Rearrangeable Operation Of Large Crosspoint Switching Networks

Abstract

A major impediment to building large crosspoint chips for configuring crosspoint switching networks is the simultaneous switching (Delta-I) noise problem that is caused by the switching of a large number of line drivers driving the output pins of the package. This limits the size of the largest crosspoint chips that can be operated reliably. An architectural solution to this problem is presented for networks constructed from one-sided crosspoint switching chips. The approach seeks to minimize the maximum number of active-drivers in the individual chips by distributing the active drivers in the network uniformly among the chips. Uniform distribution of the active drivers among the chips is achieved by allowing rearrangements of existing connections when a new connection is made. We consider one-sided crosspoint networks with N = rn ports constructed from individual switching chips of size n x m /2. When all the N ports are active, the lower bound on the number of active drivers in a chip is m r. We show that this lower bound can be achieved in practice when m/r is an even number. The maximum number of rearrangements needed is min (m /2 — 1, 2r — 1). In addition, the rearrangements are confined to two chip-columns of the matrix. A graph model is used to determine the number and location of rearrangements. We also show an allocation scheme based on a simplified graph model that achieves a 50% reduction in the maximum number of active drivers per chip as compared to a random allocation strategy. A maximum of three rearrangements are sufficient to obtain this reduction. © 1990 IEEE