Communication device related to measurement report and hand-over

Abstract

To provide an improved procedure for measurements and hand-over in a communication device which executes a power-related measurement in at least one wireless carrier and generates the result of the measurement on the basis of the executed power-related measurement.SOLUTION: A communication device determines whether to execute a conditioned hand-over on the basis of the result of a measurement. A first value for a ground network and a non-ground network and a second value for a non-ground network are set by a service base station along with a reference for executing a conditioned hand-over and a measurement target. The communication device determines a conditioned hand-over when the reference for executing a conditioned hand-over is satisfied on the basis of the result of measurement, by using the first value and the second value. The communication device determines a conditioned hand-over when an additional reference for executing a conditioned hand-over is satisfied on the basis of the positions of the communication device and at least a radio cell.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present disclosure relates to methods, devices, and products in communication systems such as 3GPP (registered trademark) communication systems.

Background Art

[0002] Currently, the 3rd Generation Partnership Project (3GPP) is working on technical specifications for next-generation cellular technology, also referred to as the 5th generation (5G).

[0003] One objective is to provide, at least, a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios, including enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine type communication (mMTC). For example, eMBB deployment scenarios may include indoor hotspots, dense urban areas, suburbs, urban areas, and highways. URLLC deployment scenarios may include industrial control systems, mobile health management (remote monitoring, diagnosis, and treatment), real-time vehicle control, and wide-area monitoring and control systems for smart grids. mMTC deployment scenarios may include scenarios using a large number of devices for data transmission with little impact of latency, such as smart wearables and sensor networks. eMBB services and URLLC services are similar in that both require a very wide bandwidth, but differ in that URLLC services may preferably require ultra-low latency.

[0004] A second objective is to achieve forward compatibility. Backward compatibility with Long-Term Evolution (LTE, LTE-A) cellular systems is not required, which facilitates a completely new system design and / or the introduction of new features.

Summary of the Invention

[0005] One non - limiting and exemplary embodiment contributes to providing an improved procedure for measurement and handover.

[0006] In one embodiment, the technology disclosed herein features a user equipment (UE) comprising a processing circuit that, during operation, performs power - related measurements in at least one radio carrier and generates measurement results based on the performed power - related measurements. The reporting of the measurement results by the UE is based on at least one reporting trigger condition to be satisfied. The processing circuit determines whether to adjust at least one of the measurement results and at least one of the reporting trigger conditions so as to trigger the reporting of the measurement results earlier than in the case of no adjustment. If it is determined to adjust, the processing circuit adjusts at least one of the measurement results and at least one of the reporting trigger conditions so as to trigger the reporting of the measurement results earlier than in the case of no adjustment. After adjustment, the processing circuit determines whether at least one reporting trigger condition is satisfied for reporting the measurement results based on the at least one reporting trigger condition and the measurement results. When the reporting of the measurement results is triggered, the transmitter of the UE transmits a measurement report including the measurement results.

[0007] Note that a general embodiment or a specific embodiment can be realized as a system, a method, an integrated circuit, a computer program, a storage medium, or any optional combination thereof.

[0008] Further benefits and advantages of the disclosed embodiments and various aspects will become apparent from the present specification and the drawings. These benefits and / or advantages can be obtained individually by various embodiments and features of the present specification and the drawings. However, it is not necessary to provide all of these features in order to obtain one or more of such benefits and / or advantages.

Brief Description of the Drawings

[0009] In the following, exemplary embodiments will be described in more detail with reference to the accompanying drawings.

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Mode for Carrying Out the Invention

[0010] (5G NR System Architecture and Protocol Stack) 3GPP is working on the next release of the 5th generation cellular technology, simply called 5G, which includes the development of a new radio access technology (NR) operating in the frequency range up to 100 GHz. The first version of the 5G standard was completed at the end of 2017, which has enabled the progress of trials and commercial deployment of smartphones compliant with the 5G NR standard.

[0011] In particular, the overall system architecture assumes an NG-RAN (Next Generation - Radio Access Network) including gNBs, which provides NG-radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocol terminations towards the UEs. The gNBs are interconnected with each other via the Xn interface. The gNBs are also connected to the NGC (Next Generation Core) via the Next Generation (NG) interface, more specifically, to the AMF (Access and Mobility Management Function) (e.g., a specific core entity that executes the AMF) via the NG-C interface, and also to the UPF (User Plane Function) (e.g., a specific core entity that executes the UPF) via the NG-U interface. The NG-RAN architecture is shown in Figure 1 (see, for example, 3GPP TS38.300 v15.4.0, Section 4).

[0012] Various different deployment scenarios can be supported (see, for example, 3GPP TR38.801 v14.0.0). For example, a non-collocated deployment scenario (see, for example, Section 5.2 of TR38.801; collocated deployment is shown in Section 5.4) is presented there, in which base stations supporting 5G NR can be deployed. Figure 2 shows an exemplary non-collocated deployment scenario (see, for example, Figure 5.2.-1 of TR38.801), additionally showing a user equipment (UE) connected to both a gNB and an LTE eNB and the LTE eNB. The new eNB for NR 5G may be referred to as a gNB by way of example. The LTE eNB is an evolved form of the eNB that supports connections to the EPC (Evolved Packet Core) and the NGC (Next Generation Core).

[0013] The user plane protocol stack for NR (see, for example, 3GPP TS38.300 v15.4.0, section 4.4.1) includes the PDCP (Packet Data Convergence Protocol, see section 6.4 of TS38.300), RLC (Radio Link Control, see section 6.3 of TS38.300) and MAC (Medium Access Control, see section 6.2 of TS38.300) sublayers, which are terminated at the gNB on the network side. Further, a new access stratum (AS) sublayer (SDAP (Service Data Adaptation Protocol)) is introduced above the PDCP (see, for example, section 6.5 of 3GPP TS38.300 version 15.4.0). A control plane protocol stack is also defined for NR (see, for example, TS38.300, section 4.4.2). An overview of the layer 2 functions is given in section 6 of TS38.300. The functions of the PDCP, RLC and MAC sublayers are listed in sections 6.4, 6.3 and 6.2 of TS38.300 respectively. The functions of the RRC layer are listed in section 7 of TS38.300.

[0014] For example, the Medium Access Control (MAC) layer processes logical channel multiplexing and scheduling and scheduling related functions including the handling of various numerologies.

[0015] For the physical layer, the MAC layer uses services in the form of transport channels. A transport channel can be defined by how information is transmitted over the radio interface and with what characteristics the information is transmitted. The Random Access Channel (RACH) is also defined as a transport channel that does not carry transport blocks but is processed by the MAC. One of the procedures supported by the MAC layer is the random access procedure.

[0016] The physical layer (PHY) is responsible for, for example, encoding, PHY HARQ processing, modulation, multi-antenna processing, and mapping of signals to appropriate physical time-frequency resources. The physical layer also processes the mapping of transport channels to physical channels. The physical layer provides services to the MAC layer in the form of transport channels. Physical channels correspond to a set of time-frequency resources used for the transmission of a specific transport channel, and each transport channel is mapped to a corresponding physical channel. One physical channel is the PRACH (Physical Random Access Channel) used for random access.

[0017] Use cases / deployment scenarios for NR can include enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine type communications (mMTC), which have diverse requirements regarding data rate, latency, and coverage. For example, eMBB is expected to support peak data rates on the order of three times those provided by IMT-Advanced (20 Gbps in the downlink and 10 Gbps in the uplink) and data rates experienced by the user. On the other hand, in the case of URLLC, more stringent requirements such as ultra-low latency (0.5 ms each for UL and DL for user plane latency) and high reliability (1 - 10 -5 ) within 1 ms are imposed. Finally, mMTC may preferably require a high connection density (1,000,000 devices per km 2 in an urban environment), wide coverage in harsh environments, and a very long lifespan (15 years) battery for low-cost devices.

[0018] Therefore, an OFDM numerology suitable for one use case (e.g., subcarrier spacing, OFDM symbol period, cyclic prefix (CP) period, number of symbols per scheduling interval) may not function well in another use case. For example, low-latency services may preferably require a shorter symbol period (and thus a larger subcarrier spacing) and / or fewer symbols per scheduling interval (also known as TTI) than mMTC services. Further, deployment scenarios with large channel delay spreads may preferably require a longer CP period than scenarios with short delay spreads. To maintain a similar CP overhead, the subcarrier spacing should be optimized accordingly. NR can support multiple values of subcarrier spacing. Correspondingly, subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, etc. are currently under consideration. The symbol period Tu and the subcarrier spacing Δf are directly related through the equation Δf = 1 / Tu. Similar to the LTE system, the term "resource element" can be used to represent the smallest resource unit composed of one subcarrier for the length of 1 OFDM / SC-FDMA symbol.

[0019] In the new radio system 5G-NR, for each numerology and carrier, a resource grid consisting of subcarriers and OFDM symbols is defined for the uplink and downlink, respectively. Each element in the resource grid is referred to as a resource element and is identified based on the frequency index in the frequency domain and the symbol position in the time domain (see 3GPP TS38.211 v15.4.0).

[0020] (Reference signal) Similar to LTE, several different types of reference signals (RS) are used in 5G NR (see Section 7.4.1 of 3GPP TS38.211 v15.4.0). In 5G NR, at least the following reference signals are available. · CSI-RS (Channel State Information Reference Signal) that can be used for channel state information acquisition and beam management · PDSCH DMRS (Demodulation Reference Signal) that can be used for PDSCH demodulation · PDCCH DMRS (Demodulation Reference Signal) that can be used for PDCCH demodulation · PBCH DMRS (Demodulation Reference Signal) that can be used for PBCH demodulation · PTRS (Phase Tracking Reference Signal) that can be used for phase tracking of PDSCH · Tracking reference signal that can be used for time tracking

[0021] Furthermore, PBCH DMRS can be exemplarily regarded as part of the SSB reference signal (see Section 5.1.1, "SS reference signal received power (SS-RSRP)" in 3GPP TS38.215 v15.3.0).

[0022] The main differences between the reference signals in the 5G NR communication system and those in LTE are that in 5G NR, there is no cell-specific reference signal, a new reference signal PTRS is introduced for time / phase tracking, DMRS is introduced for both the downlink channel and the uplink channel, and in NR, the reference signal is transmitted only when necessary.

[0023] As a DL-only signal, the CSI-RS received by the UE is used to estimate the channel and report the channel quality information to the gNB. During MIMO operation, NR can use different antenna techniques based on the carrier frequency. At low frequencies, the system uses a relatively small number of active antennas for MU-MIMO and adds FDD operation. In this case, the UE can use CSI-RS to calculate CSI and report CSI in the UL direction. CSI-RS can be further characterized as follows. · This is used for DL CSI acquisition. · It is used for RSRP measurement during mobility and beam management. · It is also used for frequency / time tracking, demodulation, and UL reciprocity-based precoding. · CSI-RS is uniquely configured for a UE, but multiple users can also share the same resources. · The 5G NR standard enables a high level of flexibility in CSI-RS configuration, and resources can be configured for up to 32 ports. · CSI-RS resources can start from any OFDM symbol in a slot and typically occupy 1 / 2 / 4 OFDM symbols depending on the number of configured ports. · CSI-RS can be periodic, semi-persistent, or aperiodic (due to DCI triggering).

[0024] For time / frequency tracking, CSI-RS can be either periodic or aperiodic. It is transmitted in a 2-symbol or 4-symbol burst that spans 1 or 2 slots.

[0025] (UE Measurements in 5G NR) NR devices may be configured to perform multiple different measurements and, in some cases, subsequently report the results accordingly to the network.

[0026] Briefly, to provide a basic overview of the measurements, a UE (NR device) can perform measurements based on reference signals (such as CSI-RS, SS blocks, etc.) and obtain measurement results therefrom. The measurement results may be used internally by the UE or, in some cases, by other entities such as a base station for mobility control after receiving some or all of the measurement results in the corresponding measurement report.

[0027] Exemplary detailed embodiments are presented below. The measurements may be performed by the UE for connection mode mobility and may be classified into at least three measurement types as follows. · Intra-frequency NR measurements · Inter-frequency NR measurements · Inter-RAT measurements for E-UTRA

[0028] Generally, the measurements may be configured, for example, by defining one or more measurement objects. A measurement object defines, for example, the carrier frequency to be monitored. And for each measurement object, one or more reporting configurations can be defined, including reporting criteria such as event-triggered reporting, periodic reporting, and event-triggered periodic reporting (see Section 9.1 of 3GPP TS38.300 v15.3.1).

[0029] The reporting configuration indicates a quantity or a set of quantities, such as various combinations of channel quality indicator (CQI), rank indicator (RI), precoder matrix indicator (PMI), collectively referred to as channel state information (CSI) for example. Further, the reporting configuration can indicate a report of received signal strength, more formally referred to as reference signal received power (RSRP). Historically, RSRP has been an important quantity for measurement and reporting as part of upper layer radio resource management (RRM), and it is also an important quantity in 5G NR. NR supports, for example, L1 reporting of RSRP as part of the support for beam management, thereby deriving beam quality. What is reported may more specifically be referred to as L1-RSRP, which reflects that the reporting does not include the longer-term ( "layer 3") filtering applied to upper layer RSRP reporting. L3 filtering at the RRC level can derive cell quality from multiple beams and thus can mitigate rapid changes by considering both the current input from the L1 filter and the previous output from the L3 filter.

[0030] A set of downlink resources for which measurements need to be performed is also configured. Thus, for example, L1-RSRP for beam management can be based on measurements related to either a set of SS (synchronization signal) blocks or a set of CSI-RS.

[0031] Also, there are situations where the device performs measurements without corresponding reporting to the network. One such exemplary situation is when the UE performs measurements for receiver-side downlink beamforming. The UE internally uses the measurement results to select an appropriate receiver beam. The network can then configure the UE, for example, by specifying the reference signal to measure but indicating that reporting is not required.

[0032] The UE can measure multiple beams (at least one) of a cell, and the measurement results (e.g., power values) are averaged to derive the cell quality. In doing so, the UE can be configured to consider a subset of the detected beams. Filtering is performed at two different levels, namely, at the physical layer (layer 1) to derive beam quality, and then at the RRC layer (layer 3) to derive cell quality from multiple beams. The cell quality from beam measurements is derived in the same way for both the serving cell and non-serving cells.

[0033] Measurement reports are exemplarily characterized by one or more of the following. - The measurement report includes measurement identification information of the related measurement configuration that triggered the report. - The number of cell and beam measurement quantities included in the measurement report is set by the network. - The number of non-serving cells reported can be restricted through network configuration. Cells belonging to the blacklist set by the network are not used in event evaluation and reporting. Conversely, if a whitelist is set by the network, only the cells belonging to the whitelist are used in event evaluation and reporting. - The beam measurement values included in the measurement report are set by the network (only beam identifiers, measurement results and beam identifiers, or no beam report).

[0034] Intra-frequency adjacent (cell) measurement and inter-frequency adjacent (cell) measurement are exemplarily defined as follows. - Intra-frequency measurement based on SSB: When the center frequency of the SSB of the serving cell is the same as the center frequency of the SSB of the adjacent cell, and the sub-carrier spacing of these two SSBs is also the same, the measurement is defined as an intra-frequency measurement based on SSB. - Inter-frequency measurement based on SSB: When the center frequency of the SSB of the serving cell is different from the center frequency of the SSB of the adjacent cell, or the sub-carrier spacing of these two SSBs is different, the measurement is defined as an inter-frequency measurement based on SSB. Note: For measurements based on SSB, one measurement target corresponds to one SSB, and the UE regards different SSBs as different cells. - Intra-frequency measurement based on CSI-RS: When the bandwidth of the CSI-RS resource in the adjacent cell set for the measurement is within the bandwidth of the CSI-RS resource in the serving cell set for the measurement, and the sub-carrier spacing of these two CSI-RS resources is the same, the measurement is defined as an intra-frequency measurement based on CSI-RS. - Inter-frequency measurement based on CSI-RS: When the bandwidth of the CSI-RS resource in the adjacent cell set for the measurement is not within the bandwidth of the CSI-RS resource in the serving cell set for the measurement, or the sub-carrier spacing of these two CSI-RS resources is different, the measurement is defined as an inter-frequency measurement based on CSI-RS.

[0035] Whether the measurement is non-gap-assisted or gap-assisted depends on the UE's capabilities, the UE's active BWP, and the current operating frequency. In a non-gap-assisted scenario, the UE can perform such measurements without a measurement gap. In a gap-assisted scenario, it cannot be assumed that the UE can perform such measurements without a measurement gap.

[0036] Measurement reports are defined in Section 5.5.3 of 3GPP TS38.331 v15.3.0. The network can configure the UE to derive measurement results of RSRP, RSRQ, and SINR for each cell. Measurement report triggers, including different trigger events (see the following overview), are defined in Section 5.5.4 of 3GPP TS38.331 v15.4.0. Details regarding measurement reports are provided in Section 5.5.5 of 3GPP TS38.331 v15.4.0.

[0037] Different events A1 - A6, B1, and B2 are defined, which each include a Leaving condition and an Entering condition and are associated with a time-to-trigger condition. This enables the UE to perform measurements on its own and report the results according to the criteria defined for the event. An overview is provided below. · Event A1 (the serving cell becomes better than the threshold) · Inequality A1-1 (Entering condition): Ms - Hys > Thresh · Inequality A1-2 (Leaving condition): Ms + Hys < Thresh · Event A2 (the serving cell becomes worse than the threshold) · Inequality A2-1 (Entering condition): Ms + Hys < Thresh · Inequality A2-2 (Leaving condition): Ms - Hys > Thresh · Event A3 (the neighboring cell becomes better than the offset of the SpCell) ·Inequality A3-1 (Entering condition): Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off ·Inequality A3-2 (Leaving condition): Mn + Ofn + Ocn + Hys < Mp + Ofp + Ocp + Off · Event A4 (The adjacent cell becomes better than the threshold) · Inequality A4-1 (Entering condition): Mn + Ofn + Ocn - Hys > Thresh ·Inequality A4-2 (Leaving condition): Mn + Ofn + Ocn + Hys < Thresh · Event A5 (The SpCell becomes worse than threshold 1, and the adjacent cell / SCell becomes better than threshold 2) ·Inequality A5-1 (Entering condition 1): Mp + Hys < Thresh1 ·Inequality A5-2 (Entering condition 2): Mn + Ofn + Ocn - Hys > Thresh2 ·Inequality A5-3 (Leaving condition 1): Mp - Hys > Thresh1 ·Inequality A5-4 (Leaving condition 2): Mn + Ofn + Ocn + Hys < Thresh2 · Event A6 (The adjacent cell becomes a better offset than the SCell) ·Inequality A6-1 (Entering condition): Mn + Ocn - Hys > Ms + Ocs + Off ·Inequality A6-2 (Leaving condition): Mn + Ocn + Hys < Ms + Ocs + Off · Event B1 (The adjacent cell between different RATs becomes better than the threshold) · Inequality B1-1 (Entering condition): Mn + Ofn + Ocn - Hys > Thresh ·Inequality B1-2 (Leaving condition): Mn + Ofn + Ocn + Hys < Thresh · Event B2 (The PCell deteriorates beyond threshold 1 and the inter-RAT neighbor cell improves beyond threshold 2) · Inequality B2-1 (Entering condition 1): Mp + Hys < Thresh1 · Inequality B2-2 (Entering condition 2): Mn + Ofn + Ocn - Hys > Thresh2 · Inequality B2-3 (Leaving condition 1): Mp - Hys > Thresh1 · Inequality B2-4 (Leaving condition 2): Mn + Ofn + Ocn + Hys < Thresh2

[0038] The parameters shown above are generally as follows. · Ms is the measurement result of the serving cell without considering any offset. · Mn is the measurement result of the neighbor cell without considering any offset. · Ofn is the measurement target specific offset of the reference signal of the neighbor cell (i.e., offsetMO defined within measObjectNR corresponding to the neighbor cell). · Ocn is the cell specific offset of the neighbor cell (i.e., cellIndividualOffset defined within measObjectNR corresponding to the frequency of the neighbor cell), and is set to zero if not set for the neighbor cell. · Mp is the measurement result of the SpCell without considering any offset. · Ofp is the measurement target specific offset of the SpCell (i.e., offsetMO defined within measObjectNR corresponding to the SpCell). · Ocp is the cell specific offset of the SpCell (i.e., cellIndividualOffset defined within measObjectNR corresponding to the SpCell), and is set to zero if not set for the SpCell. ·Off is the offset parameter for this event (i.e., a3-Offset defined within reportConfigNR for this event). ·Hys is the hysteresis parameter for this event (i.e., hysteresis defined within reportConfigNR for this event). ·Thresh is the threshold parameter for this event (i.e., a1-Threshold defined within reportConfigNR for this event). ·Thresh1 is the threshold parameter for this event (i.e., a5-Threshold1 defined within reportConfigNR for this event). ·Thresh2 is the threshold parameter for this event (i.e., a5-Threshold2 defined within reportConfigNR for this event). ·Mn, Mp, Ms are expressed in dBm for RSRP, and in dB for RSRQ and RS-SINR. ·Ofn, Ocn, Ofp, Ocp, Hys, Off are expressed in dB.

[0039] At least the following mechanisms are based on the measurement results obtained by the UE. · Handover decision by the gNB based on the measurement results (received via the measurement report) · Triggering of the measurement report · Radio link failure indication

[0040] (Non-Terrestrial Network (NTN)) Satellites will continue to be the most effective means of reaching areas beyond terrestrial coverage and also reaching passengers on trains, aircraft, and ships. Therefore, including satellites as an integral part of the 5G ecosystem adds resilience. The satellite industry has participated in various committees, including those in 3GPP, EC, and ITU-T, to ensure that satellite systems are securely integrated as an essential part of the 5G ecosystem. The goals are 1) to support highly available and reliable connections using satellites for use cases such as ubiquitous coverage, disaster relief, public safety requirements, emergency response, remote sensor connectivity, broadcast services, etc., 2) to support the air interface with a one-way latency of up to 275 milliseconds when satellite connections are involved, and 3) to support seamless mobility between terrestrial networks and satellite-based networks with widely varying latencies. The role and benefits of satellites in 5G have been under consideration in 3GPP Release 14, leading to specific requirements for supporting satellite access.

[0041] Figure 3 shows an exemplary NG RAN architecture based on a transparent satellite. According to an exemplary embodiment (see Section 5.1 of TR38.821 v0.3.0), the satellite payload implements frequency conversion and radio frequency amplifiers in both the uplink and downlink directions. This corresponds to an analog RF repeater. Thus, the satellite relays the NR-Uu radio interface from the feeder link (between the NTN gateway and the satellite) to the service link (between the satellite and the UE), and vice versa. The satellite radio interface (SRI) on the feeder link is NR-Uu. In other words, the satellite does not terminate NR-Uu. Figure 4 shows an exemplary NG RAN architecture based on a regenerative satellite. According to an exemplary embodiment (see Section 5.2 of TR38.321 v0.3.0), the NG-RAN logical architecture described in TS38.401 is used as a baseline for the NTN scenario. The satellite payload implements the regeneration of signals received from the Earth. The NR-Uu radio interface is on the service link between the UE and the satellite. The satellite radio interface (SRI) is on the feeder link between the NTN gateway and the satellite. The SRI (satellite radio interface) is the transport link between the NTN GW and the satellite.

[0042] The satellite payload also provides an inter-satellite link (ISL) between satellites. The ISL (inter-satellite link) is the transport link between satellites.

[0043] Discussions are underway regarding NTN's efforts in mobility. Satellite beams, satellites, or satellite cells do not necessarily need to be visible from the perspective of the UE in NTN, but it is assumed that this type of network (e.g., NTN vs. terrestrial) does not need to be distinguished at the PLMN (public land mobile network) level. Furthermore, it has been agreed that the Rel-15 design / definition will be used as a baseline for NTN, which means that the NR RRM measurement model used in Rel-15 is also the baseline for the NTN RRM measurement model.

[0044] The inventors recognized that in the case of non-terrestrial communication, the round-trip delay (RTD) can be much larger than in the case of terrestrial communication. For example, the maximum RTD in NTN is 541.1 ms for GEO (geostationary earth orbiting, e.g., at an altitude of 35786 km) and 25.76 / 41.76 ms for LEO (low earth orbiting, e.g., at altitudes of 600 / 1200 km). In terrestrial communication, the RTD can be up to 5 ms, for example.

[0045] A long RTD may lead to a high handover failure rate. This is because the network makes handover decisions based on measurement results that may already be old and thus potentially inaccurate. For example, handover failures can include cases where the handover is too late (in other cases, e.g., handover to the wrong cell). Furthermore, a long RTD in message exchange also results in the NTN handover taking longer, which may lead to a longer service interruption for the UE during the handover from one NTN network to another.

[0046] Accordingly, the inventors have identified the possibility of improving measurement reports and / or handover procedures so as to facilitate avoiding one or more of the above-mentioned drawbacks. The improved measurement reports and handover procedures may be applied to scenarios such as NTN scenarios where high latency exists. However, the NTN scenario is not the only scenario in which the improved procedures can be implemented, and other communication scenarios with high RTD and / or rapid channel variations, such as NR unlicensed scenarios where the channel quality changes rapidly, can also benefit from the improved procedures.

[0047] In the following, a UE, a base station, and procedures that meet such needs will be described for a new radio access technology assumed for a 5G mobile communication system, but these may also be used in an LTE mobile communication system. Various embodiments and variations will also be described. The following disclosure is facilitated by the above-described explanations and findings and may be based, for example, at least in part thereon.

[0048] It should be noted that many assumptions have been made in this specification so as to be able to explain clearly and understandably the principles underlying the present disclosure. However, these assumptions should be understood as merely examples made in this specification for illustrative purposes and should not be intended to limit the scope of the present disclosure. Those skilled in the art will recognize that the principles of the following disclosure as recited in the claims may be applied in ways not explicitly described in this specification to different scenarios not explicitly described herein.

[0049] Furthermore, in the context of new radio access technologies for the next 3GPP 5G communication system, even though specific terms used are not yet fully determined or may ultimately change, some of the terms such as procedures, entities, layers, etc. used hereinafter are closely related to the terms used in the LTE / LTE-A system or the current standardization of 3GPP 5G. Accordingly, the terms may be changed in the future without affecting the functions of the embodiments. As a result, those skilled in the art will recognize that the embodiments and their protection scope should not be limited to the specific terms exemplified herein due to the lack of newer terms or ultimately agreed terms, but should be more broadly understood with respect to the functions and concepts underlying the functions and principles of the present disclosure.

[0050] For example, a mobile station or a mobile node or a user terminal or a user equipment (UE) is a physical entity (physical node) within a communication network. One node can have multiple functional entities. A functional entity refers to a software module or a hardware module that implements a predefined set of functions and / or provides a predefined set of functions to other functional entities of the same node or another node or other functional entities of the network. A node can have one or more interfaces that connect the node to communication facilities or media through which the node can communicate. Similarly, a network entity can have a logical interface that connects a functional entity to communication facilities or media through which the functional entity can communicate with other functional entities or corresponding nodes.

[0051] Here, the term "base station" or "radio base station" refers to a physical entity within a communication network. Similar to a mobile station, a base station can have multiple functional entities. A functional entity refers to a software module or a hardware module that implements a predefined set of functions and / or provides a predefined set of functions to other functional entities of the same node or another node or network. The physical entity performs some control tasks for a communication device, including one or more of scheduling and configuration. Note that the functions of the base station and the functions of the communication device may be integrated within a single device. For example, a mobile terminal can also implement the functions of a base station for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used in 5G NR is gNB.

[0052] Figure 5 shows a schematic and simplified exemplary block diagram of a user equipment (also referred to as a communication device) and a scheduling device (exemplarily assumed to be located within a base station (e.g., an eLTE eNB (or referred to as ng-eNB) or a gNB in 5G NR)). The UE and the eNB / gNB communicate with each other via a (radio) physical channel using their respective transceivers.

[0053] The communication device can include a transceiver and a processing circuit. And the transceiver can include a receiver and a transmitter, and / or can function as a receiver and a transmitter. The processing circuit can be one or more processors or one or more hardware such as any LSI. There is an input / output point (or input / output node) between the transceiver and the processing circuit, and during operation, the processing circuit can control the transceiver via the input / output point (or input / output node), that is, control the receiver and / or the transmitter and exchange receive / transmit data. The transceiver can include an RF (radio frequency) front end including one or more antennas, amplifiers, RF modulators / demodulators, etc. as a transmitter and a receiver. The processing circuit can perform control tasks such as controlling the transceiver to transmit user data and control data provided by the processing circuit and / or receive user data and control data to be further processed by the processing circuit. The processing circuit can also be responsible for performing other processes such as determination, discrimination, decision, calculation, measurement, etc. The transmitter can be responsible for performing the process of transmitting and other processes related to the process of transmitting. The receiver can be responsible for performing the process of receiving and other processes related to the process of receiving, such as monitoring a channel.

[0054] Improved measurement and reporting procedures are described in relation to FIGS. 6 to 9. Further, improved conditional handover procedures are described in relation to FIGS. 10 to 12. Further, improved handover communication procedures are described in relation to FIGS. 16 to 21. Finally, improved HARQ procedures are described in relation to FIG. 22.

[0055] The solutions provided below are mainly described in relation to the 5G NR NTN scenario. As described above, the NTN (Non-Terrestrial Network) environment involves the UE communicating with the gNB via a satellite, where the gNB may be, for example, on a satellite (see Figure 4) or an NTN gateway (see Figure 3), but may also be located in other places such as outside the NTN gateway. However, the scope of the embodiments should not be limited to such NTN scenarios alone, but also includes other scenarios such as NR unlicensed.

[0056] UE mobility in such scenarios includes the UE moving between the coverages of various satellites (e.g., a flying UE). UE mobility is typically controlled by the serving gNB, but is assisted by the UE providing the serving gNB with the results of power-related measurements. The serving gNB then determines whether it is necessary or advantageous to hand over the UE to another radio cell and, if necessary or advantageous, can initiate an appropriate handover procedure.

[0057] More specifically, it is assumed that the UE, for example, periodically performs power-related measurements. For example, power-related measurements can include that RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength), SINR (Signal-to-Interference-plus-Noise Ratio) or other appropriate types of measurement values may be used by the UE in the above respects. Typically, power-related measurements may be performed, for example, on reference signals such as CSI-RS or SSB described above.

[0058] Whether and how the UE performs power-related measurements may be at least partially set by the serving gNB of the UE. This may further involve settings regarding whether the UE reports the results of the measurements to the serving base station of the UE, how to report them, and when to report them (e.g., to assist in handover decisions).

[0059] An exemplary embodiment of how to configure the measurement and reporting functions in a UE has been described above (see the description of UE measurements in 5G), and includes, for example, the definition of one or more of one or more measurement targets, reporting settings, and reporting criteria. For example, event-triggered reporting of measurement results may be defined, including reporting similar or the same trigger events as those described above (e.g., A1 - A6, B1, B2). The trigger events, especially the conditions for the trigger events, can be related to handover, for example, in terms that when the serving gNB can determine the handover of the UE from the current serving radio cell of the UE to another radio cell, the reporting trigger condition is met (e.g., event A2: "The serving cell becomes worse than the threshold", event A3: "The neighboring cell becomes a better offset than the SpCell", event A4: "The neighboring cell becomes better than the threshold").

[0060] Furthermore, it is assumed that the UE can perform measurements in various radio carriers (or what is referred to as access links or frequency bands) having the same or different radio frequencies. For example, UE measurements are performed in the serving radio carrier of the UE (of the serving radio cell of the UE controlled by the serving gNB) and in one or more neighboring radio carriers (of other radio cells controlled by neighboring gNBs).

[0061] The measurement and reporting settings are intended to be used by the UE for mobility between non-terrestrial networks and mobility between terrestrial networks. According to this solution, the measurement and reporting settings are distinguished according to whether the mobility is between terrestrial networks or between non-terrestrial networks (described in more detail below).

[0062] In the following, it is exemplarily assumed that the UE is connected to its serving gNB via a satellite and performs measurements on its radio carrier for the satellite and one or more radio carriers for other adjacent satellites. Subsequently, these UE measurement results may be used by the gNB serving the UE to control the mobility of the UE. Controlling the mobility of the UE includes whether to hand over the UE from the serving satellite to another satellite. The handover procedure initiated by the serving gNB may be, for example, a handover procedure already known from the prior art, or an improved conditional handover procedure in which the final decision on whether to hand over is delegated to the UE. The improved conditional handover procedure will be described in more detail later (see FIGS. 10 to 12).

[0063] FIG. 6 shows a simplified exemplary UE configuration according to the present solution for the improved measurement and reporting procedures, which may be implemented based on the general UE configuration described in relation to FIG. 5 above. The various components of the UE shown in this figure may be interconnected with each other, for example, using corresponding input / output nodes (not shown), to exchange control data, user data, and other signals. Although not shown for the purpose of illustration, the UE may include additional components.

[0064] As is apparent from this figure, the UE can include a measurement circuit, a measurement result generation circuit, a reporting adjustment circuit, and a measurement report transmission unit, which will be described below.

[0065] In this case, as will become apparent from the following disclosure, the processing circuit is thus exemplarily configured to at least partially perform one or more of performing measurements, generating measurement results from the performed measurements, determining whether to adjust at least one of the measurement results and the reporting trigger conditions, adjusting at least one of the measurement results and the reporting trigger conditions, and determining whether the reporting trigger conditions are satisfied.

[0066] The transmitter may be configured to at least partially perform the transmission of a measurement report including the measurement results.

[0067] Figure 7 is a sequence diagram of exemplary UE behavior according to this improved measurement and reporting procedure. As is clear from this figure, the UE performs power-related measurements on at least one radio carrier and generates measurement results from the performed power-related measurements. The power-related measurements are performed, for example, on one or more of the UE's serving radio carrier (in this particular exemplary scenario, the radio carrier connecting the UE to the satellite), the radio carrier connecting the UE to an adjacent satellite, and the radio carrier connecting the UE to a terrestrial network (such as a 5G or LTE antenna).

[0068] As described above, the UE reports the measurement results to the UE's serving base station, for example, depending on whether one or more of the reporting trigger conditions are satisfied. When one or more of the reporting trigger conditions are satisfied, the UE generates a measurement report including the obtained measurement results and transmits the measurement report to the UE's serving gNB.

[0069] According to this improved measurement and reporting procedure, before determining whether the reporting trigger condition is met, the UE first decides whether to adjust the measurement reporting procedure so as to trigger the transmission of the measurement report earlier than in the case of no adjustment. This additional step of adjusting the measurement reporting procedure is taken to account for the fact that the mobility between satellites, due to the long round-trip delay associated with the communication between the UE and the satellites, is different from, for example, the mobility between terrestrial networks. As described above, the inventors have identified drawbacks related to the long round-trip delay for the measurement procedure and thus for the handover procedure. By triggering the measurement report earlier, it may be possible to avoid or mitigate a failure event where the handover is too late. Correspondingly, a determination may be made by the UE to additionally adjust the measurement reporting procedure when the radio carrier to be measured and for which the measurement result is to be reported involves a long round-trip delay exceeding, for example, 10 ms as in the case of a non-terrestrial network. Alternatively, the UE decides whether to adjust the measurement reporting procedure according to an instruction given by the serving gNB. One option is that the instruction is given to the UE by the serving gNB through the measurement object (MO) setting for UE measurement.

[0070] Continuing with the sequence of UE behavior shown in FIG. 7, assume that an additional adjustment is performed by the UE. As described above, the adjustment is made such that the measurement report is triggered earlier than the corresponding measurement report that would be triggered in the case of no adjustment. In other words, the reporting trigger condition is met earlier, and as a result, the measurement report is transmitted to the serving base station earlier in time.

[0071] Advancing the measurement report in time in this way can be achieved in several ways, for example, by adjusting the measurement result and / or the reporting trigger condition, as will be explained and illustrated in more detail below.

[0072] After adjustment, the UE monitors whether the measurement result satisfies one of the reporting trigger conditions (the measurement result and / or the reporting trigger condition has been adjusted). Thereafter, if a measurement report is triggered, the UE proceeds to generate a measurement report including some or all of the generated measurement results and transmit it to the serving gNB. The measurement report includes, for example, the unadjusted measurement results, thereby providing the accurate measurement results to the gNB. On the other hand, instead of or in addition to the unadjusted measurement results, the UE may include the adjusted measurement results in the measurement report transmitted to the serving gNB. Thereby, the serving gNB can also derive the previous measurement results that were not transmitted to the serving gNB, and as a result, the serving gNB will have additional information for determining whether to initiate a handover procedure.

[0073] FIG. 8 shows exemplary gNB behavior related to the improved measurement and reporting procedures just described. In the exemplary gNB behavior, the gNB not only sets the measurement and reporting settings for the UE, but also, as already described above in connection with FIG. 7, is responsible for setting whether and how the UE needs to adjust the trigger of the measurement report in order to achieve earlier reporting of the measurement results.

[0074] The gNB can receive a measurement report including the measurement results from the UE and, based on it, determine whether to initiate a handover procedure for the UE to hand over the UE to another radio cell (e.g., another satellite). When initiating the handover procedure, the gNB transmits the corresponding handover command to the UE.

[0075] The above-described procedure has the advantage that it can avoid or mitigate a failure event where the handover is too late because the additional adjustment of the measurement report advances the trigger in time, resulting in the measurement report being transmitted earlier by the serving gNB and the serving gNB being able to determine the handover earlier. Furthermore, the adjustment solution is simple because it needs to rely on other information such as the UE position or the satellite position (satellite ephemeris).

[0076] An exemplary simplified sequence of the improved measurement and reporting procedures is shown in FIG. 9. As shown, the serving gNB of the UE provides a measurement configuration to the UE, and the UE performs measurements on its serving radio carrier and other neighboring radio carriers (in FIG. 9, only one neighboring gNB is shown for simplicity of illustration). Additional adjustments to the measurement reporting procedure are illustratively shown to be made after the power measurement, but may be made in parallel or before. The sequence in FIG. 9 ends with the transmission of the measurement report to the serving gNB.

[0077] In the following, some different exemplary embodiments of how to adjust measurement reports that are triggered earlier than without adjustment are described. After the adjustment is applied to the measurement result itself, the adjusted measurement result is used to determine whether the reporting trigger condition is met, or the adjustment may be applied to the reporting trigger condition. Depending on the measurement result and / or the reporting trigger condition, the adjustment may be different to achieve an earlier trigger.

[0078] According to an exemplary embodiment, one or more appropriate power offsets may be introduced to achieve that the reporting trigger condition is met earlier. The power offset may be applied, for example, to the measurement result itself, or the power offset may be applied to the reporting trigger condition. Also in this case, the amount of the offset and whether the offset is negative or positive may depend on the measurement result and / or the reporting trigger condition.

[0079] For illustrative reasons, it is illustratively assumed that some or all of the reporting trigger conditions already defined for 5G (see the description regarding the above points) are used by the UE to determine whether to send the measurement result to the serving gNB of the UE.

[0080] The Entering condition for event A1 (the serving cell becomes better than a threshold) to start sending the measurement result to the serving gNB is Ms - Hys > Thresh It is.

[0081] When applying an adjustment to this reporting trigger condition, this may be achieved by incorporating an offset (exemplarily referred to as NTN - offset) as follows: Ms + NTN - offset - Hys > Thresh

[0082] As is apparent from the above, by introducing a positive offset, it is reached faster by the threshold value ("Thresh").

[0083] The Entering condition for Event A2 (the serving cell becomes worse than the threshold value) is Ms + Hys < Thresh It is.

[0084] When applying an adjustment to this reporting trigger condition, this may be achieved by incorporating an offset as follows: Ms - NTN - offset + Hys > Thresh

[0085] As is apparent from the above - adjusted trigger condition, by introducing a negative offset, it reaches the threshold value earlier (<) than without it.

[0086] The Entering condition for Event A3 (the neighboring cell becomes a better offset than the SpCell) is Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off It is.

[0087] When applying an adjustment to this reporting trigger condition, this may be achieved by incorporating one or two offsets as follows: Mn + NTN-neighbour-offset + Ofn + Ocn - Hys > Mp - NTN-serving-offset + Ofp + Ocp + Off

[0088] According to a specific embodiment, an offset (here, the exemplary NTN-serving-offset) is defined for the trigger condition part related to the serving cell, and another offset (here, the exemplary NTN-neighbour-offset) is defined for the trigger condition part related to the adjacent cell. As a result, when determining the same trigger condition for the serving cell and other adjacent cells, the same NTN-serving-offset and the same NTN-neighbour-offset can be reused. This simplifies the adjustment. Because for each reporting trigger condition, at most two different offsets, namely one offset related to the serving cell and one offset related to the adjacent cell, are defined.

[0089] The Entering condition for Event A4 (the adjacent cell becomes better than the threshold) is Mn + Ofn + Ocn - Hys > Thresh is.

[0090] When applying an adjustment to this reporting trigger condition, this may be achieved by incorporating the offset as follows: Mn + NTN-offset + Ofn + Ocn - Hys > Thresh

[0091] As is clear from the above, by forcibly increasing the measurement result on the left side for the adjacent cell, it reaches the threshold faster.

[0092] In summary, adjusting the measurement report trigger depends on a specific trigger condition and follows the premise of reaching the condition faster.

[0093] Specific values may be set by a network (e.g., gNB) together with, for example, the remaining settings of UE measurements (e.g., measurement targets, reporting criteria, etc.).

[0094] When the NTN-specific offset is set to 0, the reporting trigger conditions are equally applicable to other scenarios.

[0095] Values of different offsets may be determined by the gNB in different ways to balance the impact of the offset on respective trigger conditions so that, for example, other handover failures (e.g., too early handover) are avoided or minimized. According to an exemplary embodiment, the gNB determines the offset value according to the round-trip delay experienced by the UE with the serving gNB.

[0096] Furthermore, for example, if it is determined that too many handover failures are caused or too many measurement reports are triggered, the gNB can also change the adjustment (e.g., offset) during operation so as to adapt an improved measurement reporting procedure. For example, the reset or cancellation of the measurement report adjustment may be performed by using a message from the RRC protocol (e.g., RRC reset message).

[0097] According to another exemplary embodiment of how to implement the adjustment of the measurement report, instead of using the adjustment set by the network, the adjustment is determined by the UE itself. The above offsets (e.g., NTN-offset, NTN-serving-offset, NTN-neighbour-offset) are determined by the UE. For example, the offset is determined for each measurement result by determining, for example, the difference between the current measurement result and the previously determined measurement result (the difference is referred to as exemplary Δmeas). In other words, the change in the measurement result is doubled, thus leading to an earlier trigger of the measurement report than when there is no offset.

[0098] For example, for the sake of illustration, take again the 5G measurement events A1, A2, A3 described above as examples.

[0099] The Entering condition for event A1 (the serving cell becomes better than the threshold) to start transmitting the measurement result to the serving gNB is Ms - Hys > Thresh That is.

[0100] When applying an adjustment to this reporting trigger condition, this may be achieved by incorporating the measurement difference Δmeas as follows: Ms + Δmeas - Hys > Thresh

[0101] As is clear from the above, by amplifying the increase in the measurement result, it reaches the threshold (「Thresh」) earlier.

[0102] The Entering condition for event A2 (the serving cell becomes worse than the threshold) is Ms +Hys < Thresh That is.

[0103] When applying an adjustment to this reporting trigger condition, this may be achieved by incorporating the measurement difference Δmeas as follows: Ms + Δmeas + Hys < Thresh

[0104] As is clear from the above adjusted trigger condition, by increasing the decrease in the measurement result, it reaches the threshold (<) earlier than otherwise.

[0105] The Entering condition for event A3 (the neighboring cell becomes better than the SpCell by an offset) is Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off That is.

[0106] When applying an adjustment to this reporting trigger condition, this may be achieved by incorporating a measurement difference Δmeas as follows: Mn + Δmeas_n + Ofn + Ocn - Hys > Mp - Δmeas_p + Ofp + Ocp + Off

[0107] As is clear from the above, the change (a measured power decrease or increase) is artificially increased by introducing an offset Δmeas to the measurement results of the serving cell and the measurement results of the neighboring cells, respectively. As a result, the trigger condition is met earlier than without an offset.

[0108] Calculating the measurement difference as an offset, rather than following the offset value set by the network, avoids the need for the gNB to set an offset for the UE and continuously adjust the offset as needed to maintain good handover performance. Furthermore, the adjustment can be more accurate as it is based on the UE's previous measurements rather than an artificial value set by the serving gNB. On the other hand, the network has less control over how the measurement reports are adjusted.

[0109] As described above, after receiving a measurement report including measurement results, the gNB finally decides to start a handover procedure with the UE. As one option, the handover procedure may be a standard handover procedure as already defined, for example, in the 3GPP standard specifications (see TS38.331 v15.4.0).

[0110] On the one hand, hereinafter, an improved conditional handover procedure that may be alternatively used by the gNB and the UE will be described with reference to FIGS. 10 to 12. Conditional handover generally shifts the final decision on whether to perform a handover from the serving gNB to the UE. This is achieved, for example, by additionally providing the UE with conditions (e.g., together with a handover command message) that the UE can use to determine whether to perform the instructed handover and when to perform it. Conditional handover contributes to the effect of reducing handover latency. This is because the serving gNB can prepare for the handover, and then the UE can perform the handover in a timely manner when necessary. At the time of performing the handover, the need to resend further measurement reports to the serving gNB to trigger the handover procedure is avoided. However, the handover may ultimately not even be used (e.g., when the UE does not perform the handover), and the target gNB needs to reserve resources for the UE (e.g., dedicated PRACH resources for random access, C-RNT) for a long time in a potential target cell.

[0111] The improved conditional handover procedure described in relation to FIGS. 10 to 12 attempts to mitigate these problems and is centered around the idea of additionally providing the UE with one or more handover rejection conditions that the UE monitors to, for example, abort a possible handover earlier instead of waiting for a timeout. This will be described in more detail below. FIG. 10 shows an exemplary message exchange between the UE, the serving gNB, and an adjacent gNB that is a possible target for handover. FIG. 11 is an exemplary sequence diagram of UE behavior, while FIG. 12 shows an exemplary sequence diagram of the behavior of the gNB acting as the serving gNB of the UE.

[0112] As described above, the handover decision is typically made by the serving gNB and is assisted by the UE by providing measurement reports on the serving radio carrier and, optionally, other adjacent radio carriers. Correspondingly, the first message shown in the message exchange diagram of FIG. 10 is a measurement report transmitted by the UE to its serving gNB. The measurement report may be generated according to an improved measurement reporting procedure as described above with reference to FIGS. 6 to 9 (e.g., the measurement report may be triggered earlier due to additional adjustment of the measurement report trigger). On the other hand, the measurement report may also be a "normal" measurement report that is triggered without the UE adjusting the trigger of the measurement reporting function.

[0113] Based on the received measurement report (and the measurement results included in the measurement report), the serving gNB may determine that a handover to another radio cell (e.g., another satellite) may be beneficial for the UE and thus initiate an appropriate handover procedure with the target gNB (adjacent gNB) and the UE.

[0114] Here, assume that the serving gNB decides to perform a conditional handover for the UE. The gNB decision to select a conditional handover can be based on various different criteria. For example, the serving gNB can decide on a conditional handover when the UE is configured as described above in relation to FIGS. 6 to 10 before performing the improved measurement and reporting procedures. More specifically, the serving gNB typically configures the UE regarding how to perform power-related measurements in addition to reporting measurement results, which can also include whether and how the UE adjusts measurement report triggers (e.g., NTN-related offset values, etc.). However, the early reporting of measurement results achieved by the improved measurement and reporting procedures described above may theoretically lead to an increase in the case where the handover is too early. This drawback can be mitigated by performing a conditional handover decision. Because the UE can perform the instructed handover to the target cell when the handover acceptance conditions are met and not too early.

[0115] Additionally or alternatively, the serving gNB may decide to perform a conditional handover instead of a normal handover based on the round-trip delay it experiences when communicating with the UE. For example, when the round-trip delay exceeds a specific threshold (e.g., 10 ms), it may be beneficial to delegate the final handover decision to the UE to avoid incorrect handover decisions resulting from a long round-trip delay.

[0116] A further additional or alternative criterion for determining to condition a handover is the handover failure rate. For example, assume that an unconditional handover procedure has been performed by a serving gNB with a UE within the radio cell of the serving gNB. However, if the handover failure rate (e.g., the failure rate of a handover that is too early) is too high, the serving gNB may determine that it is beneficial to condition the handover on conditions suitable for the UE to finally decide, and can reduce the handover failure rate.

[0117] A further additional or alternative criterion for determining to condition a handover is based on the satellite and / or UE position. For example, even if the serving gNB determines from a measurement report that a conditional handover is not necessary, if the satellite position and / or UE position indicates that the UE is located near the cell edge, the gNB can trigger a conditional handover.

[0118] Referring to FIG. 10 again, assume that the serving gNB determines a conditional handover, for example, in accordance with one or more of the criteria described above. The serving gNB prepares for the handover in the target cell (see the handover request and handover confirmation response in FIG. 10), and transmits a handover command message to the UE. As exemplarily shown in FIG. 10, the handover procedure may be started, for example, by requesting a handover and waiting for a handover confirmation response from an adjacent cell so that the adjacent gNB can confirm that it has the capacity to accommodate the further UE and can reserve resources for the UE to be handed over. After receiving the handover confirmation response from the adjacent gNB, the serving gNB proceeds with the handover procedure and transmits the corresponding handover command message to the UE.

[0119] As usual, a handover command message can include an id and additional information for identifying and connecting to a target cell. Further, the handover command message includes one or more handover acceptance conditions and handover rejection conditions. The handover acceptance conditions are checked by the UE to determine whether and when to perform the handover. If the handover acceptance conditions are met, the UE performs the handover. On the other hand, the handover rejection conditions are checked by the UE to determine whether to reject the handover instruction. If the handover rejection conditions are met, the UE can immediately reject the handover and provide corresponding information regarding the rejection to the serving gNB of the UE (this information may be used by the serving gNB to instruct the target gNB to release the resources previously reserved for the UE handover). FIG. 10 shows both the case of handover acceptance and the case of handover rejection.

[0120] The handover acceptance conditions and handover rejection conditions may be determined by the serving gNB according to specific handover scenarios. According to one embodiment of the option, the handover acceptance conditions and handover rejection conditions may be related to each other, for example, such that they are exclusive and enable to clearly determine whether the UE decides to accept or reject the handover. This is beneficial for forcing an immediate decision regarding the handover, and thus enables to minimize the resource reservation time in the target cell. Further, assuming that the UE and the serving gNB interrupt communication during handover, forcing an immediate decision by the UE regarding the instructed handover can also contribute to minimizing the communication interruption time. Because the UE and the serving gNB can immediately resume UL / DL communication. On the other hand, the handover acceptance conditions and handover rejection conditions do not have to completely complement each other. Thus, for example, there may be a measurement case where neither the handover acceptance conditions nor the handover rejection conditions are satisfied simultaneously. There is a gap between the acceptance conditions and the rejection conditions.

[0121] For example, a possible handover rejection condition is "when the serving cell is better than the target cell by more than x dB for at least y ms". Here, the parameter values x and y may be appropriately set by the gNB (for example, x may be 5 dB and y may be 50 ms). The handover acceptance condition may be, for example, "when the target cell is better than the serving cell by more than x dB for at least y ms". Here, the parameter values x and y may be appropriately set by the gNB (for example, x may be 8 dB and y may be 30 ms).

[0122] Information regarding the rejection of the handover may be transmitted to the serving gNB of the UE in several different ways and may depend, for example, on whether uplink data has been transmitted yet.

[0123] According to one exemplary solution, when there is no UL traffic, the handover rejection information may be sent as part of an RRCReconfigurationComplete message, or another RRC message such as a new RRC (Radio Resource Control protocol) message in some cases. Additionally or alternatively, the handover rejection information may be implicitly provided to the serving gNB, for example, by sending a measurement report to the serving gNB in response to a conditional handover command message. The serving gNB can then implicitly derive that the UE has rejected the handover.

[0124] According to another exemplary solution, when there is UL traffic, the handover rejection information may be included in a MAC (Media Access Control) control element (CE) together with the UL traffic data.

[0125] In any case, information that the handover has been rejected by the UE is provided to the serving gNB.

[0126] In an optional embodiment, when rejecting a handover, the UE may be configured not to send further measurement reports to the serving gNB for a specific period. This has the advantage that no further (conditional) handovers are triggered immediately after the handover has been rejected. For example, the UE can use a prohibit timer that starts when the handover is rejected. The timer may be set by the network (e.g., by the serving gNB) when configuring the measurement and reporting functions in the UE.

[0127] According to a further embodiment of the option, for example, a mechanism for extending the resource reservation in the target radio cell is incorporated to avoid the situation where the resource reservation in the target radio cell is cancelled too early. More specifically, the resource reservation in the target cell can be maintained only by the target gNB for a specific period (e.g., in some 5G implementations, controlled by an appropriate timer such as T304), but may expire before the UE makes a decision to accept or reject the handover. This problem is exacerbated when there is a long round-trip delay and the handover acceptance conditions and handover rejection conditions are defined such that the UE does not immediately decide whether to reject or accept the handover.

[0128] In such a scenario, it is beneficial for the UE to instruct the serving gNB to extend the resource reservation in the target cell when neither the handover acceptance conditions nor the handover rejection conditions are met. As shown in FIG. 11, the UE may optionally check whether the corresponding resource reservation timer has already expired. If it has already expired, a handover to the target gNB is no longer possible as intended, and the UE connects to either the UE's old serving gNB or another gNB (this involves, for example, performing an RRC connection re-establishment). The instruction may be transmitted in a similar or the same way as already described regarding how the rejection information is transmitted to the serving gNB (see the corresponding description for further details). Next, upon receiving such a resource reservation extension request, the serving gNB may contact the target gNB to extend the resource reservation. If the serving gNB does not receive such a resource reservation extension request, it may optionally assume that the handover is being performed as intended (see FIG. 12).

[0129] According to a further solution, the handover procedure is further improved by enabling the UE to continue communicating with the UE's serving gNB while performing the handover procedure to the target cell. In the prior art solution, UL / DL communication is interrupted when the UE starts the random access procedure with the target cell as part of the handover execution. However, since UL / DL communication is interrupted until the UE is connected to the new target cell (UL / DL communication continues with the target gNB) or until the UE reconnects to the serving gNB (if the handover fails), this leads to service interruption. Service interruption may not be a big problem for mobility between networks with small round-trip delays (such as terrestrial networks), but service interruption is a problem for mobility with large round-trip delays (for example, for a UE moving between different NTN networks such as satellites). In response, it is important to reduce the service interruption caused by the UE stopping UL / DL communication until the UE is connected to the target gNB or until the UE reconnects to the UE's serving gNB if the handover fails.

[0130] This can be achieved by the UE continuing to communicate with the serving gNB even after participating in a (conditional) handover and even after starting a random access procedure with the target cell. More specifically, the UE receives a handover command and starts a random access procedure to connect to the target gNB, but still continues DL / UL communication with the serving gNB. Correspondingly, this also applies to the serving gNB that continues to transmit DL data and receive UL data in the same way as before deciding to hand over the UE. However, in this case, the UE needs to perform UL / DL communication in parallel with the random access procedure, and it is beneficial to coordinate the uplink and downlink transmissions to / from the serving gNB with the uplink and downlink transmissions for random access to / from the target gNB. This can be achieved by the following solutions described with reference to FIGS. 16 to 21.

[0131] Briefly, the UE defines a DRX active period during which the UE can communicate actively, and further operates a DRX (discontinuous reception) function (described in more detail later) that provides the UE with a power saving (power saving) opportunity during the so-called DRX off period. According to one exemplary solution, the UE continues to communicate with the serving base station during the DRX active time while performing a random access procedure with the target cell using the DRX off period. In this way, the UE can communicate with the serving base station and the target base station in parallel. Therefore, once the UE establishes a connection with the target gNB, it can interrupt the communication with the serving base station. As a result, a make-before-break handover is realized so that the service interruption caused by the handover is minimized.

[0132] In the following, with reference to FIGS. 13 to 15, further details regarding the random access procedure and the DRX function are provided, and different embodiments of the improved handover communication procedure are described in more detail in relation to FIGS. 16 to 21. In the following, one specific exemplary random access procedure that can be used in this solution is described. Similar to LTE, 5G NR provides a RACH (Random Access Channel) procedure (or simply a random access procedure) (see 3GPP TS38.321, v15.3.0, section 5.1). For example, the RACH procedure may be used by a UE to access a cell discovered by the UE. The RACH procedure may be used in other contexts within NR, for example, as follows: · In the case of handover, when synchronization to the new cell should be established · To re-establish uplink synchronization to the current cell when synchronization is lost due to a long period without uplink transmission from the device · To request uplink scheduling when dedicated scheduling request resources are not configured for the device.

[0133] In the following, with reference to FIGS. 13 and 14, the RACH procedure is described in more detail. The mobile terminal may be scheduled for uplink transmission if the uplink transmission of the mobile terminal is time-synchronized. The Random Access Channel (RACH) procedure serves as an interface between an asynchronous mobile terminal (UE) and orthogonal transmission of uplink radio access. For example, random access is used to achieve uplink time synchronization for user equipment that has not yet obtained or has lost uplink synchronization. Once the user equipment achieves uplink synchronization, the base station can schedule uplink transmission resources for the user equipment. One scenario related to random access is that a user equipment in the RRC_CONNECTED state that is handing over from its current serving cell to a new target cell executes a random access procedure to achieve uplink time synchronization in the target cell.

[0134] There can be two types of random access procedures that enable access to be either contention-based (i.e., implying an inherent risk of collision) or contention-free (non-contention-based).

[0135] In the following, the contention-based random access procedure will be described in more detail in relation to FIG. 13. This procedure consists of four "steps". First, the user equipment transmits a random access preamble (i.e., message 1 of the RACH procedure) on the physical random access channel (PRACH) to the base station. After detecting the RACH preamble, the base station uses a RA (random access)-RNTI that identifies the time-frequency and slot in which the preamble was detected to transmit a random access response (RAR) message (message 2 of the RACH procedure) on the PDSCH (physical downlink shared channel) addressed in the PDCCH. If multiple user equipments transmit the same RACH preamble in the same PRACH resource (which is also referred to as a collision), those multiple user equipments will receive the same random access response message. The RAR message can carry the detected RACH preamble, a timing alignment command (TA command) for synchronization of subsequent uplink transmissions based on the timing of the received preamble, an initial uplink resource allocation (grant) for the first scheduled transmission, and an allocation of a T-CRNTI (Temporary Cell Radio Network Temporary Identifier). This T-CRNTI is used by the base station to address the mobile terminal in which the RACH preamble was detected until the RACH procedure is completed. This is because the "actual" identification information of the mobile terminal at this point is not yet recognized by the base station.

[0136] The user equipment monitors the PDCCH to receive a random access response message within a given time window (e.g., referred to as the RAR reception window) that may be set by the base station. The user equipment responds to the RAR message received from the base station and transmits the first scheduled uplink transmission on the radio resources allocated by the grant within the random access response. This scheduled uplink transmission carries an actual random access procedure message such as, for example, an RRC connection request, an RRC resume request, or a buffer status report.

[0137] If a preamble collision occurs in the first message of the RACH procedure, i.e., if multiple user equipments transmit the same preamble on the same PRACH resource, the colliding user equipments receive the same T-CRNTI within the random access response and collide on the same uplink resource when transmitting their scheduled transmissions in the third step of the RACH procedure. When the scheduled transmission from one user equipment is successfully decoded by the base station, the contention remains unresolved for one or more other user equipments. For this type of contention resolution, the base station transmits a contention resolution message (fourth message) addressed to the C-RNTI or Temporary C-RNTI. This concludes the procedure.

[0138] Figure 14 shows a simplified random access procedure without contention as compared to the contention-based random access procedure. In the first step, the base station provides a preamble for use in random access to the user equipment so that there is no risk of collision, that is, so that multiple user equipments do not transmit the same preamble. Therefore, the user equipment then transmits the preamble signaled by the base station in the uplink on the PRACH resource. Since the case where multiple UEs transmit the same preamble is avoided in the random access without contention, substantially, the random access procedure without contention ends after successfully receiving the random access response by the UE.

[0139] 3GPP is also considering a two-step RACH procedure for 5G NR, in which a message 1 corresponding to messages 1 and 3 in the four-step RACH procedure is transmitted first. Next, the gNB responds using a message 2 corresponding to messages 2 and 4 in the LTE RACH procedure. Due to the reduction in message exchange, the delay of the two-step RACH procedure can be reduced as compared to the four-step RACH procedure. The radio resources for the messages are optionally set by the network.

[0140] After introducing an exemplary random access procedure, one specific exemplary DRX function that can be assumed for this solution is described below. Battery saving is an important issue in mobile communications. To reduce the battery consumption in the UE, a mechanism that minimizes the time the UE spends monitoring the PDCCH is used, which is referred to as the discontinuous reception (DRX) function.

[0141] The DRX function may be configured for RRC_IDLE. Since the DRX function may also be configured for a UE in the "RRC_CONNECTED" state, the UE does not necessarily have to monitor the downlink channel for downlink control information (the expression that the UE monitors the downlink channel for downlink control information is simply also expressed as the UE monitors the PDCCH). (See Technical Standard TS36.321, version 15.2.0, section 5.7.)

[0142] To define the DRX UE behavior, the following parameters are available. That is, the on - duration period during which the mobile node is active (e.g., in the DRX active time) and the period during which the mobile node is in DRX (e.g., not in the DRX active time but in the DRX off - time). - On - duration: The duration of the downlink sub - frame in which the user equipment receives and monitors the PDCCH after waking up from DRX, that is, more specifically, the duration of the sub - frame containing the PDCCH (also referred to as the PDCCH sub - frame). Here, throughout the present invention, it should be noted that the term "PDCCH" refers to the PDCCH, EPDCCH (if configured, in the sub - frame), or for a relay node where R - PDCCH is configured and not suspended, R - PDCCH. If the user equipment successfully decodes the PDCCH, the user equipment remains awake / active and starts the inactivity timer. [1 - 200 sub - frames; 16 steps: 1 - 6, 10 - 60, 80, 100, 200] -DRX inactivity timer: The period in downlink subframes during which the user equipment waits to successfully decode the PDCCH since the last successful decode of the PDCCH. The UE re-enters DRX if it fails to decode the PDCCH during this period. The user equipment starts the inactivity timer again following a single successful decode of the PDCCH for the first transmission only (i.e. not for a retransmission). [1 to 2560 subframes; 22 steps, 10 spare: 1 to 6, 8, 10 to 60, 80, 100 to 300, 500, 750, 1280, 1920, 2560] -DRX Retransmission timer: Specifies the number of consecutive PDCCH subframes in which downlink retransmission is expected by the UE after the first available retransmission time. [1 to 33 subframes, 8 steps: 1, 2, 4, 6, 8, 16, 24, 33] -DRX short cycle: Specifies the periodic repetition of the on duration followed by a possible inactive period for the short DRX cycle. This parameter is optional. [2 to 640 subframes; 16 steps: 2, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640] -DRX short cycle timer: Specifies the number of consecutive subframes for which the UE will follow a short DRX cycle after the DRX inactivity timer expires. This parameter is optional. [1 to 16 subframes] -Long DRX Cycle Start offset: Specifies the periodic repetition of the on-duration followed by a possible inactive period for the long DRX cycle and the offset of the subframe at which the on-duration starts (determined by the formula defined in section 5.7 of TS36.321). [Cycle length: 10 to 2560 subframes; 16 steps: 10, 20, 30, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280, 2048, 2560; Offset is an integer between [0 - subframe length of the selected cycle]]

[0143] The total duration that the UE is awake is referred to as the "active time" or DRX active time. The active time includes, for example, the on-duration of the DRX cycle, the time during which the UE performs continuous reception while the inactivity timer has not expired, and the time during which the UE performs continuous reception while waiting for a downlink retransmission after 1 HARQ RTT. Similarly, in the uplink, the UE can receive an uplink retransmission grant, i.e., be awake (i.e., DRX active time) in a subframe every 8 ms after the initial uplink transmission until the maximum number of retransmissions is reached. Based on the above, the minimum active time is a fixed length equal to the on-duration, and the maximum value is variable, for example, depending on PDCCH activity.

[0144] The "DRX period" or "DRX off period" is the duration of a downlink subframe during which the UE can skip receiving the downlink channel for battery saving purposes, i.e., it is not necessary to monitor the downlink channel. The operation of DRX gives the mobile terminal the opportunity to repeatedly deactivate the radio circuit (according to the currently active DRX cycle) in order to save power. Whether the UE actually stays in DRX (i.e., is inactive) during the DRX period may be determined by the UE. For example, the UE may perform inter-frequency measurements that cannot be performed during normal on durations and thus need to be performed at some other time (e.g., during the DRX off time).

[0145] The parameterization of the DRX cycle involves a trade-off between battery saving and latency. To meet these conflicting requirements, two DRX cycles (a short cycle and a long cycle) may be configured for each UE. The short DRX cycle is optional, i.e., only the long DRX cycle may be used. The transitions between the short DRX cycle, the long DRX cycle, and continuous reception are controlled either by a timer or by an explicit command from the eNodeB.

[0146] Figure 15 discloses an example of DRX operation. The UE checks for a scheduling message (also referred to as a downlink / uplink grant; e.g., indicated by a C-RNTI in the PDCCH) during an "on-duration" period that is the same for both the long DRX cycle and the short DRX cycle. When a scheduling message is received during the "on-duration" period, the UE starts an "inactivity timer" and continues to monitor the PDCCH in all subframes while the inactivity timer is running. During this period, the UE may be considered to be in a "continuous reception mode". Whenever a scheduling message is received while the inactivity timer is running, the UE restarts the inactivity timer, and when inactivity expires, the UE transitions to the short DRX cycle and starts a "short DRX cycle timer" (assuming a short DRX cycle is configured). When the short DRX cycle timer expires, the UE transitions to the long DRX cycle. The short DRX cycle may also be started by a DRX MAC control element that the eNB can transmit at any time to immediately cause the UE to enter the DRX cycle, i.e., the short DRX cycle (if so configured) or the long DRX cycle (if no short DRX cycle is configured).

[0147] The basic concepts of DRX described above for LTE also apply to the new 5G NR, but there are some differences (see Section 5.7 of 3GPP TS38.321 v15.2.1).

[0148] As is then apparent, DRX for 5G NR is also based on long DRX cycles and short DRX cycles, and is based on a short DRX cycle timer. The transition between the long DRX cycle and the short DRX cycle defines an on-duration at the beginning of the DRX cycle. The DRX inactivity timer defines the duration of continuous reception after receiving a PDCCH, after which the UE goes into a sleep state. Thus, conceptually, the 5G-NR DRX mechanism functions as shown in FIG. 15.

[0149] Referring to FIG. 16, an improved handover communication solution is presented that enables a UE to access a target cell and continue to communicate with a serving cell in parallel. Corresponding UE behavior according to a simplified exemplary embodiment is shown in FIG. 17.

[0150] It is assumed that the UE is finally handed over from its serving gNB to another neighboring gNB. Correspondingly, as is apparent from FIG. 16, it is exemplarily assumed that the UE is communicating with the serving gNB in UL / DL. It is further assumed that the UE transmits a measurement report to the serving base station. The measurement report may be transmitted according to, for example, the improved measurement and reporting solutions described above in connection with FIGS. 6-9, but may also be transmitted by the UE as is generally known in the prior art. In other words, the following improved handover solution may optionally be combined with the improved measurement and reporting procedures described above, but may also be used independently.

[0151] Although not shown, it is assumed that the UE continues to communicate with the serving gNB during the start of the handover (e.g., transmits a handover request and receives a handover confirmation response while the serving gNB makes a handover decision).

[0152] The serving gNB is considered to have decided to select a handover and thus initiates a handover procedure with the neighboring gNB that is the target of the UE handover by sending a handover request message and receiving a handover confirmation response message in return. Next, the serving gNB sends a handover command message to the UE. The handover command may be an unconditional handover command that forces the UE to perform the handover. According to different solutions, the handover command message may alternatively be conditional and include at least handover acceptance conditions for the UE to finally determine whether and when to perform the handover based on the handover acceptance conditions. Further, the handover command message may optionally further include handover rejection conditions in line with the improved conditional handover solution described above in relation to FIGS. 10 to 12. In other words, the improved handover communication solution presented here may be combined with the improved conditional handover solution, but does not necessarily have to be so.

[0153] Furthermore, it is assumed that after receiving the (conditional) handover command, the UE starts the connection to the target gNB by performing a random access procedure between the UE and the target neighboring gNB. In parallel, the UE will continue to communicate with the serving gNB. This parallel operation is shown in FIG. 16 as respective boxes including arrows indicating the specific messages exchanged between the entities.

[0154] The UE and the serving gNB are operating a DRX function similar to or the same as that illustratively presented above in relation to FIG. 15. For the sake of keeping FIG. 16 clear, the DRX off period and the DRX active period are shown only for the UE's parallel communication with the serving gNB and the target gNB, but it should be understood that the DRX function is also followed earlier by the UE and the serving gNB when communicating with each other.

[0155] The DRX function alternates between a DRX active period during which the UE may communicate with the gNB (in UL and / or DL), and a DRX off period during which the UE has an opportunity to save power, for example, by not performing channel monitoring for either transmission or data reception. According to this improved handover communication solution, as also shown in FIG. 16, the UE communicates with the serving base station during the DRX active period, while communicating with the target gNB during the DRX off period. This includes transmitting random access procedure messages 1 and 3 to the neighboring gNB during the DRX off period, while receiving random access procedure messages 2 and 4 from the neighboring gNB during the DRX off period. Thus, the serving gNB and the UE can still continue DL / UL transmissions without colliding with the random access procedure executed between the UE and the target gNB.

[0156] There are several embodiments regarding how the UE can perform random access procedures during the DRX off period. Briefly, the DRX function executed in the serving radio cell is coordinated with the PRACH resources used by the UE in the target radio cell. For example, the target gNB has uplink resources reserved for random access procedures and can reserve dedicated resources among these PRACH resources for the handovered UE. These dedicated PRACH resources may then be used by the UE and the target gNB to exchange random access procedure messages.

[0157] According to an exemplary embodiment (shown in FIGS. 18 and 20), the serving gNB transmits information regarding the UE's DRX configuration to the target gNB. Next, the target gNB can adapt the PRACH resources used by the UE for the random access procedure to the DRX configuration received from the serving gNB, such that the PRACH resources used by the UE will fall within the DRX off period. This information regarding the UE's DRX configuration may be transmitted, for example, together with the handover request message (see FIG. 16), or in a message separate from the handover request message. FIG. 20 is shown to cover both of these variations. Further, information regarding the adapted PRACH resources is provided to the UE. According to one embodiment, the PRACH resource information is first transmitted to the serving gNB (e.g., together with the handover confirmation response message, as exemplarily shown in FIG. 20), and then transmitted to the UE, for example, together with (or separately from) the handover command message.

[0158] In any case, the UE receives information regarding the PRACH resources used by the UE for the random access procedure (already adapted by the target gNB) and uses the PRACH resources that fall within the off period of its DRX function as set by the target gNB. Similarly, the target gNB uses coordinated timing when transmitting random access messages 2 and 4 to the UE. Random access messages 2 and 4 may be received by the UE during the DRX off period when not communicating with the serving gNB. Correspondingly, the UE monitors during the DRX off period (e.g., the PDCCH from the target gNB) for whether the random access messages are received.

[0159] Information regarding the round-trip delay experienced by a UE when communicating with a serving gNB (e.g., a timing advance value or a reference signal time difference measurement) may be transmitted to the target gNB as well, for example, together with or separately from the DRX configuration. This information may then be used by the target gNB to more accurately align the PRACH resources with the DRX off-periods so as to avoid causing the delay in communication to make the PRACH resources belong to the DRX active period instead of the DRX off-period.

[0160] Additionally or alternatively, the round-trip delay experienced by another UE when communicating with the target gNB (e.g., a timing advance value or a reference signal time difference measurement) may be used by the target gNB to improve the coordination of dedicated PRACH resources with the DRX off-periods. In other words, the round-trip delay for another UE is used as an estimated value of the round-trip delay experienced by the UE when performing the random access procedure with the target gNB. Since the round-trip delay for other UEs is recognized by the target gNB, this is advantageous in that no exchange of information regarding the round-trip delay is required. Furthermore, the round-trip delay estimation may be more accurate as it is estimated with reference to the same target gNB that the UE is performing random access to.

[0161] In the previous embodiment, the PRACH resources were adapted while maintaining the initially configured DRX function. However, instead, according to a second exemplary embodiment described in connection with FIGS. 19 and 21, the DRX settings used by the UE at the serving base station are adapted to be coordinated with the PRACH resources at the target gNB. More specifically, the serving gNB learns about the PRACH resources at the target gNB that are used by the UE for random access, and then adapts the DRX settings so that the DRX off period for the serving radio cell matches the PRACH resources used in the target radio cell. The serving gNB can obtain information about the PRACH resources in the target radio cell, for example, from the target gNB. In an exemplary embodiment, when receiving a handover request, the target gNB provides the serving gNB with information about the PRACH resources together with a handover confirmation response message.

[0162] Alternatively, the serving gNB may obtain information about the PRACH resources based on the physical cell identification information of adjacent radio cells. The physical cell identification information (PCI) is obtained by the serving gNB, for example, from a measurement report received from the UE. Here, it is assumed that the PRACH resources are related to the physical cell identification information such that the serving gNB can derive the PRACH resources from the PCI. For example, there may be a plurality of different PRACH resource settings that can be derived based on, for example, (PCI mod 3), such as a total of three. In the above, any PCI that satisfies PCI mod 3 = 0 is associated with the PRACH resource setting 0, any PCI that satisfies PCI mod 3 = 1 is associated with the PRACH resource setting 1, and any PCI that satisfies PCI mod 3 = 2 is associated with the PRACH resource setting 2.

[0163] In any case, the DRX configuration used by the UE in the serving gNB is appropriately adapted. The adapted DRX configuration is notified to the UE, and the UE follows that configuration. For example, the adapted DRX configuration may be sent to the UE together with or separately from the handover command message (e.g., using the RRCReconfiguration message).

[0164] Similar to what has already been described in connection with the above first exemplary embodiment (adapting the PRACH resource to the DRX configuration), information regarding the round-trip delay experienced by the UE when communicating with the serving gNB may be used by the serving gNB to more accurately align the PRACH resource with the duration of the DRX function. Information regarding the RTD in the serving radio cell is already available at the serving gNB. Additionally or alternatively, information regarding the round-trip delay experienced by another UE when communicating with the target gNB is sent by the target gNB to the serving gNB, and then the serving gNB uses this round-trip delay associated with the target gNB to set the DRX off period for the dedicated PRACH resource in the target cell.

[0165] According to the improved handover communication solution described above, since communication between the UE and the serving gNB can continue even while the UE is performing random access with the target radio cell, the communication interruption caused by the handover is minimized. In fact, a make-before-break handover is realized.

[0166] One important mechanism commonly used in LTE and 5G to improve communication between the UE and the gNB is the hybrid automatic repeat request (HARQ) mechanism (see Sections 5.4.2 of 3GPP TS36.321 v15.4.0 and TS38.321 v15.4.0). According to an exemplary embodiment, the following improved retransmission function can be based on this.

[0167] To provide reliability, there are two levels of retransmission, namely, HARQ at the MAC layer and outer ARQ at the RLC layer. HARQ is a general technique for error detection and correction in packet transmission systems over unreliable channels. Hybrid ARQ is a combination of forward error correction (FEC) and ARQ. When an FEC-encoded packet is transmitted and the receiver cannot correctly decode this packet (usually, errors are checked by CRC (cyclic redundancy check)), the receiver requests retransmission of the packet.

[0168] The MAC layer includes HARQ entities responsible for transmission HARQ operations and reception HARQ operations. Transmission HARQ operations include transmission and retransmission of transport blocks and reception and processing of ACK / NACK signaling. Reception HARQ operations include reception of transport blocks, combination of received data, and generation of ACK / NACK signaling. Up to 16 parallel HARQ processes are used to support the multi-process "Stop-And-Wait" (SAW) HARQ operation to enable continuous transmission while previous transport blocks are being decoded. Each HARQ process is responsible for a separate SAW operation and manages a separate buffer.

[0169] The feedback provided by the HARQ protocol is either an acknowledgment (ACK) or a negative acknowledgment (NACK). ACK and NACK are generated according to whether the transmission was received correctly (e.g., whether decoding was successful). Further, in HARQ operations, the eNB can transmit different coded versions from the original transport block in retransmission, and as a result, the UE can obtain additional coding gain through incremental-redundancy (IR) combination via a combination gain.

[0170] If FEC - encoded packets are transmitted and the receiver cannot correctly decode these packets (usually, errors are checked by CRC (Cyclic Redundancy Check)), the receiver requests re - transmission of the packets. Generally (and throughout this document), the transmission of additional information is referred to as "re - transmission", and this re - transmission may mean the transmission of the same encoded information, but does not necessarily mean the transmission of the same encoded information. Re - transmission can also mean the transmission of any information belonging to the packet (e.g., additional redundant information), for example, by using different redundancy versions.

[0171] Therefore, as described above, HARQ is used between the UE and the gNB. This is equally applicable to the above - described scenario where the UE and the serving gNB are communicating with each other. Further, HARQ may also be used in the random access procedure between the UE and the target gNB. This is also applicable to the situation introduced above where the UE communicates in parallel with the serving base station (UL / DL communication) and the target gNB (random access) during handover (see, for example, Figure 16). For example, if a total of eight HARQ processes are available at the UE, these eight HARQ processes may be shared for communication with the serving gNB and the target gNB. However, the serving cell and the target cell do not need to coordinate the HARQ process ID.

[0172] When the UE starts a random access procedure, it is possible that all HARQ processes are already being used for communication with the serving cell. To continue using HARQ for random access with the target cell, the UE can re - allocate one of the HARQ processes it is using for communication with the serving cell to the random access procedure. Thereby, the memory associated with that one HARQ process is overwritten with data from the random access message. In effect, the UE cancels one of the HARQ processes and then uses that one HARQ process for the random access procedure.

[0173] The UE may select a HARQ process, for example, based on the priority of the data included in the HARQ process, or the UE may select a HARQ process based on the data rate of the HARQ process, or the UE may simply randomly select a HARQ process from among all the HARQ processes.

[0174] The simplified exemplary UE behavior along the above lines is shown in FIG. 22.

[0175] This one reallocated HARQ process can no longer be used to communicate with the serving gNB. However, since the serving gNB is not aware that the UE is currently using its HARQ process for a different purpose, it still uses the reallocated HARQ process. Correspondingly, the serving gNB may retransmit data for its reallocated HARQ process. However, in this case, the data from the HARQ process is no longer available (HARQ combining is not possible), and the UE attempts to decode data only from the newly received transmission. If the decoding fails, the UE can send a NACK to the serving gNB.

[0176] On the other hand, if the UE is planning to send a new uplink transmission to the serving gNB and no HARQ process is available, the UE performs the UL transmission without a HARQ process, for example, without holding the UL transmission in the HARQ buffer. If the serving gNB requests a retransmission of the UL data, the UE needs to encode the same data and send the encoded data to the serving gNB again.

[0177] Alternatively, the serving gNB may attempt to avoid all HARQ processes being used during handover. For example, if the serving gNB recognizes (via a measurement report) that the UE is approaching the cell edge, the serving gNB may reduce the DL transmission or UL grant of the serving gNB to the UE such that at least one HARQ process can be available for the UE to perform random access with the target gNB.

[0178] (Further aspect) According to a first aspect, a user equipment (UE) is provided that includes a processing circuit that performs power-related measurements in at least one radio carrier during operation and generates a measurement result based on the performed power-related measurements. The reporting of the measurement result by the UE is based on at least one reporting trigger condition to be satisfied. The processing circuit determines whether to adjust at least one of the measurement result and at least one reporting trigger condition so as to trigger the reporting of the measurement result earlier than in the case of no adjustment. If it is determined to adjust, the processing circuit adjusts at least one of the measurement result and at least one reporting trigger condition so as to trigger the reporting of the measurement result earlier than in the case of no adjustment. After adjustment, the processing circuit determines whether at least one reporting trigger condition is satisfied for reporting the measurement result based on the at least one reporting trigger condition and the generated measurement result. When the reporting of the measurement result is triggered, the transmitter of the UE transmits a measurement report including the measurement result.

[0179] According to a second aspect provided in addition to the first aspect, the adjustment of at least one reporting trigger condition includes the processing circuit applying at least one positive or negative power offset to at least one reporting trigger condition during operation. In an optional embodiment, the processing circuit determines the power offset from the configuration information received from the serving base station to which the UE is connected, or determines the power offset based on the difference between the generated measurement result and the previously generated measurement result. In another optional embodiment, one offset is determined for each of the generated measurement results and used in the adjustment. Optionally, for each reporting trigger condition, one offset is determined for the serving radio carrier or an adjacent radio carrier. In another optional embodiment, one offset is determined for the serving radio carrier and another offset is determined for the adjacent radio carrier. In another optional embodiment, one offset is determined for each reporting trigger condition and used in the adjustment.

[0180] According to a third aspect provided in addition to the first or second aspect, the adjustment of the measurement result includes the processing circuit determining the difference between the generated measurement result and the previously generated measurement result, and applying the determined difference to the generated measurement result to generate an adjusted measurement result. The processing circuit determines whether to report the measurement result based on at least one reporting trigger condition and the adjusted measurement result.

[0181] According to a fourth aspect provided in addition to any one of the first to third aspects, the execution of power-related measurements by the processing circuit includes performing measurements in at least one non-terrestrial radio carrier. In an optional embodiment, the determination of whether to perform the adjustment by the processing circuit is based on whether the radio carrier is a non-terrestrial radio carrier or a terrestrial radio carrier. In an optional embodiment, the adjustment is performed when the reporting trigger condition is based on the measurement result of the measurement performed in the non-terrestrial radio carrier.

[0182] According to a fifth aspect provided in addition to one of the first to fourth aspects, the measurement result can be used by the serving base station to which the UE is connected to determine whether to initiate a procedure for handing over the UE from the current serving radio cell controlled by the serving base station to another radio cell. At least one reporting trigger condition is set to be satisfied when the serving base station can determine to initiate a procedure for handing over the UE from the current serving radio cell to another cell.

[0183] According to a sixth aspect provided in addition to one of the first to fifth aspects, the UE further comprises a receiver that receives a conditional handover command during operation, wherein the conditional handover command message includes at least one handover acceptance condition to be satisfied for the UE to perform a handover and / or at least one handover rejection condition to be satisfied for the UE to reject a handover. The processing circuit determines whether the handover acceptance condition is satisfied, and if the handover acceptance condition is satisfied, performs a handover according to the received conditional handover command, and optionally, if the handover acceptance condition is not satisfied, transmits information regarding handover rejection. In another optional embodiment, the processing circuit determines whether the handover rejection condition is satisfied, and if the handover rejection condition is satisfied, transmits information regarding handover rejection.

[0184] According to a seventh aspect provided in addition to the sixth aspect, information regarding handover rejection is transmitted in a Radio Resource Control (RRC) message or as another measurement report. Alternatively, information regarding handover rejection is transmitted together with uplink data, and optionally, information regarding handover rejection is transmitted as a control element (CE) of a Medium Access Control (MAC) protocol. In an optional embodiment, the processing circuit determines whether uplink data is transmitted to the serving base station, and if the uplink data is not transmitted, the handover rejection is transmitted in an RRC message or as another measurement report, and if the uplink data is transmitted, the handover rejection is transmitted together with the uplink data.

[0185] According to a seventh aspect provided in addition to one of the sixth aspect to the seventh aspect, when the processing circuit determines that the handover rejection condition is satisfied, after transmitting information regarding handover rejection to the serving base station, the processing circuit decides not to transmit a measurement report for a certain period. In an optional embodiment, the certain period is set by the serving base station.

[0186] According to a ninth aspect provided in addition to one of the first aspect to the eighth aspect, when neither the handover acceptance condition nor the handover rejection condition is satisfied, during operation, the transmitter transmits a resource reservation extension request to the serving base station so as to extend the resource reservation time in the adjacent radio cell.

[0187] According to a tenth aspect provided in addition to one of the first to ninth aspects, the UE performs a handover from the current serving radio cell to another radio cell, and performing the handover includes the UE performing a random access procedure with the other radio cell. After starting to perform a handover to another radio cell, the UE continues to communicate with the serving base station in the uplink and / or downlink during a communication period of a discontinuous reception (DRX) function operated by the UE for communication with the serving base station. The UE transmits a message of the random access procedure during a sleep period of the discontinuous reception (DRX) function operated by the UE for communication with the serving radio cell, and optionally, the communication period does not overlap with the sleep period. In an optional embodiment, the UE receives a message of the random access procedure during the sleep period of the DRX function.

[0188] According to an eleventh aspect provided in addition to one of the first to tenth aspects, the UE performs a handover from the current serving radio cell to another radio cell, and performing the handover includes the UE performing a random access procedure with the other radio cell. After starting to perform a handover to another radio cell, the UE continues to communicate with the serving base station in the uplink and / or downlink using a plurality of hybrid automatic repeat request (HARQ) processes. The UE uses a plurality of HARQ processes for the random access procedure, and if all of the plurality of HARQ processes are already being used for communication with the serving base station, the processing circuit, during operation, instead determines one of the plurality of HARQ processes to be reused for the random access procedure.

[0189] According to a 12th aspect provided in addition to the 11th aspect, each HARQ process is used to store the previously transmitted data in the associated memory for possible later retransmission, or to store the previously received data in the associated memory for possible later combination with the later received data. Reusing a HARQ process for a random access procedure involves overwriting the memory associated with the reused HARQ process with data buffered for the random access procedure. In an optional embodiment, if all of the HARQ processes are in use and one of the HARQ processes is being reused for a random access procedure, the processing circuitry does not use the reused HARQ process to store new uplink transmissions during operation. In another optional embodiment, if all of the HARQ processes are in use and one of the HARQ processes is being reused for a random access procedure, the processing circuitry does not use the reused HARQ process to store received downlink transmissions.

[0190] According to a 13th aspect, the following steps are performed by a user equipment (UE), namely, performing power-related measurements in at least one radio carrier and generating measurement results based on the performed power-related measurements, wherein reporting of the measurement results by the UE is based on at least one reporting trigger condition to be satisfied, determining whether to adjust at least one of the measurement results and at least one of the at least one reporting trigger conditions so as to trigger reporting of the measurement results earlier than if no adjustment is made, if it is determined to adjust, adjusting at least one of the measurement results and at least one of the at least one reporting trigger conditions so as to trigger reporting of the measurement results earlier than if no adjustment is made, After adjustment, based on at least one reporting trigger condition and the measurement result, to determine whether at least one reporting trigger condition is satisfied for reporting the measurement result; When the reporting of the measurement result is triggered, transmitting a measurement report including the measurement result; A method including the above is provided.

[0191] According to a 14th aspect, a base station is provided that includes a processing circuit for determining whether to instruct a user equipment (UE) to adjust at least one of the measurement result and at least one reporting trigger condition so as to trigger the reporting of the measurement result earlier than when there is no adjustment. When the determination by the processing circuit is to instruct the UE, the transmitter of the base station configures the UE to adjust at least one of the measurement result and at least one reporting trigger condition so as to trigger the reporting of the measurement result earlier than when there is no adjustment. The receiver of the base station receives a measurement report from the UE. The measurement report includes the measurement result of measurements performed by the UE on at least one radio carrier, and the reporting of the measurement result by the UE is based on at least one reporting trigger condition to be satisfied.

[0192] According to a 15th aspect provided in addition to the 14th aspect, the processing circuit determines at least one positive or negative power offset for at least one reporting trigger condition. The transmitter transmits configuration information indicating the determined positive or negative power offset to the UE. In an optional embodiment, one offset is determined for each of the generated measurement results. In an optional embodiment, for each reporting trigger condition, one offset is determined for the serving radio carrier or an adjacent radio carrier. In an optional embodiment, one offset is determined for the serving radio carrier and another offset is determined for the adjacent radio carrier.

[0193] According to a 16th aspect provided in addition to the 14th or 15th aspect, a determination by a processing circuit as to whether to instruct a UE to adjust at least one of a measurement result and at least one reporting trigger condition so as to trigger reporting of the measurement result earlier than in the case of no adjustment is based on whether the radio carrier is a non-terrestrial radio carrier or a terrestrial radio carrier. In an optional embodiment, when the UE performs measurements on a non-terrestrial radio carrier, the processing circuit determines to instruct the UE to adjust.

[0194] According to a 17th aspect provided in addition to any of the 14th to 16th aspects, a transmitter transmits a conditional handover command to the UE, and the conditional handover command message includes at least one handover acceptance condition to be satisfied for the UE to perform a handover and / or at least one handover rejection condition to be satisfied for the UE to reject a handover. In an optional embodiment, a receiver receives information regarding rejection of a handover by the UE, and the transmitter transmits a request to an adjacent target base station that is a target of the handover to release resources in the adjacent radio cell reserved for the handover of the UE. In an optional embodiment, the receiver receives a first resource reservation extension request from the UE to extend a resource reservation time in an adjacent radio cell. The transmitter transmits a second resource reservation extension request to an adjacent target base station that is a target of the handover to extend the resource reservation time in the adjacent radio cell.

[0195] According to an 18th aspect provided in addition to any one of the 14th to 17th aspects, the processing circuit adapts the sleep period of the discontinuous reception (DRX) function that is operated by the UE for communication with the base station so as to match the random access resource used by the UE to execute a random access procedure with an adjacent target base station. In an optional embodiment, the processing circuit acquires information regarding the random access resource of the adjacent target base station based on the information received from the adjacent target base station or based on the cell identification information of the adjacent target base station.

[0196] According to a 19th aspect provided in addition to any one of the 14th to 18th aspects, another UE is handed over as a handover target to a base station from another base station, and the transmitter transmits a message of a random access procedure to the other UE during the sleep period of the discontinuous reception (DRX) function that is operated by the other UE for communication with the other base station, and the receiver receives a message of the random access procedure from the other UE during the sleep period of the DRX function. In an optional embodiment, the receiver receives setting information regarding the DRX function of the other UE. The processing circuit adapts the random access resource used by the other UE to execute a random access procedure with the base station so as to match the sleep period of the DRX function. The transmitter transmits information regarding the adapted random access resource to the other base station.

[0197] (Realization by Hardware and Software of the Present Disclosure) The present disclosure can be implemented by software, by hardware, or by software cooperating with hardware. Each functional block used in the description of each of the above-described embodiments can be implemented, in part or in whole, by an LSI such as an integrated circuit, and each process described in each embodiment can be controlled, in part or in whole, by the same LSI or a combination of LSIs. The LSI can be formed individually as a chip, or one chip can be formed to include part or all of the functional blocks. The LSI can include a data input / output section coupled to itself. Here, the LSI may be referred to as an IC (integrated circuit), a system LSI, a super LSI, or an ultra LSI depending on the difference in integration level. However, the technology for realizing the integrated circuit is not limited to the LSI, and can be realized by using an application-specific circuit, a general-purpose processor, or a dedicated processor. Further, an FPGA (field programmable gate array) that can be programmed after the manufacture of the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells arranged inside the LSI can also be used. The present disclosure can be realized as digital processing or analog processing. As a result of the progress of semiconductor technology or another derivative technology, if the LSI is replaced by a future integrated circuit technology, the functional blocks can be integrated using the future integrated circuit technology. Biotechnology can also be applied.

[0198] The present disclosure can be implemented by any type of device, apparatus, or system having a communication function (collectively referred to as a communication device).

[0199] Non-limiting examples of communication devices include telephones (such as mobile phones, smartphones, etc.), tablets, personal computers (PCs) (such as laptops, desktops, netbooks, etc.), cameras (such as digital still / video cameras, etc.), digital players (such as digital audio / video players, etc.), wearable devices (such as wearable cameras, smartwatches, tracking devices, etc.), game consoles, digital book readers, telehealth / telemedicine (remote healthcare / medical prescription) devices, vehicles with communication functions (such as automobiles, airplanes, ships, etc.), and combinations of the various devices described above.

[0200] The communication device is not limited to being portable or movable, and includes any type of device, apparatus, or system that is not portable or is fixed, such as smart home devices (such as household appliances, lighting devices, smart meters, control panels, etc.), vending machines, and any other "things" that can exist on the IoT (Internet of Things) network.

[0201] Communication includes data communication by cellular systems, wireless LAN systems, communication satellite systems, etc., as well as data communication by combinations of these.

[0202] In addition, the communication device also includes devices such as controllers and sensors that are connected or coupled to a communication device that executes the communication function described in the present disclosure. For example, the communication device includes controllers and sensors that generate control signals and data signals used by a communication device that executes the communication function of the communication device.

[0203] In addition, the communication device also includes infrastructure facilities, such as base stations, access points, and any other devices, apparatuses, or systems that communicate with or control the various non-limiting devices described above.

[0204] Furthermore, various embodiments may be implemented by software modules executed by a processor or directly implemented in hardware. Also, a combination of software modules and hardware implementations can be made. The software modules can be stored in any type of computer-readable storage medium such as RAM, EPROM, EEPROM, flash memory, registers, hard disk, CD-ROM, DVD, etc. Further, note that the individual features of different embodiments can be the subject of another embodiment, individually or in any combination.

[0205] Those skilled in the art will understand that numerous variations and / or modifications can be made to the present disclosure as shown in the specific embodiments. Therefore, this embodiment should be considered illustrative in all respects and not restrictive.

Claims

1. A communication device, comprising: a processing circuit configured, during operation, to perform power-related measurements in at least one radio cell and generate a measurement result based on the performed power-related measurements, wherein the processing circuit configured, during operation, to determine whether to add at least one reporting trigger condition according to the at least one radio cell being associated with a non-terrestrial network, and wherein the processing circuit configured, during operation, to determine whether the at least one reporting trigger condition is satisfied in order to report the measurement result; a transmitter configured, during operation, to transmit a measurement report including said measurement result if a report of said measurement result is triggered; Equipped with The communication device determines whether to perform a conditional handover based on the measurement result; a first value for a terrestrial network and the non-terrestrial network, and a second value for the non-terrestrial network are set by a serving base station together with a criterion and a measurement object for performing the conditional handover; determining, based on the measurement result using the first value and the second value, the conditional handover if the criterion for performing the conditional handover is met; determining said conditional handover if additional criteria for performing said conditional handover based on a location of said communication device and said at least one radio cell are met. Communications equipment.

2. In operation, the processing circuitry determines a power offset from configuration information received from a serving base station to which the communications device is connected, or determines a power offset based on a difference between the generated measurement result and a previously generated measurement result. The communication device according to claim 1 .

3. one offset is determined for each measurement result of the generated measurement results and used in the addition, and for each reporting trigger condition one offset is determined for a serving or neighboring radio cell. The communication device according to claim 1 .

4. one offset is determined for a serving radio cell and another offset is determined for a neighboring radio cell; The communication device according to claim 1 .

5. One offset is determined for each report trigger condition and used in the addition. The communication device according to claim 1 .

6. - a communication device performing power-related measurements in at least one radio cell and generating a measurement result based on the performed power-related measurements; the communication device determining whether to add at least one reporting trigger condition according to the at least one radio cell being associated with a non-terrestrial network; determining, by the communication device, whether the at least one reporting trigger condition is met to report the measurement result; if a report of the measurement result is triggered, the communication device transmits a measurement report including the measurement result; Including, The communication device determines whether to perform a conditional handover based on the measurement result; a first value for a terrestrial network and the non-terrestrial network, and a second value for the non-terrestrial network are set by a serving base station together with a criterion and a measurement object for performing the conditional handover; determining, based on the measurement result using the first value and the second value, the conditional handover if the criterion for performing the conditional handover is met; determining said conditional handover if additional criteria for performing said conditional handover based on a location of said communication device and said at least one radio cell are met. method.

7. a processing circuit configured to determine, during operation, whether to instruct the communication device to add at least one reporting trigger condition according to the at least one wireless cell being associated with a non-terrestrial network; a transmitter that, in operation, configures the communication device to add the at least one reporting trigger condition if the determination by the processing circuit is to instruct the communication device to add the at least one reporting trigger condition; a receiver adapted to receive, during operation, measurement reports from the communication device, the measurement reports comprising measurement results of measurements performed by the communication device in the at least one radio cell; Equipped with determining whether to perform a conditional handover based on the measurement result; a first value for a terrestrial network and the non-terrestrial network, and a second value for the non-terrestrial network are set by a serving base station together with a criterion and a measurement object for performing the conditional handover; determining, based on the measurement result using the first value and the second value, the conditional handover if the criterion for performing the conditional handover is met; determining said conditional handover if additional criteria for performing said conditional handover based on a location of said communication device and said at least one radio cell are met. Base station.

8. The processing circuitry, during operation, determines at least one positive or negative power offset for the at least one reporting trigger condition; and wherein the transmitter, during operation, transmits configuration information to the communication device indicative of the determined positive or negative power offset. The base station according to claim 7.

9. one offset is determined for a serving radio cell and another offset is determined for a neighboring radio cell; The base station according to claim 7.

10. determining whether the base station instructs the communication device to add at least one report trigger condition according to the at least one radio cell being associated with a non-terrestrial network; if the decision is to instruct the communication device, the base station configures the communication device to add the at least one report trigger condition; receiving, by the base station, a measurement report from the communication device, the measurement report comprising measurement results of measurements performed by the communication device in the at least one radio cell; Including, determining whether to perform a conditional handover based on the measurement result; a first value for a terrestrial network and the non-terrestrial network, and a second value for the non-terrestrial network are set by a serving base station together with a criterion and a measurement object for performing the conditional handover; determining, based on the measurement result using the first value and the second value, the conditional handover if the criterion for performing the conditional handover is met; determining said conditional handover if additional criteria for performing said conditional handover based on a location of said communication device and said at least one radio cell are met. method.

11. An integrated circuit for controlling processing of a communication device, the processing comprising: - performing, by the communication device, power-related measurements in at least one radio cell and generating measurement results based on the performed power-related measurements; a process of the communication device determining whether to add the at least one reporting trigger condition according to the at least one radio cell being associated with a non-terrestrial network; determining, by the communications device, whether the at least one reporting trigger condition is met in order to report the measurement results; When a report of the measurement result is triggered, the communication device transmits a measurement report including the measurement result; Including, The communication device determines whether to perform a conditional handover based on the measurement result; a first value for a terrestrial network and the non-terrestrial network, and a second value for the non-terrestrial network are set by a serving base station together with a criterion and a measurement object for performing the conditional handover; determining, based on the measurement result using the first value and the second value, the conditional handover if the criterion for performing the conditional handover is met; determining said conditional handover if additional criteria for performing said conditional handover based on a location of said communication device and said at least one radio cell are met. Integrated circuits.

12. An integrated circuit for controlling processing of a base station, the processing comprising: determining whether to instruct the communication device to add at least one reporting trigger condition according to at least one wireless cell being associated with a non-terrestrial network; if the decision is to instruct the communication device, configuring the communication device to add the at least one reporting trigger condition; receiving a measurement report from the communication device, the measurement report comprising measurement results of measurements performed by the communication device in the at least one radio cell; Including, determining whether to perform a conditional handover based on the measurement result; a first value for a terrestrial network and the non-terrestrial network, and a second value for the non-terrestrial network are set by a serving base station together with a criterion and a measurement object for performing the conditional handover; determining, based on the measurement result using the first value and the second value, the conditional handover if the criterion for performing the conditional handover is met; determining said conditional handover if additional criteria for performing said conditional handover based on a location of said communication device and said at least one radio cell are met. Integrated circuits.

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