white paper: heterogeneous networks - securing excellent mobile broadband user experience,...
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In 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.TRANSCRIPT
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