Surface Pro 3 - Windows 10 - WiFi (slow or limited connectivity )

I am also having issues similar to this with an SP3 I got last week and an ASUS RT-AC68U router. It came with Windows 10 and shows same symptoms. I've tested under a variety of scenarios. I'll be happy to provide any information I can for anyone at Microsoft looking into this issue.

Split from this thread.

I got my Surface Pro 3 from Amazon this week. It came with Windows 10. I am connecting to an ASUS RT-AC68U router (running the latest firmware) using the 5 GHz 802.11ac network, which has a different SSID from the 2.4 GHz one. I've found that when I test my Internet connection speeds on sites like speedtest.net or speedtest.bhn.net (from my ISP), it will initially spike up to about 15-20 Mbps and then flatten out to about 8 Mbps for the download speed. When compared to my other devices, this is not normal. I usually see over 155 Mbps on all other devices. As for the upload speed, I'll get around 11 Mbps. This is normal. The ISP advertises 150 down/10 up, but they tend to over-deliver a little bit (which is refreshing). It may also be worth noting that the network adapter properties show a negotiated link speed of around 866 Mbps while getting these dismal results during speed tests.

I installed updates on the first boot (including the 7/23 cumulative update for drivers), along with another update on Tuesday. I've gone through the various driver versions on the Surface Pro 3 Update History page, and everything looks up-to-date in Device Manager. More specifically, the Marvell AVASTAR 802.11ac network adapter driver is currently 15.68.3091.193, which matches what was included in the 6/23 update. Of course, I'd hope that would be the case since it looks like the computer was just setup/imaged on 7/25. Haven't loaded much on there yet, just Skype and Office so far.

I've done a few things to try and troubleshoot and isolate the problem already. First thing was to reboot the modem, router, and the Surface itself. Just to make sure my roommate wasn't hogging all the bandwidth, I also ran several tests from my iPhone and desktop PC. Both hit around the expected 155 down/11 up on both speed test sites mentioned above. Same for my roommate's desktop PC. I tried plugging in the Surface, in case performance was somehow being throttled on battery. I got close to the router, and tested from various distances away. I also tried disabling Bluetooth, though I didn't expect any interference on the 5 GHz network. No change in the download speed of 8 Mbps.

I took the SP3 to work the next day, where we use an assortment of Cisco Aironet 1120, 1130, 1140, 3500, and 3600 access points. I believe I was connected to a 5 GHz 802.11n network with a 144 Mbps link speed. I ran the same speed tests and got around 90 Mbps down/90 Mbps up. This is around what I get from my desktop PC using a wired network connection, so this appears to be good results. When I got home, I was still getting 8 Mbps down on 802.11ac 5 GHz. I tried switching to the 2.4 GHz network and got interesting results. The speeds were now about 45 Mbps down/9 Mbps up. Switching off Bluetooth got me up to around 66 Mbps/10 Mbps. The network adapter link speed was 75 Mbps. Still, the download speeds are less than half of what I get on other devices on my network. It would seem there is something that the SP3 and the latest updates does not like about my RT-AC68U, with either the current firmware or configuration.