Propagation Requirements for Broadband Fixed Wireless Access Dr M.J. Willis Radio Communications Research Unit Rutherford Appleton Laboratory

1 st Meeting - 20th March 2001 Hosted by The Radio Communications Research Unit at RAL 28 Attendees including representatives from –Industry, including 28 GHz operators. –Radiocommunications Agency –RRAC Mobile and Terrestrial TWP Fixed Links TWP Broadband Wireless Technical Group –UK ITU-R SG3 –Universities –Research Consultancies

Strategic Research RRAC - “The prime strategy is the efficient utilisation of spectrum and as such, is not limited solely to propagation.” –Short term = now –Medium term = next few years –Long term means 5 years ! (apparently). No longer funding core research facilities, Strategic work needs to be focused on benefiting UK industry.

Terms of Reference Prime Function: It was intended that this new group concentrate on strategic research applicable to broadband fixed wireless access systems operating at frequencies above 2 GHz. Key Result: - Efficient Spectrum Engineering

Service Characteristics Fixed wireless access –Outdoor only –Not Radio-LANs Frequencies –Around 2 GHz to around 60 GHz –Optical links (Short range Free Space) Bandwidth –Broadband

Applications Broadband Fixed Wireless Access –LMDS at 28 GHz and 42 GHz High altitude platforms Satellite systems (but not MSS) Free Space Optical links

Coverage & Interference Coverage applicable to BFWA –Typical ranges of the order of a few km Interference –Inter-operator –Inter-Service

Summary of key issues identified at the meeting

What the operators wanted Models for propagation, like ITU R P.452 but readily codable, full 0% time to 100% time, including correlation over area and for both wanted and unwanted (interference) paths. More data relevant to BFWA, e.g. low towers near the clutter height, long term statistics and for interference paths. Measured channel data for testing system response. The real effects of FDD/TDD interference on performance. Tactical issues for installation e.g. Type approved equipment for 28 GHz now ! Effect of introducing a new base station into an existing deployment Frequency planning tools

What the modellers wanted Measurement data, much more measurement data. Verification testing of ITU-R P.452 above 30 GHz. Cheap widely available terrain and clutter data for use in ITU recommendations A unified approach to terrain and clutter databases Data on the temporal and spatial variability of rain More clear air data relevant to area statistics Correlation of propagation effects over space time and bandwidth More work on Mitigation techniques

What the regulators wanted Help in Judging where specific issues are of commercial importance within strategic research. Agreed models for regulation. Cheap widely available terrain and clutter data for use in ITU recommendations. Work on antennas - especially smart antennas. Studies on Inter-operator co-existence and an assessment of the true effect on spectrum efficiency. How to improve spectrum efficiency and inter-operator boundaries. Spectrum Sharing studies. Performance characteristics and limitations of real equipment and services.

Work Plan (1) It was decided to revise preliminary terms of reference of the group. These have been circulated. A list of work areas was drawn up. –Extensive –This will need prioritising

Work Areas (1) Propagation Models Update and extension of ITU-R P.452 Fast computer algorithms for Monte Carlo simulations Predication tools for performance when antennas at clutter height Channel models for coherence, multipath, vegetation effects New Measurements Area statistics for rainfall and Clear air effects Correlation of impairments over time, space and frequency band Effect of propagation through Vegetation Long range interference at mm-wavelengths extend Rec 452 to full 0%-100% Time Optical links

Work Areas (2) Radio System Planning and Optimisation Tools Area coverage planning Optimised roll out Performance evaluation Spectrum Management Co-ordination strategies What systems are likely to require spectrum in the future Spectrum Efficiency Optimisation Minimisation of guard bands Minimisation of exclusion areas Identification of new spectrum

Work Areas (3) The implications of impairments on system design and performance Details of equipment characteristics in database Real response of systems to interference/broadband effects Required protection to other spectrum users E.g Radioastronomy 43 GHz sharing very difficult. “Spectral Windows” Models of correlation of propagation phenomena over time and space Area correlation of rainstorms Simultaneous enhancement of interference and fading (e.g. rain scatter)

Work Areas (4) Interference and Sharing Inter-operator interference, especially at boundary Inter-system interference Interference limited operation rather than noise limited Antennas & Antenna Masks, Smart Antennas Are antenna masks realistic in evaluating interference with many users ? If you integrate radiated power over the mask, is it greater than the input power ? How many antennas will really be “worst case” - statistical approach ? Beam shaping to improve rain fade margin Smart antennas to improve capacity or overcome channel impairments

Work Areas (5) Mitigation techniques COST280 Use of terrain to reduce interference Automatic power control to minimise interference Spectrum planning to maximise interference at tolerable level I.e. Planning Based on C/I not C/I = C/N - 10dB

Work Plan (2) The next action is to report to the Task Groups. A set of recommended specific tasks will be produced. –Some work packages may be proposed A report will then go to the RRAC