54,266 research outputs found
State of the cognitive interference channel: a new unified inner bound
The capacity region of the interference channel in which one transmitter
non-causally knows the message of the other, termed the cognitive interference
channel, has remained open since its inception in 2005. A number of subtly
differing achievable rate regions and outer bounds have been derived, some of
which are tight under specific conditions. In this work we present a new
unified inner bound for the discrete memoryless cognitive interference channel.
We show explicitly how it encompasses all known discrete memoryless achievable
rate regions as special cases. The presented achievable region was recently
used in deriving the capacity region of the general deterministic cognitive
interference channel, and thus also the linear high-SNR deterministic
approximation of the Gaussian cognitive interference channel. The high-SNR
deterministic approximation was then used to obtain the capacity of the
Gaussian cognitive interference channel to within 1.87 bits.Comment: Presented at the 2010 International Zurich Seminar on Communications
- an 2nd updated version
On the Capacity Region of the Two-User Interference Channel
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
Achievable and Crystallized Rate Regions of the Interference Channel with Interference as Noise
The interference channel achievable rate region is presented when the
interference is treated as noise. The formulation starts with the 2-user
channel, and then extends the results to the n-user case. The rate region is
found to be the convex hull of the union of n power control rate regions, where
each power control rate region is upperbounded by a (n-1)-dimensional
hyper-surface characterized by having one of the transmitters transmitting at
full power. The convex hull operation lends itself to a time-sharing operation
depending on the convexity behavior of those hyper-surfaces. In order to know
when to use time-sharing rather than power control, the paper studies the
hyper-surfaces convexity behavior in details for the 2-user channel with
specific results pertaining to the symmetric channel. It is observed that most
of the achievable rate region can be covered by using simple On/Off binary
power control in conjunction with time-sharing. The binary power control
creates several corner points in the n-dimensional space. The crystallized rate
region, named after its resulting crystal shape, is hence presented as the
time-sharing convex hull imposed onto those corner points; thereby offering a
viable new perspective of looking at the achievable rate region of the
interference channel.Comment: 28 pages, 12 figures, to appear in IEEE Transactions of Wireless
Communicatio
Lattice Codes for Many-to-One Interference Channels With and Without Cognitive Messages
A new achievable rate region is given for the Gaussian cognitive many-to-one
interference channel. The proposed novel coding scheme is based on the
compute-and-forward approach with lattice codes. Using the idea of decoding
sums of codewords, our scheme improves considerably upon the conventional
coding schemes which treat interference as noise or decode messages
simultaneously. Our strategy also extends directly to the usual many-to-one
interference channels without cognitive messages. Comparing to the usual
compute-and-forward scheme where a fixed lattice is used for the code
construction, the novel scheme employs scaled lattices and also encompasses key
ingredients of the existing schemes for the cognitive interference channel.
With this new component, our scheme achieves a larger rate region in general.
For some symmetric channel settings, new constant gap or capacity results are
established, which are independent of the number of users in the system.Comment: To appear in IEEE Transactions on Information Theor
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