With the announcement this week from Meru that it will demonstrate new gear based on the 802.11 draft n specification at Interop and ship this summer, is it fair to say that “n” has entered the enterprise?
Before we get too excited, let’s look at where we are today and then come back and take another look at the Meru announcement. Quite frankly, things are looking promising but there are some caveats. First, for the good news.
We recently conducted a number of lab tests with new draft n gear and the results were encouraging as far as interoperability. For the first time, MIMO gear of different manufacturers are actually talking to each other. Great!
The test included Linksys business class APs and client adapters, as well as D-Link and Netgear, operating in 802.11n only mode. The hardware included a mix of Marvell and Atheros chipsets.
With all the major laptop vendors including Dell, HP, Toshiba, and Lenovo shipping draft-n in new laptops and cards available from all the 2nd-tier networking vendors, can enterprise 802.11n be far behind? Many are waiting for the Cisco shoe to drop. If history repeats itself, Cisco is typically the last to enter a new market. They traditionally wait for standards to finalize before shipping new product.
Meanwhile, to benefit early adopters (both vendors and users), the Wi-Fi alliance (of which WildPackets is a member) will certify draft-n (Draft 2) interoperability later this year. The Wi-Fi alliance, as you may recall, gives us an early alternative, but complimentary to the 802.11 standards such as WPA before 802.11i (and now Wi-Fi WPA2), WMM before 802.11e, and so on.
Now for the caveats. While one can benefit from MIMO on a single 20 Mhz channel, 802.11n requires two channels for maximum throughput. Using OmniSpectrum during our tests, we saw that the 2nd channel allocated was 4 channels from the primary channel – i.e. channel 11 as primary and 7 as secondary, 1 primary, 5 secondary, etc.
This impacts enterprise 802.11n roll-outs. For instance, the old honey-comb coverage rule of 1-6-11 in the 2.4 Ghz b/g band need no longer apply. Think about it. At 300 Mbps using 40 MHz and two streams, there is only one non-interfering, non-overlapping deployment possible! The best all 802.11n coverage may be a 1 and 5 and 7 and 11 scenario, but channels 5 and 7 are still too close together to be practical.
And of course there are millions of legacy devices to deal with that will be with us for awhile. How to stagger and optimize coverage for n and b/g?
The ideal solution? Ressurect the 5 GHz 802.11a band (which is an important aspect of 802.11n draft 2). The 5 Ghz band certainly has some benefits including staying out of the way of b/g and it’s able to accommodate more n channels (up to 3 non-overlapping in fact). Unfortunately, 5 GHz signals peter out quicker than 2.4 GHz given the same transmit power (i.e. you get less distance with 5 GHz), so we are back to a similar problem we had with b/g vs. “a.”
Meanwhile, there is at least some performance gain even for minimal single channel n (130 Mbps promised with 2 stream MIMO) deployment. In fact Intel is pondering only single channel support to start with Centrino n, because of all the b/g legacy concerns. Some 802.11n APs will also be smart enough not to offer the 2nd channel when b/g is present. But again, this speed bump effectively throttles n when in use in the 2.4 Ghz band.
Back to Meru. Their new AP300 can carry up to two 802.11n radios or one 802.11n and one a/b/g radio. Interestingly, Meru will support 802.11n in the 5 GHz band, but where are the clients? All of the aforementioned laptop vendors currently support draft n in the 2.4 GHz band.
For of the majority of Enterprises that have rolled out b/g, it seems the best we can hope in the short term is to support pockets of selected 802.11n users that need the boost. Enterprises that have included 5 GHz in their plans and have the infrastructure to support it may be in better shape to take on 802.11n for total coverage– provided the clients are there. I would not be surprised if Cisco announces support for 802.11n in the 5 GHz band before year end. If so, expect a torrent of new client (and AP) hardware to follow from them and many others.