ZyXEL Communications ZyXEL ZyWALL 2WE User Manual page 353

ZyWALL 2 and ZyWALL 2WE
The IEEE 802.11 specifies three different transmission methods for the PHY, the layer responsible for
transferring data between nodes. Two of the methods use spread spectrum RF signals, Direct Sequence
Spread Spectrum (DSSS) and Frequency-Hopping Spread Spectrum (FHSS), in the 2.4 to 2.4825 GHz
unlicensed ISM (Industrial, Scientific and Medical) band. The third method is infrared technology, using
very high frequencies, just below visible light in the electromagnetic spectrum to carry data.
Ad-hoc Wireless LAN Configuration
The simplest WLAN configuration is an independent (Ad-hoc) WLAN that connects a set of computers with
wireless nodes or stations (STA), which is called a Basic Service Set (BSS). In the most basic form, a
wireless LAN connects a set of computers with wireless adapters. Any time two or more wireless adapters
are within range of each other, they can set up an independent network, which is commonly referred to as an
Ad-hoc network or Independent Basic Service Set (IBSS). See the following diagram of an example of an
Ad-hoc wireless LAN.
Diagram E-1 Peer-to-Peer Communication in an Ad-hoc Network
Wireless LAN and IEEE 802.11 21