SECURING EXCELLENT MOBILE BROADBAND USER EXPERIENCE, EVERYWHERE

Expectations of mobile broadband grow daily, as more people use smartphones and

tablets to stay constantly connected via apps and cloud-based services. To deliver an

excellent mobile broadband user experience everywhere and address value-added

service opportunities, operators need to both improve and densify their existing macro

networks and, where necessary, add complementary, integrated small cells – and get

them to work together seamlessly in a heterogeneous network.

ericsson White paperUen 284 23-3165 Rev B | September 2014

Heterogeneous Networks

HETEROGENEOUS NETWORKS • INTRODUCTION 2

IntroductionMobile broadband traffic is growing rapidly, driven by the increasing popularity of connected

devices, predominantly mobile broadband-enabled smartphones and tablets. What is more, user

expectations for mobile broadband are on the rise as people rely more and more on mobile

applications, video content, cloud-based services and staying connected anywhere, anytime.

Consumers have come to expect a consistent, high-quality and seamless mobile broadband

experience wherever they are, including indoors.

Meeting these expectations is a key priority for operators looking to differentiate themselves in

the Networked Society, in which everything that can benefit from a connection will be connected.

To provide the right mobile broadband experience, build customer satisfaction and brand

loyalty, and create a platform for new value-added services, especially for enterprise customers,

networks need sufficient capacity and coverage to deliver high data throughput with very low

latency. One approach is to deploy a heterogeneous network.

A heterogeneous network involves a mix of radio technologies and cell types working together

seamlessly to deliver the additional capacity, coverage and speed needed to secure excellent

user experience.

To prepare networks for surging traffic demand, operators need to improve and densify their

existing mobile broadband networks and add integrated small cells in an optimal way. How, when

and where operators migrate to heterogeneous networks will be dictated by their existing

networks, their mobile broadband strategies and broader market, technical and economic

considerations. One size does not fit all, and flexibility is needed to ensure that subscriber

expectations are met in the most cost-effective, spectrum-efficient and future-proof way.

HETEROGENEOUS NETWORKS • THE MOBILE BROADBAND CHALLENGE 3

The mobile broadband challengeWith the tremendous success of mobile broadband and smartphones, mobile operators and

vendors need to keep up with the increasing pace of change among:

> device and application providers, who continually find innovative ways to benefit from mobile

broadband connectivity

> consumers, who expect seamless connectivity with ever-increasing data rates

> competing operators, who continually improve network performance, which is a key

differentiator as services go over-the-top.

TRAFFIC GROWTH

Mobile broadband traffic is growing like never before, thanks to the increasing popularity of

data-hungry devices and rising data consumption per user. As the June 2014 Ericsson Mobility

Report [1] shows, mobile data traffic is expected to grow at a compound annual rate of around

45 percent between 2013 and 2019, resulting in a tenfold increase in mobile data volumes. The

rising number of smartphone subscriptions is the main driver of this mobile data traffic growth,

with users consuming more data per subscription, driven mainly by video.

The mobile broadband traffic challenge is most pronounced in densely populated cities, where

subscriber penetration is already high.

APPLICATION COVERAGE AND EXPECTED DATA RATES

With the high pace of innovation in the device and application industry, consumer expectations

of data rates and coverage continue to grow. Today’s mobile broadband users expect widespread

coverage with download speeds of at least 1Mbps, and typically 10Mbps.

URBANIZATION

By 2018, more than 30 percent of the world’s population is expected to live in metro and urban

areas. Although these areas represent less than 1 percent of the planet’s land area, they will

generate 60 percent of mobile traffic by 2018.

Mobile users everywhere are increasingly aware of the connection speed, data rate, coverage

and availability of their mobile broadband services. To ensure that subscribers remain satisfied,

operators need to deliver a consistent, high-quality and seamless mobile broadband experience

that meets or exceeds rising user expectations. Achieving subscriber satisfaction will require

improved data performance overall and at cell edges, especially indoors, where about 70 percent

of today’s data traffic is generated.

HETEROGENEOUS NETWORKS • MAKING THE RIGHT HETEROGENEOUS NETWORK CHOICES 4

Making the right heterogeneous network choices Mobile broadband is all about providing a seamless experience for the growing number of

smartphone, tablet and laptop users – whether on the move, in the office or at home. To meet

rising user demands and intensifying competition, operators need to improve network performance

by expanding capacity and coverage in a smooth, cost-effective way.

This will require a combination of improving and densifying the macro cellular layer for general

coverage and capacity, and adding integrated small cells in strategic locations.

Improving existing macro cell sites

involves deploying more spectrum,

advanced antennas, higher-order diversity

on the receiver or transmitter (or both), and

greater baseband processing capacity

within and between nodes. Continued

evolution of WCDMA/HSPA and LTE

technology will improve macro network

efficiency through specialized features,

such as higher-order modulation, higher

sectorization, multi-carrier and multi-

antenna solutions, as well as spectrum

refarming using hybrid radio solutions.

Increasing capacity and data rates in this

way minimizes the need for new sites.

Densifying the macro network involves the

targeted addition of strategically located

(smaller) macro cells to improve capacity and data rates, particularly when it is no longer feasible

to continue improving the macro network alone to meet demand. This approach keeps the total

number of sites relatively low, while network performance becomes less sensitive to traffic

location.

Adding small cells involves complementing macro cells with micro cells, pico cells and integrated

Wi-Fi, as well as dedicated indoor solutions. This delivers high per-user capacity and rate coverage

in high-traffic areas, with the potential to improve performance in the macro network by offloading

traffic generated in hotspots. Overall network performance will depend on the degree of integration

and coordination that can be achieved throughout the heterogeneous network.

How and when to use each approach depends on the existing networks (macro site density),

the availability of backhaul (whether owned or leased), the availability of spectrum (whether

licensed or unlicensed), estimated traffic volumes, and required data rates, as well as the technical

and economic feasibility of each individual approach.

The network as a whole needs different solutions to meet varying capacity demand.

In rural, less populated areas, the challenge is to provide cost-efficient coverage for mobile

broadband services, while maintaining good consumer experience. Improving the macro layer

is by far the most cost-efficient way to address this challenge.

In suburban and low-rise urban areas, operators need to improve and densify the macro

network, especially to meet increasing demand for higher data rates. The large coverage area of

Area traffic densityArea traffic density

ImproveDensifyAdd

ImproveDensifyAdd

ImproveDensifyImproveDensify

ImproveImprove

UrbanUrbanDense urbanDense urban SuburbanSuburban RuralRural

Figure 1 – making the right heterogeneous network choices

HETEROGENEOUS NETWORKS • MAKING THE RIGHT HETEROGENEOUS NETWORK CHOICES 5

macro cells means they are often a more cost-effective way to address such demand than

deploying small cells en masse.

In urban areas, in addition to improving and densifying macro cells, integrated small cells offer

a cost-effective complement in traffic hotspots, for serving coverage holes and in certain buildings.

Dedicated in-building solutions are required when capacity and performance are needed to

serve demanding areas, such as enterprises and airports.

DIFFERENT SOLUTIONS FOR DIFFERENT SITUATIONS

There is no ‘one size fits all’ solution for introducing heterogeneous networks. Rural, suburban

and urban areas vary widely in their coverage and capacity expansion needs, and each requires

a different deployment strategy.

In urban and dense urban areas especially, there is an increasing need to improve user

experience and network coverage, as well as capacity through heterogeneous network solutions.

How, when and where to evolve a macro cellular network into a heterogeneous network will be

dictated by a combination of the operator’s mobile broadband strategy and existing network

infrastructure, competition from other mobile and fixed broadband operators, as well as spectrum,

site and backhaul availability.

As cell sizes shrink, flexibility and a strategic network evolution path are needed to ensure that

customer expectations are met in the most cost-effective, spectrum-efficient and future-proof

way. Different solutions will be needed in different situations. For example:

> In city centers, general coverage (especially in city streets and squares, and indoors) could

be improved cost-effectively by using small macro cells or micro cells. Backhaul can be

HETEROGENEOUS NETWORKS IN ACTION

Train station/mall

A key challenge in large indoor public

hotspots such as train stations, shopping

malls and airports is the high

concentration of users in the limited

indoor area. Indoor coverage from the

surrounding macro cells is often limited

by high levels of building penetration

loss. There may also be high

requirements on mobility, especially in

train stations and airports.

Excellent user experience for speech

and data must be provided in areas with

a high degree of business and roaming

users. Interference can be a problem if

the environment consists of open areas,

such as station platforms.

One way to address these challenges

is to add indoor integrated small cells

where most traffic is located to improve

user performance and capacity. The

baseline solution is often a Distributed

Antenna System (DAS) fed by a macro

base station.

In this example, the train station is a

new deployment, which uses fiber with no

legacy system or installation. A distributed

architecture with a remote radio unit (RRU)

meets the need for high user mobility and

interference coordination in the open

areas (such as platforms and waiting

rooms), and several RRUs can be used to

create one logical cell and simplify

mobility handling. A common central

baseband processing unit, the Digital Unit

(DU), is located in the equipment room.

Each antenna point is complemented by

an integrated Wi-Fi Access Point (AP) to

support low mobility. Each RRU may be

connected to a small DAS.

By implementing distributed RAN

architecture using RRUs, advanced

functionalities such as softer handover for

coordination in WCDMA, together with

uplink and downlink coordinated multi

point (CoMP) for coordination in both

WCDMA and LTE, along with multi-cell

transmission techniques, will provide

robust mobility in such challenging

environments.

Antenna and cabling infrastructure,

such as fiber and DAS, may be shared to

support multi-operator deployment. With

shared fiber, each operator uses a

separate wavelength on the fiber and

additional lambda filters. In this case,

power backup needs to be separately

addressed. Another option is to use

separate fibers, so that each operator

deployment will be similar to the one

illustrated.

Performance/traffic demandPerformance/traffic demand

Densify macroAdd micro cellsDensify macroAdd micro cells

Add indoor small cellsAdd indoor small cells

Improve macroImprove macro

General indoor coverageGeneral indoor coverage Difficult areasDifficult areas Enterprise solutionsIndoor hotspotsRegulatory requirements

Enterprise solutionsIndoor hotspotsRegulatory requirements

Figure 2 – RAN architecture for a train station or mall

HETEROGENEOUS NETWORKS • MAKING THE RIGHT HETEROGENEOUS NETWORK CHOICES 6

achieved either by reusing fiber or by building dedicated microwave backhaul.

> In small public areas like cafés and restaurants, the cellular network could be complemented

with integrated pico cells or Wi-Fi access, or both.

> In busy city center streets and squares, coverage and capacity could be enhanced using

outdoor small radio base stations or RRUs with adequate backhaul solution.

> In large indoor locations like railway stations, malls and airports, performance could be

maximized using small RRUs (see detailed example in box section).

> In an office environment, depending on the size of the building, it may be feasible to deploy

pico cells (optionally feeding a small DAS) or some form of distributed architecture solution

(see detailed example in box section).

By integrating such small cell solutions in conjunction with an improved and densified macro

layer, operators will achieve superior performance and smooth network migration. As the network

becomes more heterogeneous, certain mechanisms will be needed to ensure a seamless user

experience, network robustness and manageability.

MEETING SPECIFIC INDOOR NEEDS

Aside from the general need to improve coverage and capacity, one specific challenge for mobile

operators is to meet consumer expectations indoors. The macro network has always been

designed to meet the needs of general indoor coverage: macro network planning takes in-building

penetration loss into account and, in general, the resulting coverage is usually good enough for

general connectivity. However, there will be areas or buildings that require improvement in order

to achieve an acceptable level of coverage.

If additional outdoor sites can be found – either for macro cells or street level micro cells – this

is an attractive option to resolve general coverage and capacity needs. To substitute one outdoor

cell with indoor solutions typically requires a number of indoor installations, whether small cells

or a larger DAS, which in turn increases the total cost of ownership (TCO) of the mobile broadband

HETEROGENEOUS NETWORKS IN ACTION

Office

In offices – including small, medium and

large enterprises, hotels and high-rise

buildings – a key challenge is to offer

excellent speech quality, high data rates

and high capacity for indoor users. With

excellent indoor radio performance,

operators can open up new opportunities

in cloud-, IMS- and packet core-based

value-added services, for example.

Coverage from the macro network is

often limited on lower floors but good on

top floors of high-rise buildings. As a

result, interference from macro cells can

be a challenge. Radio isolation between

floors is often good (around 20dB), so

distributed radio architecture with

centralized baseband provides the best

indoor coverage needed to deliver good

user experience and high capacity in

large venues.

Antenna elements connected to RRUs

can be distributed around the building to

achieve the required coverage and

capacity.

To meet the needs of small offices,

pico base stations are recommended.

These should ideally support WCDMA,

LTE and Wi-Fi, with an unobtrusive

design that enables them to be deployed

in virtually any indoor environment.

A carrier Wi-Fi network could also be

deployed, with traffic steering between

Wi-Fi and 3GPP coverage.

With many base stations in the

building, additional transport aggregation

may be useful. This would most likely be

located in the telecoms equipment room.

Low-power base stations may be

remotely powered from the equipment

room over Ethernet, or via a separate

cable if fiber is used. The equipment

room would then include AC/DC power

feed with battery backup.

ONE networkONE network

APAP APAPSmallRBSSmallRBS

SmallRBSSmallRBS

SmallRRUSmallRRU

SmallRRUSmallRRU

SmallRRUSmallRRU

MacroRBS

MacroRBS

MainunitMainunit

Core network/controllerCore network/controller

MainunitMainunit

Broadbandinternet

Broadbandinternet

RadioDot

RadioDot

RadioDot

RadioDot

Figure 3 – RAN architecture for a large office

HETEROGENEOUS NETWORKS • MAKING THE RIGHT HETEROGENEOUS NETWORK CHOICES 7

infrastructure significantly. Instead, promising potential applications for dedicated in-building

solutions include:

> locations where consumer demand for higher capacity, performance and robustness justifies

indoor solutions – for example, at enterprise sites

> indoor traffic hotspots like airports and malls, where substantial traffic is captured by the

indoor solution

> key buildings that need coverage – for example, to meet regulatory requirements, but where

outdoor-to-indoor penetration loss is high.

HETEROGENEOUS NETWORK ARCHITECTURE

A heterogeneous network is able to make the most of the

chosen set of radio-access technologies (RATs), base

station configurations and transport options. By viewing

the heterogeneous network as one network, integrated

small cells can be properly coordinated with the macro

network, and different RATs can be well integrated. By

designing and optimizing the heterogeneous network as a

whole, it can be evolved smoothly and deliver maximum

resource-efficiency and QoE.

The level of coordination that can be achieved over the

available backhaul affects the level of spectrum efficiency

and QoE. In essence, for maximum performance, the

backhaul link needs to be fast, with low latency and low

delay variation characteristics. In more coverage-driven

deployments, TCO will need to be minimized – calling for

best-effort, or internet-grade, backhaul.

Depending on performance needs,

radio conditions, cost and availability

of backhaul infrastructure, there is a

cost-effective small cell solution for

each situation. Typically, small cell

configurations support an increasing

degree of coordination and performance

as follows:

> small base stations or APs using

internet-grade backhaul

> small base stations or APs using

dedicated transmission (fiber or microwave) for higher performance

> small RRUs connected to a main unit that hosts the digital baseband for a group of RRUs – for

example, feeding small DASs in a large building

> small RRUs connected directly to a macro base station, for difficult radio environments that

justify maximum coordination between macro cells and small cells.

These configurations are all, to varying degrees, coordinated with other cells and integrated

across RATs for maximum performance. The coordination is best achieved through a centralized

controller functionality and distributed mechanisms working closely together for maximum

efficiency and seamless user experience.

COORDINATION AND ROBUSTNESS

The performance of a heterogeneous network depends greatly on the degree of radio coordination

between cells. With proper coordination, macro spectrum can be fully reused in integrated small

cells, which means the same services can be delivered using half the spectrum because the

achievable user data rate is proportional to spectrum bandwidth. Coordinated small cells also

increase capacity, so that 50-70 percent fewer small cells are needed to serve the same total

network traffic. Based on Ericsson studies, the uplink cell edge data rate can be increased by a

factor of between two (for a bandwidth-limited case) and 10 (for a power- or interference-limited

case).

Digitalunit

Digitalunit

Digitalunit

Digitalunit

AC/DC batterypower feedAC/DC batterypower feed

RRURRU

RRURRU

Technical roomTechnical room

Antenna locationAntenna location Local switchingLocal switchingMacro siteMacro site AggregationAggregation AggregationAggregationCentraloffice

Centraloffice

Waiting hallWaiting hall

PlatformsPlatforms

AntennaelementsAntennaelements

AntennaelementsAntennaelements

AntennaelementsAntennaelements

RFmulti-band

RFmulti-band

RFmulti-band

RFmulti-band

APAP

APAP

RFRF

Transport aggregationEthernet fiberTransport aggregationEthernet fiber

Ethernet over copperEthernet over copper CPRIoverfiber

CPRIoverfiber

Ethernet over copperEthernet over copper

RNCRNC WICWIC

Figure 4 – meeting specific indoor needs

HETEROGENEOUS NETWORKS • MAKING THE RIGHT HETEROGENEOUS NETWORK CHOICES 8

Traffic management, including inter-layer

mobility and load sharing, is also

increasingly important as the network

becomes heterogeneous. Only a common

approach, across layers and technologies,

can achieve a seamless user experience

at maximum efficiency. Consequently,

single-vendor solutions for heterogeneous

networks make sense from a coordination

and interworking perspective – saving

spectrum and reducing the TCO for the

small cell layer by at least 50 percent as a

result of reduced infrastructure (fewer cells

needed), rollout, operation and

maintenance costs.

To deliver a good and consistent user

experience, operators need to be able to

monitor actual performance across the

entire network, and take action when KPIs

deviate from the defined levels.

Performance management is rapidly being

transformed into user experience-driven

processes, in which broad mobile

broadband KPIs such as data rate and

latency are used as the basis for actions

and decisions. To aggregate such KPIs,

macro cells, small cells (including

integrated Wi-Fi), radio network controllers

(RNCs), core network nodes and backhaul

nodes must be able to provide quality-

related information. It must also be

possible to correlate the events and KPIs

between these nodes. Needless to say,

this is extremely challenging if different node types are uncoordinated and provided by different

vendors.

CONTINUOUS NETWORK EVOLUTION

There are a growing number of tools available to operators, yet there is a perception that networks

are congested and radio coverage is spotty. A study of network performance in comparable

markets shows that the situation varies greatly. By benchmarking network performance around

the world, we see that the best-performing networks are:

> well-dimensioned and planned – the load on the air interface as well as on backhaul and

network elements is under control

> well-tuned – parameters are consistently set and follow recommended settings

> equipped with the latest software release and functionality

> accessed by high-performance terminals, supporting high data rates, with advanced receivers

and receiver diversity.

Aside from network dimensioning, the presence of advanced, high-performance terminals is a

key differentiator. For example, speedtest.net measurements of different HSPA terminals often

show that receiver diversity and multi-carrier (42Mbps) features each double achievable data

rates – delivering a fourfold improvement throughout the cell when combined. It is also clear that

the value of proper network design, optimization, and a clear terminal strategy will grow in

importance as networks become more heterogeneous, with several technologies, frequency

bands, and a variety of cell sizes and base station configurations.

Digitalunit

Digitalunit

Digitalunit

Digitalunit

AC/DC batterypower feedAC/DC batterypower feed

RRURRU

RRURRU

Technical roomTechnical room

Antenna locationAntenna location

Antenna locationAntenna location Distributed hubDistributed hub Antenna locationAntenna location

Local switchingLocal switchingMacro siteMacro site AggregationAggregation AggregationAggregationCentraloffice

Centraloffice

LobbyLobby

AntennaelementsAntennaelements

AntennaelementsAntennaelements

RFmulti-band

RFmulti-band

DASantennaelements

DASantennaelements

DASantennaelements

DASantennaelements

RRURRU

Antenna locationAntenna location Distributed hubDistributed hub Antenna locationAntenna location

RFmulti-band

RFmulti-band

DASantennaelements

DASantennaelements

DASantennaelements

DASantennaelements

RFmulti-band

RFmulti-band

RFRF

TransportaggregationEthernet fiber

TransportaggregationEthernet fiber

CPRIoverfiber

CPRIoverfiber

RF over coaxRF over coax

RNCRNC

Figure 5 – heterogeneous network architecture

HETEROGENEOUS NETWORKS • CONCLUSION 9

conclusionIn the Networked Society, mobile broadband traffic and user expectations are growing

exponentially. Operators need to provide sufficient radio network capacity and coverage

to ensure that they can secure future competitiveness by delivering a consistent, high-quality

experience that builds customer satisfaction and brand loyalty. With excellent ‘baseline’

mobile broadband coverage and capacity, particularly indoors, operators can also address

value-added opportunities in cloud-, IMS- and packet core-based services, especially for

enterprises.

A heterogeneous network – based on a single-vendor, 3GPP-standardized and coordinated

radio network with integrated Wi-Fi, advanced traffic management and high-performance

backhaul – can help deliver a consistent, high-quality and seamless mobile broadband

experience. Making the right technology choices in the right places at the right time is key

to ensuring smooth capacity expansion with maximum efficiency.

Operators are able to leverage their existing, proven 3GPP network and terminal base,

by improving, densifying and adding to the macro infrastructure to meet surging traffic

demand. Ericsson provides high-capacity heterogeneous networks today and is paving the

way towards highly effective ways to deploy and manage dense RANs.

HETEROGENEOUS NETWORKS • GLOSSARY 10

GLOSSARYAP Access Point

CPRI Common Public Radio Interface

DAS Distributed Antenna System

DU Digital Unit

RAT radio-access technology

RF radio frequency

RNC radio network controller

RRU remote radio unit

TCO total cost of ownership

WIC Wi-Fi Controller

HETEROGENEOUS NETWORKS • REFERENCES 11

References1. Ericsson, June 2014, Ericsson Mobility Report, available at: http://www.ericsson.com/ericsson-mobility-report

HETEROGENEOUS NETWORKS • FURTHER READING 12

Further reading > Ericsson, September 2014, It all comes back to backhaul – solutions supporting superior end-to-end QoE in

heterogeneous network deployments, available at:

http://www.ericsson.com/res/docs/whitepapers/WP-Heterogeneous-Networks-Backhaul.pdf

> Ericsson, June 2013, Keeping smartphone users loyal, available at:

http://www.ericsson.com/res/docs/2013/consumerlab/keeping-smartphone-users-loyal.pdf

> Ericsson, June 2013, Wi-Fi in heterogeneous networks – an integrated approach to delivering the best user

experience, available at: http://www.ericsson. com/res/docs/whitepapers/wp-wi-fi-in-heterogeneous-networks.pdf

© 2014 Ericsson AB – All rights reserved