Electrical and Information Technology

Faculty of Engineering, LTH

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Lic. Seminar: Improving Throughput and Minimising Age of Information in dense WLANs, Using Cooperative Techniques by Antonio Franco


From: 2018-08-22 13:00
Place: E:3139
Contact: anne [dot] andersson [at] eit [dot] lth [dot] se
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Title: Improving Throughput and Minimising Age of Information in dense WLANs, Using Cooperative Techniques

Presenter: Antonio Franco - see

Reviewer: Professor Markus Fiedler, Blekinge Institute of Technology (BTH)

Supervisor: Professor Björn Landfeldt, EIT

Examiner: Universitetslektor Erik Larsson, EIT


Mobile and wireless data are in increasing demand worldwide. New trends such the Internet of Things paradigm and the Smart City paradigm describe scenarios comprising thousands of devices all exchanging informations between each others wirelessly — or through the WAN to another device, possibly connected to another WLAN. Operators and radio engineers are faced with the problem of designing efficient ways to share the electromagnetic spectrum — a scarce and expensive resource — between thousands of devices.

In this context, operators look at the unlicensed spectrum as possible solu- tion to complement the existing infrastructure. Unfortunately, the IEEE 802.11 MAC family, the most widespread MAC protocol in the unlicensed portion of the spectrum, still suffers when managing a large number of interconnected devices. In this thesis we are both addressing the open problems in the IEEE 802.11 MAC scheme and our contributions on their solution. 
Specifically, in the first part of the thesis we are going to present the IEEE 802.11 MAC scheme and the challenges it faces, along with solutions already present in literature. We are also going to show a new metric recently defined in literature called the Age of Information (AoI). This new metric is a measure how fresh is the piece of information stored in a remote receiver. It received interest in the literature, but little is known how it behaves in a IEEE 802.11 WLAN.
In the second part of the thesis we present two papers that try to address the problem of designing new protocols that let the devices cooperate in order to achieve a common goal. They specifically focus on two metrics. The first paper addresses throughput and collisions reduction through a new MAC scheme that uses RSSI to identify other devices in a WLAN, and uses a priority base access system in order to cooperate in turns with them. We show, through simulation, that this scheme outperforms the classical IEEE 802.11 DCF mode of operation, especially in WLANs subject to high loads.

The second paper addresses the AoI both in terms of average and variance, for sensor nodes immersed in a dense WLAN that send pieces of information to a remote server via a WAN connection. We study both those metrics for a link with high variance and low variance delay. We construct and test, via means of simulations, an AoI-aware MAC, called LUPMAC - Latest Update Medium Access Scheme, aimed at reducing both the average AoI and the AoI variance at the remote server side, being also resilient to variations on the wired remote connection.

In those two papers we present two schemes suitable for the unlicensed spectrum environment, addressing both scheduling and queuing policies. They are only slight modifications to the already widely deployed IEEE 802.11 MAC. They significantly improve the metrics they focus on. They tend not to rely on a centralized unit, as most random access schemes do, and let the devices cooperate to a certain extent in order not to pollute the channel with undesired retransmissions.