Roaming radio access to public land mobile networks

Abstract

A method for providing roaming radio access at a first Public Land Mobile Network (PLMN). An indicator is broadcasted from a radio access node of the first PLMN that indicates that the access node will provide connectivity service to a subscriber of a second, different PLMN despite the subscriber of the second PLMN having a prohibited PLMN list including the first PLMN.

Description

Technical Field

[0001] The present disclosure relates to providing and / or obtaining roaming radio access at a first public land mobile network (PLMN) to a subscriber of a second PLMN. A network entity of a PLMN configured to provide roaming radio access and / or a user equipment (UE) configured to operate (obtain radio access) is also contemplated. Background Art

[0002] Energy consumption in mobile (cellular) networks is an important issue for mobile network operators (MNOs). Recent studies have shown that base stations and data centers in radio access networks consume the most power of all entities in the network. Compared with systems based on earlier architectures, 5G systems typically require more antennas, operate over a wider range of frequency bands, and denser layers of small cells, all of which lead to even higher power consumption. International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Recommendation L.1470 (01 / 2020): "Greenhouse Gas Emissions Trajectories for the Information and Communication Technology Sector Compatible with the UNFCCC Paris Agreement" (International Telecommunication Union: Geneva, Switzerland, 2020) details that within a base station, the largest energy consumption comes from radio frequency (RF) equipment (power amplifiers plus transceivers and cables), which typically use about 65% of the total energy consumption, with cooling (17.5%), digital signal processing and baseband components (10%), and AC / DC converters (7.5%) making up the rest. Improved energy efficiency can be achieved through a variety of solutions to consume less energy, including smart buildings, core virtualization, and enhancing RAN efficiency through modernization of legacy equipment and implementation of low-power solutions.

[0003] Tethering has been proposed as a technique to reduce energy consumption ( https: / / networks.imdea.org / wp-content / uploads / 2020 / 10 / network_sharing.pdf ). In this approach, the radio or core network infrastructure can be shared by more than one MNO. Figure 1 , shows a schematic diagram of a range of network sharing options, some of which have been specified by the Third Generation Partnership Project (3GPP). These have different sharing options: service platform 10; home subscriber server (HSS) / home location register (HLR) 20; core network (CN) circuit switched (CS) / packet switched (PS) architecture 30; radio network controller (RNC) 40; radio access node (Node B) 50; and cell / frequency resources 60.

[0004] In site sharing 100, radio access nodes (Node Bs) for different PLMNs are co-located. In a multi-operator radio access network (MORAN) 110 (3GPP unspecified), at least a portion of the RNC 40 and the radio access node 50 are shared. In a multi-operator core network (MOCN) 120, the RNC 40, the radio access node 50, and the cell / frequency resources 60 are shared. Finally, the gateway core network (GWCN) 130 shares the CN CS / PS architecture 30, the radio access node 50, and the cell / frequency resources 60 between PLMNs. The MOCN 120 and the GWCN 130 are specified in the 3GPP Technical Specification (TS) 23.251.

[0005] Currently defined network sharing options envision close coordination of network deployment and planning between MNOs using multiple PLMNs. Along these lines, WO-2013 / 064419 describes network sharing that can handle handover of a UE from a source location to a target shared location. WO-2010 / 136452 relates to session transfer between access networks of a UE. WO-2011 / 020676 describes inter-domain roaming between a home PLMN equipped with a circuit switched over packet switched (CSoPS) interworking function (IWF) and a visited PLMN supporting a single radio voice call continuity (SRVCC) mechanism.

[0006] These approaches may not be efficient. The additional signaling required to allow one PLMN to accept subscribers from different PLMNs on an ad hoc basis is significant in existing network sharing techniques. A more flexible and robust way of handling network sharing, especially on a time-limited basis, is desirable. Summary of the invention

[0007] Against this background, the present disclosure provides a method for providing roaming radio access at a first public land mobile network (PLMN) according to claim 1, a network entity of the PLMN consistent with claim 5, a method of accessing the first PLMN at a subscriber of a second PLMN as defined by claim 6, and a user equipment (UE) consistent with claim 12. Further preferred features are disclosed with reference to the claims and in the following description.

[0008] A radio access node (e.g., a base station, eNB, or gNB) of a first PLMN broadcasts an indicator that the PLMN (and specifically, the access node) provides connectivity services to subscribers of at least one other PLMN (the at least one other PLMN is typically identified in the broadcast), even though these subscribers have a forbidden PLMN list that includes the first PLMN. In other words, the first PLMN allows these subscribers access and informs them that they can ignore the indication in its forbidden list that prevents them from seeking access to the first PLMN. A network entity such as a radio access node of a PLMN may be configured to operate according to the method.

[0009] In contrast, a subscriber of a second PLMN having a forbidden PLMN list including the first PLMN receives the broadcast and (in response) transmits a registration request for the first PLMN. This can be implemented at a UE associated with the subscriber (e.g., with a subscriber identity module SIM of the subscriber). In other words, the subscriber can ignore the information about its forbidden list and access the first PLMN. The UE can also be configured to operate according to the method.

[0010] Thus, the method allows network sharing based on roaming. Unlike conventional roaming mechanisms based on national agreements between PLMNs, the method allows roaming on a local basis and / or in a more time-limited manner.

[0011] In the case where a radio access node of a first PLMN receives a registration request from a subscriber of another PLMN, the request includes an identifier of the subscriber (e.g., an International Mobile Subscriber Identity IMSI or a Subscription Hidden Identifier SUCI), which it can use to determine the home PLMN of the subscriber. The subscriber can then be allowed access if the home PLMN is one that the first PLMN allows access to upon request. The access can be achieved by the first PLMN interfacing with the subscriber's home PLMN and an interworking function (IWF). This can allow the first PLMN to receive data about the subscriber. Based on the received data, the subscriber can register with the first PLMN (in a normal manner).

[0012] Subscribers receiving a broadcast from the first PLMN may delay transmitting a registration request, in particular according to the randomly generated time value. This may help distribute registration requests from subscribers when the same broadcast is received from the first PLMN. The maximum value of the randomly generated time value may be indicated in the broadcast from the radio access node.

[0013] After registering with the first PLMN, the subscriber may then receive services from the first PLMN. Additionally or alternatively, the subscriber may perform a PLMN search (in the normal manner when roaming). The PLMN search may then indicate that the subscriber's home PLMN (or equivalent PLMN) may be accessible and / or provide services. In response, the subscriber may then initiate a process to register with that PLMN. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The method of the present disclosure can be put into practice in various ways, one of which will now be described by way of example only and with reference to the accompanying drawings, in which:

[0015] Figure 1 a schematic diagram showing a range of network sharing options; and

[0016] Figure 2 A method for providing roaming radio access and / or accessing a PLMN from a roaming subscriber according to the present disclosure is schematically depicted. DETAILED DESCRIPTION

[0017] In the example, PLMN A provides services in a specific geographical area (e.g., an area of ​​30 km radius). If no other PLMN has an access node covering the area or if the PLMNs have switched off their access nodes covering the area, subscribers of PLMNs other than PLMN A will generally not have any radio access in the area. An exception to this would be subscribers of another PLMN that has a roaming agreement with PLMN A. Those subscribers will be able to obtain roaming access to PLMN A. Roaming agreements are generally reached on a national basis.

[0018] Subscribers to other PLMNs without a national roaming agreement (e.g., subscribers to PLMN B1 or PLMN B2, which may have a generally co-extensive geographic coverage area with PLMN A) will typically have a forbidden list that includes PLMN A. The UEs of these subscribers are configured not to access any PLMN on their forbidden list, even if there are no other PLMNs available for service. Therefore, in such areas, there is no room for UE connectivity.

[0019] In some cases, network sharing between PLMN A and one or both of PLMN B1 and PLMN B2 may be possible. For example, there may be a period of time when PLMN B1 and / or PLMN B2 choose to shut down the access nodes they provide in a certain geographical area. During this period of time, it will be desirable for subscribers of PLMN B1 and / or PLMN B2 to access PLMN A. However, each of such subscribers will have a prohibited list that includes PLMN A. Therefore, they will not be able to obtain connectivity from PLMN A.

[0020] Consistent with national roaming agreements (or the MORAN / MOCN / GWCN approach discussed above), PLMN A and PLMN B1 / B2 may be declared as equivalent PLMNs. Then, for example, one base station (gNB) from PLMN A may broadcast configurations for both PLMNs (PLMN A and PLMN B1 / B2) and connect to both core networks (the core networks of PLMN A and PLMN B1 / B2). This is complex and inefficient when simpler roaming arrangements are possible.

[0021] Changing the prohibited list of these subscribers on a limited time basis is not simple. In addition, the signaling required to do so will be significant (only supplied by the home PLMN core network), cannot be applied to only a subset of subscribers, and will need to occur before the access nodes of PLMN B1 and / or PLMN B2 are closed. Any subscriber who does not have connectivity at this time (for example, because the UE has been powered off) will miss the update and therefore do not have access. In this case, even after successfully connecting to PLMN A, an attachment request is sent to the core network of PLMN A and further to the HLR / HSS and UDM of PLMN B. In the case of this rejection (which may apply to many UEs located in areas where PLMN B still provides coverage), all of the signaling resources in the two networks are wasted. A more flexible and robust solution with more efficient signaling would be advantageous.

[0022] The method of the present disclosure improves signaling efficiency by temporarily allowing the UE to ignore the fact that PLMN A is on its forbidden list. There may not necessarily be a general or country-wide roaming or network sharing agreement between PLMNs, but only for certain areas within a country. For example, this may be the case where only one operator has deployed a particular radio access technology (e.g., 5G) in a certain geographical area.

[0023] Reference now Figure 2, schematically depicts a method for providing roaming radio access and / or accessing a PLMN from a roaming subscriber according to the present disclosure. This shows: a PLMN A Radio Access Network (RAN) 200; a PLMN A Access and Mobility Management Function (AMF) 210; an Interworking Function (IWF) 220; a PLMN B Unified Data Management (UDM) 230; and a UE 240.

[0024] In the indicator step 300, even if PLMN A is on the forbidden PLMN list of the UE, PLMN A RAN 200 broadcasts an indicator that it can provide connectivity services to subscribers (UEs) from different PLMNNs (e.g., PLMN B or a dummy PLMNN, which means that any UE is allowed with respect to this PLMN). PLMN B is referred to as a forbidden PLMN (FPLMN) hereinafter. As an example, the indicator may be broadcast by PLMN A RAN 200, which broadcasts the configuration of PLMN B with a flag to remove the PLMN B from the forbidden PLMN list.

[0025] In the UE response step 310, the UE 240 having the home PLMN as PLMN B determines that it cannot synchronize with the radio access cell of PLMN B. It should be noted that there may be various situations where a UE of an FPLMN loses the coverage provided by its home PLMN. For example, the FPLMN may not have deployed any RAN in the geographic area. In another case, the FPLMN may have deployed a RAN in the geographic area, but then the FPLMN intentionally turns it off for a period of time (e.g., part of the night or the entire night) for energy saving and / or service purposes.

[0026] In any case, the UE 240 thus reads the master information block (MISB) and system information block 1 (SIB1) of the cell from PLMN A (RAN 200). After decoding them, and based on the indicators broadcasted in step 200, the UE 240 initiates registration with PLMN A by providing the mobility identity (i.e., SUCI or more generally, IMSI). Alternatively, it may also decide not to start registration. This may be steered by the subscriber's home PLMN policy (i.e., the policy of PLMN B).

[0027] To prevent a sudden signaling "storm" of UEs attempting to simultaneously access PLMN A, the UE may start a timer with a random time value between 0 and a preset level (T). The value of T may be part of a service agreement based on a geographic area or broadcast by PLMN A as part of the configuration of PLMN B access in indicator step 300.

[0028] In an identification step 330, the PLMN AMF 210 (although this may be another entity) identifies the home PLMN of the UE 240. This is achieved by validating the received SUCI (e.g., confirming that the home PLMN of the SUCI is PLMN B).

[0029] If there is a geographical area based service agreement between PLMN A and PLMN B, the PLMN A AMF 210 performs a query step 330, in which it queries the IWF 220 by providing the received SUCI. The IWF 220 is a predefined and configured network entity for temporary interworking between PLMN A and PLMN B. The term IWF is used for convenience, and the exact mechanism of this interworking can be implemented in a number of different ways.

[0030] The IWF 220 obtains the subscriber data of the relevant UE from the PLMN B UDM 230 in an acquisition step 340 and passes it to the PLMN A AMF 210. In some cases, the PLMN B may reject the request from the PLMN A. In this case, the UE 240 is not allowed to access the PLMN A.

[0031] The normal process of handling national roaming services is followed in a roaming access step 350. This allows the UE 240 to access and receive services from the PLMN A. During this period, the UE 240 will be in connected mode and therefore a slave of the PLMN A, which allows the UE 240 to switch to a prohibited tracking area if the UE 240 is relocated during this time.

[0032] UE 240 periodically performs a search step 360 in which UE 240 performs a normal PLMN search. This is especially true when UE 240 moves out of the coverage area of ​​PLMN A. If UE 240 identifies PLMN B as available for access, it will return to PLMN B for access and service. PLMN A will remain in the forbidden list of UE 240.

[0033] In a general sense and in a first aspect, a method for providing roaming radio access at a first public land mobile network (PLMN) may be considered. A radio access node of the first PLMN broadcasts an indicator that the access node will provide connectivity services to subscribers of a second, different PLMN, even though the subscribers of the second PLMN have a forbidden PLMN list that includes the first PLMN. This aspect may additionally or alternatively reside in a network entity of the PLMN configured to provide roaming radio access from the PLMN accordingly.

[0034] Conversely and in accordance with a second aspect, a method of accessing a first PLMN at a subscriber of a second PLMN may be considered, the subscriber having a prohibited PLMN list including the first PLMN. The subscriber receives a broadcast from a radio access node of the first PLMN, the broadcast including an indicator that the access node will provide connectivity services to subscribers of the second PLMN. The subscriber then advantageously transmits a registration request for the first PLMN. This aspect may additionally or alternatively reside in a user equipment (UE) configured to operate according to such a method.

[0035] The first aspect and the second aspect may be considered individually or in combination. Optional and / or advantageous additional features may be considered. These may apply to either or both aspects as appropriate.

[0036] For example, the radio access node may receive a registration request from a subscriber of the second PLMN. Whether it is considered from the perspective of the transmission or reception of the registration request, it can be understood that the registration request generally includes an identifier of the subscriber (e.g., an international mobile subscriber identity IMSI or a subscription hidden identifier SUCI). The first PLMN can then determine the home PLMN of the subscriber based on the received identifier (this can occur at a network entity of the first PLMN, such as a radio access node, or at an access and mobility management function AMF of the first PLMN). If the determined home PLMN is the second PLMN (e.g., because the first and second PLMNs have an interoperability agreement), the first PLMN is connected to an interworking function (IWF) with the second PLMN to receive data about the subscriber of the second PLMN. This can also occur at a network entity of the first PLMN, such as an AMF. The IWF can be a specific entity or interface that allows queries between the first and second PLMNs. The first PLMN (specifically its core network) can then register the subscriber of the second PLMN with the first PLMN based on the data about the subscriber received from the interworking function.

[0037] The subscriber may delay transmitting the registration request. The duration of the delay is advantageously based on a randomly generated time value. For example, a maximum value of the randomly generated time value may be indicated in a broadcast from the radio access node.

[0038] After registering with the first PLMN, the subscriber may perform a PLMN search indicating accessibility of the second PLMN.The subscriber may then initiate a process of registering with the second PLMN in response to the PLMN search indicating accessibility of the second PLMN.

[0039] Although specific embodiments have now been described, the skilled person will appreciate that various modifications and variations are possible. In addition, any combination of specific features shown with reference to one embodiment or with reference to multiple embodiments is also provided, even if the combination is not explicitly described in detail herein.

[0040] Specific modifications and variations in alternative embodiments will now be discussed. Although the term PLMN is used throughout this disclosure, this covers mobile private networks (MPNs). Where a second PLMN (PLMN B) has been discussed herein, this may include multiple second PLMNs (e.g., PLMN B1 and PLMN B2), which may in some cases be equivalent networks to one another. Specific network entities are contemplated in this disclosure, but the skilled person will recognize that alternative entities may be used, for example with reference to different network architectures.

Claims

1. A method for providing roaming radio access at a first public land mobile network (PLMN), the method comprising: An indicator is broadcasted from a radio access node of a first PLMN that the access node will provide connectivity services to subscribers of a second, different PLMN, even though the subscribers of the second PLMN have a forbidden PLMN list that includes the first PLMN.

2. The method according to claim 1, further comprising: receiving, at the radio access node, a registration request from a subscriber of the second PLMN, the registration request including an identifier of the subscriber; determining the home PLMN of the subscriber based on the received identifier; and If the determined home PLMN is the second PLMN, interworking functions are interfaced from the first PLMN to the second PLMN to receive data about subscribers of the second PLMN.

3. The method according to claim 2, further comprising: Based on the data about the subscriber received from the interworking function, the subscriber of the second PLMN is registered with the first PLMN.

4. A method according to claim 2 or claim 3, wherein the identifier of the subscriber is an International Mobile Subscriber Identity (IMSI).

5. A network entity of a Public Land Mobile Network, PLMN, configured to provide roaming radio access from the PLMN according to the method of any preceding claim.

6. A method of accessing a first PLMN at a subscriber of a second public land mobile network PLMN, the subscriber having a forbidden PLMN list including the first PLMN, the method comprising: receiving, at a subscriber, a broadcast from a radio access node of a first PLMN, the broadcast including an indicator that the access node will provide connectivity services to subscribers of a second PLMN; as well as A registration request is transmitted from a subscriber to a first PLMN. The method of claim 6 , wherein the registration request includes an identifier of the subscriber.

8. The method of claim 7, wherein the identifier of the subscriber is an International Mobile Subscriber Identity (IMSI).

9. The method according to any one of claims 6 to 8, further comprising: The step of delaying transmission of the registration request according to a randomly generated time value.

10. The method of claim 9, wherein the maximum value of the randomly generated time value is indicated in a broadcast from the radio access node.

11. The method according to any one of claims 6 to 10, further comprising: After registering with the first PLMN, performing a PLMN search indicating accessibility of a second PLMN; as well as In response to the PLMN search indicating accessibility of the second PLMN, a process of registering with the second PLMN is initiated.

12. A user equipment UE, configured to operate according to the method according to any one of claims 6 to 11.

Images