System Overview - Nortel BayStack 650 User Manual

Using the BayStack 650/660 Wireless LAN PC Card

System Overview

The BayStack PC cards allow wireless connection for laptop computers, with a
PCMCIA slot, to an IEEE 802.11 industry standard wireless local area network
(wireless LAN). If used with the right access point (BayStack 650 Access Point or
BayStack 660 Access Point), the cards can obtain resources from any location in a
facility that is connected to an infrastructure (wired server-based) network.
If used without an access point, users can create an ad hoc network between
two or more PCs using either PC card. You can use an ad hoc network for file
sharing, print sharing, chat capabilities, and workgroup collaboration. The PC
cards employ two different technologies to make a wireless LAN connection:
• BayStack 650 PC Card
The BayStack 650 PC Card uses Frequency Hopping Spread Spectrum
(FHSS) radio frequency signals, which uses a Frequency Hopping (FH)
modulation technique to connect to a BayStack 600 Series Wireless LAN.
With FH, a radio transmits and receives on one frequency for a short period of
time and then pseudo-randomly moves to another frequency every tenth-
of-a-second. FH technology reduces susceptibility to interference from other
transmitters and noise sources in the same 2.4 GHz range since transmission
is constantly shifting from one frequency to the next. The result is better
performance, better security, and system scalability in the use of the product.
• BayStack 660 PC Card
The BayStack 660 PC Card uses Direct Sequence Spread Spectrum (DSSS)
radio frequency signals employing a DSSS modulation technique to connect
to a BayStack 600 Series Wireless LAN. DSSS takes the original data stream,
multiplies it by a spreading factor, and transmits the new altered data stream
on a contiguous group of frequencies (occupying 22 MHz of the available
spectrum). Such a group of frequencies is referred to as a DS channel.
This process provides a high-degree of security.
Note: A BayStack 650 Wireless LAN operates using an FH modulation
technique. But a BayStack 660 Wireless LAN operates using a DS modulation
technique. Since these are different modulation types, the two wireless LANs
cannot be used together.
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