Internet speed very slow only in WiFi and in just one laptop

Question

I have Xfinity internet at home. All the devices (a couple of laptops, phones, tablets, etc) are connected via WiFi, except a PS3 which is connected via ethernet cable.

A few days ago we got the Xfinity gateway (router+modem) replaced because we had problem with it. I don't know if it's a coincidence, but around the same time I started to notice very slow internet in my work laptop. I've been doing speed tests in all the devices and they all seem fine (normal speeds) with the exception of this laptop (very slow speed).

I've been doing some tests:

1. If I connect the laptop to the router via ethernet cable, the internet speed is normal again.
2. If I boot the same laptop with Windows 8 (I have it with dual boot Windows 7 and Windows 8, but I usually use Windows 7), and do a speed test, the speed is normal again.
3. I've restarted the router/laptop several times and speed via WiFi still very slow
4. I've removed the WiFi network from the remembered networks of Win7 and connected to it again as if it was new network, and speed via WiFi still very slow

By slow speed I mean around 2Mbps when normally I would get around 35Mbps. The upload speed doesn't seem to be affected by this problem, it's usually 6-10Mbps.

Any ideas how I can get my laptop to get the same speed as always?

EDIT

So following the advice given in the first answer I reinstalled the drivers of the wireless card. I've been doing some tests with it and the rest of devices, and it seems that now I'm getting more speed that before, but the download speed still slower than expected. Although it fluctuates quite a bit, most of the results I get are around 10 Mbps, when before they used to be around 35 Mbps. Besides, it seems that in the rest of devices now it happens also the same (it's hard to tell because of how much the results change on each test). Can it be a hardware problem of the router/modem? Is there any way to test that? I called Comcast the other day and everything seemed fine on their end.

Answer 1

Because you mention that it works better in Windows 8, it could be a driver problem. Make sure you have up-to-date windows updates, including optional updates which sometimes have vendor specific hardware updates. Try locating your network adapter in your device manager, right clicking the adapter and select "Update driver software..." If this is already up to date, try uninstalling and reinstalling the driver. If this is a dongle and not internal card try searching for the driver directly from the manufacturer.

Answer 2

I'm sure you've already checked this but have you checked to verify that there are no energy saving settings enforced on the wireless card (selecting the battery icon in the lower-right hand side of the task bar and seeing if you're set to use a Balanced or Power Saver mode)? Being a work laptop I wouldn't be surprised if your IT department has configured by default Balanced or Power Saver battery plans. These can adversely affect your WI-FI performance. Furthermore, these would be different between operating systems.

Check this by searching for Power Options in the Start Menu and alternating between power plans as needed. I typically recommend High Performance to see if that resolves your issue. Power settings specifically related to your internal NIC can be found by selecting Change Plan Settings; Change Advanced Power Settings; and adjusting the Wireless Adapter Settings.

Answer 3

A couple ideas in response to your edit:

Can it be a hardware problem with the modem?

Sure. A lot of things can go wrong with the modem. Modem hardware breaks. It can get hacked (it happened to me recently)... different modems can transmit with different amounts of power on different channels, and conversely, a more powerful, newer modem might lead to greater interference. There are ways to make sure different devices are talking on different channels. And if the default wireless channel changed with the new router, your neighbors might be causing interference suddenly, when they were not before.

You may (among other things) have changed the position of your router when it was reinstalled, and perhaps the new antenna is not pointed optimally as the old one was. If you moved your modem/router from the table onto the floor, for example, that would make a big difference. Running speed tests with your router in different elevations, pointed in different directions, is generally worth doing if you're covering a big house.

It might be your own devices interfering with one another. I would try turning off all other devices and if the speeds improve, try hard-wiring some of them (like the PS4) into the modem, so they don't have to interfere with your laptop.

If you know how to configure a modem/router from the default state (it isn't too hard to look up the model), it isn't a terrible idea to try doing a hard-reset to factory defaults.

Nobody mentioned this also, but... TCP Auto Tuning may be the issue if you are connected to network as type "public" in Windows 7.

Answer 4

In my case my laptop Wifi connection was slowed from 10 mpbs to 4 mbps. I was able to solve this by doing the following:

1. Uninstall wireless network card's driver in device manager without deleting the drivers.
2. Re-scan hardware your Wifi device will appear again.

Source: YouTube