May Updates

(1) A joint paper with Jean-Marie Gorce and Leonardo Cardoso on spectrum scanning for cognitive radio has been accepted:

Egan, M., Gorce, J.-M. and Cardoso, L., “Fast initialization of cognitive radio systems”, accepted in IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2017.

You can now find it on HAL.

(2) I will present in the POLARIS seminar at INRIA Grenoble on the 22nd June. Details are below.

Title: Mechanism design in on-demand transport

Abstract: Uber is one of several recent companies adopting a business model that lies in stark contrast with the standard approach used by taxi services. Underlying Uber’s business model is a new architecture–based on a market mechanism–which governs how commuters, drivers, and the company interact with each other. In this talk, we develop a new general model for on-demand transport networks with self-interested passengers and drivers. With this model, we introduce market mechanisms to allocate and price journeys, as well as the market formation subproblem. By analysis and simulation, we characterize the performance of the mechanisms and discuss insights using data obtained from a real on-demand transport provider.

(3) On Wednesday 24th May, I will be attending the GDR ISIS meeting on “Entropies, divergences et mesures informationnelles classiques et généralisées” in Paris.

(4) Mauro de Freitas from Université Lille 1 has been visiting me in Lyon from the 12th to 18th May. He presented some of our joint work on impulsive noise in communications. Here are the details:

Title: Wireless Networks in Dynamic Interference

Abstract: This work is motivated by the Internet of Things, where devices can transmit for very short periods of time. A consequence is that interference is dynamic; that is, the active transmitter set can change very rapidly. In this case, the Gaussian interference model may not be the most appropriate. In fact, dynamic interference can be better modeled by impulsive interference, particularly alpha-stable noise. In this talk, we characterize the capacity in the presence of alpha-stable noise via upper and lower bounds, and consider the behavior in medium interference regimes. This analysis reveals many similarities with the well understood Gaussian case, such as outage probability characterizations and power control in parallel channels.

April Updates

Some news:

(1) A new paper on capacity bounds for the symmetric alpha-stable noise channel is to appear in IEEE Transactions on Information Theory:

Mauro de Freitas, Malcolm Egan, Laurent Clavier, Alban Goupil, Gareth Peters and Nourddine Azzaoui, “Capacity bounds for additive symmetric alpha-stable noise channels,” to appear in IEEE Transactions on Information Theory.

(2) A new paper on molecular communication in the presence of anomalous diffusion is to appear in IEEE Communication Letters:

Trang C. Mai, Malcolm Egan, Trung Q. Duong and Marco di Renzo, “Event detection in molecular communication networks with anomalous diffusion,” to appear in IEEE Communication Letters.

(3) A new paper on capacity sensitivity in non-Gaussian noise channels is to appear in IEEE International Symposium on Information Theory:

Malcolm Egan, Samir M. Perlaza and Vyacheslave Kungurtsev, “Capacity Sensitivity in Additive Non-Gaussian Noise Channels,” to appear in IEEE International Symposium on Information Theory 2017.

An extended version of this work can be found in the INRIA report here.


Some news:

1. I have finished my contract in the Laboratoire de Mathématiques at Université Blaise Pascal in Clermont-Ferrand and will begin a new position in Département Télécommunications INSA Lyon in the middle of November working with Jean-Marie Gorce and Leonardo Cardoso.

2. With Gareth Peters, Ido Nevat, Mahyar Shirvanimoghaddam and Iain B. Collings, I have a new paper accepted:

Malcolm Egan, Gareth W. Peters, Ido Nevat, Mahyar Shirvanimoghaddam and Iain B. Collings, “A ruin theoretic design approach for wireless cellular network sharing with facilities”, to appear in Transactions on Emerging Telecommunications Technologies.

This paper concerns network sharing in facilities, which I have been discussing here and here.

3. With Andrea Tassi, Robert Piechocki and Andy Nix, I have a new paper accepted in SigTelCom2017:

Andrea Tassi, Malcolm Egan, Robert J. Piechocki and Andrew Nix, “Wireless vehicular networks in emergencies: a single frequency network approach”, in Proc. SigTelCom2017, to appear.

In related news, last week I was in Prague and presented some related work with Andrea, Robert and Andrew on mmWave communications for vehicular networks. The talk was targeted at the computer scientists working on multi-agent coordination algorithms for intelligent transport systems in the Artificial Intelligence Center in the Czech Technical University in Prague.

4. In December, I will be presenting at the CFE-CMStatistics Conference in Seville Spain. My talk is entitled: Simulation of a general class of alpha-stable processes, which is based on work with Nourddine Azzaoui, Gareth Peters and Arnaud Guillin. Here is the abstract:

The heavy-tail and extremal dependence properties of \alpha-stable processes have lead to their extensive use in fields ranging from finance to engineering. In these fields, the stochastic integral representation plays an important role both in characterizing \alpha-stable processes as well as for the purposes of simulation and parameter estimation. In order use the stochastic integral representation, constraints on the random measure must be imposed. A key constraint is the independently scattered condition, where disjoint increments of the random measure are independent. A key feature of the independently scattered condition is that the covariation is both left and right additive, which allows for simulation and estimation of this class of processes. Recently, a new generalization of the independently scattered condition has been introduced, which also preserves the left and right additivity of the covariation. This new generalization allows the characteristic function a wide class of \alpha-stable processes to be determined by a bimeasure. We deal with the problem of simulating from the bimeasure characterization of \alpha-stable processes. In particular, we prove conditions under which the bimeasure leads to a positive definite characteristic function for the case of a two-dimensional skeleton. Based on this result, we then propose a method to construct and simulate n-dimensional skeletons, for arbitrary n > 2.

Network sharing and the probability of ruin

There is now increasing interest in network sharing to support wireless communications, where the main focus is on how operators should get access to the scarce spectrum (at least in the radio bands). A more general question is how different parties can provide different components of the network. Although spectrum is one component, the physical transmitting devices and the backhaul are also key components.

In a previous post, I discussed some different ways that infrastructure can be owned by different parties, especially in the setting where users are in a facility (e.g., mine, power plant or large residential area). I briefly mentioned the need for new evaluation metrics in order to optimize network sharing agreements and it is this aspect I want to explore further in this post. In particular, I will introduce the notion of the probability of ruin.

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Gaussian noise channels at medium SNR

Shannon’s noisy channel coding theorem tells us that the capacity is the maximum rate we can transmit information reliably over a noisy channel in the class of memoryless channels. In general, computing the capacity is a difficult problem. As such, there has been extensive work on asymptotics.

In the case of the additive Gaussian noise channel, the capacity is well known. However, it is still interesting to characterize the behavior of the asymptotes (as the SNR tends to zero or infinity) for use in proofs or to provide simple design guidelines for real-world communication systems.

Despite the work on asymptotes, it is more difficult to characterize the behavior at medium SNR without using the exact expression for the capacity.

In this post, I look at the medium behavior of the Gaussian noise channel. It turns out the SNR of 0 decibels is particularly special and suggests a way of obtaining simple capacity approximations at medium SNR for general classes of additive noise channels.

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Data-Driven Market Formation in On-Demand Transport

As on-demand transport providers (e.g., Uber) are adopting increasingly sophisticated mechanisms to allocate and price both passengers and drivers, new issues are arising. In a series of posts (starting here), I have been describing different aspects of these issues including the ways to allocate and price (the mechanism design) and also simulation tools to evaluate performance in realistic environments (capturing both the road network and the behavior of passengers and drivers).

In this post, I want to turn to a different aspect: the market formation problem.

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How much does the PHY layer matter?

In wireless communications, a recurring question is whether or not the PHY layer is dead (there was even a paper with this title in 2011). While it is my view that it isn’t (there are still interesting open questions related to, for instance, impulsive noise and also vehicular communications), there are what in all probability are more pressing questions: when and how much does the PHY layer matter?

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Analyzing the effect of side information: a perturbative approach

Quite often we need to make decisions. These decisions will typically depend on some information that we have obtained, either through direct observation or because it has been communicated to us by someone (or something) else. This side information is not usually perfect. For example, our measurements will not be without error and information communicated to us will be subject to imperfections in the communication medium.

How can we understand the effect of imperfect side information on our decisions?

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