Facebook Connectivity January 2021
Fiber
Wireless Backhaul cost challenges: Unfavorable sites Poor RAN
coverage Repeaters Tall towers Poor accessibility
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RAN antennas
Backhaul with only CLOS links – have to build in tough
locations
LOS LOS
LOS LOS
City Village
Backhaul with CLOS + NLOS = fewer towers, shorter, closer to
roads
LOS Diffractive NLOS
Why Isn’t Diffractive NLOS Used in Practice Today?
The idea of using Diffraction for NLOS isn’t new, BUT
1. Lack of NLOS data & tools 2. Lack of NLOS examples 3. Lack
of NLOS guidelines
Network Designers think CLOS is a requirement for reliable,
broadband wireless backhaul
Our program goals: Assess feasibility Understand impact Provide a
reliable,
usable, efficient solution set to network designers
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Hard terrain
What is the feasibility space of NLOSv1? 6 - 8GHz bands:
site-licensed Common Carrier radio bands
Employed internationally for highly directive Point-to-Point (PtP)
microwave backhaul. Use of standard microwave backhaul radio and
antenna. Use of available link modeling & design tools.
Single main diffracting obstacle in the radio path. The main
diffracting obstacle may be partially or fully blocking the first
Fresnel zone. The blocking obstacle may have moderate foliage
coverage. < 3 degrees diffraction angle is present in the radio
path.
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Impact: Fewer towers, no repeaters Reduced tower heights Favorable
locations
Repeater sites RAN sites
CLOS links NLOS links
14 RAN towers: 7 tall, 7 shorter 2 repeater towers
14 RAN towers: all shorter 0 repeater towers
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Hard terrain
Today network designers have confidence only in Clear LOS, and
think all else need repeaters -> hurts rural BCA
NLOS v1 expands the opportunity space for MW BH
NLOSv1 has launched in Internet para Todos (IpT) de Peru &
Mayutel
NLOS v1 is poised to enter PathLoss™ , the largest microwave design
software
NLOS v2 will address medium terrain cases -> ongoing R&D
efforts
Passive reflectors, designed surfaces are being considered for the
hardest cases
The State of Our NLOS Research Program
Data
Many datasets are available under open science umbrella: from
Plexus Controls, OSU, UPM.
Some datasets are from drone-based measurements (systematic and
dense).
Long-term measurements are ongoing.
Link design
Empirical models such as Longley-Rice, ITM, TIREM can benefit from
new calibration data, e.g., our collaboration with PathLoss
™.
New physics-based models are in development with our partners,
e.g., OSU, UMich.
Network design
High-level tools are valuable, see for example Facebook’s Advanced
Network Planning (ANP).
Assessment of techno-economic impact of NLOS(and other projects) is
ongoing, e.g., Oxford/GMU project.
Deployment Tools
Drone-based channel sounder developed by Plexus Controls is
available for purchase.
Value has been proven in the field, e.g., field surveys show tower
could be built shorter, address uncertainty in RF prediction.
Data: Systematic Propagation and Path Loss
Systematic data, especially in the vertical axis, has been very
valuable.
We compared and tuned commercially-available algorithms as
implemented in PathLoss™ 5.0.
We developed and published open-sourced Python and MATLAB
implementations of Longley-Rice / ITM algorithm.
Systematic data, especially in the vertical axis, has been very
valuable.
We compared and tuned commercially-available algorithms as
implemented in PathLoss™ 5.0.
We developed and published open-sourced Python and MATLAB
implementations of Longley-Rice / ITM algorithm.
Measurement hardware design & implementation are documented and
can be shared. Drone + integration can be purchased from partner
Plexus Controls.
A simple processing + visualization software “rf-coverage-maps” is
available as open-source.
Tuned commercially-available algorithms as implemented in PathLoss
™ 5.0 can be used in conjunction with modest error margins (~6-8
dB) with network designer input & adjustments.
Workflow can be reviewed in the Telecom Infra Project
Network-as-a-Service Solutions Group deliverables section.
Physics-based models have potential to improve performance and
quantify uncertainty, BUT we need to understand input data
requirements and their impact.
We have a number of reports published and more upcoming, please
visit the Facebook Research page.
Cluster-level impact has been quantified in a number of design
studies, we welcome your collaboration. Country-level impact study
is ongoing to quantify cost-capacity-coverage.
Deployment Tools: Current Work
Drone-based channel sounder to assess challenging deployment cases,
provides valuable services: manage risk, assess optimal tower
placement and height
Hard terrain
Today network designers have confidence only in Clear LOS, and
think all else need repeaters -> hurts rural BCA
NLOS v1 expands the opportunity space for MW BH
NLOSv1 has launched in Internet para Todos (IpT) de Peru &
Mayutel
NLOS v1 is poised to enter PathLoss™ , the largest microwave design
software