Patent Description:
Furthermore, the present invention relates to a system, according to independent claim <NUM>, for improved handling of IP multimedia subsystem calls and configuration of a user equipment in the situation that the user equipment attempts or is able to attempt an IP multimedia subsystem emergency call or a IP multimedia subsystem call, and the user equipment being connected to a visited mobile communication network via a radio access network of or associated with the visited mobile communication network.

Additionally, the present invention relates to a user equipment, according to independent claim <NUM>, for improved handling of IP multimedia subsystem calls and configuration of the user equipment in the situation that the user equipment attempts or is able to attempt an IP multimedia subsystem emergency call or a IP multimedia subsystem call, and the user equipment being connected to a visited mobile communication network via a radio access network of or associated with the visited mobile communication network.

Furthermore, the present invention relates to a program, according to independent claim <NUM>, and to a computer-readable medium, according to independent claim <NUM>, for improved handling of IP multimedia subsystem calls or IP multimedia subsystem emergency calls.

The present invention generally relates to user equipment attaching to a mobile communication network using different access methods - such as, e.g., voice over LTE or the like - together with IP multimedia subsystem technology in order to initiate calls, either non-emergency calls (i.e. "normal" calls) or emergency calls.

The IP multimedia subsystem technology in order to initiate calls can be used with different access technologies, such as voice over LTE. However, one major challenge - especially when using voice over LTE access methods - is the comparatively heavy fragmentation of voice over LTE deployments. This means that a voice over LTE devices or user equipment (such as mobile phones, tablet computers or phablet devices, etc.. ) need to maintain tens if not hundreds of parameters and adjust call parameter values based on the current network operator. Voice over LTE relevant parameters are defined in GSMA PRD IR. <NUM> "IMS Profile for Voice and SMS", Version <NUM> (or Version <NUM>), Annex C. These parameters can be conveyed to the user equipment (especially a voice over LTE device or user equipment) either as part of Late Customization (defined in GSMA PRD TS. <NUM> "Technical Adaptation of Devices through Late Customization" , Version <NUM>), or by two alternative configuration methods, OMA DM v. <NUM> (defined in OMA-ERELD-DM-V1. <NUM> Enabler Release Definition for OMA Device Management Approved Version <NUM>), and HTTP based RCS configuration (defined in GSMA PRD RCC. <NUM>, "Service Provider Device Configuration", Version <NUM>).

However, such configuration methods when using different access technologies based on IP multimedia subsystem calls are typically only applied by the home operator and the parameters are only related to the home network. For example, for voice over LTE, typically different roaming models, namely local break-out and S8HR (both defined in GSMA PRD IR. <NUM> (IMS Roaming, Interconnection and Interworking Guidelines, Version <NUM>) and GSMA PRD IR. <NUM> (LTE and EPC Roaming Guidelines, Version <NUM>)), are used. However, regardless of the roaming model, the emergency calls must always be handled locally in the visited mobile communication network. Such emergency calls (e.g., voice over LTE emergency calls) will therefore have the challenge, that the user equipment must execute the procedures in the visited network, but the relevant parameters are configured according to the home network, leading, in the worst case, to failed emergency calls because of such potential parameter mismatch.

Within the context of IMS emergency calls document <CIT> describes a method in which a roaming user equipment initiates a normal voice call to an emergency call number and is then instructed by the home network to trigger an emergency call procedure. Document <CIT> describes a method for transmitting and receiving emergency PDN connection related signals and document <CIT> describes a method that allows the user equipment to dispense with the special IMS registration for emergency calls if the user equipment is already registered in the IMS.

An object of the present invention is to provide an effective and simple solution to realize an improved handling of IP multimedia subsystem calls and an improved configuration of a user equipment in the situation that the user equipment attempts either an IP multimedia subsystem emergency call or a non-emergency call while connected to a visited mobile communication network.

The object of the present invention is achieved by a method according to claim <NUM>.

It is thereby advantageously possible according to the present invention to provide a procedure for the visited network to avoid the above mentioned potential parameter mismatch, especially by means of adjusting the relevant parameters for emergency calls (i.e. IP multimedia subsystem emergency calls, especially voice over LTE emergency calls) in a roaming user equipment (e.g. a voice over LTE device), i.e. by providing a mechanism such that such a potential parameter mismatch cannot occur. Furthermore, such relevant parameters for emergency calls in a roaming user equipment are defined. Additionally, the invention can advantageously be applied also to the situation of the user equipment attempting a non-emergency call (i.e. a normal IP multimedia subsystem call) while attached to a visited mobile communication network (especially when local breakout is used as the IP multimedia subsystem roaming model, especially the voice over LTE roaming model): According to this alternative, the invention is applied in general (i.e. regardless of whether the roaming user equipment is attempting an emergency call or a non-emergency call, i.e. a normal call), and in such a situation, the visited mobile communication network always configures the IP multimedia subsystem parameters (especially voice over LTE parameters) and the roaming user equipment (typically a voice over LTE user equipment) applies these parameters in general for IP multimedia subsystem calls. According to the present invention, a normal call either corresponds - according to one variant of the invention - to a normal audio call (i.e. providing at least one audio channel (and especially no additional video channel)) between the parties of the call. Furthermore, according to the present invention, a normal call might also correspond - according to a further variant of the invention - to a normal video call (i.e. providing at least one audio channel and additionally at least one video channel) between the parties of the call.

It is thereby advantageously possible that the previously stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters are related to the visited mobile communication network or to another visited mobile communication network, and that, after an update of the values of such call parameters, the previously stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters are able to be applied in the visited mobile communication network (or in another visited mobile communication network), at least during a certain validity time interval of, e.g., one hour or one day or two or three days or one week or the like. This means that the stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters (stored in the user equipment) are considered correct in case that the last update has occurred within such a validity time interval.

According to the present invention, the improved handling of IP multimedia subsystem calls and improved user equipment configuration supposes that the user equipment attempts or is able to attempt an IP multimedia subsystem emergency call or an IP multimedia subsystem call, while being connected to a visited mobile communication network (typically using a radio access network of or associated with the visited mobile communication network). According to the present invention, in a first step, an IP multimedia subsystem call parameter information or an IP multimedia subsystem emergency call parameter information is transmitted by the visited mobile communication network to the user equipment, and in a second step, during or subsequent to the first step, the user equipment - upon attempting an IP multimedia subsystem emergency call or an IP multimedia subsystem call - applies or acts according to the content of the IP multimedia subsystem call parameter information and/or of the IP multimedia subsystem emergency call parameter information.

According to the present invention, when the user equipment attempts an IP multimedia subsystem emergency call - in the second step - the IP multimedia subsystem emergency call parameter information, received during the first step, are applied by the user equipment when performing IP multimedia subsystem emergency call procedures, especially emergency attach, IP multimedia subsystem emergency registration, IP multimedia subsystem emergency call procedure.

Analogously according to the present invention, when the user equipment attempts an IP multimedia subsystem call, i.e. a non-emergency (or normal) call - in the second step - the IP multimedia subsystem call parameter information, received during the first step, are applied by the user equipment when performing IP multimedia subsystem call procedures, especially access network attach, IP multimedia subsystem registration, IP multimedia subsystem call procedure.

Thereby, it is advantageously possible - for both cases, i.e. for the situation that the user equipment attempts an IP multimedia subsystem emergency call, and for the situation that the user equipment attempts an IP multimedia subsystem call, i.e. a non-emergency (or normal) call - that the correct piece or pieces of parameter information is or are used such that the corresponding IP multimedia subsystem call or IP multimedia subsystem emergency call is able to be performed sufficiently quickly and correctly.

According to the present invention the method comprises a third step, prior to the first step, wherein during the third step, the user equipment roams to the visited mobile communication network with IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters being stored in the user equipment according to previously stored values of these IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters, wherein the IP multimedia subsystem call parameter information and/or the IP multimedia subsystem emergency call parameter information comprises parameter information that are adjusted to the visited mobile communication network to which the user equipment is attached to or is attempting to be attached to, such parameter information especially being stored and applied rather than IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters being stored in the user equipment according to previously stored values of these IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters.

According to the present invention the call related parameters (i.e. the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters) actually being used or applied, by the user equipment, in connection to the visited mobile communication network the user equipment is currently roaming to are those call related parameters (i.e. the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters) the user equipment receives during the first step form the corresponding visited mobile communication network. The previously stored values of such parameters (i.e. previously stored in the user equipment, prior to receiving the call related parameters, from the visited mobile communication network, in the first step) might either be preconfigured values of such parameters initially stored in the user equipment, or values of such parameters that have been received from the respective (visited) mobile communication network upon a previous attachment of the considered user equipment with the considered (visited) mobile communication network. In any way, in case such previously stored values (either initially stored in the user equipment or subsequently received) are - if need be - overwritten (or partly overwritten) by the call related parameters (IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters) newly received in the first step according to the present invention.

According to the present invention it is furthermore preferred that the previously stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters are related to the visited mobile communication network or to another visited mobile communication network, wherein especially a plurality of previously stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters, related to different visited mobile communication network are stored within the user equipment.

According to the present invention, it is thereby advantageously possible that, after an update of the values of such call parameters, the previously stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters are able to be applied in the visited mobile communication network or in another visited mobile communication network, at least during a certain validity time interval of, e.g., one hour or one day or two or three days or one week or the like. This means that the stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters (stored in the user equipment) are considered correct in case that the last update has occurred within such a validity time interval. Additionally, it is advantageously possible that a plurality of previously stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters - such a plurality of stored values being related to different visited mobile communication networks - are stored within the user equipment, e.g. in a list of, for example, three or five or <NUM> different sets of such stored parameters (i.e. for three, or five or <NUM> different visited mobile communication networks). This makes it possible to perform the first step once during a validity time interval (in order to have the corresponding stored values of the IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters up to date), and then to use the list (or the plurality of previously stored values) of up to date values corresponding to specific visited mobile communication networks. This is especially advantageous in case that the user equipment frequently roams within a rather static set of different mobile communication networks (such as, e.g., three or five or <NUM> different mobile communication networks) which are typically contacted during a certain time period of typically user equipment usage.

According to a further preferred embodiment of the present invention, the IP multimedia subsystem call parameter information and/or the IP multimedia subsystem emergency call parameter information relates either to different management objects or to only one management object, especially a management object or management objects according to or being 3GPP IP multimedia subsystem management object(s). Throughout the present disclosure, the term management object or management objects is used to especially relate to a management object or management objects according to or being 3GPP IP multimedia subsystem management object(s).

According to the present invention it is furthermore preferred that the IP multimedia subsystem call parameter information and/or the IP multimedia subsystem emergency call parameter information is transmitted to the user equipment by means of at least one out of the following transport protocols:.

According to the present invention, it is thereby advantageously possible that the IP multimedia subsystem call parameter information and/or the IP multimedia subsystem emergency call parameter information is transmitted in an effective and reliable manner.

Furthermore, the present invention relates to a system according to claim <NUM>.

Thereby, it is advantageously possible to provide a system such that the user equipment knows about the correct IP multimedia subsystem call parameter information and/or of the IP multimedia subsystem emergency call parameter information to be applied in the respective visited mobile communication network.

Furthermore, the present invention additionally also relates to a user equipment according to claim <NUM>.

Additionally, the present invention relates to a computer-readable medium according to claim <NUM> and a program according to claim <NUM>.

The drawings described are only schematic and are nonlimiting.

In <FIG>, a home mobile communication network <NUM>, a visited mobile communication network <NUM>, and a user equipment <NUM> according to the present invention are schematically shown. A corresponding inventive system comprises the user equipment <NUM> and the visited mobile communication network <NUM>.

According to the present invention the user equipment <NUM> is connected to the visited mobile communication network <NUM>, wherein, in a first step, an IP multimedia subsystem call parameter information <NUM> or an IP multimedia subsystem emergency call parameter information <NUM> is transmitted by the visited mobile communication network <NUM> to the user equipment <NUM>. In a second step, during or subsequent to the first step, the user equipment <NUM> - upon attempting an IP multimedia subsystem emergency call or an IP multimedia subsystem call - applies or acts according to the content of the IP multimedia subsystem call parameter information <NUM> and/or of the IP multimedia subsystem emergency call parameter information <NUM>. Hence, when the user equipment <NUM> is roaming in a visited mobile communication network <NUM> that supports IP multimedia subsystem calls, the visited mobile communication network <NUM> transports to the IP multimedia subsystem call enabled user equipment <NUM> the IP multimedia subsystem emergency call relevant parameters with the values adjusted to this particular visited mobile communication network <NUM>. The user equipment <NUM> then applies these parameters when performing IP multimedia subsystem call emergency procedures (especially voice over LTE emergency procedures), i.e. emergency attach, emergency registration and emergency call, as defined in GSMA PRD IR. <NUM>, 3GPP TS <NUM>, 3GPP TS <NUM> and 3GPP TS <NUM>. In case this is also applied to non-emergency calls, the visited mobile communication network <NUM> always configures the IP multimedia subsystem call parameters (i.e. the IP multimedia subsystem call parameter information <NUM> and/or of the IP multimedia subsystem emergency call parameter information <NUM>) and the IP multimedia subsystem call enables user equipment <NUM>, especially voice over LTE user equipment <NUM>) applies them for such calls. Typically, this makes sense in connection with a local breakout roaming model.

In <FIG>, a home mobile communication network <NUM> and a user equipment <NUM> are schematically shown. A corresponding system comprises the user equipment <NUM> and the home mobile communication network <NUM>. This system is not encompassed by the wording of the claims but is considered as useful for understanding the invention.

The user equipment <NUM> is connected to the home mobile communication network <NUM>, wherein, in a first step, an IP multimedia subsystem emergency call parameter information <NUM> is transmitted by the home mobile communication network <NUM> to the user equipment <NUM>. In a second step, during or subsequent to the first step, the user equipment <NUM> - upon attempting an IP multimedia subsystem emergency call or an IP multimedia subsystem call - applies or acts according to the content of the IP multimedia subsystem emergency call parameter information <NUM>. According to such a use of the invention in the home mobile communication network <NUM>, a set of emergency call relevant parameters are either stored in the user equipment <NUM> or transported to the user equipment <NUM> via a configuration protocol. The user equipment <NUM> then applies these parameters when performing IP multimedia subsystem emergency call procedures, i.e. emergency attach, emergency registration and emergency call, as defined in GSMA PRD IR. <NUM>, 3GPP TS <NUM>, 3GPP TS <NUM> and 3GPP TS <NUM>; in such a situation, there is the benefit that the emergency call setup is able to be configured in a simplified manner, i.e. all extensions and additional features that are there for IP multimedia subsystem calls in order to provide optimized user experience, can be turned off, which makes the emergency call setup more robust.

According to an embodiment of the invention, the first and second step of the inventive method are performed by means of transmitting the IP multimedia subsystem call parameter information <NUM> and/or of the IP multimedia subsystem emergency call parameter information <NUM> during an attach procedure (e.g. LTE attach) triggered, e.g., by voice over PS supported indication or an emergency call indication).

In a first processing step, the user equipment <NUM> roams to the visited network <NUM>. The emergency call related parameters (i.e. the IP multimedia subsystem emergency call parameter information <NUM>) and/or the non-emergency call related parameters (i.e. the IP multimedia subsystem call parameter information <NUM>) are stored in the user equipment <NUM> with their home network default values. In a second processing step, the user equipment <NUM> receives the indication during an attach procedure (such as LTE attach in the LTE case), if voice over PS is supported and/or if emergency services are supported. This triggers the procedure to receive the IP multimedia subsystem (emergency) call parameter values (i.e. the IP multimedia subsystem call parameter information <NUM> and/or of the IP multimedia subsystem emergency call parameter information <NUM>) from the visited mobile communication network <NUM> in a third processing step (i.e. the first step of the inventive method). In case the IP multimedia subsystem enabled user equipment <NUM> receives the parameters (i.e. the IP multimedia subsystem call parameter information <NUM> and/or of the IP multimedia subsystem emergency call parameter information <NUM>) in a fourth processing step, it applies the received values in the future for the emergency procedures (or for non-emergency procedures) in a fifth processing step. In case the IP multimedia subsystem enabled user equipment <NUM> does not receive the parameters, the default parameters are applied in a sixth processing step.

In case non-emergency IP multimedia subsystem calls are also concerned, the third processing step would be triggered by the voice over PS indication, regardless of any emergency service support indication in the second processing step.

According to the present invention, it is essential that a certain number of IP multimedia subsystem emergency call relevant parameters (i.e. the IP multimedia subsystem emergency call parameter information <NUM>) and/or a certain number of non-emergency call related parameters (i.e. the IP multimedia subsystem call parameter information <NUM>) - are able to be modified by the visited mobile communication network <NUM>. Besides the one purely emergency call related parameter ("Anonymous Emergency Call Allowed" with possible values of <NUM> = not allowed, and <NUM>= allowed) which should - according to the present invention - be altered (if applicable), by the visited mobile communication network <NUM>, at least one other emergency call relevant parameter (or a plurality of other emergency call relevant parameters) might be accessible to be adjusted by the visited mobile communication network <NUM>.

As an example, one or a plurality of the following parameters (especially of the voice over LTE configuration parameters from GSMA PRD IR. <NUM> Table C. <NUM>) are able to be modified by the visited mobile communication network <NUM> according to the present invention. In the following, a first variant of these parameters (to be transmitted to the user equipment <NUM> in the second step) are specifically discussed with regard to the call being either an emergency audio-only call - in the visited mobile communication network - or the call being an emergency video call - likewise in the visited mobile communication network. The home network default values - as defined in IR. <NUM> and typically used or as used in a typical implementation in a home mobile communication network - of the different parameters are indicated as well as the values of the different parameters as suggested to be used according to the present invention (in the visited mobile communication network):.

As a summary, only a subset of all voice over LTE parameters are relevant for emergency calls, the home network default values are adjusted, by the visited mobile communication network <NUM>, especially for the context of emergency calls.

As a further example, one or a plurality of the following parameters (especially of the voice over LTE configuration parameters from GSMA PRD IR. <NUM> Table C. <NUM>) are able to be modified, by the visited mobile communication network <NUM>, according to the present invention. In the following, a second variant of these parameters (to be transmitted to the user equipment <NUM> in the second step) are specifically discussed with regard to the call being either a normal audio-only call in the visited mobile communication network or the call being a normal video call in the visited mobile communication network. The home network default values - as defined in IR. <NUM> and typically used or as used in a typical implementation in a home mobile communication network - of the different parameters are indicated as well as the values of the different parameters as suggested to be used according to the present invention (in the visited mobile communication network):.

As a summary, only a subset of all voice over LTE parameters are relevant for emergency call, the home network default values are adjusted, by the visited mobile communication network <NUM>, especially for the context of normal calls.

The parameters to be transmitted to the user equipment <NUM> in the second step can be of different Management Objects. These parameters could be transported separately, or a new Management Object can be created for the transmission in the first step, i.e. for the transmission of the IP multimedia subsystem call parameter information <NUM> and/or of the IP multimedia subsystem emergency call parameter information <NUM>.

Claim 1:
Method for improved handling of IP multimedia subsystem calls and configuration of a user equipment (<NUM>) in the situation that the user equipment (<NUM>) is able to attempt an IP multimedia subsystem emergency call or an IP multimedia subsystem call, and the user equipment (<NUM>) being connected to a visited mobile communication network (<NUM>) via a radio access network of or associated with the visited mobile communication network (<NUM>),
wherein the method comprises the following steps:
-- in a first step, an IP multimedia subsystem call parameter information (<NUM>) or an IP multimedia subsystem emergency call parameter information (<NUM>) is transmitted by the visited mobile communication network (<NUM>) to the user equipment (<NUM>),
-- in a second step, during or subsequent to the first step, the user equipment (<NUM>) - upon attempting an IP multimedia subsystem emergency call or an IP multimedia subsystem call - applies or acts according to the content of the IP multimedia subsystem call parameter information (<NUM>) and/or of the IP multimedia subsystem emergency call parameter information (<NUM>), wherein the method is characterized by comprising a third step, prior to the first step, wherein during the third step, the user equipment (<NUM>) roams to the visited mobile communication network (<NUM>) with IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters being stored in the user equipment (<NUM>) according to previously stored values of these IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters, wherein the IP multimedia subsystem call parameter information (<NUM>) and/or the IP multimedia subsystem emergency call parameter information (<NUM>) received in the first step comprises parameter information that are adjusted to the visited mobile communication network (<NUM>) to which the user equipment (<NUM>) is attached, such parameter information being stored and applied - at least during a certain validity time interval - rather than IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters being stored in the user equipment (<NUM>) according to previously stored values of these IP multimedia subsystem call related parameters or IP multimedia subsystem emergency call related parameters.