Rooted level-disjoint partitions of Cartesian products

In interconnection networks one often needs to broadcast multiple messages in parallel from a single source so that the load at each node is minimal. With this motivation we study a new concept of rooted level-disjoint partitions of graphs. In particular, we develop a general construction of level-disjoint partitions for Cartesian products of graphs that is efficient both in the number of level partitions as in the maximal height. As an example, we show that the hypercube Q n   for every dimension n=3·i2n=3·2i or n=4·i2n=4·2i where i ≥ 0 has n   level-disjoint partitions with the same root and with maximal height 3n−23n−2. Both the number of such partitions and the maximal height are optimal. Moreover, we conjecture that this holds for any n ≥ 3.