Professor Mike Warrington

Professor Michael WarringtonProfessor of Radio Communications Engineering

Tel: +44 (0)116 252 2561
Email: emw@le.ac.uk
Location: Room 10, R Block, Engineering

Personal details

BSc (Durham), PhD (Leicester), CEng, FIET, MURSI, FHEA

  • Programe Director: Teaching and Feedback Quality
  • Coordinator of BEng/MEng Communications and Electronic Engineering Degree

Research

The Radio Systems Laboratory within the Group specialises in experimental studies of the influence of the propagation medium on radio systems and on the development of techniques to overcome or to take into account propagation related system performance limitations.

An underlying theme of the projects is the development of a better understanding of the effects of the atmospheric (principally the ionospheric) environment on the propagation characteristics of radio waves, and the development of techniques to account for these effects in radio system operation, development and planning. All of my projects are experimentally based and involve the development, deployment and operation of equipment at a number of sites away from Leicester, for example over-sea paths in the Channel Islands in support of UHF studies and long distance paths (often in the Arctic) in support of investigations within the HF band.

Ionospheric radiowave propagation

Ionospheric radio wave propagation effects are of long-standing interest. Communications within the high latitude region is of growing importance for civil airlines operating trans-polar routes as these may form the shortest path between significant destinations (e.g. New York to Hong Kong), reducing travel time, cost and carbon emissions. Operation over polar routes began with a small number of flights in 1999, and by 2014, polar routes were operated by more than 10 major airlines, with over 12,000 cross-polar flights . However, in the polar cap above 82°N geostationary satellites lie below the horizon, and geographic and geopolitical considerations mean there are limited VHF radio air-traffic control facilities. Thus HF radio propagation via the ionosphere is of critical importance in maintaining communications. Adverse space weather conditions, leading to ionospheric disruption that in turn affects HF radio propagation, is of critical importance when considering whether polar routing is viable in the hours in advance of a flight (forecasting) and to the management of HF communications during a flight (nowcasting). Our research is currently directed towards the nowcasting and forecasting requirements.

Adaptive multi-channel reception / HF MIMO

One of the major limitations in the performance of HF long range radio communications operating over paths subject to severe ionospheric distortion (e.g at northerly latitudes) is the imposition of large delay and Doppler spreads on the signal. The magnitude of these dispersions is such as to severely limit the data throughput capabilities of communication systems.

Techniques have been investigated whereby the signals from several receivers connected to a spaced element antenna array are combined in such a way as to reduce the apparent level of dispersion by means of spatial filtering. Initial studies yielded very promising results and a paper on this topic was awarded the 2002 IEE Maxwell Premium Prize.

Recent developments, in particular by the mobile radio community, with the aim of exploiting multi-path propagation to increase the data throughput through the use of multiple antennas at both the transmitter and receiver (a so-called MIMO system) have been made for systems operating in the UHF radio bands with some significant success. The application of this technology to systems operating in the HF band has not yet received significant attention, and in order to address this issue an experimentally based investigation with EPSRC support has been undertaken. The project is being undertaken jointly with Durham University, and involves active collaboration with the University of Rennes 1.

VHF / UHF propagation over sea paths

Measurements over two periods in excess of a year have been made to investigate the propagation characteristics of VHF and UHF signals propagating over the sea. Initial studies were undertaken at frequencies around 300MHz, of particular interest for communications between ships at the extreme limits of propagation. Subsequently, the study has been extended to 2GHz to aid the development of tools available for the planning and operation of UHF systems, and appropriate statistical data have been provided to the International Telecommunication Union to improve the recommendations used by the industry in the planning of future systems.

Several issues arose when modelling the propagation characteristics observed in the experimental programmes. Whilst it is well known that local meteorological conditions play an important role in determining the propagation characteristics of these types of radio link, we found that under certain conditions the atmospheric structure is well understood and the propagation can be modelled to a reasonable accuracy whereas under other atmospheric conditions this is not the case. Proposals are currently being developed for further funding to address this issue.

Some recent publications

E.M. Warrington,  A.J. Stocker, D.R. Siddle, J. Hallam, H.A.H. Al-Behadili, N.Y. Zaalov, F. Honary, N.C. Rogers, D.H. Boteler, and D.W. Danskin. Observations of HF radio propagation at high latitudes and predictions using data-driven simulations. ionospheric Effects Symposium (IES) 2017, 9-11 May, Alexandria, USA.

N.C.  Rogers, A. Kero, F. Honary, P.T. Verronnen, E.M. Warrington and D.W. Danskin. Improving the twilight model for polar cap absorption nowcasts. Space Weather, 14, 950–972, doi:10.1002/2016SW001527.

Warrington EM, Rogers NC, Stocker AJ, Hallam J, Siddle DR, Al-Behadili HAH, Zaalov NY, Honary F, Boteler DH, Danskin DW. Progress towards a propagation prediction service for HF communications with aircraft on trans-polar routes. Nordic HF Conference, 15-17 August 2016

E.M. Warrington,  A.J. Stocker, D.R. Siddle, J. Hallam, H.A.H. Al-Behadili, N.Y. Zaalov, F. Honary, N.C. Rogers, D.H. Boteler, and D.W. Danskin. Near real-time input to a propagation model for nowcasting of HF communications with aircraft on polar routes. Radio Science, 51, 1048-1059, doi: 10.1002/2015RS005880, 2016.

A.J. Stocker, E.M. Warrington and D.R. Siddle. Observations of Doppler and multipath spread on HF signals received over polar cap and trough paths. Radio Science, 48(5), 638-645, doi: 10.1002/2013RS005264, 2013.

D.R. Siddle, A.J. Stocker, E.M. Warrington, N.Y. Zaalov, M.J. Homam. Simultaneous observations of trans-ionospheric and HF propagation within the polar cap. Radio Science, 48(5), 564-572, doi: 10.1002/rds.20062, 2013.

N.Y. Zaalov, H. Rothkaehl, A.J. Stocker and E.M. Warrington.  Comparison between HF propagation and DEMETER satellite measurements within the mid-latitude trough. Journal of Advances in Space Research, 52, 781-790, doi: 10.1016/j.asr.2013.05.023, 2013.

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