Radio Challenges and Opportunities for Large Scale Small Cell Deployments

Radio Challenges and Opportunities for
Large Scale Small Cell Deployments
Keima Wireless
Small Cell SIG Event
Cambridge, Oct 2012

Cell Planning 1947 to 1984
• “Mobile radiotelephones” first encounter interference
effects in 1946.
• The cellular concept1,2 invented c. 1946.
• Cell planning is managing interference while we:
– increase site numbers; and
– shrink the reuse distance.
2 D.H. Ring, Bell Labs – Telephony – Wide Area Coverage, 11 December 1947
1 J.R. Brinkley – J.I.E.E. – 1946, 93, Part III, pp.159-166

1947
“Cellular” Design in New York
8 km

Disruptive Events – Racal vs. BritishTelecom
• The start of the macro era:
• Cell Phones for the Masses…
• The new Vodafone network was launched on 1st January
1985. The smaller company’s innovative approach to
network planning allowed them to compete with the
UK’s biggest company.
• Vodafone became the largest mobile network …

1984
• Predicted coverage, Guildford 1984
• Main input: terrain

Cell Planning since 1984
25 25
1600
0
200
400
600
800
1000
1200
1400
1600
1800
Quantity of
Spectrum
Cell Spectrum
Efficiency
Number of
Cells
How do we provide capacity
to match Cooper’s demand
progression?

Disruptive Event - iPhone
The growth of data demand has doubled
Every 1 year
A rate greater than Cooper’s predictions.
Macros networks no longer effective.
Reduction in the cell size => small cells

The “Super Cooper” Expansion Challenges 1
1984 & 2012: cell location is still the key factor
64 QAM
64 QAM
64 QAM
Small Cell
Size : 100m
Macro Cell
Size : 500m
Wi-Fi AP
Size : 40m
QPSK

Quantisation Error
• Cell Radius, R.
• Quantisation1
ΔX < R/40
• So, if a cell is ~ 400 m, ΔX < 10 m.
1 Pete Bernardin and Kanagalu Manoj – IEEE Transactions on Vehicular Technology, Vol 49, No. 5, 2000

• We need to model the environment to 1 m accuracy.
Quantisation
Type R ΔX
Macro 500 m 12.5 m
Small Cell 100 m 2.5 m
Wi-Fi 40 m 1 m

Demand estimates should take account of non uniformity. Techniques that
cannot identify usage clustering at the scale of the cell radius will have
limited use.
Non Uniform Demand
64 QAM
64 QAM
Clusters of
demand

Clustering Accuracy
• New small cells should be placed to coincide with areas of
highest demand (e.g. hotspots) to maximise capacity.
• Small cells have radii ~100 m which means their spectrally
efficient 64-QAM zones are ~50 m or less.
• Demand estimates should take account of non uniformity and
be capable of resolving clustering accuracy <50 m.
• Geotagged social data (Twitter, foursquare, …) use Wi-Fi
assisted GPS for location accuracy (including indoors) ~ 20 m or less
…
• (And using the Bernadine rule, we must use 1 m quantisation to
resolve such small demand clustering.)

7 km
Images generated in Overture by Keima
Twitter London

3 km
Twitter London

1.5 km
Twitter London

0.8 km
Twitter London

400 m
High demand areas
Twitter London

Demand is complex:
Road users;
Pedestrians;
Residential;
Business;
Railroads;
Etc.

200 m
Overall Demand (composite map)

200 m
Indoor Demand

200 m
Outdoor Demand

What is the deployment focus?
Macro / outdoors, continuous coverage;
Macro / high mobility demand, highways;
Small cells / outdoors, hotspots;
Small cells + Wi-Fi / offload, POIs;
Etc
200 m
Outdoor Demand with Small Cells (light blue) and Wi-Fi + Small Cells (dark blue)

Interference Continuum - Macro / Small Cell Power
Difference
Macros are 10 – 20 dB more powerful
Distant macros can have a significant effect on small cells
Interference
It is important to deal with such an interference continuum by
predicting the signal and interference across entire cities.

Interference continuum
Boston
8 km

Boston
4 km

Boston
1 km

Boston

Boston
250 m

Boston
100 m

Combinatorial Explosion – Complex interplay of dependent
objectives.
Cell planners will have to consider for each new cell during future
100,000+ rollouts:
Location, configuration and technology parameters;
Backhaul proximity and wireless clearance;
Rental costs;
Latency;
Etc.

2012
N2012 ~ 290,000
Macros
500 km

2015
N2015 ~ 600,000
Macros + Small Cells (estimate)
500 km

Cells will only be deployed in areas where there is a positive
return on investment.
Return on investment should consider:
Sites that pay their way by locating near high demand “hotspots”;
Sites with manageable interference impact; AND
Backhaul or rental costs are affordable.
Only by considering ALL objectives can we maximise return on
investment: plan small cells holistically.

• Automation seeks to maximise RoI by considering:
– Optimal traditional towers;
– Optimal utility poles;
– Optimal wall mounting;
– Suggesting search ring;
– Backhaul costs; rental costs;
– Etc.

Example 1
• New York Case Study:
– Low powered small cells (1W);
– Street furniture: lighting fixtures, kiosks, power lines, etc.;
– Primary and secondary attachments;
– Wireless and fiber backhaul;
– High spectral efficiency.

Total candidate set: > 470,000
Small cells (1W) required: 1852
Primary location – green
Secondary location – orange
Manhattan
1 km

All candidate locations are street
furniture elements -> road alignment
0.5 km
Manhattan

0.5 km
Manhattan
Number of cells
follows demand

Holistic
Analyses
1 km
Manhattan

Wireless @ 60 GHz
0.5 km
Manhattan

Wireless @ 10 GHz
0.5 km
Manhattan

Fibre Routes
250 m
Manhattan

0.5 km
Manhattan
CINR
1 Mbps cell edge performance

100 m
Manhattan

Manhattan

Location is key to maximise spectral efficiency
Data accuracy more important than ever (1m resolution)
Interference continuum
Different environments and different cell types
Non uniform demand
Design focus is to maximise spectrum utilisation
Demand clusters served by 64 QAM zone
Automation
Deployable business case depends on holistic network design
The “Super Cooper” Expansion Conclusions

Example 2
• London Case Study:
– Low powered small cells (2 W) + Wi-Fi systems;
– Street furniture: lighting fixtures, kiosks, power lines, etc.;
– Wireless and fibre backhaul;
– High spectral efficiency.

Indoors Demand Outdoor Demand with selected Small Cells and Wi-Fi
Small cell service area Wi-Fi service area

800 m
NLOS Connections
London

800 m
10 GHz Fresnel Connections
London

800 m
60 GHz Fresnel Connections
London

London

Thank You
Contact Us
Iris Barcia
iris.barcia@keima.co.uk
Simon Chapman
simon.chapman@keima.co.uk

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