Energy Efficiency of Fixed-Rate Wireless Transmissions under Queueing Constraints and Channel Uncertainty

TL;DR

This paper analyzes the energy efficiency of fixed-rate wireless transmissions considering queueing constraints and channel uncertainty, revealing how power and bandwidth influence bit energy in different regimes.

Contribution

It provides a comprehensive analysis of the spectral efficiency--bit energy tradeoff under queueing constraints and channel estimation errors, deriving key performance metrics.

Findings

Bit energy increases without bound in low-power regime as power vanishes.

Bit energy decreases to minimum in wideband regime as bandwidth increases.

Optimal training power fraction is identified for energy-efficient transmission.

Abstract

Energy efficiency of fixed-rate transmissions is studied in the presence of queueing constraints and channel uncertainty. It is assumed that neither the transmitter nor the receiver has channel side information prior to transmission. The channel coefficients are estimated at the receiver via minimum mean-square-error (MMSE) estimation with the aid of training symbols. It is further assumed that the system operates under statistical queueing constraints in the form of limitations on buffer violation probabilities. The optimal fraction of of power allocated to training is identified. Spectral efficiency--bit energy tradeoff is analyzed in the low-power and wideband regimes by employing the effective capacity formulation. In particular, it is shown that the bit energy increases without bound in the low-power regime as the average power vanishes. On the other hand, it is proven that the bit energy diminishes to its minimum value in the wideband regime as the available bandwidth increases. For this case, expressions for the minimum bit energy and wideband slope are derived. Overall, energy costs of channel uncertainty and queueing constraints are identified.