42,669 research outputs found
On the Capacity Region of the Deterministic Y-Channel with Common and Private Messages
In multi user Gaussian relay networks, it is desirable to transmit private
information to each user as well as common information to all of them. However,
the capacity region of such networks with both kinds of information is not easy
to characterize. The prior art used simple linear deterministic models in order
to approximate the capacities of these Gaussian networks. This paper discusses
the capacity region of the deterministic Y-channel with private and common
messages. In this channel, each user aims at delivering two private messages to
the other two users in addition to a common message directed towards both of
them. As there is no direct link between the users, all messages must pass
through an intermediate relay. We present outer-bounds on the rate region using
genie aided and cut-set bounds. Then, we develop a greedy scheme to define an
achievable region and show that at a certain number of levels at the relay, our
achievable region coincides with the upper bound. Finally, we argue that these
bounds for this setup are not sufficient to characterize the capacity region.Comment: 4 figures, 7 page
Capacity of All Nine Models of Channel Output Feedback for the Two-user Interference Channel
In this paper, we study the impact of different channel output feedback
architectures on the capacity of the two-user interference channel. For a
two-user interference channel, a feedback link can exist between receivers and
transmitters in 9 canonical architectures (see Fig. 2), ranging from only one
feedback link to four feedback links. We derive the exact capacity region for
the symmetric deterministic interference channel and the constant-gap capacity
region for the symmetric Gaussian interference channel for all of the 9
architectures. We show that for a linear deterministic symmetric interference
channel, in the weak interference regime, all models of feedback, except the
one, which has only one of the receivers feeding back to its own transmitter,
have the identical capacity region. When only one of the receivers feeds back
to its own transmitter, the capacity region is a strict subset of the capacity
region of the rest of the feedback models in the weak interference regime.
However, the sum-capacity of all feedback models is identical in the weak
interference regime. Moreover, in the strong interference regime all models of
feedback with at least one of the receivers feeding back to its own transmitter
have the identical sum-capacity. For the Gaussian interference channel, the
results of the linear deterministic model follow, where capacity is replaced
with approximate capacity.Comment: submitted to IEEE Transactions on Information Theory, results
improved by deriving capacity region of all 9 canonical feedback models in
two-user interference channe
A digital interface for Gaussian relay and interference networks: Lifting codes from the discrete superposition model
For every Gaussian network, there exists a corresponding deterministic
network called the discrete superposition network. We show that this discrete
superposition network provides a near-optimal digital interface for operating a
class consisting of many Gaussian networks in the sense that any code for the
discrete superposition network can be naturally lifted to a corresponding code
for the Gaussian network, while achieving a rate that is no more than a
constant number of bits lesser than the rate it achieves for the discrete
superposition network. This constant depends only on the number of nodes in the
network and not on the channel gains or SNR. Moreover the capacities of the two
networks are within a constant of each other, again independent of channel
gains and SNR. We show that the class of Gaussian networks for which this
interface property holds includes relay networks with a single
source-destination pair, interference networks, multicast networks, and the
counterparts of these networks with multiple transmit and receive antennas.
The code for the Gaussian relay network can be obtained from any code for the
discrete superposition network simply by pruning it. This lifting scheme
establishes that the superposition model can indeed potentially serve as a
strong surrogate for designing codes for Gaussian relay networks.
We present similar results for the K x K Gaussian interference network, MIMO
Gaussian interference networks, MIMO Gaussian relay networks, and multicast
networks, with the constant gap depending additionally on the number of
antennas in case of MIMO networks.Comment: Final versio
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