Wireless Network

Hi all,
I have a router (Huawei Aolynk DR 814) provided by my internet provider and an ADSL link of 24 MB.
If i conect there a pc i get 14MB, less but ok.
But if i conect there a D-Link DIR-655 Wireless Router i only get 3MB on any pc.
Anyone knows why ???
Any help will be great. Thanks in advance.
Joaquim
jafspt@gmail.com