Programme – contenu détaillé de l’UE
Introduction: After a fast development during the last decade, wireless networks are everywhere. While cellular networks allow a large-scale mobility, local networks such as WLAN offer a friendly wireless link in local areas. During the near past, new advances focused on improving each technology exploiting a reserved frequency bandwidth.
The future opens new trends. Future technologies will have to share the same radio resource and to fit the quality of the radio environment: the cognitive or opportunistic radio is ongoing. This new approach will offer a wide set of new services: the future terminal will be multi-mode, reconfigurable, and less energy consuming.
To achieve this mutation, the future terminal will have to comply with the complexity of the real wireless medium. It is true that radio offers mobility and friendly wireless access, but in turns exhibits strong problems: packet error rate, fading, interference.
To manage the wireless medium, the standard network model (OSI model) has been enhanced by introducing the MAC layer which allows the data link layer to manage the physical layer. The MAC layer introduces rules to share efficiently the medium between terminals.
Lot of routing and MAC protocols are evaluated on the basis of a very simple physical layer model (circular, threshold). Some of them may fail when used in a realistic environment.
To improve these protocols, a better knowledge about the physical layer is needed. New ideas will probably come from cross-layer studies and cross-layer protocols. MAC-PHY protocols are those taking into account carefully the reality of the physical medium.
To understand these trends, the students working on protocols for wireless networks should first acquire basics of the physical layer. Secondly, they should be aware of mathematical tools for modelling this physical layer. This course aims to help students in computer sciences to improve their knowledge about both.
Scheduling :
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The mistaken axioms of wireless network (2h, JMG)
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What are the common assumptions about wireless networks and why they are false?
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Propagation modelling (2h, MDO)
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The common models are described: path-loss models and shadowing and fading.
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Modulation, BER and radio link quality (2h, JMG)
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Starting from the standard circular threshold model, real assumptions are studied: a BER (bit error rate) is introduced. Channel coding effect, …
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Interference (2h, JMG)
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What are the main laws of interference : equivalent noise, rejection capability,
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How interference can be introduced in wireless networks? More specifically in ad hoc or sensor networks.
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Resource sharing (4h, MDO)
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Because lot of recent works are devoted to multi-channel techniques, it is important to detail how a frequency band can be shared: TDMA/FDMA/CDMA/OFDMA/…
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Lot of works assume a perfect orthogonality between sub-channels. This is not true. How the multi-channels interfere will be modelled.
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A practical study based on a wLAN deployment (2h, JMG)
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A complete development on how these assumptions can be introduced in a wLAN modelling
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A practical study for ad hoc/sensor networks (2h, MDO)
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Introducing some of these realistic assumptions in ad hoc network modelling is discussed
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Scientific papers presentation (4h, JMG/MDO) :
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Students will present some articles about the topic of the course. 3 presentations per hour up to 12.
Compétences acquises
Méthodologiques :
Realistic modelling of the physical layer of radio networks
Techniques :
Radio technologies
Modelling tools for signal processing
Signal processing (only few principles)
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