Why do I have such a low WiFi speed?

Question

Ok, first of all I've had an internet plan for 100mbps for about two years now and my speeds looked like this:

(Results from www.speedtest.net)

Wired: Download - 92mbps , Upload - 94mbps

WiFi (using 2.4GHz): Download - 60mbps, Upload - 70mbps

Yesterday I've decided that I want an upgrade and went for 300mpbs plan.

Here are the results:

Wired Download - 280mbps, Upload - 290mbps

WiFi(using 2.4Ghz) Download - 67mbps, Upload - 80mpbs.

As you can see my wired speeds increased a lot where WiFi is almost at the same place. Why is that? Is there anything I can do about it? I've been reading about using 40Mhz,using n instead of b,g,n mixed, switching to 1,6,11 channels instead of auto and a lot more. My router supports both 2.4Ghz and 5Ghz, and yes 5Ghz is slightly faster but not a lot.

Router I'm using is TP-LINK N750. On the website they say Simultaneous 2.4GHz 300Mbps and 5GHz 450Mbps connections for 750Mbps of total available bandwidthhowever I can't see those speeds. One more thing that's weird for me is that it says speed 150mpbs when I click on my WiFi connection properties. Why is that? I'm so confused with all theese numbers and upset with theese results because I'd like to have much higher WiFi speeds with this plan.

Answer 1

The fact of the matter is that you are getting about the best speeds you should be on an 802.11 network with the hardware you are using.

While your router is capable of higher data rates using multiple spatial streams, your Intel Dual Band Wireless-AC 3165 is only capable of using a single spatial stream. This means that it will never connect at data rates higher than 150 Mbps on 2.4GHz. This data rate is not related to throughput like the results from the speed test. Instead it is merely a measure of how fast your client thinks it can send data to the AP (at that moment in time - it can and often does change).

Now you are likely saying that you should have a higher throughput on your speedtest results, but 802.11 traffic is half-duplex and shared bandwidth. This means that only one device on your wireless network can "talk" at any given time for successful communication to take place. Further, any other 802.11 networks or devices in the same area use part of the "airtime" as well.

There are also management frames such as acknowledgements (frames that are sent to the sender on successful receipt of a data frame) in both directions (client->AP or AP->Client) which use some of the airtime. Management frames also include frames that allow devices to find AP's, such as beacons, probe requests and probe responses. There are still other management frames that silently take care of the wireless network as well, such as the frames that are used when a device wishes to join and leave an 802.11 network, etc. Many management frames will go at a much lower data rate than the 150 Mbps data rate your device is connecting at and as such will take more time on the channel.

So, if you take your 150 Mbps data rate, factor in the 802.11 acknowledgements, other management traffic, and other 802.11 devices in the area or on the network then it is never going to be possible to achieve throughput on par with the data rate. Typically, you will get throughput anywhere from 30-50% of the achievable data rate, depending on the environment. Especially busy or clean environments may result in throughput outside these ranges.

Answer 2

Wi-Fi has a lot of overhead compared to wired Ethernet, and you rarely get the top PHY rate (the raw per-packet signaling rate before overhead) that your equipment is capable of unless you're within ~5 meters of router with direct line-of-sight, and only if there's no interference / competition on the channel.

With 802.11a/b/g without any kind of vendor-proprietary frame aggregation, the rule of thumb was to expect TCP/IPv4 application throughput at 50% of whatever mean PHY rate you were getting, assuming no interference or competition for airtime on the channel.

802.11n and 802.11ac add frame aggregation which lowers the overhead, but you still see not much more than 60% efficiency with value-priced equipment, and less than 80% efficiency even with the best equipment. Again, that's assuming no interference or competition for airtime on the channel.

Note that those efficiency targets are relative to whatever PHY rate you happen to be getting at your distance from the AP, and if you're far enough away from your AP, your PHY rate could fall all the way down to 1 Mbps (the lowest 2.4GHz PHY rate from 802.11-1997 DSSS) or 6Mbps (the lowest 5GHz PHY rate from 802.11a).

All told, if you want to reliably get 300Mbps of application throughput over Wi-Fi, you must use 802.11ac with at least two spatial streams, 80MHz-wide channels, and MCS 9 (256QAM). That means the 867Mbps flavor of 802.11ac or better, and that's when only counting the 5GHz capabilities of the AP, not adding in the 2.4GHz capabilities like slimy marketers like to do.