AML Triton Wireless Handheld Terminal - Manual (Page 22)

1 - 16
USER’S GUIDE Triton Wireless Hand-held Terminal
The Triton Internal Radio
The Triton has a multi-color LED to indicate when the unit has scanned a bar code The
Triton Hand-held Terminal comes equipped with an internal 802.11b/g/n radio and diversity
antenna. This internal radio is specifically designed to communicate with any 802.11b/g/n
access point. The range of the internal radio depends greatly on the quality of the Access
Point and the RF communication characteristics of the environment where the device is
used. The typical range for an 802.11b/g radio is 500 feet through free air. Additional Access
Points must be added to improve coverage in a larger area, or in electrically noisy RF
environments.
802.11b/g/n Fallback Mode
Wireless LAN technology is designed to make maintaining a connection between
two devices as reliable and consistent as possible. Since the speed of the connection
between wireless devices will vary as range and signal quality varies, the wireless devices
will intentionally sacrifice throughput (data rate or connection speed as measured in bits
per second) in exchange for maintaining a reliable connection. In other words, a reliable
connection at a lower speed is preferred over an unreliable connection at a higher speed
(i.e., it is easier to maintain the connection if data rate is deliberately reduced, or put
another way, lower data rates will tolerate a higher range and/or worse signal quality). This
characteristic is known as fallback. As an example, an 802.11b/g system will fallback from 11
Mbps to 5.5 Mbps as range increases or signal quality decreases. Subsequent fallbacks from
5.5 Mbps to 2 Mbps and 1 Mbps are also supported.
Interference and Coexistence
802.11b/g operates in a range of radio frequencies known as an “unlicensed” band (i.e.
the FCC does NOT require the use of a license in order to operate a radio transmitter in
this range). This means that commercially available radio devices other than wireless LAN
devices are permitted to use the same frequency band as 802.11b/g. Consequently, these
co-existing radio devices can interfere or “jam” the wireless LAN (and vice versa). Ironically,
the most troublesome devices are cordless telephones and microwave ovens.
Fortunately, higher quality cordless phones tend to “listen” for a clear channel before
becoming active and will thus avoid interfering with a wireless LAN (i.e., the cordless phone
seeks a clear channel for itself so naturally avoids being interfered with or being a source
of interference). Jamming from microwave ovens is more severe but is usually restricted
to the upper frequency range for 802.11b/g (it should be noted that 802.11b/g divides
the available frequency band into 11 channels. The higher numbered channels are most
susceptible to microwave oven interference).
In each instance, jamming occurs only when the cordless telephone or microwave oven is
active.