Adaptive Frequency Hopping; Security - Motorola RD5000 Integrator Manual

8 - 2 RD5000 RFID Integrator Guide

Adaptive Frequency Hopping

Adaptive Frequency Hopping (AFH) is a method of avoiding fixed frequency interferers. AFH can be used with
Bluetooth voice. All devices in the piconet (Bluetooth network) must be AFH-capable in order for AFH to work.
There is no AFH when connecting and discovering devices. Avoid making Bluetooth connections and discoveries
during critical 802.11b communications. AFH for Bluetooth can be broken-down into four main sections:
•
Channel Classification - A method of detecting an interference on a channel-by-channel basis, or pre-defined
channel mask.
•
Link Management - Coordinates and distributes the AFH information to the rest of the Bluetooth network.
•
Hop Sequence Modification - Avoids the interference by selectively reducing the number of channels.
•
Channel Maintenance - A method for periodically re-evaluating the channels.
When AFH is enabled, the Bluetooth radio "hops-around" (instead of through) the 802.11b high-rate channels. AFH
coexistence allows Motorola readers to operate in any infrastructure, AFH is always enabled.
The Bluetooth radio in this reader operates as a Class 2 device power class. The maximum output power is 2.5mW
and the expected range is up to 32.8 feet (10 meters). A definitive definition of ranges based on power class is
difficult to obtain due to power and device differences, and whether one measures open space or closed office
space.
NOTE It is not recommended to perform Bluetooth wireless technology inquiry when high rate 802.11b operation
is required.

Security

The current Bluetooth specification defines security at the link level. Application-level security is not specified. This
allows application developers to define security mechanisms tailored to their specific need. Link-level security is
really between devices not users, while application-level security can be implemented on a per-user basis. The
Bluetooth specification defines security algorithms and procedures needed to authenticate devices, and if needed,
encrypt the data flowing on the link between the devices. Device authentication is a mandatory feature of Bluetooth
while link encryption is optional.
Pairing of Bluetooth devices is accomplished by creating an initialization key that is used to authenticate the
devices and create a link key for them. Entering a common PIN number in the devices being paired generates the
initialization key. The PIN number is never sent over the air. By default, the Bluetooth stack responds with no key
when a key is requested (it is up to user to respond to the key request event). Authentication of Bluetooth devices
is based-upon a challenge-response transaction. Bluetooth allows for a PIN number or passkey that is used to
create other 128-bit keys used for security and encryption. The encryption key is derived from the link key used to
authenticate the pairing devices. Also worthy of note is the limited range and fast frequency hopping of the
Bluetooth radios that makes long-distance eavesdropping difficult.
It is recommended:
•
Perform pairing in a secure environment
•
Keep PIN codes private and do not store the PIN codes in the reader
•
Implement application-level security