Efficient mobile backhaul

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Efficient Mobile Backhaul

Next generation thinking

John NaylonMobile World Congress, Barcelona - 29 February 2012

www.cbnl.com Commercial in confidence 2

'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


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


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


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!


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


• 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)


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


• 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



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






Peak:Mean:

15.12 Mbps4.18 Mbps










Peak:Mean:

17.45 Mbps7.61 Mbps










Peak:Mean:

14.51 Mbps4.64 Mbps








Peak:Mean:

15.83 Mbps5.69 Mbps








Peak:Mean:

17.85 Mbps6.67 Mbps








Peak:Mean:

15.98 Mbps2.93 Mbps








Peak:Mean:

15.18 Mbps5.49 Mbps


Spectrum required =

Point-to-Point

• Spectrum required = 15.4 MHz


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


Mean channel utilisation (efficiency) =

Point-to-Point

• Efficiency = 32.2%


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


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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Efficient mobile backhaul