WO2025159485A1 - Methods and apparatus for performing relaxed measurements in a wireless communication system - Google Patents

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present invention relates to performing relaxed measurements. The method includes receiving, by the UE (301), indication from a lower layer that indicates that LTM cell switch or RACH-less handover is completed for a configured CG. Further, the method includes setting reference RSRP value to a reference Layer 3 RSRP measurement (SS-RSRP Ref) of a special cell based on SSB upon receiving the indication, when the UE is configured with low mobility criteria. Further, the method includes performing relaxed measurements according to low mobility criteria based on the SS-RSRP Ref. Also, the method includes setting reference stationary connected RSRP value to a L3 RSRP of SpCell based on a SSB upon receiving the indication, and performing, by the UE, the relaxed measurements according to the stationary criteria based on SS-RSRPRefStationaryConnected, when the UE is configured with stationary criteria.

Description

METHODS AND APPARATUS FOR PERFORMING RELAXED MEASUREMENTS IN A WIRELESS COMMUNICATION SYSTEM

This application is based on and derives the benefit of Indian Provisional Application 202441004328 filed on 22nd January 2024, the contents of which are incorporated herein by reference. The proposed embodiments relate to a telecommunication network system. More particularly, the present disclosure relates to performing relaxed measurements.

5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in “Sub 6GHz” bands such as 3.5GHz, but also in “Above 6GHz” bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

Moreover, there has been ongoing standardization in air interface architecture/protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture/service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

The present disclosure relates to wireless communication systems and, more specifically, the present disclosure relates to performing relaxed measurements in wireless communication system.

The principal object of the embodiments herein is to perform relaxed measurements in wireless networks.

Yet another object of the invention is to perform relaxed measurements such as RRM measurement relaxation for a UE configured with low mobility criteria and/or stationary criteria and has performed Lower Layer Triggered Mobility (LTM) cell switch. .

Yet another object of the invention is to perform relaxed measurements for a UE configured with low mobility criteria and/or stationary criteria and has performed RACH-less handover.

Yet another object of the invention is to provide conditions for setting reference RSRP used for determining whether to perform relaxed measurements upon an LTM cell switch or RACH-less handover according to low mobility criteria.

Yet another object of the invention is to provide conditions for setting reference RSRP used for determining whether to perform relaxed measurements upon an LTM cell switch or RACH-less handover according to stationary criteria.

Yet another object of the invention is to provide a UE that sets the reference RSRP used for detecting whether a cell needs to perform relaxed measurements according to low mobility criteria upon performing an LTM cell switch or RACH-less handover.

Yet another object of the invention is to provide a UE that sets the reference RSRP used for detecting whether a cell needs to perform relaxed measurements according to stationary criteria upon performing an LTM cell switch or RACH-less handover.

In an aspect, the objectives are achieved by providing a method for performing relaxed measurements for a UE in a communication system. The method includes receiving by the UE an indication from a lower layer. The indication indicates that a LTM cell switch and a RACH-less handover are completed for a configured Cellgroup (CG). Further, the method includes setting by the UE a reference RSRP value to a reference Layer 3 Reference Signal Received Power (RSRP) measurement (SS-RSRP Ref) of a Special cell (SpCell- The Primary cell of the CG) based on a Synchronization Signal Block (SSB) upon receiving the indication when the UE is configured with low mobility criteria. Further, the method includes performing by the UE the relaxed measurements according to low mobility criteria based on the SS-RSRP Ref. Further, the method includes setting by the UE a reference stationary connected RSRP value (SS-RSRPRefStationaryConnected) to an L3 RSRP of SpCell based on an SSB upon receiving the indication. Further, the method includes performing by the UE the relaxed measurements according to the stationary criteria based on SS-RSRPRefStationaryConnected when the UE is configured with stationary criteria.

In another aspect, the objectives are achieved by providing a UE for performing relaxed measurements. The UE includes a processor and a relaxed measurement controller communicatively coupled to the processor. The relaxed measurement controller receives the indication from the lower layer. The indication indicates that at least one of a Long-Term Mobility (LTM) cell switch and a RACH-less handover is completed for a configured Cellgroup (CG) and the UE is configured with relaxed measurement criteria for low mobility. Further, the relaxed measurement controller sets the reference RSRP value to the reference Layer 3 RSRP measurement (SS-RSRP Ref) of the SpCell based on the Synchronization Signal Block (SSB) upon receiving the indication. Further, the relaxed measurement controller performs the relaxed measurements according to low mobility criteria based on the SS-RSRP Ref. Further, the relaxed measurement controller sets a reference stationary connected RSRP value (SS-RSRPRefStationaryConnected) to an L3 RSRP of SpCell based on an SSB upon receiving the indication. Further, the relaxed measurement controller performs the relaxed measurements according to the stationary criteria based on SS-RSRPRefStationaryConnected when the UE is configured with stationary criteria.

In another aspect, a method performed by a user equipment (UE) in a wireless communication system, the method comprising: receiving, from a lower layer, an indication indicating that at least one of a long term mobility (LTM) cell switch or a random access channel (RACH)-less handover is completed for a configured cell group; determining a reference synchronization signal reference received power (SS-RSRP) based on information for a relaxed measurement criterion configured for the UE; based on the determined reference SS-RSRP, identifying whether a criterion of a relaxed measurement is fulfilled; and in case that the criterion of the relaxed measurement is fulfilled, performing the relaxed measurement is configured.

In another aspect, a user equipment (UE) in a wireless communication system, the UE comprising: a transceiver, and a controller coupled with the transceiver configured to: receive, from a lower layer, an indication indicating that at least one of a long term mobility (LTM) cell switch or a random access channel (RACH)-less handover is completed for a configured cell group, determine a reference synchronization signal reference received power (SS-RSRP) based on information for a relaxed measurement criterion configured for the UE, based on the determined reference SS-RSRP, identify whether a criterion of a relaxed measurement is fulfilled, and in case that the criterion of the relaxed measurement is fulfilled, perform the relaxed measurement is configured.

These and other aspects of the embodiments will be better understood with the following description and accompanying drawings. The descriptions, while indicating preferred embodiments and specific details, are for illustration and not limitation. Many changes and modifications can be made within the scope of these embodiments.

According to an embodiment of the disclosure, a wireless communication can be performed efficiently. Especially, performing relaxed measurements in wireless communication system can be performed more efficiently.

These and other features, aspects, and advantages of the present embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

Fig. 1 is a schematic diagram that illustrates NG-RAN architecture according to prior art.

Fig. 2 is a sequence diagram that illustrates the signaling procedure for LTM according to prior arts.

Fig. 3 is a block diagram of a UE for performing relaxed measurements for UE in a communication system according to embodiments disclosed herein.

Fig. 4 is a flow diagram that illustrates a method for performing measurements for UE in a communication system according to embodiments disclosed herein.

Fig. 5 is a flow diagram that illustrates a method for performing relaxed measurement for low mobility during cell switch according to embodiments disclosed herein.

Fig. 6 is a flow diagram that illustrates a method for performing relaxed measurement for stationary UE during cell switch according to embodiments disclosed herein.

Fig. 7 is a flow diagram that illustrates a method for performing relaxed measurement for low mobility during RACH-less handover in NTN according to embodiments disclosed herein.

Fig. 8 is a flow diagram that illustrates a method for performing relaxed measurement criteria for stationary UE during RACH-less handover in NTN according to embodiments disclosed herein.

Fig. 9 is a flow diagram that illustrates a method for performing relaxed measurement for low mobility during SCG ReconfigurationWithSync according to embodiments disclosed herein.

Fig. 10 is a flow diagram that illustrates a method for performing the relaxed measurement criteria for stationary UE during SCG ReconfigurationWithSync according to the embodiments disclosed herein.

The Next Generation Radio Access Network (NG-RAN) architecture, as depicted in Fig. 1, illustrates a set of gNodeBs (gNBs) connected to the 5G Core (5GC) through the NG interface. The gNBs can be interconnected via the Xn interface and typically comprise a gNB Central Unit (gNB-CU) and one or more gNB Distributed Units (gNB-DUs), which are connected through the F1 interface. This architecture is designed to support the advanced capabilities and requirements of 5G networks.

One of the critical aspects of NG-RAN is the efficient management of radio resources, which includes the measurement and management of radio signal quality and network conditions. Measurement relaxation is a technique employed within this architecture to reduce the frequency and intensity of these measurements, primarily for power saving and improved Radio Resource Management (RRM).

For identifying the most suitable target cell and the most apt moment for the movement to the new cell, network may configure the UE to perform measurements. A UE which is stationary or moving at low speed is less likely to move to a new serving cell, so by relaxing the measurements the measurement resources such as the UE power can be saved. Typically, UE is required to perform a specific number of measurements in a defined time interval. To save the resources used for measurements such as UE power, UE may be configured for performing relaxed measurements. In NR, network may configure UE with low mobility criteria. A UE configured with low mobility criteria (SpCell configured with the low mobility criteria) may evaluate the criteria for identifying if the UE is in low mobility and if this criteria is satisfied, the UE performs relaxed measurements. Simialrly, network also may configure the UE with a stationary criteria. A UE configured with stationary criteria may evaluate this criteria for identifying if the UE is stationary and if the criteria is satisfied, the UE performs relaxed measurements.

Measurement relaxation can be enabled or disabled by the network, particularly in various Radio Resource Control (RRC) states such as a RRC_CONNECTED, a RRC IDLE and a RRC INACTIVE. When measurement relaxation is enabled, a User Equipment (UE), including (e)RedCap UEs, are allowed to relax their neighbor cell RRM measurements under certain conditions, such as when the stationary criterion is met or when both the stationary and not-at-cell-edge criteria are satisfied. The stationary criterion can be configured by the network for the UEs in a RRC CONNECTED state, and the UEs report their RRM measurement relaxation status using UE Assistance Information when the criteria are met or no longer met.

Further, Relaxed Measurement (RLM) and Beam Failure Detection (BFD) relaxation can be separately enabled or disabled through RRC Configuration. RLM relaxation can be configured on a per Cell Group basis, while BFD relaxation can be configured on a per serving cell basis.

Relaxed measurement criteria may be defined for low mobility and for stationary UEs, as below:

All the variables and procedures are defined in 3gpp specifications such as TS 38.331, TS 38.300, TS37.340, TS38.321 etc. The R18.0 version of the specification is considered as background for the proposed invention. However, the relaxed measurement handling based on various types of mobility such as lower layer triggered mobility (LTM) or RACH-less mobility is not addressed in the background.

Thus, it is desired to address the above-mentioned disadvantages, issues, or other shortcomings, or at least provide a useful alternative.

It may be noted that, to the extent possible, like reference numerals have been used to represent like elements in the drawing. Furthermore, those of ordinary skill in the art will appreciate that elements in the drawing are illustrated for simplicity and may not necessarily have been drawn to scale. For example, the dimensions of some of the elements in the drawing may be exaggerated relative to other elements to improve the understanding of aspects of the invention. Further, the elements may have been represented in the drawing by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the drawing with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As is traditional in the field, embodiments are described and illustrated in terms of blocks that carry out a described function or functions. These blocks, which are referred to herein as managers, units, modules, hardware components, or the like, are physically implemented by analog and/or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, and the like, and may optionally be driven by firmware and software. The circuits, for example, may be embodied in one or more semiconductor chips or on substrate supports such as printed circuit boards and the like. The circuits constituting a block may be implemented by dedicated hardware or by a processor (e.g., one or more programmed microprocessors and associated circuitry) or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method. Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the proposed method.

Mobility in wireless networks, particularly in technologies like 5G NR, involves devices moving across different cells. This mobility is managed using a procedure called cell reselection in RRC_IDLE mode. Until NR Release 17, mobility in RRC CONNECTED mode is performed using a procedure called handover. Network-controlled mobility applies to UEs in RRC CONNECTED mode and requires explicit RRC signaling to be triggered by the gNB in NR.

Handover in NR typically consists of three steps: handover preparation, handover execution, and handover completion. The gNB may configure the UE to report measurements. Based on these reported measurements or its own understanding of the network topology, the gNB sends an RRC Reconfiguration message to handover the UE from the source cell to the target cell. The UE then accesses the target cell and sends an RRC Reconfiguration complete message.

An alternative method introduced in 3GPP NR Release 16 allows the gNB to configure the UE with execution conditions for triggering handover. Once these conditions are satisfied, the UE may move to the target cell and send the RRC Reconfiguration complete message. Additionally, 3GPP introduced a new handover method called DAPS handover in Release 16.

In all these methods, the UE performs handover by sending layer 3 (RRC) messages, which can cause considerable signaling overhead and latency issues. Handover and conditional handover (CHO) are referred to as layer 3 mobility. In the case of dual connectivity, the UE may perform PSCellChange or Conditional PSCellChange, which are also considered layer 3 mobility. Specifically, PSCellChange or Conditional PSCellChange can be referred to as SCG layer 3 mobility, while handover and CHO are referred to as MCG layer 3 mobility in the context of dual connectivity.

3GPP Release 18 is considering Lower Layers (L1/L2 layers) Triggered Mobility, also known as LTM, to address issues related to latency, signaling overhead, and other challenges associated with Layer 3 mobility. The goal of LTM, as per 3GPP, is to enable a serving cell change via L1/L2 signaling to reduce latency overhead and interruption time. The network (gNB) may configure the UE with multiple candidate cells to allow fast application of configurations for these candidate cells. Additionally, the network may send MAC CE or L1 signaling to dynamically switch the UE from a source cell to one of the configured candidate cells. LTM can also be triggered based on L1 measurements rather than L3 measurements. The 3GPP proposes performing LTM without resetting lower layers like MAC to avoid data loss and reduce the additional delay of data recovery wherever possible.

The gNB CU may provide LTMCandidateConfiguration, i.e., configure LTM candidate cells through one RRCReconfiguration message for a candidate target cell. Additionally, the gNB may release or modify the candidate configurations. A UE may store the LTM configuration of other candidate cells even after moving to a candidate cell through LTM. The gNB CU also may provide the UE with configurations for performing LTM measurements for different candidate frequencies and candidate cells, and reporting based on the performed LTM measurements. Furthermore, the gNB may release or modify the candidate configurations. A UE may store the LTM configuration of other candidate cells even after moving to a candidate cell through LTM. The gNB also may provide the UE with configurations for performing LTM measurements for different candidate frequencies and candidate cells, and reporting based on the performed LTM measurements. The 3GPP supports subsequent LTM, i.e., after one LTM candidate cell becomes a source cell due to LTM, the UE may store LTM candidate configuration and continue to report LTM measurements (L1 measurements for LTM). The new serving cell may send an LTM cell switch command to the UE, and the UE performs LTM. Such an LTM is called subsequent LTM.

The UE performs Layer 1 (L1) measurements on both the source cell and candidate cell, reporting these measurements through Channel State Information (CSI) reports to the gNodeB Distributed Unit (gNB DU) of the source cell. The gNB DU may send a Medium Access Control Control Element (MAC CE), such as an LTM MAC CE or cell switch MAC CE, instructing the UE to switch to another cell, which is an LTM candidate cell. During the LTM cell switch, the UE may perform random access, or the cell switch may be RACH-less. A timer, referred to as T3xx in this invention, may guard the cell switch.

Before the cell switch, the UE may be requested to perform random access on a candidate cell so that the network can calculate the timing advance and inform the UE either through a random access response or within the MAC CE sent for the cell switch. The gNB may configure the UE to perform random access towards one or more LTM candidate cells to receive the timing advance (TA) before the cell switch is performed. This process is known as Early TA, Early Sync TA, or TA for Early Sync. Random access performed on LTM candidate cells for timing advance reception is known as random access for early TA. UE also may be identify the timing advance on its own, using a method called UE based TA.

To initiate RACH for TA measurement for candidate cells, the gNB sends a Physical Downlink Control Channel (PDCCH) order. Upon receiving this PDCCH order from the serving cell, the UE initiates RACH for TA measurement for candidate cells on one or more candidate cells. The UE sends a RACH preamble to the candidate cells and receives the TA value from the candidate cell. The TA for candidate cells may also be received from the source cell. Normally, the TA will be received in the random access response, but it may also be received through a MAC CE. If the source DU indicates that the UE should retransmit the RACH for early TA, the UE retransmits it. The gNB may also send a PDCCH order to retransmit RACH for TA measurement, also known as RACH for early sync.

The LTM is a procedure in which a gNB receives L1 measurement report(s) from a UE and, on their basis, the gNB changes the UE's serving cell by a cell switch command signaled via a MAC CE. The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through RRC signaling. Then the UE switches to the target cell according to the cell switch command. The LTM procedure can be used to reduce the mobility latency as described.

The network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition is triggered by PDCCH order or through UE-based TA measurement. The network indicates in the cell switch command whether the UE shall access the target cell with an RA procedure if a TA value is not provided or with PUSCH transmission using the indicated TA value. For RACH-less LTM, the UE either monitors PDCCH for dynamic scheduling from the target cell upon LTM cell switch or the UE selects the configured grant occasion associated with the beam indicated in the cell switch command.

The principles apply to LTM includes the UE does not update its security key in LTM and subsequent LTM is supported.

The LTM supports both intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. Additionally, LTM supports inter-frequency mobility, including mobility to an inter-frequency cell that is not a current serving cell. The following scenarios are supported: 1. PCell change in a non-CA scenario, 2. PCell change in a CA scenario, and 3. Dual connectivity scenario, at least for the PSCell change without MN involvement case, i.e., intra-SN PSCell change.

A supervision timer can be used to detect the failure of an LTM cell switch procedure. The LTM procedure fails if the LTM supervision timer expires, upon which the UE initiates an RRC connection re-establishment procedure. While the UE has stored LTM candidate cell configurations, it can also execute any L3 handover command sent by the network. The network is responsible for avoiding any issues due to a collision between LTM execution and L3 handover execution, such as avoiding sending an LTM cell switch command and an L3 handover command simultaneously. The cell switch command is conveyed in a MAC CE, which contains the necessary information to perform the LTM cell switch.

Fig. 2 is a sequence diagram that illustrates the signaling procedure for LTM according to prior arts. The overall procedure for LTM is shown in Fig. 2. Subsequent LTM is done by repeating the early synchronization, LTM execution, and LTM completion steps without releasing other LTM candidate cell configurations after each LTM completion.

Consider at step S1 the UE (201) is in the RRC CONNECTED state.

At step S2 the UE (201) sends a MeasurementReport message to the gNB (105). The gNB (105) decides to configure LTM and initiates candidate cell(s) preparation. At step S3 the gNB (105) performs the LTM candidate preparation. At step S4 the gNB (105) transmits an RRCReconfiguration message to the UE (201) including the LTM candidate cell configurations of one or multiple candidate cells. At step S5 the UE (201) stores the LTM candidate cell configurations and transmits an RRCReconfigurationComplete message to the gNB (105). At step S6a the UE (201) performs DL synchronization with candidate cell(s) before receiving the cell switch command.

Further, at step S6b, the UE (201) performs the early TA acquisition with candidate cell(s) requested by the network before receiving the cell switch command. This is done via CFRA triggered by a PDCCH order from the source cell, following which the UE (201) sends a preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE (201) doesn't receive RAR for the purpose of TA value acquisition, and the TA value of the candidate cell is indicated in the cell switch command. The UE (201) doesn't maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

Furthermore, at step S7, the UE (201) performs L1 measurements on the configured candidate cell(s) and transmits lower-layer measurement reports to the gNB (105). L1 measurement should be performed as long as the RRC reconfiguration in step 2 applies. At step S8, the gNB (105) decides to execute a cell switch to a target cell, and at step S9, the gNB (105) transmits a MAC CE triggering cell switch by including the candidate configuration index of the target cell. At step S10, the UE (201) switches to the target cell and applies the configuration indicated by the candidate configuration index. At step S11, the UE (201) performs the random access procedure towards the target cell when the UE (201) does not have a valid TA of the target cell. At step S12, the UE (201) completes the LTM cell switch procedure by sending an RRCReconfigurationComplete message to the target cell. If the UE (201) has performed an RA procedure, then the UE (201) considers that LTM execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE (201) considers that LTM execution is successfully completed when the UE (201) determines that the network has successfully received its first UL data.

The steps 6-12 can be performed multiple times for subsequent LTM cell switches using the LTM candidate cell configuration(s) provided in step 4.

Some of the mechanisms of RACH-less LTM can be extended to mobility based on Layer 3 signalling and RACH-less handover may be performed for Layer 3 mobility.

In the prior arts, UE performs relaxed measurements based on the reference RSRP set while being in a previous cell after LTM or RACH-less handover. This prevents the UE from relaxing measurements efficiently. For e.g. the UE may have moved from a small cell to a macro cell or from a cell in higher frequency such as a cell in Frequency Range 2 (FR1) to a cell in a lower frequency such as cell in a Frequency Range 1 (FR1) or from a cell in FR1 to FR2. Relaxing measurements based on the RSRP in the previous cell may lead either to the UE not perform relaxed measurements when the measurement relaxation should have been performed or inappropriately relaxing measurements when the measurement relaxation leads to radio link failures or other mobility related failures.

Fig. 3 is a block diagram of a UE for performing relaxed measurements for UE in a communication system according to embodiments disclosed herein. The UE (301) includes a processor (303), a memory (305), an I/O interface (307), and a random access reporting controller (309). Furthermore, the processor (303) of the UE (301) communicates with the memory (305), the I/O interface (307), and the relaxed measurement controller (309). The processor (303) is configured to execute instructions stored in the memory (305) and to perform various processes. The processor (303) can include one or a plurality of processors, can be a general-purpose processor such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and/or an Artificial Intelligence (AI) dedicated processor such as a neural processing unit (NPU).

Furthermore, the memory (305) of the UE (301) includes storage locations that can be addressed through the processor (303). The memory (305) is not limited to volatile or non-volatile memory and can include one or more computer-readable storage media. Non-volatile storage elements such as magnetic hard disks, optical discs, floppy discs, flash memories, EPROM, or EEPROM memories can also be included in the memory (305). Further, the memory (305) of the UE (301) can store various information received from lower layers of the UE (301) and from the network. The UE (301) can store several pieces of information such as indications about the completion of LTM handover or RACH-less handover.

The I/O interface (307) transmits information between the memory (305) and external peripheral devices, which are input-output devices associated with the UE (301). The I/O interface (307) receives various information from the lower layers of the UE (301). This interface is used to maintain seamless communication between the UE (301) and external devices, ensuring that data is transmitted and received.

The relaxed measurement controller (309) communicates with the I/O interface (307) and the memory (305) for performing the relaxed measurement in the communication system. The relaxed measurement controller (309) is an innovative hardware that is realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

The relaxed measurement controller (309) receives the indication from the lower layer. The indication indicates that the LTM cell switch or the RACH-less handover is completed for the configured CG. Further, the relaxed measurement controller (309) sets the reference RSRP value to the SS-RSRP Ref of the special cell based on the SSB upon receiving the indication, when the UE (301) is configured with low mobility criteria. Further, the relaxed measurement controller (309) performs the relaxed measurements according to low mobility criteria based on the SS-RSRP Ref. Further, the the relaxed measurement controller (309) sets the reference stationary connected RSRP value (SS-RSRPRefStationaryConnected) to the L3 RSRP of SpCell based on a SSB upon receiving the indication. Further, the relaxed measurement controller (309) performs the relaxed measurements according to the stationary criteria based on SS-RSRPRefStationaryConnected, when the UE (301) is configured with stationary criteria.

In an embodiment, to perform the relaxed measurements the relaxed measurement controller (309) measures the current RSRP (SS-RSRP) of the SpCell based on the SSB. Further, the relaxed measurement controller (309) determines the relaxed measurement criterion for low mobility is fulfilled by detecting whether a difference between a current SS-RSRP and the SS-RSRP Ref is less than a predefined search delta parameter. Further, the relaxed measurement controller (309) performs the relaxed measurements according to low mobility criteria in RRC CONNECTED state, when the difference between current RSRP value and the reference RSRP value is less than the predefined search delta parameter. Also, the relaxed measurement controller (309) performs the measurements without measurement relaxation according to low mobility criteria in RRC CONNECTED state, when the difference between current RSRP value and the reference RSRP value is not less than the predefined search delta parameter.

In an embodiment, the UE (301) is the RedCap or enhanced reduced capability UE (301).

In an embodiment, to perform the relaxed measurements according to the stationary criteria the relaxed measurement controller (309) measures the current SS-RSRP of the SpCell based on SSB. Further, the relaxed measurement controller (309) determines the relaxed measurement criterion according to the stationary criteria is fulfilled by detecting whether the difference between the current SS-RSRP and the RSRPRefStationaryConnected value is less than the predefined search delta parameter for stationary connected. Further, the relaxed measurement controller (309) performs the relaxed measurements for the UE (301) according to the stationary criteria in RRC CONNECTED state, when the difference between current RSRP value and the RSRPRefStationaryConnected value is less than the predefined search delta parameter for stationary connected. Further, the relaxed measurement controller (309) performs the measurements without measurement relaxation for the UE (301) according to the stationary criteria in RRC CONNECTED state, when the difference between current RSRP value and the RSRPRefStationaryConnected value is not less than the predefined search delta parameter for stationary connected.

For the purpose of proposed solution, the 3gpp specifications such as TS38.300, TS38.331, TS 38.321, TS 37.340, TS 38.213 is considered as relevant background. We refer to the version V18.0.0 as background.

A set of known specification extracts for the LTM with respect to the discussions in the 3gpp for TS 38.331 are given below:

Upon receiving cell switch command, the UE (301) MAC may perform the following steps as shown in below table:

For a RACH-less LTM cell switch, the UE (301) considers that the LTM execution procedure is successfully complete when the UE (301) determines the NW has successfully received its first UL data. In RACH-less LTM, the target cell is aware of the UE's (301) arrival based on the reception of the first UL transmission from this the UE (301). For MCG RACH-less LTM, RRCReconfigurationComplete can be the content of the first UL MAC PDU/transmission to indicate UE arrival.

For RACH-less LTM, the UE (301) determines successful reception of its first UL data based on receiving a PDCCH addressing the UE's (301) C-RNTI in the target cell scheduling a new transmission after the first UL data.

A section of TS 38.321 which describes the behavior of RACH-less LTM is given below:

Dual connectivity, or more technically, multi-radio dual connectivity, is specified by 3GPP in specifications such as TS 37340. A summary of the details on dual connectivity and measurement gap operations with dual connectivity is given below.

NG-RAN supports Multi-Radio Dual Connectivity (MR-DC) operation in which the UE (301) in RRC CONNECTED is configured to utilize radio resources provided by two distinct schedulers located in two different NG-RAN nodes connected via a non-ideal backhaul, one providing NR (New Radio) access and the other one providing either E-UTRA (Evolved UMTS Terrestrial Radio Access) or NR access. One node acts as the master node (MN) and the other as the secondary node (SN). The MN and SN are connected via a network interface, and at least the MN is connected to the core network. The NG-RAN supports NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC) in which the UE (301) is connected to one ng-eNB (an E-UTRA base station that can connect to 5G core) that acts as an MN and one gNB (5G base station) that acts as an SN. NG-RAN also supports NR-E-UTRA Dual Connectivity (NE-DC) in which the UE (301) is connected to one gNB that acts as an MN and one ng-eNB that acts as an SN. SCG can be deactivated in dual connectivity.

Non-Terrestrial Networks (NTN) are defined in 3GPP Release 17, as outlined in TS 38.300. An NTN provides non-terrestrial NR access to the UE by means of an NTN payload and an NTN Gateway. The NTN payload transparently forwards the radio protocol received from the UE (via the service link) to the NTN Gateway (via the feeder link) and vice-versa. The NTN payload supports the following connectivity: a gNB may serve multiple NTN payloads, and multiple gNBs may serve an NTN payload.

Non-Geosynchronous Orbit (NGSO) includes Low Earth Orbit at altitudes approximately between 300 km and 1500 km and Medium Earth Orbit at altitudes approximately between 7000 km and 25000 km.

Three types of service links are supported. Earth-fixed service links are provisioned by beams continuously covering the same geographical areas all the time (e.g., the case of GSO satellites). Quasi-Earth-fixed service links are provisioned by beams covering one geographic area for a limited period and a different geographic area during another period (e.g., the case of NGSO satellites generating steerable beams). Earth-moving service links are provisioned by beams whose coverage area slides over the Earth's surface (e.g., the case of NGSO satellites generating fixed or non-steerable beams).

With NGSO satellites, the gNB can provide either quasi-Earth-fixed cell coverage or Earth-moving cell coverage, while gNB operating with GSO satellites can provide Earth-fixed cell coverage. 3GPP supports RACH-less handover for NTN. UE may be configured with configured grants (cg-NTN-RACH-Less-Configuration) for performing RACH-less handover. the UE (301) also may receive a parameter in the ReconfigurationWithSync (such as rach-LessHO in NTN), which will inform the UE (301) to perform the handover as RACH-less handover.

Fig. 4 is a flow diagram that illustrates a method for performing measurements for UE in a communication system according to embodiments disclosed herein. At block 401, the method includes receiving an indication from a lower layer. The indication indicates that at least one of a Long-Term Mobility (LTM) cell switch and a RACH-less handover is completed for a configured Cellgroup (CG). At block 403, the method includes setting a reference RSRP value to the reference Layer 3 RSRP measurement (SS-RSRP Ref) of a serving cell (SpCell) based on a Synchronization Signal Block (SSB) upon receiving the indication when the UE is configured with low mobility criteria. At block 405, the method includes performing the relaxed measurements according to low mobility criteria based on the SS-RSRP Ref. At block 407, the method includes setting a reference stationary connected RSRP value (SS-RSRPRefStationaryConnected) to a L3 RSRP of SpCell based on a SSB upon receiving the indication. Further, at block 409, the method includes performing the relaxed measurements according to the stationary criteria based on SS-RSRPRefStationaryConnected, when the UE is configured with stationary criteria.

Fig. 5 is the flow diagram that illustrates the method for performing relaxed measurement for low mobility during cell switch according to embodiments disclosed herein. At block 501, the method includes receiving the indication from the lower layers of the UE (301) that indicates that the LTM cell switch or RACH-less LTM cell switch procedure is completed. At block 503, the method includes setting S-RSRPRefStationaryConnected as the reference L3 RSRP measurement of the SpCell (i.e., S-RSRPRefStationaryConnected = the reference L3 RSRP measurement of the SpCell) based on SSB (dB) upon indication from the lower layer that the LTM cell switch execution has been successfully completed for the CG. At block 505, the method includes setting the SS-RSRP value to the current L3 RSRP measurement of the SpCell based on SSB (dB) (i.e., SS-RSRP = current L3 RSRP measurement).

Further, at block 507, the method includes determining whether the difference between SS-RSRPRef and SS-RSRP is less than the predefined search delta parameter (i.e., (SS-RSRPRef - SS-RSRP) < SSearchDeltaP-Connected). At block 509, the method includes performing the relaxed measurements according to low mobility criteria in the RRC-CONNECTED state when the difference between SS-RSRPRef and SS-RSRP is less than the predefined search delta parameter. Upon performing the relaxed measurements, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell. At block 511, the method includes performing cell measurements without measurement relaxation according to low mobility criteria in the RRC-CONNECTED state when the difference between SS-RSRPRef and SS-RSRP is not less than the predefined search delta parameter. Further, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell.

Fig. 6 is a flow diagram that illustrates a method for performing relaxed measurement for stationary UE during cell switch according to embodiments disclosed herein. At block 601, the method includes receiving the indication from the lower layers of the UE (301) that indicates that the LTM cell switch or RACH-less LTM cell switch procedure is completed. At block 603, the method includes setting the SS-RSRPRefStationaryConnected value to the reference L3 RSRP measurement of the SpCell (i.e., SS-RSRPRefStationaryConnected value = the reference L3 RSRP measurement of the SpCell) based on SSB (dB) upon indication from the lower layer that the LTM cell switch execution has been successfully completed for the CG.

Further, at block 605, the method includes setting the SS-RSRP value to the current L3 RSRP measurement of the SpCell (i.e., SS-RSRP = current L3 RSRP measurement) based on the SSB (dB). At block 607, the method includes determining whether the difference between the SS-RSRPRefStationaryConnected and the SS-RSRP is less than the predefined search delta parameter (i.e., (SS-RSRPRefStationaryConnected - SS-RSRP) < SSearchDeltaP-StationaryConnected). At block 609, the method includes performing the relaxed measurement according to stationary criteria in the RRC-CONNECTED state when the difference between the SS-RSRPRefStationaryConnected and the SS-RSRP is less than the predefined search delta parameter. Upon performing the relaxed measurements, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell. Furthermore, at block 611, the method includes performing cell measurements without measurement relaxation for the UE (301) according to the stationary criteria in the RRC-CONNECTED state when the difference between the current RSRP value and the RSRPRefStationaryConnected value is not less than the predefined search delta parameter for stationary connected. Further, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell.

Fig. 7 is a flow diagram that illustrates a method for performing relaxed measurement for low mobility during RACH-less handover in NTN according to embodiments disclosed herein. At block 701, the method includes performing execution of the ReconfigurationWithSync where RACH-less HO was included in reconfigurationWithSync included in spCellConfig. Further, receiving the indication from the lower layers indicating the completion of the RACH-less handover. At block 703, the method includes setting S-RSRPRefStationaryConnected as the reference L3 RSRP measurement of the SpCell (i.e., S-RSRPRefStationaryConnected = the reference L3 RSRP measurement of the SpCell) upon receiving the indication from the lower layers that the RACH-less handover has been successfully completed when RACH-less HO was included in reconfigurationWithSync included in spCellConfig.

Further, at block 705, the method includes setting the SS-RSRP value to the current L3 RSRP measurement of the SpCell based on SSB (dB) (i.e., SS-RSRP = current L3 RSRP measurement). At block 707, the method includes determining whether the difference between SS-RSRPRef and SS-RSRP is less than the predefined search delta parameter (i.e., (SS-RSRPRef - SS-RSRP) < SSearchDeltaP-Connected). Furthermore, at block 709, the method includes performing the relaxed measurements according to low mobility criteria in RRC-CONNECTED state when the difference between SS-RSRPRef and SS-RSRP is less than the predefined search delta parameter. Upon performing the relaxed measurements, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell At block 711, the method includes performing cell measurements without measurement relaxation according to low mobility criteria in RRC-CONNECTED state when the difference between SS-RSRPRef and SS-RSRP is not less than the predefined search delta parameter. Further, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell.

Fig. 8 is a flow diagram that illustrates a method for performing relaxed measurement criteria for stationary UE during RACH-less handover in NTN according to embodiments disclosed herein. At block 801, the method includes performing execution of the ReconfigurationWithSync where rach-LessHO was included in reconfigurationWithSync included in spCellConfig. Further, the method includes receiving the indication about the completion of the RACH-less handover. At block 803, the method includes setting the SS-RSRPRefStationaryConnected value to a the reference L3 RSRP measurement of the SpCell (i.e., SS-RSRPRefStationaryConnected value = the reference L3 RSRP measurement of the SpCell) based on SSB (dB) upon indication from the lower layer that the RACH-less handover execution has been successfully completed when rach-LessHO was included in reconfigurationWithSync included in spCellConfig.

Further, at block 805, the method includes setting the SS-RSRP value to the current L3 RSRP measurement of the SpCell based on SSB (dB) (i.e., SS-RSRP = current L3 RSRP measurement). At block 807, the method includes determining whether the difference between the SS-RSRPRefStationaryConnected and the SS-RSRP is less than the predefined search delta parameter (i.e., (SS-RSRPRefStationaryConnected - SS-RSRP) < SSearchDeltaP-StationaryConnected). Furthermore, at block 809, the method includes performing the relaxed measurement according to stationary criteria in the RRC-CONNECTED state when the difference between the SS-RSRPRefStationaryConnected and the SS-RSRP is less than the predefined search delta parameter. Upon performing the relaxed measurements, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell. At block 811, the method includes performing cell measurements without measurement relaxation for the UE (301) according to the stationary criteria in the RRC-CONNECTED state when the difference between the current RSRP value and the RSRPRefStationaryConnected value is not less than the predefined search delta parameter for stationary connected. Further, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell.

Fig. 9 is a flow diagram that illustrates a method for performing relaxed measurement for low mobility during SCG ReconfigurationWithSync according to embodiments disclosed herein. At block 901, the method includes determining an occurrence of the PSCell addition or change where SCG is deactivated. At block 903, the method includes setting the SS-RSRPRef = the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the RRC ReconfigurationComplete for the PSCell change or PSCell addition is successfully transmitted and when the SCG is deactivated during reconfigurationWithSync. At block 905, the method includes setting the SS-RSRP value to the current L3 RSRP measurement (i.e., SS-RSRP = current L3 RSRP measurement) of the SpCell based on SSB (dB).

Further, at block 907, the method includes determining whether the difference between the SS-RSRPRef and SS-RSRP is less than the predefined search delta parameter (i.e., (SS-RSRPRef - SS-RSRP) < SSearchDeltaP-Connected). At block 909, the method includes performing the relaxed measurements according to low mobility criteria in the RRC-CONNECTED state when the difference between SS-RSRPRef and SS-RSRP is less than the predefined search delta parameter. Upon performing the relaxed measurements, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell. At block 911, the method includes performing cell measurements without measurement relaxation according to low mobility criteria in the RRC-CONNECTED state when the difference between SS-RSRPRef and SS-RSRP is not less than the predefined search delta parameter. Further, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell.

Fig. 10 is a flow diagram that illustrates a method for performing the relaxed measurement criteria for stationary UE during SCG ReconfigurationWithSync according to the embodiments disclosed herein. At block 1001, the method includes determining the occurrence of the PSCell addition or change where SCG is deactivated. At block 1003, the method includes setting SS-RSRPRefStationaryConnected = the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the RRC ReconfigurationComplete for the PSCell change or PSCell addition is successfully transmitted when the SCG is deactivated during reconfigurationWithSync. At block 1005, the method includes setting the SS-RSRP = current L3 RSRP measurement of the SpCell based on SSB (dB).

Further, at block 1007, the method includes determining whether the difference between the SS-RSRPRefStationaryConnected and the SS-RSRP is less than the predefined search delta parameter (i.e., (SS-RSRPRefStationaryConnected - SS-RSRP) < SSearchDeltaP-StationaryConnected). At block 1009, the method includes performing the relaxed measurement according to stationary criteria in the RRC-CONNECTED state when the difference between the SS-RSRPRefStationaryConnected and the SS-RSRP is less than the predefined search delta parameter. Upon performing the relaxed measurements, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell. At block 1011, the method includes performing cell measurements without measurement relaxation for the UE (301) according to the stationary criteria in the RRC-CONNECTED state when the difference between the current RSRP value and the RSRPRefStationaryConnected value is not less than the predefined search delta parameter for stationary connected. Further, the UE (301) continues to set the SS-RSRP value to the current L3 RSRP measurement of the SpCell.

In an embodiment, the UE (301) performs relaxed measurements while in RRC CONNECTED when the difference between the L3 RSRP measurement of the SpCell based on SSB (dB) after performing a cell switch and the current L3 RSRP measurement of the SpCell based on SSB (dB) is less than a threshold (such as SSearchDeltaP-Connected).

In an embodiment, the reference L3 RSRP measurement of the SpCell based on SSB (dB) is set upon an indication from the lower layer that the LTM cell switch execution has been successfully completed for the CG.

In an embodiment, the relaxed measurement criterion for low mobility is as below (reference to TS 38331):

In an embodiment, relaxed measurement criterion for low mobility is as below:

In an embodiment, the network (such as gNB) doesn't configure the UE (301) with the low mobility criteria when LTM is configured. In an embodiment, the network (such as gNB) doesn't configure the UE (301) with the TSearchDeltaP-Connected when LTM is configured. In an embodiment, the UE (301) doesn't perform the relaxed measurements for low mobility when the LTM cell switch is performed.

In an embodiment, the relaxed measurement criterion for low mobility is as below:

In an embodiment, when the reconfigurationWithSync is for SCG and the SCG is deactivated and the MAC of the CellGroup doesn't perform random access after applying a reconfigurationWithSync, the UE (301) sets the reference RSRP measurements such as SS-RSRPRef as the the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the successful completion of the reconfigurationWithSync procedure. In an example embodiment, for the UE (301) not performing random access due to the SCG deactivation case, the UE (301) sets SS-RSRPRef as the the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the RRC ReconfigurationComplete for the PSCell change or PSCell addition is successfully transmitted to MCG.

In an embodiment, the relaxed measurement criterion for the low mobility are described below (reference to TS 38.331):

In an example for the UE (301) not performing random access due to RACH-less handover (e.g., for NTN), the UE (301) sets the reference RSRP measurements such as SS-RSRPRef as the the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the lower layers indicate that RACH-less handover has been successfully completed.

In an embodiment, the SS-RSRP Ref is set as below:

In an embodiment, the relaxed measurement criterion for the low mobility is described below:

In an embodiment, the UE (301) performs relaxed measurements for a stationary Redcap UE while in RRC CONNECTED when the difference between the L3 RSRP measurement of the SpCell based on SSB (dB) after RRC receives an indication from lower layers that cell switch is successfully completed and the current L3 RSRP measurement of the SpCell based on SSB (dB) is lesser than a threshold (such as SSearchDeltaP-StationaryConnected).

In an embodiment, the UE (301) performs relaxed measurements for a stationary Redcap UE while in RRC CONNECTED when the difference between the LTM RSRP measurement of the SpCell based on SSB (dB) after RRC receiving an indication from lower layers that cell switch is successfully completed and the current LTM RSRP measurement of the SpCell based on SSB (dB) is lesser than a threshold (such as SSearchDeltaP-StationaryConnected).

In an embodiment, the reference L3 RSRP measurement of the SpCell for a stationary the UE (301) based on SSB (dB) is set upon an indication from lower layers that the LTM cell switch execution has been successfully completed for the CG.

In an embodiment, relaxed measurement criterion for a stationary UE is as below (reference to TS 38.331 v18.0.0):

In an embodiment, relaxed measurement criterion for a stationary UE is as below:

In an embodiment, the network (such as gNB) doesn't configure the UE (301) with the relaxed measurement criteria for a stationary the UE (301) when LTM is configured. In an embodiment, the network (such as gNB) doesn't configure the UE (301) with the TSearchDeltaP-Connected when LTM is configured. In an embodiment, the UE (301) doesn't perform the relaxed measurements for a stationary the UE (301) when the LTM cell switch is performed.

In an embodiment, relaxed measurement criterion for low mobility is as below:

In an embodiment, when the reconfigurationWithSync is for SCG and the SCG is deactivated and the MAC of the CellGroup doesn't perform random access after applying a reconfigurationWithSync, the UE (301) sets the reference RSRP measurements such as SS-RSRPRef in relaxed measurement criteria for a stationary the UE (301) as the the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the successful completion of the reconfigurationWithSync procedure. In an example embodiment, for the UE (301) not performing random access due to the SCG deactivation case, the UE (301) sets SS-RSRPRef in relaxed measurement criteria for a stationary the UE (301) as the the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the RRC ReconfigurationComplete for the PSCell change or PSCell addition is successfully transmitted to MCG.

In an embodiment, relaxed measurement criterion for low mobility is as below (reference to TS 38.331):

In an example embodiment, for the UE (301) not performing random access due to RACH-less handover (for e.g. for NTN) the UE (301) sets the reference RSRP measurements such as SS-RSRPRef as the the reference L3 RSRP measurement of the SpCell based on SSB (dB) after the lower layers indicate that RACH-less handover has been successfully completed.

In an embodiment, the SS-RSRPRef is set as below:

In an embodiment, the relaxed measurement criterion for a stationary (e)RedCap UE is described below:

Lower layers in the above embodiment, in general refer to MAC layer.

In an embodiment, the UE (301) performs measurement relaxation (i.e., it performs measurements with a lower frequency) if it is configured by the network. In an embodiment, gNB configures the UE (301) whether the UE (301) is allowed to perform measurement relaxation for LTM using an IE in RRCReconfiguration. gNB may configure information such as a flag for a cell group or for the entire LTM-Config or for each LTM candidate cell, which will inform whether the UE (301) is allowed to perform LTM measurement relaxation. Alternatively, gNB may also configure the UE (301) whether it is prevented from performing the LTM measurement relaxation. If the UE (301) is configured (e.g., through allowed or not prevented) from performing the LTM measurement relaxation, the UE (301) checks whether the criteria for performing the LTM measurement relaxation are fulfilled. The criteria may be to identify if the signal strength is good or when the UE (301) is stationary or when the UE (301) is low mobility, etc. It is also possible that the UE (301) may also be configured with the criteria without a separate configuration for performing the LTM measurement relaxation.

In an embodiment, the UE (301) performs the LTM measurement relaxation if the criteria for relaxation of L3 measurements are fulfilled. The criteria may be for low mobility evaluation and stationary evaluation. In an embodiment, according to the TS 38.331, for the low mobility evaluation criteria:

In an embodiment, while evaluating relaxed measurement criteria for stationary UEs (301) for LTM measurements, the UE (301) considers the L1 RSRP measurements for the SS-RSRP and the SS-RSRPref, for example, as below. The network also configures the UE (301) with separate parameters for criteria for the relaxation of L1 measurements and L3 measurements. the UE (301) performs the LTM measurement relaxation if the criteria for relaxation of the LTM measurements are fulfilled.

In an embodiment, for the evaluation of the stationary criteria where same criteria is used for the LTM and L3 measurements.

In an embodiment, according to TS 38.331, for the stationary criteria.

In an embodiment, for the low mobility evaluation, the network also configures the UE (301) with separate parameters for criteria for the relaxation of L1 measurements for LTM and L3 measurements. The UE (301) the performs the LTM measurement relaxation if the criteria for relaxation of the LTM measurements are fulfilled. If separate parameters for criteria for relaxation of the L1 measurements for the LTM are configured, a separate flag may not be necessary. The configuration of criteria itself acts as the configuration for relaxation of the L1 measurements for the LTM.

In an embodiment:, the owMobilityEvaluationConnectedLT is described as follows:

In an embodiment, while evaluating relaxed measurement criteria for low mobility for LTM measurements, the UE considers the L1 RSRP measurements for the SS-RSRP and the SS-RSRPref. An example is described below:

In an embodiment, the UE (301) performs relaxed measurements for a stationary Redcap UE while in RRC CONNECTED when the difference between the LTM L1 RSRP measurement of the SpCell based on SSB (dB) after performing a cell switch and the current LTM L1 RSRP measurement of the SpCell based on SSB (dB) is less than a threshold (such as SSearchDeltaP-StationaryConnected). In an embodiment, UE (101) performs relaxed measurements while in RRC CONNECTED when the difference between the LTM measurement of the SpCell based on SSB (dB) after performing a cell switch and the current LTM RSRP measurement of the SpCell based on SSB (dB) is less than a threshold configured by the network (such as SSearchDeltaP-Connected). In an embodiment, the UE (301) is communicated to the network. Both the UE and network include a memory, a processor, a communicator, and a relaxed measurements controller.

The foregoing description of specific embodiments reveals their general nature, allowing others to modify or adapt them for various applications without departing from the core concept. Such adaptations and modifications are within the scope of the disclosed embodiments. The terminology used is for description, not limitation. While preferred embodiments are described, those skilled in the art will recognize that modifications are possible within the described scope.

Claims (15)

1. A method performed by a user equipment (UE) in a wireless communication system, the method comprising:

   receiving, from a lower layer, an indication indicating that at least one of a long term mobility (LTM) cell switch or a random access channel (RACH)-less handover is completed for a configured cell group;

   determining a reference synchronization signal reference received power (SS-RSRP) based on information for a relaxed measurement criterion configured for the UE;

   based on the determined reference SS-RSRP, identifying whether a criterion of a relaxed measurement is fulfilled; and

   in case that the criterion of the relaxed measurement is fulfilled, performing the relaxed measurement.
2. The method of claim 1,

   wherein, in case that the information for the relaxed measurement criterion configured for the UE is a low mobility in a radio resource control (RRC) connected, the reference RSRP corresponds to a reference level 3 (L3) RSRP measurement of a serving primary cell (SpCell) based on a synchronization signal block (SSB).
3. The method of claim 2, further comprising:

   identifying a current SS-RSRP of the SpCell based on the SSB;

   identifying whether a difference between the current SS-RSRP and the reference SS-RSRP is less than a predefined search delta parameter;

   in case that the difference between the current SS-RSRP and the reference SS-RSRP is less than the predefined search delta parameter, determining the criterion of the relaxed measurement is fulfilled; and

   setting the reference SS-RSRP to the current SS-RSRP of the SpCell.
4. The method of claim 3, further comprising:

   in case that the difference between the current SS-RSRP and the reference SS-RSRP is not less than the predefined search delta parameter, determining the criterion of the relaxed measurement is not fulfilled; and

   performing a measurement without the relaxed measurement.
5. The method of claim 1,

   wherein, in case that the information for the relaxed measurement criterion configured for the UE is a stationary, a reference stationary connected SS-RSRP corresponds to a value of the reference SS-RSRP based on a synchronization signal block (SSB).
6. The method of claim 5, further comprising:

   identifying a current SS-RSRP based on the SSB;

   identifying whether a difference between the reference stationary connected SS-RSRP and the current SS-RSRP is less than a predefined stationary connected search delta parameter;

   in case that the difference between the reference stationary connected SS-RSRP and the current SS-RSRP is less than a predefined stationary connected search delta parameter, determining the criterion of the relaxed measurement is fulfilled; and

   setting the reference stationary connected SS-RSRP to the current SS-RSRP.
7. The method of claim 6, further comprising:

   in case that the difference between the reference stationary connected SS-RSRP and the current SS-RSRP is not less than the predefined stationary connected search delta parameter, determining the criterion of the relaxed measurement is not fulfilled; and

   performing a measurement without the relaxed measurement.
8. The method of claim 5,

   wherein the UE is at least one of a reduced capability (RedCap) device or a enhanced RedCap (eRedCap) device.
9. A user equipment (UE) in a wireless communication system, the UE comprising:

   a transceiver, and

   a controller coupled with the transceiver configured to:

   receive, from a lower layer, an indication indicating that at least one of a long term mobility (LTM) cell switch or a random access channel (RACH)-less handover is completed for a configured cell group,

   determine a reference synchronization signal reference received power (SS-RSRP) based on information for a relaxed measurement criterion configured for the UE,

   based on the determined reference SS-RSRP, identify whether a criterion of a relaxed measurement is fulfilled, and

   in case that the criterion of the relaxed measurement is fulfilled, perform the relaxed measurement.
10. The method of claim 9,

    wherein, in case that the information for the relaxed measurement criterion configured for the UE is a low mobility in a radio resource control (RRC) connected, the reference RSRP corresponds to a reference level 3 (L3) RSRP measurement of a serving primary cell (SpCell) based on a synchronization signal block (SSB).
11. The method of claim 10, wherein the controller is further configured to:

    identify a current SS-RSRP of the SpCell based on the SSB,

    identify whether a difference between the current SS-RSRP and the reference SS-RSRP is less than a predefined search delta parameter,

    in case that the difference between the current SS-RSRP and the reference SS-RSRP is less than the predefined search delta parameter, determine the criterion of the relaxed measurement is fulfilled, and

    set the reference SS-RSRP to the current SS-RSRP of the SpCell.
12. The method of claim 11, wherein the controller is further configured to:

    in case that the difference between the current SS-RSRP and the reference SS-RSRP is not less than the predefined search delta parameter, determine the criterion of the relaxed measurement is not fulfilled, and

    perform a measurement without the relaxed measurement.
13. The method of claim 9,

    wherein, in case that the information for the relaxed measurement criterion configured for the UE is a stationary, a reference stationary connected SS-RSRP corresponds to a value of the reference SS-RSRP based on a synchronization signal block (SSB), and

    wherein the UE is at least one of a reduced capability (RedCap) device or a enhanced RedCap (eRedCap) device.
14. The method of claim 13, wherein the controller is further configured to:

    identify a current SS-RSRP based on the SSB,

    identify whether a difference between the reference stationary connected SS-RSRP and the current SS-RSRP is less than a predefined stationary connected search delta parameter,

    in case that the difference between the reference stationary connected SS-RSRP and the current SS-RSRP is less than a predefined stationary connected search delta parameter, determine the criterion of the relaxed measurement is fulfilled, and

    set the reference stationary connected SS-RSRP to the current SS-RSRP.
15. The method of claim 14, wherein the controller is further configured to:

    in case that the difference between the reference stationary connected SS-RSRP and the current SS-RSRP is not less than the predefined stationary connected search delta parameter, determine the criterion of the relaxed measurement is not fulfilled; and

    perform a measurement without the relaxed measurement.