We consider the problem of assigning a numerical channel to each transmitter in a large regular array such that multiple levels of interference, which depend on the distance between transmitters, are avoided by sufficiently separating the channels. The goal is to find assignments that minimize the span of the labels used. A previous paper of the authors introduced a model for this problem using real number labellings of (possibly infinite) graphs G. Given reals k1, k2, . . . , kp 0, one denotes by (G; k1, k2,
Jerrold R. Griggs, Xiaohua Teresa Jin