Wireless LAN technology is nothing new. But something different is happening in the wireless industry this year. Vendors across the board are shipping truly interoperable hardware that delivers data rates approaching those of Ethernet. The wireless industry is finally gaining some momentum in the enterprise market. Perhaps it's due to lighter, more portable notebooks. Perhaps it's because of WECA, the Wireless Ethernet Compatibility Alliance (www.weca.net), a highly active group of vendors with a mission to guarantee interoperability across all 802.11b products. Or maybe it's attributable to the broadband revolution, which is enabling Wayport and others to provide low-cost 802.11b connectivity to many hotels and airports. By far, the most compelling reasons are interoperability, cost and performance. Vendors have made quantum leaps in all three areas, making wireless LANs a viable technology for the masses.

Whatever the reason, vendors are embracing and investing in 802.11b high-speed wireless LANs. With Cisco Systems' recent acquisition of Aironet, all the major enterprise infrastructure providers--Cisco, Enterasys Networks, Lucent Technologies and Nortel Networks--have a wireless story to sell. Never before has there been such a strong backing of wireless technology. Is it time for you to consider a wireless solution?

In the Schneider National labs in Green Bay, Wis., we tested 802.11 high-rate (802.11b) wireless solutions from 11 vendors. We evaluated products from BreezeCom, Cisco, Compaq Computer Corp., Enterasys, Farallon Communications, Intermec Technologies, Lucent, NoWires Needed, 3Com Corp., Zcomax Technologies and Zoom Telephonics. We also tested products that are designed to coexist in an 802.11b environment (see "Top Ten Things To Know About Wireless.")

Cisco's Cisco Aironet 340 Series PCI Adapter (AIR-PCI342) and Cisco Aironet 340 Series PC Card (AIR-PCM342) led the pack, with raw throughput under Microsoft Windows 98 topping out at almost 6 Mbps--not bad for 11-Mbps wireless solutions. We were also impressed by Cisco's access-point solution, the Cisco Aironet 340 Series Access Point (AIR-AP342E2C), which earned top marks for manageability and ease of use.

Wireless Scalability

The ability to scale the amount of bandwidth and the number of users your wireless LAN can support is critical. Specifically, most vendors claim they can support 65 users or more per wireless LAN segment. But what effects do multiple wireless users have on segments? We did extensive testing to find out how well the technology scales. To test different aspects of scalability, we used three wireless clients and 12 workstations to generate our traffic load. We tested in three configurations: three notebooks associated to a single access point; three notebooks associated to three access points using the same frequencies but different network IDs; and three notebooks associated to three different access points, all using different frequencies. These configurations show how wireless scales in a single access-point environment, a multiple access-point environment and a multichannel, multiple access-point environment.

Our tests revealed a few important facts about 802.11b. A single PC Card can saturate a wireless segment. Whether you have one user or 50 on a segment, they will contend for the same amount of bandwidth. After all, this is a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) network, and like shared Ethernet, this shared network has a finite capacity and a certain amount of overhead associated with it.

Deploying multiple access points on the same frequency adds range and fault tolerance but won't increase your overall bandwidth. We found that deploying multiple access points can increase the fault tolerance of a wireless segment. When one access point in a segment fails, the wireless clients seamlessly roam to the other access points without interrupting service.

Using three clients on three different frequencies dramatically improves performance. The use of multiple channels is similar to using a switch instead of a repeater on a wired network. Each wireless channel provides about 5 Mbps of throughput in the wireless environment. Cisco, Enterasys and Lucent solutions wowed us with 14 Mbps of aggregate throughput to three wireless clients, each on its own frequency. Unfortunately, most of the units did not let us force association to a particular access point. Thus, to achieve these rates, you must build multiple overlapping cells with different frequencies. This can be tedious if the vendor does not let you specify which access point to associate to. It boils down to manually entering the network ID on the client. Which access point you associate to is based entirely on signal strength for most products; unfortunately, access-point load should play into that equation. 3Com's setup is an exception: It takes both signal strength and load into consideration when associating to an access point.

In the 802.11b standard, under U.S. FCC rules there are 11 distinct channels. These channels represent the center frequency of the wireless transmission wave. In practicality, you can have only three operational frequencies in a given area; thus, 14-Mbps aggregate throughput is close to the best you're going to get using today's technology. This reveals the biggest weakness in wireless LAN--it's not Ethernet, and there is significant overhead in the 802.11b protocol and associated CSMA/CA architecture.