Specifications

Infrastructure Network
3-2 Designing and Implementing a Wireless Network
Infrastructure Network
To plan a wireless infrastructure network, determine the following:
• Coverage area - the area where the clients are located. If the clients are mobile, this is
the area where the clients can connect to the network.
• Supported users - the number of clients that you expect to support.
• Network utilization - how users intend to use the network. Utilization includes
frequently transferring large files (heavy utilization) or only accessing e-mail (light
utilization).
These factors, described in the following sections, help you to determine the amount of
Access Points needed. Afterwards, you need to examine the Access Point hardware
requirements and the wireless client system requirements.
When designing a wireless network, consider the security issues for your environment.
Security can include keeping the Access Point in a locked closet, preventing unauthorized
users from joining the wireless network, and using data encryption to ensure that sensitive
data is kept private.
Determining the Coverage Area and Supported Users
Coverage area is determined by a number of factors, including physical obstructions and
noise levels as shown in Figure 3-1.
The following is an example of the coverage area in a semi-open environment, which is
defined as work space divided by shoulder-height, hollow wall elements. The distances in
your environment may be different.
• 11 Mbit/s - 165 feet (50 meters)
• 5.5 Mbit/s - 230 feet (70 meters)
• 2 Mbit/s - 300 feet (90 meters)
• 1 Mbit/s - 375 feet (115 meters)
The faster the transmit speed, the shorter the coverage area at that speed. An Access Point
with an 11 Mbit/s PC Card can communicate with clients up to a distance of 375 feet in a
semi-open environment. However, only clients within the first 165 feet can communicate
at 11 Mbit/s. Clients between 165 and 230 feet communicate at 5.5 Mbit/s. Clients between
230 and 300 feet communicate at 2 Mbit/s; and clients between 300 to 375 feet
communicate at 1 Mbit/s.
Noise levels in the radio frequencies can reduce the coverage area. Such noise can be
generated by microwave ovens and elevator motors.