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Radiocommunications Agency

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

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Radiocommunications Agency

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  1. Radiocommunications Agency Annual technical research report November 2002 Trevor Clarkson Head of Engineering and Research Unit

  2. 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

  3. 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

  4. 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

  5. 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

  6. £4M total RAL core Current research portfolio Details of projects listed can be found at www.radio.gov.uk

  7. 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 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 ...

  8. 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 ...

  9. 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 Rec.452 RAL Current research portfolio ...

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

  11. Typical ADSL measurement 9 - 450kHz with a characteristic hump

  12. 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

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

  14. Task Group: Mobile and Terrestrial Propagation

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. Terrain Databases Some editing required - especially for inland seas not at 0m ASL! BT Exact visual editing tool.

  22. Ray Tracing Rapid Pipeline Development Tool Malvern • 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

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

  24. 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)

  25. 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)

  26. Imaging the ionosphere using GPS LEO orbit Path Radio Occultation Path Low Earth Orbiter (LEO) Global Positioning Satellite (GPS) Input: GPS signals received on the ground (phase & time delay) Space-based LEO GPS receivers 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

  27. Electron concentration (x1011 m-3) Vertical total electron content in TECUs (x1016 m-2) TEC measurements using MIDAS Kp 5 4 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

  28. 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

  29. 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).

  30. 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

  31. 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

  32. 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 http://ionosphere.rcru.rl.ac.uk/

  33. 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

  34. 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

  35. 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

  36. 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

  37. 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

  38. 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

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