TRANSFORMATIONS ON CHANNEL GRAPHS

A channel graph is a directed acyclic graph with a unique source verte x and a unique sink vertex, in which all edges are partitioned into st ages according to their distance from the source. Edges cannot vertice s in consecutive stages only. The blocking probability of a channel gr aph is the probability that every source to sink path is blocked. A ge neral transformation is developed that never decreses the blocking pro bability. This transformation leads to a short proof of a generalizati on of a theorem of Takagi, and a theorem of Chung and Hwang, in the ca se of the binomial model.