  Consider a battery limited energy harvesting communication system with online
power control. Assuming independent and identically distributed (i.i.d.) energy
arrivals and the harvest-store-use architecture, it is shown that the greedy
policy achieves the maximum throughput if and only if the battery capacity is
below a certain positive threshold that admits a precise characterization.
Simple lower and upper bounds on this threshold are established. The asymptotic
relationship between the threshold and the mean of the energy arrival process
is analyzed for several examples.
