Network Error Correction With Unequal Link Capacities

We study network error correction with unequal link capacities. Previous results on network error correction assume unit link capacities. We consider network error correction codes that can correct arbitrary errors occurring on up to z links. We find the capacity of a network consisting of parallel links, and a generalized Singleton outer bound for any arbitrary network. We show by example that linear coding is insufficient for achieving capacity in general. In our example, the capacity is 50% greater than the linear coding capacity and we achieve using a nonlinear error detection strategy. We also present a method for finding an upper bound on the linear coding capacity for arbitrary network. We show that even for a single source and single sink network, it may be necessary for intermediate nodes to do coding, nonlinear error detection or error correction. This is unlike the equal link capacity case, where coding only at the source and forwarding at intermediate nodes suffices for a single source and sink network. We conjecture that the generalized Singleton outer bound is not achievable in general.