Patent ID: 7079585

Claim:
A hierarchical QAM transmission system, comprising: a source of data symbols (DATA 1 , DATA 2 ), each representing a multibit binary value; a hierarchical QAM transmitter ( 102 , 104 , 106 , 108 , 110 , 111 ), responsive to the value of a data symbol for transmitting one of a constellation of data points in the I-Q plane, each data point in the constellation associated with a respective value of a symbol such that symbol values of adjoining constellation data points differ by no more than one bit; and a hierarchical QAM receiver ( 302 , 304 , 306 , 308 , 310 , 312 ), responsive to a received data point, for generating a received symbol (DATA 1 ′, DATA 2 ′), and characterized by the transmitter comprising: a level 1 QPSK modulator ( 104 ), responsive to a level 1 portion (DATA 1 ) of a data symbol, for generating respective I and Q signals representing a center point of a predetermined one of four quadrants associated with the value of the level 1 portion of the data symbol; a level 2 QPSK modulator ( 110 ), responsive to a level 2 portion of the data symbol (DATA 2 ), for generating respective I and Q signals representing a center point of the predetermined one of four quadrants associated with the value of the level 2 portion of the data symbol; a signal combiner ( 106 , 111 ; 106 (I), 106 (Q)), coupled to the level 1 modulator ( 104 ) and the level 2 modulator ( 110 ), for weighting the respective I and Q signals from the level 2 QPSK modulator ( 110 ) by a weighting factor of 0.5 and combining the weighted level 2 I and Q signals with the respective I and Q signals from the level 1 modulator; and a gray code mapper ( 112 ), coupled between the level 2 QPSK modulator ( 110 ) and the signal combiner ( 106 , 111 ), for remapping the respective I and Q signals from the level 2 QPSK modulator ( 110 ) responsive to the first portion (DATA 1 ) of the data symbol (DATA 1 , DATA 2 ).