COMMUNICATION DEVICE, METHOD FOR CONTROLLING A COMMUNICATION DEVICE AND PROGRAM

Description

TECHNICAL FIELD

[0001] The present invention relates to a communication apparatus, a method for controlling the communication apparatus, a program, and a storage medium.BACKGROUND ART

[0002] The 3GPP (3rd Generation Partnership Project) Release 12 (Rel-12) specification defines Dual Connectivity (DC) for simultaneous communication with multiple base stations. With dual connectivity, a User Equipment (UE) performs simultaneous transmission using Component Carriers (CC) provided by multiple base stations (PTL 1). Specifically, the UE divides an EPS (Evolved Packet System) bearer or packet sequence and simultaneously transmits the divided packet sequences to CCs provided by multiple base stations. More specifically, the UE transmits the divided packet sequences to a master base station serving as a master node (MN) and a secondary base station serving as a secondary node (SN). After receiving packets, the master base station or the secondary base station reorders the received packet sequence and the packet sequence received from the other base station to reconstruct the packet sequence from the UE. After reconstructing the packet sequence, the master base station or the secondary base station transfers the reconstructed packet sequence to a core node (CN).

[0003] In 5G as well, which is a next-generation communication standard currently being formulated by 3GPP, it is defined that DC can be used in a non-standalone mode in which there is cooperation between 5G and LTE (Long Term Evolution), which are different wireless systems. This allows a UE to carry out LTE communication and 5G communication at the same time, thus improving user throughput. PTL2, published after the date of filing of the present application, relates to disconnecting a public network when a public network disconnection instruction is received. PTL3 relates to performing radio communication via a cell belonging to a master cell group and a cell belonging to a secondary cell group.CITATION LISTPatent Literature

[0004] PTL1: Japanese Patent Laid-Open No. 2016-127383 PTL2: EP 3 836 609 A1 PTL3: CN 108 605 328 A SUMMARY OF INVENTIONTECHNICAL PROBLEM

[0005] As mentioned above, when a UE performs LTE communication and 5G communication at the same time, an improvement in performance can be expected with DC, but an increase in power consumption is expected due to using communication circuits for multiple systems at the same time for data communication. For example, if a digital camera serving as the UE performs LTE communication and 5G communication at the same time in order to upload captured images to a server, the battery may run out earlier than in the case where only LTE communication is used. In other words, if the digital camera is in a state where DC is always activated, the battery may run out prematurely. As a result, the image capturing function, which is the main function of the digital camera, cannot be used, thus reducing user convenience.

[0006] In such a case, in order to reduce power consumption while maintaining communication, it is conceivable for the digital camera to stop DC and continue with only LTE communication. However, since the throughput in LTE communication is about one tenth of the throughput in 5G communication, it is expected that data communication will take a long time to complete if only LTE communication is used. In such a situation, the user of the digital camera cannot end the data communication as they desire, thus reducing user convenience. Note that a similar problem may occur when downloading captured images.

[0007] In view of the above problems, the present disclosure provides a technique according to which the communication mode to be used after dual connectivity (DC) is stopped can be determined by user selection.SOLUTION TO PROBLEM

[0008] As means for achieving the above object, a communication apparatus of the present invention is defined in claim 1, a method is defined in claim 5, a program is defined in claim 6 and a storage medium is defined in claim 7. The other claims relate to further developments.ADVANTAGEOUS EFFECTS OF INVENTION

[0009] According to the present invention, the communication mode to be used after DC is stopped can be determined by user selection, and user convenience can be improved over conventional technology.

[0010] Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings. Note that the same reference numerals denote the same or like components throughout the accompanying drawings.BRIEF DESCRIPTION OF DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain principles of the invention. FIG. 1 is a diagram showing an example of the hardware configuration of a digital camera according to an embodiment. FIG. 2 is a diagram showing an example of the software functional configuration of the digital camera according to an embodiment. FIG. 3 is a diagram showing an example of a network configuration according to an embodiment. FIG. 4 is an operation flow diagram of processing when DC is stopped in a first embodiment. FIG. 5 is a diagram showing an example of a screen for confirming whether or not captured image data transfer is to continue in the first embodiment. FIG. 6 is a diagram showing another example of a screen for confirming whether or not captured image data transfer is to continue in the first embodiment. FIG. 7 is an operation sequence diagram for the digital camera and an LTE base station according to the first embodiment. FIG. 8 is an operation flow diagram of processing when DC is stopped according to a second embodiment. FIG. 9 is a diagram showing another example of a screen for confirming whether or not captured image data transfer is to continue in the second embodiment. FIG. 10 is an operation sequence diagram for the digital camera and the LTE base station according to the second embodiment. DESCRIPTION OF EMBODIMENTS

[0012] Hereinafter, the present invention will be described in detail by way of examples of embodiments with reference to the accompanying drawings. Note that the configurations shown in the following embodiments are merely examples, and the present invention is not limited to the illustrated configurations. The scope of the invention is defined by the appended claims.First EmbodimentNetwork configuration

[0013] An example of the network configuration of the present embodiment is shown in FIG. 3. The network configuration shown in FIG. 3 includes a digital camera 301, an LTE base station 302, and a 5G base station 303. The LTE base station 302 can perform communication according to the LTE communication system, which conforms to the 3GPP standard, and the 5G base station 303 can perform communication according to the 5G communication system, which conforms to the 3GPP standard. The digital camera 301, which is a UE, is located in the cell (communicable range) of both the LTE base station 302 and 5G base station 303, and supports dual connectivity (DC) capability for communicating with both of the base stations at the same time. In the present embodiment, the digital camera 301 uses DC to transmit captured image data to the LTE base station 302 and the 5G base station 303 in order for the captured image data to be uploaded to a network device (not shown) such as a server that is connected to a core network 304. The LTE base station 302 and the 5G base station 303 transmit the captured image data received from the digital camera 301 to the network device (not shown) connected to the core network 304.

[0014] In the present embodiment, the LTE base station 302 functions as a master base station (MN), and the 5G base station 303 functions as a secondary base station (SN). In DC communication, the LTE base station 302, which is the master base station, controls simultaneous communication between the digital camera 301 and the LTE base station 302 and between the digital camera 301 and the 5G base station 303, and also controls communication with the higher core network 304.Digital camera configuration

[0015] FIG. 1 shows an example of the hardware configuration of the digital camera 301 according to the present embodiment. As an example of the hardware configuration, the digital camera includes a control unit 101, a storage unit 102, a wireless communication unit 103, a display unit 104, an antenna control unit 105, an antenna 106, an input unit 107, and an image capturing unit 108. The control unit 101 performs overall control of the digital camera 301 by executing a control program stored in the storage unit 102. The storage unit 102 stores the control program executed by the control unit 101 and various types of information such as captured image data, communication parameters, and authentication information. The communication parameters and authentication information can be used when connecting with the LTE base station 302 and the 5G base station 303. Various types of operations of the digital camera 301, which will be described later, can be performed by the control unit 101 executing the control program stored in the storage unit 102. The wireless communication unit 103 performs cellular network communication by LTE, 5G, or the like, and wireless communication by Wi-Fi or the like. The display unit 104 has a function for outputting visually recognizable information, as with an LCD or LED, and a function for sound output, as with a speaker or the like, and performs various types of display. The antenna control unit 105 controls the antenna 106 in order to perform wireless communication. The input unit 107 has an operation function for operating the digital camera 301, and accepts various types of inputs / operations performed by the user. Note that the input unit 107 and the display unit 104 may be configured as a user interface (UI) by functioning together in combination. The image capturing unit 108 has an image capturing function, performs image capturing processing, and generates captured image data.

[0016] FIG. 2 shows an example of the software functional configuration of the digital camera 301 according to the present embodiment. As an example of the software functional configuration, the digital camera has a transmission unit 201, a reception unit 202, a connection control unit 203, a determination unit 204, a display control unit 205, and a data transfer control unit 206.

[0017] The transmission unit 201 and the reception unit 202 each transmit signals (e.g., various types of messages / information and captured image data) to partner apparatus(es) and receive signals (e.g., various types of messages / information) via the wireless communication unit 103. The connection control unit 203 controls and manages connections with the LTE base station 302 and the 5G base station 303 through the transmission and reception of predetermined signals by the transmission unit 201 and the reception unit 202. During communication with the LTE base station 302, the determination unit 204 executes communication continuation determination processing, which is processing for determining whether or not communication needs to continue, based on a predetermined condition. The display control unit 205 controls the display performed by the display unit 104. Further, in the case where the display unit 104 functions as both the input unit 107 and the UI, the display control unit 205 may control the UI. The data transfer control unit 206 controls and manages data communication (data transfer) of captured image data stored in the storage unit 102. Note that in the following description, data may be treated as a data file.

[0018] The following describes an example of communication continuation determination processing performed by the determination unit 204. As one example, the determination unit 204 can confirm whether or not it has been determined that the digital camera 301 needs to perform cellular network communication. As a specific example, the determination unit 204 can confirm whether or not the control unit 101 is executing an application (service) that requires cellular network communication. One example of such an application is an application for remotely controlling the digital camera 301 via cellular network communication. In this case, the determination unit 204 can determine that it is necessary to continue communication with the LTE base station 302 while the control unit 101 is executing the application (service). In other words, the determination unit 204 can determine that it is not necessary to continue communication with the LTE base station 302 when the control unit 101 is not executing the application (service). As another example, when captured image data transfer is being performed under the control of the data transfer control unit 206, the determination unit 204 may confirm whether or not the remaining time required for captured image data transfer is less than or equal to a predetermined time (predetermined value). In this case, the determination unit 204 can determine that it is necessary to continue communication with the LTE base station 302 if the remaining time is less than or equal to the predetermined time, and, if otherwise, can determine that it is not necessary to continue communication with the LTE base station 302. The remaining time can be calculated by the data transfer control unit 206 based on the remaining amount of captured image data that needs to be transferred and the average throughput so far in communication with the LTE base station 302.Processing flow

[0019] The following describes the operation of the digital camera 301 of the present embodiment with reference to FIG. 4. FIG. 4 is a flowchart of processing when DC is stopped in the present embodiment. In the case where the digital camera 301 is executing DC communication and transferring captured image data, the processing shown in FIG. 4 may be started in response to the fact that the control unit 101 determined that DC communication is to be stopped. The determination to stop DC communication may be made in response to, for example, the fact that the control unit 101 detected that the remaining battery level of the digital camera 301 is less than a predetermined value during DC communication. Also, while the control unit 101 is executing an captured image data transfer application, it may be determined that DC communication is to be stopped at a suitable timing in the program of the application that is being executed. Further, the control unit 101 may determine that DC communication is to be stopped in accordance with a user instruction given via the input unit 107.

[0020] First, in step S401, the connection control unit 203 performs processing for stopping 5G communication with the 5G base station 303 (SN). At this time, the connection control unit 203 can control the state of the digital camera 301. For example, the connection control unit 203 may change the state of the digital camera 301 to the RRC Idle state, which means a standby state as a 5G UE state. Also, the connection control unit 203 may change the state of the digital camera 301 to the RRC Inactive state, which means an intermediate state between standby and connection as a 5G UE state. Further, the connection control unit 203 may change the state of the digital camera 301 to a state having no state as a 5G UE by completely stopping the 5G communication function of the digital camera 301.

[0021] After the connection control unit 203 stops 5G communication with the 5G base station 303, the transmission unit 201 notifies the LTE base station (MN) that 5G communication with the 5G base station 303 has been stopped (S402). Here, the transmission unit 201 may, for example, transmit a link failure information message to the LTE base station 302, or transmit another message indicating that communication with the 5G base station 303 has stopped.

[0022] Subsequently, in step S403, the determination unit 204 executes communication continuation determination processing to determine whether or not communication with the LTE base station 302 (communication with MN) needs to continue. The communication continuation determination processing is as described above. If it is determined that communication with the LTE base station 302 needs to continue (Yes in S404), the connection control unit 203 ends this processing while continuing communication with the LTE base station 302. On the other hand, if it is determined that communication with the LTE base station 302 does not need to continue (No in S404), processing moves to step S405. In step S405, the display control unit 205 displays a screen on the display unit 104 for confirming whether or not to continue the captured image data transfer, and confirms with the user whether or not to continue the captured image data transfer.

[0023] FIGS. 5 and 6 show an example of a screen for confirming whether or not to continue the captured image data transfer. In FIG. 5, a screen including the message "Continue data transfer by LTE communication?" is displayed in order to confirm with the user whether or not to continue the captured image data transfer. Also, in FIG. 6, a screen including the remaining time required for captured image data transfer, which was calculated by the data transfer control unit 206 through the above-mentioned method or the like, is displayed in order to confirm with the user whether or not to continue the captured image data transfer. In the screen examples of both of the figures, if "Yes" is selected by the user via the input unit 107, the connection control unit 203 ends this processing while continuing communication with the LTE base station 302. On the other hand, if "No" is selected, the data transfer control unit 206 ends the transfer of the captured image data, and the connection control unit 203 stops LTE communication with the LTE base station 302 (communication with the MN) (S407) and ends this processing.

[0024] After LTE communication is stopped in step S405, the connection control unit 203 can control the state of the digital camera 301. For example, the connection control unit 203 may change the state of the digital camera 301 to the RRC Idle state, which means a standby state as an LTE UE state. Also, the connection control unit 203 may change the state of the digital camera 301 to a state having no state as an LTE UE by completely stopping the LTE communication function.

[0025] Note that if the data transfer control unit 206 is performing multiple types of captured image data transfer processing, such as when the control unit 101 is executing multiple captured image data transfer applications, confirmation processing may be performed for all of the various types of captured image data transfer processing in step S405. In this case, in the subsequent step S406, if the continuation of communication with the LTE base station 302 is not selected for all of the types of captured image data transfer processing, the connection control unit 203 may stop communication with the LTE base station 302 and end this processing.

[0026] The following describes the flow of signals when DC is stopped in the present embodiment with reference to FIG. 7. FIG. 7 shows a sequence of processing operations performed between the digital camera 301 and the LTE base station 302 when DC is stopped. Note that FIG. 7 assumes that it has not been determined in advance that communication by the digital camera 301 requires cellular network communication.

[0027] When the remaining battery level of the digital camera 301 falls below the predetermined value during DC communication, the DC stop processing illustrated in FIG. 4 is started, and the digital camera 301 stops communication with the 5G base station 303 (F701, S401). After communication with the 5G base station 303 is stopped, the digital camera 301 transmits a link failure information message notifying the LTE base station 302 that communication with the 5G base station 303 has been stopped (F702, S402). Upon receiving the link failure information message, the LTE base station 302 executes processing for stopping DC communication, and transmits an RRC connection reconfiguration message, which is a notification for updating settings for connection with the base station, to the digital camera 301 (F703). In response to the RRC connection reconfiguration message, the digital camera 301 transmits an RRC connection reconfiguration completion message to the LTE base station 302 (F704).

[0028] If it has been determined that communication with the LTE base station 302 does not need to continue (No in S404), the digital camera 301 confirms with the user whether or not captured image data transfer is to continue (F705, S405). If the user chooses to not continue the captured image data transfer (F706, No in S406), the digital camera 301 stops communication with the LTE base station 302 (F707, S407).

[0029] As described above, according to the present embodiment, if DC communication is stopped, whether or not the digital camera 301 is to continue communication with the LTE base station 302 (MN) is determined by user selection. As a result, when low-throughput communication does not meet the user's wishes, it is possible to stop communication with the LTE base station 302 at the user's discretion, and as a result, user convenience is improved.Second Embodiment

[0030] In the first embodiment, a method is described in which the user confirms whether or not to continue communication with the LTE base station 302 after the digital camera 301 has performed communication continuation determination processing regarding communication with the LTE base station 302. Hereinafter, as a second embodiment, a method is described in which the digital camera 301 determines whether or not to continue communication with the LTE base station 302 and the 5G base station 303 after the user has confirmed whether or not to continue communication with the LTE base station 302. In the following, differences from the first embodiment will be described.Processing flow

[0031] The following describes the operation of the digital camera 301 according to the present embodiment with reference to FIG. 8. FIG. 8 is a flowchart of processing when DC is stopped in the present embodiment. The processing shown in FIG. 8 may be started in response to the control unit 101 determining to stop DC communication while the digital camera 301 is executing DC communication and transferring captured image data. The determination to stop DC communication may be made in response to, for example, the fact that the control unit 101 detected that the remaining battery level of the digital camera 301 is less than a predetermined value during DC communication. Also, while the control unit 101 is executing an captured image data transfer application, it may be determined that DC communication is to be stopped at a suitable timing in the program of the application that is being executed. Further, the control unit 101 may determine that DC communication is to be stopped in accordance with a user instruction given via the input unit 107.

[0032] First, in step S801, the display control unit 205 displays a screen on the display unit 104 for confirming whether or not captured image data transfer is to continue, and confirms with the user whether or not captured image data transfer is to continue. FIG. 9 shows an example of a screen for confirming whether or not to continue the captured image data transfer. In FIG. 9, a screen including the message "End data transfer?" is displayed in order to confirm with the user whether or not to continue the captured image data transfer. If "Yes" is selected by the user via the input unit 107 in the screen shown in FIG. 9, the connection control unit 203 ends this processing while continuing communication with the LTE base station 302. On the other hand, if "No" is selected, the data transfer control unit 206 ends the transfer of the captured image data, and the connection control unit 203 stops 5G communication with the 5G base station 303 (SN) (S803).

[0033] After the connection control unit 203 stops 5G communication with the 5G base station 303, the transmission unit 201 notifies the LTE base station (MN) that 5G communication with the 5G base station 303 has been stopped (S804). Subsequently, in step S805, the determination unit 204 executes communication continuation determination processing to determine whether or not communication with the LTE base station 302 needs to continue. The communication continuation determination processing is as described above. Note that since the transfer of captured image data is ended in step S803, the determination unit 204 may determine whether or not it is necessary to continue communication with the LTE base station 302 based on, for example, whether or not the control unit 101 is executing an application (service) that requires cellular network communication. If it is determined that communication with the LTE base station 302 needs to continue (Yes in S806), the connection control unit 203 ends this processing while continuing communication with the LTE base station 302. On the other hand, if it is determined that communication with the LTE base station 302 does not need to continue (No in S806), the connection control unit 203 stops LTE communication with the LTE base station 302 (communication with MN) (S807) and ends this processing.

[0034] The following describes the flow of signals when DC is stopped in the present embodiment with reference to FIG. 10. FIG. 10 shows a sequence of processing operations performed between the digital camera 301 and the LTE base station 302 when DC is stopped. Note that FIG. 10 assumes that it has not been determined in advance that communication by the digital camera 301 requires cellular network communication.

[0035] If the remaining battery level of the digital camera 301 falls below the predetermined value during DC communication, the DC stop processing illustrated in FIG. 9 is started, and the digital camera 301 confirms with the user whether or not to continue captured image data transfer (F1001, S801). If the user chooses to not continue the captured image data transfer (F1002, No in S802), the digital camera 301 ends the captured image data transfer and stops communication with the 5G base station 303 (F1003, S803). After communication with the 5G base station 303 is stopped, the digital camera 301 transmits a link failure information message for notifying the LTE base station 302 that communication with the 5G base station 303 has been stopped (F1004). Upon receiving the link failure information message, the LTE base station 302 executes processing for stopping DC communication, and transmits an RRC connection reconfiguration message, which is a notification for updating settings for connection with the base station, to the digital camera 301 (F1005).

[0036] In response to the RRC connection reconfiguration message, the digital camera 301 transmits an RRC connection reconfiguration completion message to the LTE base station 302 (F1006). If the digital camera 301 determined that communication with the LTE base station 302 does not need to continue (No in S806), the digital camera 301 stops communication with the LTE base station 302 (F1007, S807).

[0037] As described above, according to the present embodiment, the digital camera 301 can determine whether or not communication with the LTE base station 302 (MN) and the 5G base station 303 (SN) can continue after confirming whether data transfer can continue. This makes it possible to continue data transfer without stopping communication with the 5G base station if the user prioritizes communication for data transfer over power consumption.

[0038] In the embodiments described above, cases where the MN is an LTE base station and the SN is a 5G base station have been described, but the present invention is not limited to this. The MN may be a 5G base station and the SN may be an LTE base station. In this case, the present invention can be applied by replacing the 5G base station and the LTE base station of the embodiments with each other.

[0039] Further, in the embodiments described above, the case where the digital camera 301 uploads captured image data has been described, but the above processing can also be applied to the case where the digital camera 301 downloads captured image data. The amount of data to be downloaded may be predetermined, such as being known to the digital camera 301 in advance. In this case, the transfer of captured image data in the above embodiments is replaced with the downloading of captured image data when processing is performed.

[0040] Further, in the embodiments described above, it is confirmed with the user whether or not to continue captured image data transfer at the timing when communication with the 5G base station 303 (SN) is stopped (DC communication is stopped), but the timing of the confirmation is not limited to this. For example, a setting indicating whether or not the user wishes to continue captured image data transfer may be set in advance in the digital camera 301. Further, in the embodiments described above, the confirmation is performed through a screen (as shown in FIG. 5, 6, or 9), but the confirmation may be performed by any method, and may be performed without using such a screen.Other Embodiments

[0041] The present invention can be implemented by processing of supplying a program for implementing one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and causing one or more processors in the computer of the system or apparatus to read out and execute the program. The present invention can also be implemented by a circuit (for example, an ASIC) for implementing one or more functions.

[0042] The present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims

1. A communication apparatus (301) comprising: an image capturing device (108) for generating image data by performing image capturing processing; communication means (103) for performing data communication using a master base station which is an LTE base station of 3GPP standard and a secondary base station which is a 5G base station of the 3GPP standard, wherein the data communication using the master base station which is the LTE base station and the secondary base station which is the 5G base station includes data communication regarding a data transfer function for uploading the generated image data generated by the image capturing device to an external apparatus; first stopping means (203) for stopping communication with the secondary base station when the communication means is performing the data communication using the master base station and the secondary base station; display control means (104) for displaying a message confirming with a user about battery saving and a key on a display device of the communication apparatus in a case where a remaining battery level of the communication apparatus falls below a predetermined value; and receiving means (205) for receiving a user operation for selecting the key before communication with the base station is stopped by the first stopping means, and second stopping means (203) for stopping, in accordance with the reception of the user operation for selecting the key by the receiving means, the data communication regarding to the data transfer function with using the master base station and the secondary base station, wherein the first stopping means (203) stops communication of the secondary base station by releasing connection with the secondary base station, in accordance with the reception of the user operation for selecting the key by the receiving means.

2. The communication apparatus according to claim 1, characterized by further comprising: determining means for determining whether or not communication with the master base station needs to continue, wherein when communication with the secondary base station is stopped by the first stopping means, in a case where the determining means determined that communication with the master base station does not need to continue, third stopping means stops communication of the master base station by disconnecting the connection with the master base station.

3. The communication apparatus according to claim 2, characterized in that in a case where the communication apparatus is not executing a service that requires cellular network communication, the determining means determines that communication with the master base station does not need to continue.

4. The communication apparatus according to claim 2 or 3, characterized by further comprising: notifying means for, in a case where communication with the secondary base station was stopped by the first stopping means, notifying the master base station that communication with the secondary base station was stopped, wherein the determining means determines whether or not communication with the master base station needs to continue after the notifying means gives the notification.

5. A method for controlling a communication apparatus comprising an image capturing device for generating image data by performing image capturing processing, comprising: a communication step (S801) of performing data communication using a master base station which is an LTE base station of 3GPP standard and a secondary base station which is a 5G base station of the 3GPP standard, wherein the data communication using the master base station which is the LTE base station and the secondary base station which is the 5G base station includes data communication regarding a data transfer function for uploading the generated image data generated by the image capturing device to an external apparatus; a first stopping step (S803) of stopping communication with the secondary base station when the data communication is being performed using the master base station and the secondary base station in the communication step; a display control step (S802) of displaying a message confirming with a user about battery saving and a key on a display device of the communication apparatus in a case where a remaining battery level of the communication apparatus falls below a predetermined value; and a receiving step (S802) for receiving a user operation for selecting the key before communication with the base station is stopped by the first stopping step, and a second stopping step (S803) of stopping, in accordance with the reception of the user operation for selecting the key by the receiving step, the data communication regarding to the data transfer function with using the master base station and the secondary base station, wherein the first stopping step (S803) stops communication of the secondary base station by releasing connection with the secondary base station, in accordance with the reception of the user operation for selecting the key by the receiving step.

6. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of claim 5.

7. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of claim 5.