Router wifi speed poor compared to lan speed

I have a router from dlink. It was first used by my friend. I am having a bit issue with the internet connection here. When I use the internet on my pc which is directly connected to the router through lan, it is not giving me a good speed. I have a 2mbps line and I can download ample of things really fast. But when I try to use the same on wifi the speed is very slow. I cannot even stream a video on YouTube continuously. It keeps on buffering. I want some help here through which I can make the wifi speed same as lan.

Just for testing purpose, try some other device. I am quite sure you are using your smartphone or tablet. Just test the same thing on any other device. If the speed works well then your mobile or tablet has a issue. Your network chip might not be so strong to get the full speed. And if the issue is same on new devices also then it means you have to update the router firmware. Just get a new version or rewrite the existing one. And test back. It might start working fine unless it does not has any hardware flaws.

This is a antenna issue. There are two things you have to do. Bring the mobile phone near to the router and check speed. If it is not proper then you have to replace the router antenna. You can find that easily in market or on web. This antenna are cheap to buy and you can replace that manually. You can find the antenna specification in the router details. Just check what antenna it is. It can be a 2db or higher. Use the one that is used on the router right-now. Don't go with higher one.