Capacity of the energy harvesting Gaussian MAC

We consider an energy harvesting multiple access channel where the transmitters are powered by an exogenous stochastic energy harvesting process and equipped with finite batteries. We characterize the capacity region of this channel as n-letter mutual information rate and develop inner and outer bounds that differ by a constant gap. An interesting conclusion that emerges from our results is that in a symmetric system, where transmitters are statistically equivalent to each other, the largest achievable common rate point approaches that of a standard AWGN MAC with an average power constraint, as the number of users in the MAC becomes large.