Abstract:
Detecting a wireless terminal being taken from a facility. In a first embodiment, a base station is assigned to each exit from the facility. The base station uses a directional antenna which only communicates with wireless terminals within the exit area. When a wireless terminal enters the exit area and registers on the base station, the base station transmits the registration information to a wireless switching system that immediately places a telephone call to the user of the wireless terminal to inform them that they have not turned in their wireless terminal. Alernatively, in a third embodiment, after the wireless terminal is registered, the base station rather than the wireless switching system places a telephone call to the user of the wireless terminal to inform them that they have not turned in their wireless terminal. In a second embodiment of the invention, a transmission signal separate from the frequencies utilized for voice and data communication by the wireless switching system is utilized to alert the wireless terminal to the fact that the wireless terminal is in an exit area. The wireless terminal is responsive to this alerting to place a call to the wireless switching system to inform the wireless switching system of this fact. The wireless switching system then alerts the user via the wireless terminal.

Description:
TECHNICAL FIELD 
     This invention relates wireless telecommunication, and in particular, to wireless terminals. 
     BACKGROUND OF THE INVENTION 
     The utilization of personal communication service (PCS) wireless terminals and switching systems is increasing for office buildings, large retail stores, hospitals, etc. The capability of being able to communicate with employees where ever they may be in a facility has proven to be worth the cost of the installation of PCS systems. Within office buildings where the employees work the same set of hours, it is necessary to assign to each employee their own PCS wireless terminal. However, within large retail stores and hospitals where multiple shifts are worked during the day, it is sufficient to have a number of PCS wireless terminals equal to the number of employees on a given shift. The sharing of PCS terminals in this manner greatly reduces the cost of installing a PCS system. 
     Problems have arisen because of the small size of the PCS terminals, and the fact that employees become accustomed to having the PCS terminal on their person. The end result is that an employee leaving for the day has a reasonable probability of leaving the facility with the PCS terminal; thus, leaving another employee on the next shift without a PCS terminal. In general, the problem is not so much that the employees are trying to steal the PCS terminals, but rather that they are simply forgetting to turn the PCS terminal in at the end of their shift. 
     What is needed is a procedure and mechanism whereby the employees will be alerted if they attempt to leave the facility with a PCS terminal. 
     SUMMARY OF THE INVENTION 
     The preceding problem is solved and a technical advance is achieved by an apparatus and method that allows the detection of a wireless terminal leaving a facility by a wireless switching system. Advantageously, in a first embodiment, a base station is assigned to each exit from the facility. The base station uses a directional antenna which only communicates with wireless terminals within the exit area. When a wireless terminal enters the exit area and registers on the base station, the base station transmits the registration information to a wireless switching system that immediately places a telephone call to the user of the wireless terminal to inform them that they have not turned in their wireless terminal. 
     Advantageously, in a second embodiment of the invention, a transmission signal separate from the frequencies utilized for voice and data communication by the wireless switching system is utilized to alert the wireless terminal to the fact that the wireless terminal is in an exit area. The wireless terminal is responsive to this alerting to place a call to the wireless switching system to inform the wireless switching system of this fact. The wireless switching system then alerts the user via the wireless terminal. In addition, if the wireless terminal is in a standby mode when it enters the exit area, it is responsive to the separate transmission signal to power up the wireless terminal so that the wireless terminal can alert the wireless switching system. The separate transmission signal may be a low radio frequency, a high radio frequency, an optical transmission, etc. 
     Advantageously, in a third embodiment of the invention, a base station is assigned to each exit from the facility. The base station uses a directional antenna which only communicates with wireless terminals within the exit area. When a wireless terminal enters the exit area and registers on the base station, the base station performs the normal registration operations with a wireless switching system. After the wireless terminal is registered, the base station places a telephone call to the user of the wireless terminal to inform them that they have not turned in their wireless terminal. 
     These and other features and advantages of the invention will become more apparent from the following description of an illustrative embodiment of the invention considered together with the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 illustrates a system for implementing a first embodiment of the invention; 
     FIG. 2 illustrates a block diagram of a wireless terminal for use with the first embodiment of the invention; 
     FIG. 3 illustrates a system for implementing a second embodiment of the invention; and 
     FIG. 4 illustrates a block diagram of a wireless terminal for use with the second embodiment of the invention; 
     FIG. 5 illustrates, in flow chart form, steps performed by a wireless switching system in implementing the first embodiment of the invention; 
     FIG. 6 illustrates, in flow chart form, steps performed by a wireless switching system in implementing the second embodiment of the invention; 
     FIG. 7 illustrates, in flow chart form, steps performed by a wireless terminal in implementing the second embodiment of the invention; 
     FIG. 8 illustrates, in block diagram form, a base station for implementing the third embodiment of the invention; and 
     FIG. 9 illustrates, in flow chart form, steps performed by a controller of a base station in implementing the third embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a block diagram of a telephone system that implements the first embodiment of the invention. FIG. 1 illustrates wireless switching system  102  communicating with public telephone network  101  via links  1   17  to provide public access for wireless terminals  111 - 112  via base stations  104 - 106  and antennas  108 - 109 . Wireless terminals  111 - 112  operate with wireless switching system  102  via base stations  104 - 106  using well known techniques in the art. Base stations  103 - 106  are standard base stations. Base station  103  is different in that it utilizes a directional antenna  107  that limits its wireless coverage area to an area of an exit from a facility. In FIG. 1, this area is denoted as area  113 . Antennas  103 - 109  do not have their wireless coverage areas inhibited. As is well known in the art, when a wireless terminal moves from an area covered by one base station to an area covered by another base station, the wireless terminal registers on the base station whose transmission signal is the strongest. For example, when wireless terminal  111  moves from the coverage area of base station  104  into area  113 , wireless terminal  111  will be receiving a stronger transmission signal from base station  103  via directional antenna  107  then from base station  104  via antenna  108 . Wireless terminal  111  registers on base station  103 . Base station  103  is responsive to the registration of wireless terminal  111  to implement standard registration procedures with wireless switching system  102 . Wireless switching system  102  performs the operations necessary to register wireless terminal  111  on base station  103 . In addition, wireless switching system  102  establishes a wireless link or a telephone call to wireless terminal  111 . Wireless switching system  102  then notifies the user of wireless terminal  111  that the user is about to exit the facility with wireless terminal  111 . This notification to the user can simply be an auto tone via the wireless link that wireless switching system  102  has wireless terminal  111  produce or it may be a recorded message that is delivered to the user when the user answers the telephone call. A voice path does not have to be set up to wireless terminal  111  to produce an audio warning tone if the wireless link is used. Greater details on this operation is set forth with respect to FIG.  2 . 
     Wireless terminal  111  is advantageously illustrated in greater detail in FIG.  2 . The other wireless terminals are similar in design. Wireless set  111  implements a wireless protocol that allows wireless terminal  111  to establish a wireless signal link with wireless switching system  102  via base stations  103 - 106 . One air interface that can be used is the Japanese PHS protocol as set forth in “User-Network Interface and Inter-Network Interface Standards for PHS”, the Telecommunication Technology Committee, 1995, and “Personal Handy Phone System RCR Standard”, Version 1, RCR STD- 28 , Dec. 20, 1993. The message set of the PHS protocol is similar to the ISDN message set. Overall control of the wireless terminal is provided by control unit  201 . Units  202 ,  203 ,  206 ,  207 ,  208 , and  209  provide the RF communication capabilities for the wireless terminal. Elements  204 ,  210 , and  211 - 214  provide the audio information received and transmitted to the user; whereas, elements  216 - 218  and  205  provide the basic user interface. 
     Considering the following example of the operation of wireless terminal  111 . When control unit  201  via single strength monitor  202  determines that the transmission signal being received from base station  103  is stronger than the transmission signal being received from base station  104 , control unit  201  performs the registration procedures with base station  103 . Upon detecting the registration of wireless terminal  111  on base station  103 , wireless switching system  102  can transmit via the wireless signal link a message which will activate audio tranducer  217  and also may send a message to indicate on display  216  that wireless handset  111  is being carried out of the facility. Also, wireless switching system  102  may set up a voice telephone call to wireless terminal  111 . When the user answers this call, wireless switching system  102  plays a recorded message to the user utilizing elements  204 ,  206 ,  210 ,  211 , and  213 . The voice message informs the user that wireless terminal  111  is about to be taken out of the facility. 
     FIG. 3 illustrates another system having a second embodiment for implementing the invention. FIG. 3 illustrates wireless switching system  302  communicating with public telephone network  301  via links  317  to provide public access for wireless terminals  311 - 312  via base stations  304 - 306  and antennas  308 - 309 . Wireless terminals  311 - 312  operate with wireless switching system  302  via base stations  304 - 306  using well known techniques in the art. It is assumed that base station  304  via antenna  308  provides coverage for area  313 . When a wireless terminal, such as wireless terminal  311 , moves into area  313 , wireless terminal  311  receives a low frequency transmission from low frequency transmitter  303  via directional antenna  307 . Wireless terminal  311  is responsive to this low frequency transmission to establish a wireless signaling link with wireless switching system  302  via base station  304 . Note, the wireless signal link may be already established. Over this wireless signaling link, wireless terminal  311  informs wireless switching system  302  that it is receiving the low frequency transmission. Wireless switching system  302  then alerts the user of the wireless terminal  311  using operations previously described with respect to FIGS. 1 and 2. One skilled in the art could readily envision that low frequency transmitter  303  could transmit at any RF frequency or could be an optical transmitter with the wireless terminals having the capability of receiving this type of transmission. Advantageously, if wireless terminal  311  is in the standby mode, upon receiving the transmission from low frequency transmitter  303 , wireless terminal  311  is activated so as to establish the wireless signaling link. 
     Wireless terminal  311  is advantageously illustrated in greater detail in FIG.  4 . The other wireless terminals are similar in design. Wireless set  311  implements a wireless protocol that allows wireless terminal  311  to establish a wireless signal link with wireless switching system  302  via base stations included in wireless switching system  302 . One air interface that can be used is the Japanese PHS protocol as set forth in “User-Network Interface and Inter-Network Interface Standards for PHS”, the Telecommunication Technology Committee, 1995, and “Personal Handy Phone System RCR Standard”, Version 1, RCR STD-28, Dec. 20, 1993. The message set of the PHS protocol is similar to the ISDN message set. Overall control of the wireless terminal is provided by control unit  401 . Units  402 ,  403 ,  406 ,  407 ,  408 , and  409  provide the RF communication capabilities for the wireless terminal. Elements  404 ,  410 , and  411 - 414  provide the audio information received and transmitted to the user; whereas, elements  416 - 418  and  405  provide the basic user interface. The low frequency transmission from low frequency transmitter  303  is received by low frequency receiver  418  via antenna  419 . Upon reception of the low frequency transmission, low frequency receiver  418  transmits a control signal to control unit  401 . Control unit  401  is responsive to this signal to power up if in the standby mode and to establish a wireless signaling link with wireless switching system  302 . Once the wireless signaling link has been established, control unit  401  transmits a message to wireless switching system  302  to inform it that wireless terminal  311  is receiving the low frequency transmission. Wireless switching system  302  then alerts the user of wireless terminal  311  using similar operations as performed by wireless switching system  302  with wireless terminal  311 . 
     FIG. 5 illustrates, in flow chart form, the steps performed by wireless switching system  102  in the first embodiment of the invention. Decision block  501  is responsive to an operation to determine if this operation is a registration request from a base station located at an exit to the facility. If the answer is no, the operation is processed in a normal fashion by block  502  before control is transferred back to decision block  501 . 
     If the operation is a registration at a base station located at an exit, block  503  registers the wireless terminal and then transfers control to block  504 . The latter block alerts the wireless terminal either by transmission of a message that causes an audio alerting signal in the wireless terminal, transmission of an alphanumeric display message, or a voice message transmitted via a telephone call. One skilled in the art could readily see that all or a combination of these alerting operations could be utilized in block  504 . Block  506  then transmits a message inquiring if the wireless terminal will be returned to the facility within a predefined amount of time. This message can be transmitted either via an alphanumeric display on the wireless terminal or as a recorded voice message. The user of the wireless terminal then responds utilizing the keyboard. This is done so as to allow users to temporarily leave the facility for lunch breaks, etc. After execution of block  506 , decision block  507  determines if a message was received from the wireless terminal indicating that the wireless terminal will be returned within the predefined amount of time. If the answer is yes, block  508  marks the wireless terminal as having been temporarily removed before transferring control back to decision block  508 . If the answer in decision block  507  is a message stating no from the user or no message is received from the user at all, control is transferred to block  509  which marks the wireless terminal as having been removed from facility. Block  511  then alerts the facility management to the fact that the wireless terminal has been removed. The facility management is alerted so that the management can take steps to assure that there are adequate wireless terminals available for the next shift. After execution, block  511  transfers control back to decision block  501 . 
     FIG. 6 illustrates, in flow chart form, the steps performed by wireless switching system  302  in implementing the invention in accordance with the second embodiment. Decision block  601  determines if a message is being received from a wireless terminal indicating that it is in area  313 . If the answer in no, control is transferred to block  602  for normal processing. After execution of block  602 , control is transferred back to decision block  601 . If the answer is yes in decision block  601 , control is transferred to block  604 . Block  604  alerts the wireless terminal either by transmission of a message that causes an audio alerting signal in the wireless terminal, transmission of an alphanumeric display message, or a voice message transmitted via a telephone call. One skilled in the art could readily see that all or a combination of these alerting operations could be utilized in block  604 . Block  606  then transmits a message inquiring if the wireless terminal will be returned to the facility within a predefined amount of time. This message can be transmitted either via an alphanumeric display on the wireless terminal or as a recorded voice message. The user of the wireless terminal then responds utilizing the keyboard. This is done so as to allow users to temporarily leave the facility for lunch breaks, etc. After execution of block  606 , decision block  607  determines if a message was received from the wireless terminal indicating that the wireless terminal will be returned within the predefined amount of time. If the answer is yes, block  608  marks the wireless terminal as having been temporarily removed before transferring control back to decision block  608 . If the answer in decision block  607  is a message stating no from the user or no message is received from the user at all, control is transferred to block  609  which marks the wireless terminal as having been removed from facility. Block  611  then alerts the facility management to the fact that the wireless terminal has been removed. The facility management is alerted so that the management can take steps to assure that there are adequate wireless terminals available for the next shift. After execution, block  611  transfers control back to decision block  601 . 
     FIG. 7 illustrates, in flow chart form, the steps performed by control unit  401  of FIG. 4 in implementing the second embodiment of the invention. Decision block  701  determines if a message has been received from wireless switching system  302  via the signaling link to produce an alerting signal on audio transducer  417 . If the answer is yes, block  702  produces the desired audio alert alerting signal. Note, that this can be any audio alerting message from wireless switching system  302 . If the answer in decision block  701  is no, decision block  703  determines if a message has been received from wireless switching system  302  to be displayed on display  416 . If the answer is yes, block  704  performs this display function before transferring control back to decision block  701 . If the answer in decision block  703  is no, decision block  706  determines if a message has been received from wireless switching system  302  that pertains to call processing functions, e.g., call setup, disconnect, connect, alerting, etc. If the answer is yes in decision block  706 , block  707  performs normal call processing. Note, if wireless switching system  302  chooses to alert the user by placing a telephone call to the wireless terminal and playing a recorded message, blocks  706  and  707  perform these operations within the wireless terminal. If the answer in decision block  706  is no, decision block  708  determines if a signal is being received from low frequency receiver  418 . If the answer is no, block  709  performs normal processing before returning control to decision block  701 . If the answer in decision block  708  is yes, block  711  sends a message to wireless switching system  302  defining that the wireless terminal is at an exit to the facility before transferring control back to decision block  701 . 
     FIG. 8 illustrates an embodiment of base station  103  of FIG. 1 for implementing the third embodiment of the invention. Controller  802  communicates control information with wireless switching system  102  via link  114  and ISDN interface  801 . ISDN interface  801  communicates audio information with transceiver  803 . Controller  802  controls transceiver  803 . Transceiver  803  transmits and receives transmission signals with wireless terminals via directional antenna  107 . 
     FIG. 9 illustrates, in flow chart form, the steps performed by controller  802  in implementing the third embodiment of the invention. Decision block  901  determines if a registration request has been received from a wireless terminal. If a registration request has not been received, block  902  performs normal processing before returning control back to decision block  901 . Block  902  would perform all normal call processing operations of a base station which are well known in the art. If the answer is yes in decision block  901 , this means that a wireless terminal has entered area  113  of FIG.  8  and is attempting to register. If the answer is yes in block  901 , control is transferred to block  903  which processes the registration request from the wireless terminal in the normal manner. Block  904  then sets up a call to the wireless terminal. Note, that the call being set up may be a voice call or simply a call that establishes a signaling link to the wireless terminal. After execution of block  904 , control is transferred to decision block  905 . The latter decision block determines when the call set up in block  904  has been completed to the wireless terminal. When the call has been completed, control is transferred to block  906  which alerts the wireless terminal to the fact that it is exiting the building. This alerting may be any of the methods described with respect to the first and second embodiments. 
     It is to be understood that the above-described embodiments are merely illustrative of the principles of the invention and that other arrangements may be devised by those skilled in the art without departing from the spirit or scope of the invention.