Hybrid ARQ retransmission method with reduced buffer size requirement and receiver therefor

A hybrid ARQ retransmission method in a communication system, wherein data packets comprising at least one identical or partly identical modulation symbol having more than one bit encoded with a forward error correction technique prior to transmission are retransmitted based on a repeat request and subsequently bit-level combined on the basis of soft-information values which are input into a decoder, the method comprising:

• (a) calculating and buffering soft-information values of the most significant bits, MSBs, of each transmitted and retransmitted modulation symbol,
• (b) combining, for matching modulation symbols, the current soft-information values of the most significant bits of a received modulation symbol with the buffered soft-information values of at least one of the previous received transmitted modulation symbols, and
• (c) calculating soft-information values for bits other than the most significant bits of the received modulation symbol, whose soft-information values are combined, from the combined soft-information values.