  This paper presents the achievable rate region frontiers for the n-user
interference channel when there is no cooperation at the transmit nor at the
receive side. The receiver is assumed to treat the interference as additive
thermal noise and does not employ multiuser detection. In this case, the rate
region frontier for the n-user interference channel is found to be the union of
n hyper-surface frontiers of dimension n-1, where each is characterized by
having one of the transmitters transmitting at full power. The paper also finds
the conditions determining the convexity or concavity of the frontiers for the
case of two-user interference channel, and discusses when a time sharing
approach should be employed with specific results pertaining to the two-user
symmetric channel.
