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Before you read I apologize in advance for the mile long post, it's only so long because of the pictures.

I recently purchased an ASUS wireless adapter to replace my TP-Link wireless adapter. After configuring it I downloaded some files, I noticed the consistency wasn't any better, if not worse than my TP-Link which is 802.11n instead of 802.11ac which I had set specifically to use in device manager. I decided to do some investigating because this wireless adapter seems cool and I like ASUS, but I've never used their wireless before.

For those curious I was using my Dell XPS 15 9550 laptop for the testing, it has a M.2 NVMe SSD, no chance of a bottleneck with that.

The drive used in the server is a 250GB 7200RPM Western Digital that has a fresh install of Ubuntu 18.04 LTS server with virtually no space used. Capable of ~100MB/s speeds. This server is wired into the router.

The router used in testing is a CenturyLink C2100T with 802.11ac capabilities.

Please note: In the course of testing wireless connections I disabled any other wireless connections I had the ability to before testing the device. This is to minimize interference.

Wireless Adapters:

  • ASUS AC56 (Used with on board USB 3.0)
    • BeamCap: VHT BEAM TX|RX
    • EnableAdaptivity: Auto
    • High Adhoc Mode: Disable
    • HLDiffForAdaptivity: 7
    • L2HForAdaptivity: F5
    • LdpcCap: VHT LDPC TX|RX & HT LDPC TX|RX
    • Preferred Band: 3. 5G First
    • QoS Support: Auto
    • StbcCap: VHT STBC TX|RX & HT STBC TX|RX
    • USB SF Mode: Disable
    • USB Switch Mode: Auto
    • VHT 2.4G: Disable
    • VHT 2.4G IOT: Disable
    • WiFi Config: Performance
    • Wireless Mode: IEEE 802.11ac
  • KillerWireless 1535 (On board for laptop)
    • D0 PacketCoalescing: Disable
    • Dynamic MIMO Power Save: Disable
    • Network Address: Not Present
    • Preferred Band: 3 - Prefer 5GHz Band
    • Roaming aggressiveness: 3.Medium
    • Wireless Mode: 10 - 11 a/n/ac

Both devices had power saving turned off and correct drivers to make sure there are no bottle necks.

Note: I only did most of these tests once, take them with a grain of salt.

Here are the Ethernet connection graphs from transferring a 1GB file. Download file over Ethernet

Upload file over Ethernet

I started downstairs from the router to see if there was interference how much there was compared to sitting right next to the router. Here is the ASUS wireless from downstairs transferring that same file.

Download file over ASUS AC56

Upload file over ASUS AC56

Not terrible speeds, especially considering there's all sorts of crap in the ceiling/walls that would cause interference.

Here is the on board wireless of my laptop.

Download file over KillerWireless 1535

Upload file over KillerWireless 1535

A bit better in the download, didn't strike me as odd. Consistency not so great either.

ASUS advertises 867Mbps over the 5GHz band, here are the same tests but only about a foot away from the router.

ASUS AC56 (Ran two tests each)

Download file over ASUS AC56 next to router

Upload file over ASUS AC56 next to router

KillerWireless 1535

Download file over KillerWireless 1535

Upload file over KillerWireless 1535

You can see the on board of my laptop is a bit better than the ASUS, not really the point though. The point is I can't even reach the non-boosted speed they advertise. I'm not sure why this is, if anyone has any incite, would be greatly appreciated.

If you noticed 802.11n displayed in task manager for ASUS AC56, it's because Windows bugs out and doesn't like 802.11ac on external devices. The utility shows it's using 802.11ac at 80MHz. A good portion of the device settings I have no idea what purpose they serve, I was copying this setup.

I also want to test the drivers on Linux to see if the issue remains there. I'll keep this post updated if I make any progress.

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  • Your router doesn't state any kind of expected speeds (centurylink.com/asset/home/help/downloads/internet/…) though it does advertise "ac" wireless. It is entirely possible that the router cannot sustain higher speeds over Wifi.
    – Mokubai
    Jan 23 '19 at 18:52
  • You might just be right, 802.11ac has a throughput of 1gigabit but only as multistation. It has a 500mbit/s throughput at single, which is about what I was getting. en.wikipedia.org/wiki/IEEE_802.11ac
    – user632164
    Jan 24 '19 at 0:24
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So, I had a look at the specs of both your router & your Asus card.

The router has 2x2MIMO capabilities @ 2.4GHz & 4x4MIMO capabilities at 5GHz.

I'm assuming a "common" system of 1300mbps of speed that are split up like this:

2x 150mbps @2.4GHz = 300mbps
4x 250mbps @5GHz = 1000mbps

Your wireless card on the other hand is 2x2MIMO capable on both 2.4GHz & 5GHz. This means that it's 1300mbps are split like (checked the specs):

2x 200mbps @2.4GHz = 400mbps
2x 433mps @5GHz = 867mbps

So your new card is theoretically capable of 867mbps of speed, but your router can't give that much on 2 streams, it would require 4 streams. Since only 2 streams are used your router gives out the maximum it can on 2 streams. Therefore you get a theoretical top speed of 500mbps on your machine which as shown by your tests is ~450mbps in real life situations which are actually very good results.

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