Patent Publication Number: US-2023135662-A1

Title: Power saving feature assistance information in 5gs and eps

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. § 119 from U.S. Provisional Application No. 63/274,575, entitled “PEIPS and non-3GPP access and EPS,” filed on Nov. 2, 2021, the subject matter of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate generally to wireless communication systems, and, more particularly, to power efficient paging mechanism with paging early indication or wakeup signal with assistance information for emergency PDU session or PDN connection for emergency bearer service (emergency PDN connection). 
     BACKGROUND 
     Third generation partnership project (3GPP) and 5G New Radio (NR) mobile telecommunication systems provide high data rate, lower latency and improved system performances. In 3GPP NR, 5G terrestrial New Radio (NR) access network (includes a plurality of base stations, e.g., Next Generation Node-Bs (gNBs), communicating with a plurality of mobile stations referred as user equipment (UEs). Orthogonal Frequency Division Multiple Access (OFDMA) has been selected for NR downlink (DL) radio access scheme due to its robustness to multipath fading, higher spectral efficiency, and bandwidth scalability. Multiple access in the downlink is achieved by assigning different sub-bands (i.e., groups of subcarriers, denoted as resource blocks (RBs)) of the system bandwidth to individual users based on their existing channel condition. In LTE and NR networks, Physical Downlink Control Channel (PDCCH) is used for downlink scheduling. Physical Downlink Shared Channel (PDSCH) is used for downlink data. Similarly, Physical Uplink Control Channel (PUCCH) is used for carrying uplink control information. Physical Uplink Shared Channel (PUSCH) is used for uplink data. In addition, physical random-access channel (PRACH) is used for non-contention-based RACH. 
     One important use of broadcast information in any cellular systems is to set up channels for communication between the UE and the gNB. This is generally referred to as paging. Paging is a procedure the wireless network uses to find a UE, before the actual connection establishment. Paging is used to alert the UE of an incoming session (e.g., mobile terminated voice call, or downlink IP packets). In most cases, the paging process happens while UE is in radio resource control (RRC) idle mode or inactive mode. This means that UE has to monitor whether the networking is sending any paging message to it, and it has to spend some energy to run this “monitoring” process. During idle/inactive mode, a UE gets into and stays in sleeping mode defined in discontinuous reception (DRX) cycle. UE periodically wakes up and monitors PDCCH to check for the presence of a paging message. If the PDCCH indicates that a paging message is transmitted in a subframe, then the UE demodulates the paging channel to see if the paging message is directed to it. 
     In NR, paging reception consumes less than 2.5% of the total power. However, due to synchronization signal block (SSB) transmission scheme in NR, LOOP operations (including AGC, FTL, and TTL) and measurements (MEAS) can only be performed in certain occasions. As a result, the gap between the SSBs for LOOP/MEAS and paging occasion (PO) is longer, and UE may enter light sleep mode in the gap. If there is an indication before paging and UE monitors PO only if the indication exists, then UE can save power not only for paging reception, but also for the light sleep between the last SSB and PO gap. 
     In 5G system, paging early indication (PEI) notifies UEs of potentially relevant incoming paging such that these UEs are then able to skip POs in which the UEs are (definitely) not being paged, thus saving power (decoding POs being more power hungry than decoding PEI). To this effect, UE subgrouping is introduced that allows waking up subgroups of UEs for potentially relevant paging. The RAN and UE may use a Paging Early Indication with Paging Subgrouping (PEIPS) to reduce the UE&#39;s power consumption in RRC_IDLE and RRC_INACTIVE over NR. The Paging Subgrouping can be based on either the UE&#39;s temporary ID or a paging subgroup allocated by the AMF. Similar power saving features are also available in 4G EPS via the use of wakeup signals (WUS). 
     When UE has an active emergency PDU session or PDN connection (associated with 3GPP access) established, the UE behavior of applying PEIPS or WUS for power saving needs to be re-defined. 
     SUMMARY 
     A method of applying power-saving feature assistance information for emergency PDU session or PDN connection for emergency bearer service (emergency PDN connection) associated with 3GPP access is provided. In 5GS, when an emergency PDU session (associated with 3GPP access) is successfully established after the UE received the Negotiated PEIPS assistance information IE during the last registration procedure, the UE does not use the PEIPS assistance information until the successful completion of the handover of the emergency PDU session from 3GPP access to non-3GPP access and/or the successful completion of the transfer of the emergency PDU session from N 1  mode to S 1  mode (or 5GS to EPS/ePDG connected to EPC). In EPS, when an emergency PDN connection is successfully established after the UE received the Negotiated WUS assistance information IE during the last registration (Attach/TAU) procedure, the UE does not use the WUS assistance information until the successful completion of the handover of the emergency PDN connection from 3GPP access to non-3GPP access and/or the successful completion of the transfer of the emergency PDN connection from S 1  mode to N 1  mode (or EPC to 5GS). 
     In one embodiment, a UE registers to a 5G system (5GS) over 3GPP access in a wireless communication network, wherein the UE receives power-saving feature assistance information during the registration procedure, wherein the power-saving feature is a Paging Early Indication with Paging Subgrouping (PEIPS). The UE establishes an emergency protocol data unit (PDU) session over the 3GPP access. The UE stops applying the power-saving feature assistance information when the emergency PDU session is established successfully. The UE resumes applying the power-saving feature assistance information upon the emergency PDU session is successfully moved out of the 5GS 3GPP access. 
     In another embodiment, a UE registers to an evolved packet system (EPS) by a user equipment (UE) in a wireless communication network, wherein the UE receives power-saving feature assistance information during the registration(Attach/TAU) procedure, wherein the power-saving feature is a wakeup signal (WUS). The UE establishes an emergency packet data network (PDN) connection. The UE stops applying the power-saving feature assistance information when the emergency PDN connection is established successfully. The UE starts applying the power-saving feature assistance information upon the emergency PDN connection is successfully moved out of the EPS. 
     Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention. 
         FIG.  1    illustrates the concept of paging reception with paging early indication (PEI) in a 5G New Radio (NR) network for power saving and the application of PEI with paging subgrouping (PEIPS) assistance information in accordance with one novel aspect. 
         FIG.  2    is a simplified block diagram of a UE and a base station in accordance with various embodiments of the present invention. 
         FIG.  3    illustrates handover and transfer for a PDU session between 5GS 3GPP/non-3GPP access and EPC 3GPP/non-3GPP access. 
         FIG.  4    illustrates handover and transfer for a PDN connection between EPC 3GPP/non-3GPP access and 5GS 3GPP/non-3GPP access. 
         FIG.  5    illustrates a sequence flow between a UE and 5GS network the reception, suspend, and resume of PEIPS assistance information in one novel aspect. 
         FIG.  6    illustrates a sequence flow between a UE and EPS network the reception, suspend, and resume of WUS assistance information in one novel aspect. 
         FIG.  7    is a flow chart of a method of suspending and resuming PEIPS assistance information in a 5G/NR network in accordance with one novel aspect of the present invention. 
         FIG.  8    is a flow chart of a method of suspending and resuming WUS assistance information in a 4G EPS network in accordance with one novel aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
       FIG.  1    illustrates the concept of paging reception with paging early indication (PEI) in a 5G New Radio (NR) network  100  for power saving and the application of PEI with paging subgrouping (PEIPS) assistance information in accordance with one novel aspect. In 3GPP NR, 5G NR access network, a plurality of base stations, e.g., Next Generation Node-Bs (gNBs), communicating with a plurality of mobile stations referred as user equipment (UEs). Orthogonal Frequency Division Multiple Access (OFDMA) has been selected for NR downlink (DL) radio access scheme due to its robustness to multipath fading, higher spectral efficiency, and bandwidth scalability. In both LTE and NR networks, Physical Downlink Control Channel (PDCCH) is used for downlink scheduling. Physical Downlink Shared Channel (PDSCH) is used for downlink data. Similarly, Physical Uplink Control Channel (PUCCH) is used for carrying uplink control information. Physical Uplink Shared Channel (PUSCH) is used for uplink data. In addition, physical random-access channel (PRACH) is used for non-contention-based RACH. 
     In 5G system, paging early indication (PEI) notifies UEs of potentially relevant incoming paging such that these UEs are then able to skip paging occasions (POs) in which they are (definitely) not being paged, thus saving power (decoding POs being more power hungry than decoding PEI).  FIG.  1    depicts the synchronization signal block (SSB) transmission scheme in NR, where LOOP operations (including AGC, FTL, and TTL) and measurements (MEAS) can only be performed in certain occasions, e.g., during SSB bursts. UE wakes up for SSBs, e.g., every 20 ms (every 2 radio frames). UE may enter light sleep mode in the gap between the SSBs for LOOP/MEAS and PO. When PEI is introduced, UE can skip PO monitoring if PEI indicates negative, e.g., entering deep sleep in the gap between PEI and PO. PEIs are always transmitted and are located near SSB bursts, thus aiming at power saving not only PO monitoring but also light sleep and state transitions when no UE is paged. UE may or may not need extra time for PEI monitoring in addition to SSB. 
     In  FIG.  1   , PEI  112  is located next to the SSB burst  111 . If the PEI indicates that no UEs in the UE group is paged (PEI is negative), then UE enters deep sleep in  113 , e.g., entering deep sleep in the gap between PEI and PO. Further, UE paging subgrouping is introduced that allows waking up subgroups of UEs for potentially relevant paging. The RAN and UE may use a Paging Early Indication with Paging Subgrouping (PEIPS) to reduce the UE&#39;s power consumption in RRC_IDLE and RRC_INACTIVE over NR. The Paging Subgrouping can be based on either the UE&#39;s temporary ID or a paging subgroup allocated by the network. Similar power saving features are also available in 4G EPS via the use of wakeup signals (WUS). 
     In accordance with one novel aspect, a method of applying power-saving feature assistance information is provided. In step  121 , a UE registers to 5GS/EPS and receives power-saving assistance information. In step  122 , the UE establishes an emergency PDU session in 5GS or PDN connection in EPS, over 3GPP access. In step  123 , the UE stops (suspend) using the power-saving assistance information. In step  124 , the UE starts (resume) to use the power-saving assistance information. In 5GS, when an emergency PDU session (associated with 3GPP access) is successfully established after the UE received the Negotiated PEIPS assistance information IE during the last registration procedure, the UE does not use the PEIPS assistance information until the successful completion of the handover of the emergency PDU session from 3GPP access to non-3GPP access and/or the successful completion of the transfer of the emergency PDU session from N 1  mode to S 1  mode (or 5GS to EPC). In EPS, when an emergency PDN connection (associated with 3GPP access) is successfully established after the UE received the Negotiated WUS assistance information IE during the last registration (Attach/TAU) procedure, the UE does not use the WUS assistance information until the successful completion of the handover of the emergency PDN connection to non-3GPP access and/or the successful completion of the transfer of the emergency PDN connection from S 1  mode to N 1  mode (or EPC to 5GS). When UE has emergency session ongoing, the power saving is not important anymore, thus the UE stops using power saving features. 
       FIG.  2    is a simplified block diagram of wireless devices  201  and  211  in accordance with embodiments of the present invention. For wireless device  201  (e.g., a base station), antennae  207  and  208  transmit and receive radio signal. RF transceiver module  206 , coupled with the antennae, receives RF signals from the antennae, converts them to baseband signals and sends them to processor  203 . RF transceiver  206  also converts received baseband signals from the processor, converts them to RF signals, and sends out to antennae  207  and  208 . Processor  203  processes the received baseband signals and invokes different functional modules and circuits to perform features in wireless device  201 . Memory  202  stores program instructions and data  210  to control the operations of device  201 . 
     Similarly, for wireless device  211  (e.g., a user equipment), antennae  217  and  218  transmit and receive RF signals. RF transceiver module  216 , coupled with the antennae, receives RF signals from the antennae, converts them to baseband signals and sends them to processor  213 . The RF transceiver  216  also converts received baseband signals from the processor, converts them to RF signals, and sends out to antennae  217  and  218 . Processor  213  processes the received baseband signals and invokes different functional modules and circuits to perform features in wireless device  211 . Memory  212  stores program instructions and data  220  to control the operations of the wireless device  211 . 
     The wireless devices  201  and  211  also include several functional modules and circuits that can be implemented and configured to perform embodiments of the present invention. In the example of  FIG.  2   , wireless device  201  is a base station that includes an RRC connection handling module  205 , a scheduler  204 , a paging and mobility management module  209 , and a control and configuration circuit  221 . Wireless device  211  is a UE that includes a connection handling module  215 , a measurement and reporting module  214 , a paging and mobility handling module  219 , and a control and configuration circuit  231 . Note that a wireless device may be both a transmitting device and a receiving device. The different functional modules and circuits can be implemented and configured by software, firmware, hardware, and any combination thereof. The function modules and circuits, when executed by the processors  203  and  213  (e.g., via executing program codes  210  and  220 ), allow base station  201  and user equipment  211  to perform embodiments of the present invention. 
     In one example, the base station  201  establishes connection for UE  211  via connection handling circuit  205 , schedules downlink and uplink transmission for UEs via scheduler  204 , performs paging, mobility, and handover management via mobility management module  209 , and provides paging, measurement, and measurement reporting configuration information to UEs via configuration circuit  221 . The UE  211  handles connection via connection handling circuit  215 , performs measurements and reports measurement results via measurement and reporting module  214 , performs paging monitoring and mobility via paging and mobility handling module  219 , and obtains configuration information via control and configuration circuit  231 . In one novel aspect, UE  211  receives power-saving assistance information and monitors PO accordingly. UE  211  stops using the assistance information for emergency connection over 3GPP access, and starts to use the assistance information upon the emergency connection is moved out of 5GS 3GPP access or EPS 3GPP access. 
       FIG.  3    illustrates handover and transfer for a PDU session between 5GS 3GPP/non-3GPP access and EPC 3GPP/non-3GPP access. In 5GS, a PDU session can be associated with 3GPP access ( 301 ) or associated with non-3GPP access ( 302 ). The PDU session is considered to be associated with 3GPP access when it is established over 3GPP access in NR, or in EUTRA connected to 5GS. Depending on different scenarios, the PDU session can be handover or transferred. In  311 , the PDU session is handover to 5GS non-3GPP access (which has no paging procedure). In  312 , the PDU session is transferred to 4G EPS (which implies 3GPP access), e.g., to EUTRA that is connected to EPC (which includes both 3GPP and non-3GPP access). In  313 , the PDU session is transferred to 4G non-3GPP access, e.g., to ePDG that is connected to EPC. The PDU session can be a regular PDU session or an emergency PDU session. 
       FIG.  4    illustrates handover and transfer for a PDN connection between EPC 3GPP/non-3GPP access and 5GS 3GPP/non-3GPP access. In EPC, a PDN connection can be associated with 3GPP access ( 401 ) or associated with non-3GPP access ( 402 ). The PDN connection is considered to be associated with 3GPP access when it is established over 3GPP access in EPS (EUTRA connected to EPC). Depending on different scenarios, the PDN connection can be handover or transferred. In  411 , the PDN connection is handover to EPS non-3GPP access (ePDG connected to EPC). In  412 , the PDN connection is transferred to 5GS 3GPP access. In  413 , the PDN connection is transferred to 5GS non-3GPP access. The PDN connection can be a regular PDN connection or an emergency PDN connection. 
       FIG.  5    illustrates a sequence flow between a UE and 5GS network the reception, suspend, and resume of PEIPS assistance information in one novel aspect. In step  511 , UE  501  registers to the 5GS network over 3GPP access. During the last registration procedure, UE  501  obtains the power-saving feature assistance information IE. In 5GS, the power saving feature can be PEIPS (NR), and the power saving feature assistance information can be PEIPS (NR) assistance information, which comprises paging early indicators for monitoring paging occasions with power-saving. In step  512 , UE  501  monitors paging according to the PEIPS assistance information to save power consumption. In step  521 , an emergency PDU session is established successfully over 3GPP access, and both the UE and the network (AMF) should not use the PEIPS assistance information until a later event. In step  522 , UE  501  stops (suspends) using the PEIPS assistance information. 
     Later on, UE  501  detects an event occurred to the emergency PDU session. The event may include 1) the successful complete of the PDU session release procedure of the emergency PDU session; 2) the UE receives PEIPS assistance information during the registration procedure with PDU session status IE or upon successful completion of a service request procedure, if the UE or the network locally releases the emergency PDU session; 3) the successful completion of handover of the emergency PDU session from 3GPP to non-3GPP access; or 4) the successful transfer of the emergency PDU session in 5GS to EPS (EUTRAN) or ePDG connected to EPC (EPC+ePDG) (since PEIPS is only applicable in NR). For example, in step  531 , UE  501  determines that the emergency PDU session is handover (to non-3GPP) or transferred (to EPC). Accordingly, in step  532 , UE  501  starts (resumes) to use the PEIPS assistance information. 
       FIG.  6    illustrates a sequence flow between a UE and EPS network the reception, suspend, and resume of WUS assistance information in one novel aspect. In step  611 , UE  601  registers to the EPS network over 3GPP access. During the last registration(Attach/TAU) procedure, UE  601  obtains the power-saving feature assistance information IE. In EPS, the power saving feature can be wakeup signal (WUS), and the power saving feature assistance information can be WUS assistance information, which comprises signals for monitoring paging occasions with power-saving. In step  612 , UE  601  monitors paging according to the WUS assistance information to save power consumption. In step  621 , an emergency PDN connection is established successfully over 3GPP access, and both the UE and the network (MME) should not use the WUS assistance information until a later event. Accordingly, in step  622 , UE  601  stops (suspends) using the WUS assistance information. 
     Later on, UE  601  detects an event occurred to the emergency PDN connection. The event may include 1) the successful complete of the PDP connectivity release procedure of the emergency PDN connection; 2) the UE receives WUS assistance information during the registration procedure with PDP connectivity status IE or upon successful completion of a service request procedure, if the UE or the network locally releases the emergency PDN connection; 3) the successful completion of handover of the emergency PDN connection from 3GPP to non-3GPP access; or 4) the successful transfer of the emergency PDN connection in EPS to 5GS 3GPP or to 5GS non-3GPP. For example, in step  631 , UE  601  determines that the emergency PDN connection is handover (to EPC non-3GPP) or transferred (to 5GS). Accordingly, in step  632 , UE  601  starts (resumes) to use the WUS assistance information. 
       FIG.  7    is a flow chart of a method of suspending and resuming PEIPS assistance information in a 5G/NR network in accordance with one novel aspect of the present invention. In step  701 , a UE registers to a 5G system (5GS) over 3GPP access in a wireless communication network, wherein the UE receives power-saving feature assistance information during the registration procedure, wherein the power-saving feature is a Paging Early Indication with Paging Subgrouping (PEIPS). In step  702 , the UE establishes an emergency protocol data unit (PDU) session over the 3GPP access. In step  703 , the UE stops applying the power-saving feature assistance information upon the emergency PDU session is established. In step  704 , the UE resumes applying the power-saving feature assistance information upon the emergency PDU session is successfully moved out of the 5GS 3GPP access. 
       FIG.  8    is a flow chart of a method of suspending and resuming WUS assistance information in a 4G EPS network in accordance with one novel aspect of the present invention. In step  801 , a UE registers to an evolved packet system (EPS) over 3GPP access by a user equipment (UE) in a wireless communication network, wherein the UE receives power-saving feature assistance information during the registration procedure, wherein the power-saving feature is a wakeup signal (WUS). In step  802 , the UE establishes a packet data network (PDN) connection for emergency bearer service. In step  803 , the UE stops applying the power-saving feature assistance information upon the PDN connection for emergency bearer service is established. In step  804 , the UE starts applying the power-saving feature assistance information upon the PDN connection for emergency bearer service is successfully moved out of EPS (the EPC 3GPP access). 
     Although the present invention is described above in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.