Abstract:
A WLAN router connected via a cellular network (e.g. LTE) to the Internet is disclosed; a plurality of SIMs (subscriptions), each associated with a user of the router, may be plugged into the router (or soft SIMs used); simultaneous Internet access for a plurality of users is achieved, even if the WLAN router does only have one TX/RX equipment, by the following features: the WLAN router—when receiving a portion of network traffic for a user—determines the subscription that the portion is associated with and updates a data usage quota for the subscription accordingly by an amount of data corresponding to said portion; thereafter, it is decided whether future network traffic for that subscription shall be transmitted over the same network connection or another subscription&#39;s network connection based on the updated data usage quota; thus, the router carries out load balancing between the subscriptions.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to load balancing between at least two subscriptions in a routing apparatus. Specifically, load balancing between at least two subscriptions in a routing apparatus, wherein each subscription is associated with a dedicated connection, and wherein each subscription is associated with a certain data usage quota. 
       BACKGROUND 
       [0002]    The number of Internet connections using mobile broadband continues to rise. With the introduction of flat rate—i.e. fixed price for an (almost) free data amount (or at least reasonable large, around 20 GB/month)—in combination with high performance modems for 3GPP High Speed Packet access (HSPA or HS) or 3GPP Long Term Evolution (LTE) cellular systems, many users actually skip fixed line subscriptions, such as Asynchronous Digital Subscriber Lines (ADSLs), and only rely e.g. on a Mobile Broadband (MBB) connection. 
         [0003]    Recently, there have been a number of 3 rd  Generation (3G) and 4 th  Generation (4G) routers out on the market, where the user uses a subscription—e.g. by plugging in a Subscriber Identity Module (e.g. SIM) into the router, or into a modem assigned to the router (e.g. via Universal Serial Bus, USB)—and then via a short range communication system (such as Wireless Local Area Network, WLAN) included in the router, the entire household of the user may be connected to the Internet. 
         [0004]    In many applications, it is to be expected that more than one device is connected e.g. to a gateway/router using e.g. short range communication (such as WLAN or Bluetooth®), and that in turn, the gateway/router is connected to the Internet e.g. via a cellular system connection, such as LTE, Wideband Code Division Multiple Access-High Speed (WCDMA-HS) or Enhanced General Packet Radio Service (EGPRS). One example may be Machine-to-Machine (M2M) applications, for instance sensors, performing a measurement and sending a report on the measurement e.g. to the router. Further, the sensors may feed the information e.g. via a network connection to a data base. 
         [0005]    Another example could be MBB users in a house with several apartments. Each apartment (which may constitute a user) may be connected to such a (cellular) router (e.g. a high end LTE-advanced modem). Instead of all users having their own (low-end) router (or modem), they share one high-end modem for high speed connection to Internet. Such a router (or modem) could be placed on an optimized position in order to exploit the best available radio channel conditions. 
         [0006]    In the above-mentioned use-cases, the different users (or their respective devices) may have different network subscriptions (implemented e.g. by a Subscriber Identity module, SIM), typically placed in respective users smart phone, but via for instance a so-called soft SIM (involving a so-called Bluetooth® SIM connect CHECK message), the high-end modem may be used (and then, for example, 1 Gbit/s instead of 10 Mb/s as may be possible in the smart phone alone, can be achieved). 
       PROBLEMS WITH EXISTING SOLUTIONS NOT REALIZED BY THE PRIOR ART 
       [0007]    There has been proposed a mobile phone with dual-SIM capability and a single baseband (for instance, a single transceiver, TRX). In such a solution, only one subscription (or SIM) could be the active at a time, i.e. in case there is one incoming call to one subscription, the other subscription is detached from the network and the speech service is enabled for the first subscription. 
         [0008]    However, such a voice centric approach does not support MBB scenarios, where several users/devices with different MBB subscription may simultaneously need connection to the Internet, i.e. as in the examples described above. One naïve approach would be to have separate network modems, or a router having dual (or multiple) SIMs and dual (or multiple) transceivers. This will typically add cost and complexity to such a router (which would have to support n subscriptions implying n transceivers). 
       SUMMARY 
       [0009]    Accordingly, there is a need for an implementation of a scheme that avoids one or more of the problems discussed above, or other problems. In particular, in one embodiment, there is a need for low cost single transceiver routers/devices capable to handle simultaneously MBB traffic for multiple subscriptions. 
         [0010]    In other words, the present invention solves, for example, the problem of how to balance the data usage between different subscriptions (e.g. SIMs) in a multi-SIM router without any need for dual (or multi) transceivers. In the above-described scenarios, it would be fair to pay for the MBB connection in relation to the corresponding amount of data used. In order to be able to solve this issue, as said, a router capable of managing multiple subscriptions (e.g. SIMs) is needed. 
         [0011]    In a first aspect, there is provided a method for load balancing between at least two subscriptions in a routing apparatus, wherein each subscription is associated with a dedicated connection, wherein each subscription is associated with a certain data usage quota, and wherein the method is performed in the routing apparatus and comprises the steps of receiving a portion of network traffic attributable to one of the at least two subscriptions over a first dedicated connection associated with a first subscription; determining the one subscription the portion of network traffic is associated with; updating the data usage quota of the determined subscription by an amount of data corresponding to the portion of network traffic; and deciding, based on the updated data usage quota of the determined subscription, continuing usage of the first dedicated connection associated with the first subscription for subsequent network traffic associated with the determined subscription or enabling a second dedicated connection associated with at least one other subscription different from the first subscription for subsequent network traffic associated with the determined subscription. 
         [0012]    In a first refinement of the first aspect, the enabling step may further comprise disabling the first dedicated connection of the determined subscription. In this way, resources are efficiently used. 
         [0013]    In a second refinement, the portion of network traffic may be one of a data packet, a burst of data packets and a data frame. If so, each subscription may be associated with an Internet Protocol, IP, address, and the determining step may be performed based on an IP address of the data packet. Moreover, the association between each subscription and the IP address may be performed by an interface on which an external communication device is associated with a particular subscription. In this way, the present invention is implemented efficiently, using available system resources as far as possible. 
         [0014]    In a third refinement, a pre-association between each subscription and a dedicated access key may be defined, and the association between each subscription and the IP address may be performed when an external communication device authenticates with one of the access keys. Also in this way, the present invention is implemented efficiently, using available system resources as far as possible. 
         [0015]    In a fourth refinement, the determining and updating steps may be performed for portions of network traffic on an Uplink, UL, of the first dedicated connection, a Downlink, DL, of the first dedicated connection, or both of the UL and DL of the first dedicated connection. If so, in the UL case, the first dedicated connection may be a fixed line; in the DL case, the first dedicated connection may be a cellular network connection; or in case of both UL and DL, the first dedicated connection may be a short range wireless connection (such as WLAN). 
         [0016]    In a fifth refinement, the deciding step may comprise load balancing the total amount of network traffic transported by means of the determined subscription proportional to the amount of network traffic actually associated with the determined subscription over a predetermined time period. If so, the predetermined time period may be a fixed periodic time interval; alternatively, the predetermined time period may be event-based. Moreover, in the fifth refinement, the enabled subscription may be selected according to which subscription owes the highest amount of data to the determined subscription. Alternatively, the enabled subscription may be pre-selected for offload, and another enabled subscription may be selected according to which subscription owes more amount of data to the determined subscription than the currently pre-selected enabled subscription. As still another alternative, the enabled subscription may be pre-selected from a list of candidate enabled subscriptions, and another enabled subscription may be selected from the list according to which subscription owes more amount of data to the determined subscription than the currently pre-selected enabled subscription. In this way, it is ascertained that the switching between the subscription is performed in a “fair” way, meaning that substantially all subscription allow the basically the same amount of “foreign” network traffic. 
         [0017]    In a sixth refinement, the enabling step may involve a connection release procedure for the connection of the determined subscription. In addition or alternatively, the enabling step may involve a connection setup procedure for the connection of the enabled subscription. In this way, the present invention may be practised more efficiently by exploiting reusability of existing standard measures (here: connection release/setup) as far as possible. 
         [0018]    In a seventh refinement, the method may further comprise, in response to the enabling step, transmitting subsequent portions of network traffic associated with the determined subscription over the first dedicated connection of the enabled subscription. 
         [0019]    In a second aspect, there is provided a computer program product comprising program code portions for performing the method of the first aspects (and its refinements) when the computer program product is executed on one or more computing devices. Moreover, the computer program product may be stored on a computer readable recording medium. 
         [0020]    It is to be noted that a network entity (or several entities) may implement any of the technical details set forth for the method aspects herein, and thus achieves the same advantages. In other words, the network entity (or entities) may comprise components adapted to perform any of the method steps disclosed herein. There is also provided, in a third aspect, a routing apparatus comprising one or more of such entities. 
         [0021]    In a first refinement of the third aspect, the apparatus further comprises means for accommodating at least two Subscriber Identity Module, SIM, cards. Alternatively, there may be accommodated at least two soft Subscriber Identity Modules, SIMs. As another alternative, there may be accommodated at least one virtual Subscriber Identity Modules, SIMs. In the latter case, a (e.g. physical) SIM may be accommodated in the apparatus and may constitute the virtual SIM for an external communication device which is associated with the SIM. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The embodiments of the technique presented herein are described herein below with reference to the accompanying drawings, in which: 
           [0023]      FIG. 1  shows a network system employing a first or second example of the exemplary device embodiment of the present invention; 
           [0024]      FIG. 1A  shows components comprised in a first exemplary device embodiment realized in the form of router; 
           [0025]      FIG. 1B  shows a network system employing a second exemplary device embodiment realized in the form of router; 
           [0026]      FIG. 2  shows a method embodiment which also reflects the interaction between the components of the device embodiment; and 
           [0027]      FIG. 2A  shows a first exemplary embodiment of the method embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    In the following description, for purposes of explanation and not limitation, specific details are set forth (such as particular signalling steps) in order to provide a thorough understanding of the technique presented herein. It will be apparent to one skilled in the art that the present technique may be practised in other embodiments that depart from these specific details. For example, the embodiments will primarily be described in the context of a HS/LTE-type communication system; however, this does not rule out the use of the present technique in other communication systems. 
         [0029]    Moreover, those skilled in the art will appreciate that the services, functions and steps explained herein may be implemented using software functioning in conjunction with a programmed microprocessor, or using an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP) or general purpose computer. It will also be appreciated that while the following embodiments are described in the context of methods and devices, the technique presented herein may also be embodied in a computer program product as well as in a system comprising a computer processor and a memory coupled to the processor, wherein the memory is encoded with one or more programs that execute the services, functions and steps disclosed herein. 
         [0030]    Moreover, concerning the terms “router” or “routing apparatus” as used for the purpose of this description, for instance, an entity may be referred to, in which e.g. the modem part of a combined router and modems (e.g. WLAN/cellular) device is altered, or which implements the “router” as described as an extension that is external to both the ordinary router and modem, as long as it is ascertained that subscriptions may be switched for the modem and measurements on the traffic to/from the modem. In addition or alternatively, if the router/modem apparatus has support for wireless subscriptions (or SIMs), the “router” as described may be implemented external to the router/modem by performing the measurements of network traffic externally (e.g. in the computers from operators or based on information from operators), and by instructing the modem to switch the subscription based on the decision to be described herein below. However, preferably, the “router” as described is provided inside the ordinary router/modem apparatus. 
         [0031]    In addition, the present description shows the special case of “Dual-SIM”. However, “Dual-SIM” is to be construed to “Multi-SIM”, in the sense that the present disclosure also covers routers capable of handling triple, quadruple etc. subscription routers. Furthermore, the present disclosure covers physical SIM cards of any size, as well as soft-SIM solutions. The present disclosure also covers “virtual SIM” solutions, i.e. where the SIM is physically placed in an external unit, but via e.g. a wireless connection to the router, the route has access to the SIM (for instance, using Bluetooth® SIM access profile). 
         [0032]    Without being restricted thereto, as an example, the present invention proposes a method and apparatus implemented e.g. in a single (e.g. LTE, HS) transceiver router capable of managing multiple subscriptions (e.g. SIMs), such that the amount of data delivered over a respective subscription network connection is in proportion to the total amount of data used by a user/device associated with the respective subscription over a specified time period. 
         [0033]    In contrast to the prior art—the dual-SIM approach used e.g. for voice services—, a specific application data packet to/from a first user (e.g. having a first SIM subscription) not necessarily needs to be transmitted over a network connection for that subscription, as long as the total amount of data transmitted/received over a specific network connection using a first subscription is substantially equivalent to the total amount of data packets associated with a user of the first subscription (over a specified time period, such as an hour/day/week/month etc.). As an example, it may be assumed that a user of subscription (e.g. SIM #1) uses 60% of data, and another user uses another subscription (e.g. SIM #2) for 40% of data. At the end of the time period, 60% of data should be delivered over the (first) subscription&#39;s dedicated connection, and 40% should be delivered over the other subscription&#39;s dedicated connection. As will be described herein below in greater detail, a control unit implemented in the router may solve this problem. 
         [0034]      FIGS. 1 ,  1 A and  1 B show a general embodiment of the router  1001  as well as two examples of the routers  1001 , wherein the first and second examples might supplement one another. As shown in  FIGS. 1 ,  1 A and  1 B, the router  1001  comprises a core functionality (e.g., one or more of a central processing unit (CPU), dedicated circuitry and/or a software module)  10011 , an optional memory (and/or database)  10012 , an optional transmitter  10013  and an optional receiver  10014 . Moreover, the router  1001  comprises a determiner  10015 , an updater  10016 , a decider  10017 , a continuer  10017   a , an enabler (or disabler)  10017   b  (the continuer  10017   a  and the enabler  10017   b  may be comprised in the decider  10017 ), an optional accommodator  10018  (for accommodating either physical or soft SIMs  101 ), a short range communication unit (e.g. WLAN)  10019 , a cellular communication unit (that may support at least one of the following cellular systems LTE, HS and/or GSM)  100110 , an interface unit  100111 , and a switching unit  100112 . 
         [0035]    As partly indicated by the dashed extensions of the functional block of the CPU  10011 , the determiner  10015 , the updater  10016 , the decider  10017 , the continuer  10017   a , the enabler (or disabler)  10017   b , the accommodator  10018 , the short range communication unit  10019 , the cellular communication unit  100110 , the interface unit  100111 , and the switching unit  100112  (of the Router  1001 ) as well as the memory  10012 , the transmitter  10013  and the receiver  10014  may at least partially be functionalities running on the CPU  10012 , or may alternatively be separate functional entities or means controlled by the CPU  10011  and supplying the same with information. For the router  1001 , the transmitter and receiver components  10013 ,  10014  may be realized to comprise suitable interfaces and/or suitable signal generation and evaluation functions. 
         [0036]    The CPU  10011  may be configured, for example, using software residing in the memory  10012 , to process various data inputs and to control the functions of the memory  10012 , the transmitter  10013  and the receiver  10013  (as well the determiner  10015 , the updater  10016 , the decider  10017 , the continuer  10017   a , the enabler (or disabler)  10017   b , the accommodator  10018 , the short range communication unit  10019 , the cellular communication unit  100110 , the interface unit  100111 , and the switching unit  100112  (of the router  1001 )). The memory  10012  may serve for storing program code for carrying out the methods according to the aspects disclosed herein, when executed by the CPU  10011 . 
         [0037]    It is to be noted that the transmitter  10013  and the receiver  10014  may be provided as an integral transceiver, as is indicated in  FIG. 1A . It is further to be noted that the transmitters/receivers  10013 ,  10014  may be implemented as physical transmitters/receivers for transceiving via an air interface or a wired connection (e.g., between the Router  1001  and a base station  10021  when they are embodied as separate entities), as routing/forwarding entities/interfaces between network elements (e.g., between the Router  1001  and the base station  10021 ,  10021  when they are embodied as functionally adjacent entities), as functionalities for writing/reading information into/from a given memory area (e.g., between the Router  1001  and the base station  10021 ,  10021  when they are embodied as two (or more) logical units disposed on one physical unit) or as any suitable combination of the above. At least one of the above-described determiner  10015 , updater  10016 , decider  10017 , continuer  10017   a , enabler (or disabler)  10017   b , accommodator  10018 , short range communication unit  10019 , cellular communication unit  100110 , interface unit  100111 , and switching unit  100112  (of the router  1001 ), or the respective functionalities, may also be implemented as a chipset, module or subassembly. 
         [0038]      FIG. 1B  shows a network system employing a first or second example of the exemplary device embodiment of the present invention. As shown in  FIG. 1 , as a non-limiting example, the router  1001  may be a multi-SIM router; the router  1001  may be connected to one or more users M 1 , M 2 , . . . , Mn (or their respective terminals)  1003 ,  1004 ,  1005 . Still further, the router  1001  may be in communication with said base stations  10021 ,  10022 , which base stations may in turn serve as an access point to the Internet  1002  (e.g. via the first or second subscriptions network). In this case, the router may have an internal modem (which may be constituted by the cellular communication unit  100110 ), and the accommodator  10018  serves for supporting (at least) two SIM cards  101 . The router  1001  may further comprise the short range wireless communication unit  10019  (employing e.g. WLAN, Bluetooth® etc.), the switching unit  100112  for switching to the SIM to be used, and a control unit (or CPU)  10011  controlling e.g. the switch unit  100112  (note that the switch unit  100112  may be based on connection release and connection setup procedures). The control unit  10011  may utilize information from the connection and from the cellular communication unit  100110  for setting the (SIM) switching unit  100112 . 
         [0039]      FIG. 1B  shows a network system employing a second example of the exemplary device embodiment of the present invention (supplementing the first example). As shown in  FIG. 1B , as a non-limiting example, the router  1001  may be the dual-SIM router. Here, as said, the router  1001  may comprise the cellular communication unit  100110 , supporting e.g., LTE WCDMA/HS or similar, the short range wireless communication unit  100  e.g.  19  (WLAN, Bluetooth® etc.) (or fixed connection), the switch unit  100112  switching which subscription (e.g. SIM) to use, and the control unit (or CPU)  10011  controlling the switching unit  100112 . The SIMs  101  could either be placed physically in the router/device  1001  (e.g. by means of the accommodator  10018 ), or could be a virtual SIM, with the SIM information being transferred over a wireless link, as described above. The router  1001  may also have the memory (storage means)  10012  for storing data bases/tables according to description above; for instance, the memory  10012  may store the quota for each subscription. 
         [0040]      FIG. 2  illustrates an embodiment of a method for managing connection states of at least two subscriptions. In the signalling diagram of  FIG. 2 , time aspects between signalling are reflected in the vertical arrangement of the signalling sequence as well as in the sequence numbers. It is to be noted that the time aspects indicated in  FIG. 2  do not necessarily restrict any one of the method steps shown to the step sequence outlined in  FIG. 2 . This applies in particular to method steps that are functionally disjunctive with each other. For instance, all steps S 1  to S 5  are shown to be timely substantially flowing; however, especially steps S 4 - 2   a  (disabling) and S 5  (transmitting) may or may not be carried out (directly) subsequently, timely overlapping, (substantially) concurrently, and also (substantially) simultaneously. 
         [0041]    Referring still to the signalling diagram of  FIG. 2  (to be read along with the router  1001  illustrated in  FIGS. 1 ,  1 A and  1 B), each subscription  101  is associated with a dedicated connection, wherein each subscription is associated with a certain data usage quota. As shown in  FIG. 1B , as a non-limiting example, the first subscription  101  #1 may involve physical SIM cards in both the router  1001  and the external unit  1003 , whereas the second subscription  101  #2 may be a virtual SIM as described above. 
         [0042]    In step S 1 , the receiver  10014  (possibly in conjunction with the short range communication unit  10019  and/or the interface unit  100111 ) of the router  1001  performs receiving a portion of network traffic (e.g. data packet (DP), DP burst or entire frame) attributable to one of the at least two subscriptions. 
         [0043]    In step S 2 , the determiner  10015  (possibly in conjunction with the CPU/control unit  10011 ) performs determining the one subscription (e.g. SIM  101  #1) the portion of network traffic is associated with. 
         [0044]    In step S 3 , the updater  10016  (possibly in conjunction with the CPU/control unit  10011 ) performs updating the data usage quota of the determined subscription by an amount of data corresponding to the portion of network traffic. For instance, if the portion of network traffic is a data packet, the size of the DP e.g. in bits may be deducted from or added to the quota of the determined subscription. 
         [0045]    Lastly, in step S 4 , the decider  10017  (possibly in conjunction with the CPU/control unit  10011 ) performs deciding, based on the updated data usage quota of the determined subscription. On the one hand, in step S 4 - 1 , the continuer  10017   a  (possibly in conjunction with the CPU/control unit  10011 ) performs continuing usage of the dedicated connection of the determined subscription for subsequent network traffic associated with the determined subscription  101  #1; otherwise, the enabler  10017   b  (possibly in conjunction with the CPU/control unit  10011 ) performs enabling a dedicated connection associated with at least one other subscription  101  #2 different from the determined subscription for subsequent network traffic associated with the determined subscription. 
         [0046]    In an optional step S 4 - 2   a , the disabler  10017   b  (possibly in conjunction with the CPU/control unit  10011 ) performs disabling the dedicated connection of the determined subscription. 
         [0047]    Finally, in an optional step S 5 , the transmitter  10014  (possibly in conjunction with the CPU/control unit  10011 , the short range communication unit  10019 , the cellular communication unit  100110 , and/or the interface unit  100111 ) performs transmitting subsequent portions of network traffic associated with the determined subscription over the dedicated connection of the enabled subscription. 
         [0048]      FIG. 2A  shows a first exemplary embodiment of the method embodiment, to the details of which the present disclosure is not to be restricted to. 
         [0049]    As said, the above-described router/device  1001  includes communication possibilities, e.g. wired or wireless (such as WLAN or Bluetooth®) to the external/remote devices  1003 ,  1004 , using the different subscriptions (e.g. SIM)  101 . Recall that the router  1001  may also include the Cellular (network) communication  100110  unit, capable of supporting (at least) data communication according to cellular protocols, such as EGPRS, WCDMA/HS or LTE. For example, via the switch unit  100112 , the cellular communication unit  100110  is connected to a network node using subscription (e.g. SIM) i (thus embodying an optional preparatory step S 0 ). 
         [0050]    A data packet (as an example for the network traffic portion) is received, e.g. via the cellular communication unit  100110  or from one of the remote units  1003 ,  1004  connected to the router/device  1001  (thus embodying step S 1 ). 
         [0051]    The control unit/CPU  1001  (determiner  10015 ) determines the origin (or destination) of the packet in terms of which device the packet is sent from, or is delivered to (thus embodying step S 2 ). 
         [0052]    As an example, the origin (or destination) can be determined by identifying the packet&#39;s associated IP address. In turn, the IP address(es) of each device  1003 ,  1004  may be associated to one subscription (e.g. SIM)  101  (wherein the association process is described herein below in greater detail). The control unit  1001  (updater  10016 ) then updates e.g. a data base (such as a list/table or similar) including information of consumed data (one embodiment of the quota) for respective connected set of device(s)  1003 ,  1004  associated to a particular subscription (e.g. SIM i). The control unit  1001  (updater  10016 ) also updates the total amount (another embodiment of the quota) of data consumed over the network connection with the particular SIM i (thus embodying step S 3 ). 
         [0053]    In one example, only the DL data (e.g. from a network node via base stations  10021 ,  10022 ) is counted and stored (in the quota), in another example, only the UL data (to the network node) is counted and stored, and in yet another example, both UL and DL—concerning the quota—are updated and stored (for instance, in the same record or in separate records). Hence, it is achieved that a data packet associated with a first subscription (e.g. SIM)  101  #1 may be delivered (transmitted or received) over a network connection associated with a second SIM  101  #2. The control unit  10011  (decider  10017 ) may then, based on the amount of data each user has consumed and also the total amount of data the respective network connection with respective SIM has consumed (one or both of the amount and total amount embodying the quota), determine whether a switch (by means of the switch unit  100112 ) in the network detection is needed (thus embodying step S 4 ). 
         [0054]    The control unit  10011  may be considered to strive for allocating the same amount of consumed data from device(s)  1003 ,  1004  associated with a particular subscription  101  on this subscription over a given time period. Hence, the router  1001  is to balance the consumed data amount on a subscription  101  in proportion to the data originating from/designating for devices  1003 ,  1004  associated with that subscription (detailed description of such a scheme is described below). The time period, as a non-limiting example, may be not less than 10 to 30 minutes (but may also be in the order of hours, days, weeks or months) or, alternatively, can be event based when devices  1003 ,  1004  or subscriptions  100  connect or disconnect. 
         [0055]    A subscription may be paid for on a per-day to a per-month basis, and hence, the balancing proposed may be made on a smaller time scale than the subscription payment period. The switching may be performed by a regular connection release and connection setup procedures, according to the respective cellular communication protocol, as described above. If the switching time is e.g. in the order of 100 ms to 2,000 ms, than the switching is not necessarily performed per data packet (which might have a negative effect on the throughput), but, as described above, is performed e.g. not more often than on a per-minute basis. 
         [0056]    Alternatively or in addition, the switching may be performed when low data traffic is measured over the network connection, for instance during times at which the network connects to a lower communication state (for instance, LTE Radio Resource Connection, RRC_connected with a long discontinuous reception, DRX, or down-switch to idle state, or in WCDMA/HS when switching from Cell Dedicated Channel, Cell_DCH to Cell Forward Access Channel, Cell_FACH, or to Universal Mobile Telecommunications System Terrestrial Radio Access Network Registration Area Paging Channel, URA_PCH/idle.). 
         [0057]    As described above, the balancing mechanism may be triggered by network events (idle), device/SIM events (attach/detach) or (periodic) time events or a combination thereof. In an example, one balance method may reside in selecting the subscription which owes the most amount of data to other subscriptions. This can be performed by completely sorting the above-described records e.g. based on SIM associated consumption subtracted with all transfers on that SIM. The most favourable result is selected (this approach is preferred since the complexity of parsing a complete sort is likely reasonable). Another alternative resides in selecting any first encountered subscription during search of the records that owes more than the current selected subscription. Yet another alternative resides in keeping a short list of candidate subscriptions of which the one that owes most is selected similarly as to the complete sort. Preferably, to get on the short list, a subscription that consumes above a certain threshold of amount of data during a time period is selected. 
         [0058]    As described above, the association of an IP-address of a device  1003 ,  1004  and subscription SIM  101  can be established in several ways. For example, the router  1001  may have the interface unit  100111  on which the device  1003 ,  1004  connects and requests to be associated with a particular subscription  101 . Such an interface unit  100111  may be realized e.g. over a local network and may use the Hyper Text Transfer Protocol (Secure) (HTTP(S)). Alternatively, the subscription/SIM  101  may be identified e.g. by the phone number and by authenticating (e.g. by supplying the Personal Identification Number, PIN, code). The IP-address could be supplied either explicitly or implicitly in the request; implicitly by the device  1003 ,  1004  using e.g. a certain IP address to communicate with the router  1001 . Alternatively, the router  1001  may be configured to have several wireless Local Access Network (LAN) authentications, e.g. several Wi-Fi™ Protected Access (WPA) keys, each pre-associated with a SIM subscription  101 . The device  1003 ,  1004  (IP-address) then authenticating using a particular WPA key may be associated with the subscription  101 . 
       ADVANTAGES OF THE INVENTION 
       [0059]    With the proposed invention, multiple users associated with different subscriptions (e.g. SIMs) may simultaneously use a multiple SIM, single TRX modem/router/device and at the same time, achieve a fair proportion (fair charge) of the data allocated on respective subscription (e.g. SIM). 
         [0060]    It is believed that the advantages of the technique presented herein will be fully understood from the foregoing description, and it will be apparent that various changes may be made in the form, constructions and arrangement of the exemplary aspects thereof without departing from the scope of the invention or without sacrificing all of its advantageous effects. Because the technique presented herein can be varied in many ways, it will be recognized that the invention should be limited only by the scope of the claims that follow.