This document discusses the benefits of planning for wireless LAN (WLAN) requirements when installing or upgrading a structured cabling plant. It is more cost effective to install all cabling, including for WLAN access points, during initial construction before walls and ceilings are completed. Automated site planning tools allow network designers to determine optimal access point locations and cabling needs before a building is constructed. The document provides guidance on key considerations for the WLAN design such as coverage needs, 802.11 standards, access point placement, and ensuring sufficient switch ports.

1. Introduction
When installing or upgrading a structured cabling plant, IT departments can demonstrate
significant time and money savings by determining their wireless LAN (WLAN) requirements
and folding them into the project right from the start. The reason is that while WLANs
Smart Planning for New provide over-the-air communication in the access network in areas where mobility and
Network Infrastructures portability are needed, they also create new cabling requirements at the back end, often
in hard-to-reach places. It’s far less expensive and labor intensive to do all cabling at once,
When you have the luxury to cable a
building from scratch, it pays to include
without ceilings, walls and other obstructions in the way, than to install WLAN cabling
wireless networks in your upfront plan later as a separate project.
and budget.
The most common way of deploying WLAN access points (APs) is to mount them in ceilings and
cable them directly to an Ethernet switch port. Generally, a 15- to 20-foot piece of cable called a
By Ahmet Tuncay,
Chief Technology Officer and
service loop is left in the ceiling (Figure 1) in case an AP later needs to be moved slightly to tune
Vice President, Trapeze Networks
coverage or avoid interference from other RF devices, such as wireless phones and microwave
and Paul Kish, Director of ovens. Planning for those cable runs upfront, in addition to your other network cabling needs, is
Systems and Standards, Belden financially and operationally prudent, allowing your organization to purchase all the necessary
materials and labor in bulk with a corresponding volume discount.
If you consider only your wired network as you plan for your new infrastructure, you’ll likely
have to pull additional cabling for your wireless equipment as a separate project. You might
also have to change out some switches and power injectors. That situation can be painful
on a number of fronts.
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Where to Install Wireless Cable
After-the fact Costs . . . . . . . . . . . . . . . . . . . . . 2
Other Floors
How to Plan for WiFi . . . . . . . . . . . . . . . . . . . . 2
Telecommunications Room First Floor
Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 4
Cable and Power Types . . . . . . . . . . . . . . . . . . 6 PoE
Service
Ethernet
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Loop
Switch
Telecommunications
Room
Equipment
Room or Application Servers
Data Center Data Video Voice
Riser Public Switched
Cable Telephone Network
Main Cross-
connect Internet
Ethernet Router/
Switch Firewall
Figure 1 . Additional cabling from telecommunications room switches to Wi-Fi mounting locations in ceilings should
be accounted for in the upfront cabling plan, leaving a 15- to 20-foot service loop at the end as wiggle room in case AP
locations later require adjusting.

2. After-the-fact Costs
The after-the-fact approach involves the Ethernet switches, Power over Ethernet (PoE) network design and cabling infrastructure as
cost of opening up ceilings and walls, as well switches and power injectors, phone system one cohesive project makes installing wireless,
as the possible cost of business downtime elements and uninterruptible power supplies, when you are ready, a smooth process with
while the environment remains ripped apart. for example. These active devices require minimal associated costs and headaches.
These factors can increase the overall cabling heating, ventilation and air conditioning
How to Plan for Wi-Fi
project cost by 2 to 4 times, depending on the (HVAC) and AC or DC power and can thus be
size and structural complexity of the property. more costly if installed after the building has If your new building is under construction,
The greater the importance of aesthetics in been constructed. how do you know where ceilings will be for
a building, the more difficult and expensive mounting APs? How do you plan around
These are among the reasons that a
the after-the-fact cabling job is likely to be sources of interference that might eventually
universal IT best practice is to evaluate all
(Figure 2). be present? Don’t you have to wait until the
network infrastructure requirements any
building is actually constructed to figure this
For example, there might be costs associated time a property is built or opened up for
out–when it’s too late to reap the costs of
with patching or repairing walls and ceilings. remodeling. IT personnel are accustomed
pre-planning? Fortunately, the latest Wi-Fi
Network integrator quotes that include to taking these opportunities to visit the
surveying and planning tools eliminate this
structured cabling often do not account for cabling requirements of traditional Ethernet
chicken-and-egg situation by allowing you
these expenses, which can rear their heads switches, desktops, printers, servers and
to electronically pre-design the WLAN before
as unexpected “change orders” not covered routers. But wireless is a comparatively new
the building is even constructed.
by your budget. network type for mainstream use. It simply
might not occur to planners to piggyback Historically, most companies installing
An additional consideration is the cost of the
the network design and cabling aspects Wi-Fi have conducted a physical site survey
cable itself. The cable can cost more if bought
of a current or future wireless project by walking around the building, mounting
in an add-on, incremental quantity, rather
onto the wired one. independent APs in places estimated to be
than as part of your initial volume order.
appropriate for the desired coverage and
Both have significant cabling components
Note, too, that the telecommunications hoping for the best. If there were coverage
to them, though, so they should both be taken
room contains most of the equipment holes or irregular performance in certain
into consideration. Viewing the wired-wireless
required for the distribution network that areas, they have carried handheld or laptop-
supports the wireless APs: based spectrum analysis tools to the area to
troubleshoot the problem. They could then
remount APs or change AP channels to
Sample Wireless Installation Costs
improve performance and coverage.
Building That process has historically worked well
100,000 square feet for small installations of one or two APs.
But it quickly becomes unwieldy as wireless
Option 1
networks become mainstream throughout
Site Survey After Building is In
(without automated tools) Approx . $8,400
the building. A healthy dose of automation
is now necessary to appropriately plan and
Option 2 scale building-wide Wi-Fi networks.
Pre-build Automated Site Survey Approx. $1,500
Site Audit After Equipment is Installed Approx. $3,500
Total Approx . $5,000
Figure 2 . The site survey after building is more accurate than an automated survey, but then you cannot afford
to audit the site for accuracy. An automated site survey gives you good accuracy and low follow up (audit) costs,
making it a better value overall.
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3. Automated Site Planning Tools
Figure 3 . Using automated site planning tools, which rely on blueprint information, allows you to know ahead of time where your AP cable drops will need to be.
Use Automated Site Planning Tools Such site-planning tools account for the is more difficult to predict in a mobile user
impact of building materials, glass windows, environment than in a traditional wire-line
It has become possible to easily design the
metal doors and other RF attenuators. They environment, where PC-to-Ethernet switch
entire wireless network before the building is
base their design decisions primarily by taking port connections remain stationary. However,
even constructed. All you need is a blueprint
into account these variables on the blueprint. your organization should decide whether it
for the structure and an automated Wi-Fi site
But they also require some basic information intends to give users near-ubiquitous coverage
survey tool. You can import the blueprint into
from you. So you need to make a few upfront throughout the building or whether coverage
the electronic survey and planning program,
decisions, described below. in common areas will suffice.
and it will automatically tell you where to
place APs and how many you will need, That decision might depend on the wireless
based on your wireless goals and what type Make Certain Decisions Upfront applications you wish to support. For example,
of Wi-Fi equipment you intend to purchase. wireless networks that will be supporting
First you need to decide where in the building
Voice over IP (VoIP) as all or part of an internal
One such tool is the RingMaster® management you want network connectivity. Then decide
mobile voice strategy usually require a more
product from Trapeze Networks, a Belden for each location whether that connectivity
dense, overall AP deployment than those that
brand. RingMaster works with Trapeze’s Wi-Fi should be wired, wireless or both.
provide wireless data access. Data networking
WLAN infrastructure equipment both to
Ideally, to create an accurate electronic is far more tolerant of packet loss, delivery
automatically create the wireless network
Wi-Fi design, you should know what delays and jitter than voice. Voice requires
design and to manage the wireless network
applications your WLAN will support, who stable, ubiquitous coverage and minimum
post-deployment (Figure 3).
will have access to the network and where delays when connections are handed off
they are likely to roam throughout the from AP to AP as a user roams.
building. Obviously, the location component
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4. Installing an AP in each of a few public areas Note that while 802.11a operates in the your facilities using a CAD drawing or even a
(such as meeting rooms, cafeteria and lobby) 5 GHz frequency band, 802.11g operates in clean JPG file. You simply input information
might be sufficient for data access; however, the 2.4 GHz band. 802.11n can operate in about the desired coverage area of the
consistent and predictable voice and location both. These frequencies are relevant network. Then, you ask the program to
service support will require coverage nearly because the higher the frequency, generally, calculate how many APs you’ll need, where
everywhere. That means more APs and, the shorter distance a transmission will travel. the APs should be placed and on what
consequently, more cabling runs to Also, RF signals at higher frequencies channels they should operate so as not to
more places. attenuate more as they travel through interfere with one another. The program will
channels with obstacles, further limiting automatically build the layout and specify at
The same density consideration applies to
signal reach. Because of these transmission what power levels each AP should transmit for
data connections in areas where large groups
traits in the 5 GHz band, it might be necessary the best overall operation, keeping in mind
of people are likely to congregate and use
to deploy a greater number of APs to achieve FCC and other regulatory power limitations.
the network simultaneously, such as in a
the desired coverage (range of transmission)
university lecture hall or in a conference The tool will automatically assign a
than when operating in the lower frequencies.
room at a trade show. channel plan to the wireless network.
Your automated site-planning tool will Your channel plan maps each AP to a specific
figure out the math that goes along with non-interfering channel in the frequency
Choose an 802.11 Technology
these issues to determine appropriate band in which it works. This is somewhat
You’ll also need to decide what Wi-Fi placement and coverage. analogous to creating “virtual cabling” over
technology you will use in your network: the air such that communications don’t
802.11n, 802.11g, 802.11a or some combination. bump into one another.
APs, Placement and Channel Planning
This decision will affect cabling because these
Once your wireless network design
WLAN types run at differing throughput Once you decide on the 802.11
has been created, you can calculate your
speeds and coverage ranges. They also differ technology(ies) you will be using and
physical AP cabling requirements to those
in capability and performance. You might where you need wireless connectivity,
spots and include them in your overall
elect to install a greater number of legacy you can use your site-planning tools
project plan and bid.
APs for coverage or select an AP that supports to automatically lay out the wireless
the latest standards for greater coverage network for you. You upload a floor plan for
and capacity.
Ideally, it makes sense for an organization to
install the newest technology (Draft 802.11n)
available in WLAN equipment, which generally Deployment Tip
offers per-radio data-connect rates of up to
Note that Draft 802 .11n is backward compatible with 802 .11a/b/g networks, so
300 Mb/s. Reasons to do so might include
continuing to install these earlier technologies won’t preclude moving to 11n in the
the following:
future . However, when mixed 802 .11a/b/g/n nodes share the air space in backward-
• A reluctance to invest in so-called “legacy” compatibility mode, 11n clients are likely to take a performance hit . This is because,
technologies. (See Deployment Tip Sidebar) despite a number of airtime fairness mechanisms in Wi-Fi systems, the slowest
device on the network is the gating device .
• A true need for Ethernet-like bandwidth
because of high-consumption applications To avoid compromised 11n performance in a mixed-mode network, use an AP with two
such as multimedia or all-wireless radios: one tuned to the 5 GHz band and the other tuned to the 2 .4 GHz band . Use the
user access. 5 GHz band for 802 .11n APs and clients, creating a “pure 11n” network in that band .
• Stability of cabling for wireless. Because Allow legacy 802 .11g clients to communicate with a 2 .4 GHz “G” radio in the other slot .
you’ll be deploying the latest technology, This way, legacy clients continue to operate as before, without impacting the newer,
you likely won’t have to change your WLAN faster 11n nodes . If you wish to maintain some 802 .11a (a 5 GHz technology) in the mix,
design–or the associated cabling–for the be prepared for 802 .11n to slow down .
foreseeable future.
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5. Telecommunications Room Typical Capacity of Legacy Infrastructure†
Considerations
Wireless Access Network Telecom Room Data Center
Note that once you know how many APs 11-54 Mb/s 10/100 Mb/s 10/100 Mb/s
you’ll need on each floor, you should make
sure to account for them in the number of
WLAN Controller
Ethernet switch ports you purchase for your
new or upgraded environment. Traditionally,
network planners total up the number of
desktops and printers they plan to have on
a given floor, the number of servers in the
data center, and the occasional router,
storage device and other wired network device
that may need to be connected. From there, PoE Backbone
they usually purchase and install a switch of Ethernet Switch Ethernet Switch
sufficient size in each telecommunications
room–one with at least as many ports as
needed for known devices on that floor or in
the data center plus a few extra for wiggle
room and growth. That port count, on Client Devices Access Points
Ethernet Switches or PoE Switches and power
injectors, should also account for cabled AP Figure 4 . Legacy environments easily accommodate Wi-Fi’s 54 Mb/s maximum data connect rates with Category 5e or
ports, a factor that might easily escape Category 5 cabling and 10/100 Ethernet switches.
network planners. In addition, where you
place your WLAN controllers*–management Typical Capacity of an 802.11n Infrastructure†
appliances that enable AP provisioning and
management–plays a role in how many Wireless Access Network Telecom Room Data Center
switch ports you need on a given floor. If you 108-540 Mb/s 10/100/1000 Mb/s 10/100/1000 Mb/s
deploy a cluster of virtualized controllers all in
the data center, for example, you’ll need a WLAN Controller
corresponding number of data center switch
ports available to support them. If you
distribute some out to the floors, the
controller ports will have to be covered in the
telecommunications room switch purchase. 1 Gb/s x N
Today, it’s advisable to procure gigabit-
speed Ethernet switches for connecting PoE Backbone
wireless APs and controllers, given that Ethernet Switch Ethernet Switch
products supporting the most current WLAN
technology, Draft 802.11n technology, contain
gigabit-speed uplinks. The reason for the
gigabit-speed uplinks is that multiple users
with 100 Mb/s or faster connections will be Client Devices Access Points
accessing an AP simultaneously. The uplink
capacity should be sufficient to support the Figure 5 . If you are deploying a Draft 802.11n Wi-Fi, strongly consider Category 6 cabling for supporting the gigabit-speed
aggregate of the user connection speeds. uplinks of 802.11n equipment. Similarly, telecommunications room switches and data center switches connected to APs and
controllers should support gigabit speeds, and pay attention to the power requirements of the 11n gear.
Otherwise, the telecommunications room
will become a wireless communications †
Controller-based architecture
bottleneck (Figures 4 and 5).
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6. It is also advisable to install PoE switches or PoE Trapeze Networks 802.11n gear requires Companies that design the wired and
injectors that can supply higher power levels to one 802.3af PoE injector supplying power wireless network environments together
comply with IEEE 802.3at requirements. This to one port of a dual-radio AP in order for the also make sure that they account for wireless
allows nearly every type of Access Point to AP to operate in 2x3 MIMO mode (with two APs and WLAN controllers* in the number
operate at its maximum performance levels transmitting and three receiving antennas). of Ethernet and PoE switch ports that they
(as some advanced features, such as future With 802.3af PoE on both ports, both radios procure for their telecommunications
MMO designs, may require more power than can support full 3x3 MIMO (with three room and data centers.
is available from legacy IEEE 802.3af transmitting and three receiving antennas).
It’s now possible to plan and design the
compliant PoE sources).
An emerging follow-on IEEE power wired/wireless network environment together
standard, commonly referred to as PoE+, before buildings are even constructed, thanks
Cable Types and Power Delivery is in development by the 802.3at task force. to automated site survey tools that are now
If you deploy 802.11n now or plan to in With ratification expected during the second available. Such tools, including Trapeze
the future and procure gigabit-speed switch half of 2009, 802.3at will run across Category Networks RingMaster, gather data about
ports accordingly, it is advisable to install 5e-and-higher Category cabling to provide up the environment from a building blueprint
minimum Category 6 copper cabling from to 24 Watts of power, or nearly twice that of and combine it with information entered
your telecommunications room out across traditional PoE. Pre-standard 802.3at switches by the network administrator about desired
your floors and throughout the walls and and injectors are available from a number wireless throughput at a given range and
ceilings. The reason is that Category 6 twisted- of vendors. In the case of Trapeze gear, 802.11 technology requirements. From there,
pair cabling provides better noise immunity draft 802.3at-compliant power used on only the tool determines how many APs and
and more “Signal-to-Noise” headroom for one AP port will power both radios in an controllers are required and where to install
supporting gigabit-per-second speeds across 802.11n AP in full 3x3 mode. the APs for optimum performance.
Ethernet’s 100-meter standard distance. If you find yourself embarking on a new Network planners are advised to keep the
Installing Category 6 or higher Category network infrastructure project later this latest standards for cabling and PoE in mind
cabling at your earliest opportunity, then, year, keep in mind the benefits of Category 6 as they plan their new environments.
should future-proof your cabling plant for cabling to support gigabit speeds and the Depending on timing, it may be desirable to
some time to come. availability of 802.3at power sourcing install higher performing cabling and PoE +
That being said, another somewhat thorny equipment as you make your equipment capable equipment to ensure having the
consideration as you are building out your and cabling decisions. gigabit-speed cabling and power support
unified wired/wireless infrastructure is device in place to keep your company covered for
Using 802.3at-powered equipment allows
requirements for power. The Power over many years to come.
nearly every type of wireless AP to operate at
Ethernet (PoE) standard today, IEEE 802.3af, its maximum performance levels without * In controller-based Wi-Fi networks
is widely deployed. It powers most Wi-Fi and having to make any tradeoffs in terms of
cabled devices requiring up to 12.95 Watts performance or feature support.
sustained over Ethernet’s 100-meter limit
across Category 3-and-higher Category
Conclusion
copper wiring.
Planning the wired and wireless network
Be sure to check the requirements of the
infrastructure cabling together can lower
Wi-Fi equipment vendor you use, particularly
overall cabling project costs by 2 to 4 times.
if you decide to deploy 802.11n. To take
Companies realize these savings largely by
advantage of all the enhancements to the
avoiding “after the fact” cable pulls that might
802.11 standard for improved throughput,
require breaking open ceilings and walls and
coverage, and interference avoidance, some
having to purchase extra cable in smaller
802.11n systems require more power than
volume at a higher price.
PoE can provide.
Belden Technical Support 1 .800 .BELDEN .1 www.belden.com Wired-Wireless WP 2009
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