small cell deployment strategies august 2012 1 and best ... · small cell deployment strategies and...
TRANSCRIPT
Small Cell deployment strategies
and best practice backhaul
August 2012 1
Small Cell deployment strategies
and best practice backhaul
August 2012 2
Contents
Executive summary .............................................................................................. 3
1 Introduction - different ways to deploy small cells ............................................ 4
1.1 Capacity or Coverage - what’s the difference? ......................................... 5
2 Consumer/Enterprise self-deployed (femtocells) .............................................. 6
3 Operator deployed small cells ........................................................................... 7
3.1 Targeted capacity hot-spot ....................................................................... 7
3.2 Non-targeted (‘peppered’) QoE enhancement.......................................... 8
3.3 Outdoor and indoor coverage not-spots ................................................. 10
4 Summary ......................................................................................................... 11
5 Glossary .......................................................................................................... 12
6 About Cambridge Broadband Networks Limited ............................................. 12
Author
Julius Robson is a Wireless Technology Specialist at Cambridge Broadband Networks Limited.
Julius leads the NGMN Small Cell Backhaul Group and is Vice Chair of the Small Cell Forum’s
Backhaul special interest group.
Front cover image courtesy of Keima Wireless Ltd
Small Cell deployment strategies
and best practice backhaul
August 2012 3
Executive summary
Virtually all operators now include small cells in their strategy to provide ubiquitous mobile
broadband, and this paper considers the different approaches that might be adopted to deploy
them, and the implications for backhaul.
The decision tree below summarises factors which differentiate between deployment styles:
whether they are consumer or operator deployed and whether they are predominantly needed to
enhance the capacity of an existing service, or whether the small cell will bring new coverage to an
area. The combinations of these factors lead to five deployment styles, each with differing
implications for the best backhaul solution. Whilst consumer deployed femtocells are likely to be
the most numerous, they will mostly use leased backhaul from a service provider. Consumers will
not be too concerned on the backhaul technology choice provided the service level is acceptable.
Operators will also deploy small cells and backhaul, and will use different approaches depending
on the particular problem they wish to address:
Persistent demand hot spots can be targeted providing a site within range can be acquired
and suitable backhaul connectivity provided. This approach is demanding from both
backhaul coverage and capacity perspectives. Non-line of sight solutions may be needed
in the places where high capacity fibre and line of sight (LOS) wireless cannot reach.
Consumer Quality of Experience can also be enhanced by ‘peppering’ small cells in
general areas of high demand, making the most of available sites that can be easily
backhauled with high capacity LoS wireless or fibre.
Operators will also use small cells to address not-spots in both outdoor and indoor
locations. Where coverage is the primary motivation, lower capacity backhaul solutions can
be considered. Uncovered outdoor areas are likely to be in remote locations, requiring long
rage solutions such as satellite or point-to-point microwave. Indoor small cells might
connect into the building’s LAN or use a Distributed Antenna System.
In summary, our examination of different small cell deployment styles helps to understand when to
select a particular tool in the backhaul solution toolbox.
Small Cell deployment strategies
and best practice backhaul
August 2012 4
1 Introduction - different ways to deploy small cells
The small cell banner incorporates micro, pico, femto and metrocells which are collectively
expected to constitute almost 90% of all basestations by 20161.
They have been heralded as the answer to a range of issues faced by operators in their bid to keep
up with the ever-growing appetite for broadband mobile access.
However, significant challenges remain in deploying small cells, connecting them up and switching
them on. A recent survey found 56% of operators citing backhaul as one of the greatest
challenges, second only to fundamental issues of site acquisition, power etc2.
In our previous white paper, ‘Easy Small Cell Backhaul’3 we took a detailed look at the
requirements for backhaul and considered how the different types of solutions matched up against
these.
Six months on and with many small cell trials underway, we now
examine the different approaches that operators are considering
in rolling out small cells.
We have grouped these deployment styles into broad use case
categories defining the primary motivation and style of
deployment as follows:
Consumer/Enterprise self-deployed (femtocells)
Operator deployed small cells:
o Targeted capacity hot-spot
o Non targeted (‘peppered’) Quality of Experience
(QoE) enhancement
o Outdoor and indoor coverage not-spots
This paper considers in which situations each strategy might be
used and gives example scenarios. The implications for
backhaul are also considered, and the types of solutions that are
most appropriate.
In this consideration of backhaul solutions, it is the operator deployed scenarios that are of most
interest, as operators represent the main market for these technologies.
Consumers and enterprises deploying small cells will likely leased lines from service providers
(DSL, Cable, Fibre), and are less likely to be interested in deploying backhaul solutions
themselves.
1 “Small cells to make up almost 90% of all base stations by 2016”, Small Cell Forum, Feb 2012,
http://goo.gl/4W9Pv 2 “Small Cells Market Status”, Informa Telecoms and Media Small Cell Survey, June 2012, http://goo.gl/ZQ8f4
3 “Easy small cell backhaul”, Cambridge Broadband, Feb 2012, http://cbnl.com/resources/easy-small-cell-
backhaul
56% of operators cite
backhaul as one of
the greatest
challenges, second
only to fundamental
issues of site
acquisition2
Small Cell deployment strategies
and best practice backhaul
August 2012 5
1.1 Capacity or Coverage - what’s the difference?
The use cases differentiate between small cells providing capacity and those providing coverage.
However, de facto adding a small cell to the network provides a degree of both, so what’s the
difference?
Our definition, which was adopted by the NGMN4, considers whether the small cell is deployed in
addition to existing macro coverage, or whether it brings a new service to an area where is was
previously unavailable. In the days of voice, the service is either there or not. However in the age of
mobile data the ‘service’ can range from GSM EDGE with a few kbps, to multi-megabit HSPA or
LTE.
A general definition is that coverage enhancement brings a new service (or level of service) to an
area where it could not previously be experienced, even during quiet times with only one user
accessing the network.
Capacity enhancement can be considered as a way of increasing the number of people that can
have a given level of broadband experience in an area during the busy times. Although a small cell
will likely improve both coverage and capacity, the definitions consider the operators primary
motivation for deployment.
The following sections consider each use category in turn.
4 “Small Cell Backhaul Requirements”, NGMN Alliance, June 2012, http://goo.gl/eHHtx
Small Cell deployment strategies
and best practice backhaul
August 2012 6
2 Consumer/Enterprise self-deployed (femtocells)
Description
The vast majority of small cells will be self-deployed by consumers or enterprises in order to
provide coverage or enhance the QoS of cellular connectivity in their home or office. Femtocells or
‘home basestations’ have required the development of true plug and play technologies, as well as
those for Self Organising Networks (SONs). End users deploy the small cell where they believe it is
most needed and where they can provide power and network connectivity.
Self-deployed residential and enterprise femtocells typically use leased internet
connections for backhaul. Image courtesy of Ubiquisys
A key limitation of self-deployed femtocells is that most consumers would prefer to restrict access
to themselves and a limited ‘white list’ of users.
These ‘closed access’ small cells therefore do not improve coverage for all of an operator’s
subscribers. As such, operators are looking to leverage the benefits of femtocell technologies for
low-cost deployment, but in an ‘open access’ mode available to all subscribers.
Backhaul implications
Femtocells typically use the consumers’ existing leased line internet connection for backhaul which
may be via DSL, Fibre, Cable or Satellite. Femtocell owners themselves are not concerned with the
type of technology used for backhaul – this is the domain of their Internet Service Provider (ISP).
Applicable backhaul solutions
Leased DSL
Fibre
Cable
Small Cell deployment strategies
and best practice backhaul
August 2012 7
3 Operator deployed small cells
3.1 Targeted capacity hot-spot
Description
The small cell is deployed at the centre of an area of high-demand density. Macro coverage is
already present at the location, but hot-spot demand causes congestion and poor Quality of
Service (QoS) during busy times. The hotspot small cell provides both better propagation and less
sharing of the mobile spectrum, improving QoS for the users it serves. Offloading this traffic also
improves QoS for users who continue to be served by the macro layer.
Hot-spot deployment requires identification of the high-demand locations, and for them not to move
during the lifetime of the small cell. Data mining techniques based on social media (e.g. geo-tags
from Flickr photos or tweets) can indicate concentration of smartphone usage and potential
capacity hot-spots. Targeted hot-spot deployment further requires that a site can be acquired close
enough to the optimal location for the small cell’s coverage to match with the area of high demand.
Because the coverage area of a small cell is, by definition, small, this may be very difficult to
achieve in practice.
Demand hot-spots can potentially be located from geo-tagged social media data. Source:
Keima5
Examples
Dense urban hot-spot
Transport hub (train/bus station, airport), metro station exit
Point of interest generating significant mobile traffic (e.g. photo uploads at landmarks)
Special events – stadiums, festivals, pop concerts
Disaster scene needing additional capacity for emergency services
5 Image courtesy of Keima Wireless Ltd: http://keima.co.uk
Small Cell deployment strategies
and best practice backhaul
August 2012 8
Backhaul implications
The ideal backhaul solution would have very flexible coverage to be able to reach the ideal hotspot
location. As identified by the NGMN, backhaul for hot-spots must also have high capacity so as not
to limit in any way the amount of traffic demand that the small cell can soak up.
Flexible coverage points towards the non-line of sight backhaul solutions, yet these are recognised
to have low capacity due to the limited amount of <6GHz spectrum economically available. Where
line of sight to a backhaul hub is available, a high-capacity microwave or mm-wave link can be
deployed. Otherwise, multi-hop or non-line of sight can be considered. Since an underlay macro
service is already available, the customer QoE is less sensitive to the availability of the small cell
backhaul connection. Costs can be reduced for example, by not using redundancy.
Applicable backhaul solutions
Fibre
Line of sight: point-to-multipoint (PMP) microwave, millimetre wave
Non-line of sight where fibre or line of sight microwave not available
3.2 Non-targeted (‘peppered’) QoE enhancement
Description
The ‘peppered’ approach deploys many small cells in areas of high demand for general
enhancement of consumer QoE over an existing underlay macro coverage. Site selection is less
focussed on pinpointing the perfect locations, and instead makes use of available sites which can
easily be acquired and backhauled.
The intrinsic non-line of sight propagation provided by the small cells themselves mitigates the sub-
optimal placement of the small cell units. This blanket approach has a reduced RF planning effort
compared to the targeted approach. It is also more suited to areas of high-demand significantly
larger than the coverage area of a single small cell.
Although in theory ‘peppered’ is likely to be marginally less efficient than a targeted approach, in
practice the difficulties in pinpointing long-term hotspots and acquiring optimal site locations with
backhaul will erode the benefits. The overall Total Cost of Ownership (TCO) for the peppered
approach may well be lower for a given level of user QoE.
Examples
Urban areas with a set of municipality owned sites (street furniture, public buildings etc.)
Suburban capacity infill
Local authority managed service deployed over set of owned locations.
Small Cell deployment strategies
and best practice backhaul
August 2012 9
Peppering of small cell sites in an area of general high demand, where high capacity line of
sight or fibre backhaul is available
Backhaul implications
The peppered approach makes use of sites which can be more easily acquired and backhauled, so
to some extent the backhaul topology can influence site locations. Existing fibre can be leveraged,
or sites with line of sight to a nearby hub or repeater in a multi-hop topology.
As with the targeted approach, the presence of the underlay macro coverage means small cell
backhaul availability can be relaxed without impacting consumer QoE.
Applicable backhaul solutions
Line of sight point-to-multipoint (PMP) microwave
Millimetre wave
Fibre
Small Cell deployment strategies
and best practice backhaul
August 2012 10
3.3 Outdoor and indoor coverage not-spots
Description
Small cells can be deployed in areas with no existing macro coverage often called ‘not-spots’.
These may be isolated locales where it is not cost-effective to deploy a macro-site, but a lower cost
small cell would suffice. They might also be large indoor areas in public buildings such as shopping
malls or airports. As regulators are mandating ever higher coverage obligations6 7,‘not-spot’ small
cells may help operators extend coverage to the last few per-cent of the population, both outdoors
and indoors.
Potential outdoor and indoor not-spots
Examples
Outdoor
o Underserved villages and town locations
Indoor
o Rural areas with marginal outdoor coverage
o Shopping malls, airports, museums
o ‘On board’ a ferry, train or aeroplane
Privately owned homes and businesses needing coverage might be better suited to a self-deployed
‘femtocell’ approach
Backhaul implications
Traditionally, long range microwave point-to-point links have been used to reach remote locations.
However, the cost of setting up the link may prove too much compared to the revenue that can be
generated from the small number of people served. The combination of a low-cost small cell with
low-capacity satellite backhaul is becoming a viable option for remote locations8.
NGMN requirements show that for not-spot small cells, lower backhaul capacities are acceptable.
However, since there is no existing coverage to act as a safety net, backhaul availability must be
as high as a normal macrocell.
Many indoor locations are likely to have existing fibre or copper connectivity providing fixed
telephone or data services. In some of the more remote cases, site connectivity might be provided
via rooftop microwave links.
6 “Ofcom unveils plans for 4G auction of the airwaves”, Ofcom, July 24 2012, http://goo.gl/83GGj
7 “Mobile Broadband Coverage – Balancing Costs And Obligations”, Analysys Mason, 28 June 11,
http://goo.gl/mOYGe 8 “Informa Study Shows How Satellite Backhaul And Small Cells Can Help Mobile Operators Affordably Reach Untapped Markets”,iDirect, 2 May 2012, http://goo.gl/IblxV
Small Cell deployment strategies
and best practice backhaul
August 2012 11
Applicable backhaul solutions
Outdoor not-spot
o Satellite
o Line of sight point-to-point (PTP) microwave
o DSL
Indoor not-spot
o Fibre
o DSL
o Cable where available or microwave
4 Summary
We have considered a number of use cases for small cells to improve the coverage and capacity of
an operator’s network, and identified different styles of deployment which might be used. These
are summarised in the table below.
Summary of deployment styles, backhaul requirements and applicable solution
Deployment
Style
Primary
Motivation
Deployed
by
Backhaul
requirements
Applicable
backhaul
solutions
Comment on backhaul
Capacity Coverage
Femtocell Coverage or capacity
Consumer Consumer choice whether to relax
Leased DSL, fibre, cable
Consumer leased internet connection
Targeted hot-spot
Capacity Operator High Extensive Fibre and LoS microwave where available, non-line of sight microwave otherwise
Extensive coverage and high capacity difficult to achieve with single solution
Peppered Capacity Operator High Flexible PMP microwave, millimetre wave
Flexible coverage requirement allows for high-capacity line of sight solutions
Outdoor not-spot
Outdoor coverage
Operator Relaxed Long range to remote locations
Satellite, PTP microwave, DSL
Low-cost connection to remote locations a struggle
Indoor not-spot
Indoor coverage
Operator Relaxed To building Fibre, DSL, cable where available or microwave
Backhaul can use existing site connectivity and LAN
The table shows that operators are likely to use a range of deployment styles for different small cell
use cases. In each case differing requirements suggest different types of backhaul solution are
most applicable.
In general we see that where possible, Fibre or line of sight wireless techniques should be used to
provide high capacity connectivity. Non-line of sight solutions can then be used to extend coverage
to specific hot-spots or not-spots that could not otherwise be reached.
Small Cell deployment strategies
and best practice backhaul
August 2012 12
5 Glossary
Quality of Service (QoS): the data rates, latency availability offered by a connection.
Quality of Experience (QoE): the perceived quality of a service or application by the user.
Impacted by both the offered QoS and the type of application e.g. QoE of streaming video is not
impacted by latency, but voice is.
Total Cost of Ownership (TCO): Capital Expenditure plus Operational Expenditure
Not-spot: Area with no coverage of a service (or given level of service)
Hot-spot: An area with high-demand density. In this paper we consider the hot-spot areas have an
acceptable coverage of the required service during quiet times, but that congestion during busy
times degrades the service below acceptable levels. Additional capacity is required.
About Cambridge Broadband Networks Limited
Pioneering the development and global deployment of next generation microwave transmission
equipment since 2000, Cambridge Broadband Networks’ VectaStar platform is deployed by more
operators, in more markets, than any other point-to-multipoint (PMP) microwave solution and
operates at the heart of the world’s busiest mobile data network.
VectaStar is proven to deliver results in the most demanding network environments whilst also
being deployable in 3G, 4G, small cell and LTE backhaul networks.
With a network of offices around the globe, CBNL’s solutions provide operators with both capital
and operational savings and manage spectrum, an increasingly scarce resource, dynamically and
efficiently.
For more information on Cambridge Broadband Networks’ small cell backhaul solutions and
planning tools, please contact:
Cambridge Broadband Networks Limited
Selwyn House
Cambridge Business Park
Cowley Road
Cambridge
CB4 0WZ
United Kingdom.
T +44 1223 703000
F +44 1223 703001
www.cbnl.com
© 2012 Cambridge Broadband Networks Limited. All rights reserved.