ZyXEL Communications ZyWALL 5 User Manual page 485

A wireless LAN (WLAN) provides a flexible data communications system that you can use to access
various services (navigating the Internet, email, printer services, etc.) without the use of a cabled
connection. In effect a wireless LAN environment provides you the freedom to stay connected to the
network while roaming around in the coverage area.
Benefits of a Wireless LAN
Wireless LAN offers the following benefits:
1. It provides you with access to network services in areas otherwise hard or expensive to wire, such
as historical buildings, buildings with asbestos materials and classrooms.
2. It provides healthcare workers like doctors and nurses access to a complete patient's profile on a
handheld or notebook computer upon entering a patient's room.
3. It allows flexible workgroups a lower total cost of ownership for workspaces that are frequently
reconfigured.
4. It allows conference room users access to the network as they move from meeting to meeting,
getting up-to-date access to information and the ability to communicate decisions while "on the
go".
5. It provides campus-wide networking mobility, allowing enterprises the roaming capability to set
up easy-to-use wireless networks that cover the entire campus transparently.
IEEE 802.11
The 1997 completion of the IEEE 802.11 standard for wireless LANs (WLANs) was a first important
step in the evolutionary development of wireless networking technologies. The standard was
developed to maximize interoperability between differing brands of wireless LANs as well as to
introduce a variety of performance improvements and benefits. On September 16, 1999, the 802.11b
provided much higher data rates of up to 11Mbps, while maintaining the 802.11 protocol.
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). The
following diagram shows an example of desktop and notebook computers using wireless adapters to
form an Ad-hoc wireless LAN.
Wireless LAN and IEEE 802.11
Wireless LAN and IEEE 802.11
ZyWALL 5 Internet Security Appliance
Appendix E
E-1