Patent ID: 7133462

Claim:
A method of determining a modulation scheme for a retransmission in a communication system using at least three modulation schemes, where at an initial transmission of sub-packets, information is modulated in a lowest-order modulation scheme if a first MPR (Modulation order Product code Rate), which is defined as an average number of information bits per modulation symbol, is less than a first threshold, and in a modulation scheme having a modulation order higher than the lowest modulation order if the first MPR is greater than or equal to the first threshold, the first MPR being proportional to N W 1 × S 1 , wherein N is an EP (Encoder Packet) size W 1 is a number of available Walsh codes, and S 1 is a number of slots per sub-packet that are used for the initial transmission, the method comprising the steps of: calculating a second MPR indicating a spectral efficiency for the retransmission using an EP size, the number of available Walsh codes, and the number of slots per sub-packet that are used for the retransmission; selecting the lowest-order modulation scheme if the second MPR is equal to or less than a second threshold greater than a first threshold; calculating an equivalent MPR (MPR e ), using the first MPR and the second MPR if the second MPR is greater than the second threshold and equal to or less than a third threshold which is greater than the second threshold, selecting another order modulation scheme among the plurality of modulation schemes which has a higher modulation order than the lowest-order modulation scheme if MPR e is less than a fourth threshold, and selecting a further order modulation scheme among the plurality of modulation schemes which has a higher modulation order than the lowest-order modulation scheme and the other modulation scheme if MPR e is greater than or equal to the fourth threshold; and selecting a highest-order modulation scheme if the second MPR is greater than the third threshold.