Upgrading to 802.11ac

802.11ac will yield enormous speed and capacity, but what are the points you need to consider?

First of all, 802.11ac is defined only for 5GHz band, 2.4GHz band will continue to use 802.11n. Higher frequences fade more quickly, so you will need more 5GHz access points, because they need to be closer to each other. The 5GHz band was already in use with 802.11n, so this has usually already been taken care of.

The new speeds in AC use wider channels (80MHz and 160MHz) and more precise modulation (256-QAM). High precision modulation requires very good reception, in practice it requires clear line-of-sight to the access point. You won't get AC-speed if the access point is on the other side of a wall. This is another reason you usually will want more access points when upgrading to AC. You also gain more capacity so the network can support the increasing number of users and their requirements. When you add more access points you need to turn down the transmit power so the access points won't interfere with each other, otherwise adding access points will degrade performance instead.

The third challenge is more technical. AC access point require more electric power. If they have their own power supllies this won't be a problem. If the power is fed through the Ethernet cable from the switch, the switch may need to be upgraded. Only the latest 802.3at (aka PoE+) can feed the power hungry AC access points. The older standard was 802.3af (aka PoE without a plus).

You may need to consider the data bandwidths as well. 802.11n of the today already exceeded the capacity of 100Mbps Ethernet. 802.11ac requires at least gigabit Ethernet connection – the more powerful access points have two Ethernet ports, because at least in theory you may exceed the capacity of one. In any case dual cabling will add redundacy, but will require more switch ports. If you have connected multiple access points to the same switch, you may need to upgrade the uplink to network core as well to avoid bottlenecks.

4 thoughts on “Upgrading to 802.11ac”

  1. Good day to you Mr. Riihikallo from Spruce Grove, Alberta, Canada, on the other side of the planet.

    In my case, my ISP is Telus and I had 150 mb/sec internet access, for approx $80.00/Canadian.

    Telus was offering a gigabit speed upgrades, for essentially no cost increase, the caveat being one had to sign a to year contract; I thinking, no extra money and and I can change my mind after two years as I see fit.

    In the process, it required upgrading my cable modem, wifi router and then also, every laptop [x 3] wifi card in the house, to .802’AC’ [as opposed to ‘N’] to be able to achieve gigabit speeds from Telus, thru my infrastructure in the house, to my laptop wirelessly. Or so I thought.

    It must be said, that my ISP Telus doesn’t mention any of the above requirements [at least in large bold print] as a part of their ‘Gigabit’ promotion.

    In the end, once everything was upgraded to AC, mitigating all previous .802n bottlenecks, the best I’ve been able to achieve to the wireless laptop is 300 mb/sec. Which is still double what I had previously, [given it’s not costing me more] so I’m not going to complain too much.

    My strategy moving forward is to:

    a. ensure I have run CAT5/6 cable everywhere in my next home [in which case I could realize gigabit speeds hardwired]; and

    b. once the two year contract is up here, [if we haven’t moved by then (refer to a. above)] I’ll have them throttle the speed back to 300 mb/sec and pay the lower fee for that.

    1. 802.11ac maximum nominal speed is 200Mbps per radio at 40MHz channel width. Mobile devices typically have only one or at most two radio chains, because each radio eats battery life, increases production costs and takes room inside the device. MacBook Pros have three radio chains (3×3) like some high end PC laptops. That would mean 600Mbps nominal speed. In real life 50% of the nominal speed is what you can get under perfect conditions. I guess you have achieved just that in your experiments ?

      If you need more bandwidth for a single device, you can try to widen the channel. At 80MHz the nominal maximum is 433Mbps and at 160MHz 867Mbps per radio. (Expect to get half of that effective at most.) How well that works out will depend on the environment: your building structure and your neighboring wireless networks. (I understand there ARE neighbors in Canada as well 🙂

      Does that mean the 1Gbps connection is useless? Not at all! If you add more access points, then you can have three APs that provide 300Mbps each (at 40MHz channel width). You can have three devices connected to different APs achieving 300Mbps effective throughput. That is plenty enough for most uses.

      If you have a gigabit switch then you can try whether your devices and APs can connect at 1Gbps. For short distances your existing CAT5 cabling may suffice. Recabling is always a fuzz.

  2. A second issue Petri, is now that I have upgraded my AP to Telus’s ‘T3200M’ to facilitate ‘AC’ gigabit speeds, I find that in the 5ghz range of channels, I can no longer manually select my channel to be in the middle of the range; even tho those channels are displayed in the software.

    I’m left competing with my neighbors for channels on the left in the 36-44 range, or 148 – 164 on the right.

    Apparently, “upgrading” to more advanced AP technology, means that we have fewer channels to select from.

    My research shows that incredulously those middle channels are [in first world countries] now the domain of weather radars…

    Cheers, and Thank You very much for the very interesting and informative blog.

    1. That depends on the AP and country settings. Your manufacturer has decided to disable all DFS channels for your region for some reason. I’m not familiar with the regulations for Canada. Do you follow U.S. FCC? Have you set the country code properly? That doesn’t have anything to do with 802.11ac vs. 802.11n.

      U-NII 3 used to be for radars in general. Channels 120-128 are for weather radars. See: What are WiFi DFS frequencies and should I care?

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