ROUTING CALLS USING DIRECT NUMBERS DURING MARKING INSTEAD OF TEMPORARY ROUTING NUMBERS
FIELD OF THE INVENTION The invention relates in general terms to the establishment and routing of calls in a wireless telecommunications system and, more particularly, to the administration of temporary routing numbers used to route calls. BACKGROUND OF THE INVENTION Figure 1 illustrates a wireless telecommunications system in which a public switched telephone network PSTN, a public land mobile network PLMN (e.g., AMPS, GSM, PDC) and a private wireless network (e.g., cellular) they are interconnected among them. A mobile gateway switching center GMSC of PLMN is connected to the PSTN for communication with it, and is also connected to an address location register HLR of the PLMN. The PSTN is connected for communication with the private network, as is the HLR of the PLMN. The private network includes what is known as a WOS Wireless Office System connected to the HLR. The WOS offers a mobile extension of wired communication systems used in office environments. Typical workspaces that can benefit from a WOS technology include
corporate facilities, health facilities, manufacturing facilities, hotel chains, retail stores, etc. The WOS is in communication with HLR during the establishment of a call in the same way as in the case of a conventional mobile switching center (MSC). A local PSTN LE exchange communicates with the WOS through a PBX private branch exchange in the private network. In some systems, the functionality of the PBX private branch exchange is included in the WOS such that the local exchange LE of the PSTN communicates directly with the WOS, as indicated in the diagram by the interrupted line connection in the Figure 1. Figure 1 shows mobile stations (mobile subscriber units) MSI and MS2 registered and operating in the WOS. The WOS offers basic wireless telephony services in addition to the PBX services offered by private networks. WOS does not generally offer its services to PLMN subscribers who move in the WOS coverage area. The communications between the HLR and the GMSC in 12, and between the HLR and the WOS in 14 are carried out, for example, using the IS-41 protocol of the D-AMPS standard, or the MAP protocol used in the GSM systems. The communication links in 16, 17 and 18 in the PSTN can be, for example, based on R2 or ISDN. With reference now also to figure 2, when a
call to a mobile station registered in the WOS is received in 21 in the GMSC, a location request is sent in 23 from the GMSC to the HLR. The HLR then makes a routing request at 25 to the WOS to obtain from there a temporary routing number at 27, which the HLR transfers to the GMSC at 29. In the establishment request 21 received at the GMSC, a mobile directory number MDN (ie, the published directory number) associated with the mobile station receiving the call is included, and the GMSC transfers that MDN mobile directory number in the location request 23 to the HLR. The HLR translates the MDN into a mobile identification number MIN (each mobile station has a unique MIN conventionally coded there), and then includes this mobile identification number MIN in the routing request 25 to the WOS. The WOS then responds in exactly the same way as a conventional visited MSC (VMSC) that is, assigning a temporary local directory number TLDN to be used in the routing of the call. The WOS sends the TLDN to the HLR at 27 (exactly as in the case of a VMSC), and the HLR transfers the TLDN to the GMSC at 29. This sequence is well known in the art. Then, as shown in Figure 3, the GMSC uses the TLDN to route a call through the PSTN and access the WOS from the nearest local LE exchange. He
The traffic block illustrated in Figure 1 and also designated in Figure 3 represents a conventional routing path from the GMSC through the PSTN to the local exchange LE closest to the WOS. The routing path represented by the transit block may include, for example, several conventional exchanges or switches in the PSTN. Figure 4 illustrates a routing handler 41 in the WOS of Figure 1 (or in a conventional VMSC). The routing handler receives the mobile identification number of the HLR, and provides the HLR with the temporary local directory number TLDN from a set of TLDNs assigned to the WOS by the PSTN operator. The TLDNs are part of a series of public numbers issued by the PSTN operator. Thus, if the WOS requires additional TLDNs due for example to heavy traffic conditions, such new TLDNs must be issued in a disadvantageous manner by the local PSTN operator. Likewise, the TLDNs are typically assigned only for a short period of time (for example, 30 seconds) in such a way that, if the GMSC does not use the assigned TLDN to route a particular call, (for example, the person performing the call hangs), the TLDN will be free to use it in other calls. This feature minimizes the size of the TLDN set that is required but disadvantageously requires
that the routing handler 41 implements a timer / elapsed time function. In accordance with the present invention, a private network such as a WOS (which includes a WOS) offers the PLMN numbers in the direct dialing process instead of temporary routing numbers, and therefore profitably requires an amount significantly less resources to handle temporary routing numbers than compared to the prior art arrangement. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a known telecommunications system in which the present invention can be implemented. Figure 2 is a sequence diagram illustrating steps performed to obtain a temporary routing number in the system of Figure 1. Figure 3 is a sequence diagram illustrating a call routing procedure executed in the system of the figure 1. Figure 4 illustrates a conventional routing handler of the conventional wireless office system of Figure 1. Figure 5 is a sequence diagram illustrating the steps performed to obtain a routing number in accordance with the present invention. Figure 6 is a sequence diagram illustrating a
call routing in accordance with the present invention. Figure 7 illustrates a routing handler in accordance with the present invention for use in a wireless office system. Figure 8 illustrates in greater detail a portion of the converter of Figure 7. Figure 9 is a flow diagram illustrating exemplary operations of the routing handler of Figure 7. DETAILED DESCRIPTION OF THE INVENTION The present invention employs the fact that mobile registered in private networks such as the WOS of Figure 1 typically receive a direct number in the dialing process (DID). The DID number can be assigned, for example, by the PSTN operator and is used to dial the mobile station directly through PSTN without the need to establish a contact with an operator or an answering service to direct the call to the correct number . As shown in the example of Figure 5, in accordance with the invention, when the WOS receives from the HLR a routing request 51 including MIN, the WOS responds at 53 by sending back to the HLR the DID of the mobile station identified by the MIN instead of sending a TLDN to the HLR. The HLR then transfers the DID number to the GMSC at 55. As shown in the example of Figure 6, the GMSC then uses
the DID number to route the call through the PSTN to the WOS. Figure 7 illustrates an exemplary routing handler 71 that can, according to the invention, be implemented in WOS of Figure 1 to provide the DID number to the HLR in response to receiving the MIN in the routing request from HLR. The routing handler 71 includes a MIN to DID converter 73 connected between the input 75 and the output 77. Figure 7 also indicates that the routing handler 71 can provide a TLDN to the HLR in the case in which there is no number DID for a particular station registered in the WOS. In these cases, the call is established and routed as shown in Figures 2 and 3. Figure 8 illustrates an example of how the converter from MIN to DID 73 can map MINs into DID numbers, ie, a reference table 81 stored in a suitable memory device 83 in the converter 73. In the reference table, the DID numbers DID1, DID2, etc., assigned to the mobile stations by the PSTN operator are indexed against the MINs identifying the respective mobile stations . By way of example, if the MIN received from the HLR is MIN2, then the reference table of Figure 8 indicates that the mobile station identified by the mobile station identification number MIN2 (for example, mobile station MS2 of the
Figure 1) has a corresponding DID number of DID2. Thus, DID2 is returned to the HLR in response to the MIN2 routing request. The reference table is easily updated as new DID numbers are assigned to new mobile stations in the WOS. Since it can be expected that almost all mobile stations registered in WOS will have a DID number, the routing manager 71 of Figure 7 rarely requires access to a set of TLDNs and send a TLDN in response to a routing request from the HLR. Consequently, requests for the PSTN operator to issue a new TLDN are even less frequent. Thus, the issuance of new TLDNs by the PSTN operator will be significantly more frequent than in the prior art, and of the PSTN operator by way of new TLDNs will be less frequent than in the prior art. Figure 9 illustrates exemplary operations of the routing handler 71 of Figure 7. When a routing request with MIN is received at 91, it is then determined at 93 whether the mobile station identified by the MIN has an assigned DID number. If this is not the case, then at 95 the routing handler 71 conventionally obtains a TLDN to be used to route the call. Then, at 99, the routing handler 71 sends the
HLR a message that includes the TLDN. If the mobile station identified by the MIN has a DID number already assigned there, then, at 97, the routing handler 71 represents the MIN at a DID number (for example, it obtains the DID number from the memory table of FIG. 8). ), and then at 99 it sends a message to the HLR that includes the DID number. After sending the message to 99, the next routing request / MIN is expected at 91. It can be seen from the description of the above that the present greatly simplifies the operation of the routing management function in a Wireless Office system or another private network arrangement whose registered mobile stations already have DID numbers. The routing management function of the present invention offers, in response to a request for a temporary routing number, a direct number in the dialing process that had previously been assigned to this mobile station for example by the PSTN operator. It will be apparent to those skilled in the art that the modalities of Figures 4-9 can be easily implemented in programmatic, equipment, or in a combination of programmatic and equipment, in a portion of the appropriate data processing circuit of the routing manager. of a WOS or VMSC of the prior art. Even when exemplary modalities of the
present invention with details above, this does not limit the scope of the invention that can be practiced in various ways.