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3 things to consider in selecting 3x3:3 MIMO Wi-Fi access points

by Hemant Chaskar on Oct 18, 2012

Currently, market is inundated with announcements from vendors on 3-stream MIMO APs. Sure enough AirTight has also launched one being at the forefront of Wi-Fi technology. But what sticks out of some of those announcements is lopsided mention of high speed wireless connectivity, even to the extent of misleading claim of 900 Mbps for the dual radio 3-stream APs albeit with a sneaky word "upto" before the number. While connectivity speed is important consideration (actually now a commodity available out of 3-stream Wi-Fi chipsets), that consideration alone does not help to come up with a good game plan for deploying 3-stream Wi-Fi. A more holistic thinking taking into account real world performance, security, and next generation Wi-Fi architecture is required when selecting 3-stream MIMO APs.

1. Understand caveats that impact link performance.
First let us analyze the 900 Mbps connectivity claim – like network engineers. In order to obtain total 900 Mbps connectivity, each radio has to deliver 450 Mbps. Now 450 Mbps is achievable (at short distance from AP, typically less than 25 feet) only when radio operates with 40 MHz channel bandwidth, and that is where the catch is! We all know that it is not possible to operate 2.4 GHz radio with 40 MHz channel bandwidth in real network setting, due to narrow width of 2.4 GHz band and due to interference in that band. These so called 900 Mbps dual radio APs have one radio in 5 GHz band and another in 2.4 GHz band - they are all made from standard ODM designs. If you can’t operate with 40 MHz bandwidth, maximum link speed of that 3-stream 2.4 GHz radio is 216.7 Mbps precisely. So, the AP marketed as 900 Mbps maximum connectivity instantly shrinks to AP with 667 Mbps maximum connectivity when it arrives into your network! So please don’t lose your money on that 25% of claimed Mbps that you are never going to see in your network.

Also, to leverage 3-stream radio on the AP, you need 3-stream radio on the client. I was looking for a good reference on tablet radios, when I came across this Amazon Kindle Fire announcement. It states, and shows in comparative graph with iPad3 and Google tablet (which are called 1 antenna, to be read 1-stream radio in this context), that Kindle Fire is the only dual antennas (to be read 2-stream radio in this context) tablet available today. I do not have such concise reference on laptops, though I know newer high-end laptops have 3 antennas and 3-stream radios in them. However, there is a fundamental multiple access principle that when you mix low and high speed clients, the aggregate performance of the AP will be dominated by low speed clients. This is because, multiple access protocol of Wi-Fi is fair in terms of granting access to clients, but once access is obtained, low speed clients unfairly consume longer time on the channel due to low transmission speeds compared to high speed clients. So, when you have meaningful percentage of sub-3-stream clients like iPads, iPhones, Androids, Kindle Fires, VoIP phones, old laptops, POS terminals in your network, real life total throughput would be more like 1- or 2- stream, rather than 3-stream! To get full mileage out of 3-stream radios, you will need to have some strategy on clients side as well.

2. Build security into DNA of your Wi-Fi.
Just like we expect high-speed car to also have anti-lock brakes, we ought to expect 3-stream APs to give you both speed and security. Traditionally, Wi-Fi and wireless intrusion prevention had to be addressed and budgeted separately. That kept many networks deprived of comprehensive security cover. But 3-stream Wi-Fi selection or upgrade offers another opportunity to change that. If you select 3-stream APs which can combine comprehensive “dual-band” “full-time” scanning wireless intrusion prevention with state-of-the-art 3-stream Wi-Fi radio in single device that is fully software configurable, you can get two birds in one stone. And when you select AP platform that has security built into its DNA, you don’t pay extra licensing or feature cost even for the absolute best security. You can also reduce scanning radios BOM by 50% when you select right 3-stream AP platform. AirTight can proudly meet both those benchmarks with its new C60 3-stream AP.

A word of caution on security: Just as eyewash 900 Mbps claims in some announcements, there are also eyewash claims on WIPS (wireless intrusion prevention system) features in many annoucements. Eyewash security means your network can be washed away by breaches and policy violations in the scale and complexity of the real world deployment and you would be forced to allocate abundant human resources to manage on a daily basis lacunas of the security system such as false alarms and need for extensive configuration and maintenance. Security has to be run through the most stringent criteria for both the strength and the TCO.

3. Shun the inefficient controllers.
3-stream AP selection or migration also presents excellent opportunity to lay the foundation for the next generation Wi-Fi architecture. The future of Wi-Fi is controller-less, and you don’t want to be left with outdated network architecture right after you deploy 3-stream radios. So, when you put in APs with contemporary 3x3:3 radios, you can also graduate to contemporary Wi-Fi architecture by putting out controllers. While flying from New York to Dallas, if you don’t prefer flying through San Francisco; why would you have your wireless traffic traverse controllers when it goes from your iPad to Exchange Server or between VoIP phones which are nowhere near the controllers? Is it just because those APs are “tethered” to controllers due to legacy architecture and incapable of providing full service to your traffic at the edge due to their legacy architecture? The case for bypassing the central points of failure like controllers is even stronger when wireless speeds go up, like what happens when you deploy 3x3:3 radios.

All in all, selection of 3-stream Wi-Fi cannot to be dictated by misleading claims and lopsided analysis. A holistic thinking taking into account performance, security, and architecture helps arrive at better game plan to get the most out of investment into 3-stream Wi-Fi for the enterprise.

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Topics: WLAN planning