What does 802.11ac "wave 2" mean and do you need it?
Matthew Gast discusses the ins and outs of 802.11ac wave 2 in this series. Discover what this evolution of 802.11ac means for your network.
In the past month, I’ve given several talks on 802.11ac, and I’ve been receiving many of the same questions repeatedly. So, I’m going to turn them into another blog series on 11ac, with the first entry (this one) discussing the “wave 1” and “wave 2” terminology.
The 802.11ac “wave” terms are marketing terms, not technology terms. The IEEE 802.11 working group develops the basic connectivity technology in the Wi-Fi world, and they finished the 802.11ac specification in 2013. After six months, anybody can get a free copy of the specification for any purpose – to build products, to cure insomnia, to count the number of pages. So, what does the source have to say about wave 1, wave 2, and all the future technology waves that we can expect? Go read the specification, or do a full text search on “wave 2,” then come back and we’ll discuss your findings.
Nope, there’s no description of technology waves. The “wave” terminology is a marketing term, not a technology term, and as a result, does not have the same level of precision as terms taken directly from the standard.
When discussing technology waves, it’s useful to think of a specification as a grab bag of capabilities that product developers are free to implement or ignore. Very broadly speaking, the 802.11ac specification has four features:
(1) Wider channels
(2) Additional MIMO spatial streams
(3) 256-QAM modulation
(4) Multi-user MIMO (MU-MIMO)
What describes the order in which these capabilities get implemented?
The specification itself labels features as optional or mandatory (see Annex B if you want the details), but the labels in the specification are not always applied rigorously. In practice, most vendors – like us at Aerohive! – build products to meet requirement of the Wi-Fi Alliance’s certification programs.
Creating a Wi-Fi Alliance certification program requires assembling a “test bed” of devices that provide multiple independent implementations of a technology capability. Because the test bed is composed of real products, development of the certification program reflects the highest risk/reward tradeoffs of the technology capabilities in the standard.
What's in wave 1?
So, how did we get “wave 1”? It is the features which had the lowest implementation risk. In practice, all vendors had similar wave 1 products:
- 80 MHz channels, because it was a straightforward extension of the 40 MHz capabilities in existing 11n devices
- 3 spatial streams, because the products could re-use much the 3-stream 11n design. 4-stream design was too difficult to do in the 802.3af power budget, and there wasn’t demand from system vendors like Aerohive for 4-stream chips
- 256-QAM, because it was relatively easy to do
What's in wave 2?
When creating second-generation 802.11ac products, the risk/reward tradeoffs are not quite as obvious. The two components that will be in every “wave 2” product are:
- A fourth spatial stream
- Multi-user MIMO, which is a topic complex enough to get its own post in this series.
Some products labeled “wave 2” may also add 160 MHz channels, which will enable the “big number on the packaging” to be larger, even if your radio regulations and environment make using such wide channels impossible in practice.
So, to sum up, here’s how the “wave” terms map on to features in the underlying specification. Roughly speaking, wave 1 consists of the features on the left side of my picture, and wave 2 is the right side of the picture.
If you’re reading this as a technology buyer, what does this mean for you? “Wave 2” is an imprecise term, so don’t ask for a “wave 2” access point. Ask instead for the technology capabilities that you want over and above wave 1 – and if you don’t need 160 MHz channels, the fourth spatial stream, or MU-MIMO, don’t bother with wave 2.
Other posts in this series: