User's Manual

41
It is very important to recognize that good signal strength is absolutely necessary for reliable
operation. Signal strength below 25% is likely to cause problems. Signal strength above 50% will
provide robust operation. Signal strength is not merely a factor of the distance between the
printer antenna and the access point antenna. Other factors such as ambient noise, intervening
walls and other nearby wireless equipment can result in poor signal strength. See the
Troubleshooting chapter for suggestions for improving signal strength.
Noise Floor
The noise floor is an instantaneous measure of the ambient noise that the wireless radio sees
when it is not transmitting or receiving a packet. There is always ambient thermal noise at a
level of -100 dBm that cannot be avoided. Added to this is manmade noise coming from:
microwave ovens, cordless telephones, baby monitors, wireless cameras, remote car starters,
DECT and residential wireless phones and Bluetooth products to name just a few. When you
add the noise sources together, the typical noise floor the wireless radio should see is
approximately -90 ±5 dBm. A more negative number is better (-95 is less noise than -90). The
noise floor value can be useful to evaluate whether the ambient noise is too high for robust
wireless operation. If the noise floor is higher than -85 dBm, then you may want to take steps to
reduce the noise level the wireless radio sees (see the Troubleshooting chapter). By using the
Signal Strength and Noise Floor values, the actual signal level can be calculated as follows:
Signal Level (dBm) = Noise Floor (dBm) + (40 * Signal Strength (%) / 100)
Data Rate
The data rate shown in the Wireless Info display can provide some insight into how well the
wireless interface is working. When there is a good SNR, the radio should typically show the
maximum data rate the router can support (11 Mbps for 802.11b and 54 Mbps for 802.11g).
You may notice at times that lower speeds are displayed. This is expected as long as the
maximum speed appears most of the time, particularly when a print job is being received.
When the SNR is poor, data will be sent at a slower speed to improve the signal quality
(receiver sensitivity is better at slower data rates). If you consistently see a low data rate, then
you may want to take steps to improve the signal quality (see Troubleshooting chapter).
DHCP & MAC Address Info Page
Using first the INFO button then the NEXT button, go to the next page after the Wireless Info
page shown above. The display should look like: