BFWAtg - BFWA sharing with RAS at 43 GHz Slide 1 Re-examination of the protection requirements for the Radio Astronomy Service in light of the Broadband Fixed Wireless Access Multimedia Wireless Systems proposed for the 42.5 - 43.5 GHz frequency band John Pahl and Steve Munday Transfinite Systems Ltd
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John Pahl and Steve Munday Transfinite Systems Ltd
Re-examination of the protection requirements for the Radio Astronomy Service in light of the Broadband Fixed Wireless Access Multimedia Wireless Systems proposed for the 42.5 - 43.5 GHz frequency band. John Pahl and Steve Munday Transfinite Systems Ltd. Presentation Structure. - PowerPoint PPT Presentation
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BFWAtg - BFWA sharing with RAS at 43 GHzSlide 1
Re-examination of the protection requirements for the Radio Astronomy Service in light of the Broadband Fixed Wireless Access Multimedia Wireless
Systems proposed for the 42.5 - 43.5 GHz frequency band
John Pahl and Steve Munday
Transfinite Systems Ltd
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 2
Presentation Structure
• Project objectives and approach• System parameters used• Approach to analysis• Results of runs• Conclusions
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 3
Project objectives
• To analyse the feasibility of BFWA operating in the 42.5 - 43.5 GHz band, taking into account the need to protect the RAS
• Determine the conditions that would facilitate sharing, such as operating restrictions
• Evaluate existing work and approaches to sharing such as in ERC Report 36
• Derive, where necessary, methodologies to model interference and assist in sharing
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 4
System Parameters• Obtained from review of previous studies, current literature
and discussion with operators • Data sets developed for different types of BFWA systems:
– 3 types of Mesh system - low, medium and high density– 6 types of Point-to-Multipoint system
• Urban Symmetric and Asymmetric models• Sub-urban Symmetric and Asymmetric models• Rural Symmetric and Asymmetric models
– 2 types of Feeder link
• Variations to analyse impact of modeling assumptions and mitigation
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 5
BFWA Baseline Models
• From the data sets, the following were selected as baseline reference models for use in the analysis:– P-MP Urban, Commercial, Symmetric Model (UCS)
– P-MP Rural, Residential, Asymmetric Model (RRA)
– Low Density Mesh Model
– High Density Mesh Model
– Feeder Link Model
• P-MP models included both BS and UT transmit, giving a total of 7 BFWA models
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 6
BFWA Mitigation
• Study alternative modeling assumptions and to facilitate sharing
• BFWA mitigation models included:– Realistic model
• Baseline model with antenna modeled as Bessel function
– Pointing model• Realistic model with restriction to avoid pointing at RAS
site
– Full Mitigation• Pointing model with antenna height restriction, shielding
and spreading loss
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 7
RAS Reference Models-1
8 potential sites that could operate RAS at 43 GHz
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 8
RAS Reference Models-2• Three RAS sites considered - Jodrell Bank,
Defford and Cambridge• Protection criteria obtained from ITU-R Rec.
RA.769 for three types of observation:
ObservationType
Harmful Interference not to beexceeded for 10% of time
Continuum -220.6 dBW/MHz
Spectral Line -204.1 dBW/MHz
VLBI -178.6 dBW/MHz
RAS protection criteria / 1 MHz
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 9
RAS Reference Models-3
• Baseline model:– Gain pattern Rec. SA 509-2, ie 32-25log()
– Minimum elevation 5°
• Realistic model:– Baseline model with antenna modeled as Bessel
function
• Pointing model:– Realistic model with minimum elevation of 19°
In all cases observation time 2000 seconds
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 10
RAS gain patterns
Bessel
Rec 465
dB
Off Axis Angle
-20
-40
-60
0
20
40
60
80
100
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Up to 35 dB difference !
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 11
Summary
Summary of Baseline and Mitigation Models
Model Baseline Realistic Pointing mitigation Full mitigationP-MP UCS BS Tx EN 301 215 CS2
20m antenna heightBessel antenna Bessel antenna
45 pointing restrictionBessel antenna45 pointing restriction15m antenna height3 dB Spreading loss
• Traditionally based upon distance, D• Not appropriate when including terrain:
– azimuth dependent
– does not linearly increase along azimuth
• Propose use of new EZ method:– Exclude all locations where L452(10%) < X
• Compare these two EZ methods• Change size of EZ (D or X) using iteration
until just meet RAS criteria
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 29
EZ for RRA BS smooth earth analysis D=66km
EZ based upon distance
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 30
EZ for RRA BS with terrain L452(10%) < -176 dB
EZ based upon L452(10%) < X
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 31
Impact of L452(10%) method
• Easy to define and implement• Reduces area excluded
– e.g. from 13,872 km2 to 2,816 km2
• Excludes points such as tops of mountains unlikely to be used anyhow
Note: L452(10%) is height dependent, so must specify maximum tx/rx antenna heights
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 32
Multi-Zone approach
R estric ted Zone
E xclusionZone
S m ooth E arth m odel used toca lcu la te exclusion d istance
U nrestric ted Zone
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 33
Analysis and Results-3
• Following Multi-Zone approach:– EZ: no BFWA operation– RZ: BFWA operating with pointing mitigation– UZ: BFWA operating unrestricted
• Boundaries EZ/RZ and RZ/UZ based upon where L452(10%) = X1, X2 (derived in analysis)
• Distribution of BFWA cells based upon UK Census data
• Multiple runs for alternative RAS assumptions
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 34
Production of realistic BFWA distribution
• Mapped 1991 UK Census data to BFWA types based on populated weighted density (persons / km2) :
UK Census Density Group BFWA System Type
3027 or over P-MP UCS
1669 to 3027 P-MP UCS
913 to 1669 Mesh LD
502 to 913 Mesh LD
200 to 502 uneconomic
under 200 uneconomic
• Mesh LD rather than P-MP RRA used for low population areas as needed ability to mitigate
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 35
Key: circles = P-MP in urban areas, crosses = mesh LD in rural areas
Realistic BFWA distribution
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 36
Worst case: RAS mask gain pattern + no BFWA mitigation
Single EZ - RAS Baseline and BFWA Realistic
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 37
Improvement due to use of MZ and Bessel gain pattern
Key: circles = BFWA cells in UZ, crosses = BFWA cells in RZMulti-Zone - RAS Realistic
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 38
RAS observing method
• Analysis above based upon RAS most stringent criteria -220.6 dBW/MHz
• This is to protect a single RAS site making Continuum observations
• Criteria to protect VLBI and Spectral line observations are higher
• Analysis was also done against these thresholds
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 39
Results: VLBI• Based upon:
– BFWA using MZ (EZ/RZ/UZ)
– RAS modelled using higher elevations and Bessel gain patterns
– Comparing against VLBI threshold
• Conclusion:– BFWA can operate close (~10 km) of RAS site
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 40
Locations of EZ/RZ/UZ for VLBI
Key: circles = BFWA cells in UZ, crosses = BFWA cells in RZ
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 41
Best case sharing scenarioRAS:• operates only as VLBI and SL (single site)• antenna gain pattern similar to Bessel function• generally operates at elevations 19°
BFWA:• uses multiple zones EZ/RZ/UZ
• zones based upon L452(10%)
• at least pointing mitigation used within RZ• frequency plan takes account of SL frequencies
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 42
Impact of RAS assumptions• Worst case - sharing very difficult with large areas
excluded:– RAS single site Continuum observations, gain pattern 32-
25log()
• Intermediate case - sharing possible but significant areas excluded:– RAS single site Continuum observations, gain similar to Bessel
• Best case - sharing possible almost everywhere except very close to RAS site:– RAS VLBI & Spectral line observations, gain pattern similar to
Bessel, elevation angles 19°
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 43
Conclusions• On its own, an exclusion zone of 50 km as in ERC Report 36 is
insufficient to protect the RAS• The methodology and assumptions used to derive this figure are
inappropriate for BFWA scenarios• New methodology described here can be used to calculate aggregate
interference BFWA RAS
• Use of Exclusion Zones based upon L452(10%) are more efficient than using distance
• Multiple zones can be used to improve coverage without requiring mitigation everywhere
• The characteristics of RAS operating in this band will determine the extent for which BFWA can be deployed
BFWAtg - BFWA sharing with RAS at 43 GHzSlide 44
Areas for Further Study• The following require further study:
– whether the RAS will use the 43 GHz band to make Continuum observations from single sites
– what is the average gain pattern of RAS antennas towards the horizon over typical observation time
From above can determine EZs to protect RAS for specified BFWA systems
Further work also needed to define how to model correlation of propagation effects using Rec. 452.
• More runs could analyse wider range of scenarios