5,230 research outputs found
A New Outer Bound and the Noisy-Interference Sum-Rate Capacity for Gaussian Interference Channels
A new outer bound on the capacity region of Gaussian interference channels is
developed. The bound combines and improves existing genie-aided methods and is
shown to give the sum-rate capacity for noisy interference as defined in this
paper. Specifically, it is shown that if the channel coefficients and power
constraints satisfy a simple condition then single-user detection at each
receiver is sum-rate optimal, i.e., treating the interference as noise incurs
no loss in performance. This is the first concrete (finite signal-to-noise
ratio) capacity result for the Gaussian interference channel with weak to
moderate interference. Furthermore, for certain mixed (weak and strong)
interference scenarios, the new outer bounds give a corner point of the
capacity region.Comment: 20 pages, 8 figures, submitted to IEEE Trans. Inform. Theory
Capacity Results for Interference Networks and Nested Cut-Set Bound
In this thesis, a full characterization of the sum-rate capacity for degraded interference networks with any number of transmitters, any number of receivers, and any possible distribution of messages among transmitters and receivers is established. It is proved that a successive decoding scheme is sum-rate optimal for these networks. Moreover, it is shown that the transmission of only a certain subset of messages is sufficient to achieve the sum-rate capacity for such networks. Algorithms are presented to determine this subset of messages explicitly. The sum-rate expression for the degraded networks is then used to derive a unified outer bound on the sum-rate capacity of arbitrary (non-degraded) interference networks. Several variations of degraded networks are identified for which the derived outer bound is sum-rate optimal. Specifically, noisy interference regimes are derived for certain classes of multi-user/multi-message large interference networks. Also, network scenarios are identified where the incorporation of both successive decoding and treating interference as noise achieves their sum-rate capacity.
Next, by taking insight from the results for degraded networks, an extension to the standard cut-set bound for general communication networks is presented which is referred to as nested cut-set bound. This bound is derived by applying a series of cuts in a nested configuration to the network first and then bounding the information rate that flows through the cuts. The key idea for bounding step is indeed to impose a degraded arrangement among the receivers corresponding to the cuts. Therefore, the bound is in fact a generalization of the outer bound for interference networks: here cooperative relaying nodes are introduced into the problem as well but the proof style for the derivation of the outer bound remains the same. The nested cut-set bound, which uniformly holds for all general communication networks of arbitrary large sizes where any subset of nodes may cooperatively communicate to any other subset of them, is indeed tighter than the cut-set bound for networks with more than one receiver. Moreover, it includes the generalized cut-set bound for deterministic networks reported by Shomorony and Avestimehr which was originally a special case of the outer bound established for the interference networks by the author (2012).
Finally, capacity bounds for the two-user interference channel with cooperative receivers via conferencing links of finite capacities are investigated. The capacity results known for this communication scenario are limited to a very few special cases of the one-sided channel. One of the major challenges in analyzing such cooperative networks is how to establish efficient capacity outer
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bounds for them. In this thesis, by applying new techniques, novel capacity outer bounds are presented for the interference channels with conferencing users. Using the outer bounds, several new capacity results are proved for interesting channels with unidirectional cooperation in strong and mixed interference regimes. A fact is that the conferencing link (between receivers) may be utilized to provide one receiver with information about its corresponding signal or its non-corresponding signal (interference signal). As an interesting consequence, it is demonstrated that both strategies can be helpful to achieve the capacity of the channel. Lastly, for the case of Gaussian interference channel with conferencing receivers, it is argued that our outer bound is strictly tighter than the previous one derived by Wang and Tse
On the High-SNR Capacity of the Gaussian Interference Channel and New Capacity Bounds
The best outer bound on the capacity region of the two-user Gaussian
Interference Channel (GIC) is known to be the intersection of regions of
various bounds including genie-aided outer bounds, in which a genie provides
noisy input signals to the intended receiver. The Han and Kobayashi (HK) scheme
provides the best known inner bound. The rate difference between the best known
lower and upper bounds on the sum capacity remains as large as 1 bit per
channel use especially around , where is the symmetric power
constraint and is the symmetric real cross-channel coefficient. In this
paper, we pay attention to the \emph{moderate interference regime} where
. We propose a new upper-bounding technique
that utilizes noisy observation of interfering signals as genie signals and
applies time sharing to the genie signals at the receivers. A conditional
version of the worst additive noise lemma is also introduced to derive new
capacity bounds. The resulting upper (outer) bounds on the sum capacity
(capacity region) are shown to be tighter than the existing bounds in a certain
range of the moderate interference regime. Using the new upper bounds and the
HK lower bound, we show that characterizes the capacity of the symmetric real
GIC to within bit per channel use in the moderate interference regime
at any signal-to-noise ratio (SNR). We further establish a high-SNR
characterization of the symmetric real GIC, where the proposed upper bound is
at most bit far from a certain HK achievable scheme with Gaussian
signaling and time sharing for . In particular,
is achievable at high SNR by the proposed HK scheme and turns out to be the
high-SNR capacity at least at .Comment: Submitted to IEEE Transactions on Information Theory on June 2015,
revised on November 2016, and accepted for publication on Feb. 28, 201
Capacity Regions and Sum-Rate Capacities of Vector Gaussian Interference Channels
The capacity regions of vector, or multiple-input multiple-output, Gaussian
interference channels are established for very strong interference and aligned
strong interference. Furthermore, the sum-rate capacities are established for Z
interference, noisy interference, and mixed (aligned weak/intermediate and
aligned strong) interference. These results generalize known results for scalar
Gaussian interference channels.Comment: 33 pages, 1 figure, submitted to IEEE trans. on Information theor
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