Device and method for mobile communication

Aspects of the disclosure provide a method for use in a mobile communication device having at least a first communication system and a second communication system. The method includes conducting a network search with the first communication system to obtain network search information and providing the network search information to the second communication system in the mobile communication device to reduce a network search time of the second communication system.

BACKGROUND

A mobile communication device can be configured to support multiple subscriber identity module (SIM) cards and operate on multiple mobile communication networks. A user of such a mobile communication device is able to choose from one of the communication networks to place a phone call. In addition, each SIM card can support multiple types of mobile communication networks that use different wireless access technologies, for example, a Global System for Mobile Communications (GSM) network, a Universal Mobile Telecommunications System (UMTS) network and a Long Term Evolution (LTE) network.

SUMMARY

Aspects of the disclosure provide a method for use in a mobile communication device having at least a first communication system and a second communication system. The method includes conducting a network search with the first communication system to obtain network search information and providing the network search information to the second communication system in the mobile communication device to reduce a network search time of the second communication system.

Embodiments of the method further include providing a first portion of the network search information to the second communication system to select a same cell as the first communication system, when a first subscriber identity module (SIM) card corresponding to the first communication system and a second SIM card corresponding to the second communication system belong to a same mobile network operator and have a same network mode configuration. In an embodiment, the first portion of the network search information is a carrier frequency of the same cell that is selected by the first communication system.

Additionally, embodiments of the method further include providing a second portion of the network search information to the second communication system to allow the second communication system to conduct a power scan on carrier frequencies that are not scanned by the first communication system. In an embodiment, the second portion of the network search information is carrier frequencies that are scanned by the first commination system.

The method further includes detecting that the second communication system is in a first network mode and receives a request of the network search in a second network mode that is different from the first network mode, and the first communication system is in the second network mode, and transferring the request to the first communication system to perform the network search in the second network mode. In an embodiment, the network search information is public land mobile network (PLMN) identity information of available networks that are found by the first communication system during the network search.

Embodiments of the method further include providing the network search information to the second communication system to reselect a cell that is reselected by the first communication system, when a first subscriber identity module (SIM) card corresponding to the first communication system and a second SIM card corresponding to the second system belong to a same mobile network operator and the first communication system and the second communication system are in a same network mode. In an embodiment, the network search information is a carrier frequency of the cell that is reselected by the first communication system.

In alternative embodiments, the first communication system and the second communication system are configured to operate in one of a Global System for Mobile Communications (GSM) network mode, a Universal Mobile Telecommunications System (UMTS) network mode and a Long Term Evolution (LTE) network mode.

Aspects of the disclosure provide a mobile communication device. The mobile communication device includes a first communication system having a first interface configured to access a first card identifying a first mobile network operator, a second communication system having a second interface configured to access a second card identifying a second mobile network operator, and a network search information sharing channel enabling information sharing between the first communication system and the second communication system. The network search information sharing channel is configured to provide network search information obtained during a network search conducted by the first communication system to the second communication system to reduce a network search time of the second communication system.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1shows a block diagram of a mobile communication device100according to an embodiment of the disclosure. The mobile communication device100includes a first communication system110coupled with a first subscriber identity module (SIM) card101via a first SIM card interface115and a second communication system120coupled with a second SIM card102via a second SIM card interface125. As shown, the first communication system110and the second communication system120can be coupled together by a network search information sharing channel130.

According to an aspect of the disclosure, the mobile communication device100utilizes the two communication systems110and120to realize dual-card communication functions. Specifically, the first communication system110manages communications between the mobile communication device100and a first mobile communication network based on configurations of the first SIM card101, while the second communication system120manages communications between the mobile communication device100and a second mobile communication network based on configurations of the second SIM card102. A user of the mobile communication device100can choose one of the two communication systems110and120to communicate, for example, by placing a phone call through, or receiving a phone call from either the first mobile communication network or the second mobile communication network.

According to an aspect of the disclosure, the network search information sharing channel130enables the first communication system110and the second communication system120to share network search information. In an embodiment, during a network search process, such as a power-on network search process, a background manual network search process, a cell reselection process and the like, the network search information sharing channel130provides network search information generated in one of the two communication systems110and120to the other one of the two communication systems110and120in order to reduce a search time of a network search in the other one of the two communication systems110and120. In various embodiments, the network search information sharing channel130can be implemented with suitable software.

In theFIG. 1example, the first communication system110and the second communication system120share a group of hardware140. Accordingly, when one of the communication systems110and120is in a process of communicating with a mobile communication network, the other communication system is restricted. For example, when the first communication system110is processing a phone call, the second communication system120cannot receive or place a phone call. It is noted that, in another example, the first communication system110and the second communication system120have independent hardware.

In theFIG. 1example, the first communication system110includes a protocol stack entity116and the hardware140. Similarly, the second communication system120includes a protocol stack entity126and the hardware140. The protocol stack entity116includes a non-access stratum (NAS) module111, a Global System for Mobile Communications (GSM) access stratum (AS) module112, a Universal Mobile Telecommunications System (UMTS) AS module113, a Long Term Evolution (LTE) AS module117, and a physical layer adapter114. Similarly, the protocol stack entity126includes a NAS module121, a GSM AS module122, a UMTS AS module123, a LTE AS module127, and a physical layer adapter124.

At the protocol stack entity116, the NAS module111is coupled with the GSM AS module112, the UMTS AS module113and the LTE AS module117; the physical layer adapter114is coupled with the GSM AS module112, the UMTS AS module113, the LTE AS module117, and a group of hardware140. At the protocol stack entity126, similarly, the NAS module121is coupled with the GSM AS module122and the UMTS AS module123and the LTE AS module127; the physical layer adapter124is coupled with the GSM AS module122, the UMTS AS module123, the LTE AS module127, and the hardware140.

The hardware140includes a UMTS signal processing circuit141, a GSM signal processing circuit142, an LTE signal processing circuit144and a radio frequency (RF) module143. Additionally, the mobile communication device100includes a processor150and a memory module160. In an embodiment, the two protocol stack entities116and126are implemented using software that is stored in a non-volatile memory included in the memory module160. When the mobile communication device100is powered on, the processor150executed the software and performs the functions of the two protocol stack entities116and126.

According to an aspect of the disclosure, the mobile communication device100can operate in multiple network modes. A network mode refers to an operation state of a mobile communication device, such as the mobile communication device100, or a communication system, such as the two communication systems110or120, when the communication device or the communication system operates on a specific type of mobile communication network. For example, the first communication system110can operate on a GSM network, a UMTS network or an LTE network. When the first communication system110operates on a GSM network, the first communication system110is in GSM network mode; when the first communication system110operates on a UMTS network, the first communication system110is in UMTS network mode; when the first communication system110operates on an LTE network, the first communication system110is in LTE network mode. Similarly, the second communication system120can operate on a GSM network, a UMTS network or an LTE network. When the two communication systems110and120are in different network modes, for example, the first communication system110is in GSM mode and the second communication system120is in UMTS mode, the mobile communication device100is in GSM mode and UMTS mode at the same time. Accordingly, the mobile device100supports triple-mode communication.

GSM network is a mobile communication network based on GSM communication standard, UMTS network is a mobile communication network based on UMTS communication standard, and LTE network is a mobile communication network based on LTE communication standard. All the GSM, UMTS and LTE communication standards are developed by the 3rd Generation Partnership Project (3GPP) organization.

It should be understood that a communication system, such as the communication system110or120, can operate in any number of different modes, and that any number of such communication systems can be included in the mobile communication device100.

In an embodiment, each of the two communication systems110and120is configured to operate in one of the GSM mode, UMTS mode or LTE mode at a time. For example, when the first communication system110is in GSM mode, in the protocol stack entity116, the GSM AS module112is active; however, the UMTS AS module113and the LTE AS module117are deactivated. While, for another example, when the first communication system110is in UMTS mode, the UMTS AS module113is active; however, the GSM AS module112and the LTE AS module117are deactivated. In addition, the two communication systems110and120can operate in a same mode or in different modes. For example, the two communication systems can be in GSM mode, UMTS mode or LTE mode at the same time. Or, in another example, the first communication system110is in GSM mode while the second system120is in UMTS mode.

During operation, the protocol stack entities116and126manage communications between the respective communication systems110and120and corresponding mobile communication networks. For example, in the protocol entity116, the NAS module111establishes and maintains communication sessions between the NAS module111and network equipment inside of the mobile communication network on which the first communication system operates; while one of the AS modules112,113or117establishes and maintains radio connections between the AS module and radio network equipment at edge of the mobile communication network. The radio connections are provided to the NAS module111by the AS module as channels used for the communication sessions between the NAS module111and the network equipment inside of the mobile communication network. In other words, signals from the NAS module111go through the radio connections and reach the network equipment inside of the mobile communication network.

The physical layer adapters114and124perform functions of hardware drivers and provide an interface for upper AS modules to transmit and receive signals through the hardware140.

The hardware140is configured to support operations of the two communication systems110and120when the two communication systems are in same or different network modes. At the hardware140, the signal processing circuits141,142and144generally process traffic signals and control signals according to specific communication standards, for example, the GSM, UMTS or LTE communication standards. The traffic signals carrying voice or data information are generated from user applications (not shown inFIG. 1). The control signals are generated from the protocol stack entities116and126. In operation, when the first communication system110and the second communication system120are in different network modes, the two protocol stack entities116and126can each control one of the three signal processing circuits141,142and144to process the control signals. For example, when the first communication system110is in GSM mode and the second communication system120is in UMTS mode, the UMTS signal processing circuit141can be controlled by the protocol entity126to process control signals generated from the protocol entity126, and the GSM signal processing circuit142can be controlled by the protocol entity116to process control signals generated from the protocol entity116. However, when the two communication systems110and120are in the same mode, the two protocol stack entities116and126have to share a same signal processing circuit based on certain resource sharing mechanism. For example, when both the two communication systems110and120are in GSM mode, the two protocol stack entities can share the GSM signal processing circuit142in a time division manner.

The hardware140also includes a radio frequency (RF) module143for receiving and transmitting signals. To receive signals, the RF module143receives an RF signal from the air via an antenna (not shown) and down converts the RF signal to a baseband signal that is sent to one of the two signal processing circuits141and142for further processing. To transmit signals, the RF module up converts a baseband signal coming from the two processing circuits141and142to an RF signal and transmits it into the air.

The SIM cards101and102each contains an integrated circuit and one or more suitable applications, such as a SIM application or a universal subscriber identification module (USIM) application, that enable the SIM cards to support multiple-mode communication. In one embodiment, the SIM cards101and102each carries a USIM application that supports GSM, UMTS and LTE triple-mode communication.

In addition, each of the SIM cards101or102can store user application data, such as a phone book, and data related with mobile communication networks, such as international mobile subscriber identity (IMSI), temporary information related to the local network, multiple public land mobile network (PLMN) lists, wireless access technologies, carrier frequency information, and the like. A PLMN is a mobile communication network that is operated by a mobile network operator. A PLMN can use multiple wireless access technologies and include multiple types of mobile communication networks.

PLMN lists in a SIM card are configured by a mobile network operator or a user. The PLMN lists tell a mobile communication device in what order of PLMNs a network search process is conducted. In an embodiment, each entry of the PLMN lists includes the following information: PLMN identity information including a mobile country code (MCC) and a mobile network code (MNC), associated wireless access technologies, such as GSM wireless access technology, wideband code division multiple access (WCDMA) wireless access technology, LTE wireless access technology, carrier frequency information associated with each wireless access technology, and the like. PLMN identity information can be used to identify a specific PLMN. The carrier frequency information can include lists of carrier frequency bands assigned to a respective PLMN, or a list of carrier frequencies of a PLMN that the mobile communication device100last visited.

The processor150generally executes software, such as protocol stack entity software, user application software, and the like. The memory module160can include different types of devices such as random access memory (RAM), read only memory (ROM) and flash memory. In an embodiment, software code of the protocol entities116and126is stored in a non-volatile memory such as a flash memory or a ROM when a mobile communication device is powered off. The software code can be loaded into a RAM instantly when the mobile communication device is powered on.

The two SIM card interfaces115and125provide two slots holding the SIM cards101and102, respectively.

In various network search processes, the network search information sharing channel130enables network search information to be shared between the two communication systems110and120, and reduces network search time. The network search processes are now explained in detail with reference toFIGS. 2, 3 and 4.

FIG. 2shows a flow chart of a power-on network search process200in the mobile communication device100according to an embodiment of the disclosure.

In the embodiment, during the power-on network search process200, the network search information sharing channel130provides network search information generated by one of the two communication systems110and120to the other one of the two communication systems110and120to reduce a network search time at the other one of the two communication systems110and120. For example, after the mobile communication device100is powered on, the first communication system110performs a first part of the power-on network search process (steps from S211to S215and S218inFIG. 2), and stores the related network search information including carrier frequencies the first communication system110has scanned and a carrier frequency of a cell the first communication system110has selected. Thereafter, based on PLMN information stored in the two SIM cards101and102, the network search information sharing channel130determines whether the two SIM cards101and102belong to a same mobile network operator and have a same network mode configuration.

In an embodiment, the network search information sharing channel130compares the PLMN entries of the two SIM cards101and102to determine whether the two SIM cards101and102belong to a same mobile network operator. Specifically, each of the SIM cards101and102includes a Home-PLMN (HPLMN) entry in the PLMN lists, and the HPLMN entry includes PLMN identity information that indicates a mobile network operator from which a user of a SIM card subscribes services. By checking the PLMN identity information of the HPLMNs, the network search information sharing channel130can know the respective mobile network operators for the SIM cards101and102.

In an embodiment, the network search information sharing channel130checks the wireless access technologies associated with the PLMN entries in the two SIM cards101and102, respectively, to determine whether the two SIM cards101and102have the same network mode configuration. A network mode configuration refers to the order of the wireless access technologies associated with each PLMN entry in a SIM card. The network mode configuration can be configured by an operator or a user. Based on the network mode configuration, one of the communication systems110and120, can choose a wireless access technology to start the network search process after the mobile communication device100is powered on and a PLMN is selected. For example, a HPLMN entry in the SIM card101has three associated wireless access technologies: the first one is GSM wireless access technology, the second one is WCDMA wireless access technology and the third one is LTE wireless access technology. Therefore, the HPLMN includes a GSM network corresponding to the GSM wireless access technology, a UMTS network corresponding to the WCDMA wireless access technology, and an LTE network corresponding to the LTE wireless access technology. When the mobile communication device100is powered on, the communication system110first select the HPLMN, then, based on the network mode configuration, chooses the GSM wireless access technology, to perform the power-on network search process searching for the GSM network of the HPLMN; if the GSM network is not found, the communication system110, based on the network mode configuration, chooses the WCDMA wireless access technology, to continue the power-on network search process searching for the UMTS network of the HPLMN; if the UMTS network is not found, the communication system110, based on the network mode configuration, chooses the LTE wireless access technology, to continue the power-on network search process searching for the LTE network of the HPLMN.

If the two SIM cards belong to a same mobile network operator and have a same network mode configuration, the network search information sharing channel130causes the second system to directly select the same cell selected by the first communication system110(step S240inFIG. 2). Consequently, a second part of the power-on network search process200(steps from S231to S235and S238inFIG. 2) can be skipped and the network search time is reduced. Otherwise, the network search information sharing channel130causes the second communication system120to perform the second part of the power-on network search process200(steps from S231to S235and S238inFIG. 2). However, a power scan process of the second part of the process200is only carried out on a reduced scope of carrier frequencies, such that the network search time of the second part of the process200is still reduced.

The detail of the power-on network search process200with support of the network search information sharing channel130is described below.

As shown inFIG. 2, the power-on network search process200starts at S201and proceeds to S211. From S211to S215and S218, after the mobile communication device100is powered on, one of the two communication systems110or120, for example, the first communication system110first conducts the first part of the network search process200.

At S211, the NAS module111selects a PLMN with highest priority from PLMN lists and a wireless access technology associated with the selected PLMN. Specifically, the NAS module111first retrieves information, such as PLMN lists, wireless access technologies and carrier frequency bands, from the first SIM card101. Next, the NAS module111selects the PLMN of highest priority from the PLMN lists. Thereafter, the NAS module111chooses a first one from a list of wireless access technologies associated with the selected PLMN, for example, GSM technology. Next, the NAS module111indicates the selected PLMN, associated wireless access technology chosen, and associated carrier frequency bands to an AS module that is activated. For example, if GSM wireless access technology is chosen, the GSM AS module112is activated, if WCDMA wireless access technology is chosen, the UMTS AS module113is activated, while if LTE wireless access technology is chosen, the LTE AS module117is activated.

At S212, the first communication system110performs a carrier frequency power scan process. In one embodiment, the active AS module, either112,113or117, instructs the hardware140to scan through all carrier frequencies included in the carrier frequency bands and measure power level of received signals corresponding to each carrier frequency. As a result, a list of carrier frequencies in a descending order of signal power level and having a signal strength above a specific threshold is obtained.

At the end of the power scan process, the NAS module111stores information of the carrier frequencies that have been scanned and the list of carrier frequencies having a signal strength above a specific threshold in a memory, such as the memory module160, for possible use of the second communication system120.

At S213, the first communication system110performs a cell search process based on the list of carrier frequencies having a signal strength above a specific threshold obtained at S212. In an example, the GSM AS module112is activated. Starting from the first frequency of the list of carrier frequencies having a signal strength above a specific threshold obtained at S212, the GSM AS module112decodes system information of cells corresponding to the carrier frequencies included in the list to obtain PLMN identity information of the cells. As described above, a cell's PLMN identity information includes the mobile country code (MCC) and the mobile network code (MNC). If a cell's PLMN has the same MCC and MNC as the PLMN selected at S211, this cell belongs to the PLMN selected at S211. The cell search process continues until a first cell belonging to the PLMN selected at S211is found.

At S214, if a first such cell is found at S213, the process proceeds to S215. Otherwise, the process proceeds to S216.

At S215, the first communication system110selects the cell that is found at S213and adjusts its own parameters according to parameters received from the cell, entering a state of camping on the cell. In the example raised at S213, the GSM AS module112informs the NAS module111and the NAS module111accordingly performs a registration process to register to the PLMN selected at S211. In addition, the NAS111stores carrier frequency of the selected cell, PLMN entity information of the PLMN selected at S211and wireless access technology associated with the PLMN selected at S211, for example, in the memory module160for possible use by the second card communication system120.

At S216, the NAS module111checks if there is another available wireless access technology associated with the PLMN selected at S211. If so, the process proceeds to S211where the other wireless access technology with highest priority is selected, and the process repeats from S211to S214. Otherwise, the process proceeds to S217.

At S217, the NAS module111checks if there is another available PLMN included in the PLMN lists retrieved from the SIM card101. If so, the process proceeds to S211where the other PLMN with the highest priority but having not been selected before is selected and the process repeats from S211to S214. Otherwise, the process proceeds to S218.

At S218, the first communication system110enters a state of out of service (OSS). In an example, when in OSS state, the first communication system110selects and camps on a cell of a PLMN that is available in surrounding environment but is irrelevant with PLMNs included in the PLMN lists stored in the SIM card101. In addition, the first card system110cannot use any service from the camped network except making an emergency call. In addition, the NAS111stores carrier frequency of the selected cell, PLMN entity information of selected PLMN and wireless access technology associated with the selected PLMN, for example, in the memory module160for possible use by the second communication system120.

After the first communication system110completes the first part of the process200, the process200proceeds to S220.

At S220, the network search information sharing channel130determines whether the second SIM card102and the first SIM card101belong to a same operator and have a same network mode configuration as described above. If the second SIM card102and the first SIM card101belong to the same operator and have the same network mode configuration, the process200proceeds to S240; otherwise, the process200proceeds to S231.

At S240, the network search information sharing channel130causes the second communication system120to select the cell that is selected by the first communication system110. In an example, the network search information sharing channel130obtains carrier frequency of the selected cell, PLMN entity information of selected PLMN and wireless access technology associated with the selected PLMN, which are generated by the first communication system110, from the memory module160and transmits it to the second communication system120. Accordingly, an AS module in the second communication system120corresponding to the selected wireless access technology is activated. For example, when the GSM technology is finally selected by the first communication system110during the first part of the network search process, the GSM AS module122is activated. Based on the carrier frequency of the selected cell received from the network search information sharing channel130, the GSM AS module122decodes system information of the selected cell. Accordingly, the second communication system120adjusts its own parameters according to parameters received from the cell and enters a state of camping on the cell. The process200proceeds to S299and terminates at S299.

Start from S231, the network search information sharing channel130causes the second communication system120to perform the second part of the power-on network search process from S231to S235and S238. The second part of the process performed by the second communication system120is similar to the first part of the process performed by the first communication system110, but based on information stored in the second SIM card102. Operations in steps from S231to S238except S232and S233are similar to that in steps from S211to S218except S212and S213, therefore description of these similar operations are omitted. However, operations at S232and S233are different from that at S212and S213, and will be described below.

At S232, the power scan process of the network search process is only carried out in a reduced scope of carrier frequencies, such that network search time of the second part of the process is reduced. In an example, the network search information sharing channel130obtains information of the carrier frequencies that has been scanned from the memory module160(the information is stored in the memory module160at S212), and transmits information of the scanned carrier frequencies to the second communication system120. Based on the information of the scanned carrier frequencies, the second communication system120performs the power scan process in a reduced scope. For example, at S231, a PLMN is selected and carrier frequency bands associated with this selected PLMN is obtained based on information stored in the second SIM card102. When conducting the power scan process at S212, the second communication system120scans carrier frequencies included in the carrier frequency bands obtained from the second SIM card102but excludes the carrier frequencies already scanned by the first card communication system110. As a result of the power scan process, a new list of carrier frequencies having a signal strength above a specific thresh hold is obtained.

At S233, in the example, the network search information sharing channel130obtains the stored list of carrier frequencies having a signal strength above a specific threshold from the memory module160(the information is stored in the memory module160at S212), and transmits the stored list to the second communication system120. Accordingly, the second communication system120performs cell search process using a list including the following two groups of carrier frequencies: (1) the new list of carrier frequencies acquired at S232; and (2) carrier frequencies included in the stored list and, at the same time, included in the carrier frequency bands obtained from the second SIM card102.

After operations at S235and S238, the power-on network search process200proceeds to S299and terminates at S299.

It is to be understood that applicability of power-on network search process200is not limited to scenarios when a mobile communication device is powered on. For example, when a mobile communication device, such as the mobile communication device100, loses coverage of a mobile communication network, the power-on network search process200can be carried out by the mobile communication device100to search for a cell to be camped on.

FIG. 3shows a flow chart of a background manual network search process300in the mobile communication device100according to an embodiment of the disclosure.

During the background manual network search process300, a user of the mobile communication device100manually issues a command through a user application to request the mobile communication device100to search for all available mobile communication networks corresponding to a specific wireless access technology in surrounding environment of the mobile communication device100. In an example, the user of the mobile communication device100requests the first communication system110of the mobile communication device100to perform a network search in GSM mode to search for all available GSM networks. To perform the network search in GSM mode, first, the NAS modules111and121can collect PLMN entries associated with GSM wireless access technology from, depending on user's command, one or two of the two SIM cards101and102, and group these PLMNs into a to-be-found PLMN list. Next, based on this to-be-found list, the GMS AS module112of the first communication system can perform a network search in GSM mode to search for the PLMNs in the to-be-found list. Specifically, starting with the first PLMN in the to-be-found list, the GMS AS module112first requests the hardware140to perform the power scan process using information of carrier frequency bands associated with the first PLMN. Accordingly, a list of carrier frequencies having certain signal strength is obtained. Next, the GMS AS module112performs the cell search process. If a cell having a PLMN identity identical to the first PLMN is found, the first PLMN is found. In the similar way, the GSM AS module112continues the process until all PLMNs in the to-be-found list have been traversed. At the end, all PLMNs that have been found are reported to the user application.

In an embodiment, a user of the mobile communication device100requests the mobile communication device100to perform a “background” manual network search process. During the background manual network search process, network search operations do not affect the mobile communication device100receiving a paging message and are carried out within intervals between paging message monitoring actions. Specifically, in the mobile communication device100, after a power-on network search process, each of the two communication systems110and120, camps on a cell and enters a discontinuous reception (DRX) state. When in DRX state, there is no radio connection between the mobile communication device100and mobile communication networks. In addition, the hardware140periodically wakes up from a power down status to monitor the paging message broadcasted in the cells associated with the active AS modules. When a call is coming in, identity (ID) information of a SIM card, such as an international mobile subscriber identity (IMSI) number, is included in the paging message; the corresponding AS module sees this ID information and knows it is being called, and takes action to receive the call. During the intervals between the paging message monitoring actions, the manual network search operations are performed, thus paging message monitoring is not disturbed.

In an embodiment, the two communication systems110and120adopt a time division manner to share the hardware140to perform their respective paging message monitoring operation and network search operation. For example, the two communication systems110and120are in a same network mode, for example, GSM mode. During a first period, the first communication system110controls the GSM signal processing circuit142and the RF module143in the hardware140. It performs paging message monitoring, and then performs network search operation. During a second period, the second communication system120controls the GSM signal processing circuit142and the RF module143in the hardware140to conduct its respective operations in a way similar to the first communication system110. During a third period, the first communication system110controls the hardware140again. For another example, the two communication systems110and120are in different network modes, for example, the first communication system110is in GSM mode and the second communication system120is in UMTS mode. In this case, the first communication system110can use the GSM signal processing circuit142exclusively, while the second communication system120can use the UMTS signal processing circuit141exclusively. During different periods, the two communication systems only switch the control of the RF module143, and no switch of signal processing circuit happens.

It is possible that a background manual network search process of each system may continue for multiple periods before its termination. It is also possible that, in other embodiments, during process described above, there can be only one system, either the first communication system110or the second communication system120, that performs background network search operations.

According to an aspect of the disclosure, during a background manual network search process in the mobile communication device100, the network search information sharing channel130detects that the second communication system120is in a first network mode and the first communication system110are in a second network mode, and the second communication system120requests a result of a background manual network search in a second network mode. Subsequently, the network search information sharing channel130causes the first communication system110to perform the background manual network search in the second network mode, and provide the result of the network search process to the second communication system120. For example, in the mobile communication device100, the second communication system120is in GSM mode and the first communication system110is in UMTS mode, and a user issues a command asking the second communication system120to perform a background manual network search for available UMTS networks for the second communication system120. Accordingly, a background manual network search in UMTS mode needs to be performed. To do so, the network search information sharing channel130triggers the first communication system110to conduct a background manual network search process in UMTS mode and provide result of the search process to the second communication system120.

In the above example, time of the network search process in UMTS mode is reduced. Specifically, in the above example, if the second communication system120in GSM mode performs the search in UMTS mode by itself, it needs to switch between GSM mode and UMTS mode to conduct GSM mode paging message monitoring and UMTS mode network search alternately; in addition, the second system needs to share the UMTS signal processing circuit141in the hardware140with the first communication system110which is in UMTS mode, thus additional switch of hardware resource control takes place. The switch operations consume additional time. Therefore, the background manual network search process described above is preferred.

The background manual network process300will now be described in more detail. As shown, the process300starts at5301and proceeds to S310.

At S310, a user of the mobile communication device100issues a command to the second communication system120requesting a background manual network search for, for example, available GSM networks corresponding to the second SIM card102. Therefore, the network search mode for the search is GSM mode. The NAS module121transmits this request to the network search information sharing channel130.

At S320, the network search information sharing channel130determines whether the network search mode is the same as the second communication system120's network mode. If the second communication system120is in GSM mode, the process300proceeds to S343. Otherwise, if the second communication system120is in UMTS mode, the process300proceeds to S330.

At S343, the network search information sharing channel130requests the second communication system120to do the network search. The second system is in GSM mode and performs the search in GSM mode. The process300proceeds to S344.

At S330, the network search information sharing channel130determines whether the network search mode is the same as the first communication system110's network mode. If it is not, for example, the first communication system110is in a UMTS mode the same as the second system, the process300proceeds to S341. Otherwise, if the network search mode is the same as the first communication system110's network mode (GSM mode), the process300proceeds to S342.

At S341, the network search information sharing channel130requests the second communication system120to do the network search in GSM mode although the second system130is in UMTS mode. The second communication system120switches between UMTS mode and GSM mode to monitor paging message from a UMTS network and to perform the network search in GSM mode, alternately. The switch may take place for multiple rounds until the background search is completed. The process300proceeds to S344.

At342, the network search information sharing channel130requests the first communication system110to do the network search in GSM mode. As discussed above, the first communication system110, currently in GSM mode, performing the network search in GSM mode reduces the time of background manual network search compared with the second system, currently in UMTS mode, performing the network search in GSM mode. The process300proceeds to S344.

From S344to S347, a system, either the first or the second communication system, performs a background network search for all available GSM networks.

At S344, a system, for example, the first communication system110, starts the background network search. The NAS module111selects a PLMN from a to-be-found PLMN list. The to-be-found PLMN list is generated at the NAS module121in the second system120, and the NAS module111receives the to-be-found PLMN list via the network search information sharing channel130from the NAS module121. The to-be-found PLMN list includes all PLMNs associated with GSM wireless access technology in the second SIM cards. In case the second communication system120starts the background search at S344, the NAS module121selects a PLMN from the to-be-found PLMN list.

At S345, the GSM AS module112supported by the hardware140performs a power scan process using carrier frequency band information associated with the PLMN selected at S344. A list of carrier frequencies having a signal strength above a threshold is obtained.

At S346, the GMS AS module112supported by the hardware140performs a cell search process. Starting from a first carrier frequency until the last carrier frequency in the list of carrier frequencies having a signal strength above a threshold obtained at S345, the GMS AS module decodes system information of each cell of respective carrier frequency to look for PLMN identity information that is identical to that of the PLMN selected at S344. If such a cell is found, the PLMN selected at S344is available. Otherwise, the PLMN selected at S344is not available.

At S347, the NAS module111determines whether another PLMN in the PLMN list received at S354is available. If there is another one available, the first communication system110repeats the steps from S344to S347to search for another possible available PLMN. If all PLMNs included in the to-be-found PLMN list received at S344have been searched for, the process300proceeds to S350.

At S350, a list of PLMN identity information of available PLMNs found at S346is reported to the user application. In the case that the first system110performs the network search, the list of available PLMNs is provided to the second system120by the information sharing channel, and the NAS module121reports the list to the user application. In the case that the second system120performs the network search, the NAS module121directly reports the list to the user application. Thereafter, the process300proceeds to S399and terminates at S399.

FIG. 4shows a flow chart of a cell reselection process400in the mobile communication device100according to an embodiment of the disclosure.

In an embodiment, after a power-on network search process as described above, the mobile communication device100enters a discontinuous reception (DRX) state. When in DRX state, in addition to monitoring paging messages, an active AS module in each communication system110and120in the mobile communication device100continuously inspects signal strength measurement reports of neighboring cells provided by the hardware140. When a cell reselection criterion is satisfied for one communication system110or120, the corresponding active AS module starts a cell resection process (from S411to S415inFIG. 4) that is part of the cell reselection process400.

According to an aspect of the disclosure, in the cell reselection process400, when, for example, the first communication system110initiates and completes the cell reselection process, the network search information sharing channel130instructs the second communication system120to reselect the same cell as the first communication system110has selected when certain conditions are satisfied. Accordingly, the second communication system120needs not to perform a cell search process in its cell reselection process, thus a search time of the second communication system120's cell reselection process is avoided. Specifically, the network search information sharing channel130determines whether the SIM cards101and102belong to a same mobile network operator and the two communication systems110and120are in the same network mode. If the determination is positive, the second communication system120reselects the same cell as the first communication system110has selected. In an embodiment, to determine whether the SIM cards101and102belong to the same mobile network operator, the network search information sharing channel130checks PLMN identity information of each HPLMN in each SIM card101or102. If the PLMN identity information of the two HLPMNs is the same, the SIM cards101and102belong to the same mobile network operator.

The cell reselection process400in the mobile communication device100will now be described in more detail. As shown, the process400starts at S401and proceeds to S411. From S411to S415, the first communication system110performs a cell reselection process.

At S411, the hardware140continuously performs signal strength measurements on the mobile communication device100's neighboring cells for the two communication systems110and120. An active AS module in each of the two communication systems110and120monitors measurement reports provided by the hardware140. When, for example, the AS module112in the first communication system110detects that cell reselection criteria are satisfied, for example, the received signal strength of current cell is below a threshold, the GSM AS module112initiates the cell reselection process.

At S412, the GSM AS module112chooses a candidate cell from the neighboring cells being monitored, and obtains system information from the candidate cell.

At S413, the GSM AS module112determines whether the candidate cell can be camped on based on the obtained system information. If the determination is positive, the process400proceeds to S415. Otherwise, if the candidate cell cannot be camped on, for example, there is no enough capacity to accept a new mobile communication device to the cell, the process400proceeds to S414.

At S414, the GSM module112determines whether there is another candidate cell available among the neighboring cells. If the other candidate cell is available, the cell reselection process proceeds to S412. Otherwise, the process400proceeds to S499and terminates at S499.

At S415, the first communication system110reselects the candidate cell and adjusts its parameters according to the obtained system information and camps on the candidate cell. If a location area information in the obtained system information is not the same as stored information in the communication system110, the NAS module111can perform a location registration process. Thereafter, the communication system110enters a discontinuous reception (DRX) state. In addition, a carrier frequency of the candidate cell is stored in the memory module160for possible use of the second communication system120.

At S420, the network search information sharing channel130detects that the first communication system110completes the cell reselection process and determines whether the two SIM cards101and102belong to a same mobile network operator and the two communication systems110and120are in the same network mode. As described above, the network search information sharing channel130can check HPLMN entity information in each SIM card101or102. If the HPLMN entity information is the same, the two SIM cards101and102can be determined to belong to the same mobile network operator. When the determination is negative, the process proceeds to S499and terminates at S499. Otherwise, the process400proceeds to S430.

At S430, the network search information sharing channel130provides the carrier frequency of the candidate cell the first system has reselected to the second communication system120and instructs the second communication system120to camp on the cell reselected by the first communication system110. Thereafter, the process400proceeds to S499and terminates at S499.

FIG. 5shows a flowchart of a process500for sharing network search information between two communication systems in a mobile communication device according to an embodiment of the disclosure. The process500is used in the processes200,300, and400in the mobile communication device100.

As shown, the process500starts at S501and proceeds to S510. At S510, a first communication system in the mobile communication device100conducts a network search to obtain network search information.

In the example of the process200, the communication system110first performs a cell search process. During the cell search process, network search information, such as a carrier frequency of a cell selected by the first communication system110and a list of carrier frequencies scanned by the first communication system110, is obtained. In the example of the process300, the communication system110first performs a background manual network search for certain type of available networks when the network search information sharing channel130detects that the communication systems110and120are in different mode and the communication system120requests a background network search in a mode the same as the mode of the communication system110. At the end of the background manual network search, network search information, such as a list of PLMN identity information of available networks, is obtained. In the example of the process400, the communication system110first performs a cell reselection process, and network search information, such as a carrier frequency of a cell reselected by the communication system110, is obtained.

At S520, the network search information sharing channel130provides the network search information to a second communication system in the mobile communication device to reduce a network search time of the second communication system.

In the example of the process200, the cell search time of the second communication system120is reduced. In the example of the process300, the search time of the background manual network search requested by the second communication system120is reduced. In the example of the process400, the cell reselection time of the second communication system120is reduced. Thereafter, the process500proceeds to S599and terminates at S599.

It is noted that although aspects of the present disclosure are described using embodiments based on GSM, UMTS and LTE mobile communication networks and related wireless access technologies, embodiments employing any other types of mobile communication networks and technologies can be made without departing from the spirit and scope of the invention.