Patent Publication Number: US-2006019724-A1

Title: Reducing power consumption in a networked battery-operated device using sensors

Description:
RELATED APPLICATIONS  
      This application is a continuation of U.S. patent application Ser. No. 10/124,720, filed Apr. 17, 2002, entitled REDUCING POWER CONSUMPTION IN A NETWORKED BATTERY-OPERATED DEVICE USING SENSORS, now pending. 
    
    
     TECHNICAL FIELD OF THE INVENTION  
      The present invention relates generally to mobile computing devices, and more particularly, to power consumption reduction in a mobile computing device using sensors.  
     BACKGROUND OF THE INVENTION  
      With the advent of extreme miniaturization in electronic components, many new types of devices and activities have become possible and even prevalent. For example, the use of many types of mobile devices that use radio frequency signals for connectivity has become routine. One such device is a cell phone, and another is a personal information device, i.e. a handheld computing device that is usable for tasks such as scheduling appointments as well as tasks such as communicating over a network with another user having a similar or other device.  
      While mobile computing devices such as those mentioned above, as well as others, confer many benefits on their users, there are certain limitations imposed by such devices that are not experienced with non-mobile devices. For example, one dominant problem associated with mobile devices is the problem of operational lifetime between battery charges. As the user uses a device, the device power source, typically a battery, becomes depleted, eventually falling below a level required for operation of the device. At such time, the user must recharge or rejuvenate the power supply before continuing to use the device. This requirement for battery renewal can be problematic for several reasons. First, if the battery becomes depleted unexpectedly, the user may be greatly inconvenienced if he or she was relying on the device for some functionality, such as emergency calling etc. Additionally, even if the user is aware of the depletion and responds by beginning to charge the battery, the device will generally not be mobile and usable until after the charge cycle is complete, decreasing the overall general usefulness of the device.  
      Today&#39;s mobile devices often recognize the limited capacity of battery power sources by incorporating certain power-saving features. Such features include activating a screen or other user interface element only when the device is actively used by a user. For example, a cell phone may always be ready to receive an incoming call, but the device display screen may remain dark or blank until a user receives a call. Some personal information devices also incorporate features to activate the device only when it is being held and used. Furthermore, many mobile devices incorporate a power switch so that the device may be entirely powered down for a desired period. For example, a cell phone user may turn the phone completely off when no calls are expected to be made or received. However, such measures do not take full advantage of environmental cues to reduce power consumption.  
      In addition, while battery technologies have advanced rapidly in past years, the current rate of battery technology development is not keeping pace with the increasing capabilities and power drain of mobile devices. Thus, although techniques such as those mentioned above have been useful in somewhat increasing mobile device battery life, device operational lifetimes continue to be fairly limited, and better mobile device power management techniques are required to further reduce battery consumption and increase device operational lifetimes.  
     SUMMARY OF THE INVENTION  
      To address the deficiencies in existing mobile device power systems and techniques, an improved system and method of mobile device power consumption minimization are disclosed. In an embodiment of the invention, a mobile device supports a plurality of behavior modification techniques that can cooperate to collectively reduce the instantaneous power consumption of the device. Sensors located at, on, or within the device are used to establish a set of context conditions for the device, which context conditions are then used to selectively establish the state of each of the plurality of behavior modification techniques. In a further embodiment, the sensors detect and yield an output relating to the device&#39;s motion, tilt, proximity to a user, contact with a user, and orientation with respect to a user. In a further embodiment, the sensors detect the temperature of an ambient mass such as ambient air, or the temperature of a contacting body such as a hand or table.  
      Additional features and advantages of the invention will be made apparent from the following detailed description of illustrative embodiments that proceeds with reference to the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      While the appended claims set forth the features of the present invention with particularity, the invention and its advantages may be best understood from the following detailed description taken in conjunction with the accompanying drawings, of which:  
       FIG. 1  is a schematic diagram of an exemplary computer network environment including a mobile computing device, within which embodiments of the invention may be implemented;  
       FIG. 2  is a schematic diagram illustrating the architecture of an exemplary mobile computing device according to an embodiment of the invention;  
       FIG. 3A  is a table illustrating a configuration of sensor outputs usable in an embodiment of the invention to determine whether a mobile computing device is moving;  
       FIG. 3B  is a table illustrating a configuration of sensor outputs usable in an embodiment of the invention to determine whether a mobile computing device is in a pocket;  
       FIG. 3C  is a table illustrating a configuration of sensor outputs usable in an embodiment of the invention to determine whether a mobile computing device is being looked at by a user;  
       FIG. 3D  is a table illustrating a configuration of sensor outputs usable in an embodiment of the invention to determine whether a mobile computing device is close to a user;  
       FIG. 4  is a flow chart illustrating a process for applying context information to affect the behavior of a mobile computing device according to an embodiment of the invention; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The invention relates to a method and system for reducing power consumption in a mobile device through the use of sensors. In particular, an array of sensors are provided on a device, and their combined outputs are used to affect the power consumption of the device. In this manner, much longer device operational lifetimes may be achieved without a decrease in device usability.  
      Referring to  FIG. 1 , a basic network topology is shown within which a mobile device may be used according to an embodiment of the invention. Typically, a mobile device  101  is transiently connected to a closest access point  103  of a plurality of access points  103 ,  105 ,  107 . The access points  103 ,  105 ,  107  serve to interface the mobile device  101  to an infrastructure  109  such as a network. The access points may be for example wireless network access points such as according to the IEEE 802.11 standard for mobile computers and other devices, or cell phone cell transceivers where the mobile device  101  is a cell phone. The reason for providing a number of access points is that the range of the wireless medium, typically a radio frequency communication channel, is spatially limited, while the user is spatially unconstrained and may move about, hence moving into or out of range with respect to a particular access point. The underlying infrastructure  109  is typically predominantly not mobile, and may be a telephone infrastructure such as is typically interfaced to a cell transceiver, or other network such as a corporate LAN or the Internet interfaced to a wireless access point.  
      When a mobile device  101  communicates information to an access point  103 , the purpose is generally to communicate with another device  111 , mobile or otherwise, also interfaced to, or part of, the infrastructure  109 . The other device  111  may be another similar device such as a computer, cell phone, or hand held information device used by another user, or may be a different type of device such as a server. The latter case includes but is not limited to the situation where a mobile device registers with a server within the infrastructure  109 .  
      Generally, the mobile device  101  initially establishes a connection with the closest access point  103 , and periodically thereafter informs the access point  103  of its continued presence while the device  101  remains within radio range. As the device  101  is moved out of radio range of one access point  103  and into radio range of another access point  105 , the connection process may be repeated with respect to the new access point  105 , while the connection to the old access point  103  times out or is explicitly ended. When the device  101  is out of radio range of any access point  103 ,  105 ,  107 , the device  101  is no longer able to interface with the infrastructure  109 . In such a case it will still typically be usable for functions that do not require any information beyond what is stored on the device itself. For example, if the device  101  is a mobile computer or personal information device, it will still be usable for any functions that do not require communication to the infrastructure  109 .  
      Referring to  FIG. 2 , an example of a basic configuration for a computing device, such as device  101 , on which the system described herein may be implemented is shown. In its most basic configuration, the computing device  220  typically includes at least one processing unit  242  and memory  244  although such is not required. Depending on the exact configuration and type of the computing device  220 , the memory  244  may be volatile (such as RAM), non-volatile (such as ROM or flash memory) or some combination of the two. This most basic general configuration is illustrated in  FIG. 2  by dashed line  246 . Additionally, the computing device may also have other features/functionality. For example, device  220  may also include additional removable data storage components  221  and/or non-removable data storage components  223  including, but not limited to, magnetic or optical disks or tape. Computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by the computing device  220 . Any such computer storage media may be part of the computing device  220 .  
      The computing device  220  also preferably contains communication connections  248  that allow the device to communicate with other devices. Such communications connections preferably include an interface, such as a network interface card (NIC) to a wireless device such as another device similar to device  220  or a wireless access point to a network or infrastructure. A communication connection is an example of a communication medium. Communication media typically embodies readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. The term computer readable media as used herein includes both storage media and communication media.  
      A computing device  220  may also have input devices  247  such as a keyboard, mouse, pen, voice input device, touch input device, etc. Preferably output devices such as a ringer  249  and/or vibrator  251  are also included when appropriate, such as for a cell phone or paging device. Furthermore, for wireless mobile devices, the computing device  220  is preferably provided with a portable power source  250 , such as a battery pack, fuel cell or other power module. The power source  250  acts as a primary source of power for computations and wireless data transmissions to be performed by the device. The device may support a standby mode of operation wherein the device  220  consumes less power than in an ordinary mode of operation, perhaps at the expense of increased response time with respect to incoming communications, decreased bandwidth, and/or decreased radio range.  
      Device  220  also embodies a sensor array  252  including a plurality of sensors to detect and convey the context of the device  220  for power reduction as described more fully hereinafter. Exemplary sensors include a temperature sensor  253 , a proximity sensor  255 , one or more accelerometers  257 , a tilt sensor  259 , a touch sensor  261 , and an IR ranging sensor  263  such as using an IR LED. Each sensor yields an output indicative of the sensed quantity or quality. Exemplary sensor details will be discussed below, although the invention is not limited to the sensors shown or the features described with respect to each sensor.  
      The temperature sensor  253  is preferably disposed so as to measure the temperature of the device  220  at a location on the surface of the device  220 . Ideally, the temperature sensor  253  is mounted so that it will contact a user&#39;s hand when the device  220  is held in a typical location for use. In this manner, the temperature sensor  253  will indicate a different temperature when the device  220  is held by a user than when the device is not held, such as when it is on a table, etc. The temperature sensor  253  also preferably reacts to the ambient environmental temperature through convection and/or radiative heating effects when heating via a user&#39;s touch is not predominant. Any of the commercially available temperature sensors may be utilized for the temperature sensor  253 .  
      The proximity sensor  255  is preferably a capacitive device that detects the proximity of a user within a fairly close range such as less than 0.5 meters. In an embodiment of the invention, the proximity sensor  255  is a single-plate capacitive device that detects a change in capacitance with respect to the plate caused by the nearness of a body such as a user. In an alternative embodiment, the proximity sensor  255  is a two-plate capacitive device, which is typically capable of detecting a body at a greater distance than a similar single-plate device. Generally, capacitive sensors detect change in capacitance by observing the decay characteristics of a circuit that includes the capacitive element, such as a plate, and any parasitic capacitance such as caused by a nearby individual. In particular, in one mechanism, the capacitive plate is pulsed by an output pin which pin is then used as an input to observe the plate voltage decay rate. Higher capacitance will generally lead to a detectably slower voltage decay rate.  
      The accelerometers  257  preferably comprise a grouping of linear accelerometers for detecting movement of the device  220  in any direction. Typically, this will require the use of three accelerometers, one for each axis of potential movement. Alternatively, the accelerometer group  257  may comprise a triaxial accelerometer, or one or more biaxial accelerometers. The accelerometers  257  may be of any type, including mass/spring, such as the ADXL50 produced by ANALOG DEVICES, or the ADXL105, ADXL202, and ADXL210 also produced by ANALOG DEVICES, or any other type. The accelerometers  257  yield an indication of when and to what degree the device accelerates along any axis. Alternatively, the accelerometers  257  may yield an indication of acceleration only along one or two axes.  
      The tilt sensor  259  comprises any device capable of sensing a tilting of the device  220  either via tilt angle measurement or angular acceleration measurement, or otherwise. The tilt sensor  259  yields an output indicative of the amount of tilt experienced by the device  220 , or yields an output from which can be derived the same information. The tilt sensor preferably detects an absolute amount of tilt from a horizontal position in one or more axes of the device  220 , but may alternatively detect a relative amount of tilt, referenced only to a prior position. Note that an accelerometer may be used as a component of the tilt sensor in one embodiment. This is especially true of accelerometers that can measure static acceleration such as the aforementioned devices produced by ANALOG DEVICES. A mass/spring accelerometer detects displacement of a mass, which can occur due to either dynamic acceleration, such as caused by a sudden displacement, or static acceleration, such as caused by gravity when the mass translation axis is tilted from horizontal.  
      The touch sensor  261  provides similar information to that provided by the proximity sensor but is much more limited in range. Thus, the touch sensor  261  detects and yields an output indicative of a condition wherein a user&#39;s hand or other part of their body is either in contact with the device  220  or is substantially in contact with the device  220 , such as through a glove. The touch sensor is preferably a capacitive device such as those described above with respect to the proximity sensor  255 , adapted to provide the required short range. Alternatively, the touch sensor comprises a pressure sensitive element that senses direct contact without necessarily sensing other degrees of proximity. Such pressure sensitive element may be either a micro switch, or a solid state device such as a strain gauge, or otherwise, without limitation. The touch sensor  261  can also be distributed in two or more noncontiguous regions on the device  220 . For example, the touch sensor  261  may comprise two or more separate elements operating on the same or different principles of operation.  
      Finally, the IR ranging sensor  263  is disposed so as to detect the presence in front of the device  220  of a body such as an operator. Preferably the IR ranging sensor  263  comprises an IR light emitting diode (LED), operable to send from the front of the device  220  a coded beam of IR radiation, the reflection of which can be detected and processed to determine the presence and approximate distance in front of the device  220  of an operator or other body. In particular, the IR ranging sensor  263  preferably transmits a beam of IR radiation having a known data content. Subsequently, an IR detector associated with the IR ranging sensor  263  detects any return reflection of the transmitted beam. The data content of the return reflection, if any, is compared to the known data content of the transmitted beam, and a measure of the errors between the two is generated. The degree of error is then used to give an approximate range estimation of the distance between the device  220  and the reflecting body. For example, at very close ranges, such as 6 cm or less, the error rate between the transmitted and reflected beam may be almost zero, whereas at greater distances such as 60 cm, the error rate may exceed 50%. One alternative technique is to alter the duty cycle of a transmitted pulse train, and detect the threshold duty cycle at which a detectable reflection occurs, from which information an approximate range to the reflecting body may be derived.  
      While the aforementioned techniques can be used to approximate a range, it will be understood that these techniques are not exact and may, for example, be significantly affected by the color and reflectance of the detected body. If higher accuracy is required in a specific implementation of the invention, then a more accurate range detector will preferably be employed. In any case, a different range detection technique or device may be utilized without departing from the scope of the invention.  
      Note that collection of information from the sensors may be performed according to any one or more standard techniques. For example, the sensor outputs maybe periodically polled, the sensors may trigger an event periodically when output information changes, or the sensor outputs may be written to a common area of memory to be gathered at a later time. Those of skill in the art will appreciate that there are a number of other techniques that may be used additionally or alternatively to gather sensor output information, and the foregoing list is therefore exemplary rather than exhaustive.  
      The use of some or all of the aforementioned sensors or sensor groups to affect the power consumption of the device  220  will now be described by reference to  FIGS. 3   a - 3   d . There are a number of context variables that the aforementioned sensor array can detect and report. For example, the sensors can be used to determine whether a device is moving or not, whether the device is in the user&#39;s pocket or not, whether the device is close to the user or not, and whether the device is being looked at or not. The power consumption variables that can be controlled based on these context variables include at least the device&#39;s screen power, ring power, vibrator power, and radio power used during registration updating. If the device  220  supports a low power standby mode of operation, entry into and exit from this mode may also be controlled according to the context variable values.  
      Each of  FIGS. 3   a - 3   d  describes a set of context variable values that leads to one or more conclusions regarding device context and hence regarding device power savings steps to be taken. Note that the context conditions described with respect to the figures are not necessarily mutually exclusive. For example, a person may be walking with the device  220  and may also have the device  220  in his or her pocket.  FIG. 3   a  shows the likely context variable values read when the device  220  is being moved, or transported, by the user walking. In this case, most of the sensor readings will be indeterminate, and hence not useful in determining whether the user is walking with the device  220  or not. These variables are marked with “NA” in the figure.  
      However, the accelerometers  257  will likely show a highly variable output when the user is walking with the device  220 . In addition, depending upon the technology used to implement the tilt sensor  259 , this sensor may also show increased activity with high variability while the user is walking with the device  220 . The reaction of the accelerometers  257  and potentially the tilt sensor  259  is due to the fact that the motion used in walking subjects the device  220  to semi-periodic shock acceleration loads, such as when a foot strikes the floor, as well as semi-periodic translational acceleration loads such as when the user swings his hand with the device  220  in it, or when the user moves forward after a foot fall. In addition, there are a number of other acceleration loads, periodic or otherwise, that the device  220  may be subjected to while the user walks.  
       FIG. 3   b  shows the likely context variable values read when a user has the device  220  in his or her pocket. As can be seen, many of the sensor readings will be indeterminate with respect to whether the user has the device  220  in his or her pocket, and these variables are thus marked with “NA” in the figure. Three of the sensors will, however, likely have a distinct reaction when the user has the device  220  in a pocket. In particular, the proximity sensor  255  will likely give a reading indicating a close proximity, since the user will most likely be quite close on the opposite side of the pocket material. Note that the touch sensor  261 , which reacts only to much closer contact, preferably will not react when the device  220  is in a pocket, and will thus indicate no touch occurring. In addition, the IR ranging sensor  263  will experience great reflectivity due to the closeness of the pocket material, and will hence likely yield a reading indicative of an adjacent body at very close range.  
       FIG. 3   c  shows the likely context variable values read when a user is looking at the screen of the device  220 . In particular, the proximity sensor  255  should yield a reading indicative of high proximity if the user is close enough to observe the screen of the device  220 . Typically, a user will view a screen from a distance of approximately 24 cm, corresponding roughly to the relaxed focus point of the human eye. In addition, for many devices optimized for hand held operation, the user will naturally tilt the device  220  toward themselves, and thus the tilt sensor  259  for the device  220  will yield an output indicative of a substantial tilt such as 45 degrees from horizontal. As well, for devices optimized for hand held operation the user will generally be gripping the device  220  during viewing, and hence the touch sensor  261  will typically yield an output indicating that the device  220  is being touched when the user is looking at the screen of the device  220 . Finally, since the user will typically look at the screen of the device  220  from a position in front of the device  220 , and at a fairly close range, generally less that 1 meter, the IR ranging sensor  263  should yield a reading indicative of a body at close range in front of the device  220 .  
       FIG. 3   d  shows the likely context variable values read when a user is simply close to the device  220 . In particular, the proximity sensor  255  will detect the presence of the user within a certain range of the device as discussed above. Thus, in the situation where the user is close to the device  220  (such as close enough to hear a ringer of reduced, or lower than normal ring volume) the proximity sensor  255  should yield an output so indicating. The touch sensor  261  and IR ranging sensor  263  may also give a reading indicating touch and/or proximity in front of the device  220  respectively, but such need not be the case. For example, the user may have the device  220  resting untouched and face down on a nearby table.  
      Note that the temperature sensor reading is not explicitly used in the determinations of FIGS.  3 A-D, but may be used to help make a determination in certain ambiguous cases. For example, many readings will be the same whether the device  220  is in a backpack on the user&#39;s back or in a user&#39;s pocket. However, the temperature sensor will probably detect a colder temperature when the device  220  is in the backpack because it will be more insulated from the user&#39;s body heat. In contrast, the temperature reading while in the user&#39;s pocket will be higher, and may approach body temperature in some cases. Other ambiguous cases may also be solved by use of the temperature sensor output. For example, a sudden change in temperature may be used to indicate exit from or entry to a building. In the case of entry to a building, the normal settings for a moving device may apply, but in the case of leaving a building, it may be assumed that access points will be fewer and further between, and hence the registration frequency may be decreased over what it may otherwise be for a device in otherwise similar circumstances. Given the described architecture, those of skill in the art will appreciate the myriad of other uses to which the temperature sensor may be put.  
      The determination of whether a device  220  is moving, is in a pocket, is being looked at, and/or is close to a user can be used to modify the power consumption of the device  220 , as will be discussed hereinafter with reference to  FIG. 4 .  FIG. 4  gives a table linking observed device contextual properties to modifications in device power consumption. In particular, columns  401 ,  403 ,  405 , and  407  describe the state of a context variable, while column  409  describes the resultant power consumption modification techniques applicable given a particular set of context variable values.  
      Beginning with row  411 , it can be seen that the device  220  is not moving, is not in the user&#39;s pocket, is not being looked at (at the screen), and is not close to the user. This set of context variable values generally corresponds to the situation where the device  220  has been set down somewhere, perhaps in the same room as the user, but not very close to the user. In this situation, as described in row  411  it is assumed that the device is not being actively used, at least for outgoing communications, and hence the device is placed in a low power standby mode, such as via a mode of its primary wireless channel or via a secondary low power channel. In addition, the ringer is set to high power so that the user has a higher probability of hearing it if and when it is used, and the vibrator is deactivated so that it will not actuate upon an incoming communication, since the user is not close enough to feel any vibration. Further, the screen is darkened since the user is not close enough to use it, and the frequency of registration updates to a wireless access point is set at a decreased rate since the device is not moving, making a change in registration unlikely.  
      With reference to row  413 , it can be seen that the device  220  is not moving, is not in the user&#39;s pocket, is not being looked at (at the screen), and is close to the user. This set of context variable values generally corresponds to the same situation described by row  411 , except that the user is now closer to the device  220 . In this case, the power consumption behavior of the device is changed from that described in row  411  by setting the ringer to a lower volume setting, since the user is now closer to the device  220 , and should be able to hear a lower volume ringer than when the user is further from the device  220 .  
      Row  415  describes a combination of context variables that is unlikely to occur absent a malfunction of one or more sensors. In particular, row  415  describes a situation wherein the user is looking at the screen but is not close to the device  220 . As with row  415 , the context variable values represented in row  419  are unlikely to occur absent a sensor failure. In particular, it is unlikely that the device  220  would be in the user&#39;s pocket while not being close to the user. Similarly, rows  423  (in pocket and being looked at),  425  (same inconsistency as row  423 ),  431  (same inconsistency as row  415 ),  435  (same inconsistency as row  415 ),  439  (same inconsistencies as rows  423  and  419 ), and  441  (same inconsistency as row  423 ) describe unlikely combinations of context variable values, and would most likely represent a sensor failure. Thus, when the context variable value combinations in any of rows  415 ,  419 ,  423 ,  425 ,  431 ,  435 ,  439 , and  441  occur, a visual or audible signal is preferably conveyed to the user to indicate probable sensor failure. Alternatively or additionally, the device  220  may enter a default mode of operation, such as the mode described with respect to row  411 .  
      The situation described by the context variable values presented in row  417  most likely corresponds to a user standing still, holding the device  220 , while looking at the device screen. In such a situation, the device  220  is preferably placed in a normal mode ready to send and receive on the assumption that the user will imminently send or receive information at that point. Preferably, the screen is set to a normal display value rather than being darkened or dimmed, and the ringer and vibrator are deactivated since the user will likely detect any incoming call simply by watching the device screen. Since the user is not moving, the frequency of registration updates to a wireless access point is set at a decreased rate.  
      With reference to row  421 , it can be seen that the device  220  is not moving, is in the user&#39;s pocket, is not being looked, and is close to the user. This set of context variable values generally corresponds to the situation where the device  220  is in the pocket of a user who is standing relatively still. In this case, the power consumption affecting properties of the device are modified so that the device is in a normal mode of operation, as opposed to low power standby, the ringer is deactivated and the vibrator activated, the screen is darkened (i.e. no power to the screen), and the frequency of registration updates is set to a decreased value.  
      With reference to row  427 , it can be seen that the device  220  is moving, is not in the user&#39;s pocket, is not being looked at (at the screen), and is not close to the user. This set of context variable values is generally unlikely to occur, and could correspond to a situation where the device  220  had been placed down on a movable object such as an audio visual support cart. If this situation were to occur, the power consumption behaviors described with respect to row  411  would be appropriate, with the exception that the registration update frequency should be at a normal rate since the device  220  is moving.  
      The context variable value combination described in row  429  will generally occur when the user is holding the device  220  and walking with it, without placing it in a pocket and without observing the screen. In this situation, the device  220  is preferably placed-in a normal power mode due to likely imminent use, the ringer is set to a lower volume, the vibrator is deactivated, the screen is darkened, and the registration update rate is set to a normal rate as opposed to a decreased rate due to the fact that the device  220  is moving.  
      With reference to row  433 , it can be seen that the device  220  is moving, is not in the user&#39;s pocket, is being looked at, and is close to the user. This set of context variable values generally corresponds to the situation where the user is holding the device  220  and walking with it, while observing the screen. In this case, it is preferable that the power consumption characteristics be set as in row  417 , with the exception that the update rate should be set to normal rather than decreased since the device  220  is moving.  
      Finally, the context variable value combination represented in row  437  corresponds to a situation where the user is walking with the device  220  in a pocket. In this situation, the power consumption characteristics should be set as in row  421 , except that the update rate should be set to normal rather than decreased since the device  220  is moving. In particular, the device  220  should be in a normal rather than low power stand by mode, should have the ringer deactivated, the vibrator activated, the screen darkened, and the registration update frequency set to normal rather than decreased.  
      Information such as that corresponding to the table of  FIG. 4  is preferably stored electronically in a table or other data structure within the memory of the device  220 . The exact format or content of the information so stored is not critical, but it preferably describes sets of power consumption variable responses linked to various context variable value sets, so that the power consumption of the device  220  is decreased on average by modifying the behavior of the device according to the table in response to the presence of certain context variable values.  
      Also note that the foregoing description of linking sensed values to types of environmental conditions and ultimately to a listing of power consumption variable settings is given for the convenience of the reader and is not exhaustive. For example, sensed value sets may be linked directly to listings of power consumption variable settings. Additionally, it is not required that the linkage between sensed values and listings of power consumption variable settings be performed via a tabulated mapping. For example, the linkage may be made by way of a formula or set of formulae, whereby entry of the relevant sensed values or derived environmental context conclusions yields an appropriate group of power consumption variable settings. Thus it will be appreciated that the given illustration is exemplary rather than exhaustive.  
      Although the examples herein focus on specific power consumption variables to be modified in response to measured context variable value combinations, other power consumption variables and context variables or values thereof may be used alternatively or additionally without limitation. Furthermore, the specific responses shown as responsive to certain context variable value combinations are exemplary, rather than limitative. As such, any other response of the same or other power consumption variables may be used to reduce the power consumption of a device without departing from the scope of the invention.  
      It will appreciated that a novel power management technique and system have been disclosed for reducing power consumption in mobile devices communicably linked to one or more other machines or devices by controlling a plurality of power affecting behaviors. In view of the many possible embodiments to which the principles of this invention may be applied, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of invention. For example, those of skill in the art will recognize that the elements of the illustrated embodiments shown in software may be implemented in hardware and vice versa or that the illustrated embodiments can be modified in arrangement and detail without departing from the spirit of the invention. Therefore, the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof.