smsCoop is a tool for mobile phones that exploits cooperative mechansims to send SMS messages free of charge over 2G networks.
In the '60s Marshall McLuhan coined the phrase "The Medium is the Message" claiming that the medium over which information is transported is sometimes more important than the information itself. He was referring to the upcoming importance of television, but still 40 years later this sentence has some importance for the work we are describing in this paper. We would like to motivate our idea by a short example out of the GSM world.
At the beginning of the GSM deployment, there was a phenomenon in Italy called squillo. People, mostly young people, would just ring each other (hanging up before the other side could pick up) using their mobile phones to say hello or to convey some other predefined messages. This kind of communication was very popular as it was not billed (still in many countries it is not). Inspired by this idea, we envision a scheme where multiple phones could be used to convey data over existing wireless networks using the signalling plane without any additional costs for the user.
In the figure below a possible setup and example is given. The bits gained are of course paid for by the network provider and far fewer bits are conveyed than the network provider has to invest to make this transmission possible. Therefore it may be referred to as a trick.
Data Transmission over the GSM signalling plane with two groups of four mobile phones. Both groups have one master (M) each and three slaves (S) communicating over Bluetooth among group members. One sending phone, acting as a master, has the information to be conveyed to the master of the receiving group.
The four sending and receiving phones are identified by their phone numbers and to each entity a two bit address is assigned. This assignment is known to both masters of the group. The sender master will read the digital message and by using the first two bits one phone of the sender group is chosen to call over GSM a phone of the receiver group, which is identified by the second two bit tuple. In this example, first the master itself (00) will call the second phone of the receiving group (01).
The receiving phone, by using the intra group communication, informs the master about the received call (also which phone in the sending group made the call), which the master in turn can demap into four bits of information (0100). The second call from phone number four of the sender group (11) to the third phone of the receiver group (10) will be transformed into the information (1011). By each call four bits of information is transmitted.
smsCoop for Series 60 2nd Edition FP1 Devices
Compatible with: 6600, 7610, etc.
Compatible with: 6630, 6680, etc.
Compatible with: N70, N90, etc.