networking - What can cause this variation in ping?

I have a problem with my internet connection and I don't know what is causing it.

My router is a Linksys E3200 and my computer is equipped with Windows 8 and a WIFI adapter TP-Link WDN3200 (Ralink 5572) with the newest drivers from Ralink.

Using inSSIDer3 I get the following statistics:

I think the gap between my router and my neighbours should be adequate.

When doing a ping test towards my router I get the following statistics:

C:\>ping 192.168.0.1 -n 1000

Pinging 192.168.0.1 with 32 bytes of data:
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1586ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1995ms TTL=64
Reply from 192.168.0.1: bytes=32 time=13ms TTL=64
Reply from 192.168.0.1: bytes=32 time=3ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1993ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=2000ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=4ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1994ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1995ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1990ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
Reply from 192.168.0.1: bytes=32 time=1ms TTL=64
...

I'm curious to the 2-good-1-bad pattern displayed here and it rarely deviate from this. Occationally I get a Request timed out.

With my cell phone (Samsung Galaxy Nexus) using WIFI only (data disabled), I get continuously good replies from my router during a ping test.

Using VPN + Remote Desktop for my work is not a good experience and I do seem to get a slow lookup when trying to get access to a website in a browser.

Can anyone guide me to determine what the problem is?

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Updates:

Using a cabled LAN connection gives me <1ms ping results all the time.