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Radiocommunications Agency. Overview of current technological research Trevor Clarkson Head of Engineering and Research Unit. RA’s Role . Planning and Management of most of the civil radio frequency spectrum

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radiocommunications agency
Radiocommunications Agency

Overview of current technological research

Trevor Clarkson

Head of Engineering and Research Unit

ra s role
RA’s Role
  • Planning and Management of most of the civil radio frequency spectrum
  • Co-ordination of UK views and representation of all UK interests in international negotiations on the use of radio
  • Authorising use of radio by licensing or exemption
  • Formulating technical and operating standards for radio
  • Enforcement of legislation and investigating interference
ra s technical research
RA’s Technical Research
  • spectrum management
  • spectrum efficiency
  • interference and EMC issues
  • propagation studies
  • impact of new technologies

Technical research ...

  • a necessary part of the Agency’s activity so that the spectrum resource can be efficiently planned and maintained
research facilities
Research facilities
  • Radio Technology and Compatibility Group
  • 3 Task Groups:
    • Ionospheric Effects on Radio Systems
    • Propagation Factors Governing Terrestrial Fixed Service Outages at and above 13GHz
    • Mobile and Terrestrial Propagation
  • Contracted research to universities and industry
    • numerous projects placed each year
  • Rutherford Appleton Laboratory (RAL)
    • Core funding programme
radio technology and compatibility group rtcg
Radio Technology and Compatibility Group (RTCG)
  • Major projects:
  • IR2008 studies for RIS
  • TV compatibility studies
  • emissions from car headlamps
  • radiation from SDSL units
  • ETSI studies using OATS and FAC
  • ITU-R Rec 1546 antenna height gain
  • UWB interference to C-band earth stations
current research portfolio

£4M total

RAL core

Current research portfolio

Details of projects listed can be found at

current research portfolio1

Indoor Wideband Measurements


Intermittent & Wideband EMC disturbances

Uni of Bath

Finalisation of the UK Rain Intensity Map

Uni of Bath

Bounds for frequency assignment problem

Uni of Cardiff

Auto Tune Antennas

Uni of Herts

EMC in Home Networking

Uni of Herts

CASE Studentship

Uni of Oxford

Higher Order Constraint Techniques

Uni of Wales

Unstructured Conductive network for Transmission

Uni of York

Measure digital hardware & related circuits

Uni of York

Impact of EMC emissions from unstructured networks

Uni of York

Dithered Clock Osc. On Digital radio services

Uni of York

Method for testing EMC emissions from fluorescent lamps

Uni of York

Research into the EMC susceptibility of certain receivers

Uni of York

Choke Tunnel Design in 900MHZ ISM Machines

Uni of York

Railway Electromagnetic Compatibility Study

Uni of York

Current research portfolio ...
current research portfolio2

Ultra Wide Band Compatibility Issues

Aegis Systems

Tech Sty to determine feasibility of sharing HDFSS & BSS

Aegis Systems

Protection of civil aero and maritime services

BAE Systems

Avoidance of discontinuities in Rec ITU-R P452

BT Exact

Channel Trading

Smith Inst.

Radio Channel Assignment

Smith Inst.

Optimising a staged band reversal process


Compatibility between IMT 2000 & MSS @ 2.5GHz

Transfinite Sys

Protection for the Radio Astronomy Service

Transfinite Sys

DSL Related systems on radio services

ERA Tech.

EMC emissions above 1GHz phase 2

ERA Tech.

Study on effects of deployment of ADSL


Freq.Sel.Windows to reduce unwanted emissions on radio


Spectrum Management Strategies for LES

Mason Comms

Emissions from future electric transport, phase 2


Current research portfolio ...
current research portfolio3

European Radio Research Activities


Refractivity Index in Clear Air at 38GHz


Propagation through vegetation


Impact of loss of GPS signals


Propagation Mechanisms Frequencies > 71GHz


RAL Core programme


RCRU Dissemination of Information


Bolton Overlay Project


ITU-R Rainscatter Model


Freq Sharing between transmitting FSS & FS


Numerical Integration rain scatter method for ITU-R Rec.452


Current research portfolio ...
broadband measurements
Broadband Measurements
  • Long-term measurements of xDSL broadband installations
  • Short-term measurements of PLT installations
    • effects on HF systems?
typical adsl measurement
Typical ADSL measurement

9 - 450kHz with a characteristic hump

current research portfolio4
Current research portfolio ...

Airborne VHF Radio Direction Flying Platform


Mobile VCE

Mobile VCE

Ionosondes Programme


Mobile Phone Health Effects


Airborne DF Platform

  • 4th generation mobile systems
    • Software Based Systems
    • Networks and Services
    • Wireless Access
task groups

Mobile and Terrestrial Propagation

Ionospheric Effects on Radio Systems

Propagation Factors Governing Terrestrial Fixed Service Outages at and above 13GHz

Task Groups
task group
Task Group:

Mobile and Terrestrial Propagation

vegetation multipath
Vegetation & Multipath
  • The effects of trees in multipath modelling for 3G can not be neglected
    • A new model for tree scattering
    • Y Nechayev & C.C.Constantinou, University of Birmingham
  • 2 transmitter locations
  • 2 receivers
    • multiple antennas

A typical Network Analyser measurement, shows strong multipath components

vegetation multipath1
Vegetation & Multipath

Paths between Tx1 and Rx1 are shown

  • significant scatterers can be identified from the geometry
  • results for individual trees are compared with predictions
  • a tree model produced for ray tracing applications
propagation in buildings
Propagation in Buildings

Yi Huang, University of Liverpool

Real buildings are measured

400 MHz to 3 GHz

Large variability in material parameters

Data on building materials is limited

  • Research topics:
  • building entry loss
  • in-building propagation
propagation in buildings1
Propagation in Buildings

The multipath return is analysed to determine its most likely cause

  • Can determine:
    • number of material layers
    • layer thickness
    • permittivity of each layer
    • conductivity of each layer
channel sounders

Array Antenna

Channel Sounders
  • University of Bristol - Medav RUSK BRI sounder
  • •1910-1930MHz & 2110-2130MHz
  • • 6.4 ms excess delay (~2km)
  • • ±45 ° polarisation
  • • +40dBm transmit power
  • Fixed RX, Mobile TX

Channel Impulse Response & Azimuth of multipath components along a route

terrain databases
Terrain Databases

BT Exact - Automated generation of coastal zone data from GTOPO 30 arc sec data

The Coastal Zone is defined as land less than 100m high and within 50km of the sea.

Applications are in ITU-R propagation models. For example ITU-R P1546


terrain databases1
Terrain Databases

Some editing required - especially for inland seas not at 0m ASL!

BT Exact visual editing tool.

ray tracing
Ray Tracing

Rapid Pipeline Development Tool


  • Ray tracing package developed for local multi-point distribution coverage planning
  • Uses Mobile & Terrestrial TG 3D Building Database format & Databases
  • Generates path loss and multipath data between all potential sites
  • Recent work to include Diffraction effects
ray tracing1
Ray Tracing

Example application- IST Embrace Project




3D building

and terrain


User, hub and

cost model


Cell designer

and optimiser

From Embrace Workshop


Task Group:

Ionospheric Effects on Radio Systems

  • radio systems, radar, navigation and radiolocation
  • effects of extreme space weather on propagation
  • ground wave effects
  • Areas for research include
  • e.g. • adaptive and frequency agile MF/HF communications
    • digital modulation methods
    • higher data rates
    • improvement of spectrum utilisation
    • impact of PLT and DSL technologies
    • trans-ionospheric effects on satellite-to-satellite and satellite–to-ground systems (e.g. GPS and GALILEO)
validation of total electron content measurements
Validation of Total Electron Content Measurements
  • Ionospheric effects on many radio systems are dependent on the total electron content (TEC) along the ray path
  • Discrepancies between different measurements is studied under COST271
  • Global Positioning Satellites (GPS) signals and Navy Ionospheric Monitoring System (NIMS) satellites are used

The plot shows a comparison of GPS TEC measurements at Chilbolton by the RAL group with NIMS observations by the Aberystwyth group, showing general agreement (except one outlier)

multi instrument data analysis system midas


GPS signals received on the ground (phase & time delay)

Space-based LEO GPS receivers


4-D images (‘movies’) of electron concentration or TEC

Multi-instrument data analysis system (MIDAS)
  • Advantages of using GPS:
  • No need to deploy any equipment
  • Continuous 5 years of free data supplied over the internet

Electron concentration (x1011 m-3)

Vertical total electron content in TECUs (x1016 m-2)

TEC measurements using MIDAS




The images shown were obtained from the centre frame of a one hour 4-D inversion ‘movie’

Vertical TEC (left) and electron concentration cross section (right) obtained from MIDAS inversion of GPS data Europe 14 July, 1800 UT


HF propagation

  • Off-great circle HF propagation:
    • measurements of gross deviations of ionospherically propagated HF signals
    • development of ionospheric models with ray tracing studies
    • development of rules to estimate its influence on communications links, radiolocation systems and OTH radars
    • building the rules into software for use with current prediction software
  • Cause:
    • localised, time varying, enhancements in the electron density distribution of the high latitude ionosphere
    • model of the convecting patches and arcs of enhanced electron density has been built
    • good agreement the simulated and experimental measurements

Propagation along mid-latitude trough

  • Over 1 year’s measurements of trough from Uppsala to LeicesterMeasured:
  • direction of arrival
  • time of flight
  • delay spread
  • Doppler spread
  • The direction of arrival and time of flight characteristics were used to validate and improve current trough models
  • Delay and Doppler spread are important for HF digital communication systems (e.g. DRM)

Diurnal variation of Doppler spread on a 10 MHz signal received over the Uppsala - Leicester path during winter (black curve) and summer (green curve).

residual height variation of f2
Residual height variation of F2

Practical Implications of Long Term Trends in the Critical Frequency and the Height of the F2 Layer above Tromsø (70°N, 19°E)

  • Many HF propagation tools based on CCIR ionogram characteristics database
  • CCIR database (‘Oslo coefficients’) measured at ionosondes worldwide in 1954 to 1958 and in 1964
  • Lesser problem for URSI ‘88 coefficients (1975-1979)
  • ITU-R propagation tools reliant on old CCIR (Oslo) database will yield ground range errors ~ 100km per hop (c. 2000)
  • CCIR (and URSI ‘88) datasets may need to be revised

Trend in hmF2 from 1950 to 2000 is -4.16 km per decade

radio wave scintillation
Radio-Wave Scintillation
  • Scintillation due to ionospheric irregularities can cause severe degradation to radio systems, including GPS operations.
  • An interest group has been established under COST271 to investigate the problem over northern Europe.
  • Experimental results from observations at VHF for several years at sub-auroral, auroral and polar locations by the University of Wales, Aberystwyth group have been presented as a contribution to the study

Interactive foF2, MUF(3000)F2, TEC maps across Europe and associated archive database

TEC plots for each European observational location and associated archive database

Ionospheric long-term prediction and short-term forecasting computational tools

Ionospheric Propagation Group


Task Group:

Propagation Factors Governing Terrestrial Fixed Service Outages at and above 13GHz

  • establish reason for outages
  • assess possible improvements in
    • specific attenuation
    • path reduction factor
  • examine rain duration statistics
  • update the UK Rain Grid
  • assess sleet as a contributor
  • revise models
uk rain map
UK Rain Map
  • Rain maps are generally derived from Met Office data
  • Met Office and RA requirements may differ:
  • the intensity and duration of rain events is of high priority to radio users
  • all precipitation, not only that which reaches the ground, is required for propagation prediction

The RA supports a rain research activity at RAL using the Chilbolton radar

transportable rain radar
Transportable Rain Radar

The Chilbolton radar has a long range, but is fixed (near Andover)

  • Operates at 3 GHz
  • Commissioned July ‘01
  • Uses DSP to combat low antenna gain

A portable dish is used to make measurements at a site in Scotland

transportable rain radar1
Transportable Rain Radar
  • Existing microwave fixed links are monitored
  • (shown as short lines)
  • link performance is correlated with the meteorological data from the rain radar at St Andrews
  • (beam width shown by long V-lines)

The results are used to develop and improve propagation prediction software used in fixed link assignment

transportable radar data
Transportable Radar Data

February 7, 2002 Cold - 2 - 6º


The performance of the microwave links during the same periods shows increased attenuation when sleet is present on the link

March 10 2002

Temperatures between -2 º and 1º with sleet and snow

new technologies
New technologies


  • UWB, software defined radio
  • frequency selective structures (FSS), smart antennas, MIMO
  • high altitude platforms (HAP), micro-satellites
  • fixed wireless access, ad hoc and adaptive networks, mesh networks
  • new propagation scenarios
  • convergence, e.g. digital radio and television
  • coexistence with non-radio systems, EMC and transmitter/receiver immunity issues
  • metrics for spectrum efficiency