Energy-efficient modulation selection and feedback quantization

In this paper, we consider the energy efficiency (EE) of a single-link system, requiring feedback for reliable transmission. A quantized value of the signal-to-noise ratio is sent back to select the scheme that achieves maximum EE. Besides the energy consumption at the transmitter, we account for the energy consumed at the receiver to feedback the channel state information to the transmitter, which depends on the quantization and the energy needed for each feedback bit. For a given number of quantization intervals, we employ 0-1 fractional programming to carry out the optimization, resulting in an optimal modulation selection policy. Applying this policy over a range of feedback bits, we show that an optimal number of feedback bits exists for given parameters. Furthermore, these results are illustrated by simulations.