20120531 Nokia Siemens Networks Deployment Strategies for Heterogeneous Networks Final

8/11/2019 20120531 Nokia Siemens Networks Deployment Strategies for Heterogeneous Networks Final

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White paper

Deployment strategies forHeterogeneous Networks


2/162 Deployment strategies for Heterogeneous Networks

The growing demand for affordable

mobile broadband connectivity is driving

the development of Heterogeneous

Networks (HetNets). A range of different

Radio Access Technologies (RATs) and

Wi-Fi will all co-exist, and macro cells

will be complemented by a multitude of

smaller cells, such as micro, pico and

femto cells. Such heterogeneous

systems will be significantly more

complex to deploy than todays

networks and therefore require simple

and robust deployment strategies.

The first step is to ensure mobile

broadband (MBB) coverage, which

involves extending existing macro

base stations, for example, using

lower frequency bands such as

UMTS900 and LTE800.

The next step is to increase

capacity using additional spectrum

(such as 2600 MHz), applying

higher sectorization and adding

more macro base stations. This

Executive summary

Contents

Executive Summary 2

Many technology options 3

for operators

Single RAN Macro 5

layer evolution

Outdoor small cell 7

densification

Indoor small cell offload 9

Cost considerations 12

Nokia Siemens Networks 14

supports operators

Abbreviations 15

combined with site renewal,

for example, by upgrading with

Active Antenna Systems (AAS)

will minimize additional site

acquisition/upgrade costs.

Once all these measures have

been exhausted, deploy outdoor

and indoor base stations to

create smaller cells in congested

network areas, for example hot

zones, but ensure that this

network densification is well

integrated and managed with the

existing Single Radio Access

Network (RAN).

This white paper outlines key

deployment strategies for HetNets and

explains how Nokia Siemens Networks

can help operators to address them. It

discusses how to design roadmaps to

expand the macro layer and how to

use outdoor and indoor small cell

layers to handle the increasing traffic.

Existing

networkOutdoor

small cells

Macro

extension

Offload to indoor

Strategic

decisionOptions

Deployment benefit in priority order

(macro, small cells & indoor independently)

Tilt optimizations Minimize interference to increase

capacity at very low cost

MulticarrierEnhance capacity with high

coverage Including refarming

Sectorization increases both coverage and

capacity without macro site densification6-Sectorization

Provides marginal improvements in capacity

and coverage where there is abundant fiberC-RAN

Deployment for capacity enhancements,

especially in high traffic areasWi-Fi

Deployment for indoor coverage and

capacity for large indoor hot zonesPico cluster

Deployment for coverage but focused on capacity

in indoor public and private hot zonesMicro

Similar to micro cells with low backhaul costPico Cluster

Suitable to provide cost-efficient

coverage in large-sized buildingsDAS

Deployment for capacity enhancements,

especially in high traffic areasFemto

Figure 1. Deployment options for Heterogeneous Networks.


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The reason for Multi-RAT

deployments is simple. Operators

typically already have wide-area GSM

coverage and HSPA in densely

populated urban areas. Theyre

probably deploying LTE in hotspots/

hot zones or in rural areas in order to

exploit the digital dividend, as is the

case in Germany.

The impact of LTE

The prospects for LTE deploymentover the next three years:

Early adopters launched a data-

only service using USB dongles

before the end of 2010.

By mid-2011 the first wave of LTE

smartphones and tablets were

introduced.

Although 2011 and 2012 are the

key years for commercial

launches, many operators do not

intend to launch commercial LTE

services until 2013 or later.

LTE is expected to reach themass-market threshold in 2014,

based on LTE device availability.

LTE coverage will focus on urban

areas to provide highly scalable

infrastructure to support the

exponential growth of mobile

broadband traffic.

A few operators are targeting

aggressive nationwide rollout,

including rural areas that lack the

wireline infrastructure to support

DSL or fiber optic fixed networks.

Many operators are also considering

re-farming existing GSM frequency

bands to HSPA or LTE, so they can

update their equipment gradually

to more spectrally efficient radio

standards. GSM, HSPA and LTE will

continue to coexist and evolve in the

long term for several reasons:

GSM may be the only system

providing ubiquitous voice

coverage and is being used by a

large population of legacy terminal

users, for example, pre-paid

customers, roamers from foreigncountries, or machine-to-machine

(M2M) applications such as

smart metering.

Many technology options for operators

3Deployment strategies for Heterogeneous Networks

Todays smartphones all rely on

HSPA as the underlying MBB

technology.

The schedule for migration towards

LTE-only networks depends on the

LTE terminal penetration rate and

the availability of attractive LTE

terminals (including voice support).

It will take time to achieve mass

market terminal support for new

3GPP releases and features.

It usually takes 15-18 months

from 3GPP release until the first

commercial devices appear, but ittakes around five years for terminal

penetration to exceed 50%.

However, subsidies can speed up

the process significantly.

The evolving roles of small cells

In the early days of GSM and until

recently with HSPA, small cells were

used mainly for fill-in purposes.

However, small cells will play a key

role in future operators networks with

the large majority of small cell

deployments supporting the macro

layer to add capacity when and

where required.

The cellular standards already mentioned

will continue to exist alongside local area

technologies such as Wi-Fi. In fact,

offloading data traffic from cellular to

Wi-Fi is highly attractive for operators

from a cost point of view, allowing them

to reduce traffic in their HSPA and LTE

networks and use comparatively

inexpensive backhaul infrastructure.

Offloading will mainly take place in

homes and offices. A mobile operator

that also owns the Wi-Fi access

infrastructure can deliver a seamless

data experience for end users in public

premises. It is also expected that all new

smartphones will have Wi-Fi capabilities.

Many networks will include an overlay of

cells of different sizes. For instance,

outdoor terminals may be served by a

combination of macro, micro and pico

cells. Pico cells may provide both

outdoor and indoor coverage/capacity in

hotspots/hot zones such as train stations

or shopping malls, with a typical cell

radius of up to 200 meters. Femto cells

are used indoors in cells of no more than

10-25m radius. While pico cells are

deployed by an operator, femto cells are

typically user-deployed.

Hot Zone not sized up for a single Pico

Macro layerco-existence

Transport andEPC impact

Backhaulconnectivity

MobilityQoS

O&M

Offloading andlocal routing

Performanceand scalability Ease ofinstallation

100K Small cells underlay challenges

Office

building

85Pico Cells

Pedestrian

Zone

15Pico Cells

Capacity problems in Hot Zones

Denseurban Suburban Rural

Figure 2. Hot zones dene the needs for dif ferent and more holistic small cell capacity solutions.


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WCDMA/HSPA

LTE

Upgrade to 6-sector

Upgrade to 2ndcarrier

Add HSPA macro sites Add HSPA micro cells

Upgrade to 3rdcarrierExisting macro sites Upgrade to 2ndcarrier

Upgrade to 6-sector

Add LTE micro cells

(new or reused HSPA micro sites)

New LTE RAT

at existing HSPA sites

The take-up time of

LTE strongly depends

on spectrum and LTE

terminal availability

4 Deployment strategies for Heterogeneous Networks

Theres also a distinction between

open and closed subscriber group

(OSG/CSG) femto cells, where

CSG cells serve a constrained

set of users. The trend towards

multi-layer deployments, or small cell

densification, is driven by the need to

provide better (indoor) service quality,

for added capacity in hot zones, and to

respond to heterogeneous traffic

demands, as well as by cost and

energy efficiency considerations. But

how can operators determine the right

expansion roadmap?

In most 3G networks today, operators

are also seeing capacity demand in

some areas growing much more

rapidly than in the rest of their

networks. These former hotspots have

effectively evolved into much larger hot

zones, outdoor and indoor areas that

cannot be covered by a single or a few

Micro/Pico cells. Small cells have a key

role to play in supporting capacity and

better subscriber performance in these

hot zones. Yet the nature of such

dense small cell deployments and the

high volumes of new small cells in

operators networks are bringing their

own challenges. This will mean that

operators will need to revisit the

TCO equation to find a cost effective

approach to small cell underlay for

capacity.

An optimal network expansion

roadmap depends on various

operator location-specific

parameters and assumptions,

such as:

The legacy infrastructure in

terms of sites, base stations and

backhaul.

Availability, or lack, of new sites.

Health regulation in terms of

authorized emitted RF power.

The availability of spectrum and

terminals for specific RATs.

Traffic demand, user mobility and

revenue forecasts for a particular

area and the area parameters.

Cost-related aspects (such as

backhaul infrastructure, site

rental, labor and energy).

General strategic decisions

regarding services to be provided

and the metric to be optimized

(such as ubiquitous connectivity

anytime and for anybody versus

peak data rates for certain

consumers).

Figure 3. Example of wide-area expansion roadmap: multi-RAT (HSPA to LTE) and multi-layer (macro to micro).

Establishing an expansion roadmap

requires a holistic performance

evaluation methodology, detailed

cost models and measurement data.

The impact of the uncertainty inherent

in parameters such as traffic forecasts

can be mitigated by investing in flexible

base stations, where changes can be

made later via a software upgrade.

Figure 3 shows an example of a

derived expansion roadmap by Nokia

Siemens Networks in cooperation with

key customers.

The traffic distribution can vary widely

throughout a given network. This,

combined with the practical deployment

limitations of different upgrade options,

means that operators may pursue

several expansion paths simultaneously.

Operators need an automated process

to identify which parts of the network

need upgrading and to identify the best

solution for now and in the future. In the

long run, many operators will also be

managing networks in which equipment

from different vendors is used in the

same geographical area. In this

case, it is particularly important that all

network management functions are

multi-vendor-capable.


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Figure 5. Nokia Siemens Networks Single RAN Advanced for the macro cell network.

Radio frequency

(Multiband & RAT agnostic)

Baseband

(Multi-RAT)

Shared antenna

Shared multi-radio RF

Multi-band

load balancing

Multi-band carrier

aggregation

Shared backhaul

5

The number of RATs and frequency

variants increases the complexity of

mobile networks. Operators will

typically have three RATs (GSM,

HSPA and LTE) and up to five

frequency variants running in parallel,

as illustrated in Figure 4.

At the same time, network operation

must be simplified and the base

station site solution must be compact.

These requirements can all be

tackled with single RAN base

stations. Single RAN brings benefits

in terms of common antennas and

backhaul transmission between

multiple RATs. Single RAN Advanced

from Nokia Siemens Networks

provides the most compact macro

site solution with future-proof

evolution by software upgrades.

A multi-carrier upgrade is a simple

and cost-efficient method for

upgrading the macro network where

spectrum is available. Refarming part

of the 2G spectrum, such as 850/900

MHz to HSPA enables better MBB

coverage, especially indoors. It also

allows micro/pico cells to be deployed

on the existing 3G spectrum, such as

2100 MHz.

New LTE bands such as 700, 800,

AWS and 2600 MHz are available,

including re-farming the 1800 MHz

band from GSM to LTE. Many

networks were designed based on

voice coverage and with the increase

in data rates the coverage area may

shrink owing to power limitations in

user devices. Therefore, macro site

upgrades may require additional

densification, increased base station

output power or further cell-splitting

or sectorization.

Higher order sectorization can be

deployed in both the horizontal plane

by increasing the number of

antennas/sectors and/or in the

vertical plane by introducing AAS. An

example of sectorization is shown inFigure 6.

Single RAN Macro layer evolution

Figure 4. Typical future single RAN configuration in Europe.

2600 MHz

800 MHz

2100 MHz

1800 MHz

900 MHz

LTE 20 MHz

HSPA 15 MHz

GSM + LTE 10-20 MHz

GSM + HSPA 5 MHz

LTE 10 MHz

Deployment strategies for Heterogeneous Networks

Figure 6. Different sectorization options.

3 sector layout - 3x1 6 sector layout - 6x1 6 sector layout - 3x2



Many operators are facing challenges

such as lack of new site locations,

challenging operating frequencies with

limited coverage and performance and

ever-growing demand for a high-quality

end-user experience. With multi-

sectorization, operators can improve

their rollout and meet the challenge of

traffic growth by providing more coverage

and more capacity simultaneously, as

well as improving end-user service

quality without having to invest heavily in

new base station sites. Deploying multi-

sectorization will also reduce the need

for new macro sites.

Nokia Siemens Networks provides site

solutions for multi-sectorization

increasing mobile broadband capacity

and coverage as follows:

Up to 80% more capacity for 6x1

deployment (compared to 3x1).

Up to 65% more capacity for 3x2

deployment (compared to 3x1).

Up to 40% increased coverage.

Antenna tilt optimization is a cost-efficient

way to increase the signal-to-interference

noise ratio (SINR) in the macro network.

A typical initial deployment was focused

on coverage and now that capacity is the

limiting factor the antenna tilt can be

optimized in many networks. Figure 7

shows an example of full-scale network

antenna tilt optimization were the median

gain was ~2dB compared to the

deployed network. The tilt settings can

be tuned either by mechanical tilt (on-site

modifications) or by electrical tilt (remote

modifications), which will be used by self-

optimization functions.

C-RAN, also known as Cloud-RAN,

is a scaleable radio-over-fiber-based

centralized network architecture.

With a centralized architecture,

baseband pooling can provide energy

savings for operators and advanced

multi-cell techniques can be introduced

(such as CoMP and joint multi-cell RRM).

However, it provides only marginal

capacity and coverage improvements.

The key pre-requisite for C-RANis an abundance of high-speed

fiber connections.

Figure 7. Example of full-scale HSPA network SINR improvement by tilt optimization.

0

0.2

0.4

0.5

0.8

0.1

0.3

0.7

0.6

1.0

0.9

-5-10 0 5 10

SINR (dB)

15 20 25

Optimized tilt settting

Non-optimized tilt setting

CDF

The macro network still has great

potential for improving both network

coverage and capacity. Recommendedupgrades are summarized in Table 1.

These macro cell enhancements will

delay the need to deploy small cells.

Table 1. Macro cell deployment recommendations.

Macro cell Recommendations

extensions

Tilt optimization Antenna tilt should be optimized based on the current deployment.

This is one of the most cost-efcient ways of optimizing the

macro network.

Multi carrier Refarm spectrum for improved coverage. Use


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Figure 8. An example of a full-scale European metropolitan network upgrade.

0

50

100

200

150

250

Macro upgrades

Microcells

Two-carrier Macro upgrades

Two-carrier Micros

#

ofcells

0 2 4 6

Traffic volume multiplier

Number of micro and macro cells, inband micro deployment


When traffic increases in mobile

networks, macro cell network capacity

can be increased by the methods

explained in the previous chapter.

Macro cell evolution may still not

be sufficient to provide the required

capacity and coverage enhancements.

Adding more macro sites is expensive,

and it may be a more cost-effective

option to deploy small cells to add

capacity with limited spectrum and

non-uniform traffic demand in hot

zones/spots.

Macro vs micro cells

deployment

Figure 8 shows an example of a

European metropolitan network

upgrade with a deployment of 3G

micro cell and additional macro cell

carriers. The example compares

the number of new macro cells the

operator would need to deploy with

the number of micro cells. The most

efficient deployment of micro cell

versus additional macro carriersdepends on the spectrum availability

and traffic density.

At low to medium traffic density the

network needs the same amount of

microcells regardless of the microcell

carrier frequency. However more

macro cells are needed in the in-band

micro cell deployment. Single carrier

in-band 3G micro deployment is not

feasible for high traffic volumes,

because it requires the deployment of

an excessive number of micro cells.

An out-band micro cell solution gives a

balanced performance and even two-

carrier in-band (or out-band if spectrum

allows) micro is a viable solution.

Furthermore, as the data rate

increases, the coverage area for

each cell may shrink. The link budget

for todays deployment is typicallydesigned for voice data rates in HSPA

and most operators reuse their macro

sites in LTE deployment. Therefore, the

initial deployment of micro cells will be

most efficient at the macro cell edges,

while any further deployment of micro

cells should be positioned based on

traffic density.

Outdoor small cell densication

Table 2. Micro/Pico cell deployment recommendations.

Medium trafc density High trafc density e.g. Hot zones

Suburban/urban areas Dense urban areas

1-2 HSPA carriers Use all carriers for macro. Single macro carrier deployment

1 LTE carrier Eventually consider in-band and out-band micro/pico cell

deployment of micro/pico cells. deployment (when applicable).

3 HSPA carriers Use all but one carrier for Use all but one or two carriers for

2 LTE carriers macro and eventually consider macro and consider (dual) out-band

single out-band micro/pico cell micro/pico cell deployment.

deployment.



In-band versus

out-band deployment

In the performance analysis, we see a

breakeven of in-band vs. out-band

deployment of around five micro cells per

macro site depending on the traffic load.

An in-band solution is more attractive,

with a lower number of micro cells.

Meanwhile out-band performs better with

a high micro cell density. The out-band

deployment is a cost efficient way of

increasing network capacity and

coverage if spectrum is available.

Efficiency is highly dependent on site and

backhaul costs. The in-band deployment

increases network capacity and coverage

and is recommended if spectrum is

limited and macro networks are fully

developed. The cost efficiency is lower

than with out-band micros. The typical

evolution is to start with in-band micro

cells. When the micro cell density

increases and it can carry enough traffic,

the frequency could be fully dedicated to

micro/pico cells.

TX power recommendation

for 3G micro cell deployment

The larger the area of 3G micro

dominance, the more user equipment it

attracts. The dominance area depends on

the transmission (TX) power and the

uplink/downlink (UL/DL) bias of the micro

cell or on the cell selection parameters.

For high traffic volumes the microcells DL

direction may become congested. In this

case its better to provide an additional

micro-carrier than to reduce the micro TXpower. Reducing TX power in outdoor

micro cells together with increased data

rates increases the probability of

coverage holes. Site densification

reduces user equipment TX power rapidly

and reduces the UL interference. For UL-

limited network performance there is no

reason to reduce the microcells TX

power. A microcell TX power of 37dBm

(5W) is recommended for coverage and

some selected hotspots, while 30dBm

(1W) is sufficient for capacity extension in

hotspot/ hot zones areas. Bias in cellselection can be used if microcell

shrinking is desired.

UL vs DL trafc load driving

network upgrade

Some networks are DL performance-

limited while others are UL performance-

limited. The breakeven for UL/DL traffic

load is ~1:5. The ideal network upgrade

depends on which link is currently limiting

the performance. UL performance

limitations often result from a tight link

budget. In this case, additional macro

carriers will not improve the performance

while micro/pico cell deployment at the

cell edges has the biggest impact.

In contrast, a DL-limited network will

immediately gain from the addition of

more macro carriers, since a significant

part of the UL traffic comes from

smartphone signaling. Once traffic grows

further, it is expected that the UL signaling

overhead will not grow at the same rate

as data traffic. The ratio of UL signaling

and downlink traffic will decrease as a

result and growth will arise mainly from

DL traffic growth and increase the UL

performance. Furthermore, UL inference

will be further reduced by 3GPP features

such as CPC in Release 7 and HS-

RACH/HS-FACH in Release 8. The best

solution therefore depends on spectrum

availability, as well as traffic distribution,

macro network layout and long-term

traffic evolution.

Zone deployment of small cells

Deploying small outdoor cells in clusters

can further enhance performance,

reduce TCO, and simplify the backhaulfor small cells. A zone topology deploying

small cells is composed of two key

elements access points and a zone

controller. The zone deploymentenables operators to deliver wireless

broadband access outdoors at street

level using clusters of coordinated small

cells or indoor clusters, for example in

hot zones like shopping malls or

airports, see Figure 9.

The zone architecture can use wireless

Near Line of Sight (NLOS) backhaul to

cost-effectively deliver outdoor street-

level deployments and place the access

point deep into a hot zone for better

performance with only one connection tothe Evolved Packet Core (EPC) for up to

100 access points. The radio

deployment aspects of the access

points remains unchanged, but the

backhaul for the zone deployment

significantly reduces the TCO.

The zone and local controller

architecture further allow interference

and scheduling to be coordinated within

the zone. Even if the same spectrum is

used for the macro network and zone-

deployed cells, the interference isreduced from the macro network, raising

the customer experience. Furthermore,

this hides the access point architecture

from the macro network and thus eases

interworking and management. Also,

thanks to IP offloading and zone level

mobility, it significantly reduces the

EPC cost of extensive small cell

deployments. Finally, with up to

100 access points being managed as

one entity plus Self-Organizing

Networks (SON) for heterogeneous

networks, the operations andmaintenance (O&M) impact and

complexity are reduced significantly.

APAP AP

APAP

APAP

EPC

ZONE

Controller

Traffic offload

Figure 9. Small Cell Zone architecture and deployment.


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In high-traffic density areas the

recommended first step for macro layercapacity enhancement is to deploy

outdoor out-band lower power micro/

pico cells. However, in dense traffic

hotspots such as train stations,

airports, shopping malls, and office

buildings, indoor cells provide an

additional option to offload traffic using

small nodes such as femto cells, pico

clusters, distributed antennas, or Wi-Fi.

Figure 10 shows an example of typical

spectrum allocation in such dense

traffic hotspots.

The indoor offload potential is quite

significant, since more than 80% of

global wireless data traffic will be

generated indoors and most of all new

smartphones and laptops are equipped

with Wi-Fi and cellular data

connectivity. The indoor offload will

connect users to the nearest

connectivity node, reducing

interference and transmission power,

increasing capacity and reducing

battery consumption.

Load-based traffic steering between

the macro, micro, pico clusters and

femto layers will be needed in order to

use the available spectrum efficiently.

Furthermore, automatic authentication

is needed for Wi-Fi offload to reach

its full potential, because manual

authentication will prevent some

users from going through the process

of registration.

Figure 11 shows an example of indoor

data offloading to either femto or Wi-Ficells in a macro and micro overlaid

network based on the spectrum

allocation in Figure 10. It shows that

fewer Wi-Fi nodes are needed to

provide the same performance as

femto nodes, since there is additional

spectrum available for Wi-Fi.

Indoor small cell ofoad


Spectrum allocation

21xx MHz 21xx MHz 21xx MHz 2400 MHz

5 MHz 5 MHz 5 MHz 20 MHz

Macro MacroOut-band

FemtoIndoor WiFi

Out-band

Micro

Figure 10. An example of 3G spectrum allocation including indoor offload.

30 Micros 30 Micros

+ 50 WiFi

30 Micros

+ 100 WiFi

30 Micros

+ 500 Femto

30 Micros

+ 1000 Femto

NetworkOutage%

Indoor

Outdoor

Macro-Micro-Indoor Deployment

Figure 11. Example of network performance in a traffic hot spot equipped with a macro network,

30 outdoor micro cells and further femto/Wi-Fi indoor offload.



Indoor ofoad by femto cells

Femto cells were originally designed

for voice coverage but they also have

the potential to provide indoor data

offload. Femto cells for voice

coverage are expected to have limited

appeal in Europe, where customers

are reluctant to pay for network

coverage deficiencies. In the short

term, HSPA femto cells will dominate

the markets as LTE femto cells are

not required until LTE voice terminals

achieve mass market status.

The deployment of femto cells has

the same challenges as outdoor small

cell deployments. In-band deployment

provides the best performance for

limited spectrum or a low number

of femto cells, while femto cells

perform better deployed out-band

in large-scale deployments as outdoor

small cells.

The challenges of femto deployment

become even more pronounced

when a femto cell is configured with

a CSG identity. A user that is not part

of the CSG group will connect to

the micro of macro network and

experience/cause significant

interference problems as normal

mobility is overruled by the subscriber

group admissions.

The optimum performance will be

achieved by configuring all femto cells

as open subscriber groups (OSG).

However, femto cells provide excellent

voice coverage extensions and the

low transmission power and building

attenuation isolate the femto cells very

well from the macro cells.

Indoor ofoad by Distributed

Antenna Systems (DAS)

Distributed antennas inside stadiums,

office buildings or shopping malls

provide a good supplement to indoor

small cells. DAS provide very good

indoor coverage as the transmit power

is higher than that of femto cells and

Wi-Fi. However, DAS is more

expensive than femto cells and Wi-Fi

for providing large-scale data offload

and thus the recommendation is acombination of DAS for indoor

coverage and femto cells or Wi-Fi for

high data offload. Upgrading installed

DAS systems to LTE and/or new

frequency bands may limit MIMO

capabilities to keep costs low.

However, even non-MIMO-capable

LTE DAS deployments will provide

good indoor coverage and superior

date rates.

Indoor ofoad by Wi-Fi

Wi-Fi is an important local area

technology option for heterogeneous

networks, complementing mobile

technologies to improve performance

from the user perspective and offload

capacity. One of the criteria for Wi-Fi to

become a successful part of the mobile

network is the automatic attachment/

authentication procedure that enables

seamless Wi-Fi/mobile access and a

better user experience. Such automatic

attachment and authentication is

supported by Nokia Siemens Networks

Smart WLAN Connectivity solution,

called SWLANC.

The use of Wi-Fi technology is the

preferred means of offloading data from

macro cells for users at home or in the

office. Smartphones should use Wi-Fi

where possible. For public Wi-Fi

deployment, careful selection is crucial

for effective offload while providing the

best user experience. Outdoor Wi-Fi

deployment has limited potential where

mature macro networks are already

installed. It also requires careful planning

to limit interference sources from the

unlicensed spectrum. Furthermore,

many DSL lines are limited to less than

10 Mbps, which is slower than a typical

LTE macro cell.

The total Wi-Fi offload potential is ~40%

(0.8 x 0.8 x 0.8 x 0.8) assuming:

~80% of all traffic is generated

indoors.

~80% of total global handset traffic is

generated by smartphones.

~80% of all smartphone users have

Wi-Fi available.

~80% of all smartphone users

connect to the Wi-Fi (capture rate).


11/1611Deployment strategies for Heterogeneous Networks

Indoor coverage and capacity

with Pico Cluster (Fig.12)

Many indoor public or enterprise areas

are evolving into hot zones, and a new

approach that marries the benefits and

simplicity of Wi-Fi with robustness and

guaranteed QoE of 3GPP Micro/Picos

will be required.

Nokia Siemens Networks Flexi Zone is

such a solution and takes into account

the future need for very high celldensity with a Pico cluster of Multi-RAT

to leverage the installed Ethernet

network as backhaul. It aggregates

connected access points and local

break out to limit network impact and

provide local routing to enterprise LAN

servers if required. To achieve even

more cost-effective deployments,

SON principles are used to simplify

O&M. Interference management

techniques are used to ensure

scalability (low impact/fast deployment

of new Pico) and allow operators tocost effectively support the growth in

demand in indoor locations.

Recommendations

Indoor Wi-Fi deployment achieves

the lowest cost, lowest energy

consumption, and best network

performance in a high-traffic urban

environment. An out-band indoor femto

cell deployment requires more access

points to provide the same

performance, since it shares the

spectrum with the micro cell layer.

However, an indoor femto deployment

can provide significantly higher

average user equipment throughput

performance compared to indoor Wi-Fi

deployment, thanks to the higher

number of access points. DAS is a

good supplement to femto cells and

Wi-Fi for indoor coverage in large

indoor traffic hot spots. The summary

of the indoor offload recommendation

can be seen in Table 3.

Figure 12. Example Pico Cluster indoor deployment.

Ofoad Recommendations

technology

Wi-Fi Deployment for capacity enhancements, especially in high trafc

areas. Indoor deployment preferred to manage interference.

3G/4G Pico Deployment for coverage but focused on capacity in indoor public

Cluster in and private hot zones. High number of cells deployed with easy,

or out of band low impact and fast scalabil ity.

DAS Suitable to provide cost-efcient coverage in large-sized buildings.

Less cost-efcient for capacity-driven scenarios and small

buildings compared to femto cells/WiFi.

Femto Deployment for capacity enhancements, especially in high trafc

out-band areas. High number of cells deployed.

Femto Deployment for coverage and low/medium capacity

in-band enhancements. Large-scale deployment causes interference

with macro cells.

Table 3. Cost-efficient indoor offload recommendation in traffic hot spot areas.



Total Cost of Ownership (TCO) is one

of the most important deciding factors

when choosing a network deployment

path. However, the TCO in each case

depends on the operators current

installed base, its spectrum situation

and user equipment penetration. The

different deployment paths have been

analyzed from a TCO perspective to

outline the key TCO trends.

The target of a TCO calculation is to

aggregate all the costs that occur over

the entire lifetime of a technical solution

(in this case complete network evolution

scenarios over 5 to 10 years) in a single

figure. The comparison of TCO values

for different network evolution scenarios

then allows the business value to

operators of the different deployment

options to be evaluated. The underlying

assumption for a fair comparison is that

the different network evolution scenarios

perform the same way and satisfy the

same traffic requirements. They are

then called ISO-performance scenarios.

Typically the TCO is calculated as the

sum of three components: capital

expenditure (CAPEX), implementation

expenditure (IMPEX) and operational

expenditure (OPEX). CAPEX and

IMPEX are one-off costs, while OPEX is

a recurring cost that must be specified

for a certain period of time. In this case

its the time taken for the network to

evolve. The deployment options already

described now have very different

characteristics regarding their cost

structure. These are:

Macro network extension

Multicarrier

If spectrum is available, adding more

carriers to already existing macro sites

provides easy and low-cost capacity

enhancements at macro sites. The main

cost is in CAPEX and IMPEX

(equipment and deployment), OPEX for

the base station increases only slightly

(electricity, O&M, backhaul). Howeverdedicating spectrum to micro cells can

provide an even bigger increase in

capacity. Therefore traffic growth and

Cost considerations

traffic hot spots play an important role

in any site evolution strategy.

Furthermore, refarming of spectrum is

a cost-efficient way to increase both

coverage and capacity. The most

cost-efficient approach is to deploy the

lower spectrum initially for coverage

and deploy the higher spectrum later

for macro or micro cells, depending

on the traffic density and spectrum

availability. LTE deployment should

be co-sited with HSPA sites to

minimize deployment costs. A new

site will have significantly higher cost

compared to the already existing

infrastructure at an existing site,

plus the site acquisition cost.

Sectorization

Sectorization in the vertical or

horizontal plane provides a simple yet

cost-efficient way to increase capacity

in the macro network. The main portion

of the cost is CAPEX and IMPEX

(equipment, antennas and deployment)

but OPEX is also raised owing to

higher electricity costs, backhaul and

additional site rent for new antennas.

Six sectorization is most efficient for

uniform traffic distribution and may

not be the best option in localized

areas of high traffic or in very dense

urban deployments where vertical

sectorization by Active Antenna

System (AAS) would be more

beneficial.

Tilt optimization

A very cost-efficient method for SINR

optimization and thereby increases

network capacity. Tilt optimization

should always be pursued before any

further optimizations.

C-RAN

Is expected to save money at macro

sites, since there is less equipment

on-site (with the baseband pooled at a

central location). Compared to legacy

base station deployments, additional

infrastructure such as shelters, power

supplies and so on can all be saved.But it also gives rise to additional costs

for building and operating the hotel

location for the centralized baseband

systems. C-RAN is only affordable if

operators have abundant legacy fiber

and the techniques are mature enough

for high-speed fiber connection

(~10Gbps) and advanced multi-cell joint

processing. OPEX may be lower thanks

to lower energy consumption.

Outdoor small cell

Micro/Pico cell deployment is a

cost-efficient way of increasing network

capacity and coverage. The realizationof outdoor small cells by micro base

stations means CAPEX for compact

micro equipment, but OPEX is very

significant for backhaul and site rental.

Also IMPEX for site acquisition and

deployment (including a power supply)

are relevant cost factors. Micro cells

should be deployed in dedicated

spectrum if available. In-band

deployment of micro cells may be more

expensive for high-traffic-density areas if

the spectrum is not already deployed on

the macro layer, since both layers wouldneed to be deployed. However, for

low/medium traffic-density-areas or

already-deployed macro spectrum,

in-band deployment is the preferred

cost solution.

Outdoor pico cluster

For outdoor hot zones, future

multi-RAT pico cluster solutions can

provide a very cost-effective approach

compared to other traditional solutions

and cell site splitting. For example,

Nokia Siemens Networks Flexi Zone

features a zone architecture that,

together with other innovations, helps

to reduce TCO by simplifying backhaul,

managing inter-intra layer interference

and limit the amount of spectrum

planning. This results in virtually

unlimited scalability, with limited impact

on the EPC and with local break out to

simplify installation and operations.

A pico cluster solution provides

up to 50% TCO benefit when addingcapacity compared to macro cell splitting

or the traditional micro/pico approach.



Indoor ofoading

Wi-Fi is always a low-cost supplement

to macro and micro/pico cell

deployments, since the spectrum is

freely available. However, the cost of

Wi-Fi depends on the particular

scenario with regard to backhaul and

site acquisition. Wi-Fi and femto cells

have very similar TCO performance,

with similar CAPEX and almost identical

installation and operational costs.

The decision on Wi-Fi versus femto

should be based on the spectrum

situation and a combined Wi-Fi/femto

deployment would provide the best

performance and operability in most

cases, since it would serve all user

equipment. Both Wi-Fi and femto cells

offer big benefits for residential and

office installations, while public

installations should be based on the

traffic density and the available

spectrum. The underlying assumption

for residential and office scenarios is

that backhaul at the deployment

locations can be reused without

incurring site costs. The cost in offices

is assumed to be about four or five

times higher than the cost in a

residential scenario.

Future Multi-RAT Pico cluster solutions

such as Nokia Siemens Networks Flexi

Zone, will provide a best-of-both-

worlds approach with Wi-Fi and HSPA/

LTE support, and a cost effective and

scalable solution for indoor coverage

and capacity deployments.

Recommendations

The financial impact of the

deployment options mentioned was

investigated in different real-network

scenarios with operators. Although

the conditions in different networks

vary quite significantly, some general

results and recommendation could

be derived. The preferred

deployment solution from both a

performance and cost perspective is

a combination of a perfect macro cell

deployment for coverage and high

mobility users, outdoor micro/pico

cell deployment for dense traffic

areas and indoor offload for

extremely dense traffic areas with

low mobility. The recommendations

are summarized in Figure 13.

Macro

Extension

Offload to

Indoor

C-RAN

Cost Savings

Can provide Opex benefits when compared to

legacy RAN and assuming extensive fibre. But

modern distributed RAN is more profitable today.

Wi-Fi Offload

Enhanced Capacity

at lower cost

Provides significant outage and capacity enhance-

ments especially in high traffic areas. Depending on

the scenario the cost for Wi -Fi is very low.

Multicarrier

Enhanced

Capacity, High

Profitability

Provides easy and low cost capacity

enhancement at macro site. However

dedicating spectrum to micro can provide even

higher capacity increase.

Pico Cluster

Enhanced Capacity

at lower cost

Provides significant outage and capacity

enhancements especially in high traffic areas.

Provides cost efficient deployment.

6-Sectorization

Enhanced

Capacity, High

Profitability

In general very efficient for capacity increase but

not a viable option if high traffic ares are very

localized or in very dense urban deployments.

Femto

Enhanced Capacity

at lower cost

Provides outage and coverage/capacity

enhancements. Large deployment density causes

interference challenges with macro.

Tilt Optimization

Enhanced

Coverage

Though impact of antenna tilting was overestimated

in statistical propagation models it is still a cost

efficient method of SINR optimization in general.

DAS

Enhanced Coverage

at lower cost

Suitable to provide cost-efficient coverage in large

-sized buildings. Less cost-efficient for capacity

driven scenarios and small buildings.

Outdoor

Small Cells

Micro

Enhanced

Coverage and

Capacity

Cost efficient means to increase network capacity

and coverage. Inband deployment if spectrum is

limited otherwise outband deployment.

Pico Cluster

Enhanced

Coverage and

Capacity

Cost efficient means to increase network capacity

and coverage.

Fully recommended

Recommended except certain scenarios

Partly recommended

Figure 13. Deployment cost considerations.


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Abbreviations

3GPP Third Generation partnership Project

AAS Active Antenna Systems

AWS Advanced Wireless Services

CAPEX Capital Expenditure

C-RAN Cloud RAN

CSG Closed Subscriber Group

DAS Distributed Antenna Systems

DL Downlink

DSL Digital Subscriber lines

EPC Evolved Packet Core

FACH Forward Access Channel

HetNets Heterogeneous Networks

HSPA High Speed Package Access

IMPEX Implementation expenditure

LTE Long Term Evolution

M2M Machine to Machine

MBB Mobile Broadband

MIMO Multiple input multiple output

NLOS Non line of Sight

OPEX Operational Expenditure

OSG Open Subscriber Group

QoE Quality of Experience

RACH Random Access Channel

RAN Radio Access Network

RAT Radio Access Technology

SINR Signal to Interference and Noise Ratio

SON Self Organizing Networks

TCO Total cost of Ownership

UL Uplink

Wi-Fi 802.11xx


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