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Cooperative wireless relaying

Over the past decade, Internet access became essentially wireless, with 802.11 technologies providing a low cost broadband support for a flexible and easy deployment. However, channel conditions in wireless networks are subjected to interference and multi-path propagation, creating fading channels and decreasing the overall network performance. While fast fading can be mitigated by having the source retransmitting packets, slow fading, caused by obstruction of the main signal path, makes retransmission useless, since periods of low signal power lasts the entire duration of the transmission. Extensive research has been done to mitigate the effect of shadowing in wireless networks, being mostly focused on Multiple-Input Multiple-Output (MIMO) systems. 

Recently, cooperative relaying techniques have been investigated to increase the performance of wireless systems by using diversity created by different single antenna devices, aiming to reach the same level of performance of MIMO systems. Cooperation occurs when overhearing relays assist the transmission from source to destination by transmitting different copies of the same signal from different locations, allowing the destination to get independently faded versions of the signal that can be combined to obtain an error-free signal.

The definition of MAC cooperative schemes poses several challenges, specially in the presence of mobile nodes. A major challenge is related to relay selection, which aims to identify the most suitable relay(s) for assisting transmissions between any pair of nodes. 

The goal of our research activity is to investigate solutions able to ensure accurate and fast relay selection, posing minimum overhead and reducing the dependency upon CSI estimations, which is essential to increase the system performance in scenarios with mobile nodes.

Book Chapters

Tauseef Jamal, Paulo Mendes "Cooperative Relaying for Wireless Local Area Networks", Springer Lecture Notes in Computer Science, Wireless Networking for Moving Objects: Models, Approaches, Techniques, Protocols, Architectures, Tools, Applications and Services, 2014

Tauseef Jamal, Paulo Mendes, “Cooperative Relaying in User-Centric Wireless Networks”, Springer Lecture Notes in Social Networks, User-Centric Networking: Future Perspectives, ISBN 978-3-319-05217-5, May 2014

Journal Publications

Tauseef Jamal, Paulo Mendes, “Cooperative Relaying in Dynamic Wireless Networks under Interference Conditions, IEEE Communications Magazine, Special issue on User-centric Networking and Services, December 2014

Tauseef Jamal, Paulo Mendes, Andre Zuquete, "Wireless Cooperative Relaying Based on Opportunistic Relay Selection", International Journal On Advances in Networks and Services, Vol. 5, no. 1&2, July 2012

Conference Publications

Tauseef Jamal, Paulo Mendes, André Zúquete, "Analysis of Hybrid Relaying in Cooperative WLAN", in Proc. of Wireless Days, Valencia, Spain, November 2013

Tauseef Jamal, Paulo Mendes, Andre Zuquete, "Opportunistic Relay Selection for Wireless Cooperative Network", IFIP NTMS, Istanbul, Turkey, May 2012

Tauseef Jamal, Paulo Mendes, André Zúquete "Interference-Aware Opportunistic Relay Selection", in Proc. of ACM CoNext, Tokyo, Japan, December 2011

Tauseef Jamal, Paulo Mendes, "RelaySpot: A Framework for Opportunistic Cooperative Relaying", In Proc. of IARIA International Conference on Access Networks, Luxembourg, June 2011

Tauseef Jamal, Paulo Mendes, “Relay Selection Approaches for Wireless Cooperative Networks”, in Proc. of IEEE WiMob, Niagara Falls, Canada, October 2010


Cooperative Relaying for Dynamic Networks. Number: EP13182366 (2013-08-30)


RelaySpot (2012): A Cooperative MAC Protocol for Dynamic Wireless Networks for Linux. OMNET++ module. (Authors: Tauseef Jamal, Paulo Mendes). Developed in the ULOOP project. SITI-SW-12-04

Technical Reports

Tauseef Jamal, Luis Amaral Lopes and Paulo Mendes, Towards Implementing Cooperative Relaying, COPELABS, number COPE-TR-13-06, 2013

Tauseef Jamal and Paulo Mendes, 802.11 Medium Access Control In MiXiM, COPELABS, Universidade Lusófona, number SITI-TR-13-02, 2013