PUBLIC SAFETY (IOPS)

BACKGROUND

[0001] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features, and advantages of the enclosed embodiments will be apparent from the following description.

[0002] Mission Critical (MC) communication services are essential for the work performed by public safety users, e.g. police and fire brigade. The MC communications service requires preferential handling compared to normal telecommunication services including handling of prioritized MC calls for emergency and imminent threats. Furthermore, the MC communication services require several resilience features that provide a guaranteed service level even if part of the network or backhaul infrastructure fails.

[0003] The most commonly used communication method for public safety users is Group Communication (GC) which requires that the same information is delivered to multiple users. One type of GC is the Push to Talk (PTT) service. Thus, a MC PTT (MCPTT) service is an example of a MC communication services. A GC system can be designed with a centralized architecture approach, in which a centralized GC control node provides full control of all group data, e.g. group membership, policies, user authorities, and prioritizations. Such an approach requires a network infrastructure that provides high network availability. This type of operation is sometimes known as Trunked Mode Operation (TMO) or on- network operation.

[0004] A contrary approach is a design where each user radio device is controlling the GC. In this case, the group data (which is similar to but normally a subset of the group data as listed in the previous paragraph) must be pre provisioned to each device. This type of solution is sometimes known as Direct Mode Operation (DMO) or off-network operation, which means that the GC can take place without any support from network infrastructure.

[0005] In the current GC system, both approaches mentioned above are supported. Furthermore, the current GC system may provide a resilience feature that allows the local radio base station (a.k.a. base station) to provide local connectivity and GC to the users within the coverage of the radio base station even if the local radio base station loses it connections to other parts of the network. This is in some deployments is known as Local Site Trunking.

[0006] In a Third Generation Partnership Project (3GPP) based network that provides GC services like MC PTT (MCPTT), the service can be guaranteed even in the case of backhaul failure by using the feature known as Isolated Evolved Universal Terrestrial Radio Access Network (RAN) (E-UTRAN) Operations for Public Safety or any similar Isolated RAN Operations for Public Safety (IOPS), with reference to the 3GPP Technical Specification (TS) 23.401 V16.1.0 and Annex K. The IOPS functionality provides local connectivity to the public safety users' devices that are within the communication range of E-UTRAN radio base station(s) (e.g. enhanced or evolved Node B(s) (eNB(s)) that supports IOPS, i.e. one or more lOPS-capable base stations. A lOPS-capable eNB(s) or similar radio base station is co-sited with a local Evolved Packet Core (Local EPC) or similar core network, which is used in IOPS mode. The Local EPC may include one or more of the following functional entities: Mobility Management Entity (MME), Serving Gateway (S-GW), Packet Data Network Gateway (P-GW), and Home Subscriber Server (HSS).

[0007] The IOPS system can be used in different types of deployments. One common scenario is when a radio base station is located on a remote location (e.g., an island) and the radio base station is connected to the macro core network via, e.g., a microwave link. If there is a microwave link failure, it is critical for public safety users to be able to at least have local connectivity for the communication between the users in the coverage of the lOPS-capable eNBs or similar.

[0008] Problems and solutions are described herein within the context of a 3GPP-based Long Term Evolution (LTE) network, i.e. an Evolved Packet System (EPS) including E-UTRAN and EPC. However, the problems and solutions described herein are equally applicable to wireless access networks and User Equipments (UEs) implementing other access technologies and standards (e.g., a Fifth Generation (5G) system including 5G core network and 5G RAN that correspond to the EPC network and the E-UTRAN respectively). Further, LTE is used as an example technology in which the solutions described herein are suitable; as such, LTE is used in the description and is particularly useful for understanding the problems and solutions to those problems disclosed herein. Furthermore, the present disclosure focuses on the IOPS system mode scenario; however, the problems and solutions described herein are also equally applicable to other scenarios, e.g. for the case of implementing a private network with a local EPC to provide any service to authorized users within the private network coverage area.

[0009] There currently exist certain challenge(s). To provide GC with an acceptable service level in IOPS (see 3GPP TS 23.401 V16.1.0), it is required that the GC service data is synchronized between a centralized GC control node and the local GC application that resides in or in the proximity of the radio base station that will provide the resilience feature in IOPS. Besides synchronization of persistent data, there is also dynamic application data that is typically not stored prior, during, or after a switch between IOPS mode of operation and normal operations.

[0010] GC systems based on 3GPP technology compared with current GC networks are typically deployed with a higher density of radio base stations. Hence, the data synchronization issue becomes even larger.

[0011] Hence, there is still a need for an improved architecture and methods for data handling and distribution to the local application that provides GC in the radio base station(s) that is/are IOPS capable. SUMMARY

[0012] Certain aspects of the present disclosure and their embodiments may provide solutions to the

aforementioned or other challenges. In some embodiments, methods for wireless devices and IOPS systems to implement a discovery procedure when entering the IOPS operation mode are disclosed. In some embodiments, a method for an IOPS discovery procedure of other devices served by the IOPS system is provided by implementing a minimal local MC server for storing and updating information about served users. Also, in some embodiments, methods are disclosed for devices to publish presence of the associated user, subscribe to presence of other relevant users, and receive notifications about other relevant users. In some embodiments, these methods may be implemented to switch to an off-network like operation (similar to Proximity Services (ProSe) - 3GPP TS 23.303) for a "direct” communication based on IOPS EPS Internet Protocol (IP) connectivity. Hence, the MC services are provided directly from the MC service client available at the user's devices.

[0013] In some embodiments, an IOPS discovery procedure is based on a minimal local MC server functionality implementation and there is no need for data synchronization to support off-network, like GC supported by an IOPS system.

[0014] There are proposed herein various embodiments which address one or more of the issues disclosed herein.

[0015] One embodiment is directed to a method performed by a wireless device in a wireless communication system, the wireless communication system comprising at least one base station wherein the wireless device is served by a serving base station connected to or otherwise associated with a Mission Critical, MC, server and a local core network which enables the serving base station to provide radio connectivity for the wireless device to the local core network, the method comprising:

registering with the MC server connected to or otherwise associated with the serving base station;

sending a publish request towards the MC server to get the wireless device discovered at the MC server, the publish request comprising information about one or more configurations of the wireless device related to a MC

communication service provided by the MC server;

sending a subscription request towards the MC server to get notification about one or more other discovered wireless devices served by the serving base station, or served by other base station(s) connected to or otherwise associated with the MC server; and

receiving a subscription notification sent by the MC server, the subscription notification comprising information that notifies the wireless device about the one or more other discovered wireless devices served by the serving base station or served by other base station(s) connected to or otherwise associated with the MC server.

[0016] Another embodiment is directed to a method performed by a serving base station serving a plurality of wireless devices, which base station is connected to or otherwise associated with a Mission Critical, MC, server and a local core network which enables the serving base station to provide radio connectivity for the wireless devices to the local core network, the method comprising: receiving a publish request sent by one or more of the plurality of wireless devices to get the one or more of the plurality of wireless devices discovered at the MC server, where each publish request comprises information about one or more configurations of the wireless device related to a MC communication service provided by the MC server; receiving a subscription request sent by a first wireless device among the plurality of wireless devices to get notification about one or more other discovered wireless devices among the plurality of wireless devices served by the serving base station, or served by other base station(s) connected to or otherwise associated with the MC server; and

sending towards the first wireless device, a subscription notification comprising information that notifies the first wireless device about the one or more other discovered wireless devices among the plurality of wireless devices served by the serving base station, or other discovered wireless devices served by other base station(s) connected to or otherwise associated with the MC server.

[0017] Certain embodiments may provide one or more of the following technical advantage(s).

• Minimal hardware requirements compared to an MC services system (Central Processing Unit (CPU), memory, storage). This is important if, e.g., this functionality resides in 100s or even 1000s of nodes compared to only a few instances for a central system.

• Lower operational complexity since there is no need for synchronization of data between the central system and all distributed MC over IOPS systems.

• Coverage and capacity are considerably better when "direct” communication is supported by an IOPS system (e.g. based on IOPS EPS IP connectivity) compared to off-network communication utilizing ProSe.

• Also, latencies can be reduced compared to GC supported by a central MC system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in a constitute a part of this application, illustrate certain non-limiting embodiments of inventive concepts.

In the drawings:

Figure 1 illustrates one example of a cellular communications system 100 according to some embodiments of the present disclosure;

Figures 2A- 2C illustrate an example embodiment of a system operating on IOPS mode and the operation of the system in accordance with at least some embodiments the present disclosure;

Figure 3 is a schematic block diagram of a radio access node 300 according to some embodiments of the present disclosure;

Figure 4 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node 300 according to some embodiments of the present disclosure;

Figure 5 is a schematic block diagram of the radio access node 300 according to some other embodiments of the present disclosure; Figure 6 is a schematic block diagram of a UE 600 according to some embodiments of the present

disclosure;

Figure 7 is a schematic block diagram of the UE 600 according to some other embodiments of the present disclosure.

DETAILED DESCRIPTION

[0019] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0020] Radio Node: As used herein, a "radio node” is either a radio access node or a wireless device.

[0021] Radio Access Node: As used herein, a "radio access node” or "radio network node” is any node in a RAN of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a 3GPP 5G NR network or an eNB in a 3GPP LTE network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), and a relay node.

[0022] Core Network Node: As used herein, a "core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a MME, a P-GW, a Service Capability Exposure Function (SCEF), or the like.

[0023] Wireless Device: As used herein, a "wireless device” is any type of device that has access to (i.e., is served by) a cellular communications network by wirelessly transmitting and/or receiving signals to a radio access node(s). Some examples of a wireless device include, but are not limited to, a UE in a 3GPP network and a Machine Type Communication (MTC) device.

[0024] Network Node: As used herein, a "network node” is any node that is either part of the RAN or the core network of a cellular communications network/system.

[0025] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

[0026] Note that, in the description herein, reference may be made to the term "cell”; however, particularly with respect to 5G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0027] Figure 1 illustrates one example of a cellular communications system 100 according to some embodiments of the present disclosure. In the embodiments described herein, the cellular communications system 100 is an LTE system; however, the present disclosure is not limited thereto. For example, the cellular communications system 100 may alternatively be a 5G System (5GS) including a 5G NR RAN and a 5G core. In this example, the cellular communications system 100 includes base stations 102-1 and 102-2, which in LTE are referred to as eNBs and in 5G NR are referred to as gNBs, controlling corresponding macro cells 104-1 and 104-2. The base stations 102-1 and 102-2 are generally referred to herein collectively as base stations 102 and individually as base station 102. Likewise, the macro cells 104-1 and 104-2 are generally referred to herein collectively as macro cells 104 and individually as macro cell 104. The cellular communications system 100 may also include a number of low power nodes 106-1 through 106-4 controlling corresponding small cells 108-1 through 108-4. The low power nodes 106-1 through 106-4 can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells 108-1 through 108-4 may alternatively be provided by the base stations 102. The low power nodes 106-1 through 106-4 are generally referred to herein collectively as low power nodes 106 and individually as low power node 106. Likewise, the small cells 108-1 through 108-4 are generally referred to herein collectively as small cells 108 and individually as small cell 108. The base stations 102 (and optionally the low power nodes 106) are connected to a core network 110.

[0028] The base stations 102 and the low power nodes 106 provide service to wireless devices 112-1 through 112- 5 in the corresponding cells 104 and 108. The wireless devices 112-1 through 112-5 are generally referred to herein collectively as wireless devices 112 and individually as wireless device 112. The wireless devices 112 are also sometimes referred to herein as UEs.

[0029] While not illustrated, at least some of the base stations 102 and/or low power nodes 106 include or are connected to a local core (e.g., a Local EPC for LTE) and a minimal MC server, i.e. a local MC server. The minimal MC server may be part of the local core or separate from the local core. In the example embodiments described herein in which the cellular communications system 100 is an LTE system, the base stations 102 are eNBs, and one or more of these eNBs that support IOPS. Further, using IOPS, the cellular communications system 100 provides a GC service(s) (e.g., MCPTT) and enables the GC service(s) even in the case of backhaul failure by using the lOPs feature.

[0030] In this regard, the discussion now turns to some example embodiments implemented in an LTE system to provide MC service(s) (e.g., MC GC service(s) such as, e.g., MCPTT) using IOPS to guarantee the MC service(s) even when there is a failure in the backhaul network (i.e., the network connecting the eNB(s) to the EPC).

[0031] Throughout the present disclosure it is assumed that the UEs of public safety users, also referred to herein simply as UEs, have been provided with the configuration needed to utilize any MC service, e.g. during off-network operation mode. Such a configuration, which is also assumed to be stored by the UEs, may be the MC service UE configuration data, MC service user profile data, MC service group configuration data, and MC service configuration data or similar (see, e.g., details in 3GPP TS 23.280 Annex A). This configuration can be provided by either offline procedures or after the UEs have been authenticated and registered with the central MC system.

[0032] When there is a link failure between the RAN, i.e. eNBs, and the core network, i.e. the macro EPC, the IOPS system can provide local connectivity to UEs which are in the coverage of one or more lOPS-capable eNBs connected to the same IOPS core system, i.e. a Local EPC. [0033] In some embodiments, a minimal MC server (i.e. a local MC server) functionality is connected to the IOPS system to manage minimal MC service information and configurations. In some embodiments, the minimal MC server functionality is a minimum amount of functionality needed to support MC services when entering IOPS operation mode.

In some embodiments, the minimal MC server functionality may be implemented to switch to an off-network like operation. In this way, the required footprint is less and, therefore, better for a local implementation. The information to be managed comprises preconfigured basic information for the authentication and registration of users which may intend to utilize MC services over the IOPS system. Also, the minimal MC server is capable of storing and updating further configuration parameters about the served MC UEs. These parameters may comprise MC service UE configuration data, MC service user profile data, MC service group configuration data, and MC service configuration data or similar to be used during off-network operation mode, e.g. as described in 3GPP TS 23.280 Annex A for the MC service UE.

[0034] Those parameters are managed by the minimal MC server in subscription's tables. The subscription's tables are used to store the configuration of served UEs being discovered (i.e. published) by the minimal MC server. The information of the subscription's tables is utilized by the minimal MC server to notify served UEs about the presence of discovered relevant UEs within the IOPS system coverage area. Relevant UEs are defined based on any entry of the tables described in 3GPP TS 23.280 Annex A and 3GPP TS 23.379 Annex A for the MC service UE. For instance, relevant UEs can be the ones belonging to and/or associated with the same MC service group Identifier (ID).

[0035] As a further embodiment, the implementation description of the minimal MC server can also be extended for the implementation of a local MC system server connected to the IOPS system but comprising lower storage and synchronization requirements to be used for an on-network operation over IOPS. In other words, the minimal MC server may be specially utilized during IOPS operation to switch to an off-line network like operation (e.g., ProSe-like operation). However, the described implementation may also be considered for the implementation of, e.g., an MCPTT server connected to the local EPC during IOPS operation and normal on-network operation.

[0036] In another embodiment, the public safety UEs send a user configuration publish request to the minimal MC server connected to the IOPS system. The publish request may contain information about one or more of: the current MC service UE configuration, MC service user profile, MC service group configuration, and MC service configuration or MCPTT UE configuration, MCPTT user profile configuration, MCPTT related group configuration, and MCPTT service configuration or similar which is stored at the UE for off-network operation (the specific parameters are described in 3GPP TS 23.280 Annex A and 3GPP TS 23.379 Annex A for the MC service and MCPTT service U E/off-network). As described above, the information is then stored/updated into subscription's tables by the minimal MC server. In one embodiment, the minimal MC server sends a publish response, e.g. an acknowledge (ACK). This defines that the UE has been discovered (i.e. published) by the minimal MC server.

[0037] Furthermore, as a further embodiment, UEs send a subscription request to the minimal MC server to get notifications about the presence of other discovered relevant users, i.e. potential users for specific MC service communications, e.g. users within the same MC service group ID. As an additional embodiment, the publish request and subscription request can be combined as one publish/subscription request from the UEs. [0038] The subscription notifications are sent by the minimal MC server to the subscribed users (UEs) relying on the related information of the discovered relevant users contained in the subscription's tables. The subscription notifications include information that notifies the subscribed UEs about the presence of other discovered relevant UEs, i.e. potential UEs for specific MC service communications, e.g. UEs within the same MC service group ID. For example, a subscription notification may include a list of all discovered relevant UEs to the subscribed UE, respectively. In one embodiment, the subscription notification message is sent to the subscribed users as a response to the subscription request. In another embodiment, a subscription notification message is further sent periodically to the subscribed users.

In a further embodiment, a notification message is further triggered and sent from the minimal MC server when a new user is discovered and it is defined as a relevant user for other already subscribed users. For the case of the publish/subscription request there is only one response message, that is the subscription notification message.

[0039] Hence, the IOPS discovery procedure notifies served users of the IOPS system about the presence of other discovered relevant users within the IOPS system coverage area. The UEs store and utilize the subscription notification message for potential direct communications. Based on this procedure, it becomes clear that the IOPS system provides a much larger capacity and coverage area than ProSe for MC service communications between public safety UEs.

[0040] Thereby, as a further embodiment, for the IOPS operation mode implementing the IOPS discovery procedure, the UEs perform a direct communication for a specific MC service with the support of the IOPS system, e.g. based on, e.g., EPS IP connectivity. Based on this, lower delays/latencies are also expected as no MC application server connected to the EPC is involved in the communication between the UEs. For the EPS IP connectivity support, there are some possible solutions already specified in 3GPP. For instance, the Local IP Access (LIPA) function described in 3GPP TS 23.401.

[0041] Figures 2A through Figure 2C illustrate an example of a system operating on IOPS mode and the operation of the system in accordance with at least some of the embodiments described above. In particular, Figures 2A through 2C illustrate the operation of the system in multiple phases, namely, Phase A - initiation of IOPS operation mode (Figure 2A), Phase B - IOPS discovery procedure (Figure 2B), and Phase C - direct communication based on Local EPS IP connectivity (Figure 2C). In this example, it is assumed that UE1 and UE2 are defined as relevant UEs to each other.

[0042] Before proceeding with this discussion, some discussion of some key terms is beneficial. These key terms are as follows:

• Macro Network: As used herein, a "macro network” is wireless communication system including a macro RAN (e.g., a LTE RAN or 5G RAN or similar) and a macro core network (e.g., an EPC or 5G core or similar). For the macro network, the radio access nodes (e.g., base stations) forming the macro RAN are connected to the macro core network. In the example embodiment described below, the macro network is the LTE network including the LTE RAN and the EPC.

• Local Network: As used herein, a "local network” is a network including: (a) a local RAN provided by a radio access node(s) when the radio access node(s) are not connected to the macro core network (e.g., due to link failure) and (b) a local core network (e.g., a Local EPC or local 5G core or similar) connected to or otherwise associated with (e.g., implemented within) the radio access node(s) providing the local RAN. One example of a local RAN is that which is provided by an eNB(s) using IOPS, i.e. lOPS-capable eNB(s). The lOPS-capable eNB(s) may be part of the macro network as well. In the example embodiment described below, the local network is the IOPS system including the local RAN provided by the eNB using IOPS and the Local EPC, where the minimal MC server (i.e. local MC server) is connected to the Local EPC.

[0043] Phase A - Initiation of IOPS operation mode (Figure 2A):

1. UEs are attached to the macro network (e.g., macro Public Land Mobile Network (PLMN)). Here, the macro network is the LTE network including the shown lOPS-capable eNB(s) or similar and potentially other eNBs or similar (not shown) forming the LTE RAN and the (macro) EPC. Note that the EPC is referred to herein as the macro EPC to distinguish it from the Local EPC. Alternatively, the LTE network may be a 5G network including an lOPS-capable gNB and potentially other gNBs or similar base stations forming a 5G RAN. Similarly, the macro EPC may alternatively be a macro 5G core and the local EPC may alternatively be a local 5G core. However, for the sake of simplicity the example IOPS system illustrated in figures 2A-2C is described with reference to a LTE network including an lOPS-capable eNB, a local EPC and a macro EPC.

2. The lOPS-capable eNB(s) detects link failure to the macro EPC. Hence, UEs are detached from the macro network.

3. The lOPS-capable eNB(s) initiate and announce IOPS operation mode. It is assumed that the local EPC and minimal MC server connected to the local EPC are activated and are reachable by the lOPS-capable eNB(s). Note that the local EPC and the minimal MC server (i.e. the local MC server) can be implemented, e.g., within the eNB(s) or on separate node(s) connected to the eNB(s). Also note that while the communication service in this example is a MC service (e.g., MCPTT) and thus the server is referred to as a minimal MC server (i.e. a local MC server), the present disclosure is not limited thereto. The server may more generally be referred to as a communication server that supports a communication service.

4. The UEs detect the IOPS network (also referred to herein as the IOPS PLMN or more generally the local network) and perform an attach procedure. During the attachment procedure to the local EPC a local IP address is assigned to the UE as per the standard procedure when attaching to a Macro EPC. The Local EPC, therefore, acts as an IP router among the UEs locally attached to the same IOPS network.

[0044] Phase B - IOPS Discovery Procedure (Figure 2B):

5. The UEs served by lOPS-capable eNB(s) or similar (i.e. the serving base station(s)) perform authentication and registration with the minimal MC server associated with the eNB(s) or similar. The minimal MC server confirms MC service registration based on basic user information preconfigured in the minimal MC server.

6. The UEs send publish requests to the minimal MC server to get the UE published at the MC server

connected to or otherwise associated with the eNB(s). The publish request contains actual MC service user configuration profiles stored at the UEs (e.g., stored by MC service clients operating on the UEs). For each UE, the MC service user configuration profile may comprise information (e.g., static data) needed for configuration of the MC communication service (e.g., a MCPTT service) that is supported by the UE in question. For each UE, the MC communication service user configuration profile may, e.g., comprise information about at least one of: the current UE configuration, user profile, group configuration (e.g., group ID indicating a GC group to which the UE is associated), and service configuration data or similar which is stored at the UE for off-network operation (the specific parameters are described in 3GPP TS 23.280 Annex A and 3GPP TS 23.379 Annex A for the MC service and MCPTT service U E/off-network).

7. The minimal MC server stores or updates user configuration parameters for each UE based on the MC service user configuration profile(s) received in the publish requests into subscription's tables. In this step, the UEs are defined as discovered (e.g. defined as published) by the minimal MC server in response to the publish request received by the MC server.

8. (Optional) The minimal MC server sends publish responses to the UEs. The publish responses may be, e.g., ACKs.

9. The UEs send subscription requests to the minimal MC server to get notifications about the presence of other relevant UEs, preferably defined as discovered (e.g. defined as published) by the minimal MC server. The subscription request may comprise request information indicating that the UE requests notifications about the presence of other UEs served by the serving base station(s) within the IOPS system, for example potential users for specific MC service communications, e.g. users associated with the same group ID (e.g., MC service group ID).

10. The minimal MC server notifies the UEs about the status of their subscriptions via respective subscription notification messages, i.e. notifications about other relevant UEs, i.e. UEs that are preferably defined as discovered (e.g. defined as published) by the minimal MC server. For example, in step 10a, UE1 gets notified about the presence of UE2. Likewise, in step 10b, UE2 gets notified about the presence of UE1.

The subscription notification message may also be referred to herein as a subscription notification, a presence notification message, or a presence notification. The subscription notification includes information that notifies the subscribed UE about the presence of other discovered relevant UEs, i.e. potential UEs for specific MC service communications, e.g. UEs within the same MC service group ID. For example, a subscription notification may include a list of all discovered relevant UEs to the subscribed UE. The UEs store notification message information comprised in the respective presence notification messages. In this step, the UEs are defined as discovered by the other UEs served by the minimal MC server.

[0045] Phase C - Direct Communication based on Local EPS IP Connectivity (Figure 2C):

11. Based on the received subscription notification messages, the UEs performs a MC service communication, e.g. MCPTT, preferably utilizing the IOPS system for IP connectivity. For instance, relevant UEs can perform MC service communication with UEs belonging to and/or associated with a certain MC service group identified by a certain Identifier (e.g., group ID) or by other information in the MC service user configuration profile(s) of the UEs in question.

[0046] Figure 3 is a schematic block diagram of a radio access node 300 according to some embodiments of the present disclosure. The radio access node 300 may be, for example, a base station 102 or 106. As illustrated, the radio access node 300 includes a control system 302 that includes one or more processors 304 (e.g., CPUs, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 306, and a network interface 308. The one or more processors 304 are also referred to herein as processing circuitry. In addition, the radio access node 300 includes one or more radio units 310 that each includes one or more transmitters 312 and one or more receivers 314 coupled to one or more antennas 316. The radio units 310 may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) 310 is external to the control system 302 and connected to the control system 302 via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) 310 and potentially the antenna(s) 316 are integrated together with the control system 302. The one or more processors 304 operate to provide one or more functions of a radio access node 300 as described herein (e.g., one or more functions of the lOPS-capable eNB described above, e.g., with respect to Figures 2A through 2C and, in some embodiments, one or more functions of the Local EPC and/or the minimal MC server described above, e.g., with respect to Figures 2A through 2C). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 306 and executed by the one or more processors 304.

[0047] Figure 4 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node 300 according to some embodiments of the present disclosure. This discussion is equally applicable to other types of network nodes. Further, other types of network nodes may have similar virtualized architectures.

[0048] As used herein, a "virtualized” radio access node is an implementation of the radio access node 300 in which at least a portion of the functionality of the radio access node 300 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the radio access node 300 includes the control system 302 that includes the one or more processors 304 (e.g., CPUs, ASICs, FPGAs, and/or the like), the memory 306, and the network interface 308 and the one or more radio units 310 that each includes the one or more transmitters 312 and the one or more receivers 314 coupled to the one or more antennas 316, as described above. The control system 302 is connected to the radio unit(s) 310 via, for example, an optical cable or the like. The control system 302 is connected to one or more processing nodes 400 coupled to or included as part of a network(s) 402 via the network interface 308. Each processing node 400 includes one or more processors 404 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 406, and a network interface 408.

[0049] In this example, functions 410 of the radio access node 300 described herein (e.g., one or more functions of the lOPS-capable eNB described above, e.g., with respect to Figures 2A through 2C and, in some embodiments, one or more functions of the Local EPC and/or the minimal MC server described above, e.g., with respect to Figures 2A through 2C) are implemented at the one or more processing nodes 400 or distributed across the control system 302 and the one or more processing nodes 400 in any desired manner. In some particular embodiments, some or all of the functions 410 of the radio access node 300 described herein (e.g., one or more functions of the lOPS-capable eNB described above, e.g., with respect to Figures 2A through 2C and, in some embodiments, one or more functions of the Local EPC and/or the minimal MC server described above, e.g., with respect to Figures 2A through 2C) are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 400. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 400 and the control system 302 is used in order to carry out at least some of the desired functions 410. Notably, in some embodiments, the control system 302 may not be included, in which case the radio unit(s) 310 communicate directly with the processing node(s) 400 via an appropriate network interface(s).

[0050] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of radio access node 300 or a node (e.g., a processing node 400) implementing one or more of the functions 410 of the radio access node 300 (e.g., one or more functions of the lOPS-capable eNB described above, e.g., with respect to Figures 2A through 2C and, in some embodiments, one or more functions of the Local EPC and/or the minimal MC server described above, e.g., with respect to Figures 2A through 2C) in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non -transitory computer readable medium such as memory).

[0051] Figure 5 is a schematic block diagram of the radio access node 300 according to some other embodiments of the present disclosure. The radio access node 300 includes one or more modules 500, each of which is implemented in software. The module(s) 500 provide the functionality of the radio access node 300 described herein (e.g., one or more functions of the lOPS-capable eNB described above, e.g., with respect to Figures 2A through 2C and, in some embodiments, one or more functions of the Local EPC and/or the minimal MC server described above, e.g., with respect to Figures 2A through 2C). This discussion is equally applicable to the processing node 400 of Figure 4 where the modules 500 may be implemented at one of the processing nodes 400 or distributed across multiple processing nodes 400 and/or distributed across the processing node(s) 400 and the control system 302.

[0052] Figure 6 is a schematic block diagram of a UE 600 according to some embodiments of the present disclosure. As illustrated, the UE 600 includes one or more processors 602 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 604, and one or more transceivers 606 each including one or more transmitters 608 and one or more receivers 610 coupled to one or more antennas 612. The transceiver(s) 606 includes radio-front end circuitry connected to the antenna(s) 612 that is configured to condition signals communicated between the antenna(s) 612 and the processor(s) 602, as will be appreciated by on of ordinary skill in the art. The processors 602 are also referred to herein as processing circuitry. The transceivers 606 are also referred to herein as radio circuitry. In some embodiments, the functionality of the UE 600 described above (e.g., one or more functions of the UE described above, e.g., with respect to Figures 2A through 2C) may be fully or partially implemented in software that is, e.g., stored in the memory 604 and executed by the processor(s) 602. Note that the UE 600 may include additional components not illustrated in Figure 6 such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the UE 600 and/or allowing output of information from the UE 600), a power supply (e.g., a battery and associated power circuitry), etc.

[0053] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the UE 600 according to any of the embodiments described herein (e.g., one or more functions of the UE described above, e.g., with respect to Figures 2A through 2C) is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0054] Figure 7 is a schematic block diagram of the UE 600 according to some other embodiments of the present disclosure. The UE 600 includes one or more modules 700, each of which is implemented in software. The module(s) 700 provide the functionality of the UE 600 described herein (e.g., one or more functions of the UE described above, e.g., with respect to Figures 2A through 2C).

Some Embodiments Described Above May Be Summarized in the Following Manner

Group A Embodiments

1. A method performed by a wireless device (112) in a wireless communication system, the wireless

communication system comprising at least one base station (102, 106, 300) wherein the wireless device is served by a serving base station (102, 106, 300) connected to or otherwise associated with a Mission Critical, MC, server (210) and a local core network (220) which enables the serving base station to provide radio connectivity for the wireless device to the local core network, the method comprising:

registering (5) with a MC server (210) connected to or otherwise associated with the serving base station; sending (6) a publish request towards the MC server to get the wireless device discovered at the MC server, the publish request comprising information about one or more configurations of the wireless device related to a MC communication service provided by the MC server;

sending (9) a subscription request towards the MC server to get notification about one or more other discovered wireless devices served by the serving base station, or served by other base station(s) connected to or otherwise associated with the MC server; and

receiving (10) a subscription notification sent by the MC server, the subscription notification comprising information that notifies the wireless device about the one or more other discovered wireless devices served by the serving base station, or served by other base station(s) connected to or otherwise associated with the MC server. 2. The method of embodiment 1 , the method further comprises communicating with at least one of the one or more other discovered wireless devices via the MC communication service.

3. The method of embodiment 2 wherein communicating with the at least one of the one or more other discovered wireless devices via the MC communication service comprises communicating with at least one of the one or more other discovered wireless devices via the communication service based on Evolved Packet System, EPS, or 5G System, 5GS, Internet Protocol, IP, connectivity.

4. The method of any one of embodiment 1-3 wherein the MC communication service is a MC Group

Communication, GC, service (e.g., a MC Push to Talk, MCPTT, communication service).

5. The method of any one of embodiments 1 -4 wherein, the publish request comprises at least one of:

• information about a current configuration of the wireless device (e.g. a Group Identifier ( Group ID) indicating a GC group to which the wireless device is associated);

• a MC service user profile configuration of the wireless device; and/or

• GC and service configuration data.

6. The method of any one of embodiments 1-5 wherein the subscription request comprises a Group ID indicating a GC group to which the one or more other discovered wireless devices are associated.

7. The method of any one of embodiment 1-6 wherein receiving the subscription notification comprises receiving the subscription notification sent by the MC server in response to sending the subscription request.

8. The method of any one of embodiment 1-7 wherein receiving the subscription notification comprises receiving periodic subscription notifications, including the subscription notification, transmitted by the MC server.

9. The method of any one of embodiments 1-8 wherein the subscription request and the publish request are sent separately, or wherein the subscription request and the publish request are sent as a combined publish and subscription request.

10. The method of any one of embodiments 1 -9 wherein the wireless device and the one or more other discovered wireless devices belong to or are associated with the same Group ID, indicating a GC Group to which the wireless device and the one or more other discovered wireless devices are associated. Group B Embodiments

11. A method performed by a serving base station (102, 106, 300) serving a plurality of wireless devices (112), which base station is connected to or otherwise associated with a Mission Critical, MC, server (210) and a local core network (220) which enables the serving base station to provide radio connectivity for the wireless devices to the local core network, the method comprising:

receiving (6) a publish request sent by one or more of the plurality of wireless devices to get the one or more of the plurality of wireless devices discovered at the MC server, where each publish request comprises information about one or more configurations of the wireless device related to a MC communication service provided by the MC server; receiving (9) a subscription request sent by a first wireless device among the plurality of wireless devices to get notification about one or more other discovered wireless devices among the plurality of wireless devices served by the serving base station, or served by other base station(s) connected to or otherwise associated with the MC server; and sending (10) towards the first wireless device, a subscription notification comprising information that notifies the first wireless device about the one or more other discovered wireless devices among the plurality of wireless devices served by the serving base station, or other discovered wireless devices served by other base station(s) connected to or otherwise associated with the MC server.

12. The method of embodiment 11, wherein the serving base station is enabled to provide the local radio access network via an Isolated Radio Access Network Operations for Public Safety, IOPS, feature, and wherein the local core network is a local Evolved Packet Core, EPC or a local 5G core network.

13. The method of any one of embodiment 11-12, wherein the MC communication service is a MC Group

Communication, GC, service (e.g., a MC Push to Talk, MCPTT, communication service).

14. The method of any one of embodiment 11-13, wherein the publish request comprises:

• information about a current configuration of the first wireless device (e.g. a Group Identifier (Group ID) indicating a GC group to which the wireless device is associated);

• a MC service user profile configuration of the wireless device; and/or

• GC and service configuration data,

stored at the wireless device for off-network operation.

15. The method of any one of embodiments 11-14 wherein the subscription request comprises a Group ID indicating a GC group to which the one or more other discovered wireless devices are associated.

16. The method of any one of embodiment 11-15, wherein sending the subscription notification comprises sending the subscription notification to the first wireless device in response to receiving the subscription request. 17. The method of any one embodiment 11-16, wherein sending the subscription notification comprises sending periodic subscription notifications, including the subscription notification, towards the first wireless device.

18. The method of any one of embodiments 11-17, wherein the subscription request and the publish request are received separately, or wherein the subscription request and the publish request are received as a combined publish and subscription request.

19. The method of any one of embodiments 11-18, wherein the first wireless device and the one or more other discovered wireless devices are associated with the same Group ID, indicating a GC group to which the first wireless device and the one or more other published wireless devices are associated.

Group C Embodiments

20. A wireless device (112) for a wireless communication system, the wireless communication system comprising at least one base station (102, 106, 300), wherein the wireless device is served by a serving base station (102, 106, 300), the wireless device comprising:

one or more transmitters;

one or more receivers; and

processing circuitry associated with the one or more transmitters and the one or more receivers, the processing circuitry configured to cause the wireless device to perform any of the steps of any of the Group A embodiments.

21. A wireless device for a wireless communication system, the wireless communication system comprising at least one base station (102, 106, 300), wherein the wireless device is served by a serving base station (102, 106, 300), and wherein the wireless device adapted to perform any of the steps of any of the Group A embodiments.

22. A serving base station (102, 106, 300) serving a plurality of wireless devices (112), which base station is connected to or otherwise associated with a Mission Critical, MC, server (210) and a local core network (220) which enables the serving base station to provide radio connectivity for the wireless devices to the local core network, the serving base station comprising:

one or more transmitters;

one or more receivers; and

[0055] processing circuitry associated with the one or more transmitters and the one or more receivers, the processing circuitry configured to cause the serving base station to perform any of the steps of any of the Group B embodiments. [0056] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data

communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

[0057] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

Abbreviations

At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

3GPP Third Generation Partnership Project

5G Fifth Generation

5GS Fifth Generation System

ACK Acknowledgement

ASIC Application Specific Integrated Circuit

CPU Central Processing Unit

DMO Direct Mode Operation

DSP Digital Signal Processor

eNB Enhanced or Evolved Node B

EPC Evolved Packet Core

EPS Evolved Packet System

E-UTRAN Evolved Universal Terrestrial Radio Access Network

FPGA Field Programmable Gate Array

GC Group Communication

GCPTT Group Communication Push to Talk

gNB New Radio Base Station • HSS Home Subscriber Server

• ID Identifier

• IOPS Isolated Evolved Universal Terrestrial Radio Access Network Operations for Public

Safety

• IP Internet Protocol

• LI PA Local Internet Protocol Access

• LTE Long Term Evolution

• MC Mission Critical

• MCPTT Mission Critical Push to Talk

• MME Mobility Management Entity

• MTC Machine Type Communication

• NR New Radio

• P-GW Packet Data Network Gateway

• PLMN Public Land Mobile Network

• ProSe Proximity Service

• PTT Push to Talk

• RAM Random Access Memory

• RAN Radio Access Network

• ROM Read Only Memory

• RRH Remote Radio Head

• SCEF Service Capability Exposure Function

• S-GW Serving Gateway

• TMO Trunked Mode Operation

• TS Technical Specification

• UE User Equipment