December 12, 2000, 3:37 PM — Before you purchase components for a wireless LAN, make sure you specify what the
system should do. Surprisingly, many businesses overlook this crucial step. Incomplete
and missing requirements are the major reason such LANs fail, leading to time-consuming
and expensive attempts to correct the inadequacies of the installed system.
Be certain to first define the following requirements:
- Coverage and mobility. Specifying the coverage, or
area where the end-users will operate the wireless devices, helps the designer
determine the number and location of wireless LAN access points. Mobility
requirements derive from the movement of users through the coverage areas. For example,
a wireless network in a hospital may need to provide continuous connectivity in
specific wards and clinics, but not within operating rooms and office areas.
It's generally best to illustrate the coverage areas on drawings of the facility or
of the software that will operate over the wireless LAN. For example, warehouse
management system software requires the transmission of relatively low-bandwidth
bar-code information between wireless handheld bar-code scanners and a host computer. A
> desktop video application, however, requires the transmission of realtime video
signals. How frequently you expect to use these different information types helps
determine the design specifications for your data transmission rate and
require access to the wireless LAN. Be sure to allow for future expansion.
computers, bar-code data collectors, and mobile patient monitors. You should identify
the available physical interfaces -- such as PC Card, PCI, ISA, or USB -- for each
specify the length of time the end-user devices need to operate on a set of batteries.
A mobile patient-monitoring device, for example, may need to operate for at least 72
hours, the typical length of an inpatient hospital stay. This information indicates
whether wireless LAN components need to support power-management functions.
interface with existing systems such as Ethernet networks, applications, and databases.
The system interface requirements describe the architectures and communications
protocols of these systems.