Radiocommunications Agency
Annual technical research report
November 2002
Trevor Clarkson
Head of Engineering and Research Unit
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
•
•
•
•
•
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
• 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)
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
Details of projects
listed can be found at
www.radio.gov.uk
Current research portfolio ...
Indoor Wideband Measurements
UMIST
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 lampsUni 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 ...
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
TCI
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
NPL
Freq.Sel.Windows to reduce unwanted emissions on radio NTU/Warwick
Spectrum Management Strategies for LES
Mason Comms
Emissions from future electric transport, phase 2
MIRA
Current research portfolio ...
European Radio Research Activities
QinetiQ
Refractivity Index in Clear Air at 38GHz
QinetiQ
Propagation through vegetation
QinetiQ
Impact of loss of GPS signals
QinetiQ
Propagation Mechanisms Frequencies > 71GHz
QinetiQ
RAL Core programme
RAL
RCRU Dissemination of Information
RAL
Bolton Overlay Project
RAL
ITU-R Rainscatter Model
RAL
Freq Sharing between transmitting FSS & FS
RAL
Numerical Integration rain scatter method for ITU-R
RAL Rec.452
Broadband Measurements
Long-term measurements of xDSL
broadband installations
Short-term measurements of PLT
installations
• effects on HF systems?
Typical ADSL measurement
9 - 450kHz with a characteristic hump
Current research portfolio ...
Airborne VHF Radio Direction Flying Platform
RA/NATS
Mobile VCE
Mobile VCE
Ionosondes Programme
PPARC
Mobile Phone Health Effects
DTI
www.mthr.org.uk/
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 Group:
Mobile and Terrestrial
Propagation
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 & 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
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 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
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
Array Antenna
Channel Impulse Response & Azimuth of multipath components along a route
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
GTOPO 30
Terrain Databases
Some editing required - especially for inland seas not at 0m ASL!
BT Exact visual editing tool.
Ray Tracing
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
Rapid Pipeline Development Tool
Malvern
Ray Tracing
Example application- IST Embrace Project
3D building
and terrain
databases
User, hub
and
cost model
parameters
RPD
propagation
tool
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
• 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)
Imaging the ionosphere using GPS
LEO orbit
Path
Low Earth Orbiter
(LEO)
Radio Occultation
Path
Global Positioning Satellite
(GPS)
Input:
GPS signals received on the ground (phase & time delay)
Space-based LEO GPS receivers
Advantages of using GPS:
Output:
4-D images (‘movies’) of
electron concentration or TEC
• No need to deploy any equipment
• Continuous 5 years of free data
supplied over the internet
TEC measurements
using MIDAS
Kp
5
4
Electron concentration (x1011 m-3)
Vertical total electron content in TECUs (x1016 m-2)
Vertical TEC (left) and electron concentration
cross section (right) obtained from MIDAS
inversion of GPS data Europe 14 July, 1800 UT
The images shown were
obtained from the centre
frame of a one hour 4-D
inversion ‘movie’
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 Leicester
Measured:
• direction of arrival
• time of flight
• delay spread
• Doppler spread
The direction of arrival and time of flight
characteristics were used to validate
Diurnal variation of Doppler spread
and improve current trough models
Delay and Doppler spread are
important for HF digital communication
systems (e.g. DRM)
on a 10 MHz signal received over
the Uppsala - Leicester path during
winter (black curve) and summer
(green curve).
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)
Trend in hmF2 from
1950 to 2000 is
-4.16 km per decade
• 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
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
Ionospheric Propagation Group
• 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
http://ionosphere.rcru.rl.ac.uk/
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
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
The Chilbolton radar has a
long range, but is fixed
(near Andover)
A portable dish is used to
make measurements at
a site in Scotland
• Operates at 3 GHz
• Commissioned July ‘01
• Uses DSP to combat low
antenna gain
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
February 7, 2002
Cold - 2 - 6º
Sleet
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
Examples:
– 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