ADAPTIVE HYBRID ARQ CODING SCHEMES FOR SLOW FADING CHANNELS IN MOBILE RADIO SYSTEMS

摘要

A method and apparatus for performing adaptive hybrid automatic repeat request(ARQ) coding in which the coding is modified based on the acknowledgements returnedby the receiver. In accordance with one illustrative embodiment of the present invention,the state of the channel is implicitly determined by the transmitter based upon thefrequency of acknowledgments (ACKs and NACKs) arriving from the receiver. Forexample, since a NACK implies a weak received signal strength, the code rate of the FECis advantageously reduced in response to such an acknowledgement. On the other hand,the code rate of the FEC is advantageously increased in response to an ACK. Inaccordance with another illustrative embodiment of the present invention, theacknowledgement returned by the receiver is modified to convey the number of errors inthe corresponding received data packet. In particular, a Reed-Solomon (RS) outer codeis employed in the FEC to enable the receiver to determine the number of errors in thereceived data packet. If the acknowledgement indicates a large number of errors at thereceiver, the code rate of the FEC is advantageously reduced in response thereto.