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. British Telecom

• 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?

1947

“Cellular” Design in New York

8 km

2008

Macros

8 km

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

Boston

Boston, raster clutter @ 25m

Boston, PV clutter @ 0.5 m

Boston

JFK Airport

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 [email protected]

Simon Chapman [email protected]