Why is my Wi-Fi connection speed much slower than a wired connection?

When I plug my laptop via LAN cable and check speed on speedtest.net I have over 32 Mb/sec. When I unplug the cable and connect to the same router I have less than 15 Mb/sec. I tried to change channels already but this didn't help. I'm sitting just near the router.

What can it be? The router is a Dlink 400.

Solution 1:

The wireless connection is the bottleneck. Even 802.11g, with theoretical bandwidth of 54Mbit/s, can typically only achieve 22Mbit/s average throughput under ideal conditions. It is likely that the laptop only supports 802.11g, rather than the higher speed 802.11n.

Solution 2:

Wireless access speeds are known to be slower than wired connections, for now at least. However, your router is capable of more than 15Mbps.

Sitting right next to the router means you might not actually get the best reception. Try sitting a couple yards away with direct line of sight and running speed test again. Also, make sure your router isn't next to large metal objects or electrical items as they can interfere with the wireless signal and turn off WEP and enable WPA2/AES instead, WEP can kill your wireless speed.

I strongly suggest you look through this guide for possible causes once you have done those basic things.