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Examining small cell backhaul requirements

Next generation thinking

15 February 2012

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Examining small cell backhaul requirements

Are small cells really the next big thing? Lance Hiley, VP Marketing, Cambridge Broadband Networks Ltd

Agenda

The challenges

How will operators deploy small cells?

Key design considerations for small cell backhaul Julius Robson, Wireless Technology Consultant and Leader, NGMN Small Cell Backhaul Requirements Group

The solutions

How do different solutions compare against the requirements? Lance Hiley

Your questions Q&A open for 10 minutes

2

5 mins

10 mins

15 mins

10 mins

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• Formed in 2000

• Global marketshare leader

in line of sight multipoint

microwave technology

• Suitable for LTE network

backhaul

• Selling to 7 of the top

10 mobile operator groups

Who we are

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Lance Hiley

VP Marketing

Cambridge Broadband Networks Limited

Are small cells really

the next big thing?

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• 1% smartphone users consume

50% of mobile data

(what happens when

others catch on?)

• More recent and realistic version

of Cisco VNI still shows growth

• New devices and apps will use

whatever capacity is available

• Industry is organising itself to speed

small cells to market

Are small cells really the next big thing?

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Small cells could be the answer

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• Mobile cellular networks were initially designed

for voice

• The popularity of mobile broadband multimedia

services has redefined the RAN and backhaul

requirements of mobile networks: data is

dominant

• Mobile networks have to evolve to transport

packet data traffic efficiently: data is different

• Reducing cell size is one of the most effective

ways to improve the spatial reuse of radio

resources and increases network capacity

• Bringing bandwidth closer users improves

customer quality of experience

“Best Signal Quality in Cellular Networks: Asymptotic

Properties and Applications to Mobility Management in

Small Cell Networks”, Alcatel-Lucent, 2010 http://jwcn.eurasipjournals.com/content/2010/1/690161

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Small cells can ease congestion

in busy areas by serving hot

spots and indoor users, leaving

macro-layer to deal with wide-area

high-mobility outdoor users

In this webinar we consider

the implications of this trend

on the backhaul…

Small cells could be the answer

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The challenges:

How will operators deploy small cells?

Resulting requirements for small cell backhaul

Julius Robson

Wireless Technology Consultant

Leader, NGMN Small Cell Backhaul Requirements Group

www.cbnl.com

Why deploy small cells?

A small cell will improve both coverage and capacity,

but the primary motive is important

when considering backhaul requirements 9

macro

…for Hot spots and Not spots

Easing congestion

within macro coverage

New coverage in

addition to macro

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Where will they be?

•Small cell sites typically 4-6 m above street

level, on sides of buildings or street furniture

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Need to densify

Smaller unit

= less power

= shorter range

Small

cells

Congestion on fully

upgraded macro sites

No rooftop space left

smaller units needed to

fit available locations

Small, low power cells

close to users

Near street level

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Case study: what density of small cells is needed?

•Case study of how demand

density will be supplied with a

mix of HSPA, LTE and small cells

•Gives site densities and spacing

5 sites/km2 dense macro rooftop network

Small cells exceed this in ~2013,

requiring below rooftop

Spacing will be lower than average in

pockets of high demand ~100-200m

•Assumptions Demand growth from PA consulting1

Spectral efficiency evolution Ofcom2

Macro site density 5/km2 (Holma3)

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1 “Predicting areas of spectrum shortage”, PA Consulting, April 2009

2 "4G Capacity Gains", Real Wireless for Ofcom, Dec 2010

3 “LTE for UMTS: Evolution to LTE Advanced”, Harri Holma, Wiley 2010

Dense macro

Variation due to

non uniform deployment

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The ‘what’ and ‘how’ of backhaul requirements

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1) Fundamentals

What

Coverage

Capacity

Cost

Architecture Small Cell

Backhaul

Solution

2) Practicalities

How

• Size & weight

• Spectrum bands

• Integration

• Installation

• Backhaul features

(QoS, Sync etc)

• Availability/latency

Implementation

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The backhaul coverage challenge…

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Small Cells

PoP

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Backhaul coverage requirements

Coverage from: Points of Presence

− PoP locations: e.g. rooftop macrosites

− PoPs density ~5 sites /km2

Coverage to: Small cell sites

− Locations:4-6m above street level

− Densities: increasing over time…

− Estimate 30 sites per km2

− ~100-200m spacing

in areas of high demand

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PoP

PoP

Coverage = Connectivity between PoP and small cell sites

…with sufficient QoS

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“Macrocells might be ‘quality not quantity’

….but the reverse is not true for small cells”

Quality of Service over Backhaul

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Aspect

of backhaul QoS

Small cell deployed primarily for…

New coverage @Not Spot

Easing congestion @Hot Spot

Availability same as macro relaxed

Delay (Latency, jitter) same as macro same as macro

Capacity provisioning relaxed greater than small cell

Where coverage overlaps, macro layer

acts as fall back for small cells

Where easing congestion, RAN capacity

should not be limited by the backhaul

•Operators want consumer QoE to be independent of the access topology

•Backhaul QoS should be driven by services offered

•Some aspects of backhaul QoS may change according to deployment scenario:

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Backhaul capacity provisioning

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6

12

18

34

42

84

75

150

0 50 100 150 200

HSDPA 2x2 64 QAM

DC HSDPA 2x2 64 QAM

LTE 10MHz 2x2

LTE 20MHz 2x2

DL Capacity Provisioning per small cell, Mbps

Loaded Peak

Assumptions • Modified version of NGMN’s macrocell

backhaul capacity provisioning [1,2]

• Includes user plane traffic plus overheads for

transport, X2 and IPsec

• Loaded macrocell throughputs scaled by

125% according to 3GPP simulations • [1] "Guidelines for LTE Backhaul Traffic Estimation",

NGMN Alliance, July 2011, http://goo.gl/EWQQg

• [2] “NGMN Alliance – Optimised backhaul solutions

for LTE, challenges of Small Cell deployment and Co-

ordinated QoS”, NGMN Alliance, Layer 123 LTE/EPC

& Converged Mobile Backhaul, December 2011

• [3] "Further advancements for E-UTRA physical layer

aspects", 3GPP TR 36.814 V9.0.0 (2010-03)

•Loaded figure represents busy times.

•Peak represents maximum capability of the RAN during quiet times

•Small cell sites will initially be single carrier, single cell and single generation, hence

need less backhaul capacity than multi-sector, carrier and operator macros

•This reduces on site aggregation gains so backhaul traffic will be burstier

?

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Backhaul cost requirements

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Cost per bit is likely to be similar to that of macro sites,

but many small cells will be needed to supply same capacity as a macro

…so cost per small cell site will need to be much lower

$ TCO

per site

Capex

Opex

Equipment

Installation

Site rental

Power

Last mile backhaul

Maintenance

leased line

spectrum

RAN

backhaul

etc…

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Physical design requirements

The small cell and backhaul unit combined should be…

•Small enough to fit in available street level locations − Planning/zoning may impose volume/dimension restrictions

•Lightweight to facilitate installation − A one man lift & mount can reduce costs

•Innocuous rather than sexy − Should not draw attention to itself

•Touch safe and tamper proof − Some sites may be within reach of the public

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Weight

Size

Power

Installation &

Commissioning

Reliability

Environmental

Backhaul/RAN integration

Appearance

Connectivity

Planning

Permission ?

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Lance Hiley

VP Marketing

Cambridge Broadband Networks Limited

How do different

solutions compare?

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Small cell backhaul options

Conventional PtP

• For: High capacity

• Against: Coverage awkward, spectrum opex, high installation costs

E-band

• For: High capacity

• Against: High capex and opex

Fibre (leased or built)

• For: High capacity (if you pay enough)

• Against: Recurring charges, availability and time to deploy

Non-line of sight multipoint microwave

• For: Good coverage, low cost of ownership

• Against: Low capacity, spectrum can be expensive

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www.cbnl.com

Tree (point-to-point) Multipoint Mesh

pop

small cell

Ring

Links low capacity high capacity with redundancy

Key

How does it all connect up - wirelessly

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Point-to-Point (PtP) microwave

PtP Microwave • Lots of bandwidth microwave frequencies available

at 10-60GHz

− but oversubscribed in many urban centres

• PtP spectrum is link-licensed; high recurring opex

− Area licensing can address this when available

• PtP links use two radios: each requiring space,

installation, energy: high recurring opex

PtP E-band • 10GHz of spectrum available at 71-76 and 81 GHz

− a window between peaks of high atmospheric absorption

• Light licensing conditions reduces spectrum opex in

many markets

• Installation of equipment is trickier than conventional

PtP

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Multiple radios, antenna’s per site to support ring/mesh topologies

makes PtP difficult to deploy at street level

PtP The most common microwave topology − For N links, 2N radios − Dedicated RF channel for each node B served − Well-suited to constant bit rate traffic − Well-suited to long links − Conventional and E-Band frequencies

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34 mbps 140 mbps 280 mbps 500 mbps

Installation $ 2,000 $2,000 $2,000 $2,000

Yearly rental fees $10,000 $14,000 $20,000 $30,000

Fibre

Fibre

•Great where already available,

otherwise slow and costly to install

•High-capacity, low-latency connection

•High recurring cost – even in

competitive markets

UK published fibre pricing

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Non-line of sight (NLoS) microwave

•Good for coverage,

capacity limited by

available spectrum

•NLoS propagation requires

low carrier frequencies

prized for mobile access

itself

•Free spectrum worth every

penny...but Wi-Fi uses the

entire unlicensed low

frequency spectrum

•Spectral efficiency

advances unlikely to

compensate: access and

backhaul operating in

same (NLoS) environment

• Unpaired TDD spectrum could be used for NLoS

backhaul, but quantity of is small compared to the

LTE and HSPA bands it has to backhaul

•The 3.5 GHz band is large and underused,

however 3GPP is planning UMTS (HSPA) and LTE

specifications

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Multipoint microwave: fastest growing microwave topology today

− For N links, N+1 radios − Shared RF channel amongst all sites − Well-suited to variable bit rate

(bursty) traffic − Well-suited to dense environments − Spectrum under-subscribed in most

markets

Line of sight (LoS) multipoint microwave

Multipoint microwave designed for street-

level deployment

High-capacity multipoint microwave

operating at ETSI PMP frequencies: 10.5,

26 and 28GHz. Other bands in

consideration

Backhaul 8 remote terminals per access

point with up to 300Mbps backhaul capacity

Integrated antenna for maximum

deployment flexibility/lowest operational

cost

Point-to-Multipoint (PMP) aggregates

packet traffic from multiple RT’s

Uses 40% less spectrum

Only one radio per small cell site

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Small cell backhaul revolution

PMP hubs beam high-capacity multipoint bandwidth down urban canyons

Large numbers of links for small cells, with high peak to average data

traffic favour PMP aggregation capabilities

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PMP best fit across small cell backhaul requirements

•LoS PTP and eBand

requirement of two

radios per link impacts

equipment/installation costs

•NLoS wireless capacity

is limited

•Leased line connections

have high repetitive costs

•Wi-Fi range compromises

backhaul application

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Architecture contributes to lowering cost of transport

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•As traffic builds on a small cell

network, cost of transport

drops with all solutions (blip seen for fibre caused by

transitioning to higher-capacity

service)

•Multipoint architecture delivers

lower cost of transport sooner -

from the moment of installation

£0

£1,000

£2,000

£3,000

£4,000

£5,000

£6,000

£7,000

£8,000

£9,000

32 Mb/s 80 Mb/s 120 Mb/s 150 Mb/s

Co

st

per

Mb

/s t

raff

ic c

arr

ied

Small Cell TCO (Capex & Opex)

Fiber, leased Eband PTP

PMP Expon. (PMP)

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Summary

•Operators need high-capacity, low-opex

backhaul for small cell network densification

•Small cells needed to supply Hot Spots and

densify network, offloading macro for high-mobility users

•Multipoint LoS microwave is a mature

technology option for backhaul: − High-capacity

− Short deployment time

− Low cost of ownership

− Spectrum readily available

•Cambridge Broadband Networks VectaStar

Metro meets the small cell backhaul challenge

• Read our whitepaper: http://cbnl.com/resources/white-papers

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Lance Hiley: lhiley@cbnl.com Julius Robson: jrobson@cbnl.com Download the white paper: http://cbnl.com/resources/white-papers Copyright © Cambridge Broadband Networks Limited. All rights reserved.

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