  Energy detection (ED) is an attractive technique for symbol detection at
receivers equipped with a large number of antennas, for example in millimeter
wave communication systems. This paper investigates the performance bounds of
ED with pulse amplitude modulation (PAM) in large antenna arrays under single
stream transmission and fast fading assumptions. The analysis leverages
information-theoretic tools and semi-numerical approach to provide bounds on
the information rate, which are shown to be tight in the low and high
signal-to-noise ratio (SNR) regimes, respectively. For a fixed constellation
size, the impact of the number of antennas and SNR on the achievable
information rate is investigated. Based on the results, heuristics are provided
for the choice of the cardinality of the adaptive modulation scheme as a
function of the SNR and the number of antennas.
