Method for adaptive quadrature amplitude modulation signal constellation remapping for data packet retransmissions
A simplified QAM signal constellation symbol-wise remapping scheme for data packet retransmissions to improve performance at a high coding rate. The simplified QAM signal constellation symbol-wise remapping scheme takes advantage of the separate I and Q labeling bits in a QAM signal to reduce the complexity of a receiving node. A method for adaptive switching between bit-wise and symbol-wise constellation remapping for data packet transmissions according to channel coding rate to achieve optimum performance across the range of channel coding rates.
1. A method for adaptively selecting a signal constellation for data modulation and demodulation during data packet retransmissions, the method comprising:
receiving a data signal including channel coding information extracted from a received retransmission of a current data packet;
determining whether a channel coding rate is higher than a predetermined channel coding threshold;
adaptively switching between bit-wise and symbol wise signal constellations;
adaptively selecting a signal constellation for data modulation based on whether the channel coding rate is higher than the predetermined threshold; and
selecting a constellation remapping table according to a modulation type of the current data packet transmission.
2. The method of claim 1 further comprising selecting a signal constellation according to a transmission number of the current data packet transmission.
3. The method of claim 1 wherein the signal constellation is selected from a bit-wise constellation remapping table when the channel coding rate is lower than the predetermined channel coding threshold thereby indicating a strong channel coding.
4. The method of claim 1 wherein the signal constellation is selected from a symbol-wise remapping table when the channel coding rate is higher than the predetermined channel coding threshold thereby indicating a weak channel coding.
5. The method of claim 1 wherein the data modulation uses a 16 quadrature amplitude modulation (QAM) constellation mapping.
6. The method of claim 1 wherein the data modulation uses a 64 quadrature amplitude modulation (QAM) constellation mapping.
7. The method of claim 1 wherein the transmitting node is a wireless transmit/receive unit (WTRU).
8. The method of claim 1 wherein the transmitting node is a base station.