I assume you want a wireless connection between the two routers and then to allow
systems to wifi connect to either (or both with multiple systems).
The normal practice is to use an Access Point(A/P) for the second router, as it has the feature
you need (using a Bridge Connection) and which is missing in most routers
(typically restricted to
Infrastructure Mode; if you find a router which has that feature, then you can use it as well)
The setup looks like
Code:
ISP==YourConnection--->PrimaryRouter - - - Access Point
The Primary and the A/P can use the same SSID and passphrase, but separating the channels (1 vs 11) will reduce the interference.
Now you're down to getting ISP==YourConnection--> to work.
Besides the Cell phone data plan charges (which can be exorbitant), the issue becomes
YourConnection--->PrimaryRouter.
Try using the Cell phone for a single system connection to determine the requirements for dialing the connection - -
if it's easy enough, you may be able to use YourConnection--->PrimaryRouter
otherwise, you may need to put one system in the link like
YourConnection--->system#1-->PrimaryRouter
which requires Internet Connection Sharing on system#1 (and that system must be active for all systems on the Primary or A/P to get any service).
SO. Where does that leave you?