On the Capacity of the Multiuser 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 $Q \to \infty$, $S = \gamma Q$ and $0 < \gamma < \infty$) upper and lower bounds on the relative (per subchannel) capacity are derived. The lower bound for the coordinated case is shown to increase when $\gamma$ grows. At the same time the relative capacity for the uncoordinated case is upper bounded by a constant.