Patent Publication Number: US-9414397-B2

Title: Selecting base station at a multi-SIM communication device

Description:
TECHNICAL FIELD 
     The present invention relates in general to the field of computer networks. More particularly, the present invention relates to methods and systems for a multi-SIM communication device to establish wireless connections to at least one wireless communication network using at least one RF unit. 
     BACKGROUND ART 
     Some of multi-SIM communication devices are capable of connecting to two or more wireless communication networks. A multi-SIM communication device may have one RF unit and thus only one SIM card is in use to transmit and receive data. As received signal quality of a base station may impact network performance of the multi-SIM communication device significantly, it is preferred to connect to a base station that has better received signal quality. Received signal quality with a base station may change frequently as the multi-SIM communication device may move and may also be affected by other wireless communication device. Further, the multi-SIM communication device may not be able to connect to a base station, which has better received signal quality, as the multi-SIM communication device may not be equipped with a SIM card that is capable of establishing wireless connection with the base station. Therefore, the ability to keep observing received signal quality with other base stations, especially the base stations that the multi-SIM communication device can be connected to, even when a wireless connection has already been established becomes important. 
     DISCLOSURE OF INVENTION 
     Summary 
     The present invention discloses methods and devices on selecting one or more base stations by a multi-SIM communication device. The multi-SIM communication device comprises a plurality of SIM card interfaces, a plurality of RF units and at least one processing unit. The at least one processing unit is capable of instructing one or more of the RF unit to scan for base stations for observing received signal quality. 
     According to one embodiment of the present invention, the received signal quality is observed by a first RF unit and the first RF unit transmits data packets based in part on the received signal quality through at least one of the RF units. 
     According to one embodiment of the present invention, the selection of a first base station is based in part on the received signal quality when it is above a threshold and establishing a wireless connection with the first base station using the second RF unit. 
     According to another embodiment of the present invention, the processing unit instructs the second RF unit to become available and establish a wireless connection with the first base station if the second RF unit is unavailable and the second base station is below the threshold. 
     According to another embodiment of the present invention, a first tunnel and a second tunnel are established through the wireless connections established with the first base station and the second base station respectively. The first tunnel and second tunnel can be aggregated together to form an aggregated connection and data packets are transmitted through the first and the second tunnels. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of two wireless communication networks configured according to one of the embodiments of the present invention. 
         FIG. 2A  is a block diagram of multi-SIM communication device with at least two RF units configured according to one of the embodiments of the present invention. 
         FIG. 2B  is a block diagram of multi-SIM communication device with a SIM card interface selector configured according to one of the embodiments of the present invention. 
         FIG. 2C  is a block diagram of multi-SIM communication device with two SIM cards and one RF unit configured according to one of the embodiments of the present invention. 
         FIG. 2D  is a block diagram of multi-SIM communication device with two SIM cards and two RF units configured according to one of the embodiments of the present invention. 
         FIG. 3A  is a flowchart of a process for transmitting data packets based in part on observed received signal quality configured according to one of the embodiments of the present invention. 
         FIG. 3B  is a flowchart of a process for adjusting data transmission performance metric monitoring frequency based on observed received signal quality configured according to one of the embodiments of the present invention. 
         FIG. 3C  is a flowchart of a process for selecting a base station based in part on observed received signal quality configured according to one of the embodiments of the present invention. 
         FIG. 4A  is a flowchart of a process for selecting a base station with a threshold based in part on observed received signal quality configured according to one of the embodiments of the present invention. 
         FIG. 4B  is a flowchart of a process to select an available RF unit to connect to a base station based in part on observed received signal quality configured according to one of the embodiments of the present invention. 
         FIG. 5  is a flowchart of a process for event triggers configured according to one of the embodiments of the present invention. 
         FIG. 6  is a flowchart of a process to select an operational SIM card configured according to one of the embodiments of the present invention. 
         FIG. 7  is a block diagram of the SIM card interface selector configured according to one of the embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates two wireless communication networks, each of which may include a number of base stations and other network entities. For simplicity,  FIG. 1  also illustrates four base stations  111 ,  112 ,  113  and  114  and two network controllers  121  and  122 . A base station may be a fixed station that communicates with the multi-SIM communication devices and may also be referred to as an access point, a node, an evolved node, etc. A base station may provide communication coverage for a particular geographic area. The overall coverage area of a base station may be partitioned into smaller areas, and each smaller area may be served by a respective base station subsystem. The term “cell” can refer to a coverage area of a base station and/or a base station subsystem serving this coverage area, depending on the context in which the term is used. For illustration purpose only, a first wireless communication network includes base stations  111  and  112 , and network controller  121 ; a second wireless communication network includes base stations  113  and  114 , and network controller  122 . The first wireless communication network and the second wireless communication network, for illustration purpose only, may be operated by a first network operator and a second network operator respectively. 
     Multiple Subscriber Identification Module (multi-SIM) device  101  may be one of many devices receiving wireless communication services by the first wireless communication network and the second wireless communication network. Multi-SIM communication device  101  can be a mobile phone, a router and access terminal (AT), a mobile station (MS), a wireless modem, a user equipment (UE), a subscriber unit, a station, a desktop computer, a laptop computer, a cordless phone, a wireless local loop (WLL) station, personal digital assistant (PDA), or any other networking nodes that have been developed to allow users to manage and use more than one phone number via one device and via more than one SIM card such as SIM card  201   a - c , SIM card  251   a - c , SIM card  291   a  and  291   b , and SIM card  262   a  and  262   b .This invention may cover physical SIM cards of any size, as well as soft-SIM solutions or virtual-SIM solutions. 
     Multi-SIM communication device  101  may be stationary or mobile and may communicate with a base station via the downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to multi-SIM communication device  101 , and the uplink (or reverse link) refers to the communication link from multi-SIM communication device  101  to the base station. 
     The techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. CDMA 2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and EUTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) is a UMTS that uses E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). CDMA 2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). 
       FIG. 2A  illustrates one of embodiments according to the present invention. Multi-SIM communication device  101   a  has at least two radio units. There can be more number of SIM card interfaces than the number of radio frequency (RF) units. RF units, such as RF units  221   a  and  221   b , are connected to embedded/external antennas respectively. A RF unit can be connected to one or more SIM card interface. An external device connected to multi-SIM communication device  101  may also house RF units and SIM card interfaces, and thus RF units and SIM card interfaces are not housed by multi-SIM communication device  101 . A SIM card can be placed in the external device. For example, the external device is a Universal Serial Bus (USB) 3GPP modem. In another example, the external device is a Universal Serial Bus (USB) LTE modem. Multi-SIM device  101  is capable of connecting to one or more external devices. For example, a USB modem is connected to the USB interface of multi-SIM device  101 . According to one of the embodiments of the present invention, the RF unit or the multi-SIM device to be reset in order for it to be able to use another SIM card. One of the methods to reset to RF unit is to power-cycle the RF unit. For example RF unit  221   a  is connected to SIM card interface  211   a  only and RF unit  221   b  is connected to SIM card interfaces  211   b  and  211   c . When RF unit  221   b  is using SIM card  201   b , RF unit  221   b  cannot use SIM card  201   c . Processing unit  231 , for example, can instruct RF unit  221   b  to use SIM cards  201   b  and  201   c  in tandem through SIM card interfaces  211   b  and  211   c  respectively. In another example, processing unit  231  can instruct RF unit  221   b  to use only one of SIM cards  201   b  and  201   c  until an event that triggers processing unit  231  to instruct RF unit  221   b  to use another SIM card. 
     Memory, such as  234 ,  285 ,  297  and  266  may represent one or more devices for storing data in a volatile state. These devices may include random access memory (RAM), magnetic RAM, core memory and/or other machine readable mediums for storing volatile data. 
     A storage unit, such as storage unit  232 ,  282 ,  296  and  267  may represent one or more devices for storing data, including read only memory (ROM), magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information. 
     The term “machine-readable medium” includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data. A machine readable medium can be realized by virtualization, and can be a virtual machine readable medium including a virtual machine readable medium in a cloud-based instance. Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium such as storage medium. 
     A processing unit, such as processing unit  231 ,  281 ,  295  and  265  may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc. A processing unit(s) can be realized by virtualization, and can be a virtual processing unit(s) including a virtual processing unit in a cloud-based instance. 
     A SIM card interface, such as SIM card interfaces  261   a - 261   c ,  211   a - 211   c ,  292   a  and  292   b , and  263   a  and  263   b , is used to access and write information to and from a SIM card. There are many SIM card interfaces available from different manufacturers. Some of the SIM card interfaces provide functions of power supply, card reset signal, card clock signal and data exchange. A data exchange can be performed between the SIM card and processing unit  231 , SIM Card Interface Selector  284  or RF units  221 . Some of SIM card interfaces can only be connected with one SIM card while some can be connected to a plurality of SIM cards. Examples of SIM card interface include ON Semiconductor&#39;s NCN6804 and NCN8024, and Fairchild Semiconductor&#39;s FXLP4555. 
     A network interface, such as network interface  233   a ,  233   b ,  283   a ,  283   b ,  294   a ,  294   b ,  268   a  and  268   b  in multi-SIM communication device  101 , may be an Ethernet interface, a frame relay interface, a fibre optic interface, a cable interface, a DSL interface, a token ring interface, a serial bus interface, an universal serial bus (USB) interface, Firewire interface, Peripheral Component Interconnect (PCI) interface, etc. There may be more than one network interface in multi-SIM communication device  101 . A network interface may be used as a local area network (LAN) interface or a wide area network (WAN) interface. 
     System bus such as  240 ,  241 ,  242  and  243  allows multi-SIM communication device  101  to have increased modularity. For example, System bus  240  couples processing unit  231  to storage unit  232 , RF unit  221   a , network interface  233   a , network interface  233   b , and RF unit  221   b . System bus can be any of several types of bus structures including a memory bus, a peripheral bus, and a local bus using any of a variety of bus architectures. 
     Multi-SIM communication device  101   a  may be within the coverage of multiple base stations. More than one of base stations may be selected from these multiple base stations to serve multi-SIM communication device  101   a . The selection of one or more serving base stations may be referred to as server selection. The selection of base station to server multi-SIM communication device  101   a  (server selection) may be initiated by multi-SIM communication device  101   a , by a base station, and/or by the wireless communication network. Multi-SIM communication device  101   a  may request to be served by a base station. The base station may accept or reject the request. The wireless communication network may also accept or reject the request. A base station or wireless communication network may consider one or more factors to determine whether to accept or reject the request, including network capacity, processing capacity, number of concurrent connections, and etc. 
     In one example, when the server selection is initiated by a base station, multi-SIM communication device  101   a  may or may not be able to reject the server selection if multi-SIM communication device  101   a  decides to connect to the same network. Then base station  111  or base station  112  may instruct multi-SIM communication device  101   a  to connect to base station  111  when multi-SIM communication device  101   a  has already been connected with base station  112 . If multi-SIM communication device  101   a  refuses to connect to base station  111 , multi-SIM communication device  101   a  will not be able to connect to the first wireless communication network through base station  112  as base station  112  will later disconnect with multi-SIM communication device  101   a.    
     In one example, multi-SIM communication device  101   a  may try to connect to a particular base station, such as base station  112 . Multi-SIM communication device may send the request to the first wireless communication. If the request is authorized, then multi-SIM communication device can then connect to base station  111 . 
     A base station is a qualified base station if the received signal quality from the base station is above a threshold and multi-SIM communication device  101   a  can be authorized to connect to the base station by using information from one of SIM cards  201 . In one variant, if a base station can only be connected through a RF unit that is capable of establishing a wireless connection with a LTE network, the base station can only be a qualified base station when using the RF unit. The base station may not be a qualified base station when using another RF unit, which is not capable of establishing a wireless connection with a LTE network. 
     When processing unit  231  determines to establish a wireless connection with a base station, the base station is the Selected Base Station. The Selected Base Station is connected using one of RF units  221  using authentication information retrieved from a corresponding SIM card. It is possible that a Selected Base Station cannot be connected to because of many reasons, including lack of capacity at the Selected Base Station, refusal by the Selected Base Station, etc. 
     A RF unit is available when it has not established any wireless connection. If a RF unit is not available, the RF unit cannot be used to establish an additional wireless connection. In one example, in order to have a RF unit that is originally unavailable to become available, the RF unit may need to disconnect established wireless connection before establishing another wireless connection. 
       FIG. 3A  illustrates one of the embodiments according to the present invention. At step  301 , processing unit  231  instructs one of RF units  221  (Scanning RF Unit) to scan for base stations that multi-SIM communication device  101   a  can be connected to. Although multi-SIM communication device  101   a  may find many base stations during the scan, multi-SIM communication device  101   a  only observes received signal quality for those base stations that multi-SIM communication device  101   a  can connect to. Multi-SIM communication device  101   a  can only connect to base stations operated by network operators that authorize SIM cards  201  to connect to. For example, use of SIM cards  201   a ,  201   b  and  201   c  allows multi-SIM communication device  101   a  to connect to a base station of a wireless communication network operated by a first network operator, a second network operator and a third network operator respectively. As base stations  111  and  112  are operated by the first network operator and base stations  113  and  114  are operated by the second network operator, multi-SIM communication device  101   a  can connect to base stations  111 - 114  by using SIM cards  201   a  or  201   b . In another example, a plurality of SIM cards  201  may be used by processing unit  231  to enable multi-SIM communication device  101   a  to establish more than one wireless connection with a base station. 
     When processing unit  231  selects SIM cards  211   b  or  221   c  for RF unit  221   b  for use, processing unit  231  instructs RF unit  221   b  to select SIM card interface  211   b  or  211   c  for SIM cards  211   b  or  211   c  respectively according to the instruction sent by processing unit  231 . Alternatively, RF unit  221   b  does not connect to SIM card interfaces  211   b  and  211   c  directly. Instead, SIM card interfaces  211   b  and  211   c  are connected to bus  240 . In such case, SIM card information is retrieved from SIM card interfaces  211   b  and/or  211   c  and then sent to RF unit  221   b . Alternatively, there could be a SIM card interface selector, like the one illustrated in  FIG. 7  for the embodiment illustrated in  FIG. 2B , connects SIM card interfaces  211   b  and  211   c  to RF unit  221   b  and is controlled by processing unit  231 . Examples of a SIM card interface selector for two SIM card interfaces include TXS02326 Dual-Supply 2:1 SIM Card Multiplexer/Translator supplied by Texas Instruments and LTC4557 Dual SIM/Smart Card Power Supply and Interface supplied by Linear Technology. 
     At step  302 , the Scanning RF Unit observes received signal quality of the base stations  111 ,  112 ,  113  and  114 . Both RF units  221   a  and  221   b  can be the Scanning RF Unit. For example, RF unit  221   b  is the Scanning RF Unit, while RF unit  221   a  is not Scanning RF Unit and will not perform received signal quality observation. In one example, RF unit  221   a  is a Scanning RF Unit for a period of time and then not being the Scanning RF Unit for another period of time. Therefore, RF unit  221   a  may be able to perform other non-received signal quality observation functions when RF unit  221   a  is not a Scanning RF Unit. It is preferred that only one of RF units  221   a  and  221   b  is a Scanning RF Unit at any particular moment as the benefits of more than one RF units to observe received signal quality is limited. As some RF units may not be able to provide data communication functions when being a Scanning RF Unit, the shorter period of time a RF unit is a Scanning RF, the more time the RF unit can provide data communication functions. In one variant, as different RF units are used as Scanning RF Units, it is possible that observed received signal qualities associated with a base station are different. Processing unit  231  may average the observed received signal qualities or choose the most recent observed received signal quality before further processing. 
     Steps  301  and  302  may be performed all the time, periodically and/or upon an instruction received by processing unit  231 . The more frequent step  301  is performed, the sooner multi-SIM communication device  101   a  may be able to connect to a base station that has better received signal quality and may result in higher data throughput. If a RF unit is not able to perform steps  301  and/or step  302  while being wirelessly connected with a base station, step  301  and/or step  302  should be not performed. If a RF unit is not able to perform scanning while transmitting or receiving data from the wireless connected base station, step  301  and/or step  302  should be performed less frequently in order to avoid interruptions to data transmission and receiving. 
     In one variant, the frequency of performing steps  301  and  302  can be different. The frequency of performing step  302  is preferred to be performed more frequently than of step  301 . The number of base stations available to be connected does not change significantly if multi-SIM communication device  101   a  does not move much. However, received signal quality may change even if multi-SIM communication device  101   a  is stationary. After step  301  is performed, step  302  may be performed a number of times before step  301  is performed again. In one example, step  301  is performed every thirty seconds and step  302  is performed ten times every thirty seconds. 
     At step  303 , processing unit  231  transmits data packets based in part on observed received signal quality after observing received signal quality of base stations  111 - 114 . The Scanning RF Unit may be able to observe received signal quality of base stations other than base stations  111 - 114 . It is preferred that processing unit  231  does not transmit data packets based in part on observed received signal quality of base stations other than base stations  111 - 114  because multi-SIM communication device  101   a  cannot connect to base stations other than base stations  111 - 114 . For example, when processing unit  231  determines that received signal quality with base station  111  is the best among the received signal qualities with base stations  111 - 114 , processing unit  231  transmits more data packets through base station  111  than through base stations  112 ,  113  and  114 . In another example, when processing unit  231  determines that received signal quality with base station  111  and base station  113  are the best among the received signal qualities with base stations  111 - 114 , procession unit  231  transmits data packets through base stations  111  and  113 . In one variant, as RF unit  221   a  can only connect to one of base stations  111  and  112  and RF unit  221   b  cannot connect to any of base stations  111  and  112 , multi-SIM communication device  101   a  can only connect one of base stations  111  and  112  through SIM card  201   a  and RF unit  221   a . Therefore, even if received signal qualities with base stations  111  and  112  are better than received signal qualities with base stations  113  and  114 , processing unit  231  will transmit data packets through RF units  221   a  with one of base stations  111  and  112  and through RF unit  221   b  with one of base stations  113  and  114 . 
       FIG. 3B  illustrates one of the embodiments according to the present invention. The difference between the processes in  FIG. 3B  and  FIG. 3A  is that step  303  is replaced by step  313 . At step  313 , processing unit  231  adjusts data transmission performance metric monitoring frequency based in part on observed received signal quality. As received signal quality of a wireless connection changes and if a RF unit is transmitting and/or receiving through the wireless connection, data transmission performance metric may be affected by the received signal quality change. When the received signal quality is good, there is less need to monitor the data transmission performance metric frequently. On the other hand, when the received signal quality is below a threshold, the data transmission performance metric monitoring should be performed more frequently as it is possible that the wireless connection can become unstable quickly. In one example, RF unit  221   a  is the Scanning RF Unit and RF unit  221   b  is transmitting data packets through a wireless connection established between RF unit  221   b  and base station  114 . When RF unit  221   a  has observed the received signal quality of the wireless connection between RF unit  221   b  and base station  114  has dropped below a threshold, processing unit  231  monitors data transmission performance metric for data packets transmitted through RF unit  221   b  more frequently. When the received signal quality of the wireless connection between RF unit  221   b  and base station  114  has improved and is above the threshold, processing unit  231  monitors data transmission performance metric for data packets transmitted through RF unit  221   b  at a regular frequency. When processing unit  231  has found a wireless connection is unstable, it stops transmitting data packets through the wireless connection. In one variant, if the wireless connection with base station  114  is unstable, processing unit  231  then disconnects the wireless connection with base station  114  and tries to establish another wireless connection with another base station. 
       FIG. 3C  illustrates one of the embodiments according to the present invention. The difference between the processes in  FIG. 3B  and  FIG. 3A  is that step  303  is replaced by steps  323  and  324 . At step  323 , processing unit  231  selects a base station (Selected Base Station) based in part on observed received signal quality. The better the observed received signal quality with a base station being observed, the more likely the base station is selected. The Selected Base Station should also be a base station that can be connected by one of RF units  221 . If received signal quality with a base station is highest among all received signal qualities observed but the base station cannot be connected through any of RF units  221 , the base station will not be selected by processing unit  231  and cannot be a Selected Base Station. In one variant, in order for processing unit  231  to select a base station to be the Selected Base Station, the received signal quality with the base station has to be higher than a threshold. 
     At step  324 , processing unit  231  instructs one of RF units  221  to connect to the Selected Base Station if processing unit  231  decides so. For example, if the Selected Base Station is base station  114  and only RF unit  221   b  can be used to connect to base station  114 . Processing unit  231  will then instruct RF unit  221   b  to connect to base station  114 . In one variant, processing unit  231  will only instruct RF unit  221   b  to connect to base station  114  if RF unit  221   b  has not established any wireless connection with another base station in order to avoid breaking established communication. In one variant, processing unit  231  will only instruct RF unit  221   b  to connect to base station  114  if RF unit  221   b  has established a wireless connection with another base station but the received signal quality with the another base station is lower than a threshold. The received signal quality with the another base station is observed at step  302 . In one variant, processing unit  231  will only instruct RF unit  221   b  to connect to base station  114  if the received signal quality with RF unit  221   b  is above a threshold. 
     In one variant, steps  301  and  302  are being performed continuously after multi-SIM communication device  101   a  is powered up therefore processing unit  231  can continuously find base stations that are qualified to be the Selected Base Station. 
       FIG. 2B  illustrates one of the embodiments according to the present invention. Multi-SIM communication device  101   b  has at least two radio units. There can be more number of SIM card interfaces than the number of radio frequency (RF) units. RF units, such as  271   a  and  271   b , are connected to embedded/external antennas respectively. SIM card interface selector  284  provides access for RF units  271  to connect to SIM card interfaces  261 . Instructed by processing unit  281 , one or more SIM card interfaces  261  may be selected by SIM card interface selector  284  to establish wireless connections using RF units  271 . In this example, SIM card interface selector  284  may select SIM card interface  261   a ,  261   b  or  261   c  for use by RF unit  271   b . Furthermore, SIM card interface selector  284  may select SIM card interface  261   a ,  261   b  or  261   c  for use by RF unit  271   a . Therefore, SIM card interface selector  284  is capable of allowing any RF unit  271  to use any SIM card  251  by using multiplexing technique known to those skilled in the art. Processing unit  281  instructs RF unit  271   b  to perform other tasks when RF unit is not used to establish a wireless connection. Other tasks may include serving as a Scanning RF Unit to scan for base stations or to establish a wireless connection. 
     In one example, SIM card interface selector  284  is a multiplexer that allows RF unit  271   a  and RF unit  271   b  connects to any of SIM card interfaces  261   a ,  261   b  and  261   c  as illustrated in  FIG. 7 . Preferably, when a SIM card interface is already connected to one of RF units  271 , the other of RF unit  271  cannot connect to the same SIM card interface as most wireless communication networks only allow one SIM card to establish one wireless connection at any time. However, there is no limitation that one SIM card interface must be connected to one RF unit only. There is no limitation on the number of SIM card interfaces that a SIM card interface selector can connect to. Similarly, there is no limitation on the number of RF units that a SIM card interface selector can connect to. 
     In another embodiment, multi-SIM communication device  101   b  performs according to the steps illustrated in  FIG. 3C . At step  301 , processing unit  281  instructs one of RF units  271  (Scanning RF Unit) to scan for base stations that multi-SIM communication device  101   b  can be connected to. Although multi-SIM communication device  101   b  may find many base stations during the scan, multi-SIM communication device  101   b  only observes received signal quality for those base stations that multi-SIM communication device  101   b  can connect to or may observe no signal at all. 
     Multi-SIM communication device  101   b  can only connect to base stations operated by network operators that authorize SIM cards  251  to connect to. For example, use of SIM cards  251   a ,  251   b  and  251   c  allows multi-SIM communication device  101   b  to connect to a base station of a wireless communication networks operated by a first network operator, a second network operator and a third network operator respectively. As base stations  111  and  112  are operated by the first network operator and base stations  113  and  114  are operated by the second network operator, multi-SIM communication device  101   b  can connect to base stations  111 - 114  by using SIM cards  251   a  and  251   b . Multi-SIM communication device  101   b  may not be able to connect to the third wireless communication network using SIM card  251   c  when there are no base stations providing wireless communications service from the third wireless communication network. 
     In one example, a plurality of SIM cards  251  may be selected by SIM Card Interface Selector  284 , and used by processing unit  281  to enable multi-SIM communication device  101   b  to establish more than one wireless connection with a base station. The selection may also be performed by processing unit  281 . For example, processing unit  281  may instruct RF unit  271   a  and RF unit  271   b  to use SIM card  251   a  and SIM card  251   b  to establish wireless connections with base station  111  and base station  113  respectively. Processing unit  281  instructs SIM card interface selector  281  to provide RF units  271  access to SIM card interface  261 . This may allow multi-SIM communication device  101   b  to have at least one wireless connection established with a wireless communication network. For example, when multi-SIM communication device  101   b  is out of coverage of the second wireless communication network, multi-SIM communication device  101   b  can stay connected with the first wireless communication network using SIM card  251   b . In one variant, since SIM card  251   b  is operating without the coverage of its authorized communication network which is the second wireless communication network, multi-SIM communication device  101   b  may be configured to be operating on a roaming network and may incur network roaming charges. 
     At step  302 , the Scanning RF Unit observes received signal quality of the base stations  111 ,  112 ,  113  and  114 . Both RF units  271   a  and  271   b  can be the Scanning RF Unit. For example, RF unit  271   b  is the Scanning RF Unit while RF unit  271   a  is not Scanning RF Unit and will not perform received signal quality observation. In one example, RF unit  271   a  is a Scanning RF Unit for a period of time and then is not for another period of time. Therefore, RF unit  271   a  may be able to perform other non-received signal quality observation functions when RF unit  271   a  is not a Scanning RF Unit. It is preferred that only one of RF units  271   a  and  271   b  is a Scanning RF Unit at any particular moment as the benefits of more than one RF units to observe received signal quality is limited. As some RF units may not be able to provide data communication functions when being a Scanning RF Unit, the shorter period of time a RF unit is a Scanning RF Unit, the more time the RF unit can provide data communication functions. In one variant, as different RF units are used as Scanning RF Units, it is possible that observed received signal qualities associated with a base station are different. Processing unit  281  may average the observed received signal qualities or choose the most recent observed received signal quality before further processing. 
     At step  323 , processing unit  281  selects a base station (Selected Base Station) based in part on observed received signal quality. The better the observed received signal quality with a base station being observed, the more likely the base station is selected. The base station may also be selected by processing unit  281  based in part on policies or algorithms or centralized management methods. The Selected Base Station should also be a base station that can be connected by one of RF units  271 . If received signal quality with a base station is highest among all received signal qualities observed but the base station cannot be connected through any of RF units  271 , the base station will not be selected by processing unit  281  and cannot be a Selected Base Station. In one variant, in order for processing unit  281  to select a base station to be the Selected Base station, the received signal quality with the base station has to be higher than a threshold. 
     At step  324 , processing unit  281  through SIM card interface selector  284 , instructs RF units  271  to use SIM cards  251  through at least one of SIM card interface  261  to connect to the Selected Base Station. Alternatively, processing unit  281  instructs SIM card interface selector  284  to provide information retrieved from one of SIM cards  251  to one of RF units  271  and processing unit  281  also instructs the one of RF units  271  to connect to the Selected Base Station based in part on the information retrieved at the same time if processing unit  281  decides so. For example, the Selected Base Station is base station  114  and any RF unit  271  can be used to connect to base station  114  because any of RF unit  271  can use any of the SIM cards  251 . 
     In one example, base stations  113  and  114  belong to the second wireless communication network and are operated by the second network operator. Base station  114  is the Selected Base Station based in part on the threshold. Processing unit  281  also determines RF unit  271   b  will be used to establish a wireless connection with Selected Base Station  114 . Processing unit  281  then instructs SIM card interface selector  284  to select SIM card interface  261   b  to connect with a SIM card that has the corresponding authentication information, in this example, SIM card  251   b.    
     In one variant, processing unit  281  will only instruct SIM card interface selector  284  to select SIM card  251   b  to be served by RF unit  271   b  to connect to base station  114  if RF unit  271   b  has established a wireless connection with another base station and the received signal quality is below the threshold. The received signal quality with the another base station is observed at step  302 . This ensures that multi-SIM communication device  101   b  establishes wireless connections with qualified base stations that have observed signal qualities above the threshold. 
       FIG. 4A  illustrates one of the embodiments according to the present invention. At step  401 , processing unit has already observed received signal quality of the base stations  111 ,  112 ,  113  and  114  through a Scanning RF Unit. At step  430 , processing unit  231  selects a base station from the list of base stations that are qualified to be the Selected Base Station based in part on observed received signal quality. A base station is qualified if the received signal quality with the base station is higher than a threshold. When there is more than one base station qualified, processing unit  231  selects one of the base stations to be Selected Base Station. The selection may be performed according to received signal quality, predefined priority, preferences, price and etc. In case after step  437 , the Selected Base Station cannot be used, processing unit  231  will select another base station from the qualified base stations. For illustration purpose, base station  114  is the Selected Base Station. At step  431 , processing unit  231  determines whether a RF unit is available to connect to the Selected Base Station. When there is no RF unit available to connect to the Selected Base Station, processing unit  231  determines whether any of received signal quality with each connected base station, which has established a wireless connection with multi-SIM communication device  101   a , is below a threshold at step  432 . In an example, for illustration purpose, when RF units  221   a  and  221   b  have already established wireless connections with base stations  111  and  113  respectively, there is no RF unit available at step  431 . Then processing unit  231  determines whether the received signal quality of the wireless connection established by RF unit  221   a  and base station  111  or the received signal quality of the wireless connection established by RF unit  221   b  and base station  113  is below than a threshold at step  432 . If none of the received signal quality is below the threshold, the Selected Base Station is not used to establish a wireless connection and the process stops at step  402 . If one of the received signal qualities with the base stations is below the threshold, for example, the received signal quality of wireless connection established by RF unit  221   b  and base station  113  is below the threshold, step  434  is performed. 
     For illustration purpose, when the received signal quality of wireless connection established by RF unit  221   b  and base station  113  is lower than the threshold, then at step  434 , processing unit  231  instructs RF unit  221   b  to terminate the wireless connection with base station  113 . The termination frees resources at RF unit  221   b  and allows RF unit  221   b  to establish a new wireless connection. At step  435 , processing unit  231  instructs RF unit  221   b  to connect to the Selected Base Station. At step  436 , processing unit  231  checks whether RF unit  221   b  is able to establish a wireless connection with the Selected Base Station which is base station  114 . If RF unit  221   b  has successfully established a wireless connection with base station  114 , processing unit  231  can then transmitting and receiving IP packets through RF unit  221   b  and base station  114  at step  438 . Those who are skilled in the arts would appreciate that IP packets can be transmitted using transmission control protocol (TCP), user datagram protocol (UDP), or other protocols. If RF unit  221   b  cannot establish a wireless connection with base station  114 , processing unit  231  checks if there is another qualified base station to be the Selected Base Station at step  437 . If there is at least one more qualified base station, step  430  is performed to select the at least one more qualified base station. If there is no more qualified base station, the process stops at step  402 . In one variant, when there is no more base station qualified to be connected to at step  437 , processing unit  231  will attempt to connect to the base station that was disconnected from at step  434 . This allows processing unit  231  to try to return to have the same number of wireless connections. In one variant, if a RF unit is capable of establishing a wireless connection without disconnection another wireless connection that has already been established, steps  431 ,  432  and  434  will then be performed after step  438  in order not to terminate an established wireless connection too early. 
     In one variant, step  430  is preferred to be performed after step  431  or step  434  as shown in  FIG. 4B . As there is no RF unit available and none of the received signal quality for established wireless connection is worse than a threshold, step  434  is avoided in order to reduce the probability of interrupting ongoing data communications and step  430  is also not performed in order to reduce computing resources. 
       FIG. 4B  illustrates one of the embodiments according to the present invention. At step  401 , processing unit has already observed received signal quality of the base stations  111 ,  112 ,  113  and  114  through a Scanning RF Unit. 
     At step  431 , processing unit  281  determines whether any RF unit is available to connect to the Selected Base Station. When there is no RF unit available to connect to the Selected Base Station, processing unit  281  determines whether any of received signal quality with each connected base station, which has established a wireless connection with multi-SIM communication device  101   b , is below a threshold at step  432 . 
     In an example, for illustration purpose, when RF units  271   a  and  271   b  have already established wireless connections with base stations  111  and  113  respectively, there is no RF unit available at step  431 . Then processing unit  281  determines whether the received signal quality of the wireless connection established by RF unit  271   a  and base station  111  or the received signal quality of the wireless connection established by RF unit  271   b  and base station  113  is below a threshold at step  432 . If none of the received signal quality is below the threshold, the selected base station is not used to establish a wireless connection and the process stops at step  402 . If one of the received signal qualities with the base stations is below the threshold, for example, the received signal quality of wireless connection established by RF unit  271   b  and base station  113  is below the threshold, step  434  is performed. 
     At step  434 , processing unit  281  instructs RF unit  271   b  to disconnect from base station  113  so that RF unit  271   b  can become an available RF unit. 
     At step  430 , processing unit  281  selects a base station from the list of base stations that are qualified to be the Selected Base Station based in part on observed received signal quality. When there are more than one base stations qualified, processing unit  281  selects one of the base stations to be Selected Base Station. The selection may be performed according to received signal quality, predefined priority, preferences, price etc. At step  430 , base station  114  is the selected base station after processing unit  281  determines the observed signal quality of base station  114  to be above the threshold. In one variant, at step  436  the Selected Base Station is found not capable of being used and there is no more qualified base station at step  437 , step  430  restarts and processing unit  281  will select another base station from the qualified base stations. This is to try to ensure multi-SIM communication device  101   b  always has at least one established wireless connection with the qualified base station that has the observed received signal quality above the threshold. In one variant, if there is no base station that can offer wireless communication service with observed received signal quality above the threshold, multi-SIM communication device  101   b  may attempt to establish wireless connections with a base station with the highest observed received signal quality. 
     At step  435 , SIM card  251   b  is connected to SIM card interface  261   b  and is authorized to connect with the second wireless communication network and base station  114 . Processing unit  281  instructs SIM card interface selector  284  to select SIM card interface  261   b , which is connected to SIM card  251   b , to establish a wireless connection with the Selected Base Station  114  through RF unit  271   b.    
     At step  436 , processing unit  281  instructs SIM card interface selector  284  to select a SIM card interface  261 , then verifies whether RF unit  271  is able to establish a wireless connection with a Selected Base Station. If RF unit  271  successfully establishes a wireless connection a base station, processing unit  281  can then transmit and receive IP packets through RF unit  271  and the base station at step  438 . If RF unit  271   b  successfully establishes a wireless connection with base station  114 , processing unit  281  then transmits and receives IP packets through RF unit  271   b  and the base station  114  at step  438 . If RF unit  271   b  cannot establish a wireless connection with base station  114 , processing unit  281  checks if there is another qualified base station to be the Selected Base Station at step  437 . If there is at least one more qualified base station, step  430  is performed to select the at least one more qualified base station. If there is no more qualified base station, the process stops at step  402 . In one variant, when there is no more base station qualified to be connected to at step  437 , processing unit  281  may instruct RF unit  271  to connect to the base station that was disconnected from at step  434 . This allows multi-SIM communication device  101   b  to try to have at least one established wireless connection with the qualified base station that has the observed signal quality above the threshold. In one variant, if a RF unit is capable of establishing a wireless connection without disconnecting another wireless connection that has already been established, steps  431 ,  432  and  434  will then be performed after step  438  in order not to terminate the established wireless connection too early. 
     In one variant, step  430  is preferred to be performed after step  431  or step  434 . As there is no RF unit available and none of the received signal quality for established wireless connection is worse than a threshold, step  434  is avoided in order to reduce the probability of interrupting ongoing data communications and step  430  is also not performed in order to reduce computing resources. 
       FIG. 1  also illustrates a network environment that a multi-SIM is capable of transmitting and receiving data packets through an aggregated tunnel according to one of the embodiments of the present invention. Multi-SIM communication device  101 , such as multi-SIM communication device  101   a ,  101   b  and  101   d , that has more than one RF unit, and has established at least two wireless connections between at least two RF units and at least one base station. Multi-SIM communication device  101   c  cannot be used for this embodiment as it only has one RF unit  293   a  unless RF unit  293   a  is able to establish more than one wireless connection. An aggregated tunnel is then established through the at least two wireless connections. Within each of the established wireless connections, a tunnel is established between multi-SIM communication device  101  and network node  119  for transmitting and receiving data packets. The data packets may be encapsulated by using a tunneling protocol packet. The aggregated tunnel may be an aggregated virtual private network (VPN) connection. Multi-SIM communication device  101  and network node  119  may first negotiate tunnel configuration variables, such as address assignments, compression parameters and encryption methods before transmitting and receiving data packets. Multi-SIM communication device  101  transmits the encapsulated data packets across interconnected networks  117 . Network node  119  may decapsulate the encapsulated data packets to retrieve the data packets upon receiving the encapsulated data packets. 
     In one example, multi-SIM communication device  101  establishes a tunnel using RF unit  221   a  with base station  111  on the first wireless communication network and another tunnel with RF unit  221   b  with base station  113  on the second wireless communication network. For the purpose of illustration, the tunnel established using RF unit  221   a  is referred to as tunnel A and the tunnel established using RF unit  221   b  is referred to as tunnel B. Tunnel A and tunnel B together are used to form an aggregated tunnel. 
     When the established wireless connections between multi-SIM communication device  101  and both base station  111  and  113  are stable, multi-SIM communication device  101  are able to transmit data packets through the aggregated tunnel using both tunnel A and tunnel B without many packet drops. When the established wireless connection between multi-SIM communication device  101  and base station  111  is stable but the established wireless connection between multi-SIM communication device  101   a  and base station  113  is unstable, tunnel B may become broken. Multi-SIM communication device  101  then transmits data packets through the aggregated tunnel using tunnel A and stops transmitting data packets through tunnel B. In one variant, after the wireless connection between multi-SIM communication device  101   a  and base station  113  is stable again and tunnel B is re-established, multi-SIM communication device then transmits data packets using both tunnel A and tunnel B. In one variant, when the Scanning RF Unit has observed that received signal quality of the wireless connection between multi-SIM communication device  101   a  and base station  113  is worsening, multi-SIM communication device  101  may not use tunnel B even though tunnel B is not broken in order to reduce packet loss. 
       FIG. 5  is a flowchart illustrating the steps according to various embodiments of the present invention. Multi-SIM communication devices  101   a ,  101   b  and  101   c  can be viewed in conjunction with  FIG. 5  respectively to illustrate how event triggers could be used to select one of more SIM cards. Event triggers include but are not limited to a geographic location trigger, a data usage trigger, a received signal quality trigger, a time trigger, a duration of usage trigger, a billing cycle trigger etc. Event triggers may be referred to as a first event trigger and a second event trigger as illustrated in  FIG. 5 , step  501  and  503  respectively. In one variant, a plurality of triggers can be combined to form an event trigger. For example, the first event trigger can be based on a geographic location trigger and a data usage trigger. In another example, the second event trigger can be based on the duration of usage trigger and the billing cycle information trigger. In one variant, the first event trigger and the second event trigger can be based on the same trigger(s). 
     Multi-SIM communication device has two SIM cards  291   a  and  291   b , two SIM card interfaces  292   a  and  292   b , one processing unit  295 , one storage unit  295  and one RF unit  293   a . There are also two wireless communication networks available where SIM  291   a  is authorized for a first wireless communication network, and SIM  291   b  is authorized for a second wireless communication network. 
     Multi-SIM communication device  101   c  originally uses SIM card  291   a  for illustration purpose only, as the first SIM card to establish a wireless communication. At step  501 , when a first event trigger has occurred, SIM card  291   a  cannot be used. The wireless connection established using SIM card  291   a  and RF unit  293   a  may have been broken or terminated. 
     At step  502 , multi-SIM communication device  101   c  uses a second SIM card to establish a wireless connection, which is SIM card  291   b  in this example. After RF unit  293   a  has disconnected from the established wireless connection with the first wireless communication network, it can be used to establish another wireless connection with another wireless communication network as SIM  291   b  is authorized to establish wireless connections with the second wireless communication network, therefore it is selected by processing unit  295  to be served by RF unit  293   a  through SIM card interface  292   b  to establish a wireless connection with the second wireless communication network. As there are two SIM cards, SIM card  291   a  and  291   b , SIM card  291   b  is the only SIM card that can be the second SIM card in step  502 . If multi-SIM communication device  101   c  has more SIM cards, one of SIM card  291   b  and the more SIM cards and can be selected to be the second SIM card in step  502 . The selection can be based on one or more criteria. For example, the least used SIM card is selected to be the second SIM card. In another example, the SIM card that has the corresponding lowest tariff price is selected to be the second SIM card. In another example, the SIM card that has the expected network performance is selected to be the second SIM card. In another example, each of the SIM card is assigned with a priority and the selection is based on the priority. The priority can be entered by a user of multi-SIM communication device  101   c , the manufacturer of multi-SIM communication device  101   c , the position of the SIM sockets used to house the SIM cards, or retrieved from a remote server. The network performance may be determined by using results reported by a Scanning RF Unit. 
     At step  503 , processing unit monitors for a second event trigger or is notified by a second event trigger. The second event trigger may occur due to but not limited to the following reasons: a duration of usage, conditions of the current connection, reaching the cap of a data usage plan, and geographical location. When the second event trigger does not occur, processing unit  295  continues monitoring for the second event trigger and multi-SIM communication device  101   c  continues using SIM card  291   b . On the other hand, when the second event trigger occurs, for example, after a duration of usage has been reached, processing unit  295  will perform step  504 . 
     One example for the second event trigger may be based on duration of usage trigger. The duration of usage may be set by the vendor of multi-SIM communication device  101   c , a user of multi-SIM communication device  101   c  or retrieved from a remote server. One such purpose may be due to a preference in the use of a specific wireless communication network. The user may specify that the second wireless communication network should only be used for sixty minutes per session. In one variant, if multi-SIM communication device  101   c  disconnects from the second wireless communication network, the sixty minute session ends and is restarted when another wireless connection is established with the second wireless communication network at a later time. After sixty minutes has been reached, the second event trigger occurs and step  504  is performed. Similarly, the first event trigger can also be based on the duration of usage, for example, when the duration of usage has been reached, the first event trigger occurs. 
     In another variant, it is known that while received signal quality may be above the threshold, it is possible that data packets cannot be transmitted. There are many reasons for this but one example may be when multi-SIM terminal  101   c  has already established a wireless connection with base station  111 , but the connection between network controller and interconnected networks  117  is slow. Processing unit  295  may use the observed signal quality as a trigger, in conjunction with a network performance trigger. The network performance trigger may be based on the bandwidth and packet drop rate with network node  119 . For example, if the wireless connection established with SIM  291   a  has signal quality above the threshold but the network performance is below another threshold, the second event trigger occurs. If the signal quality is above a threshold and the network performance above the another threshold, the second event trigger does not occur. 
     In another example, the second event trigger may be based on geographic location data. Geographic location data may include geographic coordinate data based on the geographic coordinate system. The geographic location data may be received by the RF unit such as RF unit  293   a . It may also be received by an embedded or external GPS receiver which is not illustrated in  FIG. 2C . The geographic location data may be predefined as a trigger. This may be set by the vendor of multi-SIM communication device  101   c , the user of multi-SIM communication device  101   c  or the data may be retrieved from a remote server. For example, is possible to locate multi-SIM communication device  101   c  on a map in real-time as it receives geographic location data. Similarly, the first event trigger can also be based on geographic location data, for example when the geographic location is known to be without of the coverage area of a wireless communication network, the first event trigger occurs. One scenario where this may be used is when the multi-SIM communication device is without the coverage area of a wireless communication network. In order to continue transmitting data and not incur wireless communication network roaming charges or to incur charges from another wireless communication network with a higher tariff pricing, the second event trigger occurs as soon as its geographic location data matches the predefined geographic location trigger. For example, the predefined threshold is a location fence for geographic location A. The geographic location data received by multi-SIM communication device  101   c  is determined by processing unit  295  to be above the threshold when it is outside of the geographic location A and therefore the second event trigger occurs so that multi-SIM communication device  101   c  may select another operational SIM card. 
     In one example, the second event trigger is based on tariff pricing information. The tariff pricing information typically includes at least the monthly cellular subscription cost, the monthly data usage limit, the premium for exceeding the monthly data usage limit, and the premium for using a roaming network. The tariff pricing information may be inputted by a user or retrieved from a remote server, and then stored in storage unit  296  for later retrieval. For illustration purpose only, when processing unit  295  has determined that the tariff price of the second SIM card, which is SIM card  291   b , is not the cheapest, a second event trigger occurs. Those who are skilled in the art would appreciate that there are myriad of reasons why the tariff price of SIM card  291   b  is not the cheapest. Similarly, the first event trigger can also be based on tariff pricing information, for example when the tariff price of SIM card  291   a  is no longer the cheapest, the first event trigger occurs. 
     In one variant, processing unit  295  monitors tariff pricing information from network operators corresponding to SIM cards  291   a  and  291   b  as it is possible that network operators may change tariff prices. Those who are skilled in the art would appreciate that there are myriad of reasons why network operators change tariff prices. For example, due to congested network environment, a network operator may increase the tariff price in real-time. When processing unit  295  has discovered that the tariff price of the SIM card  291   b  is not the cheapest, the second event trigger occurs. 
     In another variant, the second trigger occurs based on both the tariff pricing information and the data usage for both SIM cards  291   a  and  291   b . For example, network operators may have different tariff prices based on data usage especially after the data usage limit has been reached. When processing unit  295  determines that SIM card  291   b  is no longer the cheapest based on data usage, the second event trigger occurs. 
     In another example, the second event trigger may be based on the billing cycle information. A billing cycle is when the period of a cellular subscription for communication service, usually monthly. It is common that once a billing cycle ends, the data usage counter ceases for the month and a new billing cycle begins. Similarly, the first event trigger can also be based on the billing cycle information. For example, when the billing cycle is about to end, the first event trigger occurs. 
     The billing cycle period may be set by the vendor of multi-SIM communication device  101   c , a user of multi-SIM communication device  101   c  or the trigger data may be retrieved from a remote server. One scenario where this may be used is when data traffic per month is capped and a balanced data usage across two SIM cards may be desirable. For the purpose of illustration, the first wireless communication network and second wireless communication network each allows for one gigabyte of data to be transmitted per month and data exceeding the allowance is charged at a high premium. The billing cycle of the first wireless communication network is from the first day to the last day of every month and the billing cycle of the second wireless communication network is from the fourteenth day of the current month to the fourteenth day of the next month. The user estimates that SIM  291   a  would be nearing its data usage allowance by the end of the month and hence sets a higher priority based on usage for the second wireless communication network when it is near the end of the month. Similarly, the user sets a higher priority based on usage for the first wireless communication network near the middle of the month as he estimates that SIM  291   b  would be nearing its data usage allowance by the middle of the month, when its billing cycle is nearing its end. Therefore, the second event trigger occurs near the end of the month and multi-SIM communication device  101   c  attempts to use SIM  291   b . Similarly, the second event trigger occurs near the middle of the month and multi-SIM communication device  101   c  attempts to use SIM  291   a . In one variant, the user sets the billing cycle as above, as well as sets communication network priority based on data usage according to the billing cycle. So while SIM  291   b  has higher priority based on usage near the end of a month, if the data usage on the second wireless communication network is already nearing one gigabyte which is the limit in this illustration, SIM  291   a  may be selected for use. 
     In another example, processing unit  295  may receive the second event trigger from RF unit  293   a  when the observed signal quality is below a threshold. For the purpose of illustration, RF unit  293   a  is capable of activating the second event trigger when it has determined that the signal quality has fallen to less than the threshold. One example of the threshold is −100 dB. Similarly, the first event trigger can also be based on the observed signal quality. For example, when the observed signal quality is below a threshold, the first event trigger occurs. 
     In another example, processing unit  295  receives the second event trigger which is based on geographic location data from the operating system, processing unit  295  then collects signal quality data from RF unit  293   a  and stores both sets of data to storage unit  296 . For the purpose of illustration, processing unit  295  combines both sets of data over a period of time, creating a record of different geographic area and their prevailing signal quality. With this information, multi-SIM communication device  101   c  may be able to anticipate areas where the signal quality is below a threshold and activate the second event trigger in order to use another wireless communication network. 
     Another example for the second event trigger may be based on a time trigger. The time trigger may be set by the vendor of multi-SIM communication device  101   c , the user of multi-SIM communication device  101   c , retrieved from a remote server or retrieved internally from the multi-SIM communication device. The user may set for the second trigger to occur based on time. There are many reasons why this may be used but one example may be when the second network operator sets its tariff prices to be more expensive between certain time of the day. The user may set the time trigger to occur at a specific time for SIM  292   b , when SIM  292   b  was used by RF unit  293   a  to establish a wireless connections with the second communication network. Similarly, the first event trigger also be based on the time trigger, for example, when a specified time of the day has been reached, the first event trigger occurs. 
     In one embodiment of the present invention, a trigger monitor is implemented into multi-SIM terminal  101 . The trigger monitor monitors for how frequent the SIM cards are being selected based on a predefined time period. There are many reasons for why the SIM cards are being selected frequently such as when the first and second event triggers are occurring frequently. For example, when a SIM card such as SIM card  291   a  from  FIG. 2C  is no longer operational, the first event trigger occurs as step  501 . A second SIM card such as SIM card  291   b  is used in step  502 . When SIM card  291   b  is no longer operational, the second event trigger occurs at step  503 . At step  504 , an operational SIM card may be SIM  291   a , SIM  291   b  or another SIM card. When the selected operation SIM card is no longer operational again, the first event trigger may occur again, leading to the second event trigger and so on. The reason why the SIM card may no longer be operational could be due but not limited to failure of the wireless communication networks, failure of the SIM card, being outside of the coverage area of any base station etc. When the SIM card selection frequency reaches a threshold and a specified period of time has lapsed, the processing unit may apply a time delay to one or both event triggers so that the performance of step  504  is delayed. If after another predefined period of time, the frequency of SIM card selection still has the characteristics of for example, a SIM card failure, processing unit may instruct the RF units to perform an action such as power-cycle, enter sleep mode, enter a low power mode etc. The purpose of this implementation is to minimize the chance of the first and the second event trigger from occurring repeatedly. 
     After the second event trigger has occurred, step  504  is performed by processing unit  295  to select an operational SIM card. The operational SIM card can be the first SIM card, the second SIM card or another SIM card. As there is no SIM card other than SIM cards  291   a  and  291   b  in this example, there is no another SIM card. If there are other SIM cards other than SIM cards  291   a  and  291   b  in multi-SIM communication device  101   c , the other SIM cards can be the another SIM card. After a SIM card is selected to be the operational SIM card, processing unit  295  can use the operational SIM card to establish a wireless connection. There can be no SIM card selected to be the operational SIM card and result in no wireless connection being able to be established. 
     In one variant, after step  504 , processing unit  295  will go back to step  501  when the first event trigger is triggered. This allows the first SIM card be used again in case the first event trigger is triggered. For example, the operational SIM card is SIM card. 
       FIG. 6  illustrates processes according to one of embodiments of the present invention that an operational SIM card can be selected in step  504 . There is no limitation that the processes of  FIG. 6  are the only processes to perform step  504 . 
     At step  601 , processing unit  295  determines the list of SIM cards that can be used as the operational SIM card. As multi-SIM communication device  101   c  has SIM cards  291   a  and  291   b , the list of SIM cards is consisted of SIM cards  291   a  and  291   b . If one of the SIM cards  291   a  and  291   b  is removed, the removed SIM card is not in the list of SIM cards. If a multi-SIM communication device has ten SIM cards, the list of SIM cards is consisted of the ten SIM cards. In one variant, SIM cards that can be included in the list of SIM cards are subject to one or more rules. For example, a rule can be that the second SIM card, which is SIM  291   b  in this embodiment, cannot be in the list of SIM cards as the conditions for triggering the second event trigger may still apply. In another example, SIM card(s) that is(are) being used by other RF unit(s) cannot be in the list of SIM cards as the SIM card(s) has(have) already being used. The rule can be entered by a user of the multi-SIM communication device, the manufacturer of the multi-SIM communication device or retrieved from a remote server. 
     At step  602 , processing unit  295  select a SIM card from the list of SIM cards. Multi-SIM communication device  101   c , for illustration purpose only, selects SIM card  291   a . The selection can be based on one or more criteria. For example, the SIM card that has the lowest price tariff is selected. In another example, the SIM card that may have the best network performance is selected. The network performance may be determined by using results reported by a Scanning RF Unit. In one variant, the one or more criteria at step  602  may be the same as the one or more criteria at step  502 . 
     At step  603 , if there is no SIM card can be selected, the selection process stops at step  607  that no operational SIM card is selected. When all the SIM cards in the list of SIM cards have been used to establish corresponding wireless connections at step  604  and no wireless connection can be established at  605 , there will be no further SIM card in the list of SIM cards can be selected at step  602  and results in no operational SIM card is selected. 
     At step  604 , the selected SIM card is used to establish a wireless connection. For example, selected SIM card at step  603  is SIM card  291   a , then processing unit  295  tries to use RF unit  293   a  and SIM card  291   a  to establish a wireless connection. If a wireless connection can be established, this indicates that the SIM card selected, i.e. SIM card  291   a  in this example, can be the operational SIM card at step  606 . If no wireless connection can be established, then step  602  will be performed to select another SIM card from the list of SIM cards. There are myriads reasons why a wireless connection cannot be established. For example, multi-SIM communication device  101   c  is out of the coverage area of the network of the network operator corresponding to SIM card  291   a  or the quota of SIM card  291   a  is used up. 
     In one embodiment, multi-SIM communication device  101   a  may apply the processes in  FIG. 5  and  FIG. 6  to RF unit  221   b  and SIM cards  201   b  and  201   c  that RF unit  221   b  are capable of connecting to through SIM card interfaces  221   b  and  211   c  respectively. However, multi-SIM communication device  101   a  does not apply the processes in  FIG. 5  and  FIG. 6  to RF unit  221   a  and SIM cards  201   a  as RF unit  221   a  is only accessible to SIM card  201   a . For illustration purpose only, in this embodiment, SIM card  201   b  is the first SIM card and SIM card  201   c  is the second SIM card. In one variant, RF unit  221   a  can be used as a Scanning RF Unit to provide received signal qualify information for processing unit  231  to select operational SIM card at step  502  and/or step  504  when received signal qualify is a criteria for step  502  and/or step  504 . In one variant, RF unit  221   a  is not used as a Scanning RF Unit and instead is used to establish a wireless connection. This allows two wireless connections established at multi-SIM communication device  101   a.    
     In one embodiment, multi-SIM communication device  101   a  may apply the processes in  FIG. 5  and  FIG. 6  to SIM cards  201   a ,  201   b  and  201   c . For illustration purpose only, in this embodiment, SIM card  201   a  is the first SIM card and SIM card  201   b  is the second SIM card. When SIM card  201   a  is used, RF unit  221   a  is used to establish a wireless connection while RF unit  221   b  is not used to establish a wireless connection or is used as a Scanning RF Unit. When SIM card  201   b  used at step  502 , RF unit  221   b  is used to establish a wireless connection while RF unit  221   a  is not used to establish a wireless connection or is used as a Scanning RF Unit. Therefore, only one of SIM cards  201   a ,  201   b  and  201   c  is used to establish a wireless connection and other two SIM cards can be used as backups. 
     In one embodiment, multi-SIM communication device  101   a  may apply the processes in  FIG. 5  and  FIG. 6  to SIM cards  201   a ,  201   b  and  201   c . For illustration purpose only, in this embodiment, SIM card  201   b  is the first SIM card, SIM card  201   a  is the second SIM card and operational SIM card can be selected from SIM card  201   b  or SIM card  201   c . This allows SIM card  201   a  to be used quickly when SIM card  201   b  is not used due to the first event trigger. This also allows processing unit  295  to have adequate time to determine whether to use SIM cards  201   b  or  201   c  as the operational SIM card as only one of SIM cards  201   b  and  201   c  can be used by RF unit  221   b  at any moment to establish a wireless connection. 
     In one variant, RF unit  221   a  can be used as a Scanning RF Unit to provide received signal qualify information for processing unit  231  to select operational SIM card at step  502  and/or step  504  when received signal qualify is a criteria for step  502  and/or step  504 . 
     In one embodiment, multi-SIM communication device  101   b  may apply the processes in  FIG. 5  and  FIG. 6  to RF units  271   a  and  271   b  and SIM cards  251   a ,  251   b  and  251   c  that RF units  271   a  and  271   b  are capable of connecting to through SIM card interface selector  284 , and then SIM card interfaces  261   a ,  261   b  and  261   c  respectively. When processing unit  281  selects SIM cards for use as the first SIM card, the second SIM card and the operational SIM card, processing unit  281  can instruct SIM card interface selector  284  to select one of SIM cards  251   a ,  251   b  and  251   c  for RF units  271   a  or  271   b . In one example, SIM cards  251   a  is the first SIM card and the operational SIM card; SIM card  251   b  is the second SIM card and SIM card  251   c  is used for a Scanning RF unit to allow frequent observation of received signal quality. 
     In one variant, multi-SIM communication device  101   b  is configured in such a way where RF unit  271   a  is able to use SIM cards  251   a  and  251   b  as the first SIM card, the second SIM card and the operational SIM card. RF unit  271   b  is able to use SIM card  261   c  only. When processing unit  281  selects SIM cards  251   a  and  251   b  to the first SIM card, the second SIM card and the operational SIM card, processing unit  281  can instruct SIM card interface selector  284  to perform the selection. Therefore, multi-SIM communication device  101   b  is capable of establishing two wireless connections. A plurality of tunnels can be established in the two wireless connections. Data packets can be transmitted and received through the plurality of tunnels. Further, the plurality of tunnels can be aggregated to form one aggregated VPN connection. 
     There is no limitation for number of RF units in a multi-SIM communication device for the present invention. The number of SIM cards is at least two. It is preferred to have more SIM cards and RF units as a RF unit needs at least one SIM card in order to establish a wireless connection.