Enhanced cell reselection procedure to support network energy reduction

Abstract

To perform cell reselection, the user equipment (UE) receives a network energy reduction (NES) offset value from the radio access network (RAN) corresponding to the adjustment in the signal meter for cell reselection (1806), performs measurements on multiple candidate cells while the radio connection between the UE and the RAN is idle (1816), and performs cell reselection based on the measurements and offset value (1818).

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority and the benefits as of the filing date of Provisional U.S. Patent Application No. 63 / 501,675, entitled "Enhanced Cell Reselection Procedure Supporting Network Energy Saving," filed on 11 May 2023. The entire content of the Provisional Application is expressly incorporated herein by reference.

[0002] This disclosure relates in general to wireless communications, and more specifically to enabling network energy reduction features of base stations and enabling user equipment (UE) to camp on to other base stations in a timely manner without enabling network energy reduction features. [Background technology]

[0003] This background information is provided for the purpose of providing a general overview of the background to this disclosure. Within the scope of the background information section, the work of the inventors named herein, as well as aspects of this specification that may not meet the requirements of prior art at the time of filing, are not expressly or implicitly recognized as prior art to this disclosure.

[0004] The objectives behind the development of fifth-generation (5G) technology include providing an integrated framework for types of communications such as advanced mobile broadband (eMBB), ultra-high reliability, low latency communications (URLLC), and massive machine-type communications (mMTC).

[0005] Reducing network energy consumption is crucial for environmental sustainability because it can lessen environmental impacts (e.g., greenhouse gas emissions) and is beneficial for saving operating costs. As 5G covers an increasing number of communication types and regions, higher data rates are required to handle more sophisticated services and applications. As a result, networks need to be deployed more densely, using more antennas, wider bandwidth, and more frequency bands. The environmental impact of 5G needs requires proper control and the development of advanced solutions to improve network energy consumption.

[0006] Energy consumption is a significant component of operators' operating costs. Most energy consumption is attributed to the wireless access network, particularly active antenna units (AAUs), with data centers and fiber transport accounting for a smaller proportion. Power consumption in the wireless access network occurs through dynamic operation, when devices consume power while transmitting / receiving data, and through static operation, when devices continuously consume power to maintain the necessary wireless access functions even when data transmission / reception is not in progress.

[0007] Currently available technologies in the time and frequency domains aim to reduce power consumption by turning off some symbols / slots / frames on one or more carriers, thereby allowing the BS to perform some micro / light / deep sleep. Technologies in the space and power domains aim to reduce power consumption in the transceiver chain and power amplifier (PA), reduce transmission power, and / or improve the efficiency of the PA by turning off space elements.

[0008] In these cases and others, network power saving technologies in the time and frequency domains may increase latency for UEs to access the network because, if base stations are allowed to sleep, UEs may not always be able to communicate with the base station. This can be an unacceptable limitation for UEs with stringent data latency requirements, especially if base stations must sleep for very long periods, such as more than an hour. If those UEs cannot tolerate such long network access latency, it is important to allow the UEs to re-select and camp on to a cell that does not enable network power saving technologies, or a cell that is not currently in use, or a cell that minimizes the impact on those UEs that need to establish a radio connection with the RAN for data transmission and / or reception. [Overview of the project]

[0009] In general, the technology of this disclosure enables idle / inactive UEs to initially camp on a cell that allows NES features to appropriately and efficiently reselect other cells and camp on to this other cell.

[0010] An exemplary embodiment of these technologies is a cell reselection method. The method is implemented in a user device (UE) and includes receiving a network energy reduction (NES) offset value from a radio access network (RAN) corresponding to an adjustment in the signal meter for cell reselection; performing measurements on a plurality of candidate cells while the radio connection between the UE and the RAN is idle; and performing cell reselection based on the measurements and offset value.

[0011] Another exemplary embodiment provides a method for evaluating cell reselection criteria using a common NES offset before a cell inactivity period occurs. The method is implemented within a UE and includes receiving a system information message from a base station indicating which adjacent cell(s) are operating in cell discontinuous transmit / receive (DTX / DRX) mode; receiving a common NES offset from the base station via the system information message or via a dedicated radio resource control (RRC) message; initiating measurements on adjacent cell(s) before the serving cell enters a cell inactivity period; and evaluating cell reselection criteria with the common NES offset applied to all cells operating in cell DTX / DRX mode.

[0012] Another exemplary embodiment is a method for evaluating cell reselection criteria using cell-specific NES offsets before a cell inactivity period occurs. The method is implemented within the UE and includes receiving information from the base station, via system information messages or dedicated RRC messages, about which adjacent cell(s) are operating in cell DTX / DRX mode; receiving cell-specific NES offsets for each cell operating in DTX / DRX mode from the base station, via system information messages or dedicated RRC messages; initiating measurements on adjacent cell(s) before the serving cell enters a cell inactivity period; and evaluating cell reselection criteria with each cell-specific NES offset applied to the associated / corresponding cell.

[0013] Another exemplary embodiment of these technologies is a UE, which comprises one or more processors and is configured to implement one of the methods described above. [Brief explanation of the drawing]

[0014] [Figure 1A] This is a block diagram of an exemplary wireless communication system in which the user devices and base stations of this disclosure can implement the reselection technology of this disclosure. [Figure 1B] The central unit (CU) and the distributed unit (DU) are block diagrams of an exemplary base station that can operate in the system of FIG. 1A. [Figure 2A] It is a block diagram of an exemplary protocol stack. The UE in FIG. 1A communicates with the base station according to this protocol stack. [Figure 2B] It is a block diagram of an exemplary protocol stack. The UE in FIG. 1A communicates with the CU and the DU according to this protocol stack. [Figure 3A] It is a messaging diagram of an exemplary scenario in which the UE evaluates cell reselection criteria by applying a common NES offset to all cells operating in cell DTX / DRX mode after receiving a common message notifying the occurrence of a cell inactive period. [Figure 3B] It is a messaging diagram of an exemplary scenario similar to the scenario of FIG. 3A, but in which the UE receives a dedicated message notifying the occurrence of a cell inactive period. [Figure 3C] It is a messaging diagram of an exemplary scenario in which the UE evaluates cell reselection criteria by applying a common NES offset to all cells operating in cell DTX / DRX mode before the occurrence of a periodic cell inactive period. [Figure 4A] It is a messaging diagram of an exemplary scenario in which the UE evaluates cell reselection criteria by applying a cell-specific NES offset to the corresponding cell after receiving a common message notifying the occurrence of a cell inactive period. [Figure 4B] It is a messaging diagram of an exemplary scenario similar to the scenario of FIG. 4A, but in which the UE receives a dedicated message notifying the occurrence of a cell inactive period. [[ID=二十四]] [Figure 4C] It is a messaging diagram of an exemplary scenario in which the UE evaluates cell reselection criteria by applying a cell-specific NES offset to the corresponding cell before the occurrence of a periodic cell inactive period. [Figure 5A]This is a messaging diagram of an exemplary scenario in which the UE evaluates the cell reselection criteria by considering the time when the cell begins its cell inactivity period after receiving a common message notifying it of the occurrence of a cell inactivity period. [Figure 5B] This is a messaging diagram illustrating an exemplary scenario similar to the scenario in Figure 53A, but where the UE receives a dedicated message notifying it of the occurrence of a cell inactivity period. [Figure 5C] This is a messaging diagram of an exemplary scenario in which the UE evaluates the cell reselection criteria by considering the time when a cell begins its cell inactivity period before the occurrence of a periodic cell inactivity period. [Figure 6A] This is a messaging diagram illustrating an exemplary scenario in which the UE decides whether to perform an adjacent cell measurement after receiving a common message notifying it of a period of cell inactivity. [Figure 6B] This is a messaging diagram illustrating an exemplary scenario in which the UE determines whether adjacent cell measurements are necessary before a period of periodic cell inactivity occurs. [Figure 7] This is a messaging diagram of an exemplary scenario in which a connected UE triggers a candidate cell evaluation for a conditional handover (CHO) based on timing information provided in the CHO configuration. [Figure 8] Figure 1A is a flowchart illustrating an exemplary method for evaluating cell reselection criteria using a common NES offset before a cell inactivity period occurs, which can be implemented in the UE. [Figure 9] This is a flowchart illustrating an exemplary method for evaluating cell reselection criteria using cell-specific NES offsets before a cell inactivity period occurs, which can be implemented in the UE of Figure 1A. [Figure 10] Figure 1A is a flowchart illustrating an exemplary method for determining when a BS (Bridge System) initiates a cell inactivity period, based on a broadcast notification from the BS, which can be implemented in the UE (User Environment). [Figure 11]Figure 1A is a flowchart illustrating an exemplary method for a BS to determine when to initiate a cell inactivity period based on a dedicated RRC message from the BS, which can be implemented in the UE. [Figure 12] Figure 1A is a flowchart illustrating an exemplary method for a BS to determine when to initiate a cell inactivity period based on a periodic cell DTX / DRX configuration transmitted by the BS, which can be implemented in the UE. [Figure 13] This is a flowchart of an exemplary method for evaluating cell re-selection criteria using the remaining active time of a cell before a cell inactivity period occurs, which can be implemented in the UE of Figure 1A. [Figure 14] Figure 1A is a flowchart illustrating an exemplary method for determining whether a UE should trigger an adjacent cell measurement before a serving cell enters a cell inactivity period, which can be implemented in the UE. [Figure 15] Figure 1A is a flowchart illustrating an exemplary method for notifying the UE of adjacent cells (or more) operating in cell DTX / DRX mode, and the common NES offset associated with these cells, which can be implemented in the BS. [Figure 16] Figure 1A is a flowchart illustrating an exemplary method for notifying the UE of adjacent cells (or more) operating in cell DTX / DRX, and the cell-specific NES offsets associated with these cells, which can be implemented in the BS. [Figure 17] Figure 1A is a flowchart illustrating an exemplary method for an adjacent cell to notify the UE of the time when it will begin its cell inactivity period, which can be implemented in the BS. [Figure 18] This is a flowchart illustrating an exemplary cell reselection method that can be implemented in the UE of Figure 1A. [Modes for carrying out the invention]

[0015] As will be described in more detail below, a user device (UE) and / or a network node of a radio access network (RAN) can use the techniques of this disclosure to manage data communications and to transition the UE between protocol states for controlling radio resources between the UE and the RAN.

[0016] Referring first to Figure 1A, the exemplary wireless communication system 100 includes a UE 102, a base station (BS) 104, a BS 106, and a core network (CN) 110. BS 104 and 106 can operate with a RAN 105 connected to the CN 110. The CN 110 can be implemented, for example, as an evolutionary packet core (EPC) 111 or a fifth-generation (5G) core (5GC) 160. The CN 110 can also be implemented as a sixth-generation (6G) core in another example.

[0017] BS104 covers cell 124, and BS106 covers cell 126. If BS104 is a gNB, then cell 124 is an NR cell. If BS104 is an ng-eNB or eNB, then cell 124 is an Evolutionary Universal Terrestrial Radio Access (E-UTRA) cell. Similarly, if BS106 is a gNB, then cell 126 is an NR cell, and if BS106 is an ng-eNB or eNB, then cell 126 is an E-UTRA cell. Cells 124 and 126 may be in the same Radio Access Network Advertisement Area (RNA) or in different RNAs. Generally, RAN105 can contain any number of base stations, and each base station may cover one, two, three, or any other suitable number of cells. UE102 may support at least a 5G NR (or simply "NR") or E-UTRA air interface to communicate with BS104 and 106. Each of the base stations 104 and 106 can be connected to CN110 via an interface (e.g., S1 or NG interface). Base stations 104 and 106 can also be interconnected via an interface (e.g., X2 or Xn interface) for interconnecting NG RAN nodes.

[0018] Among other components, the EPC111 may include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 is generally configured to forward user plane packets related to voice calls, video calls, internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 provides connectivity from the UE to one or more external packet data networks (e.g., an internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network). The 5GC160 includes a User Plane Function (UPF) 162, an Access and Mobility Management Function (AMF) 164, and / or a Session Management Function (SMF) 166. Generally speaking, UPF162 is configured to forward user plane packets related to audio calls, video calls, and internet traffic; AMF164 is configured to manage authentication, registration, paging, and other related functions; and SMF166 is configured to manage packet data unit (PDU) sessions.

[0019] As shown in Figure 1A, BS104 supports cell 124 and BS106 supports cell 126. Since cells 124 and 126 may partially overlap, UE102 can select one of cell 124 or cell 126, switch between them, or switch from one to the other. To directly exchange messages or information, BS104 and BS106 can support X2 or Xn interfaces. In general, CN110 can be connected to any appropriate number of base stations that support NR cells and / or EUTRA cells.

[0020] As described in detail below, UE102 and / or RAN105 may utilize the techniques of this disclosure when the radio connection between UE102 and RAN105 is suspended, for example, when UE102 is operating in an inactive or idle state of the protocol for controlling radio resources between UE102 and RAN105. For clarity, the following examples refer to the RRC_INACTIVE or RRC_IDLE state of the RRC protocol.

[0021] BS104 comprises processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and non-temporary computer-readable memory for storing instructions executed by the one or more general-purpose processors. Additionally or alternatively, processing hardware 130 may include special-purpose processing units. In an exemplary embodiment, processing hardware 130 includes a processor 132 for processing data transmitted by BS104 in the downlink direction or for processing data received by BS104 in the uplink direction. Processing hardware 130 may also include a transmitter 136 configured to transmit data in the downlink direction. Processing hardware may further include a receiver 134 configured to receive data in the uplink direction. BS106 may include generally similar components. In particular, components 140, 142, 144, and 146 of BS106 may be similar to components 130, 132, 134, and 136, respectively.

[0022] The UE102 comprises processing hardware 150, which may include one or more general-purpose processors such as a CPU, non-temporary computer-readable memory for storing machine-readable instructions executable by one or more general-purpose processors, and / or a special-purpose processing unit. In an exemplary embodiment, the processing hardware 150 includes a processor 152 for processing data transmitted by the UE102 in the uplink direction or for processing data received by the UE102 in the downlink direction. The processing hardware 150 may also include a transmitter 156 configured to transmit data in the downlink direction. The processing hardware may further include a receiver 154 configured to receive data in the uplink direction.

[0023] Figure 1B shows one or more exemplary distributed or non-aggregated embodiments of base stations 104, 106. In these embodiments, base stations 104, 106 include a central unit (CU) 172 and one or more distributed units (DUs) 174. The CU 172 includes processing hardware such as one or more general-purpose processors (e.g., CPUs), computer-readable memory for storing machine-readable instructions executable by the general-purpose processors, and / or special-purpose processing units. For example, the CU 172 may include a packet data convergence protocol (PDCP) controller, an RRC controller, and / or an RRC inactive controller. In some embodiments, the CU 172 may include a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures. In further embodiments, the CU 172 does not include an RLC controller.

[0024] Each DU174 also includes processing hardware which may include one or more general-purpose processors (e.g., CPUs), computer-readable memory for storing machine-readable instructions executable by one or more general-purpose processors, and / or special-purpose processing units. For example, the processing hardware may include a MAC controller configured to manage or control one or more media access control (MAC) operations or procedures (e.g., random access procedures), and / or an RLC controller configured to manage or control one or more RLC operations or procedures. The process hardware may also include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0025] In some embodiments, RAN105 supports Integrated Access Backhaul (IAB) functionality. In some embodiments, DU174 acts as an IAB node and CU172 acts as an IAB donor. In some embodiments, RAN105 supports Non-Terrestrial Network (NTN) functionality.

[0026] In some embodiments, CU172 may include a logical node CU-CP172A that hosts the control plane portion of CU172's PDCP. CU172 may also include a logical node CU-UP172B that hosts the user plane portion of CU172's PDCP and / or Service Data Adaptive Protocol (SDAP). CU-CP172A can transmit control information (e.g., RRC messages or F1 application protocol messages), and CU-UP172B can transmit data packets (e.g., SDAP PDUs or Internet Protocol packets).

[0027] A CU-CP172A can connect to multiple CU-UP172Bs via the E1 interface. The CU-CP172A selects the appropriate CU-UP172B for the service requested by the UE102. In some embodiments, a single CU-UP172B can connect to multiple CU-CP172As via the E1 interface. A CU-CP172A can connect to one or more DU174s via the F1-C interface. A CU-UP172B can connect to one or more DU174s via the F1-U interface under the control of the same CU-CP172A. In some embodiments, a single DU174 can connect to multiple CU-UP172Bs under the control of the same CU-CP172A. In such embodiments, the connection between the CU-UP172B and the DU174 is established by the CU-CP172A using bearer context management functionality.

[0028] Figure 2A shows a simplified exemplary protocol stack 200, which UE102 can communicate with an eNB / ng-eNB or gNB (e.g., one or more of base stations 104, 106) according to the protocol stack 200.

[0029] In an exemplary stack 200, the EUTRA physical layer (PHY) 202A provides a transport channel to the EUTRA MAC sublayer 204A, which then provides a logical channel to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides an RLC channel to the EUTRA PDCP sublayer 208, and possibly to the NR PDCP sublayer 210. Similarly, the NR PHY 202B provides a transport channel to the NR MAC sublayer 204B, which then provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides data transfer services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 can then provide data transmission services to the Service Data Adaptive Protocol (SDAP) 212 or the Radio Resource Control (RRC) sublayer (not shown in Figure 2A). In some embodiments, the UE102 supports both EUTRA and NR stacks, as shown in Figure 2A, supports handover between EUTRA base stations and NR base stations, and / or supports DC via EUTRA and NR interfaces. Furthermore, as shown in Figure 2A, the UE102 can support layering of an NR PDCP 210 on top of an EUTRA RLC 206A, and an SDAP sublayer 212 on top of an NR PDCP sublayer 210.

[0030] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 receive packets that may be referred to as Service Data Units (SDUs) (e.g., from the Internet Protocol (IP) layer, which is layered directly or indirectly on top of PDCP layer 208 or 210) and output packets that may be referred to as Protocol Data Units (PDUs) (e.g., to RLC layer 206A or 206B). For simplification, this disclosure refers to both SDUs and PDUs as “packets” unless the difference between SDUs and PDUs is relevant.

[0031] On the control plane, the EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 provide a signal-transmitting radio bearer (SRB) or an RRC sublayer (not shown in Figure 2A) to exchange, for example, RRC messages or non-access layer (NAS) messages. On the user plane, the EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide a data radio bearer (DRB) to support data exchange. The data exchanged on the NR PDCP sublayer 210 may be SDAP PDUs, Internet Protocol (IP) packets, or Ethernet packets.

[0032] Figure 2B shows a simplified exemplary protocol stack 250 that enables UE102 to communicate with DU (e.g., DU174) and CU (e.g., CU172). The radio protocol stack 200 is functionally divided by the radio protocol stack 250 in Figure 2B, as shown. The CU, located in either base station 104 or 106, can hold all control and higher-layer functions (e.g., RRC214, SDAP212, NR PDCP210), while lower-layer operations (e.g., NR RLC206B, NR MAC204B, and NR PHY202B) are delegated to the DU. To support connectivity to 5GC, NR PDCP210 provides an SRB to RRC214, and NR PDCP210 provides a DRB to SDAP212 and an SRB to RRC214.

[0033] Generally speaking, cell DTX / DRX can be applied to at least UEs that are currently operating in a connected state. In the case of a cell DTX / DRX configuration, the BS can set periodic cell DTX / DRX (i.e., active and inactive periods) for each serving cell via UE-specific RRC signaling. Furthermore, the BS can activate or deactivate the cell DTX / DRX mode via dynamic L1 / L2 signaling and UE-specific RRC signaling. In cell DTX / DRX mode, there are generally four possibilities for BS behavior during inactive (i.e., off) periods: (i) the BS may turn off all transmission and reception of data traffic and reference signals during cell DTX / DRX inactive periods; (ii) the BS may turn off its transmission / reception of only data traffic during cell DTX / DRX inactive periods (i.e., the BS still transmits and / or receives reference signals); (iii) the BS may turn off its dynamic data transmission / reception during cell DTX / DRX inactive periods (i.e., the BS still performs transmission and / or reception using periodic resources, including SPS, CG-PUSCH, SR, RACH, and SRS); and (iv) the BS may transmit only reference signals (e.g., CSI-RS for measurement).

[0034] If a BS implements approach (i) or (iv) above, all idle / inactive UEs that need to listen for paging during a cell inactivity period may need to leave the BS before the BS initiates the cell inactivity period. These UEs need to camp on to other BSs that do not affect the UE's behavior regarding paging monitoring. However, without knowing the exact time when a serving cell will initiate a cell inactivity period, UEs may experience service interruptions if they are unable to trigger a neighbor cell measurement in time after the serving cell has initiated its inactivity period. Furthermore, idle / inactive UEs evaluate / rank cells (including serving and neighbor cells) based on current cell reselection criteria without considering the impact of network energy reduction features. As a result, even if a UE is able to trigger a neighbor cell measurement in time, the UE may remain on the serving cell or reselect another cell that still has a cell inactivity period that overlaps with the UE's paging occasion (PO).

[0035] Next, several exemplary scenarios in which the UE and / or RAN implement the techniques of this disclosure to support network energy reduction through enhanced cell reselection procedures are illustrated with reference to Figures 3–6. Generally speaking, similar events in Figures 3–6 are labeled with similar reference numbers, and the differences are explained below as needed. For example, event 306 is similar to event 406, event 310 is similar to events 410 and 510, event 316 is similar to event 616, and event 318 is similar to events 418 and 518. To simplify the following explanation, the term “idle state” may be used to represent the RRC_IDLE state or the RRC_INACTIVE state, and the term “connected state” may be used to represent the RRC_CONNECTED state.

[0036] Figure 3A is a messaging diagram for exemplary scenario 300A, an exemplary scenario in which the UE evaluates the cell reselection criteria by applying a common NES offset to all cells operating in cell DTX / DRX mode after receiving notification of the occurrence of a cell inactivity period via a common message.

[0037] In Figure 3A, UE102 first establishes a connection with the cell managed by BS104 and then operates in the connected state (302). Meanwhile, another cell managed by BS106 is available to UE102 as an adjacent cell, and this adjacent cell is configured to operate in a non-NES mode for the entire duration of the exemplary scenario 300 (304) (i.e., the cell does not and will not operate in an NES mode such as cell DTX / DRX mode (304)). After operating in the temporary connected state (302), UE102 receives an RRC release message from BS104, which optionally includes a common NES offset (306). UE102 then transitions to an idle state (308).

[0038] While operating in an idle state, UE102 receives system information from BS104, in the IntraFreqNeighCellList / InterFreqNeighCellList IE, indicating whether an adjacent cell is in cell DTX / DRX mode. In one embodiment, to indicate whether an adjacent cell is in cell DTX / DRX mode, BS104 uses an IE / flag associated with that cell, and the presence of the IE / flag means that the associated cell is currently in cell DTX / DRX mode or will become cell DTX / DRX mode in the future. Alternatively, UE102 receives system information from BS104 that includes a list of adjacent cells that are operating / will operate in cell DTX / DRX mode. The system information transmitted by BS104 (310) may also include a common NES offset if the common NES offset is not included in the RRC release message in event 306.

[0039] Subsequently, BS104 decides to initiate a cell inactivity period (a period during which BS104 may turn off the transmission and / or reception of data and / or reference signals) in order to reduce energy consumption (312). BS104 sends / broadcasts a notification to UE102 indicating when the cell will begin its cell inactivity period (314). The notification sent by BS104 (314) may be included in system information, a common RRC message (e.g., a paging message), a DL MAC CE, or a DCI (e.g., a short message in a paging DCI). In one embodiment, the indication of when the cell will begin its cell inactivity period is an exact time instance described in a specific time format (e.g., Coordinated Universal Time (UTC)). In other embodiments, the indication of when the cell will begin its cell inactivity period is a timer that starts operating when UE102 receives the indication and expires at the start of the cell inactivity period. In yet another embodiment, the indication of when a cell will begin a cell inactivity period may include a time instance and a duration, the time instance being described in the format of a system frame number (SFN) and a subframe number, and the duration being described in seconds, mini-seconds, system frames, or subframes. In one embodiment, the (314) notification transmitted by BS104 may include the duration of the upcoming cell inactivity period.

[0040] After receiving the notification of the cell non-active period (314), UE 102 determines to perform adjacent cell measurements before starting the cell non-active period (316). In one embodiment, UE 102 determines to perform adjacent cell measurements in units of X time before starting the cell non-active period (316), where X can be an integer or a floating-point value, and the time unit can be in minutes, seconds, milliseconds (mini-second), frames, sub-frames, or slots. Next, based on the measurement results obtained by UE 102 (316), UE 102 evaluates the cell reselection criteria by applying a common NES offset (obtained in event 306 or 310) to all cells operating in the cell DTX / DRX mode. For example, when determining the cell rank (the higher the better) of the serving cell (R S ) and the adjacent cell (R n ), the UE typically uses the following formula. R s =Q meas,s +Q hyst -Qoffset temp R n =Q meas,n -Qoffset-Qoffset temp (Equation 1), where

Table 1

Table 2

[0041] In one embodiment, the common NES offset is always a negative value, which lowers the rank of cells operating in cell DTX / DRX mode, and therefore these cells are less desirable in the cell reselection procedure.

[0042] Based on the evaluation results obtained by UE102 (318), UE102 decides to re-select the adjacent cell managed by BS106 and therefore begins to synchronize with and camp on the cell managed by BS106 (380). Subsequently, the original serving cell (i.e., the cell managed by BS104) begins a cell inactivity period (320).

[0043] Figure 3B is a messaging diagram for Scenario 300B, in which the UE evaluates the cell reselection criteria by applying a common NES offset to all cells operating in cell DTX / DRX mode after receiving notification of a cell inactivity period via a dedicated message.

[0044] Scenario 300B is similar to Scenario 300A in Figure 3A, but the differences are described below. In Scenario 300B, BS104 decides to start the cell inactivity period earlier (compared to Scenario 300A), i.e., before sending the RRC release message to UE102 (307) (312). Thus, when BS104 sends the RRC release message to UE102 (307), BS104 also indicates in the RRC release message when the cell will begin its cell inactivity period. In one embodiment, the indication of when the cell will begin its cell inactivity period is an exact time instance described in a specific time format (e.g., UTC). In other embodiments, the indication of when the cell will begin its cell inactivity period is a timer that starts operating when UE102 receives the indication and expires at the start of the cell inactivity period. In yet another embodiment, the indication of when a cell will begin a cell inactivity period may include a time instance and a duration, the time instance being described in the format of a system frame number (SFN) and a subframe number, and the duration being described in seconds, mini-seconds, system frames, or subframes. In one embodiment, the (307)RRC release message transmitted by BS104 includes the duration of the upcoming cell inactivity period.

[0045] Figure 3C is a messaging diagram illustrating Scenario 300C, in which the UE evaluates the cell reselection criteria by applying a common NES offset to all cells operating in cell DTX / DRX mode before the occurrence of a periodic cell inactivity period. The messaging diagram in Figure 3C is similar to that in Figure 3A, but the differences are explained below.

[0046] In scenario 300C, BS104 initiates a periodic cell inactivity period, which occurs once per cell DTX / DRX cycle instead of dynamically initiating a cell inactivity period. Thus, after UE102 connects to BS104, BS104 sends or broadcasts (305) an RRC message to UE102 indicating the cell DTX / DRX configuration (including the DTX / DRX cycle, the length of the cell inactivity period, etc.), and the RRC message can be a system information message, a common control channel (CCCH) message, or a dedicated control channel (DCCH) message.

[0047] In one embodiment, when UE102 receives a cell DTX / DRX configuration (305), it deems the cell DTX / DRX mode to be deactivated. In this case, BS104 needs to send / broadcast (315) other activation notifications to UE102 to activate the cell DTX / DRX mode set in UE102 earlier, and these activation notifications may be system information, dedicated / common RRC messages, and DL MAC CE or DCI.

[0048] Figure 4A is a messaging diagram illustrating Scenario 400A, in which the UE evaluates the cell reselection criteria by applying a cell-specific NES offset to the corresponding cell after receiving a common message notifying the UE of a period of cell inactivity.

[0049] Scenario 400A is generally similar to Scenario 300A in Figure 3A, but the differences are described below. In Figure 4A, instead of sending a common NES offset to UE102 via an RRC release message or via system information, BS104 sends a cell-specific NES offset to UE102 for each neighboring cell operating in cell DTX / DRX mode (410). In one embodiment, BS104 sends each cell-specific NES offset along with the cell identity of the corresponding cell via system information (e.g., within an IntraFreqNeighCellList / InterFreqNeighCellList IE). In another embodiment, UE102 receives system information from BS104 that includes a list of neighboring cells operating / will operate in cell DTX / DRX mode, and a cell-specific NES offset for each cell in that list (410).

[0050] After receiving notification of a cell inactivity period (414), UE102 decides to perform an adjacent cell measurement before initiating the cell inactivity period (316). Then, based on the measurement results obtained by UE102 (416), UE102 evaluates the cell reselection criteria by individually applying the cell-specific NES offset (obtained in event 410) to the corresponding cell, which operates in cell DTX / DRX mode (418). As described above, the serving cell (R S ) and adjacent cells (R n While determining the cell rank (higher is better) of a cell, the UE typically uses Equation 1 and Table 1 described above. By applying a cell-specific NES offset to the corresponding cell operating in cell DTX / DRX mode, the formula becomes Equation 2 described above, but Table 2B is used instead of Table 2A which defines the parameters. [Table 3]

[0051] In one embodiment, the cell-specific NES offset is always a negative value, which lowers the rank of cells operating in cell DTX / DRX mode, and therefore these cells are less desirable in the cell reselection procedure.

[0052] Figure 4B is a messaging diagram for an exemplary scenario 400B, in which the UE evaluates the cell reselection criteria by applying a cell-specific NES offset to the corresponding cell after a dedicated message notifies the UE of the occurrence of a cell inactivity period. The messaging diagram in Figure 4B is similar to that in Figure 4A, but the differences are explained below.

[0053] In Figure 4B, BS104 decides to start the cell inactivity period earlier (compared to scenario 400A), i.e., before sending the RRC release message to UE102 (412). Thus, when BS104 sends the RRC release message to UE102 (407), BS104 also indicates in the RRC release message when the cell will begin its cell inactivity period. In one embodiment, the indication of when the cell will begin its cell inactivity period is an exact time instance described in a specific time format (e.g., UTC). In another embodiment, the indication of when the cell will begin its cell inactivity period is a timer that starts operating when the UE receives the indication and expires at the start of the cell inactivity period. In yet another embodiment, the indication of when the cell will begin its cell inactivity period includes a time instance and may include a duration, the time instance is described in the format of a system frame number (SFN) and subframe number, and the duration is described in seconds, mini-seconds, system frames, or subframes. In one embodiment, the (407)RRC release message transmitted by BS104 includes the duration of the upcoming cell inactivity period.

[0054] Figure 4C is a messaging diagram for an exemplary scenario 400C in which the UE evaluates the cell reselection criteria by applying a cell-specific NES offset to the corresponding cell before the occurrence of a periodic cell inactivity. Scenario 400C is generally similar to scenario 400A, but the differences are explained below.

[0055] In scenario 400C, instead of dynamically initiating a cell inactivity period, BS104 initiates a periodic cell inactivity period once per cell DTX / DRX cycle. Thus, after UE102 connects to BS104, BS104 sends or broadcasts (405) an RRC message to UE102 indicating the cell DTX / DRX configuration (including the DTX / DRX cycle, the length of the cell inactivity period, etc.), and the RRC message can be a system information message, a CCCH message, or a DCCH message.

[0056] In one embodiment, when UE102 receives a cell DTX / DRX configuration (405), it deems the cell DTX / DRX mode to be deactivated. In this case, BS104 needs to send / broadcast other activation notifications to UE102 (414) in order to activate the cell DTX / DRX mode set in UE102 earlier, and the activation notifications may be system information, dedicated / common RRC messages, and DL MAC CE or DCI.

[0057] Figure 5A is a messaging diagram for Scenario 500A, an exemplary scenario in which the UE evaluates the cell reselection criteria by considering the time when the cell begins its cell inactivity period, after receiving notification of the occurrence of a cell inactivity period via a common message. The scenario in Figure 5A is similar to that in Figure 3A, but the differences are explained below.

[0058] In Figure 5A, instead of sending a common NES offset to UE102 via an RRC release message or system information, BS104 sends timing information to UE102 regarding the time to initiate a cell inactivity period for each neighboring cell operating in cell DTX / DRX mode (510). In one embodiment, BS104 sends the timing information via system information (e.g., within an IntraFreqNeighCellList / InterFreqNeighCellList IE) along with the cell identity of the corresponding cell. In another embodiment, UE102 receives a system information message from BS104 containing a list of neighboring cells operating / will operate in cell DTX / DRX mode, and timing information regarding the time to initiate a cell inactivity period for each cell in that list (510). In one embodiment, the timing information is an exact time instance described in a specific time format (e.g., UTC). In another embodiment, the timing information is a timer that starts operating when the UE receives this information and expires at the start of the cell inactivity period. In other embodiments, the timing information may include time instances and durations, the time instances being described in the format of system frame number (SFN) and subframe number, and the duration being described in seconds, mini-seconds, system frames, or subframes.

[0059] After receiving notification of a cell inactivity period (514), UE102 decides to perform an adjacent cell measurement before the cell inactivity period begins (516). Then, based on the measurement results obtained in event 516, UE102 evaluates the cell reselection criteria by considering the time when the cell begins its cell inactivity period (518). As described above, serving cell (R S ) and adjacent cells (R n To determine the cell rank (higher is better), UE typically uses Formula 1 and Table 1 described above. To account for the time when a cell begins its inactive period, the formula becomes: Rs =Q meas,s +Q hyst -Qoffset temp -Qoffset NES R n =Q meas,n -Qoffset-Qoffset temp -Qoffset NES (Formula 3), where: [Table 4]

[0060] Figure 5B is a messaging diagram for an exemplary scenario 500B in which the UE evaluates the cell reselection criteria by considering the time when the cell begins its cell inactivity period after receiving notification of the occurrence of a cell inactivity period via a dedicated message. Scenario 500B is generally similar to scenario 500A, but the differences are explained below.

[0061] In Scenario 500A, BS104 decides to start the cell inactivity period earlier (compared to Scenario 500A), i.e., before sending the RRC release message to UE102 (507) (512). Thus, when BS104 sends the RRC release message to UE102 (507), BS104 also indicates in the RRC release message when the cell will begin its cell inactivity period. In one embodiment, the indication of when the cell will begin its cell inactivity period is an exact time instance described in a specific time format (e.g., UTC). In other embodiments, the indication of when the cell will begin its cell inactivity period is a timer that starts operating when the UE receives the indication and expires at the start of the cell inactivity period. In yet another embodiment, the indication of when a cell will begin a cell inactivity period may include a time instance and a duration, the time instance being described in the format of a system frame number (SFN) and a subframe number, and the duration being described in seconds, mini-seconds, system frames, or subframes. In one embodiment, the RRC release message sent in event 507 may include the duration of the upcoming cell inactivity period.

[0062] Figure 5C is a messaging diagram for an example of Scenario 500C, which illustrates how the UE evaluates the cell reselection criteria by considering the time it takes for a cell to begin its periodic cell inactivity before the occurrence of that periodic cell inactivity. The messaging diagram in Figure 5C is similar to that in Figure 5A, but the differences are explained below.

[0063] In scenario 500C, instead of dynamically initiating the cell inactivity period, BS104 periodically initiates the cell inactivity period once per cell DTX / DRX cycle. Thus, after UE102 connects to BS104, BS104 sends or broadcasts (505) an RRC message to UE102 indicating the cell DTX / DRX configuration (including the DTX / DRX cycle, the length of the cell inactivity period, etc.), and the RRC message can be a system information message, a CCCH message, or a DCCH message.

[0064] In one embodiment, when UE102 receives a cell DTX / DRX configuration (505), it deems the cell DTX / DRX mode to be deactivated. In this case, BS104 needs to send / broadcast (514) other activation notifications to UE102 to activate the cell DTX / DRX mode set in UE102 earlier, and these activation notifications may be system information, dedicated / common RRC messages, and DL MAC CE or DCI.

[0065] Figure 6A is a messaging diagram for an exemplary scenario 600A in which the UE decides whether to perform an adjacent cell measurement after receiving notification of a cell inactivity period via a common message. The messaging diagram in Figure 6A is similar to that in Figure 3A, but the differences are explained below.

[0066] In scenario 600A, UE102 does not receive any information about the common NES offset, nor any information about adjacent cells that are operating / will operate in cell DTX / DRX mode.

[0067] After receiving notification of a cell inactivity period (614), UE102 decides whether to perform an adjacent cell measurement before the cell inactivity period begins, based on whether UE102 can monitor paging DCI even after the serving cell has entered cell DTX / DRX mode. In this example, UE102 decides not to trigger a measurement for an upcoming cell inactivity period on the grounds that the UE's paging occasion (PO) does not overlap with the cell inactivity period, or on the grounds that UE102 and BS104 can adjust / shift / extend the UE's PO (616).

[0068] Next, BS104 initiates a cell inactive period (620), and then, if the PO falls within the cell inactive period, UE102 may stop monitoring the paging DCI during the PO (630). Subsequently, BS104 restarts the cell active period (632), and then UE102 may begin monitoring the paging DCI within the original PO and / or the shifted / adjusted PO (634).

[0069] Figure 6B is a messaging diagram for an exemplary scenario 600B in which the UE determines whether adjacent cell measurements are necessary before the occurrence of a periodic cell inactivity. Scenario 600B is generally similar to scenario 600A, but the differences are explained below.

[0070] In scenario 600B, instead of dynamically initiating the cell inactivity period, BS104 periodically initiates the cell inactivity period once per cell DTX / DRX cycle. Thus, after UE102 connects to BS104, BS104 sends or broadcasts (605) an RRC message to UE102 indicating the cell DTX / DRX configuration (including the DTX / DRX cycle, the length of the cell inactivity period, etc.), and the RRC message can be a system information message, a CCCH message, or a DCCH message.

[0071] In one embodiment, when UE102 receives a cell DTX / DRX configuration (605), it deems the cell DTX / DRX mode to be deactivated. In this case, BS104 must send / broadcast (614) other activation notifications to UE102 to activate the cell DTX / DRX mode set in UE102 earlier, and these activation notifications may be system information, dedicated / common RRC messages, and DL MAC CE or DCI.

[0072] Figure 7 is a messaging diagram for an exemplary scenario 700 in which a UE in a connected state triggers a candidate cell evaluation for a conditional handover (CHO) execution based on timing information provided to the conditional handover (CHO) configuration. In scenario 700, UE102 first establishes a connection with a cell managed by BS104 and then remains in a connected state (702). Meanwhile, another cell managed by BS106 is available to UE102 as an adjacent cell, and this adjacent cell does not operate in NES mode (e.g., cell DTX / DRX mode) for the entire duration of this example, and will not operate in that mode (704).

[0073] In scenario 700, BS104 decides to periodically initiate a cell inactivity period once per cell DTX / DRX cycle. Therefore, after UE102 connects to BS104, BS104 sends an RRC message to UE102 indicating the cell DTX / DRX configuration (including the DTX / DRX cycle, the length of the cell inactivity period, etc.) (705), and the RRC message can be a system information message, a CCCH message, or a DCCH message.

[0074] Next, BS104 prepares CHO candidates for UE102 in anticipation of future potential cell inactivity periods by sending a handover request message to these candidates (including BS106) (740). In response to the handover request message, BS106 sends a handover request acknowledgment message to BS104 to accept the handover request (742). Upon receiving the handover request acknowledgment message, BS104 sends a conditionalReconfiguration IE to UE102 (via an RRCReconfiguration message) (744) containing one or more candidate cell configurations, at least one of which contains a CHO execution condition (i.e., MeasId) and a timestamp associated with the CHO execution condition. In one embodiment, the timestamp is an exact time instance described in a specific time format (e.g., UTC). In other embodiments, the timestamp includes a timer that starts operating when UE102 receives the timestamp and expires at the time intended by the timestamp. In yet another embodiment, the timestamp may include a time instance and a duration, the time instance being described in the format of a system frame number (SFN) and a subframe number, and the duration being described in seconds, mini-seconds, system frames, or subframes.

[0075] After receiving a conditionalReconfiguration IE containing at least one CHO execution condition (i.e., MeasId) associated with a timestamp (744), UE102 periodically determines whether the current time has elapsed to the timestamp associated with the CHO execution condition. In event 746, since the current time has elapsed to the timestamp associated with the CHO execution condition of the cell managed by BS106, UE102 begins evaluating the CHO execution condition of the cell managed by BS106. Finally, UE102 decides to execute the CHO on the cell in BS106 once the cell's CHO execution condition is met (748). UE102 then synchronizes and executes CHO 750 with the cell in BS106.

[0076] Figure 8 is a flowchart of exemplary method 800, which may be implemented in an idle state by a UE (e.g., UE 102 in this disclosure) to evaluate cell reselection criteria using a common NES offset before a cell inactivity period occurs. First, in block 810A, the UE receives system information from the BS indicating adjacent cells(s) operating in cell DTX / DRX mode. In one embodiment, an indication of whether an adjacent cell is in cell DTX / DRX mode is transmitted within an IntraFreqNeighCellList / InterFreqNeighCellList IE and associated with a cell, and the presence of the indication means that the associated cell is in / is in cell DTX / DRX mode. In other embodiments, the indication of whether an adjacent cell is in cell DTX / DRX mode is determined based on whether that cell is included in a list of NES / DTX / DRX cells.

[0077] The UE also receives the common NES offset from the BS, either via a system information message in block 810B or via a dedicated RRC message. The sequences in blocks 810A and 810B can be modified in this flowchart. In block 816, the UE begins measuring the adjacent cell(s) before the serving cell enters its cell inactivity period. In other embodiments, the UE begins measuring the adjacent cell(s) in block 816 even if the serving cell has not entered / will not enter its cell inactivity period.

[0078] Based on the measurement results obtained in block 816, the UE evaluates the cell reselection criteria in block 818, with a common NES offset applied to all cells operating in cell DTX / DRX mode.

[0079] Figure 9 is a flowchart of exemplary method 900, which can be implemented in an idle state by a UE (e.g., UE 102 in this disclosure) to evaluate cell reselection criteria using cell-specific NES offsets before a cell inactivity period occurs. In block 910A, the UE receives information from the BS, either via system information messages or dedicated RRC messages, about adjacent cells operating in cell DTX / DRX mode. In one embodiment, information about adjacent cells operating in cell DTX / DRX mode is delivered via an "NES_mode" or "DTX / DRX_mode" IE / flag associated with the cell identity in an existing cell list. In other embodiments, information about adjacent cells operating in cell DTX / DRX mode is delivered via a list of NES / DTX / DRX cells.

[0080] In block 910B, the UE also receives a cell-specific NES offset for each cell operating in cell DTX / DRX mode from the BS, either via system information or a dedicated RRC message. In block 916, the UE initiates measurements against adjacent cells before the serving cell enters a cell inactivity period. In other embodiments, in block 916, the UE initiates measurements against adjacent cells even if the serving cell has not entered / will not enter a cell inactivity period.

[0081] Based on the measurement results obtained in block 916, the UE evaluates the cell reselection criteria in block 918, with each cell-specific NES offset applied to the associated / corresponding cell.

[0082] Figure 10 is a flowchart of exemplary method 1000 that can be implemented in an idle state by a UE (e.g., UE 102 in this disclosure) to determine when a BS will initiate a cell inactivity period based on a broadcast notification transmitted by the BS. In block 1006, the UE receives an RRC release message from the BS. In block 1008, in response to the RRC release message, the UE transitions to an idle state.

[0083] In block 1014, the UE receives a notification from the BS indicating the arrival of a cell inactivity period. In one embodiment, the notification received by the UE in block 1014 is an exact time instance described in a specific time format (e.g., UTC). In another embodiment, the notification received by the UE in block 1014 is a timer that starts operating when the UE receives this notification and expires at the start of the cell inactivity period. In yet another embodiment, the notification received by the UE in block 1014 may include a time instance and a duration, the time instance described in the format of a system frame number (SFN) and subframe number, and the duration described in seconds, mini-seconds, system frames, or subframes. In one embodiment, the notification received by the UE in block 1014 may include the duration of the upcoming cell inactivity period. Blocks 1006, 1008, and 1014 together are referred to in Figure 10 as procedure 1060 for “receiving a broadcast notification of a cell inactivity period”.

[0084] The flow then proceeds to block 1015, where the UE determines, based on the information received in block 1014, when the serving cell will begin its cell inactivity period. Subsequently, in block 1016, the UE begins measuring the adjacent cell(s) before the serving cell enters its cell inactivity period.

[0085] Figure 11 is a flowchart of exemplary method 1100, which may be implemented in idle state by a UE (e.g., UE 102 in this disclosure) to determine when a BS will begin a cell inactivity period based on a dedicated RRC message transmitted by the BS. In block 1106, the UE receives an RRC release message from the BS indicating when the cell will begin a cell inactivity period.

[0086] In block 1108, the UE transitions to an idle state in response to the RRC release message. Alternatively, in block 1106, the indication of when a cell will begin a cell inactivity period is received by the UE in a dedicated RRC message other than the RRC release message. In one embodiment, the indication of when a cell will begin a cell inactivity period is an exact time instance described in a specific time format (e.g., UTC). In another embodiment, the indication of when a cell will begin a cell inactivity period is a timer that starts operating when the UE receives the notification and expires at the start of the cell inactivity period. In yet another embodiment, the indication of when a cell will begin a cell inactivity period includes a time instance and may include a duration, the time instance is described in the format of a system frame number (SFN) and subframe number, and the duration is described in seconds, mini-seconds, system frames, or subframes. In one embodiment, the indication of when a cell will begin a cell inactivity period may include the duration of an upcoming cell inactivity period. Blocks 1106 and 1108 together are referred to in Figure 11 as step 1160 for "receiving a special notification for a cell inactivity period."

[0087] The flow then proceeds to block 1115, where the UE determines, based on the information received in block 1106, when the serving cell will begin its cell inactivity period. In block 1116, the UE begins measuring the adjacent cell(s) before the serving cell enters its cell inactivity period.

[0088] Figure 12 is a flowchart of exemplary method 1200, which can be implemented in an idle state by a UE (e.g., UE 102 in this disclosure) to determine when a BS will initiate a cell inactivity period based on a periodic cell DTX / DRX configuration transmitted by the BS. In block 1206, the UE receives an RRC message (e.g., a DCCH or CCCH message) from the BS, which includes a cell DTX / DRX (periodic) configuration, which may include the DTX / DRX cycle length and the length of the cell inactivity period. The UE then receives an RRC release message from the BS in block 1206. In response to the RRC release message, the UE transitions to an idle state in block 1208.

[0089] In one embodiment, when UE102 receives the cell DTX / DRX configuration in block 1205, it deactivates the cell DTX / DRX mode. In this case, UE receives other activation notifications in block 1214 to activate the cell DTX / DRX mode that was set earlier in UE, and these activation notifications can be system information, dedicated / common RRC messages, and DL MAC CE or DCI. Blocks 1205, 1206, 1208, and 1214 are collectively referred to as procedure 1260 for “receiving periodic cell DTX / DRX configuration” in Figure 12.

[0090] The flow then proceeds to block 1215, where the UE determines, based on the information received in block 1205 and optionally block 1214, when the serving cell will begin its cell inactivity period. In block 1216, the UE begins measuring the adjacent cell(s) before the serving cell enters its cell inactivity period.

[0091] Figure 13 is a flowchart of exemplary method 1300, which may be implemented in an idle state by a UE (e.g., UE 102 in this disclosure) to evaluate cell reselection criteria using the remaining active time of a cell before a cell inactivity period occurs. In block 1310, the UE receives information from the BS, either via a system information message or a dedicated RRC message, indicating when a cell will begin its cell inactivity period. In one embodiment, the information indicating when a cell will begin its cell inactivity period is an exact time instance described in a specific time format (e.g., UTC). In another embodiment, the information indicating when a cell will begin its cell inactivity period is a timer that starts operating when the UE receives this information and expires at the start of the cell inactivity period. In yet another embodiment, the information indicating when a cell will begin its cell inactivity period may include a time instance and a duration, the time instance being described in the format of a system frame number (SFN) and subframe number, and the duration being described in seconds, mini-seconds, system frames, or subframes.

[0092] In block 1316, the UE initiates measurements against adjacent cells(s) before the serving cell enters a cell inactivity period. In other embodiments, in block 1316, the UE initiates measurements against adjacent cells(s) even if the serving cell has not entered / will not enter a cell inactivity period. Based on the measurements obtained in block 1316, the UE evaluates the cell reselection criteria in block 1318 by considering when the cell will begin its cell inactivity period.

[0093] Figure 14 is a flowchart of exemplary method 1400, which may be implemented in an idle state by a UE (e.g., UE 102 in this disclosure) to determine whether the UE should trigger an adjacent cell measurement before a serving cell enters a cell inactivity period. In block 1415, the UE determines, based on information obtained from steps 1060, 1160, or 1260, when the serving cell will begin its cell inactivity period.

[0094] Next, the flow proceeds to decision block 1458, where the UE determines whether it can still receive paging from the serving cell operating in cell DTX / DRX mode. If the decision in decision block 1458 is negative, the flow proceeds to block 1416A, where the UE must begin making measurements to the adjacent cell(s) before the serving cell enters a cell inactivity period.

[0095] On the other hand, if the decision in decision block 1458 is affirmative, the flow proceeds to block 1416B, where the UE decides not to trigger adjacent cell measurement for the upcoming cell inactivity period. After the serving cell has started / entered a cell inactivity period, the UE may stop monitoring paging occasions in block 1430. If the UE chooses to stop monitoring paging occasions, the UE may resume monitoring paging occasions in block 1434 after the serving cell has returned to a cell active period.

[0096] Figure 15 is a flowchart of exemplary method 1500 that can be implemented by a BS (e.g., BS104 in this disclosure) to inform the UE of adjacent cells (or more) operating in cell DTX / DRX mode and the common NES offset associated with these cells. First, in block 1510A, the BS transmits system information to the UE indicating adjacent cells (or more) operating in cell DTX / DRX mode. In one embodiment, an indication of whether an adjacent cell is in cell DTX / DRX mode is transmitted within an IntraFreqNeighCellList / InterFreqNeighCellList IE and associated with a cell, and the presence of the indication means that the associated cell is in / is in cell DTX / DRX mode. In other embodiments, the indication of whether an adjacent cell is in cell DTX / DRX mode is determined based on whether the cell is included in a list of NES / DTX / DRX cells.

[0097] Furthermore, in block 1510B, BS transmits a common NES offset via a system information message or a dedicated RRC message, and this common NES offset is applied to these cells operating in cell DTX / DRX mode. The sequence of blocks 1510A and 1510B can be modified in this flowchart.

[0098] Figure 16 is a flowchart of exemplary method 1600 that can be implemented by a BS (e.g., BS104 in this disclosure) to notify the UE of adjacent cells (or more) operating in cell DTX / DRX mode and the cell-specific NES offsets associated with these cells. First, in block 1610A, the BS sends system information or a dedicated RRC message to the UE indicating adjacent cells (or more) operating in cell DTX / DRX mode. In one embodiment, the indication of whether an adjacent cell is operating in cell DTX / DRX mode is sent within an IntraFreqNeighCellList / InterFreqNeighCellList IE and associated with the cell, and the presence of the indication means that the associated cell is in / is in cell DTX / DRX mode. In other embodiments, the indication of whether an adjacent cell is in cell DTX / DRX mode is determined based on whether the cell is included in a list of NES / DTX / DRX cells.

[0099] In block 1610B, the BS transmits a cell-specific NES offset to the UE for each adjacent cell operating in cell DTX / DRX mode, either via a system information message or a dedicated RRC message.

[0100] Figure 17 is a flowchart of exemplary method 1700 that can be implemented by a BS (e.g., BS104 in this disclosure) to notify the UE of the time when an adjacent cell will begin its cell inactivity period. In block 1709, the BS determines the time when the adjacent cell will begin its cell inactivity period. Next, in block 1710, the BS sends a system information message or dedicated RRC message containing information about the time when the adjacent cell will begin its cell inactivity period. In one embodiment, the information indicating when a cell will begin its cell inactivity period is an exact time instance described in a specific time format (e.g., UTC). In another embodiment, the information about the time when a cell will begin its cell inactivity period is a timer that starts operating when the UE receives this information and expires at the start of the cell inactivity period. In yet another embodiment, the information about the time when a cell will begin its cell inactivity period may include a time instance and a duration, the time instance being described in the format of a system frame number (SFN) and subframe number, and the duration being described in seconds, mini-seconds, system frames, or subframes.

[0101] Finally, Figure 18 shows an exemplary method 800 that a suitable UE (e.g., UE102) may implement to perform cell reselection. In block 1806, the UE receives an NES offset value from the RAN corresponding to the adjustment of the signal meter for cell reselection (e.g., events 306, 307, 410, 810B, 910B). In block 816, the UE operates in an idle state of the radio connection between the UE and the RAN (e.g., RRC_IDLE) and performs measurements on candidate cells, such as adjacent cells (e.g., events 316, 416, 516, 1016, 1116, 1216, 1316). In block 1818, the UE performs cell reselection based on the measurements and offset value (e.g., events 318, 418, 518, 818, 918, 1318).

[0102] The following list of embodiments reflects the various embodiments expressly intended by this disclosure.

[0103] Example 1. A cell reselection method, the method being implemented in a user device (UE), and comprising: receiving a network energy reduction (NES) offset value from a radio access network (RAN) corresponding to an adjustment in the signal measurement quantity for the cell reselection; performing measurements on a plurality of candidate cells while the radio connection between the UE and the RAN is idle; and performing the cell reselection based on the measurements and the offset value.

[0104] Example 2. The method according to Example 1, wherein the execution of the cell reselection comprises ranking the plurality of candidate cells based on each of the measurements, wherein the execution of the cell reselection comprises adjusting at least one of the measurements by the NES offset value, and performing the cell reselection according to the ranking.

[0105] Example 3. The method according to Example 2, wherein the NES offset value is common to all of the multiple candidate cells operating in NES mode.

[0106] Example 4. The method according to Example 2, wherein the NES offset value is specific to one of the multiple candidate cells operating in NES mode.

[0107] Example 5. The method according to Example 3 or 4, further comprising receiving a listing of the plurality of candidate cells from the RAN, the listing indicating which of the plurality of candidate cells will operate in NES mode.

[0108] Example 6. The method according to any one of Examples 3 to 5, wherein the NES offset value is negative in order to lower the ranking of the candidate cell when the candidate cell operates in the NES mode.

[0109] Example 7. The ranking is performed with respect to each of the multiple candidate cells, where R=Qmeas -Qoffset-Qoffset temp- Qoffset NES This includes calculating each rank according to the formula, where Q meas Qoffset is a measurement of Reference-Signal-Receive-Power (RSRP), and Qoffset is an offset that depends on whether the candidate cells correspond to adjacent cells within different frequencies or within the same frequency. temp This is a temporarily applied offset, Qoffset NES The method according to any one of Examples 2 to 6, wherein is the offset value corresponding to the adjustment of the signal measurement amount of the cell reselection.

[0110] Example 8. The method according to any one of Examples 2 to 7, wherein the NES mode is an adaptation of the discontinuous transmit (DTX) / discontinuous receive (DRX) mode.

[0111] Example 9. The method according to any one of Examples 2 to 8, wherein performing the cell reselection includes synchronizing with the highest-ranked cell among the plurality of candidate cells and camping on to the highest-ranked cell.

[0112] Example 10. The method according to any of the prior embodiments, wherein the NES offset value is received in a command to release the wireless connection when the UE is operating in the active state of the wireless connection.

[0113] Example 11. The method according to any of the prior embodiments, wherein the NES offset value is received via broadcast.

[0114] Example 12. The method according to any of the prior embodiments, further comprising the UE receiving an indication from the RAN of the time when the serving cell operating therein begins an NES inactive period before transitioning to idle mode, and the execution of the measurement is in response to the reception of the indication.

[0115] Example 13. The method according to Example 12, wherein the NES inactive period is the DTX / DRX inactive period.

[0116] Example 14. The method according to Example 12, wherein the indication of the time when the serving cell initiates the NES inactive period is included in the periodic NES configuration.

[0117] Example 15. The method according to Example 14, wherein the periodic NES configuration includes either or both the duration of the DTX / DRX cycle or the duration of the DTX / DRX inactivity period.

[0118] Example 16. The method according to any one of Examples 8 to 15, wherein the execution of the measurement is started a predetermined number of time units before the time when the NES inactive period begins.

[0119] Example 17. The method according to any one of Examples 12 to 16, wherein the indication of the time when the serving cell begins the DTX / DRX inactive period is included in one of (i) a radio resource control (RRC) paging message, (ii) a downlink (DL) medium access control (MAC) control element (CE), or (iii) downlink control information (DCI).

[0120] Example 18. The method according to any one of Examples 12 to 16, wherein the indication of the time when the serving cell begins the NES inactive period is received before the UE transitions to the idle mode.

[0121] Example 19. The method according to any one of the embodiments of Examples 12 to 16, wherein the indication of the time when the serving cell starts the NES inactive period is a system information message transmitted by the serving cell.

[0122] Example 20. The method according to any one of the embodiments of Examples 12 to 16, wherein the indication of the time when the serving cell starts the NES inactive period is a timer value, and the method further includes, when the serving cell receives the indication of the time when the NES inactive period starts, starting a timer by the timer value and determining that the NES inactive period starts at the time when the timer expires.

[0123] Example 21. A user device (UE) comprising a transceiver and processing hardware, configured to implement the method described in any of the prior embodiments.

[0124] Example 22. A cell reselection method implemented in a user device (UE), comprising: receiving a network energy reduction (NES) offset value for the cell reselection from a radio access network (RAN); performing measurements on a plurality of adjacent cells while the radio connection between the UE and the RAN is idle; ranking the plurality of adjacent cells based on the measurements, including applying the NES offset value to adjust the ranking; and performing the cell selection based on the ranking.

[0125] Example 23. The method according to Example 22, wherein the NES offset value is an indication of the time when the serving cell on which the UE operates begins a DTX / DRX inactive period before transitioning to the idle mode.

[0126] Example 24. The method according to Example 22, wherein the NES offset value corresponds to the adjustment of the signal measurement amount for cell reselection.

[0127] Example 25. A cell reselection method, the method being implemented in a user device (UE), and comprising receiving an indication from a radio access network (RAN) and during idle radio connectivity between the UE and the RAN's serving cell for the time when the serving cell will initiate a network energy reduction (NES) inactive period, and deciding, based on the indication, to refrain from performing measurements on a plurality of neighboring cells.

[0128] Example 26. The method of Example 25, further comprising monitoring paging in the serving cell during the NES inactive period.

[0129] Example 27. The method of Example 25, further comprising refraining from monitoring paging in the serving cell during the NES inactive period.

[0130] Example 28. The method of Example 27, further comprising resuming the monitoring of the paging in the serving cell when the NES inactive period ends.

[0131] The following explanation may apply to the explanation above.

[0132] Generally speaking, the explanation for one of the above figures can also be applied to the other figures above. The above examples, embodiments, and methods can be combined, provided they do not conflict. The above events or blocks can be optional or omitted. For example, events or blocks with dashed lines in the figures can be optional. In some embodiments, “message” is used and can be replaced with “information element (IE),” and vice versa. In some embodiments, “IE” is used and can be replaced with “field,” and vice versa. In some embodiments, “configuration (singular)” can be replaced with “configuration (plural)” or “configuration parameter,” and vice versa. In some embodiments, “several” means “one or more.” In some embodiments, “at least one” means “one or more.”

[0133] A user device (e.g., UE102) that can implement the technology of this disclosure may be any suitable wireless communication device, such as a smartphone, tablet computer, laptop computer, mobile game console, point-of-sale (POS) terminal, health management device, drone, camera, media streaming dongle or other personal media device, wearable device such as a smartwatch, wireless hotspot, femtocell, or broadband router. Furthermore, the user device may optionally be embedded in an electronic system such as a vehicle head unit or advanced driver-assistance system (ADAS). In addition, the user device may operate as an Internet of Things (IoT) device or a mobile internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0134] Certain embodiments described in this disclosure include logic or several components or modules. A module may be a software module (e.g., code or machine-readable instructions stored in a non-temporary machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in certain ways. A hardware module may include dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor such as a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC), or a digital signal processor (DSP)) to perform certain operations. A hardware module may also include programmable logic or circuitry that is temporarily configured by software (e.g., contained within a general-purpose processor or other programmable processor) to perform certain operations. The decision of whether to implement a hardware module with dedicated, permanently configured circuitry or with temporarily configured circuitry (e.g., configured by software) may be made considering cost and time.

[0135] When implemented in software, techniques may be provided as part of an operating system, a library used by multiple applications, or a specific software application. The software can run on one or more general-purpose processors or one or more special-purpose processors.

[0136] As used herein, “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variation thereof are intended to encompass non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to these elements alone, and may include other elements not expressly enumerated or inherent in such process, method, article, or apparatus. Furthermore, unless expressly stated otherwise, “or” refers to an inclusive or not an exclusive or. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist); A is false (does not exist) and B is true (or exists); and both A and B are true (or exist).

[0137] Those skilled in the art will understand, by reading this disclosure, further additional and alternative structural and functional designs for handling mobility between base stations through the principles disclosed herein. Thus, while specific embodiments and applications have been described and outlined, it will be understood that the disclosed embodiments are not limited to the exact structures and components disclosed herein. Various modifications, changes, and variations obvious to those skilled in the art may be made in the arrangement, operation, and details of the methods and apparatus disclosed herein without departing from the spirit and scope of the appended claims.

Claims

1. A method for re-selecting cells, the method being implemented in a user device (UE), Receiving a network energy reduction (NES) offset value from the wireless access network (RAN) corresponding to the adjustment of the signal measurement amount for cell reselection, The measurement is performed on multiple candidate cells while the wireless connection between the UE and the RAN is idle. Performing the cell reselection based on the measurement and the offset value, Methods that include...

2. Performing the aforementioned cell reselection means Ranking the plurality of candidate cells based on each of the measurements, including adjusting at least one of the measurements by the NES offset value, The cell reselection is performed according to the aforementioned ranking, The method according to claim 1, including the method described in claim 1.

3. The method according to claim 2, wherein the NES offset value is common to all of the plurality of candidate cells operating in NES mode.

4. The method according to claim 2, wherein the NES offset value is unique to one of the plurality of candidate cells operating in NES mode.

5. The method according to claim 3 or 4, further comprising receiving a listing of the plurality of candidate cells from the RAN, the listing indicating which of the plurality of candidate cells operates in NES mode.

6. The method according to any one of claims 1 to 5, wherein the NES offset value is received in a command to release the wireless connection when the UE is operating in the active state of the wireless connection.

7. The method according to any one of claims 1 to 6, wherein the NES offset value is received via broadcast.

8. The method further includes the UE receiving an indication from the RAN of when the serving cells operating therein will begin a NES inactive period before transitioning to idle mode. The method according to any one of claims 1 to 7, wherein performing the measurement is in response to the receipt of the indication.

9. The method according to claim 8, wherein the indication of when the serving cell will begin the NES inactive period is included in the periodic NES configuration.

10. The method according to claim 8 or 9, wherein performing the measurement starts a predetermined number of time units before the time the NES inactive period begins.

11. The indication of when the serving cell will begin a DTX / DRX inactive period is: (i) Radio Resource Control (RRC) paging messages, (ii) Downlink (DL) media access control (MAC) control element (CE), or (iii) Downlink control information (DCI), A method according to any one of claims 10 to 12, which is included in one of the following.

12. The method according to any one of claims 10 to 12, wherein the indication of when the serving cell will initiate the NES inactive period is received before the UE transitions to the idle mode.

13. The method according to any one of claims 10 to 12, wherein the indication of when the serving cell will begin the NES inactive period is a system information message transmitted in the serving cell.

14. The indication of when the serving cell begins the NES inactive period is a timer value, and the method further, When the serving cell receives the indication of when the NES inactive period will begin, it starts the timer according to the timer value. It is determined that the NES inactive period begins when the timer expires, The method according to any one of claims 10 to 12, including the method described in any one of claims 10 to 12.

15. Transceiver and, Processing hardware and User equipment (UE) including, The aforementioned UE is configured to carry out the method described in any one of claims 1 to 14.

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