Meru makes first move on enterprise 802.11n WLANs

Vendor promises 300Mbps wireless

The first enterprise-class wireless LAN products supporting the IEEE 802.11n draft standard, and promising data rates of 300Mbps, have been announced this week by Meru Networks.

Meru says it will ship this summer a two-radio access point, a five-blade controller and new software that handles wireless data traffic at the edge of the network instead of routing all of it through a central wireless controller.

The new draft 11n products will be showcased at the Interop Las Vegas show later this May. They won’t be cheap. The new access point will be priced at about $1,500, which is nearly two times the price of Meru’s current high-end 802.11a/b/g access point. Pricing for the new controller is expected to be about $65,000.

Bluesocket last year introduced an enterprise access point based on the same technology that forms the heart of the 11n high-throughput project. And there are some “draft 11n” or “pre-11n” WLAN products already on the market today. But these are typically aimed at home or small business office networks, which usually are created using just one access point. Data rates range from just under to just over 100Mbps. Meru executives say that deploying 11n in big enterprise WLANs could mean upgrading wireless switches and possibly even parts of the wired switch fabric, because of the greatly increased 11n throughput.

Risks of going prestandard

The company is taking a risk marketing a product that complies with only a draft, and not a final, IEEE standard. But two considerations may outweigh the usual enterprise demand for standards-based products. One is that the IEEE 11n working group earlier this year approved draft 2 of the high-throughput standard. WLAN vendors and industry experts say they expect very few changes, and expect those changes to be made via software updates, between now and the final standard in 2008. And the Wi-Fi Alliance is about to begin certifying interoperability between draft 2 11n gear, as it has done for the 11a/b/g standards.

Second, 11n wireless LANs promise a very large increase in data rates and useable throughput. With the standard 20-Mhz channels for 802.11, users of 11n gear should see minimal data rates in the 100-150Mbps range, compared to 54Mbps for 11g and 11a WLANs today. But using 40-Mhz channel option specified in 11n, with a 3-antenna setup for each WLAN device, will double that to 300Mbps.

That’s the configuration and the data rate Meru executives are promising for the AP300 family of thin access points, and the new, high-end wireless controller, the MC5000. Actual throughput, shared among 11n clients attached to an 11n access point, will likely be about half or somewhat more than half of the data rate, according to Meru executives.

The 11n standard relies on a technology called multiple input multiple output (MIMO), which separates a data stream into usually two or three sub-streams, each one transmitted via a separate antenna. Typically, radio transmissions bounce around and reflect off objects, creating interference called multipath. But MIMO uses several techniques in effect to collect the capacity of these paths, and reassembles the sub-streams via two or three receiving antennas. The result is a multiplication of wireless data rates, and the ability to sustain higher data rates at much longer distances compared to today’s WLANs.

Wireless LAN access point and controller

The AP300 will be able to carry one or two radios, both based on radio chipsets from Atheros Communications. The two radios could be both 11n or one 11n and one 11a/b/g to support existing WLAN clients. The device has one 10/100/1000Mbps Ethernet port.

The new MC5000 is a five-slot chassis. Each of the five boards can support up to 200 access points, and up to 1Gbps of throughput.

Meru’s architecture will let enterprises deploy 11n on both 2.4- and 5-Ghz bands, the former used today for 11b/g client, the latter for 11a clients, says Steve Troyer, vice president of product marketing. Meru’s WLAN can be set up to create three 40-Mhz channels in the 5-Ghz band and one 40-Mhz channel in the 2.4-Ghz band with one 20-Mhz channel left over. Troyer says Meru is the only vendor today that can run 11n clients at the full 11n data rate in the 2.4-Ghz band. Assuming the 11n client also has a 3-antenna configuration, it could be assigned to any of these four 40-Mhz channels, each with a data rate of 300Mbps.

The remaining 20-Mhz channel will have 54Mbps. Legacy 11b/g clients could then be segregated on that channel. Otherwise, Troyer says, these as well as existing 11a clients will force the 11n channel to slow down to accommodate them.

Wireless LAN software

To handle all this additional capacity, Meru is introducing an optional software update for its controllers, a program called the 3-Tier Traffic Distribution System. In effect, the software lets each controller distinguish between regular data packets and the control packets used in administering the WLAN. The new TDS will let network administrators create a hierarchy of existing and new Meru controllers. Each controller, including the new MC5000, can be configured to handle only control traffic, or only data traffic, or both.

That means a controller on the network edge now can be set up to pass control packets back to a central controller for processing, but on its own send data packets directly to the destinations within its domain. The goal is to minimize 11n data traffic being sent back to a core wireless controller that could otherwise create a bottleneck, according to Troyer.

The 40-Mhz channels create a new issue for enterprise deployments, according to Troyer. By combining two channels in the 5-Ghz band, 11n reduces to three the number of non-overlapping channels (channels that have the cleanest signals because there is no co-channel interference). That’s the same number of non-overlapping channels available today for 11b/g WLANs, a fact that can limits the number of access points you can group to serve lots of users or give users maximum throughput.

Troyer says that Meru’s WLAN architecture sidesteps these problems in 11n as it does in traditional WLANs. All Meru access points in an enterprise WLAN can be put on the same non-overlapping channel (creating a single “virtual” access point, having one Basic Service Set Identifier or BSSID), and clients associating with any access point get the full bandwidth available. If more capacity is needed, the second and third channels can be made available on each access point, and clients on those channels also get the full 802.11 bandwidth available (whether 11g, 11a or 11n).

Learn more about this topic

Wireless vendors target high-bandwidth gear

IEEE approves next draft of 802.11n

Q&A: Wi-Fi Alliance exec defends about-face

NW ClearChoice Tests [one-time registration needed]: MIMO, 'draft n' gear blazes near 100Mbps

Foundry airs high-density WLAN gear

Overview of Meru’s WLAN technology

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