77 research outputs found
Degraded Broadcast Diamond Channels with Non-Causal State Information at the Source
A state-dependent degraded broadcast diamond channel is studied where the
source-to-relays cut is modeled with two noiseless, finite-capacity digital
links with a degraded broadcasting structure, while the relays-to-destination
cut is a general multiple access channel controlled by a random state. It is
assumed that the source has non-causal channel state information and the relays
have no state information. Under this model, first, the capacity is
characterized for the case where the destination has state information, i.e.,
has access to the state sequence. It is demonstrated that in this case, a joint
message and state transmission scheme via binning is optimal. Next, the case
where the destination does not have state information, i.e., the case with
state information at the source only, is considered. For this scenario, lower
and upper bounds on the capacity are derived for the general discrete
memoryless model. Achievable rates are then computed for the case in which the
relays-to-destination cut is affected by an additive Gaussian state. Numerical
results are provided that illuminate the performance advantages that can be
accrued by leveraging non-causal state information at the source.Comment: Submitted to IEEE Transactions on Information Theory, Feb. 201
Clean relaying aided cognitive radio under the coexistence constraint
We consider the interference-mitigation based cognitive radio where the
primary and secondary users can coexist at the same time and frequency bands,
under the constraint that the rate of the primary user (PU) must remain the
same with a single-user decoder. To meet such a coexistence constraint, the
relaying from the secondary user (SU) can help the PU's transmission under the
interference from the SU. However, the relayed signal in the known dirty paper
coding (DPC) based scheme is interfered by the SU's signal, and is not "clean".
In this paper, under the half-duplex constraints, we propose two new
transmission schemes aided by the clean relaying from the SU's transmitter and
receiver without interference from the SU. We name them as the clean
transmitter relaying (CT) and clean transmitter-receiver relaying (CTR) aided
cognitive radio, respectively. The rate and multiplexing gain performances of
CT and CTR in fading channels with various availabilities of the channel state
information at the transmitters (CSIT) are studied. Our CT generalizes the
celebrated DPC based scheme proposed previously. With full CSIT, the
multiplexing gain of the CTR is proved to be better (or no less) than that of
the previous DPC based schemes. This is because the silent period for decoding
the PU's messages for the DPC may not be necessary in the CTR. With only the
statistics of CSIT, we further prove that the CTR outperforms the rate
performance of the previous scheme in fast Rayleigh fading channels. The
numerical examples also show that in a large class of channels, the proposed CT
and CTR provide significant rate gains over the previous scheme with small
complexity penalties.Comment: 30 page
On the Multiple Access Channel with Asymmetric Noisy State Information at the Encoders
We consider the problem of reliable communication over multiple-access
channels (MAC) where the channel is driven by an independent and identically
distributed state process and the encoders and the decoder are provided with
various degrees of asymmetric noisy channel state information (CSI). For the
case where the encoders observe causal, asymmetric noisy CSI and the decoder
observes complete CSI, we provide inner and outer bounds to the capacity
region, which are tight for the sum-rate capacity. We then observe that, under
a Markov assumption, similar capacity results also hold in the case where the
receiver observes noisy CSI. Furthermore, we provide a single letter
characterization for the capacity region when the CSI at the encoders are
asymmetric deterministic functions of the CSI at the decoder and the encoders
have non-causal noisy CSI (its causal version is recently solved in
\cite{como-yuksel}). When the encoders observe asymmetric noisy CSI with
asymmetric delays and the decoder observes complete CSI, we provide a single
letter characterization for the capacity region. Finally, we consider a
cooperative scenario with common and private messages, with asymmetric noisy
CSI at the encoders and complete CSI at the decoder. We provide a single letter
expression for the capacity region for such channels. For the cooperative
scenario, we also note that as soon as the common message encoder does not have
access to CSI, then in any noisy setup, covering the cases where no CSI or
noisy CSI at the decoder, it is possible to obtain a single letter
characterization for the capacity region. The main component in these results
is a generalization of a converse coding approach, recently introduced in [1]
for the MAC with asymmetric quantized CSI at the encoders and herein
considerably extended and adapted for the noisy CSI setup.Comment: Submitted to the IEEE Transactions on Information Theor
D11.2 Consolidated results on the performance limits of wireless communications
Deliverable D11.2 del projecte europeu NEWCOM#The report presents the Intermediate Results of N# JRAs on Performance Limits of Wireless Communications and highlights the fundamental issues that have been investigated by the WP1.1. The report illustrates the Joint Research Activities (JRAs) already identified during the first year of the project which are currently ongoing. For each activity there is a description, an illustration of the adherence and relevance with the identified fundamental open issues, a short presentation of the preliminary results, and a roadmap for the joint research work in the next year. Appendices for each JRA give technical details on the scientific activity in each JRA.Peer ReviewedPreprin
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