Method and communication device for handling re-establishment procedures

Abstract

The present invention provides a method and a communication device for handling re-establishment procedures. [Solution] A method for processing a re-establishment procedure of a communication device includes the steps of: initiating a re-establishment procedure; selecting a target cell according to a cell selection procedure; and, after selecting a target cell according to the cell selection procedure, determining whether the target cell is a cell on which the communication device can camp on, according to a stored SIB1, in the event that the target cell does not provide a System Information Block 1 (SIB1).

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 747,900, filed on January 22, 2025. The content of the application is incorporated herein by reference.

[0002] This 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 3rd Generation Partnership Project (3GPP (registered trademark, the same hereinafter)) Rel - 8 standard and / or 3GPP Rel - 9 standard has been developed by 3GPP as a successor to the Universal Mobile Telecommunications System (UMTS) to further enhance the performance of UMTS in order to meet the increasing 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 at faster switching between power states, improving performance at the edge of the coverage of evolved Node - B (eNB), improving 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) supporting 3GPP Rel-15 to 3GPP Rel-19 standards are being developed. 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. Therefore, how to handle the re-establishment procedure is a critical issue that needs to be addressed. [Overview of the project] [Means for solving the problem]

[0007] Therefore, in order to solve the above-mentioned problems, this disclosure provides a method and a communication device for handling a re-establishment procedure.

[0008] A method for processing a re-establishment procedure for a communication device includes the steps of: initiating a re-establishment procedure; selecting a target cell according to a cell selection procedure; and, after selecting a target cell according to the cell selection procedure, determining whether the target cell is a cell on which the communication device can camp on, in accordance with the stored SIB1, depending on whether the target cell does not provide a System Information Block 1 (SIB1).

[0009] A method for handling the re-establishment procedure of a serving cell includes the step of sending a Wake-Up Signal (WUS) configuration set to a communication device, the WUS configuration set including multiple identities (IDs) of multiple cells, multiple frequencies corresponding to multiple cells, and multiple WUS configurations corresponding to multiple cells, the multiple cells including a serving cell and at least one adjacent cell of the serving cell.

[0010] A method for handling the re-establishment procedure of a network energy saving (NES) cell includes the step of receiving a re-establishment request message from a communication device in response to the communication device selecting an NES cell according to a cell selection procedure and determining, according to a stored system information block 1 (SIB1), that the NES cell is a cell that the communication device can camp on.

[0011] 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]

[0012] [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 diagram shows a schematic representation of a specific period for verifying whether a stored SIB1 is valid, as illustrated by the examples in this disclosure. [Figure 9] This diagram shows a schematic representation of a specific period for verifying whether a stored SIB1 is valid, as illustrated by the examples in this disclosure. [Modes for carrying out the invention]

[0013] 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).

[0014] 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.

[0015] 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.

[0016] Furthermore, network 12 may include at least one of UTRAN / E-UTRAN / NG-RAN and a core network, 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 wireless network controller (RNC), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), and 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 decisions corresponding to the information may be made in UTRAN / E-UTRAN / NG-RAN. In another example, UTRAN / E-UTRAN / NG-RAN may forward the information to the core network, and decisions corresponding to the information may be made in the core network after the core network has processed the information. In one example, information may be processed by both UTRAN / E-UTRAN / NG-RAN and the core network, and decisions are made after coordination and / or cooperation are performed by UTRAN / E-UTRAN / NG-RAN and the core network.

[0017] The communication device 14 may be a user device (UE), a very small aperture terminal (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.

[0018] 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.

[0019] 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 can be accessed 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 identification module (SIM), a read only memory (ROM), a flash memory, a random access memory (RAM), a compact disk read only memory (CD-ROM), a digital versatile disk ROM (DVD-ROM), a Blu-ray disk ROM (BD-ROM), a magnetic tape, a hard disk, an optical data storage device, a non-volatile memory device, a non-transitory computer-readable medium (e.g., a tangible medium), etc. 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.

[0020] 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.

[0021] Step 300: Start.

[0022] Step 302: Start the re-establishment procedure.

[0023] Step 304: Follow the cell selection procedure to select the target cell.

[0024] Step 306: After selecting a target cell according to the cell selection procedure, if the target cell does not provide System Information Block 1 (SIB1), it is determined, according to the stored SIB1, whether the target cell is a cell on which a communication device can camp on.

[0025] Step 308: Finish.

[0026] According to process 30, the communication device initiates a re-establishment procedure. The communication device then selects a target cell according to the cell selection procedure. After selecting a target cell according to the cell selection procedure, the communication device determines (e.g., verifies) whether the target cell is a cell that the communication device can camp on to, according to the stored SIB1 (e.g., by stored SIB1), depending on whether the target cell does not provide an SIB1. That is, if the target cell does not provide an SIB1, the communication device applies the stored SIB1 to perform the re-establishment procedure. The communication device does not need to perform an on-demand SIB1 (OD-SIB1) procedure to request an SIB1 from the target cell. Thus, delays caused by performing the OD-SIB1 procedure can be overcome.

[0027] The implementation of process 30 is not limited to the above description. The following examples may be applied to implement process 30.

[0028] In one example, the cell on which a communication device can camp on is the highest-ranked cell based on measurements. In one example, the stored 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 a communication device can camp on. In one example, the NES cell provides on-demand SIB1 (OD-SIB1) on demand (i.e., does not provide OD-SIB1 regularly).

[0029] In one example, the step of selecting a target cell according to a cell selection procedure includes at least one of the following: configuring at least one candidate target cell using at least one candidate target cell configuration; performing the cell selection procedure to find a selected cell that satisfies the cell selection criteria; and determining that the selected cell is the target cell, depending on whether the selected cell is one of at least one candidate target cell. In one example, the communication device configures at least one candidate target cell using at least one candidate target cell configuration before performing (or starting) a re-establishment procedure. In one example, the stored SIB1 is stored in at least one candidate target cell configuration.

[0030] In one example, the communication device determines that the stored SIB1 is (for example, always) valid. In another example, the communication device initiates a re-establishment procedure in response to a normal handover failure. In yet another example, the communication device initiates a re-establishment procedure in response to a conditional handover failure. In yet another example, the communication device initiates a re-establishment procedure in response to an LTM or C-LTM failure. In yet another example, the communication device receives the stored SIB1 in a handover command message from the target cell. In yet another example, the communication device receives the stored SIB1 in a Radio Resource Control (RRC) message (for example, condRRCReconfig or LTM-Candidate) from the target cell (or at least one candidate target cell).

[0031] In one example, the communication device determines that a stored SIB1 is valid depending on whether the system frame number (SFN) of the current radio frame is within a first specific period (e.g., SIB1_ValidPeriod). In another example, the communication device determines that a stored SIB1 is invalid depending on whether the SFN of the current radio frame is outside of the first specific period. In yet another example, the communication device determines that a stored SIB1 is invalid at the end of the first specific period.

[0032] In one example, the communication device determines a first specific period (for example, a range of a first specific period). In one example, the step of determining the first specific period includes at least one of the following steps: determining whether the communication device is configured with a first system information (SI) change indicator before initiating a re-establishment procedure; monitoring the first SI change indicator for a third timer (for example, T310), depending on the communication device that does not have a first SI change indicator; monitoring the first SI change indicator at the beginning of each default paging cycle, depending on the communication device that does not have a first SI change indicator; starting the first specific period when monitoring the first SI change indicator begins; ending the first specific period at the boundary of a first correction period, depending on receiving the first SI change indicator from the serving cell of the communication device; and ending the first specific period at the boundary of the next first correction period, depending on not receiving the first SI change indicator. In other words, the communication device determines the end of a first specific period based on whether or not it receives a first SI change indicator.

[0033] In one example, a communication device receives an SI change indicator from a serving cell during a first correction period. In one example, the boundary of the first correction period is the end of the first correction period. In one example, the boundary of the next first correction period is the end of the next first correction period. In one example, the next first correction period is the period following the first correction period in which the communication device receives an SI change indicator from the serving cell. In one example, the first SI change indicator is broadcast (for example, via a short message).

[0034] In one example, the communication device does not trigger the OD-SIB1 procedure depending on whether the stored SIB1 is valid. In another example, the communication device triggers the OD-SIB1 procedure on the target cell according to the stored wake-up signal (WUS) configuration depending on whether the stored SIB1 is invalid.

[0035] 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 SFN of the current radio frame is within a second specific period (e.g., WUS_ValidPeriod); and determining that the stored WUS configuration is invalid at the end of the second 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 second 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 the start of a re-establishment procedure.

[0036] In one example, the communication device determines the end of a second specific period. In one example, the step of determining the end of a second specific period includes receiving a second SI change indicator from the serving cell during the second modification period and ending the second specific period at the boundary of the second modification period. That is, the communication device determines the end of a second specific period by whether it receives a second SI change indicator during the second modification period. In one example, the second SI change indicator is broadcast (e.g., via short message). In one example, the boundary of the second modification period is the end of the second modification period. In one example, the boundary of the second modification period is defined by at least one SFN value. In one example, the SFN value is divisible by the number of radio frames (RFs) that make up the second 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 terminates a second specific period at the boundary of the next second modification period in response to a second SI change indication that is not set. In one example, the boundary of the next second modification period is the end of the next second modification period. In one example, the communication device terminates a second specific period at the boundary of the second modification period in response to a second SI change indication that is set.

[0037] In one example, the communication device checks whether a second SI change indicator is set to determine the range of a second specific period. In another example, the communication device monitors the second SI change indicator when a radio link failure (RLF) condition occurs, while a third timer (e.g., T310) is running. In yet another example, the communication device monitors the second SI change indicator at the beginning of each correction period.

[0038] In one example, the first SI change marking and the second SI change marking may be the same or different. In one example, the first specific period and the second specific period may be the same or different. In one example, the first amendment period and the second amendment period may be the same or different. In one example, the following first amendment period and the following second amendment period may be the same or different.

[0039] In one example, the OD-SIB1 procedure includes at least one of the following steps: starting a watch window; watching (e.g., receiving) an OD-SIB1 request acknowledgment (ACK) (e.g., a random access response (RAR) or a media access control (MAC) control element (CE)) during 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.

[0040] 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.

[0041] 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.

[0042] In one example, a communication device enters idle mode from connected mode in response to a failed re-establishment procedure. In another example, a communication device recovers the connection (for example, from a serving cell to a target cell) in response to a successful re-establishment procedure.

[0043] 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.

[0044] In one example, a communication device sends a re-establishment request message (e.g., Msg3) to a target cell, depending on whether the target cell is a cell on which the communication device can camp on. In another example, after the communication device sends the re-establishment request message to the target cell, it receives a re-establishment message (e.g., Msg4) from the target cell. In yet 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).

[0045] 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. In one example, multiple cells include at least one candidate target cell. In one example, multiple WUS configurations include at least one candidate WUS configuration.

[0046] In one example, a WUS configuration set further includes multiple indicators corresponding to multiple WUS configurations (for example, each of them). In one example, each of the indicators 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.

[0047] In one example, the communication device determines that a target cell is not a cell that the communication device can camp on to, based on the fact that 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, based on the fact that the target cell does not support the OD-SIB1 procedure.

[0048] 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 a cell that the communication device can camp on to, depending on whether the number of retries does not exceed the corresponding threshold among the multiple thresholds. In one example, the communication device determines (e.g., release) the WUS configuration set depending on whether the number of retries exceeds the corresponding threshold among the multiple thresholds.

[0049] 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.

[0050] 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:

[0051] Step 400: Start.

[0052] 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.

[0053] Step 404: Finish.

[0054] 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.

[0055] The implementation of process 40 is not limited to the above description. The following examples may be applied to implement process 40.

[0056] In one example, multiple cells include a serving cell. In another example, multiple cells include at least one adjacent cell to the serving cell.

[0057] In one example, the WUS configuration set is transmitted via SIB. In one example, the WUS configuration set further includes multiple indicators corresponding to multiple WUS configurations (for example, each of them). In one example, each of the indicators indicates whether the corresponding WUS configuration is supported by a connected mode communication device.

[0058] 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.

[0059] In one example, a WUS configuration set further includes multiple thresholds, each corresponding to a multiple WUS configuration. 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.

[0060] An example of process 30 may be applied to process 40, which will not be described herein for the sake of brevity.

[0061] 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:

[0062] Step 500: Start.

[0063] Step 502: The communication device selects an NES cell according to the cell selection procedure and, in accordance with the stored SIB1, determines that the NES cell is a cell that the communication device can camp on to, and receives a re-establishment request message from the communication device.

[0064] Step 504: Finish.

[0065] According to process 50, the NES cell receives a re-establishment request message (e.g., Msg3) from the communication device in response to the communication device selecting the NES cell according to the cell selection procedure and determining (e.g., verifying) that the NES cell is a cell that the communication device can camp on to (e.g., by the stored SIB1). That is, since the communication device applies the stored SIB1 to perform the re-establishment procedure, the NES cell does not need to provide the SIB1 to the communication device. Therefore, the OD-SIB1 procedure is not performed, and the delay caused by the performance of the OD-SIB1 procedure can be overcome.

[0066] In one example, the cell on which a communication device can camp on is the highest-ranked cell based on measurements. In one example, a stored SIB1 is stored in at least one candidate target cell configuration. In one example, the stored 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, the PLMN information is used to determine whether the target cell is a cell on which a communication device can camp on.

[0067] In one example, the stored SIB1 is valid (for example, always). In another example, the stored SIB1 is valid (or determined to be valid) depending on whether the SFN of the current radio frame is within a specific period (for example, the first specific period in the example of process 30). In another example, the stored SIB1 is invalid (or determined to be invalid) depending on whether the SFN of the current radio frame is outside a specific period. In yet another example, the stored SIB1 is invalid at the end of a specific period.

[0068] In one example, the NES cell sends a re-establishment message (e.g., Msg4) to the communication device in response to a re-establishment request message.

[0069] Examples of processes 30-40 may be applied to process 50 and are not described herein for the sake of brevity.

[0070] 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 sends at least one candidate target cell configuration of at least one candidate target cell to the communication device CM. The at least one candidate target cell configuration includes a stored SIB1. In step 602, the communication device CM configures at least one candidate target cell. In step 604, the communication device CM selects a target cell TC according to the cell selection procedure. The target cell TC is one of the at least one candidate target cell. In step 606, the communication device CM determines, according to the stored SIB1, whether the target cell TC is a cell that the communication device CM can camp on to. In step 608, 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.

[0071] 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 to the communication device CM at least one candidate target cell configuration of at least one candidate target cell. The at least one candidate target cell configuration includes a stored SIB1. In step 702, the communication device CM configures at least one candidate target cell. In step 704, the communication device CM discovers a problem with the radio link and starts a first timer. In step 706, the communication device CM declares an RLF in response to the first timer expiring. In step 708, the communication device CM initiates a re-establishment procedure. In step 710, the communication device CM selects a target cell TC according to a cell selection procedure. The target cell TC is one of the at least one candidate target cell. In step 712, the communication device CM determines, according to OD-SIB1, whether the target cell TC is a cell on which the communication device CM can camp on. In step 714, depending on whether the target cell TC is a cell on which the communication device CM can camp on, the communication device CM sends a re-establishment request message to the target cell TC. In step 716, the target cell TC sends a re-establishment message to the communication device CM in response to the re-establishment request message. In step 718, the communication device CM camps on to the target cell TC in accordance with the re-establishment message.

[0072] Figure 8 is a schematic diagram of a specific period SP for verifying whether a stored SIB1 is valid, according to an example of the present disclosure. Figure 8 has a time-domain axis T, on which there are two correction periods MP1-MP2 and three correction period boundaries MPB1-MPB3. 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 begins to monitor for SI change indications from the serving cell. That moment is the beginning of a specific period SP. The communication device does not receive any SI change indications and therefore terminates the specific period SP at boundary MPB3. Thus, the communication device determines that the stored SIB1 is valid, depending on whether the SFN of the current radio frame is within the specific period SP. The communication device determines that the stored SIB1 is invalid at the end of the specific period SP.

[0073] Figure 9 is a schematic diagram of a specific period SP for verifying whether a stored SIB1 is valid, according to an example of the present disclosure. Figure 9 has a time-domain axis T, on which there are two correction periods MP1 and MP2 and three boundaries 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 begins monitoring for an SI change indication from the serving cell. That moment is the beginning of a specific period SP. The communication device receives an SI change indication and therefore ends the specific period SP at boundary MPB2. Thus, the communication device determines that the stored SIB1 is valid, depending on whether the SFN of the current radio frame is within the specific period SP. The communication device determines that the stored SIB1 is invalid at the end of the specific period SP.

[0074] The terms “first,” “second,” and “third” above are used to distinguish related descriptions and do not limit the order of related descriptions. 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.”

[0075] 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.

[0076] 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.

[0077] Examples of software may include a set of code, a set of instructions, and / or a set of 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., a 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, a set of instructions, and / or a set of functions may cause at least one processor, module, hardware, and / or electronic system to perform the relevant steps.

[0078] 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.

[0079] In summary, embodiments of the present disclosure provide a method and a communication device for handling a re-establishment procedure. The communication device does not need to apply a stored SIB1 and execute an OD-SIB1 procedure to request an SIB1 from a target cell in order to perform the re-establishment procedure. Thus, the problem of handling a re-establishment procedure can be solved.

[0080] 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]

[0081] 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

Claims

1. A method for handling the re-establishment procedure of a communication device, The steps include: initiating the aforementioned re-establishment procedure, The steps involve selecting the target cell according to the cell selection procedure, A method comprising the step of selecting a target cell according to the cell selection procedure, and then determining whether the target cell is a cell on which the communication device can camp on, in accordance with the stored SIB1, depending on whether the target cell does not provide a system information block 1 (SIB1).

2. The step of selecting the target cell according to the cell selection procedure is, At least one candidate target cell is configured using at least one candidate target cell configuration. To find selected cells that satisfy the cell selection criteria, perform the cell selection procedure described above. The method according to claim 1, comprising at least one of the following: determining that the selected cell is the target cell, depending on that the selected cell is one of the at least one candidate target cell.

3. The method according to claim 2, wherein the communication device configures the at least one candidate target cell using the at least one candidate target cell configuration before performing the re-establishment procedure.

4. The method according to claim 1, wherein the stored SIB1 is stored in at least one candidate target cell configuration.

5. The method according to claim 1, further comprising the step of determining that the stored SIB1 is valid.

6. The step of determining whether the stored SIB1 is valid in accordance with the fact that the system frame number (SFN) of the current wireless frame is within a specific period, The method according to claim 1, further comprising the step of determining that the stored SIB1 is invalid in accordance with the fact that the SFN of the current wireless frame is outside the specific period.

7. A method for handling the re-establishment procedure of a serving cell, The process includes the step of sending a Wake-Up Signal (WUS) configuration set to a communication device, 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. A method wherein the plurality of cells include the serving cell and at least one adjacent cell of the serving cell.

8. The method according to claim 7, wherein the WUS configuration set further includes a plurality of markings corresponding to the plurality of WUS configurations.

9. The method according to claim 8, wherein each of the plurality of markings indicates whether the corresponding WUS configuration is supported by the communication device in connection mode.

10. The further step includes sending a cell list to the aforementioned communication device, The method according to claim 7, wherein the cell list indicates which WUS configurations of the WUS configuration set are supported by the communication device in connection mode.

11. The method according to claim 7, wherein the WUS configuration set further includes a plurality of thresholds corresponding to the plurality of WUS configurations.

12. The method according to claim 11, 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.

13. A method for processing the re-establishment procedure of a network energy saving (NES) cell, A method comprising the steps of receiving a re-establishment request message from a communication device in response to the communication device selecting the NES cell according to a cell selection procedure and determining, according to a stored system information block 1 (SIB1), that the NES cell is a cell that the communication device can camp on to.

14. The method according to claim 13, wherein the stored SIB1 is stored in at least one candidate target cell configuration.

15. The method according to claim 13, wherein the stored SIB1 is valid.

16. The method according to claim 13, wherein the stored SIB1 is valid depending on whether the system frame number (SFN) of the current wireless frame is within a specific period.

17. The method according to claim 13, wherein the stored SIB1 is invalid in accordance with the fact that the SFN of the current wireless frame is outside a specific period.

Images