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802.11AC WIFI, Hype or Speed

April 30, 2016
802.11ac WIFI

Have you ever wondered about 802.11AC WIFI speeds?  Do you need it, how fast is it or what is it?  Lets look at the history of WIFI technologies.

WIFI started to become mainstream in the late 1990’s with the introduction of 802.11A and 802.11B.  The only real difference was the bands they used 802.11A used the 5ghz band and 802.11B used the 2.4ghz band.  Right away 802.11A was destined for failure, mostly due to the fact that the 5ghz band does not cover as much distance (especially when there are obstructions).  Unfortunately the 2.4ghz band was already crowded with lots of other devices using this unlicensed band.  The way the bands 11 channels are divided (up to 14 in some other countries outside North America), there were only 3 usable channels, as you really need 3 channels per stream.  This left 802.11B destined to only normally use channels 1, 6 and 11.  Unfortunately 802.11A went the way of Betamax and was never fully adopted.  When 802.11N was introduced it complicated real world speeds.  There were three key technologies used to help boost speed.  The first was to start using the 5ghz band again.  They had started to realize that to achieve the super fast speeds of 802.11N they needed an uncluttered band where microwaves, remote control cars etc would not cause errors so they added support both for the 2.4ghz band (for backward compatibility with slower devices and the 5ghz band.  Another was by changing the bandwidth from a 20mhz wide band, to increasing it to 40mhz for 802.11N for devices that supported it.  Another technology added was MIMO (Multiple In Multiple Out), a fancy word for grab a couple of streams and glue them together to make one big one.  2×2 MIMO uses two streams, 3×3 MIMI uses 3 streams.  All these factors meant that under ideal circumstances (a lab, using 5ghz, with 40ghz wide band and 3×3 MIMO) you could get up to 300mbps.  802.11AC further muddied the waters by adding 80 and 160mhz wide bands and allowing up to 8×8 MIMO and breaking it down into two “Waves” Wave 1 and Wave 2.  Currently the hardware that you are buying today (late 2015) is Wave1.

Real world speeds

802.11A: theoretical max speed 54mbps, real world max speed 54mbps

802.11B: theoretical max speed 11mbps, real world max speed 11mbps

802.11G: theoretical max speed 54mbps, real world max speed 54mbps

802.11N: theoretical max speed on 2.4ghz 150mbps, on 5ghz 600mbps, real world max 135mbps on 2.4ghz and 270mbps on 5ghz

802.11AC Wave1: theoretical max speed 1.69gbps, real world speeds so far are looking to be about 780mbps peak

802.11AC Wave2: theoretical max speed 6.77mbps, to early to tell what the real world speeds will be

Factors

  • The speeds in the various specifications, the marketing speeds and the real world speeds actually vary greatly with real world performance being significantly lower.
  • Speeds are also affected by stationary vs moving with it being significantly slower when you are moving (in some cases 10x slower when moving).
  • The 2.4ghz band tends to be more crowded especially in urban areas vs the 5ghz band thus leading to more errors and retransmissions which leads to slower speeds.
  • The 5ghz band tends to not penetrate walls as well as the 2.4ghz and as overall range is lower, it means areas that are noticeably slower unless you double the number of access points you have.
  • In many cases many of the early adopters of 802.11N found out that their version of 802.11N was only on the 2.4ghz band and the devices had no 5ghz radio in them which cut the possible max speeds in half.
  • MIMO involves multiple streams which means there is a need for multiple antennas on both the access point and the laptop/wireless device.  Currently many 802.11N laptops/phones etc do not have a second, third or eighth antenna on them to leverage the full speeds of 802.11N or AC.  This is particularly problematic when using external antennas, as most people only mount 1 antenna externally which will cap the speeds to 1×1 MIMO speeds.  In order to leverage the full speeds with external antennas you would need up to 8 different external antennas mounted to an 802.11AC access point.  Having a huge antenna array on the roof tends to not be practical for users of RV’s, Boats or Tiny Homes on Wheels.
  • In many cases a lot of access points or end devices tend to use the 20mhz wide band as the default (the narrowest band) and in many cases end devices that do support 802.11N or AC do not support 40, 80 or 160mhz wide bands which prevents them from leveraging the full speeds of 802.11N or AC

So what does this all mean?  Unfortunately the advertised speeds of 802.11 do not meet the expected speeds in the real world.  As a new standard comes out it becomes harder and harder to reach the theoretical max speeds that they are advertising.  The reality is today the vast majority of people using 802.11N are running on the 2.4ghz at up to 135mbps (best case).  Also the vast majority of users of 802.11AC routers have no AC devices anyway and are running at N speeds.  Also the vast majority of users using any external antenna setup are limited to the speeds that a single antenna can deliver which is well below the advertised speeds.

How about the talk about this new Wave2 technology.  To be frank, they cannot yet deliver anywhere close to 802.11AC Wave1 speeds on an AC network, most users cannot even achieve full 802.11N speeds.  So do we need Wave2… well maybe we will actually get full 802.11N speeds when the Wave2 hardware comes out:)  Just one final thought to consider, most mechanical hard drives cannot read/write faster than 300mbps, which is still a lot of laptops being used today, so in reality these devices will never realize faster than 802.11N anyway.  However Solid State drives (which are in many higher end computers and all tablets/phones can reach up to about 1-2gbps speeds theoretical max, but just like WIFI and Cellular, they are also under delivering on that as well, so even if you can get close to 802.11AC max speeds it is very unlikely your computer/tablet/phone could keep up anyway.

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