7,169 research outputs found
Incremental Relaying for the Gaussian Interference Channel with a Degraded Broadcasting Relay
This paper studies incremental relay strategies for a two-user Gaussian
relay-interference channel with an in-band-reception and
out-of-band-transmission relay, where the link between the relay and the two
receivers is modelled as a degraded broadcast channel. It is shown that
generalized hash-and-forward (GHF) can achieve the capacity region of this
channel to within a constant number of bits in a certain weak relay regime,
where the transmitter-to-relay link gains are not unboundedly stronger than the
interference links between the transmitters and the receivers. The GHF relaying
strategy is ideally suited for the broadcasting relay because it can be
implemented in an incremental fashion, i.e., the relay message to one receiver
is a degraded version of the message to the other receiver. A
generalized-degree-of-freedom (GDoF) analysis in the high signal-to-noise ratio
(SNR) regime reveals that in the symmetric channel setting, each common relay
bit can improve the sum rate roughly by either one bit or two bits
asymptotically depending on the operating regime, and the rate gain can be
interpreted as coming solely from the improvement of the common message rates,
or alternatively in the very weak interference regime as solely coming from the
rate improvement of the private messages. Further, this paper studies an
asymmetric case in which the relay has only a single single link to one of the
destinations. It is shown that with only one relay-destination link, the
approximate capacity region can be established for a larger regime of channel
parameters. Further, from a GDoF point of view, the sum-capacity gain due to
the relay can now be thought as coming from either signal relaying only, or
interference forwarding only.Comment: To appear in IEEE Trans. on Inf. Theor
On the Corner Points of the Capacity Region of a Two-User Gaussian Interference Channel
This work considers the corner points of the capacity region of a two-user
Gaussian interference channel (GIC). In a two-user GIC, the rate pairs where
one user transmits its data at the single-user capacity (without interference),
and the other at the largest rate for which reliable communication is still
possible are called corner points. This paper relies on existing outer bounds
on the capacity region of a two-user GIC that are used to derive informative
bounds on the corner points of the capacity region. The new bounds refer to a
weak two-user GIC (i.e., when both cross-link gains in standard form are
positive and below 1), and a refinement of these bounds is obtained for the
case where the transmission rate of one user is within of the
single-user capacity. The bounds on the corner points are asymptotically tight
as the transmitted powers tend to infinity, and they are also useful for the
case of moderate SNR and INR. Upper and lower bounds on the gap (denoted by
) between the sum-rate and the maximal achievable total rate at the two
corner points are derived. This is followed by an asymptotic analysis analogous
to the study of the generalized degrees of freedom (where the SNR and INR
scalings are coupled such that ), leading to an asymptotic characterization of this gap which is
exact for the whole range of . The upper and lower bounds on
are asymptotically tight in the sense that they achieve the exact asymptotic
characterization. Improved bounds on are derived for finite SNR and
INR, and their improved tightness is exemplified numerically.Comment: Submitted to the IEEE Trans. on Information Theory in July 17, 2014,
and revised in April 5, 2015. Presented in part at Allerton 2013, and also
presented in part with improved results at ISIT 201
- …