A New Lower Bound on the Maximal Error Probability for Discrete Memoryless Multiple-Access Channels

In this paper, a new lower bound for the maximal error probability of a two-user Discrete Memory-less (DM) Multiple-Access Channel (MAC) is derived. This is the first bound of this type that explicitly imposes independence of the users' input distributions (conditioned on the time-sharing auxiliary variable) and thus results in a tighter sphere-packing exponent when compared to the tightest known exponent derived by Haroutunian. An interesting problem in network information theory is to determine the minimum probability of error which can be achieved on a Discrete Memory-less (DM), Multiple-Access Channel (MAC).