Vendors take different approaches to WLAN design

Although this was mainly a performance test, we also compared products in terms of their feature sets (see "Features Table"). We should note that vendors responded to a features questionnaire, and we did not verify every answer.

Architecturally, we saw multiple approaches to wireless LAN design. The Bluesocket and Siemens systems are controller-based, with the controller pushing out configurations and performing dynamic RF management. Both vendors say they can manage other vendors' access points, providing captive portal and access control functions. Motorola also offers controller-based systems, but it supplied its new standalone AP-7131s for this project. The Aerohive system's design is unique: Instead of a central controller, multiple access points acting as a "hive" collectively perform that function. The vendor also supplied a central management system, but it's not required for access points to operate.

In terms of RF features, these access points are more alike than different. As noted previously, all use Atheros 802.11a/b/g/n radio modules. All currently use two transmit antennas, although all have at least three transmit antennas in place to make use of so-called 3x3 multiple-in, multiple-out (MIMO) radios once these are available. Data rates are likely to rise once 3x3 radios start appearing either later this year or sometime in 2009.

The Siemens AP-3620 offers three antennas that carry signals from both its 2.4- and 5-GHz radios, while all other access points offer six antennas – three apiece for each radio. Siemens' access points also differed in supporting 2x3 MIMO operation (two transmit antennas, three receivers), while all other access points used 2x2 MIMO.

All systems except Motorola's supported dynamic RF control, adjusting signal strength in response to changes in the radio environment. All systems supported multiple ESSID (extended service set IDs) per access point, a key feature when supporting multiple workgroups.

In the QoS arena, all systems support 802.11e/WMM (wireless multimedia) prioritization mechanisms to reduce latency and jitter for voice and video. All systems except Motorola's also prioritize traffic from Spectralink phones, which use a proprietary protocol.

All systems support the 802.11i/WPA2 suite of security mechanisms to provide authentication, confidentiality and message integrity. We used WPA2 personal mode to secure all test traffic. Also in the security arena, all systems have intrusion detection and prevention features, and all except the Siemens system provide a stateful firewall. Bluesocket's security feature set is especially extensive, not surprising considering the company's heritage in wireless monitoring and access control.

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