with quadrature amplitude modulation in oppositely transporting channels, which comprises:modulating a first carrier signal with a first normal digital data signal and a first quadrature digital data signal at a first symbol frequency fT(0) for generating a first modulated carrier signal; transmitting the first modulated carrier signal in a first direction in an upper channel having a relatively higher frequency band foÂ±Bo/2; modulating a second carrier signal with a second normal digital data signal and a second quadrature digital data signal at a second symbol frequency fT(u) for generating a second modulated carrier signal; transmitting the second modulated carrier signal in a second direction in a lower channel having a relatively lower frequency band fuÂ±Bu/2, the lower frequency band not overlapping the higher frequency band; sampling the first modulated carrier signal received via the upper channel at a sampling frequency fAo and sampling the second modulated carrier signal received via the lower channel at a sampling frequency fAu; subsequently demodulating a pulse train resulting from the sampling step; and subsequently low-pass filtering and sampling at the symbol frequency of the respective digital data signal for recovering the first and second normal and quadrature digital data signals used for modulation; wherein the following frequencies are defined: fo=center frequency of the upper channel; Bo=bandwidth of the upper channel; fu=center frequency of the lower channel; Bu=bandwidth of the lower channel; fT=symbol frequency of the digital data signal; fAo=sampling frequency of a receiver-end sampling of the upper channel prior to demodulation; fAu=sampling frequency of the receiver-end sampling of the lower channel prior to demodulation; and wherein: fo>fu, fAo>fT, fAu>fT; fo/fu is a rational number; and fAo=2fo.