Wireless Networking

802.11?

What's with all the suffixes?

Standard Data Rate Mbps RF GHz Channels Range in feet Comment
802.11 2, 1       Non starter
802.11a 54, 48, 36, 24, 18, 12, 9, 6 5
(5.725 to 5.850)
12 Up to 500 High density
802.11b 11, 5.5, 2, 1 (2.4 to 2.4835) 3 Up to 1,000 Common
802.11g 54, 48, 36, 24, 18, 12, 9, 6,11, 5.5, 2, 1 (2.4 to 2.4835)  3 Up to 1,000 Replacement
for 802.11b
with higher
data rate and better security

A History

The 802.11 Standard

The IEEE ratified the initial 802.11 standard. The initial products sucked big time!  No interoperability. Just like modems! Never learn eh!?!

802.11a

The cost disadvantage of an 802.11a system is not limited to the price of the individual components. Total cost of ownership of an 802.11a system must take into account the number of access points required to cover the network geography.

Range is reduced because it uses the higher 5 GHz frequency band: it's half the range of 108.11b.

More sensitive to obstructions.

802.11b

802.11b has a theoretical speed of 11 megabits per second.  5 Mbps typical

This is the mature standard running at 2.4 GHz.

802.11g


Products

Linksys WPC54G Wireless-G - 22 Mbps

Netgear FM-114P winner

Linksys BEFW11S4 second

D-Link DI711 At a distance of 23 meters, this unit still manages a speed of 450 kilobytes per second.

Here's what I ended up with.

Security and other optional features

Wired Equivalent Privacy (WEP) was added to the 802.11 standard to provide a level of security that was equivalent to the level of physical boundaries on a wired network.

This uses RC4 encryption algorithm between the client and the access point. WEP not only offers privacy, but also adds authentication by requiring an encryption key for access.

Most 802.11b products include it. Enabling WEP will decrease performance.

WEP key format ASCII and Hexadecimal. Some products expect you to know your ASCII table!

SSID (Wireless Network Name)

ESSID

The ESSID (Extended Service Set ID) defines the access point's network name. Your client machines need to be configured to associate with an access point with that ESSID. Some clients allow a wild card in the ESSID configuration. In this mode, they will associate with the strongest access point, regardless of its ESSID.

Session keys

MAC address filtering

VPN system

SSL

Response Time  as in ping - 1ms - negligible impact.

Kit

Client Adapters

access points (AP)

Ethernet bridge - probably a required feature

used to be simple:

Access Points had just one mode, which allowed client devices operating in Infrastructure mode to associate (connect) and access the wired LAN to which the Access Point was connected.

wireless client adapters

new class of products, also capable of wireless bridging. These products, such as Linksys' WET11, and Hawking's WB320, go by different names, but provide the ability to take any device with an Ethernet connector and connect it to a wireless network.

an Access Point is a wireless transceiver that connects a wired LAN with wireless clients.

An AP in its basic form can only connect to wireless clients, and not to another AP.

"Bridge" refers to a device that connects two LANs

Some access points include this feature.

most companies support bridging between their products only

wireless router a AP with DHCP and firewall

Wireless Ethernet Bridges

The most important thing you need to know about devices of this class is that they cannot act as Access Points! This means that you can't set them to a mode where wireless clients that are set to Infrastructure mode will be able to associate, or connect, to them.

radio channel

WEB config - default IP may be silly! 192.168.1.254

Chip sets

Linksys  Broadcom

NETGEAR MA401 (Original Intersil PRISM II based card)

ORiNOCO Gold (Agere Systems chipset)

D-Link DWL-650+ (TI ACX100 chipset)

D-Link's Intersil PRISM GT-based products

NETGEAR WAB501 (Atheros 5100X dual-band chipset)

Antennas

RP-SMA Male

RP-TNC female

SNMP - features..

Firmware releases

Absolutely dire - just like modems!

Advice recommendations...

SMC wireless AP 2652w Belkin

PC world. Linksys wap + pcmcia card 100

Use good quality cards / dongles. The cheaper ones tend to have poorer receiver performance which reduces their range in noisy environments. Make sure you can attach external antennas to whatever you buy.

Cisco and Lucient/Avayra/Orinoco are IMO the best bets. If you are concerned about bandwidth you may wish to consider 802.11A (Hiperlan 1) - the prices have fallen dramatically over the last year or so.

Make sure you enable security and use a good shared secret on the hub and cards. You may wish to consider using VPN and authentication over the radio link. Assume that anything you transmit can be monitored and that services are available to anyone who has a WLAN card.

I recently say a comparison on receiver performance. Linksys came out badly with their access point having a very poor BER, speed and range in the presence of noise.

Links

Wi-Fi Alliance (formally Wireless Ethernet Compatibility Alliance

Toms hardware

http://www.smallnetbuilder.com/Sections-article15-page2.php

www.54g.org

http://www.kcip.com/wireless/

http://www.wlan.org.uk/operational_wlan_sites.html

http://www.bt.com/broadband/

http://www.wlan.org.uk/