Abstract:
A cellular telephone ( 116 ) and a pager ( 118 ) having a common battery ( 256 ) are integrated into a single unit. The unit is maintained in a low-power receive page mode when not in use. An incoming call is processed first as a conventional pager message. The device receives the page and wakes from the low-power page mode. When the device has gone to full-power active mode, a cellular phone call is connected. A smart battery controller ( 254 ) for the unit is provided. The smart battery controller ( 254 ) monitors the power level left in the battery ( 256 ) and stops allowing telephone operations when power reaches a minimum level. For example, the level may be configurable by the user as the number of hours of paging that may be accommodated after cell phone operations are no longer permitted.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to telecommunications systems and, particularly, to an improved notification system and method for cellular telephones. 
     Many users rely on one or more portable devices, such as pagers and cellular telephones, to maintain a telecommunications link while traveling. Pagers are advantageous in that they are small and consume relatively little battery power. For example, a pager can typically run as long as a month on a single AA battery. In addition, the cost of maintaining a pager service is typically minimal. However, pagers do not allow for duplex communication. 
     Cellular telephones, on the other hand, have been developed which are extremely small, but consume large amounts of battery power. For example, a cellular telephone can discharge its battery in a single day even in standby mode waiting for a call to be received. Thereafter, several hours are required to recharge the battery. 
     Often, users carry both a pager and a cellular telephone. The pager is maintained as an initial notification device. When a call is received on the pager, typically a return phone number is delivered, either manually or by a caller-ID mechanism. To return the call, the user must then turn on the cell phone and dial the number. To enhance such usability, pagers and cellular phones have been developed which are packaged together in the same housing. In particular, U.S. Pat. Nos. 5,737,707 and 5,802,470 describe a personal communications device including both a pager and a cellular telephone. The cellular telephone is normally kept off and draws no power. When an incoming call for the cellular telephone arrives at the cellular exchange, and it is determined that the cellular phone has not been registered with a base station, a paging system transmits a paging signal to the integrated pager. The pager receives the signal and wakes the cellular telephone, which then processes the call. When the call is completed, a second paging message is provided, and the cellular telephone shuts down. 
     While the system described in the &#39;707 and &#39;470 patents is useful in conserving battery power, it is still possible for the cellular telephone to draw too much power and cause the paging system to have to shut down (even though the pager draws much less power than the cell phone). 
     Accordingly, there is a need for a combined cellular telephone/pager wherein power may be conserved and messaging capabilities preserved. 
     SUMMARY OF THE INVENTION 
     These disadvantages in the prior art are overcome in large part by a system and method according to the present invention. According to one aspect of the invention, a cellular phone and a pager having a common battery are integrated into a single unit. The unit is maintained in a low-power receive page mode when not in use. An incoming call is processed first as a conventional pager message. The device receives the page and wakes from the low-power page mode. When the device has gone to full-power active mode, a cellular phone call is connected. A smart battery controller for the unit is provided. The smart battery controller monitors the power level left in the battery and stops allowing phone operations when power reaches a minimum level. For example, the level may be configurable by the user as the number of hours of paging that may be accommodated after cell phone operations are no longer permitted. 
     A better understanding of specific embodiments of the invention is obtained when the following detailed description is considered in conjunction with the following drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram illustrating a cellular phone and paging system according to an embodiment of the invention; 
     FIG. 2 is a block diagram illustrating a personal communication device according to an embodiment of the invention; 
     FIG. 3 is a block diagram illustrating a power control unit according to an embodiment of the invention; 
     FIG. 4 is a diagram of a voltage profile of a battery that may be used in an embodiment of the invention; 
     FIGS. 5A-5B show a flowchart illustrating system operation according to an embodiment of the invention; and 
     FIG. 6 is a flowchart illustrating operation of an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a telecommunications system generally identified by the reference numeral  90  according to an embodiment of the invention. The telecommunications system  90  includes a combined cellular telephone and paging system. In particular, the system  90  includes one or more metropolitan switching centers (MSC)  104 , which serve as wireless call exchanges and provide wireless call processing and call routing services. A network control point  103  is coupled to the MSC  104  and provides a database of information about the configuration of the cellular system. A plurality of base stations  108   a ,  108   b  are provided, which connect to the MSC  104  and provide wireless call service to the cellular telephones presently located in the respective cells serviced by the base stations. 
     A paging exchange  105  is further provided which provides paging services to one or more pagers (not shown). Typically, the area serviced by the paging system encompasses one or more cells. To provide call capability between the wireless telephones and landline phones (not shown), the MSC  104  is connected to the public switched telephone network (PSTN)  102 . 
     According to an embodiment of the invention, at least some cellular system users, such as users  110   a ,  110   b , are equipped with personal communications devices which include both a cellular telephone  116   a ,  116   b  and a pager  118   a ,  118   b , respectively. The telecommunications system  90  further includes an adjunct processor  107  that is coupled to the MSC  104 , NCP  103 , and paging exchange  105 , and that provides for cellular-call completion with the aid of the paging system. Such a processor is generally described in U.S. Pat. No. 5,802,470, which is incorporated by reference in its entirety as if fully set forth herein. 
     An exemplary personal communications device  110  according to an embodiment of the invention is shown in FIG.  2 . The personal communications device  110  includes a pager  118  and a cellular phone  116  integrated into a single unit. The cellular phone  116  includes a known transceiver  250  operating under control of a cellular phone controller  252  and powered by a battery  256 . The transceiver  250  and cellular phone controller  252  are coupled to the battery  256  through a power control circuit  254 , which switches power to the cellular phone  116  when a page is received and, as will be described in greater detail below, when there is sufficient “remaining” power left for phone operation. The cellular phone controller  252  further is coupled to receive inputs from a keypad or other input device  260 , and provide audio signals to an audio control or I/O unit  258 . A display  262 , which may be a liquid crystal or other type of display, may also be provided. In addition, as will be described in greater detail below, the display  262  or the audio I/O  258  may be used to provide notification of how much charge remains, or how long the phone may be used. 
     The pager  118  includes a conventional paging receiver  200  connected to a conventional paging controller  202  which performs paging decoding. The paging controller  202  also interfaces to the power control circuit  254 . The paging receiver  200  and the paging controller  202  are powered by the battery  256 , and are always turned on. When the paging controller  202  decodes a received incoming-call indication, it not only alerts the user thereof but also causes the power control circuit  254  to close a switch (not shown), if sufficient power remains for phone operation, thereby connecting the cellular phone controller  252  and the cellular phone transceiver  250  to the battery  256  and turning the cellular phone  116  on. This causes the cellular phone  116  to undergo registration in a known manner and thus become able to receive the incoming call. When the paging controller  202  decodes a received power turn-off indication, it causes the power control circuit  254  to open the switch, thereby disconnecting the transceiver  250  and the cellular telephone controller  252  from the battery  256  and turning the cellular phone  116  off, whereby the cellular phone  116  again becomes unable to receive incoming calls. 
     In particular, an exemplary power control circuit  254  according to an embodiment of the present invention is illustrated in greater detail in FIG.  3 . The power control circuit  254  includes a power control processor  302  coupled to receive inputs from the keypad  260  (FIG. 2) and the paging controller  202 . In addition, the power control circuit  302  is coupled to a read-only memory  304  which stores a look-up table related to a power consumption profile of the cellular phone  116 . A random access memory  308  is also coupled to the power control processor  302 , to act as a temporary storage for current power consumption information. Finally, the power control processor  302  is coupled to control a switch  307  for coupling power to the cellular telephone  116  (FIG.  2 ). 
     Generally, the power control processor  302  monitors duration of use of the cellular telephone  116 , as well as duration of use of the pager  118 , and inhibits operation of the cellular phone  116  if its use will provide too great a drain on available remaining power. To do so, the ROM  304  stores the battery charge capacity and, if necessary, a profile of the paging power consumption, as well as a profile of cell phone power consumption. The power control processor  302  then monitors current discharge over time of the battery  256 , and integrates the current discharge curve to arrive at a battery discharge level. Remaining battery capacity is then the full charge level minus the discharge. Such a method is described in U.S. Pat. No. 5,648,717, which is hereby incorporated by reference in its entirety as if fully set forth herein. The power control processor  302  then compares the profile of paging and cell phone power consumption to determine how many hours of paging operation are available. (Since reception of paging messages consumes more power than waiting for paging messages, the number of past paging messages may also be taken into account in this calculation). 
     Because inaccuracies in the current integration can build up over time, an additional check on the charge level remaining may be provided, by monitoring battery voltage levels. In particular, FIG. 4 illustrates the voltage discharge characteristic of an exemplary device battery, e.g., nickel-cadmium battery. Typically, this profile is stored in the ROM  304 . The profile has a substantially flat characteristic A extending from a maximum charge on the left hand side for a major portion of the battery charge, where battery charge is relatively high. It also has a rapidly falling region B in a minor portion of battery charge, where battery charge is relatively low. The major portion  101  of battery charge is represented by the area beneath the characteristic from 100% on the left hand side to the drop point in the profile at a predetermined charge level of approximately 10% of maximum battery charge. The minor portion  101  of battery charge is represented by the area under the graph from the profile drop point to the right hand side, where the remaining battery charge is virtually zero. 
     The power control processor  302  monitors the battery voltage and compares the measured voltage with a voltage threshold V t  which is stored in memory. When the measured voltage crosses the threshold V t , the power control processor  302  updates the charge level or time remaining, overriding the value obtained from the integration calculation. This value is then used for the duration calculation. 
     In addition, the power control processor  302  may receive as an input a desired period of operation. More particularly, the user may input “24 hours” as the desired period, meaning that it is desired that the personal communications device be capable of receiving pages for a period of 24 hours. If no particular time is input, a default level may be set. 
     When a call is received at the pager, the power control processor  302  determines the battery discharge level (using either the integration method or the voltage profile method), the number of hours remaining in the pre-set charge period, and the amount of charge necessary to power the pager. So long as sufficient power remains to power the pager for the time remaining, the call will be completed. If, however, insufficient power remains, the call will not be completed (so that the device has adequate power reserves to accommodate future pages to be received for the duration of the pre-set charge period). Additionally, if a call is completed and during the call the charge level approaches the threshold, the call may be disconnected, after providing appropriate notification and the opportunity to gracefully terminate the call. 
     More particularly, the power control circuit  254  may provide a signal to the cell phone controller  252  indicative of the amount of time the cell phone may be used before charge drops below a level adequate to power the pager during the remaining period. As that time is approached, the controller  252  may provide a message either on the display  262  or via the audio I/O  256  indicating that the threshold is being approached or the amount of remaining time available for phone use. Such a message may be stored in memory (not shown) in the controller  252 . Moreover, if an audio message is provided, it may be provided in a known manner such that only the user, and not the other party, hears the message. 
     Operation of the present invention is illustrated in flowchart form in FIGS. 5A-5B. When the MSC  104  receives a call incoming for a cellular phone  116   a , either from a landline telephone via the PSTN  102  or from another cellular phone  116   b  it attempts to extend the call to the cellular phone  116   a  in a step  5002 . First, in a step  5004 , the MSC  104  sends a query containing the called number to the NCP  103  to determine if the called cellular phone  116   a  is registered with any base station  108   a ,  108   b , and if so, which one. The NCP  103  responds to the query by searching its data to determine if the called cellular phone  116   a  is registered, in a step  5006 . If the called cellular phone  116   a  is registered, it is able to receive the incoming call; the NCP  103  conventionally sends the information back to the MSC  104  in a query response, and the MSC  104  conventionally extends the call to the called cellular phone  116   a  via the one of the base stations with which cellular phone  116   a  is registered, in a step  5008 . However, if the NCP  103  finds that the called cellular phone  116   a  is presently not registered with any base station, it is not able to receive the incoming call and the attempt at extending the call to the cellular phone  116   a  cannot be completed, and the NCP  103  notifies the MSC  104  thereof, in a step  5010 . In response, the MSC  104  sends another query to the NCP  103  inquiring whether alternative call treatment is being provided for this cellular phone  116   a , in a step  5012 . Alternative treatment may include a call-coverage path, such as connecting the call to the called party&#39;s mailbox in a voice messaging system (not shown). According to the invention, the data in the NCP  103  provide for alternative call treatment for the cellular phone  116   a , and the first alternative call destination in the coverage path of cellular phone  116   a  is specified to be the adjunct processor  107 . The NCP  103  makes this determination and sends a notice thereof to MSC  104 . In response, the MSC  104  routes and connects the call to the adjunct processor  107  in a step  5014 . The adjunct processor  107  receives the call and puts it on hold in a step  5016 . While the call is on hold, the adjunct processor  107  plays a pre-recorded announcement to the caller informing the caller to stay on the line while the called party is paged. The adjunct processor  107  also sends a paging query for the called cellular phone  116   a  to the NCP  103  in a step  5018 . The NCP  103  finds the pager number of the pager  118   a  that is associated with the cellular phone  116   a  in its records for cellular phone  116   a  in a step  5020  and sends this pager number to the adjunct processor  107  in a step  5022 . In response, the adjunct processor  107  sends a paging request to the paging exchange  105  in a step  5024 . The paging request contains the pager number of the pager  118   a  and a request to send it an incoming-call indication. The adjunct processor  107  also starts a timer (not shown) that gives the cellular phone  116   a  a predetermined amount of time to become registered in a step  5026 . In response to the paging request, the paging exchange  105  broadcasts an incoming-call-indicative paging signal containing the pager number provided by the adjunct processor  107  and an incoming-call-indication code in a step  5028 . 
     When the pager  118   a  receives and recognizes the incoming-call-indicating paging signal, it responds by causing the power control processor  302  to make a determination of whether sufficient power remains for the completion of the cellular phone call, in a step  5032 . If it does not, the call may terminate, in a step  5030  (or the caller may be directed to voicemail). If sufficient power does remain, then the cellular phone  116   a  is turned on in a step  5034 . In response, the cellular phone  116   a  automatically undergoes registration with the base station  109  that serves the cell in which the cellular phone  116   a  is presently located in a step  5036 . The base station  109  notifies the MSC  104  of the registration and the MSC  104  in turn notifies the NCP  103  causing the NCP  102  to update its records for cellular phone  116   a  in a step  5038 . 
     In the meantime, the adjunct processor  107  periodically polls the NCP  103  for the status of the cellular phone  116   a . Until the cellular phone  116   a  registers with a base station, the NCP  103  replies to the poll with an indication that the cellular phone  116   a  is not registered. In response to the indication of non-registration, the adjunct processor  104  repeats polling of the NCP  103  until the timer that adjunct processor  107  had started times out in a step  5040 . 
     As shown in FIG. 5B, if the cellular phone  116   a  registers with a base station and the NCP  103  is informed thereof before the timer times out (as determined in a step  5042 ), the NCP  102  replies to a poll with an indication that the cellular phone  116  is registered and an identification of the base station  109  with which the cellular phone  116   a  is registered. In response to this indication, the adjunct processor  107  resets the timer that it had started. The timer now begins to time an interval during which the cellular phone  116   a  must answer the call. The adjunct processor  104  also bridges the call back to the MSC  104 . This results in the call being connected back to the MSC  104  through the adjunct processor  104 , thereby allowing the adjunct processor  107  to monitor the call. The MSC  104  responds to the bridged call as if it had just received the call, and attempts to connect the call to the cellular phone  116   a  in the conventional manner, at step  5050 . 
     The controller  252  also may receive a signal indicating how long the user may use the phone if it is desired to continue page mode for the duration of the pre-set period. Further, if the period is approached, an appropriate indication is given to the user. For example, the controller  252  may access its memory (not shown) for a predetermined message to be displayed via the display  262  or delivered via the audio I/O  256 . 
     The adjunct processor  107  continues monitoring the call in a step  5054 . If the base station  109  connects the call to cellular phone  116   a , and the cellular phone  116   a  answers the call before the timer that adjunct processor  104  had reset times out, the adjunct processor  104  detects the call answer. In response, the adjunct processor  104  turns off the timer and continues to monitor the call, at step  5054 . When one of the parties to the call hangs up the call, e.g., at step  5056 , and the base station  109  proceeds to disconnect the call, at step  5058 , the adjunct processor  107  detects this condition. In response, the adjunct processor  107  sends a power turn-off paging request for the pager number of the pager  11   8   a  to the paging exchange  105 , at step  5060 . The paging exchange  105  responds by broadcasting the request via a paging signal. The pager  118   a  receives and recognizes the paging signal, in a step  5062 , and responds thereto by turning off the cellular phone  116   a , in a step  5064 . 
     Returning to step  5042  of FIG. 5B, if the timer that was reset times out before the adjunct processor  107  detects that the cellular phone  116   a  answered the call, the adjunct processor  107  sends a power turn-off paging request for the pager number of pager  118   a  to paging exchange  105 , at a step  5044 . The paging exchange  105  responds by broadcasting the request via a paging signal, in a step  5046 . The pager  118   a  receives and recognizes the paging signal and responds thereto by turning off cellular phone  116   a  in a step  5048 . 
     Turning now to FIG. 6, a flowchart illustrating operation of the power control circuit  254  according to an embodiment of the invention is illustrated. As discussed above, the power control circuit  254  receives as a user input via a keypad  260  a “working time period,” in a step  1000 . The working time period is representative of the period for which the personal communications device should be able to remain active to receive pages. The working time period may be a default period, rather than requiring individual setting. This information is stored in RAM  306 . From the working time period information, the power control processor  302  may continually calculate how much charge is required to maintain the personal communications device in page receive mode for the time remaining of the working time period. 
     Next, in a step  1002 , the power control processor receives as an input the current drain on the battery. Then, in a step  1004 , the power control processor  302  performs an integration of the current versus time function to obtain the charge information. In a step  1006 , the power control processor  302  determines how much of the remaining charge is required to maintain the personal communications device in page receive mode for the remaining portion of the working time period. Any excess charge may be used to process cellular phone calls. 
     In addition, in one embodiment, the output voltage of the battery may be measured, in a step  1008 . The output voltage is compared to the threshold V t . If the voltage is at or below the threshold, as determined in a step  1010 , then the time and charge remaining before complete discharge is updated, in a step  1014 . Otherwise, the values obtained through the integration process are maintained, in step  1012 . 
     Next, in a step  1016 , a page indicative of an incoming cellular telephone call may be received, as described above. In a step  1018 , the power control processor  302  determines whether sufficient charge is available for the unit to process the cell phone call. If so, then in a step  1022 , the call is connected and processed as described above. If not, however, then in a step  1020 , a busy signal may be provided (or the call may be routed to voicemail). In any case, the call is not connected, though a page message may still be provided to the user. Finally, in a step  1024 , the charge calculation is updated. 
     In some embodiments, back in step  1018 , the power control circuit  254  may provide a signal to the control processor  252  indicating how much charge remains; and the control processor  252  in turn may provide an indication to the user of how long a cell phone conversation may be carried on before the threshold is reached. Alternatively, the control processor  252  may continue to monitor and provide an indication when the threshold has been reached (or immediately before). 
     Although the specific embodiments of the present invention are discussed in the context of a cellular telephone environment, the present invention also has application in any cordless telephony devices such a cordless phone, a personal digital assistant, or a wireless telephony-over-local area network (ToL) device.