Effective ARQ protocols using adaptive modulation and symbol mapping diversity

We propose a generalized ARQ protocol that employs adaptive modulation and symbol mapping diversity for EEC-coded systems. By adapting the bit-to-symbol mapping for each retransmission, effective signal processing techniques can be developed to combine multiple transmissions to improve bit error rates (BER) and data throughput. Moreover, adapting the modulation for each retransmission can produce better bandwidth or energy efficiency, while maintaining good error rate performance through proper mapping selections. We discuss this proposed protocol, and develop a method for choosing mappings that optimize system performance. Simulation results indicate that rather substantial gains are achieved by mapping diversity.