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Tools of the trade for small cell backhaul
Dr John Naylon CTO, Cambridge Broadband Networks Limited
Small Cell World Summit, 26 June 2012
The essential role of wireless technologies
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• What’s different about
small cell backhaul?
• Wireless technology
fundamentals
• Three tools for every toolbox
• Current CBNL
small cell backhaul trials
• Conclusion
Agenda
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About Cambridge Broadband Networks Limited (CBNL)
• Founded in 2000
• Specialists in innovative microwave
backhaul for data-centric mobile networks
• Leaders in the small cells backhaul space:
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• Lead NGMN LTE Provisioning
Guidelines project
• Leading Small Cell Backhaul
Requirements project
• Vice Chair of Backhaul SIG
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• What’s different about
small cell backhaul?
• Wireless technology
fundamentals
• Three tools for every toolbox
• Current CBNL
small cell backhaul trials
• Conclusion
Agenda
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What’s different about small cell backhaul?
• Location, location, location
− Outdoor small cells aren’t in traditional locations
− Consequence: fibre is much less of an option
• The numbers
− Many more units to backhaul
− Consequence: sharing backhaul more attractive
• The traffic
− Fewer UEs in the cell, which means…
− Less aggregation in the RAN, which means…
− Peak-to-mean ratio of small cell traffic is higher
− Consequence: aggregation desirable in backhaul
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Traffic characteristics of mobile backhaul traffic
• Mobile backhaul traffic is already quite bursty, because it is data dominated:
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HSPA+ Macro Node B backhaul traffic Peak:
Mean:
Ratio:
23.31 Mbps
5.54 Mbps
4.20 Mbps
Mbps
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Bursty traffic is hard to carry efficiently
• Efficiency = mean channel utilisation
peak channel capacity =
1 peak to mean ratio
= 25% average
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HSPA+ Macro Node B backhaul traffic Peak:
Mean:
Ratio:
23.31 Mbps
5.54 Mbps
4.20 Mbps
Mbps
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Small cell mobile backhaul traffic is even burstier
• Higher peak data rates (better user geometries); lower mean data rates (fewer
users), so…
• peak-to-mean ratio of traffic goes up, estimate for mature networks ~10:1, so…
• dedicated backhaul link efficiency goes down to ~10%, so…
• much more equipment running at much lower efficiency, so…
• CFO has a heart attack!
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Western European small cell backhaul traffic Peak:
Mean:
Ratio:
31.17 Mbps
0.49 Mbps
63.61Mbps
Mbps
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• What’s different about
small cell backhaul?
• Wireless technology
fundamentals
• Three tools for every toolbox
• Current CBNL
small cell backhaul trials
• Conclusion
Agenda
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Wireless fundamentals: Capacity versus Coverage
10
High capacity and NLOS capability are
mutually exclusive requirements Commercial in confidence
NLOS ⇒ low frequency
Spectrum scarce, expensive
Low frequency ⇒ low capacity
Very low aggregation factor
High capacity ⇒ high frequency
Spectrum plentiful, inexpensive
High frequency ⇒ LOS only
Coverage not uniform
Coverage Capacity
Cells in cluttered locations
Uncertain LOS to PoPs Aggregating 10 cells to a PoP
requires 10 × mean cell demand
Requirement:
Implications:
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PTP and PMP cost scales differently versus density
Point-to-Multipoint (PMP)
1 ODU / truck roll / rental per link (+1)
On-air aggregation
Simpler “single-ended” installation
Shared capacity
Lower TCO per link
Point-to-Point (PTP)
2 ODUs / truck rolls / rentals per link
Zero aggregation on-air
Complex installation
Dedicated capacity
Higher TCO per link
Wireless fundamentals: Point-to-Point versus Point-to-Multipoint
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Efficiency = mean channel utilisation
peak channel capacity
Statistical multiplexing gain = 51.0 32.2
= 1.58
Point-to-Point backhaul
• Efficiency = 32.2%
Traffic fundamentals: bursty traffic and efficiency
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Multipoint backhaul
• Efficiency = 51.0%
Cumulative Peak: 77.9 Mbps Cumulative Mean: 39.7 Mbps Cumulative Peak: 123.2 Mbps Cumulative Mean: 39.7 Mbps
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• Given the requirements and the fundamentals of wireless technology, is there
a one-size-fits-all backhaul panacea for small cells? No (or not yet anyway).
• Given the requirements and the fundamentals of wireless technology, is there
a one size fits all backhaul panacea for small cells?
The story so far
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Edited by CBNL NLOS ⇒ low frequency
Spectrum scarce, expensive
Low frequency ⇒ low capacity
Very low aggregation factor
High capacity ⇒ high frequency
Spectrum plentiful, inexpensive
High frequency ⇒ LOS only
Coverage not uniform
Coverage Capacity Cells in cluttered locations
Uncertain LOS to PoPs Aggregating 10 cells to a PoP
requires 10 × mean cell demand
Cost
Density
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• What’s different about
small cell backhaul?
• Wireless technology
fundamentals
• Three tools for every toolbox
• Current CBNL
small cell backhaul trials
• Conclusion
Agenda
www.cbnl.com
Three tools for every toolbox
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Capacity
Coverage
Efficiency
Ease of install and licensing
Non-LOS Multipoint
Low
Very good, area coverage
Good
Very easy
Microwave Multipoint
High
Good, area coverage
Good
Easy
E-Band Point-to-
Point
Very High
Point coverage
Poor
Hard
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Non-LOS Multipoint: use it when…
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Capacity
Coverage
Efficiency
Ease of install and licensing
Non-LOS Multipoint
Low
Very good, area coverage
Good
Very easy
High Frequency Multipoint
High
Good, area coverage
Yes
Easy
E-Band Point-to-
Point
Very High
Point coverage
No
Hard
• Motivation for small cells is increased
RAN coverage (‘not-spots’) rather
than capacity
• Density of small cells is low (limit of
1—2 sites per backhaul sector)
• Lower quality of experience
acceptable
• Position of small cell is particularly
adverse
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E-Band Point-to-Point: use it when…
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Capacity
Coverage
Efficiency
Ease of install and licensing
E-Band Point-to-
Point
Very High
Point coverage
Poor
Hard
High Frequency Multipoint
High
Good, area coverage
Yes
Easy
E-Band Point-to-
Point
Very High
Point coverage
No
Hard
• Very high capacity sites (more like
macro)
• Middle-mile solution when traffic is
already aggregated
• Difficulty of installation not an issue –
e.g. low number of sites
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Microwave Multipoint: use it when…
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Capacity
Coverage
Efficiency
Ease of install and licensing
Microwave Multipoint
High
Good, area coverage
Good
Easy
High Frequency Multipoint
High
Good, area coverage
Yes
Easy
E-Band Point-to-
Point
Very High
Point coverage
No
Hard
• Motivation for small cells is increased
network capacity
• Good quality of experience is
required
• Density of small cells is high
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Small cell backhaul toolbox summary
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Low capacity
Adverse location
Cost effective
High capacity
Normal
small-cell
locations
Cost effective
Extreme capacity
Middle mile
Most expensive
Nu
mb
er
of sm
all
ce
ll site
s
Non-LOS Multipoint
Microwave Multipoint
E-Band Point-to-
Point
Fibre if accessible
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• What’s different about
small cell backhaul?
• Wireless technology
fundamentals
• Three tools for every toolbox
• Current CBNL
small cell backhaul trials
• Conclusion
Agenda
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VectaStar
Backhaul
lightRadio
• Building on years of macro backhaul experience, CBNL are actively
trialling small cell backhaul with numerous operators and vendors
Current CBNL small cell backhaul trials
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Metro
WiFi
VectaStar
Backhaul
LTE Picocell
Antennas
VectaStar
Backhaul
22 22 22
Conclusions
•Small cell backhaul is different:
many more cells to backhaul, non-
traditional locations and even
burstier data
• Good end-user quality of
experience requires much more
backhaul capacity than there is low
frequency backhaul spectrum
• No single technology matches the
requirements for small cell backhaul
perfectly, so a toolbox approach is
needed
• Multipoint microwave is a cost
effective, rapidly deployable
solution for small cell backhaul in
many use cases
VectaStar from Cambridge Broadband Networks is the market leader in multipoint microwave
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