WO2023085995A1

WO2023085995A1 - Handling of survival time during handover

Info

Publication number: WO2023085995A1
Application number: PCT/SE2022/051019
Authority: WO
Inventors: Zhenhua Zou; Nianshan SHI
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2021-11-09
Filing date: 2022-11-07
Publication date: 2023-05-19
Anticipated expiration: 2024-05-09

Abstract

A method and network node for handling survival time during handover are disclosed. According to one aspect, a method in a network node includes receiving a handover request from a source network node. The method also includes determining whether a time sensitive communication assistance information (TSCAI) of the WD 5 indicates a survival time. The method further includes when the TSCAI indicates a survival time, then allocating radio resources to the WD based at least in part on the survival time.

Description

HANDLING OF SURVIVAL TIME DURING HANDOVER

TECHNICAL FIELD

The present disclosure relates to wireless communications, and in particular, to handling survival time during handover.

BACKGROUND

The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD), as well as communication between network nodes and between WDs.

In the 5G quality of service (QoS) framework, a QoS flow is established in the 5G system and can be mapped to a data radio bearer (DRB). The QoS flow is associated with QoS parameters, 5Q QoS Indicator (5QI), such as packet delay budget (PDB). The 5G radio access network (RAN) scheduling packets of this QoS flow (mapped to a DRB in 5G RAN) shall thus deliver packets within this PDB. Another metric considered in the industrial automation communication context, related to PDB, is so called “survival time.” According to 3GPP Technical Standard (TS) 22.261 V18.4.0/TS 22.104 vl8.2.0, survival time is defined as the time that an application consuming a communication service may continue without an anticipated message. The message is anticipated at the end of the PDB, and the survival time is the maximum additional time that a message is expected after PDB.

For time sensitive communication (TSC) traffic types (typical in industrial automation communication), 3GPP TS 23.501 vl7.2.0 specifies TSC assistance information (TSCAI) signaling, with which further information on the QoS flow traffic can be provided from 5G core network to RAN. The knowledge of TSC traffic pattern is useful for 5G-AN (Access network) to allow it to efficiently schedule periodic, deterministic traffic flows either via Configured Grants, Semi -Persistent Scheduling or with Dynamic Grants. A survival time may be provided by TSN AF/AF either in terms of maximum number of messages (message is equivalent to a burst) or in terms of time units. Single burst is expected within a single time period referred to as the periodicity.

See Table 1 taken from 3GPP TS 23.501 vl7.2.0:

Table 1

Once the survival time (ST) period starts (which is referred to as entering the survival time mode ), a RAN implementation may schedule the radio resource more robustly to make sure any subsequent messages can be delivered successfully before the survival time is violated. If the message is successfully delivered, the robust resource allocation can be replaced with a normal resource allocation. This is illustrated FIG. 1.

A more robust resource allocation is only needed if previous message(s) are not successfully delivered while in all other cases, a normal resource allocation is needed. Note that the message failure rate is already a very rare event. For example, standard 5QI value of Delay Critical GBR QoS flows (from 82 to 86) in 3GPP TS 23.501 v 17.2.0 has a packet error rate target of 10^A-4 or 10^A-5. The mechanism of survival time can be one way to ensure an even higher communication service availability target value (for example, l-10^A-9).

According to one scheduling mechanism, the network always allocate more radio resources for all data transmissions. However, this is not spectrally efficient since the survival time requirement, which is referred to as communication service availability and is calculated as the probability that the communication service is not stopped, is very stringent as low as in the range of 1 - 10^A-9. These opportunistic radio resource allocations are more efficient to meet the communication service requirement while keeping the radio resource allocation within a reasonable capability amount. One question concerning the above radio resource allocation is how to trigger the resource allocation shift. For periodic traffic, the gNB (hereafter referred to as a network node) is aware of the packet arrival at either the WD or the network node (i.e., by using TSCAI parameters) and then the network node can observe whenever a packet is not delivered within the packet delay budget. Upon observing this, a network node can schedule the subsequent packet with higher reliability to help ensure the survival time is not violated. This can be done by, for example, sending a (re)-activation command for uplink (UL) configured grant (CG) or a dynamic uplink grant with a more robust modulation and coding scheme (MCS), or even by activating packet data convergence protocol (PDCP) duplication.

During handover of the WD from the source Next-Generation RAN (NG-RAN) to the target NG-RAN, the user plane data transmission is interrupted. If one UL packet is still under transmission (e.g., waiting for hybrid automatic repeat request (HARQ) retransmission or even radio link control (RLC) retransmission) during the handover, then this packet would be re-transmitted in the target cell and might not meet the packet delay budget.

Even the survival time is not triggered in the source NG-RAN node before the handover, due to the fact that the handover procedure takes time. For example, the handover interruption time is between 43 and 160 milliseconds (ms) in different cases. It becomes uncertain if the survival time is triggered during handover interruption time. The survival time is often set to: 500 ps to 2 ms for Motion control, 10 ms to 50 ms for control -to-control in motion control; 40 ms to 500 ms for mobile robots. The packet delay budget is set, e.g., for low latency evolved mobile broadband (eMBB) applications Augmented Reality as 10 ms; for Electricity Distribution- high voltage as 5 ms. If the handover is via the core network, the handover interruption time would be even longer.

Even though Dual Active Protocol Stack (DAPS) has been specified in the 3GPP Rel-16 to support zero millisecond interruption, it only calculates the interruption time from the connection point of view but not from individual packet point of view. DAPS handover is a handover procedure that maintains the source network node connection after reception of RRC message for handover and until releasing the source cell after successful random access to the target network node. After the WD successfully completes random access in the target cell, the PDCP entity switches from the source RLC entity to target RLC entity for new packets. However, the source RLC entity may still perform retransmissions of "old" packets until the source cell is released.

There are some further restrictions for DAPS. For example, DAPS does not apply for FR2-to-FR2 handover, and it cannot be used together with PDCP duplication.

In other words, the current mechanism during the handover cannot track whether or not the packet under transmission has been delivered according to the PDB, i.e., whether the survival time has been triggered or not. This consequently means that it is not clear how the target network node, e.g., network node, should perform radio resource allocation to ensure that the survival time requirement is met (i.e., the communication service is not stopped due to failure delivery of messages at the expected time).

SUMMARY

Some embodiments advantageously provide methods, systems, and apparatuses for handling survival time during handover.

For a target Next Generation (NG)-Radio Access Network (RAN), upon receiving a handover request from a source NG-RAN, if the time sensitive communication assistance information (TSCAI) of the wireless device (WD) indicates the survival time is included in the TSCAI, then the target NG-RAN is specified to consider that the survival time is triggered for the WD, i.e., more radio resources are allocated in the target NG-RAN.

The survival time requirement can be met even during handover, which introduces non-negligible user plane data transmission interruption.

According to one aspect, a method in a target network node configured to communicate with a source network node and a wireless device, WD, is provided. The method includes receiving from the source network node a handover request and information about survival time. The method also includes determining whether a survival time mode has been triggered. The method also includes allocating radio resources to the WD based at least in part on whether the survival time mode has been triggered. The method further includes transmitting to the WD a packet according to a first target packet error rate when the survival time mode has been triggered and according to a second target packet error rate when the survival time has not triggered.

According to this aspect, in some embodiments, the information about survival time includes an indication of whether the survival time mode is triggered at the source network node before handover. In some embodiments, the information about survival time includes an indication of whether time sensitive communication assistance information (TSCAI) includes a survival time. In some embodiments, when the information about survival time includes an indication that TSCAI includes the survival time, then the survival time mode is triggered, and when the information about survival time does not include an indication that TSCAI include the survival time, then the survival time is not triggered. In some embodiments, the first target packet error rate is a target packet error rate only for packets not transmitted by the source network node in one of a downlink direction and an uplink direction. In some embodiments, the method also includes reallocating resources to achieve a second target packet error rate when resources have been allocated to the WD according to the first target packet error rate and when transmission of the packet by the target network node according to the first target packet error rate is successful. In some embodiments, the second target packet error rate is larger than the first target packet error rate. In some embodiments, when the packet transmitted by the target network node is successful, further comprising one of deactivating packet data convergence protocol, PDCP, duplication for at least one split secondary radio link control entity, reactivating one of a type 2 configured grant and a configured downlink assignment, scheduling a packet transmission using one of a dynamic uplink grant and a dynamic downlink assignment. In some embodiments, the transmission of the packet to the WD by the target network node is considered successful when, for an uplink packet, the target network node has received the packet before an expected time, and for a downlink packet, the target network node has received a positive acknowledgment before the expected time. In some embodiments, the method also includes configuring and activating a packet data convergence protocol, PDCP, duplication with a plurality of split secondary radio link control entities in a radio resource control, RRC, message for a handover. In some embodiments, the method also includes activating one of a type 2 configured grant and a configured downlink assignment using downlink control information, DCI, after the WD completes a random access procedure in a cell of the target network node. In some embodiments, the method also includes scheduling the packet transmission using at least one of a dynamic uplink grant and a dynamic downlink assignment. In some embodiments, allocation of radio resources is based at least in part on a number of packets that may be lost by the target network node before a communication service to the WD is terminated.

According to another aspect, a target network node configured to communicate with a source network node and a wireless device, WD, is provided. The target network node includes a radio interface configured to receive from the source network node a handover request and information about survival time> The target network node includes processing circuitry in communication with the radio interface and configured to: determine whether a survival time mode has been triggered; and allocate radio resources to the WD based at least in part on whether the survival time mode has been triggered. The radio interface is further configured to transmit to the WD a packet according to a first target packet error rate when the survival time mode has been triggered and according to a second target packet error rate when the survival time mode has not been triggered.

According to this aspect, in some embodiments, the information about survival time includes an indication of whether the survival time mode is triggered at the source network node before handover. In some embodiments, the information about survival time includes an indication of whether time sensitive communication assistance information (TSCAI) includes a survival time. In some embodiments, when the information about survival time includes an indication that TSCAI includes the survival time, then the survival time mode is triggered, and when the information about survival time does not include an indication that TSCAI include the survival time, then the survival time is not triggered. In some embodiments, the first target packet error rate is a target packet error rate only for packets not transmitted by the source network node in one of a downlink direction and an uplink direction. In some embodiments, the processing circuitry is further configured to reallocate resources to achieve a second target packet error rate when resources have been allocated to the WD according to the first target packet error rate and when transmission of the packet by the target network node according to the first target packet error rate is successful. In some embodiments, the second target packet error rate is larger than the first target packet error rate. In some embodiments, when the packet transmitted by the target network node is successful, further comprising one of deactivating packet data convergence protocol, PDCP, duplication for at least one split secondary radio link control entity, reactivating one of a type 2 configured grant and a configured downlink assignment, scheduling a packet transmission using one of a dynamic uplink grant and a dynamic downlink assignment. In some embodiments, the transmission of the packet to the WD by the target network node is considered successful when, for an uplink packet, the target network node has received the packet before an expected time, and for a downlink packet, the target network node has received a positive acknowledgment before the expected time. In some embodiments, the processing circuitry is further configured to configured and activate a packet data convergence protocol, PDCP, duplication with a plurality of split secondary radio link control entities in a radio resource control, RRC, message for a handover. In some embodiments, the processing circuitry is further configured to activate one of a type 2 configured grant and a configured downlink assignment using downlink control information, DCI, after the WD completes a random access procedure in a cell of the target network node. In some embodiments, the processing circuitry is further configured to schedule the packet transmission using at least one of a dynamic uplink grant and a dynamic downlink assignment. In some embodiments, allocation of radio resources is based at least in part on a number of packets that can be lost by the target network node before a communication service to the WD is terminated.

According to yet another aspect, a method in a source network node configured to communicate with a target network node and a wireless device, WD, is provided. The method includes transmitting to the target network node an indication that a survival time mode has been triggered, the survival time mode being associated with a survival time, the survival time being a maximum additional time after a packet data buffer duration. The method also includes transmitting to the target network node a handover request that includes time sensitive communication assistance information, TSCAI.

According to this aspect, in some embodiments, the method includes transmitting an indication of a number of packets the target network node may lose before a communication service to the WD is terminated. In some embodiments, the number of packets is a number of only packets that have not been transmitted in a source cell of the source network node. In some embodiments, the TSCAI includes a survival time.

According to another aspect, a source network node configured to communicate with a target network node and a wireless device, WD, is provided. The source network node includes a radio interface configured to: transmit to the target network node an indication that a survival time mode has been triggered, the survival time mode being associated with a survival time, the survival time being a maximum additional time after a packet data buffer duration; and transmit to the target network node a handover request that includes time sensitive communication assistance information, TSCAI.

According to this aspect, in some embodiments, the radio interface is further configured to transmit an indication of a number of packets the target network node may lose before a communication service to the WD is terminated. In some embodiments, the number of packets is a number of only packets that have not been transmitted in a source cell of the source network node. In some embodiments, the TSCAI includes a survival time.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 illustrates resource allocation relative to survival time;

FIG. 2 is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein;

FIG. 3 is a block diagram of a network node in communication with a wireless device over a wireless connection according to some embodiments of the present disclosure;

FIG. 4 is a flowchart of an example process in a network node for handling survival time during handover according to some embodiments of the present disclosure;

FIG. 5. is a flowchart of an example process in a target network node for handling survival time during handover according to some embodiments of the present disclosure;

FIG. 6 is flowchart of an example process in a source network node for handling survival time during handover according to some embodiments of the present disclosure; and

FIG. 7 illustrates an exchange of messages for handover according to some embodiments of the present disclosure. DETAILED DESCRIPTION

Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to handling survival time during handover. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and/or wireless connections.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The term “network node” used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (network node), evolved Node B (eNB or eNodeB), Node B, multi -standard radio (MSR) radio node such as MSR BS, rnulti- cell/multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node.

In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The WD herein can be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as wireless device (WD). The WD may also be a radio communication device, target device, device to device (D2D) WD, machine type WD or WD capable of machine to machine communication (M2M), low-cost and/or low-complexity WD, a sensor equipped with WD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device, etc.

Also, in some embodiments the generic term “radio network node” is used. It can be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, network node, Multi -cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH).

Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and/or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

Note further, that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and/or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Some embodiments are directed to handling survival time during handover. Referring again to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 2 a schematic diagram of a communication system 10, according to an embodiment, such as a 3 GPP -type cellular network that may support standards such as LTE and/or NR (5G), which comprises an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, network nodes or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include many more WDs 22 and network nodes 16.

In some embodiments, a first network node 16a may act as a source network node from which a WD 22s is to be handed over to a target network node 16c. In some embodiments, the source network node 16a may be in a first radio access network (RAN) and the target network node 16c may be in a second radio access network. In some embodiments, both RANs are 5G RANs.

Also, it is contemplated that a WD 22 can be in simultaneous communication and/or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a WD 22 can have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, WD 22 can be in communication with an eNB for LTEZE-UTRAN and a network node for NR/NG-RAN.

A network node 16 (eNB or network node) is configured to include a TSCAI unit 24 which is configured to determine whether a TSCAI of the WD indicates a survival time and when the TSCAI indicates a survival time, then allocate radio resources to the WD based at least in part on the survival time. The TSCAI unit 24 may also be configured to determine whether a survival time mode has been triggered and allocate radio resources to the WD based at least in part on whether the survival time mode has been triggered.

Example implementations, in accordance with an embodiment, of the WD 22 and network node 16 discussed in the preceding paragraphs will now be described with reference to FIG. 3.

The communication system 10 includes a network node 16 provided in a communication system 10 and including hardware 28 enabling it to communicate with the WD 22. The hardware 28 may include a radio interface 30 for setting up and maintaining at least a wireless connection 32 with a WD 22 located in a coverage area 18 served by the network node 16. The radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers. The radio interface 30 includes an array of antennas 34 to radiate and receive signal(s) carrying electromagnetic waves.

In the embodiment shown, the hardware 28 of the network node 16 further includes processing circuitry 36. The processing circuitry 36 may include a processor 38 and a memory 40. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 36 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 38 may be configured to access (e.g., write to and/or read from) the memory 40, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read- Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read- Only Memory).

Thus, the network node 16 further has software 42 stored internally in, for example, memory 40, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 42 may be executable by the processing circuitry 36. The processing circuitry 36 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by network node 16. Processor 38 corresponds to one or more processors 38 for performing network node 16 functions described herein. The memory 40 is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software 42 may include instructions that, when executed by the processor 38 and/or processing circuitry 36, causes the processor 38 and/or processing circuitry 36 to perform the processes described herein with respect to network node 16. For example, processing circuitry 36 of the network node 16 may include a TSCAI unit 24 which is configured to determine whether a TSCAI of the WD indicates a survival time and when the TSCAI indicates a survival time, then allocate radio resources to the WD based at least in part on the survival time.

In some embodiments, the network node 16, a radio interface 30 and/or processing circuitry 36 are configured to: receive a handover request from a source network node 16a; determine whether a time sensitive communication assistance information (TSCAI) of the WD 22 indicates a survival time; and when the TSCAI indicates a survival time, then allocate radio resources to the WD 22 based at least in part on the survival time.

In some embodiments, the radio resources are allocated to achieve a first target packet error rate. In some embodiments, the radio resources are allocated to achieve a first target packet error rate only for packets that have not been transmitted via of the source network node. In some embodiments, the network node 16, processing circuitry 36 and/or radio interface 30 are further configured to discard packets not used to meet a survival time condition. In some embodiments, the network node 16, processing circuitry 36 and/or radio interface 30 are further configured to allocate resources to achieve a second target packet error rate larger than the first target packet error rate to account for packet delivery after the survival time has started. In some embodiments, the network node 16, processing circuitry 36 and/or radio interface 30 are configured to: receive from the source network node a handover request and information about survival time; determine whether a survival time mode has been triggered; allocate radio resources to the WD based at least in part on whether the survival time mode has been triggered and transmit to the WD a packet according to a first target packet error rate when the survival time mode has been triggered and according to a second target packet error rate when the survival time mode has not been triggered. In some embodiments, the network node 16, processing circuitry 36 and/or radio interface 30 are configured to transmit to the target network node an indication that a survival time mode has been triggered, the survival time mode being associated with a survival time, the survival time being a maximum additional time after a packet data buffer duration; and transmit to the target network node a handover request that includes time sensitive communication assistance information, TSCAI.

The communication system 10 further includes the WD 22 already referred to. The WD 22 may have hardware 44 that may include a radio interface 46 configured to set up and maintain a wireless connection 32 with a network node 16 serving a coverage area 18 in which the WD 22 is currently located. The radio interface 46 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers. The radio interface 46 includes an array of antennas 48 to radiate and receive signal(s) carrying electromagnetic waves.

The hardware 44 of the WD 22 further includes processing circuitry 50. The processing circuitry 50 may include a processor 52 and memory 54. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 50 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 52 may be configured to access (e.g., write to and/or read from) memory 54, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).

Thus, the WD 22 may further comprise software 56, which is stored in, for example, memory 54 at the WD 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the WD 22. The software 56 may be executable by the processing circuitry 50. The software 56 may include a client application 58. The client application 58 may be operable to provide a service to a human or non-human user via the WD 22.

The processing circuitry 50 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by WD 22. The processor 52 corresponds to one or more processors 52 for performing WD 22 functions described herein. The WD 22 includes memory 54 that is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software 56 and/or the client application 58 may include instructions that, when executed by the processor 52 and/or processing circuitry 50, causes the processor 52 and/or processing circuitry 50 to perform the processes described herein with respect to WD 22.

In some embodiments, the inner workings of the network node 16 and WD 22 may be as shown in FIG. 3 and independently, the surrounding network topology may be that of FIG. 2.

The wireless connection 32 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and/or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc. In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. Although FIGS. 2 and 3 show various “units” such as TSCAI unit 24 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

FIG. 4 is a flowchart of an example process in a network node 16 for handling survival time during handover. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the TSCAI unit 24), processor 38, and/or radio interface 30. Network node 16 such as via processing circuitry 36 and/or processor 38 and/or radio interface 30 is configured to receive a handover request from a source network node (Block S10). The process also includes determining whether a time sensitive communication assistance information (TSCAI) of the WD indicates a survival time (Block S12). The process also includes, when the TSCAI indicates a survival time, allocating radio resources to the WD based at least in part on the survival time (Block S14).

In some embodiments, the radio resources are allocated to achieve a first target packet error rate. In some embodiments, the radio resources are allocated to achieve a first target packet error rate only for packets that have not been transmitted via of the source network node. In some embodiments, the method further includes discarding packets not used to meet a survival time condition. In some embodiments, the method also includes allocating resources to achieve a second target packet error rate larger than the first target packet error rate to account for packet delivery after the survival time has started.

FIG. 5 is a flowchart of an example process in a target network node 16 for handling survival time during handover. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the TSCAI unit 24), processor 38, and/or radio interface 30. Network node 16 such as via processing circuitry 36 and/or processor 38 and/or radio interface 30 is configured to receive from the source network node a handover request and information about survival time (Block SI 6). The method also includes determining whether a survival time mode has been triggered (Block SI 8). The method also includes allocating radio resources to the WD based at least in part on whether the survival time mode has been triggered (Block S20). The method further includes transmitting to the WD a packet according to a first target packet error rate when the survival time mode has been triggered and according to a second target packet error rate when the survival time has not triggered (Block S22)

In some embodiments, the information about survival time includes an indication of whether the survival time mode is triggered at the source network node before handover. In some embodiments, the information about survival time includes an indication of whether time sensitive communication assistance information (TSCAI) includes a survival time. In some embodiments, when the information about survival time includes an indication that TSCAI includes the survival time, then the survival time mode is triggered, and when the information about survival time does not include an indication that TSCAI include the survival time, then the survival time is not triggered. In some embodiments, the first target packet error rate is a target packet error rate only for packets not transmitted by the source network node in one of a downlink direction and an uplink direction. In some embodiments, the method also includes reallocating resources to achieve a second target packet error rate when resources have been allocated to the WD according to the first target packet error rate and when transmission of the packet by the target network node according to the first target packet error rate is successful. In some embodiments, the second target packet error rate is larger than the first target packet error rate. In some embodiments, when the packet transmitted by the target network node is successful, further comprising one of deactivating packet data convergence protocol, PDCP, duplication for at least one split secondary radio link control entity, reactivating one of a type 2 configured grant and a configured downlink assignment, scheduling a packet transmission using one of a dynamic uplink grant and a dynamic downlink assignment. In some embodiments, the transmission of the packet to the WD by the target network node is considered successful when, for an uplink packet, the target network node has received the packet before an expected time, and for a downlink packet, the target network node has received a positive acknowledgment before the expected time. In some embodiments, the method also includes configuring and activating a packet data convergence protocol, PDCP, duplication with a plurality of split secondary radio link control entities in a radio resource control, RRC, message for a handover. In some embodiments, the method also includes activating one of a type 2 configured grant and a configured downlink assignment using downlink control information, DCI, after the WD completes a random access procedure in a cell of the target network node. In some embodiments, the method also includes scheduling the packet transmission using at least one of a dynamic uplink grant and a dynamic downlink assignment. In some embodiments, allocation of radio resources is based at least in part on a number of packets that may be lost by the target network node before a communication service to the WD is terminated.

FIG. 6 is a flowchart of an example process in a target network node 16 for handling survival time during handover. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the TSCAI unit 24), processor 38, and/or radio interface 30. Network node 16 such as via processing circuitry 36 and/or processor 38 and/or radio interface 30 is configured to transmit to the target network node an indication that a survival time mode has been triggered, the survival time mode being associated with a survival time, the survival time being a maximum additional time after a packet data buffer duration (Block S24). The method also includes transmitting to the target network node a handover request that includes time sensitive communication assistance information, TSCAI (Block S26).

In some embodiments, the method includes transmitting an indication of a number of packets the target network node may lose before a communication service to the WD is terminated. In some embodiments, the number of packets is a number of only packets that have not been transmitted in a source cell of the source network node. In some embodiments, the TSCAI includes a survival time.

In some embodiments, a wireless device is configured to communicate with a network node, the wireless node configured to, and/or comprising a radio interface and/or comprising processing circuitry configured to interoperate with the network node to receive allocated resources from the network node based on any one or more of the arrangements described herein. In some embodiments, a method is implemented in a wireless device configured to communicate with a network node in which the method causes the wireless device to interoperate with the network node to receive allocated resources from the network node based on any one or more of the arrangements described herein.

Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for handling survival time during handover. Implicit indication to trigger the entry of the survival time mode

In some embodiments, for a target NG-RAN, it is specified that upon receiving a handover request from a source NG-RAN, if the TSCAI of the WD 22 indicates that the survival time is included in the TSCAI, then the target NG-RAN considers that the survival time mode is triggered for the WD 22.

An example of such solution is to specify in 3GPP TS 38.423, in 8.2.1 Handover Preparation that “If Survival Time IE in the TSC Traffic Characteristics information element (IE) is included in the QoS Flows To Be Setup List in the packet data unit (PDU) Session Resource To Be Setup List IE, the target NG-RAN node shall, if supported, consider that the survival time is triggered for the WD and the radio resources should be allocated accordingly.”

In some embodiments, if the survival time mode is triggered for the WD 22, the network, such as via network node 16, may allocate radio resources to achieve a target packet error rate, say PER_SUrvivaiTime. The network, such as via network node 16, may use one or more of the following configuration/scheduling decisions:

1. The network, such as via network node 16, may configure and activate PDCP duplication (via RRC) with two, three or four split secondary RLC entities in the RRC reconfiguration message for handover;

2. The network, such as via network node 16, may activate a type 2 configured grant or configured downlink assignment using downlink control information (DCI) after the WD 22 has successfully completely the random access in the target cell. The targeted MCS is supposed to be

MC S survivalTime

3. The network, such as via network node 16, may schedule the packet transmission using dynamic UL grant or dynamic downlink assignment. The targeted MCS is supposed to be MCSsu vamme •

In some embodiments, the network, such as via network node 16, allocates radio resources to achieve a targeted packet error rate, say PER_SUrvivaiTime only for those packets that have not been transmitted via the source cell either in the UL or in the DL direction. This is to assume that the packets that have been under transmission in the source cell would fail the PDB target and so the survival time mode is triggered for the subsequent packets that would be transmitted via the target cell.

In some embodiments, the network, such as via network node 16, discards the packets that have been transmitted via the source cell. For example, for DL packets, the network does not transmit those packets and for UL packets, the network does not schedule a retransmission. This is to ensure that the radio resources in the target cell are not used for the packet transmissions that are not essential to meet the survival time requirement.

In some embodiments, after the handover, if the transmission of any one packet at the target cell has been successful, the network, such as via network node 16, changes the allocation of the radio resources to another target packet error rate, say PERnormai. The PERnormai is generally larger than the PER_SUrvivaiTime to account for that the fact that packet delivery must be successful when the survival time mode has started, and thus a smaller packet error rate can be used as compared to when the survival time mode has not been started. Otherwise, the application running at the WD 22 that requires periodic data transmission might fail/stop. The network, such as via network node 16, may use one or more of the following example configuration/ scheduling deci sions :

1. The network, such as via network node 16, may de-activate PDCP duplication via medium access control (MAC) control element (CE) for some of the associated split secondary RLC entities or even de-activate PDCP duplication;

2. The network, such as via network node 16, re-activates a type 2 configured grant or configured downlink assignment using DCI. The target MCS is supposed to be MCSnormai so that the BLER target is higher than the one with MCSsurvivamme; and/or

3. The network, such as via network node 16, may schedule the packet transmission using dynamic UL grant or dynamic downlink assignment. The target MCS is supposed to be MCSnormai so that the BLER target is higher than the one with MCSsurvivairime.

In some embodiments, the transmission of one packet is considered successful if:

1. for UL packet, the network, such as via network node 16, has received the packet at or before the expected time, i.e., burst arrival time + periodicity * N + PDB, where N denotes the N-th packet; and/or

2. for DL packet, the network, such as via network node 16, has received the positive acknowledgement at or before the expected time, i.e., burst arrival time + periodicity * N + PDB, where N denotes the N-th packet. The positive acknowledgement here may be the HARQ ACK feedback.

1. For UL packet, the network, such as via network node 16, has received the packet at or before its PDB and this packet has not been transmitted to the source cell from the WD 22; and/or

2. For DL packet, the network, such as via network node 16, has received the positive acknowledgement at or before the PDB of the packet, and this packet has not been transmitted to the WD 22 via the source cell.

In another variant, the above mechanism applies only if the survival time value in the TSCAI is non-zero. In case the survival time is zero, the RAN may not be able to meet the survival time requirement, and in the case that such a code point is supported for other purposes, the target NG-RAN should be able to distinguish and not trigger the above relevant actions. Time sensitive communication (TSC) flow is unidirectional. See FIG. 7, which shows that when a data transmission is successful in either the uplink or the downlink (dashed arrows), an allocation of resources according to the WD 22 by the target node is according to a normal time mode wherein the target packet error rate is PERnormal-

Remaining survival time in number of remaining packets

In this scenario, it is assumed that the survival time mode has been triggered in the source cell during the handover.

In some embodiments, the source NG-RAN indicates to the target NG-RAN that the survival time mode has been triggered.

In some embodiments, the source NG-RAN indicates to the target NG-RAN the number of packets that the NG-RAN may lose before the communication service cannot continue. In some embodiments, the number of packets only include those that have not been transmitted in the source cell.

In one example:

• Suppose the traffic periodicity is 10 milliseconds, the PDB is equal to 10 milliseconds, and the survival time is three times the periodicity (i.e., 30 milliseconds). Suppose the survival time has started (i.e., one packet has missed the PDB), one more packet has not met the PDB in the source cell and there is one packet already under transmission in the source cell. The source NG-RAN may indicate to the target NG- RAN that the target NG-RAN must deliver the next packet (i.e., there is only one last chance remaining) that is transmitted under the target cell. Otherwise the survival time requirement would not be met (i.e., the application would be stopped).

In some embodiments, upon receiving such an indication, the target NG-RAN may consider that the survival time is triggered for the WD 22 and may then allocate radio resources with a targeted packet error rate, according to how many packets the target NG-RAN may lose before the communication service is stopped (i.e., the number of the packets is transferred from the source NG-RAN according to the above embodiments): o If there is one packet remaining, with PER = PER_SUrvivaiTime_i; o If there are two packets remaining, with PER = PER_SUrvivaiTime_2; and o If N packets are remaining, with PER = PER_SUrvivaiTime_N.

In some embodiments, the network node 16 allocates radio resources so that PERsurvivalTime l ^<~~ PERsurvivalTime_2 ^<~~ • • • PERsurvivalTime N-l ^<~~ PERsurvivalTime N .. , where “<=” means smaller than or equal to. Here, the rationale is that the closer to the survival time expiry, more radio resources should be allocated to the WD 22 so that the survival time requirement is met.

In some embodiments, after the handover, if the transmission of any one packet at the target cell has been successful, the network node 16 changes the allocation of the radio resources to another target packet error rate, say PERnormai. The PERnormai is larger than the PERsurvivalTime N.

Some embodiments may include one or more of the following:

Embodiment Al . A network node configured to communicate with a wireless device (WD), the network node configured to, and/or comprising a radio interface and/or comprising processing circuitry configured to: receive a handover request from a source network node; determine whether a time sensitive communication assistance information (TSCAI) of the WD indicates a survival time; and when the TSCAI indicates a survival time, then allocate radio resources to the WD based at least in part on the survival time.

Embodiment A2. The network node of Embodiment Al, wherein the radio resources are allocated to achieve a first target packet error rate.

Embodiment A3. The network node of Embodiment A2, wherein the radio resources are allocated to achieve a first target packet error rate only for packets that have not been transmitted via of the source network node.

Embodiment A4. The network node of any of Embodiments A1-A3, wherein the network node, processing circuitry and/or radio interface are further configured to discard packets not used to meet a survival time condition.

Embodiment A5. The network node of any of Embodiments A1-A4, wherein the network node, processing circuitry and/or radio interface are further configured to allocate resources to achieve a second target packet error rate larger than the first target packet error rate to account for packet delivery after the survival time has started.

Embodiment Bl. A method implemented in a network node that is configured to communicate with a wireless device, the method comprising: receiving a handover request from a source network node; determining whether a time sensitive communication assistance information (TSCAI) of the WD indicates a survival time; and when the TSCAI indicates a survival time, then allocating radio resources to the WD based at least in part on the survival time.

Embodiment B2. The method of Embodiment Bl, wherein the radio resources are allocated to achieve a first target packet error rate.

Embodiment B3. The method of Embodiment B2, wherein the radio resources are allocated to achieve a first target packet error rate only for packets that have not been transmitted via of the source network node.

Embodiment B4. The method of any of Embodiments B1-B3, further comprising discarding packets not used to meet a survival time condition.

Embodiment B5. The method of any of Embodiments B1-B4, further comprising allocating resources to achieve a second target packet error rate larger than the first target packet error rate to account for packet delivery after the survival time has started.

Embodiment Cl . A wireless device configured to communicate with a network node, the wireless node configured to, and/or comprising a radio interface and/or comprising processing circuitry configured to interoperate with the network node to receive allocated resources from the network node based on any one of Embodiments A1-A5.

Embodiment DI . A method implemented in a wireless device configured to communicate with a network node, the method causing the wireless device to interoperate with the network node to receive allocated resources from the network node based on any one of Embodiments Bl -B5.

As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and/or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and/or functionality described herein may be performed by, and/or associated to, a corresponding module, which may be implemented in software and/or firmware and/or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that can be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD- ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

Some embodiments are described herein with reference to flowchart illustrations and/or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable memory or storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

It is to be understood that the functions/acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments can be combined in any way and/or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

What is claimed is:

1. A method in a target network node (16) configured to communicate with a source network node (16) and a wireless device, WD (22), the method comprising: receiving (SI 6) from the source network node (16) a handover request and information about survival time; and determining (SI 8) whether a survival time mode has been triggered; allocating (S20) radio resources to the WD (22) based at least in part on whether the survival time mode has been triggered; and transmitting (S22) to the WD (22) a packet according to a first target packet error rate when the survival time mode has been triggered and according to a second target packet error rate when the survival time has not triggered.

2. The method of Claim 1, wherein the information about survival time includes an indication of whether the survival time mode is triggered at the source network node (16) before handover.

3. The method of any of Claims 1 and 2, wherein the information about survival time includes an indication of whether time sensitive communication assistance information (TSCAI) includes a survival time.

4. The method of Claim 3, wherein, when the information about survival time includes an indication that TSCAI includes the survival time, then the survival time mode is triggered, and when the information about survival time does not include an indication that TSCAI include the survival time, then the survival time is not triggered.

5. The method of any of Claims 1-4, wherein the first target packet error rate is a target packet error rate only for packets not transmitted by the source network node (16) in one of a downlink direction and an uplink direction.

6. The method of any of Claims 1-5, further comprising reallocating resources to achieve a second target packet error rate when resources have been allocated to the WD

27 (22) according to the first target packet error rate and when transmission of the packet by the target network node according to the first target packet error rate is successful.

7. The method of any of Claims 1-6, wherein the second target packet error rate is larger than the first target packet error rate.

8. The method of any of Claims 1-7, wherein, when the packet transmitted by the target network node (16) is successful, further comprising one of deactivating packet data convergence protocol, PDCP, duplication for at least one split secondary radio link control entity, reactivating one of a type 2 configured grant and a configured downlink assignment, scheduling a packet transmission using one of a dynamic uplink grant and a dynamic downlink assignment.

9. The method of any of Claims 1-8, wherein the transmission of the packet to the WD (22) by the target network node (16) is considered successful when, for an uplink packet, the target network node (16) has received the packet before an expected time, and for a downlink packet, the target network node (16) has received a positive acknowledgment before the expected time.

10. The method of any of Claims 1-9, further comprising configuring and activating a packet data convergence protocol, PDCP, duplication with a plurality of split secondary radio link control entities in a radio resource control, RRC, message for a handover.

11. The method of any of Claims 1-10, further comprising activating one of a type 2 configured grant and a configured downlink assignment using downlink control information, DCI, after the WD (22) completes a random access procedure in a cell of the target network node (16).

12. The method of any of Claims 1-10, further comprising scheduling the packet transmission using at least one of a dynamic uplink grant and a dynamic downlink assignment.

13. The method of any of Claims 1-12, wherein allocation of radio resources is based at least in part on a number of packets that may be lost by the target network node (16) before a communication service to the WD (22) is terminated.

14. A target network node (16) configured to communicate with a source network node (16) and a wireless device, WD (22), the target network node (16) comprising: a radio interface (30) configured to receive from the source network node (16) a handover request and information about survival time; and processing circuitry (36) in communication with the radio interface (30) and configured to: determine whether a survival time mode has been triggered; and allocate radio resources to the WD (22) based at least in part on whether the survival time mode has been triggered; and the radio interface (30) being further configured to transmit to the WD (22) a packet according to a first target packet error rate when the survival time mode has been triggered and according to a second target packet error rate when the survival time mode has not been triggered.

15. The method of Claim 14, wherein the information about survival time includes an indication of whether the survival time mode is triggered at the source network node (16) before handover.

16. The method of any of Claims 14 and 15, wherein the information about survival time includes an indication of whether time sensitive communication assistance information (TSCAI) includes a survival time.

17. The method of Claim 16, wherein, when the information about survival time includes an indication that TSCAI includes the survival time, then the survival time mode is triggered, and when the information about survival time does not include an indication that TSCAI include the survival time, then the survival time is not triggered.

18. The target network node (16) of Claim 14-17, wherein the first target packet error rate is a target packet error rate only for packets not transmitted by the source network node (16) in one of a downlink direction and an uplink direction.

19. The target network node (16) of any of Claims 14 and 18, wherein the processing circuitry is further configured to reallocate resources to achieve a second target packet error rate when resources have been allocated to the WD (22) according to the first target packet error rate and when transmission of the packet by the target network node according to the first target packet error rate is successful.

20. The target network node (16) of Claim 14-19, wherein the second target packet error rate is larger than the first target packet error rate.

21. The target network node (16) of any of Claims 14-20, wherein, when the packet transmitted by the target network node (16) is successful, the processing circuitry is further configured to one of deactivating packet data convergence protocol, PDCP, duplication for at least one split secondary radio link control entity, reactivating one of a type 2 configured grant and a configured downlink assignment, scheduling a packet transmission using one of a dynamic uplink grant and a dynamic downlink assignment.

22. The target network node (16) of any of Claims 14-21, wherein the transmission of the packet to the WD (22) by the target network node (16) is considered successful when, for an uplink packet, the target network node (16) has received the packet before an expected time, and for a downlink packet, the target network node (16) has received a positive acknowledgment before the expected time.

23. The target network node (16) of any of Claims 14-22, wherein the processing circuitry (36) is further configured to configured and activate a packet data convergence protocol, PDCP, duplication with a plurality of split secondary radio link control entities in a radio resource control, RRC, message for a handover.

24. The target network node (16) of any of Claims 14-23, wherein the processing circuitry (36) is further configured to activate one of a type 2 configured grant and a configured downlink assignment using downlink control information, DCI, after the WD (22) completes a random access procedure in a cell of the target network node (16).

25. The target network node (16) of any of Claims 14-23, wherein the processing circuitry (36) is further configured to schedule the packet transmission using at least one of a dynamic uplink grant and a dynamic downlink assignment.

26. The target network node (16) of any of Claims 14-25, wherein allocation of radio resources is based at least in part on a number of packets that can be lost by the target network node (16) before a communication service to the WD (22) is terminated.

27. A method in a source network node (16) configured to communicate with a target network node (16) and a wireless device, WD (22), the method comprising: transmitting (S24) to the target network node (16) an indication that a survival time mode has been triggered, the survival time mode being associated with a survival time, the survival time being a maximum additional time after a packet data buffer duration; and transmitting (S26) to the target network node (16) a handover request that includes time sensitive communication assistance information, TSCAI.

28. The method of Claim 27, further comprising transmitting an indication of a number of packets the target network node (16) may lose before a communication service to the WD (22) is terminated.

29. The method of Claim 28, wherein the number of packets is a number of only packets that have not been transmitted in a source cell of the source network node (16).

30. The method of any of Claims 27-29, wherein the TSCAI includes a survival time.

31. A source network node (16) configured to communicate with a target network node (16) and a wireless device, WD (22), the source network node (16) comprising a radio interface (30) configured to:

31 transmit to the target network node (16) an indication that a survival time mode has been triggered, the survival time mode being associated with a survival time, the survival time being a maximum additional time after a packet data buffer duration; and transmit to the target network node (16) a handover request that includes time sensitive communication assistance information, TSCAI.

32. The source network node (16) of Claim 31, wherein the radio interface (30) is further configured to transmit an indication of a number of packets the target network node (16) may lose before a communication service to the WD (22) is terminated.

33. The source network node (16) of Claim 32, wherein the number of packets is a number of only packets that have not been transmitted in a source cell of the source network node (16).

34. The source network node (16) of any of Claims 31-33, wherein the TSCAI includes a survival time.

32