As part of planning a wireless LAN deployment, you need to define the tasks
necessary for completing the project. This involves realizing applicable steps,
such as requirements analysis, design, and installation, which are common to
any system solution. To minimize deployment
risks and ensure a successful project, be sure to address the following
steps as they relate to wireless LANs:
- Requirements. Before getting too far with the project, understand
as much as possible about requirements, such as needs of users and applications,
interfaces with existing systems, facility composition, and so on. This provides
the basis for making decisions when designing the solution. If you don’t do
a good job of defining the requirements, then the solution may not meet the
needs of users.For smaller networks, the requirements gathering process could be as simple
as spending a couple days thinking about requirements and preparing a two to
three page document that defines them. Larger systems, however, will likely
need for a more involved process because of a broader base of users and systems.
If requirements are not well understood, then consider using prototyping and
construct a solution based on known requirements. The testing of a small prototype
with a limited number of users will often lead to better understood requirements.
We also have details
on defining requirements.
- Design. The design produces a definition of how the wireless LAN
will satisfy requirements. This includes technical elements such as developing
the system architecture, identifying standards (e.g., 802.11b or 802.11a),
selecting an access
point vendor, specifying antennas
types, identifying MAC
Layer settings, and so on. The end result of the design will be a bill
of materials and diagrams that indicate the interconnection of related software
and hardware components. Of course this leads to the cost of the system, something
important to know before moving on.Be sure to perform an RF
site survey to determine the optimum location and number of access points.
Also investigate the presence of RF
interference and recommend appropriate countermeasures to maximum the performance
of the network. In larger more complex networks, consider the use of a simulation
(e.g., OPNET), which leads to making better
decisions on access point settings based on various user activity and network
configurations.
- Feasibility. Once the requirements and design are known, it may be
worthwhile (and required by some companies) to perform a feasibility analysis
before spending the money to purchase components and install the system. The
idea is to identify benefits and determine whether the costs of the system
will result in a positive return on investment. For some applications, such
as inventory management and price marking, gains in efficiency and accuracy
are relatively easy to define with well understood costs savings and rapid
returns on investment. The deployment of a wireless LAN in a corporate environment,
though, may be more difficult to defend in terms of user efficiency cost savings.
In this case, focus on ease of installation and long-term support cost savings
in addition to meeting needs for mobility. Get more details
on the feasibility of wireless LANs in offices.
- Development. Some wireless applications require the development of
client software to implement certain functions. For example, requirements
may call for the utilization of handheld data collectors with built in scanners
to perform inspections throughout a manufacturing plant. Users may scan a
bar code at a particular point and answer question prompts on the data collector.
This application would likely require custom software. In these cases, programmers
must fully understand wireless impairments such as RF interference and limited
coverage in order to include appropriate error recovery mechanisms. A wireless
LAN is often referred to as transparent to the user, but this is only if the
programmer takes into account issues related to wireless connectivity.
- Installation and Testing. The installation phase of the project is
when the tires hit the pavement. If the design is done effectively, then the
installation should be a smooth process. For example, the design should specify
where to mount the access points. It’s generally best to place the access
points as high as possible, but be practical. Warehouses have high ceilings;
however, avoid mounting the access points so high that you need expensive
equipment to reach them. Also, consider using Power over Ethernet (PoE) to
run electricity to the access points. This avoids the time and costs of installing
electrical outlets throughout the facility.After completing the installation, be sure to test for proper operation and
coverage using 802.11 analyzers such as those from Airmagnet,
Berkeley Varitronics, and Wildpackets.
The testing may indicate the need to move some access points and possibly use
different settings. Be certain to document access point locations and configurations
if changed from the design. This will provide an aid to the people when supporting
the operational system.In order to reduce risks in larger system deployments, think about starting
with one or more pilot sites to test the solution with a limited number of users.
The feedback from users during the pilot testing will often uncover problems
with the design. Keep in mind that it’s much less expensive to fix a problem
with the design before installing the system throughout the entire company.
- Operational Support. Before allowing users on the network, ensure
there’s definition and activation of adequate operational support. This includes
elements such as trouble resolution (e.g., help desk and technical support),
periodic maintenance, and system monitoring. What most people don’t realize
is that this phase of the system’s life can be much more expensive than the
cost of the installation. As a result, define enough details of the support
elements to provide an ongoing budget.To ensure effective support, be sure there’s a single phone number to call
if problems arise. In most cases, this requires that the wireless users call
an existing support system; however, be sure that the support providers understand
how to handle peculiar wireless problems. Impairments, such as RF
interference and multipath
propagation, can baffle support staff not familiar with wireless LANs. The support
staff will also need to fully understand the wireless LAN configuration and
settings and have appropriate test tools to effectively troubleshoot and fix
problems.
Jim Geier provides independent consulting
services to companies developing and deploying wireless network solutions.
He is the author of the book, Wireless LANs (SAMs, 2001),
and regularly instructs workshops
on wireless LANs.
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