IraqiGeek’s Blog

3G to WiFi router

November 25, 2005 on 7:49 pm | In Technology |

Ok, this is not a brand new idea for a new product. What I am trying to do here is find a DYI version of acommercial product.

Such a device could be used in the car, turning it into a mobile hotspot, or in any place where there is network coverage for instant online capabilities for a group of users. Other uses would be to provide the ability to use a WiFi VOIP phone to make cheap VOIP calls while on the move, or even providing life feeds of a web camera.

The idea is to make a small device, that is capable of operating on battery power for several hours, and that is small enough to fit in your pocket, well, it will have to be a rather large pocket. The final device should have a DHCP server and preferably able to do MAC filtering to keep unwanted visitors out of the network.

The above criteria led me to think about using a PDA, either with built in WiFi and a CF slot, a PDA with an SD and CF slots (like the Sharp Zaurus which runs linux natively), or probably an iPAQ with the dual PCMCIA sleeve (which is my favorite solution), and using that CF slot with a CF to PC Card adapter to (no need in the case of the iPAQ with the PCMCIA sleeve) and one of those wireless WAN (WWAN) PC Cards (like UMTS, EDGE, EvDO, or WCDMA) to the mix. In the case of the dual PCMCIA sleeve on an iPAQ, one slot would be used for a WiFi PC card, and the second for the wireless WAN data card.

In an ideal world, this would be all that need to be done to get the router, but this is the real world, so there have to be some hardles to oercome. The thing is, Micro$ofts Pocket PC (or Windows Mobile) operating system doesn’t come with TCP/IP routing capabilities, like its desktop windows siblings.

From my readings, I doubt that routing capabilities can be added to any PPC powered PDA in the form of a third party application, but would LOVE to be proven wrong by any PPC developer out there.

So, the other way I could come up with to do this on PPC OS is by running it as a proxy. Not my ideal way for solving this, because it won’t be a router anymore. It will be a WWLAN to WiFi proxy. But even this turned to be not that easy. Apparently, there arent many people who want to run their PDAs as a proxy for anything (duh). The only “proxy” I could find for PPC was PocketPCProxy, whose development is at alpha stage at best.

Other than the proxy program, the proxy PDA would need to run a DHCP server, so the clients would be able to get an IP address automatically once connected. But even then, the WiFi adapter on the PDA would still show as a client other devices search for it, rather than an access point, but I guess this is something that can be lived with, if everything else works as its supposed to.

So, in order to be able to turn an old PPC PDA into a proxy between your 3G network data plan, and your WiFi network, you would need to either write, or get someone to write you proxy server and DHCP server applications for Pocket PC. What a mess.

All this talk about network services (DHCP, IP routing, proxy) led me to think about Linux. After all, this is what linux is best at, networking.

For starters, there already are many PDAs that run Linux, and there is a linux “distro” for the iPAQ, so why not use any of these? While this would be more than ideal for running such a solution, and would put the solution back to being a router, the only hardle is the lack of supporting drivers for Linux, at least not any that I am aware of. Again, if anyone is aware of something that contradicts what I am saying, I would be glad to be proved wrong.

If any of the WWAN cards has Linux drivers, and someone had ported those drivers to a Linux PDA, then all that would be needed is to install iproute, and a dhcp server, which I don’t think is a hard thing to do.