DYNAMIC ALLOCATION OF ROAMER ROUTING NUMBERS SYSTEM AND METHOD

Abstract: The present invention provides a communications system including at least one mobile transceiver; at least one mobile switching center, said the at least one mobile switching center including means for allocating a temporary routing number for the at least one mobile transceiver to facilitate call set-up; and means for releasing the temporary routing number to make it available for reuse. The present invention also provides a mobile services switching center or exchange for establishing communications with at least one mobile subscriber, this exchange including means for allocating a temporary routing number for the at least one mobile subscriber to facilitate call set-up and means for releasing the temporary routing number to make it available for reuse. Still further, the present invention provides a method employed by both the system and the exchange described above.

Description: DYNAMIC ALLOCATION OF ROAMER ROUTING NUMBERS SYSTEM AND METHOD BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to communications systems having mobile subscribers. More particularly, the present invention relates to a method of routing calls to such mobile subscribers under certain circumstances. Description of Related Art In certain communication systems, such as in some radiotelephon systems, the whole service area of the systems are divided into a plurality of local service areas. In each local area, radio access units are located at one or more key points to establis radio links between mobile subscribers and mobile switchin centers. Mobile subscribers are permanently assigned uniqu telephone numbers recognized by the public switched network an they are also temporarily assigned a different number wheneve they roam into another local area. Assignment of such a temporar subscriber number requires that the system be provided wit information on the current location of each mobile subscriber. Each of the mobile subscribers of the system must therefore b registered exclusively in one of the local areas. To maintai this exclusivity, whenever a mobile subscriber moves to anothe local area, the old registration must be cancelled in the are departed and a new registration made in the area in which th mobile subscriber just arrived. Heretofore, whenevera subscriberwith automaticroamingcapabili ties was first detected in a cooperating exchange, the subscribe was immediately registered as an automatic visitor within th exchange. Upon registration, the subscriber was allocated subscriber number. This number was employed to assist an in terrogation exchange or the visitor's home exchange in routing call to the subscriber. If all calls were only routed within a cooperating exchange network, the numbers could be assigned by the exchange itself. However, these numbers would not be recognized by other systems (i.e., the Public Switched Telephone Network). To accommodate calls that require routing outside the cooperating network, subscriber numbers often have to be leased from an outside source. It should also be recognized that heretofore, the subscriber numbers allocated at connection of the automatic visitor have not been released until the visitor has disconnected. As a result, it has been necessary to have as many subscriber numbers as there are registered automatic visitors. This has been to ensure that each registered automatic visitor has the capability of receiving a call. Needless to say, however, leasing subscriber numbers from an outside source can be expensive. As prior art systems have uniformly required at least one leased number per registered automatic visitor, these prior art systems have all been implemen¬ ted at relatively high cost. Based upon these facts, it is clear that lacking a method of reducing the number of leased subscriber numbers in prior art communication systems is a deficiency and shortcoming of the prior art. Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed and claimed herein, a number of prior art references exist that discuss subject matter that bears some relation to matters discussed herein. Such prior art references are U. S. Patent Numbers 4,228,319, 4,612,415, 4,748,655, 4,794,635, 4,833,701 and 4,833,702. Each of these references is discussed briefly below. U. S. Patent 4,228,319 to De Jager et al. relates to an automatic mobile subscriber system. De Jager et al. teach stationary stations which repeatedly transmit through their cell channel a channel number of a free duplex speech channel which is stored in a storage device in mobile stations receiving the call channel. De Jager et al. also teach use of the stored channel number for automatically selectingthe free duplex speech channel in response to a connection set-up command. U. S. Patent 4,612,415 to Zdunek et al. relates to a method and means for controlling telephone interconnect traffic in a trunked radio system. Zdunek et al. teach continuously monitoring all types of communication traffic on ^ the system and, in response to an increasing dispatch access delay, reserving certain repeaters for dispatch use only during a predetermined period. Zdunek et al. also teach a system in which the number of simultaneous telephone interconnect calls permitted on the system during the predetermined period is dynamically altered in response to system loading. Still further, Zdunek et al. teach establishment of a variable, periodically updated, maximum interconnect call length based on the current system dispatch access delay. U. S. Patent 4,748,655 to Thrower et al. relates to portable telephones. According to the teachings of Thrower et al., a personal portable telephone allows a user access to a cellular radio network via a number of different gateways including a communal unit, user's mobile telephone set, home telephone or office PABX. The telephone can also be used as a paging unit for use within the cellular radio network. The communal radio unit is a multi-channel arrangement capable of servicing a large number of personal telephones within its service area which is small compared to that of a normal cellular radio cell. The communal units may be transportable and located in public areas such as railway stations, airports and on trains or coaches. The telepho- ne automatically transmits its identification number to a gateway when it enters its service area enabling the subscriber to be accessed by callers without their knowing his whereabouts. U. S. Patent 4,794,635 to Hess teaches a two-way radio communi¬ cation system having a limited number of channels which assigns calls in a max-minimum method. Hess's method also ascertains the type of call, handoff or first assignment, and assigns a server with a given central controller to a channel frequency within the requestor sector that minimizes interference to present users. In a second embodiment of his method, Hess teaches requesting assignment to a limited number of channels to reduce adjacent channel interference to and from the requestor with respect to present users operating on a system by utilizing one or more thresholds toarrange channel assignmentsbaseduponprogressively larger or smaller values of received signal strength. U. S. Patent 4,833,701 to Comroe et al. relates to a trunked communications system with nationwide roaming capability. According to the teachings of Comroe et al. , selected regional trunkingsystems areequippedwithtelephone interchange capabili¬ ty and provided with local computers, which communicate with a national hub computer. At each selected trunking system, several ID'S are reserved as "roaming ID's" to be temporarily assigned to roaming subscribers. When a subscriber determines that he has roamed into a new trunk system, he requests a roaming ID. A roaming ID is assigned and transmitted to the subscriber, which thereafter operates within the new trunked system using its roaming ID. The roaming assignment is also transmitted to the national hub computer so that interconnect calls may be properly forwarded. This differs from the present invention, wherein a roaming number assignment is requested at each call attempt rather than transmitted to the national hub computer. Referring again to Comroe et al. 's teachings, the roaming subscriber continues to operate under the assigned roaming ID until it roams out of range of the current system and into yet another trunked system. In this way, the subscriber may roam from system to system. U. S. Patent 4,833,702 to Shitara et al. relates to telephone registration and cancellation control in a wide area cordless telephone system. Specifically, Shitara et al. teach a method for making a registration of a roaming cordless telephone in one of a plurality of local service areas and cancelling the registration. Review of each of the foregoing patents reveals no disclosure or suggestion of a system or method such as that described and claimed herein. Summary of the invention • To overcome the deficiencies and shortcomings of the prior art discussed above, the present invention provides a communications system including at least one mobile transceiver and at least one visited mobile switching center or MSC. According to the tea¬ chings of the present invention, the at least one visited MSC includes means for allocating a temporary routing number for the at least one mobile transceiver to facilitate call set-up, and means for releasing the temporary routing number to make it available for reuse. In embodiments of the present invention, the at least one mobile transceiver may be at least one mobile subscriber. Also, according to the teachings of the present invention, the means for allocating a temporary routing number for the at least one mobile subscriber to facilitate call set-up may be a means for allocating a temporary routing number for the at least one mobile subscriber to facilitate incoming call set-up. Additionally, the means for releasing the temporary routing number to make it available for reuse may be a means for releasing the temporary routing number to make it available for reuse after the incoming call set up. The present invention also provides a visitedMSC for establishing communicationswith at leastonemobile subscriber. Inembodiments of the mobile switching center or exchange of the present in- vention, the means for allocating a temporary routing number for the at least one mobile subscriber to facilitate call set-up may be an optionally selectable means for allocating a temporary routing number for the at least one mobile subscriber to facilita¬ te call set-up. In such an embodiment, the means for releasing the temporary routing number to make it available for reuse may be an optionally selectable means for releasing the temporary routing number to make it available for reuse. The present invention also provides a method of routing a call to at least one mobile subscriber in a communications system including at least two MSC's. The method according to the tea¬ chings of the present invention includes the steps of allocating a temporary routing number to the at least one mobile subscriber to facilitate call set-up, and releasing the allocated temporary routing number for reuse after call set-up. Accordingly, it is an object of the present invention to effici¬ ently route incoming calls to roaming subscribers in a communica¬ tions system. Another object of the present invention is to economically dynamically allocate roamer routing numbers in a communications system. Brief description of the drawings For a more complete understanding of the present invention, and the further objects and advantages thereof, reference may now be had to the accompanying description taken in conjunction with the accompanying drawings in which: FIG. 1 is a block diagram of a mobile subscriber system according to the teachings of the present invention; FIG. 2 is a more detailed block diagram of a portion of FIG. 1; FIG. 3 is .a block diagram of a mobile switching center according to the teachings of the present invention; and FIG. 4 is a schematic diagram of a MRNUM block according to the teachings of the'present invention. Detailed Description of the Drawings Referring now to FIG.1, a cellular radio network according to the teachings of the present invention is shown therein. This network may be seen to comprise a plurality of mobile services switching centers (MSC's) 2, 4, 6 linked to the public switched telephone network (PSTN) 8. Each MSC 2, 4, 6 is shown to be directly connected (via links 10, 12, 14) to the PSTN 8. Associated with each MSC is a base station, such as base station 16 shown associated with MSC-V in Fig. 1. The "V" designation of MSC 4, as well as the "I" and "H" designations of MSC's 2 and 6 respectively, will be explained below. Via base stations such as base station 16, radio links may be established between the various MSC's and mobile subscribers (MS's) , such as MS's 18 and 20 shown in FIG.1. Such a radio connection, generally designated by reference numeral 29, is more explicitly shown in FIG. 2. It may be seen therein that radio communications may be transmitted between a MS 20 and a base station 16 associated with a MSC-V 4. Each MS has a phone set with a uniquely assigned MS phone number. Likewise, each MS has a home exchange, designated MSC-H. Refer¬ ring again to FIG. 1, it may be considered that MSC-H 6 is the home exchange of MS 20. Routing of calls to MS 20 may be undertaken solely by MSC-H 6 as long as MS 20 remains in the area serviced by MSC-H 6. However, quite frequently, mobile subscribers such as MS 20 travel outside of the coverage area of its MSC-H and into the area of another MSC, designated a visited exchange, or MSC-V, e.g. MSC-V 4 shown in FIG. 1. Needless to say, during such "roaming", it is very important to efficiently and correctly keep track of the MS's location. Various registration procedures have been established to help accomplish this. These registration procedures involve transmitting the MS number of the phone set to the base station 16 servicing the MSC-V 4. Effectively, the base station 16 serves to relay data between a visiting MS 20 and the visited MSC 4. At that point, the MSC-V 4 attempts to identify the MS 20 by analyzing the relayed phone set number. Assuming the MSC-V 4 determines that the MS 20 is a visitor from a cooperating MSC, e.g. MSC-H 6, the MSC-V 4 provides service to the visitor by allocating a subscriber number for it. Then, via communication link 22, the visiting MS's MSC-H 6 is notified of the visitor's location in the network, that is, in the coverage area of MSC-V 4. Continuing to refer to FIG. 1, the procedures according to the teachings of the present invention for routing a call to the visitor (MS 20) may now be considered. Such a call can be placed by an "ordinary" PSTN subscriber, designated by the telephone symbol 24, to MS 20 while visiting MSC-V 4. In such a case, once the digits dialed by subscriber 24 are received by the PSTN 8, the PSTN 8 routes the call to a MSC exchange designated as an entry into the overall cellular or Mobile Telephone Network. For purposes of discussion, this exchange is designated by reference numeral 2 in FIG. 1. Such a designated exchange is known to those skilled in the art as an interrogating exchange (MSC-I) . The MSC-I 2 analyzes the dialed digits relayed to it by the PSTN 8 and generates destination data for a roaming signalling message sent to the same MSC, that is, MSC-H 6, of the called MS 20. This is provided that MSC-I does not identify the subscriber through the dialed number as its own. For the purpose of this explanation, it is assumed this is not the case. This message, which is of the form "the routing inquiry message", requests information on how the call shall be routed to the MS 20. In FIG. 1, this "the routing inquiry message" should be understood to be sent from the MSC-I 2 to the MSC-H 6 via communication link 26. Upon receiving the "routing inquirymessage" from the MSC-I 2, the MSC-H 6 identifies the subscriber through the dialed number as its own, and determines that the MS has travelled into the coverage area of another MSC, MSC-V 4. At this point, in order to route the call to the MSC-V 4, a roaming number is needed. Destination data is obtained for a roaming signalling message to be sent to the visited MSC-V 4. This message, "the roaming number interrogation message", is sent to the MSC-V 4. "The roaming number interrogation message" contains the MS number of the called visitor 20. It should be recognized at this point that the dialed subscriber numbers cannot be used because those numbers are not stored in the MSC-V 4 and would not, therefore, be recognized. Once the MSC-V 4 receives the message, a roamer routing number is allocated and the MS number is stored within its record. The roamer routing number is then returned as the roaming number to the MSC-H 6. The MSC-H 6 then forwards the number to the MSC-I 2. The foregoing transfers between the various MSC's are all accomplished via roaming signalling messages and inter-MSC communication links 22 and 26. The MSC-I 2 analyzes the roamer routing number and, as a result, returns the call to the PSTN 8. The PSTN 8 then analyzes the roamer routing number, the result of which analysis is routing of the call directly from the PSTN 8 to the MSC-V 4 via communication link 12. Once the incoming call is received by the MSC-V 4, analysis of the roamer routing number leading to the previously stored MS number can be undertaken. At that point, according to the teachings of the present invention, the roamer routing number is then released so as to be available for use in routing of other calls. At that point, the MS number can be used to determine the subscriber number allocated to the visitor 20. Analysis of this subscriber number results in paging of the MS 20 via the MS number through the base station 16 and link 28 between the MSC-V 4 and the base station 16 and radio link 30 between the base station 16 and the MS 20. Now, for an even more complete understanding of aspects of the present invention, especially with regard to an exchange or MSC constructed and/or configured to implement the present invention, it is helpful to recognize all blocks in an exchange that could be employed in such an embodiment of the present invention before discussing that embodiment in detail. Such blocks are depicted i FIG.3. Those persons skilled in the art should recognize each o these blocks generally, and should also be aware of and understan other blocks that may be found in typical exchanges. Thos skilled in the art should also know the interrelationships i structure and operation among all the blocks, whether or no shown. However, for the purpose of fully understanding on embodiment of the present invention, noteworthy details regardin the blocks shown in FIG. 3 are set forth immediately below. Referring to FIG. 3, reference numeral 30 depicts the Mobile Telephone Signalling block (SIGBLOC) . This block handles signalling messages for inter-MSC communication. The MDA/MDAV (Mobile Telephone Digit Analyzed/Mobile Telephone Digit Analysis for Visitors) blocks, designated by reference numeral 32, execute the mobile subscriber number analysis. More specifically, theMDAVblockanalyzes themobile subscribernumber for visitors. The MRNUM block 34, that is, the Mobile Telephone Roamer Routing Number block, handles the selection of roamer routing number for call setup to a cooperating exchange during automatic roaming. TheMobileTelephoneA-Subscriber (MTA) block 36, performs traffic handling functions for originating calls. The MTA block 36 has a controlling function for each call and constitutes the interface towards other subsystems. The MTB block, that is, the Mobile TelephoneB-Subscriberblock, alsodesignatedbyreferencenumeral 36, performs traffic handling functions for terminating calls. The MTV block, that is, the Mobile Telephone Visiting Subscriber, Automatic Roaming block, designated by reference numeral 38, handles subscriber data allocated within mobile telephone system for visitors belonging to a cooperating exchange during automatic roaming. Continuing to refer to FIG.3, reference numeral 42 designates the mobile telephone visitor routing data provision (MVRP) block, which block contains functions for determining roamer routing numbers for visiting mobile subscribers upon request from the subscriber's home exchange. Reference numerals 44 and 46 designate a subsystem register function and subscriber category, respectively. The register function block 44 stores the incoming digits and handles the set¬ up of calls. The subscriber category block 46 stores subscriber categories for all subscribers connected to the exchange. To assist those skilled in the art in fully understanding the operation of the blocks discussed immediately above, as well as other blocks, shown and not shown, set forth immediately below are descriptions of signals that are routed between the blocks as shown in FIG. 3. With reference to FIG. 3, group 1 signal may be seen to pass between blocks 30 and 42, group 2 signals between blocks 32 and 42, and so on. Understanding what happens in the various blocks, as described above, and further understanding the type of information that passes between the blocks as indicated below, those skilled in the art should fully understand operation of an exchange configured according to the teachings of the present invention. SIGNALS Group 1 Description Sender Receive MRIMI Roaming number interrogation, SIGBLOC MVRP incoming message MNRMO Roaming number, outgoing message MVRP SIGBLOC MRNRO Roaming number rejected, outgoing MVRP SIGBLOC message Group 2 IDENTMS Identify mobile subscriber MVRP MDA/MDA MSIDENT Mobile subscriber identified MDA/MDAV MVRP MSNOIDENT Mobile subscriber not identified MDA/MDAV MVRP Group 3 FINDMS Find subscriber data for mobile MRNUM MDA/MDA station number (MSNB) MSFOUND Subscriber data for MSNB found MDA/MDAV MRNUM MSNOFOUND Subscriber data for MSNB not MDA/MDAV MRNUM found Group 4 FETCHMSDATA Fetch mobile subscriber data MRNUM MTV FETCHMSDATAR Result of fetching a mobile MTV MRNUM subscriber data GETVSUBINFO Fetch the subscriber information MRNUM MTV for the call set up from the visiting subscriber block GETVSUBINFOR Result of fetching visiting MTV MRNUM subscriber information for call set up OFSEIZE Read the linked MTA/MTV MRNUM MTV reference and connection status OFSEIZERD Linked MTA/MTB reference and MTV MRNUM and connection status returned Group 5 GETMSDATA Read mobile subscriber data MRNUM MTA/MT GETMSDATAR Result of reading of mobile MTA/MTB MRNUM subscriber data Group 6 FETCHRNB Order selection of roaming MVRP MRNUM number FETCHRNBR Result of selection of roaming MRNUM MVRP number REFO Transfer of fault parameters APZ MRNUM to print unit REFOACK Acknowledge signal to signal MRNUM APZ REFO Group 9 TRSCIND Order translation of SC-pointer MRNUM TCS/SC into a subscriber number TRSCINDR Subscriber number returned TCS/SC MRNUM Group 10 CALL Digits ready for transmission OBNR Available digits OCODE End of selection code OCONG Congestion at ' selection of an MRNUM TCS/RE outgoing individual ODISC Release outgoing individual from TCS/RE MRNUM RE ODISCED Outgoing junction released from RE OFBNR Rerouting, Restart B-number analysis OGRA(4) Request available B-number digits OGR1 B-number digit ORG4 Transmission of B-number completed ONEXTBD Request next available B-number digit OSEIZED Outgoing individual selected SEIZEOLINK Select an outgoing individual STOREMTSDATA Store RE-information, MTS specific Based on the foregoing, it should be understood that according to the teachings of the present invention, roaming number interroga¬ tions are routed from the home mobile telephone exchange to the visited mobile telephone exchange. The mobile station number is sent in the roaming number interrogation. Depending upon whether or not the dynamic allocation of roamer routing numbers system according to the present invention is activated, the roaming number can be either read from the SC block 46 in the form of the visitor's subscriber number or selected among the available roaming routing numbers (RRNB's) . This nuinber can be sent in the routing message to the home exchange. In the event dynamic allocation of roamer routing numbers has been activated, time supervision is initiated for the delivery of the call, i.e. , the routing of the call back to the visited exchange. After a successful seizure by the RE block 44, the block MRNUM 34 receives the roamer routing number digits. Upon reception of all, e.g., ten, RRNB digits, a pointer to the RRNB record is cal¬ culated, using the internal route pointer, received in the signal SEIZEOLINK, and the last two RRNB digits received from the RE block 44. The pointed RRNB record contains the associated mobile station number (MSNB) . The roamer routing number may then be freed so that it can be used for other call attempts. After a successful translation of the MSNB into an MTV pointer, the SC- pointer is obtained, providing the visitor's subscriber number. The subscriber number (SNB) is passed to the RE block 44 in order to allow restart of the B-number analysis. With regard to reception of roaming number interrogation, the signalling block SIGBLOC 30 receives the roaming number in¬ terrogation from the home exchange and directs the request to the function block MVRP 42. This is via the MRIMI signal. The identi¬ fication ofthemobile subscriber follows after successful seizure of the MVRP task individual and after the check for sufficient central processor capability has been successfully completed. Otherwise, a roaming number rejected message (that is, a MRNRO signal) can be sent to the roaming signalling block SIGBLOC 30. With regard to identification of the mobile subscriber, the block MVRP 42 orders the analysis and connection of the received mobile station number (MSNB) in blocks MDA/MDAV 32, by sending signal IDENTMS to the MDA block 32. Within the MDA block 32, the MVRP block 32 causes analysis of the visitor's MSNB and, if necessary, the connection or seizure of the visitor subscriber data record by sending the signal IDENTVMS to the MDAV block 32. In the event of an unsuccessful MSNB analysis or connection, the signal MSNOIDENT is received from the MDA/MDAV block 32, resulting in the roaming number rejection message, that is, the signal MRNRO sent to the SIGBLOC block 30. Otherwise, the MSIDENT is received from the MDA/MDAV block 32 as an acknowledgment of successful analysis and connection and, if a subscriber type is correct, roaming number determination takes place. If the subscriber is not a visitor, the roaming number rejected message is returned via a MRNRO signal to the signalling block SIGBLOC 30. With regard to roaming number determination, the MVRP block 42 orders the selection of the roaming number in block MRNUM 34 by sending the signal FETCHRNB. The return signal FETCHRNBR is received from the block MRNUM 34 regardless of the result of the roamingnumberdetermination, i.e., eitherwiththe roamingnumber digits in the event of a successful roaming number selection, or with congestion as a reason for rejection of the call. Upon reception of signal FETCHRNB, an idle MRNUM task individual is to be seized. If no available MRNUM individuals are found, the roaming number rejection message, that is, signal MRNRO, is sent to the block SIGBLOC 30. Otherwise, a check is made to verify if the subscriber data record is connected, and if so, if his categories havebeen retrieved. This latter check involves signal pair GETVSUBINFO/GETVSUBINFOR. If the subscriber data record is not connected, the signal FETCHRBNR is returned to the MVRP block 42 (with congestion as the reason for the rejection of the call) . The seized MRNUM individual is released, and the roaming number rejection message (signal MRNRO) is sent to the block SIGBLOC 30. If the subscriber is connected, and the categories have been found, a selection of the roaming number is performed, depending upon the dynamic allocation of roamer routing numbers activity status. Still further on the subject of roamer number determination, it is important to consider what happens if the visitor's SNB is selected and returned as a roaming number. If the dynamic allocation of roamer routing number is not activated, the block MRNUM 34 requests translation of the SC-pointer, previously fetched from the block MTV 38 by the signal pair GETVSUBINFO/- GETVSUBINFOR, into an SNB by sending the signal TRSCIND. As a result, a subscriber number (SNB) is received in signal TRSCINDR and will be returned as a roaming number in the signal FETCHRNBR to the block MVRP 42. The number is then sent in the roaming number message (MRNMO) to the roaming signal block SIGBLOC 30. The seized MRNUM individual is freed and available for another call set-up. The MVRP individual is then also released. Still yet further with respect to roaming number determination, it is also important to consider what happens when the dynamically allocated roamer routing number is selected and returned as a roaming number. If dynamic allocation of roamer routing numbers is activated (by means of an exchange parameter, MIS1, in the command EXRBC) , then, an idle roamer routing number (RRNB) record is selected. If no idle RRNB record is found, congestion is marked in return signal FETCHRNBR to the MVRP block 42 and a roaming number rejection message is sent from the MVRP block 42 to the SIGBLOC block 30. Both MVRP and MRNUM individuals seized for a roaming number determination are released. Otherwise, the selected RRNB record is marked "busy", i.e. , "selected as a roamer routing number" and the visitor's MSNB is stored in the .selected record. If less than a certain number, e.g. , twenty percent, of the roamer routing numbers available for selection are idle, an advance congestion alarm can be set (signal FAULT) . An appropriate printout can then be initiated in an alarm signal. Upon reception of the fault parameters from ALA in signal REFO, the MRNUM block 34 can print the user part of the alarm printout. Signal REFOACK can then be sent to ALA as an acknowledgment. Upon a successful selection of the roamer routing number, time supervision is started in the MRNUM block 34 for the call delive¬ ry, i.e. , the routing of the call from the visitor's home exchange to the visited/cooperating exchange. The selected RRNB is then sent to the MVRP block 42 in signal FETCHRNBR and the MRNU individual is released. The roaming number message (signal MRNMO) , containing the selected RRNB to answer the roaming numbe inquiry, can be sent to the roaming signalling block SIGBLOC 30. The MVRP individual can then be released. With respect to call delivery, after a roamer routing number has been selected and sent to the home exchange, the call can b expected to be routed back to the visiting exchange. This event i time supervised. It should be recognized that two possible event may occur: either the call may be routed back to the visite exchange or the time supervision period may elapse in the MRNUM block 34. The time supervision timeout will occur if the call was not properly routed to the visited exchange. In such a case, the time supervision is stopped, the roamer routing number is released for another call. When the call is properly routed to the visited exchange, the signal SEIZEOLINK is received from the RE block 44, ordering the seizure of an idle MRNUM individual for a call delivery. If no idle MRNUM individual is available, the signal OCONG is sent to the block RE 44 and the call is rejected. When an idle task individual is seized in the block MRNUM 34, the signal OSEIZED is sent to the RE block 44 to acknowledge the seizure. Once the MRNUM individual has been successfully seized by the RE block 44 for call delivery, the signal ODISC from the block 44 may be received in the MRNUM block 34 at any time, indicating a disconnection order determined in the RE block 44. In such a case, the MRNUM individual is released, and the signal ODISCED is to be sent to the RE block 44 as an acknowledgment. Otherwise, the RE block 44 informs the MRNUM block 34 that the digits are ready for transmission by sending the signal CALL. Upon reception of the CALL signal, the MRNUM block 34 requests the roamer routing number digits from the RE block 44 by sending the signal 0GRA(4) . The first available digits are sent with the signal OBNR. As it is possible that not all available digits were transmitted in OBNR, the signal ONEXTBD is sent to the RE block 44 to request the next available digit. If there are no remaining digits left, the signal OGR4 is returned to the MRNUM block 34 as an acknowledgment of the end of digital transmission. Otherwise, the next digit is received from the RE block 44 within the signal OGRl. The MRNUM block 34 then requests the transmission of another digit from the RE block 44, by sending the signal ONEXTBD. This will continue until the signal OGR4 is received from the RE block 44 to indicate that the transmission of roamer routing number digits has been successfully completed. If the length of the received roamer routing number is not correct, i.e., if the number of digits is not equal to, e.g., 10, the signal OCODE with an end of sel -_e*-*ction code can be sent to the RE block 44 in order to reject the call and initiate a disconnec- tion ordered by the RE block 44 which can be accomplished by a signal pair ODISC/ODISCED. The MRNUM individual seized for call delivery may then be released. In order to access the RRNB record holding the associated MSNB, a pointer to the record may be calculated. The internal routing number, received in the signal SEIZEOLINK is multiplied by, e.g. , 100, in order to get the RRNB series starting pointer. The last two RRNB digits are then added to the RRNB series start point in order to get the pointer to the desired RRNB record. If the roamer routing number is not valid, e.g., if the route assigned to the actual roamer routing number series is not active, an end of selection code can be sent to the RE block 44 via signal OCODE in order to reject the call. This will initiate a disconnec¬ tion order by the RE block 44 via signal pair ODISC/ODISCED. The MRNUM individual seized for call delivery may then be released. As mentioned earlier, the call delivery event is time supervised. In case the time supervision has elapsed, the roaming routing number may be freed for the next call set-up by marking the time supervised RRNB record idle and stopping the time supervision. Since the occurrence of the time supervision timeout does not affect the transmission of the concerned RRNB digits from the RE block 44, it is possible for a seizure attempt of that particular RRNB record for call delivery may follow after it has already been freed due to the timeout. Accordingly, this will result in rejection of the call, caused by the incorrect state of the RRNB record ("idle" instead of "selected as a roamer routing number", as is expected in a normal case) . Once the roamer routing number is determined to be valid, tim supervision is stopped. A check is then done to see if the seize RRNB record is in the correct state, i.e., busy ("selected as roamer routing number") . If the state is correct, the previously stored MSNB is copied into the MRNUM individual and the RRNB is to be released. Otherwise, if the record is marked idle, an end of selection code (signal OCODE) may be sent to the RE block 44 in order to reject the call. A disconnection determined in the RE block 44 may follow via a signal pair ODISC/ODISCED. Then, the MRNUM individual seized for call delivery may be released. The release of the roamer routing number (RRNB) involves resetting of the congestion alarm if more than a certain percentage e.g., thirty percent, of the roamer routing numbers are available for selection and the alarm has been previously activated. The signal COFAULT may be sent to the alarm system in order to cancel the alarm by deleting the alarm from the alarm list. An appropriate alarm ceasing printout may then be initiated in the alarm system. Upon reception of the fault parameters from ALA in signal REFO, the MRNUM block 34 may print the user part of the alarm printout. Signal REFOACK may then be sent to ALA as an acknowledgment. The MRNUM block 34 sends the signal FINDMS to the MDA block 32 (resulting in sending of the signal FINDVMS to MDAV) to translate the MSNB into an MTV-pointer in order to find the visitor data record. As already mentioned, the signal ODISC may be received from the RE block 44 at any time indicating a disconnection determined in the RE block 44. If that is the case, the event may be buffered and then, as a result, the MRNUM block 34 may send an end of selection code to the RE block 44 via signal OCODE in order to reject the call. Then, both the RRNB record and the MRNUM individual seized for call delivery may be released. A disconnection may be acknowledged by means of the ODISCED signal returned to the RE block 44. An unsuccessful translation, e.g., if a data record for the MSNB is not found, may be indicated by reception of the signal MSNO- FOUND from the MDA/MDAV block 32. If translation is successful, a subscriber block reference and a pointer are returned in an MSFOUND signal. A check may be done for subscriber type. In cas of either an unsuccessful translation or incorrect subscribertyp (other than a visitor connected with automatic roaming) an end o selection code may be sent to the RE block 44 via signal OCODE i order to reject the call. A disconnection procedure may then b ordered by the RE block 44 via signal ODISC/ODISCED and th release of RRNB and MRNUM individual seized for call delivery ma take place. Otherwise, the SC-pointer and the visitor's actua connection status are fetched from the MTV block 38 with th signal pair FETCHMSDATA/FETCHMSDATAR using the MTV-pointer i order to verify that the subscriber is a visitor connected as a automatic roamer. If that is not the case, an end of selectio code will be sent to the RE block 44 via signal OCODE, resultin in an already described disconnection procedure determined in th RE block 44, which procedure involves signal pair ODISC/ODISCED. Normally, translation of the SC-pointer into a subscriber numbe (SNB) is then requested from the SC block 46 by means of the signa TRSCIND. The subscriber number is returned to the MRNUM block 3 and the signal TRSCINDR. If a disconnection has been receive from the RE block 44, disconnection procedure will take place a described above. The subscriber number (SNB) is then sent to th RE block 44 with an order to restart the B-number analysi involving signal OFBNR. The RE block 44 will then order dis connection of the MRNUM block 34 by sending the ODISC signal. Th MRNUM individual may then be released. The MRNUM block 34 ma acknowledge a disconnection by sending the ODISCED signal to th RE block 44. Referring now to FIG.4, further details regarding the MRNUM bloc 34 are set forth. The MRNUM block 34 may be seen to consist of size alterable route file 52 and an associated roamer routing fil 54. For each route record, 50 RRNB records may be allocated. Th RRNBs available for selection from the route are put into an idl list. At the seizure of a roamer routing number, an active route wit available roamer routing numbers may.be selected. An RRNB recor is then selected from the associated idle list and updated with the visitor's MSNB. The roamer routing number is then used to answer the roaming number inquiry. At call delivery, i.e., at seizure of an MRNUM route by RE, the internal route pointermultiplied by 100 gives a start pointer for the RRNBs. By adding the last two digits of the RRNB to the start pointer the record holding the MSNB may be accessed. Once the SNB is obtained, it may be passed to the RE to restart the B-number analysis. The RRNB may then be returned to the idle list. A size alterable task file may also be necessary to handle roaming number inquiry and call delivery procedures. By way of example only, set forth immediately below is a sequence diagram that should be of significant value for those skilled in the art in completelyunderstanding the structure and operation of the present invention. LABEL FUNCTION * INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP START CONDITION THE MSNB (_MSI) OF A VISITOR HAS BEEN RE¬ CEIVED FOR THE ROAMING DETERMINATION RECEPTION OF A ROAMING NUMBER INTERROGATION SIGBLOC ROAMING NUMBER INTER¬ MRIMI Dl SEND. IND. ROGATION RECEIVED D2 SEND.BL.R D3 MSNB LEN D4 MSNB DIG 1 D5 MSNB DIG 5 D6 MSNB DIG 9 SEIZE AN IDLE MVRP- INDIVIDUAL IF <MVRP-ROUTE NOT DEFINED > THEN MARK CONGESTION SEND THE ROAMING SIGBLOC NUMBER REJECTED MRNRO Dl REC. IND MESSAGE D2 REASON END ENDIF IF <NO MVRP-INDIVI- DUAL AVAILABLE > THEN MARK CONGESTION SEND THE ROAMING SIGBLOC NUMBER REJECTED MRNRO Dl REC. IND MESSAGE D2 REASON END ENDIF OMS ASK PROCESSOR CAPACITY SEIZECAPT Dl ROUTE ID. D2 SEND. IND. D3 SEND.BL.R CASE < CAPACITY > OMS < INSUFFICIENT CAP¬ ACITY > CAPCONG Dl REC. IND. GOTO 100 OMS LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP <CAPACΠΎ SEIZED> CAPSEIZED DI REC. IND. ENDCASE MOBILE SUBSCRIBER IDENTIFICATION PERFORM THE MSNB ANAL¬ IDENTMS Dl SEND. IND. YSIS TO DETERMINE THE D2 SEND.BL.REF TYPE OF A SUBSCRIBER D3 MSNB LENGT AND ORDER THE CONNEC¬ D4 MSNB DIG 1-4 TION, IF NECESSARY D5 MSNB DIG 5-8 D6 MSNB DIG 9-1 CASE <ANALYSIS / CONNECTION RE¬ SULT <UNSUCCESSFUL> MSNOIDENT Dl REC. IND. D2 REASON MARK CONGESTION GOTO 100 <SUCCESSFUL> MSIDENT Dl REC. IND. D2 MSB REF. D3 MSB IND. D5 SUBSCR. TYP IF <SUBSCRIBERTYPE IS NOT A VISITOR WITH AUTOMATIC ROAMING > THEN MARK CONGESTION GOTO 100 END ENDIF ENDCASE 4. ROAMING NUMBER DETERMINATION ORDER SELECTION OF A FETCHRNB D2 SEND. REF. ROAMING NUMBER D3 SEND. IND. D4 MTV BLCK.R D5 MTV IND. D6 MSNB DIG 1-4 D7 MSNB DIG 5-8 D8 MSNB DIG 9-1 SEIZE AN IDLE MRNUM-INDIVIDUAL IF < NO MRNUM-INDIVI¬ DUAL AVAILABLE > LABEL -FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP THEN MARK CONGESTION FETCHRNBR Dl REC. IND. D2 RESULT CO GOTO 100 ENDIF FETCH VISITING SUB¬ GETVSUBINFO Dl REC. IND. SCRIBER'S INFORMATION D2 SEND. REF. D3 SEND. IND. RESULT OF FETCHING GETVSUBINFOR Dl REC. IND. VISITING SUBSCRIBER'S D2 CONN. STA INFORMATION D3 CATEG. ST D4 GLOBAL ST D5 SC-POINTE D6 LOC.AREA. IF < SUBSCRIBER CONNECTED > THEN IF < CATEGORIES RECEIVED > THEN GOTO 10 ENDIF ENDIF MARK CONGESTION FETCHRNBR Dl REC. IND. D2 RESULT CO RELEASE MRNUM-IN- DIVIDUAL GOTO 100 10 IF < DYNAMIC ALLOC A- TION OFTHE ROAMER ROUTING NUMBERS IS ACTIVATED ITHIN THE SYSTEM > THEN GOTO 30 END IF 4.1. A VISITOR'S SNB TO BE RETURNED AS A ROAMING NUMBER TCS-SC ORDER TRANSLATION OF < = = = TRSCIND Dl REC. IND. THE SC-POINTER INTO D2 SEND. REF A SNB D3 SEND. IND. TCS-SC SNB RECEIVED TRSCINDR Dl REC. IND. D3 SNB LENG D4 SNB DIG 1- LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP D5 SNB DIG 5-8 D6 SNB DIG 9-10 SNB RETURNED AS A FETCHRNBR Dl REC. IND. ROAMING NUMBER D2 RESULT CO D3 SNB LENGT D4 SNB DIG 1-4 D5 SNB DIG 5-8 D6 SNB DIG 9-10 RELEASE MRNUM- INDIVIDUAL SIGBLOC SEND THE ROAMING MRNMO Dl REC. IND. NUMBER MESSAGE D3 RNB LENGT D4 NB DIG 1-4 D5 RNB DIG 5-8 D6 RNB DIG 9-10 RELEASE MVRP- INDJVIDUAL END 4.2. A DYNAMICALLY ALLOCATED ROAMER ROUTING NUMBER TO BE RETURNED AS A ROAMING NUMBER 30 SELECT AN IDLE ROAMER ROUTING NUMBER CASE <RRNB SELECTION RESULT > <NO RRNB AVAILABLE> MARK CONGESTION FETCHRNBR Dl REC. IND. D2 RESULT COD RELEASE MRNUM- INDIVIDUAL GOTO 100 <RRNBSELECTED> MARKRRNBSELECTED ASROAMERROUTING NUMBER STORETHEMSNBIN ASELECTEDRRNB LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP RECORD ENDCASE IF <LESS THAN 20% OF THE RRNB'S ARE IDLE AND THE LOAD SUPER¬ VISION ALARM HAS NOT BEEN SET > THEN APZ-AL SET THE LOAD SUPER¬ FAULT Dl SEND.BL.RE VISION ALARM D2 ALARMCLAS D3 ALARM CAT. D8 VSA POINTE END IF START TIME SUPERVISION FOR CALL DELIVERY RRNB IS RETURNED AS A FETCHRNBR Dl REC. IND. ROAMING NUMBER D2 RESULT CO D3 RRNB LENG D4 RRNB DIG 1- D5 RRNB DIG 5- D6 RRNB DIG 9- RELEASE MRNUM-INDIVIDUAL SIGBLOC SEND THE ROAMING NUMBER = > MRNMO Dl REC. IND. MESSAGE D3 RNB LENGT D4 RNB DIG 1-4 D5 RNB DIG 5-8 D6 RNB DIG 9-1 RELEASE MVRP-INDIVIDUAL CALL DELIVERY BLOCK MRNUM IS WAITING FOR THE ROUTING OF THE CALL TO THE VISITED EX¬ CHANGE CASE < EVENT > <T_ME SUPERVISION TIME OUT > DO S300 (RELEASE-RRNB) LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP STOP TIME SUPER¬ VISION END < CALL ROUTED TO TCS-RE THEVISΠΈD EX- SEIZEOLINK Dl INT.ROUTE N CHANGE> D2 SEND.BL.REF D3 SEND. IND. ENDCASE SEIZE AN IDLE MRNUM INDIVIDUAL CASE < SEIZURE RESULT > SUCCESSFUL SEIZURE> TCS-RE INDIVIDUAL SEIZED OSEIZED Dl REC. IND. D2 SEND.BL.REF D3 SEND. IND. < CONGESTION > TCS-RE CALL REJECTED OCONG Dl REC. IND. END ENDCASE 40 CASE < NEXT EVENT > TCS-RE <THE RRNB DIGITS CALL Dl REC. IND. READY FOR TRANS¬ D3 SIGNAL INFO MISSION > TCS-RE REQUEST THE RRNB OGRA(4) Dl REC. IND. DIGITS D2 SIG.NUMBER GOTO 40 TCS-RE <FIRST AVAILABLE OBNR DlREC.IND. RRNB DIGITS RE¬ D2RRNBLENGT CEIVED > D3RRNBDIG 1-4 D4RRNBDIG5-8 D5RRNBDIG9-1 D10ENDMARK LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP TCS-RE REQUEST THE NEXT < = = = = = = ONEXTBD Dl REC. IND. RRNB DIGIT GOTO 40 TCS-RE <REMA1NING RRNB = = = = = = = > OGRl Dl REC. IND. DIGIT TRANSMITTED > D2 RRNB DIGI TCS-RE REQUEST THE NEXT < = = = = = = ONEXTBD Dl REC. IND. RRNB DIGΓΓ GOTO 40 TCS-RE < END OF RRNB DIGITS = = = -= -= = > OGR4 Dl REC. IND. TRANSMISSION > D2 END TRAN IF < INCORRECT RRNB LENGTH > THEN TCS-RE CALL REJECTED < = = = = = = OCODE Dl REC. IND. D2 EOS CODE GOTO 40 ENDIF CALCULATE A POINTER TO THE RRNB RECORD, USING THE INTERNAL ROUTE POINTER AND THE LAST TWO RRNB DIGITS IF <RRNB NOT VALID > THEN TCS-RE CALL REJECTED OCODE Dl REC. IND. D2 EOS CODE GOTO 40 ENDIF STOP TIME SUPERVISION CASE <RRNB STATE > LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP <SELECTED AS ROAMER ROUTING NUMBER> GOTO 50 <_DLE> <SEIZED FOR CALL DELIVERY > ENDCASE TCS-RE CALL REJECTED OCODE Dl REC. IND. D2 EOS CODE GOTO 40 TCS-RE DISCONNECTION ODISC Dl REC. IND. ORDERED BY RE> RELEASE MRNUM- INDIVIDUAL TCS-RE DISCONNECTION ODISCED D2 REC. IND. ACKNOWLEDGED END ENDCASE 50 DOS300 (RELEASE-RRNB) COPY MSNB INTO MRNUM TASK INDIVIDUAL ORDER TRANSLATION OF FINDMS Dl SEND. IND. THE MSNB INTO A MTV- D2 SEND.BL.RE POINTER (FIND VISITOR D3 MSNB. LENG DATA RECORD) D4 MSNB DIG 1- D5 MSNB DIG 5- D6 MSNB DIG 9- 60 CASE <NEXT EVENT > <TRANSLATION UN¬ MSNOFOUNDDl REC. IND. SUCCESSFUL, DATA D2 RESULT CO RECORD FOR GIVEN D6 SUBSC. TYP MSNB NOT FOUND > TCS-RE CALL REJECTED OCODE Dl REC. IND. D2 EOS CODE LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP MARK WAITING FOR DISCONNECTION GOTO 60 <TRANSLATION SUC¬ MSFOUND Dl REC. IND. CESSFUL, MSB REF¬ D2 MSB BL.REF ERENCE AND POINTER D3 MSB IND. RETURNED > D5 SUBSC. TYP IF SUBSCRIBER TYPE OTHER THAN VISITOR WITH AUTO¬ MATIC ROAMING > THEN TCS-RE CALL REJECTED OCODE Dl REC. IND. D2 EOS CODE MARK WAITING FOR DISCON¬ NECTION GOTO 60 END IF IF DISCONNECTION ORDERED BY RE > THEN GOTO 200 ENDIF READ THE SC-POINTER FETCHMSDATA Dl REC. IND. AND VISITOR'S CON¬ D2 SEND.BL.RE NECTION STATUS D3 SEND. IND. GOTO 60 < VISITING SUBSCRIBER'S FETCHMSDATAR Dl REC. IND. DATA RECEIVED > D2 RESULT CO D4 SC-POINTER IF <VISITOR NOT CON¬ NECTED > THEN TCS-RE CALL REJECTED OCODE Dl REC. IND. D2 EOS CODE LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP MARK WATTING FOR DISCONNECTION GOTO 60 ENDIF IF < DISCONNECTION ORDERED BY RE > THEN GOTO 200 ENDIF TCS-SC ORDER TRANSLATION OF TRSCIND Dl REC. IND. THE SC-POINTER INTO A D2 SEND.BL.R SNB D3 SEND. IND. GOTO 60 TCS-SC < SNB RETURNED > TRSCINDR Dl REC.IND. D3 SNB LENGT D4 SNB DIG 1-4 D5 SNB DIG 5-8 D6 SNB DIG 9-1 IF < DISCONNEC¬ TION ORDERED BY RE> THEN GOTO 200 ENDIF TCS-RE SEND THE SUBSCRI¬ OFBNR Dl REC. IND. BER NUMBER (SNB) D2 OBA INDIC WITH AN ORDER TO D3 NEW OBA RESTART THE B- D4 SNB LENGT NUMBER ANALYSIS D5 SNB DIG 1-4 D6 SNB DIG 5-8 D7 SNB DIG 9-1 D8 SNB DIG 13- D9 SNB DIG 17- MARK WAITING FOR DISCONNECTION GOTO 60 DISCONNECTION DETER¬ MINED IN RE> LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP TCS-RE DISCONNECTION ODISC Dl REC. IND. ORDER IF <WAΓΠNG FOR DISCONNECTION MARKED > THEN GOTO 200 ENDIF MARK DISCONNECTION ORDERED BY RE GOTO 60 ENDCASE GOTO 60 END 6. SENDING OF THE ROAMING NUMBER RE¬ JECTED MESSAGE SIGBLOC 100 SEND THE ROAMING NUMBER ■ = = = = > MRNRO Dl REC. IND. REJECTED MESSAGE D2 REASON RELEASE MVRP-INDIVIDUAL END 7. DISCONNECTION DE¬ TERMINED IN RE 200 RELEASE MRNUM-INDIVIDUAL TCS-RE DISCONNECTION ACKNOW¬ ODISCED D2 REC. IND. LEDGED END 8. ALARM HANDLING PRINT LOAD SUPERVISION ALARM APZ-ALA PRINT ALARM REFO Dl I/O IDENT. LABEL FUNCTION INTERWORK SIGNAL DATA EXT MDA/MDAV MTV OTHER MRNUM MVRP "ROAMER ROUTING D2 AL.PRINT C NUMBER LOAD SUPER¬ D5 VSA POINTE VISION" APZ-ALA PRINT ACKNOWLEDGED REFOACK Dl ERR. CODE 9. SUBROUTINE 9.1 RELEASE-RRNB S300 RELEASE THE ROAMER ROUTING NUMBER IF <MORE THAN 3096 OF THE RRNB'S AVAILABLE FOR SELECTION ARE IDLE AND THE SUPERVISION ALARM IS SET > THEN APZ-AL REQUEST ALARM COFAULT Dl SEND.BL.RE CEASED PRINTOUT D2 ALARMCLAS D3 ALARMCAT. D8 VSA POINTE ENDIF RETURN An aspect of certain embodiments of the present invention which is worth noting relates to releasing numbers of incompleted calls. For example, it is possible that after the MSC-H requests a roamer routing number from the MSC-V, such a number is selected by the MSC-V, and the number is passed back to the MSC-H, the MSC-H may determine that the mobile subscriber is not willing to pay for the call to the visited exchange. At that point the process stops, with a number seized within the MSC-V. To solve this problem, embodiments of the present invention can include means for releasing such a number when not used after a predetermined period of time, e.g., ten seconds. Based on the foregoing, it should be clear that the present invention provides a means and method for allocating a temporary number to a visiting mobile station during call set-up. Once the call has been routed back to the visited exchange, the roamer routing number can then be released for use with other incoming call attempts to automatic visitors. The means and method of the present invention is an improvement over the prior art because it provides an inexpensive alternative to leasing a separate subscriber number for each visitor in a system. Obviously, numerous modifications and variations are possible in view of the above teachings. Accordingly, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.

Claims: What is Claimed Is: 1. A communications system comprising: at least one mobile transceiver; at least one mobile switching center, said at least one mobile switching center comprising means for allocating a temporary routing number for said at least one mobile transceiver to facilitate call set-up, and means for releasing said temporary routing number to make it available for reuse after call set-up. 2. A system as recited in claim 1, wherein said at least one mobile transceiver is at least one mobile subscriber. 3. A system as recited in claim 2, wherein said means for alloca¬ ting a temporary routing number for said at least one mobile subscriber to facilitate call set-up is a means for allocating a temporary routing number for said at least one mobile subscriber to facilitate incoming call set-up. 4. A system as recited in claim 3, wherein said means for releasing said temporary routing number to make it available for reuse is a means for releasing said temporary routing number to make it available for reuse after said incoming call has been routed back to said at least one mobile switching center number, said tempora¬ ry routing number released and said mobile subscriber found. 5. A system as recited in claim 1, wherein said means for alloca¬ ting a temporary routing number for said at least one mobile transceiver to facilitate call set-up is an optionally selectable means for allocating a temporary routing number for said at least one mobile transceiver to facilitate call set-up. 6. A system as recited in claim 5, wherein said means for releasing said temporary routing number to make it available for reuse is an optionally selectable means for releasing said temporary routing number to make it available for reuse. 7. A system as recited in claim 1, further comprising means fo releasing said temporary routing number if not used within predetermined period of time for call set-up. 8. A system as recited in claim 7, wherein said predetermine period of time is on the order of ten seconds. 9. A mobile switching center for establishing communications wit at least one mobile subscriber, said mobile switching cente comprising: means for allocating a temporary routing number for said a least one mobile subscriber to facilitate call set-up; and means for releasing said temporary routing number to make i available for reuse. 10. An mobile switching center as recited in claim 9, wherein sai means for allocating a temporary routing number for said at leas one mobile subscriber to facilitate call set-up comprises mean for selecting a roamer routing number. 11. An exchange as recited in claim 9, further comprising mean for receiving roaming number interrogation. 12. An exchange as recited in claim 11, wherein said means fo receiving roamer number interrogation comprises a means fo handling messages between exchange subsystems. 13. An exchange as recited in claim 9, further comprising mean for identifying mobile subscribers. 14. An exchange as recited in claim 13, wherein said means fo identifying mobile subscribers comprises a mobile telephon visitor routing data provision block. 15. A method of routing a call to at least one mobile transceive in a communications system including at least one MSC, said metho comprising the steps of: allocating a temporary routing number to said at least one mobile subscriber to facilitate call set-up; and releasing said allocated temporary routing number for reuse after call set-up. 16. A method as recited in claim 15, wherein said at least one mobile transreceiver comprises a mobile subscriber. 17. A method as recited in claim 16, wherein said step of alloca¬ ting a temporary routing number to said at least one mobile subscriber to facilitate call set-up is a step of allocating a temporary routing number to said at least one mobile subscriber to facilitate incoming call set-up. 18. Amethod as recited in claim 17, wherein said step of releasing said allocated temporary number for reuse after call set-up is a step of releasing said allocated temporary routing number to make it available for reuse after said incoming call has been routed back to said at least one MSC. 19. A method as recited in claim 15, wherein said step of alloca¬ ting a temporary routing number for said at least one mobile subscriber to facilitate call set-up is an optionally selectable step of allocating a temporary routing number for said at least one mobile subscriber to facilitate call set-up. 20. Amethod as recited in claim 19, wherein said step of releasing said allocated temporary routing number for reuse after call set¬ up is an optionally selectable step of releasing said allocated temporary routing number for reuse after call set-up.

Inventors: KUNZ DAVID PAUL, KUNZ, DAVID, PAUL
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON
Application year: 1991
Main classification: H04Q7
IPC codes: H04W8