Patent ID: 8509352

Claim:
A system for increasing a diversity of a communication system using QAM modulation, comprising: a receiver device to receive and jointly decode N spread QAM symbols received over N different independent channels; and a transmitter device to spread and rotate N QAM symbols and then transmit the N spread and rotated QAM symbols over N different independent channels, wherein the transmitter device further comprises a spreading rotation component to multiply the N QAM symbols by a pre-specified N×N integer spreading rotation matrix, wherein, the diversity for the communication system is optimally increased while maintaining the same transmission rate, and wherein the pre-specified N×N integer spreading rotation matrix is the integer 2×2 integer spreading rotation matrix I 16 , 2 = 1 17 ⁡ [ 4 ⁢ 1 1 - 4 ] which spreads 16-QAM symbols into regular 256-QAM symbols, and the 2×2 integer spreading rotation matrix that spreads 64-QAM symbols and 256-QAM symbols are I 64 , 2 = 1 65 ⁡ [ 8 1 1 - 8 ] ⁢ ⁢ and ⁢ ⁢ I 256 , 2 = 1 257 ⁡ [ 16 1 1 - 16 ] respectively.