Some bounds on the capacity of communicating the sum of sources

We consider directed acyclic networks with multiple sources and multiple terminals where each source generates one i.i.d. random process over an abelian group and all the terminals want to recover the sum of these random processes. The different source processes are assumed to be independent. The solvability of such networks has been considered in some previous works. In this paper we investigate on the capacity of such networks, referred as {\it sum-networks}, and present some bounds in terms of min-cut, and the numbers of sources and terminals.