Wifi Access Points and a Decoder ring


Now that Apple is out of the business, it's time once again to look for a reliable and fast wifi network for home and small business. But it is really hard to figure out what is going on without at least some background in wifi and how it has evolved. So, this is a huge post filled with facts, but the tl;dr will help you.


Some of the criteria for a home router are:

  1. Fast. I've had plenty of small ones that will lock up with any traffic. In the prosumer space, you want a router which can handle 1M packet per second. They cost a little more, but are worth it. My own experience with Linksys WRT-54g routers was that they would lock up under load which was one reason I switched to Apple Airport Extreme. Now with Apple out, what's a good router to look at. I have two small business routers that I have tried yet doing 1-2M packets per second. It used to be fairly easy, there was 802.11b, g, n, a and then finally ac, now it is really confusing with MU-MIMO and 2x2, 3x3 and even 4x4 systems showing up.
  2. Broad coverage. There is nothing more frustrating that intermittent wifi in a house. The symptoms are really strange and hard to diagnose. It's one reason we switch to Unifi because they had great coverage. So for a long time, I would recommend the Unifi/Apple combination.
  3. Quality and reliability. The main problem isn't the point speed, but having stuff that is reliable and just well works for a long time. I've had plenty of access points hang and routers crash. It's one reason I've been using business grade access points like Unifi for a long time. They actually do not cost more, but they do require you have a management console and understand what is going on.

With all that here are the recommendations:

  1. If you have a small house (defined to be 2,500 square feet), then you want one powerful signal. If you want something rock solid and powerful, get a Unifi AC LR (AC1300) as the access point and connect a small business router like the Linksys or Unifi  and then to your cable modem. If you are cheap, the a Netgear Nighthawk AC1750 should be fine but beware that you may have software failures and hardware failures.
  2. If you have a big house or office (defined to be 3,500 square feet) and you have wired ethernet cables. You should get a collection of Unifi AC Pro (AC1750) and spread them around your house. Put them close to the places where you compute (your office, your bedroom).
  3. If you have a big house without wired ethernet. Then you need a mesh system. The Amplifi and Netgear Orbi have gotten good reviews (but I've not tried it). I would probably hat tip to Amplifi just because it comes from Unifi, but that's me.

Hardware Decoder Ring: Modem vs. Router vs. Access Points

So what now what's person to do, first some terms:

  1. Cable Modem. Many boxes are combinations, but there are three basic pieces. First is the modem that converts your internet service provider to what your house has. It might seem pretty obvious, but if you do not have servers in your house, then no matter how fast your wifi is you won't see anything faster than the 20-50Mbps that the cable modem has. Translation, you do not need an AC5300 router (see below) if all you will every need is an N50 worth of bandwidth. Most of the time you want all this stuff separate so you can upgrade it. That is the cable modem separate from the router separate from the wifi access points if you are a nerd.
  2. Router vs Wifi Access Point. The router is what takes all the wired and wireless connections and routes them. They are basically rated by how many packets per second they can pass and how much memory they have. The small business ones might have two connections (called WAN or wide area network) connection so you can have multiple ISPs. Then there are Wifi access points, most consumers end up with a single combination Router+Access Point (or if they buy from Comcast for instance, they met get a Modem+Router+AP). This works in smaller houses where the router is central or they are very sensitive. Many houses though will do better if they have use wired infrastructure and then have APs on multiple floors.

Wifi Decoder Ring

Beyond 802.11ac there is a lot of hype. OK first some terminology. Instead of the various acronyms vendors have started talking about total available bandwidth across all the channels. That is not what an individual client can see, but what is the bandwidth that the wifi access point can handle. So for instance, the most basic form of 802.11/ac might have 1700Mbps of total bandwidth. That is at 2.4GHz a 300MHz channel and at 5 GHz 1.2Gpbs worth and thus be called an AC1700 access point.
One crazy thing about this terminology is that the backhaul from a wifi access point is 1Gbps, so there is no way to actually get 1.7Gbps of total bandwidth to your ethernet. So most of this actually marketing hype. Also with interference, when they say you can get 450Mbps from 2.4Ghz, that assumes that there is no interference at all which is obviously not true and you are very close.

Frequencies to Channels

A quick decoder ring (which I think I posted before) is a little technical, but here is how channels are allocated, at 2.4GHz, there are 11 "channels", but they all overlap. These channels are non-overlapping with the oldest standard 802.11b or g/n at 1, 6 and 11. For 802.11g/n, the non-overlapping at slightly different at 1, 6and 11. As an aside when you setup your wifi, if you are a nerd, you will see lots of folks at channel 3 for instance which of course interferes with 1 and 6, but most access points "sniff" the environment and try to find the frequencies that are cleanest. Wifi Explorer on the Mac is my favorite app for exploring this
In the rest of the world, thing are a little different since  you can use up to channel 13, they are 1, 5, 9. This gives a total of 20MHz for each 3 channels each is 150Mbps maximum. That is how you get to 450Mbps available in the best case at 2.4GHz. This is of course beyond the best case, since it assume no interference at all from other sources and great signal to noise ratios.
You can by the way bond these to 40MHz channels as well so, outside of the US, you can have two non-overlapping 40MHz channels at channels 3 (sometimes called 1+5) and 11 (sometimes called 9+13). Note that in the US, you can't actually use channels 12 and 13, so there is really only one 40MHz channel legally available there called channel 3 or 1+5.
With 5GHz, things are even more confusing because many bands are allocated for other uses. So in the US, the available 20MHz bands (this time non overlapping  bands) are 36, 40, 44 and 48. These can be bonded into 40Mhz bands called 38 (or 36+40), 46 (or 44+48). You can also bond them all into one gigantic 80MHz band called 42 (or 36+40+44+48). This is also called the "Lower 80Mhz".
Then there are some other frequencies and the 20MHz channels called 149, 153, 157, 161 and 165. As with the lower 5GHZ you can bond them into two 40Mhz channels 151 (aka 149+151) and 159 (aka 157+161) plus a 20Mhz one. And you can bond the two 40MHz into a single 80MHz channel called 155 (aka 151+159). It is kind of cool you just take the arithmetic average of each bond to get the new channel number.
There are some other channels that are "shared" with other users mainly weather radar. You have to use DFS (dynamic frequency selection) to access them and the world is very fragmented, but in the US, these channels:

  • Channels 36-48. Completely free but will interfere with other wifi users.
  • Channels 50-64 (so directly above the "low" 36-48) that must turn off if there are weather radars operating
  • Channels 100-144 a totally separate group that also must defer to weather radar
  • Channels 151-159 assuming that there are no radars operating there.

802.11b to 802.11g Decoder Ring

So now we can see how much each channel can carry. To really understand this, it's easiest to look backwards and see how each standard 802.11b, then g then 802.11n have increased the width of the channel and the modulation techniques. With 802.11b, in a single 20MHz channel, you could get 11Mbps using DSSS modulation. With 802.11g, in a 20Mhz channel you could get 54Mbps because they switched to the more efficient OFDM. These are maximums, what really happens is that when the signal degrades, it will drop down by half. This is how you end up getting low performance but longer range.
OFDM is the big trick and thus 54Mbps for 20 MHz of spectrum is kind of the building
By the way as an useless factoid, ISM actually stands for Industrial, Scientific and Medical spectrum but of course 2.4GHz have been "hijacked" for Bluetooth and Wifi. And the correct name for 5GHx is also ISM but is officially called U-NII

802.11n MIMO

With 802.11n launched in 2009, the simple change was to increase coding efficiency so the basic building block is 72Mbps on a 20MHz channel (using technically 1 antenna, 64-QAM, 5/6 coding rate which means 5 data bits for 6 total bits, so there is one redundancy bit in convolutional coding). And in a 40MHz channel, you get a little more efficiency because you do not need guard MHz which gives you the basic 150Mbps in 40MHz.
Getting more bandwidth, things took a big step forward with the introduction of MIMO (Multiple Input and Multiple Output). This takes advantage of a phenomena in the real world called multipath propagation. What happens is that different signals bounce around off of walls and things. You see this on old time analog TV as ghosts on the screen.
But you can also use this to in effect transmit more signals over the same spectrum. This is how you get beyond just 54Mbps/20MHz by using the ghosts with a modulation called MIMO-OFDM. This requires a separate antenna for each stream which is why in phones there are actually multiple antennas built in and the routers sometimes have antennas sprouting out of them. It gives rise to figure that show how many input and how many output antennas. So if a system is 2x2 MIMO it means that it has 2 input antennas and 2 output antennas.
So in a single 20MHz channel, 802.11n can have a maximum of 4 streams so you get 4x72=288 in 20MHz. With a 40MHz channel, you get more efficiency so that leads to 4x150Mbps  600Mbps. These numbers should start to look familiar in specs. When you have an N600 modem, what this means is that it can handle 4x150Mbps.
Now practically speaking there are not many places where you can actually get 40MHz of clean spectrum. This is why most of these specifications are way to high to be theoretically true. In a 2.4GHz, you need to have the entire spectrum clear to get to 150Mbps x 4 streams = 600Mbps. In 5GHz, you only have two choices a low and a high band for 1.2Gbps total if the 5GHz spectrum is totally clean.

802.11ac MU-MIMO and 160MHz channels (aka Wave 2)

802.11ac is the next iteration. At 2.4GHz, you get exactly the same bandwidth as the old 802.11n standard because you are using the same encodings (16-QAM, 5/6 encoding). But at 5GHz, you get more with these optimizations:

  • Move from 2x40MHz in 5GHZ to a single 80MHz channel (only available in 5GHz of course and there are only two blocks for it). This of course improves efficiency as you do not need as much in terms of guard frequencies.
  • 256-QAM up from 64-QAM so more data just by more coding

Now using the MIMO trick to get more spatial streams to a single client. So if you a transmitter with 2 antennas and client with 2 (aka 2x2) you can get up to 2x433 = 866Mbps up at 5GHz. The net of this is that whereas you could 150Mbps/40MHz with 802.11n, the new "building block" maximum is now 433Mbps/80MHz with 802.11ac. So the two tricks above improve efficiency by 433/(150x2) = 44% high efficiency improvement. Of course this is only because Moore's law means that we can do more decoding.
There are however there are two cutting edge tricks to get more. The first is 160MHz mode that relies on the additional new channels that have been allocated. originally there was just 36-44 and 149-165, but now There is only one 160MHz block available and it is only at 5GHz (so pretty short range) at channel 36-64. The other method is  Bonded 80+80MHz. This is kind of tricky so the cutting edge research is how to create signal processing that can bond (80+80MHz). And as before this only works with very clean spectrum and 5GHz is much shorter range than 2.4GHz anyway.
Second is multi-user MIMO. In all the previous systems, the assumption is that there is one client spoken to at a time. So if you have say 10 clients on a single MIMO, then time division split the bandwidth. Client 1 takes a turn, then client 2, etc.
With MU-MIMO cooperating clients can transmit at the same time so that multiple clients can talk simultaneously. This is a pretty special case because all clients and all access points have to support MU-MIMO for it to work. One technique is something called client steering, so when a client PC or phone connects, the access point tells it which channel to you use. You want only MU-MIMO clients together to make it work. If you do, then if you have a 4 client MU-MIMO, you again increase the bandwidth (so the trick are MIMO to use the the same frequencies 4-8x to any one client and MU-MIMO get that for multiple clients.
The main trick to get MU-MIMO working is something called beam forming. You basically use the multiple antennas to directly "point" the streams (like phased array radar) to different clients.

What do the AC ratings mean?

So the marketing folks came up a with a brilliant idea. Without having to explain all of this come up with single specification that tells you in the first what network standard (N for 802.11n and AC for 802.11ac). That means an "N600" router has a maximum capability for 802.11n and 600Mbps so we know that 802.11n has a basic building block of 150Mbps/40MHz, so that means somehow this thing can handle 4 channels of 150Mbps each. This could be 1x1 at 2.4GHz and 3x3 at 5GHz.
Now, they take it farther and look at the total bandwidth across the best case where all 2.4 and 5GHz spectrum is completely clean. As you can see if it basically impossible to every get that 600Mbps number.
So for 802.11ac there are some magic numbers that you see quite a bit so the math is complicated, but for the very common AC1750 routers, the derivation is:

  • 3x3 (that is a total of six antennas on the thing)
  • 2.4GHz assuming the full 40MHz at MCS 7 (64-QAM 5/6 bit encoding) gives you 450Mbps
  • 5GHz, you get to 1.3Gbps at 80MHz using 3 streams at MCS 9 (256-QAM 5/6 encoding)

Now of course this is pretty unrealistic  because these routers are only connected to 1Gbps Ethernet, so unless you are talking about a USB3.0 disk attached directly to the access point (USB 3.0 is 5Gbps) there is now way to actually use 1.3Gbps and you have to be really really close to use the full 80MHz at 5GHz.
And for the so-called AC3200 access points, this assumes you have MU-MIMO enabled clients with the math:

  • 2.4GHz you move to MCS 9 (256QAM) which gives you a 33% improvement to 600MBps using the full 40MHz with a 3x3
  • 5GHz there are even more tricks, two clients can talk simultaneously so 2x1.3Gbps which as we've said before only really works if the two clients are talking to each other. There is no way that Gigabit ethernet could support it.

Because antenna design in the real world matters so much it is why say a Unific AC Pro a AC1750 device can out perform a theoretically better AC3200 one if it handles the garbage out there well. And in fact a Unifi AC LR which is just AC1300 can deliver much long range with higher bandwidth than a fancy AC5400 particularly if non of the clients are really MU-MIMO anyway.

What does it mean in the real world?

The real net of this is that access points are really moving to massive specmanship without any real benefit. Instead, you have to see how real devices work in the more limited noise free spectrum. So looking right now at the laptop I'm using, it's an "old" MacBook 2010 that supports 802.11n and 3x3 antennas and it is talking to an old Unifi AC Pro also with 2x2 MIMO 802.11ac, I'm seeing at 25 feet away in a noisy office tower, 300Mbps at 40MHz. Even the newer MacBook Pro 2014 with 3x3 MIMO is actually connects to an 80MHz channel at 585Mbps using MCS 7 (64-QAM 5/6 encoding) compared with 866Mbps that is possible  at MCS-9 (256-QAM, 5/6 encoding).
Why the fall off? Well when the world gets noisy, the router backs off on encoding from 256 to 16 points and adds more error correction so that 33% of the bits are error connecting.

Specific Hardware

So in lieu of these reviews, here are some highly opinionated ideas about what to get in order:

Unifi: Tried and True for Techies or small houses

Unifi. Ok this is really for prosumers, but if you have lots of equipment and really want something trouble free, then the Unifi small business line is the way to go. Seems to work super well in the six (?!) different homes and small businesses that I support. The main drawback is needing a management console and figuring out which model to pick. Also, if you have a big house, you need to figure out how to get ethernet to different access points. So either you are nerd with Ethernet in your walls or your house is small enough to get away with one access point. Also this is just a wifi access point, so you still need a cable modem/router, but it makes a nice add-on to an existing installation.
UAP AP AC LR (Amazon carries it for $96) (Ok that's a terrible name I know!) for home because you really want the reach and setting up lots of wifi access points is a pain. It supports 450MBps at 2.4GHz and 867Mbps at 5GHz, so spec-wise it doesn't compare with the consumer products, but the range and reliability are key factors.
UAP AP AC Pro (Amazon $125) If you can afford it though the more expensive UAP AC Pro is indoor/outdoor and also uses standard POE charging and it supports 3x3 MiMO to get you to the full 1300Gbps. Remember this only matters if you have servers in your home, otherwise, you do not need anything like this bandwidth to use the internet. On the other hand the cost difference is nominal, you might as well get the AC Pro.

For big unwired houses, maybe try mesh Orbi or Amplifi

Wirecutter has a good overview of the various systems. They are expensive at $200-400 for a set of 2-3 nodes and they have limitations as you need to do wireless backhaul. They like the Netgear Orbi the best. They say that it is just two units and easier to setup. $380 from Amazon. One interesting note here is that a single powerful access point like the Archer C7 can be much better than these mesh systems. The main reason they didn't like the Amplifi has to do with it's design. The end units are supposed to be plugged directly into the wall so are too low. It's a strange review, since the simple solution is to just get a short extension cord so you can put the unit anywhere.
Anyway some more about Amplifi:
Amplifi just launched (also from Unifi) and it hasn't gotten many reviews, although my Facebook buddies like it. It gets wifi connections with "mesh" networking. This means that you do not need wires for multiple access points. They use a separate 5GHz back channel to backhaul from the remote access points to the router. It's a little more expensive at $349 SRP but Digitrends also liked it. It's most useful for big Maxhouses with coverage holes.
The thing looks really cool (not like the UFO design of the Unifi), you get a white box that is the router and then there are two small antennas that plug into power that you deploy into the nether regions of your house. Arstechnica does a good job explaining the SKUs which are a little confusing since all have a base plus two mesh points but the technology used is different

  • Amplifi Standard. $199. 2x2 MIMO, Max Power is 24Dbm (base) and 22 dBm (mesh) enough for a 10,000 square foot house (egads!)
  • Amplifi LR. $299 boosts power by 2Dbm to 26Dbm base and 24 dBM mesh. Claims this increases range for a 20,000 square foot (?!!!) house.
  • Amplifi HR. $349 goes to 3x3 MIMO and 26dBM at both base and mesh, so more throughput.

Looking at this, it looks like a good choice for the big houses that do not have ethernet inside or where a more consumer friendly look and application make sense.

For the cost sensitive I'm not sure

Wirecutter likes the TP-Link Archer C7 which is an AC1750 router (450Mbps at 2.4GHz and 1.3Gbps at 5GHz) but Amazon folks have found reliability problems which isn't surprising given the $75 very nominal cost.
It looks like the Netgear AC1750 and it's family is loved by Amazon, but they just glom together all the reviews of different devices so it is hard to tell which is better. Also Amazon reviews are increasingly getting spammed because of paid reviews, things like couponclub.com, so I do not take 5 star reviews too seriously, you need to look at the 1-star reviews to really figure out what is going on.
Overall, just reviewing Amazon, it does look like these routers are a nest of issues with reliability and updates, so caveat emptor.

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