A systematic study of Physical LAyer Network coding: from information-theoretic understanding to practical DSP algorithm design (P.L.A.N)

Lead Research Organisation: Lancaster University
Department Name: Computing & Communications


High spectral efficiency is the holy grail of wireless networks due to the well-known scarcity of radio spectrum. While up to recently there seemed to be no way out of the apparent end of the road in spectral efficiency growth, the emerging approach of Network Coding has cast new light in the spectral efficiency prospects of wireless networks [1]. Initial results have demonstrated that the use of network coding increases the spectral efficiency up to 50% [2, 3]. Such a significant performance gain is crucial for many important bandwidth-hungry applications such as broadband cellular systems, wireless sensor networks, underwater communication scenarios, etc. Currently network coding has received a lot of attention from the wireless communication community; however, many existing works focused on the application of network coding to upper layers and the study of its impact on the physical layer (PHY) design only began recently. The aim of this proposal is to systematically study network coding at the physical layer, where we will not only characterize the fundamental limits of physical layer network coding, but also design practical digital signal processing (DSP) algorithms to realize the performance gain promised by those theoretic results. The novelty of the proposed project lies on the fact that this project will be the first UK effort to bridge information-theoretic studies and DSP algorithm design for PHY network coding. This will be done by first deriving the capacity region of network coding, which provides us the upper bound of the system performance. With such a better understanding, we will develop efficient transmission protocols and DSP algorithms to realize such optimal performance in practice. Interference alignment, a technology recently developed to cope with co-channel interference, will be applied to network coding transmissions for further performance improvement. Information-theoretic results, such as outage and symbol error probabilities, will be developed and testbed-based experimental evaluation will be carried out, so a more insightful understanding for our developed schemes can be obtained.

Planned Impact

This work is proposed at a time when network coding has been envisioned to bring the fundamental changes to the way communication systems are designed, operated and understood. Significant performance gain promised by network coding is important to broadband mobile communications, where both the uplink and downlink data rate can be improved dramatically. Other applications of network coding include real-time sensor networks which can be used for environmental monitoring of physical and biological indicators, tactical surveillance, disaster prevention, undersea exploration, assisted navigation, etc. However, compared to the significant progress in the application of network coding to the upper layer design, there is less progress reported to date on studying network coding at the physical layer, especially in the UK. The novelty of this project is four-fold: firstly characterize the data rates achieved by network coding for various multi-user scenarios; secondly devise spectrally efficient transmission protocols by utilizing the concept of interference alignment and efficiently combating co-channel interference; thirdly design new low-complexity mapping and receive DSP algorithms to realize the performance gain of network coding in practical systems; fourthly carry out experimental evaluations to investigate how the proposed algorithms perform in practice in conjunction with leading technology providers and end-users. The proposal systematically addresses the fundamental issues of network coding from the information-theoretic aspect to DSP-enabled communications, which is beneficial for the communications community to get a better understanding of network coding. Also such obtained insights provide a precise guideline for the efficient design of practical and reliable wireless systems. Following this, the outcomes of this research will also be of considerable value to UK companies involved in developing broadband communication systems or real-time wireless sensor networks for the purpose of infrastructure monitoring or military controlling, as well as robust vehicular networks to support diverse quality of service. Indeed, the potential of the project cannot be overstated and this is evidenced by strong industrial support from Bell-Lab, BP and Infineon.


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Related Projects

Project Reference Relationship Related To Start End Award Value
EP/I037423/1 05/03/2012 30/09/2014 £239,625
EP/I037423/2 Transfer EP/I037423/1 01/10/2014 28/02/2015 £36,485
Description 1. During the project, we have developed a framework of network coding bases solutions, and identified the key and promising applications of network coding in future communication networks. One example is that we have applied network coding to MIMO cognitive radio communication systems, which will be important to improve the spectral efficiency of wireless transmissions. (e.g. Z. Zhao, Z. Ding, M. Peng, W. Wang and J. Thompson, "On the Design of Cognitive Radio Inspired Asymmetric Network Coding Transmissions in MIMO Systems", IEEE Trans. Vehicular Technologies, 2015).

2. We have combined network coding with many promising communication techniques, such as cooperative relaying and physical layer security, so not only the spectral efficiency of the wireless communication systems can be significantly improved, but also the security of wireless transmissions can be improved. Note that realizing secure transmission in wireless systems is particularly difficult because of the broadcast nature of radio transmissions. The use of network coding brings a new way to realize physical layer security. One example is to cooperative jamming, which can be viewed as a special case of physical layer network coding, where the destination is to send jamming information.
( P. Xu, Z. Ding, X. Dai and G. K. Karagiannidis, Simultaneously Generating Secret and Private Keys in a Cooperative Pairwise Independent Network, IEEE Trans. on Information Forensics and Security, to appear in 2016. )

3. While studying network coding, the concern for the fact that network coding can consume a lot of energy at the relay motivated us to study how to prolong the lifetime of these relaying nodes. By using the emerging concept, wireless power transfer, the relays in network coding systems are to use the energy harvested from those RF signals to power relay transmissions (Z. Ding, C. Zhong, D. W. Ng, M. Peng, H. A. Suraweera, R. Schober and H. V. Poor, "Application of Smart Antenna Technologies in Simultaneous Wireless Information and Power Transfer", IEEE Communication Magazine, 2015 )

4. Another important finding from this project is that the idea of network coding can be perfectly applied to multiple access in cellular networks. Recall that orthogonal multiple access, such as TDMA and CDMA, has been used in the previous generations of telecommunication networks. The study of network coding whose key idea is to allow signal superposition shed light on how information should be transmitted in a multi-user scenario. Particularly we have developed new results for multiple access, which is based on the concept of non-orthogonal multiple access. (Z. Ding, M. Peng and H. V. Poor, "Cooperative Non-Orthogonal Multiple Access in 5G Systems", IEEE Communication Letters, 2015, and
Z. Ding, Z. Yang, P. Fan and H. V. Poor, "On the Performance of Non-Orthogonal Multiple Access in 5G Systems with Randomly Deployed Users", IEEE Signal Processing Letters, 2014).
Exploitation Route All our results have been published in the top journals, including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEE Transactions on Signal Processing, etc.

In addition, we have actively engaged with other researchers, and participated in many international conferences. For example, as the workshop chair, Prof. Ding has organized IEEE WCNC-2013 Workshop on New Advances for Physical Layer Network Coding. Our group members have been provided technical presentations at the flagship conferences in communications, such as IEEE International Conference in Communications, IEEE Global Communication Conference, IEEE Wireless Communications and Networking Conference, etc.
Sectors Digital/Communication/Information Technologies (including Software)

URL http://www.lancaster.ac.uk/staff/dingz/
Description During the project, we have proposed a framework of solutions for wireless network coding, which not only characterize the fundamental limits of physical layer network coding, but also yield practical digital signal processing (DSP) algorithms for realizing the performance gain promised by those theoretic results. Most of the results obtained from this project have been disseminated at high profile international conferences, e.g., invited talks and keynote speeches, as well as at international leading journals, such as IEEE transactions, IET Proceedings, etc.
First Year Of Impact 2015
Sector Digital/Communication/Information Technologies (including Software)
Impact Types Societal