A Perspective on Wireless Standards and Their Applications

A Perspective on Wireless Standards and Their Applications
BICSI news
advancing information transport systems
May/June 2006
president’s message
bicsi update
bicsi update
course schedule
course schedule
standards report
Volume 28,
27, Number 35
Using the New ANSI/TIA/EIA-606-A Label Standard as a Way to Compete
Determining the Appropriate Separation of Data and Power Cables SS 20
So Many Wireless Standards to Choose From SS 26
Connectivity: Wiring Trends in Optical Data Centers SS 35
So Many Wireless
Standards to Choose From
A perspective on wireless standards and their applications.
By joe bardwell
You have probably heard the comment, “The nice
thing about standards is that there are so many
to choose from.” In the wireless data network
marketplace this is an applicable statement.
In the Wi-Fi world, the IEEE 802.11a/b/g standards
are entrenched and IEEE 802.11n is emerging. In
the cellular world, enhanced data Global System for
Mobile Communications environment (EDGE), code
division multiple access (CDMA), universal mobile
telecommunications service (UMTS), and high speed
packet data access (HSPDA) are potential “1000 pound
gorillas” for high speed mobile connectivity. Soon the
IEEE 802.22 ultrahigh frequency (UHF) standards may
offer single transmitter solutions for coverage zones up to
64 km (40 mi) and, don’t forget IEEE 802.16 worldwide
interoperability for microwave access (WiMAX).
Within information transport systems (ITS), the
structured cabling marketplace has fully entered a new
era. With it, two dramatic changes are confronting
those of us who make a living creating today’s complex
communications infrastructure.
The first challenge is that essentially every customer
who is installing cable for a wired data network is also
cabling to support Wi-Fi access. While wall jack locations
for wired Ethernet and telephone can be specified based
on furniture and floorplan layouts, Wi-Fi access point (AP)
locations can only be determined after a radio frequency
(RF) engineer has performed a site survey. This means that
you face a workflow challenge when pulling cable. You
want to pull cable once but you’re faced with two different
sets of specifications for cable drop locations.
The second challenge is that the evolution of
wireless data networking offers an alternative to wiring
at some office, hospitality and government sites. As
wireless technology continues to grow in capability
and acceptance, the shift from a wired to a wireless
infrastructure will continue to grow. If you are pulling a
lot of cable today you are going to be pulling less cable
26 | advancing information transport systems | www.bicsi.org
in the years to come. Now is the time to watch, learn and
plan for what will be a reasonably certain future.
Within a five-year time frame you want to be
positioned to deal with the wireless infrastructure with
the same level of expertise that you deal with the wired
infrastructure today. It is probable that you are going
to expand your staff to include RF engineering and site
survey design resources. Today you may expand your
capabilities by partnering with a third-party RF design and
survey contracting company either to provide capabilities
you may not have in-house or to augment your current
staff. In both cases, the challenge is to identify the
evolving needs of your end-users, get the resources to
meet those needs, and develop an active plan to meet
those needs.
This year marks a significant point of demarcation in
the wireless network marketplace. Many technologies that
were uncertain “futures” in the past few years have now
become part numbers in manufacturer’s and distributor’s
catalogs. It may be cliché, but it’s true, “the future is now.”
A case in point is the Apple iPhone™. Over 500,000
units were sold immediately after it was released. What is
significant is that a Wi-Fi and cellular multimode device,
with audio, video, voice, and data transfer capabilities, has
now made an impact into the marketplace. Convergence
between voice, video and data is becoming an assumed,
necessary aspect of daily life. Today (in some markets), you
can buy a cell phone with monthly converged Wi-Fi and
cellular service. When you walk into a hotspot the phone
finds its way through the Internet, back to the provider,
and roams off the more expensive cellular network onto
the voice over Internet protocol (VoIP) Internet. No
local VoIP gateway is required at the hotspot. In most
cases, testing has confirmed that this technology does
find its way through proxy servers and firewalls without
requiring special configuration. Access to a converged
communications infrastructure is becoming an assumed,
necessary part of daily life.
Recall when touch-tone telephones arrived in the
marketplace. Today, caller-ID, callback and other phone
services are the status quo. Many of us remember the days
of the “brick” mobile phone and car phone. Today it is
surprising when someone does not have a cell phone and,
in the business world, a Blackberry or other wireless PDA.
In the future we will look back to the days (today) when
localized hotspots limited the places where high-speed
wireless data was publicly available. In the workplace, the
complexity of computer and voice system portability will
be a thing of the past.
You need to have a solid perspective on wireless
technology today and that perspective has to grow into a
strong proficiency in the coming years. This discussion
lays out some of the wireless standards that you are
going to encounter. Let’s approach this from the
standpoint of end-user application requirements and
see the degree to which various standards, current and
emerging, meet the needs.
One way to categorize the various wireless
communication standards is to compare and contrast
the coverage range typically expected from a single base
station transmitter. Diagram 1 shows how different
standards provide service in the personal area network
(PAN) range, through the local area network (LAN),
wide area network (WAN), metropolitan area network
(MAN), wide area network (WAN), and the global
connectivity network.
The Mobile User
Anyone in cars, subways, work trucks, trains and airports
need to stay in touch with their office and with coworkers, exchange documents, work orders, or other data,
access databases to look up client information, equipment
specifications, and other information. This may, or may
not, involve the Internet and the World Wide Web.
Consider package delivery companies, public service and
law enforcement, and other groups that have internal
requirements that probably do not demand the Internet.
The first thing that must be considered is the geographic
range spanned by the end-user community. An electrical
contractor, limousine service or local delivery service may
only require connectivity with a 50-mile radius of the
office. Today, analog radio communications are common
in this environment.
In the emerging market there are some interesting
alternatives. 3G cellular has the advantage of wide
geographic scope with the downside of monthly
subscription costs. You will see data rates growing from
768 kb/s up to the 2 Mb/s range. Standards such as CDMA,
EDGE, HSPDA, MediaFlo, and UMTS are part of the
cellular space, providing data and voice communications
with options for video.
A company could purchase a WiMAX (IEEE 802.16e)
base station and mount an antenna on their central
building. While today’s WiMAX offerings are hard pressed
to cover a five mile radius, the future has the potential for
Diagram 1: As range increases (from left to right in the diagram) the power must increase, the receiver’s sensitivity must increase, or the bit-rate must decrease.
100 ft
<1 Mbps
3G Cellular
Wireless USB
Nomadic WiMax
1,000 ft
100 Mbps
28 | advancing information transport systems | www.bicsi.org
Regional Area
10,000 ft
1 Gbps
100,000 ft
155 Mbps
1.367 x 1015 ft
<10 Mbps (500 Kbps today)
wider coverage range. The advantage to WiMAX is that
you own the system (one-time up-front cost) with the
downside that the geographic scope is limited. Again, you
get voice, data and video services using a laptop computer.
There are no mobile WiMAX handsets in common use
but the year 2009 may see that start to change. Several
cellular carriers (including Sprint and AT&T) are starting to
roll out WiMAX metro-area services in limited markets. In
Australia, WiMAX is already in larger cities. WiMAX data
rates are higher than 3G cellular but the range is smaller.
The IEEE 802.11 Wi-Fi standards (IEEE 802.11b, g, a, and
n) are unsuitable for central-radio service outdoors. A
mobile Wi-Fi user must be relatively close to an AP radio to
get high-speed service. We are talking under 305 m (1000
ft). Add a little noise and interference in an outdoor Wi-Fi
environment, and put in a requirement for VoIP or video
and the range starts to drop below 122 m (400 ft) in some
cases. This means that a large number of specialized WiFi radios must be deployed over a metro area, truck yard
or warehouse facility, corporate or educational campus,
Indoor installations typically use
power-over-Ethernet (PoE) to
power wall- or ceiling-mounted
APs. Concern for aesthetics and
tamper-prevention indoors is
much more significant than when
installing outdoor equipment.
Outdoor equipment often
requires a 120 Volt alternate
current power source and
working with Type-N connectors
and LMR-type cable is a skill
set similar to, but not exactly
like terminating ANSI/TIA/EIA568-B Ethernet (e.g., you’ll
need a Type-N crimping tool and
coaxial cable stripper). The use
of 38 mm (1-1/2 in] galvanized
steel pipe for antenna masts
up to 3 m (10 ft) in length is
appropriate with 1.2 m (4 ft)
being held securely at the base
(with Unistrut or Y-brackets on
the building exterior) and 1.83 m
(6 ft) above the top attachment
point. The rule-of-thumb is “1
down, 2 up” meaning that 1/3
of the mast length is attached
to the building and 2/3 are
30 | advancing information transport systems | www.bicsi.org
coverage it is not unexpected to find that some offices,
or other outdoor area to provide consistent, high-speed
outdoor coverage. The terms mesh router and wireless
conference rooms, or other places indoors lack suitable
distribution system (WDS) refer to integrated systems of
coverage. The cell tower on the hillside may not be able
Wi-Fi APs used to provide outdoor Wi-Fi coverage. The
to light up the entire indoor campus area.
WiMAX may be a good solution from the standpoint
radio technology is similar in these devices but the mesh
router has more features and capabilities while WDS
of data rate and range; however, the availability of
systems generally require manual configuration and lack
notebook computer WiMAX is very limited today. Intel
many of the redundancy features in a wireless mesh. On
has been talking about their commitment to mobile
the flip-side, a mesh router may carry a $3000 to $5000
WiMAX for a number of years but we have yet to see
price tag while a WDS radio may be less SCT_Half_PageAdIsland.qxp
than $2000 (and,
HP, Dell, IBM,
Fujitsu, or any other notebook computer
12/4/06 3:32 PM Page 1
sometimes, less than $1000).
The Wi-Fi mesh or WDS
provides throughput in the range
of 20 Mb/s to 30 Mb/s (using 54
Mb/s IEEE 802.11g or 802.11a
modulation) and up to 60 Mb/s
or more using IEEE 802.11n.
These data rates fall off quickly
beyond 500 ft from the Wi-FiAP.
The new standard on the
horizon (5+ years or more in
the future) is called IEEE 802.22.
This standard speaks to the
transmission of high-speed
data in the ultrahigh frequency
(UHF) television frequencies
that will be de-allocated by the
FCC as part of the move to HD,
digital television. IEEE 802.22
may provide central-radio
data connectivity with range
similar to over-the-air broadcast
television (e.g., 64 km [40 mi]
New Megger SCT2000
or more).
It’s already known
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There are two key
distinguishing factors for the
campus user. First, mobility is
limited to a small area, perhaps
less than a 1.6 km (l mi)
radius from a central location.
Secondly, throughput and quality
requirements are generally much
more demanding than those of
a fully mobile user. In addition,
the campus user will be moving
in and out of buildings, and will
probably have an office in one of
the buildings.
In this case there is an
inherent downside to 3G cellular
service. Unless a local repeater
is installed to assure in-building
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manufacturer bring an internal WiMAX radio to the mass
market to match the way Centrino® wireless has become a
de facto standard.
The same is generally true for IEEE 802.11a. All
notebook computers have the option for an internal IEEE
802.11b/g radio, and IEEE 802.11n is close on its heels.
Not everyone offers an internal IEEE 802.11a radio. The
advantage of IEEE 802.11a is, primarily, the fact that
fewer people use it. Hence, there is less interference from nearby IEEE
802.11 transmitters. There are some technical advantages
to the 5.8 gigahertz (GHz) frequency band used by IEEE
802.11a but, at the end of the day, the technology is
effectively the same as IEEE 802.11g in the 2.4 GHz band.
In both cases you get a 54 Mb/s “modulation rate” with
roughly 30 Mb/s of maximum TCP/IP data throughput. In
both cases you can often “bond” two adjacent channels
to get double the throughput (using vendor-specific,
proprietary methods).
To summarize, WiMAX is rare or non-existent in the
notebook computer space, IEEE 802.11a networks have
much less interference than IEEE 802.11b/g but not all
notebooks support IEEE 802.11a, and IEEE 802.11n is still
a draft standard.
It is common to see a campus network covered with
a Wi-Fi network utilizing a centralized wireless LAN
(WLAN) switch system. APs in a WLAN switch system
are referred to as “lightweight.” This is because some or
all of the management and control functionality that
is associated with a Wi-Fi AP is removed from the radio
unit and relocated in a central hardware device to which
the APs are attached. The advantage of the WLAN switch
system is that the central controller is aware of the overall
configuration of the system and the location of the users.
Power levels, channel configuration, and load balancing
between APs is controlled by the central switch.
There are some similarities between WLAN switch systems
and mesh router systems. In both cases, the radios are
aware of each other’s presence and power levels, channels,
and load balancing is available. The difference lies in the
awareness of individual client devices. Mesh routers are
essentially aware only of each other, not as much of the
behavior of the client devices.
A mesh router is responsible for determining a best
path back through the mesh architecture to get to a
point of Ethernet egress. The paths are through wireless
links and most mesh routers are not connected to an
Ethernet network; they talk to each other to get back to
the point where an Ethernet (and, hence, the Internet or
the corporate server) is accessible. In the WLAN switch
system all the APs are already connected to an Ethernet/IP
infrastructure. They receive wireless traffic from wireless
clients and send that traffic back to the WLAN switch. It’s
the WLAN switch that becomes the actual point of origin
32 | advancing information transport systems | www.bicsi.org
for the traffic back onto the wired network for delivery to
the ultimate wired destination.
Mesh routers are intended for deployment when
wiring is not an option (e.g., between light poles) WLAN
switch systems are connected to an existing Ethernet
network—then the system self-organizes to create a
homogenous Wi-Fi network. It is centrally managed
and controlled and provides a level of security and
functionality that goes far beyond simply deploying a
large number of standard (“fat”) APs.
It is generally recognized that any enterprise-class WiFi network with more than a handful of APs is best served
by a WLAN switch system. Hospitals, hotels, warehouses
and other large-scale deployments are all based on one
or another vendor’s WLAN switch system. If you are
considering a Wi-Fi system for more than 5575 m2 (60,000
ft2) you will want to strongly consider the advantages of a
WLAN switch system.
All the WLAN switch systems have options for
combined IEEE 802.11b/g and IEEE 802.11a integration in
a single, homogenous network. Most vendors have IEEE
802.11n on their near-term roadmap. WiMAX and 3G
cellular are completely different technologies relative to
WLAN switches and they aren’t part of the WLAN switch
The key integration challenges in a campus network
relate to subnet roaming. When a user connects to the
network in Building #1 and then walks across to Building
#2 they are physically in a location served by a different
IP subnet. The APs in Building #2 are connected to a
different side of a router than those in Building #1.
Something has to be implemented to allow the client’s IP
address to work properly in both buildings.
There are two basic approaches to solving this
problem—virtual LAN (VLAN) tunneling and mobile
IP. While different vendors have different specific ways
of implementing subnet roaming the basics of the two
methods can be described in general terms.
VLAN tunneling involves configuring a virtual
connection between the AP and the WLAN switch
through the use of packet-level “tags” on the data
packets related to theAP. The tags define a virtual
“tunnel” that conceptually acts like a separate network
within the network. In this case, the VLAN existing as a
completely separate network, is
a single IP subnet that extends through the switches
and routers in the network, transcending the actual IP
routed infrastructure of the actual physical network.
The user obtains an IP address that’s consistent with
the VLAN and the VLAN extends throughout the entire
corporate campus.
Mobile IP is a technology that is defined by various
Internet request for comments (RFCs) and has been a
standard in the wired world for many years. A router that
supports mobile IP has special software running in it that
listens for an attempt on the part of a mobile client device
to contact the “home” router (the router in the other
building.) The mobile IP software (called foreign agent
software) pretends to be the router in the “other” building
and the client believes it’s still on the original subnet. The
foreign agent software then sends the data packet back to
the original, home router where the data is placed on the
home network for delivery to the final destination.
In one case, the routers must support VLAN
tunneling—in the other case,
the routers must support mobile
IP. Some WLAN switch vendors
offer clever, vendor-proprietary
solutions to pass traffic back from
remote APs to the WLAN switch
with a minimum of router and
switch reconfiguration.
What should be evident
in this discussion is that there
are complexities in the campus
environment that are minimized
in the metro-area environment.
By the same token, there are
challenges in the metro-area
mobile environment that are not
present on the campus.
While medical data rate requirements are typically low,
there is often the requirement for wireless VoIP in the
hospital. This demands slightly higher data rates but,
more importantly, it requires absolutely high-quality
connections with a minimum of “jitter” (variance in the
rate of delivery of data packets). Even a small amount
of environmental noise or interference can dramatically
introduce jitter to a wireless network which, while it won’t
negatively impact data transfer, will wreak havoc on a
VoIP system.
The In-Building User
Corporate enterprises have
users that meet in conference
rooms, roam to different parts of
the building or different building
floors, and generally demand
high-speed data transfer over
the wireless network They’re
comparing the 1 Mb/s to 30 Mb/s
Wi-Fi data throughput rates to
the 100 Mb/s wired Ethernet
data rates. (Remember that data
throughput for IEEE 802.11b/g
and 802.11a is generally half the
“modulation rate” of 11 Mb/s or
54 Mb/s or less.)
Nurses and doctors in a
hospital using computer on
wheels patient monitoring
and management mobile carts
have very low data throughput
requirements. They are looking
up patient medical information
and uploading blood pressure,
temperature, and other datarelated information to a server.
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BICSINEWS | September/October 2007 | 33
A computer-on-wheels medical cart used in hospital
In the hospitality sector, hotel guests are typically
provided with minimum bit-rate service at the edges of
coverage areas. One strong challenge in hospitality relates
to capacity planning. Today’s guest may be satisfied with a
1 Mb/s connection (512 kb/s throughput) to check email
and lookup an address on an Internet map. In the near
future, , that same guest will expect VoIP roaming for their
cellular handset, iPhone, or other wireless PDA. They will
expect support for streaming video so they can watch
their favorite movie. The hospitality sector is probably
trailing when it comes to the future evolution of wireless
networking. They have created networks that offer a
minimal level of service and they are entering an era when
users will demand high levels of service and capacity.
We could detail warehouse and manufacturing
networks, wireless video security systems, multi-tenant
dwellings, school classroom buildings and more. At the
end of the day, the bottom line always comes back to the
bandwidth, jitter and coverage quality requirements of the
end-user community.
Developing an In-Building System Design
You will be able to obtain specific engineering
requirements from manufacturers of wireless VoIP
equipment, wireless video cameras, or simply
requirements regarding data throughput and the number
of simultaneous users that will be active on the wireless
network. From this you develop your set of performance
metrics. Some representative of the kind of metrics you
might develop include general office workers that load
and save documents, spreadsheets, and other files that
do not use wireless VoIP. The wireless network is used in
addition to a wired Ethernet to every desktop.
In this case you can assume a 10:1 oversubscription rate
(meaning that only 1 in every 10 users will be active at
any given moment). If each user is given 2 Mb/s of data
throughput that implies that they’ll need at least 5.5
Mb/s IEEE 802.11b modulation (or 6 Mb/s IEEE 802.1g).
This implies that RF power levels of at least -80 dBm to
-85 dBm will probably be required (depending on which
vendor’s equipment is selected for the project.) A single
AP can support roughly 20 simultaneous low-bit-rate users
so, with the oversubscription rate, up to 200 users could
be served with oneAP. In reality, one AP may provide
coverage out to roughly a 24 m (80 ft) radius (at 5.5 Mb/
s) indoors. A 24 m (80 ft) radius is roughly a 1860 m2
(20,000 ft2) area. This would give a 200 user community a
3 m x 3 m (10 ft X 10 ft) workspace for each person. This
scenario is realistic.
If these same general office workers are going to use
wireless VoIP then signal coverage must be provided
34 | advancing information transport systems | www.bicsi.org
at roughly -65 dBm to -70 dBm for most vendor’s
VoIP handsets. The coverage radius probably drops to
something approaching 15 m (50 ft), which shrinks the
coverage zone to roughly 740 m2 (8000 ft2). The result is
that four times more APs will be required to support VoIP
compared to support for data only. Moreover, a single AP
may only support between four and ten simultaneous
VoIP calls (with some vendors making more generous
claims). In this case, it may be the user density, rather
than the RF signal strength, that becomes the limiting
factor. If users occupy 9.3 m2 (100 ft2)each (e.g., cubicles,
offices, and hallway circulation space), and if you are
using an AP that supports ten VoIP calls, then you’ll need
an access point for every 93 m2 (1000 ft2).
Assume the network requires support for streaming
video. This may be from security cameras, users accessing
YouTube.com or other on-line video sites, or because the
corporate training department makes instructional videos
available on the company’s intranet. A video stream may
require a 1 Mb/s throughput. It turns out that the signal
power levels required for wireless VoIP are greater than
those required for streaming video so the VoIP design
becomes the controlling factor.
Wireless VoIP requires high power levels (-65
dBm) to overcome noise and interference that would
cause jitter and degrade call quality. Recall that jitter
is the characteristic when data packets carrying voice
conversations arrive at differing times and with
different delays between them. VoIP is not particularly
data intensive. Wireless, non-real-time video typically
tolerates jitter because the video stream is buffered on
the receiving end to smooth out variances in receive
times. At -65 dBm (for the VoIP) a device will be
operating at 54 Mb/s modulation for IEEE 802.11g or
802.11a. This provides up to 30 Mb/s of throughput in
the air. Hence, the 10 users connected to the AP share 30
Mb/s and, even if they transfer data simultaneously, they
each have 3 Mb/s of actual TCP/IP throughput.
There are some specific variables that relate to each
other. In any design and implementation you develop
specifications based on user community requirements,
manufacturer’s equipment specifications, and the
results of an on-site RF survey or virtual RF survey
using 3-dimensional RF CAD modeling and simulation
software. The RF survey tells you how and where the
signal will penetrate through the building, and what the
signal power levels will be in each area. The vendor’s
specifications tell you how the equipment will perform
in the presence of each level of RF power. The user
requirements tell you how much equipment will be
necessary, and what wireless standards should be used, to
provide sufficient bandwidth capacity, jitter limitations,
and simultaneous access support. Then you pull the cable
to the AP locations, hook everything up, and turn it on.
A Contemporary “Gotcha”
The disturbing aspect of these considerations is
that often the requirements are based on current usage
scenarios without due consideration for what’s coming
on the horizon. You must consider the requirements that
will be applied over the expected lifetime of the network.
If a company installs a wireless system today they’re not
going to want to rip it out in three years and replace it
with something faster and better. That’s not to say that
something faster and better won’t be available in three
years. It’s to say that the network is going to have to
support reasonable user’s requirements over a period of
time that is acceptable to the finance department.
Today, Windows Vista is on everyone’s mind.
Microsoft has positioned Vista as the next great thing
in the PC world. Buying a new PC without Vista verges
on being difficult. Does that mean that every corporate
network is planning to throw out all the old PC hardware
than can’t support Vista and upgrade all the XP and
Windows 2000 machines? Absolutely not. Windows XP is
going to be around for quite some time. There are
even some machines out there, still doing their
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originally intended jobs, running Windows 98! Wireless
network technology has a similar story to tell. IEEE
802.11g has been around for several years and all new
wireless notebooks come with IEEE 802.11b/g radios.
The security flaws with WEP (wired equivalent privacy)
have been well-addressed by WPA (Wi-Fi protected access)
and AES (Advanced Encryption Standard) Nonetheless, handheld inventory scanners that support
only IEEE 802.11b with WEP-only encryption remain in
service in the retail space and promise to delivery many
more years of reliable use.
The Local User
In this category are standards related to the wireless
replacement for printer, keyboard, and mouse cables.
It’s here that wireless technologies like Bluetooth (IEEE
802.14) connect headsets to cell phones, printers to
desktop or notebook computers, and support wireless
keyboards and mice. Ultra wideband (UWB) is an
emerging standard in the local connectivity space.
The Big-Picture Summary
There are many wireless standards from which to
choose, but the laws of physics shape each technology
standard to be more appropriately suited to a particular
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BICSINEWS | September/October 2007 | 35
application. Remember the trade-offs:
To get longer range—You need more power, a more sensitive receiver, or you must reduce the bit-rate
To get higher throughput—You’ll get less range unless you either increase power or receiver sensitivity
And (very important!) remember that the weaker
transmitter or receiver becomes the limiting factor. A
whiz-bang, high-power transmitter on a pole won’t help
a weak notebook computer radio get its signal back to
that pole. Range and throughput are always limited by
the less capable side of the communications link.
Today, and at least through Q1 2008, IEEE 802.11b/
g, 802.11a, and 3G cellular data solutions are solid
potential solutions for wireless data. WiMAX is currently
being deployed for point-to-point links at distances
greater than 1.6 km(1 mi) and mobile WiMAX is starting
to enter the marketplace. Look for more mobile WiMAX
in 2009. There is a generally consistent relationship
between data rates and range. When you go further
you go slower. Hence, the maximum required data rate
for a network will eliminate some standards from the
list of possible selections for deployment because some
standards won’t provide the required bit rates.
3G cellular has a monthly subscription rate
associated with it from AT&T, Sprint, Verizon Wireless, or
whichever cellular carrier is used. Often, data access adds
additional fees to the monthly bill. New cell phone plans
(and hardware) that allow the phone to roam off the 3G
network and onto an in-building Wi-Fi network mitigate
the monthly costs but demand proper design support
from the in-building network.
Ultimately, the standards you choose will have
to provide data rates, user density support, and jitter
limitations that meet the specifications for the vendor’s
equipment that you’re deploying.
The option and combinations are not infinite,
although sometimes they seem to be. Remember that
there are a handful of variables that must be nailed down
as part of a system design and implementation. The user
community, the vendor’s equipment specifications, and
the RF survey give you the values of the variables. The
communication standards provide support for various
levels of service. Put it all together, make the appropriate
trade-offs, and you’ve got a successful RF system. n
Joe Bardwell
Joe Bardwell is chief scientist with Connect802
Corporation, a systems integrator and wireless
network design consulting firm based in California.
Joe can be reached at +1 925.552.0802 or at
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