Abstract:
When a cellular telephone is powered down, it sends a power-down message to a network it was previously registered with. If the network does not send, or if the cellular telephone does not receive, an acknowledgement of the power-down message from the network, a status bit referred to as a flag is set (or reset) in a non-volatile memory device in the cellular telephone. The power-down sequence is concluded by the cellular telephone and, the cellular telephone is shut off or put into a reduced power consumption state. When the telephone is turned back on, i.e., returned to its previous state, the flag is evaluated or “tested” to see if it was set (or reset) during the course of powering down. The status or value of the flag when the phone is powered up is then used by the cellular telephone to determine whether it should make a network access request to a network the telephone was registered to, during the power-up operation in order to cause that cellular network to update its database regarding the whereabouts of the powered-up cellular telephone.

Description:
BACKGROUND 
       [0001]      FIG. 1  depicts a prior art wireless communication system. The system  100  is comprised of a communications tower  102  at the top of which is an antenna  104 . Radio frequency signals  106  emanate from, and are picked up by the antenna  104  in the course of providing two-way wireless communications to compatible communications devices, such as a conventional cellular telephone  108  in a motor vehicle  110  or which can be carried about by a person, not shown. 
         [0002]    In  FIG. 1 , the cellular telephone  108  in the vehicle  110  provides both two-way voice communications to users of a motor vehicle  110  and telematics data services to the motor vehicle  110 . A telematics data service is a wireless data connection between sensors located on a vehicle  110  and a service provider that monitors the state of such sensors via a connection provided by a cellular telephone or other compatible wireless communications network. The General Motors ON-STAR™ system is an example of a telematics data service. 
         [0003]    The cellular telephone  108  maintains communication with a cellular network, not shown, by the radio frequency signals that are exchanged between the cellular radio  108  and the antenna  104  so long as the cellular radio  108  is within a geographic coverage area  110  or cell within which radio communications with a cellular radio  108  can be maintained. 
         [0004]    When the cellular radio  108  is powered down, it sends a power-down or de-registration message  112  to a cellular network controller, not shown, via the tower  102  service the cell  110  within which the cellular telephone  108  is operating. When the cellular system receives the power-down or de-registration signal  112 , the cellular system acknowledges the power-down message  112  by the transmission of an acknowledgment message or “ACK” message, which when received by the cellular telephone  108  notifies the telephone  108  that the power-down sequence was received by the network. On the other hand, it a response to a power down, de-registration message  112  is not received by the cellular telephone  108 , it will subsequently power-up in an indeterminate state vis-a-vis the network. The network might not know whether the cellular telephone  108  is “present” on the system or within the cell  110  or otherwise reachable. Among other things, text messages transmitted to the telephone  108  while it was powered down (off) might be sent to the telephone  108  by the network without the network being able to determine whether the messages were actually received. A method and apparatus for avoiding the ambiguity and operating state when a cellular radio powers-down but does not receive an acknowledge signal from the network would be an improvement over the prior art. 
       BRIEF SUMMARY 
       [0005]    In accordance with embodiments of the invention, when a cellular telephone is powered down, it sends a power-down message to a network it was previously registered with. If the network does not send, or if the cellular telephone does not receive, an acknowledgement of the power-down message from the network, a status bit referred to as a flag is set (or reset) in a non-volatile memory device in the cellular telephone. The power-down sequence is concluded by the cellular telephone and, the cellular telephone is shut off or put into a reduced power consumption state. When the telephone is turned back on, i.e., returned to its previous state, the flag is evaluated or “tested” to see if it was set (or reset) during the course of powering down. The status or value of the flag when the phone is powered up is then used by the cellular telephone to determine whether it should make a network access request to a network the telephone was registered to, during the power-up operation in order to cause that cellular network to update its database regarding the whereabouts of the powered-up cellular telephone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  depicts a prior art wireless communication system; 
           [0007]      FIG. 2  is a block diagram of an apparatus for restoring wireless communications to a wireless communications device; 
           [0008]      FIG. 3  is a flowchart of a part of a method of restoring wireless communications to a wireless communications device after the device has been powered down; 
           [0009]      FIG. 4  depicts an alternate method of restoring wireless communication to a wireless communications device; and 
           [0010]      FIG. 5  is a power-up sequence. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 2  is a block diagram of an apparatus  200  for restoring wireless communications to a wireless communications device, such as a cellular telephone, after the wireless communications device is powered-down. The apparatus  200  is comprised of a conventional, prior art wireless communications system transmitter  202  and a conventional prior art wireless communications system receiver  204 . The transmitter  202  and the receiver  204  are both coupled to a conventional prior art antenna  206  through a conventional duplexer (not shown) to which is coupled a conventional transmission line  208 . 
         [0012]    A user interface  210  includes, but is not limited to, a conventional telephone handset, a speaker phone and a display device, through which a person can place and receive telephone calls and/or send and receive text and data messages via radio frequency signals sent to and received from a communication end point, such as a telematics service provider, another cell phone, or a data network. A communication end point is not shown in the figures for brevity. 
         [0013]    The apparatus is also comprised of a processor  212 , which is connected to and thereby controls at least the transmitter  202 , the receiver  204 , and the user interface  210  via a conventional prior art address, data and control bus  214 . As used herein, the term “bus” refers to electrically parallel conductors or circuits that connect components of a computer system to each other and which allow the transfer of electric impulse energy from one connected component to another. The bus  214  thus connects the transmitter  202 , receiver  204  and user interface  210  and the processor  212  inter-operatively to each other. 
         [0014]    As shown in the figure, the bus  214  is also coupled between the processor  212  and a non-volatile memory device  216 . In an alternate embodiment however, wherein the processor is part of a single-chip microcontroller or microprocessor, the processor  212  can be connected to the non-volatile memory device  216  via a separate bus  218  commonly found in single chip microcontrollers and microprocessors and which connects a central processing unit to a memory devices that are co-located with the CPU on the same silicone substrate. 
         [0015]    A telematics system controller  220  embodied as a separate computer or processor, monitors the state of various vehicle sensors to which the telematics system controller  220  is connected by way of several different connections  224 . Such sensors can include accelerometers or tilt sensors, collision or impact sensors, air bag deployment sensors and the like. If the telematics system controller  220  receives a signal from a monitored sensor, it is configured to direct the processor  212  of the apparatus  200 , to cause the transmitter  202  to broadcast an appropriate notification message to a telematics service provider, not shown. Control signals provided to the processor  212  from the telematics system controller  220  are preferably carried over a separate bus  226  connected between the telematics system controller  220  and the processor  212 . 
         [0016]    In at least one alternate embodiment, the processor  212  is configured to perform the functionality of a separate telematics system controller  220 . In such an embodiment, the processor  212  would have additional input/output ports or memory-mapped input/output ports that allow the processor  212  to monitor the state of various inputs and sensors. 
         [0017]    In a preferred embodiment, the processor  212  is configured to receive a signal on an input port  228  the logical condition of which directs or causes the processors  212  to power-up or power-down the communication apparatus  200 . Powering down the apparatus  200  occurs when a vehicle is shut-off in order to save power and reduce battery drain. 
         [0018]    When a power-down signal is received by the processor  212 , the processor  212  is configured to execute program instructions stored within it or the non-volatile memory  216 , which when executed cause the processor  212  to execute an enhanced power-down sequence. When the apparatus  200  is powered up, the enhanced power-down sequence enables the apparatus  200  to be able to quickly determine whether a network that the apparatus  200  had been registered with, acknowledged the apparatus&#39; state change from powered up to powered down. 
         [0019]    Program instructions in one or more non-volatile memory devices, such as device  216 , and which are coupled to the processor  200 , when executed, cause the processor to effectuate the transmission of a conventional power-down or de-registration message, from the transmitter  202  to a wireless communication network with which communication between the apparatus  200  and such network had previously been established. After the power-down message is transmitted, additional program instructions cause the processor to enter a wait state or wait condition for a fixed and predetermined period of time during which the processor  212  continuously polls or scans the receiver  204  for receipt of an acknowledgement signal, also known as an “ACK” signal, sent from a wireless communications network, indicating to the apparatus  200  that the network received the power-down message and that the network will de-register the apparatus  200  from the network thus preventing the network from trying to route calls and messages to the apparatus after it has fully powered down. 
         [0020]    The enhanced power-down sequence is comprised in part of program instructions in the non-volatile memory  216 , which when executed, cause the processor  212  to set (or reset) one or more binary digits (bits) in a register  230  co-located on the substrate with the processor  212  or, set (or reset) one or more bits in one or more memory locations  232  in a non-volatile memory device  216 . The setting or resetting of one or more binary digits is considered herein to be setting a “flag” the state of which is subsequently used in a power-up sequence to determine whether an acknowledgement of a power-down message was received by the apparatus  200 . The flag is considered herein to be a network response message, status flag. 
         [0021]    One or more binary digits are set or reset as the case may be if the receiver  204  does not detect the receipt of an acknowledgment by the wireless communication network to the de-registration message, which is also referred to herein after as a power-down registration message. If the power-down registration message is not received, it is likely because a network that the apparatus was registered to, did not receive or failed to process a power-down or de-registration message. The network will thus continue to treat the apparatus as if it is still powered up and operating. 
         [0022]    Program instructions in the non-volatile memory device  216  control the processor  212  during its power-up sequence, causing the processor  212  to check the status of the network response message status flag to determine whether the previously transmitted power-down registration message was acknowledged by a network. 
         [0023]      FIG. 3  is a flowchart of a part of a method  300  of restoring wireless communications to a wireless communications device after the device has been powered down. The method  300  can be performed by the apparatus in  FIG. 2  and equivalents thereof. 
         [0024]    At an initial step  302 , the communications device or apparatus  200  is functioning normally and continues to do until a power-down message is input to the device, as happens when a user depresses a shut-down or power-off button on a conventional cell phone or a vehicle user turns off the vehicle&#39;s ignition. At step  304  a power-down command is received by the apparatus. After the power-down command is received at step  304  the method  300  proceeds to step  306  whereat a power-down or de-registration message is transmitted by the apparatus  200  to a network to which the apparatus  200  had been previously registered with. Once the power-down registration message is transmitted, the wireless device should receive an acknowledgement, albeit within a finite period of time that is typically established by network service providers but which can also be operationally programmed into the communications apparatus itself. It can also be programmed by the user or operator of the device. 
         [0025]    Step  308  depicts the establishment of a network response message, time-out timer limit. The time-out timer limit can be specified by a service provider, a phone manufacturer or even an input by a user. Nevertheless, once a power-down registration message is transmitted at step  306 , the wireless communications device or apparatus  200  should receive an acknowledgement (ACK) within a finite time thereafter. That time limit is depicted in  FIG. 3  as being set at step  308 . 
         [0026]    Step  310  shows that if the acknowledgement response is received, the method  300  proceeds to step  312  where the wireless communications device completes the execution of its power-down sequence. The apparatus  200  then goes into a sleep, stand-by or complete shut-down mode at step  314 , where it stays until the device is powered up. 
         [0027]    If after sending the power-down registration message at step  306 , an acknowledgement is not received immediately, the method  300  proceeds to step  316  where the time-out timer count value is decremented in a loop comprised of steps  310 ,  316  and  318 . If the time-out timer value is exceeded, which means that no acknowledgement to the power-down registration has been received within the time period previously established, at step  318  the method proceeds to step  320  where the processor sets a network response message flag described above, which when set indicates to the apparatus upon power up that no acknowledgement message was received in response to the previously-executed power-down sequence. After the flag is set, the method  300  proceeds to finish its power down sequence at step  312 . 
         [0028]      FIG. 4  depicts an alternate method  400  of restoring wireless communication to a wireless communications device or apparatus  200  after the apparatus has been sent a power-down command. From its normal operating mode  402 , the apparatus  200  receives a power-down command at step  404 , which causes the device or apparatus  200  to initiate its power-down sequence at  406 . Near the end of the power-down sequence  406 , but as a part of that sequence, a power-down, de-registration message is transmitted from a transmitter  202  at step  408 . The method of  FIG. 3  and method of  FIG. 4  thus differ by whether the power-down registration message is sent before or after the initiation of the power-down sequence. 
         [0029]    As with the method shown in  FIG. 3 , a response time-out timer limit is set at step  410 . Thereafter, the method immediately checks for the reception of an acknowledgement at step  412 . If a response is received, the method shown in  FIG. 4  finishes the power-down sequence at step  414 . If no acknowledgement is received, at  412  the time-out timer is decremented at step  416 , checked for exhaustion at step  418  and if the time has exhausted or expired, and no acknowledgement has been received a no acknowledgement flag is set at step  420  and the power-down sequence concluded as before at step  414 . 
         [0030]    Setting a “flag” to indicate that a power-down ACK signal was not received enables a wireless communications device to quickly determine upon power up whether the a previously-transmitted power-down registration message was received. If the flag is set (or reset) a previously registered-to network might consider the device to have been registered with the network for the entire time that the apparatus  200  was powered down. 
         [0031]    Referring now to  FIG. 5 , a power-up sequence  500  is shown. When a power-up message or command is detected at step  502 , as happens when a user presses the power-on button of his cellular telephone or the vehicle ignition is turned on, the device attempts to register with a local network in step  504  using conventional prior art techniques for registering a wireless communications device with a wireless communications network. At step  506 , and after registration has been accomplished, the method  500  checks to determine whether the acknowledgement flag described above has been “set” indicating whether an acknowledgement to a previously-transmitted power-down registration message was received and acknowledged by the wireless network. If the flag is set, the wireless communications device thus knows that it needs to request a network access in order to notify the network of its existence. At step  508 , the method initiates a method access request, such as requesting a voice channel, by which the registered-to network (step  504 ) becomes aware of the wireless communications device and notifies a home network of its existence. If the flag is not set as determined at step  506 , the wireless communications device enters its normal operating state at step  510  as happens after the network access request is made at step  508 . 
         [0032]    Those of ordinary skill in the art to which the appurtenant claims are directed will recognize that a power-down state and a power-down sequence are device and system dependent. In some embodiments, a power-down state will be an operating state where power consumption is reduced by not zero. In other embodiments, a power-down state exists when no power is being consumed. 
         [0033]    Those of ordinary skill in the art will recognize that the setting of a status bit or bits can be effectuated by setting one or more bits to either a logic  1  or a logic  0 . A flag can also be embodied as more than one bit. Stated another way, the polarity of one or more binary digits in a memory device or a register that indicate either the reception of an ACK signal or the failure to receive an ACK signal, is a design choice. The bit or bits comprising a flag can be either a logic  1  or a logic  0 . 
         [0034]    The foregoing description is for purposes of illustration only. The true scope of the invention is set forth in the following claims.