Capacity of the Energy Harvesting Gaussian MAC

We consider an energy harvesting multiple access channel (MAC) 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 the sum-capacity approaches that of a standard additive white Gaussian noise MAC (with only an average constraint on the transmitted power), as the number of users in the MAC becomes large.