Wireless Technologies & Architectures for Small Cell...

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Wireless Technologies & Architectures for Small Cell Backhaul

In association with:

Speaker:

Greg Friesen Vice

President, Product

Management

Speaker:

Caroline Gabriel

Research Director

Maravedis-Rethink

BROADBAND WIRELESS INTELLIGENCE

www.maravedis-bwa.com© Copyright All Rights Reserved 2011 Maravedis Inc.

The new access networkCarrier survey 2011

Top objectives for LTE/A by 2015

Reduce cost of delivery by 35%

Reduce power consumption by

85%

Boost average data rates by

200%

Key methods:

Smaller cells

Self-organizing networks

New network planning

Advanced traffic management

This requires a backhaul

rethink



The rise of small

cellsRising importance of small

cells in LTE and HSPA(+)

spend

RRH/AIR dominant trend

Most rapid growth in

metrocells

Cloud versus edge RAN?

Different backhaul

requirements 0

1000

2000

3000

4000

5000

6000

2011 2012 2013 2014 2015

,000 u

nit

s

Traditional Macro/micro RRH Compact



New backhaul norms Cells move nearer ground

Two network layers, possibly in different spectrum

Commodity backhaul plus fiber

Dynamic allocation

New spectrum bands



Challenges Cost per Mbps pressures

Positioning of units

Reliability of links



Solutions Wireless

New bands (NLOS, mm

wave)

The fully integrated unit

Backhaul

WiFi

DragonWave Proprietary Information 7

Beyond Traditional

Macrocellular Infrastructures


The Challenge

Spectral efficiency and capacity gains of new wireless technologies are not keeping up with demand growth

• Mobile data traffic will increase 18X by 2016

• Spectral efficiency improvements will address less than 5% of the new capacity

Operators must improve coverage

• Reduced propagation of higher frequency 4G spectrum

• Bandwidth intensive applications are currently not well supported in indoor environments

Carriers limited to existing tower/rooftop infrastructure, there own and others

HSPA+ LTE LTE Advanced

CapacityGap

CapacityGap

CapacityGap

MoreSpectrum

MoreSpectrum

Mo

bile

Da

ta T

raff

ic D

em

an

d

Mobile Network Supply vs. Demand

SpectralEfficiency

SpectralEfficiency

SpectralEfficiency

SpectralEfficiency

More Spectrum

Sources: Cisco Visual Networking Index, DragonWave internal analysis.

1X

18X

More SpectrumSpectral

EfficiencySpectral

Efficiency

CapacityGap

2011 2012 2013 2014 2015 2016

The mobile network capacity gap is increasing


Addressing the Capacity Gap: Network Expansion Options

Obtain additional spectrum

Improve RF spectrum efficiencies

Increase system load (i.e. interference threshold)

Increase # of base station locations

Which option will scale with your traffic

requirements into the future?


Characteristics of Urban Deployments

Leverage low cost & readily available infrastructure (i.e. traffic and

light poles) for expansion

• Typically separation between light poles in urban environment is

24 to 30 m with every intersection having 4 traffic/light poles

Distance between base stations is carrier dependent on:

• Fractional frequency re-use

• System loading (i.e. interference threshold)

• Business model allowance – CAPEX/OPEX

In urban environment in 1 sq. mile there is approximately:

• 34.4 miles of road

• 4,200 microcellular total candidate locations

• 7% or 320 preferred candidate locations in target zone (ie.30m radius)

A deployable product is the difference between success and….


Microcell Backhaul Options

No backhaul at the lamp pole today

• Need to build something at every microcell

Fiber premium

• Unlimited capacity

• cost prohibitive

Wireless best value

• Medium to high capacity

• Radio planning required (Line of Site, Interference…)

• Need for small antennas determines frequency selection

• CAPEX and power impact to microcell


Microcell Reach by Frequency

At 99.990% RF link

availability – only the

58GHz configuration

at 256QAM in a high

rain rate region would

not be able to reach

350m.

5.2/5.8GHz*

Rain Rate 25mm/hr 60mm/hr

Throughput 78Mbps 130Mbps 78Mbps 130Mbps

Reach (km) 16.4 8.6 10.4 5.5

Assumptions:* ITU Methodology50MHz Channels99.99 RF Link Availability except unless noted5"-5" AnalysisVertical Polarization1+0 Config

In microcellular backhaul, reach is not the primary challenge –

finding the optimal way to connect the sites is!

24 – 58GHzRain Rate 25mm/hr 60mm/hr

Modulation QPSK 256QAM QPSK 256QAM

Throughput 67Mbps 351Mbps 67Mbps 351Mbps

Reach (km)

24GHz 9.5 3.1 5.0 1.9

28GHz 8.2 2.9 4.2 1.8

38GHz 5.3 1.9 3.0 1.2

38GHz (99.995%) 2.6 1.4 1.1 0.7

38GHz (99.999%) 1.5 0.7 0.7 0.4

58GHz 1.1 0.5 0.9 0.3


Microcell Backhaul Subnet Topologies

Hub and Spoke

Ring/Mesh

• Congestion at hub site limits subnet size

Interference and antenna loading

Antenna leasing – 8 additional

Line of sight required to each end point

Not usually possible in dense-urban

• Optional daisy chain spurs

• No path redundancy Negative impact on availability

• No congestion at hub site Path diversity

• Relaxed line of site constraints

• Optional spurs to extend subnet coverage

• Multiple backhaul links at ring and chain sites

• Higher bandwidth on ring links

• Predictable delay and delay-variability (PDV)

performance

Both single link and multiple link platforms required


Line-of-Sight vs. Non-Line-of-Sight

Line of Sight Deployment• Above traffic level

• Routed along the streets

• Zig-Zagging across streets

• BH Candidates selected based on LoS –not always getting “best” site

Non-Line-of-Sight Deployment• Lower per link capacity

• Delay of TDD systems limits application space

• Self Interference issues

• Impact of latency and jitter

• Provides resilience to partial LoS– Trees, Fresnel zone obstruction

• Connects to almost any site

Deploying a hybrid network gives the carrier much needed flexibility


Microcell Designs

Hub N Spoke – NLOS1. All Unlicensed

equipment2. Use single hops to

macro site3. 2 hops maximum

Hub N Spoke – LOS1. All Licensed equipment2. Achieve site in target

zone – within 30m3. Deploy repeater sites

when required4. 3 hop maximum

Ring – Hybrid1. Use either equipment2. Licensed on ring links3. Licensed on spurs

unless NLOS4. 1 hop to ring node

The market and various other factors will influence what solution and

architecture is best for you


Sample Urban Microcell Deployment

Assumptions:• Addition of 76 new sites

• Sites not served with MW are considered fall outs

• Site availability = > 99.990%

Network 1 Target

Downtown coverage area (sq. mi) 4.2 4.2

Number of Basestations 11 87

Number of sites per square mile 2.6 20.7

Total Coverage - Distance Between Sites (meters)

960 350

Capacity Per LTE Base Station (Mbps) >250 >250

Downtown Capacity (Gbps) 4.1 28.5

Total Coverage

With a target of 350m distance between sites, to scale the network

with new sites requires addition of 10 to 16 sites per sq. mile


Sample Urban Microcell Deployment

Identified optimal location at 350m

separation and allowed +/- 75m

Bullseye = Micro Cellular Site

ThumbTack = Macro Cellular Sites (actual

locations)

Max. of 3 MW hops back to

donor/macro cellular

Max 10 sites per ring – LoS links only

– use repeaters to close rings

NLOS – completely blocked used on

links < 700m


Architecture Comparison – 11 BSTs

Hub N SpokeLoS Only

Hub N Spoke5.8GHz

Hub N SpokeHybrid

RingHybrid

# of Macrocell Sites Used 11 11 11 9*

# of Target Microcell Sites 76 76 76 76

# of New Microcell Sites/# of Fall Out 67/9 69/7 71/5 76/0

# of Repeaters 11 0 5 5

Avg. # of Antenna’s Per Macro 2.3 4.8 2.6 2.9

# of Antenna’s Per Macro Max/Min 5/1 10/2 6/2 6/0

# of MW Links with: LoS/NLOS 79/0 22/48 61/18 71/21

Avg. Link Length (meters) 311 478 348 343

Avg. Link Capacity(Mbps) 364 151 293 293

Avg. End to End One Way Latency 0.27 1.451 0.69 0.84

• Line of Sight (LoS) solutions deliver avg. per site capacity > 300Mbps

• Ring architecture only option to serve all microcell sites while not using all

macrocell sites

• LoS microcell solution require repeater sites to ensure > 88% site coverage


Network Diagram – Hub N Spoke

Geographic distribution

of macro sites = fall

outs in H&S design

69% of 5.8GHz MW

design are NLoS links

Limit 5.8GHz solution to

single spur links

Line of Sight 5.8GHz NLoS

LegendMacro Cellular SiteNew Micro Cellar SiteRepeater SiteFall Out SiteLoS LinkNLoS Link

NLOS solution allows a more hub and spoke centric architecture.


Network Diagram – Hybrid

Hub N Spoke Hybrid Ring - Hybrid

LegendMacro Cellular SiteNew Micro Cellar SiteRepeater SiteFall Out SiteLoS LinkNLoS Link

A Hybrid NLOS/Ring solution provides full market penetration.


Link Length – 87 Sites

Link Length Hub N Spoke -LOS

Hub N Spoke -NLOS

Hub N Spoke -Hybrid

Ring -Hybrid

0 to 100m 1 0 1 1

101 to 200m 16 4 8 9

201 to 300m 19 11 17 18

301 to 400m 30 18 34 43

401 to 500m 10 11 14 17

501 to 600m 2 8 3 3

601 to 700m 0 9 1 0

701 to 800m 0 4 0 0

801 to 900m 0 3 0 0


Summary

The need for greater capacity, indoor penetration and spectral-reuse is driving the requirement for microcellular networks

Microcellular networks present their own unique deployment and backhaul challenges

LOS solutions in a hybrid ring architecture can provide the highest capacity and >90% site coverage (100% with repeaters)

A toolkit approach is needed to provide the right level of coverage and capacity for each particular microcell deployment

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