A New Sum-Rate Outer Bound for Interference Channels with Three   Source-Destination Pairs
  This paper derives a novel sum-rate outer bound for the general memoryless interference channel with three users. The derivation is a generalization of the techniques developed by Kramer and by Etkin et al for the Gaussian two-user channel. For the three-user Gaussian channel the proposed sum-rate outer bound outperforms known bounds for certain channel parameters. 
Daniela Tuninetti
cs.IT math.IT