We will need a router with upgraded firmware. There are specific router models, for example, Linksys WRT54G, D-Link DIR-300, etc. To check if this router is supported by DD-WRT, please click here and visit the online database. Just type in the name of the model of the router and it will show whether this model is supported or not.

Every router has its own means of flashing DD-WRT. With some models, such as DIR-300, the process is more difficult. With some models, such as Buffalo, it is simpler.
The instructions of how to do it are given in almost every DD-WRT installation package or they are displayed on the download page, in the software data base.
After the flashing the firmware we need the QoS (quality of service). So we select the protocol http to have the priority against other protocols.

We also can set one additional setting to allow, for example, to use only 2 MB of bandwidth for each user on wireless connection.

Additional information about DD-WRT can be found here.
DD-WRT supported wireless router database is here.
The list of functions is here.