Abstract:
A mobile telephone has a conventional wireless network call handling unit having a sound output for audibly outputting sound information received from a call in progress. In addition a wireless broadcast unit is provided for broadcasting information locally. The user can command the mobile telephone to broadcast the sound information from the call to one or more receivers in a neighborhood of the mobile telephone. Thus others can listen in on the call. Depending on commands by the users, the receivers may broadcast information back to the mobile telephone, for transmission via the call, together with sound information from the mobile telephone itself.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims priority of European Application No. 01305709.6 filed on Jul. 2, 2001.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to a mobile telephone.  
           [0004]    2. Description of Related Art  
           [0005]    Telephone users often have the desire to share their calls with others. In the prior art, this desire has been addressed by various solution. First of all telephone sets have been provided with loudspeakers to make the sound of an incoming call heard throughout the room in which a telephone set is located. If the user wants to share the call with a number of people in the room, he or she switches on the loudspeakers and possibly a microphone.  
           [0006]    In another solution, the telephone network provides for conference calls. A conference call connects a group of more than two users. In a conference call the telephone network routes sound from each member of the group to all other members of the group. Basically, the conference call solution and the loudspeaker solution serve two different situations: one in which participants in a call are located in different locations and another in which a number of participants are located in the same room. Of course, the two can be combined when a sub-group of participants in a conference call are gathered in a single room. The loudspeaker solution has the advantage that it does not require additional connection costs. Also it does not have the complexity involved with establishing conference calls (finding telephone number of participants, dialing etc.).  
           [0007]    Both the loudspeaker solution and the conference call solution could be applied to mobile telephones as well. However, the loudspeaker solution is less attractive for mobile telephones, first of all because loudspeakers tend to be bulky and secondly because, unlike conventional telephones, mobile telephones tend to be used in public spaces where speaking conversations out loud is undesirable. Thus, for mobile telephones effectively only the conference call solution is available, at the expense of greater complexity to establish the call and increased connection costs.  
         SUMMARY OF THE INVENTION  
         [0008]    Amongst others, it is an object of the invention to allow mobile telephone users to share calls without the additional network costs involved with conference calls.  
           [0009]    The invention provides for a mobile telephone, comprising  
           [0010]    a wireless network call handling unit having a sound output for audibly outputting sound information received from a call in progress;  
           [0011]    a wireless broadcast unit for broadcasting information distinguished from transmission/reception by the call handling unit;  
           [0012]    a user interface for receiving a share command from a user;  
           [0013]    a connection unit controlled by the user interface and arranged to supply information representing the sound information to the wireless broadcast unit, for rebroadcast of the information to one or more receivers in a neighborhood of the mobile telephone upon the share command, the information representing the sound information being broadcast via an inaudible medium. The mobile telephone according to the invention provides for broadcast of a signal that can be used in another device (preferably another mobile telephone) near the broadcasting mobile telephone to output the call received by the mobile telephone. Thus, on one hand no conference call is necessary to distribute the call and on the other hand the call does not have to be output from the mobile telephone as sound that is audible for everyone near the mobile telephone.  
           [0014]    Preferably, the mobile telephone is also equipped to receive such broadcasts from other telephones and to output the sound represented by the broadcast via the normal telephone sound output. Thus, the mobile telephone can be used to listen in to a call received by a nearby mobile telephone, without establishing a call for itself, if the user of that mobile telephone has indicated that that call may be shared. In a further embodiment the mobile telephone can also be used to add talk from the nearby mobile telephones to the shared call. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    These and other objects and advantages of the mobile telephone according to the invention will be described in more detail using the following drawing.  
         [0016]    [0016]FIG. 1 shows a mobile telephone; and  
         [0017]    [0017]FIG. 2 shows cooperation between a number of mobile telephones. 
     
    
     DETAILED DESCRIPTION  
       [0018]    [0018]FIG. 1 shows a mobile telephone. The conventional part  10  of the mobile telephone unit contains a network call handling unit  100 , an antenna  102 , a sound output  104  and a sound input  106 . In addition to the conventional part  10 , the mobile telephone contains a broadcast receiver  12  with a transmission input  14  and a broadcast transmitter  16  with a transmission output  18  and a user interface  19 . (In practice the transmission input  14  of the receiver  12  and the transmission output  18  of the transmitter  16  may be combined in a single antenna, which may even be the antenna  102  of the conventional mobile telephone part  10 ). The receiver  12  and the transmitter  16  are coupled to the call handling unit  100 . The user interface  19  is coupled to the receiver  12  and the transmitter  16 . The user interface  19  may also have connections (not shown) to the call handling unit  100 .  
         [0019]    [0019]FIG. 2 shows cooperation between a first mobile telephone  20 , a second mobile telephone  28 , a number of further mobile telephones  22   a,    22   b  and a network  25 . At least the first mobile telephone  20  and further mobile telephones  22   a,b  are realized as shown in FIG. 1. One or more further mobile telephones  22   a,b  may be present; by way of example two are shown. A call provides a connection between the first mobile telephone  20  and the second mobile telephone  28 , via a first base station  24  in the network which exchanges wireless signals with the first mobile telephone  20 , and a second base station  26  in the network  25  which exchanges wireless signals with the second mobile telephone  28 . Between the first and second base station  24 ,  26  the network  25  may also contain a core network (not shown), or a single base station may cover both mobile telephones  20 ,  28 . By way of example a second mobile telephone  28  is shown, but this is not necessary for the invention: any kind of telephone connected to the network  25  may be used instead of second mobile telephone  28 .  
         [0020]    In operation the first mobile telephone  20  exchanges local signals with further mobile telephones  22   a,b.  A call is established via the network  25  connecting the first mobile telephone  20  and the second mobile telephone  28  in a conventional way, for example using the GSM standard. When the user of the first mobile telephone  20  wants others to share the call he or she commands the mobile telephone  20  via the user interface  19  to start sharing the call. The user interface  19  may for example be menu operated, the user selecting a sharing menu and a start sharing current call option in that menu. When the user has commanded the mobile telephone to start sharing the call, user interface  19  activates transmitter  16  to take a signal that is fed to sound output  104  and feeds this signal to transmission output  18 .  
         [0021]    In an embodiment, call handling unit  100  outputs a combined signal to transmitter  16 , combining the signal that is normally fed to sound output  104  and a signal received from sound input  106 , which is normally passed to the second mobile telephone  28  via the network  25 . In another embodiment where the mobile telephones  20 ,  22   a,b  are only intended to operate shared calls at such close range that users can hear each others voice directly, this combination of signals may be omitted, or made optional, to be activated by a command via the user interface.  
         [0022]    Transmitter  16  converts the sound information from the call handling unit  100  for example into a high frequency electromagnetic signal radiated from output  18 . For example, a blue tooth type of signal may be used. But other kinds of protocols and other kinds of signal, such as modulated ultrasound signals or infrared signals may be used. Preferably, the sound information is encoded digitally into the transmitted signal.  
         [0023]    The users of the further mobile telephones  22   a,b  have the option to command their further mobile telephones  22   a,b  via their respective user interfaces  19  to join the shared call. This is realized for example by selecting an appropriate menu option on the relevant further telephone  22   a,b.  In response to the command, the further mobile telephone  22   a,b  activates its receiver  12  to receive the signals broadcast by the transmitter of the first mobile telephone  20  and to pass the received signal to the network call handling unit  100 . The call handling unit  100  outputs the sound corresponding to the signal to the sound output  104  that is normally used for outputting the sound from network calls. Thus, the user of the further mobile telephone  22   a,b  is able to listen in to the sound signal received by the first mobile telephone  20  from the network  24 ,  26  and preferably also to the sound spoken by the user of the first mobile telephone unit for transmission to the network  25 .  
         [0024]    The latter may be user selectable, so that a user can select between transmitting and/or outputting sound information from second mobile telephone  28  and the words spoken at the first mobile telephone or only sound from the second mobile telephone. Thus, if a further mobile telephone  22   a,b  is close to the first mobile telephone  20 , a user may opt to listen to the words of the user of the first mobile telephone  20  “live” only, i.e. not via the further mobile telephone  22   a,b  and when the user is further away he or she may opt to listen to these words via further mobile telephone  22   a,b.  This may be realized by selecting between local sound/no local sound menu options on the first mobile telephone  20 , which command whether sound information from sound input  106  is added to the signal transmitted by transmitter  16 . Alternatively, both information from sound input  106  and from second mobile telephone may be transmitted separately via transmitter, the user of the further mobile telephone  22   a,b  using a menu option on the further mobile telephone to command whether both or only a single one of the signals is output at the further mobile telephone. Thus, the users of different further mobile telephones  22   a,b  may decide to operate in different modes according to their distance to first mobile telephone  20 .  
         [0025]    Preferably, mobile telephones  20 ,  22   a,b  also have the option to pass back words spoken by the users of the further mobile telephones  22   a,b  to the first mobile telephone  20  for output to the second mobile telephone  28  via the network  25  and/or to the sound output  104  of the first mobile telephone  20 . For this purpose, the transmitter  16  in the further mobile telephone  22   a,b  and receiver  12  in first mobile telephone  20  may be activated. First mobile telephone  20  and/or further mobile telephone has a menu option to control this activation. Thus, the users of the further mobile telephones  22   a,b  can join in the conversation.  
         [0026]    In an embodiment the local transmission or reception may be used also when no call is active, for local communication between mobile telephones. Preferably, the mobile telephone supports activation of local communication from a call only during the call. That is, local communication for each call must be activated once the call has been started, or within a predetermined (short) time before the start of a call (typically less than a minute before the start of the call). Local communication for the call cannot be preactivated an arbitrary time before the call starts. Thus, it is prevented that others may inadvertently be able to listen to a call.  
         [0027]    In an embodiment, the privacy of communication between the first mobile telephone  20  and the further mobile telephone  22   a,b  is protected by encryption, for example by including an encyphering unit or channel hopping unit (not shown) in the transmitter  18 . As very high security is not required a simple decryption system, such as summing the signals with numbers from a pseudo random sequence may be used. The receiving mobile telephone  20 ,  22   a,b  contains a corresponding decryption or hopping unit (not shown) in the receiver  12 .  
         [0028]    At least at the start of call sharing the first mobile telephone  20  and the further mobile telephones  22   a,b  exchange information to enable decryption and/or corresponding hopping, such as a seed of the random sequence. In an embodiment this exchange is time selective, the exchange occurring only if the users of the first mobile telephone  20  and the further mobile telephone activate sharing substantially simultaneously (e.g. less than 1 more seconds from one another). In another embodiment this exchange occurs by means of a highly directional transmitter and receiver (not shown) in the mobile telephone  20 ,  22   ab,  such as a directed infrared signal, which is coupled to the encryption and decryption unit for example. Thus, the information to enable encryption is exchanged only when the users point their mobile telephones  20 ,  21   a,b  at each other and select a menu option to enable exchange of information.  
         [0029]    By now it will be appreciated that the invention provides for call sharing between different mobile telephones using locally transmitted signals without to use the telephone network to share signals between the locally present mobile telephones. Of course, the signals may be received also with devices other than mobile telephone (such as special “listen in” devices).