efficient mobile backhaul
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Efficient Mobile Backhaul
Next generation thinking
John NaylonMobile World Congress, Barcelona - 29 February 2012
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'08 '09 '10 '11 '12 '13 '14 '150%
25%
50%
75%
100%
Microwave Fibre Copper
The Problem Space: Mobile Backhaul• Need to connect mobile base stations (node Bs) to core network
− Could use copper, fibre or microwave radio− Microwave is the dominant choice− ~0.5M new microwave backhaul connections
per annum
?
Worldwide MobileBackhaul Connections
Source: Infonetics Research
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The Problem Space: Mobile Backhaul Traffic Properties
Sample backhaul demands for 3 tri-cell node Bs in a live, busy HSPA+ network:
Can we exploit statistical properties of this data to make our backhaul more efficient?
Mbps
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First Property: Data is Bursty• Data is bursty, i.e. has sharp transient peaks and a much lower mean
− This characteristic is driven by user and application behaviour− Burstiness still present when traffic is aggregated within a node B/eNode B
Node B backhaul trafficPeak:Mean:Ratio:
23.31 Mbps5.54 Mbps4.20 Mbps
Handset traffic (10 Devices)Peak:Mean:Ratio:
12.07 Mbps1.44 Mbps8.37 Mbps
Handset traffic (one iPhone 4)Peak:Mean:Ratio:
11.44 Mbps0.14 Mbps
79.20 Mbps
Mbps
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First Property: Data is Bursty (2)
• Network-wide average of peak-to-mean ratio is approximately 4:1 in this HSPA+ example network
− Major implication for efficiency since it is mandatory to provision backhaul that can accommodate the offered peak load
− However if we have a dedicated link the mean utilisation de facto cannot be greater than the mean offered load
− Therefore the mean utilisation will be approximately in the ratio of 1:4 to the peak, i.e. approximately 25%
− So the data’s properties mean that:
Dedicated backhaul links are 75% idle!
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Mbps
• Peak bandwidth demand does not occur simultaneously at adjacent node Bs
Second Property: Peak Demand is not Synchronised
− Peaks are of short duration (seconds, not hours like the daily ‘swells’)
− Peaks arise from random, independent actions of network end users
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• Peak bandwidth demand does not occur simultaneously at adjacent node Bs
Second Property: Peak Demand is not Synchronised (2)
− Peaks are of short duration (seconds, not hours like the daily ‘swells’)
− Peaks arise from random, independent actions of network end users
− In the studied HSPA+ network, average cross-correlation factor of pairs of node Bs in geographical proximity is 0.16 indicating very weak correlation (network-wide correlation is even lower, at 0.06)
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Point-to-Point
• Non-uniform data rate and absence of correlation lets us share, or multiplex, resources instead of using dedicated resources (just as we do in the RAN)
Using These Properties to Improve Backhaul Efficiency
Point-to-Multipoint
Shared radio + antenna for all links
Dedicated radio + antenna per linkDedicated RF
channel per linkShared RF channel for all links
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• We examine measured backhaul profiles from a group of eight node Bs− Live network, large middle-eastern operator, heavy data usage− HSPA+ tri-cellular node Bs− Theoretical maximum throughput 64.8Mbps per site
• Consider the amount of spectrum needed for each of the two topologies− Use the bare minimum of spectrum to carry exact data profile (no ‘headroom’)
Savings from Point-to-Multipoint Architecture: Spectrum
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Savings from Point-to-Multipoint Architecture: Spectrum
Peak:Mean:
11.29 Mbps2.47 Mbps
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Cumulative Peak: 11.3 Mbps
Cumulative Mean: 2.5 Mbps
Cumulative Peak: 11.3 Mbps
Cumulative Mean: 2.5 Mbps
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Savings from Point-to-Multipoint Architecture: Spectrum
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Peak:Mean:
15.12 Mbps4.18 Mbps
Cumulative Peak: 19.5 Mbps
Cumulative Mean: 6.6 Mbps
Cumulative Peak: 26.4 Mbps
Cumulative Mean: 6.6 Mbps
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Savings from Point-to-Multipoint Architecture: Spectrum
Cumulative Peak: 30.9 Mbps
Cumulative Mean: 14.2 Mbps
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Peak:Mean:
17.45 Mbps7.61 Mbps
Cumulative Peak: 43.9 Mbps
Cumulative Mean: 14.2 Mbps
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Savings from Point-to-Multipoint Architecture: Spectrum
Cumulative Peak: 42.9 Mbps
Cumulative Mean: 18.9 Mbps
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Cumulative Peak: 58.4 Mbps
Cumulative Mean: 18.9 Mbps
Peak:Mean:
14.51 Mbps4.64 Mbps
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Savings from Point-to-Multipoint Architecture: Spectrum
Cumulative Peak: 51.7 Mbps
Cumulative Mean: 24.6 Mbps
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Cumulative Peak: 74.2 Mbps
Cumulative Mean: 24.6 Mbps
Peak:Mean:
15.83 Mbps5.69 Mbps
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Savings from Point-to-Multipoint Architecture: Spectrum
Cumulative Peak: 60.2 Mbps
Cumulative Mean: 31.2 Mbps
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Cumulative Peak: 92.0 Mbps
Cumulative Mean: 31.2 Mbps
Peak:Mean:
17.85 Mbps6.67 Mbps
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Savings from Point-to-Multipoint Architecture: Spectrum
Cumulative Peak: 67.8 Mbps
Cumulative Mean: 34.2 Mbps
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Cumulative Peak: 108.0 Mbps
Cumulative Mean: 34.2 Mbps
Peak:Mean:
15.98 Mbps2.93 Mbps
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Savings from Point-to-Multipoint Architecture: Spectrum
Cumulative Peak: 77.9 Mbps
Cumulative Mean: 39.7 Mbps
Point-to-Point Microwave Radio, Star Topology Point-to-Multipoint Microwave Radio
Cumulative Peak: 123.2 Mbps
Cumulative Mean: 39.7 Mbps
Peak:Mean:
15.18 Mbps5.49 Mbps
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Spectrum required =
Point-to-Point
• Spectrum required = 15.4 MHz
Savings from Point-to-Multipoint Architecture: Spectrum
Point-to-Multipoint
• Spectrum required = 9.7 MHz
* 256-QAM assumed
Cumulative Peak: 77.9 Mbps Cumulative Mean: 39.7 MbpsCumulative Peak: 123.2 Mbps Cumulative Mean: 39.7 Mbps
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Mean channel utilisation (efficiency) =
Point-to-Point
• Efficiency = 32.2%
Savings from Point-to-Multipoint Architecture: Spectrum
Point-to-Multipoint
• Efficiency = 51.0%
Cumulative Peak: 77.9 Mbps Cumulative Mean: 39.7 MbpsCumulative Peak: 123.2 Mbps Cumulative Mean: 39.7 Mbps
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40% power saving per link
Point-to-Point
37W per radio, 2 radios per link
74W per link
Savings from Point-to-Multipoint Architecture: Power
Point-to-Multipoint
35W per radio, mean of 4 remotes per sector 1.25 radios per link
44W per link
* Figures reflect market leaders in both categories
212121
Conclusions
• Mobile broadband backhaul traffic has specific properties we can exploit to design more efficient backhaul networks
• Point-to-multipoint architecture dramatically improves spectral efficiency and power efficiency per link
• Dedicated backhaul links operate at a very low efficiency: ~25% (!!) something blah something different something
• Less equipment deployed means additional environmental, capex and opex benefits
VectaStar from Cambridge Broadband Networks is the market leader in point-to-multipoint
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