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MN002859A01-A
Chapter 8: Wireless
Bluetooth Device
The LEX L10ig supports Motorola Operations Critical Wireless (OCW) Push-to-talk Pod (NNTN8127)
and Bluetooth-enabled device (accessory) through a wireless Bluetooth connection.
Adaptive Frequency Hopping
Adaptive Frequency Hopping (AFH) is a method of avoiding fixed frequency interferers, and 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 consists of 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 interference by selectively reducing the number of hopping
channels.
•
Channel Maintenance - A method for periodically re-evaluating the channels.
The Bluetooth radio in this device operates as a Class 2 device power class. The maximum output
power is 2.5 mW and the expected range is 10 meters (32.8 ft.). A 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.
NOTICE: It is not recommended to perform Bluetooth wireless technology inquiry when high
rate 802.11b operation is required.
Bluetooth 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 occurs between devices, not users, while application-level security can be
implemented on a per-user basis. The Bluetooth specification defines security algorithms and
procedures required 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 used to authenticate the
devices and create a link key for them. Entering a common personal identification number (PIN) in the
devices being paired generates the initialization key. The PIN 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 or passkey 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.
Recommendations are:
•
Perform pairing in a secure environment
•
Keep PIN codes private and do not store the PIN codes in the device
•
Implement application-level security
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Troubleshooting
