One of the key open problems in network information theory is to obtain the
capacity region for the two-user Interference Channel (IC). In this paper, new
results are derived for this channel. As a first result, a noisy interference
regime is given for the general IC where the sum-rate capacity is achieved by
treating interference as noise at the receivers. To obtain this result, a
single-letter outer bound in terms of some auxiliary random variables is first
established for the sum-rate capacity of the general IC and then those
conditions under which this outer bound is reduced to the achievable sum-rate
given by the simple treating interference as noise strategy are specified. The
main benefit of this approach is that it is applicable for any two-user IC
(potentially non-Gaussian). For the special case of Gaussian channel, our
result is reduced to the noisy interference regime that was previously
obtained. Next, some results are given on the Han-Kobayashi (HK) achievable
rate region. The evaluation of this rate region is in general difficult. In
this paper, a simple characterization of the HK rate region is derived for some
special cases, specifically, for a novel very weak interference regime. As a
remarkable characteristic, it is shown that for this very weak interference
regime, the achievable sum-rate due to the HK region is identical to the one
given by the simple treating interference as noise strategy.Comment: 12 pages. In this paper a noisy interference regime is identified for
any two-user interference channel (potentially non-Gaussian). For conference
publicatio