Method for controlling an intersystem handover

Abstract

According to the invention, a reduced set of transport format combinations is signalled to a subscriber station which has established a link to a second radio communication system in a second signalling channel of said second radio communication system. The transport format indicator is then selected from the reduced set of transport format combinations and used to initiate a link transfer to the first signalling channel of a first radio communication system. A full set of transport format combinations is subsequently signalled to the subscriber station in the first signalling channel.

What is claimed is: 
     
       1. A method of controlling an intersystem handover between first and second radio communication systems having first and second signaling channels, respectively, comprising:
 signaling to a subscriber station a reduced set of transport format combinations related to setting up a connection to the second radio communication system, in one of a dedicated second signaling channel and a radio channel of the second radio communication system; 
 selecting a transport format indicator from the reduced set of transport format combinations for initiation of a handover to at least one of a first signaling channel and a data channel of the first second radio communication system; and 
 signaling a complete set of transport format combinations to the subscriber station in the first signaling channel. 
 
     
     
       2. A method according to  claim 1 , further comprising initiating the handover to a signaling and/or data channel of the first radio communication system. 
     
     
       3. A method according to  claim 2 , further comprising coding the transport format indicator by bitmap coding. 
     
     
       4. A method according to  claim 3 , wherein the first radio communication system is a UMTS mobile radio system and the second radio communication system is a GSM mobile radio system. 
     
     
       5. A method according to  claim 4 , wherein the second signaling channel of the second radio communication system is one of a stand-alone dedicated control channel and a radio control channel. 
     
     
       6. A communication system subscriber station for use in an intersystem handover between first and second radio communication systems having first and second signaling channels, respectively, comprising:
 a memory to store data of a reduced set of transport format combinations related to setting up a connection to the second radio communication system, in one of a dedicated second signaling channel and a radio channel of the second radio communication system; and 
 a processor, coupled to said memory, to select a transport format indicator from the reduced set of transport format combinations for initiation of a handover to at least one of a first signaling channel and a data channel of the first second radio communication system; and to receive a complete set of transport format combinations transmitted to the subscriber station via the first signaling channel. 
 
     
     
       7. A communication system network station for use in an intersystem handover between first and second radio communication systems having first and second signaling channels, respectively, comprising:
 a memory to store data of a reduced set of transport format combinations related to setting up a connection to the second radio communication system, in one of a dedicated second signaling channel and a radio channel of the second radio communication system; and 
 a processor, coupled to said memory, to select a transport format indicator from the reduced set of transport format combinations for initiation of a handover to at least one of a first signaling channel and a data channel of the first second radio communication system; and to receive transmit a complete set of transport format combinations to the subscriber station via the first signaling channel.