802.11ac Benefits: The Myths And The Reality

Marketing hype about how 801.11ac will benefit users obscures the true gains we'll see with the new wireless standard.

Craig Chabot

December 4, 2013

3 Min Read
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As the ever-ambitious wireless manufacturers rush to get their own iterations of devices supporting 802.11ac on the shelves, hype about how the average end user will benefit from this new wireless standard overshadows its real advantages.

Like 802.11n before it, there are so many impressive and exciting features defining 802.11ac that people are having difficulty grasping the reality of the standard and how it will improve user experience. As a result, many manufacturers try to nonchalantly summarize the new standard and its advances in bumper sticker fashion: First Gigabit Wireless! Nearly 7Gbps potential! Wireless switching! In a typical manner for the marketing in this industry, the average user is misled.

For example, it should be obvious that no one will be getting their hands on an eight spatial stream device -- the only way of attaining the theoretical max rate of 6993Mbps. As was the case with RIFS, STBC, the virtually non-existent fourth spatial stream, and other "enhancements" within the 802.11n standard, aspects of the new standard likely will not come to fruition.

The 802.11ac marketing claims also ignore the technical fact that the calculated data rates at the physical layer do not accurately depict the true observable throughput, which is ultimately what a consumer is thinking about when he or she reads the advertised "speeds" on the box of their next wireless device.

It should be said that in no way am I trying to demean or downplay 802.11ac. The new capabilities and features within the ac standard of 802.11 are truly impressive and a significant jump forward in wireless technology.

Yet, if we look to history (802.11n) we can see that the important question is: What new features are the most relevant and likely to be seen in a widespread manner? For 802.11n, the features that offered the most significant improvements were the second and third spatial streams, 40MHz channel width operation, and MPDU Aggregation.

Due to the proliferation of smart phones and mobile device evolution, we should be assessing these new standards on the lowest common denominator chipsets utilizing them. Because low power consumption is such a high priority for these devices, single radio applications will far and away be the most common configuration of all 802.11ac devices to come. In my opinion, the additional five spatial streams, beamforming, and most notably, MU-MIMO, are compelling but overhyped features.

[Read how WLAN Q3 sales are the beginning of what a research firm predicts will be a five-year upgrade cycle to 802.11ac in "WLAN Market Grew 10 Percent in Q3, Report Says."]

The increased channel width operations (mandatory 80MHz, optional 160MHz, and 80+80MHz), 256-QAM, and mandatory MPDU aggregation are the most significant developments introduced with the new standard. These are the advancements within 802.11ac that every new wireless device will have the ability of utilizing, and therefore, will have the most noticeable impact on user experience.

Considering all of this, we begin to get an idea of what realistic gains are available today and what will be available in the near future. Let us assume an initial lack of support for the very wide 160MHz and 80+80MHz channel width operations. A single radio device can achieve a rate at the physical layer of 433.3Mbps, assuming the use of Short Guard Interval. This single radio scenario nearly matches the rarely-seen optimal three-radio scenario from 802.11n!

Furthermore, we get a linear increase of this stunning rate for each extra spatial stream. It won't be long before we see the implementation of the aforementioned very wide channel widths. Once this is solidified, the linear relationship between spatial streams and throughput will double.

When this scenario is considered, it's easy to realize that the true stars of this standard will be the linear rate gains in 80MHz, and eventually 160MHz channel width paired with a 33% gain from 256-QAM, and more efficient use of the medium through mandatory MPDU aggregation.

Which features of 802.11ac do you think will have the greatest impact on the end user experience? Share your thoughts in the comment space below.

About the Author(s)

Craig Chabot

Technical Manager, Wireless Consortium, University of New Hampshire InterOperability Laboratory

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