Communications Quality; Signal Level - Cabletron Systems RoamAbout Access Point Manual

A fixed transmit rate does not affect the receive rate. For example, an Access Point and a
client both have 11 Mbit/s PC Cards, but the client is fixed to only transmit at 2 Mbit/s. The
Access Point can send data at 11 Mbit/s to the client, and the client can respond by sending
data at 2 Mbit/s.
However, you should not set the Access Point to a fixed rate of more than 2 Mbit/s if you
have clients with 11 Mbit/s and 2 Mbit/s PC Cards. Otherwise, the 2 Mbit/s clients cannot
communicate with the Access Point. The 2 Mbit/s clients can only receive data at a
maximum of 2 Mbit/s.

Communications Quality

Communications quality is measured by the Signal to Noise Ratio (SNR). The SNR is a
dynamic indicator that indicates the relative strength of the radio signal (signal level) versus
the radio interference (noise level) in the radio signal path. In most environments, SNR is
a good indicator for the quality of the radio link between transmitter and receiver. A higher
SNR value means a better quality radio link.
At the client, the RoamAbout Client Utility allows you to monitor the SNR, signal level,
and noise level at the client. The client utility is provided in the RoamAbout PC Card kit.
For the Access Point, the Access Point Manager provides a Link Test diagnostic tool that
monitors the SNR, signal level, noise level, and remote station capabilities.

Signal Level

The signal level values give you an indication of the distance between wireless devices.
Using the RoamAbout Client Utility, you can observe a decrease of the signal level value
when you move a client away from its Access Point. As an indicator for the
communications quality, signal level should always be interpreted in combination with
noise level:
•
A high signal level with a low noise level provides excellent communications quality.
•
A high signal level with a high noise level results in an average or poor SNR.
Communications may not be as good as expected despite the strong signal level.
•
A low signal level may still provide adequate communications when the noise level is
Understanding Wireless Network Characteristics 2-5
Communications Quality