TRANSMITTER FOR PERFORMING AN 8-QAM OR A 7-QAM MODULATION AND CORRESPONDENT RECEIVER

摘要

The present invention relates to a receiver for a digital communication system comprising - a demodulator arranged for receiving a quadrature amplitude modulated stream of digital symbols and for outputting a sequence of demodulated digital symbols, - a bit demapper arranged for being fed with the sequence of demodulated symbols and for determining a three-bit representation for the demodulated symbols associated with points of a predefined constellation, said three-bit representation being a set of probability values for each bit position, said predefined constellation having a first and second point of different amplitude and zero reference phase, a third point having an amplitude equal to the amplitude of the first point and a 180 degree reference phase, a fourth point having an amplitude equal to the amplitude of the second point and a 180 degree reference phase, and - a decoder arranged for receiving the set of probability values and for determining values for each bit, characterised by said predefined constellation further having a fifth and a sixth point having real magnitudes substantially larger than the amplitude of the first point and equal imaginary magnitudes of opposite sign, and seventh and eighth points having substantially equal to a negation of the amplitude of the fifth and sixth points and equal imaginary magnitudes of opposite sign. The present invention relates to transmitter and a receiver for a digital communication system, the transmitter comprising:•- an encoder for encoding a sequence of information bits and for outputting a sequence of coded bits,•- a bit mapper arranged for being fed with said sequence of coded bits and for mapping said coded bits three-by-three to digital symbols, said digital symbols being a point of a predefined quadrature amplitude modulation constellation, said constellation having a first (B) and second point (H) of different amplitude and zero reference phase, a third point (A) having an amplitude equal to the amplitude of said first point and a 180 degree reference phase, a fourth point (G) having an amplitude equal to the amplitude of said second point and a 180 degree reference phase,•- a modulator arranged for receiving said sequence of said digital symbols and for applying a linear modulation to said sequence of said digital symbols, so that a transmit waveform is obtained, characterised by said predefined con said predefined constellation further having a fifth (D) and a sixth point (F) having real magnitudes larger than the real amplitude of said first point and equal imaginary magnitudes of opposite sign, and seventh (C) and eighth (E) points having real values equal to a negation of the real amplitude of said fifth and sixth points and equal imaginary magnitudes of opposite sign.