1. Technical Field
The present invention relates to a communication system comprising first and second communication devices each capable of communicating with a telecommunications network, and both being connectable to each other by a data link for information transfer as well as to a method for operating such a system.
2. Discussion of Related Art
WO 02/089449 A2 discloses a radiotelephone system including a first and a second radiotelephone, e.g. a mobile telephone and a car telephone, wherein the second radiotelephone if connected to the first radiotelephone can use SIM information and actual connection parameters of the first radiotelephone to establish a connection to a telecommunications network without going through the usual channel searching procedures etc. Therefore, a connection of the first radiotelephone to the telecommunications network can be switched over to the second radiotelephone.
Thus, a user of a telecommunications network who owns e.g. a mobile telephone and a car telephone can use his/her car telephone in his/her vehicle instead of his/her mobile telephone after switching over the connection, but can be contacted by anyone using the subscriber number of the mobile telephone.
A similar radio system is known from WO 02/21867 A2 which is concerned with the management of portable radiotelephones which are equipped with functionality to allow them to communicate with one another using a local wireless connection, such as low powered radio frequency (LPRF) link, a Bluetooth connection, or other communication means such as an infra-red link. Through the wireless link, the radiotelephone is able to acquire information from the SIM contained in another radiotelephone which is in the coverage range of the wireless link functionality to enable the one radiotelephone to function as if it had the SIM of the other radiotelephone inserted within itself. Thus, the radiotelephone that uses SIM information of another telephone is regarded as the other telephone in a telecommunications network so that all calls made to the other radio telephone will be received by that using the information of the other telephone. Additionally any calls made by the one radio telephone will be as if made by the other radiotelephone and will be billed accordingly. Furthermore, it has to be noted that the one radiotelephone may be used by more than one user each having her/his own (portable) radio telephone.
EP 0 406 985 B1 is concerned with a first mobile cellular radiotelephone and a second hand portable cellular radiotelephone that can be connected to the first radiotelephone via a fixed-wired electrical data link, an optical data link, or a radio data link.
When the two radiotelephones are connected with each other, the first one uses the subscriber number retrieved from a NAM (number assignment module that is comparable with a SIM (subscriber identification module)) of the second one whereas the R.F. circuits of the second one are switched off. According to a specific embodiment, information from the NAM of the second radiotelephone can be downloaded into a memory of the first one. A microprocessor of the first radiotelephone coupled to the NAM of the second radiotelephone or the memory uses NAM information of the second one so that the first radiotelephone assumes the identity of the second radiotelephone.
In addition, both radiotelephones may be provided with a RAM for variable data like abbreviated dialing codes, frequently dialed telephone numbers, or other data. In this case, variable data stored in the RAM of the second radiotelephone can be downloaded into that of the first one and can be used with the first one after the first radiotelephone assumed the identity of the second one.
Furthermore, the Bluetooth SIM Access Profile (SAP) enables one mobile radiotelephone to get wireless, remote access to a SIM card inserted in another radio telephone when both radio telephones are in a Bluetooth range of less than 10 meter. This feature is a specific Bluetooth profile that is standardized in the BT SIG (Bluetooth Special Interest Group), car working group.
The principal operation according to this specific Bluetooth profile is: a first mobile radiotelephone is registered with identification information from a local SIM card in a cellular network, i.e. a radio communications network.
When a second mobile radio telephone comes into a range of approximately less than 10 meters (Bluetooth range) both radio telephones can enter either automatically or by being manually triggered a so called remote SIM mode. In this mode the first radio telephone with the local SIM card leaves the wireless network while the second radiotelephone can access the SIM card of the first radiotelephone remotely via a Bluetooth wireless data link. In addition, the first radio telephone deactivates all functions that are related to wireless communication, i.e. deactivates the radio part thereof. Within this mode the second radiotelephone uses the SIM information acquired via the SIM access over Bluetooth to register with the same user identification in the cellular network. Finally the second radio telephone gets the active radiotelephone whereas the first radiotelephone remains passive as long as the remote SIM mode is active.
When the remote SIM mode is left both radio telephones go back to local mode, in which the first radio telephone is now active again.
If the first radiotelephone is a mobile telephone and the second is a car telephone there is a seamless “handover” from the mobile telephone radio part to the car telephone radio part when a user enters the car without using two different SIM cards. Since the mobile telephone gets active again when the remote SIM mode is left, there is a problem in case it is required to switch-off any radiotelephone, e.g. near at a patrol station, or other areas where explosive materials are handled, since a simple switch-off of the car telephone would not lead to switching-off all telephones because in this case both radio telephones would fall back to local mode, resulting in activating the mobile telephone again. Thus the mobile telephone would not have been switched-off simultaneously with the car telephone.
Another problem that might occur is a loss of received information if the active second radio telephone, e.g. a car telephone has less functionality than the first radiotelephone, e.g. a mobile telephone. The mobile telephone may be able to receive SMS, MMS, Calendar entries (vCal) and Business cards (vCard) and the like whereas the car telephone does not support such features. Therefore, received information according to these features may be lost.
Another problem occurs if a user of a first radio telephone who has to use the second radiotelephone instead of the first one wants to use his/her user specific data in the form of contact cards, telephone book entries, calendar information, voice text, notes, and the like stored his/her mobile telephone when he/she has to use the car embedded radio telephone.