The R2D2 project

R2D2 was an 18-month research project supported by EPSRC under the First Grant scheme (EP/L006251/1), which was completed in July 2015. This website will keep being updated until all project-related outcomes have been disseminated. Alas, this project did not aspire to develop a prototype of R2D2, the famous droid in the Star Wars films. The focus of the project was on network error control and the research problem under investigation was not in the least less challenging or exciting!

Long-Term Evolution (LTE), the dominant system for fourth generation (4G) networks, has introduced state-of-the-art fountain coding to support wireless content streaming and downloading. Even though fountain coding can be combined with collaborative network coding to reduce network overhead and improve bandwidth efficiency, there is great scope for tailoring transceiver designs to the requirements of content distribution and for developing radically new paradigms capable of supporting high quality media in next generation systems. The aims of the R2D2 project can be summarised into the following two points:

Define novel mathematical frameworks

Develop a mathematical framework to identify key relationships between various network parameters, contribute to the understanding of network dynamics and assist in the system-level optimisation of network-coded architectures.

Delve into practical applications

Delve into the emerging research field of network coding and network error correction and develop practical implementations that can offer high reliability, high energy efficiency and low decoding complexity.

The R2D2 team

Project members and affiliated members

Ioannis Chatzigeorgiou

Principal Investigator (Feb. 2014 - Jul. 2015)
Lecturer in Communication Systems

Ioannis joined Lancaster University in October 2010. He received the Dipl.-Ing. degree in Electrical Engineering from Democritus University of Thrace, Greece in 1997, the MSc degree in Satellite Communication Engineering from the University of Surrey in 2000 and the PhD degree from the University of Cambridge in 2007. Before joining Lancaster University, he was a post-doctoral research associate at the Computer Laboratory, University of Cambridge and an ERCIM research fellow at the Norwegian University of Science and Technology (NTNU). His research interests focus on the application of communication theory and signal processing techniques for the study, analysis and design of wireless networks.

For more information, visit the personal page of Ioannis.

Andrea Tassi

Project member (Feb. 2014 - Jul. 2015)
Post-doctoral Research Associate

Andrea completed his PhD in "Telecommunication Systems and Telematics" at the University of Florence (Firenze, Italy). His research activity has been mainly devoted to the mathematical modelling and optimization of broadcast and multicast communications over LTE/LTE-Advanced networks. In particular, his dissertation deals with defining resource allocation models, which ensure that all the users (or a given subset of them) successfully recover delivered data flows with a certain probability. Communication reliability is ensured by optimized network coding schemes. He took part in several research activities aiming at optimizing broadcast and multicast layered video services (namely, H.264-based video streams) over Single Cell- and Single Frequency Network-eMBMS telecommunication systems.

Andrea moved to the University of Bristol in June 2015. For more information, visit his personal page.

Amjad Saeed Khan

Affiliated member (Oct. 2014 - Jul. 2015)
Ph.D. candidate

After completing his MSc degree in Digital Signal Processing and Intelligent Systems with distinction from Lancaster University, Amjad started his Ph.D. at Lancaster University under the supervision of Dr. Ioannis Chatzigeorgiou. His focus is on Network Error Control for Content Streaming Data and his research contributes to the objectives of the R2D2 project.

Alumni

Andrew Jones

Affiliated member (Feb. 2014 - Aug. 2015)
Postgraduate student (MSc by Research in Communication Systems)

After finishing his A Levels in Mechanical Maths, Physics and Computing at Yale College Wrexham, he moved to Lancaster University. After four years, he was awarded a 1st Class MEng in Computer Systems Engineering. He joined the R2D2 team in February 2014 and contributed to the outputs of the EPSRC-funded R2D2 project. He successfully defended his thesis entitled "Performance assessment of fountain-coded schemes for progressive packet recovery" on the 21st of November 2014 and was awarded the MSc by Research degree with Distinction.

Andrew joined Jaguar Land Rover (JLR) in September 2014.

Research

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Talk on 'Network Coding for Rapid and Reliable Data Delivery'

Ioannis Chatzigeorgiou (representing the R2D2 team)
Talk Wednesday 11th March 2015, University of Liverpool

Abstract

Network coding has the potential to significantly improve network reliability by mixing packets at a source node or at intermediate network nodes prior to transmission. In this talk, the concept of network coding will be presented and extended to the case of data comprising multiple layers of different importance levels and require unequal error protection. The idea of unequal error protection will then form part of a resource allocation framework, whose objective can be either provider-centric or user-centric. In the former case, the provider optimises the number of transmitted coded packets and the adopted modulation and coding scheme in order to offer a service to a minimum fraction of users without violating an existing service lever agreement. In the latter case, the aim is to maximise the ratio between the number of recoverable layers by the users (users' profit) and the total number of coded packet transmissions (provider's cost). The impact of the adopted network coding method (i.e., systematic or non-systematic transmission) on performance and the effect of sparse network coding on packet transmissions and decoding complexity will also be briefly discussed. The talk will conclude with a mapping of the aforementioned practical problems to theoretical problems related to the determination of the rank of constrained random matrices over Galois fields.

Talk 'On Optimization of Network-coded Scalable Multimedia Service Multicasting'

Andrea Tassi, Ioannis Chatzigeorgiou
Talk Thursday 5th February 2015, University of Bristol

Abstract

In the near future, the delivery of multimedia multicast services over next-generation networks is likely to become one of the main pillars of future cellular networks. In this extended abstract, we address the issue of efficiently multicasting layered video services by defining a novel optimization paradigm that is based on an Unequal Error Protection implementation of Random Linear Network Coding, and aims to ensure target service coverages by using a limited amount of radio resources.

Talk on Resource Allocation Schemes for Layered Video Broadcasting

Andrea Tassi, Ioannis Chatzigeorgiou
Talk Friday 28th November 2014, University of Edinburgh

Abstract

The explosive growth of content-on-the-move, such as video streaming to mobile devices, has propelled research on multimedia broadcast and multicast schemes. Multi-rate transmission strategies have been proposed as a means of delivering layered services to users experiencing different downlink channel conditions. In this presentation, we consider multiple Unequal Error Protection implementations of the Network Coding strategy for their inherent reliability features. In addition, we formulate resource allocation frameworks which are capable of jointly optimizing both the NC scheme in use and the system transmission parameters. Our proposed frameworks are adapted to the LTE stack and the integrated eMBMS technology. Furthermore, we establish that the choice of the NC technique and the way we define a resource allocation model, play a critical role in the radio resource footprint associated with a multimedia service.

Talk on Resource Allocation Strategies for Layered Multimedia Multicast Services

Andrea Tassi, Ioannis Chatzigeorgiou
Talk Monday 9th June 2014, University College London (UCL)

Abstract

The explosive growth of content-on-the-move, such as video streaming to mobile devices, has propelled research on multimedia broadcast and multicast schemes. Multi-rate transmission strategies have been proposed as a means of delivering layered services to users experiencing different downlink channel conditions. In this presentation, we consider random linear network coding for its inherent reliability features and study two encoding approaches, which are appropriate for layered services. We derive packet error probability expressions and use them as performance metrics in the formulation of resource allocation frameworks. The aim of these frameworks is both the optimization of the transmission scheme and the minimization of the number of broadcast packets on each downlink channel, while offering service guarantees to a predetermined fraction of users. Our proposed frameworks are adapted to the LTE stack and the integrated eMBMS technology. We focus on the delivery of a video service based on the H.264/SVC standard and demonstrate the advantages of layered network coding over multi-rate transmission. Furthermore, we establish that the choice of both the network coding technique and the resource allocation method play a critical role in the footprint of a service, as determined by the quality of each received video layer.

Rethinking the Intercept Probability of Random Linear Network Coding

Amjad Saeed Khan, Andrea Tassi, Ioannis Chatzigeorgiou
Journal Paper IEEE Communications Letters, to appear

Abstract

This letter considers a network comprising a transmitter, which employs random linear network coding to encode a message, a legitimate receiver, which can recover the message if it gathers a sufficient number of linearly independent coded packets, and an eavesdropper. Closed-form expressions for the probability of the eavesdropper intercepting enough coded packets to recover the message are derived. Transmission with and without feedback is studied. Furthermore, an optimization model that minimizes the intercept probability under delay and reliability constraints is presented. Results validate the proposed analysis and quantify the secrecy gain offered by a feedback link from the legitimate receiver.

Resource Allocation Frameworks for Network-coded Layered Multimedia Multicast Services

Andrea Tassi, Ioannis Chatzigeorgiou, Dejan Vukobratović
Journal Paper IEEE Journal on Selected Areas in Communications - Special Issue on Fundamental Approaches to Network Coding in Wireless Communication Systems, vol.33, no.2, pp.141-155, February 2015

Abstract

The explosive growth of content-on-the-move, such as video streaming to mobile devices, has propelled research on multimedia broadcast and multicast schemes. Multi-rate transmission strategies have been proposed as a means of delivering layered services to users experiencing different downlink channel conditions. In this paper, we consider Point-to-Multipoint layered service delivery across a generic cellular system and improve it by applying different random linear network coding approaches. We derive packet error probability expressions and use them as performance metrics in the formulation of resource allocation frameworks. The aim of these frameworks is both the optimization of the transmission scheme and the minimization of the number of broadcast packets on each downlink channel, while offering service guarantees to a predetermined fraction of users. As a case of study, our proposed frameworks are then adapted to the LTE-A standard and the eMBMS technology. We focus on the delivery of a video service based on the H.264/SVC standard and demonstrate the advantages of layered network coding over multi-rate transmission. Furthermore, we establish that the choice of both the network coding technique and resource allocation method play a critical role on the network footprint, and the quality of each received video layer.

Performance Analysis of Random Linear Network Coding in Two-Source Single-Relay Networks

Amjad Saeed Khan and Ioannis Chatzigeorgiou
Conference Paper IEEE ICC 2015, Workshop on Cooperative and Cognitive Mobile Networks (CoCoNet), London, UK, June 2015, to appear

Abstract

This paper considers the multiple-access relay channel in a setting where two source nodes transmit packets to a destination node, both directly and via a relay node, over packet erasure channels. Intra-session network coding is used at the source nodes and inter-session network coding is employed at the relay node to combine the recovered source packets of both source nodes. In this work, we investigate the performance of the network-coded system in terms of the probability that the destination node will successfully recover the source packets of the two source nodes. We build our analysis on fundamental probability expressions for random matrices over finite fields and we derive upper bounds on the system performance for the case of systematic and non-systematic network coding. Simulation results show that the upper bounds are very tight and accurately predict the decoding probability at the destination node. Our analysis also exposes the clear benefits of systematic network coding at the source nodes compared to non-systematic transmission.

Optimized Network-coded Scalable Video Multicasting over eMBMS Networks

Andrea Tassi, Ioannis Chatzigeorgiou, Dejan Vukobratović, Andrew Jones
Conference Paper IEEE ICC 2015, London, UK, June 2015, to appear

Abstract

Delivery of multicast video services over fourth generation (4G) networks such as 3GPP Long Term Evolution-Advanced (LTE-A) is gaining momentum. In this paper, we address the issue of efficiently multicasting layered video services by defining a novel resource allocation framework that aims to maximize the service coverage whilst keeping the radio resource footprint low. A key point in the proposed system mode is that the reliability of multicast video services is ensured by means of an Unequal Error Protection implementation of the Network Coding (UEP-NC) scheme. In addition, both the communication parameters and the UEP-NC scheme are jointly optimized by the proposed resource allocation framework. Numerical results show that the proposed allocation framework can significantly increase the service coverage when compared to a conventional Multi-rate Transmission (MrT) strategy.

Binary Systematic Network Coding for Progressive Packet Decoding

Andrew Jones, Ioannis Chatzigeorgiou, Andrea Tassi
Conference Paper IEEE ICC 2015, London, UK, June 2015, to appear

Abstract

We consider binary systematic network codes and investigate their capability of decoding a source message either in full or in part. We carry out a probability analysis, derive closed-form expressions for the decoding probability and show that systematic network coding outperforms conventional network coding. We also develop an algorithm based on Gaussian elimination that allows progressive decoding of source packets. Simulation results show that the proposed decoding algorithm can achieve the theoretical optimal performance. Furthermore, we demonstrate that systematic network codes equipped with the proposed algorithm are good candidates for progressive packet recovery owing to their overall decoding delay characteristics.

Conditions for Cooperative Transmission on Rayleigh Fading Channels

Ioannis Chatzigeorgiou
Conference Paper VTC 2014 Fall, Vancouver, Canada, September 2014

Abstract

We consider a system of two nodes transmitting to an access point on quasi-static Rayleigh fading channels. We use signal-to-noise ratio (SNR) thresholds to characterize the requirements of each node, in terms of throughput and reliability, and we study their impact on outage probability. Given the average quality of the uplink channels, we formulate conditions on the SNR thresholds for decode-and-forward cooperation to be beneficial; that is, for nodes to experience an improvement in their outage probabilities if they switch from non-cooperative to cooperative transmission. We derive analytical bounds and propose tight approximations, which can be applied by the nodes to make decisions in favor or against cooperation.

Performance Assessment of Fountain-coded Schemes for Progressive Packet Recovery

Andrew Jones, Ioannis Chatzigeorgiou, Andrea Tassi
Conference Paper CSNDSP 2014, Manchester, UK, July 2014

Abstract

Fountain codes are gradually being incorporated into broadcast technologies, such as multimedia streaming for 4G mobile communications. In this paper, we investigate the capability of existing fountain-coded schemes to recover a fraction of the source data at an early stage and progressively retrieve the remaining source packets as additional coded packets arrive. To this end, we propose a practical Gaussian elimination decoder, which can recover source packets "on-the-fly". Furthermore, we introduce a framework for the assessment of progressive packet recovery, we carry out a performance comparison of the investigated schemes and we discuss the advantages and drawbacks of each scheme.

On Optimization of Network-coded Scalable Multimedia Service Multicasting

Andrea Tassi, Ioannis Chatzigeorgiou, Dejan Vukobratović
Conference Abstract SNOW 2015, Geilo, Norway, March 2015

Abstract

In the near future, the delivery of multimedia multicast services over next-generation networks is likely to become one of the main pillars of future cellular networks. In this extended abstract, we address the issue of efficiently multicasting layered video services by defining a novel optimization paradigm that is based on an Unequal Error Protection implementation of Random Linear Network Coding, and aims to ensure target service coverages by using a limited amount of radio resources.

This paper summarises the main findings presented in "Resource Allocation Frameworks for Network-coded Layered Multimedia Multicast Services" (IEEE JSAC 2015) and "Optimized Network-coded Scalable Video Multicasting over eMBMS Networks" (IEEE ICC 2015). Please scroll up to find copies of both papers.

News

Paper was accepted for publication in IEEE Communications Letters

Friday 14 August 2015

We are pleased to share with you the news that our paper "Rethinking the intercept probability of random linear network coding" will appear in a forthcoming issue of the IEEE Communications Letters. This short paper presents an analysis of the probability that an eavesdropper will intercept a sufficient number of linearly independent coded packets and decode a network-coded message that was meant for a legitimate receiver. We also proposed a resource allocation model to minimize the intercept probability, while satisfying delay and reliability constraints, and showed that the legitimate receiver is not required to have knowledge of the presence of the eavesdropper.

Paper was accepted for publication in the IEEE Journal on Selected Areas in Communications

Thursday 20 November 2014

We are thrilled to announce that our paper "Resource allocation frameworks for network-coded layered multimedia multicast services" has been accepted for publication in the IEEE JSAC and will appear in the Special Issue on Fundamental Approaches to Network Coding in Wireless Communication Systems. IEEE JSAC, which was ranked #4 among the top journals in telecommunications by impact factor (IF: 4.138), is the flagship journal of the IEEE Communications Society.

Five papers were accepted for publication in the proceedings of international conferences

Various dates between April 2014 and July 2015

In the course of the project, the research outcomes of the R2D2 team have appeared or will appear in the proceedings of the following conferences: CSNDSP 2014 in Manchester, UK (1 paper), VTC 2014 Fall in Vancouver, Canada (1 paper) and ICC 2015 in London, UK (3 papers).

Successful defense of Master's thesis

Friday 21 November 2014

Congratulations to Andrew Jones on the successful defense of his MSc thesis entitled "Performance assessment of fountain-coded schemes for progressive packet recovery" and the recommendation for the "MSc by Research" degree with Distinction.

Assignment of first PhD research project

Wednesday 1 October 2014

Amjad Saeed Khan joined the R2D2 team as a candidate for a PhD degree in Communication Systems. His research is fully funded by a scholarship offered by the Faculty of Science and Technology at Lancaster University. His work is concerned with the performance assessment of network coding in relay-aided systems.

Official start date of the R2D2 project

Saturday 1 February 2014

Andrea Tassi joined our team and signalled the start of the 18-month R2D2 project.

Vacancy in Joint Coding Designs for Error Correction is filled

Monday 25 November 2013

Andrea Tassi filled the position of post-doctoral Research Associate. Andrea has completed his PhD studies at the University of Florence (Firenze, Italy). During the last three years, he joined several research teams formed by people belonging to both the academic and the industrial world. In particular, he developed strong links with researchers at different universities, such as the University of Edinburgh and the University of Novi Sad, who work on coding theory and multimedia communications over 3GPP's systems.

Assignment of first Master's research project

Tuesday 1 October 2013

Andrew Jones joined the School as a postgraduate student pursuing an MSc by Research in Communication Systems. He is affiliated to the R2D2 project and his work is concerned with the definition, implementation and validation of different fountain and random linear network coding strategies with a focus on multimedia service delivery over next-generation cellular networks.

Vacancy in Joint Coding Designs for Error Correction

Saturday 21 September 2013

Applications for the position of post-doctoral Research Associate in Joint Coding Designs for Error Correction are invited from the 21st of September until the 20th of October 2013.

Membership to the COST Action IC1104

Wednesday 10 July 2013

Ioannis became a member of the COST Action IC1104 Random Network Coding and Designs over GF(q) and will participate in the second Working Group (WG2), which focuses on the development of encoding/decoding schemes and practical aspects of Network Coding. He also joined the Management Committee of IC1104 as a substitute member of the UK team.

Meeting of ICT panel and recommendation

Tuesday 11 June 2013

The EPSRC Information and Communication Technologies (ICT) panel met in early June to assess the submitted proposals and ranked the R2D2 project first among the eleven submitted First Grant proposals.

Peer review completed, feedback received

Wednesday 8 May 2013

The Peer Review process was completed and EPSRC forwarded the feedback to us. Our sincere thanks to the anonymous and independent reviewers for their overwhelmingly supportive and enthusiastic comments on our proposal.

Project proposal submitted to EPSRC

Monday 25 March 2013

The proposal for the R2D2 project under the First Grant scheme of the Engineering and Physical Sciences Research Council (EPSRC) and all required supporting documents were submitted to the Joint Electronic Submissions (Je-S) system. Fingers crossed!

Get in touch

The R2D2 research team is based at InfoLab21, Lancaster University and can be reached at the following address:


Principal Investigator

Dr Ioannis Chatzigeorgiou - i.chatzigeorgiou (followed by @lancaster.ac.uk)
Room B43, InfoLab21, South Drive, School of Computing and Communications, Lancaster University, Lancaster LA1 4WA, United Kingdom.