Patent Description:
Wireless telecommunication systems are under constant development. There is a constant need for higher data rates and high quality of service. Reliability requirements are constantly rising and ways and means to ensure reliable connections and data traffic while keeping transmission delays minimal are constantly under development.

In communication systems, and communication systems supporting multiple access nodes or base stations in particular, handover is one of the key procedures carried out for mobility while in connected. In many systems, handover procedure of a user terminal is initiated based on the measurement report received from user terminal when a reference signal received power level from a nearby node is better than the reference signal received power level from the serving node. Source node initiates handover request to target node and upon successful handover, the communication link or links are transferred to the target node.

Developing networks enable new services to customers. One suggested service is Network Slicing, which enables offering connectivity, quality of service and data processing solutions tailored to specific customers' requirements. A network slice is a logical end-to-end virtual network that can be dynamically created and that provides specific capabilities and characteristics.

User terminals may utilise one or more slices in communication. To ensure smooth handovers and efficient mobility between the nodes slices should be taken into account.

<CIT> discloses communications for network slicing using resource status information.

<CIT>, <CIT> and <CIT> disclose communications utilising network slicing. <CIT> discloses transmission of base station load status to another base station.

According to an aspect of the present invention, there is provided an apparatus of claim <NUM>.

According to an aspect of the present invention, there is provided a method of claim <NUM>.

According to an aspect of the present invention, there is provided computer program of claim <NUM>.

In the following, different exemplifying embodiments will be described using, as an example an access architecture to which the embodiments may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A), enhanced LTE (eLTE), or new radio (NR, <NUM>), without restricting the embodiments to such an architecture, however. It is obvious for a person skilled in the art that the embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems may be the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E-UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), or any combination thereof.

<FIG> shows user devices <NUM> and <NUM> configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e/g)NodeB) <NUM> providing the cell. The physical link from a user device to a (e/g)NodeB is called uplink or reverse link and the physical link from the (e/g)NodeB to the user device is called downlink or forward link. It should be appreciated that (e/g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage.

A communications system typically comprises more than one (e/g)NodeB in which case the (e/g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for data and signaling purposes. The (e/g)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The (e/g)NodeB may also be referred to as a base station, an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (e/g)NodeB includes or is coupled to transceivers. From the transceivers of the (e/g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e/g)NodeB is further connected to core network <NUM> (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobile management entity (MME), User Plane Function (UPF), etc..

One technology in the above network may be denoted as narrowband Internet of Things (NB-Iot). The user device may also be a device having capability to operate utilizing enhanced machine-type communication (eMTC).

CPS may enable the implementation and exploitation of massive amounts of interconnected, ICT, devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations.

<NUM> enables using multiple input - multiple output (MIMO) antennas, perhaps more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. <NUM> mobile communications support a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. <NUM> is expected to have multiple radio interfaces, namely below <NUM>, and mmWave, and also being integrable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and <NUM> radio interface access comes from small cells by aggregation to the LTE. In other words, <NUM> is planned to support both inter-RAT operability (such as LTE-<NUM>) and inter-RI operability (inter-radio interface operability, such as below <NUM> - cmWave, above <NUM> -mmWave). As mentioned, one of the concepts considered to be used in <NUM> networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure.

The low latency applications and services in <NUM> require to bring the content close to the radio which leads to local break out and mobile edge computing, (MEC). Mobile edge computing provides a distributed computing environment for application and service hosting.

It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be non-existent.

In an embodiment, <NUM> may also utilize satellite communication to enhance or complement the coverage of <NUM> service, for example by providing backhauling. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed).

It is obvious for a person skilled in the art that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e/g)NodeBs, the user device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the (e/g)NodeBs may be a Home(e/g)nodeB.

As mentioned, radio access network may be split into two logical entities called Central Unit (CU) and Distributed Unit (DU). In prior art, both CU and DU supplied by the same vendor. Thus, they are designed together and interworking between the units is easy. The interface between CU and DU is currently being standardized by 3GPP and it is denoted F1 interface. Therefore, in the future the network operators may have the flexibility to choose different vendors for CU and DU. Different vendors can provide different failure and recovery characteristics for the units. If the failure and recovery scenarios of the units are not handled in a coordinated manner, it will result in inconsistent states in the CU and DU (which may lead to subsequent call failures, for example). Thus there is a need to enable the CU and DU from different vendors to coordinate operation to handle failure conditions and recovery, taking into account the potential differences in resiliency capabilities between the CU and DU.

As mentioned above, network slicing is a concept where network resources of an end-to-end connection between a user terminal and another end point in a public land mobile network (PLMN) are sliced. Similar network slicing may be employed also in private networks. A network slice may be understood as a logical end-to-end network that can be dynamically created and/or modified. The network(s) between the end devices may all be sliced from one end device to the other end device, the slices thus forming logical pipelines within the network(s). User terminal may access a slice over a radio interface. Each pipeline/slice may serve a particular service type. So far, three different network slice/service types have ben been standardized: eMBB (slice suitable for the handling of <NUM> enhanced Mobile Broadband), URLLC (slice suitable for the handling of Ultra-Reliable Low Latency Communications) and MIoT (slice suitable for the handling of massive Internet of Things). Communications Service Providers (CSPs) are able to define additional network slice/service types if needed. A given user terminal may access to multiple slices over the same Access Network ( over the same radio interface, for example).

Thus, network slicing enables a communications service provider to provide dedicated virtual networks over a common network infrastructure. The different virtual or logical networks may be designed to provide different networking characteristics such as different qualities of service (QoS). For example, the virtual networks may be customized to meet specific needs of various applications, services, devices, customers and/or operators.

In a system where network slicing is utilized, a single physical network or a group of networks is sliced into multiple virtual networks (slices) that can support different radio access networks (RANs) or different service types running across a single RAN. The network slicing may be used to partition a core network of a cellular communication system such as a <NUM> system, but it may also be implemented in the RAN such as the WLAN.

Each network slice may be optimized to provide resources and network topology for the specific service and traffic that will use the slice. Network resources may be allocated according to requirements in terms of mobility, capacity, connectivity and coverage such that particular demands of each use case will be met. Physical network components or resources may be shared across different network slices.

The slices supported by nearby base stations or access nodes may vary. In the existing mobility procedure, the handover of a user terminal from a source base station to a target base station is initiated only based on the measurement report received from the user terminal. However, slice aware admission and load status of the target base station is not being evaluated by the source base station before the initiation of handover request. Hence there is a possibility of a rejection of handover by the target base station based on slice or resource availability.

In an embodiment of the invention, selection of handover target base station is performed not only based on the user terminal measurement report but also for slice availability and congestion status for the specific slice. This will help to find the best suitable neighbour cell based on the slices.

<FIG> is a signalling chart illustrating an embodiment, <FIG> is a flowchart illustrating the operation of a source gNB and <FIG> is a flowchart illustrating the operation of a a gNB in general in an embodiment.

<FIG> illustrates an example where a user terminal <NUM> is connected to a gNB1 <NUM>. The user terminal utilises slices in communication. In this simplified example there are two nearby gNBs, gNB2 <NUM> and gNB3 <NUM>.

In phase <NUM>, the gNBs are configured to indicate to other gNBs slices supported by the gNBs. In an embodiment, the gNBs obtain the information from NG-RAN Node configuration Update-message.

In phase <NUM>, the gNBs are configured to determine current load per slice.

The gNBs are configured to determine indicate to other gNBs if there are slices that have overload, i.e. lack of resources to receive new connections. In this example, gNB2 <NUM> has overload on a slice. The gNB2 indicates <NUM> the overload to gNB1 <NUM> and gNB3 <NUM>.

The user terminal <NUM> transmits <NUM> a measurement report to the gNB1 <NUM>. The measurement report may comprise Reference Signal Received Power, RSRP, Reference Signal Received Quality, RSRQ and/or Signal-to-Interference-plus-Noise Ratio, SINR, measurements performed by the user terminal regarding the source gNB1 and nearby gNBs.

Based on the measurement report the source gNB1 <NUM> determines in this example that a handover is needed for the user terminal <NUM>.

In phase <NUM>, the gNB1 <NUM> is configured to determine the target gNB for the handover. In an embodiment, the gNB1 <NUM> is configured to select from the surrounding base stations a target base station for handover based on the measurement report, slices supported by the base stations and the information on overloaded slices.

In this example, the source gNB1 selects gNB3 as the target gNB because gNB2 has indicated that it had overload. The source gNB1 transmits a handover request message <NUM> to the gNB3.

Let us study an embodiment a bit closer referring to <FIG> illustrates examples of the operation of an apparatus or a network element configured to control handover of user terminals In an embodiment, <FIG> illustrates the operation of gNB or a part of an gNB.

In step <NUM> of <FIG>, the apparatus is configured to obtain information on slices supported by surrounding base stations. In an embodiment, the apparatus obtains the information from NG-RAN Node configuration Update-message.

In step <NUM> of <FIG>, the apparatus is configured to obtain information on overloaded slices used by the surrounding base stations. In an embodiment, the apparatus may receive messages from surrounding base stations via Xn interface. In an embodiment, the apparatus may receive messages from surrounding base stations via Core Access and Mobility Management Function, AMF, of the communication system, which is a control plane core connector for radio access network and can be seen from this perspective as the <NUM> version of Mobility Management Entity, MME, in LTE.

In step <NUM> of <FIG>, the apparatus is configured to receive a measurement report from a user terminal utilizing slices in communication. As mentioned, the measurement report may comprise RSRP, RSRQ and/or SINR, measurements performed by the user terminal regarding the source gNB1 and nearby gNBs, for example.

In step <NUM> of <FIG>, the apparatus is configured to determine, based on the measurement report, that a handover is needed for the user terminal. The signal quality reported from a surrounding gNB may be better than that the source gNB may offer, for example.

In step <NUM> of <FIG>, the apparatus is configured to select from the surrounding base stations a target base station for handover based on the measurement report, slices supported by the base stations and the information on overloaded slices.

As a numeric example, referring to <FIG>, RSRP of gNB2 may be -44dB and RSRP of gNB3 may be -60dB. However, gNB2 has reported eMMB slice load to be over a given overload limit, for example <NUM>%, whereas gNB3 has not reported overload. In this example, gNB1 may select gNB3 as the target gNB for handover, as it has resources available whereas gNB2 has not, in spite of gNB2 having better RSRP than gNB3. The trade-off between RSRP and load status can be decided based on the history of RSRP range required for specific slice, for example.

In an embodiment, if in the surrounding base stations only one is acceptable based on the measurement report, that base station may be selected as the target base station.

In an embodiment, if in the surrounding base stations more than one is acceptable based on the measurement report, the source gNB may select as a target base station the base station offering maximum number of non-overloaded slices required by the user terminal.

In an embodiment, the source gNB may receive from surrounding base stations indication of slices supported by the base stations that have load exceeding a given first overload limit.

In an embodiment, the source gNB may receive from surrounding base stations indication of slices that previously had load exceeding a given first overload limit have load reduced below a given second overload limit. This is illustrated in <FIG>, which may be a continuation to the example of <FIG>, where gNB2 reported a slice having overload. In phase <NUM>, the gNBs are configured to determine current load per slice. In this example, gNB2 <NUM> determines that the load of the given slice which previously had overload, has reduced below a given limit. Now gNB2 indicates <NUM> to other gNBs, that the slice has no longer a overload situation.

<FIG> is a flowchart illustrating an example useful in understanding embodiments. <FIG> illustrates examples of the operation of an apparatus or a network element. In an embodiment, <FIG> illustrates the operation of gNB or a part of an gNB.

In step <NUM> of <FIG>, the apparatus is configured to determine the resource availability of the slices the apparatus is supporting.

In step <NUM> of <FIG>, the apparatus is configured to determine if one or more slices have load exceeding a given overload limit.

If so, the apparatus is configured to, in step <NUM>, indicate to surrounding base stations that one or more slices have load exceeding a given overload limit.

In step <NUM> of <FIG>, the apparatus is configured to determine if one or more slices that previously had load exceeding a given overload limit have load fallen below a given second overload limit.

If so, the apparatus is configured to, in step <NUM>, indicate to surrounding base stations that one or more slices that previously had load exceeding a given overload limit have load fallen below a given second overload limit.

In an embodiment, the first and second overload limits are received from the communication system. In an embodiment, the operator of the communication system can define the limits for the slice resource in terms of bandwidth usage, number of Packet Data Unit, PDU, sessions, number of flows or even processor/buffer memory usage, for example. Load exceeding the first overload limit denotes that a slice has an overload, and load dropping below the second overload limit denotes the end of overload. Typically, to avoid frequent indication messages, the first overload limit is larger than the second overload limit. For example, the first overload limit may be <NUM>% and the second overload limit may be <NUM>%. These non-limiting numerical values are for illustrative purposes only.

The procedure described in <FIG> may be continuous or performed at given time intervals. As soon as overload or end of overload is detected it may be indicated to surrounding gNBs.

<FIG> illustrates an embodiment. <FIG> shows four gNBs <NUM>, <NUM>, <NUM>, <NUM>. The gNB2 <NUM> determines load of supported slices. In the example of <FIG>, gNB2 <NUM> utilises an Xn control message to indicate overload or end of overload. The Xn control message will be broadcasted to all the Xn neighbors.

<FIG> illustrates another embodiment. <FIG> shows six gNBs <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. Part of the gNBS are connected to gNB <NUM> with Xn interface, part of the gNBs are connected to Core Access and Mobility Management Function, AMF <NUM>, of the communication system. The gNB2 <NUM> determines load of supported slices. In the example of <FIG>, gNB2 broadcasts Xn control message to all the Xn neighbors <NUM>, <NUM>, <NUM>, <NUM> and to AMF <NUM>. The AMF <NUM> can in turn broadcast the message to all the gNBs <NUM>, <NUM> in the (slice)registration area.

<FIG> illustrates an embodiment. The figure illustrates a simplified example of an apparatus applying embodiments of the invention. In some embodiments, the apparatus may be a gNB, or any other entity or network element of the communication system provided that the necessary inputs are available and required interfaces exists to transmit and receive required information.

It should be understood that the apparatus is depicted herein as an example illustrating some embodiments. It is apparent to a person skilled in the art that the apparatus may also comprise other functions and/or structures and not all described functions and structures are required. Although the apparatus has been depicted as one entity, different modules and memory may be implemented in one or more physical or logical entities.

The apparatus <NUM> of the example includes a control circuitry <NUM> configured to control at least part of the operation of the apparatus. The control circuitry may be realized as a processor or more than one processors, for example.

The apparatus may comprise a memory <NUM> for storing data. Furthermore the memory may store software <NUM> executable by the control circuitry <NUM>. The memory may be integrated in the control circuitry.

The apparatus may comprise one or more interface circuitries <NUM>, <NUM>. The interface(s) may connect the apparatus to other network elements of the communication system. The interface(s) may provide a wired or wireless connection to the communication system. The interface(s) may be operationally connected to the control circuitry <NUM>.

The software <NUM> may comprise a computer program comprising program code means adapted to cause the control circuitry <NUM> of the apparatus to perform the embodiments described above and in the claims.

In an embodiment, the apparatus comprises at least one processor or control circuitry <NUM> and at least one memory <NUM> including a computer program code <NUM>, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the functionalities of the apparatus <NUM> according to any one of the embodiments of described above and in the claims.

According to an aspect, when the at least one processor or control circuitry <NUM> executes the computer program code, the computer program code causes the apparatus to carry out the functionalities according to any one of the embodiments described above and in the claims.

According to another embodiment, the apparatus comprises the at least one processor or control circuitry <NUM> and at least one memory <NUM> including a computer program code <NUM> , wherein the at least one processor or control circuitry <NUM> and the computer program code <NUM> perform the at least some of the functionalities of the apparatus <NUM> according to any one of the embodiments described above and in the claims. Accordingly, the at least one processor or control circuitry <NUM>, the memory, and the computer program code form processing means for carrying out some embodiments of the present invention in the apparatus <NUM>.

In an embodiment, the apparatus comprises means for obtaining information on slices supported by surrounding base stations; means for obtaining information on overloaded slices used by the surrounding base stations; means for receiving a measurement report from a user terminal utilizing slices in communication; means for determining based on the measurement report that a handover is needed for the user terminal and means for selecting from the surrounding base stations a target base station for handover based on the measurement report, slices supported by the base stations and the information on overloaded slices.

In an embodiment, the apparatus comprises means for determining the resource availability of the slices the apparatus is supporting, means for indicating to surrounding base stations if one or more slices have load exceeding a given first overload limit; and means for indicating to surrounding base stations if one or more slices that previously had load exceeding a given overload limit has load fallen below a given second overload limit.

In an embodiment, the processes or methods described in above figures may also be carried out in the form of one or more computer processes defined by one or more computer program. A separate computer program may be provided in one or more apparatuses that execute functions of the processes described in connection with the figures. The computer program(s) may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include transitory and/or non-transitory computer media, e.g. a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package. Depending on the processing power needed, the computer program may be executed in a single electronic digital processing unit or it may be distributed amongst a number of processing units.

The steps and related functions described in the above and attached figures are in no absolute chronological order, and some of the steps may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps or within the steps. Some of the steps can also be left out or replaced with a corresponding step.

The apparatuses or controllers able to perform the above-described steps may be implemented as an electronic digital computer, which may comprise a working memory (RAM), a central processing unit (CPU), and a system clock. The CPU may comprise a set of registers, an arithmetic logic unit, and a controller. The controller is controlled by a sequence of program instructions transferred to the CPU from the RAM. The controller may contain a number of microinstructions for basic operations. The implementation of microinstructions may vary depending on the CPU design. The program instructions may be coded by a programming language, which may be a high-level programming language, such as C, Java, etc., or a low-level programming language, such as a machine language, or an assembler. The electronic digital computer may also have an operating system, which may provide system services to a computer program written with the program instructions.

The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, and a software distribution package, for example.

The apparatus may also be implemented as one or more integrated circuits, such as application-specific integrated circuits, ASICs. Other hardware embodiments are also feasible, such as a circuit built of separate logic components. A hybrid of these different implementations is also feasible. When selecting the method of implementation, a person skilled in the art will consider the requirements set for the size and power consumption of the apparatus, the necessary processing capacity, production costs, and production volumes, for example.

Claim 1:
An apparatus of a base station of a communication system, the apparatus comprising
at least one processor;
at least one memory including computer program code;
the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:
obtain (<NUM>) information on slices supported by surrounding base stations;
obtain (<NUM>) information on overloaded slices of the surrounding base stations;
receive (<NUM>) a measurement report from a user terminal utilizing slices in communication, the report comprising Reference Signal Received Power measurements performed by the user terminal regarding source base station and the surrounding base stations;
determine (<NUM>) based on the measurement report that a handover is needed for the user terminal;
select (<NUM>) from the surrounding base stations a target base station for handover based on the measurement report, slices supported by the base stations and the information on overloaded slices, characterised in that
deciding the trade-off between Reference Signal Received Power and load status of slices in the selection of the target base station based on the history of Reference Signal Received Power range required for the slices, and
if in the surrounding base stations more than one is acceptable based on the measurement report, select as the target base station the base station offering the maximum number of non-overloaded slices required by the user terminal.