Radiocommunications Agency Annual technical research report November 2002 Trevor Clarkson Head 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 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 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

Current research portfolio... Indoor Wideband MeasurementsUMIST Intermittent & Wideband EMC disturbancesUni of Bath Finalisation of the UK Rain Intensity MapUni of Bath Bounds for frequency assignment problemUni of Cardiff Auto Tune AntennasUni of Herts EMC in Home NetworkingUni of Herts CASE StudentshipUni of Oxford Higher Order Constraint TechniquesUni of Wales Unstructured Conductive network for TransmissionUni of York Measure digital hardware & related circuitsUni of York Impact of EMC emissions from unstructured networksUni of York Dithered Clock Osc. On Digital radio servicesUni 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 MachinesUni of York Railway Electromagnetic Compatibility StudyUni of York

Current research portfolio... Ultra Wide Band Compatibility IssuesAegis Systems Tech Sty to determine feasibility of sharing HDFSS & BSSAegis Systems Protection of civil aero and maritime servicesBAE Systems Avoidance of discontinuities in Rec ITU-R P452BT Exact Channel TradingSmith Inst. Radio Channel AssignmentSmith Inst. Optimising a staged band reversal processTCI Compatibility between IMT 2000 & 2.5GHzTransfinite Sys Protection for the Radio Astronomy ServiceTransfinite Sys DSL Related systems on radio servicesERA Tech. EMC emissions above 1GHz phase 2ERA Tech. Study on effects of deployment of ADSLNPL Freq.Sel.Windows to reduce unwanted emissions on radioNTU/Warwick Spectrum Management Strategies for LESMason Comms Emissions from future electric transport, phase 2MIRA

Current research portfolio... European Radio Research ActivitiesQinetiQ Refractivity Index in Clear Air at 38GHzQinetiQ Propagation through vegetationQinetiQ Impact of loss of GPS signalsQinetiQ Propagation Mechanisms Frequencies > 71GHzQinetiQ RAL Core programmeRAL RCRU Dissemination of InformationRAL Bolton Overlay ProjectRAL ITU-R Rainscatter ModelRAL Freq Sharing between transmitting FSS & FSRAL Numerical Integration rain scatter method for ITU-R Rec.452RAL

Broadband Measurements Long-term measurements of xDSL broadband installations Short-term measurements of PLT installations effects on HF systems?

Typical ADSL measurement kHz with a characteristic hump

Current research portfolio... Airborne VHF Radio Direction Flying PlatformRA/NATS Mobile VCE Ionosondes ProgrammePPARC Mobile Phone Health EffectsDTI Airborne DF Platform 4th generation mobile systems Software Based Systems Networks and Services Wireless Access

Task Groups Propagation Factors Governing Terrestrial Fixed Service Outages at and above 13GHz Mobile and Terrestrial Propagation Ionospheric Effects on Radio Systems

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 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 Buildings Yi Huang, University of Liverpool Real buildings are measured 400 MHz to 3 GHz Research topics: building entry loss in-building propagation Large variability in material parameters Data on building materials is limited

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 MHz & MHz 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 Databases BT 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 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 Malvern Rapid Pipeline Development Tool

Ray Tracing Example application- IST Embrace Project From Embrace Workshop 3D building and terrain databases Cell designer and optimiser User, hub and cost model parameters RPD propagation tool

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: 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

Low Earth Orbiter (LEO) Global Positioning Satellite (GPS) LEO orbit Path Radio Occultation Path 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) 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 (x10 16 m -2 ) Electron concentration (x10 11 m -3 ) The images shown were obtained from the centre frame of a one hour 4-D inversion ‘movie’ 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 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 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 and improve current trough models Delay and Doppler spread are important for HF digital communication systems (e.g. DRM) Propagation along mid-latitude trough

Residual height variation of F2 Trend in hmF2 from 1950 to 2000 is 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 ( ) 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 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 Ionospheric 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: Propagation Factors Governing Terrestrial Fixed Service Outages at and above 13GHz

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 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 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 º Sleet March 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 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