OA19327A - Coordination of simultaneous multi-rat camping - Google Patents

Abstract

The present invention relates to the coordination of simultaneous multi-RAT camping in in a wireless communication network that provides radio access for a terminal device via at least a first and second wireless radio access operating with different radio access technologies. The improved multi-RAT camping is achieved by transmitting, by a network node, an indication regarding a set of camping areas, CAs, including a first set of camping areas being associated with the first RAT and a second set of camping areas being associated with the second RAT; performing, by the terminal device, camping in a coverage area defined based on the set of CAs; and updating, by the terminal device, the communication network with a geographic location of the terminal device a) when the terminal device enters a new coverage area being different from the coverage area defined by both the first and second set of CAs as a first mechanism, or b) when the terminal device enters a new coverage area being different from the coverage area defined by one of the first and second set of CAs as a second mechanism.

Description

In the following, embodiments are described with reference to the appended Figures. It is noted that the following description contains examples only and should not be construed as limiting the invention. A person skilled in the art will recognize additional features and advantages upon reading the following detailed description. Further, similar or same reference signs indicate similar or same éléments or operations.

Embodiments of the présent invention facilitate having a terminal device (UE) to simultaneously camp on at least two different wireless radio access technologies (RATs) when an interworking or intégration between the two RATs is employed to increase the flexibility for the UE to move around the coverage of different RATs without having to update the network when it moves from one RAT to another. Here, the terminal device (which is also referred to as UE in the following) may be a mobile or a fixed terminal device. The terminal device is a wireless terminal device, and may be a (fixed or mobile) user device (UE) or a MTC device, for example a “self-driving car”, capable of having a radio access over at least two different radio access technologies to one more base station (eNB). Further, the network node (base station) is a radio access network node of a wireless communication network, in particular a radio access node for providing a radio access to the terminal device, and also has a coverage area (including based on the beam-forming process, as described above) in which it may provide the radio access. It is also noted the base station may also support multiple radio accesses, such as the LTE Evolution radio access technology and the 5G radio access technology (NR). Such a radio access may be of any spectrum or standard (GSM, GPRS, 3G, 4G, LTE, 5G, NR, WiFi, even DECT, etc.). Furthermore, the radio access network (RAN) node may be connected with a core network node (such as the MME) and/or other RAN nodes, as explained above.

A particular technical problem of the 5G technology is the “tight intégration” with LTE. This means that 5G Systems providing a first type of radio access technology, i.e. a NR RAT, and LTE Systems providing a second different type of radio access technology, i.e. a LTE RAT, will hâve a very tight coopération and intégration level. Traditionally, a terminal device (UE) in a dormant state, e.g. idle mode/inactive state/suspended state, camps in one cell within one RAT, e.g. GSM, UMTS, or LTE. By “camp” or “camping”, it is meant that the UE monitors a set of downlink control channels. For LTE, this means that the UE is monitoring the PCI and reference signais which are cell spécifie and reads the system information when appropriate. In addition, the UE in LTE monitors the PDCCH to check for pages at its spécifie paging occasions. The UE has therefore acquired the system information and is ready to access the cell.

With NR-LTE tight intégration, it is proposed here that a terminal device (UE) has the capability to camp in both NR and LTE cells at the same time, which is also referred to as dual camping in the following. This means that the UE will be able to monitor the corresponding downlink control channels, read the system information, and receive paging in both LTE and NR RAT Systems. This may also mean that the UE could possibly access multiple RATs simultaneously.

The network may configure a UE to allow performing dual camping. Further, the network may configure the UE to use different mechanisms for page monitoring and for updating the network with the location of the UE. Hence, in the context of the present invention the term Camping Area (CA) is defined as a general term for the kind and/or size of an area (such as an area being related to a cell, a coverage area that relies on beamforming, a tracking area, a set of beams represented by beam identifiers, and the like), and can be used to build up a définition of an area in which a UE is allowed to move around without informing the network of its whereabouts. In LTE a CA is realized as a Tracking Area. With this term, the procedure of reporting the UE's location to the network is generally referred to as Camping Area Update or CA Update or CAU. The network indicates presence of a CA by broadcasting the CA’s CA Identifier (CAI) (e.g. the Tracking Area Identifier (TAI) in LTE).

The general concept of the present invention is based on a network or policy based control mechanisms governing the camping behavior of the UE that can monitor channels on multiple RATs in areas with overlapping (geographical) coverage. The control mechanism may be based on different properties such as UE type/capabilities, type of (typically used and/or possibly ongoing) services, the network slicing instance(s) the UE might belong to, the need to quickly establish multi-connectivity such as dual connectivity and/or carrier aggregation, UE battery conditions, the coverage pattern of one RAT vs. another and/or the overlapping coverage area and/or stability of that.

According to a concept of the present invention the network may configure the UE with rules (mechanisms) for how to behave when camping in idle mode (or a similar mode like dormant or sleep mode) and there is more than one RAT available, in particular LTE and NR. The rules apply to the UE's behavior in terms of updating the network with the location of the UE as well as how/what to monitor to check for pages. This rule configuration preferably occurs when the UE is configured with a set of CA(s), i.e. Tracking Areas in LTE and some corresponding areas in NR, covering both/all RATs or, altematively, one set for each RAT, in which UE can move around without informing the network of its whereabouts and in which the network may potentially page the UE.

Figure 7 illustrâtes a flow diagram of a method in a wireless communication network according to an embodiment. Here, the wireless communication network provides, via one or more network nodes (eNBs) 30_η 30₂ radio access for a terminal device 10 via at least a first (RAT1) and a second (RAT2) type of wireless radio accesses that operate with different RATs. Here, the radio access may be provided in a coverage area that has, at least partially, an overlapping coverage of RAT 1 and RAT2.

According to step S110 of Figure 7 at least one network node (eNBs) 30^ 30₂ transmits an indication regarding a set of camping areas, CAs, including a first set of camping areas (CARAT1) being associated with the first RAT and a second set of camping areas (CA-RAT2) being associated with the second RAT. In particular, the indication information may be transmitted in a synchronized manner via multiple network nodes (eNBs) 30^ 30₂. Here, a camping area CARAT 1 being associated with the first RAT may not necessarily be the same as the camping area CA-RAT2 being associated with the second RAT. For example, camping area in LTE (RAT1) may be given by a cell while a camping area in NR (RAT2) may be given by a beam or a system information coverage area (which may be referred to as system area). As will be further described below, the indication of CA(s) may be reported by CA Identifier, via dedicated signalling or common signaling, e.g. within a single list or a list per RAT. The indication may thus include a list or a set of lists indicating one or more CAs of the first set of camping areas CA-RAT1 and/or indicating one or more CAs of the second set of camping areas CA-RAT2. Here, the list may be one list that is common for both RAT1 and RAT2. In other words, a current (e.g. available at the current position of the terminal device) set of camping areas may either be indicated to the terminal device 10 with regard to only one of the RATs or with regard to both RAT1 and RAT2. This provides a dynamic updating capability which is sufficiently flexible to update the relevant set of camping areas, for example when the terminal device 10 moves into areas where only the set of camping areas with regard to one of the two RATs change.

As illustrated in Figure 8A, the first set of camping areas CA-RAT1 may define a (géographie) area that is at least partially overlapping with a second set of camping areas CA-RAT2. That is, the combination of CA-RAT1 and CA-RAT2 may define a common coverage area in which radio access is available via both the first and second RAT and in which radio access is available via only the first or the second RAT. Such a situation may occur in a non-collocated scénario, i.e. where LTE and NR are implemented by different network nodes 30^ 30₂. This situation may also occur in a co-located scénario, i.e. where LTE and NR are implemented by the same network node (e.g. only in 30₁ or 30₂), and where the NR air interface has a lower coverage, a spottier coverage (e.g. mainly at a cells center), relies on beamforming or the like. The combination of CA-RAT1 and CA-RAT2 further defines a (geographical) coverage area in which the terminal device 10 is allowed to move around without informing the network of its whereabouts. Altematively (not shown), the first set of camping areas CA-RAT1 may define a (géographie) area that is essentially completely overlapping with the second set of camping areas CA-RAT2, such as in co-located situations. Further, Figure 8B indicates an exemplary list in which the set of camping areas being associated with the first RAT includes four CAs, i.e. CA-RAT1a, CA-RAT1b, CA-RAT1c, CA-RAT1d, and which the set of camping areas being associated with the second RAT includes three CAs, i.e. CA-RAT2a, CA-RAT2b, CA-RAT2c. Needless to say, this example of a set of first and second CAs (CA-RAT1 and CA-RAT2) is only provided for the purpose of explaining the concept of the présent invention and is not limiting in any way. Based on the above transmission step S110 in Figure 7, the presence of such a set of CAs is indicated to the terminal device 10.

Each of the CAs included in the indication, as shown for example in Figure 8B, may further be provided with a priority indication. Such a priority may indicating a preferred CA the terminal device should select to access the network, in particular in a case where the terminal device is in a location that belongs to multiple CAs. Such a priority may further indicate a preferred RAT of the plural RATs that the terminal device should preferably select to access the network. The preferred RAT in the preferred CA may be area/location dépendent, or the like. Here, the CA priority indication may be replaced with a RAT preference indication. As such, the UE may prioritizes one of the RATs when performing access, when there is a choice, and, for example, when load condition of the overall network warrant such a distribution of RATs.

Further, according to step S120 of Figure 7 the terminal device 10 performs camping in the coverage area that is defined based on the transmitted set of CAs, i.e. CA-RAT1 and CA-RAT2. Such a configuration may be triggered by a radio network node 30 or a core network node 50, which allows the terminal device 10 to, for example, perform dual camping if the terminal device 10 is in the coverage area of both RAT1 and RAT2. Here, dual camping may be performed during a “dormant state”, i.e. during an idle mode, an inactive state, a suspended state of the terminal device 10, or the like. As explained above, dual camping means that the terminal device 10 camps in both the first and second RAT simultaneously, monitors corresponding downlink control channels (for example, in at least one of the RATs), reads the system information (CA Identifiers in the area, as signalled by the network via common signaling), may receive paging commands in both the first and second RATs, and potentially accesses multiple RATs simultaneously.

Further, according to step S130 of Figure 7 the terminal device 10 may be configured, by the network side, with at least a first and a second mechanism that concern the behavior of the terminal device 10 in cases when (a) the terminal device 10 enfers a new coverage area being different from the coverage area defined by both the first and second set of CAs (CA-RAT1,

CA-RAT2), for example ail CAs as illustrated in Figure 8B, and in cases when (b) the terminal device 10 enters a new coverage area being different from the coverage area as defined by only one of the first and second set of CAs, for example CA-RAT2a, CA-RAT2b, CA-RAT2c as illustrated in Figure 8B. In another embodiment, the trigger condition to perform an update of the géographie location of the terminal device may be based on a condition when the terminal device leaves the coverage area defined by both the first and second set of CAs (CA-RAT1, CA-RAT2) (case a) or when the terminal device leaves the coverage area as defined by only one of the first and second set of CAs (case b).

Here, according to the first mechanism, case (a), the terminal device 10 may use a Camping Area Update to provide the communication network with an update as to a présent géographie location when a new coverage area is entered or when the common coverage area is left. In particular, a Camping Area Update message may be transmitted from the terminal device 10 to a network node 30^ 30₂ which may subsequently transmit the Camping Area Update information to a core network node 50, such as MME. In other words, the terminal device 10 does not provide a reporting/updating of its location (e.g. perform CA Update) as long as the terminal device 10 remains within the géographie coverage ofthe both the first and second set of CAs.

Further, according to the second mechanism, case (b), the terminal device 10 may use a Camping Area Update to provide the communication network with an update as to a présent géographie location when the coverage area of only one of the first or second set of CAs is left. This update of the géographie position may thus be conducted even if the terminal device 10 is still in the coverage area of the other one (i.e., the one that is not left) of the set of CAs. In other words, the UE can be configured to report its location (e.g. perform CA Update) as soon as it leaves the coverage area of the configured set of CA(s) in one of the RATs or as soon as it exits a new coverage area that is different from the configured set of CA(s) in one of the RATs, even if it is still in coverage of a CA in the configured set in the other RAT(s).

Further, terminal device 10 may be configured, by the network side, with a third mechanism as to the update of the géographie location of the terminal device 10. Here, the first RAT being associated with the first set of camping areas CA-RAT1 may be a priority RAT and the second RAT being associated with the second set of camping areas CA-RAT2 maybe a backup RAT. According to this classification of the RATs, the third mechanism configures the terminal device 10 to (c) update the communication network with a géographie location of the terminal device when the terminal device 10 leaves the coverage area that is defined by the first set of camping areas CA-RAT1, i.e. when the terminal device 10 loses coverage by the priority RAT, or when the terminal device 10 enters a coverage area that is different from the coverage area that is defined by the first set of camping areas CA-RAT1. This update of the géographie position may thus be conducted even if the terminal device 10 is still in the coverage area of the backup RAT as defined by the second set of camping areas CA-RAT2. With regard to the exemplary situation illustrated in Figure 8B, the terminal device 10 would thus perform a Camping Area Update when the coverage area as defined by CA-RAT1a, CA-RAT1b, CA-RAT1c, CA-RAT1d is left, even if the terminal device 10 is still within the coverage area of CA-RAT2a, CA-RAT2b, CA-RAT2c. According to this classification ofthe RATs, the third mechanism further configures the terminal device 10 to (d) not update the communication network with a géographie location of the terminal device when the terminal device 10 leaves the coverage area defined by the second set of camping areas (CA-RAT2), i.e. the backup RAT, but remains within the coverage area defined by the first set of camping areas (CA-RAT1), i.e. the priority RAT.

With regard to the updating step S130 described above, in particular with regard to the first, second, and third mechanism (case c), the Camping Area Update of the terminal device may be an update for the first RAT and/or the second RAT, i.e. a single update with regard to only one RAT or a combined update for both RATs.

Further, the terminal device 10 may be provided with a control instruction from the network node 30η 30₂ which configures the terminal device to apply the first, second, or third mechanism. Such a control instruction, which is preferably set by a core network node or a policy control mechanism that is implemented in the terminal device, may be based on at least one of:

the terminal device type, the terminal device capabilities, type of service,

- the communication network slicing instance(s) the terminal device might belong to,

- a need to establish multi-connectivity such as dual connectivity and/or carrier aggregation,

- a battery condition of the terminal device, and a coverage pattern of the first and second RAT, the overlapping coverage area, and a stability of the overlapping coverage area.

Figure 12 schematically illustrâtes a terminal device 10 being accessible via a first radio access network node 30τ and a second radio access network node 30₂ to a respective first and second type of wireless radio accesses operating with different radio access technologies. The radio access network nodes 30^ 30₂ are further illustrated to hâve a communication connection (wireline or wireless) with another network node 50 which may be a core network node (such as a MME) or another network node, for example operating as an anchor node in the context of RAN internai paging. Such a scénario illustrâtes a noncollocated air interface, i.e. where RAT1 and RAT2 are implemented in different radio access network nodes 30₁ and 30₂. This is, however, not limiting, and the concept of the présent invention also applies for a collocated scénario in which RAT1 and RAT2 are both implemented in the same radio access network nodes 30^

The terminal device 10 is provided with a radio transceiver module 14 that provides an air interface to the corresponding radio transceiver modules 32! and 32₂ of the respective radio access network nodes (eNBs) 30^ 3O₂.The radio transceiver modules 12 and 34 may respectively include transmitter circuits, receiver circuits, and associated control circuits that are collectively configured to transmit and receive signais and messages according to a respective different radio access technologies. The network node 50 is provided with a transceiver module 52 that provides the communication connection (wireline or wireless) with the radio access network nodes (eNBs) 30^ 30₂.

As further illustrated in Figure 12 the terminal device 10, the radio access network nodes 30^ 30₂, and the (core or anchor) network node 50 further comprise a processing module 12, 34_1; 34₂, 54, respectively, that are configured to control the radio transceiver module 14, the radio transceiver modules 32! and 32₂, and the transceiver module 52 respectively. Each of the processing modules 12, 34ί, 34₂, 54 comprises one or more processors, e.g. one or more microprocessors, microcontrollers, multi-core processors, or the like. More generally, the processing module(s) may comprise fixed circuitry or programmable circuitry that is specifically configured via the execution of program instructions implementing the functionality taught therein, or may comprise combinations of fixed and programmable circuitry. Each of the processing modules also include and are connected to a respective memory module 16, 36_Ί, 36₂, and 56 respectively. The memory module(s), in some embodiments, store one or more computer programs and, optionally, configuration data. The memory module provides nontransitory storage for the computer program and it may comprise one or more types of computer-readable media, such as disk storage, solid-state memory storage, or any combination thereof. By way of non-limiting example, the memory module may comprise any one or more of SRAM, DRAM, EEPROM, and FLASH memory, which may be in the processing module 12, 34!, 34₂, and 54 respectively and/or separate from the processing module. In general, the memory module comprises one or more types of computer-readable storage media providing non-transitory storage of the computer program and any configuration data used by the terminal device/network node. Here, “non-transitory” means permanent, semi-permanent, or at least temporarily persistent storage and encompasses both long-term storage in non-volatile memory and storage in working memory, e.g., for program execution.

Figure 9 illustrâtes a flow diagram of a method in a wireless communication network according to another embodiment. Further to the steps S110, S120, and S130 as illustrated above, and in response to the update (Camping Area Update) according to the first, second, or third mechanisms (as described above) as to the current géographie position of the terminal device when the terminal device leaves an indicated coverage area or enters a new coverage area that is different from the indicated coverage area, the communication network, in particular a core network node 50, such as MME, or a core network functionality assigns in step S140 a new first set of camping areas CA-RAT1 and/or a new second set of camping areas CA-RAT2. This new set of camping areas is assigned according to the current géographie position of the terminal device, and may be transmitted to the terminal device by a radio network node (eNB) 30^ 30₂ which may be a standalone base station providing LTE radio access (RAT1) or a standalone base station providing NR radio access (RAT2) in a non-collocated scénario, or maybe a base station in which RAT1 and RAT2 are co-located. The assignment process in step S140 may also be performed in a way that takes into account, for example, the current load conditions in the RATs, or by taking other factors of the RATs at the current geographical position of terminal device 10 into account. The newly assigned set of camping areas is subsequently indicated to the terminal device 10, for example on the basis of a transmission step as described above in step S110.

Figure 10 illustrâtes a flow diagram of a method in a wireless communication network according to another embodiment. Further to the steps S110, S120, and S130 (and optionally also including step S140 as described above), the terminal device 10 continuously détermines whether a RAT coverage is lost. When coverage is not lost in any of RAT1 and RAT2, the terminal device continues dual camping as described above in step S120. When, on the other hand, it is determined by the terminal device 10 that a coverage, as defined by the current set of CAs, is lost and the terminal device moves out of the coverage area as defined by the current set of CAs, then the terminal device may détermine in which of the different RATs the coverage is lost.

If the coverage is, for example, lost for the priority RAT, then the terminal device proceeds with step S150 of Figure 10 to report a loss of RAT coverage, here loss of priority RAT coverage, one or both of to the communication nodes 30^ 30₂. Based on the current géographie location of the UE in the RAT, which is used for the reporting, new CA(s) for the lost RAT (priority RAT) and/or new CA(s) for the RAT (backup RAT) the UE is using for reporting may be assigned in the core network and indicated to the terminal device. If the coverage is, on the other hand, lost (only) for the backup RAT, then the terminal device proceeds with step S155 of Figure 10 to continue a camping on the priority RAT, and may additionally attempt to first try to access another carrier of the same (lost) RAT, e.g. in a lower frequency with likely better propagation conditions.

Figure 11 illustrâtes a flow diagram of a method in a wireless communication network according to another embodiment. According to step S170 of Figure 11, a decision is made, for example by a radio access network node 30 in which both RAT1 and RAT2 are implemented (co-located) or a core network node, whether the terminal device 10 is paged in both of the first and second RAT, or whether the terminal device 10 is paged in only one of the first RAT and the second RAT. Paging over both RATs may maximize the chance that the UE receives a page (e.g., within a given timeframe). Paging over only one RAT, optionally followed by paging in the other RAT, may minimize page signaling. Further, depending on the load conditions in the different RATs, it may be selected to first page in the priority RAT (P-RAT) and to subsequently page in the backup RAT (B-RAT) only if there is no response. Accordingly, the UE may be configured to monitor the paging channel(s) of one or more RAT(s), e.g. the paging channel of one RAT at a time, or to monitor the paging channels of both RAT1 and RAT2. Altematively, the UE may be configured to monitor the paging channel(s) only the priority RAT or both the priority RAT and the backup RAT.

Here, paging is usually initiated from the core network node 50. In LTE the MME sends a S1AP Paging message to each eNB 30^ 30₂to participate in the paging and this triggers the eNBs 3O-|, 30₂ to send an RRC Paging message to the terminal device (UE) 10. A paging message is sent on the PDSCH just like any other higher layer control plane message or user plane message. A différence from other messages is that it is addressed to a certain RNTI, the Paging RNTI (P-RNTI), which ail UEs can listen for on the PDCCH. The actual RRC Paging message on the PDSCH includes an identifier in a paging record indicating which UE the page is directed to. Paging information for the UE is being carried on the PDSCH in the resource blocks indicated by the PDCCH. To respond to the paging the terminal device (UE) may perform a random access procedure and may send a NAS Service Request message to be forwarded by the eNB to the MME.

According to step S180 of Figure 11, the terminal device 10 accesses the communication network via the radio network node (eNB) 30_1f 30₂, either as a response to the paging command in step S170 or as a terminal device initiated access, in one of the first and second RAT, in particular the P-RAT, or in both of the RATs. Here, the steps S170 and S180 of Figure 11 may be performed in conjunction with the steps S110, S120, S130, S140, S150, and S155 described above.

The following describes additional aspects with regard to the above illustrated first, second, and third mechanisms, according to preferred embodiments.

According to a preferred embodiment being related to the first mechanism and a first step of the first mechanism, a network node ofthe communication network configures the UE via dedicated signaling or via common signaling (e.g. system information via common channel(s)) with a list or set of lists wherein a list contains one or more CA(s) (or codes/identifiers assigned to the signaled CA(s)). A list may be common, i.e. both RATs utilize the same CA(s), or it may be provided per RAT, e.g. one list for LTE and another list for NR.

Such a list may contain one or more CA(s) (CA-RAT1, CA-RAT2) covering both RATs to which the UE is assigned so that the UE does not need to provide a CA Update while it is moving within the nodes/cells which belong to the CA(s) assigned to the UE. With the first mechanism this configuration is relaxed in the sense that the UE will do a CA Update when it enters a new coverage area or leaves the assigned CA(s) in both RATs, but not as long as it remains in the coverage of a CA in the list of at least one of the RATs. This list is henceforth referred to as “CA list” or “list of CAs” or “list of CA(s)”. This list may be mandatory.

Such a list may also contain one or more CA(s) for one or more RAT(s) to which the UE is allowed to register. This list is henceforth referred to as “whitelist”. This list may be optional.

Such a list may also contain one or more not allowed CA(s) for one or more RAT(s) to which the UE is not allowed to register. This list is henceforth referred to as “blacklist”. This list may also be optional.

In addition, each CA signaled in such a CA list may hâve a priority indication. This means that the network may indicate to the UE in which CA the UE should preferably choose to access the network, e.g. in case the UE needs to access the network for some reason, in a situation where the UE is in a location (e.g. cell/node) which belongs to multiple CAs. This could be also applied in the case where overlapping CAs within the same RAT are used, i.e. the same cell/node belongs to more than one CA in the same RAT and broadcasts the corresponding identities/codes. It may also be applied to steer the UE to a preferred RAT which may be area/location dépendent, when the UE is covered by a CA in each RAT, e.g. one CA in LTE and one CA in NR.

Similarly, each CA signaled in the whitelist may hâve a priority indication. These priority indications hâve a similar purpose as the optional priority indications in the CA list and are used in a similar way. A différence is that in the case of the whitelist, the priority indications are means to steer in which CA a UE should register, e.g. perform CA Update, when this is needed.

The network may optionally replace the priority indications in a CA list or a whitelist with a RAT preference indication, so that the UE always prioritizes one of the RATs, when there is a choice.

The network may also configure the UE with paging information via dedicated signaling or via common signaling (e.g. system information) or using a combination of both. This information may contain at least one of the following: DRX configuration (possibly including input parameter(s) for a paging occasion algorithm), one or more paging channels (i.e. for one RAT or both RATs) and related paging information.

The network may also configure the UE via dedicated signaling or via common signaling (e.g. system information) with the CA mechanism (i.e. first mechanism in this example) which the UE should apply.

When, according to a second step ofthe first mechanism, the UE camps in an area, it monitors the relevant control signaling in at least one of the RATs and reads the CAI in the area, or CAIs in case the UE monitors both RATs when performing dual camping. The CAI of an area is signaled by the network via common signaling.

According to a third step of the first mechanism, the UE monitors the paging channel(s) in at least one of the RATs, as configured by the network. It is noted that this can also be seen as an inhérent aspect of camping, in which case this step is redundant, since it is implicitly included in the preceding step.

According to a fourth step of the first mechanism, the UE applies the configured CA mechanism. In this case, the first mechanism indicates that the UE should perform a CA Update when it no longer detects any CA matching any of the assigned CA(s). In other words, if a CA list is provided for each RAT, no match should be found in any of the assigned CA lists for any of the RATs to trigger the UE to perform a CA Update. This CA Update may be a combined update for both RATs, i.e. a combined Tracking Area Update in LTE and corresponding update in NR.

The above described first mechanism may therefore reduce signaling since the CA update is only performed when the UE no longer detects any CA matching any of the assigned CA(s).

The following describes a preferred embodiment being related to the second mechanism.

According to a first step ofthe second mechanism, the network configures the UE via dedicated signaling or via common signaling (e.g. system information) with a list or set of lists wherein a list contains one or more CA(s) (or codes/identifiers assigned to the signaled CA(s)). A list may be common i.e. both RATs utilize the same CA(s), or it may be provided per RAT, i.e. one list for LTE and another list for NR.

A list may contain one or more CA(s) (covering both RATs) to which the UE is assigned so that the UE does not need to provide a CA Update while it is moving within the nodes/cells which belong to the CA(s) assigned to the UE. According to the second mechanism this configuration is applied per RAT, which means that the UE will do a CA Update when it leaves the assigned CA(s) in any of the RATs. That is, if it leaves the CA(s) in the list in one of the RATs (e.g. CARAT1) and enters a CA that is not included in the list, it performs a CA Update, even if it is still in the coverage of a CA in the list (e.g. CA-RAT2) of the other RAT. In accordance with the above defined terminology, such a list is a CA list. This list may be mandatory.

A list may also contain one or more CA(s) (for one or more RAT(s)) to which the UE is allowed to register, i.e. a whitelist. This list may be optional. A list may also contain one or more not allowed CA(s) (for one or more RAT(s)) to which the UE is not allowed to register, i.e. a blacklist.

The network may also configure the UE with a spécial “out of RAT coverage” capability/behavior governing the UE’s behavior in case it loses coverage of one of the two different RATs, for example when the UE loses coverage of RAT1. When this happens the UE’s behavior may (according to the configuration) be either of the following:

a) The UE uses the other RAT, i.e. RAT2 in the above example, to report the loss of RAT coverage to the network. The network may or may not configure the UE with new CA(s) for the lost RAT (i.e. RAT1), e.g. based on the UE’s location in the RAT used for the reporting. The network may also take the opportunity to configure the UE with new CA(s) for the RAT the UE is using for reporting, i.e. RAT2. That is, the network may make this a single RAT CA update (for RAT 1 ) or a combined CA update (for both RAT 1 and RAT2), or none of them.

b) The UE does nothing, except to keep camping on the still available RAT, i.e. RAT2 in the above example.

The UE can also be configured with different carriers of the same RAT so that it can first try to access another carrier of the same RAT, e.g. in a lower frequency likely with better propagation conditions.

In addition, each signaled CA may hâve a priority indication (or a “summarizing” RAT preference indication as explained above in the first mechanism), which would serve the same purpose as in the first mechanism.

The network may also configure the UE with paging information via dedicated signaling or via common signaling (e.g. System information) or using a combination of both. This information may contain at least one of the following: DRX configuration (possibly including input parameter(s) for a paging occasion algorithm), at least one paging channel for each RAT of the different RATs (i.e. the UE is configured to monitor the paging channels of both RATs) and related paging information.

The network may also configure the UE via dedicated signaling or via common signaling (e.g. system information) with the CA mechanism (i.e. the second mechanism in this embodiment) which the UE should apply.

When, according to a second step of the second mechanism, the UE performs dual camping in an area, it monitors the relevant control signaling in both RATs and reads the CAIs of both of the different RATs in the area. The CAI of an area is signaled by the network via common signaling.

According to a third step of the second mechanism, the UE monitors the paging channels of both RATs. In this solution the network can select if it wants to page the UE in both RATs to maximize the chance that the UE should receive a page (within a given timeframe) or if it should only page in one of the RATs to minimize the page signaling (optionally followed by paging in the other RAT in case the UE does not respond to the page in the first RAT). The network may also take into account the load in the different RATs so that the UE would be paged and respond in the RAT with a lower load. In the case the network has to page many dual camping UEs, it may also distribute the load over both RATs, i.e. paging some UEs in one RAT and other UEs in the other RAT. This could be seen as speeding up multi-RAT load balancing and could be configured in scénarios where high load is occurring.

According to a fourth step of the second mechanism, the UE applies the configured CA mechanism. Here, the second mechanism indicates that the UE should perform a CA Update when it no longer detects any CA matching any of the assigned CA(s) in one of the RATs, i.e. either in RAT1 or in RAT2. In other words, if a CA list is provided for each RAT, as soon as no match is found in the list of one of the RATs, because it has entered a CA that is not in the list, for example in CAT-RAT1, the UE should perform CA Update, even if it is still covered by a CA présent in the list of the other RAT, e.g. CAT-RAT2. Upon a CA Update, the network should assign a new CA list, or set of lists (as described above in step 0, to the UE. The network may assign new CA(s) to the UE for both (ali) RATs, even though the CA Update was triggered because the UE left the assigned CA(s) of only one of the RATs. This may be préférable, in case the UE is assigned multiple CAs to move around in in the other RAT and the previously assigned CAs are no longer optimal. This CA Update may be a combined update for both RATs, i.e. a combined Tracking Area Update in LTE and corresponding update in NR.

Furthermore, if the UE loses coverage of one of the RATs, it follows the out of RAT coverage behavior configuration (if any), as described above. That is, it either uses the still available RAT to report the loss of coverage of one of the RATs or keeps camping on the still available RAT without informing the network. In the former case, as described above, the network may configure the UE with new CA(s) in either or both of the RATs (or none of them).

As described above, the second mechanism combines the benefits of maximized reliability and either a minimized paging delay or a minimized paging signaling.

The following describes a preferred embodiment being related to the third mechanism.

The third mechanism may be considered as a hybrid mechanism between the first and second mechanisms described above, where one ofthe RATs, e.g. RAT1, is treated in accordance with the first mechanism and the other RAT, e.g. RAT2, is treated in accordance with the second mechanism.

Here, the network may classify the RATs as a priority RAT (P-RAT) and a backup RAT (B-RAT). In a scénario with more than two RATs, this can be generalized to a set of priority RATs (possibly with different priorities) and a set of backup RATs.) The P-RAT is in principle treated in accordance with the second mechanism, while the B-RAT in principle is treated in accordance with the first mechanism. The UE is configured to always prefer the P-RAT when it is available and to only use (e.g. camp on) the B-RAT when there is no coverage ofthe P-RAT.

According to a first step of the third mechanism, the network configures the UE via dedicated signaling or via common signaling (e.g. system information) with a list or set of lists wherein a list contains one or more CA(s) (or codes/identifiers assigned to the signaled CA(s)). A list may be common, i.e. both RATs utilize the same CA(s), or it may be provided per RAT, i.e. one list for LTE and another list for NR.

A list may contain one or more CA(s) (covering both RATs) to which the UE is assigned so that the UE does not need to provide a CA Update while it is moving within the nodes/cells which belong to the CA(s) assigned to the UE. Within the third mechanism this configuration is applied per RAT and the configuration is different for the P-RAT than for the B-RAT. To this end, if the UE leaves the assigned CA(s) in the P-RAT, e.g. CA-RAT1, and enters a CA that is not in the list, it performs a CA Update, even if it is still in the coverage of a CA in the list of the B-RAT, i.e. CA-RAT2 in this example. On the other hand, if the UE leaves the assigned CA(s) in the B-RAT, CA-RAT2 in this example, and enters a CA that is not in the list (which the UE may not even notice because it may camp only on the P-RAT), it does not perform any CA update. In accordance with the above defined terminology, such a list is a CA list. This list may be mandatory.

A list may also contain one or more CA(s) (for one or more RAT(s)) to which the UE is allowed to register, i.e. a whitelist. This list may be optional. A list may also contain one or more not allowed CA(s) (for one or more RAT(s)) to which the UE is not allowed to register, i.e. a blacklist as described above.

Here, the UE’s configured out of coverage behavior in accordance with the third mechanism is as follows:

If the UE loses coverage of the P-RAT, it camps on the B-RAT and uses it to report to the network that it has lost coverage of the P-RAT. If the UE loses coverage of the B-RAT, it does nothing. It is noted that the UE may not even notice if it loses coverage of the B-RAT, because it may be camping only on the P-RAT. The network may (or may not) configure the UE with new CA(s) for the (lost) P-RAT (based on the UE’s location in the B-RAT). The network may also take the opportunity to configure the UE with new CA(s) for the B-RAT. That is, the network may make this a single RAT CA update or a combined CA update (or none of them).

The network may also configure the UE with paging information via dedicated signaling or via common signaling (e.g. system information) or using a combination of both. This information may contain at least one of the following: DRX configuration (possibly including input parameter(s) for a paging occasion algorithm), at least one paging channel for each RAT (i.e. the UE is configured to monitor the paging channels of both RATs) and related paging information. The network may also configure the UE via dedicated signaling or via common signaling (e.g. system information) with the CA mechanism (i.e. the third mechanism in this example) which the UE should apply.

When, according to a second step ofthe third mechanism, the UE camps in an area, it monitors the relevant control signaling in at least the P-RAT and reads the CAIs of at least the P-RAT in the area. The CAI of an area is signaled by the network via common signaling.

According to a third step of the third mechanism, the UE monitors the paging channels of at least the P-RAT. In this solution the network can select if it wants to page the UE in both RATs to maximize the chance that the UE should receive a page (within a given timeframe) or if it should only page in the P-RAT to minimize the page signaling. It is the choice of the network operator to configure the network’s paging behavior, but for the third mechanism, it is preferred that the network first only pages the UE in the P-RAT and pages in the B-RAT only if not response is received for the page in the P-RAT. This recommendation can be motivated by the configuration that the UE monitors paging in the P-RAT as long as it is available and the situation that the UE monitors only the B-RAT when the P-RAT is lost and then the UE should (as described above) report this loss of P-RAT coverage to the network. An operator may however still choose to configure the network to page in both RATs immediately (possibly dépendent on the urgency of the downlink data to be delivered), because even if a UE has P-RAT coverage, it may fail to receive the paging message, e.g. due to a very temporary fading dip.

According to a fourth step of the third mechanism, the UE applies the configured CA mechanism. In this case, the third mechanism indicates that the UE should perform a CA Update when it no longer detects any CA matching any of the assigned CA(s) in the P-RAT, i.e. when it has entered a CA in the P-RAT which is not included in the CA list. Upon a CA Update, the network should assign a new CA list, or set of lists (as described above in step 0, to the UE. The network may assign new CA(s) to the UE for both the P-RAT and the B-RAT, even though the CA Update was triggered because the UE left the assigned CA(s) of the P-RAT. This may be préférable, in case the network détermines that the UE has left its assigned CA(s) in the B-RAT or if the network has assigned multiple CAs to move around in in the B-RAT and the previously assigned CAs are no longer optimal. This CA Update may be a combined update for both RATs, i.e. a combined Tracking Area Update in LTE and corresponding update in NR.

If the UE loses coverage of the P-RAT, it starts camping on the B-RAT and uses the B-RAT to report the loss of P-RAT coverage to the network. If the UE, when starting to camp on the BRAT, detects that it has entered a CA in the B-RAT that is not included in the CA list, the report of P-RAT coverage loss is combined with a CA update for the B-RAT. As described above, upon receiving the report of loss of P-RAT coverage, the network may configure the UE with new CA(s) in either or both of the RATs (or none of them). If the report of loss of P-RAT coverage is combined with a CA update for the B-RAT, the network configures the UE with new CA(s) for the B-RAT and may or may not also configure the UE with new CA(s) for the P-RAT.

The abovementioned aspects focus on the monitoring aspects of the UE in the case of multiRAT camping. Another relevant aspect is how the UE camping on both RATs should access the system when needed, either as a response to paging and/or as a UE initiated access. Especially in the case the UE is configured to monitor multiple channels, such as the paging channel, the UE can be configured to respond when it receives pages in multiple RATs. For instance, the UE may be configured to respond in the higher priority RAT, the one with the strongest radio conditions or both simultaneously. Similarly for the UE initiated access, the UE can be configured to access a higher priority RAT, the one with the strongest radio conditions or both simultaneously.

In addition, it is noted that even though the embodiments hâve been described with the combination of LTE and NR, as the first and second RATs, as the main scénario in mind, the présent concept may easily be extended to more than two RATs.

In addition, it is also noted that the described embodiments hâve focused on the multi-RAT camping and extensively use that term. However, the présent concept is also applicable for the case the UE camps on multiple carriers (sometimes called RAT or air interface variant) of a single RAT. These different carriers can for example hâve different numerologies or even be associated with multiple cells where one can be a macro cell in lower frequencies and a small cell in higher frequencies, outdoor/indoor or other combinations of these.

The above respective modules may be implemented by a processing unit that include one or a plurality of processors, a microprocessor or other processing logic that interprets and executes instructions stored in a main memory, i.e. memory modules 16, 36-i, 36₂, and 56. The main memory may include a RAM or other type of dynamic storage device that may store information and instructions for execution by the respective modules/units. For example, the radio transceiver modules 12, 32-, and 32₂and the corresponding processing module 12, 34! and 34₂ as well as the transceiver module 52 and the corresponding processing module 54 discussed above with respect to Figure 10 may be realized by the processing unit/processor. The ROM may include a ROM device or another type of static storage device that may store static information and instructions for use by the processing unit.

As mentioned above, the radio access network nodes (base stations) 3Û! and 30₂ as well as the terminal device 10 and the (core or anchor) network node 50 may perform certain operations or processes (acquiring, identifying, transmitting, predicting, decision making, etc.) described herein. These operations may be performed in response to the processing unit/processor executing software instructions contained in a computer-readable medium, such as the main memory, ROM and/or storage device. A computer-readable medium may be defîned as a physical or a logical memory device. For example, a logical memory device may include memories within a single physical memory device or distributed across multiple physical memory devices. Each of the main memory, ROM and storage device may include computer19327 readable media with instructions as program code. The software instructions may be read into the main memory for another computer-readable medium, such as a storage device or from another device via the communication interface.

Further, the software instructions contained in the main memory may cause the processing unit(s) including a data processor, when executed on the processing unit, to cause the data processor to perform operations or processes described herein. Altematively, hard-wired circuitry may be used in place or on in combination with the software instructions to implement processes and/or operations described herein. Thus, implémentations described herein are not limited to any spécifie combination of hardware and software.

The physical entities according to the different embodiments of the invention, including the éléments, units, modules, nodes and Systems may comprise or store computer programs including software instructions such that, when the computer programs are executed on the physical entities, steps and operations according to the embodiments of the invention are carried out, i.e. cause data processing means to carry out the operations. In particular, embodiments of the invention also relate to computer programs for carrying out the operations/steps according to the embodiments of the invention, and to any computer-readable medium storing the computer programs for carrying out the above-mentioned methods.

Where the term module is used, no restrictions are made regarding how distributed these éléments may be and regarding how gathered these éléments may be. That is, the constituent elements/modules/units of the base stations 30τ and 30₂ as well as the terminal device 10 and the network node 50 may be distributed in different software and hardware components or other devices for bringing about the intended function. A plurality of distinct elements/modules may also be gathered for providing the intended functionality. For example, the elements/modules/functions of the UE/nodes may be realized by a microprocessor and a memory similar to the above node including a bus, a processing unit, a main memory, ROM, etc. The microprocessor may be programmed such that the above-mentioned operations, which may be stored as instructions in the memory, are carried out.

Further, the elements/modules/units of the apparatus may be implemented in hardware, software, Field Programmable Gâte Arrays (FPGAs), application-specific integrated circuits (ASICs), firmware or the like.

It will be apparent to those skilled in the art that various modifications and variations can be made in the entities and methods of this invention as well as in the construction of this invention without departing from the scope or spirit of the invention.

The invention has been described in relation to particular embodiments and examples which are intended in ail aspects to be illustrative rather than restrictive. Those skilled in the art will appreciate that many different combinations of hardware, software and/or firmware will be suitable for practicing the présent invention.

Moreover, other implémentations of the invention will be apparent to those skilled in the art from considération of the spécification and practice of the invention disclosed herein. It is intended that the spécification and the examples be considered as exemplary only, wherein abbreviations used in the above examples are listed below. To this end, it is to be understood that inventive aspects lie in less than ail features of a single foregoing disclosed implémentation or configuration. Thus, the true scope and spirit of the invention is indicated by the following daims.

The invention has been described in relation to particular embodiments and examples which are intended in ail aspects to be illustrative rather than restrictive. Those skilled in the art will appreciate that many different combinations of hardware, software and/or firmware will be suitable for practicing the présent invention.

	ABBREVIATIONS
	3GPP	3rd Génération Partnership Project
	5G	5th Génération
5	Al	Air Interface
	B-RAT	Backup RAT
	CA	Camping Area
	CAI	Camping Area Identifier
	CDMA	Code Division Multiple Access
10	CN	Core Network
	CP	Control Plane
	DRX	Discontinuous Réception
	ECM	EPS Connection Management
	eNB	Evolved NodeB
15	EPS	Evolved Packet System
	E-UTRAN	Evolved UTRAN
	EV-DO	Evolution-Data Optimized
	GPRS	General Packet Radio Service
	GSM	Global System for Mobile communication
20	IE	Information Element
	LTE	Long Term Evolution
	MAC	Medium Access Control
	MeNB	Master eNB
	MME	Mobility Management Entity
25	NAS	Non Access Stratum
	NR	New Radio (3GPP’s name for the 5G RAN to be standardized
	NW	Network
	PCI	Physical Cell Identity

	31
PDCCH	Physical Downlink Control Channel
PDCP	Packet Data Convergence Protocol
PDU	Packet Data Unit
PHY	Physical layer
5 P-RAT	Priority RAT
RACH	Random Access Channel
RAN	Radio Access Network
RAT	Radio Access Technology
RLC	Radio Link Control
10 RRC	Radio Resource Control
S1*	S1 interface evolved for 5G, i.e. the interface between a 5G RAN (NR or evolved E-UTRAN) and a 5G core network.

Claims (20)

1. A method in a wireless communication network, said wireless communication network providing radio access for a terminal device via at least a first and second type of wireless radio accesses operating with different radio access technologies, RATs, wherein the method is for coordinating mechanisms for simultaneous multi-RAT camping and comprises the steps of:

- transmitting, by at least one network node, an indication regarding a set of camping areas, CAs, including a first set of camping areas (CA-RAT1) being associated with the first RAT and a second set of camping areas (CA-RAT2) being associated with the second RAT;

performing, by the terminal device, camping in a coverage area defined based on the set of CAs (CA-RAT1, CA-RAT2);

updating, by the terminal device, the communication network with a géographie location of the terminal device

a) when the terminal device enters a new coverage area being different from the coverage area defined by both the first and second set of CAs (CA-RAT1, CA-RAT2) as a first mechanism, or

b) when the terminal device enters a new coverage area being different from the coverage area defined by one of the first and second set of CAs (CA-RAT1, CARAT2) as a second mechanism;

wherein the first RAT being associated with the first set of camping areas (CA-RAT1) is a priority RAT and the second RAT being associated with the second set of camping areas (CA-RAT2) is a backup RAT, and wherein said updating the communication networkwith a géographie location ofthe terminal device is, as a third mechanism,

c) performed when the terminal device enters a new coverage area being different from the coverage area defined by the first set of camping areas (CA-RAT1), and

d) is not performed when the terminal device leaves the coverage area defined by the second set of camping areas (CA-RAT2) but remains within the coverage area defined by the first set of camping areas (CA-RAT1.)

2. The method in a wireless communication network according to claim 1, wherein said indication includes a list or a set of lists indicating one or more CAs of the first set of camping areas (CA-RAT1) and/or indicating one or more CAs of the second set of camping areas (CA-RAT2).

3. The method in a wireless communication network according to any of claims 1 - 2, wherein said updating the communication network with a géographie location of the terminal device is an update for the first RAT and/or the second RAT.

4. The method in a wireless communication network according to any of claims 1 - 3, wherein said network node, in response to said updating, assigns a new first set of camping areas (CA-RAT1) and/or a new second set of camping areas (CA-RAT2).

5 whether terminal device is paged in one of the first and second RAT.

23. A terminal device, adapted to perform the method according to any of claims 12-19.

24. A network node, adapted to perform the method according to any of claims 20 - 22.

25. A computer-readable storage medium, having stored thereon a computer program including instructions which, when executed on one or a plurality of processors, to cause the processor or the plurality of processors to execute the method of any one of claims 12 to 19.

26. A computer program, comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any of claims 20 to 22.

5. The method in a wireless communication network according to any of claims 1 - 4, further comprising the steps of, when the terminal device loses coverage of one of the first and second RATs, in particular the priority RAT of claim 2:

- using the other one of the first and second RATs, in particular the backup RAT of claim 2, to report a loss of RAT coverage to the communication node, or continuing a camping on the other one of the first and second RAT.

6. The method in a wireless communication network according to any of claims 1 - 5, wherein each CA included in the indication is provided with a priority indication, said priority indicating a preferred CA the terminal device should select to access the network and/or said priority indicating a preferred RAT the terminal device should select to access the network.

7. The method in a wireless communication network according to claim 6, wherein the CA priority indication may be replaced with a RAT preference indication.

8. The method in a wireless communication network according to any of daims 1 - 7, further comprising the step of:

- selecting, by the network node, whether the terminal device is paged in both the first and second RAT, or whether terminal device is paged in one of the first and second RAT.

9. The method in a wireless communication network according to any of daims 1 - 8, further comprising the step of:

- accessing the communication network, by the terminal device, as a response to paging and/or as a terminal device initiated access in one of the first and second RAT, in particular the priority RAT of claim 2, or in both the first and second RAT.

10. The method in a wireless communication network according to any of daims 1 - 9, wherein the terminal device is provided with a control instruction from the network node which configures the terminal device to apply the first, second, or third mechanism.

11. The method in a wireless communication network according to claim 10, wherein the control instruction is based on at least one of the terminal device type, the terminal device capabilities,

- type of service,

- the communication network slicing instance(s) the terminal device might belong to,

- a need to establish multi-connectivity such as dual connectivity and/or carrier aggregation, a battery condition of the terminal device, and

- a coverage pattern of the first and second RAT, the overlapping coverage area, and a stability of the overlapping coverage area.

12. A method in a terminal device, said terminal device being capable of monitoring channels via at least a first and second type of wireless radio accesses operating with different radio access technologies, RATs, wherein the method is for coordinating mechanisms for simultaneous multi-RAT camping and comprises the steps of:

receiving an indication regarding a set of camping areas, CAs, including a first set of camping areas (CA-RAT1) being associated with the first RAT and a second set of camping areas (CA-RAT2) being associated with the second RAT;

performing camping in a coverage area defined based on the set of CAs (CA-RAT1, CA-RAT2);

updating the communication network with a géographie location of the terminal device

a) when the terminal device enters a new coverage area being different from the coverage area defined by both the first and second set of CAs (CA-RAT1, CARAT2), as a first mechanism, or

b) when the terminal device enters a new coverage area being different from the coverage area defined by one ofthe first and second set of CAs (CA-RAT1, CARAT2), as a second mechanism;

wherein the first RAT being associated with the first set of camping areas (CA-RAT1) is a priority RAT and the second RAT being associated with the second set of camping areas (CA-RAT2) is a backup RAT, and wherein said updating the communication network with a géographie location ofthe terminal device is, as a third mechanism,

c) performed when the terminal device enters a new coverage area being different from the coverage area defined by the first set of camping areas (CA-RAT1), and

d) is not performed when the terminal device leaves the coverage area defined by the second set of camping areas (CA-RAT2) but remains within the coverage area defined by the first set of camping areas (CA-RAT1.).

13. The method in a terminal device according to claim 12, wherein said updating the communication network with a géographie location of the terminal device is an update for the first RAT and/or the second RAT.

14. The method in a terminal device according to any of claims 12-13, further comprising the steps of, when the terminal device loses coverage of one of the first and second RATs, in particular the priority RAT of claim 14:

- using the other one of the first and second RATs, in particular the backup RAT of claim 14, to report a loss of RAT coverage to the communication network, or

- continuing a camping on the other one of the first and second RAT.

15. The method in a terminal device according to any of claims 12 - 14, wherein each CA included in the indication is provided with a priority indication, said priority indicating a p_ref_erred CA the terminal device should select to access the network and/or said priority indicating a preferred RAT the terminal device should select to access the network.

16. The method in a terminal device according to claim 15, wherein the CA priority indication may be replaced with a RAT preference indication.

17. The method in a terminal device according to any of claims 12-16, further comprising the step of:

monitoring paging channels in both the first and second RAT or in one of the first and second RAT.

18. The method in a terminal device according to any of claims 12-17, further comprising the step of:

accessing the communication network as a response to paging and/or as a terminal device initiated access in one ofthe first and second RAT, in particular the priority RAT of claim 14, or in both the first and second RAT.

19. The method in a terminal device according to any of claims 12-18, further comprising the step of receiving a control instruction which configures the terminal device to apply the first, second, or third mechanism.

20. A method in a network node, said network node providing one or more channels via a first and/or second type of wireless radio accesses operating with different radio access

37 technologies, RATs, wherein the method is for coordinating mechanisms for simultaneous multi-RAT camping and comprises the steps of:

- transmitting, to a terminal device, an indication regarding a set of camping areas, CAs, including a first set of camping areas (CA-RAT1) being associated with the first RAT and a second set of camping areas (CA-RAT2) being associated with the second RAT;

- transmitting a control instruction to configure the terminal device to apply a CA update mechanism to

a) update a géographie location ofthe terminal device when the terminal device enters a new coverage area being different from the coverage area defined by both the first and second set of CAs (CA-RAT1, CA-RAT2), as a first mechanism, or

b) update a géographie location ofthe terminal device when the terminal device enters a new coverage area being different from the coverage area defined by one of the first and second set of CAs (CA-RAT1, CA-RAT2), as a second mechanism;

wherein the first RAT being associated with the first set of camping areas (CA-RAT1) is a priority RAT and the second RAT being associated with the second set of camping areas (CA-RAT2) is a backup RAT, and wherein said control instruction further configures the terminal device to apply a third CA update mechanism to

c) update a géographie location ofthe terminal device when the terminal device enters a new coverage area being different from the coverage area defined by the first set of camping areas (CA-RAT1), and

d) not update a géographie location of the terminal device when the terminal device leaves the coverage area defined by the second set of camping areas (CA-RAT2) but remains within the coverage area defined by the first set of camping areas (CARAT1.)

21. The method in a network node according to claim 20, wherein said network node, upon said updating, assigns a new first set of camping areas (CA-RAT1) and/or a new second set of camping areas (CA-RAT2).

22. The method in a network node according to any of claims 20-21, further comprising:

selecting whether the terminal device is paged in both the first and second RAT, or

20 27. A carrier containing the computer program of the previous claim 25 or claim 26, wherein the carrier is one of an electrical signal, optical signal, radio signal, or computer-readable storage medium.