Chapter 5 Bluetooth; Introduction; Adaptive Frequency Hopping - Motorola ET1 User Manual

CHAPTER 5 BLUETOOTH

Introduction

Bluetooth-equipped ET1 can communicate without wires, using frequency-hopping spread spectrum (FHSS)
radio frequency (RF) to transmit and receive data in the 2.4 GHz Industry Scientific and Medical (ISM) band
(802.15.1). Bluetooth wireless technology is specifically designed for short-range (10 meters (30 feet))
communication and low power consumption.
ET1s with Bluetooth capabilities can exchange information (e.g., files, appointments, and tasks) with other
Bluetooth enabled devices such as printers, access points, and other mobile devices.

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 ET1 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 feet). 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.