Reprinted with permission from the CWNP Wi-Fi Blog by Marcus Burton
At the Wireless Mobility Symposium, I had the privilege of introducing/moderating the discussion on gigabit Wi-Fi and asking a lot of the questions. Here’s my quick summation of the gigabit conversation.
- 802.11ac is 5 GHz only. This “limitation” is possibly the most important development because it will bring about a shift in client device support for the cleaner band with more usable spectrum. Mobile devices should adopt quickly if they want to stay “cutting edge” on the spec sheet, and because mobile devices are consumer products, the marketing of speed-based specs carries vast importance. Pervasive client adoption of 5 GHz will improve aggregate performance across the enterprise. 2.4 GHz is a garbage band; Wi-Fi is taking the goods to 5 GHz and leaving its refuse in 2.4.
- The IEEE has a “reach for the stars” attitude with the 802.11ac spec. Unfortunately, the marketing hype of “gigabit Wi-Fi” is way overdone. The few features that really drive the maximum data rate up are not immediately, or possibly ever, relevant to the enterprise.
- Very large channels—certainly 160 MHz, and likely 80 MHz as well—can ruin aggregate capacity, especially with high client densities and lots of 20 MHz only mobile devices. Some experts call these large channels a “gimmick.” Marketing departments love it.
- The other big data rate boost is more spatial streams (up to 8). As a reminder, today’s products incorporate only 3 (and rarely utilize them all) of the possible 4 spatial streams specified in 802.11n, so the likelihood of ever utilizing 8 is very slim. Adding more spatial streams to real-world products will take a lot of time.
- MU-MIMO promises better spectral efficiency with simultaneous transmissions to multiple users. However, this feature relies on better support (heck, let’s start with some support) of client beamforming as well as significant queuing modifications, and even then, there are still questions about achieving sufficient signal isolation between target clients. MU-MIMO doesn’t change the raw data rate, but it’s one of those marketed theoretical features that won’t be in the first, or first several, generation of products.
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