Why is my wi-fi so much slower than expected?

My internet connection is gigabit AT&T Fiber via an Arris BGW210-700 residential gateway (and its admin page shows that it does achieve 900 Mbps+).

From there, an ethernet cable with "gigabit" stamped on it connects to a Netgear R6300, which claims:

Up to 1300 Mbps wireless speeds achieved when connecting to other 802.11ac 1300 Mbps devices.

has been topping out around only 340 Mbps when using multiple devices, including my Pixel 3 or my Windows PC with AC 1300M USB WiFi Adapter which says:

Connection Speed Combined up to 1300Mbps

Is there an easy way for me to diagnose what the root cause is, such as whether the short ethernet cable isn't actually working at gigabit speed?

If I need to buy a new router to achieve 900 Mbps+ wirelessly, that would be unfortunate but not surprising, given how old this R6300, but I really want to avoid buying a new wifi router only to discover that the Arris BGW210-700 is the problem (e.g. maybe its ports aren't actually gigabit).

P.S. I understand that hardware marketing is full of overstatements and blatant lies, but 340 Mbps is so much slower than 1000-1300 Mbps that I figured it's worth asking about.

2 Answers

What you have here is a combination of unfortunate circumstances. But first of all you should test your internet speed with a wired connection and a powerful PC (important because speed test websites require a beefy CPU). Just to get an idea of what you could expect with "infinite" local bandwidth.

First, about your router. Its spec sheet says:

Use laptop with 3x3 450 Mbps adapter like Centrino® 6300/5300, or 3x3 802.11ac adapter for maximum performance

From this, we can infer that it supports 80 MHz channels and 3 spatial streams.

Your Wi-Fi adapter claims to support 867 Mbps connections over a single antenna (meaning a single spatial stream), so it probably supports 160 MHz channels. To achieve full performance, make sure it's connected to a USB 3.0 port on the PC.

The problem is when they come together: At 80 MHz with a single spatial stream, you can get up to 433.3 Mbps link speed. So that's pretty much what you get. 340 Mbps is actually very good.

For desktop computers, I recommend getting one of Gigabyte's Wi-Fi cards. They have Intel chipsets with 2×2 capabilities. That'll still only get you 867 Mbps, but that's double the speed. As a bonus, you also get Bluetooth.

For laptop computers, you should upgrade the internal Wi-Fi adapter if at all possible.

On mobile phones and tablets, you're out of luck. They often have slow Wi-Fi that cannot be upgraded.

The wireless speed might not be the relevant here (802.11ac should be able to get you 500 Mbit/s single-link or 1.1 Gbit/s multi-station). Most likely, the (NAT) router itself isn't able to process a higher throughput, whether used over Wi-Fi or Ethernet. After all, the model you've linked went on sale in 2012. Sadly, Netgear doesn't specify total throughput.

Of course, wireless throughput can be hampered by many other factors like distance, obstacles, nearby wireless networks on the same or adjacent channels, or other wireless applications (e.g. Bluetooth) in the same frequency band.

I'd try over wired Ethernet to actually see the routing capacity and if that's really much better you might want to optimize your Wi-Fi setup: select a less crowded channel, improve installation location, add access points with wired backhaul, ...