I. Introduction
Protocol sequences for a multiple-access channel (collision channel) without feedback have been investigated by several researchers [3], [4], [6], [5], [8], [10]. In such a multiple-access channel model (see [1] and [7]), the time axis is partitioned into slots whose duration corresponds to the transmission time for one packet and all users are supposed to have slot synchronization, but no other synchronization is assumed. In a particular slot, if none of the users is sending a packet (in which case it is said that each user “sends” the silence symbol), then the channel output in that slot is the silence symbol. If exactly one user is sending a packet in a particular slot, then the packet is transmitted successfully and the channel output in that slot is this packet value in GF for some, in general large, . If more than one users are sending packets in a particular slot simultaneously, then there is a conflict and the channel output in that slot is the collision symbol.