WO2019214806A1

WO2019214806A1 - User device based handover

Info

Publication number: WO2019214806A1
Application number: PCT/EP2018/061832
Authority: WO
Inventors: Ali Masoomzadeh-Fard; Tai-Ann Chen
Original assignee: Nokia Technologies Oy
Priority date: 2018-05-08
Filing date: 2018-05-08
Publication date: 2019-11-14
Also published as: CN112335289A; EP3791625A1

Abstract

To speeden up a handover in certain areas, a serving cell determines, based at least on measurement reports received from a user device, one or more candidate cells and parameters defining handover criteria, and sends them to the user device. Further, the candidate cells are prepared for the handover. The user device monitors, whether any of the candidate cells fulfill the handover criteria, and if a candidate cell fulfills the handover criteria, the user device triggers a handover to the candidate cell.

Description

USER DEVICE BASED HANDOVER

TECHNICAL FIELD

Various example embodiments relates to wireless communications. BACKGROUND

Wireless communication systems are under constant development. The need for faster communication and huge increase of the data amount create chal lenges for the wireless communications systems. Wireless communications system include a number of base stations, each simultaneously supporting communication for multiple user devices. A base station may direct, by sending a corresponding message, a user device to measure a quality of quality of a communication link be tween the user device and a serving cell provided by the base station or between the user device and other potential links. The measurements are used, for example, for handover, the purpose of which is to provide seamless service when the user device moves from a service area of the base station to another service area..

BRIEF DESCRIPTION

According to an aspect, there is provided the subject matter of the inde pendent claims. Some embodiments are defined in the dependent claims.

An aspect provides a network node configured to provide wireless ac cess by means of beams, the network node comprising at least one processor; and at least one memory including computer program code; the at least one memory and computer program code configured to, with the at least one processor, cause the network node at least to perform: determining, based on information received in a measurement report of a user device and a beam overlapping status of a beam serving the user device, whether or not to apply a user device -based handover; performing, in response to determining that the user device -based handover is to be applied, the following: selecting one or more candidate cells amongst the cells in the measurement report and one or more pre-configured parameters for the user device -based handover based at least on the beam serving the user device; causing configuring the user device for the user device -based handover by sending information on the one or more candidate cells and the parameters to the user de vice; and causing preparing the one or more candidate cells for the user device - based handover by sending user device -related data to the candidate cells. In an aspect, the at least one memory and computer program code con figured to, with the at least one processor, further cause the network node at least to perform sending at least a time-to-trigger and filtering coefficient of the beam serving the user device as the parameters.

In another aspect, the at least one memory and computer program code configured to, with the at least one processor, further cause the network node at least to perform releasing, in response to receiving from one of the one or more candidate cells, a notification informing the handover to the one candidate cell, re sources reserved for the user device.

In another aspect, the at least one memory and computer program code configured to, with the at least one processor, further cause the network node at least to perform applying the user device -based handover at least in response to the user device being served by a beam having a low overlap area with beams of other serving cells.

Another aspect provides a user device comprising at least one proces sor; and at least one memory including computer program code; the at least one memory and computer program code configured to, with the at least one processor, cause the user device at least to perform: monitoring, in response to receiving in measurement configurations one or more candidate cells and parameters defining handover criteria, whether any of the candidate cells fulfill the handover criteria; and triggering, in response to a candidate cell fulfilling the handover criteria, a handover to the candidate cell.

In an aspect, the at least one memory and computer program code con figured to, with the at least one processor, further cause the user device at least to perform the triggering the handover by sending a random access request to the candidate cell.

In another aspect, the at least one memory and computer program code configured to, with the at least one processor, further cause the user device at least to perform a contention-free random access to the candidate cell.

In another aspect, the at least one memory and computer program code configured to, with the at least one processor, further cause the user device at least to perform: measuring signal strength of the serving cell and the one or more can didate cells; comparing signal strengths of the one or more candidate cells to a sig nal strength of the serving cell; and determining that the handover criteria is met if the signal strength in one of the one or more candidate cells is over the signal strength of the serving cell. In another aspect, the at least one memory and computer program code configured to, with the at least one processor, further cause the user device at least to perform determining that the handover criteria is met if the signal strength in one of the one or more candidate cells is over the signal strength of the serving cell at a predetermined time, the predetermined time being received in the parameters.

In another aspect, the at least one memory and computer program code configured to, with the at least one processor, further cause the user device at least to perform: filtering the signal strengths of the one or more candidate cells by a filtering coefficient received in the parameters before comparing; and comparing filtered signal strengths of the one or more candidate cells to a signal strength of the serving cell.

An aspect provides a method comprising: performing, in response to determining that the user device -based handover is to be applied, by a network node configured to provide wireless access by means of beams, the following: se lecting one or more candidate cells amongst the cells in the measurement report and one or more pre-configured parameters for the user device -based handover based at least on the beam serving the user device; causing configuring the user device for the user device -based handover by sending information on the one or more candidate cells and the parameters to the user device; and causing preparing the one or more candidate cells for the user device -based handover by sending user device -related data to the candidate cells.

Another aspect provides a method comprising: monitoring, by a user device, in response to receiving in measurement configurations one or more can- didate cells and parameters defining handover criteria, whether any of the candi date cells fulfill the handover criteria from a serving cell; and triggering, in re sponse to a candidate cell fulfilling the handover criteria, a handover to the candi date cell.

A further aspect provides a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: determining, based on information received in a measurement report of a user device and a beam overlapping status of a beam serving the user device, whether or not to apply a user device -based handover; performing, in response to determining that the user device -based handover is to be applied, the following: selecting one or more candidate cells amongst the cells in the measurement report and one or more pre-configured parameters for the user device -based handover based at least on the beam serving the user device; causing configuring the user device for the user device -based handover by sending information on the one or more candidate cells and the parameters to the user device; and causing preparing the one or more candidate cells for the user device -based handover by sending user device -related data to the candidate cells.

An aspect provides a non-transitory computer readable medium com prising program instructions for causing an apparatus to perform at least the fol lowing: monitoring, in response to receiving in measurement configurations one or more candidate cells and parameters defining handover criteria, whether any of the candidate cells fulfill the handover criteria; and triggering, in response to a can didate cell fulfilling the handover criteria, a handover to the candidate cell.

An aspect provides a computer program comprising instructions for causing an apparatus to perform at least the following: determining, based on in formation received in a measurement report of a user device and a beam overlap ping status of a beam serving the user device, whether or not to apply a user de vice -based handover; performing, in response to determining that the user device -based handover is to be applied, the following: selecting one or more candidate cells amongst the cells in the measurement report and one or more pre-configured parameters for the user device -based handover based at least on the beam serving the user device; causing configuring the user device for the user device -based handover by sending information on the one or more candidate cells and the pa rameters to the user device; and causing preparing the one or more candidate cells for the user device -based handover by sending user device -related data to the candidate cells.

An aspect provides a computer program comprising instructions for causing an apparatus to perform at least the following: monitoring, in response to receiving in measurement configurations one or more candidate cells and param eters defining handover criteria, whether any of the candidate cells fulfill the hand over criteria; and triggering, in response to a candidate cell fulfilling the handover criteria, a handover to the candidate cell.

A further aspect provides a signal with embedded data comprising at least measurement configurations for user device -based handover, the measure ments configurations comprising one or more candidate cells and parameters de fining handover criteria. In an aspect the signal further comprises event A3 or A5 to indicate the user device -based handover.

One or more examples of implementations are set forth in more detail in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

In the following, example embodiments will be described in greater de tail with reference to the attached drawings, in which

Figures 1 illustrates an exemplified wireless communication system;

Figure 2 is a schematic block diagram;

Figures 3 to 5 illustrate exemplified processes; and

Figures 6 and 7 are schematic block diagrams.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The following embodiments are only presented as examples. Although the specification may refer to "an”, "one”, or "some” embodiments] and/or exam- ple(s] in several locations of the text, this does not necessarily mean that each ref erence is made to the same embodiments] or example(s], or that a particular fea ture only applies to a single embodiment and/or example. Single features of differ ent embodiments and/or examples may also be combined to provide other embod iments and/ or examples.

Embodiments and examples described herein may be implemented in any communications system comprising wireless connection(s]. In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access ar chitecture based on long term evolution advanced (LTE Advanced, LTE-A] or new radio (NR, 5G], without restricting the embodiments to such an architecture, how ever. 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 ad justing parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS] radio access network (UTRAN or E-UTRAN], long term evolution (LTE, the same as E-UTRA], beyond 5G, wireless local area network (WLAN or WiFi], worldwide in teroperability for microwave access (WiMAX], Bluetooth®, personal communica tions services (PCS], ZigBee®, wideband code division multiple access (WCDMA], systems using ultra-wideband (UWB] technology, sensor networks, mobile ad-hoc networks (MANETs] and Internet Protocol multimedia subsystems (IMS] or any combination thereof.

Figure 1 depicts examples of simplified system architectures only show ing some elements and functional entities, all being logical units, whose implemen tation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in Figure 1.

The embodiments are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communi cation systems provided with necessary properties.

The example of Figure 1 shows a part of an exemplifying radio access network.

Figure 1 shows user devices 101 and 101' 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] 102 providing the cell. An example of an access node and a cell provided is described in more detail with Figure 2. 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 100 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 signalling purposes. The (e/g]NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point, an access node, 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 an tenna unit may comprise a plurality of antennas or antenna elements. The (e/g]NodeB is further connected to core network 105 (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], etc.

The user device (also called UE, user equipment, user terminal, terminal device, etc.} illustrates one type of an apparatus to which resources on the air in terface are allocated and assigned, and thus any feature described herein with a user device may be implemented with a corresponding apparatus, such as a relay node. An example of such a relay node is a layer 3 relay (self-backhauling relay] towards the base station.

The user device typically refers to a portable computing device that in cludes wireless mobile communication devices operating with or without a sub scriber identification module (SIM], including, but not limited to, the following types of devices: a mobile station (mobile phone], smartphone, personal digital as sistant (PDA], handset, device using a wireless modem (alarm or measurement de vice, etc.}, laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video cam era loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (IoT] network which is a scenario in which objects are provided with the ability to transfer data over a network with out requiring human-to-human or human-to-computer interaction. The user de vice may also utilise cloud. In some applications, a user device may comprise a small portable device with radio parts (such as a watch, earphones or eyeglasses] and the computation is carried out in the cloud. The user device (or in some em bodiments a layer 3 relay node] is configured to perform one or more of user equip ment functionalities. The user device may also be called a subscriber unit, mobile station, remote terminal, access terminal, user terminal or user equipment (UE] just to mention but a few names or apparatuses.

Various techniques described herein may also be applied to a cyber physical system (CPS] (a system of collaborating computational elements control ling physical entities}. CPS may enable the implementation and exploitation of mas sive amounts of interconnected ICT devices (sensors, actuators, processors micro controllers, etc.} embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. Additionally, although the apparatuses have been depicted as single en tities, different units, processors and/or memory units (not all shown in Figure 1} may be implemented.

5G enables using multiple input - multiple output (MIMO] antennas, many more base stations or nodes or corresponding network devices 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. 5G mobile communications supports a wide range of use cases and related applications including video stream ing, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive] machine-type communications (mMTC], in cluding vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also being integradable 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 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G] and inter-RI operability (in ter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave]. One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances] may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

The current architecture in LTE networks is fully distributed in the ra dio and fully centralized in the core network. The low latency applications and ser vices in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC]. 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environ ment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer- to-peer ad hoc networking and processing also classifiable as local cloud/fog com- puting and grid/mesh computing, dew computing, mobile edge computing, cloud let, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and/or latency critical], critical communications (autono mous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications].

The communication system is also able to communicate with other net works, such as a public switched telephone network or the Internet 106, or utilise services provided by them. The communication network may also be able to sup port the usage of cloud services, for example at least part of core network opera tions may be carried out as a cloud service (this is depicted in Figure 1 by "cloud” 107]. The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for exam ple in spectrum sharing.

Edge cloud may be brought into radio access network (RAN] by utilizing network function virtualization (NVF] and software defined networking (SDN]. Us ing edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base sta tion comprising radio parts. It is also possible that node operations will be distrib uted among a plurality of servers, nodes or hosts. Application of cloudRAN archi tecture enables RAN real time functions being carried out at the RAN side (in a dis tributed unit, DU 102] and non-real time functions being carried out in a central ized manner (in a centralized unit, CU 104].

It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements probably to be used are Big Data and all-IP, which may change the way networks are being con structed and managed. 5G (or new radio, NR] networks are being designed to sup port multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB]. It should be appreciated that MEC can be applied in 4G networks as well.

5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M] or Internet of Things (IoT] devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway/maritime/aeronautical communications. Satellite communication may utilise geostationary earth orbit (GEO] satellite systems, but also low earth orbit (LEO] satellite systems, in partic ular mega-constellations (systems in which hundreds of (nano]satellites are de ployed}. Each satellite 103 in the mega-constellation may cover several satellite- enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay node 102 or by a gNB located on-ground or in a satellite.

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 plu rality 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 or may be a Home(e/g}nodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or um brella cells] which are large cells, usually having a diameter of up to tens of kilome ters, or smaller cells such as micro-, femto- or picocells. The (e/g]NodeBs of Figure 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer net works, one access node provides one kind of a cell or cells, and thus a plurality of (e/g]NodeBs are required to provide such a network structure.

For fulfilling the need for improving the deployment and performance of communication systems, the concept of "plug-and-play” (e/g]NodeBs has been introduced. Typically, a network which is able to use "plug-and-play” (e/g]Node Bs, includes, in addition to Home (e/g]NodeBs (H(e/g]nodeBs], a home node B gate way, or HNB-GW (not shown in Figure 1}. A HNB Gateway (HNB-GW], which is typ ically installed within an operator's network may aggregate traffic from a large number of HNBs back to a core network.

Below different exemplified examples are described using term base station as a generic term for access nodes, such as (e/g]NodeBs, or any correspond ing network node providing wireless access, and term user device as a generic term for any communication device/equipment that can be served by base stations.

Figure 2 illustrates a zoom in view of an example a wireless system 200. More precisely, the portion depicted in Figure 2 illustrates a base station 220 providing services to user devices 210 (only one illustrated in Figure 2} by means of beams 201 (only portion of them being shown in Figure 2}. In the illustrated example, the beamforming system comprises a set of beams, or a grid of beams, that are predetermined (pre-configured).

The base station 220 is configured to support handover that takes into account the challenges caused by the beamforming for handovers. Herein such a handover is called a user device -based handover, shortly UE-based handover. It should be appreciated that any corresponding term, such as a conditional hando ver, may be used instead. For the UE-based handover, the base station 200 com prises an enhanced handover configuration unit (e-ho-c-u) 221 and in a memory 222 there are predetermined (pre-configured] beam parameters to be used for providing parameters for the UE-based handover. Naturally, the memory 222 may comprise temporarily maintained, handover related information.

Assuming that two parameters, layer-3 filtering coefficient k and time- to-trigger TTT are the parameters whose values are to be provided for the UE- based handover, and that beams 1 to 14 illustrated in Figure 2 are part of a square cell with 14x4 grid of beams, an outerline of the square cell following dashdot line 207, the preconfigured beam parameters in the memory 222 may be as listed in table 1.

The values in the table are determined with following assumptions, and the example illustrated in Figure 2:

3dB beamwidth contour is used as design base in a 100 meters x 100 meters square cell.

Measuring filtering follows formula (1}

F_n = (l - a) - F_n-1 + a - M_n (1) where F_n is the updated filtered measurement,

F_{n !} is the last filtered measurement,

M_n is the latest received measurement from LI

a = 1/2 C^k/⁴1 , and k is the filter coefficient configured by the base station.

Depending on how they overlap with neighboring cells, beams are assigned, based on their 3dB-beamwidth tip-to-edge distance, to high beam overlap areas 202, 206, medium beam overlap areas 203, 205 and a low beam overlap area 202, for assigning value for a fil tering coefficient k, assuming that value k=8, based on 200 millisec ond sampling rate, is typically used, and therefore assigned to beams in medium overlap areas. Increasing the value of k causes the filter ing to emphasize the past average. That in turn reduces the impact of channel variation at the cost of increasing filtering delay. Decreas ing the value of k decreases the filtering delay at the cost of increas ing the impact of channel variation.

Time-to-trigger TTT values are assigned for beams, based on their 3dB-beamwidth tip-to-edge distance, from a set comprising follow- ingvalues in milliseconds: 0, 40, 64, 80, 100, 128, 160, 256, 320, 480, 512, 640, 1024, 1280. The typical value is assumed to be 512 milli seconds, and used for beams with nearest to zero values of 3dB- beamwidth tip-to-edge distance.

It should be appreciated that the above is a simplified example to illus trate what the beam parameters can be. Any other way to determine them may be used. For example, contours of a different beamwidth definition may be used. Fur ther, when the determining a beam overlapping status (i.e. the beam overlap area for a beam], all potential handover neighbouring beams should be considered, when appropriate parameters are selected. For example, assuming that a neigh bouring cell is a mirror of the one depicted in Figure 2, a user device served by beam 2 depicted in Figure 2, may handover to beam 1, 2 or 3 in the neighbouring cell, and they all, i.e. every possibility, should be taking into account, when param eters are selected. Thereby they also should affect to the beam parameters.

The user device 210 illustrated in Figure 2 is also configured to support the UE-based handover. For that purpose the user device comprises a UE-based handover unit (UE-ho-u) 211 and in the memory 212 temporary information for the handover, and measurement reporting, such as the parameters.

Figure 3 is a flow chart illustrating functionality of a user device config ured to support the UE-based handover. More precisely, it illustrates functionality of the UE-based handover unit. In the illustrated example it is assumed that the user device has just connected to a new cell through a handover from another cell, or otherwise establishes a new connection. During such processes, a user device is configured with the measurement procedure for triggering future handovers. Fur ther, it is assumed that no conventional network-based handover is triggered.

Referring to Figure 3, measurement configurations for channel quality measurements are received in block 301 from a base station, as part of the initial attachment. The measurement configurations may be indicated by a specific indi cation and/or by providing values for a certain parameter, like event A4, used in LTE and 5G. A typical event A4 assigns the condition for a user device to trigger a candidate report of neighboring cells, if one or more of its neighboring cells meet the condition. It usually includes parameters such as the hysteresis and the report ing threshold for neighboring-cell signal strength monitoring.

The user device performs in block 302 measurements, i.e. measures and monitors, beams of the serving cell and neighbouring cells periodically, based on the configuration parameters received in block 301. The measurements are used for calculating cell quality metrics for the serving and neighbouring cells.

Performing the measurements are repeated (block 303: no] until the report criteria received in block 301 is met (block 303: yes}. Then the user device determines in block 304 those cells, the quality metrics of which fulfill/satisfy the quality criteria received in block 301 in the measurement configurations. Once de termined, reporting measurements results of those cells, is caused in block 305. Then new measurement configurations are received in block 306. (As will be de scribed with Figure 4, the base station sets the new measurement configurations based on the report sent in block 305.} It is checked in block 307, whether the con figurations indicate UE-based handover. The UE-based handover may be indicated by a specific indication and/or by providing values for one or more certain param eters, like setting of event A3 and/or event A5, used in LTE and 5G.

If the UE-based handover is not indicated (block 307: no], the process continues to block 302 to perform measurements according to the new measure ment configurations.

If the UE-based handover is indicated (block 307: yes], the configura tions indicate one or more neighbouring cells amongst those cells whose measure ments results were reported in block 305. The configurations further comprise the criteria for the user device to trigger a handover, for example filtering coefficient k. Then the user device performs in block 308 measurements on the indicated one or more cells, based on the handover criteria received in block 306, and applies in block 309 the filtering coefficient to the measurement results. In other words, the user device applies the filtering coefficient received in block 306 on signals re ceived from each neighboring cell indicated in the configurations received in block 306. Then it is determined in block 310, whether handover criteria is met. The handover criteria is met, if any of the signals exceeds the signal of the current serv ing cell for a certain amount of time. The time may be a time-to-trigger (TTT} that may be received in the configurations.

The measurement are repeated (block 310: no] periodically until handover criteria of one cell is met (block 310: yes}.

When the handover criteria is met (block 310: yes}, the user devices starts handover to the cell, which is a target cell, directly by detaching in block 311 from the serving cell and synchronizing in block 311 to the target cell including performing a random access procedure, without reporting the measurement re sults to the serving base station, without receiving a handover command from the serving cell (source serving cell} and without informing the source serving cell on the handover. In a conventional network-based handover, measured channel qual ities are reported to the serving cell, and handover -related functionalities, such as detaching from the serving cell, synchronizing with an indicated target cell and per forming random access to the target cell, are performed, if a handover command is received from the serving cell.

Figure 4 is a flow chart illustrating functionality of a base station config ured to support the UE-based handover. More precisely, it illustrates functionality of the enhanced handover configuration unit, regarding one user device that has just finished handover to a cell, or otherwise has established a new connection to the cell that is provided by the base station. In the example, it is assumed that the user device is configured to support the UE-based handover and that the UE-based handover takes place, not the conventional network-based handover.. Naturally there are plurality of corresponding processes running in parallel, when multiple user devices are served.

Referring to Figure 4, when an initial attachment is received in block 401 from a user device, the user device is configured in block 402 by measurement configurations for channel quality measurements by sending them to the user de vice. When the measurement report on cells fulfilling the quality criteria set in con figurations is received in block 403, it is checked in block 404, using the infor mation in the measurement report together with the beamforming information, for example, whether a UE-based handover should be applied. For example, if the measurement results indicate that the user device is served in the low beam over lap area, it may be determined, that the UE-based handover should be applied. Nat urally additional criteria may be used.

If the UE-based handover is not to be applied (block 404: no], the pro cess returns to block 402 to configure the user device to perform measurements. The new measurement configurations take into account the information received in block 403.

If the UE-based handover should be applied (block 404: yes], the user device is configured in block 405 with the UE-based handover. In other words, based on the measurement reports, one or more candidate cells are selected in block 405 , to be potential target cells. The one or more candidate cells are selected amongst the cells that were included in the measurement report. The base station may check loading conditions in the neighboring cells and use that information to select the one or more candidate cells. Beam parameters in the memory are se lected for the one or more candidate cells, based at least on the serving beam, from the pre-configured beam parameters.

Once the candidate cells and corresponding parameters are selected, the user device measurements are reconfigured in block 406 by sending the pa rameter values and handover criteria to the user device. In other words, configur ing the user device for the UE-based handover is caused. Also the selected one or more candidate cells are prepared for the possible handover by causing in block 407 potential target cells preparation. The preparation includes the base station sending user device data in the base station to the potential target cells so that when the user device performs the handover to any of the potential target cells, the transmission can start immediately so that the user device does not experience call quality drop before and after the handover.

Then, at some point it is detected that the user device has started at tachment procedure to the new target cell, causing the base station to perform in block 408 handover (HO] finalization, which includes detaching the user device from the previous serving cell provided by the base station, switching the data path for the user device from the previous serving cell to the target cell, retransmitting traffic that was not delivered successfully to the user device to the target cell, and to release resources reserved for the user device at the previous serving cell.

Figure 5 illustrates an example of information exchange using messages defined for LTE as an example of messages, without limiting the example to those messages. In the example, functionality described in connection with the user de vice describes also the functionality of the UE-based handover unit, and the func tionality of the serving cell describes the functionality of the enhanced handover configuration unit. Naturally, although not illustrated in Figure 5, when the candi date cell is the new serving cell after handover, it may perform the same function ality as described with Figure 5 as functionality of the serving cell.

Referring to Figure 5, the user device UE establishes a radio resource control (RRC] connection to the serving cell in point 5-1. No changes to the estab lishment procedure are suggested, and any kind of procedure may be used. When the radio resource control connection has been established, in the illustrated ex ample the serving cell determines in point 5-2 that UE-based handover will be used. Therefore message 5-3 is an RRC Connection Reconfiguration message containing an event A4 with corresponding quality criteria. The event A4 configures the user device to report proper candidate neighbouring cell(s] that satisfy the quality cri teria.

The user device configures itself correspondingly and informs the serv ing cell correspondingly by sending message 5-4. Message 5-4 may be an RRC Con nection Reconfiguration Complete message. When the event A4 criteria are met in the user device, i.e. a UE-based report event is detected in point 5-5, the user device communicates the neighbouring cells that satisfy the criteria and their measure ment reports to the serving cell in message 5-6. Message 5-6 may be a layer 3 mes sage Measurement report. The serving cells detects that UE-based handover should be applied and selects in point 5-7 one or more candidate cells, and for each candidate cell param eter values based on the serving beam. In the example of Figure 5, it is assumed for the sake of clarity, that one candidate cell is selected. For example, using the table 1, assuming that the serving beam is beam 2, the parameter values would be 16 for the filtering coefficient and 1024 milliseconds for TTT, whereas if the serving beam is beam 7, the parameter value for the filtering coefficient would be 4, and for TTT 320 milliseconds. Hence, instead of fixed values, beam -dependent values will be used.

The serving cell prepares the selected candidate cells in point 5-8 for the handover. Further, information on the selected candidate cell(s}, and the se lected parameter values are sent in message 5-9 to the user device. Message 5-9 may be an RRC Connection Reconfiguration message containing an event A3 and/or an event A5 with corresponding quality criteria, and the selected values.

The user device performs measurements according to the received se lected values on the selected candidate cell, calculates metrics from the measure ment results and compares the metrics to the quality criteria. (The quality criteria may be that one of the candidate cells is better than the currently serving cell a predetermined time.} When it is detected that a quality criteria is met, the user de vice starts in point 5-10 a handover to the candidate cell (target candidate cell] by detaching in point 5-11 from the serving cell and by synchronizing in point 5-12 with the candidate cell. Further, in point 5-12, the user device performs a conten tion-free Random Access to the candidate cell (target candidate cell}. This includes receiving measurements configurations from the candidate cell. The handover pro cedure in the user terminal ends when the user terminal sends message 5-13 to the new serving cell (candidate target cell}. Message 5-13 may be the same message as message 5-4, i.e. an RRC Connection Reconfiguration Complete message.

As is evident from the above, since the candidate neighboring cells are prepared at the same time when the user device is configured for the UE-based handover, the user device can start the handover directly without having to signal to the base station providing the original serving cell.

The handover process between the serving cell and the candidate cell (target candidate cell, new serving cell} continues according to the conventional handover process by switching in point 5-14 the data path of the user device from the serving cell to the target cell, after which retransmission of the not delivered data, if any exists, takes place in point 5-15. In other words, in point 5-15 packet data convergence protocol (PDCP] packet data units (PDUs] are retransmitted via the target cell to the user device using radio link control (RLC] acknowledged mode, and the serving cell, or more precisely, the previous serving cell, releases in point 5-16 resources reserved for the user device.

The above may be implemented also to allow the user device to moni tor/measure/ report neighboring cells based on each of its possible serving beam ing, using parameters associated with its current serving beam, wherein the user device may be configured to signal to the base station to trigger a network based handover at a more appropriate time.

As is evident from the above examples, the UE-based handover enables, for example, adjustment of delay in triggering a handover by taking into account how much a beam in a serving cell overlaps with a beam in one or more target cells, thereby enabling a fast handover when it is needed because of a small overlap area but yet allowing a more delay in triggering the handover when the overlap area is bigger. Consequently, by having variable parameter values, it is possibly to lower the number of pre-matured handovers, i.e. handovers happening too early, causing possibly back and forth handovers, and the number of too much delayed hando vers, causing possible call/connection drops.

The blocks, related functions, points, and information exchanges de scribed above by means of Figures 3 to 5 are in no absolute chronological order, and some of them may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between them or within them, and other information may be sent. For example, the candidate cells, and the user device may be configured to maintain the user device data only a certain time, and the user device may be configured to perform a contention-free random access to the serving cell, or send the measurement results on the candidate cells to the serv ing cell. Some of the blocks/points or part of the blocks /points or one or more pieces of information can also be left out or replaced by a corresponding block or part of the block or one or more pieces of information.

For example, the user device may be configured, in addition to the UE- based handover, also perform conventional neighboring cell measurement, and if reporting such measurements is triggered before the UE-based handover is trig gered, the measurement report is sent, and the configuration for the UE-based handover may be deleted. The base station then process the measurement report as described above, and may reconfigure the UE-based handover. The techniques and methods described herein may be implemented by various means so that an apparatus/device/node configured to support used de vice -based handover based on at least partly on what is disclosed above with any of Figures 1 to 5, including implementing one or more functions/operations of a corresponding base station (network node configured to provide wireless access, device] or one or more functions/operations of a corresponding user device de scribed above with an embodiment/example, for example by means of any of Fig ures 1 to 5, comprises not only prior art means, but also means for implementing the one or more functions/operations of a corresponding functionality described with an embodiment, for example by means of any of Figures 1 to 5, and it/they may comprise separate means for each separate function/operation, or means may be configured to perform two or more functions/operations. For example, one or more of the means and/or the enhanced handover configuration unit, or its sub units, and/or the user device -based handover unit, or its sub-units described above may be implemented in hardware (one or more devices], firmware (one or more devices], software (one or more modules], or combinations thereof. For a hardware implementation, the apparatuses] of embodiments may be imple mented within one or more application-specific integrated circuits (ASICs], digital signal processors (DSPs], digital signal processing devices (DSPDs], programmable logic devices (PLDs], field programmable gate arrays (FPGAs], processors, control lers, micro-controllers, microprocessors, logic gates, decoder circuitries, encoder circuitries, other electronic units designed to perform the functions described herein by means of Figures 1 to 5, or a combination thereof. For firmware or soft ware, the implementation can be carried out through modules of at least one chip- set (e.g. procedures, functions, and so on] that perform the functions described herein. The software codes may be stored in a memory unit and executed by pro cessors. The memory unit may be implemented within the processor or externally to the processor. In the latter case, it can be communicatively coupled to the pro cessor via various means, as is known in the art. Additionally, the components de scribed herein may be rearranged and/or complemented by additional compo nents in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

Figures 6 and 7 provide apparatuses according to some embodiments of the invention. Figure 6 illustrates an apparatus (e.g. an access node] configured to carry out at least the functions described above in connection with a base station. In other words, the apparatus 600 of Figure 6 depicts a network node configured to provide wireless access according to what is described above using term base station. Figure 7 illustrates an apparatus (e.g. a mobile device] configured to carry out the functions described above in connection with the user device. In other words, the apparatus 700 of Figure 7 depicts a user device according to what is described above. Each apparatus may comprise one or more communication con trol circuitry, such as at least one processor 602, 702, and at least one memory 604, 704 including one or more algorithms 603, 703, such as a computer program code (software] wherein the at least one memory and the computer program code (soft ware] are configured, with the at least one processor, to cause the apparatus to carry out any one of the exemplified functionalities of each respective apparatus.

Referring to Figure 6, at least one of the communication control circuit ries in the apparatus 600 is configured to provide the enhanced handover configu ration unit, or its sub-units, and to carry out functionalities of a base station de scribed above by means of any of Figures 1 to 5 by one or more circuitries.

Referring to Figure 7, at least one of the communication control circuit ries in the apparatus 700 is configured to provide at least the user device -based handover unit, or its sub-units, and to carry out functionalities of a user device de scribed above by means of any of Figures 1 to 5 by one or more circuitries.

The memory 604, 704 may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The memory 604 in the apparatus 600 may store the predetermined beam parameters described above.

The apparatus may further comprise different interfaces 601, 701 such as one or more communication interfaces (TX/RX] comprising hardware and/or software for realizing communication connectivity according to one or more com munication protocols. The one or more communication interface may provide the apparatus with communication capabilities to communicate in the cellular commu nication system and enable communication between different network nodes and between the user device and the different network nodes, for example. A commu nication interface may comprise standard well-known components such as an am plifier, filter, frequency-converter, (de]modulator, and encoder/decoder circuit ries and one or more antennas. The communication interfaces may comprise radio interface components providing the base station and/or the user device with radio communication capability in the cell. The communication interfaces may comprise optical interface components providing the device with optical fibre communica tion capability. Further, the apparatus 700 may comprise one or more user inter faces (not depicted separately], such as a screen, microphone and one or more loudspeakers for interaction with the user.

As used in this application, the term 'circuitry' may refer to one or more or all of the following: (a] hardware-only circuit implementations, such as imple mentations in only analog and/or digital circuitry, and (b] combinations of hard ware circuits and software (and/or firmware], such as (as applicable]: (i] a combi nation of analog and/or digital hardware circuits] with software/firmware and (ii] any portions of hardware processor^] with software, including digital signal processor^], software, and memory(ies] that work together to cause an apparatus, such as a base station, to perform various functions, and (c] hardware circuit(s] and processor(s], such as a microprocessors] or a portion of a microprocessors], that requires software (e.g. firmware] for operation, but the software may not be present when it is not needed for operation. This definition of 'circuitry' applies to all uses of this term in this application, including any claims. As a further example, as used in this application, the term 'circuitry' also covers an implementation of merely a hardware circuit or processor (or multiple processors] or a portion of a hardware circuit or processor and its (or their] accompanying software and/or firmware. The term 'circuitry' also covers, for example and if applicable to the par ticular claim element, a baseband integrated circuit for a base station, or other com puting device or network device.

In embodiments, the at least one processor, the memory, and the com puter program code form processing means or comprises one or more computer program code portions for carrying out one or more operations according to any one of the embodiments of Figures 1 to 5 or operations thereof.

Embodiments as described may also be carried out in the form of a com puter process defined by a computer program or portions thereof. Embodiments of the methods described in connection with Figures 1 to 5 may be carried out by running at least one portion of a computer program comprising corresponding in structions. 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. For example, the com puter program may be stored on a computer program distribution medium reada ble by a computer or a processor. The computer program medium may be, for ex ample but not limited to, a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package, for example. The computer program medium may be a non-transitory me dium. Coding of software for carrying out the embodiments as shown and de scribed is well within the scope of a person of ordinary skill in the art.

Even though the invention has been described above with reference to examples according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be com bined with other embodiments in various ways.

Claims

1. A network node configured to provide wireless access by means of beams, the network node comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and computer program code configured to, with the at least one processor, cause the network node at least to perform:

determining, based on information received in a measurement report of a user device and a beam overlapping status of a beam serving the user device, whether or not to apply a user device -based handover;

performing, in response to determining that the user device -based handover is to be applied, the following:

selecting one or more candidate cells amongst the cells in the measure ment report, and one or more pre-configured parameters for the user de- vice -based handover, based at least on the beam serving the user device;

causing configuring the user device for the user device -based handover by sending information on the one or more candidate cells and the parameters to the user device; and

causing preparing the one or more candidate cells for the user device - based handover by sending user device -related data to the candidate cells.

2. The network node of claim 1, wherein the at least one memory and computer program code configured to, with the at least one processor, further cause the network node at least to perform sending at least a time-to-trigger and filtering coefficient of the beam serving the user device as the parameters.

3. The network node of claim 1 or 2, wherein the at least one memory and computer program code configured to, with the at least one processor, further cause the network node at least to perform releasing, in response to receiving from one of the one or more candidate cells, a notification informing the handover to the one candidate cell, resources reserved for the user device.

4. The network node of claim 1, 2 or 3, wherein the at least one memory and computer program code configured to, with the at least one processor, further cause the network node at least to perform applying the user device -based hand over at least in response to the user device being served by a beam having a low overlap area with beams of other serving cells.

5. A user device comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and computer program code configured to, with the at least one processor, cause the user device at least to perform:

monitoring, in response to receiving in measurement configurations one or more candidate cells and parameters defining handover criteria, whether any of the candidate cells fulfill the handover criteria; and

triggering, in response to a candidate cell fulfilling the handover crite ria, a handover to the candidate cell.

6. The user device of claim 5, wherein the at least one memory and com puter program code configured to, with the at least one processor, further cause the user device at least to perform the triggering the handover by sending a random access request to the candidate cell.

7. The user device of claim 6, wherein the at least one memory and com puter program code configured to, with the at least one processor, further cause the user device at least to perform a contention-free random access to the candi date cell.

8. The user device of claim 5, 6, or 7, wherein the at least one memory and computer program code configured to, with the at least one processor, further cause the user device at least to perform:

measuring signal strength of the serving cell and the one or more can didate cells;

comparing signal strengths of the one or more candidate cells to a signal strength of the serving cell; and

determining that the handover criteria is met if the signal strength in one of the one or more candidate cells is over the signal strength of the serving cell.

9. The user device of claim 8, wherein the at least one memory and com puter program code configured to, with the at least one processor, further cause the user device at least to perform determining that the handover criteria is met if the signal strength in one of the one or more candidate cells is over the signal strength of the serving cell at a predetermined time, the predetermined time being received in the parameters.

10. The user device of claim 8 or 9, wherein the at least one memory and computer program code configured to, with the at least one processor, further cause the user device at least to perform:

filtering the signal strengths of the one or more candidate cells by a fil tering coefficient received in the parameters before comparing; and

comparing filtered signal strengths of the one or more candidate cells to a signal strength of the serving cell.

11. A method comprising:

performing, in response to determining that the user device -based handover is to be applied, by a network node configured to provide wireless access by means of beams, the following:

selecting one or more candidate cells amongst the cells in the measure ment report and one or more pre-configured parameters for the user device -based handover based at least on the beam serving the user device;

12. A method comprising:

monitoring, by a user device, in response to receiving in measurement configurations one or more candidate cells and parameters defining handover cri teria, whether any of the candidate cells fulfill the handover criteria from a serving cell; and

13. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following:

14. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following:

15. A computer program comprising instructions for causing an appa ratus to perform at least the following:

selecting one or more candidate cells amongst the cells in the measure ment report and one or more pre-configured parameters for the user device -based handover based at least on the beam serving the user device; causing configuring the user device for the user device -based handover by sending information on the one or more candidate cells and the parameters to the user device; and

16. A computer program comprising instructions for causing an appa ratus to perform at least the following:

17. A signal with embedded data comprising at least measurement con figurations for user device -based handover, the measurements configurations comprising one or more candidate cells and parameters defining handover criteria.

18. The signal of claim 17, further comprising event A3 or A5 to indicate the user device -based handover.