The Radio Frequency Systems Bulletin
3rd quarter 2004
S h a re d a n d s c u l p t e d : L A b ro a d c a s t i n g i n t h e l i m e l i g h t Connections, corrugations and costs Alberta SuperNet—broadband for the future Minimizing microwave antenna interference
The Clear Choice™
Expansion vs QoS: striking the balance
4 What’s New BDA/duplexer series supports in-building 3G Broadband Optimizers complete 90-degree range Ultra-compact manifold combiner Dual function DAB Band III filter family
Microwave antenna options for minimizing interference
18 In Touch 3G focus for Chinese expo RFS shines the DTT light in Hungary IBC 2004: RFS to display digital solutions Kerrang! rocks with FM solution PREVIEW: Base station technology—an RF interface evolution
6 Cover Story Shared and sculpted: LA broadcasting in the limelight
WorldWideWeb: http://www.rfsworld.com Publisher: Jörg Springer Executive Editor/Editor Asia Pacific: Peter Walters Editor EMAI: Regine Suling Editor Americas: Ann Polanski Managing Editor: Dr Ellen Gregory Production Editor: Christian Michatsch Art Director: Marilu Krallmann
Authors: Allan Alderson, Dr Ellen Gregory, Anita Talberg Photos: RFS archives, Alcatel Canada, CMS Wireless, inform archives, Getty Technical illustrations: Pamela Seaman Cover images: RFS archives Cover art: Marilu Krallmann Print: Print Design, Minden
8 Feeder Systems
Layout and Graphics: inform Advertising, Hannover
Connections, corrugations and costs—the feeder cable debate
IMPRINT
Radio Frequency Systems
14 Technology Focus
3 Editorial
Editorial Services: Relate Technical Communications, Melbourne
11 Microwave
Trademarks: CELLFLEX®, BDA®, FLEXWELL®, MicroTenna™, Optimizer®, RADIAFLEX®, Radio Frequency Systems®, RFS®, RFS CompactLine®, SlimLine® and The Clear Choice™ are trademarks, service marks or registered trademarks of Radio Frequency Systems.
Alberta SuperNet—broadband for the future
On the cover: Dual RFS broadband panel arrays provide sculpted digital/analogue signals for four Los Angeles television broadcasters at Mount Wilson in California.
INDEX
8
BDA/duplexer series supports in-building 3G A new series of bi-directional amplifiers (BDA) and duplexers offers a convenient and inexpensive means of overlaying UMTS on existing 2G in-building RF distribution systems.
Connections, corrugations and costs— the feeder cable debate To make sense of base station feeder cable technology, start where it all begins and ends: at the base station site with the site crews and network development teams.
14 11 Alberta SuperNet—broadband for the future From Alberta’s Rocky Mountains to its northern ice lakes, RFS microwave antenna solutions play an important role in realizing province-wide broadband connectivity.
6 Shared and sculpted: LA broadcasting in the limelight An innovative, shared broadcast system atop Mount Wilson provides four LA broadcasters with high performance—and highly sculpted —digital and analogue television coverage.
Microwave antenna options for minimizing interference With microwave network density on the rise, the potential for signal interference is also increasing. RFS looks at ways of minimizing interference-causing distortion of radio frequency signals.
RF interference—one of the greatest challenges of network optimization and a by a remote antenna tilt system, the RF
A
recent
report
by
global
wireless
It is a well-known industry maxim that it
control afforded by the Optimizer range will
some
costs four times as much to attract a new
ensure operators can offer premium QoS
interesting points about the threat of
customer than to retain an existing one.
both now and in the future.
subscriber churn for mobile operators.
With this very real cost of churn in mind, it
But many factors come into play—in
Based on a survey of UK mobile phone
makes business sense for mobile operators
particular, a focus on total system solutions.
users, the report states that operators risk
to maintain a tight focus on customer
Carefully
losing a full third of their customers due to
satisfaction. If, as LogicaCMG points out,
performance at a component level, the
poor quality of service. It even goes so far
many mobile operators are focusing on
RFS range of high-performance cellular
as to put a figure on what this might
business expansion at the expense of
antennas, low-attenuation transmission
cost the UK telecoms industry in 2004—an
improving quality of service, they are clearly
line and RF conditioning components also
estimated _3 billion.
shooting themselves in the feet.
combine to provide fully integrated base
And the rate of subscriber churn in the
This choice between network expansion
station solutions that meet the most
telecommunications
consultancy,
LogicaCMG,
raises
industry
engineered
for
optimum
remains
and enhancing network performance is not
stringent demands of operators. Ongoing
significant. In May this year, the global
a new dilemma. Network optimization is an
QoS objectives are achieved through
average across fixed and mobile sectors
ongoing challenge for operators the world
precise RF control and tuning flexibility;
was estimated by communications research
while the broadband functionality and
group, Chorleywood, to be at 22 per cent.
built-in future-proofing streamline the path
Dr Klaus-Dieter Mischerikow Radio Frequency Systems President
EDITORIAL to network expansion and migration to
operators is what might happen to their
4
has been carefully engineered to combat
primary key to ensuring QoS. Complemented
Yet of perhaps greater concern to mobile
Normalised radiation [dB]
2
Expansion vs QoS: striking the balance
new technologies. In other words, RFS
bottom line if LogicaCMG’s predictions
over--a constant balancing act between
offers both expansion capability and quality
come to pass and the rate of churn increases.
coverage, capacity and quality of service
of service in the one solution set.
TNS Asia Telecoms Index has also revealed
(QoS). To-date, these have often been
The dilemma is unlikely to go away; the
that, compared with a year ago, 33 per
regarded as mutually exclusive; one to be
choice between network expansion and
cent more Asian mobile users are indicating
prioritized at the expense of the others. But
enhancing network performance has been
they’d like to change networks within the
this doesn’t have to be the case.
the ‘lot’ of wireless operators since the
next six months.
Radio Frequency Systems has developed a
inception of mobile services. In fact,
What is causing this rising dissatisfaction
comprehensive suite of RF products that
operators will face even more of a juggling
with mobile services? The attraction of
allow operators to consider more than one
act
more competitive pricing has long been a
goal at a time. This suite permits operators
technologies such as push-to-talk, WiFi and
factor, but new issues related to the service
to achieve both immediate and long-term
mobile video.
itself are coming to the fore. Surveys have
expansion objectives, plus fulfil immediate
RFS is committed to these next-generation
cited problems with coverage, reception,
and long-term goals for improvements in
technologies. Our focus is on providing
customer service, billing and roaming as
QoS—not to mention a generous dose of
optimal RF solutions in order for them to be
strong
future-proofing.
realized. Both network expansion and
customers to seek alternative providers. If
Our Optimizer range of high-performance
quality of service are important and, with
the service is not up to scratch, then the
cellular base station antennas is an ideal
the right technology, the choice of how to
fight over how much to pay for it becomes
case-in-point. Featuring a host of advanced
act can be made easier. It’s all about striking
somewhat moot.
features such as reduced side lobes and an
the right balance.
and
legitimate
reasons
for
as
they
deploy
next-generation
extended tilt range, the Optimizer series
Klaus-Dieter Mischerikow
3
B DA / d u p l e x e r s e r i e s supports in-building 3G
Ultra-compact manifold combiner and uplink, and are provided in two output
requirements can be realized ‘locally’ via the
power ratings, 18 dBm and 9 dBm. Used in
unit’s power port, or ‘remotely’ via the RF
The latest addition to the leading UHF
features double temperature compensation,
combination with the new duplexer, the
coaxial feeds, permitting the units to be
combiner range of Radio Frequency Systems
and exhibits low losses for its given filter
bi-directional amplifiers may be used to
cascaded in a wide range of combinations.
is an ultra-compact manifold combiner
sizes. According to Broad, a key differentiator
A new series of bi-directional amplifiers
I-DUX2G/3G combination is one of the
support a ‘3G on 2G’ overlay on an existing
The I-DUX2G/3G-1 duplexer is uniquely
ideal for low-power digital television (DTV)
is the availability of coaxial filters of up to
(BDA) and duplexers from Radio Frequency
first on the market to offer a cost-effective
broadband in-building system.
broadband, with its 2G port supporting
broadcast sites. Designed for combining
7-poles, offering semi-adjacent channel
Systems offers a convenient and inexpensive
and
Both I-BDA2100 models support the full
frequencies between 800 and 1880 MHz.
digital channels up to 250 W, the UHF
combining and transmitter DTV masking.
means of overlaying universal mobile
this situation.”
UMTS band, and provide automatic gain
It provides particularly low insertion loss at
manifold combiner offers an economical
Although the manifold configuration can
telecommunication services (UMTS) on
The series comprises two band-specific
control in accordance with the Third
both the 2G and 3G ports, and comes
and space-efficient alternative to balanced
only combine channels down to semi-adjacent
existing second-generation (2G) in-building
UMTS bi-directional amplifiers (I-BDA2100-1
Generation Partnership Project’s (3GPP)
complete with two separate on-board
modules.
spacings, it can be used with balanced
RF distribution systems.
and I-BDA2100-2), plus a broadband
specified UMTS requirements. Manual gain
dc power input ports, allowing even
“The manifold combiner has been developed
modules in a hybrid system to realize adjacent
“RFS has had the foresight to build in
duplexer (I-DUX2G/3G-1). The new BDAs
control is also provided for final system
greater
in direct response to requests from broad-
channel combining. “Essentially, the semi-
future-proofing in its 2G in-building RF
supply 35 dB nominal gain in RF downlink
levelling. The unit’s 10-30Vdc power
configuration.
simple
means
of
overcoming
flexibility
in
system
power
casters for an ultra-compact solution,”
coverage solutions—as a result, these are
The new series of bi-directional amplifiers (BDA) and duplexers from RFS is used for overlaying UMTS on existing 2G in-building RF distribution systems.
sufficiently broadband to support the simple overlay of new third-generation (3G) UMTS services,” said Peter Raabe, RFS Global Product Manager for Wireless
4
exiting
Broadcast, Graham Broad.
system can be fed into
“It’s a fully integrated unit,
system, and adjacent
used within
levels may prove inadequate, due to the
our balanced
higher insertion losses of the 2G network
combiner
cabling. The new RFS I-BDA2100 and
modules. For
I-DUX2G/3G-1
B ro a d b a n d O p t i m i z e rs c o m p l e t e 9 0 - d e g re e ra n g e
the wideband input
than half the components
IBDA2100-2
manifold
of a balanced combiner
many cases though, the UMTS RF power
WHAT ’S N EW
the
and contains less
Distributed Communications Systems. “In
IBDA2100-1
adjacent combined channels
said RFS Area Product Manager
channels inserted,” said Broad.
“This
means
that
multiple adjacent channels can be combined using half-balanced and half-manifold units, resulting in a highly
instance, the manifold
compact and low-cost system.”
configuration has just one
Designed for wall mounting or installation
50E filter instead of two, and the whole unit
within a standard 19-inch rack, the manifold
is therefore less than half the weight, has
combiner units alone can be used to combine
half the footprint, and is lower in cost.”
up to six semi-adjacent channels, with a
Displaying similar performance characteristics
combined maximum output power of 750 W.
to RFS’s low-power integrated balanced
This equates to 6 x 125 W or 3 x 250 W of
‘cellular’
combiner, the manifold model is also
potential input powers into the combiner,
850 MHz, trunking/specialized mobile radio
tuneable over the entire UHF band (470 to
providing superior flexibility for broadcasters
(SMR) 800 MHz, and global system for
860 MHz) for 6, 7 or 8 MHz bandwidths,
operating low power sites.
the
APX86-90914L
supports
mobile communications (GSM) 900 MHz 90-degree
“The 90-degree aperture cellular antenna is
circle. RFS now offers complete antenna
services. The APXV18-20914/15 antennas
beamwidth cellular antennas have joined
proving to be a vital complement to
solutions in both 65- and 90-degree
support
Radio Frequency Systems’ high-performance
conventional
beamwidths, ensuring network planners
communication services (PCS) 1900 MHz
Optimizer family. The new additions—the
antennas,” said Patrick Nobileau, RFS Vice
greater network optimization flexibility.”
and universal mobile telecommunications
In support of global digital audio broadcasting (DAB) deployments, Radio Frequency Systems
variable electrical tilt APXV18-20914 and
President Base Station Antenna Systems.
Importantly,
system (UMTS) 2100 MHz services. As
is launching a new family of DAB Band III coaxial filters. Tuneable over the entire VHF Band III,
APXV18-20915,
tilt
“In some cases, 65-degree proves the best
broadband, with the APXV18-20914 and
operators
the new filters offer a compact and flexible solution for both transmitter mask filtering and
APX86-909014L—complete the Optimizer
choice, as it results in a minimal bit error
APXV18-20915 supporting frequencies in
roll-out multiple and often co-located
digital RF channel combining.
90-degree aperture series, making it one of
rate. In other cases, a 90-degree aperture is
the 1710 to 2170 MHz band, while the
wireless platforms, the broadband nature
The DAB filter range is founded on RFS’s world-leading RF combining technology and utilizes
the most comprehensive of its kind
optimal, as in a tri-sector configuration it
APX86-90914L accommodates frequencies
of the optimizer 90-degree antennas
a similar platform of components to the company’s VHF Band III digital television combiners.
available today.
provides coverage that is closer to a perfect
in the 806 to 960 MHz band. As a result,
provides them with a powerful means
Six and eight-pole versions of the coaxial filters will be available in three cavity sizes
of rationalizing and reducing antenna
(100 mm, 180 mm and 270 mm), accommodating transmitter powers of 500 W, 1500 W
inventories.
and 2500 W respectively. The nominal bandwidth is 1.54 MHz, as specified by the global
Three
new
broadband
and
the
fixed
65-degree
aperture
all
three
antennas
RFS 90-degree beamwidth Optimizer antennas
are
GSM
1800
and
MHz,
OEMs
personal
worldwide
Dual function DAB Band III filter family
All three antennas exhibit the superior
‘Eureka 147’ DAB standard.
Type
Model No.
Bandwidth
Tilt
Length
Gain
performance
common
The eight-pole DAB filters can be incorporated within transmitters to provide critical mask
Low band fixed tilt
APX86-90914L-T0 and T6
824 - 940 MHz
Fixed 0 and 6 degrees
2 metres
15.5 dBi
to all members of the RFS Optimizer
filtering of the digital RF signal, in keeping with global DAB standards. When used as the key
Low band variable tilt
APXV86-90914
824 - 940 MHz
Variable 0 -10 degrees
2 metres
15 dBi
antenna family. This includes side lobe
components of a balanced DAB combiner, the eight-pole filters can achieve both critical
High band fixed tilt
APX18-209014 -T2 and T5
1710 - 2170 MHz
Fixed 2 and 5 degrees
1.3 metres
15.8 dBi
suppression typically better than 20 dB
transmitter masking and adjacent channel combining simultaneously, eliminating the need
High band fixed tilt
APX18-209015 -T2 and T5
1710 - 2170 MHz
Fixed 2 and 5 degrees
1.8 metres
17.5 dBi
across the entire frequency and tilt range,
for additional filters within the transmitter.
High band variable tilt
APXV18-20914
1710 - 2170 MHz
Variable 0 -10 degrees
1.3 metres
16.5 dBi
significantly increased gain, and superior
Exhibiting low losses for these cavity sizes, the RFS DAB Band III filters are of compact design,
High band variable tilt
APXV18-20915
1710 - 2170 MHz
Variable 0 -10 degrees
1.8 metres
17.5 dBi
front-to-back ratio.
with the 100-mm models able to be installed within a standard 19-inch rack.
characteristics
5
S h a re d a n d s c u l p t e d : L A b ro a d c a s t i n g i n t h e l i m e l i g h t An innovative, shared broadcast system atop Mount Wilson provides four LA broadcasters with high performance—and highly sculpted—digital and analogue television coverage.
Crucial combining
which were tuned to optimize system
was introduced at the top of the 20-level
A crucial component of the system is the
performance. In addition, a total of eight
panel antenna column. This comprises
pair of parallel RFS directional waveguide
5-inch
coaxial
stainless steel tanks filled with a specifically
combiner chains, which support the dual
transmission lines were installed to feed the
calculated volume of ethylene glycol, which
broadband arrays. The channel combiner
panel array—four for each sub-array.
moves against the modes of vibration,
sub-systems each comprise five directional
The
waveguide filters and one blank section to
transmission line system was reflected
characteristic from around 0.0025 to 0.05
allow for the introduction of additional
power so low across all channels that
(that is, reducing the magnitude of
channels. The total system is also designed
several
oscillations by a factor of 20).
RFS
net
HELIFLEX
flexible
performance
transmitters’
result
reflected
of
the
power
potentially
increasing
the
damping
The advent of digital television and simulcast
combining. Dual sub-systems
to accommodate future channel reallocation,
indicators did not even move when the
digital/analogue services has undeniably
also allow greater flexibility for
and its compact nature means that space is
transmitters were energized.
changed the face of global broadcasting.
main/standby services, as well as
available in the building for two additional
With mountain real estate often at a
accommodating the different
combiner systems, if required for future
Structural challenges
more than four years, the final RFS combiner/
premium, plus escalating potential for
pattern tailoring requirements
expansion.
Owing to both the congested nature and
antenna system at Mount Wilson has the
interference and the considerable cost of
of the stations.
In order to accommodate the high
potential seismic activity of the Mount
capacity to accommodate a total of 12 digital or analogue services from channel 32 to 56.
deploying new infrastructure, many broad-
Team effort Conceived and designed over a period of
transmitted powers of analogue services
Wilson site, installation of the combiner
casters have made the bold move toward
Sculpting the signal
on channels 50 and 56, a new ‘full-
system proved an interesting challenge. A
multi-service systems.
Accurate sculpting of the broad-
wavelength’ directional waveguide combiner
newly constructed combiner room was
For four Los Angeles broadcasters (KDOC,
cast signal was one of the
was developed. This incorporates resonators
built as a bridge suspended over an existing
KJLA, KOCE, and KXLA) seeking to add
primary performance require-
a full wavelength in height (instead of half
building; and the entire combiner and
DTV to existing analogue services, these
ments of the system. A number
wavelength), providing twice as much
separate digital mask filter systems were
considerations ultimately have led to
of
surface area to dissipate the greater heat
bolted onto several steel frameworks, also
the deployment of a shared broadcast
restrictions
or
generated by losses in the high-power,
suspended from groups of four vertical
facility atop the city’s premier site—Mount
toward San Diego to the south-
higher-frequency channels. This means that
steel members. Seismic horizontal ties,
channels required signal over
Mexico
east, and it was desirable to reduce wasted power over the
6
COVER STORY
ocean for all channels, while ensuring
premium
coverage
The panel arrays were installed in four sections in October 2003.
Dual broadband panel arrays from RFS provide sculpted digital/analogue signals for four Los Angeles broadcasters at Mount Wilson.
7
for all of Los Angeles and its western satellite cities. The only Wilson.
Envisaged,
co-designed
and
way of achieving this level of
connecting the steel frameworks to the
overseen by broadcast consultant, S. Merrill
pattern sculpting, without compromising
signal phasing on the pattern is tightly
building structure itself, prevent the frame-
Weiss, the solution incorporates a dual,
performance, was through use of broadband
integrated—such that a change of phasing
works from excessive swinging during
broadband panel antenna/combiner system
panel arrays.
on one face has cascaded effects on other
seismic activity.
The combiner chains were installed in the
designed and manufactured by Radio
The dual, 10-level broadband panel arrays
antenna parameters. Finally, due to the
This was not the only structural innovation.
first half of 2003, followed by the raising
Frequency Systems.
deployed at Mount Wilson were designed
broadband nature of the antenna (580 to
The internal cavity of the antenna column
of the two stacked panel arrays in October
As an experienced provider of broadband
by RFS in close collaboration with Merrill
756 MHz), any adjustments for one
needed to be expanded in order maintain
of the same year, and rigid line optimization
RF solutions, RFS joined the project when it
Weiss. Early in the project, it was decided
frequency lead to follow-on effects across
human access, as well as contain a large
in early 2004. Currently configured for
became clear that a shared system was
to use panels arrayed on three faces of a
the bandwidth, so that the design is
volume of equipment—including the eight
nine channels (including two standby
required. Not only is the Mount Wilson site
five-sided column, with panels omitted on
effectively four dimensional.
flexible feeders and the branch feeders and
services), the first services went on-air in
highly congested, but since adjacent
the two northern faces, since coverage was
The process of ensuring optimum coverage
power dividers used for pattern sculpting.
April 2004, with the others joining in the
channels were involved, each of these
not required over the nearby mountains to
for each of the services—and particularly,
forced air cooling is not required to ensure
The result was an asymmetrical cross-
following months.
services needed to be broadcast from the
the north. Using sophisticated computer
that the signal restrictions over Mexico
that the operating combiner will not exceed
section, which led to issues with the
The project as a whole was undeniably
same location to prevent interference. In
modelling
of
didn’t degrade the performance of those
the design temperature rise.
antenna/tower interface. This was solved
a team effort—not only between the
order to move the analogue services from
electrically tilting the three faces individually,
channels not requiring it—involved many
Complementing the combiner system is a
in collaboration with the tower designer
consultant, Merrill Weiss, and RFS, but
elsewhere to Mount Wilson, plus deploy
coupled with power distribution and
iterations of the key design variables.
network of rigid transmission lines linking
through
development
also between the tower and transmitter
the new digital services, a shared system
phasing adjustments, were assessed to
Interference issues and the challenge of
the transmitters, mask filters, combiners,
of a unique multi-dimensional antenna
designers, installation and construction
was
determine
imperative.
It
also
offered
the
techniques,
the
effects
The panel arrays are supported by a pair of parallel RFS directional waveguide combiner chains—including a new ‘full-wavelength’ directional waveguide combiner.
the
fast-track
achieving the required gain within specified
and flexible coaxial feeders, which are each
clamping mechanism.
crews, the site owner, and the four
advantage of economy of scale.
each antenna.
power limitations were also taken into
in different locations owing to the crowded
An additional design consideration was the
broadcasters themselves. After extensive
For the seven channels to be broadcast
This antenna pattern optimization process
account, with the ultimate result being
nature of the site. Care was taken during
minimization of tower harmonics due to
theoretical design and modelling, the
(32, 44, 48, 49, 50, 51, and 56), dual
involves numerous variables. The act of
two separate stacked panel arrays (each
the design phase to minimize the reflections
wind-induced
physical
antenna/combiner
sub-systems
the
optimum
pattern
for
vibrations.
To
provide
realization
of
the
individual
were
changing the beam-tilt on individual faces
capable of handling up to 195 kW total
that might otherwise have occurred due to
dynamic
antenna
components, and the ultimate installation
conceived for a number of reasons. The first
leads to ‘transition regions’ in the pattern
average power input) that meet the
the number of components in the rigid feed
structure—which comprises the two RFS
and commissioning, the RF broadcast
of these was to simplify the combiner system,
that require careful analysis during the
stringent performance requirements of all
system; this involved the development of
panel arrays plus a third antenna mounted
system met all performance objectives
removing the need for adjacent channel
design
four broadcasters.
high-performance, broadband ‘elbows’,
on top of these—a tuned, liquid damper
right from the start.
process.
Also,
the
effect
of
stability
to
the
C o n n e c t i o n s, c o r r u g a t i o n s a n d costs—the feeder cable debate Making sense of the base station feeder cable technology debate is no easy task.The best place to start is where it all begins and ends: at the base station site with the site crews and network development teams.
8
For these reasons, the appearance of
“We put a lot of thought into this with the
smooth-wall feeder cable on the base
development of CELLFLEX ‘A’,” explains
station scene is something of a curiosity.
Chris Adams. “We knew crush strength was
“To-date, rigid smooth-wall feeder cable
vital in the field, so we didn’t compromise
hasn’t been seen much in European base
the CELLFLEX crush resistance, while
station applications, but it’s common all
dropping attenuation up to six per cent.”
over the world in its ‘native’ application— that of cable television (CATV) signal
Make the connection
routing,” says RFS’s Adams. “Here, it’s
Dressing or ‘connectorizing’ the cable—
The ubiquitous coaxial feeder cable provides
end-to-end wireless project development
buried deep beneath the ground—where
finishing the cable so it is fitted with a
the RF link on cellular base stations from
services, from site acquisition and base
the thermal conditions are comparatively
universal 7/16-inch DIN connector—is the
Moscow to Minneapolis. Bought by the
station design, through to installation,
stable—and routed in long straight runs
second area where Wilson sees problems.
metre, its ‘buy and install’ cost is negligible
commissioning and maintenance.
with few bends, so it thrives.”
These, he believes, are often caused by
on the total base station price scale. In
And it is at the maintenance end that
In the vastly different environs of the cellular
cable manufacturers. “There are some
many quarters, the feeder system is regarded
Wilson sees feeder costs really blow-out.
base station, things are quite different.
brands out there that have three different
merely as a network ‘consumable’. Some
“We often get called out to repair faults on
“When we get called out on a site repair
types of connectors and connector tools, to
believe that ‘a cable, is a cable, is a cable’.
non-CMS Wireless sites. The majority of the
where rigid smooth-wall cable has been
do three different cable models, all by the
“Wrong,” say the experts—the network
feeder cable problems we see here are as a
used, we always check for the kinks first,”
same manufacturer!” Wilson says. He
operators and planners, and the site
result of poor connectorization, problems
installation and maintenance crews. If
at bends, and cuts and crush faults in the
poorly selected and managed, the potential
cable run,” says Wilson. These manifest in
total life-cycle costs of a transmission line
poor signal strength, or intermodulation
system can be very high indeed.
problems.
RFS uses a slotted brass finger claw on the RAPIDFIT connector to maximize the contact with the outer—this provides around twice the electrical contact, and better long-term performance.
firmly believes this is a recipe for disaster— It’s about striking a balance, and remem-
and he’s witnessed the results. “We’ve
bering that the feeder systems are ultimate-
actually just repaired a site where the
ly destined to be installed by real installers
installer made the wrong connector fit
on real base station sites, not in labs!”
the cable. There was no signal strength
FEEDE R SYSTEMS
9
”We attach great importance to the
According to Wilson, it’s a frustrating and
reliability and quality of feeder cables, as
costly business for the operator. “The end-
they directly influence both the quality of
user is putting out maintenance money to
the services we provide our subscribers, and
repair what should’ve been done right in
the ongoing expansion costs of the system
the first place,” he says. The cost isn’t limited
corrugated cable, and rigid smooth-wall cable
Bend and crush
says Wilson. “We also check the ground
at all—it was completely open!” The
as a whole. It is for this reason we search
to that of raw maintenance; there are also
—plus a dizzying range of accompanying
Accommodating cable bends—sometimes
kits and connectors—cutting into the outer
well-known cable brand name matched
out a specific grade and quality of cable,“
the costs of base station down-time, and
connector systems and tools. There is also
up to six bends in a single run on a modern
conductor seems to be a common problem
that of the connector, but the models didn’t
says Valery Ulianov, Director of Regional
resultant subscriber churn.
wide diversity in installation crews’ skill levels
urban site—is an area where problems can
with smooth-wall installs. If it’s cut, then
match up.
Network
Technical
Wilson cites the limited nature of the feeder
and experience, plus a broad range of site
occur. Most problematic is the rigid
thermal
expansion
Worse yet, the wide variety of tools can be
Director of Moscow region with leading
system commissioning/testing regime as a
layouts, weather conditions and so on. This
smooth-wall feeder cable. Without the
eventually make an opening for water
expensive, bulky and difficult to use. As
Russian
something of a problem. The common
mix makes achieving repeatable long-term
corrugations of conventional cable, it
to get in.”
Wilson explains, it can be an uphill battle
Ulianov is involved in the operator’s massive
voltage
feeder performance a challenge.
exhibits minimum bend radii of up to two
Some ‘high-performance’ (reduced attenu-
ensuring you have just the right tool for
network expansion program that will see
‘sweep’ test simply doesn’t truly measure
“We were well aware of this real-world,
and a half times that of corrugated cable,
ation) cables can also pose site problems. In
each job.
Vimpelcom’s popular ‘BeeLine GSM’ service
the long-term quality of the install. “You
multi-variable situation when we developed
and bending moments as much as six times
the quest to minimize attenuation, some
RFS’s Adams agrees that cross-range and
further expanded in the so-called macro-
can tighten a connector down and make
our
high-performance
greater. “From an installer’s point of view,
manufacturers have used dielectric foams
backward compatibility of connectors, plus
regions of Russia.
the sweep pass today, but over time and
corrugated feeder cable,” says Chris
this is the hardest cable to install,” says
with densities so low that crush resistance is
simplicity of tooling is an essential in
temperature cycles a poor install will
Adams,
of
Wilson. “It’s hard to bend, and if you
severely compromised. “They’re looking at
getting it right at site. Equally important
Mounting costs
deteriorate,” he says. “You’ll start seeing
Transmission Lines with Radio Frequency
re-bend, it tends to kink. If you bend it
gaining a quarter of a dB, but losing crush
though, is ensuring the RF and electrical
Fast forward from base station planning
reflective power over time.”
Systems. “All too often, feeder cable
once and need to bend it back, it
strength in a big way,” Wilson says. “When
robustness of the connector design itself.
and roll-out, to where the feeder system
The challenge facing both operators and
technology groups focus too hard on
generally snaps.”
you take the cable out and put a hoisting
There are three basic designs for connectors
costs really mount up: during long-term
installation crews is dealing with the
achieving performance in one or two key
The ‘kinks’ that ultimately occur in rigid
grip on it, it puts indentations in the
—two of which rely on clamping down on
maintenance and repair. Aaron Wilson is
number of variables in the transmission line
areas—say
or
smooth-wall cable represent a great deal
cable 'cause it's so thin.” This, he says,
the outer of the cable, which is ultimately
Technical Maintenance Manager with CMS
‘equation’. These include a wide selection
connector VSWR. The end result is they
more than visual blights—they are weak
becomes an even greater problem on
problematic.
Wireless, an Arkansas USA-based wireless
of feeder technologies—such as corrugated
have something that might perform well in
points that crack or deteriorate over time,
collocation sites, where obstructions and
“Smooth-wall cable is an entirely glued
base station developer. His company provides
cable, low-attenuation ‘high-performance’
the laboratory, but is a disaster in the field.
and ultimately reduce signal strength.
bends are many.
assembly—inner conductor to dielectric to
Development cellular
and
operator,
Vimpelcom.
standing
wave
ratio
(VSWR)
CELLFLEX Global
‘A’
Product
attenuation,
Manager
flexibility,
contraction
and
Alberta SuperNet— b ro a d b a n d f o r t h e f u t u re
outer conductor to jacket. This means you can’t flare the outer to electrically clamp it from both sides, as you do with corrugated cable connectors,” Adams says. As a result,
The wireless component of the project is divided again into two elements, the ‘transport’ or backbone links, and the
From Alberta’s Rocky Mountains to its northern ice lakes, RFS microwave antenna solutions play an important role in realizing province-wide broadband connectivity.
the cable outer is clamped from the outside only, using a ‘slip ring’. “Over time, the outer starts to collapse under the slip ring and gives way. Installers tell us that you can
‘access’ links. The transport links provide high-capacity point-to-point microwave connectivity (20
to
over
120
longer
kilometres),
distances at
data
leave an installation nice and tight, then
In some parts of the world, rolling out
Ingenious concept
throughputs of either 45 or 155 Mbps. The
return to find the connector can almost
community-wide
network
SuperNet is ingenious in its concept and
access links are shorter microwave hops
spin on the cable. This leads to inconsistent
infrastructure is far from straightforward.
design. The network is made up of two
(10 to 40 kilometres), providing connectivity
behaviour, dropped calls, intermodulation
Alberta, Canada’s fourth largest province, is
elements—a ‘base area’ and an ‘extended
between the transport network and remote
and so on.”
a case-in-point. Half its three million people
area’ network. The base area network is
facilities.
The other basic design that applies pressure
live in just two cities, Edmonton and
optical fibre-based, and provides gigabit
The Canadian arm of global communications
Calgary. The balance is thinly distributed
connectivity to 27 larger communities. The
solutions provider, Alcatel, was appointed
across far-flung rural and semi-rural centres.
extended area network is made up of a mix
by Bell in the second half of 2003 to provide
The province is roughly the same size as
of optical fibre and microwave wireless
the RF equipment radios (antennas and
to the cable outer conductor, is one used with some corrugated cable connectors.
Aaron Wilson, Technical Maintenance Manager with Arkansas USA-based wireless base station developer, CMS Wireless.
While the outer is flared and clamped in the
broadband
conventional manner, a ring of ball-bearings
Leader with the German installation group
just what is installed at site and how. “Stick
France, and its terrain varies wildly from
technologies,
SuperNet’s
associated equipment) that make up the
within the connector head is used to
Hestra-Antennenmontage. “If the connectors
with what works,” advises CMS Wireless’s
mountains, to rolling hills and plains,
connectivity to 395 smaller communities
2,000-kilometre/60-hop transport network.
achieve extra electrical connection on the
are correctly installed and sealed, you have
Wilson. “To me, that’s corrugated cable.
through to marshy peat lands. As a result,
across the province. For many of these
Alcatel, in turn, selected Radio Frequency
ridge of one corrugation. “This design is
no problems. We have base stations that
My suggestion is to find a cable with just
providing cost-efficient broadband access
smaller locations, access to high-speed
Systems to provide all the necessary
flawed, as the bearing ring only grabs a
are almost a decade old, and none have
one type of connector and stick with it.
to
internet
microwave antennas, waveguide, and
small portion of the available conductor.
experienced water problems.”
Make sure you keep the crush strength up
challenging, to say the least.
most
of
Alberta’s
population
is
and
services
extends
is
an
entirely
new
experience.
associated installation hardware.
there, as well.” While feeder cable might be purchased as a
10
FEEDER SYSTEMS
MICROWAVE
site-consumable, its potential long-term cost implications are in the ‘major capital item’ league. Ulianov’s experience with Vimpelcom suggests this is very much the
Instead, RFS uses a slotted brass finger claw
Adams concurs with this view. “The glued
case, and is the core reason Vimpelcom
Hops in time
on the RAPIDFIT connector to maximize the
assembly of the rigid smooth-wall cable
opts for CELLFLEX ‘A’. ”The vastness of
The 60 microwave hops are located across
contact with the outer,” Adams says. “It
stops water moving from within its connector
Russia, coupled with the fast-paced and
the province within 44 wireless ‘service areas’
gives us around twice the electrical contact,
to the cable. But water in the connector in
all-embracing
services
(see map on page 13). Each hop is powered
and better long-term performance.”
a cellular installation is enough to totally
expansion program, forces us to work
by Alcatel’s MDR-8000 low to high-capacity
nature
of
our
disrupt transmission!,” he says. “Our view
under diverse economic and climatic
microwave digital radios. These are coupled
The water myth
is that the only place water belongs is outside
conditions,” Ulianov concludes. ”At the
with RFS’s high-performance single-polarized
Water ingress in the cable is another area of
the transmission line. Where it gets in is
same time, we insist on providing unique
DA series microwave antennas, using RFS’s
debate. The rigid smooth-wall camp claims
either via a cut in the cable outer, or via a
quality standards in all the services we offer.
low-loss FLEXWELL elliptical waveguide to
its cable’s glued construction prevents water
poor quality connector. Keeping water out
For this reason we take the choice of the right
form each radio-to-antenna link.
ingress, whereas flexible corrugated cable is
of the connector comes down to two
cable systems very seriously”. The bottom
“The reason we selected the RFS DA series
susceptible. Nonsense, say the users. “I
factors—simplicity of connectorizing and
line, it would seem, is that subscribers the
antennas was to ensure we got the best RF
have been using corrugated cable here in
quality three-point sealing, rather than
world over justifiably expect operators to
performance,” says Alcatel Canada’s Senior
North Germany for many years now, and
simple ‘crest-seal’ O-rings.”
get it right the first time. There are no
Account Director, Terry Pettigrew. The RFS
have never experienced water ingress
Minimizing feeder system total life-cycle
‘second
DA series, he says, provides premium
problems,” says Stefan Kraege, Project
costs, it would seem, starts and finishes with
needs to be chosen accordingly.
chances’—feeder
technology
front-to-back
performance,
and
the
In early 2001, the Government of Alberta
The complete network is being built by
precision radiation pattern envelope (RPE),
took
It
leading next-generation communications
sharp beamwidth and reduced side lobe
conceptualized a province-wide broadband
this
challenge
head-on.
company, Bell, and independently managed
radiation demanded by the Canadian
network—the Alberta SuperNet. Its core
by Axia SuperNet, a subsidiary of the
spectrum authority, Industry Canada.
goal was to ensure affordable high-speed
broadband networks project group Axia
A further, and equally important, reason
network connectivity to schools, libraries,
Netmedia. This ensures cost-controlled
was RFS’s ability to deliver a proven product
businesses and homes in 422 communities
access for all service providers, plus a
in accordance with a demanding delivery
across Alberta.
healthy and competitive ISP market from
schedule. “The timeline was certainly one
which subscribers can choose.
of the biggest challenges,” says RFS Area
11
use ‘quad diversity’—a combination of
scale before—for example, State-wide
both space and frequency diversity—on the
deployments in Florida and Philadelphia—
single hop.
the time lines were more spread out.”
“We use either space or frequency diversity
The first deliveries of RFS antenna systems
in other hops, but this is the only link on this
and Alcatel radios to Bell were in October
project where we’ve actually combined
2003, with the entire program completed
them together,” says Alcatel’s Director
by the end of the second quarter of 2004.
Wireless Communications Division, Marc
The antennas and radios are progressively
Vandeberg. To achieve the space diversity,
being delivered and installed at the
Vandeberg explains, the link uses a massive
120 sites by the project’s installation
pair of 15-foot diameter RFS DA antennas,
contractors, Radian and West Tower.
plus a pair of 12-foot diameter antennas,
Time was tight on this project due in part to
each mounted with around 60 metres of
Alberta’s unique seasonal and geographic
vertical separation. While the balance of
conditions. An example is the marshy peat
the SuperNet transport hops operate in
lands in the north-east of the province—
the 8-GHz band, the Fort Chipewyn-to-
sites in this area are only accessible by road
Birch Mountain link uses channels in the
during the winter months, via ice roads cut
lower 6-GHz band, to reduce the hop
through the snow. After the spring thaw,
attenuation. Two pairs of non-adjacent
the only option for moving equipment into
channels, separated by 177.9 MHz, are
these sites is via helicopter—a prohibitively
used to achieve the link’s frequency
costly option.
diversity.
Lake Athabasca
Fort Chipewyn Wood Buffalo National Park
British Columbia
service level agreement, Alcatel opted to
had completed microwave projects of this
Birch Mountain
J
Bitumount Fort Mackay
Edmonton
S IN TA UN O M
Banff National Park
Long-distance link
Trials and success
One particular ice road-accessed hop also
Jointly designed by Alcatel, the project’s
The balance of
proved to be the project’s most technically
lead contractor, Morrison & Hershfield, and
the 60 transport
demanding—the hop linking the remote
design group Planetworks, the link was
hops are expected
centres of Fort Chipewyn and Birch
simulated and trialled in early April 2004 at
to
Mountain, in the province’s far north-east.
Alcatel’s two US facilities (Longview and
commissioned before the end
Located in the project’s wireless service area
Plano). The radios were connected to long
of September 2004, marking a
‘J’, the 120-kilometre microwave hop runs
lengths of microwave waveguide to model
significant milestone in the development of
over boggy marsh lands and alongside the
the space diversity in the 120-kilometre
SuperNet. “Once we got things rolling and a
vast Wood Buffalo National Park, home to
hop. Fixed and variable paths were used
process established, it all went incredibly
2,200 rare wood buffalo. “We had to get
to simulate fading activity, plus test
smoothly,” says Pettigrew. “Of all Bell’s
the antennas and radios in no later than the
equipment to simulate dispersive fade
suppliers, I know they are very pleased with
second week of March,” recalls Pettigrew.
characteristics.
RFS and Alcatel and the work we have done.”
“I think we had one of the last trucks on the
Once the link was proven in the factory, the
The responsiveness of the RFS/Alcatel team,
ice road to get in and out of there!”
Alcatel radios were air-freighted from
coupled with the tried and proven nature of
is
Edmonton, Alberta, to the remote Fort
the RFS DA series microwave antenna and
understood to be one of the longest
Chipewyn and Birch Mountain sites, where
the Alcatel MDR-8000 radio, have played
‘Optical Carrier Level 3’ (OC3) microwave
they joined the already-installed 15-foot
links in the world—presented a great
and 12-foot diameter RFS DA antennas.
challenge to the link’s designers. This was
be
installed
Calgary
an Saskatchew
MICROWAVE
Legend Wireless service area Wireless service area J National park area 0
100 km
13
200 km
and
A m i c ro w a v e solution for Alberta
standards such as ETSI, FCC, Industry
an important part in the success and
The RFS DA antenna series is a high-
provides superior flexibility and installation
efficiency of the transport network rollout.
performance solid-body antenna family,
efficiency,
On the first weekend in July 2004, the Bell
“There was no experimentation, beta-version
providing reduced side lobe suppression for
conventional, rigid rectangular waveguide.
exacerbated by the ponds and marshes
installation
crews
radio software or unproven RF systems,”
more exacting applications. Available in 4,
Available in a wide selection of frequency
scattered along the link, which represented
finally proved the design was correct—one
says Zoberi. “What we offered in the DA
6, 8, 10, 12 and 15-foot diameters, the
bands from 2 to 40 GHz, FLEXWELL
reflection and multipath sources. As the
of the world’s longest OC3 microwave
antenna was world class, proven technology
DA single-polarized antenna series features
provides both low loss and low VSWR
Government of Alberta specifies ‘five
links was up and running, and ‘Fort Chip’
—nothing less. It was the optimal choice
RPE that meets applicable international
performance.
nines’ reliability (99.999 per cent) in its
was on the air!
for the SuperNet.”
The
The 15-foot and 12-foot diameter RFS DA antennas mounted with around 60 metres of vertical separation at Fort Chipewyn.
Lake Mamawi
Alberta
Y CK RO
12
Product Manager, Asad Zoberi. “While we
long
hop
distance—the
link
and
commissioning
Canada and so on. The antennas also feature low VSWR performance and high front-to-back ratios, and are designed for the harshest of environments, with a survival wind speed of 200 km/h. RFS FLEXWELL elliptical waveguide when
compared
with
M i c ro w a v e a n t e n n a o p t i o n s f o r m i n i m i z i n g i n t e r f e re n c e With microwave network density on the rise, the potential for signal interference is also increasing. Dr Daniel Wojtkowiak, Vice President of Microwave Antenna Systems RFS, looks at ways of minimizing interference-causing distortion of radio frequency signals.
the antenna gain also reduced. Greater
Figure 2 is valid for the ‘ideal’ case, where
dependent on the wavelength (and hence
radio power would then be required to
wave fronts hit the wall perpendicularly.
frequency) to be used in the application.
achieve the desired radiation power, resulting
Now consider the situation for signals
Assuming a dielectric constant between 2.5
in a corresponding increase of side lobe
not having this ideal orientation. Given
Optimizing the radome
and 3, typical solid radome thicknesses for
radiations. This illustrates the fact that
the longer effective wave path through
Radomes are used for two main applications
different frequencies would be: 6 mm (14 GHz),
correct radome design is critical not only
the radome material as they hit the
in radio link antenna design. The first is to
4 mm (22 GHz), and 2.4 mm (38 GHz).
for optimizing link budget, but also for
wall obliquely, the optimum thickness
cover the antenna feed system in order to
It is important to note that if a radome of
interference control, since an increase in
is now also dependent on the angle of
protect it from the dirt, snow and ice of our
incorrect thickness is used, the transmitted
side lobe radiations would raise the potential
incidence (θ), measured as the deviation
power will be reduced, and consequently
for interference.
from the normal.
Over the past decade microwave links
potential for these to interact with one
natural environment. In addition, a radome
have proven a popular solution for the
another and cause interference. Since any
significantly reduces the windload of an
In practice, however, angles of incidence of
telecommunications industry. The relative
distortion of the signal reduces the quality
antenna system, by preventing the dish and
up to 20 degrees have negligible effect on
ease and economy of installation has seen
of service, controlling interference is now
shield from ‘catching’ wind. However, both
the optimum radome thickness. This is
them deployed in an increasing number
the mandate of any radio network operator
radome material selection and thickness need
of point-to-point and point-to-multipoint
and national authority. A good starting
to be carefully considered to optimize the
applications—from communications back-
point for consideration is the design and
power transmitted through the radome,
bones, to branch links and distribution
location of the source of the signal—the
while at the same time ensuring the side
networks, not to mention applications in
microwave antenna (Figure 1).
lobes are not increased to detrimental effect.
the broadcast industry and private enterprise.
Figure 1 shows the main beam at 0 degrees,
Figure 2 shows a plot of the reflection
With the rise of new cellular operators
plus side lobes that are significant to
characteristics at a plane wall radome for
and new technologies, overall microwave
about ±90 degrees from the main beam.
different materials. Each of these materials
network density is undeniably escalating.
It is these side lobes that can cause
are characterized by a relative dielectric
TECHNOLOGY FOCUS
Amplitude reflection coefficient [R] Amplitude reflection coefficient [R]
illustrated for flexible radome materials in Figure 3, which shows the relationship between angle of incidence (θ) and d/λο (where λο is the free space wavelength), for achieving 95 per cent power transmission through materials with different dielectric constants. For values of θ up to 20 degrees, the optimum thickness is barely impacted—particularly for low loss materials,
15
Yet this intensification of microwave
interference with adjacent point-to-point
constant of εr = 2; however each material
which should be those considered for
communications brings added challenge.
links, and it is these side lobes that must be
has a different loss parameter, tan δ, where
radome design purposes.
The greater the number of point-to-point
minimized through careful antenna design
tan δ ranges from 0.0018 (low loss) to
links in a given area, the greater the
and installation.
18 (high loss). Figure 2 shows that for low
A similar relationship holds for solid Figure 2—Reflection characteristics at a plane wall radome
minimum values of the reflection coefficient,
microwave antenna designers. A small
transmission of incident power. These correspond to design values where the ratio of radome wall thickness (d) to microwave wavelength in the sheet (λ) is close to either zero or 0.5. The first case of d/λ ≈ 0 is practically realized as d