Wireless Local Area Networks

• Used where cable isn't possible - remote sites; also when mobility is important.
• Use transceivers or access points to send and receive signals between the wired and wireless network.

There are 4 techniques for transmitting data

• Infrared transmission consists of four types;
1. Line of sight
2. Scatter: good within 100 ft.
3. Reflective
4. Broadband optical telepoint: used for multimedia requirements; as good as cable.
• Laser requires direct line-of-sight.
• Narrow-band (single frequency) radio
• Cannot go through steel or load-bearing walls.
• Requires a service handler.
• Limited to 4.8 Mbps
• Spread-Spectrum Radio
• Signals over a range of frequencies.
• Uses hop timing for a predetermined length of time.
• Coded for data protection.
• Quite slow; Limited to 250 Kbps.

Point to Point Transmission

• Transfers data directly from PC to PC (NOT through cable or other peripherals)
• Uses a point to point link for fast error-free transmission.
• Penetrates objects.
• Supports data rates from 1.2 to 38.4 Kbps up to
• 200 feet indoors or
• 1/3 of a mile with line of site transmission.
• Also communicates with printers, bar code readers, etc.

Multipoint Wireless Bridge

• Provides a data path between two buildings.
• Uses spread-spectrum radio to create a wireless backbone up to three miles.

Long-Range Wireless Bridge

• Uses spread-spectrum technology to provide Ethernet and Token-Ring bridging for up to 25 miles.
• This costs less than T1, but T1 will transmit at 1.544 Mbps

Mobile Computing

• Uses wireless public carriers to transmit and receive using;
• Packet-radio communication.
Uplinked to satellite, broadcast only to device which has correct address.
• Cellular networks.
CDPD same as phone, subsecond delays only, real time transmission, can tie into cabled network.
• Satellite stations.
Microwave, most common in USA, 2 X directional antennas, building to building, building to satellite
• Slow transmission rate: 8 Kbps - 19.2 Kbps