Full-Duplex For Underwater Acoustic Communications

Lead Research Organisation: Newcastle University
Department Name: Sch of Engineering

Abstract

In recent years, there has been an immense interest in developing underwater acoustic communication (UAC) systems related to remote control and telemetry applications for the off-shore oil & gas industry. In practice, the only feasible method to achieve sub-sea communications is by means of acoustic signals. However, due to the limited bandwidth of the UAC channel, past research concentrated on the half-duplex (HD) mode of operation using time-division duplexing (TDD). Recently, full-duplex (FD) transmission attracted attention in wireless communications due to its potential to nearly double the throughput of single-hop wireless communication links. However, there is an evident absence of equivalent in-depth research in FD for UAC systems, despite the severe bandwidth limitations of the UAC channel. Hence, we outline 3 crucial challenges to be addressed in this research project:
Challenge 1-Understanding the Self Interference (SI) in FD UAC systems: FD comes with the promise of theoretically doubling the throughput. However, in practice, SI induced by the large power difference between the distant and local transmissions will result in signal to interference and noise loss, and in turn throughput performance degradation. For acoustic waveforms and UAC modems little is known with regard to the statistical properties of SI and the impact of non-ideal/non-linear characteristics of hardware components operating in FD mode. In order to design effective self interference cancellation (SIC) methods, a comprehensive understanding and accurate models of SI are required.
Challenge 2-SIC methods: To fully exploit the potential of FD transmission, effective SIC methods are required capable of providing cancellation up to approximately 100 dB. Passive and active SIC methods have been proposed for wireless communications, however, they have not been investigated at all for UAC waveforms, and we believe that there is significant potential in their utilisation, as well as in developing new and improved approaches.
Challenge 3-To realise the benefits of FD in UAC networks: The enhanced physical layer capability offered by FD links can only be fully realised if the medium access control (MAC) layer is suitably designed for simultaneous transmission and reception on the same frequency channel. This calls for highly adaptive scheduling based on varying traffic demands, channel conditions and local interference. The long propagation delays demand efficient assignment of capacity using methods adopted for satellite systems, including free, predictive assignment of capacity, and FD-enabled physical layer network coding.

To address these challenges we propose 5 work packages (WP) at Newcastle University (NU) and University of York (UoY) with the aim to design an FD-enabled UAC system that nearly doubles the throughput of equivalent HD systems under the same power and bandwidth constraints. WP A (NU) will study the effects of SI for UAC waveforms and hardware, and provide analytical models capturing the characteristics of SI. WP B (UoY) will study the performance of joint analog and digital SIC and beamforming methods to enable FD operation of acoustic modems. WP C (NU) and WP D (UoY) will investigate the design and performance of FD single and multi-hop relaying methods at physical layer and efficient MAC protocols. WP E (NU) will be used for experimental validation, refinement and integration of the proposed FD system. Experiments will be carried out in the anechoic water tank at NU and using full-scale sea trials conducted in the North Sea in realistic shallow-water channels using NU's research vessel.

The research in this proposal is potentially transformative and will contribute to the development of FD-based underwater networking and communication capabilities required by applications such as oil & gas exploration, oceanographic data collection, pollution monitoring, disaster prevention, and security.

Planned Impact

Full-duplex technology will potentially double the capacity of the underwater acoustic communication channel, thus, the immediately foreseeable beneficiaries of the project will be in the following sectors and the involvement of ATLAS Elektronik UK (AEUK) provides a natural conduit for exploration and technical transfer:
-Offshore oil & gas, and renewable energy-Enabling more cost effective data gathering for maintenance of subsea assets and environmental impact monitoring.
-Marine science and governance-Efficient environmental data gathering.
-Defence/homeland security-Extended network area coverage and improved data throughput will enable new monitoring applications with higher data demands.
-Subsea equipment manufacturers-New families of modem products for underwater applications exploiting the full-duplex technology will be feasible.
Communication and Engagement:
-Scientific Publications: We will disseminate our research findings in top tier international journals. These include IEEE Trans. on Communications, on Wireless Communications, on Vehicular Technology as well as on Signal Processing. Major IEEE conferences (IEEE OCEANS, EUSIPCO, IEEE-ICC, IEEE-WCNC, IEEE-GlobeCom and IEEE-ICASSP) will also be considered. We will summarise all research findings also in the form of tutorial/magazine papers as well as in a monograph in order to coherently disseminate our project findings. We will host all of our publications at the EPrints repository of Newcastle University (NU) at http://eprint.ncl.ac.uk, as well as the equivalent repository at the University of York (UoY) at http://eprints.whiterose.ac.uk, and use our websites and Twitter feed to highlight progress.
Industrial Liaison: We will visit our industrial partner ATLAS Elektronik UK, who have expressed their interests in our research, for presenting our research findings. We will also contribute to diverse other research fora and summits as well as host workshops aiming at expanding our academic and industrial links. NU has experience in hosting technology showcase events, such as the three EXTREME Technologies conferences hosted in Newcastle between 2008-2011 that attracted companies such as BP, BAE Systems, Rolls Royce, HP, Bosch, GE and many others. In May 2017, we will also host a themed day in Underwater Sensing, Signal Processing and Communications for the University Defence Research Collaboration in Signal Processing (UDRC), which is an ongoing joint venture between the Ministry of Defence (MOD) and the Engineering & Physical Sciences Research Council (EPSRC), which will be a trigger for further engagement.
-EU Project Consortia: NU is currently participating in an FP7-funded project Cognitive Autonomous Diver Assistant (CADDY) developing communications and positioning for an autonomous diver assistance vehicle that will be used as a further avenue for disseminating the research outcomes. The project consortium consists of several industrial and academic institutions across Europe.
Collaboration and Exploitation:
-Collaboration with British Industry: We will disseminate our results to our industrial partner, AEUK, and find further avenues of exploitation and commercialization. More specifically, seminars, professional tutorials and visits to AEUK, and other interested key industrial partners in UK and abroad will be arranged to disseminate research findings and exploit technology transfer.
-Collaboration with Global Researchers and Research Visits: Both the PI and CIs have established collaboration links with various world leading research groups in the telecommunications field from the UK, Europe, US, and Far-east. These research collaborations will be maintained, while other formal collaboration opportunities will be sought with well-established research groups.
-Patents will be sought where possible prior to publication of the research. The research outlined in this project is pre-competitive, but it is aimed at exploitation in the UK where possible
 
Description During the Summer of 2018 we have conducted seatrials in the North East and acquired data required for the characterisation of self interference resulting for full-duplex operation. The data set that will be made available to the academic community and relevant industries will be used to provide realistic channel models for the local reverberation present in this communication links. Initial findings indicate that self interference is not negligible and can extend up to 1.5 seconds after the end of the packet transmission.

A small-scale acoustic simulator was developed that enables long distance simulations of transmission links to be performed within a small tank with dimension 3m x 3m x 3m.
Exploitation Route The research findings from the seatrial data analysis will be useful to underwater acoustic modem designers and relevant offshore industries looking to develop communication technologies for the Oil & Gas industry. They can be used to access the hardware complexity required for the implementation of self interference cancellation techniques required for the full-duplex operation.

Design of the small-scale acoustic simulator will be made public so that both academia and industry may benefit from the advantages of performing long distance simulations using "wet" signals in a small tank.
Sectors Digital/Communication/Information Technologies (including Software)

URL https://research.ncl.ac.uk/fduac/