Deploying the WLAN
Deploying your WLAN will likely be a complex process-driven
effort. It will require careful project management and scheduling to ensure
smooth transitions between each set of tasks. In this, it is not unlike any
other technology implementation once the architecture and design have been
defined.
There are usually multiple groups or teams involved in a WLAN
deployment. These will include your core IT wireless team, your cabling vendor,
the group responsible for workplace resources (power, occupational health and
safety, office management, and so on), your technical support organization,
network operations staff, and any external vendors you select to assist in the
deployment. Large enterprises will most likely also have a program management
team to oversee the multiple installations and sites, manage the multiple
projects, report to the stakeholders, and controls costs. Although the program
management team may not be considered an integral part of the deployment per se,
it will likely be involved in the day-to-day implementation.
Figure 6-2 shows the
relationships among groups involved in a typical deployment. It is important to
carefully manage these relationships and ensure that good project management
techniques are used to avoid unnecessary delays or problems.
The following section describes some of the key tasks and
activities required during the deployment phase.
Pre-Deployment Tasks
At this stage, you should have decided whether to use external
vendors to assist in the deployment. If you have chosen to use external vendors,
ensure that they are familiar with your existing network infrastructure, the scope of deployment, the locations of
each site, and the fundamentals of your wireless architecture. Some time spent on transferring information to your vendor
will help avoid later confusion and delays.
Independent of retaining outside help, you should have a
detailed project plan and implementation schedule in place. The relevant IT
resources should be assigned, and the team should be familiar with the
architecture. It is possible that a pilot network will have been undertaken to
validate your architectural decisions, familiarize your IT staff with the
technology, and test the solution. Indeed, for larger deployments, a pilot is
highly recommended.
A communication plan should by now have been undertaken, and
your end users should be aware of the upcoming technology, your security
standards and wireless policies, when they can expect to receive their client
hardware (if necessary), and when the service will be launched at their
site.
Managing the Deployment
The actual deployment of the WLAN will most likely follow a
number of common steps for each site. The makeup of the teams involved will
depend upon your choice of IT staff, the use of internal staff or external
vendors, and whether local resources are available. Each set of tasks should be
assigned to a team, yet all teams should understand the entire end-to-end
process.
Figure 6-3 shows a
typical process flow for common tasks in a large multisite deployment. The list
is not intended to be all-inclusive but rather is indicative of the process flow
and task assignment you will likely encounter. The illustrated case uses a WLAN
solutions provider (the "vendor") to provide additional project resources. Even
if you use your own internal resources for the entire project, the tasks and
process flow would remain roughly the same.
Site Data Collection and
Validation
Ensure that you have a comprehensive list of all sites in which
you will deploy. Site contacts (local IT staff, reception, shipping, health and
safety, and office management) should be collected in a "site database" or
contact list, including phone, fax, and e-mail addresses. A "site owner" could
be assigned from your IT team. This person would be responsible for configuring
the devices or managing the specific site installation; alternatively, a project
manager can fill this role.
Ensure that you have details such as office opening and closing
times, local delivery restrictions, and any upcoming events such as office
closures, construction, vacations, and so on.
Finally, it is recommended that you source or produce current
floor plans for your office. You should note the location of all cabling (if
possible), power outlets, and ideally the composition of internal walls, because
these will affect WLAN signal strength, and ultimately quality and throughput.
This information is useful during the site survey phase. Most of this
information can be found in architectural or office blueprints if you have
them.
Local Infrastructure Upgrade or
Modification
Have your site owner (the IT staff member responsible for the
site) take stock of existing infrastructure at each site before your installation team visits. The site owner
should do the following:
-
Confirm that there is enough inline power or power points
available
-
Make sure that you have sufficient rack space
-
Ensure that you have enough switch ports available
-
Verify that you have sufficient console ports available if you
are cabling the access points for console access
Much of this is predicated upon earlier architectural
decisions, but it is important that you collate and validate information on each
site to avoid surprises later.
If you do not have sufficient infrastructure capacity, you
should plan to modify, upgrade, or install what you need before the first site
visit by a WLAN team. This in turn will affect your project plan and resource
requirements. In other words, make sure the supporting or foundational enabling
infrastructure is capable of supporting the access points and controllers. Don't
leave yourself vulnerable to discovering halfway through an installation that
you've run out of Ethernet ports on your switch, for example.
Firmware and Configuration
Updates
Ensure wireless network adapters have the latest firmware and
software drivers. This may require manually flashing each card or downloading
the latest software. The same is true for embedded wireless clients (such as
those in ASDs or embedded wireless cards in newer-model laptops). Note that for
large deployments of several thousand client devices, updating firmware and
software drivers becomes an increasingly complex and time-consuming challenge.
We recommend a structured and tested approach for managing such environments.
Refer to Chapter 8 for recommended
practices.
Client Distribution
Understand how you will distribute the cards and software. You
may wish to ship client adaptors to a local mailroom or IT contact for each site
and delegate the distribution among your users to them. Alternatively, you may
use internal mail to send client hardware to each user individually, or you may
select a "client pickup" model. Ensure that your users and local staff are aware
of which option you choose. Also ensure that you also provide training or
informational collateral to your users at this stage. FAQs and installation
instructions are usually included.
Shipping and Handling
Assign responsibility for actual shipping of hardware to each
site. This includes not only the client adaptors as described in the preceding
section, but also the access points and any wireless switches or dedicated
hardware you may need. If you need to upgrade local infrastructure, make sure it
is dispatched and installed before the wireless equipment.
The management of shipping and handling alone can be a
significant administrative overhead, especially in international deployments.
Ensure that you have a team that is familiar with this process. Expect customs
requirements (and delays) and plan accordingly.
Decide on whether and where you will maintain a stock of
standby and replacement equipment, for example, at each site or in a centralized location.
Site Survey
The site survey is perhaps the most important of all deployment
tasks. This process dictates where you will locate the individual access points
to provide the level of service you have defined in your architecture. The
throughput you require for your applications and the estimated number of
concurrent users will provide you with a rough estimate of the number of access
points you will need per floor or site.
Your solutions architecture, or automated WLAN management
tools, will dictate such issues as desired cell overlap, throughput required to
support your applications, user to access point ratio, radio transmission power,
and whether you lock your access points to a single speed (data rate). Using
this information in conjunction with the floor plans you collected earlier will
allow you to plan for the number of access points per site. No amount of
planning can account for environmental issues impacting your WLAN, local site
interference, or attenuation caused by internal office construction. You must
install the access points in locations and configure their settings such that
they actually provide the service you require. A formal site survey will
validate this information and find the most appropriate location for the access
points.
Site surveys can typically be undertaken in two ways:
You may select an automatic site survey (sometimes called RF Prediction) and use tools provided by your WLAN equipment
vendor to configure the access points once they are physically installed. These WLAN management products (like the Cisco Wireless LAN
Solutions Engine or Wireless Control System) not only offer assisted or
semi-automatic site survey capabilities but also allow you
to import floor plans to get a visual representation of your WLAN, interference,
client data, and so on. The access points are then powered
up, and the centralized wireless controller or management device auto-discovers
and auto-configures them with optimum settings.
In some circumstances, an automatic or assisted site survey may
require you to take measurements at various locations throughout the floor to
add additional data points. These can help improve the accuracy and
appropriateness of the automatic configuration settings. Finally, some WLAN
products (like the Cisco Centralized WLAN Solution using wireless LAN
controllers) automate the access point configuration entirely and your IT staff
need not configure them at all. This can offer significant savings in time,
effort, and expense because your IT staff members do not have to be wireless
experts or spend time configuring each access point.
The traditional site survey technique calls for a manual
process. The engineers choose locations for the access points based upon "best
guess," taking into account the floor plan, the transmit power, and cell overlap
defined by the design and then temporarily place access points in these locations. They then perform a walkabout measuring the signal strength,
cell size, and roaming characteristics using a wireless site survey software
application. This can be the software provided by the WLAN equipment
manufacturer (such as the site survey utility Cisco bundles into its software)
or a third-party tool designed specifically for site surveys or wireless
diagnostics, such as AirMagnet. If any dead spots are discovered, or if the
signal strength and overlap do not meet the defined characteristics, the access
points are moved and fine-tuned. Challenging environments like factories
sometimes employ external, more powerful or directional antennas.
Whatever survey strategy you select, the output is the same.
The result is a list of access point locations and settings that provide the
coverage and bandwidth you need for that individual site. The list is then used
by the implementation team to identify the exact placement of access points
during the deployment, as well as by operations staff as an asset log for
troubleshooting purposes.
It is important for you to document the site survey. Create a
"site pack" for each location, which includes copies of the floor plans, showing
the final locations of the access points, a table of all access points with
information on their name, configuration (transmit power, channel, antenna type,
and so on), and details such as their switch and console port number. It is also
useful to include a digital photograph of the AP location. Don't forget to
update the site-pack whenever changes are made or new access points are
installed. An outdated site-pack can cause more problems than none at all.
Cabling
Once you have calculated the position of the access points, you
must cable each location. Typically, this will require the use of plenum-rated
cable (cable certified for fire resistance) to enable you to string the cable
through raised floors or dropped ceilings. Each access point will require at
least one network cable. If you have opted to provide console access to your
access points, an additional cable will be needed. Console access will allow you
to engage in out-of-band management and troubleshooting.
Finally, you will need to ensure that the access point is
provided with DC current. This may require the installation of an AC mains power socket at or near the
access point location. Alternatively,
you can power some access points with inline power that is provided by the
network switch via the Category 5 twisted pair cable. This is known as Power
over Ethernet.
Access Point Installation
Next comes the physical installation of the access point. You
may choose to fit the access points to office walls or building columns or hide
the access point in the dropped ceiling and only leave the antennas visible.
Special plenum-rated metal or NEMA enclosures are also used and are sometimes
required for manufacturing or industrial areas. In any case, this is when your
team physically installs the access point, connects it to the cabling previously
laid, and powers up the device.
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