802.11a Wireless Networking with Windows XP
Published: July 29, 2002
By Barb Bowmanm, Windows XP Expert Zone Community Columnist
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For the typical SOHO user with a broadband connection that tops out at 3 Mbps downstream, an 11 Mbps 802.11b wireless LAN used for Web browsing, e-mail, occasional file transfers between local computers, and audio streaming on a local area network is more than adequate. But the effective throughput of 802.11b tops out at around 6 Mbps. So it doesn't have the horsepower needed for streaming local video or for moving large files and graphics over a LAN rapidly. I transfer lots of files between computers on my network and want to stream video locally, and I've been somewhat disappointed with the slower speeds my 802.11b networks provide.
Here's the good news: a faster wireless kid on the block, 802.11a, provides wireless throughput speeds fast enough for streaming video. Its LAN performance changes everything! 802.11a provides the required speed and performance for file and data transfers between computers on a network that just aren't possible with 802.11b. The D-Link and Linksys wireless access points and client adapters I've been using have demonstrated a 20-22 Mbps effective throughput in my environment, where computers are used two or three floors away from one of the 802.11a access points. This more than triples the performance of my 802.11b equipment and provides near wired speeds.
I'm now in the fast lane and with the amount of data I transfer between computers every day, I'm saving time and increasing my productivity as the result of this faster technology.
Comparing the 802.11a and 802.11b Standards
The Institute of Electrical and Electronics Engineers (IEEE) 802.11a wireless standard has a maximum stated throughput of 54 Mbps in the 5-GHz band and uses orthogonal frequency division multiplexing (OFDM) modulation technology. (For more information about this technology, see the OFDM Forum.)
The IEEE 802.11a specification will be used as a basis for devices certified for interoperability by the Wireless Ethernet Compatibility Alliance (WECA). Certification of the first 802.11a hardware is now underway and devices carrying the certification should reach the market by the fall of 2002.
A complete comparison of 802.11a and 802.11b technologies merits a larger discussion. However, a high level overview of the two technologies is provided in the chart below. Note that both standards operate in unlicensed bands and that currently, 802.11b shares the 2.4 GHz band with some cordless telephones, microwave ovens and other devices and that 802.11g will share the same 2.4 GHz band and issues.
Stated Maximum Throughput | 54 Mbps | 11 Mbps |
Effective Throughput | 20 Mbps | 5 Mbps |
Data Rates (Mbps) | 54, 48, 36, 24, 18, 12, 9, 6 | 11, 5.5, 2, 1 |
Band | 5.150 GHz-5.350 GHz | 2.412 GHz-2.462 GHz |
Discrete Non-Overlapping Channels | 8 | 3 |
Modulation Technology | OFDM (orthogonal frequency division multiplexing) | DSSS (Direct Sequence Spread Spectrum) |
Approx. Maximum Rated Indoor-Outdoor Range | 300 feet indoors-1000 feet outdoors | 300 feet indoors-1000 feet outdoors |
Easy Installation and Configuration
Although wireless 802.11b technology was available for some time before the launch of Windows XP, few 802.11b vendors were able to supply drivers with full wireless zero configuration support on the date of launch. The 802.11a client cards that are now appearing on the market are based on the Atheros 802.11a reference design and drivers that fully support Windows XP. The drivers supplied with the client 802.11a PC Cards from both D-Link and Linksys, as well as the D-Link 802.11a PCI adapter that I'm using on my SOHO LANs both support the Wireless Zero Configuration service in Windows XP, including auto discovery of available wireless LANs, WEP security (40/64 and 104/128 bit), 802.1x authentication support, and ad hoc or infrastructure configuration.
As expected, after installing the card and driver for any of these 802.11a cards, Windows XP automatically displays the available 802.11a wireless access points, as shown in Figure 1).
Figure 1
1. | Click the Advanced button to access the Wireless Networks tab and configuration options. |
2. | From the list of Available networks, select the wireless access point, and click Configure as shown in Figure 2.  Figure 2 |
3. | Specify WEP settings in the Wireless Networks Properties dialog box, as shown in Figure 3.  Figure 3 |
Configuring Non-Standard Settings
Note that Atheros has included two proprietary enhancements in their reference design and drivers that have been adopted in varying degrees by the vendors offering hardware based on the Atheros 5000 chip. These enhancements included a non-standard 152-bit WEP encryption level and an extension to the 802.11a specification at 72 Mbps called Turbo mode. You can't configure these through the Wireless Networks tab in Windows XP and in some cases, they're not available at all on a Windows XP-based computer.
If Turbo mode is desired and the vendor has made it available in the Windows XP driver, the access point must be configured to enable this speed, and all 802.11a wireless clients must be configured for Turbo access as well. (This column is based on the standard 802.11a and 64- or 128-bit WEP.)
On the client side, these extra, non-standard settings are handled and documented differently by each vendor. For example, Linksys is currently documenting that these additional settings are not available for Windows XP users. D-Link takes advantage of the capability of a driver to add a property page to the user interface, and has added a properties page named Settings that lets the user specify all WEP settings. D-Link's Settings properties page includes the ability to set WEP at 152 bits by means of a Security tab and an interface to set the optional Turbo mode using a General tab.
It's too early in the roll out of 802.11a equipment to speculate whether the 152-bit encryption extension to WEP and the Turbo speed extension to the 802.11a standard will achieve critical mass and become a necessity.
Upping the Hardware Ante
The 802.11a PC Cards are 3.3 volt CardBus (32 bit interface) in architecture, which the higher networking speeds of 802.11a require. Most modern laptops are equipped with CardBus slots that can accept both CardBus and the older PC Card (16 bit) devices. Note that the speed capabilities of the older 16-bit PC Card architecture tops out at around 20 Mbps, which explains the need for moving to CardBus. USB 1.1 is not able to supply the speed needed for high speed 802.11a wireless networking, thus the unavailability of a USB 1.1 device for desktops. If your needs include 802.11a enabling a desktop, D-Link today is alone in the field with a high quality 802.11a PCI adapter.
Access Points and Their Interfaces
The D-Link DWL-5000AP and the Linksys WAP54A have a very similar feature set and use an internal Web page for setup and monitoring. This is a welcome change from many of the proprietary SNMP or USB clients and tools used for a large number of 802.11b access points. For security, D-Link provides settings to change both the administrative user name and password, while Linksys offers the ability to change only the password. Both Access Points are supplied with static IPs; D-Link is set at 192.168.0.50, which complies with the default IP range of D-Link brand routers of 192.168.0.* Linksys is set at 192.168.1.252, which complies with the standard 192.168.1.* range used by default in the Linksys brand routers.
If the existing network does not use the appropriate range, first-time configuration will need to be performed using a wired Ethernet adapter, statically configured in the same IP range as the access point. Once reconfigured with the appropriate IP and subnet, future maintenance can be done over wireless, using Internet Explorer.
D-Link includes a console port and cable with the DWL-5000AP for a direct cable connection using HyperTerminal. I found this particularly useful after changing the IP of the access point and forgetting to write it down. Using the command line interface in HyperTerminal, typing "help" invoked a list of command parameters. I was able to specify a new IP for the access point and then configure the access point normally using Internet Explorer over the wireless connection. (And I've added the URL to my Internet Explorer favorites so future memory lapses don't require as much effort.)
One of the best features of the Web browser interface for both access points is the connectivity information available from the embedded statistics application. Each access point or client station's status is displayed, along with its respective MAC address.
Selecting the MAC address opens a Web page that supplies information on either the access point itself or the associated/authenticated clients. In figure 4 below, the access point uptime is shown as 1 day and a little over 18 hours and the number of times the access point has authenticated one or more clients is shown as 8.
Figure 4
Similar information on each individual client includes both receive and transmit speed, errors, and associations/disassociations. It is impressive to watch this information update dynamically in real time every few seconds.
Mixing Wireless Technologies
Is your 802.11b wireless SOHO LAN and equipment obsolete? Absolutely not. You can easily add an 802.11a access point to your existing network even if you've already implemented 802.11b connectivity. Even if your network includes a wireless 802.11b wireless router, you can create a mixed wireless network by plugging an 802.11a access point in to an available port on the router. The two technologies will not interfere with each other in any way as they use completely different frequencies (2.4GHz for 802.11b and 5 GHz for 802.11a).
Several vendors have announced dual-radio (both 802.11a and 802.11b in the same device) access points, targeted at the enterprise market. My workhorse SOHO LAN now includes a UPnP router connected to my cable modem, both 802.11a and 802.11b access points connected to the UPnP router, and client devices including an 802.11b video security camera (see my column, Adding a Wireless Internet Camera, for more information), and multiple computers that are equipped with either 802.11a or 802.11b client cards. My travel kit now includes both 802.11b and 802.11a PC Cards. Although there are no public 802.11a networks available at this time, it's possible that some existing wireless providers may add dual-radio access points at some future date.
New Wireless Products
By the end of 2002, a new generation of Atheros chipsets will power smarter wireless client adapters and access points. Additionally, Cisco, Intel, Intersil, and others should be entering the market with similar multiple radio adapters. Looking ahead to the next generation computer-based personal/digital video recorders, a wireless 802.11a LAN will enable streaming video from the living room to a computer and connected playback device in a bedroom or den. Am I excited by the promise of what my wireless home will look like in the next few years and what kinds of devices I will be able to connect? The answer is a resounding yes.
And in the coming months, as my wireless world expands to include new devices and technologies, you'll be able to read about it here in the Expert Zone.
Suggestions for Future Columns
If you use Windows XP at home and have a topic you'd like to see covered in a future column, feel free to write me at: barb@mvps.org. I'll be glad to receive ideas and suggestions. Please understand that I can not answer individual e-mail messages or even acknowledge them.
Barb Bowman enjoys sharing her own experiences and insights into today's leading edge technologies. She is a product development manager for AT&T Broadband Internet Services, but her views here are strictly personal.
