A Fault-Tolerant Distributed Control VLSI Permutation Network

In this paper we present a fault-tolerant permutation network suitable for VLSI implementation, and distributed algorithms for switch self setting. The network, called Fault-Tolerant Mesh of Trees (FTMT for short), is obtained from Mesh of Trees interconnection scheme, by adding spare links. An n inputs, n outputs FTMT occupies O(n2log2n) area, has O(log n) crossing time, and a constant setting time for its switches, thus leading to an O(log n) overall operational time. So, FTMT is almost optimal in a VLSI setting since O(n2) area and O(log n) time lower bounds for VLSI permutation networks have been established. FTMT works properly even in presence of faulty switches and links. Fault patterns destroying the full access property of the network are studied. Distributed algorithms for switch setting are proposed. We show that such algorithms allow the network to establish the desired I/O connection in O(log n) time whenever the pattern of faulty elements makes it possible.