Symbol Technologies Spectrum24 AP-4131 - Manual (Page 13)

Introduction
AP-4131 Access Point Product Reference Guide 3
1.2 Radio Basics
Spectrum24 devices use electromagnetic waves to transmit and receive
electric signals without wires. Users communicate with the network by
establishing radio links between MUs and APs.
Spectrum24 products use DSSS (direct sequence spread spectrum) to transmit
digital data from one device to another. Using FM, a radio signal begins with
a carrier signal that provides the base or center frequency. The digital data
signal is encoded onto the carriers using a DSSS “chipping algorithm”. The
radio signal propagates into the air as electromagnetic waves. A receiving
antenna in the path of the waves absorbs the waves as electrical signals. The
receiving device demodulates the signal by reapplying the direct sequence
chipping code. This demodulation results in the original digital data.
Spectrum24 uses the environment (the air and certain objects) as the
transmission medium. Spectrum24 radio devices transmit in the
2.4 to 2.5-GHz frequency range, a license-free range throughout most of
the world. The actual range is country-dependent.
Spectrum24 devices, like other Ethernet devices, have unique, hardware-
encoded Media Access Control (MAC) or IEEE addresses. MAC addresses
determine the device sending or receiving data. A MAC address is a 48-bit
number written as six hexadecimal bytes separated by colons.
For example:
00:A0:F8:24:9A:C8
1.2.1 S24 Network Topology
The variations possible in Spectrum24 network topologies depend on the
following factors:
•
the AP function in the network
• the data transfer rate
• the wireless AP (WLAP) interface.