Method, apparatus and computer program

Abstract

There is provided a method, apparatus, and computer program for causing a first apparatus to perform: switching an active steering mode of a multi-access session from a first steering mode to a second

Description

[0002] A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and / or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and / or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0003] In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Some wireless systems can be divided into cells, and are therefore often referred to as cellular systems.

[0004] A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and / or receive communications on the carrier.

[0005] The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and / or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (3G radio). Other examples of communication systems are the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology and so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3GPP). SUMMARY

[0006] According to a first aspect, there is provided a first apparatus comprising means for performing: switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the first apparatus for the multi-access session; and transmitting, to a second apparatus, a first steering mode switching notification that indicates the switching of the active steering mode of the multi-access session from the first steering mode to the second steering mode.

[0007] According to a second aspect, there is provided a first apparatus comprising: at least one processor; and at least one memory comprising code that, when executed by the at least one processor, causes the first apparatus to perform switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the first apparatus for the multi-access session; and transmitting, to a second apparatus, a first steering mode switching notification that indicates the switching of the active steering mode of the multi-access session from the first steering mode to the second steering mode.

[0008] According to a third aspect, there is provided a method for a first apparatus, the method comprising: switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the first apparatus for the multi-access session; and transmitting, to a second apparatus, a first steering mode switching notification that indicates the switching of the active steering mode of the multi-access session from the first steering mode to the second steering mode.

[0009] According to a fourth aspect, there is provided a first apparatus comprising: switching circuitry for switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the first apparatus for the multi-access session; and transmitting circuitry for transmitting, to a second apparatus, a first steering mode switching notification that indicates the switching of the active steering mode of the multi-access session from the first steering mode to the second steering mode.

[0010] The following may be performed by each of the first to fourth aspects.

[0011] The first apparatus may be caused to perform: receiving, from the second apparatus, a steering mode switching request corresponding to the multi-access session.

[0012] The first apparatus may be caused to perform: receiving, from an application, a request to enable a steering mode switching override mode; and comprising, in the first steering mode switching notification based on said received request, an indication to enable an overriding steering mode for the multi-access session.

[0013] The first apparatus may be caused to perform: receiving, from an application, a request to disable a steering mode switching override mode; and comprising, in the first steering mode switching notification based on said received request, an indication that switching the active steering mode of the multi-access session is to be based on at least one steering mode transition rule.

[0014] The first apparatus may be caused to perform: receiving, from the second apparatus, a second steering mode switching notification that indicates the switching the steering mode of the muiti-access session to the second steering mode.

[0015] The switching may comprise: determining whether a performance metric fulfils at least one preconfigured criterion by: evaluating at least one performance metric to obtain a performance metric value that quantifies a quality of service and / or quality of experience corresponding to the multi-access session; comparing the performance metric value to a threshold value corresponding to at least one preconfigured criterion; and determining that the performance metric fulfils the at least one preconfigured criteria when the performance metric value meets the threshold value of the at least one preconfigured criterion; and performing said switching based on the determining.

[0016] The switching may comprise: determining whether a performance metric fulfils at least one preconfigured criterion by: evaluating at least one performance metric over a plurality of measurement durations to obtain a respective plurality of performance metric values, each performance metric value quantifying a quality of service and / or quality of experience corresponding to the multi-access session during its respective measurement duration; comparing the performance metric values to each other to determine a variation in the performance metric values; and determining that the performance metric value fulfils the at least one preconfigured criterion when the variation is within a predetermined range; and performing said switching based on the determining.

[0017] The switching may be performed based on receiving a request from another apparatus to switch from the first steering mode to the second steering mode.

[0018] The switching may be performed based on receiving an indication from an application to switch from the first steering mode to the second steering mode.

[0019] According to a fifth aspect, there is provided a second apparatus, comprising means for performing: receiving, from a first apparatus, a first steering mode switching notification indicating that the first apparatus is switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the second apparatus for the multi-access session.

[0020] According to a sixth aspect, there is provided a second apparatus, comprising: at least one processor; and at least one memory comprising code that, when executed by the at least one processor, causes the second apparatus to perform: receiving, from a first apparatus, a first steering mode switching notification indicating that the first apparatus is switching an active steering mode of a multiaccess session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the second apparatus for the multi-access session.

[0021] According to a seventh aspect, there is provided a method for a second apparatus, the method comprising: receiving, from a first apparatus, a first steering mode switching notification indicating that the first apparatus is switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the second apparatus for the multi-access session.

[0022] According to an eighth aspect, there is provided a second apparatus, comprising: receiving circuitry for receiving, from a first apparatus, a first steering mode switching notification indicating that the first apparatus is switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the second apparatus for the multi-access session.

[0023] The following may be performed by each of the fifth to eigth aspects.

[0024] The second apparatus may be caused to perform: when the first steering mode switching notification further indicates using an overriding steering mode for the multi-access session, switching a steering mode of the multi-access session to the second steering mode.

[0025] The second apparatus may be caused to perform: switching, based on at least one of: at least one least one steering mode transition rule or the first steering mode switching notification, a steering mode of the multi-access session to the second steering mode.

[0026] The second apparatus may be caused to perform: said switching based on determining that the second steering mode corresponds to a synchronisation steering mode.

[0027] The first steering mode switching notification may further indicate switching the steering mode of the multi-access session is to be based on at least one steering mode transition rule.

[0028] The switching may comprise performing: determining whether a performance metric fulfils at least one preconfigured criterion by: evaluating at least one performance metric to obtain a performance metric value that quantifies a quality of service and / or quality of experience corresponding to the multi-access session; comparing the performance metric value to a threshold value corresponding to at least one preconfigured criterion; and determining that the performance metric fulfils the at least one preconfigured criteria when the performance metric value meets the threshold value of the at least one preconfigured criterion; and performing said switching based on the determining.

[0029] The switching may comprise: determining whether a performance metric fulfils at least one preconfigured criterion by: evaluating at least one performance metric over a plurality of measurement durations to obtain a respective plurality of performance metric values, each performance metric value quantifying a quality of service and / or quality of experience corresponding to the multi-access session during its respective measurement duration; comparing the performance metric values to each other to determine a variation in the performance metric values; and determining that the performance metric value fulfils the at least one preconfigured criterion when the variation is within a predetermined range; and performing said switching based on the determining.

[0030] The second apparatus may be caused to perform: transmitting, to the first apparatus, a second steering mode switching notification indicating the switching the active steering mode of the multi-access session to the second steering mode has or will be performed.

[0031] The second apparatus may be caused to perform: transmitting, to the first apparatus, an active steering mode switching request corresponding to the multiaccess session.

[0032] The second apparatus may be caused to perform: determining at least one steering mode transition rule is met, wherein the transmitting of the active steering mode switching request associated with the multi-access session is based on the determination that the at least one steering mode transition rule is met.

[0033] The following may be performed by each of the first to eighth aspects.

[0034] Said transmitting and / or receiving may be performed using user plane signalling.

[0035] The apparatus may be caused to perform: receiving, for each of the first and second steering mode configurations, a corresponding set of transition rules, wherein each set of transition rules comprise rules for determining when to switch from using that steering mode configuration to using another steering mode configuration and for selecting a steering mode configuration to switch to.

[0036] The apparatus may be caused to perform: receiving the first and second steering mode configurations when the multi-access session is established.

[0037] The apparatus may be caused to perform: updating the first and second steering mode configurations based on modifications to the multi-access session.

[0038] The apparatus may be comprised in a terminal and / or in functionality of a user plane function.

[0039] According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus to perform at least the method according to any of the preceding aspects.

[0040] In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above. DESCRIPTION OF FIGURES

[0041] Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

[0042] Figure 1A shows a representation of a network system according to some example embodiments;

[0043] Figures 1B illustrates rules configured at different entities;

[0044] Figure 2 shows a representation of a control apparatus according to some example embodiments;

[0045] Figure 3 shows a representation of an apparatus according to some example embodiments;

[0046] Figure 4A illustrates example configurations at a communicating apparatus;

[0047] Figure 4B illustrates example transitions between steering modes;

[0048] Figure 5 illustrates example signalling between apparatus described herein; and

[0049] Figures 6 and 7 illustrate example operations that may be performed by apparatus described herein. DETAILED DESCRIPTION

[0050] The following relates to mechanisms for routing traffic between a terminal (e.g., a user equipment) and a user plane function via at least one access network when the terminal is capable of simultaneously routing traffic via multiple access networks. Routing traffic is such a situation is also known as steering.

[0051] Sessions involving the capability to route traffic to multiple network accesses are referred to as multi-access (MA) protocol data unit (PDU) sessions. In more detail, an MA PDU session is a PDU session that can use one 3GPP access network or one non-3GPP access network at a time, or simultaneously one 3GPP access network and one non-3GPP access network. In general, an MA PDU session can be established when the terminal is registered to the same public land mobile network (PLMN) over 3GPP access network and non-3GPP access network or registered to different PLMNs over 3GPP access network and non-3GPP access network respectively. A terminal can initiate MA PDU session establishment when the terminal is registered to a PLMN over both 3GPP access network and non-3GPP access network, or only registered to one access network. Therefore, at any given time, the MA PDU session can have user-plane resources established on both 3GPP access and non-3GPP access, or on one access only (either 3GPP access or non-3GPP access), or can have no user-plane resources established on any access.

[0052] Mechanisms for routing traffic for MA PDU sessions are defined in 3GPP standards in relation to Access Traffic Steering-Switching-Splitting (ATSSS), in which both 3GPP access and non-3GPP access are simultaneously available for signalling user plane traffic between a terminal and a user plane function. ATSSS was introduced in 3GPP Release 16, and was expanded in 3GPP Release 17.

[0053] ATSSS defines a plurality of sets of ATSSS rules for routing user plane traffic through at least one of the 3GPP access and the non-3GPP access. Each respective set of rules (which are also referred to herein as a “steering mode configuration") corresponds to a type of “steering mode”. Each steering mode corresponds to a different way of splitting user plane traffic to be routed between the 3GPP and non-3GPP accesses.

[0054] There are currently five steering modes defined, although it is understood that this may vary depending on implementation and developments in standards. These current five steering modes are known as: 1. Active-standby steering mode 2. Smallest delay steering mode 3. Static load-balancing steering mode 4. Priority-based steering mode 5. Redundant steering mode

[0055] For active-standby steering mode, all traffic of the multi-access protocol data unit (PDU) (MA PDU) session is sent to only one of the two accesses. The access to which the traffic is sent is called the “active” access, while the other access is called a “standby” access. Traffic is routed to the standby access only when the active access becomes unavailable.

[0056] For the smallest delay steering mode, data traffic is routed to whichever of the two accesses is determined to provide a smallest round trip time for data traffic communication to and / or from the terminal and a data server (not shown). To assist with this, the PMF may determine the latency of each access link for calculating respective round trip times for each access.

[0057] For the static Load-Balancing steering mode, a weight information element is defined that specifies a fraction, x, of traffic to be routed via the 3GPP access network and a fraction 1-x of traffic to be routed via the non-3GPP access network. These specified fractions are used to route traffic to and / or from the terminal via the two accesses such that the ratio of routed traffic is in accordance with x:1-x.

[0058] For priority-based steering mode, each of the two accesses are assigned a respective (and different) priority. Initially, all of the traffic is sent via only the access having the highest priority value of these respective priorities. Subsequently, when it is determined that there is congestion on the access being used (e.g., that there is congestion on the high priority access), new data flows of the session are signalled via the lower priority access. Further, similar to the active-standby steering mode, when the higher priority access becomes suddenly unavailable, all traffic is forwarded to the other lower priority access.

[0059] For redundant steering mode, an apparatus is configured to duplicate the traffic corresponding to a service data flow and send the traffic across one access and the duplicated traffic across another access. Stated differently, an apparatus using redundant steering mode signals the same data traffic across multiple types of accesses (e.g., 3GPP and non-3GPP).

[0060] The rules corresponding to each of these respective steering modes are predefined. Further, the rules corresponding to each of these respective steering modes are ordered such that when a data flow matches a rule, the data flow gets routed according to this rule and the remaining rules are not considered. While traffic is routed according to a specific rule, sudden changes to the network status will not affect how traffic is routed (e.g., the same steering mode is maintained).

[0061] In the following, certain examples are explained with reference to mobile communication devices capable of communication via a wireless cellular system and mobile communication systems serving such mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system, access systems thereof, and mobile communication devices are briefly explained with reference to Figures 1A and 1B to assist in understanding the technology underlying the described examples.

[0062] Figure 1A shows a schematic representation of a terminal 101 (e.g., a user equipment (UE) that is able to connect to a 5G core network (5GC) via a 3GPP access network 102 and / or via a non-3GPP access network 103.

[0063] The 3GPP access network 102 may comprise New Radio (NR). The non-3GPP access network 103 may comprise a wireless local area network (WLAN), such as IEEE 802.11. The 3GPP access network 102 is illustrated as connecting to a user plane function (UPF) 105. The non-3GPP access network is illustrated as connecting to the UPF 105 via an interworking function 104 (such as, for example, a non-3GPP interworking function (N3IWF)).

[0064] The UPF 105 comprises a performance management function (PMF) 106. An analogous PMF may be comprised in the terminal 101 (although not shown). Each of these PMFs may be configured to provide real-time metrics for transmitted data (e.g., on received downlink data transmissions at the terminal 101, and on received uplink data transmissions at the UPF 105). PMF implements a user datagram protocol (UDP)-based server-client protocol called PMF Protocol (PMFP), whose packets share a same protocol data unit (PDU) layer for user-plane data. Currently, PMFP is based on RFC8972. In this way, round trip time(s) and load measures determined by the PMF will reflect the actual conditions of traffic on the whole data path between the terminal 101 and the UPF 105.

[0065] The UPF 105 is illustrated as being connected to a session management function (SMF) 107. The interface connecting the UPF 105 to the SMF 107 is known as an N4 interface. The SMF 107 is also illustrated as being connected to the terminal 101 via an access and mobility management function (AMF) 108. Both the SMF 107 and the AMF 108 are illustrated as being connected to a policy control function (PCF) 109. A general function of the SMF 107 is to provide instructions to various apparatus for controlling and delivering a desired (e.g., target) quality of service (QoS) and / or Quality of Experience (QoE).

[0066] In relation to Figure 1A the PCF 109 is configured to provide policy and charging configuration (PCC) rules for each service data flow (SDF) type to the SMF 107. The SMF 107 converts these PCC rules into N4 rules for use by the UPF 105, and provides these N4 rules (e.g., multi-access (MA) rules) to the UPF 105. N4 rules are rules that are used controlling how signalling is performed over the N4 interface, while MA rules are rules for how to signal traffic corresponding to an MA PDU session. 3GPP provides various examples rules and rule table for N4 and MA PDU sessions. For example, see 'Table 6.14.1: N4 Rules to support ATSSS' in 3GPP TS 23.793” for N4 Rule definition, and see 'Table 6.14.1: Multi-access control Rule' in 3GPP TS 23.793” for MA Rule definition. The MA rules may be considered to be a subset of the N4 rules. For example, an N4 rule may comprise an MA Rule identifier, and / or an MA Rule may refer to N4 rule via an N4 session identifier comprised therein. Stated differently, although N4 and MA rules are defined separately, the N4 rules may be considered as being at a Toot level” to which MA Rules refer.

[0067] Further, the SMF 107 converts these PCC rules into ATSSS rules, which are provided to the terminal 101 via the AMF 108. Stated differently, the SMF 107 defines traffic steering rules for UPF 105 that are called MA rules, and defines traffic steering rules for a terminal 101 that are called ATSSS rules, and provides these rules to the respective entities.

[0068] Stated differently, a subscriber’s traffic can be described as a session. Since sessions may have different QoS requirements, the context for achieving a specific QoS for a session is set by an SMF. Stated differently, the SMF creates, updates, and removes the contexts in the UPF for a subscriber’s session using policy rules obtained from the PCF and delivered to the UPF via the N4 interface.

[0069] The consequent configuration of the UPF 105 and the terminal is illustrated with respect to Figure 1B. In Figure 1B, the UPF 105 is configured with N4 rules 110’, which are referenced by MA rules 111’. Further, the terminal 101 is configured with ATSS rules 112’. The N4 rules 110’, MA rules 111’, and ATSSS rules 112’ are all associated with a single steering mode 113’.

[0070] Stated differently, first the PCF 109 defines an ATSSS policy based on information about the terminal 101 and / or a user of the terminal 101. This information may be obtained, for example, from UE profiles and / or subscriptions stored at a unified data management (UDM) comprised in the 5G core network.

[0071] Second, the ATSSS policy is configured at the terminal. For example, more specifically, the SMF generates ATSSS function and SMF (AT3S) rules based on the PCF’s policy, and pushes MA rules for downlink traffic to the UPF 105 and ATSSS rules for uplink traffic to the terminal 101.

[0072] When downlink data subsequently arrives at the UPF 105 for transmission to the terminal, the UPF determines at least one access path(s) (e.g., 3GPP access network and / or non-3GPP access network) for routing the downlink data to the terminal based on the given MA rule, and sends the downlink data to the terminal using the determined at least one access path. A PMF in the terminal performs path performance measurements for each access path between the terminal and UPF, and reports them to SMF. Based on the performance measurement results provided by PMF to the SMF, the SMF may update the MA and / or ATSSS rules and configure the updated MA and / or ATSSS rules to the terminal and UPF.

[0073] Analogously, when uplink data subsequently arrives at the terminal 101 for transmission to the UPF 105, the terminal determines at least one access path for routing the uplink data to the UPF 105 based on the given ATSSS rule, and sends the uplink data to the UPF 105 using the determined at least one access path. A PMF in the terminal performs path performance measurements for each access path between the terminal and UPF, and reports them to SMF. Based on the performance measurement results provided by PMF to the SMF, the SMF may update the MA and / or ATSSS rules and configure the updated MA and / or ATSSS rules to the terminal and UPF.

[0074] As discussed above in relation to Figure 1B, the MA rules configured at the UPF and the ATSSS rules configured at the terminal correspond to a same (and single) steering mode.

[0075] As each of the steering modes may be best suited for different types of traffic QoS, traffic QoE, and / or network conditions, it may be that the steering mode initially selected for an MA PDU session becomes a less efficient steering mode type for the MA PDU than another steering mode type. This may be, for example, as a result of certain data of the MA PDU session traffic being associated with different traffic qualities (e.g., different delay / latency requirements, different minimum bit rate, etc.), and / or as a result of the quality of the link(s) to the access network(s) being used changing over time.

[0076] For example, an application resident on the terminal would benefit from the minimal delay, and so the Smallest Delay steering mode would be initially selected to match that requirement. However, at some point in the same applications lifecycle, the application may determine that wide bandwidth in form of a Load-Balancing steering mode would be more advantageous for signaling traffic for the application (where, as mentioned above, the load-balancing steering mode splits Service Data Flow (SDF) over both accesses, thus providing wider (effective) the bandwidth).

[0077] As another example, it may be determined by a terminal and / or by an application resident on the terminal that the current bit rate achieved using the current steering mode is below a guaranteed bit rate.

[0078] In response to such a determination that the currently used steering mode (e.g., the “active steering mode”) is not the steering mode best suited for the MA PDU traffic, a change in steering mode may be triggered. To change the steering mode, the existing MA PDU session is terminated and a new one established for configuring new MA and ATSSS rules that correspond to the new steering mode. This process utilizes control plane signalling, which means that control plane resources are reserved and used for the termination and establishment of the MA PDU sessions.

[0079] To address at least one of the above-mentioned issues, the following discloses mechanisms for reducing the amount of control plane resources used for changing steering modes.

[0080] In particular, apparatus in the following are simultaneously configured with a plurality of (e.g., two or more) sets of steering rules, each set corresponding to a respective steering mode. When a decision is made to change steering modes, this change request or change instruction is signalled using user plane signalling. Stated differently, the change in steering mode from a first steering mode to a second steering mode is effected using user plane signalling (e.g., not control plane signalling). The configured set of steering rules corresponding to the second steering mode may be used when the steering mode change is completed.

[0081] Stated differently, each of the plurality of configured steering modes in the terminal and the UPF have their own respective rules (e.g., ATSSS Rules in the terminal and MA Rules in UPF). These plurality of configured steering modes are all associated with the same MA PDU session.

[0082] The following also describes a new set of rules (labelled herein as “SM transition rules”) that are used for determining when, and how to, change steering modes. These SM transition rules express how steering mode switching can be done and under which conditions. The SM transition rules may be evaluated by at least one of: a terminal, an application resident on the terminal, a server (e.g., a server located in a data network) communicating with an application resident on the terminal, or the user plane function.

[0083] In an example, the SM transition rules may comprise synchronization information for configured steering mode(s) (SM(s)) in the MA PDU session. In this example, certain steering mode (SM) may be marked as being “synchronized SM”. When the terminal decides to switch the active SM to a steering mode that is a “synchronized SM”, the terminal indicates such an SM switching to the UPF. The UPF can determine whether the indicated steering mode corresponds to a synchronized SM based on (e.g., using) the UPF’s own local configuration, and switch the active steering mode used at the UPF to the same synchronized SM as the terminal when it is determined that the indicated steering mode in the notification corresponds to a synchronized steering mode.

[0084] In the present disclosure, “change” may refer to “switch”.

[0085] For example, the terminal may determine that a steering mode (of an MA PDU session) is to be changed subsequent to determining that criteria for changing the steering mode of the MA PDU session (e.g., the SM transition rule(s)) has been fulfilled. In response to this determination, the terminal changes the steering mode, and signals the UPF to cause the UPF to change the UPF’s steering mode. This signalling may be performed using a new PMF-based procedure in which the UPF can synchronize its own steering mode (e.g., switch the active steering mode of the UPF to the same active steering mode as the terminal) and acknowledge back to UE. All this signalling is performed without terminating the existing MA PDU (e.g., without creating a new MA PDU corresponding to the new steering mode).

[0086] As another example, an application resident on the terminal may determine that a steering mode (of an MA PDU session) is to be changed subsequent to a determination that criteria for changing the steering mode has been fulfilled. The determination may be performed by the application resident on the terminal, or by a data server (as mentioned above). In the latter case, the data server may push the result of the determination to the application resident on the terminal. In response to this determination being provided to the terminal, the terminal changes the steering mode, and signals the UPF to cause the UPF to change the UPF’s steering mode. This signalling may be performed using a new PMF-based procedure in which the UPF can synchronize its own steering mode and acknowledge back to UE. All this signalling is performed without terminating the existing MA PDU (e.g., without creating a new MA PDU corresponding to the new steering mode).

[0087] As another example, the UPF may determine that a steering mode is to be changed subsequent to determining that criteria for changing the steering mode has been fulfilled. In response to this determination, the UPF signals the terminal a request for steering mode switching. This signalling may be performed using a new PMF message called PMF Switch SM Request message. The signalling may comprise an indication of a preferred steering mode type. Once the terminal receives such a request, the terminal determines whether to keep the current steering mode or to switch to a new steering mode. This determination may be based on the steering mode transition rules described herein. When the terminal determines to switch to a new steering mode, the terminal switches to the new steering mode. The type of the new steering mode may differ to the preferred steering mode type indicated in the signalling from the UPF. After switching to the new steering mode, the terminal informs the UPF that a steering mode switch as been performed. This signalling may be performed using a new PMF procedure in which the UPF can synchronize its own steering mode and acknowledge back to UE. All this signalling is performed without terminating the existing MA PDU (e.g., without creating a new MA PDU corresponding to the new steering mode).

[0088] In the examples provided herein, there may be a single entity (referred to herein as a “steering mode switching decision making point” or "switching decision making point”) that is configured to make a decision about whether an active steering mode should be changed from active steering mode switch from a first steering mode to a second steering mode, and at least one other entity (referred to herein as a “steering mode switching assistance point” or “switching assistance point”) for providing information and / or requests to the steering mode switching decision making point for use by the steering mode switching decision making point to determine when and how to perform an active steering mode switch from the first steering mode to the second steering mode.

[0089] Further, in the provided examples, the steering mode switching assistance point is comprised in the UPF and the steering mode switching decision making point is comprised in the terminal. It is understood, however, that this is not limiting and that their location may instead be reversed. In both cases, there is a single steering mode switching decision making point and one or more steering mode switching assistance points, which is useful for avoiding the synchronization issues that are common for distributed states. Stated differently, in both cases, there is a single, centralised entity that is configured to evaluate information and determine whether to cause an active steering mode switch from a first steering mode to a second steering mode in a plurality of entities (e.g., the steering mode switching decision making point and / or one or more steering mode switching assistance points).

[0090] The steering mode switching decision making point (e.g., terminal or UPF) may be configured to locally store a plurality of steering mode configurations (for an MA PDU session), to allow the terminal and / or the UPF to perform the active steering mode switch between the steering modes of the stored plurality of steering mode configurations. The steering mode switching decision making point may maintain at least one steering mode transition rule that may be used for determining when and how to switch the active steering modes (as discussed above). This steering mode switching decision making point may monitor current communication conditions corresponding to the MA PDU session (e.g., QoS and / or QoE) while the terminal and the UPF are using a first steering mode for signalling traffic on the MA PDU session, and decide when and how to switch to using a second steering mode for the MA PDU session instead of the first steering mode. In an embodiment, the steering mode switching decision making point may receive a request from the switching mode switching assistance point, where the request is associated with switching the active steering mode of the terminal from the first steering mode to the second steering mode. The steering mode switching decision making point may determine whether to grant the received request and notify the steering mode switching assistance point of the determination result. When the active steering mode switching from the first to second steering mode has been performed (e.g., based on the received request and / or based on its own monitoring), the steering mode switching decision making point may notify the steering mode switching assistance point of this change.

[0091] The signal sent from the switching decision making point to the switching assistance point may comprise: i) a first part indicating that which new SM is now in use (SM switching done) or will be in use (SM switching timed) and ii) a second part requesting to enable (or disable) overriding the use of transition rules switching in the switching assistance point for the MA PDU session and to switch to use the given SM immediately or as timed action.

[0092] The second part may be optionally included in the signal sent from the switching decision making point to the switching assistance point. The optionality of the second part of the signal means that, when receiving it, the switching assistance point may ignore the notification based on, for example, at least one of a local policy, a local configuration, or network conditions. This is illustrated in the following examples of how the switching assistance point may respond based on the signalling.

[0093] The second part may be useful for overriding the use of the transition rules by the switching assistance point. This may be useful, for example, when there are factors affecting steering mode that are not covered by the configured transition rules. For example, an application may identify, at an application level, that the quality of experience of the end user should be changed, and issue an override instruction to the switching decision making point that indicates a specific steering mode is to be used instead of a steering mode selected using the transition rules. The override instruction may be propagated to the switching assistance point as the above-mentioned second part. It is understood that that this example is not limiting, and that the override indication (e.g., the second part sent from the switching decision making point to the switching assistance point) may be generated autonomously by the switching decision making point, or be generated by an entity external to the switching decision making point.

[0094] When the second part indicates that the switching assistance point should not use a steering mode selected by its steering mode transition rules as its active steering mode (e.g., that the override notification has been issued), the switching assistance point may respond in at least one of a plurality of different ways, depending on its configuration.

[0095] As a first example, the switching assistance point ignores the received override signal, and continues to apply and follow its configured steering mode transition rules for selecting its active steering mode. In this first example, the switching assistance point signals an identification of its active steering mode (which was selected using its preconfigured steering mode transition rule) to the switching decision making point.

[0096] As a second example, the switching assistance point obeys the received override signal, and uses the steering mode indicated in the first part of the message as its active steering mode. This is performed regardless of what steering mode would have been selected as an active steering mode by the transition rules. In this second example, the switching assistance point signals an identification of its active steering mode (which corresponds to the steering mode identified in the first part) to the switching decision making point.

[0097] In both of these examples, the switching assistance point informs the switching decision making point of the active steering mode used by the switching assistance point subsequent to receipt of the signal comprising the first and second parts. The switching decision making point may use this indication to determine whether the switching assistance point is configured to apply (e.g., obey) the override signal.

[0098] When the second part indicates that the switching assistance point should use a steering mode selected by its steering mode transition rules as its active steering mode (e.g., that the override notification has been disabled), the switching assistance point may respond in at least one of a plurality of different ways, depending on its configuration.

[0099] As a first example, the switching assistance point obeys the received disable override signal, and applies and follows its configured steering mode transition rules for selecting its active steering mode. In this first example, the switching assistance point signals an identification of its active steering mode (which was selected using its preconfigured steering mode transition rule) to the switching decision making point.

[0100] As a second example, the switching assistance point ignores the received disable-override signal, and uses the steering mode indicated in the first part of the message as its active steering mode. This is performed regardless of what steering mode would have been selected as an active steering mode by the transition rules. Stated differently, the switching assistance point continues to apply the override functionality, but using the most recently signalled steering mode from the switching decision making point as its active steering mode. In this second example, the switching assistance point signals an identification of its active steering mode (which corresponds to the steering mode identified in the first part) to the switching decision making point.

[0101] In both of these examples, the switching assistance point informs the switching decision making point of the active steering mode used by the switching assistance point subsequent to receipt of the signal comprising the first and second parts. The switching decision making point may use this indication to determine whether the switching assistance point is configured to apply (e.g., obey) the override signal.

[0102] As illustrated in all of the above examples, independently of whether the second part is present in the signal or not, and whether it was ignored or not, the switching assistance point may send the switching decision making point an indication of its current (e.g., new or requested) active steering mode SM back to the switching decision point.

[0103] When the second part was included in the signal from the switching decision making point to the switching assistance point, the switching decision point can conclude from the indication of the switching assistance point’s indication of its current active steering mode whether the switching assistance point ignored the another part or not.

[0104] When the second part wasn’t ignored, the switching decision point concludes that “override” mode for the SM switching is in use for the MA PDU session (transition rules based switching is put on hold) until the switching decision point decides to disable it (in which case SM transition rules based switching is activated again) for the session.

[0105] A steering mode switching assistance point may comprise a plurality of locally stored steering mode configurations for enabling the terminal and / or the UPF to perform the active steering mode switch. The steering mode switching assistance point may maintain at least one steering mode transition rule that may be used for determining when and how to switch active steering modes (as discussed above). The steering mode switching assistance point may monitor current communication conditions corresponding to an MA PDU session (e.g., QoS and / or QoE) while the terminal and UPF are using a first steering mode for signalling traffic on the MA PDU session and decide when and how to switch to using a second steering mode for that MA PDU session, instead of the first steering mode. When the active steering mode switch from the first to second steering mode configuration has been performed, the steering mode switching assistance point may notify another steering mode switching assistance point of this change, and / or receive an indication that this active steering mode switch has been (or will be) performed.

[0106] Example steering mode transition rules (also referred to herein as simply “transition rules”) are illustrated with respect to Figures 4A and 4B with respect to a first steering mode 401, a second steering mode 402, and a third steering mode 403. In some examples, the transition rules are maintained solely at an application being deployed at the terminal 101 (e.g., whether locally resident on the terminal or remotely located in a data network). In some examples, the transition rules are maintained solely at the terminal 101. In some examples, the transition rules are maintained at least one of the terminal 101, the UPF 105, or an application being deployed at the terminal.

[0107] Figure 4A illustrates respective configurations of the terminal 101 and the UPF 105 to which the transition rules of Figure 4B apply.

[0108] As shown in Figure 4A, the UPF 105 is configured with N4 rules 404, first MA rules 405 corresponding to the first steering mode 401, second MA rules 406 corresponding to the second steering mode 402, third MA rules 407 corresponding to the third steering mode 403, and UPF steering mode transition rules 408.

[0109] Further, the terminal 101 is configured with first ATSSS rules 409 corresponding to the first steering mode 401, first ATSSS rules 410 corresponding to the second steering mode 402, third ATSSS rules 411 corresponding to the third steering mode 403, and terminal steering mode transition rules 412 of Figure 4B. The terminal steering mode transition rules may be the same as the UPF steering mode transition rules. The terminal steering mode transition rules may correspond to steering mode transition rules for uplink and / or downlink transmission directions. The UPF steering mode transition rules may correspond to steering mode transition rules for an uplink transmission direction.

[0110] The first steering mode 401 may be considered a default steering mode that is the initial steering mode to be deployed for routing traffic between the terminal and the UPF. In an example, the first steering mode may comprise an active standby steering mode, the second steering mode may comprise smallest delay steering mode, and the third steering mode may comprise a static load balancing steering mode.

[0111] Figure 4B illustrates example steering mode transition rules. The example steering mode transition rules may correspond to the terminal steering mode transition rules 412. The example steering mode transition rules may correspond to the UPF steering mode transition rules 408.

[0112] The arrows in Figure 4B illustrate directions in which the steering modes may be transitioned between. In the present example, from the first steering mode 401, the apparatus may only switch to the second steering mode 402 along arrow R1-2. Further in the present example, from the second steering mode, the apparatus may switch to any of the first steering mode 401 along arrow R2-1 or the third steering mode 403 along arrow R2-3. Further in the present example, from the third steering mode 403, the apparatus may only switch to the first steering mode 401 along arrow R3-1.

[0113] In the example of Figure 4, the first steering mode 401 is activated during MA PDU establishment. Stated differently, initially, the first steering mode 401 is set as the active steering mode. From this first steering mode 401, there is only one state transition (R1-2) available. This single state transition R1-2 is configured to be triggered when an associated criteria is fulfilled. For example, the transition R1-2 may be triggered when an average traffic delay exceeds more than a threshold value (e.g., "if AVG(delay) >N ms, then do R1-2, where N may be any configured value). Stated differently, when the average delay is less than and / or equal to N ms the active steering mode remains as the first steering mode, and when the average delay exceeds N ms, the active steering mode changes from the first steering mode to the second steering mode (R2-1). When the second steering mode is the active steering mode, the traffic steering rules corresponding to the second steering mode are used.

[0114] Once in the second steering mode, the apparatus may monitor whether respective criteria for the two available state transitions have been fulfilled.

[0115] For example, the transition R2-1 may be triggered when the average traffic delay is less than or equal to N ms and the average variation in the measured traffic delay is within a threshold range (e.g., that the traffic delay has “stabilised” over a predetermined measurement duration). Stated differently, the transition R2-1 may be triggered when it is determined that the average traffic delay is both acceptable again and has stabilised.

[0116] As another example, the transition R2-3 may be triggered when the average delay remains over N ms for a configured length of time. Stated differently, a switch from the second transition mode 402 to the third transition mode 403 may be triggered when the second transition mode 402 does not improve the average delay enough compared to the average traffic delay when transition R1-2 occurred. The aim of the third steering mode may be to maintain overall throughput possible by using two accesses at the same time (e.g., as parallel usage of two accesses also can also lower the delay in certain traffic conditions).

[0117] Once in the third steering mode 403, the apparatus may monitor whether criteria for the single available state transitions (R3-1) have been fulfilled.

[0118] For example, the transition R3-1 may be triggered when at least one of two sets of criteria have been fulfilled.

[0119] One set of criteria for triggering transition R3-1 may be that the average traffic delay is less than or equal to N ms and the average variation in the measured traffic delay is within a threshold range (e.g., that the traffic delay has “stabilised” over a predetermined measurement duration). Stated differently, the transition R3-1 may be triggered when it is determined that the average traffic delay is both acceptable again and has stabilised.

[0120] As another example, the transition R3-1 may be triggered when the average delay remains over N ms for a configured length of time. Stated differently, a switch from the third transition mode 403 to the first transition mode 401 may be triggered when the third transition mode 403 does not improve the average delay enough compared to the average traffic delay when transition R2-3 occurred. Stated differently, the transition R3-1 may be triggered when it is determined that there has been little or no improvements in the average traffic delay.

[0121] It is understood that other criteria for determining whether to perform a steering mode state transition (e.g., a change in the steering mode used as the active steering mode) may be evaluated instead of and / or in addition to the criteria mentioned above in relation to Figures 4A and 4B. For example, when a redundant steering mode is configured (and currently active) at the terminal and / or the UPF, the criteria may relate to a level of network congestion present in the radio access network. For example, the UPF could signal the terminal a request for the terminal to switch from the Redundant steering mode, e.g., to Active-Standby steering mode when the UPF determines that network congestion in the radio access network exceeds a threshold amount. With this transition UPF aims to lower the user plane traffic in the affected leg(s) of the network.

[0122] As some of the steering modes comprise the use of a single access at any one time (e.g., Active-Standby, and Smallest Delay), while other steering modes comprise the concurrent use of multiple accesses (e.g., Load-Balancing, Priority-Based, and Redundant), it’s possible that different steering modes may be used in the terminal relative to the UPF at any one time. Stated differently, the active steering mode configuration UPF and the terminal may go out of synchronization with each other.

[0123] This loss of synchronization may happen, for example, if the UPF has rights to execute steering mode switching autonomously (e.g., without consulting the terminal). This situation is especially exacerbated when a steering mode switch happens from a steering mode that concurrently uses multiple accesses in parallel to a steering mode using a single access at any one time (e.g., that does not concurrently use multiple access in parallel). The loss of synchronization may result when the terminal does not receive an indication carrying the steering mode switching information in time because the access used by UPF may be unavailable for the terminal. Although the UPF may page the terminal for causing the terminal to activate one of its accesses, such paging is expensive in terms of both resources (e.g., time-frequency resources used for the signalling) and in terms of the time taken for causing this activation to occur. Further, not all ATSSS-supported accesses can be paged. To avoid this happening, the signaling logic may be configured such that the UPF can only suggest steering mode switching, while the actual decision to perform a steering mode switch is executed by the terminal and / or an application resident on the terminal.

[0124] The signalling that may be performed between the terminal 101 and the UPF 105 for causing a steering mode switch is described below in relation to Figure 5.

[0125] During 501, the terminal 101 and the UPF 105 are configured with a same plurality of steering mode configurations, with one of those plurality of steering mode configurations being “active” in a specific direction (e.g., uplink and / or downlink). As mentioned above, a steering mode is considered an active steering mode when that steering mode is currently being used for routing traffic between a terminal and a user plane function.

[0126] At least one of the following may be performed following 501; 502 to 503, 504, or 505. Subsequent to any of 503, 504, or 505, the operation proceeds to 506.

[0127] 502 to 503 may be optionally performed when the UPF 105 determines that a steering mode switch criteria has been fulfilled for the active steering mode.

[0128] During 502, the UPF 105 determines that a steering mode switch criteria has been fulfilled for the active steering mode. For example, the UPF 105 may determine that at least one steering mode transition rule has been fulfilled. This may be as described above in relation to Figures 4A and 4B.

[0129] During 503, the UPF 105 signals the terminal 101. This signalling may comprise a request to switch the active steering mode from the currently active steering mode to another steering mode configured during 501. This signalling may comprise an indication of another steering mode. Stated differently, this signalling may comprise an indication of a preferred type of steering mode to switch to from the type of steering mode currently used as the active steering mode. This signalling may be performed using user plane signalling. This signalling may be performed using PMF-based signalling. This signalling may be performed using a PMF switch steering mode request. From 503, the operations proceed to 506.

[0130] During 504, an application (e.g., an application resident on the terminal 101 or an application located remotely from the terminal 101) indicates a preferred type of steering mode for the active steering mode of multi-access session to switch to from the type of steering mode currently used as the active steering mode. This indication may be signalled internally in the terminal. From 504, the operations proceed to 506.

[0131] During 505, the terminal 101 determines that a steering mode switch criteria has been fulfilled for the active steering mode. For example, the terminal 101 may determine that at least one steering mode transition rule has been fulfilled. This may be as described above in relation to Figures 4A and 4B. From 505, the operations proceed to 506.

[0132] During 506, the terminal 101 determines whether to cause a switch of the steering mode type of the active steering mode from the steering mode type currently being used to another of the steering mode types already configured at the terminal 101. Stated differently, the terminal determines whether to cause a switch of the active steering mode from a first type of steering mode to a second type of steering mode, the first and second steering modes both being initially configured at the terminal during session establishment. This determination may also identify which of the steering mode types configured at the terminal will be used as the new active steering mode. In this instance, the terminal 101 may be considered to be acting as the above-described switching decision making point.

[0133] During 507, the terminal 101 causes the active steering mode to be switched from a first type (e.g., the type of steering mode that was acting as the active steering mode between 502 to 505) to a second type (e.g., the type of steering mode that will be the new active steering mode after the steering mode switch has been performed).

[0134] During 508, the terminal 101 signals the UPF 105. This signalling may indicate that the active steering mode type has changed from the first type to the second type. Additionally, this signalling may indicate a preferred steering mode to be activated in the UPF. The preferred steering mode to be activated in the UPF 105 may comprise the second type of steering mode. This signalling may be performed using user plane signalling. This signalling may be performed using PMF-based signalling. This signalling may be labelled as a “SM switching operation” signalling operation.

[0135] During 509, the UPF 105 signals the terminal 101. This signalling may comprise an indication that the UPF has completed a switch of the active steering mode from the first type to the second type. This signalling may be performed using user plane signalling. This signalling may be performed using PMF-based signalling. This signalling may be labelled as a “SM switching operation complete” signalling operation.

[0136] In the above examples, the timing of when the terminal performs the active steering mode switch may be determined in at least one of a plurality of different ways.

[0137] As a first example, signalling from the UPF may comprise an indication of when the requested active steering mode switch is to be performed. Stated differently, the above-mentioned signalling of 503 may comprise an indication of a time when the requested active steering mode switch is to be performed by the terminal. The terminal may perform an active steering mode switch at the indicated time. The terminal may perform an active steering mode switch at a different time to the indicated time.

[0138] As a second example, signalling from the UPF during 503 does not comprise an indication of when the requested active steering mode switch is to be performed. In this case, the terminal may determine to immediately switch its active steering mode (and notify the UPF that the active steering mode of the terminal has been switched), and / or to switch its active steering mode at a future time. In this latter case, the terminal may trigger the active steering mode switch to be performed at the future time and notify the UPF of the active steering mode switch either before or after the active steering mode switch has been performed.

[0139] As a third example, when the active steering mode is not triggered based on receipt of UPF signalling, the terminal may determine to immediately switch its active steering mode (and notify the UPF that the active steering mode of the terminal has been switched), and / or to switch its active steering mode at a future time. In this latter case, the terminal may trigger the active steering mode switch to be performed at the future time and notify the UPF of the active steering mode switch either before or after the active steering mode switch has been performed. The notification to the UPF may be comprised in the signalling of 508.

[0140] In the above, when parameters (e.g , the rules corresponding to an active steering mode) are changed, analogous changes may be performed for the rules corresponding to the other configured steering modes. Stated differently, when the active steering mode is modified in any way that affects its SDF and / or Traffic Descriptor(s) and / or other common information for all the configured steering modes (such as, for example, ATSSS and / or N4 rule updates performed by an SMF providing updated rules), then other (inactive) steering mode(s) may be modified accordingly by the network, e.g., by providing updated rules for all configured steering modes.

[0141] In the above, the terminal may have previously indicated to a core network entity that the terminal supports the above-described functionality of being configured with multiple steering modes simultaneously. Such capabilities may be exposed to the network during an MA PDU session establishment phase by the terminal signalling, to the network, an indication of whether the terminal can simultaneously maintain multiple steering modes for a same MA PDU, where only one of those steering modes is active at any one time. Stated differently, when the terminal can simultaneously maintain multiple steering modes for a same MA PDU, the terminal signals the network an indication that the terminal is able to be configured with multiple steering modes for a same MA PDU simultaneously. Analogously, when the terminal cannot simultaneously maintain multiple steering modes for a same MA PDU, the terminal signals the network an indication that the terminal is unable to be configured with multiple steering modes for a same MA PDU simultaneously.

[0142] At least some of the above-described features are illustrated below with reference to Figures 6 and 7. It is therefore understood that the above description may be used to further understand functionality of the features discussed below.

[0143] Figure 6 illustrates operations that may be performed by a first apparatus. The first apparatus may correspond to a switching decision making point. The switching decision making point may be comprised in a terminal (e.g., a UE). The switching decision making point may be comprised in functionality of a user plane function. Stated differently, the switching decision making point may be comprised in functionality of an entity that also causes at least one function of a user plane function to be performed. The switching decision making point may be comprised in functionality of a network function.

[0144] During 601, the first apparatus switches an active steering mode of a multiaccess session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the first apparatus for the multi-access session.

[0145] Stated differently, there is provided a first apparatus that is configured with a plurality of steering modes (e.g., first and second steering modes) for a same multiaccess session (such as a multi-access PDU session). These plurality of steering modes are simultaneously configured at the first apparatus (e.g., they exist at the first apparatus simultaneously). Only one of these configured plurality of steering modes is actively used as a steering mode at any specific point in time. At any specific point in time, the steering mode actively used as a steering mode is referred to herein as an active steering mode, while the other steering modes of the plurality of steering modes are referred to as inactive steering modes. The first apparatus changes its active steering mode for the multi-access session from a first steering mode of the plurality of steering modes to a second steering mode of the plurality of steering modes.

[0146] During 602, the first apparatus transmits, to a second apparatus, a first steering mode switching notification that indicates the switching of the active steering mode of the multi-access session from the first steering mode to the second steering mode. The second apparatus may be as described below in relation to Figure 7.

[0147] The switching of 601 may be performed before the signalling of 602. In such a case, the signalling of 602 may indicate that the switching has been performed. The switching of 601 may be performed after the signalling of 602. In such a case, the signalling of 602 may indicate a time at which the switching of 601 may be performed.

[0148] The switching of 601 may be performed based on at least one of a plurality of different trigger events occurring at the first apparatus.

[0149] As a first example, the switching may be performed based on the first apparatus receiving, from the second apparatus, a steering mode switching request corresponding to the multi-access session. Stated differently, the switching may be performed based on the first apparatus receiving, from the second apparatus, a steering mode switching request associated with the multi-access session. Stated differently, the trigger event that causes the switching to be performed may comprise receipt, from the second apparatus, of a request for the switching to be performed. As illustrated above, the request may identify the second steering mode (although it is understood that the request may instead identify a third steering mode, with the second steering mode being instead determined by the switching decision making point based on a local configuration of the switching decision making point). The switching of this first example may correspond to the example of signalling of 502 to 503.

[0150] As a second example, the switching may be performed based on receipt, from an application of a request to enable a steering mode switching override mode. Stated differently, the trigger event may comprise signalling from an application indicating that a steering mode switch is to be performed. The signalling from the application may identify the second steering mode (although it is understood that the signalling from the application may instead identify a third steering mode, with the second steering mode being instead determined by the switching decision making point based on a local configuration of the switching decision making point). The application may be resident on the second apparatus. The application may be remote from the second apparatus.

[0151] The switching decision making point may obey the steering mode switching override mode request or disobey the steering mode switching override more request, based on the switching decision making point’s local configuration.

[0152] When the switching decision making point determines to obey the steering mode switching override mode request, the switching decision making point comprises, in the first steering mode switching notification based on said received request, an indication to enable an overriding steering mode for the multi-access session. This may be as described above in relation to the override functionality.

[0153] When the switching decision making point determines to disobey (e.g., ignore) the steering mode switching override mode request, the switching decision making point comprises, in the first steering mode switching notification based on said received request, an indication that switching the active steering mode of the multi-access session is to be based on at least one steering mode transition rule. This may be as described above in relation to the disable override functionality.

[0154] As a third example, the first apparatus may autonomously determine to perform the switching based a determination that at least one of the first apparatus’ transition rules has been fulfilled.

[0155] For example, when a transition rule indicates that the steering mode switch should be performed when at least one performance metric value fulfils preconfigured criteria, the switch may be performed when this criteria is performed. Stated differently, the first apparatus may determine whether a performance metric fulfils at least one preconfigured criterion by: evaluating at least one performance metric to obtain a performance metric value that quantifies a quality of service and / or quality of experience corresponding to (e.g., associated with) the multi-access session; comparing the performance metric value to a threshold value corresponding to at least one preconfigured criterion; and determining that the performance metric fulfils the at least one preconfigured criteria when the performance metric value meets the threshold value of the at least one preconfigured criterion. The threshold value may be met when the performance metric value is above and / or equal to the threshold value, or below and / or equal to the threshold value. The switching may be performed (e.g., triggered) based on the determining.

[0156] Similarly, when the transition rule relates to determining whether the performance of the link has stabilised, the determining whether a performance metric fulfils at least one preconfigured criterion may comprise: evaluating at least one performance metric over a plurality of measurement durations to obtain a respective plurality of performance metric values, each performance metric value quantifying a quality of service and / or quality of experience corresponding to (e.g., associated with) the multi-access session during its respective measurement duration; comparing the performance metric values to each other to determine a variation in the performance metric values; and determining that the performance metric value fulfils the at least one preconfigured criterion when the variation is within a predetermined range (e.g., within a relatively narrow range when the performance of the link has stabilised, and within a relatively wide range when the performance of the link has not stabilised, with at least one boundary of the respective ranges being defined by the transition rule). The switching may be performed (e.g., triggered) based on the determining.

[0157] In an embodiment, the first apparatus performs the switching based on / in response to / after receiving an indication to switch (from the first steering mode) to the second steering mode. The indication may be from an application or another apparatus (e.g., the second apparatus).

[0158] Subsequent to the first steering mode switching notification being sent, the first apparatus may receive, from the second apparatus, a second steering mode switching notification that indicates that the second apparatus has switched its active steering mode of the multi-access session to the second steering mode.

[0159] In the present disclosure, an apparatus switching an active steering mode of the multi-access session means that the apparatus switches a local steering mode of the multi-access session. In an embodiment of the apparatus being a terminal (e.g., a UE), the local steering mode of the multi-access session refers to a steering mode of uplink traffic (to the corresponding UPF). In an embodiment of the apparatus being a UPF, the local steering mode of the multi-access session refers to a steering mode of downlink traffic (to the corresponding terminal (e.g., UE)).

[0160] Figure 7 illustrates operations that may be performed by a second apparatus. The second apparatus may comprise a switching assistance point. The second apparatus may correspond to the second apparatus of Figure 6. The switching assistance point may be comprised in a terminal (e.g., a UE). The switching assistance point may be comprised in functionality of a user plane function. Stated differently, the switching assistance point may be comprised in functionality of an entity that also causes at least one function of a user plane function to be performed. The switching assistance point may be comprised in functionality of a network function (e.g., a core network function).

[0161] During 701, the second apparatus receives, from a first apparatus, a first steering mode switching notification indicating that the first apparatus is switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the second apparatus for the multi-access session. The first apparatus may correspond to the first apparatus of Figure 6. The first steering mode switching notification may correspond to the first steering mode switching notification of Figure 6.

[0162] The second apparatus may determine that the second steering mode corresponds to a synchronisation steering mode. A synchronisation steering mode may be considered to be a steering mode to which the second apparatus should always switch when indicated in the first steering mode switching notification. The second apparatus may determine that the second steering mode corresponds to a synchronisation mode based on a preconfigured list of one or more synchronisation steering modes configured at the second apparatus. The second apparatus may determine that the second steering mode corresponds to a synchronisation steering mode based on an indication comprised in the first steering mode switching notification that identifies the second steering mode as a synchronisation signalling mode.

[0163] When the first steering mode switching notification indicates that the second apparatus should use an overriding steering mode for the multi-access session (as described above), the second apparatus may switch a steering mode of the multiaccess session to the second steering mode.

[0164] As described above in relation to the override functionality, the second apparatus may ignore the override signalling or obey the override functionality signalling. When the second apparatus ignores the override functionality signalling, the second apparatus may determine which steering mode to set as the active steering mode using transition rules configured at the second apparatus. When the second apparatus obeys the override functionality, the second apparatus does node determine which steering mode to set as the active steering mode using transition rules configured at the second apparatus: Instead, the second apparatus uses the steering mode indicated in the notification as the active steering mode. [016S] Analogously, when the first steering mode switching notification indicates that the second apparatus should disable an existing overriding steering mode functionality for the multi-access session (as described above), the second apparatus may switch a steering mode of the multi-access session to the second steering mode.

[0166] As described above in relation to the disable override functionality, the second apparatus may ignore the disable override signalling (e.g., by continuing to not determine active steering mode based on transition rules locally configured at the second apparatus, and instead using a steering mode identified in the first steering mode switching notification as the active steering mode) or obey the disable override functionality signalling (e.g., by using locally configured transition rules to determine which steering mode to use as the active steering mode).

[0167] As mentioned above, the second steering mode may be a steering mode determined by the second apparatus using at least one transition rule configured at the second apparatus. Stated differently, the second apparatus may switch, based on at least one of at least one steering mode transition rule or the first steering mode switching notification, an active steering mode of the second apparatus for the multiaccess session to the second steering mode.

[0168] For example, when a transition rule indicates that the steering mode switch should be performed when at least one performance metric value fulfils preconfigured criteria, the switch may be performed when this criteria is fulfilled. Stated differently, the second apparatus may determine whether a performance metric fulfils at least one preconfigured criterion by: evaluating at least one performance metric to obtain a performance metric value that quantifies a quality of service and / or quality of experience corresponding to (e.g., associated with) the multi-access session; comparing the performance metric value to a threshold value corresponding to at least one preconfigured criterion; and determining that the performance metric fulfils the at least one preconfigured criteria when the performance metric value meets the threshold value of the at least one preconfigured criterion. The threshold value may be met when the performance metric value is above and / or equal to the threshold value, or below and / or equal to the threshold value. The switching may be performed (e.g., triggered) based on the determining.

[0169] Similarly, when the transition rule relates to determining whether the performance of the link has stabilised, the determining whether a performance metric fulfils at least one preconfigured criterion may comprise: evaluating at least one performance metric over a plurality of measurement durations to obtain a respective plurality of performance metric values, each performance metric value quantifying a quality of service and / or quality of experience corresponding to (e.g., associated with) the multi-access session during its respective measurement duration; comparing the performance metric values to each other to determine a variation in the performance metric values; and determining that the performance metric value fulfils the at least one preconfigured criterion when the variation is within a predetermined range (e.g., within a relatively narrow range when the performance of the link has stabilised, and within a relatively wide range when the performance of the link has not stabilised, with at least one boundary of the respective ranges being defined by the transition rule). The switching may be performed (e.g., triggered) based on the determining.

[0170] The second apparatus may transmit, to the first apparatus, a second steering mode switching notification indicating the switching the active steering mode of the multi-access session to the second steering mode has or will be performed.

[0171] Prior to receiving the first steering mode switching notification, the second apparatus may have transmitted, to the first apparatus, an active steering mode switching request corresponding to (e.g., associated with) the multi-access session. This request may identify a steering mode (e.g., the second steering mode) to which the second apparatus would like to switch for the multi-access session. This request may request that the multi-access session be switched to the second steering mode and / or to a third steering mode (as discussed above in relation to Figure 6). The first steering mode switching notification may be based on the active steering mode switching mode request.

[0172] The following features apply to each of the first and second apparatus described with reference to Figures 6 and 7.

[0173] The transmitting and / or receiving between the first and second apparatus may be performed using user plane signalling.

[0174] At least one of the first and second apparatus may have received, for each of the first and second steering mode configurations, a corresponding set of transition rules, wherein each set of transition rules comprise rules for determining when to switch from using that steering mode configuration to using another steering mode configuration and for selecting a steering mode configuration to switch to. The first and second steering mode configurations may have been received when the multi-access session is established. The first and / or second steering mode configurations may have been received during a session update procedure. Stated differently, the apparatus may update the first and second steering mode configurations based on modifications to the multi-access session.

[0175] The above describes operations with respect to a user plane function and a terminal. Figures 2 and 3 illustrate apparatus that may be used to perform the functions of such entities, although it is understood that these are not limiting.

[0176] Figure 2 illustrates an example of a control apparatus 200 for controlling a function of the radio access network or the core network (e.g., a user plane function comprised in the core network) as illustrated on Figure 1A. The control apparatus may comprise at least one random access memory (RAM) 211a, at least on read only memory (ROM) 211b, at least one processor 212, 213 and an input / output interface 214. The at least one processor 212, 213 may be coupled to the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215. The software code 215 may for example allow to perform one or more steps to perform one or more of the present aspects. The software code 215 may be stored in the ROM 211 b. The control apparatus 200 may be interconnected with another control apparatus 200 controlling another function of the 5G radio access network or the 5GC. In some embodiments, each function of the 5G radio access network or the 5GC comprises a control apparatus 200. In alternative embodiments, two or more functions of the radio access network or the core network may share a control apparatus.

[0177] Figure 3 illustrates an example of a terminal 300, such as the terminal illustrated on Figure 1A. The terminal 300 may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a user equipment, a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), a personal data assistant (PDA) or a tablet provided with wireless communication capabilities, a machine-type communications (MTC) device, an Internet of things (loT) type communication device or any combinations of these or the like. The terminal 300 may provide, for example, communication of data for carrying communications. The communications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on.

[0178] The terminal 300 may receive signals over an air or radio interface 307 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 3 transceiver apparatus is designated schematically by block 306. The transceiver apparatus 306 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0179] The terminal 300 may be provided with at least one processor 301, at least one memory ROM 302a, at least one RAM 302b and other possible components 303 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The at least one processor 301 is coupled to the RAM 302b and the ROM 302a. The at least one processor 301 may be configured to execute an appropriate software code 308. The software code 308 may for example allow to perform one or more of the present aspects. The software code 308 may be stored in the ROM 302a.

[0180] The processor, storage and other relevant control apparatus can be provided on an appropriate circuit board and / or in chipsets. This feature is denoted by reference 304. The device may optionally have a user interface such as key pad 305, touch sensitive screen or pad, combinations thereof or the like. Optionally one or more of a display, a speaker and a microphone may be provided depending on the type of the device.

[0181] It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and / or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

[0182] It is noted that whilst some embodiments have been described in relation to 5G networks, similar principles can be applied in relation to other networks and communication systems (including to the planned 6G and beyond). Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

[0183] It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0184] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0185] In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0186] As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable):

[0187] a combination of analog and / or digital hardware circuit(s) with software / firmware and

[0188] (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

[0189] (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.”

[0190] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0191] The embodiments of this disclosure may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

[0192] Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

[0193] The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0194] The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

[0195] Embodiments of the disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0196] The scope of protection sought for various embodiments of the disclosure is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the 5 disclosure.

[0197] The foregoing description has provided byway of non-limiting examples a full and informative description of the exemplary embodiment of this disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in io conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this disclosure will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

1) A first apparatus, comprising means for performing:switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the first apparatus for the multi-access session; andtransmitting, to a second apparatus, a first steering mode switching notification that indicates the switching of the active steering mode of the multiaccess session from the first steering mode to the second steering mode.2) A first apparatus according to claim 1, further comprising means for performing:receiving, from the second apparatus, a steering mode switching request corresponding to the multi-access session.3) A first apparatus according to claim 1, further comprising means for performing:receiving, from an application, a request to enable a steering mode switching override mode; andcomprising, in the first steering mode switching notification based on said received request, an indication to enable an overriding steering mode for the multi-access session.4) A first apparatus according to claim 1, further comprising means for performing:receiving, from an application, a request to disable a steering mode switching override mode; andcomprising, in the first steering mode switching notification based on said received request, an indication that switching the active steering mode ofthe multi-access session is to be based on at least one steering mode transition rule.5) A first apparatus as claimed in any preceding claim, further comprising means for performing:receiving, from the second apparatus, a second steering mode switching notification that indicates the switching the steering mode of the multiaccess session to the second steering mode.6) A first apparatus as claimed in any preceding claim, wherein the means for switching comprises means for performing:determining whether a performance metric fulfils at least one preconfigured criterion by:evaluating at least one performance metric to obtain a performance metric value that quantifies a quality of service and / or quality of experience corresponding to the multi-access session;comparing the performance metric value to a threshold value corresponding to at least one preconfigured criterion; anddetermining that the performance metric fulfils the at least one preconfigured criteria when the performance metric value meets the threshold value of the at least one preconfigured criterion; and performing said switching based on the determining.7) A first apparatus as claimed in any preceding claim, wherein the means for switching comprises means for performing:determining whether a performance metric fulfils at least one preconfigured criterion by:evaluating at least one performance metric over a plurality of measurement durations to obtain a respective plurality of performance metric values, each performance metric value quantifying a quality ofservice and / or quality of experience corresponding to the multi-access session during its respective measurement duration;comparing the performance metric values to each other to determine a variation in the performance metric values; anddetermining that the performance metric value fulfils the at least one preconfigured criterion when the variation is within a predetermined range; andperforming said switching based on the determining.8) A first apparatus as claimed in any preceding claim wherein the switching is performed based on receiving a request from another apparatus or an application to switch to the second steering mode.9) A second apparatus, comprising means for performing:receiving, from a first apparatus, a first steering mode switching notification indicating that the first apparatus is switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the second apparatus for the multi-access session.10)A second apparatus according to claim 9, wherein the first steering mode switching notification further indicates using an overriding steering mode for the multi-access session,wherein the second apparatus further comprises means for performing: switching a steering mode of the multi-access session to the second steering mode.11)A second apparatus according to claim 9, further comprising means for performing:switching, based on at least one of: at least one least one steering mode transition rule or the first steering mode switching notification, a steering mode of the multi-access session to the second steering mode.12)A second apparatus as claimed in claim 11, further comprising means for performing said switching based on determining that the second steering mode corresponds to a synchronisation steering mode.13)A second apparatus according to claim 12, wherein the first steering mode switching notification further indicates switching the steering mode of the multi-access session is to be based on at least one steering mode transition rule.14)A second apparatus as claimed in any of claims 11 to 13, wherein the means for switching comprises means for performing:determining whether a performance metric fulfils at least one preconfigured criterion by:evaluating at least one performance metric to obtain a performance metric value that quantifies a quality of service and / or quality of experience corresponding to the multi-access session;comparing the performance metric value to a threshold value corresponding to at least one preconfigured criterion; anddetermining that the performance metric fulfils the at least one preconfigured criteria when the performance metric value meets the threshold value of the at least one preconfigured criterion; and performing said switching based on the determining.15)A second apparatus as claimed in any of claims 11 to 13, wherein the means for switching comprises means for performing:determining whether a performance metric fulfils at least one preconfigured criterion by:evaluating at least one performance metric over a plurality of measurement durations to obtain a respective plurality of performance metric values, each performance metric value quantifying a quality of service and / or quality of experience corresponding to the multi-access session during its respective measurement duration;comparing the performance metric values to each other to determine a variation in the performance metric values; anddetermining that the performance metric value fulfils the at least one preconfigured criterion when the variation is within a predetermined range; andperforming said switching based on the determining.16)A second apparatus according to any of claims 9 to 15, further comprising means for performing:transmitting, to the first apparatus, a second steering mode switching notification indicating the switching the active steering mode of the multiaccess session to the second steering mode has or will be performed.17)A second apparatus according to any of claims 9 to 16, further comprising means for performing:transmitting, to the first apparatus, an active steering mode switching request corresponding to the multi-access session.18)A second apparatus according to claim 17, further comprising means for performing:determining at least one steering mode transition rule is met, wherein the transmitting of the active steering mode switching request associated with the multi-access session is based on the determination that the at least one steering mode transition rule is met.19)An apparatus as claimed in any preceding claim, wherein said transmitting and / or receiving is performed using user plane signalling.20)An apparatus as claimed in any preceding claim, further comprising means for receiving, for each of the first and second steering mode configurations, a corresponding set of transition rules, wherein each set of transition rules comprise rules for determining when to switch from using that steering mode configuration to using another steering mode configuration and for selecting a steering mode configuration to switch to.21 )An apparatus as claimed in claim 20, comprising means for receiving the first and second steering mode configurations when the multi-access session is established.22)An apparatus as claimed in claim 21, further comprising means for updating the first and second steering mode configurations based on modifications to the multi-access session.23)An apparatus as claimed in any preceding claim, wherein the apparatus is comprised in a terminal and / or in functionality of a user plane function.24)A method for a first apparatus, the method comprising:switching an active steering mode of a multi-access session from a first steering mode to a second steering mode, wherein the first steering mode and the second steering mode are configured at the first apparatus for the multi-access session; andtransmitting, to a second apparatus, a first steering mode switching notification that indicates the switching of the active steering mode of the multiaccess session from the first steering mode to the second steering mode.25)A method for a second apparatus, the method comprising:receiving, from a first apparatus, a first steering mode switching notification indicating that the first apparatus is switching an active steering mode of a multi-access session from a first steering mode to a second steering5 mode, wherein the first steering mode and the second steering mode areconfigured at the second apparatus for the multi-access session.

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