Adaptive Frequency Hopping; Security; Bluetooth Profiles - Motorola LEX L10 Manual

8.3.1 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.
When AFH is enabled, the Bluetooth radio "hops around" (instead of through) the 802.11b high-rate channels. AFH
coexistence allows Motorola Enterprise Tablets to operate in any infrastructure.
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.
Note: It is not recommended to perform Bluetooth wireless technology inquiry when high rate 802.11b
operation is required.

8.3.2 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

8.3.3 Bluetooth Profiles

The LEX L10 supports the following Bluetooth services:
• Generic Access Profile (GAP) — Use for device discovery and authentication.
• Service Discovery Protocol (SDAP) — Handles the search for known and specific services and general services.
• Serial Port Profile (SPP) — Sets up a virtual serial port and connects two Bluetooth enabled devices. For example,
connecting the LEX L10 to a printer.
• Human Interface Device Profile (HID) — Allows Bluetooth keyboards, pointing devices, gaming devices and
remote monitoring devices to connect to the LEX L10.
MN001456A01-A | February 2015 |
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