Method and device for ensuring and optimizing the exchange of data in mobile M2M communication with limited connectivity

A method for transmitting data from a mobile unit to a backend system includes, when connectivity is present between the mobile unit and the backend system: receiving, by the mobile unit, a master index from the backend system, deleting, by the mobile unit, data of the local database which are contained in the master database based on a comparison of a local index with the master index and updating the local index, transmitting, by the mobile unit, data stored in the local database which are not yet contained in the master database, receiving and storing a new master index from the backend system, and deleting the transmitted data of the local database based on a comparison of the updated local index with the new master index and further updating the local index.