An outer bound region for the parallel two-way channel with interference

The classical interference channel models the communication limits of two independent, interfering streams of one-way data. In this paper we extend the classical interference channel model to a new channel model in which two streams of two-way data interfere with each other. In the absence of interference, this model would result in two parallel two-way channels (a four node channel); in the presence of interference it encompasses two-way, interference, and cooperation tradeoffs. The discrete memoryless “parallel two-way channel with interference” is considered, in which each of the four nodes is the source of one message, the receiver of another, and experiences interference from yet another transmitter. The nodes may adapt their transmissions to the past received signals in a fully two-way fashion. We present an outer bound to the four dimensional capacity region which utilizes four auxiliary random variables to constrain the input distributions, and present a looser outer bound with a single auxiliary random variable which is computable as we place bounds on this variables alphabet size.