Tutorial 3: Signal Processing Meets Network Layers: Joint Protocol-Channel Decoding

Presented by

Pierre Duhamel, Michel Kieffer


The widely used OSI layered model partitions networking tasks into distinct protocol layers. At the transmitter, each layer adds some specific information (receiver address, type of signal,...) to the transmitted packets. This facilitates network design, since a layer has not to be aware of the information introduced by other layers, allowing heterogeneous contents to be delivered via the same communication network. Moreover, upon reception, each layer extracts the required information at that level, while assuming that the lower layers behave perfectly. It then provides to the upper layers the required information. Therefore, error-detecting codes (CRC or checksums) protecting mainly headers (and sometimes the payload) are widely used at various places of the protocol stacks. They are combined with retransmission mechanisms (when feasible) for data packets deemed as corrupted. Moreover, since the layers work independently, but sometimes require the knowledge of identical (or correlated) information, some redundancy exists in the data extracted at each layer. This redundancy has been recognized and used for example in Robust Header Compression (RoHC) protocols for reducing the header lengths. Nevertheless, the existence of this redundancy can also be used (in a non exclusive manner) for other tasks, as outlined below

The role of Joint Protocol and Channel Decoding (JPCD) is to make an efficient (and joint) use of the redundancy present in all protocol layers (including that introduced at Physical layer, e.g., by channel coding) in order to obtain optimal performance at a global level. A partial effort in this direction was already done under the framework of cross layer techniques, but JPCD intends to make full use of all properties of the signal that is transmitted. With this strategy, more reliable header recovery can be performed and aggregated packets can be more efficiently delineated. More recently, it has also been shown that channel decoding may benefit from the redundancy present in the protocol stack (protocol-assisted channel decoding). As a result, one can obtain at each layer packets that are more usable, i.e., contain fewer errors.

Thus, JPCD allows one to obtain the best performance out of the received sequences without changing the structure of the transmitted signal. Clearly, since JPCD is performed within the receiver, the ability to use JPCD tools in the context of existing standards makes it potentially very practical. This tutorial explains in some details the required signal processing tools and their application to network layers, and provides examples of protocols for which this process has been implemented at all layers.

This tutorial first presents some tools that are described in the book Joint Source-Channel Decoding. A Cross-Layer Perspective with Applications in Video Broadcasting over Mobile and Wireless Networks published in 2009 by Academic Press, and extends them in a comprehensive manner, providing missing ones, and giving many application examples. End-to-end simulations of applications concerning the reliable transmission of multimedia (video and html files) contents are finally provided. This set of simulations demonstrate that a truly permeable protocol stack can be implemented at decoder side, allowing the whole set of results already obtained under the name of Joint Source-Channel Decoding techniques to be practically used. Finally, this opens the floor for a true optimization of the redundancy allocation at the various layers of the protocol stack in order to obtain the best performance.

Speaker Biography

Pierre Duhamel (Fellow IEEE, 1998, Fellow EURASIP, 2008) received the Eng. Degree in Electrical Engineering in 1975, the Dr. Eng. Degree in 1978, and the Doctorat és sciences degree in 1986. From 1975 to 1980, he was with Thomson-CSF (now Thales) and joined the National Research Center in Telecommunications (CNET) in 1980. From 1993 to Sept. 2000, he has been professor and Dept. head at ENST, Paris (National School of Engineering in Telecommunications). He is now full time researcher with L2S - CNRS/SUPELEC/Univ Paris-Sud, with activities in Signal processing for Telecommunications.

Dr. Duhamel held several positions as member and chair of several technical committees of the IEEE. He was also an associate Editor of the IEEE Transactions on Signal Processing and of the IEEE Signal Processing Letters. He was Distinguished lecturer, IEEE, for 1999, and co-technical chair of ICASSP 06. He received the "Best paper award" from the IEEE transactions on SP in 1998, and was awarded the "grand prix France Telecom" by the French Science Academy in 2000. Dr Duhamel published more than 80 papers in international journals, more than 260 papers in international conferences, and holds 28 patents. He is a co-author of the book "Joint Source and Channel Decoding: A cross layer perspective with applications in video broadcasting" which appeared in 2009, Academic Press. His research interests are at the frontier between Signal processing, Digital Communications, and Networking.

Michel Kieffer (Senior Member, IEEE, 2007) received in 1995 the Agrégation in Applied Physics at the Ecole Normale Supérieure de Cachan, France. He obtained a PhD degree in Control and Signal Processing in 1999, and the Habilitation á Diriger des Recherches degree in 2005, both from the Paris-Sud University, Orsay, France. Michel Kieffer is an associate professor in signal processing for communications at the Paris-Sud University and a researcher at the Laboratoire des Signaux et Systémes, Gif-sur-Yvette, France. Since september 2009, he is on leave at the Laboratoire de Traitement et Communication de l'Information, CNRS-Télécom ParisTech. He is also junior member of the Institut Universitaire de France.

His research interests are in joint source-channel coding and decoding techniques for the reliable transmission of multimedia contents and in signal processing for communication and networking. Michel Kieffer is co-author of more than 100 contributions in journals, conference proceedings, or books. He is one of the co-authors of the book Applied Interval Analysis published by Springer-Verlag in 2001 and of the book Joint Source-channel Decoding: A Cross-layer Perspective with Applications in Video Broadcasting published by Academic Press in 2009. Since 2008, he serves as associate editor of Signal Processing.