  In this work, we derive achievable rate regions for the three-user
interference channels with asymmetric transmitter cooperation and various
decoding capabilities at the receivers. The three-user channel facilitates
different ways of message sharing between the transmitters. We introduce two
natural ways of extending the concept of unidirectional message sharing from
two users to three users - (i) cumulative message sharing and (ii) primary-only
message sharing. In addition, we define several cognitive interference channels
based on the decoding capability of the receivers. We employ a coding
technique, which is a combination of superposition and Gel'fand-Pinsker coding
techniques, to derive an achievable rate region for each of the cognitive
interference channels. Simulation results, by considering the Gaussian channel
case, enables a visual comparison of the two message-sharing schemes considered
in this paper. It also provides useful insights into the effect of
message-splitting at the transmitters and the decoding capability of the
receivers on the achievable rates.
