contributed by vincentfox
So you just got an EV-DO, GPRS or EDGE or some other cell-modem card for your laptop. Now you have the idea to share it around.

Okay fine, you can certainly do that.

You may find it impractical because in the final analysis, a usually expensive laptop has to be running, patched, etc. all the time to do the simple packet-switching job we typically do with a cheap router.

There are many ways to solve this problem.

The first and most obvious way for most users is always PC-centric. (Give a man a hammer and everything looks like a nail on which you must use that hammer. Anyhow ...)

You do not HAVE to use a laptop for this role, you can use a desktop. You can get PCMCIA adapters that will fit in your PCI slots on a regular desktop PC. Get a PCMCIA-PCI adapter unit and scavenge an older modest PC, the job of packet-switching does not demand much CPU or memory.

The simplest way to provide WiFi broadcast is not to do it with a WiFi card in the PC. The reason is that WiFi cards are meant to be end-point devices not to be base-stations providing central service. Yes, there are certain cards and software you can get around this on, or use Adhoc mode but these may be more complex than needed for most people.

I usually recommend the use of an Ethernet adapter on the PC, connected to an external Access Point unit such as the Linksys WAP54G. It doesn't really need to do anything other than bridge the LAN to WiFi and act as that base-station unit. An AP will be a better solution than Adhoc because it can be located anywhere central that is good for spreading WiFi signal around your structure. The only needed connection is an Ethernet run. This solution is also more flexible since if you need a little more coverage all you need to do is add an ethernet switch, and run Ethernet cable to another AP for the additional area.

So as far as the PC is concerned, we are doing something fairly simple - sharing Internet coming in on one adapter (the cell-modem) out to another adapter (the ethernet port). For this we can easily use ICS, the MS-approved Internet Connection Sharing program that has been built-in on Windows for some years now. Plenty of tutorials and FAQs for this, the Networking Forum FAQ being a great place to start. See sections 2.2 and 2.3 about connection sharing, link below:

»Networking Forum FAQ

The second obvious way would be to use a commercial proxy software which is a fancier and more featured version of the same PC-centered idea. Wingate and many software out there.

The third way would be to buy a dedicated router device; these do exist which accept a cell-modem and handle the router job for you. They are not cheap, but usually a lot cheaper than a laptop and are meant to be left on 24x7. A bit of Googling should find you a product that will do the job. Example I found quickly for EV-DO would be the Kyocera KR1 router. Another, less expensive alternative in the UK is the Linksys WRT54G3G.

I would also check around on some cellphone forums, you are more likely to find some vendor-specific examples there.