Field of the disclosure

The present disclosure relates to an apparatus, a method, and a computer program for performing a pending conditional handover from a source master node to a selected target master node and providing an indication to a secondary node upon detecting a radio link failure or a radio link problem with the source master node in a cellular network, in particular when master cell group fast recovery is configured.

Background

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

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

The communication system and associated devices typically operate in accordance with a required standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (3G radio). Another example of an architecture that is known as the long-term evolution (LTE) or the Universal Mobile Telecommunications System (UMTS) radio-access technology. Another example communication system is so called 5G radio or new radio (NR) access technology.

Summary

According to an aspect there is provided an apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the apparatus at least to: detect a radio link failure or a radio link problem with a source master node; provide an indication that the radio link failure or the radio link problem with the source master node has been detected to a secondary node; and perform a pending conditional handover from the source master node to a selected candidate target master node. The apparatus may be configured with master cell group fast recovery.

The radio link problem with the source master node may occur prior to a radio link failure with the source master node. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: perform at least one signal measurement the at least one candidate target master node; select the candidate target master node among the at least one candidate target master node based on the at least one signal measurement.

The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: provide an indication that the pending conditional handover from the source master node to the selected candidate target master node is to be performed to the secondary node.

Detecting the radio link problem with the source master node may comprise detecting the start of a first timer.

Detecting a radio link problem with the source master node may comprise detecting the expiration of a second timer following the start of a first timer.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: provide an indication of the selected candidate target master node to the secondary node.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: receive an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: receive an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node regardless whether a condition associated with the conditional handover is met.

According to an aspect there is provided an apparatus comprising circuitry configured to: detect a radio link failure or a radio link problem with a source master node; provide an indication that the radio link failure or the radio link problem with the source master node has been detected to a secondary node; and perform a pending conditional handover from the source master node to a selected candidate target master node.

The apparatus may be configured with master cell group fast recovery.

The radio link problem with the source master node may occur prior to a radio link failure with the source master node.

The apparatus may comprise circuitry configured to: perform at least one signal measurement the at least one candidate target master node; select the candidate target master node among the at least one candidate target master node based on the at least one signal measurement.

The apparatus may comprise circuitry configured to: provide an indication that the pending conditional handover from the source master node to the selected candidate target master node is to be performed to the secondary node.

Detecting the radio link problem with the source master node may comprise detecting the start of a first timer.

Detecting a radio link problem with the source master node may comprise detecting the expiration of a second timer following the start of a first timer.

The apparatus may comprise circuitry configured to: provide an indication of the selected candidate target master node to the secondary node.

The apparatus may comprise circuitry configured to: receive an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The apparatus may comprise circuitry configured to: receive an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node regardless whether a condition associated with the conditional handover is met.

According to an aspect there is provided an apparatus comprising means for: detecting a radio link failure or a radio link problem with a source master node; provide an indication that the radio link failure or the radio link problem with the source master node has been detected to a secondary node; and performing a pending conditional handover from the source master node to a selected candidate target master node.

The apparatus may be configured with master cell group fast recovery.

The radio link problem with the source master node may occur prior to a radio link failure with the source master node.

The apparatus may comprise means for: performing at least one signal measurement the at least one candidate target master node; selecting the candidate target master node among the at least one candidate target master node based on the at least one signal measurement.

The apparatus may comprise means for: providing an indication that the pending conditional handover from the source master node to the selected candidate target master node is to be performed to the secondary node.

Detecting the radio link problem with the source master node may comprise detecting the start of a first timer.

Detecting a radio link problem with the source master node may comprise detecting the expiration of a second timer following the start of a first timer.

The apparatus may comprise means for: providing an indication of the selected candidate target master node to the secondary node. The apparatus may comprise means for: receiving an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node. The apparatus may comprise means for: receiving an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node regardless whether a condition associated with the conditional handover is met. According to an aspect there is provided a method comprising: detecting a radio link failure or a radio link problem with a source master node; provide an indication that the radio link failure or the radio link problem with the source master node has been detected to a secondary node; and performing a pending conditional handover from the source master node to a selected candidate target master node.

The method may be configured by apparatus configured with master cell group fast recovery.

The radio link problem with the source master node may occur prior to a radio link failure with the source master node.

The method may comprise: performing at least one signal measurement the at least one candidate target master node; selecting the candidate target master node among the at least one candidate target master node based on the at least one signal measurement.

The method may comprise: providing an indication that the pending conditional handover from the source master node to the selected candidate target master node is to be performed to the secondary node.

Detecting the radio link problem with the source master node may comprise detecting the start of a first timer. Detecting a radio link problem with the source master node may comprise detecting the expiration of a second timer following the start of a first timer. The method may comprise: providing an indication of the selected candidate target master node to the secondary node.

The method may comprise: receiving an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The method may comprise: receiving an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node regardless whether a condition associated with the conditional handover is met.

According to an aspect there is provided a computer program comprising computer executable code which when run on at least one processor is configured to: detect a radio link failure or a radio link problem with a source master node; provide an indication that the radio link failure or the radio link problem with the source master node has been detected to a secondary node; and perform a pending conditional handover from the source master node to a selected candidate target master node.

The processor may be part of an apparatus configured with master cell group fast recovery.

The radio link problem with the source master node may occur prior to a radio link failure with the source master node. The computer program may comprise computer executable code which when run on at least one processor is configured to: perform at least one signal measurement the at least one candidate target master node; select the candidate target master node among the at least one candidate target master node based on the at least one signal measurement.

The computer program may comprise computer executable code which when run on at least one processor is configured to: provide an indication that the pending conditional handover from the source master node to the selected candidate target master node is to be performed to the secondary node.

Detecting the radio link problem with the source master node may comprise detecting the start of a first timer.

Detecting a radio link problem with the source master node may comprise detecting the expiration of a second timer following the start of a first timer. The computer program may comprise computer executable code which when run on at least one processor is configured to: provide an indication of the selected candidate target master node to the secondary node.

The computer program may comprise computer executable code which when run on at least one processor is configured to: receive an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The computer program may comprise computer executable code which when run on at least one processor is configured to: receive an indication to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node regardless whether a condition associated with the conditional handover is met. According to an aspect there is provided an apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the apparatus at least to: determine that a terminal has detected a radio link failure or a radio link problem with a source master node; determine that the terminal has performed or is to perform a pending conditional handover from the source master node to a selected candidate target master node; complete the pending conditional handover from the source master node to the selected candidate target master node.

The terminal may be configured with master cell group fast recovery. The radio link problem with the source master node may occur prior to a radio link failure with the source master node.

The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: receive an indication that the terminal has detected the radio problem or the radio link failure with the source master node from a secondary node; and receive an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: receive an indication that the terminal has detected the radio link failure with the source master node from a secondary node; and provide an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to a secondary node.

The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: receive at least one signal measurement by the terminal for at least one candidate target master node from a secondary node; and select the one candidate target master node based on the at least one signal measurements. According to an aspect there is provided an apparatus comprising circuitry configured to: determine that a terminal has detected a radio link failure or a radio link problem with a source master node; determine that the terminal has performed or is to perform a pending conditional handover from the source master node to a selected candidate target master node; complete the pending conditional handover from the source master node to the selected candidate target master node.

The terminal may be configured with master cell group fast recovery. The radio link problem with the source master node may occur prior to a radio link failure with the source master node.

The apparatus may comprise circuitry configured to: receive an indication that the terminal has detected the radio problem or the radio link failure with the source master node from a secondary node; and receive an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The apparatus may comprise circuitry configured to: receive an indication that the terminal has detected the radio link failure with the source master node from a secondary node; and provide an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to a secondary node. The apparatus may comprise circuitry configured to: receive at least one signal measurement by the terminal for at least one candidate target master node from a secondary node; and select the one candidate target master node based on the at least one signal measurements. According to an aspect there is provided an apparatus comprising means for: determining that a terminal has detected a radio link failure or a radio link problem with a source master node; determining that the terminal has performed or is to perform a pending conditional handover from the source master node to a selected candidate target master node; completing the pending conditional handover from the source master node to the selected candidate target master node. The terminal may be configured with master cell group fast recovery.

The radio link problem with the source master node may occur prior to a radio link failure with the source master node. The apparatus may means for: receiving an indication that the terminal has detected the radio problem or the radio link failure with the source master node from a secondary node; and receiving an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The apparatus may comprise means for: receiving an indication that the terminal has detected the radio link failure with the source master node from a secondary node; and providing an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to a secondary node.

The apparatus may comprise means for: receiving at least one signal measurement by the terminal for at least one candidate target master node from a secondary node; and selecting the one candidate target master node based on the at least one signal measurements.

According to an aspect there is provided a method comprising: determining that a terminal has detected a radio link failure or a radio link problem with a source master node; determining that the terminal has performed or is to perform a pending conditional handover from the source master node to a selected candidate target master node; completing the pending conditional handover from the source master node to the selected candidate target master node. The terminal may be configured with master cell group fast recovery.

The radio link problem with the source master node may occur prior to a radio link failure with the source master node.

The method may comprise: receiving an indication that the terminal has detected the radio problem or the radio link failure with the source master node from a secondary node; and receiving an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The method may comprise: receiving an indication that the terminal has detected the radio link failure with the source master node from a secondary node; and providing an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to a secondary node.

The method may comprise: receiving at least one signal measurement by the terminal for at least one candidate target master node from a secondary node; and selecting the one candidate target master node based on the at least one signal measurements.

According to an aspect there is provided a computer program comprising computer executable code which when run on at least one processor is configured to: determine that a terminal has detected a radio link failure or a radio link problem with a source master node; determine that the terminal has performed or is to perform a pending conditional handover from the source master node to a selected candidate target master node; complete the pending conditional handover from the source master node to the selected candidate target master node.

The terminal may be configured with master cell group fast recovery. The radio link problem with the source master node may occur prior to a radio link failure with the source master node.

The computer program may comprise computer executable code which when run on at least one processor is configured to: receive an indication that the terminal has detected the radio problem or the radio link failure with the source master node from a secondary node; and receive an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node from the secondary node.

The computer program may comprise computer executable code which when run on at least one processor is configured to: receive an indication that the terminal has detected the radio link failure with the source master node from a secondary node; and provide an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to a secondary node.

The computer program may comprise computer executable code which when run on at least one processor is configured to: receive at least one signal measurement by the terminal for at least one candidate target master node from a secondary node; and select the one candidate target master node based on the at least one signal measurements.

According to an aspect there is provided an apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the apparatus at least to: receive an indication that a terminal has detected a radio link failure or a radio link problem with a source master node from the terminal; and receive an indication that the terminal is to perform a pending conditional handover from the source master node to a selected candidate target master node from the terminal or from the source master node. The terminal may be configured with master cell group fast recovery.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: receive an indication that the terminal has detected the radio link failure or the radio link problem with the source master node from the terminal; receive an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node from the terminal; and provide an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node to the source master node.

The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: receive the indication that a terminal has detected the radio link failure with the source master node from the terminal; provide the indication that a terminal has detected the radio link failure with the source master node to the source master node; receive an indication that the terminal is to perform a pending conditional handover from a source master node to the selected candidate target master node from the source master node; and provide an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to the terminal.

According to an aspect there is provided an apparatus comprising circuitry configured to: receive an indication that a terminal has detected a radio link failure or a radio link problem with a source master node from the terminal; and receive an indication that the terminal is to perform a pending conditional handover from the source master node to a selected candidate target master node from the terminal or from the source master node.

The terminal may be configured with master cell group fast recovery.

The apparatus may comprise circuitry configured to: receive an indication that the terminal has detected the radio link failure or the radio link problem with the source master node from the terminal; receive an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node from the terminal; and provide an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node to the source master node.

The apparatus may comprise circuitry configured to: receive the indication that a terminal has detected the radio link failure with the source master node from the terminal; provide the indication that a terminal has detected the radio link failure with the source master node to the source master node; receive an indication that the terminal is to perform a pending conditional handover from a source master node to the selected candidate target master node from the source master node; and provide an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to the terminal.

According to an aspect there is provided an apparatus comprising means for: receiving an indication that a terminal has detected a radio link failure or a radio link problem with a source master node from the terminal; and receiving an indication that the terminal is to perform a pending conditional handover from the source master node to a selected candidate target master node from the terminal or from the source master node.

The terminal may be configured with master cell group fast recovery.

The apparatus may comprise means for: receiving an indication that the terminal has detected the radio link failure or the radio link problem with the source master node from the terminal; receiving an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node from the terminal; and providing an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node to the source master node. The apparatus may comprise means for: receiving the indication that a terminal has detected the radio link failure with the source master node from the terminal; providing the indication that a terminal has detected the radio link failure with the source master node to the source master node; receiving an indication that the terminal is to perform a pending conditional handover from a source master node to the selected candidate target master node from the source master node; and providing an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to the terminal.

According to an aspect there is provided a method comprising: receiving an indication that a terminal has detected a radio link failure or a radio link problem with a source master node from the terminal; and receiving an indication that the terminal is to perform a pending conditional handover from the source master node to a selected candidate target master node from the terminal or from the source master node.

The terminal may be configured with master cell group fast recovery.

The method may comprise: receiving an indication that the terminal has detected the radio link failure or the radio link problem with the source master node from the terminal; receiving an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node from the terminal; and providing an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node to the source master node.

The method may comprise: receiving the indication that a terminal has detected the radio link failure with the source master node from the terminal; providing the indication that a terminal has detected the radio link failure with the source master node to the source master node; receiving an indication that the terminal is to perform a pending conditional handover from a source master node to the selected candidate target master node from the source master node; and providing an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to the terminal.

According to an aspect there is provided a computer program comprising computer executable code which when run on at least one processor is configured to: receive an indication that a terminal has detected a radio link failure or a radio link problem with a source master node from the terminal; and receive an indication that the terminal is to perform a pending conditional handover from the source master node to a selected candidate target master node from the terminal or from the source master node.

The terminal may be configured with master cell group fast recovery.

The computer program may comprise computer executable code which when run on at least one processor is configured to: receive an indication that the terminal has detected the radio link failure or the radio link problem with the source master node from the terminal; receive an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node from the terminal; and provide an indication that the terminal has performed or is to perform the pending conditional handover from the source master node to the selected candidate target master node to the source master node.

The computer program may comprise computer executable code which when run on at least one processor is configured to: receive the indication that a terminal has detected the radio link failure with the source master node from the terminal; provide the indication that a terminal has detected the radio link failure with the source master node to the source master node; receive an indication that the terminal is to perform a pending conditional handover from a source master node to the selected candidate target master node from the source master node; and provide an indication that the terminal is to perform the pending conditional handover from the source master node to the selected candidate target master node to the terminal. According to an aspect, there is provided a computer readable medium comprising program instructions stored thereon for performing at least one of the above methods.

According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least one of the above methods.

According to an aspect, there is provided a non-volatile tangible memory medium comprising program instructions stored thereon for performing at least one of the above methods.

In the above, many different aspects have been described. It should be appreciated that further aspects may be provided by the combination of any two or more of the aspects described above.

Various other aspects are also described in the following detailed description and in the attached claims.

List of abbreviations

ACK: Acknowledgement

AF: Application Function

AUSF: Authentication Server Function

AMF: Access Management Function BS: Base Station

CHO: Conditional Flandover

CU: Centralized Unit

DC: Dual Connectivity

DN: Data Network DU: Distributed Unit

GNB: gNodeB

GSM: Global System for Mobile communication HO: Handover loT: Internet of Things

IP: Internet Protocol

LTE: Long Term Evolution NEF: Network Exposure Function NR: New Radio MCG: Master Cell Group MN: Master Node MS: Mobile Station MTC: Machine Type Communication PSCell: Primary Secondary Cell RACH: Random Access Control Channel RAM: Random Access Memory RAN: Radio Access Network RLF: Radio Link Failure RLP: Radio Link Problem ROM: Read Only Memory RRC: Radio Resource Control SC: Single Connectivity SCG: Secondary Cell Group SIB: System Information Block SMF: Session Management Function SN: Secondary Node SRB: Signaling Radio Bearer UDM: User Data Management UE: User Equipment UMTS: Universal Mobile Telecommunication System USB: Universal Serial Bus Wl: Work Item 3GPP: 3 ^rd Generation Partnership Project 5G: 5 ^th Generation 5GC: 5G Core network 5GRAN: 5G Radio Access Network

5GS: 5G System

References

[1] R2-1911563, Running CR to 37.340 for CA/DC enhancements, EricssonA/ivo, RAN2#107, Prague, Czech Republic, August, 2019.

[2] R2-1913484, Discussion on fast RLF recovery when applying CFIO and fast MCG recovery, ZTE, RAN2#107bis, Chongqing, China, October, 2019.

[3] RP-192340, Summary of Rel-17 email discussion on MR-DC enhancements, RAN Plenary #85, Newport Beach, USA, September, 2019. Brief Description of the Figures

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

Figure 1 shows a schematic representation of a 5G system (5GS);

Figure 2 shows a schematic representation of a control apparatus;

Figure 3 shows a schematic representation of a terminal; Figure 4 shows a signalling diagram of a process for performing a conditional handover;

Figure 5 shows a signalling diagram of a process for performing a master cell group recovery upon detecting a master cell group failure; Figure 6 shows a signalling diagram of a process for performing a master cell group recovery and ignoring a pending conditional handover upon detecting a master cell group failure; Figure 7 shows a signalling diagram of a process for performing a pending conditional handover upon detecting a master cell group failure according to a first option;

Figure 8 shows a signalling diagram of a process for performing a pending conditional handover upon detecting a master cell group problem according to a second option;

Figure 9 shows a signalling diagram of a process for performing a pending conditional handover upon detecting a master cell group failure according to a third option;

Figure 10 shows a block diagram of method for performing a pending conditional handover upon detecting a master cell group failure or a master cell group problem implemented by a terminal;

Figure 11 shows a block diagram of method for performing a pending conditional handover upon detecting a master cell group failure or a master cell group problem implemented by a source master node;

Figure 12 shows a block diagram of method for performing a pending conditional handover upon detecting a master cell group failure or a master cell group problem implemented by a secondary node;

Figure 13 shows a schematic representation of a non-volatile memory medium storing instructions which when executed by a processor allow a processor to perform one or more of the steps of the process or method of any of Figures 4 to 12. Detailed Description of the Figures

In the following certain embodiments are explained with reference to mobile communication devices capable of communication via a wireless cellular system and mobile communication systems serving such mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system, access systems thereof, and mobile communication devices are briefly explained with reference to Figures 1, 2 and 3 to assist in understanding the technology underlying the described examples.

Figure 1 shows a schematic representation of a 5G system (5GS). The 5GS may comprises a terminal, a 5G radio access network (5GRAN), a 5G core network (5GC), one or more application function (AF) and one or more data networks (DN).

The 5GRAN may comprise one or more gNodeB (GNB) distributed unit functions connected to one or more gNodeB (GNB) centralized unit functions.

The 5GC may comprise an access management function (AMF), a session management function (SMF), an authentication server function (AUSF), a user data management (UDM), a user plane function (UPF) and/or a network exposure function (NEF).

Figure 2 illustrates an example of a control apparatus 200 for controlling a function of the 5GRAN or the 5GC as illustrated on Figure 1. The control apparatus may comprise at least one random access memory (RAM) 211a, at least on read only memory (ROM) 211b, at least one processor 212, 213 and an input/output interface 214. The at least one processor 212, 213 may be coupled to the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215. The software code 215 may for example allow to perform one or more steps to perform one or more of the present aspects. The software code 215 may be stored in the ROM 211b. The control apparatus 200 may be interconnected with another control apparatus 200 controlling another function of the 5GRAN or the 5GC. In some embodiments, each function of the 5GRAN or the 5GC comprises a control apparatus 200. In alternative embodiments, two or more functions of the 5GRAN or the 5GC may share a control apparatus. Figure 3 illustrates an example of a terminal 300, such as the terminal illustrated on Figure 1. The terminal 300 may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a user equipment, a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), a personal data assistant (PDA) or a tablet provided with wireless communication capabilities, a machine-type communications (MTC) device, an Internet of things (loT) type communication device or any combinations of these or the like. The terminal 300 may provide, for example, communication of data for carrying communications. The communications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on.

The terminal 300 may receive signals over an air or radio interface 307 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 3 transceiver apparatus is designated schematically by block 306. The transceiver apparatus 306 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device. The terminal 300 may be provided with at least one processor 301, at least one memory ROM 302a, at least one RAM 302b and other possible components 303 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The at least one processor 301 is coupled to the RAM 302a and the ROM 211 b. The at least one processor 301 may be configured to execute an appropriate software code 308. The software code 308 may for example allow to perform one or more of the present aspects. The software code 308 may be stored in the ROM 302b. The processor, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 304. The device may optionally have a user interface such as key pad 305, touch sensitive screen or pad, combinations thereof or the like. Optionally one or more of a display, a speaker and a microphone may be provided depending on the type of the device.

One or more of the following aspects relate to mobility in a cellular/mobile communication network such as a LTE network or NR network.

Conditional handover (CHO) is a feature that is specified in Release 16 in two separate work items (Wl) on mobility enhancement for both LTE and NR.

Master cell group (MCG) fast recovery is a feature that is specified for multi-radio access technology dual connectivity (MR-DC) in the Wl “LTE-NR & NR-NR Dual Connectivity and NR CA enhancements”.

One or more of the following aspects proposes efficient interaction between these two features.

A CHO may be similar to a legacy HO. A simplified message sequence chart for CHO is shown in Figure 4 assuming a dual connectivity (DC) session (i.e. a UE is connected to a source master node (MN) and a secondary node (SN)). The first steps may be identical to a legacy HO from a source MN to a candidate target MN with or without SN change. A configured measurement event (e.g. A3) may trigger the UE to send a measurement report to the source MN. The measurement report may comprise one or more signal measurements (e.g. one or more signal strength measurement and/or one or more signal quality measurements) performed by the UE with one or more candidate target MNs. This is typically done at an early stage to make sure that the radio conditions with the source MN are good enough to perform the CHO. Based on the measurement report (and/or other information), the source MN may prepare the one or more candidate target MNs for the CHO. The preparation may comprise sending one or more CHO requests to the one or more candidate target MNs and receiving one or more CHO request acknowledgements (ACK) from the one or more candidate target MNs. The source MN may then send one or more CHO commands to the UE. For the legacy HO, the UE may receive only a single HO Command for one single target MN based on the one or more signal measurements. The UE may immediately access the single target MNs to complete the HO.

Instead, for the CHO the UE may only access a select one of the one or more candidate target MNs once an additional CHO condition expires. A CHO condition may be an A3 event, which may trigger when the measurement of one of the at least one candidate target MNs is better by an offset than the source MN for a predefined period (typically called time to trigger). This may guarantee that the radio conditions in the selected one of the one or more candidate target MNs are good enough to complete the CHO, even though the preparation was done very early. The CHO condition may be configured by the source MN along with the CHO command. When the CHO condition expires the UE may execute the CHO from the source MN to the selected one of the one or more candidate target MNs. For example, the UE may perform a random access channel (RACH) procedure with the select one of the one or more candidate target MNs.

An advantage of the CHO may be that the CHO command may be sent very early, when the UE is still safe with the source MN. The UE may not risk accessing the selected one among the one or more candidate target MNs which may be unstable. More details on the CHO may be found for example in [3] RP-192340, Summary of Rel-17 email discussion on MR-DC enhancements, RAN Plenary #85, Newport Beach, USA, September.

The one or more CHO Commands may be generated by each of the one or more candidate target MNs and included within the CHO request acknowledgement sent from each of the one or more candidate target MNs to the source MN. The source MN may then package the one or more CHO command into a radio resource control (RRC) reconfiguration message and may send it to the UE. 3GPP RAN2 has agreed that CHO may be configured for one or more candidate target MNs at the same time. That is, there might be one or more candidate target MNs configured in a CHO command for a UE at the same time. RAN2 is still discussing how to handle failures, such as MCG failures (i.e. radio link failures (RLF) with the source MN) when one or more candidate target MNs have been configured for a CHO and the CHO is pending (i.e. the UE has not yet selected one among the one or more candidate target MNs and/or the UE has not yet performed the CHO from the source MN to the selected one among the one or more candidate target MNs). For instance, a MCG failure may happen before the CHO condition expires. Executing such a pending CHO may be more efficient than initiating re establishment, since system information may not need to be read and contention-free random access might be possible. There may be two different possibilities to handle the MCG failure

A possibility is to assume that the pending CHO shall be executed when after MCG failure a selected one of one or more candidate target MNs has configured CHO resources (even if the CHO condition is not fulfilled). Another possibility is to execute a pending CHO even before the MCG failure (e.g. when T310 timer is started or shortly after).

A signalling diagram may be similar as in Figure 4 with a difference that the execution is not triggered by the CHO condition expiring but by the MCG failure and the subsequent selection of one of the one or more candidate target MNs.

MCG fast recovery (sometimes designated by RLF recovery) is described in the change request [1] R2-1911563, Running CR to 37.340 for CA/DC enhancements, Ericsson/Vivo, RAN2#107, Prague, Czech Republic, August, 2019. A basic idea is to exploit the existence of a SN with stable radio conditions. Figure 5 illustrates the feature in a simplified way. When a MCG failure happens, the UE may behave similarly to when a secondary cell group (SCG) failure (i.e. radio link failure with the SN) happens. The UE may not suspend all bearers, may not release the SN and may not initiate re-establishment with the SN or another MN. The UE may send out an MCG failure indication to the SN and wait for a response during a predefined period. The MCG failure indication may include further information such as one or more signal measurements performed by the UE with one or more candidate target MNs, a cause for the MCG failure or other information. The SN may forward the MCG failure indication to the source MN. Based on the information included with the MCG failure indication the source MN may select one target MN. For example, the source MN may select one target MNs for which the signal measurement performed by the UE is above a threshold (e.g. the strongest). The source MN may then prepare a legacy HO with the selected target MN. The source MN may send a HO request to the selected target MN and may receive a HO request acknowledgement from the selected target MN.

Alternatively, if there is no selectable target MN (e.g. the signal measurement performed by the UE for each of the neighboring MNs is below the threshold), the source MN may decide to send the UE to idle.

Since the source MN may not contact the UE directly (the UE is no longer connected to the source MN), the source MN may send a HO Command (or alternatively the release message) via the SN. Finally, the UE may perform the legacy HO from the source MN to the selected target MN.

This procedure may avoid a re-establishment and therefore has several advantages. System information may not need to be read from the selected target MN, contention- free random access may be used, the bearers and the SN may not need to be set up from the scratch, etc.

For the sake of completeness, it may be mentioned that this feature may require split signalling radio bearer SRB1 or SRB3 to be configured. Otherwise the RRC messages between UE and the source MN may not be exchanged via the SN. One or more of the following aspects relate to cases wherein an MCG failure happens, MCG fast recovery is configured and a CHO has been configured for one or more candidate target MNs and is pending. In such a case, the behaviour of the UE may be unclear.

This case is discussed in 0 R2-1913484, Discussion on fast RLF recovery when applying CHO and fast MCG recovery, ZTE, RAN2#107bis, Chongqing, China, October, 2019. It has to be discussed whether the UE may execute a pending CHO (CHO behaviour) or whether the UE has to initiate the MCG fast recovery. This contribution proposes to ignore the pending CHO and to initiate the MCG fast recovery. The argumentation is that the selection of one of the one or more candidate target MNs may cause a delay larger than the MCG fast recovery. Although [2] clarifies the UE behaviour (and removes uncertainty), it may be quite inefficient as shown in Figure 6. Assuming that after the MCG failure a CHO-prepared candidate target MN is relevant/may be selected (i.e. the signal measurement for this CHO-prepared candidate target MN is above the threshold), the whole HO preparation may be repeated with CHO-prepared candidate target MN which may be unnecessary.

Furthermore, 3GPP has not decided the exact CHO behaviour after MCG failure. It may be likely that the delay due to the selection of one of the one or more candidate target MNs will be much smaller than discussed in 0 R2-1913484, Discussion on fast RLF recovery when applying CHO and fast MCG recovery, ZTE, RAN2#107bis, Chongqing, China, October, 2019 which would make it more attractive to execute the pending CHO.

Another solution is to ignore the MCG fast recovery and execute the pending CHO instead as shown in Figure 4. Such a solution may also be not optimal since it ignores the existence of the SN with stable radio conditions For instance, packet forwarding from source MN to target MN may only start late, when the UE has already completed the CHO from the source MN to the selected one of the one or more candidate target

MNs (i.e. the source MN may trigger data forwarding when it receives a CHO success message from the selected one or the one or more candidate target MNs). Also, the source MN may not get relevant failure information for optimization purposes.

One or more of the following aspects propose techniques for reducing the interruption and signalling of the MCG fast recovery in cases where a UE is multi-connected to a source MN and a SN, the UE has been configured with CHO to one or more candidate target MNs and the UE suffers a MCG failure or a MCG problem (i.e. radio link problem (RLP)) with the source MN.

One or more of the following aspect propose three options which we summarize here and explain in more details further below.

In a first option a MCG failure may be detected. The UE may send an MCG failure indication to the SN (just as it does for the legacy MCG fast recovery). The MCG failure indication may be extended with an indication that informs the source MN (via SN) that the pending CHO will be performed from the source MN to a selected one among the one or more candidate target MNs. The UE may perform the pending CHO from the source MN to the selected one among the one or more candidate target MNs. The source MN may stop transmissions to the UE/ receptions from the UE, forward transmissions to the selected one among the one or more candidate target MNs and record failure information.

In a second option a MCG problem may be detected. The MCG problem may occur prior to a MCG failure. The UE may send a message to the source MN (via SN) with an indication that a MCG problem has occurred and that the pending CHO will be performed from the source MN to a selected one among the one or more candidate target MNs. The UE may perform the pending CHO from the source MN to the selected one among the one or more candidate target MNs. The source MN may stop transmissions to the UE/ receptions from the UE, forward transmissions to the selected one among the one or more candidate target MNs and record failure information. The message may be similar to the MCG failure indication, but it may be sent before a MCG failure occurs. In a third option a MCG failure may be detected. The UE may send an MCG failure indication to the SN (just as it does for the legacy MCG fast recovery). The UE waits for response (just as it does for the legacy MCG failure recovery). The source MN may receive the MCG failure indication. The source MN may determine that one or more candidate target MNs are already CHO-prepared. The source MN may decide to skip further HO preparation. Instead of the HO preparation, the source MN may immediately send a message to the UE (via SN) which instructs the UE to execute the pending CHO (e.g. even if the CHO condition is not met) from the source MN to a selected one among the one or more candidate target MNs. The UE may perform the pending CHO from the source MN to the selected one among the one or more candidate target MNs.

Figure 7 provides a signalling diagram for the first option. An MCG failure occurs and one or more candidate target MNs have been configured for CHO. If none of the one or more candidate target MN is relevant/ may be selected (i.e. a signal measurement performed by the UE for each of the one or more CHO-configured candidate target MN is below a threshold), the UE may follow the legacy MCG fast recovery and may send a legacy MCG failure indication.

Otherwise, if there is one or more relevant CHO-configured candidate target MNs, the UE may select one of the one or more relevant CHO-configured candidate target MNs. The UE may send an extended MCG failure indication to the SN. The extended MCG failure indication may carry additional CHO related information. The additional CHO related information may comprise an indication that a pending CHO is to be executed. The additional CHO related information may comprise an identification of the selected one among the one or more relevant CHO-configured candidate target MNs (or a target primary cell controlled by the selected one among the one or more relevant CHO-configured candidate target MNs). Then, the UE may execute the pending CHO from the source MN to the selected one among the one or more relevant CHO- configured candidate target MNs. It will be understood that the execution of the pending CHO may not necessarily happen after sending the MCG failure indication. The execution of the pending CHO may not necessarily happen before or whilst sending the MCG failure indication to the SN. Hence, the additional CHO related information may not necessarily comprise an indication that a pending CHO is to be executed. The additional CHO related information may comprises an indication that a pending CHO has been executed or is currently executed.

The SN may or may not send a response to the UE (e.g. an acknowledgement).

The SN may forward the MCG failure indication to the source MN. The source MN may stop transmitting to the UE/ receiving from the UE (if not already done), may start packet forwarding to the selected one among the one or more relevant CHO- configured candidate target MNs and may process the failure related information (e.g. for optimizing mobility parameters).

It may be mentioned that bearers and the SN may be kept after the MCG failure (just as for the legacy MCG fast recovery) and may not be released to be setup again (just as for the legacy MCG fast recovery). In Release 15 and Release 16 the SN may be released during the source MN HO later on (after conveying the relevant MCG failure indication). However this might be improved in Release 17 as discussed in 0 RP- 192340, Summary of Rel-17 email discussion on MR-DC enhancements, RAN Plenary #85, Newport Beach, USA, September, 2019. Figure 8 provides a signalling diagram for the second option. The procedure is similar to the first option and comprise the following differences. The MCG recovery process may not be triggered by the MCG failure, but beforehand by a MCG problem. An MCG problem may be indicated by the start of a T310 timer (e.g. if one or more CHO- prepared target MNs are relevant and one of the one or more CHO-prepared target MNs is selected) or a predefined period after the T310 timer was started (e.g. expiration of T312 timer). More details may be found in RP-192340, Summary of Rel- 17 email discussion on MR-DC enhancements, RAN Plenary #85, Newport Beach, USA, September, 2019. The UE may autonomously decide when to trigger the MCG failure recovery. Consequently, the current definition of the MCG failure indication may not be re-used as in the first option. The scope of the MCG failure indication may be extended such that it may be sent in such a pre-MCG failure situation. A new root cause may be defined in this case. Alternatively, a message similar to the MCG failure indication with similar content may be defined. In the following, the expression MCG problem indication is used as to designate the message but other expressions could be used. Moreover, the expression MCG problem indication may encompass the option of re-using the MCG failure indication in the MCG problem situation.

As for the first option, when receiving the MCG problem indication from the SN the source MN may stop transmitting to the UE/ receiving from the UE (if not already done). The source MN may start packet forwarding to the selected one among the one or more CHO-prepared target MNs.

With regard to the first option and the second option it may be remarked that the MCG failure indication or MCG problem indication may not be confused with a “bye” message which has been proposed in the context of CHO. In order to enable early forwarding by a source gNB, it has been proposed to send a “bye” message to a source gNB when a CHO condition is fulfilled. This signaling was excluded from specification since it was unreliable. The MCG failure indication or MCG problem indication as proposed in this disclosure may be sent to the SN which has a stable connection whereas CHO predominantly was discussed for the single-connectivity (SC) case and not for the dual connectivity (DC) case. Furthermore, the MCG failure indication or MCG problem indication may be triggered by detection of MCG failure or a MCG problem and not by the CHO condition being met.

Figure 9 provides a signalling diagram for the third option. The UE may detect a MCG failure. The UE may send a MCG failure indication to the SN and may wait for a response from the SN. In contrast to the first and second options, the UE may not autonomously perform a pending CHO. The source MN may receive the MCG failure indication from the SN. From the MCG failure indication (in particular from UE measurement performed with one or more CHO-configured candidate target MNs included in the MCG failure indication), the source MN may determine that a previously CHO-configured candidate target MN candidate is still relevant/may be selected. In this case, it may not necessarily initiate a further HO procedure as in the legacy MCG fast recovery procedure described in Figure 5. Instead, the source MN may directly send a short message to the UE (via the SN), which may explicitly or implicitly trigger the execution of a pending CHO from the source MN to a selected one among the one or more CHO-configured candidate target MNs. The selection may be performed by the source MN rather than the UE. This short message may comprise a flag triggering the pending CHO, an identifier of the selected one among the one or more CHO- configured candidate target MNs, an identifier of the CHO command and/or an additional CHO condition. The additional CHO execution condition may be weaker than an original CHO condition.

The short message may be smaller than a RRC reconfiguration carrying a HO command since most of the information is already available at the UE.

In the first, second and third options the UE may benefit from the fact that a candidate target MN has already been CHO-prepared (which is ignored in the solution of Figure 6). The UE may also benefit from the fact that a stable connection with the SN may exist and may be used to carry valuable information for the source MN (e.g. stop transmission/reception with the source MN or trigger early forwarding). The first, second and third options may save (re-) preparation of an already configured candidate target MN compared with a legacy MCG failure recovery procedure (i.e. X2/Xn and air interface signaling as well as the associated delay may be reduced).

The first, second and third options may reduce delays since packet forwarding may be started earlier. Further delays may be saved since the bearers and the SN are rescued and may not need to be setup again Figure 10 shows a block diagram of method for performing a pending conditional handover upon detecting a RLF or a RLP with a source MN implemented by a terminal configured with MCG fast recovery.

In step 1000, the terminal may receive a command to perform a CFIO from a source MN to at least one candidate target MN.

In step 1002, the terminal may detect a RLF or a RLP with the source MN. The radio RLP with the source MN may occur prior to a RLF with the source MN.

In step 1004, the terminal may provide an indication that the RLF or the RLP with the source MN has been detected to a source MN.

In step 1006, the terminal may perform the pending the CHO from the source MN to a selected one among the at least one candidate target MN.

The above method will now be described in more details for the first option, the second option and the third option

In the first option (illustrated on Figure 7), the terminal configured with MCG fast recovery may perform at least one measurement for at least one candidate target MN. The terminal may send a measurement report comprising the at least one measurement to a source MN.

The terminal may receive a command to perform a CHO from the source MN to the at least one candidate target MN (step 1000). The terminal may detect a RLF with the source MN (step 1002).

The terminal may determine that a CHO from the source MN to the at least one target MN is pending. The terminal may select one of the at least one candidate target MN. For example, the terminal may perform at least one signal measurement for the at least one candidate target MN. The terminal may select one the at least one candidate target MN based on the at least one signal measurement.

The terminal may provide an indication that the RLF with the source MN has been detected to a SN (step 1004).

The terminal may provide an indication that the pending CFIO from the source MN to the selected one among the at least one candidate target MN is to be performed to the SN.

The terminal may provide an indication of the selected one among the at least one target MN to the SN (e.g. an identifier of the selected one among the at least one target MN to the SN).

The terminal may perform the pending CFIO from the source MN to the selected one among the at least one candidate target MN (step 1006).

In the second option (illustrated on Figure 8), the terminal configured with MCG fast recovery may perform at least one measurement for at least one candidate target MN. The terminal may send a measurement report comprising the at least one measurement to a source MN.

The terminal may receive a command to perform a CFIO from the source MN to the at least one candidate target MN (step 1000).

The terminal may detect a RLP with the source MN (step 1002). Detecting the RLP with the source MN may comprise detecting the start of a first timer (e.g. T310) or detecting the expiration of a second timer (e.g. T312) following the start of a first timer (e.g. T310). The terminal may provide an indication that the RLP with the source MN has been detected to a SN. The terminal may determine that a CHO from the source MN to the at least one target MN is pending. The terminal may select one of the at least one candidate target MN. For example, the terminal may perform at least one signal measurement for the at least one candidate target MN. The terminal may select one the at least one candidate target MN based on the at least one signal measurement. The terminal may provide an indication that the RLP with the source MN has been detected to a SN (step 1004).

The terminal may provide an indication that the pending CFIO from the source MN to the selected one among the at least one candidate target MN is to be performed to the SN.

The terminal may provide an indication of the selected one among the at least one target MN to the SN (e.g. an identifier of the selected one among the at least one target MN to the SN).

The terminal may perform the pending CFIO from the source MN to the selected one among the at least one candidate target MN (step 1006).

In the third option (illustrated on Figure 9), the terminal configured with MCG fast recovery may perform at least one measurement for at least one candidate target MN. The terminal may send a measurement comprising the at least one measurement to a source MN.

The terminal may receive a command to perform a CFIO from the source MN to at least one candidate target MN (step 1000).

The terminal may detect the RLF with the source MN (step 1002). The terminal may provide an indication that the RLF with the source MN has been detected to a SN (step 1004). The terminal may receive an indication to perform the pending CHO from the source MN to a selected one among the at least one candidate target MN from the SN, wherein the selection is performed by the source MN based on the at least one measurement when a condition associated with the CHO is met or alternatively regardless whether a condition associated with the CHO is met.

The terminal may perform the pending the CHO from the source MN to the selected one among the at least one candidate target MN when a condition associated with the CHO is met or alternatively regardless whether a condition associated with the CHO is met) (step 1006).

Figure 11 shows a block diagram of method for performing a pending conditional handover upon detecting a RLF or a RLP with a source MN implemented by a source MN. In step 1100, the source MN may send a command to perform a CFIO from the source MN to at least one candidate target MN to a terminal configured with MCG fast recovery.

In step 1102, the source MN may determine that the terminal has detected a RLF or a RLP with the source MN.

In step 1104, the source MN may determine that the terminal has performed or is to perform a pending CHO from the source MN to a selected one of at least one candidate target MN. In step 1106, the source MN may complete the pending CHO from the source MN to the selected one of at least one candidate target MN. The source MN may forward transmissions to the selected one among the at least one candidate target MN. The above method will now be described in more details for the first option, the second option and the third option.

In the first option (illustrated on Figure 7), the source MN may receive at least one measurement performed by a terminal configured with MCG fast recovery for at least one candidate target MN from the terminal.

The source MN may prepare the at least one candidate target MN for a CHO from a source MN to the at least one candidate target MN. The source MN may send at least one CHO request to the at least one candidate target MN. The source MN may receive at least one CHO acknowledgement from the at least one candidate target MN.

The source MN may send a command to perform the CHO from the source MN to the at least one candidate target MN to a terminal configured with MCG fast recovery (step 1100).

The source MN may receive an indication that the terminal has detected a RLF with the source MN from a SN (step 1102).

The source MN may receive an indication that the terminal has performed or is to perform the pending CHO from the source MN to a selected one among the at least one candidate target MN from the SN (step 1104).

The source MN may receive an indication of the selected one among the at least one target MN from the SN (e.g. an identifier of the selected one among the at least one target MN from the SN), wherein the selection is performed by the terminal.

The source MN may complete the pending CHO from the source MN to the selected one of at least one candidate target MN. The source MN may forward transmissions to the selected one among the at least one candidate target MN (step 1106). In the second option (illustrated on Figure 8), the source MN may receive at least one measurement performed by a terminal configured with MCG fast recovery for at least one candidate target MN from the terminal.

The source MN may prepare the at least one candidate target MN for a CHO from a source MN to the at least one candidate target MN. The source MN may send at least one CHO request to the at least one candidate target MN. The source MN may receive at least one CHO acknowledgement from the at least one candidate target MN.

The source MN may send a command to perform the CHO from the source MN to the at least one candidate target MN to a terminal configured with MCG fast recovery (step 1100).

The source MN may receive an indication that the terminal has detected a RLP with the source MN from a SN (step 1102).

The source MN may receive an indication that the terminal has performed the pending CHO from the source MN to a selected one among the at least one candidate target MN from the SN (step 1104).

The source MN may receive an indication of the selected one among the at least one target MN from the SN (e.g. an identifier of the selected one among the at least one target MN from the SN), wherein the selection is performed by the terminal.

The source MN may complete the pending CHO from the source MN to the selected one of at least one candidate target MN. The source MN may forward transmissions to the selected one among the at least one candidate target MN (step 1106). In the third option (illustrated on Figure 9), the source MN may receive at least one measurement performed by a terminal for at least one candidate target MN from the terminal.

The source MN may prepare the at least one candidate target MN for a CHO from a source MN to the at least one candidate target MN. The source MN may send at least one CHO request to the at least one candidate target MN. The source MN may receive at least one CHO acknowledgement from the at least one candidate target MN.

The source MN may send a command to perform the CHO from a source MN to the at least one candidate target MN to a terminal configured with MCG fast recovery (step 1100).

The source MN may receive an indication that the terminal has detected a RLF with the source MN from a SN (step 1102).

The source MN may select one of the at least one candidate target MN based on the at least one measurement.

The source MN may determine that the terminal is to perform the pending CHO from the source MN to the selected one among the at least one candidate target MN from the SN (step 1104).

The source MN may send an indication of the selected one among the at least one target MN to the SN (e.g. an identifier of the selected one among the at least one target MN from the SN).

The source MN may send an indication that the terminal is to perform the pending CHO from the source MN to the selected one among the at least one candidate target MN to the SN (step 1104). The source MN may complete the pending CHO from the source MN to the selected one of at least one candidate target MN. The source MN may forward transmissions to the selected one among the at least one candidate target MN (step 1106). Figure 12 shows a block diagram of method for performing a pending conditional handover upon detecting a RLF or a RLP with a source MN failure implemented by a SN.

In step 1200, the SN may receive an indication that a terminal configured with MCG fast recovery has detected a RLF or a RLP with a source MN from the terminal.

In step 1202, the SN may receive an indication that the terminal is to perform a pending CHO from the source MN to a selected one among the at least one candidate target MN from the terminal or from the source MN.

The above method will now be described in more details for the first option, the second option and the third option.

In the first option (illustrated on Figure 7), the SN may receive an indication that a terminal configured with MCG fast recovery has detected a RLF with a source MN from the terminal (step 1200).

The SN may receive an indication that the terminal is to perform a pending CHO from the source MN to a selected one among the at least one candidate target MN from the terminal (step 1204).

The SN may receive an indication of the selected one among the at least one candidate target MN from the terminal (e.g. an identifier of the selected one among the at least one candidate target MN), wherein the selection is performed by the terminal. The SN may send an indication that the terminal has detected a RLF with a source MN to the source MN.

The SN may send an indication of the selected one among the at least one candidate target MN to the source MN (e.g. an identifier of the selected one among the at least one candidate target MN).

The SN may send an indication that the terminal has performed or is to perform a pending CHO from the source MN to a selected one among the at least one candidate target to the source MN.

In the second option (illustrated on Figure 8), the SN may receive an indication that a terminal configured with MCG fast recovery has detected a RLP with a source MN from the terminal (step 1200).

The SN may receive an indication that the terminal is to perform a pending CFIO from the source MN to a selected one among the at least one candidate target MN from the terminal (step 1204). The SN may receive an indication of the selected one among the at least one candidate target MN from the terminal (e.g. an identifier of the selected one among the at least one candidate target MN), wherein the selection is performed by the terminal. The SN may send an indication that the terminal has detected a RLP with a source MN to the source MN.

The SN may send an indication of the selected one among the at least one candidate target MN to the source MN (e.g. an identifier of the selected one among the at least one candidate target MN). The SN may send an indication that the terminal has performed or is to perform a pending CHO from the source MN to a selected one among the at least one candidate target to the source MN. In the third option (illustrated on Figure 9), the SN may receive an indication that a terminal configured with MCG fast recovery has detected a RLF with a source MN from the terminal (step 1200).

The SN may send an indication that the terminal has detected a RLF with a source MN to the source MN.

The SN may receive an indication that the terminal is to perform a pending CHO from the source MN to a selected one among the at least one candidate target MN from the source MN (e.g. an identifier the selected one among the at least one candidate target MN), wherein the selection is performed by the source MN (step 1204).

The SN may receive an indication of the selected one among the at least one candidate target MN from the source MN (e.g. an identifier of the selected one among the at least one candidate target MN).

The SN may send an indication that the terminal is to perform a pending CHO from the source MN to a selected one among the at least one candidate target MN to the terminal. The SN may send an indication of the selected one among the at least one candidate target MN to the terminal.

Figure 13 shows a schematic representation of non-volatile memory media 1300a (e.g. computer disc (CD) or digital versatile disc (DVD)) and 1300b (e.g. universal serial bus (USB) memory stick) storing instructions and/or parameters 1302 which when executed by a processor allow the processor to perform one or more of the steps of the processes or methods of Figures 4 to 12. It is noted that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

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

The embodiments may be implemented by computer software stored in a memory and executable by at least one data processor of the involved entities or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that any procedures, e.g., as in Figures 4 to 12, may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD.

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

Alternatively or additionally some embodiments may be implemented using circuitry. The circuitry may be configured to perform one or more of the functions and/or method steps previously described. That circuitry may be provided in the base station and/or in the communications device.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analogue and/or digital circuitry);

(b) combinations of hardware circuits and software, such as:

(i) a combination of analogue and/or digital hardware circuit(s) with software/firmware and

(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as the communications device or base station to perform the various functions previously described; and

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

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example integrated device. The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of some embodiments However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings will still fall within the scope as defined in the appended claims.