Router or Access Point

I'm working on a solution which should be used by scouts when their expeditions to the mountain. Basically every scout has a wireless device which transmits the scout's GPS location and some other information(like the quality of air surrounding them) to their backup vehicle which has a router(or AP device) that gives them internet connection(via 3G SIM card). That information should them be sent to a web server which there would be someone monitoring every step of the team in real time.

Assuming that the there would be 20 scouts, does it has to be a 3G Router(dhcp would be nice) or a simple modem 3G connected to a arduino Yun would do the trick?

Thank you for your help.

Solution

Simple answer is that it depends on what protocol the scouts are using on their devices. If they are WiFi, which I am guessing from your question, and you want use the device on the base vehicle to proxy their requests to server across the internet then you can either:

have the device on the base vehicle be a (3G) router that simply passes the messages along to the internet
have the device on the base vehicle act as a local server and collect the messages from the scouts and then send a completely separate new message to the internet, either one for each message or combining messages to reduce the total number of messages sent. So the device is acting as a server for the scouts and a client for the main server back on the other side of the internet connection. This might help if you expect to have intermittent 3G covert as this device can cache the messages also.

Of course, given that 3G coverage is bad in mountain areas, and that WiFi will have poor range and possibly bad coverage in that type of terrain also, you are probably going to lose some scouts on your trip, which may (or may not...) be unpopular with their parents.