Team hipercom

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Section: Contracts and Grants with Industry

RAF

Participants : Paul Muhlethaler, Khaldoun Al Agha.

The RAF project, Réseaux ad hoc A Forte efficacicité, belongs to the competitiveness cluster SYSTEM@TIC PARIS-REGION. It aims at designing self configuring ad hoc networks using reservation based access protocols using both time and frequency multiplexing. The project has three components : the study of ad hoc networks using a smart relaying function at the Phy/MAC level, the study and design of protocols for ad hoc networks solving simultaneously the access problem using reservation based techniques and the relaying issue for multi hop communication, the realization of a prototype using the IEEE 802.16e (WiMAX Mobile) technology.

The partners are Thalès, Alcatel Lucent, EADS, IEF, INRIA, LRI, Sagem DS, and Supelec.

In this project INRIA is more particularly in charge of optimisation and performance evaluation of Ad Hoc networks devoted to security qnd rescue applications.

INRIA has compared the time division multiple access (TDMA) approachs where time slots are reserved within a radius of n-hop around the transmitter with conventional (Carrier Sense Multiple Access) CSMA protocol controlled by the carrier sense threshold. INRIA has studied the signal to interference and noise ratio (SINR) that is obtained by the two approaches. This study shows that on medium size networks it is difficult to obtain large SINR with a high probability with the TDMA approach whereas it is easy with the CSMA approach.

INRIA has also compared these two approaches in the classical outage model where a packet is received if its SINR is above a given threshold. With this model the TDMA approach offers a sigthly better performance in terms of global throughput than the CSMA approach. The path loss exponent can be changed without changing this result.

The TDMA approach and the CSMA approach are then compared in a model of dynamic coding idealized by Shannon's well-known law. In this model TDMA sigthly outperforms CSMA for every value of path loss exponent between 3 and 5.


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