User Equipment Involved in Measurement Reports and Handovers

Abstract

The present disclosure relates to a user equipment (UE) comprising processing circuitry that performs power-related measurements on at least one radio carrier and generates a measurement result based on the measurement. Reporting of the measurement result is based on a reporting trigger condition. The processing circuitry determines whether to adjust the measurement result and / or the reporting trigger condition so as to trigger reporting of the measurement result earlier than without the adjustment. In case an adjustment is determined, the processing circuitry adjusts the measurement result and / or the reporting trigger condition so as to trigger reporting of the measurement result earlier than without the adjustment. After the adjustment, the processing circuitry determines whether the reporting trigger condition for reporting the measurement result is satisfied. In case reporting of the measurement result is triggered, a transmitter transmits a measurement report comprising the measurement result.

Description

Technical Field

[0001] The present disclosure is directed to methods, devices, and articles in a communication system such as a 3GPP communication system. Background Art

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

[0003] One goal is to provide a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios (see, for example, Section 6 of TR 38.913, version 15.0.0), which deployment scenarios include at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine type communication (mMTC). For example, the eMBB deployment scenario can include indoor hotspots, dense cities, rural areas, urban macros, and high speeds; the URLLC deployment scenario can include industrial control systems, mobile healthcare (remote monitoring, diagnosis, and treatment), real-time control of vehicles, and wide-area monitoring and control systems for smart grids; the mMTC deployment scenario can include scenarios of a large number of devices with non-time-critical data transmission (such as smart wearable devices and sensor networks). The similarity between eMBB and URLLC services is that both of them require very wide bandwidths, while the difference is that URLLC services may preferably require ultra-low latency.

[0004] A second goal is to achieve forward compatibility. Backward compatibility with long-term evolution (LTE, LTE-A) cellular systems is not required, which helps with a brand-new system design and / or the introduction of new features. Summary of the Invention

[0005] A non-limiting and exemplary embodiment helps to provide an improved process for measurement and handover.

[0006] In an embodiment, the techniques disclosed herein are characterized by a user equipment including a processing circuit that performs power-related measurements on at least one radio carrier and generates a measurement result based on the performed measurements. The UE's reporting of the measurement result is based on at least one reporting trigger condition to be satisfied. The processing circuit determines whether to adjust at least one of the measurement result and at least one reporting trigger condition so as to trigger the reporting of the measurement result earlier than without adjustment. In the case of determining an adjustment, the processing circuit adjusts at least one of the measurement result and at least one reporting trigger condition so as to trigger the reporting of the measurement result earlier than without adjustment. After the adjustment, the processing circuit determines whether at least one reporting trigger condition for reporting the measurement result is satisfied based on the at least one reporting trigger condition and the measurement result. In the case where the reporting of the measurement result is triggered, a transmitter of the UE transmits a measurement report including the measurement result.

[0007] It should be noted that the general or specific embodiments can be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

[0008] Additional benefits and advantages of the embodiments disclosed in the specification and the drawings will become apparent. The benefits and / or advantages can be obtained individually by various embodiments and features of the specification and the drawings, and in order to obtain one or more of such benefits and / or advantages, not all of the various embodiments and features need to be provided. Description of the Drawings

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

[0010] Figure 1 An exemplary architecture of the 3GPP NR system is shown;

[0011] Figure 2 An exemplary user and control plane architecture for LTE eNB, gNB, and UE is shown;

[0012] Figure 3 An exemplary NG RAN architecture based on a transparent satellite is illustrated;

[0013] Figure 4 An exemplary NG RAN architecture based on a regenerative satellite is illustrated;

[0014] Figure 5 An exemplary and simplified structure of a UE and a gNB is illustrated;

[0015] Figure 6 The structure of a UE according to an exemplary implementation of an embodiment for an improved measurement and reporting process is illustrated;

[0016] Figure 7 is a flowchart of the behavior of a UE according to an exemplary implementation of an improved measurement and reporting process;

[0017] Figure 8 is a flowchart of the behavior of a gNB according to an exemplary implementation of an improved measurement and reporting process;

[0018] Figure 9 is a signaling diagram of messages between a UE, a serving gNB, and an adjacent gNB according to an improved measurement and reporting process;

[0019] Figure 10 is a signaling diagram of messages between a UE, a serving gNB, and a target gNB according to an improved conditional handover process;

[0020] Figure 11is a flowchart of the behavior of a UE according to an exemplary implementation of an improved conditional handover process;

[0021] Figure 12 is a flowchart of the behavior of a gNB according to an exemplary implementation of an improved conditional handover process;

[0022] Figure 13 and 14 illustrate the 3-step and 4-step random access processes respectively;

[0023] Figure 15 illustrates the DRX operation of a mobile terminal (and specifically DRX opportunities and on-duration) according to short and long DRX cycles;

[0024] Figure 16 is a signaling diagram of messages exchanged between a UE, the serving gNB of the UE, and the target gNB according to an exemplary implementation of an improved handover communication process;

[0025] Figure 17 is a flowchart of the behavior of a UE according to an exemplary implementation of an improved handover communication process;

[0026] Figure 18 and 19 is a flowchart of the behavior of the serving gNB according to different implementations of an improved handover communication process;

[0027] Figure 20 and 21 is a flowchart of the behavior of the target gNB according to different implementations of an improved handover communication process; and

[0028] Figure 22 is a flowchart of the behavior of a UE according to an exemplary implementation of an improved HARQ operation process during handover.

[0029] Specific implementation

[0030] 5G NR system architecture and protocol stack

[0031] 3GPP has been working on the next version of the fifth-generation cellular technology (abbreviated 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, which allows for trials up to and commercial deployment of smartphones compliant with the 5G NR standard.

[0032] In addition, the overall system architecture assumes an 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. The gNBs are interconnected with each other via the Xn interface. The gNBs are also connected to the NGC (Next Generation Core) via the Next Generation (NG) interface, more specifically to the AMF (Access and Mobility Management Function) (e.g., a specific core entity that executes the AMF) via the NG-C interface and to the UPF (User Plane Function) (e.g., a specific core entity that executes the UPF) via the NG-U interface. The NG-RAN architecture is illustrated in Figure 1 (see, for example, 3GPP TS 38.300 v15.4.0, Section 4).

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

[0034] For the user plane protocol stack of 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), RLC (Radio Link Control, see Section 6.3 of TS 38.300), and MAC (Media Access Control, see Section 6.2 of TS 38.300) sublayers, which are terminated at the gNB on the network side. In addition, a new access stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced above the PDCP (see, for example, Subclause 6.5 of 3GPP TS 38.300 version 15.4.0). A control plane protocol stack is also defined for NR (see, for example, TS38.300, Section 4.4.2). An overview of the functions of layer 2 is given 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 Medium Access Control (MAC) layer processes logical channel multiplexing, scheduling, and scheduling-related functions, including the handling of different parameter sets.

[0036] For the Physical layer, the MAC layer uses services in the form of transport channels. A transport channel can be defined by how information is transmitted over the radio interface and with which characteristics. 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 processes supported by the MAC layer is the random access process.

[0037] The Physical layer (PHY) is responsible for, for example, coding, PHY HARQ processing, modulation, multi-antenna processing, and mapping the signal 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 can include Enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communication (URLLC), and Massive Machine-Type Communication (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 the downlink and 10 Gbps for the uplink) and user experience data rates that are approximately three times the rates provided by Advanced IMT. On the other hand, in the case of URLLC, more stringent requirements are imposed for ultra-low latency (0.5 ms for both UL and DL user plane latency) and high reliability (1 - 10 -5 ) within 1 ms. Finally, mMTC may preferably require a high connection density (1,000,000 devices / km in urban environments 2 ), large coverage in harsh environments, and long-life (15 years) batteries 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) suitable for one use case may not be well-suited for another use case. For example, low-latency services may preferably require a shorter symbol duration (and thus a larger subcarrier spacing) and / or fewer symbols per scheduling interval (also known as TTI) than mMTC services. Additionally, a deployment scenario with large channel delay spread may preferably require a longer CP duration than a scenario with short delay spread. The subcarrier spacing should be optimized accordingly to maintain a similar CP overhead. NR can support more than one subcarrier spacing value. Accordingly, subcarrier spacings of 15 kHz, 30 kHz, 60 kHz... are being considered at this moment. The symbol duration T u and the subcarrier spacing Δf are directly related by the formula Δf = 1 / T u In a similar manner to the LTE system, the term "resource element" can be used to represent 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, a resource grid of subcarriers and OFDM symbols is defined for the uplink and downlink, respectively, for each parameter set and carrier. 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 signals

[0042] Similar to LTE, 5G NR uses several different types of reference signals (RS) (see Section 7.4.1 of 3GPP TS38.211 v15.4.0). 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 for phase tracking of the PDSCH,

[0048] · A tracking reference signal that can be used for time tracking

[0049] In addition, PBCH DMRS can be exemplarily regarded as part of the SSB reference signal (see Section 5.1.1, "SS Reference Signal Received Power (SS-RSRP)" in 3GPP TS38.215 v15.3.0).

[0050] The main differences between the reference signals in the 5G NR communication system and those in LTE are that there is no cell-specific reference signal in 5G NR, a new reference signal PTRS for time / phase tracking is introduced, DMRS for both downlink and uplink channels is introduced, and reference signals are only transmitted when needed in NR.

[0051] As a signal only for DL, the CSI-RS received by the UE is used to estimate the channel and report the channel quality information back to the gNB. During MIMO operation, different antenna schemes can be used based on the carrier frequency NR. 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 as follows:

[0052] · It is used for DL CSI acquisition.

[0053] · Used for RSRP measurement during mobility and beam management

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

[0055] · CSI-RS is configured for a specific UE, but multiple users can also share the same resources

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

[0057] · CSI-RS resources can start from any OFDM symbol in a time slot. Depending on the number of configured ports, it usually occupies 1 / 2 / 4 OFDM symbols.

[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 transmitted in bursts of two or four symbols, and these bursts are spread over 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, in order to provide a basic overview of the measurement, the UE (NR device) can perform, for example, measurements based on reference signals (such as CSI-RS, SS blocks) and obtain measurement results therefrom. After receiving some or all of the measurement results in the corresponding measurement report, these measurement results can be used internally by the UE or by other entities (such as base stations 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, for example, by defining one or more measurement objects; a measurement object defines, for example, the carrier frequency to be monitored. Then, one or several reporting configurations can be defined for each measurement object, 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 a channel quality indicator (CQI), a rank indicator (RI), a precoder matrix indicator (PMI), collectively referred to as channel state information (CSI)). In addition, 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 for measurement and reporting as part of higher layer radio resource management (RRM), and it is also used in 5G NR. NR supports Layer 1 reporting of RSRP (e.g., as part of support for beam management), resulting in beam quality. What is then reported may be 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 can therefore neutralize sudden changes by considering the current input from the L1 filter and the previous output from the L3 filter.

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

[0071] There is also a situation where a device performs measurements without any corresponding reporting to the network. One such exemplary situation is when a UE performs measurements for receiver-side downlink beamforming. The UE internally uses the measurements to select a suitable receiver beam. The network can configure the UE accordingly, for example, by specifying the reference signal on which to measure, while 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 obtain the 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 obtain the beam quality, and then at the RRC layer (layer 3) to obtain the cell quality from multiple beams. For the (multiple) serving cells and (multiple) non-serving cells, the cell quality from beam measurements is obtained in the same way.

[0073] Measurement reports are characterized by one or more of the following exemplary items:

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

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

[0076] - The number of non-serving cells to be reported can be restricted by the configuration of 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 (either only the beam identifier, the measurement result and the beam identifier, or no beam report).

[0079] Intra-frequency neighbor (cell) measurements and inter-frequency neighbor (cell) measurements are defined exemplarily as follows:

[0080] - Intra-frequency measurements 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, then the measurement is defined as an intra-frequency measurement based on SSB.

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

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

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

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

[0085] Whether the measurement is non-gap-assisted or gap-assisted depends on the UE's capabilities, the UE's active BWP, and the current operating frequency. In the non-gap-assisted scenario, the UE should be able to perform such measurements without measurement gaps. In the gap-assisted scenario, it cannot be assumed that the UE can perform such measurements without measurement gaps.

[0086] Measurement reports are defined in Section 5.5.3 of 3GPP TS 38.331 v15.3.0. The network can configure the UE to obtain RSRP, RSRQ, and SINR measurement results for each cell. Measurement report triggers including different trigger events (see the overview below) are defined in Section 5.5.4 of 3GPP TS 38.331 v15.4.0. Detailed information about measurement reports is provided in Section 5.5.5 of 3GPP TS 38.331 v15.4.0.

[0087] Different events A1 - A6, B1, and B2 are defined. The different events include leaving and entering conditions respectively, and these conditions are associated with trigger time conditions. This allows the UE to perform measurements on its own and report the results according to the criteria defined for the events. The overview is given below:

[0088] · Event A1 (The service becomes better than the threshold)

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

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

[0091] · Event A2 (service becomes worse than the threshold)

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

[0093] o Inequality A2-2 (departure 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 +

[0096] Ocp + Off

[0097] o Inequality A3-2 (departure condition): Mn + Ofn + Ocn + Hys < Mp + Ofp +

[0098] Ocp + Off

[0099] · Event A4 (neighbor becomes better than the threshold)

[0100] o Inequality A4-1 (entry condition): Mn + Ofn + Ocn - Hys > Thresh

[0101] o Inequality A4-2 (departure condition): Mn + Ofn + Ocn + Hys < Thresh

[0102] · Event A5 (SpCell becomes worse than threshold 1, while neighbor / SCell becomes better than threshold 2)

[0103] o Inequality A5-1 (entry condition 1): Mp + Hys < Thresh1

[0104] o Inequality A5-2 (entry condition 2): Mn + Ofn + Ocn - Hys > Thresh2

[0105] o Inequality A5-3 (departure condition 1): Mp - Hys > Thresh1

[0106] o Inequality A5-4 (departure condition 2): Mn + Ofn + Ocn + Hys < Thresh2

[0107] · Event A6 (neighbor becomes offset better than SCell)

[0108] o Inequality A6-1 (entry condition): Mn + Ocn - Hys > Ms + Ocs + Off

[0109] o Inequality A6 - 2 (departure condition): Mn + Ocn + Hys < Ms + Ocs + Off

[0110] · Event B1 (the RAT - to - RAT neighbor becomes better than the threshold)

[0111] o Inequality B1 - 1 (entry condition): Mn + Ofn + Ocn - Hys > Thresh

[0112] o Inequality B1 - 2 (departure condition): Mn + Ofn + Ocn + Hys < Thresh

[0113] · Event B2 (the PCell becomes worse than threshold 1 and the RAT - to - RAT neighbor becomes better than threshold 2)

[0114] o Inequality B2 - 1 (entry condition 1): Mp + Hys < Thresh1

[0115] o Inequality B2 - 2 (entry condition 2): Mn + Ofn + Ocn - Hys > Thresh2

[0116] o Inequality B2 - 3 (departure condition 1): Mp - Hys > Thresh1

[0117] o Inequality B2 - 4 (departure condition 2): Mn + Ofn + Ocn + Hys < Thresh2

[0118] The parameters indicated above are generally as follows:

[0119] · Ms is the measurement result of the serving cell without considering any offset.

[0120] · Mn is the measurement result of the neighboring cell without considering any offset.

[0121] · Ofn is the measurement object - specific offset of the reference signal of the neighboring cell (i.e., the offsetMO defined in measObjectNR corresponding to the neighboring cell).

[0122] · Ocn is the cell - specific offset of the neighboring cell (i.e., the cellIndividualOffset defined in measObjectNR corresponding to the frequency of the neighboring cell), and Ocn is set to zero if not configured for the neighboring cell.

[0123] · Mp is the measurement result of the SpCell without considering any offset.

[0124] ·Ofp is the measurement object specific offset for the SpCell (i.e., the offsetMO defined in measObjectNR corresponding to the SpCell).

[0125] ·Ocp is the cell specific offset for the SpCell (i.e., the cellIndividualOffset defined in measObjectNR corresponding to the SpCell), and Ocp is set to zero if not configured for the SpCell.

[0126] ·Off is the offset parameter for this event (i.e., the a3-Offset defined in reportConfigNR for this event).

[0127] ·Hys is the hysteresis parameter for this event (i.e., the hysteresis defined in reportConfigNR for this event).

[0128] ·Thresh is the threshold parameter for this event (i.e., the a1-Threshold defined in reportConfigNR for this event).

[0129] ·Thresh1 is the threshold parameter for this event (i.e., the a5-Threshold1 defined in reportConfigNR for this event).

[0130] ·Thresh2 is the threshold parameter for this event (i.e., the a5-Threshold2 defined in reportConfigNR for this event).

[0131] ·Mn, Mp, Ms are expressed in dBm in the case of RSRP, or in dB in the case of RSRQ and RS-SINR.

[0132] ·Ofn, Ocn, Ofp, Ocp, Hys, Off are expressed in dB.

[0133] At least the following mechanisms are based on the measurement results obtained by the UE:

[0134] ·The handover decision made by the gNB based on the measurement results (received via the measurement report)

[0135] ·The triggering of the measurement report

[0136] ·The radio link failure indication

[0137] Non-Terrestrial Network, NTN

[0138] Satellites will continue to be the most effective means for reaching areas beyond terrestrial coverage and reaching passengers in trains, airplanes, and ships. Thus, including satellites as 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 inherent part of the 5G ecosystem. The goals are 1) to use satellites to support highly available and reliable connectivity for use cases such as ubiquitous coverage, disaster relief, public safety requirements, emergency response, remote sensor connectivity, broadcast services, etc.; 2) to support air interfaces with one-way latency of up to 275 milliseconds when satellite connectivity is involved; and 3) to support seamless mobility between terrestrial and satellite-based networks with widely varying latencies. Release 14 of 3GPP has studied the role and benefits of satellites in 5G, resulting in specific requirements to support satellite access.

[0139] Figure 3 An exemplary NG RAN architecture based on a transparent satellite is illustrated. According to an exemplary implementation (see Section 5.1 of TR38.821v0.3.0), the satellite payload implements frequency conversion and RF amplifiers in both the uplink and downlink directions. It corresponds to an analog RF repeater. Thus, the satellite relays the NR-Uu radio interface from the feeder link (between the NTN gateway and the satellite) to the service link (between the satellite and the UE), and vice versa. The satellite radio interface (SRI) on the feeder link is NR-Uu. In other words, the satellite does not terminate NR-Uu. Figure 4 An exemplary NG RAN architecture based on a regenerative satellite is illustrated. According to an exemplary implementation (see Section 5.2 of TR 38.321v0.3.0), the NG-RAN logical architecture described in TS 38.401 is used as the baseline for the NTN scenario. The satellite payload implements regeneration of the signals received from the Earth. The NR-Uu radio interface is on the service link between the UE and the satellite. The satellite radio interface (SRI) is on the feeder link between the NTN gateway and the satellite. The SRI (satellite radio interface) is the transmission link between the NTN GW and the satellite.

[0140] The satellite payload also provides an inter-satellite link (ISL) between satellites. The ISL (inter-satellite link) is the transmission link between satellites.

[0141] The mobility of NTN is being discussed. It is assumed that from the perspective of the UE in NTN, satellite beams, satellites, or satellite cells do not need to be visible, however this does not necessarily exclude the network types (e.g., NTN vs. terrestrial) being differentiated at the PLMN (Public Land Mobile Network) level. Additionally, it has been agreed that the Rel-15 design / definition will be used as the baseline for NTN, which means that the NR RRM measurement model used in Rel-15 will also be the baseline for the NTN RRM measurement model.

[0142] The inventors have recognized that for non-terrestrial communications, the round-trip delay (RTD) can be much larger than the delay 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 35786 km) and 25.76 / 41.76 milliseconds for LEO (Low Earth Orbit, e.g., at an altitude of 600 / 1200 km). In terrestrial communications, the RTD can be, for example, up to 5 milliseconds.

[0143] The long RTD can lead to a high handover failure rate because the network makes handover decisions based on measurements that are already outdated and may thus be inaccurate. For example, handover failures can include cases where the handover is too late (other cases are, for example, cases where the handover is to the wrong cell). Additionally, the long RTD in message exchange also results in NTN handovers taking longer, which can lead to longer service interruptions for the UE during the handover from one NTN network to another NTN network.

[0144] Therefore, the inventors have identified the possibility of improving the measurement reporting and / or handover process to help avoid one or more of the above-discussed drawbacks. The improved measurement reporting and handover process can then be applied to scenarios such as NTN scenarios where there is a high latency. However, NTN scenarios are not the only scenarios where the improved process can be implemented, and other communication scenarios with high RTD and / or fast channel change environments (such as NR unlicensed scenarios where the channel quality changes very quickly) can also benefit from the improved process.

[0145] Hereinafter, the UE, base station, and process that meet these requirements will be described for a new radio access technology envisioned for 5G mobile communication systems but also applicable to LTE mobile communication systems. Different implementations and variants will also be explained. The above-discussed discussions and findings contribute to the following disclosure, and the following disclosure can be based, for example, at least in part on them.

[0146] In general, it should be noted that many assumptions have been made in this document in order to be able to explain the basic principles of the present disclosure in a clear and understandable manner. However, these assumptions should be understood as merely examples made herein for illustrative purposes and should not limit the scope of the present disclosure. Those skilled in the art will realize that the principles disclosed hereinafter and as set forth in the claims can be applied to different scenarios and in ways not explicitly described herein.

[0147] Furthermore, some of the terms used hereinafter for processes, entities, layers, etc. are closely related to those used in the LTE / LTE-A systems or in the current 3GPP 5G standardization, even though the specific terms used in the context of the new radio access technology for the next 3GPP 5G communication system have not been fully determined or may ultimately change. Thus, the terms may change in the future without affecting the functionality of the embodiments. Therefore, those skilled in the art realize that due to the lack of updated or finally agreed terms, the embodiments and their scope of protection should not be limited to the specific terms used herein by way of example, but should be understood more broadly in terms of the functions and concepts underlying the functions and principles of the present disclosure.

[0148] For example, a mobile station or a mobile node or a user terminal or a user equipment (UE) is a physical entity (physical node) within a communication network. A node can 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 the same or another node or other functional entities of the network. A node can have one or more interfaces that attach the node to a communication facility or medium through which the node can communicate. Similarly, a network entity can have a logical interface that attaches the functional entity to a communication facility or medium through which it can communicate with other functional entities or communication nodes.

[0149] The term "base station" or "radio base station" refers herein to a physical entity within a communication network. Like a mobile station, a base station can 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 the same or another node or other functional entities of the network. The physical entity performs some control tasks regarding communication devices, including one or more of scheduling and configuration. Note that the base station function and the communication device function can also be integrated in a single device. For example, a mobile terminal can also implement the function of a base station for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used for 5G NR is gNB.

[0150] Figure 5Shows a general, simplified, and exemplary block diagram of a user equipment (also referred to as a communication device) and a scheduling device (exemplarily assumed to be located in a base station here, e.g., an eLTE eNB (alternatively referred to as an ng-eNB) or a gNB in 5G NR). The UE and the eNB / gNB communicate with each other through (wireless) physical channels using transceivers respectively.

[0151] The communication device may include a transceiver and a processing circuit. The transceiver in turn may include and / or serve as a receiver and a transmitter. The processing circuit may be one or more pieces of hardware such as one or more processors or any LSI. There is an input / output point (or node) between the transceiver and the processing circuit through which the processing circuit can control the transceiver, i.e., control the receiver and / or the transmitter and exchange received / sent data. The transceiver serving as a transmitter and a receiver may include an RF (radio frequency) front end that includes one or more antennas, amplifiers, RF modulators / demodulators, etc. The processing circuit may implement control tasks such as controlling the transceiver to send user data and control data provided by the processing circuit and / or receive user data and control data to be further processed by the processing circuit. The processing circuit may also be responsible for performing other processes, such as determining, deciding, calculating, measuring, etc. The transmitter may be responsible for performing the transmission process and other processes related thereto. The receiver may be responsible for performing the reception process and other processes related thereto, such as monitoring the channel.

[0152] will be described regarding Figures 6 to 9 an improved measurement and reporting process. Additionally, will be described regarding Figures 10 to 12 an improved conditional handover process. Furthermore, will be described regarding Figures 16 to 21 an improved handover communication process. Finally, will be described regarding Figure 22 an improved HARQ process.

[0153] The solutions provided below will be mainly described 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 a satellite, where the gNB may be, for example, in a satellite (see Figure 4 ) or in an NTN gateway (see Figure 3 ), but may also be located at other locations such as outside the 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.

[0154] UE mobility in such scenarios involves the UE moving between the coverage areas of various satellites, e.g., a UE during flight. UE mobility is typically controlled by the serving gNB, but assisted by the UE which provides power-related measurement results to the serving gNB. The serving gNB can then decide whether it is necessary or advantageous to hand over the UE to another radio cell, and in the affirmative case, initiate an appropriate handover procedure.

[0155] More specifically, it is assumed that the UE (e.g., periodically) performs power-related measurements. For example, power-related measurements can 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 can use in this regard. Typically, power-related measurements can be performed on reference signals such as CSI-RS or SSB as explained above.

[0156] Whether and how the UE performs power-related measurements can be at least partially configured by its serving gNB. This can additionally involve configuration regarding whether, how, and when the UE should report the measurement results to its serving base station (e.g., for assisting handover decisions).

[0157] An exemplary implementation of how to configure measurement and reporting functions in the UE has been explained above (see the discussion of UE measurements in 5G), and this implementation involves, for example, the definition of one or more of (a) measurement objects, reporting configurations, and reporting criteria. For example, event-triggered reporting of measurement results can be defined, which includes reporting-triggering events similar or identical to those explained above (e.g., A1 - A6, B1, B2). The triggering events (especially the conditions for the triggering events) can be related to handover, e.g., where the reporting trigger condition is satisfied when the UE is to be handed over by the serving gNB from its current serving radio cell to another radio cell (e.g., event A2: "Service becomes worse than a threshold"; A3: "Neighbor becomes offset better than SpCell"; A4: "Neighbor becomes better than a threshold").

[0158] Furthermore, it is assumed that the UE can perform measurements on various radio carriers (alternatively referred to as access links or frequency bands) having the same or different radio frequencies. For example, UE measurements are performed 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).

[0159] 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 (more details below).

[0160] Hereinafter, it will be exemplarily assumed that the UE is connected to its serving gNB via a satellite and the UE performs measurements on its radio carrier with the satellite and on one or more radio carriers to other adjacent satellites. These UE measurements can then be used by the serving gNB serving the UE to control the mobility of the UE, including whether to hand over the UE from the serving satellite to another satellite. The handover process initiated by the serving gNB can be, for example, a handover process known from the prior art or an improved conditional handover process to be discussed in more detail later (see Figures 10 - 12 ), where the final decision on whether to hand over is the responsibility of the UE.

[0161] Figure 6 Illustrates a simplified and exemplary UE structure according to the improved measurement and reporting process of the present solution and can be implemented based on the general UE structure explained above in conjunction with Figure 5 The various structural elements of the UE shown in the figure can be interconnected, for example, with corresponding input / output nodes (not shown) in order to exchange control and user data and other signals. Although not shown for illustrative purposes, the UE may include additional structural elements.

[0162] It is thus obvious that the UE may include a measurement circuit, a measurement result generation circuit, a reporting adjustment circuit, and a measurement report transmitter as will be explained below.

[0163] In the said case, as will be apparent from the following disclosure, the processing circuit can thus be exemplarily configured to at least partially perform one or more of the following: perform measurements and thereby generate measurement results, determine whether to adjust at least one of the measurement results and the reporting trigger condition, adjust at least one of the measurement results and the reporting trigger condition, and determine whether the reporting trigger condition is met.

[0164] The transmitter can in turn be configured to be able to at least partially perform the transmission of a measurement report including the measurement results.

[0165] Figure 7It is a sequence diagram of exemplary UE behavior according to the improved measurement and reporting process. It is thus obvious that the UE performs power-related measurements on at least one radio carrier and thereby generates measurement results. The power-related measurements are performed, for example, on one or more serving radio carriers of the UE (in this particular exemplary scenario, the radio carrier connecting the UE to the satellite), the radio carrier connecting the UE to an adjacent satellite, and the radio carrier connecting the UE to a terrestrial network (such as a 5G or LTE antenna).

[0166] As described above, the UE reports the measurement results to its serving base station, for example, depending on whether a specific reporting trigger condition is met. When one or more reporting trigger conditions are met, the UE compiles a measurement report with the obtained measurement results and sends the measurement report to its serving gNB.

[0167] According to this improved measurement and reporting process, before determining whether the reporting trigger condition is met, the UE determines whether to first adjust the measurement reporting process so as to trigger the measurement report transmission earlier than without the adjustment. This additional step of adjusting the measurement reporting process is to take into account that the mobility between satellites is different from, for example, the mobility between terrestrial networks due to the long round-trip delay involved in the communication between the UE and the satellite. As previously explained, the inventors have identified the disadvantages related to the long round-trip delay for the measurement process, and thus there are also such disadvantages for the handover process. By triggering the measurement report earlier, the failure event of too late handover can sometimes be avoided or mitigated. Accordingly, when the radio carrier being measured and the measurement results to be reported involve a long round-trip delay (for example, more than 10 ms for non-terrestrial networks), the UE can make a decision to additionally adjust the measurement reporting process. Alternatively, the UE determines whether to adjust the measurement reporting process according to an instruction given by the serving gNB. One option is for the serving gNB to give this instruction to the UE through the measurement object (MO) configuration for UE measurement.

[0168] Continue Figure 7 Regarding the sequence of UE behavior shown, it is assumed that an additional adjustment will be performed by the UE. As previously mentioned, the adjustment causes the measurement report to be triggered earlier than the corresponding measurement report triggered without the adjustment. In other words, the reporting trigger condition is met earlier, so that the measurement report is sent to the serving base station earlier in time. The advancement of the measurement report in time can be achieved in various ways, for example, by adjusting the measurement results and / or the reporting trigger condition, which will be explained and illustrated in more detail later.

[0169] After adjustment, the UE monitors whether the measurement result meets one of the reporting trigger conditions (the measurement result and / or the reporting trigger condition have been adjusted). Subsequently, in the case where a measurement report is triggered, the UE continues to generate and send a measurement report including some or all of the generated measurement results to the serving gNB. For example, the measurement report includes unadjusted measurement results, thereby providing accurate measurement results for the gNB. On the other hand, instead of or in addition to the unadjusted measurement results, the UE may also include the adjusted measurement results in the measurement report to be sent to the serving gNB. This will allow the serving gNB to also obtain the previous measurement results that have not been sent to the serving gNB, so that the serving gNB has more information to determine whether to initiate a handover procedure.

[0170] Figure 8 The figure illustrates 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 measurement and reporting configurations for the UE, but also responsible for configuring whether and how to adjust the triggering of the measurement report in order to achieve earlier reporting of the measurement results as described above in connection with Figure 7 what has been described.

[0171] The gNB receives a measurement report with measurement results from the UE and can, based on this, make a decision on whether to initiate a handover procedure for the UE to hand over the UE to another radio cell (e.g., another satellite). In the affirmative case, the gNB sends a corresponding handover command to the UE.

[0172] The advantage of the process discussed above is that it can avoid or mitigate late handover failure events, because the additional adjustment of the measurement report advances the triggering in time, enabling the measurement report to be sent to the serving gNB earlier, and the serving gNB can decide on the handover earlier. Additionally, the adjustment scheme is simple because it does not really require relying on other information such as UE location or satellite location (satellite ephemeris).

[0173] In Figure 9 an exemplary and simplified sequence of the improved measurement and reporting process is shown. As shown, the serving gNB of the UE provides a measurement configuration to the UE so that the UE performs measurements on its serving radio carrier and other adjacent radio carriers (in Figure 9 for the sake of illustration, only one adjacent radio carrier is shown). The additional adjustment of the measurement report process is exemplarily shown to occur after the power measurement, but it can also occur in parallel or before. Figure 9 The sequence of

[0174] In the following, some different exemplary implementations are described on how to adjust the measurement report to be triggered earlier than without the adjustment. The adjustment is thus applied to the measurement result before being used to determine whether the 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 early triggering.

[0175] According to an exemplary implementation, one or more suitable power offsets may be introduced to achieve earlier satisfaction of the reporting trigger condition. The power offset may be applied to the measurement result in this way, or the power offset may be applied to the reporting trigger condition. Likewise, the amount of the offset and whether it is negative or positive may depend on the measurement result and / or the reporting trigger condition.

[0176] For illustrative reasons, it is exemplarily assumed that some or all of the reporting trigger conditions that have been 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.

[0177] The entry condition for event A1 (service becomes better than threshold) to start sending measurements to the serving gNB is

[0178] Ms-Hys>Thresh

[0179] When applying adjustments to the report trigger condition, this may be achieved by incorporating an offset (exemplarily referred to as NTN-offset) as follows:

[0180] Ms+NTN-offset-Hys>Thresh

[0181] It is evident from the above that by introducing a positive offset, the threshold ("Thresh") can be reached earlier.

[0182] The entry condition for event A2 (service becomes worse than the threshold) is

[0183] Ms+Hys <Thresh

[0184] When adjusting this report trigger condition, this can be achieved by incorporating the offset as follows:

[0185] Ms-NTN-offset+Hys <Thresh

[0186] It is evident from the above adjusted trigger conditions that by introducing a negative offset, the threshold is reached earlier (<) than without.

[0187] The entry condition for event A3 (neighbor becomes offset better than SpCell) is

[0188] Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off

[0189] When adjusting the trigger condition for this report, this can be achieved by combining one or two offsets as follows:

[0190] Mn + NTN - neighbor - offset + Ofn + Ocn – Hys > Mp - NTN - serving - offset + Ofp + Ocp + Off

[0191] According to a specific implementation, an offset (here exemplary NTN - serving - offset) is defined for the trigger condition part of the reference serving cell, and another offset (here exemplary NTN - neighbor - offset) is defined for the trigger condition part of the reference neighboring cell. Accordingly, when determining the same trigger condition for the serving cell and other neighboring cells, the same NTN - serving - offset and the same NTN - neighbor - offset can be reused. This simplifies the adjustment because for each report trigger condition, at most two different offsets are defined, namely one for the reference serving cell and one for the reference neighboring cell.

[0192] The entry condition for event A4 (neighbor becomes better than the threshold) is

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

[0194] When adjusting the trigger condition for this report, this can be achieved by combining offsets as follows:

[0195] Mn + NTN - offset + Ofn + Ocn - Hys > Thresh

[0196] It is thus obvious that by forcing an increase in the left - hand side measurement result of the neighboring cell, the threshold is reached earlier.

[0197] In summary, adjusting the measurement report trigger depends on the specific trigger condition, provided that the condition is reached in advance.

[0198] Specific values can be configured by the network (e.g., gNB) together with the remaining UE measurements configuration (e.g., measurement objects, reporting criteria, etc.).

[0199] When the NTN - specific offset is set to 0, the report trigger condition also applies to other scenarios.

[0200] The values of different offsets can be determined by the gNB in different ways to balance the impact of the offset on each triggering condition, such as avoiding or minimizing other handover failures (such as premature handover). According to an exemplary implementation, the gNB determines the offset value depending on the round-trip delay experienced by the UE and the serving gNB.

[0201] In addition, for example, when it is determined that there are too many handover failures or too many measurement reports are triggered, the gNB can also change the adjustment (such as the offset) during operation to adapt to an improved measurement reporting process. For example, the reconfiguration or cancellation of the measurement report adjustment can be carried out by using a message from the RRC protocol (such as an RRC reconfiguration message).

[0202] According to another exemplary implementation of how to implement the adjustment of the measurement report, instead of using the adjustment configured by the network, the adjustment is determined by the UE itself. The above-mentioned offsets (such as NTN-offset, NTN-serving-offset, 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 (the difference is called the exemplary Δmeas). In other words, the change in the measurement is doubled and thus causes the measurement report to be triggered earlier than without the offset.

[0203] For example, again for illustrative purposes, the 5G measurement events A1, A2, A3 discussed above.

[0204] The entry condition for event A1 (the serving becomes better than the threshold) to send the measurement result to the serving gNB is

[0205] Ms-Hys>Thresh

[0206] When applying the adjustment to this report triggering condition, this can be achieved by incorporating the measurement difference Δmeas, as shown below:

[0207] Ms+Δmeas-Hys>Thresh

[0208] It is obvious from the above that by amplifying the growth of the measurement result, the threshold ("Thresh") is reached earlier.

[0209] The entry condition for event A2 (the serving becomes worse than the threshold) is

[0210] Ms+Hys<Thresh

[0211] When applying the adjustment to this report triggering condition, this can be achieved by incorporating the measurement difference Δmeas, as shown below:

[0212] Ms+Δmeas+Hys<Thresh

[0213] As is obvious from the triggering conditions adjusted above, by increasing the drop in the measurement result, the threshold ratio is reached no earlier (<) than without it.

[0214] The entry condition for event A3 (the neighbor becomes better than the SpCell) is

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

[0216] When applying the adjustment to this reporting triggering condition, this can be achieved by incorporating the measurement difference Δmeas, as follows:

[0217] Mn + Δmeas_n + Ofn + Ocn - Hys > Mp + Δmeas_p + Ofp + Ocp + Off

[0218] It is thus obvious that by introducing an offset Δmeas for the serving of adjacent measurements respectively, the change (the drop or increase in the measurement power) is artificially amplified. As a result, the triggering condition is satisfied earlier than without the offset.

[0219] Calculating the measurement difference as the offset, rather than following the offset value configured by the network, avoids the need for the gNB to configure the offset for the UE and allows the adjustment of the offset to be maintained for good handover performance. Additionally, the adjustment can be more precise as it is based on the UE's previous measurements rather than an artificial value set by the serving gNB. On the other hand, the network has less control over how the measurement report is adjusted.

[0220] As discussed above, after receiving the measurement report with the measurement result, the gNB will ultimately decide to initiate the handover process with the UE. As an option, the handover process can be a standard handover process, as already defined in, for example, the 3GPP standard (see TS38.331 v15.4.0).

[0221] On the other hand, in the following, reference will be made to Figures 10 - 12Describe an improved conditional handover process that can be adopted 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 the UE with a condition (e.g., in a handover command message), which the UE can use to determine whether and when to perform the indicated handover. Conditional handover has the advantage of potentially reducing handover latency, as the handover can be prepared by the serving gNB and then executed by the UE promptly when needed. When performing a handover, the need to send another measurement report to the serving gNB to trigger the handover process is avoided. However, the handover is prepared in a potential target cell, such that the target gNB needs to reserve resources for the UE for a long time (e.g., dedicated PRACH resources for random access, C-RNT), and these resources may not be used even at the end (e.g., when the UE does not perform the handover).

[0222] In combination Figures 10 - 12 The improved conditional handover process discussed attempts to mitigate these issues 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 Illustrates an exemplary message exchange between a UE, a serving gNB, and an adjacent gNB that is a possible target for a handover. Figure 11 Is an exemplary sequence diagram of UE behavior, while Figure 12 Illustrates an exemplary sequence diagram of the behavior of a gNB acting as the serving gNB of the UE.

[0223] As previously mentioned, the handover decision is typically made by the serving gNB and assisted by the UE by providing a measurement report on the serving radio carrier and possibly other adjacent radio carriers. Accordingly, Figure 10 The first message shown in the message exchange diagram of Figures 6 to 9 is the measurement report sent by the UE to its serving gNB. The measurement report can be generated according to the improved measurement report process discussed above (e.g., triggered earlier due to additional adjustments triggered by the measurement report). On the other hand, the measurement report can also be a "normal" measurement report, which is triggered when the UE does not have a trigger for adjusting the measurement report function.

[0224] Based on the received measurement report (and the measurement results included therein), the serving gNB can decide that a handover to another radio cell (e.g., another satellite) may be beneficial to the UE and thus initiate an appropriate handover process with the target gNB (adjacent gNB) and the UE.

[0225] Here it is assumed that the serving gNB decides to perform a conditional handover for the UE. The decision of the gNB supporting conditional handover can be based on various different criteria. For example, the serving gNB can decide on conditional handover in the case where the UE is configured before performing the improved measurement and reporting process as explained above in conjunction with Figures 6 to 10 . More specifically, the serving gNB typically configures the UE on how to perform power-related measurements and the reporting of measurement results, which can also include whether and how the UE adjusts the measurement report trigger (e.g., NTN-related offset values, etc.). However, the early reporting of measurement results achieved through the improved measurement and reporting process discussed above can theoretically lead to an increase in the situation of premature handover. This drawback can be alleviated by performing a conditional handover decision, because when the handover acceptance condition is met and not too early, the UE can thus perform the indicated handover to the target cell.

[0226] Additionally or alternatively, the serving gNB can also decide to perform a conditional handover instead of a normal handover based on the round-trip delay incurred in the communication with the UE. For example, if the round-trip delay exceeds a specific threshold (e.g., 10 ms), it may be beneficial to leave the final handover decision to the UE in order to avoid an incorrect handover decision due to a long round-trip delay.

[0227] A further additional or alternative criterion for deciding to make the handover conditional is the handover failure rate. For example, assume that so far, the serving gNB and the UE have performed an unconditional handover process in its radio cell. However, in the case where the handover failure rate (e.g., premature handover failure rate) is too high, the serving gNB can determine that it is beneficial to make the handover conditional with conditions suitable for the UE's final decision, and can reduce the handover failure rate.

[0228] A further additional or alternative criterion for deciding to make the handover conditional is based on the satellite and / or UE's location. For example, even if the serving gNB decides from the measurement report that conditional handover is not required, if the satellite location and / or UE location indicates that the UE is located near the cell edge, the gNB can still trigger a conditional handover.

[0229] Referring again to Figure 10 , assume that the serving gNB decides to perform a conditional handover, for example, according to one or more of the above-mentioned criteria. The serving gNB prepares the handover in the target cell (see the handover request and handover acknowledgment in Figure 10 ) and sends a handover command message to the UE. As in Figure 10As exemplarily shown in the figure, the handover process can be initiated by, for example, requesting a handover and waiting for a handover acknowledgment from the 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). After receiving the handover acknowledgment from the neighboring gNB, the serving gNB continues with the handover process and sends a corresponding handover command message to the UE.

[0230] As usual, the handover command message may include identification and additional information to identify and connect to the target cell. In addition, the handover command message includes one or more handover acceptance conditions and handover rejection conditions. The UE checks the handover acceptance conditions to determine whether and when to perform the handover. In case the handover acceptance conditions are met, the UE performs the handover. On the other hand, the UE checks the handover rejection conditions to determine whether to reject the handover instruction. In case the handover rejection conditions are met, the UE immediately rejects the handover and may provide the corresponding information about the rejection to its serving gNB (the serving gNB may use this information to indicate to the target gNB to release any resources previously reserved for the UE handover). Figure 10 Both the handover acceptance case and the handover rejection case are illustrated.

[0231] The handover acceptance conditions and the handover rejection conditions can be determined by the serving gNB depending on the specific handover scenario. According to an alternative implementation, the handover acceptance and rejection conditions can be correlated, e.g., such that they are exclusive and allow the UE to clearly decide whether to accept or reject the handover. This helps to enforce an immediate decision on the handover and thus allows minimizing the resource reservation time in the target cell. Additionally, assuming that the UE and the serving gNB interrupt communication during the handover, forcing the UE to make an immediate decision on the indicated handover can also help to minimize the communication interruption time, since the UE and the serving gNB can immediately resume UL / DL communication. On the other hand, the handover acceptance and rejection conditions do not need to be fully complementary. Thus, for example, there can be measurement situations where neither the handover acceptance conditions nor the handover rejection conditions are met at the same time. There is a gap between the acceptance and rejection conditions.

[0232] For example, a possible handover rejection condition is "if the serving cell is better than the target cell by more than x dB for at least y ms", where the parameter values x and y can be appropriately set by the gNB (e.g., x can be 5 dB and y can be 50 ms). The handover acceptance condition can be, for example, "if the target cell is better than the serving cell by more than x dB for at least y ms", where the parameter values x and y can be appropriately set by the gNB (e.g., x can be 8 dB and y can be 30 ms).

[0233] The information about rejecting the handover can be sent to the serving gNB of the UE in several different ways (which can, for example, depend on whether uplink data still needs to be sent).

[0234] According to an exemplary solution, in the absence of UL traffic, the handover rejection information can be sent as part of an RRC (Radio Resource Control protocol) message (such as an RRCReconficuationComplete message or another possible new RRC message). Additionally or alternatively, the handover rejection information can be implicitly provided to the serving gNB, for example, by sending a measurement report to the serving gNB in response to a conditional handover command message. The serving gNB can implicitly derive from it that the UE rejects the handover.

[0235] According to other exemplary solutions, in the presence of UL traffic, the handover rejection information can be included in a MAC (Media Access Control) control element (CE) together with the UL traffic data.

[0236] In any case, the serving gNB is thus provided with the information that the handover has been rejected by the UE.

[0237] In an optional implementation, when rejecting a handover, the UE can be configured to avoid sending additional measurement reports to the serving gNB for a specific period of time. This has the advantage that no additional (conditional) handovers are triggered shortly after rejecting a handover. For example, the UE can use a prohibition timer that starts when rejecting a handover. This timer can be configured by the network, for example, by the serving gNB when configuring the measurement and reporting functions in the UE.

[0238] According to another optional implementation, a mechanism is incorporated to extend the resource reservation at the target radio cell, for example, to avoid a situation where the resource reservation in the target cell is prematurely cancelled. More specifically, the resource reservation in the target cell can 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 expire before the UE makes a decision on whether to accept or reject the handover. This problem may be exacerbated in cases involving long round-trip delays and in cases where the handover acceptance and rejection conditions are defined in such a way that the UE does not immediately decide to reject or accept the handover.

[0239] In such a scenario, when neither the handover acceptance condition nor the handover rejection condition is met, it is beneficial for the UE to instruct the serving gNB to extend the resource reservation in the target cell. As Figure 11As shown, the UE can optionally check whether the corresponding resource reservation timer has expired. If it has expired, the UE cannot switch to the target gNB as expected, and the UE connects to its old serving gNB or another gNB (e.g., this involves performing RRC connection reestablishment). This instruction can be sent in a similar or identical manner as the discussion on how to convey the 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 can 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 can optionally assume that the handover is being performed as expected (see Figure 12 ).

[0240] According to a further solution, the handover process is further improved by allowing the UE to continue communicating with its serving gNB and performing the handover process to the target cell simultaneously. In the prior art solutions, as part of the handover execution, when the UE initiates a random access process to the target cell, the UL / DL communication is interrupted. However, because of the UL / DL communication interruption, this causes a service interruption until the UE connects to the new target cell (continuing UL / DL communication with the target gNB) or until the UE reconnects to the serving gNB (if the handover is not successful). While the service interruption may not be a problem for mobility between networks with small round-trip delays (such as terrestrial networks), for mobility with large round-trip delays (such as for a UE moving between different NTN networks, e.g., satellites), the service interruption is a problem. Accordingly, reducing the service interruption caused by the UE stopping UL / DL communication until the UE connects to the target gNB, or reconnecting to its serving gNB again if the handover fails, is a concern.

[0241] This can be achieved by the UE continuing to communicate with the serving gNB even after participating in a (conditional) handover and even after starting the random access process to the target cell. More specifically, the UE receives a handover command and initiates a random access process to connect to the target gNB, but still continues DL / UL transmissions with the serving gNB. This correspondingly applies to the serving gNB, which, as before the decision to hand over the UE, also continues to send DL data and receive UL data. However, in this case, the UE must perform UL / DL communication in parallel with the random access process, and it is advantageous to coordinate the uplink and downlink transmissions to / from the serving gNB and the uplink and downlink transmissions for the random access to / from the target gNB. This can be achieved by referring to Figures 16 to 21 the following solution described.

[0242] In short, the UE operates the DRX (Discontinuous Reception) function (more details are provided later). This function defines the DRX active time periods during which the UE can actively communicate, and additionally provides power saving opportunities for the UE during the so-called DRX off periods. According to an exemplary solution, the UE continues to communicate with the serving base station during the DRX active time, while using the DRX off period to perform a random access procedure with the target cell. In this way, the UE can communicate in parallel with the serving base station and the target base station. The UE can thus interrupt communication with the serving base station after establishing a connection with the target gNB. As a result, a "connect-then-disconnect" handover is achieved, minimizing service interruption due to handover.

[0243] In the following, reference is made to Figures 13 to 15 provide more details on the random access procedure and the DRX function, while referring to Figures 16 to 21 explain in more detail different implementations of the improved handover communication procedure. A specific and exemplary random access procedure that can be used for this solution will be explained below. Similar to LTE, 5G NR provides a RACH (Random Access Channel) procedure (or simply random access procedure) (see Section 5.1 of 3GPP TS 38.321, v15.3.0). For example, the UE can use the RACH procedure to access a cell it has found. The RACH procedure can also be used in other scenarios within NR, such as:

[0244] · For handover, when establishing synchronization with a new cell;

[0245] · To re-establish uplink synchronization with the current cell in case of loss of synchronization due to no uplink transmission from the device for too long;

[0246] · To request uplink scheduling in case no dedicated scheduling request resources are configured for the device.

[0247] In the following, reference will be made to Figure 13 and 14 describe the RACH procedure in more detail. If the uplink transmission of the mobile terminal is time-synchronized, the mobile terminal can be scheduled for uplink transmission. The Random Access Channel (RACH) procedure serves as an interface between an asynchronous mobile terminal (UE) and orthogonal transmissions of the uplink radio access. For example, random access is used to achieve uplink time synchronization for user equipment that has not yet obtained or has lost its uplink synchronization. Once the user equipment achieves uplink synchronization, the base station can schedule uplink transmission resources for it. One 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 and performs a random access procedure to achieve uplink time synchronization in the target cell.

[0248] There can be two types of random access processes where access is allowed either competitively (i.e., implying an inherent risk of collision) or non-competitively (non-based on competition).

[0249] In the following, the competitive random access process will be described in more detail with reference to Figure 13 This process consists of four "steps". First, the user equipment sends a random access preamble (i.e., Message 1 of the RACH process) 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 process) on the physical downlink shared channel (PDSCH) addressed by the (random access) RA-RNTI on the PDCCH, which identifies the time-frequency and time slot where the preamble was detected. If multiple user equipments send the same RACH preamble in the same PRACH resource, which is also called a collision, they will receive the same random access response message. The RAR message can convey the detected RACH preamble, a timing alignment command (TA command) for synchronization of subsequent uplink transmissions based on the timing of the received preamble, an initial uplink resource allocation (grant) for the first scheduled transmission, and the allocation 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 process, as the base station does not yet know the "true" identity of the mobile station at this time.

[0250] The user equipment monitors the PDCCH for the reception of a random access response message within a given time window (e.g., called the RAR reception window), which can 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 allocated by the grant. This scheduled uplink transmission conveys the actual random access process message, such as an RRC connection request, an RRC resume request, or a buffer status report.

[0251] In the case where a preamble collision occurs in the first message of the RACH process, i.e., multiple user equipments send the same preamble on the same PRACH resource, the colliding user equipments will receive the same T-CRNTI in the random access response and they will also collide in the same uplink resources when transmitting their scheduled transmissions in the third step of the RACH process. In the case where the scheduled transmission from one user equipment is successfully decoded by the base station, the competition for the other user equipments remains unresolved. For the solution of this type of competition, the base station sends a competition resolution message (fourth message) addressed to the C-RNTI or a temporary C-RNTI. The process ends here.

[0252] Figure 14 A simplified contention - free random access procedure as compared with the contention - based random access procedure is shown. In the first step, the base station provides a preamble for random access to the user equipment, so that there is no risk of collision (i.e., multiple user equipments sending the same preamble). Accordingly, the user equipment then sends the preamble signaled by the base station on the PRACH resource in the uplink. Since contention - free random access avoids the situation where multiple UEs send the same preamble simultaneously, essentially, the contention - free random access procedure ends after successfully receiving the random access response of the UE.

[0253] 3GPP is also researching a two - step RACH procedure for 5G NR, in which a message 1 corresponding to messages 1 and 3 in the four - step RACH procedure is sent first. Then, the gNB will respond with a message 2 corresponding to messages 2 and 4 in the LTE RACH procedure. Due to the reduced message exchange, the waiting time of the two - step RACH procedure can be reduced compared with the four - step RACH procedure. The radio resources for this message are optionally configured by the network.

[0254] After introducing the exemplary random access procedures, a specific exemplary DRX function that can be assumed for this solution will be described below. Power saving is an important issue in mobile communication. To reduce the battery consumption in the UE, a mechanism is used to minimize the time the UE spends monitoring the PDCCH, which is called discontinuous reception (DRX) functionality.

[0255] The DRX functionality can be configured for RRC_IDLE. The DRX functionality can also be configured for "RRC_CONNECTED" UEs so that it does 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).

[0256] The following parameters can be used to define the DRX UE behavior; that is, the on - duration period when the mobile node is active (e.g., during the DRX active time), and the period when the mobile node is in DRX (e.g., not during the DRX active time, during the DRX off - time).

[0257] - On-duration: In a downlink subframe, more specifically in a subframe with PDCCH (also referred to as a PDCCH subframe), the duration for which a user equipment receives and monitors the PDCCH after waking up from DRX. It should be noted throughout this invention that the term "PDCCH" refers to PDCCH, EPDCCH (when configured in a subframe), or R-PDCCH for a relay node configured with R-PDCCH and not paused. If the user equipment successfully decodes the PDCCH, the user equipment remains awake / active and starts an inactivity timer; [1 - 200 subframes; 16 steps: 1 - 6, 10 - 60, 80, 100, 200];

[0258] - DRX inactivity timer: The duration for which a user equipment waits to successfully decode a PDCCH starting from the last successful decoding of a PDCCH in a downlink subframe; when the UE fails to decode the PDCCH during this period, it re-enters DRX. The user equipment should restart the inactivity timer only for the first transmission (i.e., not for retransmissions) after a single successful decoding of a PDCCH. [1 - 2560 subframes; 22 steps, 10 spare: 1 - 6, 8, 10 - 60, 80, 100 - 300, 500, 750, 1280, 1920, 2560]

[0259] - DRX retransmission timer: Specifies the number of consecutive PDCCH subframes that the UE expects a downlink retransmission after the first available retransmission time. [1 - 33 subframes; 8 steps: 1, 2, 4, 6, 8, 16, 24, 33];

[0260] - DRX short cycle: Specifies the periodic repetition of the on-duration of a possible inactivity period following a 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];

[0261] - DRX short cycle timer: Specifies the number of consecutive subframes that the UE follows the short DRX cycle after the DRX inactivity timer expires. This parameter is optional. [1 - 16 subframes];

[0262] -Long DRX cycle start offset: Specifies the periodic repetition of the possible inactivity period following the DRX long cycle, and the offset in the subframe at the start of the inactivity period (determined by the formula defined in Section 5.7 of TS 36.321); [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 - the subframe length of the selected cycle].

[0263] The total duration of the UE wake-up is called the "active time" or DRX active time. The active time includes, for example, the inactivity duration of the DRX cycle, the time when the UE performs continuous reception when the inactivity timer does not expire, and the time when the UE performs continuous reception when waiting for a downlink retransmission after one HARQ RTT. Similarly, for the uplink, the UE is awake (i.e., in the DRX active time) at the subframes where it can receive uplink retransmission grants (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 inactivity duration and is variable depending on, for example, the PDCCH activity maximum.

[0264] The "DRX period" or "DRX off period" is the duration of a downlink subframe during which the UE can skip the reception of the downlink channel for power saving purposes, i.e., it does not need to monitor the downlink channel. The operation of DRX gives the mobile terminal the opportunity to repeatedly deactivate the radio circuitry (according to the current active DRX cycle) to save power. Whether the UE actually remains in DRX (i.e., inactive) during the DRX period can be determined by the UE; for example, the UE typically performs inter-frequency measurements that cannot be carried out during the inactivity duration and thus need to be performed at some other time (e.g., during the DRX off time).

[0265] The parameterization of the DRX cycle involves a trade-off between power saving and waiting time. To meet these conflicting requirements, two DRX cycles - a short cycle and a long cycle - can be configured for each UE; the short DRX cycle is optional, i.e., only the long DRX cycle can be used. The transition between the short DRX cycle, the long DRX cycle, and continuous reception is controlled by a timer or an explicit command from the eNodeB.

[0266] Figure 15Examples of DRX operations are disclosed. The UE checks for scheduling messages (which can also be referred to as downlink / uplink grants; e.g., indicated on the PDCCH by its cell radio network temporary identity C-RNTI) during the "on duration" period, which is the same for both long DRX cycles and short DRX cycles. When a scheduling message is received during the "on duration period", the UE starts an "inactivity timer" and continues to monitor the PDCCH of each subframe while the inactivity timer is running. During this period, the UE can be considered to be in the "continuous reception mode". Whenever a scheduling message is received while the inactivity timer is running, the UE restarts the inactivity timer, and when it expires, the UE enters the short DRX cycle and starts a "short DRX cycle timer" (assuming a short DRX cycle is configured). When the short DRX cycle timer expires, the UE enters the long DRX cycle. The short DRX cycle can also be initiated by a DRX MAC control element, which the eNB can send at any time to immediately place the UE into a DRX cycle, i.e., the short DRX cycle (if so configured) or the long DRX period (in the case where no short DRX cycle is configured).

[0267] The basic concepts of DRX explained above for LTE also apply to the new 5G NR, but there are some differences (see section 5.7 of 3GPP TS 38.321 v15.2.1).

[0268] It can be clearly seen therefrom that DRX in 5G NR is also based on long DRX cycles 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. 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 operation principle of the 5G-NR DRX mechanism is as Figure 15 shown.

[0269] Reference 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, the corresponding UE behavior is shown in Figure 17 .

[0270] If the UE finally hands over from its serving gNB to another neighboring gNB. Correspondingly and from Figure 16 it is obvious that, exemplarily assume 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 base station. The measurement report can be, for example, according to the above in combination with Figures 6 - 9The improved measurement and reporting solution discussed above is sent, but it can also be sent by the UE as known in the prior art. In other words, the following improved handover solution can be optionally combined with the improved measurement and reporting process discussed above, but can also be used alone.

[0271] 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).

[0272] 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 confirmation message. The serving gNB then sends a handover command message to the UE. The handover command may be an unconditional handover command that forces the UE to perform the handover. According to different solutions, the handover command message may instead be conditional, for example including at least a handover acceptance condition for the UE to finally decide whether and when to perform the handover based on the handover acceptance condition. In addition, the handover command message may optionally also include the above combined Figures 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.

[0273] Furthermore, it is assumed that upon receipt of 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. At the same time, the UE is expected to continue communicating with the serving gNB. This parallel operation is Figure 16 are illustrated as corresponding boxes, which then include arrows indicating specific messages exchanged between the entities.

[0274] UE and serving gNB are operating DRX functions, such as 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 concurrent communication between the UE and the serving gNB and the target gNB, although it should be understood that the DRX functionality is also followed between the UE and the serving gNB when the UE and the serving gNB communicate with each other.

[0275] 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 the opportunity to save power (e.g. by neither transmitting nor monitoring channels for receiving data). Figure 16As shown, the UE communicates with the serving base station during the DRX active time period and communicates with the target gNB during the DRX off time period. This includes sending messages 1 and 3 of the random access procedure to the neighboring gNB during the DRX off period, and receiving messages 2 and 4 of the random access procedure from the neighboring gNB during the DRX off period. Therefore, the serving gNB and the UE may still continue with DL / UL transmissions without conflicting with the random access procedure performed between the UE and the target gNB.

[0276] There are several ways to implement the UE to perform the random access procedure during the DRX off period. Briefly, the DRX function 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 for the UE to be handed over in these PRACH resources. These dedicated PRACH resources can then be used by the UE and the target gNB to exchange messages of the random access procedure.

[0277] According to one exemplary implementation ( Figure 18 and 20 as shown), the serving gNB sends information about the DRX configuration of the UE to the target gNB. Then, the target gNB can adapt the PRACH resources used by the UE for the random access procedure to the DRX configuration received from the serving gNB, so that the PRACH resources to be used by the UE will fall within the DRX off period. This information about the DRX configuration of the UE can be sent, for example, together with the handover request message (see Figure 16 ), or in a message separate from the handover request message. Figure 20 is illustrated to cover both variants. In addition, the UE will be provided with information about the adapted PRACH resources. According to one implementation, the PRACH resource information is first (e.g., as Figure 20 exemplarily shown in together with the handover acknowledgment message) sent to the serving gNB, and then (e.g., together with or separately from the handover command message) sent to the UE.

[0278] In any case, the UE will receive information about the PRACH resources (adapted by the target gNB), and the UE will use these resources for the random access procedure and use those PRACH resources configured by the target gNB that fall within the off period of its DRX function. Similarly, the target gNB also 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 accordingly monitors (e.g., the PDCCH of the target gNB) during its DRX off period to determine whether it has received a random access message.

[0279] Information about the round-trip latency 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 (e.g., together with or separately from the DRX configuration) to the target gNB. The target gNB can then use this information to more precisely align the PRACH resources with the off-periods of the DRX function, so as to avoid the PRACH resources falling into the DRX active period rather than the DRX off-period due to latency in communication.

[0280] Additionally or alternatively, the round-trip latency (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 the DRX off-period. In other words, the round-trip latency of another UE is used as an estimate of the round-trip latency that the UE will experience when performing a random access procedure with the target gNB. This is advantageous because the round-trip latency of other UEs is known at the target gNB, thus eliminating the need to exchange information about the round-trip latency. Furthermore, the round-trip latency estimate can be more accurate because it is estimated with respect to the same target gNB with which the reference UE will perform random access.

[0281] In previous implementations, the PRACH resources were adapted while keeping the DRX function as initially configured. However, conversely, according to the second exemplary implementation described in conjunction with Figure 19 and 21 the DRX configuration used by the UE and the serving base station is adapted to coordinate with the PRACH resources at the target gNB. More specifically, the serving gNB learns about the PRACH resources in the target gNB that will be used by the UE for random access, and then adapts the DRX configuration such 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 can obtain information about the PRACH resources in the target radio cell from the target gNB, for example. In one exemplary implementation, after receiving a handover request, the target gNB provides information about the PRACH resources together with the handover acknowledgment message to the serving gNB.

[0282] Alternatively, the serving gNB may obtain information on PRACH resources based on the physical cell identifiers of neighboring radio cells. The physical cell identifier (PCI) is obtained by the serving gNB, for example, from a measurement report (received from the UE). It is assumed here that the PRACH resources are related to the physical cell identifiers, such that the serving gNB can derive the PRACH resources from the PCI. For example, there may be multiple (e.g., a total of 3) different PRACH resource configurations, which can be derived, for example, based on the formula PCI mod 3, where any PCI satisfying PCImod3 = 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.

[0283] In any 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. For example, the adapted DRX configuration may be sent to the UE together with or separately from the handover command message (e.g., using the RRCReconfiguration message).

[0284] Similar to what has been explained in connection with the above first exemplary implementation (adapting PRACH resources to the DRX configuration), the serving gNB may use information on the round-trip delay experienced by the UE during communication with the serving gNB to more precisely align the PRACH resources with the time periods of the DRX function. Information on the RTD in the serving radio cell is already available at the serving gNB. Additionally or alternatively, when communicating with the target gNB, information on the round-trip delay experienced by another UE is sent by the target gNB to the serving gNB, and then the serving gNB uses this round-trip delay related to the target gNB and the dedicated PRACH resources in the target cell to configure the DRX off periods.

[0285] According to the above improved handover communication solution, the communication interruption caused by the handover is minimized because the communication between the UE and the serving gNB can continue while the UE performs random access with the target radio cell. The make-before-break handover is effectively achieved.

[0286] An important mechanism commonly used in LTE and 5G to improve communication between the UE and the gNB is the hybrid automatic repeat request HARQ mechanism (see clause 5.4.2 of 3GPP TS 36.321 v15.4.0 and clause 5.4.2 of TS 38.321 v15.4.0). According to an exemplary implementation, the following improved retransmission function can be based on this.

[0287] There are two levels of retransmission to provide reliability, namely 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 sent and the receiver fails to correctly decode the data packet (errors are usually checked by cyclic redundancy check CRC), the receiver requests retransmission of the packet.

[0288] The MAC layer includes HARQ entities, which are responsible for transmit HARQ operations and receive HARQ operations. Transmit HARQ operations include the transmission and retransmission of transport blocks, and the reception and processing of ACK / NACK signaling. Receive HARQ operations include the reception of transport blocks, the combination of received data, and the generation of ACK / NACK signaling. To enable continuous transmission while a 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 operations. Each HARQ process is responsible for a separate SAW operation and manages a separate buffer.

[0289] The feedback provided by the HARQ protocol is an acknowledgement (ACK) or a negative acknowledgement (NACK). ACK and NACK are generated depending on whether the transmission can be correctly received (e.g., whether the decoding is successful). In addition, in HARQ operations, the eNB can send different coded versions from the original transport block in retransmissions so that the UE can use incremental redundancy (IR) combining to obtain additional coding gain via combining gain.

[0290] If an FEC-encoded packet is sent and the receiver fails to correctly decode the packet (errors are usually checked by cyclic redundancy check CRC), the receiver requests retransmission of the data packet. Generally (and throughout this document), the transmission of additional information is referred to as "retransmission (of the packet)", and such retransmission can but does not necessarily mean the transmission of the same coded information; it can also mean the transmission of any information belonging to the packet (such as additional redundant information) by using different redundancy versions, for example.

[0291] As described above, HARQ is thus used between the UE and the gNB. This also applies to the scenarios discussed above, where the UE and the serving gNB are communicating with each other. In addition, HARQ can also be used in the random access procedure between the UE and the target gNB. This also applies to the situations introduced above, where the UE communicates in parallel with the serving base station (UL / DL communication) and with the target gNB (random access) during handover (see, for example Figure 16)。For example, if the UE has a total of 8 HARQ processes available, these 8 HARQ processes can be shared for communicating 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.

[0292] When the UE starts a random access procedure, it may be the case that all HARQ processes are already being used for communication with the serving cell. To still be able to use HARQ for random access with the target cell, the UE can reallocate one of the HARQ processes it uses for communication with the serving cell for the random access procedure, thereby overwriting the memory associated with the 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.

[0293] The UE can select a HARQ process, for example, based on the priority of the data contained in the HARQ process, or the UE can select a HARQ process based on the data rate of the HARQ process, or the UE can simply randomly select a HARQ process among all HARQ processes.

[0294] Figure 22 The above-described simplified and exemplary UE behavior is illustrated in.

[0295] 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 does not know 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 can send a NACK to the serving gNB.

[0296] On the other hand, if the UE wants to send a new uplink transmission to the serving gNB and no HARQ process is available, the UE performs the UL transmission without any HARQ process, for example, it does not buffer the UL transmission in the HARQ buffer. If the serving gNB requests a retransmission of this UL data, the UE needs to encode the same data and send it to the serving gNB again.

[0297] Alternatively, the serving gNB can try to avoid all HARQ processes being in use during a handover. For example, if the serving gNB knows that the UE is approaching the cell edge (through a measurement report), then it can reduce its DL transmission or UL grant to the UE so that at least one HARQ process can be idle for the UE to perform random access with the target gNB.

[0298] Another aspect

[0299] According to a first aspect, there is provided a UE comprising processing circuitry that performs power-related measurements on at least one radio carrier and generates a measurement result based on the performed measurements. Reporting of the measurement result by the UE is based on at least one reporting trigger condition to be satisfied. The processing circuitry determines whether to adjust at least one of the measurement result and the at least one reporting trigger condition so as to trigger reporting of the measurement result earlier than without adjustment. In case it is determined to adjust, the processing circuitry adjusts at least one of the measurement result and the at least one reporting trigger condition so as to trigger reporting of the measurement result earlier than without adjustment. After adjustment, the processing circuitry determines whether at least one reporting trigger condition for reporting the measurement result is satisfied based on the at least one reporting trigger condition and the generated measurement result. In case reporting of the measurement result is triggered, a transmitter of the UE transmits a measurement report comprising the measurement result.

[0300] According to a second aspect provided in addition to the first aspect, adjustment of at least one reporting trigger condition comprises the processing circuitry applying at least one positive or negative power offset to the at least one reporting trigger condition. In an alternative implementation, the processing circuitry determines the offset according to configuration information received from a serving base station to which the UE is connected or based on a difference between the generated measurement result and a previously generated measurement result. In another alternative implementation, an offset is determined for each of the generated measurement results and used in the adjustment, optionally wherein, for each reporting trigger condition, an offset is determined for a serving radio carrier or an adjacent radio carrier. In another alternative implementation, an offset is determined for a serving radio carrier and another offset is determined for an adjacent radio carrier. In another alternative implementation, an offset is determined for each reporting trigger condition and used in the adjustment.

[0301] According to a third aspect provided in addition to the first or second aspect, adjustment of the measurement result comprises: the processing circuitry determines a difference between the generated measurement result and a previously generated measurement result and applies 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 the at least one reporting trigger condition and the adjusted measurement result.

[0302] According to a fourth aspect provided in addition to any one of the first to third aspects, performance of the measurement by the processing circuitry comprises performing the measurement on at least one non-terrestrial radio carrier. In an alternative implementation, the processing circuitry determines whether to perform adjustment based on whether the radio carrier is a non-terrestrial radio carrier or a terrestrial radio carrier. In an alternative implementation, adjustment is performed when the reporting trigger condition is based on a measurement result of a measurement performed on a non-terrestrial radio carrier.

[0303] According to a fifth aspect provided in addition to one of the first to fourth aspects, measurement results can be used by a serving base station to which a UE is connected to determine whether to initiate a process of switching the UE from its current serving radio cell controlled by the serving base station to another radio cell. At least one reporting trigger condition is configured such that the condition is satisfied when the serving base station can decide to initiate the process of switching the UE from the current serving radio cell to another cell.

[0304] 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, where the conditional handover command includes at least one handover acceptance condition for the UE to perform a handover and / or further includes at least one handover rejection condition for the UE to reject a handover. The processing circuit determines whether the handover acceptance condition is satisfied, and in the case where the handover acceptance condition is satisfied, performs a handover according to the received conditional handover command, and optionally, in the case where the handover acceptance condition is not satisfied, sends information about handover rejection. In another alternative implementation, the processing circuit determines whether the handover rejection condition is satisfied, and in the case where the handover rejection condition is satisfied, sends information about handover rejection.

[0305] According to a seventh aspect provided in addition to the sixth aspect, the information about handover rejection is sent in a radio resource control (RRC) message or as another measurement report. Alternatively, the information about handover rejection is sent together with uplink data; optionally, where the information about handover rejection is sent as a control element (CE) of the media access control (MAC) protocol. In an alternative implementation, the processing circuit determines whether to send uplink data to the serving base station, and in the case where there is no uplink data to send, the handover rejection is sent in an RRC message or as another measurement report. And in the case where uplink data is to be sent, the handover rejection is sent together with the uplink data.

[0306] According to an eighth aspect provided in addition to one of the sixth to seventh aspects, in the case where the processing circuit determines that the 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 information about handover rejection. In an alternative implementation, the time period is configured by the serving base station.

[0307] According to a ninth aspect provided in addition to one of the first to eighth aspects, in the case where neither the handover acceptance condition nor the handover rejection condition is satisfied, the transmitter sends a resource reservation extension request to the serving base station to extend the resource reservation time in an adjacent radio cell.

[0308] According to a tenth aspect provided in addition to one of the first to ninth aspects, the UE performs a handover from its current serving radio cell to another radio cell, where performing the handover includes the UE performing a random access procedure with the other radio cell. After starting to perform the handover to another radio cell, during the communication time period of the discontinuous reception DRX function operated by the UE for communicating with the serving radio base station, the UE continues to communicate with the serving radio base station in the uplink and / or downlink. The UE sends a message of the random access procedure during the dormant time period of the discontinuous reception DRX function operated by the UE for communicating with the serving radio cell, optionally, where the communication time period does not overlap with the dormant time period. In an alternative implementation, the UE receives a message of the random access procedure during the dormant time period of the DRX function.

[0309] According to an eleventh aspect provided in addition to one of the first to tenth aspects, the UE performs a handover from its current serving radio cell to another radio cell, where performing the handover includes performing a random access procedure with another radio cell. After starting to perform the handover to another radio cell, the UE continues to communicate with the serving base station in the uplink and / or downlink using a plurality of hybrid automatic repeat request HARQ processes. The UE uses a plurality of HARQ processes for the random access procedure, and in the case where all of the plurality of HARQ processes have been used for communicating with the serving base station, the processing circuit alternatively determines that one of the plurality of HARQ processes will be reused for the random access procedure.

[0310] According to a 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 a HARQ process for the random access procedure includes overwriting the memory associated with the reused HARQ process with data buffered for the random access procedure. In an alternative 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 alternative 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.

[0311] According to a thirteenth aspect, a method is provided, including the following steps performed by a user equipment UE:

[0312] Perform power-related measurements on at least one radio carrier and generate measurement results based on the performed measurements, wherein the reporting of the measurement results by the UE is based on at least one reporting trigger condition to be satisfied;

[0313] Determine whether to adjust at least one of the measurement results and at least one reporting trigger condition so as to trigger the reporting of the measurement results earlier than without adjustment;

[0314] In case it is determined to adjust, adjust at least one of the measurement results and at least one reporting trigger condition so as to trigger the reporting of the measurement results earlier than without adjustment;

[0315] After adjustment, determine whether at least one reporting trigger condition for reporting the measurement results is satisfied based on the at least one reporting trigger condition and the measurement results;

[0316] In case the reporting of the measurement results is triggered, send a measurement report including the measurement results.

[0317] According to the fourteenth aspect, there is provided a base station including a processing circuit that determines whether to instruct a user equipment (UE) to adjust at least one of the measurement results and at least one reporting trigger condition so as to trigger the reporting of the measurement results earlier than without adjustment. A transmitter of the base station configures the UE to adjust at least one of the measurement results and at least one reporting trigger condition so as to trigger the reporting of the measurement results earlier than without adjustment in case the determination of the processing circuit is to instruct the UE. A receiver of the base station receives a measurement report from the UE, the measurement report including the results of measurements performed by the UE on at least one radio carrier, wherein the reporting of the measurement results by the UE is based on at least one reporting trigger condition to be satisfied.

[0318] According to the fifteenth aspect provided in addition to the fourteenth aspect, the processing circuit determines at least one positive or negative power offset for at least one reporting trigger condition. The transmitter sends configuration information indicating the determined positive or negative power offset to the UE. In an optional implementation, an offset is determined for each of the generated measurement results. In an optional implementation, for each reporting trigger condition, an offset is determined for a serving radio carrier or an adjacent radio carrier. In an optional implementation, an offset is determined for the serving radio carrier and another offset is determined for the adjacent radio carrier.

[0319] According to a sixteenth aspect provided in addition to the fourteenth or fifteenth aspect, a determination by a processing circuit as to whether to instruct a user equipment UE to adjust at least one of a measurement result and at least one reporting trigger condition so as to trigger reporting of the measurement result earlier than without the adjustment is based on whether the radio carrier is a non-terrestrial radio carrier or a terrestrial radio carrier. In an optional implementation, in a case where the UE performs measurements on a non-terrestrial radio carrier, the processing circuit determines that the instruction for the UE to adjust has been performed.

[0320] According to a seventeenth aspect provided in addition to any one of the fourteenth to sixteenth aspects, a transmitter sends a conditional handover command to the UE, where the conditional handover command includes at least one handover acceptance condition for the UE to perform a handover and / or further includes at least one handover rejection condition for the UE to reject a handover. In an optional implementation, a receiver receives information about rejecting a handover of the UE, and the transmitter sends a request to an adjacent target base station that is a handover target to release any resources reserved for the UE's handover in the adjacent radio cell. In an optional implementation, the receiver receives a first resource reservation extension request from the UE to extend the resource reservation time in the adjacent radio cell. The transmitter sends a second resource reservation extension request to the adjacent target base station that is a handover target to extend the resource reservation time in the adjacent radio cell.

[0321] According to an eighteenth aspect provided in addition to any one of the fourteenth to seventeenth aspects, a processing circuit adapts a dormant period of a discontinuous reception DRX function operated by the 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 an adjacent target base station. In an optional implementation, the processing circuit obtains information about the random access resource of the adjacent target base station based on information received from the adjacent target base station or based on a cell identifier of the adjacent target base station.

[0322] According to a nineteenth aspect provided in addition to any one of the fourteenth to eighteenth aspects, another UE hands over from another base station to a base station that is a handover target, where the transmitter sends a message of a random access procedure to the other UE during a dormant period of a discontinuous DRX function operated by the other UE for communicating with the other base station, and the receiver receives a 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 about the DRX function of the other UE. The processing circuit adapts the random access resource used by the other UE to perform a random access procedure with the base station to be consistent with the dormant period of the DRX function. The transmitter sends information about the adapted random access resource to the other base station.

[0323] Hardware and software implementations of the present disclosure

[0324] The present disclosure can be implemented by software, hardware, or a combination of software and hardware. Each functional block used in the description of each of the above embodiments can be partially or entirely implemented by an LSI such as an integrated circuit, and each process described in each embodiment can be partially or entirely controlled by the same LSI or a combination of multiple LSIs. The LSI can be formed as a single chip, or can be formed as one chip to include some or all of the functional blocks. The LSI can include data input and output coupled to itself. Depending on the degree of integration, the LSI here can be referred to as an IC (integrated circuit), system LSI, super LSI, or ultra LSI. However, the technology for implementing integrated circuits is not limited to LSI, and can be achieved by using dedicated circuits, general-purpose processors, or dedicated processors. In addition, an FPGA (field programmable gate array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit units inside the LSI can be used. The present disclosure can be implemented as digital processing or analog processing. If future integrated circuit technology replaces LSI due to advancements in semiconductor technology or other derivative technologies, future integrated circuit technology can be used to integrate the functional blocks. Biotechnology can also be applied.

[0325] The present disclosure can be implemented by any type of device, equipment, or system with communication functions, referred to as a communication device.

[0326] Some non-limiting examples of such communication devices include telephones (e.g., cell phones, smart phones), tablet computers, 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, remote health / telemedicine devices, and transportation vehicles that provide communication functions (e.g., cars, airplanes, ships) and various combinations thereof.

[0327] The communication device is not limited to portable or mobile types, and can 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.

[0328] Communication can include exchanging data through, for example, cellular systems, wireless LAN systems, satellite systems, etc., and various combinations thereof.

[0329] A communication device may include devices such as a controller or a sensor, which are coupled to a communication device that performs the communication functions described in this disclosure. For example, the communication device may include a controller or a sensor that generates a control signal or a data signal, which is used by the communication device that performs the communication functions of the communication device.

[0330] The communication device may also include infrastructure such as a base station, an access point, and any other device, equipment, or system that communicates with or controls the devices such as those in the above non-limiting examples.

[0331] In addition, various embodiments may also be implemented by software modules, which are executed by a processor or directly in hardware. A combination of software module and hardware implementation is also possible. The software modules may be stored on any type of computer-readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disk, CD-ROM, DVD, etc. It should also be noted that the various features of different embodiments may be individually or in any combination be the subject of another embodiment.

[0332] Those skilled in the art will understand that various changes and / or modifications can be made to this disclosure as shown in the specific embodiments. Therefore, this embodiment is considered illustrative rather than restrictive in all aspects.

Claims

1. A communication device, comprising: a processing circuit that generates a measurement result based on power-related measurements on at least one radio cell, wherein reporting of the measurement result by the communication device is triggered based on at least one reporting trigger condition; a transmitter that transmits a report of the measurement result when the at least one reporting trigger condition is satisfied; a receiver that receives a conditional handover command, wherein the conditional handover command includes at least one handover acceptance condition for the communication device to perform a conditional handover, and the at least one handover acceptance condition is determined by a serving base station based on the at least one radio cell being related to a non-terrestrial network and includes an additional handover trigger condition, the additional handover trigger condition including a location-based handover trigger condition and a measurement-based handover trigger condition, wherein the criteria for performing the conditional handover include the location-based handover trigger condition and the measurement-based conditional handover condition, a first value Ofn for the terrestrial network and a second value NTN-neighbour-offset for the non-terrestrial network, as well as the criteria and measurement objects, configured by the serving base station; when 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 determines the conditional handover, and when the measurement-based handover trigger condition is satisfied according to the measurement result, the communication device determines the conditional handover.

2. The communication device according to claim 1, wherein the processing circuit applies at least one positive or negative power offset to the at least one reporting trigger condition.

3. The communication device according to claim 2, wherein one offset is determined for each reporting trigger condition.

4. The communication device according to any one of claims 1 to 3, wherein the execution of the measurement by the processing circuit includes performing measurements on at least one non-terrestrial radio cell.

5. The communication device according to any one of claims 1 to 3, wherein the measurement result can be used by the serving base station to which the communication device is connected to determine whether to initiate a process of switching the communication device from its current serving radio cell controlled by the serving base station to another radio cell; and the at least one reporting trigger condition is configured such that the at least one reporting trigger condition is satisfied when the serving base station can decide to initiate a process of switching the communication device from the current serving radio cell to the other cell.

6. The communication device according to any one of claims 1 to 3, wherein, The processing circuit performs a handover according to the received conditional handover command when the handover acceptance condition is satisfied.

7. 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, wherein reporting of the measurement result by the communication device is triggered based on at least one reporting trigger condition; transmitting a report of the measurement result when the at least one reporting trigger condition is satisfied; Receive a conditional handover command, where the conditional handover command includes at least one handover acceptance condition for the communication device to perform a conditional handover, and the at least one handover acceptance condition is determined by the serving base station based on the at least one radio cell being related to the non-terrestrial network, and the at least one handover acceptance condition includes an additional handover trigger condition, and the additional handover trigger condition includes a location-based handover trigger condition and a measurement-based handover trigger condition. Where the criteria for performing the conditional handover include the location-based handover trigger condition and the measurement-based conditional handover condition. Configure, by the serving base station, a first value Ofn for the terrestrial network and the non-terrestrial network, a second value NTN-neighbour-offset for the non-terrestrial network, as well as the criteria and measurement objects. In the 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 determines the conditional handover, and In the case where the measurement-based handover trigger condition is satisfied according to the measurement result, the communication device determines the conditional handover.

8. A base station, comprising: A receiver that receives a report of measurement results performed by the communication device on at least one radio cell, where the report of the measurement results by the communication device is triggered based on at least one reporting trigger condition to be satisfied; A processing circuit that determines to perform a conditional handover of the communication device based on the measurement results; A transmitter that sends a conditional handover command to the communication device, where the conditional handover command includes at least one handover acceptance condition for the communication device to perform the conditional handover, Where the processing circuit determines that the at least one handover acceptance condition includes an additional handover trigger condition based on the at least one radio cell being related to the non-terrestrial network, and the additional handover trigger condition includes a location-based handover trigger condition and a measurement-based handover trigger condition. Where the criteria for performing the conditional handover include the location-based handover trigger condition and the measurement-based handover trigger condition. The serving base station configures a first value Ofn for the terrestrial network and the non-terrestrial network, a second value NTN-neighbour-offset for the non-terrestrial network, as well as the criteria and measurement objects. In the 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 determines the conditional handover, and In the case where the measurement-based handover trigger condition is satisfied according to the measurement result, the communication device determines the conditional handover.

9. The base station according to claim 8, where the processing circuit determines at least one positive or negative power offset for the at least one reporting trigger condition; The transmitter sends configuration information indicating the determined positive or negative power offset to the communication device.

10. The base station according to claim 9, wherein the receiver receives a first resource reservation extension request from the communication device, and wherein the transmitter sends a second resource reservation extension request to an adjacent target base station.

11. A measurement and handover method, comprising the following steps performed by a base station: Receiving, from a communication device, a report of measurement results performed by the communication device on at least one radio cell, wherein the report of the measurement results by the communication device is triggered based on at least one reporting trigger condition to be satisfied, Determining, based on the measurement results, to perform a conditional handover of the communication device; Sending a conditional handover command to the communication device, wherein the conditional handover command includes at least one handover acceptance condition for the communication device to perform the conditional handover, Wherein determining the at least one handover acceptance condition based on the at least one radio cell being related to a non-terrestrial network includes additional handover trigger conditions, the additional handover trigger conditions including a location-based handover trigger condition and a measurement-based handover trigger condition, Wherein the criteria for performing the conditional handover include the location-based handover trigger condition and the measurement-based conditional handover condition, The base station is configured with a first value Ofn for a terrestrial network and the non-terrestrial network and a second value NTN-neighbour-offset for the non-terrestrial network, as well as the criteria and measurement objects, In the 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 conditional handover is determined by the communication device, and In the case where the measurement-based handover trigger condition is satisfied according to the measurement results, the conditional handover is determined by the communication device.

12. An integrated circuit, comprising: A processing circuit that generates measurement results based on power-related measurements on at least one radio cell, wherein the report of the measurement results by a communication device is triggered based on at least one reporting trigger condition; A transmitter circuit that sends a report of the measurement results when the at least one reporting trigger condition is satisfied; A receiver circuit that receives a conditional handover command, wherein the conditional handover command includes at least one handover acceptance condition for the communication device to perform a conditional handover, and the at least one handover acceptance condition is determined by a serving base station based on the at least one radio cell being related to a non-terrestrial network to include additional handover trigger conditions, the additional handover trigger conditions including a location-based handover trigger condition and a measurement-based handover trigger condition, Wherein the criteria for performing the conditional handover include the location-based handover trigger condition and the measurement-based conditional handover condition, The serving base station is configured with a first value Ofn for a terrestrial network and the non-terrestrial network and a second value NTN-neighbour-offset for the non-terrestrial network, as well as the criteria and measurement objects, In the 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 determines the conditional handover, and in the case where the measurement-based handover trigger condition is satisfied according to the measurement result, the communication device determines the conditional handover.

13. An integrated circuit, comprising: a receiver circuit that receives, from a communication device, measurement results obtained by the communication device on at least one radio cell, wherein the reporting of the measurement results by the communication device is triggered based on at least one reporting trigger condition to be satisfied; a processing circuit that determines, based on the measurement results, to perform a conditional handover of the communication device; a transmitter circuit that sends a conditional handover command to the communication device, wherein the conditional handover command includes at least one handover acceptance condition for the communication device to perform the conditional handover, wherein the processing circuit determines that the at least one handover acceptance condition includes additional handover trigger conditions according to the at least one radio cell being related to a non-terrestrial network, and the additional handover trigger conditions include a location-based handover trigger condition and a measurement-based handover trigger condition, wherein the criteria for performing the conditional handover include the location-based handover trigger condition and the measurement-based handover trigger condition, a base station configured with a first value Ofn for a terrestrial network and the non-terrestrial network and a second value NTN-neighbour-offset for the non-terrestrial network, as well as the criteria and measurement objects, in the 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 conditional handover is determined by the communication device, and in the case where the measurement-based handover trigger condition is satisfied according to the measurement result, the conditional handover is determined by the communication device.

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