TECHNICAL BRIEF: Rugged Bluetooth Scanners
Bluetooth Radio Performance
- Class 1 vs. Class 2 Bluetooth
- Adaptive Frequency Hopping (AFH)
Motorola’s lineup of rugged cordless scanners employs the Bluetooth standard for transmitting
information wirelessly. When a scanner is paired with a cradle or other device, the data is
exchanged over a radio frequency link using the 2.4 –2.5 GHz unlicensed spectrum. Of great
importance in nearly any cordless scanner application is the radio range, which is defined as
how far apart scanner and cradle/BT device can operate without a loss of the radio connection.
This brief discusses the technical details behind radio range and presents data on the radio
range of Motorola’s Class 1 and Class 2 Bluetooth architectures used in rugged scanners.
Bluetooth Radio Range Theory
Fundamentally, radio range is dependent upon the Bluetooth radio’s transmitted radio
frequency (RF) power and receiver sensitivity, and the absorption rate of the medium the RF
waves travel through. When the medium absorbs enough of the transmitted energy to make
the signal at the receiver lower than the receiver sensitivity, the connection is lost. An
excellent analogy is human hearing. Transmitted RF power is analogous to how loud
someone is speaking, and receiver sensitivity is analogous to a listener’s hearing acuity.
When two people are having a conversation in reasonable proximity to each other, it is easy
for the listener to understand what the speaker is saying. However, if the speaker and listener
are very far apart, or are in different rooms, it may be difficult or impossible for the listener to
make out what the speaker is saying.
Dissimilar materials absorb RF energy at different rates. Therefore, it is very hard to
accurately predict the amount of RF energy lost during transmission in a given environment.
To make this prediction even more complicated, there are often multiple ways for the RF
signal to get to the receiver. So, ev