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Effective Spectral Efficiency for Adaptive QAM With Diversity and Pilot Assisted Channel Estimation

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Executive Summary

This paper investigates the effects of non-ideal channel state information in adaptive M-ary quadrature amplitude modulation systems with subset diversity. The Slow Adaptive Modulation (SAM) technique, which adapts the modulation parameters to slow channel variations, is considered. With respects to fixed scheme modulation systems, SAM achieves a good gain in terms of Spectral Efficiency (SE) and outage probability and, compared to fast adaptive modulation, reduces the system complexity by lowering the feedback rate. Resources dedicated to channel estimation affect both the system performance, in terms of error and outage probability, and the effective SE for which a proper definition is needed.

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