On the capacity of a multiple-access vector adder channel

We investigate the capacity of the $Q$-frequency $S$-user vector adder channel (channel with intensity information) introduced by Chang and Wolf. Both coordinated and uncoordinated types of transmission are considered. Asymptotic (under the conditions $Q\to\infty$, $S=\gamma Q$, $0<\gamma<\infty$) upper and lower bounds on the relative (per subchannel) capacity are derived. The lower bound for the coordinated case is shown to increase with $\gamma$. At the same time, the relative capacity for the uncoordinated case is upper bounded by a constant.