Communication apparatus, base station, measurement and handover method, and integrated circuit

Abstract

The present disclosure relates to a communication apparatus comprising: processing circuitry generating a measurement result based on a power-related measurement on at least one radio cell; a transceiver receiving a conditional handover command, the conditional handover command comprising at least one handover execution condition for the communication device to execute conditional handover and comprising a location-based handover trigger condition and a measurement-based handover trigger condition according to the at least one radio cell relating to a non-terrestrial network; the communication device performs the conditional handover in a case where the location-based handover trigger condition is satisfied according to the location of the communication device and the at least one radio cell; the communication device performs the condition switching in a case where the measurement-based switching trigger condition is satisfied according to the measurement result; and a first value for the terrestrial network and the non-terrestrial network and a second value for the non-terrestrial network are configured to perform the conditional switching.

Description

[0001] This application is a divisional application of the invention patent application with application number 202080010450.2 filed on February 4, 2020, and invention name: "User Equipment Involved in Measurement Reporting and Switching". Technical Field

[0002] The present disclosure is directed to methods, apparatus and articles in a communication system, such as a 3GPP communication system. Background Art

[0003] Currently, the 3rd Generation Partnership Project (3GPP) is working on technical specifications for the next generation of cellular technology, which is also referred to as the fifth generation (5G).

[0004] One goal is to provide a single technical framework that addresses all use cases, requirements, and deployment scenarios (see, for example, Section 6 of TR 38.913 Version 15.0.0), including at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC). For example, eMBB deployment scenarios may include indoor hotspots, dense urban, rural, urban macro, and high-speed; URLLC deployment scenarios may include industrial control systems, mobile health (remote monitoring, diagnosis, and treatment), real-time vehicle control, and wide-area monitoring and control systems for smart grids; and mMTC deployment scenarios may include scenarios with large numbers of devices with non-time-critical data transmission (such as smart wearables and sensor networks). eMBB and URLLC services are similar in that they both require very wide bandwidth, but different in that URLLC services may preferably require ultra-low latency.

[0005] The second goal is to achieve forward compatibility. Backward compatibility with Long Term Evolution (LTE, LTE-A) cellular systems is not required, which facilitates completely new system designs and / or the introduction of new features. Summary of the Invention

[0006] One non-limiting and exemplary embodiment facilitates providing an improved process for measurement and handover.

[0007] In an embodiment, the technology disclosed herein features a user equipment (UE) including processing circuitry that performs power-related measurements on at least one radio carrier and generates measurement results based on the performed measurements. Reporting of the measurement results by the UE is based on at least one reporting triggering condition being satisfied. The processing circuitry determines whether to adjust the measurement results and at least one of the at least one reporting triggering condition so as to trigger reporting of the measurement results earlier than would otherwise be the case. If an adjustment is determined, the processing circuitry adjusts at least one of the measurement results and the at least one reporting triggering condition so as to trigger reporting of the measurement results earlier than would otherwise be the case. After the adjustment, the processing circuitry determines whether the at least one reporting triggering condition for reporting the measurement results is satisfied based on the at least one reporting triggering condition and the measurement results. If reporting of the measurement results is triggered, a transmitter of the UE transmits a measurement report including the measurement results.

[0008] It should be noted that the general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

[0009] Additional benefits and advantages of the embodiments disclosed in the specification and drawings will become apparent. Benefits and / or advantages can be obtained independently of the various embodiments and features of the specification and drawings, and all of the various embodiments and features need not be provided in order to obtain one or more of such benefits and / or advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Hereinafter, exemplary embodiments will be described in more detail with reference to the accompanying drawings.

[0011] Figure 1 An exemplary architecture of a 3GPP NR system is shown;

[0012] Figure 2 An exemplary user and control plane architecture for LTE eNB, gNB, and UE is shown;

[0013] Figure 3 An exemplary transparent satellite-based NG RAN architecture is illustrated;

[0014] Figure 4 An exemplary NG RAN architecture based on regenerative satellites is illustrated;

[0015] Figure 5 An exemplary and simplified structure of a UE and a gNB is illustrated;

[0016] Figure 6 illustrates the structure of a UE according to an exemplary implementation of an embodiment for an improved measurement and reporting procedure;

[0017] Figure 7is a flow chart of behavior of a UE according to an exemplary implementation of an improved measurement and reporting procedure;

[0018] Figure 8 is a flowchart of a gNB's behavior according to an exemplary implementation of an improved measurement and reporting procedure;

[0019] Figure 9 is a signaling diagram of messages between the UE, serving gNB, and neighboring gNBs according to the improved measurement and reporting procedure;

[0020] Figure 10 is a signaling diagram of messages between the UE, serving gNB, and target gNB according to the improved conditional handover procedure;

[0021] Figure 11 is a flow chart of behavior of a UE according to an exemplary implementation for an improved conditional handover procedure;

[0022] Figure 12 is a flow chart illustrating the behavior of a gNB according to an exemplary implementation of an improved conditional handover procedure;

[0023] Figure 13 and 14 The 3-step and 4-step random access processes are illustrated respectively;

[0024] Figure 15 illustrates DRX operation of a mobile terminal according to short and long DRX cycles (and in particular DRX opportunities and OnDuration periods);

[0025] Figure 16 is a signaling diagram of messages exchanged between a UE, a serving gNB of the UE, and a target gNB for an exemplary implementation of an improved handover communication procedure;

[0026] Figure 17 is a flow chart of the behavior of a UE according to an exemplary implementation of an improved handover communication procedure;

[0027] Figure 18 and 19 is a flow chart of the behavior of the serving gNB according to different implementations of the improved handover communication procedure;

[0028] Figure 20 and 21 is a flow chart of the behavior of the target gNB according to different implementations of the improved handover communication procedure; and

[0029] Figure 22 is a flow chart illustrating behavior of a UE according to an exemplary implementation of an improved HARQ operation procedure during handover. DETAILED DESCRIPTION

[0030] 5G NR system architecture and protocol stack

[0031] 3GPP has been working on the next version of the fifth generation of cellular technology, known as 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, allowing for trials and commercial deployment of smartphones compliant with the 5G NR standard.

[0032] In addition, the overall system architecture assumes NG-RAN (Next Generation Radio Access Network), which includes gNBs that provide NG radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocol terminations to UEs. gNBs are connected to each other via Xn interfaces. gNBs are also connected to NGC (Next Generation Core) via Next Generation (NG) interfaces, more specifically to AMF (Access and Mobility Management Function) (e.g., a specific core entity that executes AMF) via NG-C interfaces and to UPF (User Plane Function) (e.g., a specific core entity that executes UPF) via NG-U interfaces. The NG-RAN architecture is Figure 1 The figure shows (see, for example, 3GPP TS 38.300 v15.4.0, Section 4).

[0033] A variety of deployment scenarios can be supported (see, for example, 3GPP TR 38.801 v14.0.0). For example, a decentralized deployment scenario is described (see, for example, Section 5.2 of TR 38.801; centralized deployment is described in Section 5.4), where 5G NR-capable base stations can be deployed. Figure 2 An exemplary decentralized deployment scenario is illustrated (see, for example, TR 38.801 Figure 5 .2.-1), also illustrating an LTE eNB and user equipment (UE) connected to both the gNB and the LTE eNB. The new eNB for NR 5G may be exemplarily referred to as a gNB. The eLTE eNB is an evolution of the eNB, supporting connectivity to both the EPC (Evolved Packet Core) and the NGC (Next Generation Core).

[0034] The user plane protocol stack for NR (see, for example, 3GPP TS 38.300 v15.4.0, Section 4.4.1) includes the PDCP (Packet Data Convergence Protocol, see Section 6.4 of TS 38.300), the RLC (Radio Link Control, see Section 6.3 of TS 38.300), and the MAC (Medium Access Control, see Section 6.2 of TS 38.300) sublayers, which terminate in the gNB on the network side. Furthermore, a new Access Stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced above PDCP (see, for example, subclause 6.5 of 3GPP TS 38.300 v15.4.0). A control plane protocol stack is also defined for NR (see, for example, TS 38.300, Section 4.4.2). An overview of Layer 2 functionality is provided in subclause 6 of TS 38.300. The functions of the PDCP, RLC, and MAC sublayers are listed in sections 6.4, 6.3, and 6.2 of TS 38.300, respectively. The functions of the RRC layer are listed in subclause 7 of TS 38.300.

[0035] For example, the media access control layer handles logical channel multiplexing, scheduling, and scheduling-related functions, including the processing of different parameter sets.

[0036] The MAC layer uses services in the form of transport channels for the physical layer. A transport channel is defined by how and with what characteristics information is transmitted over the radio interface. The Random Access Channel (RACH) is also defined as a transport channel handled by the MAC, although it does not carry transport blocks. One of the procedures supported by the MAC layer is the Random Access procedure.

[0037] The physical layer (PHY) is responsible for, for example, coding, PHY HARQ processing, modulation, multi-antenna processing, and signal mapping to appropriate physical time-frequency resources. It also handles the mapping of transport channels to physical channels. The physical layer provides services to the MAC layer in the form of transport channels. A physical channel corresponds to a set of time-frequency resources used to transmit 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.

[0038] Use cases / deployment scenarios for NR may include enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC), and massive machine type communications (mMTC), which have different requirements in terms of data rate, latency, and coverage. For example, eMBB is expected to support peak data rates (20 Gbps for downlink and 10 Gbps for uplink) and user-experienced data rates that are approximately three times higher than those provided by advanced IMT. On the other hand, in the case of URLLC, there is a strong demand for ultra-low latency (0.5ms for both UL and DL user plane latency) and high reliability (1-10 Mbps within 1ms). -5 Finally, mMTC may preferably require high connection density (1,000,000 devices / km in urban environments). 2 ), wide coverage in harsh environments, and ultra-long battery life (15 years) for low-cost devices.

[0039] Therefore, an OFDM parameter set (e.g., subcarrier spacing, OFDM symbol duration, cyclic prefix (CP) duration, number of symbols per scheduling interval) that is suitable for one use case may not be suitable for another. For example, low-latency services may preferably require a shorter symbol duration (and therefore a larger subcarrier spacing) and / or fewer symbols per scheduling interval (also known as TTI) than mMTC services. In addition, deployment scenarios with large channel delay spread may preferably require a longer CP duration than scenarios with short delay spread. The subcarrier spacing should be optimized accordingly to maintain similar CP overhead. NR can support more than one subcarrier spacing value. Accordingly, subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, ... are currently under consideration. Symbol duration T u and the subcarrier spacing Δf is obtained by the formula Δf = 1 / T u In a similar manner as in LTE systems, the term "resource element" may be used to denote the smallest resource unit consisting of one subcarrier for the length of a single OFDM / SC-FDMA symbol.

[0040] In the new radio system 5G-NR, for each numerology set and carrier, a resource grid of subcarriers and OFDM symbols is defined for uplink and downlink, respectively. Each element in the resource grid is called a resource element and is identified based on a frequency index in the frequency domain and a symbol position in the time domain (see 3GPP TS 38.211 v15.4.0).

[0041] Reference signal

[0042] As in LTE, 5G NR uses several different types of reference signals (RS) (see 3GPP TS 38.211 v15.4.0 section 7.4.1). At least the following reference signals are available in 5G NR:

[0043] • CSI-RS, a channel state information reference signal that can be used for channel state information acquisition and beam management

[0044] •PDSCH DMRS, a demodulation reference signal that can be used for PDSCH demodulation

[0045] •PDCCH DMRS, a demodulation reference signal that can be used for PDCCH demodulation

[0046] •PBCH DMRS, a demodulation reference signal that can be used for PBCH demodulation

[0047] • PTRS, a phase tracking reference signal that can be used to phase track the PDSCH,

[0048] • Tracking reference signal that can be used for time tracking

[0049] In addition, the PBCH DMRS may exemplarily be considered as a part of the SSB reference signal (see 3GPP TS 38.215 v15.3.0 Section 5.1.1 “SS Reference Signal Received Power (SS-RSRP)”).

[0050] The main differences between reference signals in 5G NR communication systems and reference signals 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 downlink and uplink channels, and in NR reference signals are sent only when needed.

[0051] As a DL-only signal, the CSI-RS received by the UE is used to estimate the channel and report channel quality information back to the gNB. During MIMO operation, NR can use different antenna schemes based on the carrier frequency. At lower frequencies, the system uses an appropriate 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 it back in the UL direction. CSI-RS can be further characterized according to the following:

[0052] •It is used for DL ​​CSI acquisition.

[0053] • RSRP measurements during mobility and beam management

[0054] • Also used for frequency / time tracking, demodulation and UL reciprocity based precoding

[0055] • CSI-RS is UE-specific, but multiple users can share the same resource

[0056] •The 5G NR standard allows a high level of flexibility in CSI-RS configuration, with resources being configured for up to 32 ports.

[0057] •CSI-RS resource can start from any OFDM symbol in the time slot and it usually occupies 1 / 2 / 4 OFDM symbols depending on the number of configured ports.

[0058] • CSI-RS can be periodic, semi-persistent or aperiodic (due to DCI triggering)

[0059] For time / frequency tracking, CSI-RS can be periodic or aperiodic. It is sent in bursts of two or four symbols spread across one or two time slots.

[0060] UE Measurements in 5G NR

[0061] NR devices can be configured to perform different measurements and in some cases subsequently report the results accordingly to the network.

[0062] In short, to provide a basic overview of measurements, a UE (NR device) can perform measurements based on, for example, reference signals (such as CSI-RS and SS blocks) and obtain measurement results. After receiving some or all of the measurement results in a corresponding measurement report, these measurement results can be used internally by the UE or by other entities (such as the base station for mobility control).

[0063] Exemplary and detailed implementations are presented below.

[0064] Measurements for connected mode mobility may be performed by the UE and may be categorized into at least three measurement types:

[0065] • Intra-frequency NR measurement,

[0066] •Inter-frequency NR measurement

[0067] • Inter-RAT measurements for E-UTRA

[0068] Typically, measurements can be configured by, for example, defining one or more measurement objects; a measurement object defines, for example, the carrier frequency to be monitored. For each measurement object, one or several reporting configurations can then be defined, including reporting criteria such as event-triggered reporting, periodic reporting, and event-triggered periodic reporting (see 3GPP TS 38.300 v15.3.1, Section 9.1).

[0069] The reporting configuration indicates a quantity or set of quantities, such as different combinations of the channel quality indicator (CQI), rank indicator (RI), and precoder matrix indicator (PMI) (collectively referred to as channel state information (CSI)). Furthermore, the reporting configuration may indicate reporting of received signal strength (more formally referred to as reference signal received power (RSRP)). RSRP has historically been a key quantity measured and reported as part of higher-layer radio resource management (RRM), and it is also used in 5G NR. NR supports Layer 1 reporting of RSRP (for example, as part of support for beam management), thereby deriving beam quality. The reported content is more specifically referred to as L1-RSRP, reflecting the fact that the report does not include the longer-term ("Layer 3") filtering applied to higher-layer RSRP reports. L3 filtering at the RRC level can derive cell quality from multiple beams and, therefore, can neutralize sudden changes by considering the current input from the L1 filter and the previous output from the L3 filter.

[0070] It also configures on which downlink resource sets the measurements should be performed. For example, L1-RSRP for beam management can therefore be based on measurements on a set of SS (synchronization signal) blocks or a set of CSI-RS.

[0071] There are also situations where a device performs measurements without any corresponding reporting to the network. One example of this is when a UE performs measurements for receiver-side downlink beamforming. The UE uses the measurements internally to select an appropriate receiver beam. The network can configure the UE accordingly, for example by specifying the reference signals to be measured on, but indicating that no reporting is required.

[0072] The UE can measure multiple (at least one) beams of a cell and average the measurement results (e.g., power values) to derive cell quality. When doing so, the UE can be configured to consider a subset of the detected beams. Filtering occurs at two different levels: 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. Cell quality from beam measurements is derived in the same manner for both serving and non-serving cells.

[0073] The measurement report may be characterized by one or more of the following:

[0074] - The measurement report includes the measurement identity of the associated measurement configuration that triggered the report;

[0075] - The amount of cell and beam measurements to be included in the measurement report is configured by the network;

[0076] -The number of non-serving cells to be reported can be limited by configuration by the network;

[0077] - Cells belonging to a blacklist configured by the network are not used for event evaluation and reporting, and conversely when a whitelist is configured by the network, only cells belonging to the whitelist are used for event evaluation and reporting;

[0078] - The beam measurements to be included in the measurement report are configured by the network (only beam identifier, measurement results and beam identifier, or no beam report).

[0079] The following are exemplary definitions of intra-frequency neighboring cell (cell) measurement and inter-frequency neighboring cell (cell) measurement:

[0080] - Intra-frequency measurement based on SSB: If the center frequency of the SSB of the serving cell is the same as the center frequency of the SSB of the neighboring cell, and the subcarrier spacing of the two SSBs is also the same, the measurement is defined as intra-frequency measurement based on SSB.

[0081] - Inter-frequency measurement based on SSB: If the center frequency of the SSB of the serving cell is different from the center frequency of the SSB of the neighboring cell, or the subcarrier spacing of the two SSBs is different, the measurement is defined as an inter-frequency measurement based on SSB.

[0082] Note: For SSB-based measurements, one measurement object corresponds to one SSB, and the UE considers different SSBs as different cells.

[0083] - Intra-frequency CSI-RS based measurement: If the bandwidth of the CSI-RS resources on the neighboring cell configured for measurement is within the bandwidth of the CSI-RS resources on the serving cell configured for measurement, and the subcarrier spacing of the two CSI-RS resources is the same, the measurement is defined as intra-frequency CSI-RS based measurement.

[0084] - CSI-RS based inter-frequency measurement: If the bandwidth of the CSI-RS resources on the neighboring cell configured for measurement is not within the bandwidth of the CSI-RS resources on the serving cell configured for measurement, or the subcarrier spacing of the two CSI-RS resources is different, the measurement is defined as an inter-frequency CSI-RS based measurement.

[0085] Whether a 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 should be able to perform such measurements without measurement gaps. In a gap-assisted scenario, it cannot be assumed that the UE can perform such measurements without measurement gaps.

[0086] Measurement reporting is defined in Section 5.5.3 of 3GPP TS 38.331 v 15.3.0. The network can configure the UE to obtain RSRP, RSRQ, and SINR measurements for each cell. Measurement reporting triggers, including different triggering events (outlined below), are defined in Section 5.5.4 of 3GPP TS 38.331 v 15.4.0. Detailed information on measurement reporting is provided in Section 5.5.5 of 3GPP TS 38.331 v 15.4.0.

[0087] Different events A1-A6, B1, and B2 are defined, each including exit and entry conditions, which are associated with triggering time conditions. This allows the UE to make its own measurements and report the results according to the criteria defined for the event. An overview is given below:

[0088] • Event A1 (Service becomes better than threshold)

[0089] o Inequality A1-1 (entry condition): Ms - Hys > Thresh

[0090] o Inequality A1-2 (leave condition): Ms + Hys < Thresh

[0091] • Event A2 (Service becomes worse than threshold)

[0092] o Inequality A2-1 (entry condition): Ms + Hys < Thresh

[0093] o Inequality A2-2 (leave condition): Ms - Hys > Thresh

[0094] • Event A3 (neighbor becomes offset better than SpCell)

[0095] o Inequality A3-1 (entry condition): Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off

[0096] o Inequality A3-2 (leave condition): Mn + Ofn + Ocn + Hys < Mp + Ofp + Ocp + Off

[0097] • Event A4 (neighborhood becomes better than threshold)

[0098] o Inequality A4-1 (entry condition): Mn + Ofn + Ocn - Hys > Thresh

[0099] o Inequality A4-2 (leaving condition): Mn + Ofn + Ocn + Hys < Thresh

[0100] • Event A5 (SpCell becomes worse than threshold 1, while neighbor / SCell becomes better than threshold 2)

[0101] o Inequality A5-1 (entry condition 1): Mp + Hys < Thresh1

[0102] o Inequality A5-2 (enter condition 2): Mn + Ofn + Ocn - Hys > Thresh2

[0103] o Inequality A5-3 (leaving condition 1): Mp - Hys > Thresh1

[0104] o Inequality A5-4 (leaving condition 2): Mn + Ofn + Ocn + Hys < Thresh2

[0105] • Event A6 (neighbor becomes offset better than SCell)

[0106] o Inequality A6-1 (entry condition): Mn + Ocn - Hys > Ms + Ocs + Off

[0107] o Inequality A6-2 (leave condition): Mn + Ocn + Hys < Ms + Ocs + Off

[0108] • Event B1 (Inter-RAT neighbor becomes better than threshold)

[0109] o Inequality B1-1 (entry condition): Mn + Ofn + Ocn - Hys > Thresh

[0110] o Inequality B1-2 (leaving condition): Mn + Ofn + Ocn + Hys < Thresh

[0111] • Event B2 (PCell becomes worse than threshold 1 and inter-RAT neighbors become better than threshold 2)

[0112] o Inequality B2-1 (entry condition 1): Mp + Hys < Thresh1

[0113] o Inequality B2-2 (enter condition 2): Mn + Ofn + Ocn - Hys > Thresh2

[0114] o Inequality B2-3 (leaving condition 1): Mp - Hys > Thresh1

[0115] o Inequality B2-4 (leaving condition 2): Mn + Ofn + Ocn + Hys < Thresh2

[0116] The parameters indicated above are generally as follows:

[0117] • Ms is the measurement result of the serving cell without considering any offset.

[0118] •Mn is the measurement result of the neighboring cells without considering any offset.

[0119] • Ofn is the measurement object specific offset of the reference signal of the neighboring cell (i.e., offsetMO defined in measObjectNR corresponding to the neighboring cell).

[0120] • Ocn is the cell specific offset of the neighbor cell (ie, cellIndividualOffset defined in measObjectNR corresponding to the frequency of the neighbor cell) and is set to zero in case it is not configured for the neighbor cell.

[0121] •Mp is the measurement result of SpCell without considering any offset.

[0122] •Ofp is the measurement object specific offset of the SpCell (ie, offsetMO defined in the measObjectNR corresponding to the SpCell).

[0123] • Ocp is the cell-specific offset of the SpCell (ie, cellIndividualOffset defined in the measObjectNR corresponding to the SpCell), and is set to zero if not configured for the SpCell.

[0124] •Off is the offset parameter of this event (ie, as defined in reportConfigNR for this event, a3-Offset).

[0125] • Hys is the hysteresis parameter for this event (ie, the hysteresis as defined in reportConfigNR for this event).

[0126] •Thresh is the threshold parameter for this event (ie, a1-Threshold as defined in reportConfigNR for this event).

[0127] • Thresh1 is the threshold parameter for this event (ie, a5-Threshold1 as defined in reportConfigNR for this event).

[0128] • Thresh2 is the threshold parameter for this event (ie, a5-Threshold2 as defined in reportConfigNR for this event).

[0129] •Mn, Mp, Ms are expressed in dBm in the case of RSRP, or in dB in the case of RSRQ and RS-SINR.

[0130] •Ofn, Ocn, Ofp, Ocp, Hys, and Off are expressed in dB.

[0131] At least the following mechanisms are based on the measurement results obtained by the UE:

[0132] • Handover decision made by the gNB based on measurement results (received via measurement reports)

[0133] • Triggering of measurement reports

[0134] • Radio Link Failure Indication

[0135] Non-terrestrial network, NTN

[0136] Satellite will continue to be the most efficient means of reaching areas beyond terrestrial coverage, as well as reaching passengers on trains, planes, and ships. Therefore, including satellite as an integral part of the 5G ecosystem adds resilience. The satellite industry participates in various committees, including 3GPP, EC, and ITU-T, to ensure that satellite systems are integrated as an intrinsic part of the 5G ecosystem. The goals are to 1) support highly available and reliable connectivity using satellite for use cases such as ubiquitous coverage, disaster relief, public safety requirements, emergency response, remote sensor connectivity, broadcast services, etc.; 2) support air interfaces with one-way latencies of up to 275 milliseconds when satellite connections are involved; and 3) support seamless mobility between terrestrial and satellite-based networks with widely varying latencies. 3GPP Release 14 has examined the role and benefits of satellite in 5G, resulting in specific requirements to support satellite access.

[0137] Figure 3 The diagram illustrates an exemplary transparent satellite-based NG RAN architecture. According to one exemplary implementation (see TR38.821 v0.3.0, Section 5.1), the satellite payload implements frequency conversion and RF amplifiers in both the uplink and downlink directions. This corresponds to an analog RF repeater. Consequently, the satellite relays the NR-Uu radio interface from the feeder link (between the NTN gateway and the satellite) to the serving 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 the NR-Uu. Figure 4This diagram illustrates an exemplary NG-RAN architecture based on regenerative satellites. According to one exemplary implementation (see Section 5.2 of TR 38.321 v0.3.0), the NG-RAN logical architecture described in TS 38.401 is used as a baseline for NTN scenarios. The satellite payload regenerates the signal received from Earth. The NR-Uu radio interface is the serving link between the UE and the satellite. The satellite radio interface (SRI) is the feeder link between the NTN gateway and the satellite. The SRI (satellite radio interface) is the transport link between the NTN gateway and the satellite.

[0138] Satellite payloads also provide inter-satellite links (ISLs) between satellites. ISLs (inter-satellite links) are transmission links between satellites.

[0139] Discussions are underway to address mobility in NTNs. It is assumed that in NTNs, satellite beams, satellites, or satellite cells do not need to be visible from the UE's perspective. However, this does not preclude the network type (e.g., NTN vs. terrestrial) from being differentiated at the PLMN (Public Land Mobile Network) level. Furthermore, it has been agreed that the Rel-15 design / definition will serve as a baseline for NTNs, meaning that the NR RRM measurement model used in Rel-15 will also serve as a baseline for NTN RRM measurement models.

[0140] The inventors have recognized that for non-terrestrial communications, round-trip delay (RTD) can be significantly greater than that in terrestrial communications. For example, the maximum RTD in NTN is 541.1 milliseconds for GEO (geostationary Earth orbit, e.g., at an altitude of 35,786 kilometers) and 25.76 / 41.76 milliseconds for LEO (low Earth orbit, e.g., at altitudes of 600 / 1,200 kilometers). In terrestrial communications, RTD can be, for example, as long as 5 milliseconds.

[0141] Long RTDs can lead to high handover failure rates because the network makes handover decisions based on outdated measurements and, therefore, may be inaccurate. For example, handover failures can include situations where the handover is too late (other situations include handovers to the wrong cell). Furthermore, long RTDs in message exchanges can cause NTN handovers to take longer, which can result in longer service interruptions for UEs during handovers from one NTN network to another.

[0142] Therefore, the inventors have identified the possibility of improving measurement reporting and / or handover procedures to help avoid one or more of the drawbacks discussed above. The improved measurement reporting and handover procedures can then be applied to scenarios such as NTN scenarios with high latency. However, NTN scenarios are not the only scenarios where the improved procedures can be implemented, and other communication scenarios with high RTD and / or rapidly changing channel environments (such as NR unlicensed scenarios where channel quality varies rapidly) can also benefit from the improved procedures.

[0143] Below, we will describe a UE, base station, and procedures that meet these requirements for a new radio access technology envisioned for 5G mobile communication systems, but also applicable to LTE mobile communication systems. We will also explain different implementations and variants. The following disclosure is facilitated by the discussions and findings described above and may, for example, be based at least in part on them.

[0144] In general, it should be noted that many assumptions have been made herein in order to explain the underlying principles of this disclosure in a clear and understandable manner. However, these assumptions should be understood as examples made herein for illustrative purposes only and should not limit the scope of this disclosure. Those skilled in the art will appreciate that the principles disclosed below and as set forth in the claims can be applied in different scenarios and in ways not explicitly described herein.

[0145] In addition, some of the terms for processes, entities, layers, etc. used below are closely related to terms used in LTE / LTE-A systems or current 3GPP 5G standardization, even though the specific terms used in the context of new radio access technologies for the next 3GPP 5G communication system have not yet been fully determined or may eventually change. As a result, the terms may change in the future without affecting the functionality of the embodiments. Therefore, those skilled in the art will appreciate that, due to the lack of updated or ultimately agreed-upon terms, the embodiments and their scope of protection should not be limited to the specific terms used exemplarily herein, but should be understood more broadly based on the functions and concepts that underlie the functions and principles of the present disclosure.

[0146] For example, a mobile station, mobile node, user terminal, or user equipment (UE) is a physical entity (physical node) within a communication network. A node may have multiple functional entities. A functional entity refers to a software or hardware module that implements a predetermined set of functions and / or provides a predetermined set of functions to other functional entities of the same or another node or network. A node may have one or more interfaces that connect the node to a communication facility or medium through which the node can communicate. Similarly, a network entity may have logical interfaces that connect the functional entity to a communication facility or medium through which it can communicate with other functional entities or communication nodes.

[0147] The term "base station" or "radio base station" here refers to a physical entity within a communications network. Like a mobile station, a base station can have multiple functional entities. A functional entity is a software or hardware module that implements a predetermined set of functions and / or provides a predetermined set of functions to other functional entities in the same or another node or network. The physical entity performs some control tasks for the communications device, including one or more of scheduling and configuration. Note that base station functionality and communications device functionality can also be integrated into a single device. For example, a mobile terminal can also perform base station functions for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used in 5G NR is gNB.

[0148] Figure 5 A general, simplified, and exemplary block diagram of a user equipment (also called a communication device) and a scheduling device (here, illustratively assumed to be located in a base station, such as an eLTE eNB (alternatively referred to as ng-eNB) or a gNB in ​​5G NR) is shown. The UE and the eNB / gNB each communicate with each other via a (radio) physical channel using a transceiver.

[0149] A communications device may include a transceiver and processing circuitry. A transceiver, in turn, may include and / or function as both a receiver and a transmitter. The processing circuitry may be one or more pieces of hardware, such as one or more processors or any LSI. Input / output points (or nodes) exist between the transceiver and the processing circuitry, through which the processing circuitry can control the transceiver—that is, control the receiver and / or transmitter and exchange receive / transmit data. A transceiver, acting as both a transmitter and a receiver, may include an RF (radio frequency) front end, which includes one or more antennas, amplifiers, and RF modulators / demodulators. The processing circuitry may perform control tasks such as controlling the transceiver to transmit user data and control data provided by the processing circuitry and / or receive user data and control data further processed by the processing circuitry. The processing circuitry may also be responsible for performing other processes, such as determinations, decisions, calculations, and measurements. The transmitter may be responsible for performing the transmission process and other related processes. The receiver may be responsible for performing the reception process and other related processes, such as monitoring a channel.

[0150] will be about Figures 6 to 9 Describe the improved measurement and reporting process. Figures 10 to 12 Describe the improved conditional switching process. In addition, Figures 16 to 21 Describe the improved handover communication process. Finally, Figure 22 Describe the improved HARQ process.

[0151] The solutions provided below will be described mainly in conjunction with the 5G NR NTN scenario. As explained above, the NTN (Non-Terrestrial Network) environment involves the UE communicating with the gNB via satellite, where the gNB can be, for example, in a satellite (see Figure 4 ) or in the NTN gateway (see Figure 3 ), but can also be located in other locations such as NTN gateway. Nevertheless, the scope of this embodiment should not be narrowed down to only those NTN scenarios, but also includes other scenarios such as NR unlicensed.

[0152] UE mobility in such scenarios involves the UE moving between the coverage areas of various satellites, such as during flight. UE mobility is typically controlled by the serving gNB but is assisted by the UE, which provides power-related measurements to the serving gNB. The serving gNB can then decide whether handing the UE over to another radio cell is necessary or advantageous and, in the affirmative, initiate the appropriate handover procedure.

[0153] In more detail, it is assumed that the UE (e.g., periodically) performs power-related measurements. For example, the power-related measurements may include RSRP (reference signal received power), RSRQ (reference signal received quality), RSSI (received signal strength indicator), SINR (signal to interference plus noise ratio), or other suitable types of measurements that the UE may use in the described aspects. Typically, the power-related measurements may be performed on reference signals such as the CSI-RS or SSB explained above.

[0154] Whether and how a UE performs power-related measurements may be configured, at least in part, by its serving gNB. This may also involve configuring whether, how, and when the UE should report measurement results to its serving gNB (e.g., to assist with handover decisions).

[0155] An exemplary implementation of how measurement and reporting functionality is configured in a UE has been described above (see the discussion of UE measurements in 5G), and this implementation, for example, involves the definition of one or more of measurement object(s), reporting configurations, and reporting criteria. For example, event-triggered reporting of measurement results can be defined, including reporting-triggering events similar or identical to those explained above (e.g., A1-A6, B1, B2). The triggering events (and, in particular, the conditions for the triggering events) can be handover-related, for example, where a reporting trigger condition is met when a UE hands over from its current serving radio cell to another radio cell, as determined by the serving gNB (e.g., events A2: "Service becomes worse than a threshold"; A3: "Neighbor becomes offset better than SpCell"; A4: "Neighbor becomes better than a threshold").

[0156] Furthermore, it is assumed that the UE may perform measurements on various radio carriers (alternatively referred to as access links or frequency bands) having the same or different radio frequencies. For example, the UE performs measurements on its serving radio carrier (of its serving radio cell controlled by the serving gNB) and one or more neighboring radio carriers (of other radio cells controlled by neighboring gNBs).

[0157] The measurement and reporting configuration is intended to be used by the UE for mobility between non-terrestrial networks and between terrestrial networks. According to the present solution, the measurement and reporting configuration is differentiated depending on whether the mobility is between terrestrial networks or between non-terrestrial networks (see below for more details).

[0158] In the following, it will be assumed that the UE is connected to its serving gNB via a satellite and that the UE performs measurements on its radio carrier to the satellite and on one or more radio carriers to other neighboring satellites. These UE measurements can then be used by the serving gNB serving the UE to control the UE's mobility, including whether to handover the UE from the serving satellite to another satellite. The handover procedure initiated by the serving gNB can be, for example, a handover procedure known from the prior art or can be an improved conditional handover procedure discussed in more detail later (see Figure 10-12 ), where the final decision on whether to switch is made by the UE.

[0159] Figure 6 The simplified and exemplary UE structure of the present solution according to the improved measurement and reporting process is illustrated and can be combined with the above Figure 5 The various structural elements of the UE shown in the figures may be interconnected, for example, using corresponding input / output nodes (not shown), for example, to exchange control and user data and other signals. Although not shown for illustrative purposes, the UE may include additional structural elements.

[0160] It is thus apparent that the UE may comprise a measurement circuit, a measurement result generating circuit, a report adjusting circuit and a measurement report transmitter as will be explained below.

[0161] In the described case, as will be apparent from the following disclosure, the processing circuitry may therefore exemplarily be configured to at least partially perform one or more of: performing measurements and thereby generating measurement results, determining whether to adjust at least one of the measurement results and the report triggering condition, adjusting at least one of the measurement results and the report triggering condition, and determining whether the report triggering condition is met.

[0162] The transmitter may in turn be configured to be capable of at least partially performing the sending of a measurement report comprising the measurement results.

[0163] Figure 7FIG2 is a sequence diagram illustrating exemplary UE behavior according to the improved measurement and reporting procedure. As can be seen, the UE performs power-related measurements on at least one radio carrier and generates measurement results therefrom. The power-related measurements are performed, for example, on one or more of the UE's serving radio carriers (in this particular exemplary scenario, the radio carrier connecting the UE to the satellite), radio carriers connecting the UE to neighboring satellites, and radio carriers connecting the UE to terrestrial networks (such as 5G or LTE antennas).

[0164] As described above, the UE reports measurement results to its serving gNB, for example, depending on whether certain reporting trigger conditions are met. When one or more reporting trigger conditions are met, the UE compiles a measurement report using the obtained measurement results and sends the measurement report to its serving gNB.

[0165] According to this improved measurement and reporting procedure, before determining whether the reporting triggering conditions are met, the UE determines whether to adjust the measurement reporting procedure to trigger measurement report transmission earlier than would otherwise be the case. This additional step of adjusting the measurement reporting procedure is performed to account for the fact that inter-satellite mobility differs from mobility between terrestrial networks, for example, due to the long round-trip delays involved in communications between the UE and satellites. As previously explained, the inventors have identified the drawbacks associated with long round-trip delays for measurement procedures, and therefore also for handover procedures. By triggering measurement reporting earlier, failures caused by handovers occurring too late can sometimes be avoided or mitigated. Accordingly, when the measured radio carriers and the measurement results to be reported involve long round-trip delays (e.g., exceeding 10 ms for non-terrestrial networks), the UE can make the additional decision to adjust the measurement reporting procedure. Alternatively, the UE determines whether to adjust the measurement reporting procedure based on instructions from the serving gNB. One option is for the serving gNB to provide this instruction to the UE via the measurement object (MO) configuration for the UE measurements.

[0166] continue Figure 7 The illustrated sequence of UE behaviors assumes that additional adjustments will be performed by the UE. As previously described, the adjustments cause the measurement report to be triggered earlier than would have been the case without the adjustments. In other words, the report triggering condition is met earlier, resulting in the measurement report being sent to the serving base station earlier in time. This earlier measurement report can be achieved in a variety of ways, such as by adjusting measurement results and / or report triggering conditions, as will be explained in more detail and illustrated later.

[0167] After the adjustment, the UE monitors whether the measurement results meet one of the reporting trigger conditions (the measurement results and / or reporting trigger conditions have been adjusted). Subsequently, if measurement reporting is triggered, the UE continues to generate and send a measurement report to the serving gNB that includes some or all of the generated measurement results. For example, the measurement report may include the unadjusted measurement results, thereby providing the gNB with accurate measurement results. Alternatively, the UE may include the adjusted measurement results in the measurement report to be sent to the serving gNB, instead of or in addition to the unadjusted measurement results. This allows the serving gNB to also obtain previous measurement results that have not yet been sent to the serving gNB, providing the serving gNB with more information to determine whether to initiate a handover procedure.

[0168] Figure 8 The figure shows an exemplary gNB behavior related to the improved measurement and reporting process just described. In the exemplary gNB behavior, the gNB is not only responsible for configuring the measurement and reporting configuration for the UE, but also for configuring whether and how to adjust the triggering of the measurement report for the UE to achieve the above-mentioned Figure 7 Earlier report of the measurements described.

[0169] The gNB receives a measurement report with the measurement results from the UE and, based on this, can decide whether to initiate a handover procedure for the UE to another radio cell (e.g., another satellite). In the affirmative, the gNB sends a corresponding handover command to the UE.

[0170] The advantage of the process discussed above is that late handover failures can be avoided or mitigated because the additional adjustment of the measurement reports is triggered earlier in time, allowing the measurement reports to be sent to the serving gNB earlier, allowing the serving gNB to make a handover decision earlier. Furthermore, the adjustment scheme is simple because it does not rely on other information such as UE location or satellite position (satellite ephemeris).

[0171] exist Figure 9 An exemplary and simplified sequence of the improved measurement and reporting procedure is shown in FIG. As shown, the UE's serving gNB provides the UE with a measurement configuration so that the UE performs measurements on its serving radio carrier and other neighboring radio carriers (in Figure 9 For ease of illustration, only one adjacent radio carrier is shown. The additional adjustment of the measurement reporting process is exemplarily illustrated as occurring after the power measurement, but may also occur in parallel or before. Figure 9 The sequence ends with the transmission of the measurement report to the serving gNB.

[0172] Below, we describe several different example implementations of how to adjust a measurement report so that it is triggered earlier than without the adjustment. The adjustment can be applied to the measurement result before determining whether a report triggering condition is met, or the adjustment can be applied to the report triggering condition. Depending on the measurement result and / or the report triggering condition, the adjustment can be different to achieve earlier triggering.

[0173] According to one exemplary implementation, one or more appropriate power offsets may be introduced to enable the reporting trigger condition to be met earlier. The power offset may be applied to the measurement result, or the power offset may be applied to the reporting trigger condition. Similarly, the amount of the offset and whether it is negative or positive may depend on the measurement result and / or the reporting trigger condition.

[0174] For illustrative reasons, it is exemplarily assumed that some or all of the reporting trigger conditions already defined for 5G (see the explanation of the above aspects) are used by the UE to determine whether to send measurement results to its serving gNB.

[0175] The entry condition for event A1 (service becomes better than threshold) to start sending measurement results to the serving gNB is

[0176] Ms - Hys > Thresh

[0177] When applying adjustments to the report trigger condition, this can be achieved by incorporating an offset (exemplarily called NTN-offset) as follows:

[0178] Ms + NTN-offset - Hys > Thresh

[0179] From the above, it is clear that by introducing a positive offset, the threshold (“Thresh”) can be reached earlier.

[0180] The entry condition for event A2 (service becomes worse than the threshold) is

[0181] Ms + Hys < Thresh

[0182] When adjusting this report trigger, this can be achieved by incorporating the offset as follows:

[0183] Ms - NTN-offset + Hys < Thresh

[0184] It is obvious from the above adjusted trigger conditions that by introducing a negative offset, the threshold is reached earlier (<) than without.

[0185] The entry condition for event A3 (neighbor becomes offset better than SpCell) is

[0186] Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off

[0187] When adjusting this report trigger, this can be achieved by incorporating one or two offsets, as shown below:

[0188] Mn + NTN-neighbor-offset + Ofn + Ocn – Hys > Mp - NTN-serving-offset + Ofp + Ocp + Off

[0189] According to one specific implementation, an offset is defined for the triggering condition portion that references the serving cell (exemplarily referred to as NTN-serving-offset), and another offset is defined for the triggering condition portion that references the neighboring cell (exemplarily referred to as NTN-neighbor-offset). Accordingly, when the same triggering condition is determined for the serving cell and another neighboring cell, the same NTN-serving-offset and the same NTN-neighbor-offset can be reused. This simplifies tuning because, for each reporting triggering condition, at most two different offsets are defined: one reference to the serving cell and one reference to the neighboring cell.

[0190] The entry condition for event A4 (neighborhood becomes better than threshold) is

[0191] Mn + Ofn + Ocn - Hys > Thresh

[0192] When adjusting this report trigger, this can be achieved by incorporating the offset as follows:

[0193] Mn + NTN-offset + Ofn + Ocn - Hys > Thresh

[0194] It is clear from this that by forcing the addition of the left measurement result of the neighboring cell, the threshold is reached earlier.

[0195] In summary, adjusting the measurement report trigger depends on a specific trigger condition, provided that the condition is met in advance.

[0196] The specific value may be configured by the network (e.g. gNB), for example, together with the rest of the UE measurement configuration (e.g. measurement objects, reporting criteria, etc.).

[0197] When the NTN-specific offset is set to 0, the reporting trigger conditions also apply to other scenarios.

[0198] Different offset values ​​may be determined by the gNB in ​​different ways to balance the impact of the offset on various triggering conditions, e.g., to avoid or minimize other handover failures (e.g., premature handover). According to one exemplary implementation, the gNB determines the offset value based on the round-trip delay experienced by the UE with the serving gNB.

[0199] Furthermore, the gNB may also change adjustments (e.g., offsets) during operation to adapt to the improved measurement reporting process, for example, when it is determined that excessive handover failures or excessive measurement reports are triggered. For example, reconfiguration or cancellation of measurement reporting adjustments may be performed using a message from the RRC protocol (e.g., an RRC reconfiguration message).

[0200] According to another exemplary implementation of how measurement reporting adjustments are implemented, instead of using network-configured adjustments, adjustments are determined by the UE itself. The aforementioned offsets (e.g., NTN-offset, NTN-serving-offset, and NTN-neighbor-offset) are determined by the UE. For example, the offset is determined for each measurement result by determining the difference between the current measurement result and the previously determined measurement result (this difference is exemplarily referred to as Δmeas). In other words, the change in the measurement is doubled, thereby triggering a measurement report earlier than would be the case without the offset.

[0201] For example, again for illustration purposes, the 5G measurement events A1, A2, and A3 discussed above.

[0202] The entry condition for sending measurement results to the serving gNB for event A1 (service becomes better than the threshold) is

[0203] Ms - Hys > Thresh

[0204] When applying adjustments to this report trigger condition, this is achieved by incorporating the measurement difference Δmeas as follows:

[0205] Ms + Δmeas - Hys > Thresh

[0206] It is obvious from the above that by amplifying the growth of the measurement result, the threshold value ("Thresh") is reached earlier.

[0207] The entry condition for event A2 (service becomes worse than the threshold) is

[0208] Ms + Hys < Thresh

[0209] When applying adjustments to this report trigger condition, this can be achieved by incorporating the measurement difference Δmeas as follows:

[0210] Ms + Δmeas + Hys < Thresh

[0211] It is obvious from the trigger conditions adjusted above that by increasing the drop in the measurement result, the threshold is reached earlier (<) than without.

[0212] The entry condition for event A3 (neighbor becomes better than SpCell) is

[0213] Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off

[0214] When applying adjustments to this report trigger condition, this can be achieved by incorporating the measurement difference Δmeas as follows:

[0215] Mn + Δmeas_n + Ofn + Ocn - Hys > Mp + Δmeas_p + Ofp + Ocp + Off

[0216] It is clear from this that by introducing the offset Δmeas for serving adjacent measurements, the changes (decreases or increases in the measured power) are artificially amplified. As a result, the trigger condition is met earlier than without the offset.

[0217] Calculating the offset from the measurement difference, rather than following a network-configured offset value, avoids the need for the gNB to configure the offset for the UE and allows the offset to be adjusted to maintain good handover performance. Additionally, the adjustment can be more precise because 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 measurement reports are adjusted.

[0218] As discussed above, after receiving the measurement report with the measurement results, the gNB will ultimately decide to initiate a handover procedure with the UE. Alternatively, the handover procedure can be a standard handover procedure, as defined in, for example, the 3GPP standard (see TS 38.331 v15.4.0).

[0219] On the other hand, in the following, reference will be made to Figure 10-12This document describes an improved conditional handover procedure that can be used by multiple gNBs and UEs. Conditional handover typically transfers the final decision on whether to perform a handover from the serving gNB to the UE. This is achieved, for example, by additionally providing conditions to the UE (e.g., in a handover command message), which the UE can use to determine whether and when to perform the indicated handover. Conditional handover offers the advantage of reducing handover latency, as the handover can be prepared by the serving gNB and then executed promptly by the UE when required. When the handover is executed, the need to send additional measurement reports to the serving gNB to trigger the handover procedure is avoided. However, the handover is prepared in the potential target cell, requiring the target gNB to reserve resources (e.g., dedicated PRACH resources for random access, C-RNT) for the UE for an extended period of time, which may not be used even at the end (e.g., if the UE does not perform the handover).

[0220] Combine Figure 10-12 The improved conditional handover procedure discussed attempts to alleviate these problems and revolves around the idea of ​​additionally providing the UE with one or more handover rejection conditions, which the UE monitors in order to abort a possible handover early, rather than waiting (e.g., for a timeout). This will be explained in more detail below. Figure 10 The figure illustrates an exemplary message exchange between a UE, a serving gNB, and a neighboring gNB that is a possible target for handover. Figure 11 is an exemplary sequence diagram of UE behavior, and Figure 12 An exemplary sequence diagram illustrating the behavior of a gNB acting as a serving gNB for a UE.

[0221] As mentioned before, the handover decision is usually made by the serving gNB and assisted by the UE by providing measurement reports on the serving radio carrier and possibly other neighboring radio carriers. Figure 10 The first message shown in the message exchange diagram is a measurement report sent by the UE to its serving gNB. Figures 6 to 9 The improved measurement reporting procedure discussed is used to generate the measurement report (e.g., the measurement report is triggered earlier due to the additional adjustment of the measurement reporting trigger). On the other hand, the measurement report may also be a "normal" measurement report, which is triggered without adjusting the triggering of the measurement reporting function of the UE.

[0222] Based on the received measurement report (and the measurement results included therein), the serving gNB can decide that handover to another radio cell (e.g. another satellite) may be beneficial for the UE and thus start an appropriate handover procedure with the target gNB (neighboring gNB) and the UE.

[0223] Here we assume that the serving gNB decides to perform conditional handover for the UE. The decision of the gNB to support conditional handover can be based on various criteria. For example, the serving gNB can combine the above Figures 6 to 10 Conditional handover decisions are made when the UE is configured before performing the improved measurement and reporting procedure as explained above. More specifically, the serving gNB typically configures the UE on how to perform power-related measurements and report the measurement results. This may also include whether and how the UE adjusts measurement reporting triggers (e.g., NTN-related offset values). However, the early reporting of measurement results enabled by the improved measurement and reporting procedure discussed above could theoretically lead to an increase in premature handovers. This disadvantage can be mitigated by implementing conditional handover decisions, as the UE can then perform a directed handover to the target cell when the handover acceptance conditions are met and not too early.

[0224] Additionally or alternatively, the serving gNB may also decide to perform a conditional handover instead of a normal handover based on the round-trip delay incurred in communicating with the UE. For example, if the round-trip delay exceeds a certain threshold (e.g., 10ms), it may be beneficial to leave the final handover decision to the UE in order to avoid erroneous handover decisions due to long round-trip delays.

[0225] A further additional or alternative criterion for deciding to make a handover conditional is the handover failure rate. For example, assume that the serving gNB has previously performed unconditional handover procedures with the UE in its radio cell. However, if the handover failure rate (e.g., premature handover failure rate) is too high, the serving gNB may determine that making the handover conditional with conditions that are suitable for the UE's final decision is beneficial and can reduce the handover failure rate.

[0226] Further additional or alternative criteria for deciding to make a handover conditional may be based on satellite and / or UE location. For example, even if the serving gNB would determine from measurement reports that a conditional handover is not required, the gNB may still trigger a conditional handover if the satellite location and / or UE location indicate that the UE is located near a cell edge.

[0227] Reference again Figure 10 , assuming that the serving gNB decides to perform conditional handover, for example based on one or more of the criteria mentioned above. The serving gNB prepares for handover in the target cell (see Figure 10 The handover request and handover confirmation in the message are received) and the handover command message is sent to the UE. Figure 10As exemplarily shown in FIG, a handover procedure may be initiated by, for example, requesting a handover and waiting for a handover confirmation from a neighboring cell (e.g., to determine that the neighboring gNB is capable of accepting another UE and to allow the neighboring gNB to reserve resources for the UE to be handed over). Upon receiving the handover confirmation from the neighboring gNB, the serving gNB proceeds with the handover procedure and sends a corresponding handover command message to the UE.

[0228] As usual, the Handover Command message may include an identifier and additional information to identify and connect to the target cell. Furthermore, the Handover Command message includes one or more Handover Accept conditions and Handover Reject conditions. The UE checks the Handover Accept conditions to determine whether and when to perform the handover. If the Handover Accept conditions are met, the UE performs the handover. On the other hand, the UE checks the Handover Reject conditions to determine whether to reject the handover instruction. If the Handover Reject conditions are met, the UE immediately rejects the handover and may provide corresponding information regarding the rejection to its serving gNB (which the serving gNB may use to instruct the target gNB to release any resources previously reserved for the UE handover). Figure 10 Both a handover accept case and a handover reject case are illustrated.

[0229] Handover acceptance and rejection conditions can be determined by the serving gNB depending on the specific handover scenario. According to an optional implementation, the handover acceptance and rejection conditions can be mutually dependent, for example, making them exclusive and allowing the UE to explicitly decide whether to accept or reject the handover. This can be advantageous in forcing an immediate handover decision and, therefore, minimizing the target cell's resource reservation time. Furthermore, assuming that the UE and serving gNB interrupt communication during the handover, forcing the UE to make an immediate decision on the indicated handover can also help minimize communication interruption time, as the UE and serving gNB can immediately resume UL / DL communication. On the other hand, the handover acceptance and rejection conditions need not be completely complementary. Thus, for example, there can be measurement situations where neither the handover acceptance nor the handover rejection conditions are met at the same time. There can be a gap between the acceptance and rejection conditions.

[0230] For example, a possible handover reject condition could be "if the serving cell is more than x dB better than the target cell for at least y ms", where the parameter values ​​x and y can be set appropriately by the gNB (e.g., x could be 5 dB and y could be 50 ms). A handover accept condition could be, for example, "if the target cell is more than x dB better than the serving cell for at least y ms", where the parameter values ​​x and y can be set appropriately by the gNB (e.g., x could be 8 dB and y could be 30 ms).

[0231] Information about the rejection of handover may be sent to the UE's serving gNB in ​​several different ways (which may depend, for example, on whether uplink data is still to be sent).

[0232] According to one exemplary solution, in the absence of UL traffic, handover rejection information can be sent as part of an RRC (Radio Resource Control) message, such as the RRCReconficuationComplete message or another, potentially new, RRC message. Additionally or alternatively, the handover rejection information can be provided implicitly to the serving gNB, for example, by sending a measurement report to the serving gNB in ​​response to the conditional handover command message. The serving gNB can implicitly infer from this that the UE rejected the handover.

[0233] According to other exemplary solutions, in the presence of UL traffic, the handover rejection information may be included in a MAC (Media Access Control) Control Element (CE) together with the UL traffic data.

[0234] In any case, the serving gNB is therefore provided with information that the handover was rejected by the UE.

[0235] In an optional implementation, when a handover is rejected, the UE can be configured to refrain from sending additional measurement reports to the serving gNB for a specified period of time. This has the advantage that no additional (conditional) handover is triggered shortly after the handover is rejected. For example, the UE can use an inhibit timer that starts when the handover is rejected. This timer can be configured by the network, for example, by the serving gNB when the measurement and reporting functionality is configured in the UE.

[0236] According to another optional implementation, a mechanism is incorporated to extend the resource reservation at the target radio cell, for example, to avoid premature cancellation of the resource reservation in the target cell. More specifically, the resource reservation in the target cell may be maintained by the target gNB for only a specific period of time (e.g., controlled by a suitable timer, such as T304 in some 5G implementations), which may however expire before the UE can make a decision on whether to accept or reject the handover. This problem may be exacerbated in scenarios involving long round-trip delays and when the handover acceptance and rejection conditions are defined in such a way that the UE does not immediately decide whether to reject or accept the handover.

[0237] In such scenarios, when neither the handover accept condition nor the handover reject condition is met, it is beneficial for the UE to instruct the serving gNB to extend the resource reservation in the target cell. Figure 11As shown, the UE may optionally check whether the corresponding resource reservation timer has expired. If so, handover to the target gNB is no longer possible as expected, and the UE is connected to its old serving gNB or another gNB (e.g., this involves performing an RRC connection reestablishment). This instruction may be sent similarly or identically to the discussion on how to convey rejection information to the serving gNB (see the corresponding description for more details). When the serving gNB receives such a resource reservation extension request, it may in turn contact the target gNB to extend the resource reservation. When the serving gNB does not receive such a resource reservation extension request, it may optionally assume that the handover is being performed as expected (see Figure 12 ).

[0238] According to a further solution, the handover process is further improved by allowing the UE to continue communicating with its serving gNB while simultaneously performing a handover procedure with the target cell. In prior art solutions, as part of the handover execution, UL / DL communications are interrupted when the UE initiates a random access procedure with the target cell. However, because of the interruption in UL / DL communications, this results in service interruption until the UE connects to a new target cell (resuming UL / DL communications with the target gNB) or until the UE reconnects to the serving gNB (if the handover is unsuccessful). While service interruption may not be a problem for mobility between networks with low round-trip delay (such as terrestrial networks), it is a problem for mobility with high round-trip delay (such as for UEs moving between different NTN networks, such as satellite). Accordingly, reducing service interruption caused by the UE ceasing UL / DL communications until it connects to the target gNB or reconnects to its serving gNB again if the handover fails is of concern.

[0239] This can be achieved by allowing the UE to continue communicating 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 the handover command and initiates a random access procedure to connect to the target gNB, but continues DL / UL transmissions with the serving gNB. This applies to the serving gNB as well, which continues to send DL data and receive UL data as before the decision to hand over the UE. However, in this case, the UE must perform UL / DL communications in parallel with the random access procedure, and it is beneficial to coordinate uplink and downlink transmissions to and from the serving gNB and those for random access to and from the target gNB. This can be achieved by referring to Figures 16 to 21 The following solution is described to achieve this.

[0240] In short, the UE operates a Discontinuous Reception (DRX) function (more details below), which defines DRX active periods during which the UE can actively communicate and additionally provides the UE with power-saving opportunities during so-called DRX off periods. According to one exemplary solution, the UE continues to communicate with the serving base station during the DRX active periods, while using the DRX off periods to perform a random access procedure with the target cell. This allows the UE to communicate with both the serving and target base stations concurrently. The UE can therefore terminate communications with the serving base station after establishing a connection with the target gNB. This results in a make-before-break handover, minimizing service interruption due to the handover.

[0241] In the following, reference Figures 13 to 15 For more details about the random access procedure and DRX functionality, refer to Figures 16 to 21 Different implementations of the improved handover communication procedure are explained in more detail. A specific and exemplary random access procedure that can be used for this solution is explained below. Similar to LTE, 5G NR provides a RACH (Random Access Channel) procedure (or simply a random access procedure) (see 3GPP TS 38.321, v15.3.0 Section 5.1). For example, a UE can use the RACH procedure to access a cell it has found. The RACH procedure can also be used in other contexts within NR, such as:

[0242] • For handover, when synchronization with a new cell is to be established;

[0243] • To re-establish uplink synchronization with the current cell in case of loss of synchronization due to the absence of any uplink transmission from the device for too long;

[0244] • To request uplink scheduling when no dedicated scheduling request resources are configured for the device.

[0245] The following will refer to Figure 13 and 14 The RACH procedure is described in more detail. If the mobile terminal's uplink transmission is time-synchronized, the mobile terminal can be scheduled for uplink transmission. The Random Access Channel (RACH) procedure acts as an interface between an unsynchronized mobile terminal (UE) and the orthogonal transmission of uplink radio access. For example, random access is used to achieve uplink time synchronization for a user equipment that has not yet acquired or has lost its uplink synchronization. Once the user equipment has achieved uplink synchronization, the base station can schedule uplink transmission resources for it. A scenario related to random access is when a user equipment in the RRC_CONNECTED state switches from its current serving cell to a new target cell, performing a random access procedure to facilitate uplink time synchronization in the target cell.

[0246] There may be two types of random access procedures where access is allowed either contention-based (ie implying an inherent risk of collision) or contention-free (non-contention-based).

[0247] In the following, reference will be made to Figure 13 The contention-based random access procedure is described in more detail. The procedure consists of four steps. First, the user equipment transmits a random access preamble (i.e., message 1 of the RACH procedure) to the base station on the physical random access channel (PRACH). After the base station detects the RACH preamble, it sends a random access response (RAR) message (message 2 of the RACH procedure) on the PDSCH (Physical Downlink Shared Channel) addressed with the (random access) RA-RNTI on the PDCCH. This message identifies the frequency and time slot in which the preamble was detected. If multiple user equipment transmit the same RACH preamble on the same PRACH resource, also known as a collision, they will all receive the same random access response message. The RAR message conveys 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 assignment (grant) for the first scheduled transmission, and the assignment of a temporary cell radio network temporary identifier (T-CRNTI). The base station uses this T-CRNTI to address at least one mobile station whose RACH preamble was detected until the end of the RACH procedure, since the base station does not yet know the "real" identity of the mobile station.

[0248] The user equipment monitors the PDCCH for random access response messages within a given time window (e.g., referred to as the RAR receive window), which may be configured by the base station. In response to the RAR message received from the base station, the user equipment sends a first scheduled uplink transmission on the radio resources assigned by the grant within the random access response. This scheduled uplink transmission carries the actual random access procedure message, such as an RRC connection request, an RRC recovery request, or a buffer status report.

[0249] If a preamble collision occurs in the first message of the RACH procedure—that is, multiple user equipment transmit the same preamble on the same PRACH resource—the collided user equipment will receive the same T-CRNTI in the random access response and will collide on the same uplink resource when transmitting their scheduled transmissions in the third step of the RACH procedure. Even if the scheduled transmission from one user equipment is successfully decoded by the base station, contention for the other user equipment remains unresolved. To resolve this type of contention, the base station sends a contention resolution message (fourth message) addressed to the C-RNTI or Temporary C-RNTI. This concludes the process.

[0250] Figure 14 This figure illustrates a simplified contention-free random access procedure compared to a contention-based random access procedure. In the first step, the base station provides a preamble to the user equipment for random access, eliminating the risk of collision (i.e., multiple user equipment transmitting the same preamble). Accordingly, the user equipment then transmits the preamble signaled by the base station in the uplink on PRACH resources. Because contention-free random access prevents multiple UEs from transmitting the same preamble simultaneously, the contention-free random access procedure essentially concludes upon successful receipt of a random access response from the UE.

[0251] 3GPP is also studying a two-step RACH procedure for 5G NR, in which Message 1, corresponding to Messages 1 and 3 in the four-step RACH procedure, is first sent. The gNB then responds with Message 2, corresponding to Messages 2 and 4 in the LTE RACH procedure. Due to the reduced message exchange, latency can be reduced compared to the four-step RACH procedure. The radio resources used for this message are optionally configured by the network.

[0252] After introducing the example random access procedure, a specific example DRX functionality that can be assumed for this solution will be described below. Power saving is an important issue in mobile communications. To reduce battery consumption in UEs, a mechanism is used to minimize the time the UE spends monitoring the PDCCH, which is called discontinuous reception (DRX) functionality.

[0253] DRX functionality can be configured for RRC_IDLE. DRX functionality can also be configured for "RRC_CONNECTED" UEs so that they do not always need to monitor the downlink channel for downlink control information (or simply put: the UE monitors the PDCCH). (See technical standard TS 36.321, version 15.2.0, chapter 5.7).

[0254] The following parameters may be used to define the DRX UE behavior; namely the OnDuration period during which the mobile node is active (eg, in DRX Active Time), and the period during which the mobile node is in DRX (eg, not in DRX Active Time, in DRX Off Time).

[0255] OnDuration: The duration that a user equipment receives and monitors the PDCCH in a downlink subframe, more specifically a subframe with a PDCCH (also called a PDCCH subframe), after waking up from DRX. It should be noted that throughout this disclosure, the term "PDCCH" refers to the PDCCH, EPDCCH (in a subframe when configured), or, for relay nodes configured with R-PDCCH and not paused, the R-PDCCH. If the user equipment successfully decodes the PDCCH, it remains awake / active and starts the inactivity timer; [1-200 subframes; 16 steps: 1-6, 10-60, 80, 100, 200];

[0256] - DRX Inactivity Timer: The duration that the UE waits for a successful PDCCH decode in a downlink subframe, starting from the last successful PDCCH decode. If the UE fails to decode a PDCCH during this period, it re-enters DRX. The UE should restart the inactivity timer only for the first transmission (i.e., not for retransmissions) after a single successful PDCCH decode. [1-2560 subframes; 22 steps, 10 spares: 1-6, 8, 10-60, 80, 100-300, 500, 750, 1280, 1920, 2560]

[0257] - DRX Retransmission Timer: Specifies the number of consecutive PDCCH subframes that the UE expects downlink retransmissions after the first available retransmission time. [1-33 subframes; 8 steps: 1, 2, 4, 6, 8, 16, 24, 33];

[0258] - DRX Short Cycle: Specifies the periodic repetition of the on-duration followed by a possible inactive period of the short DRX cycle. This parameter is optional. [2-640 subframes; 16 steps: 2, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640];

[0259] - DRX Short Cycle Timer: Specifies the number of consecutive subframes for which the UE follows the short DRX cycle after the DRX Inactivity Timer expires. This parameter is optional. [1-16 subframes];

[0260] - Long DRX cycle start offset: specifies the periodic repetition of the OnDuration following a possible inactive period of the DRX long cycle, and the offset in subframes when the OnDuration starts (determined by the formula defined in TS 36.321 section 5.7); [Cycle length 10-2560 subframes; 16 steps: 10, 20, 30, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280, 2048, 2560; the offset is an integer between [0 - subframe length of the selected cycle].

[0261] The total duration that a UE is awake is called the "Active Time" or DRX Active Time. This Active Time includes, for example, the OnDuration 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 downlink retransmissions after one HARQ RTT. Similarly, for the uplink, the UE is awake (i.e., during the DRX Active Time) in subframes where it can receive an uplink retransmission grant (i.e., 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 OnDuration, and the maximum value is variable depending on, for example, PDCCH activity.

[0262] A "DRX period" or "DRX Off period" is the duration of a downlink subframe during which the UE can skip reception of downlink channels for power conservation purposes (i.e., it does not need to monitor the downlink channels). DRX operation gives the mobile terminal the opportunity to repeatedly deactivate its radio circuitry (according to the currently active DRX cycle) in order to save power. Whether the UE actually remains in DRX (i.e., inactive) during a DRX period can be determined by the UE; for example, the UE typically performs inter-frequency measurements that cannot be performed during the On Duration and therefore need to be performed at some other time (e.g., during the DRX Off period).

[0263] Parameterizing the DRX cycle involves a trade-off between power conservation and latency. To satisfy these conflicting requirements, each UE can be configured with two DRX cycles—a short cycle and a long cycle. The short DRX cycle is optional, meaning only the long DRX cycle can be used. Transitions between the short DRX cycle, the long DRX cycle, and continuous reception are controlled by timers or explicit commands from the eNodeB.

[0264] Figure 15An example of DRX operation is disclosed. A UE checks for scheduling messages (also called downlink / uplink assignments; for example, indicated by its cell radio network temporary identity (C-RNTI) on the PDCCH) during an "On Duration" period, which is the same for both long and short DRX cycles. Upon receiving a scheduling message during the "On Duration" period, the UE starts an "Inactivity Timer" and continuously monitors the PDCCH in each subframe while the Inactivity Timer is running. During this period, the UE is considered to be in "continuous reception mode." Whenever a scheduling message is received while the Inactivity Timer is running, the UE restarts the Inactivity Timer, and upon its expiration, the UE enters a short DRX cycle and starts a "Short DRX Cycle Timer" (assuming a short DRX cycle is configured). Upon expiration of the Short DRX Cycle Timer, the UE enters a long DRX cycle. A short DRX cycle can also be initiated via a DRX MAC control element, which the eNB can send at any time to immediately place the UE into a DRX cycle, either a short DRX cycle (if configured) or a long DRX cycle (if not configured).

[0265] The basic concept of DRX explained above for LTE also applies to the new 5G NR, but with some differences (see 3GPP TS 38.321 v15.2.1 section 5.7).

[0266] It is clear from this that 5G NR’s DRX is also based on long and short DRX cycles, and the transition between them based on the short DRX cycle timer defines the on-duration at the start of the DRX cycle, and the DRX inactivity timer determines the duration of continued reception after receiving the PDCCH, after which the UE enters the sleep state. Therefore, conceptually, the working principle of the 5G-NR DRX mechanism is as follows: Figure 15 shown.

[0267] refer to Figure 16 , an improved handover communication solution is proposed, which allows the UE to access the target cell and continue to communicate with the serving cell in parallel. According to a simplified and exemplary implementation, in Figure 17 The corresponding UE behavior is shown in .

[0268] If the UE is eventually handed over from its serving gNB to another neighboring gNB. Figure 16 Obviously, it is assumed that the UE is communicating with the serving gNB in ​​UL / DL. It is also assumed that the UE sends a measurement report to the serving gNB. The measurement report can be, for example, based on the above combined Figure 6-9The improved measurement and reporting solution discussed above is sent, but may also be sent by the UE as is known in the art. In other words, the following improved handover solution may optionally be combined with the improved measurement and reporting procedure discussed above, but may also be used alone.

[0269] Although not illustrated, it is assumed that the UE remains in communication with the serving gNB during handover initiation (e.g., when the serving gNB makes a handover decision, sends a handover request, and receives a handover confirmation).

[0270] Assume that the serving gNB decides to support handover and therefore initiates a handover procedure with the neighboring gNB that is the target of the UE handover by sending a Handover Request message and in turn receiving a Handover Acknowledgement message. The serving gNB then sends a Handover Command message to the UE. The Handover Command can be an unconditional Handover Command that forces the UE to perform the handover. Depending on the solution, the Handover Command message can alternatively be conditional, for example including at least a Handover Acceptance Condition for the UE to ultimately decide whether and when to perform the handover based on the Handover Acceptance Condition. In addition, the Handover Command message can optionally include the following in conjunction with the above: Figure 10-12 In other words, the improved handover communication solution proposed in this article can be but not necessarily combined with the improved conditional handover solution.

[0271] Furthermore, it is assumed that upon receiving the (conditional) handover command, the UE starts connecting to the target gNB by performing a random access procedure between the UE and the target neighboring gNB. Simultaneously, the UE is expected to continue communicating with the serving gNB. This parallel operation is performed in Figure 16 are illustrated as corresponding boxes, which then include arrows indicating specific messages exchanged between the entities.

[0272] UE and serving gNB are operating DRX function, for example in combination with the above Figure 15 In order to make Figure 16 It is clear that the DRX off period and the DRX active period are shown only for the UE communicating with the serving gNB and the target gNB in ​​parallel, although it should be understood that the DRX functionality is also followed by the UE and the serving gNB when the UE and the serving gNB communicate with each other.

[0273] The DRX functionality alternates between DRX active periods, during which the UE can communicate with the gNB (UL and / or DL), and DRX off periods, during which the UE has an opportunity to save power (e.g., by neither transmitting nor monitoring data on channels used to receive data). Figure 16As shown in Figure 1, the UE communicates with the serving gNB during the DRX active period and with the target gNB during the DRX off period. This involves sending messages 1 and 3 of the random access procedure to the neighboring gNB during the DRX off period, while simultaneously receiving messages 2 and 4 of the random access procedure from the neighboring gNB during the DRX off period. As a result, the serving gNB and the UE can continue to have DL / UL transmissions without colliding with the random access procedure being performed between the UE and the target gNB.

[0274] There are several implementation options for how a UE can perform a random access procedure during a DRX off period. In short, the DRX functionality performed in the serving radio cell is coordinated with the PRACH resources to be used by the UE in the target radio cell. For example, the target gNB has uplink resources reserved for the random access procedure and can reserve dedicated resources within these PRACH resources for the UE being handed over. These dedicated PRACH resources can then be used by the UE and the target gNB to exchange messages for the random access procedure.

[0275] According to an exemplary implementation ( Figure 18 and 20 As shown in , the serving gNB sends information about the UE's DRX configuration to the target gNB. The target gNB can then adapt the PRACH resources used by the UE for the random access procedure to the DRX configuration received from the serving gNB so that the PRACH resources to be used by the UE fall into the DRX off period. This information about the UE's DRX configuration can be sent, for example, with a handover request message (see Figure 16 ), or sent in a message separate from the handover request message. Figure 20 is illustrated to cover both variants. In addition, information about the adapted PRACH resources will be provided to the UE. According to one implementation, the PRACH resource information is first (e.g., Figure 20 The HANDOVER CONFIRM message is sent to the serving gNB (for example, together with the HANDOVER CONFIRM message as exemplarily shown in FIG), and then sent to the UE (for example, together with the HANDOVER COMMAND message (or separately therefrom)).

[0276] In any case, the UE will receive information about the PRACH resources (as adapted by the target gNB) and will use these resources for the random access procedure, using those PRACH resources configured by the target gNB that fall within the DRX OFF period of its function. Similarly, the target gNB uses coordinated timing when sending Random Access Messages 2 and 4 to the UE, so that the UE can receive them during the DRX OFF period when it is not communicating with the serving gNB. The UE will accordingly monitor (e.g., the PDCCH with the target gNB) during its DRX OFF period to determine whether the random access message has been received.

[0277] Information about the round-trip delay experienced by the UE when communicating with the serving gNB (e.g., timing advance value or reference signal time difference measurement) can also be sent to the target gNB (e.g., together with or separately from the DRX configuration). The target gNB can then use this information to more accurately align PRACH resources with DRX off periods, in order to avoid delays in communication that cause PRACH resources to fall into DRX active periods rather than DRX off periods.

[0278] Additionally or alternatively, the round-trip delay (e.g., timing advance value or reference signal time difference measurement) experienced by another UE when communicating with the target gNB can be used by the target gNB to improve the coordination of dedicated PRACH resources with DRX off periods. In other words, the round-trip delay of the other UE is used as an estimate of the round-trip delay that the UE will experience when performing a random access procedure with the target gNB. This is advantageous because the round-trip delay of the other UE is known at the target gNB, eliminating the need to exchange information about the round-trip delay. Furthermore, the round-trip delay estimate can be more accurate because it is estimated with reference to the same target gNB with which the UE will perform random access.

[0279] In the previous implementation, the PRACH resources were adapted while maintaining the DRX functionality as initially configured. Figure 19 and 21 In a second exemplary implementation, the DRX configuration used by the UE and the serving gNB is adapted to coordinate with the PRACH resources at the target gNB. Specifically, the serving gNB learns the PRACH resources in the target gNB that the UE will use for random access and then adapts the DRX configuration so that the DRX off period for the serving radio cell is consistent with the PRACH resources to be used in the target radio cell. The serving gNB may, for example, obtain information about the PRACH resources in the target radio cell from the target gNB. In one exemplary implementation, upon receiving a handover request, the target gNB provides the PRACH resource information to the serving gNB along with a handover confirmation message.

[0280] Alternatively, the serving gNB can obtain information about PRACH resources based on the physical cell identities of neighboring radio cells. The physical cell identity (PCI) is obtained by the serving gNB, for example, from measurement reports (received from the UE). It is assumed that the PRACH resources are associated with the physical cell identity, so that the serving gNB can derive the PRACH resources from the PCI. For example, there may be multiple (e.g., three total) different PRACH resource configurations, which can be derived, for example, based on the formula PCI mod 3, where any PCI satisfying PCI mod 3 = 0 is associated with PRACH resource configuration 0, any PCI satisfying PCI mod 3 = 1 is associated with PRACH resource configuration 1, and any PCI satisfying PCI mod 3 = 2 is associated with PRACH resource configuration 2.

[0281] In either case, the DRX configuration to be used by the UE in the serving gNB is adapted accordingly. The UE is informed of the adapted DRX configuration and follows the same configuration. For example, the adapted DRX configuration may be sent to the UE together with the Handover Command message or separately (e.g., using an RRCReconfiguration message).

[0282] Similar to what has been explained in conjunction with the first exemplary implementation (adapting PRACH resources to DRX configuration) above, the serving gNB can use information about the round-trip delay experienced by the UE when communicating with the serving gNB to more accurately align PRACH resources with DRX-enabled periods. Information about the RTD in the serving radio cell is already available at the serving gNB. Additionally or alternatively, when communicating with the target gNB, information about the round-trip delay experienced by the other UE is sent by the target gNB to the serving gNB. The serving gNB then uses this target gNB-related round-trip delay and dedicated PRACH resources in the target cell to configure DRX-off periods.

[0283] With the improved handover communication solution described above, communication interruption caused by handover is minimized because communication between the UE and the serving gNB can continue while the UE performs random access to the target radio cell. This effectively implements a make-before-break handover.

[0284] An important mechanism commonly used in LTE and 5G to improve communication between UEs and gNBs is the Hybrid Automatic Repeat Request (HARQ) mechanism (see 3GPP TS 36.321 v15.4.0, Section 5.4.2 and TS 38.321 v15.4.0, Section 5.4.2). According to one exemplary implementation, the following improved retransmission functionality can be based on HARQ.

[0285] Two levels of retransmission are used to provide reliability: HARQ at the MAC layer and outer ARQ at the RLC layer. HARQ is a common 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. If an FEC-encoded data packet is transmitted and the receiver fails to correctly decode it (errors are typically detected using a cyclic redundancy check (CRC), the receiver requests retransmission of the packet.

[0286] The MAC layer includes a HARQ entity responsible for both transmit and receive HARQ operations. Transmit HARQ operations include the transmission and retransmission of transport blocks, as well as the reception and processing of ACK / NACK signaling. Receive HARQ operations include the reception of transport blocks, combining received data, and generating ACK / NACK signaling. To allow for continuous transmission while the previous transport block is being decoded, up to 16 HARQ processes can be used in parallel to support multi-process "stop-and-wait" (SAW) HARQ operation. Each HARQ process is responsible for a separate SAW operation and manages a separate buffer.

[0287] The feedback provided by the HARQ protocol is either a positive acknowledgment (ACK) or a negative acknowledgment (NACK). ACKs and NACKs are generated based on whether the transmission was correctly received (e.g., whether decoding was successful). Furthermore, in HARQ operation, the eNB can send a different coded version of the original transport block in retransmissions, allowing the UE to employ incremental redundancy (IR) combining to achieve additional coding gain via combining gain.

[0288] If an FEC-coded packet is sent and the receiver fails to decode the packet correctly (errors are usually checked by a cyclic redundancy check (CRC), the receiver requests retransmission of the data packet. Usually (and throughout this document), the transmission of additional information is called "retransmission (of a packet)", and such a retransmission may, but does not necessarily, mean the transmission of the same coded information; it may also mean the transmission of any information belonging to the packet (e.g., additional redundant information), for example, by using a different redundancy version.

[0289] As mentioned above, HARQ is therefore used between the UE and the gNB. This also applies to the scenario discussed above, where the UE and the serving gNB are communicating with each other. In addition, HARQ can also be used for the random access procedure between the UE and the target gNB. This also applies to the case described above, where the UE communicates with the serving gNB (UL / DL communication) and the target gNB (random access) in parallel during handover (see e.g. Figure 16For example, if a UE has a total of 8 HARQ processes available, these 8 HARQ processes can 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 IDs.

[0290] When a UE initiates a random access procedure, all HARQ processes may already be used for communication with the serving cell. To still be able to use HARQ for random access with the target cell, the UE may reallocate one of the HARQ processes used for communication with the serving cell to the random access procedure, thereby overwriting the memory associated with that HARQ process with data from the random access message. In effect, the UE cancels one of the HARQ processes and then uses it for the random access procedure.

[0291] The UE may select a HARQ process, for example, based on the priority of the data contained 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 select a HARQ process randomly among all HARQ processes.

[0292] Figure 22 A simplified and exemplary UE behavior consistent with the above is illustrated in FIG.

[0293] This reallocated HARQ process can no longer be used for communication with the serving gNB. However, the serving gNB still uses the reallocated HARQ process because it is unaware that the UE is now using it for a different purpose. Accordingly, the serving gNB can retransmit data for the reallocated HARQ process. However, in this case, the data from the HARQ process is no longer available (no HARQ combining is possible), and the UE attempts to decode the data from the most recently received transmission alone. If unsuccessful, the UE may send a NACK to the serving gNB.

[0294] On the other hand, if the UE is sending a new uplink transmission to the serving gNB and no HARQ process is available, the UE performs the UL transmission without any HARQ process, i.e., it does not retain the UL transmission in the HARQ buffer. If the serving gNB requests retransmission of this UL data, the UE needs to encode the same data and send it again to the serving gNB.

[0295] Alternatively, the serving gNB can try to avoid having all HARQ processes in use during handover. For example, if the serving gNB knows that the UE is approaching the cell edge (through measurement reports), it can reduce its DL transmissions or UL grants to the UE so that at least one HARQ process can be idle for the UE to perform random access with the target gNB.

[0296] Other aspects

[0297] According to a first aspect, a UE is provided, comprising processing circuitry for performing power-related measurements on at least one radio carrier and generating measurement results based on the performed measurements. Reporting of the measurement results by the UE is based on at least one report triggering condition being satisfied. The processing circuitry determines whether to adjust the measurement results and at least one of the at least one report triggering conditions so as to trigger reporting of the measurement results earlier than would otherwise be the case. If an adjustment is determined, the processing circuitry adjusts the measurement results and at least one of the at least one report triggering conditions so as to trigger reporting of the measurement results earlier than would otherwise be the case. After the adjustment, the processing circuitry determines whether the at least one report triggering condition for reporting the measurement results is satisfied based on the at least one report triggering condition and the generated measurement results. If reporting of the measurement results is triggered, a transmitter of the UE transmits a measurement report including the measurement results.

[0298] According to a second aspect provided in addition to the first aspect, adjusting at least one report triggering condition includes processing circuitry applying at least one positive or negative power offset to the at least one report triggering condition. In one optional implementation, the processing circuitry determines the offset based on configuration information received from a serving base station to which the UE is connected, or determines the offset based on a difference between a generated measurement result and a previously generated measurement result. In another optional implementation, an offset is determined for each of the generated measurement results and used in the adjustment, optionally wherein, for each report triggering condition, an offset is determined for the serving radio carrier or a neighboring radio carrier. In another optional implementation, one offset is determined for the serving radio carrier and another offset is determined for the neighboring radio carrier. In another optional implementation, an offset is determined for each report triggering condition and used in the adjustment.

[0299] According to a third aspect provided in addition to the first or second aspect, adjusting the measurement result includes: processing circuitry determining a difference between the generated measurement result and a previously generated measurement result, and applying the determined difference to the generated measurement result to generate an adjusted measurement result. The processing circuitry determines whether to report the measurement result based on at least one report triggering condition and the adjusted measurement result.

[0300] According to a fourth aspect provided in addition to any one of the first to third aspects, the performing of measurements by the processing circuit includes performing measurements on at least one non-terrestrial radio carrier. In an optional implementation, the processing circuit determines whether to perform the adjustment based on whether the radio carrier is a non-terrestrial radio carrier or a terrestrial radio carrier. In an optional implementation, the adjustment is performed when the reporting trigger condition is based on a measurement result of the measurement performed on the non-terrestrial radio carrier.

[0301] According to a fifth aspect provided in addition to one of the first to fourth aspects, a measurement result may be used by a serving base station to which a UE is connected to determine whether to initiate a procedure for handing over the UE from its current serving radio cell controlled by the serving base station to another radio cell. At least one reporting triggering condition is configured such that the condition is satisfied when the serving base station can decide to initiate a procedure for handing over the UE from the current serving radio cell to another cell.

[0302] According to a sixth aspect provided in addition to one of the first to fifth aspects, the UE further includes a receiver that receives a conditional handover command, wherein the conditional handover command includes at least one handover acceptance condition to be satisfied for the UE to perform the handover and / or also includes at least one handover rejection condition to be satisfied for the UE to reject the handover. The processing circuit determines whether the handover acceptance condition is satisfied, and if the handover acceptance condition is satisfied, performs the handover according to the received conditional handover command, and optionally, if the handover acceptance condition is not satisfied, sends information about the handover rejection. In another optional implementation, the processing circuit determines whether the handover rejection condition is satisfied, and if the handover rejection condition is satisfied, sends information about the handover rejection.

[0303] According to a seventh aspect provided in addition to the sixth aspect, information regarding the handover rejection is sent in a radio resource control (RRC) message or as another measurement report. Alternatively, the information regarding the handover rejection is sent along with uplink data; optionally, the information regarding the handover rejection is sent as a control element (CE) of a medium access control (MAC) protocol. In an optional implementation, the processing circuit determines whether to send uplink data to the serving base station, and if no uplink data is to be sent, the handover rejection is sent in an RRC message or as another measurement report. Furthermore, if uplink data is to be sent, the handover rejection is sent along with the uplink data.

[0304] According to an eighth aspect provided in addition to one of the sixth to seventh aspects, when the processing circuit determines that a handover rejection condition is satisfied, the processing circuit determines not to send a measurement report to the serving base station within a time period after sending the handover rejection information. In an optional implementation, the time period is configured by the serving base station.

[0305] According to a ninth aspect provided in addition to one of the first to eighth aspects, in a case where neither the handover accept condition nor the handover reject condition is satisfied, the transmitter transmits a resource reservation extension request to the serving base station in order to extend a resource reservation time in a neighboring radio cell.

[0306] According to a tenth aspect provided in addition to one of the first to ninth aspects, a UE performs a handover from its current serving radio cell to another radio cell, wherein performing the handover includes the UE performing a random access procedure with the other radio cell. After starting to perform the handover to the other radio cell, the UE continues to communicate with the serving radio base station in uplink and / or downlink during a communication period of a discontinuous reception (DRX) function operated by the UE for communication with the serving radio base station. The UE transmits a message for 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, optionally wherein the communication period does not overlap with the sleep period. In an optional implementation, the UE receives the message for the random access procedure during the sleep period of the DRX function.

[0307] According to an eleventh aspect provided in addition to one of the first to tenth aspects, a UE performs a handover from its current serving radio cell to another radio cell, wherein performing the handover includes performing a random access procedure with the other radio cell. After starting to perform the handover to the other radio cell, the UE continues to communicate with a serving base station in uplink and / or downlink using multiple hybrid automatic repeat request (HARQ) processes. The UE uses the multiple HARQ processes for the random access procedure, and if all of the multiple HARQ processes have already been used to communicate with the serving base station, the processing circuitry determines that one of the multiple HARQ processes is to be reused for the random access procedure.

[0308] According to the twelfth aspect provided in addition to the eleventh aspect, each HARQ process is used to store previously transmitted data in an associated memory for possible later retransmission, or to store previously received data in an associated memory for possible later combination with subsequently received data. Reusing the HARQ process for the random access procedure includes: overwriting the memory associated with the reused HARQ process with the data buffered for the random access procedure. In an optional implementation, in the case where all HARQ processes are used and one of the HARQ processes is reused for the random access procedure, the processing circuit does not use the reused HARQ process to store new uplink transmissions. In another optional implementation, in the case where all HARQ processes are used and one of the HARQ processes is reused for the random access procedure, the processing circuit does not use the reused HARQ process to store received downlink transmissions.

[0309] According to a thirteenth aspect, a method is provided, comprising the following steps performed by a user equipment UE:

[0310] performing power-related measurements on at least one radio carrier and generating measurement results based on the performed measurements, wherein reporting of the measurement results by the UE is based on at least one reporting triggering condition being satisfied;

[0311] determining whether to adjust at least one of the measurement result and the at least one reporting triggering condition so as to trigger reporting of the measurement result earlier than without the adjustment;

[0312] If it is determined that adjustment is required, adjusting at least one of the measurement result and the at least one reporting triggering condition so as to trigger reporting of the measurement result earlier than without the adjustment;

[0313] After the adjustment, determining whether at least one reporting triggering condition for reporting the measurement result is satisfied based on the at least one reporting triggering condition and the measurement result;

[0314] In a case where reporting of the measurement result is triggered, a measurement report including the measurement result is sent.

[0315] According to a fourteenth aspect, a base station is provided, comprising processing circuitry configured to determine whether to instruct a user equipment (UE) to adjust at least one of a measurement result and at least one report triggering condition so as to trigger reporting of the measurement result earlier than would otherwise be the case. A transmitter of the base station, if the processing circuitry determines that the UE is to be instructed, configures the UE to adjust at least one of the measurement result and at least one report triggering condition so as to trigger reporting of the measurement result earlier than would otherwise be the case. A receiver of the base station receives a measurement report from the UE, the measurement report including results of measurements performed by the UE on at least one radio carrier, wherein the UE's reporting of the measurement result is based on the at least one report triggering condition being satisfied.

[0316] According to the fifteenth aspect provided in addition to the fourteenth aspect, a processing circuit determines at least one positive or negative power offset for at least one report triggering condition. A transmitter transmits configuration information indicating the determined positive or negative power offset to a UE. In an optional implementation, an offset is determined for each of the generated measurement results. In an optional implementation, for each report triggering condition, an offset is determined for a serving radio carrier or a neighboring radio carrier. In an optional implementation, one offset is determined for the serving radio carrier and another offset is determined for a neighboring radio carrier.

[0317] According to a sixteenth aspect provided in addition to the fourteenth or fifteenth aspect, the determination, performed by the processing circuitry, of whether to instruct a user equipment (UE) to adjust at least one of a measurement result and at least one reporting triggering condition so as to trigger reporting of the measurement result earlier than would otherwise be the case is based on whether the radio carrier is a non-terrestrial radio carrier or a terrestrial radio carrier. In an optional implementation, the processing circuitry determines to instruct the UE that the adjustment has been made if the UE performs measurement on the non-terrestrial radio carrier.

[0318] According to the seventeenth aspect provided in addition to any one of the fourteenth to sixteenth aspects, a transmitter sends a conditional handover command to a UE, wherein the conditional handover command includes at least one handover accept condition to be satisfied by the UE for performing the handover and / or also includes at least one handover reject condition to be satisfied for the UE to reject the handover. In an optional implementation, a receiver receives information regarding rejection of the handover of the UE, and the transmitter sends a request to a neighboring target base station that is a handover target to release any resources reserved in the neighboring radio cell for the handover of the UE. In an optional implementation, the receiver receives a first resource reservation extension request from the UE to extend a resource reservation time in the neighboring radio cell. The transmitter sends a second resource reservation extension request to the neighboring target base station that is a handover target to extend the resource reservation time in the neighboring radio cell.

[0319] According to an eighteenth aspect provided in addition to any one of the fourteenth to seventeenth aspects, a processing circuit adapts a sleep period of a discontinuous reception (DRX) function operated by a UE for communicating with a base station to be consistent with a random access resource used by the UE to perform a random access procedure with a neighboring target base station. In an optional implementation, the processing circuit obtains information about the random access resource of the neighboring target base station based on information received from the neighboring target base station or based on a cell identifier of the neighboring target base station.

[0320] According to a nineteenth aspect provided in addition to any one of aspects 14 to 18, another UE is handed over from another base station to a base station serving as a handover target, wherein a transmitter transmits a message of a random access procedure to the other UE during a dormant period of a DRX function operated by the other UE for interrupting communication with the other base station, and a receiver receives the message of the random access procedure from the other UE during the dormant period of the DRX function. In an optional implementation, the receiver receives configuration information regarding the DRX function of the other UE. The processing circuit adapts a random access resource used by the other UE to perform a random access procedure with the base station to coincide with the dormant period of the DRX function. The transmitter transmits information regarding the adapted random access resource to the other base station.

[0321] Hardware and software implementations of the present disclosure

[0322] The present disclosure can be implemented through software, hardware, or a combination of software and hardware. Each functional block used in the description of each embodiment above can be partially or fully implemented by an LSI, such as an integrated circuit, and each process described in each embodiment can be partially or fully controlled by the same LSI or a combination of multiple LSIs. An LSI can be formed as a single chip, or a single chip can be formed to include some or all functional blocks. An LSI can include data inputs and outputs coupled to itself. Depending on the degree of integration, an LSI may be referred to as an IC (integrated circuit), system LSI, super LSI, or ultra LSI. However, the technology used to implement an integrated circuit is not limited to LSIs and can be implemented using dedicated circuits, general-purpose processors, or dedicated processors. Alternatively, an FPGA (field programmable gate array) that can be programmed after LSI fabrication or a reconfigurable processor that can reconfigure the connections and settings of circuit cells within the LSI can be used. The present disclosure can be implemented as either digital or analog processing. If future integrated circuit technology replaces LSI due to advances in semiconductor technology or other derivative technologies, the functional blocks can be integrated using future integrated circuit technology. Biotechnology can also be applied.

[0323] The present disclosure may be implemented by any type of device, apparatus, or system having a communication function, which may be referred to as a communication device.

[0324] Some non-limiting examples of such communication devices include phones (e.g., cellular (cell) phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), game consoles, digital book readers, telehealth / telemedicine (remote health and medical) devices, and vehicles that provide communication capabilities (e.g., cars, airplanes, ships), and various combinations thereof.

[0325] Communication devices are not limited to portable or mobile, but may also include any type of non-portable or fixed device, equipment, or system, such as smart home devices (e.g., appliances, lighting, smart meters, control panels), vending machines, and any other "things" in the "Internet of Things (IoT)" network.

[0326] Communications may include exchanging data via, for example, cellular systems, wireless LAN systems, satellite systems, etc., and various combinations thereof.

[0327] The communication apparatus may include a device, such as a controller or a sensor, coupled to a communication device that performs the communication functions described in the present disclosure. For example, the communication apparatus may include a controller or a sensor that generates a control signal or a data signal that is used by the communication device that performs the communication functions of the communication apparatus.

[0328] Communications devices may also include infrastructure such as base stations, access points, and any other devices, equipment, or systems that communicate with or control devices such as the above non-limiting examples.

[0329] In addition, various embodiments may also be implemented via software modules that are executed by a processor or directly in hardware. Combinations of software modules and hardware implementations are also possible. Software modules may be stored on any type of computer-readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROMs, DVDs, and the like. It should also be noted that various features of different embodiments may be the subject of another embodiment, individually or in any combination.

[0330] Those skilled in the art will appreciate that various changes and / or modifications may be made to the present disclosure as shown in the specific embodiments. Therefore, the present embodiments are to be considered in all aspects as illustrative and not restrictive.

Claims

1. A communication device, comprising: a processing circuit for generating a measurement result based on power-related measurements on at least one radio cell; a transceiver receiving a conditional handover command, the conditional handover command including at least one handover execution condition for the communication device to perform a conditional handover and including a location-based handover triggering condition and a measurement-based handover triggering condition in accordance with the at least one radio cell being associated with a non-terrestrial network; In a case where the location-based handover triggering condition is satisfied according to the locations of the communication device and the at least one radio cell, the communication device performs the conditional handover; In a case where the measurement-based handover triggering condition is satisfied according to the measurement result, the communication device performs the conditional handover; and The first value for the terrestrial network and the non-terrestrial network and the second value for the non-terrestrial network are configured to perform the conditional handover. 2 . The communication device according to claim 1 , wherein the first value and the second value are configured via a Radio Resource Control (RRC) message. 3 . The communication device according to claim 1 , wherein a third offset for a serving radio carrier and a fourth offset for an adjacent radio carrier are configured. 4 . The communication device of claim 1 , wherein performing the measurements by the processing circuit comprises performing measurements on at least one non-terrestrial radio cell. The communication device according to claim 1 , wherein information about a round trip delay associated with a distance between the communication device and the at least one radio cell is transmitted. The communication device according to claim 1 , wherein reporting of the measurement result by the communication device is triggered based on at least one reporting triggering condition. 7 . The communication device according to claim 1 , wherein the at least one reporting triggering condition is configured to be satisfied when the serving base station determines, using the measurement result, initiation of a procedure for handing over the communication device from a current serving radio cell to another cell. 8 . The communication device according to claim 1 , wherein a measurement target of the measurement related to power is a radio cell included in a white list configured by a network.

9. A measurement and handover method, comprising the following steps performed by a communication device: generating a measurement result based on power-related measurements on at least one radio cell; receiving a conditional handover command, the conditional handover command including at least one handover execution condition for the communication device to perform a conditional handover and including a location-based handover triggering condition and a measurement-based handover triggering condition in accordance with the at least one radio cell being associated with a non-terrestrial network; wherein the communication device performs the conditional handover if the location-based handover triggering condition is satisfied according to the locations of the communication device and the at least one radio cell; In a case where the measurement-based handover triggering condition is satisfied according to the measurement result, the communication device performs the conditional handover; and The first value for the terrestrial network and the non-terrestrial network and the second value for the non-terrestrial network are configured to perform the conditional handover.

10. A base station, comprising: processing circuitry that determines to perform a conditional handover of a communication device based on measurements performed by the communication device on at least one radio cell; a transceiver, the transceiver sending a conditional handover command, the conditional handover command including at least one handover execution condition for the communication device to execute the conditional handover; the processing circuitry including a location-based handover triggering condition and a measurement-based handover triggering condition based on the at least one radio cell being associated with a non-terrestrial network; wherein the conditional handover is performed by the communication device in a case where the location-based handover triggering condition is satisfied according to the locations of the communication device and the at least one radio cell; In a case where the measurement-based handover triggering condition is satisfied according to the measurement result, the conditional handover is performed by the communication device; and The base station configures a first value for a terrestrial network and the non-terrestrial network and a second value for the non-terrestrial network for the conditional handover.

11. The base station of claim 10, wherein the base station is configured with a third offset for a serving radio carrier and a fourth offset for a neighboring radio carrier.

12. A measurement and handover method, comprising the following steps performed by a base station: determining to perform a conditional handover based on measurements performed by the communication device on at least one radio cell; sending a conditional handover command to the communication device, wherein the conditional handover command includes at least one handover execution condition for the communication device to execute the conditional handover; including a location-based handover triggering condition and a measurement-based handover triggering condition in accordance with the at least one radio cell being associated with a non-terrestrial network; wherein the conditional handover is performed by the communication device in a case where the location-based handover triggering condition is satisfied according to the locations of the communication device and the at least one radio cell; In a case where the measurement-based switching triggering condition is satisfied according to the measurement result, the communication device determines the conditional switching; and The base station configures a first value for a terrestrial network and the non-terrestrial network and a second value for the non-terrestrial network for the conditional handover.

13. An integrated circuit comprising circuitry configured to: controlling generation of measurement results based on power-related measurements on at least one radio cell; controlling receiving a conditional handover command, the conditional handover command including at least one handover execution condition to be satisfied for the communication device to perform a conditional handover, and including a location-based handover triggering condition and a measurement-based handover triggering condition in accordance with the at least one radio cell being associated with a non-terrestrial network; wherein the communication device performs the conditional handover if the location-based handover triggering condition is satisfied according to the locations of the communication device and the at least one radio cell; In a case where the measurement-based handover triggering condition is satisfied according to the measurement result, the communication device performs the conditional handover; and The first value for the terrestrial network and the non-terrestrial network and the second value for the non-terrestrial network are configured to perform the conditional handover.

14. An integrated circuit comprising circuitry configured to: controlling a determination to perform a conditional handover of the communication device based on a measurement result performed by the communication device on at least one radio cell; controlling sending of a conditional handover command to the communication device, wherein the conditional handover command includes at least one handover execution condition for the communication device to execute the conditional handover, including a location-based handover triggering condition and a measurement-based handover triggering condition according to whether the at least one radio cell is associated with a non-terrestrial network; wherein the conditional handover is performed by the communication device in a case where the location-based handover triggering condition is satisfied according to the locations of the communication device and the at least one radio cell; In a case where the measurement-based switching triggering condition is satisfied according to the measurement result, the communication device determines the conditional switching; and The base station configures a first value for a terrestrial network and the non-terrestrial network and a second value for the non-terrestrial network for the conditional handover.

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