# Séminaires ICI : Giulia Cervia, Alexandre Marcastel, Ligong Wang

## Date et lieu des séminaires

Jeudi 8 septembre 2016, 10h.

ENSEA, salle 384

## Polar coding for empirical coordination of signals and actions over noisy channels

Giulia Cervia, PhD student, ETIS, ICI

Abstract: We develop a polar coding scheme for empirical coordination in a two-node network with a noisy link in which the input and output signals have to be coordinated with the source and the reconstruction. In the case of non-causal encoding and decoding, we show that polar codes achieve the best known inner bound for the empirical coordination region, provided that a vanishing rate of common randomness is available. This scheme provides a constructive alternative to random binning and coding proofs.

## Online Power Allocation for Opportunistic Radio Access in Dynamic OFDM Networks

Alexandre Marcastel, PhD student, ETIS, ICI

Abstract: User mobility has become a key attribute in the design of optimal resource allocation policies for future wireless networks. This has become increasingly apparent in cognitive radio (CR) systems where the licensed, primary users (PUs) of the network must be protected from harmful interference by the network’s opportunistic, secondary users (SUs): here, unpre-dictability due to mobility requires the implementation of safety net mechanisms that are provably capable of adapting to changes in the users’ wireless environment. In this context, we propose a distributed learning algorithm that allows SUs to adjust their power allocation profile (over the available frequency carriers) “on the fly”, relying only on strictly causal channel state information. To account for the interference caused to the network’s PUs, we incorporate a penalty function in the rate-driven objectives of the SUs, and we show that the proposed scheme matches asymptoti-cally the performance of the best fixed power allocation policy in hindsight. Specifically, in a system with S orthogonal subcarriers and transmission horizon T , this performance gap (known as the algorithm’s average regret) is bounded from above as O( log(S)/T ). We also validate our theoretical analysis with numerical simulations which confirm that the network’s SUs rapidly achieve a “no-regret” state under realistic wireless cellular conditions. Moreover, by finetuning the choice of penalty function, the interference induced by the SUs can be kept at a sufficiently low level, thus guaranteeing the PUs’ requirements.

## Optimal Throughput for Covert Communication over Classical-Quantum Channels

Ligong Wang, Researcher, ETIS, ICI

Abstract: This paper considers the problem of communication over a memoryless classical-quantum wiretap channel subject to the constraint that the eavesdropper on the channel should not be able to learn with high confidence whether the legitimate parties are using the channel to communicate or not. Specifically, the relative entropy between the output quantum states at the eavesdropper when a codeword is transmitted and when no input is provided must be sufficiently small. Extending earlier works, this paper proves the “square-root law” for a broad class of classical-quantum channels: the maximum amount of information that can be reliably and covertly transmitted over $n$ uses of such a channel scales like $\sqrt{n}$. The scaling constant is also determined.

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