Power management for subscriber identity module

ES 2 397 529 T3

DESCRIPTION

Power management for a subscriber identity module

Field

The present invention relates generally to wireless communication devices, and more particularly to wireless communication devices that include a subscriber identity module (SIM).

Background

A subscriber identity module (SIM), such as a removable user identity module (R-UIM), a universal subscriber identity module (USIM), or a GSM SIM, contains information regarding a user of a device wireless communications (WCD). A typical WCD can take the form of a cellular radiotelephone, a satellite radiotelephone, a PCMCIA card embedded in a computer, a PDA equipped with wireless communication capabilities, and the like.

Typically, a SIM includes a controller and memory housed in a card-like structure. The memory may contain user information, including, for example, a subscriber / user identifier, a phone book that provides a stored bank of phone numbers, messages, billing codes, encryption sequences for secure wireless data communication, and other useful information that can be retrieved during use. The memory can also store applications that are accessed by the WCD, for example for air provisioning, cryptography, web browsing or mobile commerce.

Typically, a SIM is removable, allowing a user to install the SIM into or remove the SIM from a WCD. The SIM can be removed from a first wCd, for example, and installed in a second WCD. In this way, the SIM allows the user to transfer user information from one WCD to another WCD. This can be especially useful when the user travels to regions supported by different wireless protocols, which may require the use of a different WCD.

A SIM includes a relatively simple electrical interface, including an input / output (I / O) port for serial data exchange with another device such as a WCD, a clock input to receive an external clock signal, and an input reset to receive a reset signal. Ordinarily, a SIM receives power from the device in which it is installed.

Typically, a WCD is powered by a rechargeable power source, such as a lithium ion battery. The power consumption by the SIM can be a significant factor in the total power consumption of the WCD. A SIM consumes battery reserves and can reduce the WCD standby time. Consequently, efficient management of power consumption by the SIM is highly desirable.

Document EP 0599244 A discloses that a CPU of an IC card reader-writer controls the power supply in such a way that power is supplied to the IC card only when access to the IC card is required and is stop when access to the IC card is unnecessary.

Summary

According to the present invention, there are provided a wireless communication device, WCD, according to claim 1, a corresponding method for the wireless communication device, WCD, according to claim 5, and a related computer-readable storage medium according to claim 16.

Embodiments of the invention are defined in dependent claims 2 to 4 and 6 to 15.

Brief description of the drawings

FIG. 1 is a block diagram illustrating a WCD incorporating a SIM.

FIG. 2 is a block diagram illustrating a power management system for a WCD incorporating a SIM.

FIG. 3 is a block diagram illustrating another power management system for a WCD incorporating a SIM.

FIG. 4 is a block diagram illustrating a power management routine for a WCD incorporating a SIM.

FIG. 5 is a flow chart illustrating a power management routine for a WCD incorporating a SIM.

FIG. 6 is a flow chart illustrating a security authorization procedure for a WCD incorporating a SIM.

ES 2 397 529 T3

FIG. 7 is a flow chart illustrating another exemplary power management procedure for a WCD incorporating a SIM.

Detailed description

FIG. 1 is a block diagram illustrating an exemplary wireless communication device (WCD) 10 incorporating a subscriber identity module (SIM) 16. As shown in FIG. 1, the WCD 10 may include, in addition to the SIM 16, a radio frequency transmitter / receiver 12, a modem 14, a SIM interface 18 and a radio frequency antenna 20. FIG. 1 also shows a power source 17 that can provide power to SIM 16 and SIM interface 18. Modem 14 may be configured to control power source 17 to selectively supply power to SIM 16, SIM interface 18, or both. Non-limiting examples of the WCD 10 include a cellular radiotelephone, a satellite radiotelephone, a PCMCIA card embedded in a computer, a PDA equipped with wireless communication capabilities, and the like.

The WCD 10 can output signals via the antenna that adhere to any number of communication protocols, including, for example, a code division multiple access (CDMA), WCDMA, or GSM protocol. Modem 14 includes demodulator / decoder circuitry and encoder / modulator circuitry, both of which are coupled to transmitter / receiver 12 to transmit and receive communication signals. SIM interface 18 includes circuitry that performs communication between modem 14 and SIM 16.

SIM 16 can take the form of a conventional SIM card based on ISO / IEC 7816 which can be installed in and removed from WCD 10. SIM 16 may be, for example, a removable user identity module (R-UIM), a universal subscriber identity module (USIM) or a GSM SlM. The SIM 16 can adhere to any of the following SIM standards: TIA / EIA IS-820, EtSi TS 100 977, and ETSI TS 102 221. In addition, SIM 16 may adhere to other standards emerging in the future for SIM cards and other similar devices to contain user information. The memory contained in the SIM 16 can store a variety of information, including subscriber / user identification, telephone numbers, messages, billing codes, encryption sequences, and the like, as well as applications that the WCD 10 accesses. WCD 10 accesses SIM 16 via SIM interface 18 to retrieve selected information as needed in the course of wireless communication.

As an illustration, when a user first activates the WCD 10, a CPU or other control logic, generally referred to as a processor herein, associated with the SIM 16, he can compare the subscriber / user identification with an access code, for example, a series of numbers, entered into the WCD IO by the user using a keyboard or other input device.

If the access code entered by the user is valid for SIM 16, the secure features of the SIM are activated for use by the WCD 10. If not, the secure features of SIM 16 are locked and cannot be used. Specifically, the secure features of SIM 16 can remain locked until the SIM receives a valid access code from the user via WCD 10. The optional security authorization procedure is for the purpose of verifying that the WCD 10 is in the possession of an authorized user, and is repeated each time the WCD activates the SIM 16. The WCD 10 can retrieve other information from the SIM 16, such as billing codes for use in cost accounting. In addition, the WCD 10 can retrieve encryption sequences generated by or stored in the SIM 16 to support more secure voice or data communication and access to secure applications.

In accordance with the invention, the WCD 10 executes a power management routine to conserve battery resources and extend standby time. In particular, the WCD 10 carries out a voting procedure to determine when to activate and deactivate the SIM 16. The voting procedure is designed to make the use of the SIM 16 more efficient without sacrificing performance and can be implemented in the modem 14 to control the power source 17. For example, before disabling SIM 16, the voting procedure may be designed to evaluate the current requirements of the software modules running on WCD 10 for access to SIM 16. A software module may take the form of a thread, an interrupt service routine, a device driver, an assembly routine, a state transition, or the like that runs within an operating environment on the WCD 10 under the control of a CPU or other control logic.

If a software module running on the WCD 10 has generated an order or a request, or is in any case taking some action that requires the service of SIM 16, the SIM is not deactivated. Also, if a software module running on WCD 10 votes against disabling SIM 16, the SIM is not disabled. In this case, a software module in WCD 10 can anticipate the impending need for service from SIM 16. Thus, to deactivate SIM 16, the power management routine determines that there is no pending order and that no software module has voted against disabling SIM 16. In this way, the WCD 10 can efficiently manage power SIM 16 and increase battery life and standby time while minimizing adverse effects on performance.

The WCD 10 can also be configured to buffer particular information useful in the optional security authorization procedure to increase user convenience. In particular, together

ES 2 397 529 T3 With the power management routine, the WCD 10 can buffer a memory access code associated with the WCD when the SIM on / off cycle is invoked. This added feature promotes user convenience by eliminating the need to re-enter the access code when both the security clearance procedure and the power management routine are active. Instead, the access code, buffered, can be used to complete the security authorization procedure in a seamless manner that is transparent to the user, without the need to substantially alter the security authorization procedure itself. .

When SIM 16 is activated after a deactivation invoked by the power management routine, the WCD 10 retrieves the access code from the WCD memory, if the access code was buffered, and sends it to the SIM for user authentication. The SIM 16 completes the security authorization procedure by authenticating the buffered access code and thereby keeps the WCD in the active operational state for the user. In this way, each time SIM 16 is deactivated for routine power management purposes, WCD 10 and SIM 16 jointly carry out the security clearance procedure without requiring the user to enter the security code. access on the WCD, for example via keyboard. However, when the user deactivates the WCD 10 on purpose, the user is forced to enter the access code when the security authorization procedure is active. In that case, the WCD 10 does not buffer the access code. Thus, the energy management routine can achieve greater energy efficiency without the need to substantially modify the security clearance procedure.

FIG. 2 is a block diagram illustrating an exemplary power management system for a WCD 10 incorporating SIM 16. As shown in FIG. 2, the modem 14 may incorporate a central processing unit 22 (CPU) or other control logic, generally referred to herein as a processor or CPU, and a universal asynchronous receiver / transmitter (UART) circuit 24. CPU 22 functions as a modem controller, and may be a 32-bit controller, such as a 32-bit reduced instruction set (RISC) controller. Consequently, the I / O data bus associated with the UART circuit 24 can be a 32-bit bus.

Modem 14 may also include memory 23 that contains instructions for execution by CPU 22, and provides storage space for other component information stored by CPU. In addition, the modem 14 may include an I / O port for its communication with the SIM 16. For example, modem 14 may include an I / O data port through which a transmitter and receiver in UART circuit 24 transmit data and receive data from SIM 16, respectively, under the control of CPU 22. In the example of FIG. 2, the modem 14 also includes clock out and reset ports (CLK and RST) that transmit clock and reset signals to the SIM 16 to perform synchronous communication between the modem and the SIM.

The modem 14 can selectively enable or disable the SIM_CLK clock signal to control the SIM 16. The reset signal SIM_RST can be used to reset the SIM 16, and can be selectively enabled and disabled by the modem 14. The WCD 10 and, in particular, the UART circuit 24 can substantially comply with what is described in the United States patent application, pending like this, with serial number 09 / 773,768, filed on February 2, 2001 and entitled " CIRCUIT AND METHOD FOR INTERFACING A MODEM IN A WIRELESS COMMUNICATION DEVICE TO A SUBSCRIBER INTERFACE MODULE ”.

CPU 22 can be programmed to write data and instructions to other components, such as UART circuit 24, coupled to a data bus, and can be responsive to various interrupt signals generated by the components. CPU 22 may use, for example, memory mapped access, I / O port access, or other access techniques to interact with such components. Advantageously, the CPU 22 can be used as a SIM interface controller that controls the interaction with the SIM 16 and its operation, and also as a modem controller that controls operations within the modem 14 that may not be related to SIM operation. CPU 22 can be programmed to perform various aspects of a power management routine in accordance with the invention, as well as certain aspects of a modified security clearance procedure.

SIM 16 may include a CPU 26 or other memory and control logic 28, which stores a variety of user information, such as subscriber / user identification, telephone numbers, messages, billing codes, encryption sequences, and the like. SIM 16 includes an I / O port that receives data (SIM_IO) transmitted by UART circuit 24, a clock input (SIM_CLK), and a reset input (SIM_RST). The SIM power source 30 generates power from a battery voltage Vbat associated with a battery connected to the power source 30 and applies it to the SIM 16. The SIM power source 30 of FIG. 2 may correspond to power source 17 of FIG. 1. A SIM interface circuit 32 provides control circuitry. In particular, the SIM interface circuit 32 allows the modem 14 to transmit data to the SIM 16 and receive data therefrom via a common data line, indicated by SIM_IO. As also shown in FIG 2, the SIM power source 30 can also generate power for the SIM interface circuit 32. The modem 14 receives from another power source (not shown) a modem power voltage Vmod.

In the example of FIG. 2, the modem 14 includes a power enable output that outputs a PWR_EN signal. The PWR_EN signal controls the SIM power source 30 to either supply the SIM 16 and the circuit

ES 2 397 529 T3 SIM interface power to the SIM power source 30 or to cut it off. Under the control of CPU 22, for example, modem 14 can disable SIM power source 30 or decouple it from SIM 16 and SIM interface circuit 32, for example through one or more switches that decouple respective lines. of energy supply.

When the SIM power source 30 is deactivated or uncoupled, the SIM 16 and SIM interface circuit 32 are deactivated and stop consuming battery resources. Alternatively, power to SIM 16 can be cut off under the control of CPU 22 by first cutting off the clock signal applied to SIM interface circuit 32 by modem 14. However, in this case the SIM 16 and the SIM interface circuit 32 may continue to consume a small amount of power until the power supply from the SIM power source 30 is cut off.

Before enabling or disabling the PWR_EN signal to cut off the power, the modem 14 performs a voting procedure under the control of the CPU 22 to manage the power. As an illustration, the modem 14 may continue to supply power to the SIM 16 when a service request is pending from the SIM for a software module running on the WCD 10, or when a software module running in the WCD it asks for the maintenance of the power to the SIM. In the first case, there is active, pending service by SIM 16, a request. The modem 14 may determine if a request is pending service by the SIM 16 by inspecting a request queue associated with the SIM 16. The request queue may be provided in a memory carried by the WCD 10, such as memory 23 and be accessible by CPU 22.

In the second case, there is no request pending service by SIM 16, but a software module running on WCD 10 provides for the generation of such a request and "votes" against disabling the SIM. The modem 14 may interrogate one or more processes running on the WCD 10 to obtain the necessary votes before disabling the SIM 16. Alternatively, the modem 14 may call upon voting information in the form of a data structure, such as a bit mask, that stores an indication of the votes recorded by the processes. The bit mask may include, for example, bits that correspond to software modules or processes running on WCD 10. If a software module requests power supply to SIM 16, it can enable the corresponding bit in the bit mask. If any of the bits in the bit mask is enabled, modem 14 maintains power supply to SIM 16.

The modem 14 cuts power to the SIM 16 when there is no pending service request from the SIM from the WCD 10 and no software module running on the WCD requests power supply to the SIM. Thus, the modem 14 checks that there is no pending request and that no software module anticipates such a request before disabling the SIM 16. In this manner, the modem 14 is able to efficiently manage power without significantly impairing performance. Specifically, the modem 14 avoids the latency caused by a wake-up cycle when a request is pending or anticipated, and hence the resulting degradation in performance.

After disabling the SIM 16, the modem 14 can query the processes running on the WCD 10, a request queue, or a data structure, such as a bit mask, to determine whether to resume power supply. Various software modules running on WCD 10 may require access to, or be serviced by, SIM 16, including, for example, processes for the operation of air interfaces such as AMPS (advanced mobile phone system) or CDMa that require the number assignment module (NAM) information stored in the SIM, the security clearance procedure after activation after manual lockout, encryption procedures that require access to key information provided by the SIM and the like.

FIG. 3 is a block diagram illustrating another power management system for a WCD 10 incorporating a SIM 16. The system of FIG. 3 corresponds substantially to that of FIG. 2. However, FIG. 3 illustrates the SIM interface circuit 32 in slightly greater detail, depicting the transmitted data line DATA_TX and the received data line DATA_RX coupled to the UART circuit 24. Furthermore, in the example of FIG. 3, SIM 16 and SIM interface circuit 32 have separate power sources. In particular, SIM 16 receives power from SIM power source 30, while SIM interface circuit 32 receives power from SIM power source 36. According to this example, the modem 14 can generate first and second enable signals, PWR_EN 1 and PWR_ EN 2, from power. The first power enable signal PWR_EN 1 controls a switch 34 associated with the SIM power source 30 to selectively supply and cut off the SIM 16 power.

The second power enable signal PWR_EN 2 controls a switch 38 associated with the SIM interface power source 36 to selectively supply and cut off power to the SIM interface circuit 32. In this way, the modem 14 can independently control the power of the SIM 16 and the SIM interface circuit 32 independently of each other. In some cases, for example, it may be desirable to maintain power to SIM interface circuit 32 after power failure to SIM 16. Also, as a practical matter, separate control may be necessary when SIM 16 and circuit 32 are switched on. SIM interface have different power sources.

FIG. 4 is a functional block diagram illustrating a power management routine for a WCD incorporating a SIM. In particular, FIG. 4 illustrates the operation of the modem 14 in administering a voting procedure and managing the power of a SIM. As shown in FIG. 4, a 40 of 5 routine

ES 2 397 529 T3 power management running in an operating environment provided by modem 14 can determine whether a queue 42 of SIM requests contains a pending request for service by SIM 16. As described below Next, various software modules running within the operating environment provided by modem 14 may modify a set of voting information 44. In some embodiments, the voting information 44 may take the form of a data structure, such as a bit mask, in which particular bits correspond to votes for different software modules or processes. Modem 14 may enable a corresponding vote within voting information 44 in response to a user or air interface event that requires continuous power from SIM 16. Voting can be disabled later, for example when an order or request associated with the event has been served by SIM 16, unless the software module determines that another order or request is pending.

The request may be communicated to SIM 16 via RX / TX section 52 on UART 24. In addition, power management routine 40 inspects the voting bit information 44 to determine if any of the processes being running on WCD 10 has voted to keep power to SIM 16. In the event that a request is pending in the SIM request queue 42 or a bit is enabled in the voting information bit mask 44, the power management procedure 40 maintains the power of SIM 16 and of the SIM interface 32 by continuously enabling the PWR_EN 1 and PWR_EN 2, 46, 48 signals.

FIG. 5 is a flow chart illustrating a power management routine for a WCD 10 incorporating a SIM 16. As shown in FIG. 5, the power management routine awaits either a processing request or an on / off vote indication (54). In other words, the modem 14 uses a queue of requests from SIM 16 to determine if there are any pending requests and administers a voting procedure to determine if any process has requested, directly or indirectly, the maintenance of the power supply to SIM 16. .

In the event that SIM 16 is already deactivated (56), the routine determines if a request is indicated, that is, if a software module has issued an order or other operation that must be processed (58), for example by reference to the SIM request queue. If a request is indicated, ie pending, the power management procedure activates SIM 16 (60). If no request is indicated, the routine determines if there is an activation vote (62) between any of the software modules or WCD processes that interact with the SIM

16. If so, the procedure activates SIM 16 (60). If not, the power management procedure returns to step 54.

If the SIM is not disabled (56), the power management procedure determines if there is a request indication (64). If so, the modem 14 passes the request to SIM 16 for processing in the ordinary course (66). If not, the power management procedure determines if there is an activation vote (68). If there is no activation vote between the WCD software modules that interact with SIM 16, the power management procedure proceeds to deactivate SIM 16 (70). Again, the activation vote may be represented by respective bits in a bit mask stored in memory in the WCD 10. By querying the voting information and the request queue, the power management procedure prevents SIM deactivation when a request is pending or imminent and thus promotes better performance.

FIG. 6 is a flow chart illustrating a modified security authorization procedure for a WCD 10 that incorporates a SIM 16 and provides a power management routine as described herein. Normally, when WCD 10 is disabled, SIM 16 is disabled as well. When the WCD 10 is later activated, the SIM 16 attempts to perform a security authorization procedure in which an access code, such as a cardholder verification code (CHV), is compared in the SIM CPU. with a code entered by a user through a user interface, such as a keyboard associated with the WCD 10.

When SIM 16 is deactivated as a consequence of a power management routine described with reference to FIG. 5, the SIM tries to perform the same security clearance procedure. Since SIM 16 can be activated and deactivated many times during operation as part of the power management routine, entering the access code by the user would be very inconvenient. Therefore, to promote user convenience, the WCD 10 may be configured to store or "buffer" the access code associated with the WCD.

When the access code is required upon activation after a deactivation executed by the power management routine, the WCD 10 retrieves the buffered access code from memory and sends it to SIM 16 for use in the security authorization procedure to authorize the use of the secure features of the SIM. In operation, the WCD 10 saves the access code after it is entered by the user and the successful completion of the security authorization procedure.

As shown in FIG. 6, when there is a SIM activation indication (72), the WCD 10 determines whether the activation is a consequence of the voting procedure associated with the power management routine (74). If yes, WCD 10 determines if WCD buffered (76) the access code after 6

ES 2 397 529 T3 previous deactivation. After finding the buffered access code, the WCD 10 sends the access code to SIM 16 (80) for use in the security authorization procedure. Upon successful authentication of the access code by SIM 16 (82), the WCD 10 re-buffers the access code (84) for future use.

If the activation of the SIM is not a consequence of the voting procedure (74), the WCD 10 requests the user for the access code (78), for example by notifying the user by means of a screen and receiving the code by means of a keyboard. After sending the access code to the SIM (80), if the authentication is not completed successfully, the WCD 10 clears the access code buffer (86). If there is no access code in buffer 76, the security authentication procedure is not completed. In each case, the WCD 10 and SIM 16 are then ready to process requests (88). However, if the authentication is not completed successfully, the secure operations of the SIM 16 will not be successful.

Instructions for causing a processor provided in WCD 10 or SIM 16, such as CPU 22 or CPU 26, to execute power management and security authorization procedures as described herein can be saved to media. computer readable. By way of example and not limitation, computer-readable media may comprise computer storage media and / or communication media. Computer storage media includes volatile and non-volatile, removable and fixed media implemented in any information storage technology or method, such as processor-readable instructions, data structures, program modules, or other data.

Computer storage media may include, without limitation, random access memory (RAM), read-only memory (ROM), EEPROM, flash memory, fixed or removable disk media, including optical or magnetic media, or any other medium. that can be used to store the desired information and that can be accessed by a processor within the WCD 10 of the SIM 16. In particular, the SIM 16 can carry a built-in FLASH memory for storing information and applications.

Typically, the communications media implements processor-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave or other transport medium, and includes any means of information distribution. The term "modulated data signal" means a signal that has one or more of its characteristics configured or changed in such a way that it encrypts the information in the signal. 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. Computer-readable media can also include combinations of any of the media described above.

FIG. 7 is a flow chart illustrating an exemplary procedure for verifying the integrity of SIM 16 after activation. In particular, the procedure illustrated in FIG. 7 is useful for verifying that SIM 16 has not been changed to a different SIM while it was deactivated during a power management procedure (cycle).

When the WCD 10 is activated (90), the power management routine receives a unique identifier from the currently connected SIM 16 (92). The power management routine can request from SIM 16, for example, an integrated circuit card identifier (ICCID), as defined by the ETSI TS 100 977 standard.

The power management routine then determines whether the activation indication was the result of initial power being applied to the WCD or during a power management cycle. The power management routine can determine, for example, whether the activation indication was a result of the voting procedure described above (94). If the activation indication was not the result of a voting procedure, the power management routine saves the unique identifier, for example, in random access memory (RAM) or other computer-readable medium within modem 14 or other. component of the WCD 10 (100). After saving the unique identifier, the power management routine continues with the activation procedure (106).

However, if the power management routine determines that the activation was the result of a voting procedure, the power management routine then compares the received unique identifier with a unique identifier already buffered in RAM within the WCD 10 (98). Based on the comparison, WCD 10 controls access to SIM 16. If the unique identifier received from the SIM upon activation matches the unique identifier stored in RAM, the power management routine then continues the activation procedure described herein (106). However, if the unique identifier received from SIM 16 upon activation does not match the unique identifier stored in RAM, the power management routine determines that SIM 16 has been changed and controls access to SIM 16. The WCD 10 may, for example, invalidate the access control buffer (102) and declare the SIM 16 (104) changed. Alternatively, the power management routine may restart the modified security clearance procedure or it may cut power to the SIM

16.

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In one embodiment, the WCD 10 displays a status of the SIM card upon resumption of power to the SIM 16. For example, the WCD 10 may display a message indicating whether the SIM 16 was changed based on a discrepancy between the identifier. most recent unique ID received from SIM 16 and the unique identifier stored in RAM.

In this way, the power management routine is able to detect whether the currently connected SIM 16 has been switched to a different SIM while it was deactivated. This is advantageous for verifying the integrity of SIM 16 for other hardware or software modules within WCD 10 that need to access or otherwise use SIM 16.

Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.