Abstract:
A radio communication system is disclosed comprising a Public Land Mobile Network (PLMN) where mobile radio telephones communicate with at least one mobile services switching center via corresponding base stations and where a home location register is connected to the at least one mobile services switching center. A wide area paging system sends out paging signals from at least one paging system accessible to the at least one mobile services switching center. A plurality of mobile radio telephones register their whereabouts in the home location register each time they are switched on. A plurality of pagers are associated with but physically separate from the mobile telephones. The paging system is accessed by the mobile services switching center for performing a page to a called subscriber when the called subscriber&#39;s mobile radio telephone is in an off state or cannot be reached for other reasons. An incoming call to the mobile telephone is parked until the mobile telephone is switched on and registered with the home location register and the mobile services switching center parking the incoming call is informed of the active state of the mobile telephone and is provided with a roaming number. The mobile services switching center then calls the activated mobile telephone using a page over the cellular network and the mobile telephone answers the incoming call. If the mobile telephone is not switched on and does not register within a specified time after parking the incoming call, a time out will occur and disconnect the parked incoming call.

Description:
The present invention is herewith submitted as a Division, claiming priority to U.S. application Ser. No. 08/476,041, filed on Jun. 7, 1995, which issued as U.S. Pat. No. 5,541,976 on Jul. 30, 1996; which was a Rule 62 File Wrapper Division Application of U.S. application Ser. No. 08/159,116, filed on Nov. 30, 1993 (Abandoned); which was a Rule 62 File Wrapper Division Application of U.S. application Ser. No. 7/686,600, filed on Apr. 17, 1991 (Abandoned). 
    
    
     FIELD OF THE INVENTION 
     The present invention is related to cellular telephone and paging systems, and more particularly the present invention is directed to a mobile cellular telephone system that incorporates independent paging capabilities. 
     BACKGROUND OF THE INVENTION 
     Radio paging systems are well known and widely used. Upon receipt of a page, conventional radio paging systems provide a user with audio and/or visual information from the paging party, but cannot transmit information back to the paging party. Recently, national and international paging services have been implemented so that individuals may receive a page throughout the United States or throughout Europe. Despite the advances in paging technology, a significant disadvantage of radio paging is that after an individual carrying a pager has learned that a paging party wishes to communicate, that individual must locate a telephone communication system to contact the paging party and pay for this contact. 
     Radio paging systems typically include a radio transmitter for transmitting a coded radio frequency signal associated with a party to be paged and a portable paging receiver. To contact a party carrying a pager, a person dials a telephone number. The number is transferred by the public switched telephone network (PSTN) to the radio transmitter. The transmitter transmits a page signal coded to all pagers in the range of the transmitter. Because each mobile pager responds to a different paging code, only the pager having a code corresponding to that transmitted is activated. The activated pager generates an audible tone or some other signal to notify the designated party that he or she has been paged. That party typically responds by calling a specific telephone number to receive further instructions. 
     One advantage of paging systems is that they can serve relatively large geographic areas. Another advantage is that a paging subscriber may be reached anywhere in the transmitter coverage area without the paging system knowing the location of that subscriber. As described above, the major disadvantage of paging systems is that a subscriber cannot immediately communicate with the person who initiated the call. In fact, in conventional paging systems, the subscriber cannot even acknowledge that he or she has received the page. Also, calling back later entails cost. 
     In contrast, mobile radio telephone systems allow flexible two way radio communications with a plurality of mobile subscribers. Cellular telephones allow subscribers to be paged immediately over cellular radio paging frequencies (as long as the phone unit is on). The mobile telephone responds immediately to a page and gets a voice channel assigned for the communication. In addition, cellular subscribers may of course initiate calls themselves. Unfortunately, mobile telephones cannot be paged while the mobile telephone is turned off or deactivated. Also, mobile telephones are heavier than pagers and a cellular page may not be heard by the subscriber if he/she has left the mobile telephone in an on-state in the vicinity but out of hearing distance. 
     One disadvantage with cellular telephoning is that a subscriber&#39;s location must be known to the cellular system. Subscriber location is known by registering each mobile, e.g. periodically. In contrast, conventional paging systems do not require individual pagers to register. Thus, paging services are advantageous in situations where a subscriber desires to keep his exact location secret but still wants to have the option of being contacted. 
     Recently, it has become possible to subscribe to a cellular service and to an independent paging system. Telephone calls from the land based telephone network are attempted initially with the mobile station over the cellular network. If the subscriber does not answer, the call is diverted to an FM radio paging system. A cellular pager is disclosed in U.S. Statutory Invention Registration H 610 to Focarile et al. In this system, a separate paging system is used in conjunction with the cellular telephone system. The paging system provides a backup for cellular telephone calls intended for an associated cellular telephone which has been deactivated because the subscriber is, for example, temporarily away from his automobile. Since the pager is assigned the same number as the telephone, the pager provides an alert signal to the subscriber of the cellular telephone indicating that a call has been attempted to the subscriber&#39;s telephone. Later, the subscriber may call an appropriate service number at his/her own expense for the information about the earlier call when the subscriber returns to the automobile and activates the cellular telephone. 
     UK Patent No. 2 230 162 to Rodriguez physically combines a pager and a hand held cellular mobile radio terminal whereby the pager is connected to the hand held cellular mobile radio terminal in order to be able to keep the hand held terminal in a switched off mode to save battery power, but still be accessible for incoming calls. When a call is being directed toward the handheld terminal, the pager is first paged which then automatically switches on the handheld terminal so that the handheld terminal can receive the call which is redirected to the mobile terminal. However, the method taught by Rodriguez needs a specially modified handheld terminal and pager. It would be desirable to use standard handheld terminals and pagers to achieve the same battery savings as in Rodriguez although battery savings is not such an important problem anymore due to recent technical progress in this field. Furthermore, it is desirable to give a subscriber carrying a pager in the on-state and a cellular telephone in the off-state a chance to screen incoming calls and to decide whether to answer a call rather than having the pager automatically switching the cellular telephone on. Furthermore, it is desirable for a subscriber receiving a call to have a pager and a handheld terminal which are physically separate in order to allow the user to carry only the pager while having the heavier handheld somewhere in the vicinity and still enable answering of a call. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome the deficiencies cited above by providing a radio communication system in which higher probability of cellular calls being answered can be achieved using standard hand held terminals and standard pagers. It is a further object of the present invention to relieve a called subscriber from the need to carry a handheld terminal for receiving an alert signal and instead allowing him/her to merely have the handheld terminal in the vicinity within fetching distance rather than &#34;alert-hearing&#34; distance for answering incoming calls. 
     According to one embodiment of the present invention, a radio communication system is disclosed comprising a Public Land Mobile Network (PLMN) where mobile radio telephones communicate with at least one mobile services switching center via corresponding base stations and where a home location register is connected to said at least one mobile services switching center. A wide area paging system sends out paging signals from at least one paging system accessible to the at least one mobile services switching center. A plurality of mobile radio telephones register their whereabouts in the home location register each time they are switched on. A plurality of pagers are associated with but physically separate from the mobile telephones. The paging system is accessed by the mobile services switching center for performing a page to a called subscriber when the called subscriber&#39;s mobile radio telephone is in an off state or cannot be reached for other reasons. An incoming call to the mobile telephone is parked until the mobile telephone is switched on and registered with the home location register and the mobile services switching center parking the incoming call is informed of the active state of the mobile telephone and is provided with a roaming number. The mobile services switching center then calls the activated mobile telephone using a page over the cellular network and the mobile telephone answers the incoming call. If the mobile telephone is not switched on and does not register within a specified time after parking the incoming call, a time out will occur and disconnect the parked incoming call. 
     According to a further embodiment of the present invention in the radio communication system described above, the connection problem which occurs when the called mobile radio terminal is in a switched on state but the called subscriber does not hear the alert signal of a terminating call is solved. Also in this case, the wide area paging system is accessed by the mobile services switching center for performing a wide area page to the called subscriber while the alert signals continue on the subscriber&#39;s cellular terminal. In other words, alerting is performed simultaneously on the pager terminal and the cellular terminal. The incoming call is parked until the mobile telephone terminal answers the incoming call or until a predetermined time has elapsed after the initiation of the wide area page. 
     The present invention may be summarized as an apparatus and a method for connecting a call from a first user with a first terminal to a second user with a second terminal of a cellular radio type in a communication system containing a cellular communication system and a wide area paging system, wherein a wide area pager terminal is carried by the second user and whereby the wide area pager terminal is associated with but separate from the second terminal, the method comprising the steps of: originating a call from said first terminal to said second terminal; parking the call at a mobile services switching center in the cellular communication system; attempting to cause a cellular page to the called subscriber via said cellular communication system; determining whether the step of attempting resulted in a time out due to a lack of response within a predetermined period of time; causing a page to the pager terminal of the second user via the wide area paging system when the answer to the step of determining is positive; receiving of an alert signal by the second user on any of his/her terminals; answering of the call by the second user depressing at least one key on said second terminal including a key with off-hook function within a time out limit from the time of parking; and disconnecting the call if a time out limit is reached before the step of answering. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in more detail with reference to preferred embodiments of the invention given only by way of example, and illustrated in the accompanying drawings, in which: 
     FIG. 1 illustrates a block diagram of a radio communication system according to one embodiment of the present invention; 
     FIGS. 2a-2b illustrate flow charts according to several embodiments of the present invention; 
     FIG. 3 illustrates an implementation of one embodiment of the present invention; and 
     FIG. 4 illustrates a pager according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a radio communication system according to one embodiment of the present invention. A calling subscriber &#34;A&#34; has a plain old telephone (POT) 101 connected via a connection 111 to the Public Switched Telephone Network (PSTN) 102 which in turn connects via trunks 112 and 113 to the Mobile Services Switching Centers MSC 1 and MSC 2, respectively. The MSC 1 is the MSC closest to the calling subscriber &#34;A&#34; and it is the so-called anchor MSC responsible for a call outgoing from the terminal A. The MSC 2 is the MSC closest to the called subscriber who has a cellular mobile radio terminal 107 and a wide area pager 108. The wide area paging system is represented in FIG. 1 by the antenna mast 106 and the pager 108 is in the radio coverage area of the paging system 106. The called subscriber&#39;s terminals are accessible to the paging system 106 via a downlink paging signal 118 and connectable to the cellular radio system via radio signals 117 whereby the MSC 2 has a base station (not illustrated) for this radio contact. The two radio terminals 107 and 108 do not communicate with each other. 
     According to one embodiment of the present invention, an alerting technique can be provided making use of the standard handheld terminals and pagers to alert a user that a call is incoming and to connect the incoming call wherein there is no communication between the pager and the handheld terminal. In this embodiment, the &#34;B&#34; subscriber&#39;s handheld terminal is in the off state while the associated pager is in the on state. The calling subscriber &#34;A&#34; dials the number of the handheld terminal of the subscriber &#34;B&#34; and is connected to the mobile services switching center 104 nearest to the calling subscriber &#34;A&#34;. The MSC 104 then asks the home location register HLR 103 associated with the dialed number for a roaming number of the &#34;B&#34; subscriber. The HLR in return sends back information that the handheld terminal &#34;B&#34; is off or cannot be contacted and also includes a &#34;C&#34; number to which the incoming call should be diverted, wherein the &#34;C&#34; number is the number of an associated physically independent wide area pager carried by subscriber &#34;B&#34;. In addition, the HLR 103 sends to the MSC 104 together with the &#34;C&#34; number a special indication or code, e.g., a category K, assigned to the &#34;B&#34; subscriber and stored in the HLR in order to inform the MSC that the &#34;B&#34; subscriber is of a novel type having both a handheld terminal and an associated pager and requiring the execution of the inventive call setup procedure described below. The MSC 104 tells the subscriber &#34;A&#34; to wait using a prestored voice message which indicates that a page is being performed. The MSC 104 then calls the wide area paging system using the &#34;C&#34; number received from the HLR and sends a message asking the wide area paging system to perform a page. In addition, the message may include the telephone number of the calling subscriber &#34;A&#34; with an indication (e.g., the character *) to the subscriber &#34;B&#34; that the page regards a parked incoming call that may be answered within a predetermined time. The wide area paging system sends out a paging message to the pager alerting the subscriber &#34;B&#34; and the message also contains the telephone number of the subscriber &#34;A&#34;. When the subscriber &#34;B&#34; receives the page, the subscriber &#34;B&#34; will be able to read the telephone number of the subscriber &#34;A&#34; on the display screen of the pager so as to determine whether he/she wants to answer the call. If the subscriber &#34;B&#34; decides to answer the call, the &#34;B&#34; subscriber pushes the &#34;power on&#34; key of the hand held terminal which turns on the handheld terminal. This action causes the hand held terminal to register its location with the home location register using a known procedure. The mobile services switching center 104 asks the home location register at periodic intervals, e.g., 5 seconds, for a roaming number to the handheld terminal until the answer changes from the &#34;cannot be contacted&#34; state to a roaming number &#34;X&#34; or until a timeout timer in MSC 104 has elapsed. For example, the timeout timer could be set for 30 seconds after initiating the page. If a roaming number &#34;X&#34; is received before the expiration of the timeout timer, the MSC 104 calls the handheld terminal setting up communication between the subscribers &#34;A&#34; and &#34;B&#34; in the usual way. 
     Alternatively, instead of the MSC 104 periodically asking the home location register for a roaming number, the home location register could contact the MSC when the mobile radio terminal has been switched on and has registered with the HLR. In this embodiment, the home location register stores the request for the roaming number along with other information such as the identity of the requesting MSC and the identity of the called subscriber B. When called subscriber B activates his/her terminal, the home location register checks to see if a request for a roaming number for B has been stored, and if a request has been stored, the home location register contacts the requesting MSC and gives the MSC a roaming number. 
     According to another embodiment of the present invention, the probability of terminating calls being successful can be increased by making use of the standard handheld terminals and pagers to alert a user on both terminals (telephone and pager) simultaneously. In this embodiment, the &#34;B&#34; subscriber&#39;s handheld terminal and separate pagers are both in an on state but the handheld terminal although being in the vicinity of the &#34;B&#34; subscriber is not heard by him/her. The calling subscriber &#34;A&#34; dials the number of the handheld terminal of the subscriber &#34;B&#34; and is connected to the mobile services switching center 104 nearest to the calling subscriber &#34;A.&#34; The MSC 104 then asks the HLR 103 associated with the dialed number for a roaming number of the &#34;B&#34; subscriber. The HLR in return sends back the requested roaming number together with the special category K of the &#34;B&#34; subscriber and a &#34;C&#34; number for alerting the wide area pager carried by the B subscriber if indicated. The MSC 104 sets up the call to the cellular terminal and starts a time measurement. If there is no answer within a predetermined time, e.g., corresponding to a time setting of between zero to three alert signals (rings), the MSC 104 tells the subscriber &#34;A&#34; to wait using a prestored voice message which indicates that a wide area page is being performed. The MSC 104 then calls the wide area paging system using the &#34;C&#34; number received from the HLR 103 and sends a message asking the wide area paging system to perform a page. When the subscriber &#34;B&#34; receives the page he/she will realize that he/she has not heard the cellular alert signal. The &#34;B&#34; subscriber may then proceed to answer the call on the handheld terminal. A difference between this embodiment and the previously described embodiment is that when the handheld terminal is in an on state the call may be answered directly by pushing the off-hook key whereas if the handheld terminal is in an off state, its on/off key has to be pushed first and its off-hook key afterwards. 
     In the prior art, it is known that after switching on a mobile radio terminal, the subscriber is asked to enter his/her personal identification number (PIN) in order to prevent someone from stealing the radio terminal and then using it for calls at the expense of the owner. In addition, it is the intention to prevent someone from using a stolen terminal to receive calls. A problem arises for the preferred embodiment in that when the subscriber &#34;B&#34; switches on his/her handheld terminal in order to register and then receive the parked incoming call, the time available is limited because of the use of the timeout timer. Therefore, it is desirable to modify the described authentication procedure. One such solution is described below. 
     The PIN number may be entered when switching the handheld terminal off rather than when switching the handheld terminal on. When the power off button on the handheld terminal is pushed, this order is not carried out immediately. Instead of immediately turning off, the subscriber can be asked to enter the PIN number. After doing this, the off key may be pushed again causing power off. The effect of such an authentication, if successful, would be that the next time the mobile radio terminal is switched on, the authentication process is not required. Instead, registration in the home location register takes place immediately, thus speeding up the process for receiving a parked call. It is an advantage if the cellular network for which the present invention is implemented has the function of informing the HLR when a mobile radio terminal performs power off. However, it can never be avoided that a mobile moves into a radio shadow or gets outside the radio coverage of the system and will therefore not be contactable although nothing has been reported. In this case, the cellular system will try to set up the requested connection to the addressed &#34;B&#34; mobile terminal and after a time out report that the subscriber cannot be reached which is handled according to the present invention as if the terminal was switched off. 
     It should be noted, however, that the problem of not knowing that a terminal is in an off-state is limited in time to the period of so called periodic registration. In known cellular systems there is periodic registration e.g. every 15 minutes, in order to know that a terminal is off when no registration has been received for a time exceeding the period. 
     The preferred embodiment of the present invention will now be described with reference to FIGS. 1 and 2a. When a call is originated by the subscriber &#34;A&#34; in step 201, the call is routed, in step 202, to the nearest MSC, in this case, MSC 1 since the &#34;B&#34; number specified belongs to a mobile terminal series of numbers. The MSC 1 asks, in step 203, the home location register for a roaming number for the handheld terminal 107. The home location register answers that the specified handheld terminal is of category K and that the number of the associated wide area pager is &#34;C&#34; in case it becomes necessary to initiate a wide area page. In addition, if the handheld terminal is switched off or is not contactable, the home location register informs the MSC that the handheld terminal is off and the flow continues in step 204. If the handheld terminal 107 is on, the flow continues at step 211 by directly paging the handheld terminal MS via a cellular control channel associated with the MSC 2 whereby the roaming number received by MSC 1 via link 114 from the HLR allows, in a known manner, the call to be routed from the MSC 1 to the MSC 2 via trunk lines 112 and 113 and the PSTN 102. In steps 212, 213, and 214, depending upon whether the paged terminal 107 answers or not, the call is performed or only registered for later reference. On the other hand, if the handheld telephone 107 is off or is not contactable, this fact is known by the HLR and given to the MSC 1 via connection 114 in step 203. The MSC 1 calls the wide area paging system 106 and transmits the number of the pager asking that a wide area page be performed. The wide area paging system performs the page using a signal 118 and alerts, in step 205, the called subscriber giving him/her the opportunity to manually switch on the handheld terminal 107 in order to prepare to receive the incoming call. Step 205 is preceded by step 204 that checks whether a wide area page has already been performed during the last 30 seconds in which case no new page is sent. After waiting for a period of time, typically 5 seconds, in step 206, the total wait time is checked in step 207. If a certain time limit, for example 30 seconds, is exceeded, the call from terminal A is given a busy tone by MSC 1 and the procedure ends in step 208. If the total waiting time has not yet been exceeded, the flow returns to step 203 to check if the handheld terminal 107 has been switched on and thus registered in the home location register. If the handheld terminal 107 has been switched on, the flow then continues to step 211 which has been described earlier and which may lead to the establishing of a connection between the calling and called subscriber. 
     It is possible to transmit the telephone number of the calling subscriber from the PSTN via connections 112, 116, and 118 to the pager 108 passing through MSC 1 and the paging system 106, thus informing the called subscriber of the caller&#39;s telephone number so that the subscriber may determine whether or not he/she want to accept the call. 
     An alternative to the loop of steps 204-207 is to have the HLR check autonomously when a registration of the handheld terminal 107 takes place and when this happens initiate signaling to the MSC 1 via link 114 where the incoming call is parked. 
     A slightly different embodiment of the present invention will now be described with reference to FIGS. 1 and 2b. The flow of this embodiment is identical to the one illustrated in FIG. 2a except for steps 212-214 being replaced by the steps 212b-217b. This modification takes care of the case when a called subscriber fails to hear, in step 212b, the first three alert signals on his/her handheld terminal whereby the flow continues to step 214b rather than performing the call in step 213b. In step 214b, the MSC calls the wide area paging system 106 as in step 205 and a wide area page is performed calling terminal 108. This may result in the called subscriber answering the call on the handheld terminal in step 216b or otherwise the incoming call will be disconnected in step 217b if the call is not answered within the prescribed period of time. 
     FIG. 3 illustrates a possible implementation of the present invention. The procedure described above with regard to FIGS. 2a-2b is implemented in programs located in a processor 302 in the MSC 304. The home location register 306 has a processor 308 with access to a category store 310 which has a new type of category (K) for subscribers with the cellular terminal and pager combination which allows a user to answer a call directly within, for example, 30 seconds after the reception of a wide area page. When the MSC 304 requests a roaming number for a specified called subscriber &#34;B&#34;, the HLR 306 returns the mentioned special category (K) to the MSC 304 in order to initiate the special program in the MSC 304 for handling this case, i.e., paging, waiting, etc. 
     FIG. 4 illustrates a pager 400 with on/off and programming keys 401 and a special display window 402 which is useful when using the pager together with a cellular terminal according to the invention. The special display window 402 shows the time remaining on the time-out timer. The count down displayed on the pager may be started in the pager by setting the counter to 30 seconds when the page arrives. The A-nr is displayed in window 404 and a star (*) at the end of the A-nr indicates this countdown condition. Alternatively, the count, i.e., the time-out period, can be sent to the pager by the paging system. The pager has an antenna 406 and a control and memory 408 including the function to receive and store telephone numbers of calling parties. 
     The pager 400 stores the A-numbers of calling subscribers as known in the art, in order to allow the called subscriber to remember who has been calling and for enabling him/her to call back at a later time. This function is still available when using the present invention. However, the present invention provides an addition described below which is motivated by the described direct answering feature of the invention. The addition consists in providing a cancellation message from MSC1 104 to the pager 108 via connections 116, 118 and paging system 106 informing the pager that an incoming call from a specified A-subscriber has been answered by the handheld terminal and then the field in the memory of the pager where calls are registered, the information regarding the call concerned is provided with an indication such as a flag that this call has been answered. This avoids later doubts on the part of the subscriber whether a call has been answered or not. 
     It will be appreciated by those ordinarily skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or central character thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalence thereof are intended to be embraced therein.