InformationWeek

For those looking to alleviate the costs of below-ground lines, or for those ready to expand the network, one of the wireless-bridge products we tested could be the answer. Capable of spanning distances of 25 miles or more, the products we tested claim to support transmission speeds of 10 Mbps to 12 Mbps-though our assessment revealed that, in most cases, throughput was well under half the advertised rate. All but one of the products we tested-the exception being the Western Multiplex offering-operate at half-duplex. Nonetheless, all will outperform T1 lines and represent a cost-effective solution for campus and metropolitan area network links.

Of the nine high-speed wireless bridges we evaluated, the majority use DSSS (direct-sequence spread-spectrum) radio technology, operating in the unlicensed industrial, scientific, and medical frequency bands. This eliminates the need to obtain a Federal Communications Commission license in order to operate these devices. The maximum distance supported by the tested products varies depending on radio output power, receive sensitivity, and antenna size used. On average, all the products enable links of 1 mile to 15 miles, provided a line of sight is available.

We tested BreezeCom's BreezeNet DS.11 outdoor solution; Cisco Systems' Cisco Aironet 340 Series AIR-BR340 11-Mbps DSSS Bridge; C-Spec's OverLAN RF-11 Plus Wireless Bridge/IP Router; Enterasys Networks' High-Rate RoamAbout outdoor solution; Lucent Technologies' Orinoco (formerly WaveLAN) WavePoint II Wireless Bridge; Pinnacle Communications' PinnacleLink 11/E1 Ethernet Bridge/IP Router; RadioLAN's Wireless Campus BridgeLink Model 347; Wave Wireless Networking's SpeedLAN XE 6000; and Western Multiplex's 12-Mbps Tsunami 5.8 GHz 10Base-T. Destiny Computers and Solectek were invited to participate in our tests but declined.

In our tests, we used variable attenuators to simulate RF-path loss; this let us examine the effects of distance between transceivers. In addition, we evaluated performance, ease of use, management features, and cost.

In the end, RadioLAN's Wireless Campus BridgeLink came out on top. Its ability to outperform the competition, along with its simple setup and strong Web interface, put it ahead of the other products in its class.

Western Multiplex's Tsunami Wireless Ethernet Bridge came in second, with excellent data throughput and great range. Cisco's AIR-BR340, saddled with a more difficult configuration, was third. Its performance also was not as strong as that of RadioLAN's device, but it still offers a solid solution at a reasonable price. The remaining products differed widely in performance: C-Spec's OverLAN RF-11 Plus and Enterasys' RoamAbout Access Point made decent showings, but some of the others performed quite poorly overall.

The wireless bridges we tested are best suited to joining small to midsize LANs that don't have high bandwidth requirements; the throughput we achieved with these products wouldn't be sufficient for networks that need to send large amounts of data over the air. If you're working with a larger network that has higher-bandwidth requirements, you can choose a product such as Western Multiplex's Tsunami 5.8 GHz 100Base-T or Proxim's Stratum 100, which can carry data at 45 Mbps and 100 Mbps, respectively-and carry hefty price tags as well. These products also can handle T1 data and voice traffic simultaneously. If you don't need the higher bandwidth, however, any of the nine products we tested will be cost-effective.

Proximity can be an issue, but the proper antenna can easily get you transmission lengths of anywhere from one to 15 miles, and with amplification, some products can go 25 miles and more.

We realized during our testing that we were examining two distinct classes of products: One group, made up of the C-Spec, Lucent, Pinnacle, and Wave Wireless devices, uses nearly identical management software licensed from Karlnet. Most of these products also use PC Card wireless network interface cards manufactured by Lucent.

The remaining products use other methods and technologies to tackle the issue of transferring packets-some adhere to standards, and others employ proprietary techniques. Although these approaches all have their pluses and minuses, we did notice higher performance overall with the bridges that don't use the Karlnet technology. According to Karlnet officials, this is because of the inherent limitation of the IEEE 802.11 standard to which its technology strictly adheres.

In general, configuration involved setting each device with an IP address, using software that came with the device or a serial connection. Most of the bundled software had no problem finding the hardware automatically. But some bridges required us to change the physical IP address of the machine we were working on; in those cases, for reasons we weren't able to determine, the particular autoscan function was unable to find the bridge.