Method and communication device for handling re-establishment procedures

Abstract

To provide a method and communication device for handling re-establishment procedures. [Solution] A method for a communication device to process a re-establishment procedure includes the steps of: initiating a re-establishment procedure; selecting a target cell according to a cell selection procedure; triggering an OD-SIB1 procedure on the target cell according to a stored wake-up signal (WUS) configuration when at least one on-demand system information block 1 (OD-SIB1) procedure trigger condition is met; determining whether the target cell is a cell on which a communication device can camp-on according to the SIB1 from the target cell; and sending a re-establishment request message to the target cell, depending on whether the target cell is a cell on which a communication device can camp-on.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 747,895, filed on January 22, 2025. The content of the application is incorporated herein by reference.

[0002] The present disclosure relates to methods and communication devices used in wireless communication systems, and more particularly, to methods and communication devices for handling re - establishment procedures.

Background Art

[0003] The Long - Term Evolution (LTE) system that supports the 3rd Generation Partnership Project (3GPP (registered trademark)) Rel - 8 standard and / or 3GPP (registered trademark) Rel - 9 standard has been developed by 3GPP (registered trademark) as a successor to the Universal Mobile Telecommunications System (UMTS) to further enhance the performance of UMTS in order to meet the growing needs of users.

[0004] The LTE - Advanced (LTE - A) system is an evolved version of the LTE system, as its name implies. The LTE - A system aims for faster switching between power states, improves performance at the edge of the coverage of evolved Node - B (eNB), improves peak data rate and throughput, and includes advanced technologies such as carrier aggregation (CA), uplink (UL) multiple - input multiple - output (UL - MIMO).

[0005] To further enhance the LTE-A system, next-generation radio access networks (NG-RANs) are being developed that support 3GPP® Rel-15 to 3GPP® Rel-19 standards. An NG-RAN includes one or more next-generation Node-Bs (gNBs) and features characteristics such as wider operating bandwidth, different numerologies across different frequency ranges, massive MIMO, and advanced channel coding.

[0006] A communication device requires a System Information Block 1 (SIB1) provided by a cell to check whether the cell is suitable for the communication device to perform a re-establishment procedure. If an SIB1 is not available, the communication device requests an SIB1 from the cell by performing an OD-SIB1 procedure according to the Wake-Up Signal (WUS) configuration. However, the communication device may not successfully re-establish the connection to the cell due to, for example, an invalid WUS configuration and / or delays caused by the execution of the OD-SIB1 procedure. [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, how to handle the re-establishment procedure is a crucial issue that needs to be resolved. [Means for solving the problem]

[0008] Therefore, to solve the above-mentioned problems, this disclosure provides a method and a communication device for handling a re-establishment procedure.

[0009] A communication device method for handling a re-establishment procedure includes the steps of: initiating a re-establishment procedure; selecting a target cell according to a cell selection procedure; triggering an OD-SIB1 procedure on the target cell according to a stored wake-up signal (WUS) configuration, depending on whether at least one on-demand system information block 1 (OD-SIB1) procedure trigger condition is met; determining, according to the SIB1 from the target cell, whether the target cell is a cell on which a communication device can camp-on; and sending a re-establishment request message to the target cell, depending on whether the target cell is a cell on which a communication device can camp-on.

[0010] A serving cell method for handling a re-establishment procedure includes the step of sending a Wake-Up Signal (WUS) configuration set to a communication device, the WUS configuration set including multiple identities (IDs) for multiple cells, multiple frequencies corresponding to multiple cells, and multiple WUS configurations corresponding to multiple cells.

[0011] A network energy saving (NES) cell method for handling a re-establishment procedure includes the steps of: performing an OD-SIB1 procedure with a communication device according to a stored wake-up signal (WUS) configuration in response to at least one on-demand system information block 1 (OD-SIB1) procedure trigger condition being met; and receiving a re-establishment request message from a communication device in response to the NES cell being a cell on which the communication device can camp-on.

[0012] These and other objectives of the present invention will undoubtedly become apparent to those skilled in the art after reading the following detailed description of preferred embodiments shown in various figures and drawings. [Brief explanation of the drawing]

[0013] [Figure 1]This is a schematic diagram of a wireless communication system according to an example of the disclosure. [Figure 2] This is a schematic diagram of a communication device as an example of the disclosure. [Figure 3] This is a flowchart illustrating the process as described in this disclosure. [Figure 4] This is a flowchart illustrating the process as described in this disclosure. [Figure 5] This is a flowchart illustrating the process as described in this disclosure. [Figure 6] This is a sequence diagram of a process according to the examples in this disclosure. [Figure 7] This is a sequence diagram of a process according to the examples in this disclosure. [Figure 8] This is a flowchart illustrating the process as described in this disclosure. [Figure 9] This is a flowchart illustrating the process as described in this disclosure. [Figure 10] This is a sequence diagram of a process according to the examples in this disclosure. [Figure 11] This diagram shows a schematic representation of a specific period for verifying whether a stored WUS configuration is valid, as illustrated by the examples in this disclosure. [Figure 12] This diagram shows a schematic representation of a specific period for verifying whether a stored WUS configuration is valid, as illustrated by the examples in this disclosure. [Modes for carrying out the invention]

[0014] Figure 1 is a schematic diagram of a wireless communication system 10 according to an example of the present disclosure. Briefly, the wireless communication system 10 consists of a network 12 and a plurality of communication devices 14. The wireless communication system 10 may support time-division duplex (TDD) mode, frequency-division duplex (FDD) mode, TDD-FDD joint operation mode, non-terrestrial network (NTN) mode, or licensed-assisted access (LAA) mode. That is, the network 12 and communication devices 14 may communicate with each other via FDD carriers, TDD carriers, licensed carriers (licensed serving cells), and / or unlicensed carriers (unlicensed serving cells). Furthermore, the wireless communication system 10 may support carrier aggregation (CA). That is, the network 12 and communication devices 14 may communicate with each other via a plurality of serving cells (e.g., a plurality of serving carriers), including a primary cell (e.g., a primary component carrier) and one or more secondary cells (e.g., secondary component carriers).

[0015] In Figure 1, the network 12 and communication device 14 are used simply to illustrate the structure of the wireless communication system 10. In practice, network 12 may be a universal terrestrial radio access network (UTRAN) including at least one Node-B (NB) of a universal mobile communications system (UMTS). For example, network 12 may be an evolved UTRAN (E-UTRAN) including at least one evolved NB (eNB) and / or at least one relay node, such as a Long-Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, or an evolved version of the LTE-A system. For example, network 12 may be a next-generation radio access network (NG-RAN) including at least one next-generation Node-B (gNB) and / or at least one fifth-generation (5G) base station (BS). For example, the gNB or 5G BS of network 12 may include an NTN gateway and an NTN payload. In one example, the gNB or 5G BS of network 12 may be a transmission reception point (TRP). In another example, network 12 may be any BS that conforms to a specific communication standard for communicating with the communication device 14.

[0016] New Radio (NR) is a standard defined for 5G systems (or 5G networks) to provide a unified radio interface with superior performance. gNB is deployed to enable 5G systems that support advanced features such as Enhanced Mobile Broadband (eMBB), Ultra-High Reliability Low Latency Communications (URLLC), and Massive Machine-Type Communications (mMTC). eMBB provides broadband services with wider bandwidth and low / medium latency. URLLC offers applications with higher reliability and lower latency characteristics (e.g., end-to-end communications). Examples of applications include the Industrial Internet, smart grids, infrastructure protection, remote surgery, and intelligent transportation systems (ITS). mMTC can support the Internet of Things (IoT) in 5G systems, including billions of connected devices and / or sensors.

[0017] Furthermore, network 12 may include at least one of UTRAN / E-UTRAN / NG-RAN and the core network, and the core network may include network entities such as a mobility management entity (MME), a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), a self-organizing network (SON) server and / or a radio network controller (RNC), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), an authentication server function (AUSF). In one example, after network 12 receives information transmitted by communication device 14, the information may be processed only by UTRAN / E-UTRAN / NG-RAN, and a determination corresponding to the information may be made in UTRAN / E-UTRAN / NG-RAN. In one example, UTRAN / E-UTRAN / NG-RAN may transfer the information to the core network, and a determination corresponding to the information may be made in the core network after the core network processes the information. In one example, the information may be processed by both UTRAN / E-UTRAN / NG-RAN and the core network, and the determination may be made after coordination and / or cooperation is executed by UTRAN / E-UTRAN / NG-RAN and the core network.

[0018] The communication device 14 may be a user device (UE), a very small earth station (VSAT), a low-cost device (e.g., a machine-type communication (MTC) device), a device-to-device (D2D) communication device, a narrowband Internet of Things (IoT) (NB-IoT), a mobile phone, a laptop, a tablet computer, an e-book, a portable computer system, or a combination thereof. Furthermore, the network 12 and the communication device 14 can be considered as a transmitter or a receiver depending on the direction (i.e., the transmission direction), for example, with respect to the uplink (UL), the communication device 14 is the transmitter and the network 12 is the receiver, and with respect to the downlink (DL), the network 12 is the transmitter and the communication device 14 is the receiver.

[0019] The communication device 14 may perform Layer 1 (L1) measurements to generate L1 measurement results and may change the serving cell according to the L1 measurement results. This procedure is sometimes called conditional L1 / L2 triggered mobility (C-LTM). C-LTM may support intra-gNB-distributed unit (intra-gNB-DU) mobility, intra-gNB-central unit (intra-gNB-CU) mobility, and / or inter-gNB-DU mobility. C-LTM may support intra-frequency mobility and / or inter-frequency mobility. C-LTM may be supported for spectrums requiring a license. C-LTM may support at least one of the following scenarios: a primary cell (PCell) change in a non-CA scenario and / or a non-dual-connected (non-DC) scenario, a PCell and secondary cell (SCell) change in a CA scenario, or a DC scenario. The communication device 14 may execute L3 handover commands transmitted by the network 12.

[0020] FIG. 2 is a schematic diagram of a communication device 20 according to an example of the present disclosure. The communication device 20 may be the communication device 14 or the network 12 shown in FIG. 1, but is not limited thereto in this specification. The communication device 20 may include at least one processing circuit 200 such as a microprocessor or an application specific integrated circuit (ASIC), at least one storage device 210, and at least one communication interface device 220. The at least one storage device 210 may be any data storage device that may be accessed by and store program code 214 to be executed by the at least one processing circuit 200. Examples of the at least one storage device 210 include, but are not limited to, a subscriber identity module (SIM), a read only memory (ROM), a flash memory, a random access memory (RAM), a compact disc read only memory (CD-ROM), a digital versatile disc ROM (DVD-ROM), a Blu-ray disc ROM (BD-ROM), magnetic tape, a hard disk, an optical data storage device, a non-volatile storage device, a non-transitory computer-readable medium (e.g., a tangible medium), and the like. The at least one communication interface device 220 is preferably at least one transceiver and is used to transmit and receive signals (e.g., data, messages, and / or packets) according to the processing results of the at least one processing circuit 200.

[0021] FIG. 3 is a flowchart of a process 30 according to an example of the present disclosure. The process 30 may be utilized in a communication device (e.g., the communication device 14 of FIG. 1 or the communication device 20 of FIG. 2) to process a re-establishment procedure. The process 30 may be compiled into the program code 214 and includes the following steps.

[0022] Step 300: Start.

[0023] Step 302: Start the re-establishment procedure.

[0024] Step 304: Follow the cell selection procedure to select the target cell.

[0025] Step 306: When at least one On-Demand System Information Block 1 (OD-SIB1) procedure trigger condition is met, trigger the OD-SIB1 procedure on the target cell according to the stored Wake-Up Signal (WUS) configuration.

[0026] Step 308: Determine whether the target cell is a cell on which a communication device can camp on, according to the SIB1 from the target cell.

[0027] Step 310: Depending on whether the target cell is a cell on which a communication device can camp on, a re-establishment request message is sent to the target cell.

[0028] Step 312: Finish.

[0029] According to process 30, the communication device initiates a re-establishment procedure. The communication device then selects a target cell according to a cell selection procedure. The communication device triggers (and executes) an OD-SIB1 procedure on the target cell according to the stored WUS configuration, depending on whether at least one OD-SIB1 procedure trigger condition (e.g., all OD-SIB1 procedure trigger conditions) is met. The communication device determines, according to the SIB1 from the target cell, whether the target cell is a cell on which the communication device can camp on. Depending on whether the target cell is a cell on which the communication device can camp on, the communication device sends a re-establishment request message (e.g., Msg3) to the target cell.

[0030] The implementation of process 30 is not limited to the above description. The following examples may be applied to implement process 30.

[0031] In one example, the cell on which a communication device can camp on is the highest-ranked cell based on measurements. In another example, the stored WUS configuration is included in the WUS configuration set. In another example, the WUS configuration set is received from the serving cell of the communication device and stored in the communication device.

[0032] In one example, at least one OD-SIB1 procedure trigger condition includes at least one of the following conditions: the target cell does not provide SIB1 (e.g., periodically), the target cell is a Network Energy Saving (NES) cell, and the stored WUS configuration is valid. In one example, SIB1 includes at least one of the following information: public land mobile network (PLMN) information, other SIB availability and scheduling, and access control information. In one example, PLMN information is used to determine whether the target cell is a cell on which communication devices can camp on. In one example, the NES cell provides OD-SIB1 on demand (i.e., does not provide OD-SIB1 periodically).

[0033] In one example, the communication device verifies whether a stored WUS configuration is valid. In one example, the step of verifying whether a stored WUS configuration is valid includes at least one of the following steps: determining that the stored WUS configuration is valid depending on whether the system frame number (SFN) of the current radio frame is within a specific period (e.g., WUS_ValidPeriod); and determining that the stored WUS configuration is invalid at the end of the specific period. In one example, the step of verifying whether a stored WUS configuration is valid includes determining that the stored WUS configuration is invalid depending on whether the SFN of the current radio frame is outside the specific period. In one example, the step of verifying whether a stored WUS configuration is valid includes determining that the stored WUS configuration is invalid in response to the start of a re-establishment procedure.

[0034] In one example, a communication device determines the end of a particular period. In one example, the step of determining the end of a particular period includes receiving a configured system information (SI) change indication from a serving cell during the modification period and ending the particular period at the boundary of the modification period. That is, the communication device determines the end of a particular period by whether or not it receives an SI change indication during the modification period. In one example, the SI change indication is broadcast (e.g., via short message). In one example, the boundary of the modification period is the end of the modification period. In one example, the boundary of the modification period is defined by at least one SFN value. In one example, the SFN value is divisible by the number of radio frames (RF) that make up the modification period. In one example, the number of RFs is the product of the modification period coefficient and the default paging cycle. In one example, the modification period coefficient is 2, 4, 8, or 16, but is not limited herein. In one example, the communication device ends a particular period at the boundary of the next modification period depending on any unconfigured SI change indications. In one example, the boundary of the next modification period is the end of the next modification period. In one example, a communication device terminates a specific period at the boundary of a correction period, depending on the configured SI change indication.

[0035] In one example, a communication device checks whether an SI change indication is set to determine a specific time range. In another example, the communication device monitors the SI change indication when a third timer (e.g., T310) is running in the event of a radio link failure (RLF) condition. In yet another example, the communication device monitors the SI change indication at the beginning of each correction period.

[0036] In one example, the OD-SIB1 procedure includes at least one of the following steps: sending an OD-SIB1 request (e.g., a preamble) to a target cell; starting a watch window; watching (e.g., receiving) an OD-SIB1 request acknowledgment (ACK) (e.g., a random access acknowledgment (RAR)) in the watch window; and stopping the watch window in response to receiving an OD-SIB1 request ACK from the target cell. In other words, the communication device performs the OD-SIB1 procedure to request the target cell to provide an OD-SIB1.

[0037] In one example, the step of monitoring the OD-SIB1 request ACK in a monitoring window includes determining (e.g., releasing) the stored WUS configuration in response to the expiration of the monitoring window. In another example, the step of monitoring the OD-SIB1 request ACK in a monitoring window includes at least one of the following steps: resending the OD-SIB1 request to the target cell in response to the expiration of the monitoring window; incrementing the value of a counter by 1 in response to the resending of the OD-SIB1 request to the target cell; and determining that the target cell is a barring cell (e.g., a cell from which a communication device cannot camp on) in response to the counter value being greater than a threshold (e.g., ReEst-preambleTransMax). That is, if the communication device does not receive the OD-SIB1 request ACK from the target cell, it resends the OD-SIB1 request to the target cell. In another example, the communication device determines (e.g., declares) a failure of the OD-SIB1 procedure in response to the counter value being greater than a threshold. In one example, the threshold may be 0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 20, 50, 100, or 200, but is not limited herein. In one example, the value of the counter represents the number of retries for the communication device to perform the OD-SIB1 procedure.

[0038] In one example, the communication device starts a first timer (e.g., T310) in response to detecting a problem with the wireless link. In another example, the communication device stops the first timer in response to resolving the wireless link problem. In yet another example, the communication device declares an RLF (Reconnection Limiter) in response to the first timer expiring. In yet another example, the communication device initiates a re-establishment procedure in response to the RLF declaration.

[0039] In one example, a communication device enters idle mode from connected mode in response to a failed re-establishment procedure. In another example, the communication device restores connectivity (for example, from a serving cell to a target cell) in response to a successful re-establishment procedure.

[0040] In one example, the communication device starts a second timer (e.g., T311) in response to the start of the re-establishment procedure. In another example, the communication device stops the second timer when the re-establishment procedure is complete (e.g., the communication device successfully camps on to the target cell). In yet another example, the communication device determines (e.g., declares) that the re-establishment procedure has failed when the second timer expires.

[0041] In one example, a communication device sends a re-establishment request message to a target cell and then receives a re-establishment message (e.g., Msg4) from the target cell. In another example, the communication device camps on to the target cell in accordance with the re-establishment message (e.g., re-establishes the connection to the target cell).

[0042] In one example, a communication device receives a WUS configuration set from a serving cell. In one example, the WUS configuration set is received via an SIB. In one example, after receiving the WUS configuration set, the communication device stores the WUS configuration set. In one example, the WUS configuration set includes multiple identities (IDs) for multiple cells, multiple frequencies corresponding to (for example, each of) multiple cells, and multiple WUS configurations corresponding to (for example, each of) multiple cells.

[0043] In one example, a WUS configuration set further includes multiple indications, each corresponding to a different WUS configuration. In one example, each of the multiple indications indicates whether the corresponding WUS configuration is supported by a connected mode communication device. In one example, the communication device receives a cell list from a serving cell. In one example, the cell list indicates which WUS configurations in the WUS configuration set are supported by the connected mode communication device.

[0044] In one example, the communication device determines that a target cell is not a cell that the communication device can camp on to if the target cell does not support the OD-SIB1 procedure. In another example, the communication device adds the condition "the target cell supports the OD-SIB1 procedure" to at least one OD-SIB1 procedure trigger condition if the target cell does not support the OD-SIB1 procedure.

[0045] In one example, the communication device sends an OD-SIB1 request to the target cell once. In another example, the communication device determines that the target cell is not a cell that the communication device can camp on to, based on the fact that the communication device does not receive an OD-SIB1 request ACK in the monitoring window. In yet another example, the communication device determines that the stored WUS configuration is invalid, based on the fact that the communication device does not receive an OD-SIB1 request ACK in the monitoring window. In yet another example, the communication device determines the stored WUS configuration (e.g., release) based on the fact that the communication device does not receive an OD-SIB1 request ACK in the monitoring window.

[0046] In one example, the communication device, depending on whether the stored WUS configuration is invalid, re-selects a different target cell according to the cell selection procedure.

[0047] In one example, a WUS configuration set further includes multiple thresholds (e.g., ReEst-preambleTransMax) corresponding to multiple WUS configurations (e.g., each of them). In one example, each of the multiple thresholds indicates the maximum number of retries for a connected mode communication device to perform the OD-SIB1 procedure according to the corresponding WUS configuration. In one example, the communication device determines that a target cell is one that the communication device can camp on to, depending on whether the number of retries exceeds the corresponding threshold among the multiple thresholds. In one example, the communication device determines the WUS configuration set (e.g., release) depending on whether the number of retries exceeds the corresponding threshold among the multiple thresholds.

[0048] In one example, the communication device determines the WUS configuration set (for example, release it) in response to the start of the re-establishment procedure.

[0049] Figure 4 is a flowchart of process 40 according to an example of the present disclosure. Process 40 may be used in a serving cell (or serving BS) (for example, a cell in network 12 in Figure 1, a communication device 20 in Figure 2, or a serving cell in the example of process 30) to handle a re-establishment procedure. Process 40 may be compiled into program code 214, which includes the following steps:

[0050] Step 400: Start.

[0051] Step 402: Send a WUS configuration set to the communication device, which includes multiple IDs for multiple cells, multiple frequencies corresponding to multiple cells, and multiple WUS configurations corresponding to multiple cells.

[0052] Step 404: Finish.

[0053] According to process 40, the serving cell sends a WUS configuration set to a communication device (for example, the communication device of process 30). The WUS configuration set includes multiple IDs for multiple cells, multiple frequencies corresponding to (for example, each of) multiple cells, and multiple WUS configurations corresponding to (for example, each of) multiple cells.

[0054] The implementation of process 40 is not limited to the above description. The following examples may be applied to implement process 40.

[0055] In one example, multiple cells include a serving cell. In another example, multiple cells include at least one adjacent cell to the serving cell.

[0056] In one example, the WUS configuration set is transmitted via SIB. In one example, the WUS configuration set further includes multiple indications corresponding to multiple WUS configurations (for example, each of them). In one example, each of the multiple indications indicates whether the corresponding WUS configuration is supported by a connected mode communication device.

[0057] In one example, a serving cell sends a cell list to a communication device. In another example, the cell list indicates which WUS configurations in the WUS configuration set are supported by the communication device in connected mode.

[0058] In one example, a WUS configuration set further includes multiple thresholds corresponding to multiple WUS configurations (for example, each of them). In one example, each of the multiple thresholds indicates the maximum number of retries for a connected mode communication device to perform the OD-SIB1 procedure according to the corresponding WUS configuration.

[0059] An example of process 30 may be applied to process 40, which will not be described herein for the sake of brevity.

[0060] Figure 5 is a flowchart of process 50 according to an example of the present disclosure. Process 50 may be used in an NES cell (or NES BS) (for example, the NES cell of network 12 in Figure 1, the communication device 20 in Figure 2, or the target cell of process 30) to handle a re-establishment procedure. Process 50 may be compiled into program code 214, which includes the following steps:

[0061] Step 500: Start.

[0062] Step 502: When at least one OD-SIB1 procedure trigger condition is met, perform an OD-SIB1 procedure with the communication device according to the stored WUS configuration.

[0063] Step 504: Depending on whether the NES cell is a cell on which the communication device can camp on, the NES cell receives a re-establishment request message from the communication device.

[0064] Step 506: Finish.

[0065] According to process 50, the NES cell performs an OD-SIB1 procedure with a communication device (e.g., the communication device of process 30) according to a stored WUS configuration, depending on whether at least one OD-SIB1 procedure trigger condition (e.g., all OD-SIB1 procedure trigger conditions) is met.

[0066] In one example, the cell on which a communication device can camp on is the highest-ranked cell based on measurements. In another example, the stored WUS configuration is included in the WUS configuration set. In yet another example, the WUS configuration set is sent by the serving cell device to the communication device and stored in the communication device.

[0067] In one example, at least one OD-SIB1 procedure trigger condition includes at least one of the following conditions: namely, the NES cell does not provide SIB1 (e.g., periodically), and the stored WUS configuration is valid. In one example, SIB1 includes at least one of the following information: namely, PLMN information, other SIB availability and scheduling, and access control information. In one example, PLMN information is used to determine whether the NES cell is a cell on which communication devices can camp on. In one example, the NES cell provides OD-SIB1 on demand (i.e., does not provide OD-SIB1 periodically).

[0068] In one example, the stored WUS configuration is valid (or determined to be valid) depending on whether the current wireless frame's SFN is within a specific period (e.g., WUS_ValidPeriod). In another example, the stored WUS configuration is invalid (or determined to be invalid) at the end of a specific period. In yet another example, the stored WUS configuration is invalid (or determined to be invalid) depending on whether the current wireless frame's SFN is outside a specific period. In yet another example, the stored WUS configuration is invalid (or determined to be invalid) depending on whether the communication device initiates a re-establishment procedure.

[0069] In one example, the end of a particular period lies at the boundary of a correction period in which the communication device receives a configured SI change indication from the serving cell of the communication device. That is, the particular period ends at the boundary of the correction period in accordance with the configured received SI change indication. In another example, the end of a particular period lies at the boundary of the next correction period in which the communication device receives an SI change indication that is not configured from the serving cell. That is, the particular period ends at the boundary of the next correction period in accordance with the fact that the received SI change indication is not configured.

[0070] In one example, the OD-SIB1 procedure includes at least one of the following steps: receiving an OD-SIB1 request (e.g., a preamble) from a communication device, and sending an OD-SIB1 request ACK (e.g., a RAR) to the communication device in response to the OD-SIB1 request. In one example, the NES cell sends a re-establishment message to the communication device in response to a re-establishment request message.

[0071] Examples of processes 30-40 may be applied to process 50 and are not described herein for the sake of brevity.

[0072] Figure 6 is a sequence diagram of process 60 according to an example of the present disclosure. Figure 6 includes a communication device CM, a serving cell SC of the communication device CM, and a target cell TC of the communication device CM. The communication device CM is in idle or inactive mode. In step 600, the serving cell SC transmits its WUS configuration set to the communication device CM. In step 602, the communication device CM selects the target cell TC, which is the highest-ranked cell based on measurements. In step 604, the communication device CM triggers an OD-SIB1 procedure according to a stored WUS configuration when at least one OD-SIB1 procedure trigger condition is met. The stored WUS configuration is contained in a WUS configuration set and corresponds to the target cell TC. The at least one OD-SIB1 procedure trigger condition includes at least one of the following: the target cell TC does not provide an SIB1, the target cell TC is an NES cell, and the stored WUS configuration is valid. In step 606, the communication device CM sends an OD-SIB1 request to the target cell TC. In step 608, the communication device CM starts a monitoring window and monitors the OD-SIB1 request ACK during the monitoring window. In step 610, the target cell TC sends an OD-SIB1 request ACK to the communication device CM. In step 612, the communication device CM stops the monitoring window. In step 614, the target cell TC sends an OD-SIB1 to the communication device CM. In step 616, the communication device CM determines, according to the OD-SIB1, whether the target cell TC is a cell that the communication device CM can camp on to. In step 618, if the target cell TC is a cell that the communication device CM can camp on to, the communication device CM sends a re-establishment request message to the target cell TC and camps on to the target cell TC. In step 620, after the communication device CM has camped on to the target cell TC, the target cell TC sends the WUS configuration set of the target cell TC to the communication device CM.

[0073] Figure 7 is a sequence diagram of process 70 according to an example of the present disclosure. Figure 7 includes a communication device CM, a serving cell SC of the communication device CM, and a target cell TC of the communication device CM. The communication device CM is in connection mode. In step 700, the serving cell SC transmits its WUS configuration set to the communication device CM. In step 702, the communication device CM detects a problem with the radio link and starts a first timer. In step 704, the communication device CM declares an RLF in response to the first timer expiring. In step 706, the communication device CM initiates a re-establishment procedure. In step 708, the communication device CM selects the target cell TC according to the cell selection procedure. In step 710, the communication device CM triggers an OD-SIB1 procedure according to a stored WUS configuration when at least one OD-SIB1 procedure trigger condition is met. The stored WUS configuration is included in the WUS configuration set and corresponds to the target cell TC. At least one OD-SIB1 procedure trigger condition includes at least one of the following: the target cell TC does not provide SIB1, the target cell TC is an NES cell, and the stored WUS configuration is valid.

[0074] In step 712, the communication device CM sends an OD-SIB1 request to the target cell TC. In step 714, the communication device CM starts a monitoring window and monitors for OD-SIB1 request ACKs within the monitoring window. In step 716, the target cell TC sends an OD-SIB1 request ACK to the communication device CM within the monitoring window. In step 718, the communication device CM stops the monitoring window. In step 720, the target cell TC sends an OD-SIB1 to the communication device CM. In step 722, the communication device CM determines, according to the OD-SIB1, whether the target cell TC is a cell that the communication device CM can camp on to. In step 724, depending on whether the target cell TC is a cell that the communication device CM can camp on to, the communication device CM sends a re-establishment request message to the target cell TC. In step 726, the target cell TC sends a re-establishment message to the communication device CM in response to the re-establishment request message. In step 728, the communication device CM camps on to the target cell TC in accordance with the re-establishment message.

[0075] Figure 8 is a flowchart of process 80 according to an example of the present disclosure. Process 80 may be used in a communication device (for example, communication device 14 in Figure 1, communication device 20 in Figure 2, or the communication device of process 30) to handle a re-establishment procedure. Process 80 may be compiled into program code 214, which includes the following steps:

[0076] Step 800: Start.

[0077] Step 802: Start the re-establishment procedure.

[0078] Step 804: Release the WUS configuration set received from the serving cell.

[0079] Step 806: Follow the cell selection procedure to select the target cell.

[0080] Step 808: Does the target cell provide an SIB? If so, perform step 810. Otherwise, perform step 806.

[0081] Step 810: Is the target cell a cell on which a communication device can camp on? If so, perform step 812. Otherwise, perform step 806.

[0082] Step 812: Send a re-establishment request message to the target cell.

[0083] Step 814: Finish.

[0084] Figure 9 is a flowchart of process 90 according to an example of the present disclosure. Process 90 may be used in a communication device (for example, communication device 14 in Figure 1, communication device 20 in Figure 2, or the communication device of process 30) to handle a re-establishment procedure. Process 90 may be compiled into program code 214, which includes the following steps:

[0085] Step 900: Start.

[0086] Step 902: Receive a WUS configuration set from the serving cell, which includes multiple WUS configurations and multiple indications corresponding to the multiple WUS configurations.

[0087] Step 904: Initiate the re-establishment procedure.

[0088] Step 906: Select the target cell in the cell selection procedure according to the multiple indications.

[0089] Step 908: Trigger an OD-SIB1 procedure on the target cell according to the stored WUS configuration, depending on whether at least one OD-SIB1 procedure trigger condition is met.

[0090] Step 910: Determine whether the target cell is a cell on which a communication device can camp on, according to the SIB1 from the target cell.

[0091] Step 912: Depending on whether the target cell is a cell on which a communication device can camp on, send a re-establishment request message to the target cell.

[0092] Step 914: Finish.

[0093] In step 902, each of the multiple indications indicates whether the corresponding WUS configuration is supported by the connected mode communication device. In step 904, the communication device does not select a cell that does not support the OD-SIB1 procedure. In step 906, at least one OD-SIB1 procedure trigger condition includes at least one of the following conditions: the target cell does not provide SIB1, the target cell is an NES cell, and the target cell supports the OD-SIB1 procedure.

[0094] Detailed descriptions and variations of processes 80-90 can be left to the example of process 30 and are not described herein.

[0095] Figure 10 is a sequence diagram of process 100 according to an example of the present disclosure. Figure 10 includes a communication device CM, a serving cell SC of the communication device CM, and a target cell TC of the communication device CM. In step 1000, the serving cell SC sends its WUS configuration set to the communication device CM. In step 1002, the communication device CM selects the target cell TC according to the cell selection procedure. In step 1004, the communication device CM triggers the OD-SIB1 procedure according to the stored WUS configuration when at least one OD-SIB1 procedure trigger condition is met. The stored WUS configuration is contained in the WUS configuration set and corresponds to the target cell TC. The at least one OD-SIB1 procedure trigger condition includes at least one of the following: the target cell TC does not provide an SIB1, and the target cell TC is an NES cell. In step 1006, the communication device CM sends an OD-SIB1 request to the target cell TC. In step 1008, the communication device CM starts a monitoring window and monitors for OD-SIB1 request ACKs during the monitoring window. In step 1010, if the communication device CM does not receive an OD-SIB1 request ACK during the monitoring window, the communication device CM releases the stored WUS configuration and determines that the target cell TC is not a cell on which the communication device CM can camp on.

[0096] Figure 11 is a schematic diagram of a specific period SP for verifying whether a stored WUS configuration is valid, according to an example of the present disclosure. Figure 11 has a time-domain axis T, on which there are two correction periods MP1 and MP2 and three boundary MPB1 to MPB3 of the correction periods. Boundary MPB1 is the beginning of correction period MP1. Boundary MPB2 is the end of correction period MP1 and the beginning of correction period MP2. Boundary MPB3 is the end of correction period MP2. The arrow in correction period MP1 represents the moment when the communication device receives an SI change indication from the serving cell. This moment is the beginning of a specific period SP. Since no SI change indication is set, the communication device ends the specific period SP at boundary MPB3. Therefore, the communication device determines that the stored WUS configuration is valid, depending on whether the SFN of the current radio frame is within the specific period SP. At the end of the specific period, the communication device determines that the stored WUS configuration is invalid.

[0097] Figure 12 is a schematic diagram of a specific period SP for verifying whether a stored WUS configuration is valid, according to an example of the present disclosure. Figure 12 has a time-domain axis T, on which there are two correction periods MP1-MP2 and three boundary MPB1-MPB3 of the correction periods. Boundary MPB1 is the beginning of correction period MP1. Boundary MPB2 is the end of correction period MP1 and the beginning of correction period MP2. Boundary MPB3 is the end of correction period MP2. The arrow in correction period MP1 represents the moment when the communication device receives an SI change indication from the serving cell. This moment is the beginning of a specific period SP. Since the SI change indication is set, the communication device ends the specific period SP at boundary MPB2. Therefore, the communication device determines that the stored WUS configuration is valid, depending on whether the SFN of the current radio frame is within the specific period SP. At the end of the specific period, the communication device determines that the stored WUS configuration is invalid.

[0098] The terms “first,” “second,” and “third” above are used to distinguish related discourses and do not limit the order of related discourses. The action of “determine” above may be replaced by the actions of “compute,” “calculate,” “obtain,” “generate,” “output,” “use,” “choose / select,” “determine,” or “is configured to.” The phrase “according to” above may be replaced by “in response to.” The term “via” above may be replaced by “on,” “in,” or “at.” The terms “when,” “if,” and “since” above may be replaced by “in response to.” The term “WUS configuration” above may be replaced by the term “random access (RA) procedure configuration.”

[0099] Those skilled in the art should be able to easily combine, modify, and / or alter the above description and examples. Processes comprising the above description, steps, and / or suggested steps may be implemented by means that may be hardware, software, firmware (known as a combination of a hardware device and computer instructions and data existing as read-only software on the hardware device), electronic systems, or combinations thereof. An example of such means may be a communication device.

[0100] Examples of hardware may include analog circuits, digital circuits, and / or mixed circuits. For example, hardware may include ASICs, field-programmable gate arrays (FPGAs), programmable logic devices, coupled hardware components, or combinations thereof. In other examples, hardware may include general-purpose processors, microprocessors, controllers, digital signal processors (DSPs), or combinations thereof.

[0101] Examples of software may include a set of code, instructions, and / or functions held (e.g., stored) in a storage unit, such as a computer-readable medium. The computer-readable medium may include a SIM, ROM, flash memory, RAM, CD-ROM / DVD-ROM / BD-ROM, magnetic tape, hard disk, optical data storage device, non-volatile storage unit, or a combination thereof. The computer-readable medium (e.g., storage unit) may be internally coupled (e.g., integrated) or externally coupled (e.g., isolated) to at least one processor. At least one processor, which may include one or more modules, may execute (e.g., be configured to execute) the software in the computer-readable medium. The set of code, instructions, and / or functions may cause at least one processor, module, hardware, and / or electronic system to perform the relevant steps.

[0102] Examples of electronic systems may include system-on-a-chip (SoC), system-in-package (SiP), computer-on-module (CoM), computer program products, devices, mobile phones, laptops, tablet computers, e-books, or portable computer systems, and communication devices20.

[0103] In summary, embodiments of the present disclosure provide a method and a communication device for handling a re-establishment procedure. The communication device verifies whether a stored WUS configuration corresponding to a target cell is valid. If the stored WUS configuration is valid, the communication device performs the OD-SIB1 procedure according to the stored WUS configuration. If the stored WUS configuration is invalid, the communication device re-selects a different target cell. Thus, the problem of handling a re-establishment procedure can be solved.

[0104] Those skilled in the art will readily realize that numerous modifications and alterations of the devices and methods may be made while maintaining the teachings of the present invention. Accordingly, the foregoing disclosure should be construed as being limited only by the boundaries and scope of the appended claims. [Explanation of symbols]

[0105] 10 Wireless communication systems 12 Networks 14 Communication devices 20 Communication devices 200 At least one processing circuit 210 At least one storage device 214 Program Code 220 At least one communication interface device 30 processes 40 processes 50 processes 60 processes 70 processes 80 processes 90 processes 100 processes

Claims

1. A method for a communication device to process a re-establishment procedure, The steps include: initiating the aforementioned re-establishment procedure, The steps involve selecting the target cell according to the cell selection procedure, The steps include triggering an OD-SIB1 procedure on the target cell according to a stored wake-up signal (WUS) configuration when at least one on-demand system information block 1 (OD-SIB1) procedure trigger condition is met, The steps include determining whether the target cell is a cell on which the communication device can camp on, according to the SIB1 from the target cell, Depending on whether the target cell is the cell on which the communication device can camp on, the step is to send a re-establishment request message to the target cell. Methods that include...

2. The above-mentioned at least one OD-SIB1 procedure trigger condition is the following condition, namely: The target cell does not provide the SIB1. The target cell is a network energy saving (NES) cell, and The stored WUS configuration is valid. The method according to claim 1, comprising at least one of the following.

3. The method according to claim 1, further comprising the step of verifying whether the stored WUS configuration is valid.

4. The step of verifying whether the stored WUS configuration is valid is: The stored WUS configuration is determined to be valid depending on whether the system frame number (SFN) of the current wireless frame falls within a specific period. At the end of the aforementioned specific period, it is determined that the stored WUS configuration is invalid. The method according to claim 3, comprising at least one of the following.

5. The method according to claim 4, further comprising the step of determining the end of the particular period.

6. The step of determining the end of the aforementioned specific period is: The communication device's serving cell receives a system information (SI) change indication during the correction period. The termination of the aforementioned specific period at the boundary of the aforementioned modification period. The method according to claim 5, including the method described in claim 5.

7. The OD-SIB1 procedure described above is Sending an OD-SIB1 request to the aforementioned target cell, Starting the monitoring window, In the aforementioned monitoring window, the OD-SIB1 request acknowledgment (ACK) is monitored, The monitoring window is stopped in response to the receipt of the OD-SIB1 request ACK from the target cell. The method according to claim 1, comprising at least one of the following.

8. The step of monitoring the OD-SIB1 request ACK in the aforementioned monitoring window is: The method according to claim 7, comprising determining the stored WUS configuration in accordance with the expiration of the monitoring window.

9. The step of monitoring the OD-SIB1 request ACK in the aforementioned monitoring window is: In response to the expiration of the aforementioned monitoring window, the OD-SIB1 request is resent to the target cell. In response to the retransmission of the OD-SIB1 request to the target cell, the value of the counter is incremented by 1. In accordance with the fact that the value of the counter is greater than the threshold, it is determined that the target cell is a prohibited cell. The method according to claim 7, comprising at least one of the following.

10. A serving cell method for handling a re-establishment procedure, The process includes the step of sending a Wake-Up Signal (WUS) configuration set to a communication device, A method wherein the WUS configuration set includes multiple identities (IDs) of multiple cells, multiple frequencies corresponding to the multiple cells, and multiple WUS configurations corresponding to the multiple cells.

11. The method according to claim 10, wherein the WUS configuration set further comprises a plurality of indications corresponding to the plurality of WUS configurations.

12. The method according to claim 11, wherein each of the plurality of indications indicates whether the corresponding WUS configuration is supported by the communication device in connection mode.

13. The further step includes sending a cell list to the aforementioned communication device, The method according to claim 10, wherein the cell list indicates which WUS configurations of the WUS configuration set are supported by the communication device in connection mode.

14. The method according to claim 10, wherein the WUS configuration set further includes a plurality of thresholds corresponding to the plurality of WUS configurations.

15. The method according to claim 14, wherein each of the plurality of thresholds indicates the maximum number of retries for the communication device in connection mode to perform the on-demand system information block 1 (OD-SIB1) procedure according to the corresponding WUS configuration.

16. A method for handling a re-establishment procedure for a network energy saving (NES) cell, The steps include: performing an OD-SIB1 procedure with a communication device according to a stored wake-up signal (WUS) configuration in response to the fulfillment of at least one On-Demand System Information Block 1 (OD-SIB1) procedure trigger condition; Depending on whether the NES cell is a cell on which the communication device can camp on, the step of receiving a re-establishment request message from the communication device: Methods that include...

17. The above-mentioned at least one OD-SIB1 procedure trigger condition is the following condition, namely: The NES cell does not provide SIB1, and The stored WUS configuration is valid. The method according to claim 16, comprising at least one of the following.

18. The method according to claim 16, wherein the stored WUS configuration is valid depending on whether the system frame number (SFN) of the current wireless frame is within a specific period.

19. The method according to claim 18, wherein the stored WUS configuration is invalid at the end of the specified period.

20. The method according to claim 19, wherein the end of the specific period falls on the boundary of a correction period in which the communication device receives a system information (SI) change indication set from the serving cell of the communication device.

21. The OD-SIB1 procedure described above is Receiving an OD-SIB1 request from the aforementioned communication device, In response to the aforementioned OD-SIB1 request, an OD-SIB1 request acknowledgment (ACK) is sent to the communication device. The method according to claim 16, comprising at least one of the following.

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