The thesis will be conducted as part of a Region Ile-de-France/ Digiteo project.
Cooperative communication has emerged in recent years as an important technique in wireless networks with unstable links. Cooperative relaying takes advantage of the broadcast nature of the medium and provides additional diversity against link outages (caused, e.g., by dynamic fading or shadowing effects) by allowing nearby nodes that overhear the transmitted signal to make additional transmissions to assist in delivering the data to its destination.
The extensive research on the topic has resulted in a wide variety of proposed cooperation methods. For a single relay, these range from simple decode-and-forward of the data packet itself 1, 2 to coded cooperation where the relay transmits additional error-correcting code bits rather than retransmitting the original data 3. Similar ideas have been extended to multiple-relay cooperation, where the receiver decodes the data by combining the relayed signals received either over separate multiplexed subchannels.
The vast majority of studies in the area have tackled the issue from a pure optimization perspective, focusing on strategies to maximize the performance (measured in terms of capacity or effective error rate) of the communication between a given source/destination pair with the aid of nearby relay nodes. However, when there are several pairs of nodes communicating in each other’s vicinity, the use of cooperative relaying techniques creates a conflict if the relay nodes are within range of several endpoint pairs simultaneously. Moreover, the additional transmissions by the relay node increase the interference for other links and thus adversely impact their capacities, even if the other links do not employ cooperative relaying directly. Such interactions among flows between different source/destination pairs in the presence of cooperative relaying, and distributed mechanisms for efficient allocation of cooperative relay nodes among the different flows ), remain not yet well-understood.
The major goal of this Ph.D. thesis is to explore, propose and evaluate wireless network protocols under the novel source-relay node-destination communication pattern, designed to take full advantage of the broadcast nature of the wireless medium and fluctuating propagation patterns in order to bring about networks that are efficient in their use of the radio spectrum resource, and robust by being able to quickly respond to variations in the wireless environment characteristics.
More specifically, the student is expected to conduct the following tasks:
•The student will establish the necessary theoretical foundations to study the resource allocation problem in opportunistic cooperative wireless networks in a systematic manner.
•The student will then devise practical communication protocols and distributed algorithms for wireless devices to cooperate and relay each other's data opportunistically in volatile environments, yet do so efficiently and fairly among many simultaneous data sources.
•The proposed solutions (e.g., opportunistic MAC protocols and routing protocols) will be extensively evaluated in typical network settings based on practical performance metrics.
Wireless radio background. Performance evaluation.
Status of funding
Jeudi 25 février 2010 16:10:15 CET
Jeudi 25 février 2010 16:10:15 CET
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Ecole Doctorale Informatique Paris-Sud
Nicole Bidoit Assistante
Stéphanie Druetta Conseiller aux thèses
ED 427 - Université Paris-Sud
UFR Sciences Orsay
Bat 650 - aile nord - 417
Tel : 01 69 15 63 19
Fax : 01 69 15 63 87
courriel: ed-info à lri.fr