if your modem has wireless capblility then you don't need a router.

Data flows through the modem both ways.

A modem connects your computer to the Internet. A router takes the Internet signal and splits it up and distributes it to other computers on your network. There are two types of routers, wired and wireless. A wired modem router uses a cat5 cable to connect to the modem and to connect to each computer on the network. A wireless router uses wires to connect to the modem but connects to each computer on the network without wires.

asynchronous

A modem's send light may not light up when connected to a wireless router if the two are not communicating. This can be caused by a faulty cable, an incorrect configuration, or a bad router.