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Wireless Bridges Span the Divide May 1, 2000 By Michael J. Utell and Asad Irshad
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 assessments 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 MAN (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 ISM (industrial, scientific and medical) frequency bands. This eliminates the need to obtain FCC licensing 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 one to 15 miles, provided a line of sight is available.
Our Test Field
We tested BreezeCom's BreezeNet DS.11 outdoor solution; Cisco Systems' Cisco Aironet 340 Series AIR-BR340 11-Mbps DSSS Bridge; C-Spec Corp.'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; Radio- LAN's Wireless Campus BridgeLink Model 347; Wave Wireless Networking's SpeedLAN XE 6000; and Western Multiplex's 12-Mbps Tsunami 5.8 GHz 10BaseT. Destiny Computers and Solectek Corp. were invited to participate in our tests but declined.
In our tests, we used variable attenuators to simulate RF-path loss, which let us examine the effects of distance between transceivers (see "How We Tested Wireless Ethernet Bridges"). In addition, we evaluated performance, ease of use, management features and cost.
In the end, RadioLAN's Wireless Campus BridgeLink walked away with our Editor's Choice award. 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.
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