Radiocommunications Agency

Radiocommunications Agency

Annual technical research reportAnnual technical research report

November 2002November 2002

Trevor ClarksonHead of Engineering and Research Unit

• 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 Role RA’s Role

RA’s Technical ResearchRA’s Technical Research

Technical research ...• a necessary part of the Agency’s activity

so that the spectrum resource can be efficiently planned and maintained

• spectrum management• spectrum efficiency• interference and EMC issues • propagation studies• impact of new technologies

Research facilitiesResearch 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 portfolioCurrent research portfolio

£4M total

RAL coreDetails of projects listed can be found at www.radio.gov.uk

Current research portfolio ...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 receiversUni of York

Choke Tunnel Design in 900MHZ ISM Machines Uni of York

Railway Electromagnetic Compatibility Study Uni of York

Current research portfolio ...Current research portfolio ...

Ultra Wide Band Compatibility Issues Aegis Systems

Tech Sty to determine feasibility of sharing HDFSS & BSSAegis 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 radioNTU/Warwick

Spectrum Management Strategies for LES Mason Comms

Emissions from future electric transport, phase 2 MIRA

Current research portfolio ...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 > 71GHzQinetiQ

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 Rec.452RAL

Broadband MeasurementsBroadband Measurements

Long-term measurements of xDSL broadband installationsShort-term measurements of PLT installations

• effects on HF systems?

Typical ADSL measurementTypical ADSL measurement9 - 450kHz with a characteristic hump

Current research portfolio ...Current research portfolio ...

Airborne VHF Radio Direction Flying Platform RA/NATS

Mobile VCE Mobile VCE

Ionosondes Programme PPARC

Mobile Phone Health Effects DTI

Airborne DF Platform

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

www.mthr.org.uk/

Task GroupsTask Groups

Propagation Factors Governing

Terrestrial Fixed Service Outages at and above 13GHz

Mobile and Terrestrial

PropagationIonospheric

Effects on Radio Systems

Task Group:Task Group:

Mobile and Terrestrial Propagation

Vegetation & MultipathVegetation & MultipathThe effects of trees in multipath modelling for 3G can not be neglected

A new model for tree scatteringY Nechayev & C.C.Constantinou, University of Birmingham

2 transmitter locations2 receivers

multiple antennas

A typical Network Analyser measurement, shows strong

multipath components

Vegetation & MultipathVegetation & Multipath

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

Paths between Tx1 and Rx1 are shown

Propagation in BuildingsPropagation in BuildingsYi Huang, University of Liverpool

Real buildings are measured400 MHz to 3 GHz

Research topics:• building entry loss • in-building propagation

Large variability in material

parametersData on building

materials is limited

Propagation in BuildingsPropagation 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 SoundersChannel SoundersUniversity 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

Array Antenna

Terrain DatabasesTerrain DatabasesBT Exact - Automated generation of coastal zone data from GTOPO 30 arc sec data

GTOPO 30

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

BT Exact visual editing tool.

Ray TracingRay TracingRay 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

Malvern

Rapid Pipeline Development Tool

Ray TracingRay TracingExample application- IST Embrace Project

From Embrace Workshop

3D buildingand terraindatabases

Cell designerand optimiser

User, hub andcost

modelparamete

rs

RPDpropagatio

ntool

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)

• radio systems, radar, navigation and radiolocation• effects of extreme space weather on propagation • ground wave effects

Task Group:Task Group:

Ionospheric Effects on Radio Systems

• 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)

Validation of Total Electron Content Measurements

Validation of Total Electron Content Measurements

Low Earth Orbiter Low Earth Orbiter

(LEO)(LEO)

Global Positioning SatelliteGlobal Positioning Satellite

(GPS)(GPS)

LEO orbitLEO orbitPathPath Radio OccultationRadio Occultation

PathPath

Imaging the ionosphere using GPS

GPS signals received on the ground (phase & time delay)Space-based LEO GPS receivers

Input:

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

Multi-instrument data analysis system (MIDAS)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

Kp

5

4

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

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

Electron concentration (x1011 m-3)

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

TEC measurements

using MIDAS

TEC measurements

using MIDAS

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

HF propagationHF propagation

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

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)

Propagation along mid-latitude troughPropagation along mid-latitude trough

Residual height variation of F2Residual height variation of F2

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

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

• 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

Radio-Wave ScintillationRadio-Wave Scintillation

• 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/

Ionospheric Propagation GroupIonospheric Propagation Group

• 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

Task Group:Task Group:

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

UK Rain MapUK Rain MapRain 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 RadarTransportable Rain Radar

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

antenna gain

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

Transportable Rain RadarTransportable 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 DataTransportable Radar DataFebruary 7, 2002 Cold - 2 - 6ºSleet

March 10 2002

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

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

New technologiesNew technologiesExamples:

– 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