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QAM is very favorable in high speed communication systems, because it could enhance the frequency spectrum utilization of them. In this paper, consists of two aspects. On the one hand, the theoretical algorithm of bit-level soft demodulation for 64QAM is analyzed, and two simplified algorithm to calculate LLR is developed. On the other hand, an advanced Hybrid ARQ (HARQ) with chase combing is presented, employing 64QAM modulation and signal constellation rearrangement; also introduce the application in HSPA+.