There are over 1100 devices Wi-Fi CERTIFIED™ ac. #GenMobile is clearly riding the gigabit Wi-Fi wave. Speaking of waves, there has been a lot of chatter lately about “Wave 2”. So what’s the buzz about?
Let's start with some of the innovations that came with the first Wave of 802.11ac APs.
- 3 Spatial Streams (3SS) MIMO (multiple input, multiple output) transmission to and from an Access Point; few clients support this
- 80 MHz Channels: doubles the channel width in 5 GHz band from 802.11n’s maximum of 40 MHz
- Explicit Transmit Beamforming: enhances the signal-to-noise ratio for higher data rates at a given range; most devices support this
- 256-QAM: improves data transmission rates 33% above 802.11n’s 64-QAM when near the Access Point
These innovations brought gigabit data rates to Wi-Fi with the max data rate of 1.3Gbps.
The approaching Wave 2 brings the next set of innovations, but the certification program is still a work in progress and not is expected until 2016. So, what new optional features are coming with Wave 2?
- 160 MHz Channels: again doubling the channel width that can be assigned to an Access Point…but channel planning will be a challenge for multi-AP deployments
- Multi-User MIMO (MU-MIMO) transmission from the AP
- 4 Spatial Streams (4SS) MIMO transmission
Together this has the potential to enable an AP to reach theoretical data rates of up to 3.4 Gbps. All of these changes require hardware support on the AP and on the client side. Existing Wave 1 devices will not be software upgradable to Wave 2.
Can you really catch the wave? Let’s dig a bit deeper…
Can we really deploy 160 MHz Channels?
First, let’s look at the 160 MHz channel proposition. As you can see in the above channel allocation table, there are only two 160 MHz channels available for use (1 if you exclude any DFS frequencies that weather radar utilizes). What this really means is that you won’t be able to deploy this in a multi-AP enterprise network as below and it will be limited to rural remote/home offices.
So that just cut in half our max data rate from 3.4 to 1.7 Gbps, a 33% boost over the current generation of 802.11ac from the 4th spatial stream. It is still an improvement but not the over 2.5X boost some people were hoping for.
Where are the 4SS devices?
With 4 Spatial Streams (4SS) will my smartphone surf faster? To deliver 4SS to a device it will require 4 antenna systems. That requires significantly more space and will utilize more power to drive them so I don’t expect it to show up even in high-end laptops. The vast majority of client devices for many years to come will only support 1SS or 2SS so MU-MIMO will be critical. I haven’t even heard of any vendors looking at building client radios being with 4 spatial stream support. So the maximum data rate for a single device will still peak at 1.3 Gbps that we saw with high-end 3SS devices.
MU-MIMO is where the real innovation comes
Finally, I think that MU-MIMO is the most exciting feature introduced with Wave 2. It will enable enterprises to increase the efficiency and thus device density of their AP’s. Today most AP’s support 3SS but when you have a smartphone that supports 1SS or a tablet/laptop that supports 2SS, then 1 or 2 of the spatial streams are going unused and wasting up to 2/3 of the bandwidth. Wave 1 AP’s can only transmit unicast data to a single device at a time. MU-MIMO changes this so that when there are multiple client devices that also have Wave 2 chipsets, you can transmit to them in parallel thus sending 2SS to laptop “A”, 1SS to smartphone “B” and 1SS to tablet “C”. With Wave 2 you can utilize all 4 spatial streams instead of wasting up to ¾ of the bandwidth. There will be some overhead with MU-MIMO so having this extra 4th stream is key to maximizing throughput. In theory, four 1SS clients would give you 4x 433 mbps for a data rate of 1.7 Gbps at the AP. I expect that it will be closer to 75 % of the theoretical improvement so you will reach 1.3 Gbps while transmitting to multiple clients. And there is always TCP overhead slowing things down more. It is expected that three 1SS see TCP throughputs closer to ~700 mbps. Again, not the promised 3.4 Gbps, but significantly better than the ~200-250 mbps we see when a Wave 1 AP only talks to 1 client at a time.
I expect that some vendors will start to have early Wave 2 products later this year that will enable customers to prepare their networks for when large numbers of Wave 2 clients become available in the coming years. But the reality is that you won’t see the benefits until the bulk of the client devices also have Wave 2 chipsets and that is likely to take at least a year, possibly even longer since the speed boost is less than it was with the move from 11n to 11ac Wave 1.
So should you wait? I don’t see a driver to delay your upgrade and most organizations should continue with their plans to rollout Wave 1 products. As I described, Wave 2 will be an improvement primarily in the utilization of the AP rather than an increase in throughput so will benefit most in your high density areas. This will not be as profound as the shift away from your legacy 802.11n (or even 802.11abg) products when Wave 1 became available. When Wave 2 products come out, you should look towards these first for your areas of highest density needs to leverage the benefit of MU-MIMO to simultaneously transmit from the AP to multiple Wave 2 clients. For areas of lower density across your network, continue to deploy Wave 1 AP’s and move to Wave 2 AP’s when there is no cost premium.
In contrast to Wave 1 of 802.11ac where enterprise AP vendors released products to the market AFTER the launch of the Wi-Fi Alliance’s “Wi-Fi CERTIFIED™ ac” program to ensure interoperability, it is likely that initial Wave 2 products will enter the market ahead of the certification program. As the Wi-Fi Alliance shared in their blog on Feb 6, 2015, they will announce the new certification program in 2016. So expect that it will take until late 2016 or 2017 until we have a significant portion of the clients deployed in the enterprise to be able to take advantage of the enhancements such as MU-MIMO.
As you look at your network design today with rolling out 802.11ac, Aruba Networks has the richest portfolio of 802.11ac products that can meet your varied needs today and into the future.
- 220 Series: the highest performing 802.11ac (3SS, 1.3 Gbps) with dual GigE uplinks
- 210 Series: 802.11ac (3SS, 1.3 Gbps) for high performance, moderate density
- 200 Series: 802.11ac (2SS, 867 Mbps) for lower density needs
- 270 Series: delivering 802.11ac (3SS, 1.3 Gbps) for outdoor environments with external, integrated directional or integrated omnidirectional antenna models
- 228: rugged 802.11ac (3SS, 1.3Gbps) for extreme temperatures such as stadiums, warehouses, refrigeration
- 205H: 802.11ac (2SS, 867 Mbps) for hospitality and desktop/home installations
As we have continued to gain experience from deploying large-scale 802.11ac networks since we started shipping in mid-2013, we have distilled this into our 802.11ac Migration Guide that you can download here to aid you with your migration plans.
To learn more about 802.11ac Wave 2, view the recorded webinar hosted by Infonetics and Aruba Networks that was held on Thursday February 19th here.: VIEW NOW
You can also learn about the impact of antennas for 802.11ac Wave 2 in this blog by Eric Johnson: READ BLOG
Image Sources: "802.11ac Channel Allocation" ©2013 SecurityUncorked.com
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