Plug your computer to router with LAN, if LAN speedtest same speed as wifi then no need for wifi upgrade.
This solution is only valid if all you need your wifi connection for is to route traffic from the internet to your computer. If that's the case, then this will show if you have any speed degradation once the packets hit your network. If that's all you're interested in then you may not even need to do this. Compare the speed test results at a site such as broadbandreports.com with what your ISP is rating your internet connection's bandwidth; if they're comparable then you're fine.
However, if you need to do things like stream video files from a media server on your network, then you may find your 802.11g connection isn't up to your requirements. If you directly connect one pc to your router and wirelessly connect another pc, and then transfer a file from one to the other, you can see what the transfer speed is. You can then compare that to what you would need for whatever LAN purpose is at question. Obviously that will vary by requirement; for example, streaming SD video will not be as demanding as streaming HD, etc.
Not really. You can't just compare ISP advertise speed with speedtest speed to find out wifi degradation. I am not sure what connection PO has, but if it is dsl, then the result is most invalid because advertised net speed is almost never acheived due to line signal degradation.
To test wifi speed within home network. Download Netlimiter and monitor the speed when you move files across the network.
i had a dsl connection and it came close to the speedtest results. The same is true with my current WiMax connection. Obviously you can't just run it one time.
Netlimiter is a good program. It can also give you network traffic speeds. However, it's not free (although there may be a trial version), and you get a pretty good estimate by just looking at the 'copying files' dialog box's reported transfer speed.
In any event, you want the other end to be directly attached to the router rather than connected via WiFi otherwise you will see reduced speed.