LANs /

Go ahead, cut the wires

Enterprise network managers give wireless LANs a stamp of approval.

By Jim Geier
Network World, 02/05/01

Buyer's Guide Engineers at Dow Corning in Midland, Mich., were wasting their time in too many meetings where they couldn't access the network for important documents. So network managers installed an Enterasys wireless LAN in the office to support 130 users with radio-equipped laptops. The laptops give workers access to their e-mail, the Internet and project documents. Now employees can work at their desk, in a conference room or in a colleague's office.

"Staying connected from any location lets the users communicate more effectively and participate in different workgroups throughout the day," says Jim Marshall, Dow Corning's network manager.

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In the past, companies installed wireless LANs to support applications such as inventory management in warehouses and item price marking in retail stores. Even though wireless network interface cards (NIC) cost $800, going wireless was worth the investment because of improved efficiency. High prices and relatively low data rates, however, kept corporate network managers from using wireless LANs for general applications.

With the appearance of inexpensive, high-performance 11M bit/sec products based on the IEEE 802.11b standard, acceptance of wireless LANs for enterprise applications is sharply on the rise. If you've got roaming workers, new offices or are looking to install a LAN without putting in new wires, a wireless LAN may be the answer.

Lower cost, higher efficiency

Like Dow Corning, companies are installing wireless LANs for portable access to the corporate network and providing a better means for collaborating with co-workers.

Some companies are also putting wireless LANs in remote offices, such as a sales office. This gives staffers access to headquarters without having to install an expensive wired network. The wireless LAN is also convenient for visitors from other corporate offices. For example, a manager from headquarters can access printers or e-mail from anywhere within the office, avoiding the need to find an available Ethernet tap or use someone else's computer to connect to the network.

Because of the lower prices, some companies are beginning to favor wireless over wired Ethernet to avoid costs and schedule delays associated with installing Ethernet cabling. For example, the typical price of a wireless LAN NIC is around $200 each, with some as low as $99. While Ethernet NICs (around $50 per card) are lower in cost, you still have to install an Ethernet tap, wall plate and Category 5 cabling, which can cost $200 per tap for labor and materials.

Roll Mercedes Benz USA, in Camden, N.J., installed a Lucent wireless LAN within its corporate office headquarters. For Mercedes officials, the cost savings of avoiding rewiring when moving users in its corporate offices made the project cost-effective. "As far as we're concerned, the program has been a great success," says Larry Roll, Mercedes' supervisor of Mercedes' Telecommunications Group.

Wireless LANs can also extend the network connection throughout a metropolitan area. For example, the city of Greensboro, N.C., Inspection Department uses Cisco wireless LAN access points situated at eight locations throughout the city so inspectors can access the central system at the city headquarters while in the field.

These wireless LAN "islands" connect to the city's central system via optical fiber. Throughout the day, inspectors drive to the nearest island and review itineraries, process inspection information and check e-mail. This application improves efficiency and reduces the time it takes to process inspection reports, as inspectors don't have to drive back and forth to city headquarters.

"The wireless network saves everybody a lot of time. We have calculated that it adds two hours per day per inspector, and we have 32 inspectors. That's like getting eight new people without paying for them," says Walter Simmons, codes enforcement manager for the city.

Some performance issues

While 11M bit/sec is a vast improvement over previous wireless LAN speeds, network managers say the performance tops out at a level that is comparable to shared 10M bit/sec Ethernet. That's fine for e-mail, Web browsing, file access and interaction with corporate systems, but many companies have moved to 10/100 switched Ethernet for bandwidth-intensive applications.

For example, Jim Marshall, Dow Corning's network manager, says a wireless LAN falls short when making large FTP transfers. Switched Ethernet does a good job of handling high utilization when transferring large files, but the sharing of the wireless bandwidth can mean some users will be blocked when a large file transfer is occurring.

The newer 22M bit/sec wireless LANs being released early this year, however, should push wireless LAN throughput to levels comparable to 10M bit/sec switched Ethernet.

Is interoperability the key?

Of course, the purpose of the 802.11 suite of standards is to provide interoperability, and network managers report success with operating multivendor radio cards on the same wireless LAN. While multivendor wireless LANs work, the network will only provide 802.11 functions. You'll lose the proprietary, non-802.11 performance and supportability enhancements that each vendor has added to its product line.

As a result, it's advisable to install a wireless LAN comprised of components from the same vendor to maximize the effectiveness of your wireless LAN. However, you should think about interoperability issues when you've got users who may utilize a wireless LAN at an airport, hotel or convention center for Internet access.

Also, network managers often find that wireless LANs fall short of expected range. Even though a vendor's specifications may say that the wireless has a range of 300 feet, obstacles such as walls, desks and filing cabinets can significantly decrease the range in some directions. This results in an irregular propagation pattern of the radio signal. To provide adequate radio coverage throughout work areas, you should hire someone to perform a radio frequency site survey that determines the number and location of access points, as well as uncover potential radio frequency interference.

Network managers also report a common problem dealing with the availability of electrical power when installing wireless LAN access points. For example, Mercedes' Roll encountered problems when running electrical wires to each access point. These installations generally require hiring an electrician to route and splice electrical wires to each access point. However, most of the wireless LAN vendors are beginning to offer methods to supply power to each access point over its Cat 5 cable connection to the Ethernet switch. This form of power delivery will greatly speed installations by eliminating the need to install electrical wires to the access points.

Faster data rates are on the way

By the end of 2001, vendors should begin initial shipments of IEEE 802.11a-based wireless LANs, which offer data rates of up to 54M bit/sec. Instead of using 802.11b's direct sequence spread spectrum, the 802.11a standard specifies orthogonal frequency division multiplexing (OFDM) for transmitting data in the 5-GHz frequency band. OFDM not only provides higher data rates, but can also better tolerate transmission distortions resulting from multipath propagation and radio frequency interference.

Another standard, HiperLAN/2, is based on the 5-GHz OFDM modulation. However, the standard is not scheduled for completion until early 2002. It's likely the 802.11-based products will prevail because of earlier product availability and network manager's familiarity with the 802.11 standards. Furthermore, existing frequency allocations will likely limit use of HiperLAN/2 to Europe, with 802.11a the standard in North America.

The existing and near-term 802.11 standards provide a strong basis for effective wireless LAN products, capable of supporting enterprise applications.