A Wi-Fi network uses a wireless router and a high-speed internet modem.
Depends on how you connect. Is the computer wireless? Is there a cable running from the computer to the back of the modem? If it is wireless and slow then move the computer closer to the modem. If it is wired and slow then it might be your network card is throttling the speed.
Look at How can you speed up your wireless internet? for the answer
Verizon DSL Wireless
There are many factors impacting broadband speed, only some of which you have control over. Network speed, modem speed, and internet traffic all work together to produce the broadband speed. Purchasing a faster modem and a faster network speed would be the easiest way to improve speed without changing services.
not the modem it self, but with an internet plan. im not sure if comcast's high speed internet offers wifi but i know Xfinity does
11 Mbps
Going on the assumption that you have some kind of High Speed Internet connection you will need a wireless router and a wireless Network Interface Card (NIC). You would plug the router into the high speed modem and then connect wirelessly to the router from the laptop. You'll need to also setup some security for the wireless network, but that's a whole nother can of worms.
A wireless router will usually be connected directly to a high speed modem between the modem and any other device. This allows the router to correctly pass internet requests from the local network (computers connected wirelessly or to a standard port) to the ISP (the high speed modem connected to the Internet port). Connecting a wireless router to a computer would be unusual but it could function if connected to the network port on the computer provided the router-computer connection was properly configured. In this case the computer would have to be configured to route.
I think that high speed wireless is worse then a cable modem, since it will go out during a very bad thunderstorm or any bad weather. With a cable modem you are less problems to occur an outage.
Yes you can, you have to do that like following. Connect one DSL wireless modemrouter to the cable modem, and another wireless modem connect in the first wireless modemrouter. You have to understand that internet speed on the first DSL router will be rather higher then for the second one.
You will get speed of 802.11b.