Check to see if your Wireless NIC can support the 16-20 mb/s speed. By testing the speed to your computer using the Ethernet cable, you can isolate the problem to Wifi or Ethernet connectivity to the PC. Also, you may want to try changing the wireless channel to see if interference is slowing the Wifi speed down on your computer. The channels that can be used are 1, 6, and, 11.
Sometimes the Wireless NIC can be found to not handle the bandwidth to your PC for the following reasons.
* the Wireless NIC is a Legacy one
* high Wifi traffic within the home network on the given channel
* the Wireless NIC could be faulty
It is a good idea to contact your ISP regarding this speed issue.
Every time I do a speed test from my phone and computer, it's faster on my phone by 5-13 mb/s. My computer gets 6-11 mb/s and my phone gets 16-20 mb/s from speed tests. My internet is pretty slow, but I don't see why it would be faster on my phone than my pc. I use wireless for my computer.