Cloud storage and computing and client-sever model are basic concepts in distributed systems.
Advances in Distributed Security by Nick Szabo in 2003
A transaction using the TxTenna app works as follows: Using the Samourai Wallet app the user creates a standard bitcoin transaction and signs it. This is possible while offline and without wifi or mobile access.The Samourai Wallet app then passes the offline transaction to the TxTenna App and TxTenna broadcasts it to nearby mesh nodes via a paired goTenna mesh device. Other goTenna devices in the area relay the transaction until an internet connected goTenna node also running TxTenna receives it and forwards it to the Bitcoin network.