Cellular radiotelephone system signalling protocol

Claims

What is claimed is:

1. A method of transmitting data packets in a data network connecting a plurality of mobile switching centers in a cellular radio telecommunications network providing service to a plurality of subscribers, each of said mobile switching centers containing a software package, said method comprising the steps of:

inserting into each packet a label containing an identification of a source mobile switching center and a destination mobile switching center for the packet;

inserting into said packet an information block including a message containing subscriber service data;

inserting into said packet data identifying the software package in said source mobile switching center; and

sending said packet from said source mobile switching center to said destination mobile switching center.

2. A method of transmitting data packets in a data network as set forth in claim 1 in which said step of inserting data identifying said source software package comprises the step of:

inserting said software package identification data into said information block.

3. A method of transmitting data packets in a data network as set forth in claim 1 in which said message is a request message.

4. A method of transmitting data packets in a data network as set forth in claim 3 further comprising the step of:

responding to said request message with a data packet containing a reply message sent from said destination mobile switching center to said source mobile switching center, the length of which being a function of the identity of the software package in said destination mobile switching center.

5. A method of transmitting data packets in a data network as set forth in claim 4 further comprising the step of:

inserting within said packet containing the reply message data identifying the software package in said destination mobile switching center.

6. A method of transmitting data packets in a data network as set forth in claim 5 in which said request and reply messages are part of a handshaking procedure between said source and said destination mobile switching centers preparatory to the exchange of additional messages therebetween.

7. A signalling system for communicating messages via a communications medium between an originating mobile switching center and at least one destination mobile switching center within a cellular radio telecommunications network providing service to a plurality of subscribers, each of said mobile switching centers including a software package, each of said messages relating to the cellular service being provided to one of said subscribers and comprising:

a label field containing an identification of said originating mobile switching center and said at least one destination mobile switching center;

a pair of heading codes fields; and

an information field including:

a package information block which identifies the software package within said originating mobile switching center.

8. A signalling system for communicating messages via a communications medium between an originating mobile switching center and at least one destination mobile switching center as set forth in claim 7 in which said information field further includes:

a first block of data containing an electronic serial number of a mobile station being used by said one subscriber;

a second block of data containing a multi-digit number associated with said one subscriber; and

a third block of data specifying the number of digits in said multi-digit number.

9. A signalling system for communicating messages via a communications medium between an originating mobile switching center and at least one destination mobile switching center as set forth in claim 8 in which:

said multi-digit number contained within said second block of data is the international mobile station identity number of said one subscriber.

10. A signalling system for communicating messages via a communications medium between an originating mobile switching center and at least one destination mobile switching center as set forth in claim 8 in which:

said multi-digit number contained within the second block of data is the directory number of said one subscriber.

11. A signalling system for communicating messages via a communications medium between an originating mobile switching center and at least one destination mobile switching center as set forth in claim 7 in which:

said messages are part of a handshaking procedure between said mobile switching centers preparatory to the exchange of additional messages therebetween.

12. A signalling system for communicating messages via a communications medium between an originating mobile switching center and at least one destination mobile switching center as set forth in claim 7 in which:

said messages relate to providing automatic roaming service to said subscribers within said cellular network.

13. A signalling system for communicating messages via a communications medium between an originating mobile switching center and at least one destination mobile switching center as set forth in claim 12 in which:

each of said messages is either a location update message or a location update accepted message.

14. In a cellular radiotelephone system network carrying high speed digital messages between a plurality of mobile switching centers serving mobile subscribers located in different geographic areas within said network, the combination of:

a first mobile switching center including a software package having a particular identity which provides to said center certain specific features and communications capabilities;

a second mobile switching center connected to said first center for the communication of data therebetween, said second center also including a software package having a particular identity which provides to said second center certain specific features and communications capabilities; and

a signalling system for carrying digital data messages between said first and second mobile switching centers related to the providing of mobile communications services to said subscribers, said signalling system incorporating a communications protocol including:

a data packet label comprising an identification of a source switching center and a destination switching center;

an information block including a message being sent from said source center to said destination center; and

means for identifying the particular software package within said source center from which said message originates.

15. In a cellular radiotelephone system network carrying high speed digital messages between a plurality of mobile switching centers serving mobile subscribers located in different geographic areas within said network, the combination set forth in claim 14 wherein said software package identification means is included within said information block.

16. In a cellular radiotelephone system network carrying high speed digital messages between a plurality of mobile switching centers serving mobile subscribers located in different geographic areas within said network, the combination set forth in claim 14 in which:

said message within said information block relates to providing automatic roaming service to a mobile station within said cellular network.

17. In a cellular radiotelephone system network carrying high speed digital messages between a plurality of mobile switching centers serving mobile subscribers located in different geographic areas within said network, the combination set forth in claim 16 in which:

said message is part of a handshaking procedure between said first and second mobile switching centers preparatory to the exchange of additional messages therebetween.

18. In a cellular radiotelephone system network carrying high speed digital messages between a plurality of mobile switching centers serving mobile subscribers located in different geographic areas within said network, the combination set forth in claim 17 in which

said message is either a location update message or a location update message accepted message.

19. In a cellular radiotelephone system network carrying high speed digital messages between a plurality of mobile switching centers serving mobile subscribers located in different geographic areas within said network, the combination set forth in claim 18 in which:

said protocol forms part of a signal sent within the mobile telephone user part of the C.C.I.T.T. No. 7 signalling protocol.

20. A system for transmitting data packets in a data network connecting a plurality of mobile switching centers in a cellular radio telecommunications network providing service to a plurality of subscribers, each of said mobile switching centers including a software package, said system comprising:

means for inserting into each packet a label containing an identification of a source mobile switching center and a destination mobile switching center for the packet;

means for inserting into said packet an information block including a message containing subscriber service data;

means for inserting into said packet data identifying the software package in said source mobile switching center; and

means for sending said packet from said source mobile switching center to said destination mobile switching center.

21. A system for transmitting data packets in a data network as set forth in claim 20 in which said means for inserting an identification of data identifying said source software package comprises:

means for inserting said software package identification data into said information block.

22. A system for transmitting data packets in a data network as set forth in claim 20 in which said message is a request message.

23. A system for transmitting data packets in a data network as set forth in claim 22 further comprising:

means for responding to said request message with a data packet containing a reply message sent from said destination mobile switching center to said source mobile switching center, the length of which being a function of the identity of the software package in said destination mobile switching center.

24. A system for transmitting data packets in a data network as set forth in claim 23 further comprising:

means for inserting within said packet containing the reply message data identifying the software package in said destination mobile switching center.

25. A system for transmitting data packets in a data network as set forth in claim 24 in which said request and reply messages are part of a handshaking procedure between said source and said destination mobile switching centers preparatory to the exchange of additional messages therebetween.

26. In a cellular network comprised of first and second exchanges, each of said first and second exchanges including a software package for providing services to a plurality of subscribers, a method for controlling the exchange of subscriber service information between said first and second exchanges comprising the steps of:

sending from said first exchange to said second exchange a handshake origination message including an identification of the software package in said first exchange;

sending from said second exchange to said first exchange, in response to the receipt of said handshake origination message, a handshake confirmation message including an identification of the software package in said second exchange; and

exchanging subscriber service information between said first and second exchanges based on the capabilities of said software packages in said first and second exchanges, respectively.

27. The method of claim 26 wherein said first exchange is a visited exchange to which a subscriber has roamed, said second exchange is a home exchange of said subscriber, said handshake origination message comprises a location update message and said handshake confirmation message comprises a location update accepted message.

28. The method of claim 26 wherein said first exchange is a gateway exchange which receives a call to be routed to a subscriber, said second exchange is the home exchange of said subscriber, said handshake origination message comprises a routing inquiry message and said handshake confirmation message comprises a routing response message.

29. The method of claim 26 wherein each of said handshake messages is contained in a signalling information field (SIF) of a signalling message formatted in accordance with C.C.I.T.T. No. 7 signalling protocol.

30. The method of claim 29 wherein the length of said SIF is a function of the capabilities of the software package identified therein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to mobile radio telephone systems and, more particularly, to a signalling within a cellular radiotelephone system.

2. History of the Prior Art

Originally, mobile radiotelephone service was characterized by a central site radio transmitting with high power to a limited number of mobile units in a large geographic area. More recently, cellular radiotelephone systems have divided the coverage area into contiguous smaller coverage areas (cells) served by a plurality of base stations using low power transmitters and receivers controlled by an exchange located at a central site.

A cellular system typically utilizes one radio control channel in each cell to receive requests for service from mobile subscriber units, to call mobile subscriber units and to instruct mobile subscriber units to tune to a frequency pair where a conversation may take place. The control channel in each cell is assigned the task of continuously receiving and transmitting data and is the channel to which the mobile subscriber unit tunes when not in a conversational state.

Generally speaking, each cellular system is controlled by one or more mobile telephone switching offices ("MTSO's") which handles the calls to mobile stations located within a specified geographic area. Each mobile station is assigned to a particular MTSO or "home exchange" where it is registered for service. If the mobile leaves its home exchange and enters the territory of another exchange it is said to be "roaming". Needless to say, different cellular exchanges must cooperate and communicate with one another in order for a mobile to have continuous communication as it moves from one exchange to another or for a call originating in one exchange to be completed to a mobile located in another.

To communicate between MTSO's, a common signalling protocol must be used so both exchanges communicate in the same language. That language is a series of sequentially transmitted digital bits which are grouped together in fields to define the various functions needed to set up calls, hand-off a call from one cell to another, terminate a call, etc. Such signalling protocols have been standardized to some extent so that any cellular exchange can communicate with any other exchange to enable basic communications functions. These standards have necessarily come about due to the proliferation of companies involved in mobile telephone service. For example, the so-called CCITT No. 7 signalling system is used to interface different mobile telephone exchanges for roaming and handoff purposes. This signalling system may be identified by any one of three separate CCITT standards, commonly known as the Yellow book, the Red book, and the Blue book, or the ANSI (American National Standards Institute) standards. These different signalling standards are for use in communicating between the different exchanges comprising a cellular system network.

Pursuant to one of these four signalling systems, there is employed a digital bit stream known as message signal units which comprise the Mobile Telephone User Part ("MTUP") used in signaling between MTSO's such as that employed during automatic roaming signalling within the Yellow book standard used in North America. Within such message signal units a particular field is identified as the signalling information field. That field is composed of a stream of digital bits which can be employed to identify a particular function. All data specified within this field is selectively defined by the cellular system operator. Therefore, from the user point of view this field is common regardless of which signalling system is used in sending the data.

Adjacent MTSO's must communicate with each other in order to coordinate their services. For example, when a mobile subscriber roams from one MTSO to another, the automatic roaming function contained within certain software utilizes the CCITT No. 7 signalling protocol. This signalling protocol is the vehicle that transfers the necessary data in order to implement continuous communications to a mobile as it moves from one cellular exchange to another.

One instance in which cooperative signalling between MTSO's is required is to process a subscriber service call which is a request from a mobile unit to change one or more of the features available to the subscriber. If such a request is made in a visited MTSO and the mobile has not yet registered there, the visited MTSO informs the home MTSO of the new location of the mobile in the process of executing the selected subscriber service. The selected subscriber service information is also sent to the home MTSO through the signalling system.

Because MTSO's manufactured by different suppliers frequently make up a cellular system network, it is often the case that these MTSO's have different service capabilities. Further, adjacent systems owned by the same operators may each use a MTSO manufactured by the same supplier but which still have different capabilities. The capability of an MTSO is largely defined by the specific software "package" installed within it. When a MTSO makes a request for a specific service that is not provided by another MTSO due to the absence of this service from the capabilities of its software, that request is simply ignored. This results in a waste of resources for both of the MTSO's as well as the signalling system over which the request was sent. This waste can be avoided by permitting the two MTSO's to inform each other of their respective capabilities during the initial procedures required to effect a functional interaction between MTSO's.

In current cellular system networks, the automatic roaming function transfers operational information between two MTSO's during their initial handshake procedure. Specifically, the initial handshake and related signalling between a visited MTSO and a home MTSO involves a location updating message. The content of this message includes the current location of the mobile for the home MTSO and subscriber service package information for the visited MTSO. That is, if the home MTSO determines the new location to be valid, a location updating accepted message is returned to the visited MTSO to acknowledge the new location and to specify the subscriber services information for it.

Operators may specify and purchase from manufacturers of MTSO equipment different software packages to be furnished in different MTSO's in order to customize the system to the particular regional needs of that operator. Some MTSO's may provide services not offered by others. By including a software package designation as part of the data contained within the signalling information field, an MTSO would be able to determine whether the receiving MTSO is capable of handling future requests prior to sending the request. If the capability is not present, the MTSO can then make an intelligent alternative choice on a different course of action in handling the call. Such an ability to recognize the functional capability of MTSO's would avoid loading the MTSO processors with unnecessary requests that terminate unsuccessfully and also avoid needlessly occupying signalling resources on the data links between MTSO's. This capability is particularly useful to an MTSO running a software package which includes more functional capabilities than others. The present invention implements this capability and serves as a protocol for the bit stream used for signalling between different exchanges in a cellular network and particularly for the allocation of bits for identification of different software packages supported within different exchanges.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to enable the efficient transmissions of data to and from cellular telephone exchanges and to provide a signal for identifying a particular software package used by the exchanges.

In one aspect, the system of the present invention includes a signalling system for communicating messages via a communications medium between a first location and a second location in a data communications system. The signalling system includes a variable length message which is transmitted between an originating station and received by at least one destination station and is composed of a label field containing the identification of the originating station and a destination station, a pair of heading code fields, and an information field which includes a package information block which identifies the particular software package within the originating station transmitting the variable length message. In a further aspect of the present invention both the originating station and the destination station are mobile switching centers within a cellular radio telecommunications network and the messages relate to the cellular radio service of a subscriber.

In another aspect, the system of the invention relates to a cellular radiotelephone system network carrying high speed digital messages between a plurality of mobile switching centers serving mobile subscribers located in different geographic areas within the network. In this system a first mobile switching center includes a software package having a particular identity which provides to the center certain specific features and communications capabilities. A second mobile switching center is connected to the first center for the communication of data therebetween and also includes a software package having a particular identity which provides to the second center certain specific features and communications capabilities. A signalling system carries digital data messages between the first and second mobile switching centers related to the providing of mobile communications services to the subscribers. The signalling system incorporates a communications protocol including a data packet label comprising an identification of a source switching center and a destination switching center, an information block including a message being sent from the source center to the destination center, and a means for identifying the particular software package within the source center from which the message originates.

In a still further aspect, the present invention includes a protocol for a data network including a data packet label comprising an identification of a source and a destination, an information block including a message being sent from the source to the destination, and a means for identifying the particular software package within the source from which the message originates. In one embodiment, the software package identification means is included within the information block. In another, the data network is part of a cellular radio telecommunications network and the message includes data being sent from one mobile switching center to another within the cellular network related to the cellular radio service of a subscriber. In still another the message is part of a handshaking procedure between two mobile switching centers preparatory to the exchange of additional messages therebetween.

In yet another aspect, the present invention includes a method of transmitting data packets in a data network which includes inserting into each packet a label containing an identification of the source and the destination of the packet, inserting an information block into the packet containing a message being sen