DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Information Disclosure Statement
The information disclosure statement (IDS) submitted on 11/18/2024 was filed. The submission is in compliance with the provisions of 37 CFR 1.97. Accordingly, the information disclosure statement is being considered by the examiner.
Claim Objections
Claim 18 is objected to because of the following informalities: the last line of the claim recites “the distribute unit”, which should read “the distributed unit”. Appropriate correction is required.
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 1-20 and 22 are rejected under 35 U.S.C. 103 as being unpatentable over Mildh (WO 2022/066071 A1) in view of Tamura (WO 2023/032528 A1).
Regarding claim 1, Mildh discloses: (Currently Amended) A user equipment, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the user equipment at least to:, because Mildh teaches an apparatus in a user equipment built from processing circuitry, one or more processors, and a memory in communication with the processing circuitry. The memory contains instructions that the processing circuitry executes and that make the apparatus (i.e., “user equipment” as claimed) operable to receive an instruction (i.e., “computer program code” as claimed) from a network node and act on it, which means that the user equipment comprises at least one processor and at least one memory including computer program code configured to, with the processor, cause the user equipment to carry out the operations that follow: (Mildh, page 27, lines 8-10 “Figure 14 is a schematic of an example of apparatus 1400 n a User Equipment (UE) for performing a RRC re-establishment procedure. The apparatus 1400 comprises processing circuitry 1402 (e.g. one or more processors) and a memory 1404”; Mildh, page 27, lines 17-20 “In one embodiment, the memory 1404 contains instructions executable by the processing circuitry 1402 such that the apparatus 1400 is operable to receive an instruction from a network node to perform a RRC re-establishment procedure, and transmit a RRC re-establishment request”).
Furthermore, Mildh discloses: prevent the user equipment from transitioning into a radio resource control idle mode during the failure of the first central unit., as Mildh describes the re-establishment procedure as one that a UE in the RRC_CONNECTED state initiates in order to continue its RRC connection, in which, on the network’s indication, the UE stops the timers T310, T312 and T304, starts T311 and re-establishes its control plane connection with the second control plane function while its data radio bearers continue. The network-driven procedure is faster than the NAS recovery in which the UE would have to establish the connection from scratch, such that the UE, in response to the indication and while the first control plane function is failed, stays in the connected mode and is prevented from transitioning into a radio resource control idle mode during the failure of the first central unit: (Mildh, page 5, lines 23-26 “A UE in RRC_CONNECTED state, for which AS security has been activated with SRB2 and at least one DRB setup, may initiate the RRC re-establishment procedure in order to continue the RRC connection”; Mildh, page 23, lines 13-19 “on the reception of an indication from lower layers (MAC CE) that the network requests a re-establishment Upon initiation of the procedure, the UE shall: 1> stop timer T310, if running; 1> stop timer T312, if running; 1> stop timer T304, if running; 1> start timer T311”; Mildh, page 14, lines 26-27 “A control plane re-establishment procedure is provided in some examples that does not impact the user plane data radio bearers”; Mildh, page 18, lines 25-28 “This example may in some cases lead to a delay or user plane data transmission/reception interruption, however this may still be faster in some examples than NAS recovery where the UE has to establish the connection from scratch (e.g. NAS recovery)”; Mildh, page 8, lines 31-33 “If timer T301 expires before the UE receives the RRCReestablishment message from the network, UE has to perform NAS recovery via IDLE mode”).
Although Mildh teaches the DU, on detecting the failure or unavailability of CU-CP1, triggering RRC re-establishment in the UE: (Mildh, page 18, lines 35-37), Mildh does not explicitly disclose that the user equipment is caused to receive from a distributed unit, a central unit failure indication indicative of a failure of a first central unit associated with the distributed unit.
However, Mildh in view of Tamura discloses receive from a distributed unit, a central unit failure indication indicative of a failure of a first central unit associated with the distributed unit; and since Tamura explains that the gNB-DU, on detecting the failure of the gNB-CU-CP with which its UEs have their RRC association, sends the UEs associated with the failed gNB-CU-CP an RRC message that carries a cause parameter telling the UE why it is sent, namely that re-establishment of the RRC connection is required, whereby the user equipment receives from a distributed unit a central unit failure indication indicative of a failure of a first central unit associated with the distributed unit (Tamura, para [0044], “In case that the gNB-DU 6101 detects the failure of the gNB-CU-CP 62011, all resources related to the gNB-CU-CP 62011 may be locally released in the gNB-DU 6101”; Tamura, para [0044], “The gNB-DU 6101 optionally sends the RRC release message to the UEs which have an RRC association with the failed gNB-CU-CP 62011. The RRC release message to the UEs may include cause parameter indicating that Re-establishment of the RRC connection is required”).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have the instruction that the DU of Mildh sends its UEs on detecting the failure of CU-CP1 carry, as the message that Tamura’s gNB-DU sends its UEs does, an indication with a cause parameter that tells the UE of the failure of the central unit and of the re-establishment it requires, that is, to have the user equipment receive from the distributed unit a central unit failure indication indicative of a failure of the first central unit. Tamura’s stated aim is that, when a gNB-CU-CP fails, a backup takes over its role so that the existing RRC connections continue to be served, the same continuity of the RRC connection that Mildh’s network-driven re-establishment toward CU-CP2 is for, and Tamura’s message is the signal by which the DU tells the affected UEs of the failure it has detected. Only the indication and its cause are taken from Tamura; the UE of Mildh, so informed, performs the control plane re-establishment that keeps it in the connected state rather than the release that Tamura’s message optionally commands. A UE that is told the cause knows that the failure is on the network side and that its re-establishment is toward a replacement control plane function, which is the information Mildh has the UE record as the cause value CP-Failure, so the result, a UE that receives from the DU an indication of the central unit failure and re-establishes without dropping to the idle mode, is predictable, and one of ordinary skill would have had a reasonable expectation of success because the indication travels in the same downlink message that Mildh’s DU already sends and the UE acts on it as Mildh already describes.
Regarding claim 2, which depends on claim 1, Mildh discloses (Original) The user equipment of Claim 1 wherein preventing the user equipment from transitioning into the radio resource control idle mode comprises at least one of: suspending transmission over a signaling radio bearer to the first central unit; and extending a timer if it is running or active., as Mildh further discloses the UE that is triggered by the DU initiating the re-establishment procedure of the radio resource control specification, in which the UE flushes its RLC and MAC layers and suspends all of its data radio bearers and signaling radio bearers other than SRB0, and then transmits the re-establishment request on SRB0, such that the UE, while it stays connected, suspends transmission over a signaling radio bearer to the first central unit (Mildh, page 8, lines 20-21 “all DRBs and SRBs (except SRB0, which is used for sending the re-establishment message) are suspended”; Mildh, page 19, lines 2-3 “In step 6a), RLC and MAC layers are flushed in the UE 1202, and in step 6b) RLC and MAC layers are flushed in the DU 1204”; Mildh, page 21, lines 18-20 “The UE 1202 performs integrity verification on incoming RRC packets and will detect integrity verification failure. Legacy UEs will trigger a normal reestablishment procedure”).
Claim 2 recites its alternatives joined by at least one of, so the claim is satisfied when either of them is satisfied. The alternative relied on is the recitation of suspending transmission over a signaling radio bearer to the first central unit, which is the limitation mapped above.
Regarding claim 3, which depends on claim 1, Mildh discloses (Original) The user equipment of Claim 1 wherein the user equipment is prevented from transitioning into the radio resource control idle mode for a predetermined time duration, for a time duration indicated in the central unit failure indication, or until a central unit recovery indication is received at the user equipment, and the central unit recovery indication is indicative of that a second central unit, which was configured in a standby mode, is activated and associated with the distributed unit., as Mildh further discloses that the serving control plane function CU-CP1 keeps the UE context updated in a backup control plane function CU-CP2, that the DU selects CU-CP2 and forwards the UE’s re-establishment request to it, and that CU-CP2, having taken over responsibility for the UE, sends the UE the RRCReestablishment message. The UE remains in the re-establishment procedure, with its timer running, until that message arrives, and on receiving it stops the timer and ends the procedure, whereby the UE is prevented from transitioning into the idle mode until a central unit recovery indication is received at the user equipment, the RRCReestablishment message from CU-CP2 being indicative of that the second central unit, which was kept as a backup, is activated and associated with the distributed unit (Mildh, page 19, lines 28-30 “During normal conditions, in some examples, the CU-CP1 1206 that is currently serving the UE continuously or periodically stores or updates the UE context in a backup control plane function (CU-CP2 1208) or a UE context database 1210”; Mildh, page 19, lines 12-13 “In step 9), the DU 1204 selects CU-CP2 1208. In step 10, the UE 1202 sends a RRC re-establishment request, e.g. in accordance with step 1004 described above”; Mildh, page 19, lines 13-16 “In step 11), CU-CP2 1208, which receives the request, retrieves the UE context from UE context database 1210. CU-CP2 1208 then sends a RRCReestablishment message to the UE 1202 in step 12)”; Mildh, page 17, lines 20-23 “The second base station control plane function (e.g. a CU-CP) may therefore be a control plane function that takes over responsibility for serving the UE, and thus becomes associated with the UE, for example as a result of the re-establishment procedure”; Mildh, page 8, lines 31-33 “If timer T301 expires before the UE receives the RRCReestablishment message from the network, UE has to perform NAS recovery via IDLE mode”; Mildh, page 25, lines 24-29 “1> stop timer T301; 1> consider the current cell to be the PCell; 1> if the a reestablishCP is indicated: 2> submit the RRCReestablishmentComplete message to lower layers for transmission; 2> the procedure ends”).
Claim 3 recites its alternatives joined by or, so the claim is satisfied when any one of them is satisfied. The alternative relied on is the recitation that the user equipment is prevented from transitioning into the idle mode until a central unit recovery indication is received at the user equipment, which is the limitation mapped above.
Regarding claim 4, which depends on claim 3, Mildh discloses (Original) The user equipment of Claim 3 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the user equipment at least to: resume the suspended transmission over the signaling radio bearer to the second central unit in response to the central unit recovery indication., as Mildh further discloses the UE, once it has received the RRCReestablishment message, restoring SRB1 and transmitting the RRCReestablishmentComplete message on it, and the network re-establishing and resuming SRB1 when it verifies the UE context, the reply going to CU-CP2 that sent the RRCReestablishment message, with the result that the UE resumes the suspended transmission over the signaling radio bearer to the second central unit in response to the central unit recovery indication (Mildh, page 6, lines 25-27 “Once the UE has received the RRCReestablishment message, restored some configurations (e.g. SRB1) and reestablished the connection, it will transmit the RRCReestablishmentComplete message to the network”; Mildh, page 5, lines 32-34 “When AS security has been activated and the network retrieves or verifies the UE context: - re-activate AS security without changing algorithms; - re-establish and resume SRB1”; Mildh, page 19, lines 15-17 “CU-CP2 1208 then sends a RRCReestablishment message to the UE 1202 in step 12). In step 13), the UE 1202 replies to the CU-CP2 1208 with a RRCReestablishmentComplete message”).
Regarding claim 5, which depends on claim 1, Mildh discloses (Original) The user equipment of Claim 1 wherein the central unit failure indication is carried in a radio resource control message, a medium access control control element or a physical layer message., as Mildh further discloses the instruction being received by the UE in a MAC control element, in downlink control information on the physical downlink control channel, in a flag in a system information block or in a broadcast message, or as an RRC message whose integrity verification the UE finds to fail, so that the central unit failure indication is carried in a radio resource control message, a medium access control control element or a physical layer message (Mildh, page 16, lines 29-32 “The instruction received in step 1002 may in some examples be received in a MAC control element (CE), in Downlink Control Information (DCI) transmitted over a Physical Downlink Control Channel (PDCCH), in a flag in a System Information Block (SIB), or in a broadcast message”; Mildh, page 16, lines 16-19 “receiving the instruction from the network node comprises receiving a RRC message from the network node, performing integrity verification on the RRC message using an integrity verification key, and determining that the RRC message is an instruction to perform a RRC re-establishment procedure if the integrity verification fails”).
Claim 5 recites its alternatives joined by or, so the claim is satisfied when any one of them is satisfied. The alternatives relied on are the recitations of a radio resource control message and of a medium access control control element, both of which are mapped above.
Regarding claim 6, which depends on claim 5, Mildh discloses (Original) The user equipment of Claim 5 wherein the radio resource control message carrying the central unit failure indication is encrypted with a common security key, the radio resource control message carrying the central unit failure indication has a dedicated packet data convergence protocol sequence number, and/or the radio resource control message carrying the central unit failure indication is sent with a flag over a common control channel., as Mildh further discloses the DU sending the instruction to the UE as a flag in a system information block or in a broadcast message. A system information block is an RRC message that the cell broadcasts to all of its UEs on the broadcast control channel, a control channel that is common to the UEs of the cell rather than dedicated to one of them, which means that the radio resource control message carrying the central unit failure indication is sent with a flag over a common control channel (Mildh, page 17, lines 13-16 “The instruction may be sent in a MAC control element (CE), in Downlink Control Information (DCI) transmitted over a Physical Downlink Control Channel (PDCCH), in a flag in a System Information Block (SIB), or in a broadcast message in some examples”; Mildh, page 21, lines 4-7 “the message that was used to trigger the re-establishment in step 5) may in some examples be sent from the DU 1204 using a lower layer signaling (e.g. MAC control element (CE), downlink control information (DCI), system information block (SIB) signaling, etc)”).
Claim 6 recites its alternatives joined by and/or, so the claim is satisfied when any one of them is satisfied. The alternative relied on is the recitation that the radio resource control message carrying the central unit failure indication is sent with a flag over a common control channel, which is the limitation mapped above.
Regarding claim 7, which depends on claim 1, Mildh discloses (Original) The user equipment of Claim 1 wherein the central unit failure indication comprises at least one of: cause for the failure of the first central unit; a time duration of the failure; an indicator indicative of whether a new radio resource control procedure in uplink and/or retry of an existing radio resource control procedure in uplink is permitted during the failure of the first central unit or not; an identifier or address of the first central unit; and a list of radio resource control messages sent from the user equipment buffered at the distributed unit., as Mildh further discloses the RRC re-establishment as one of the procedures that the UE initiates in the uplink, and the instruction carrying an indication, a flag or information element, that a control plane only re-establishment is to be performed, on which the UE initiates transmission of the re-establishment request, such that the central unit failure indication comprises an indicator indicative of whether a new radio resource control procedure in uplink is permitted during the failure of the first central unit (Mildh, page 4, lines 22-25 “Some RRC procedures are also initiated by the UE, such as: - Measurement reports (e.g. used for UE mobility) - RRC re-establishment in case of connection failure”; Mildh, page 15, lines 23-25 “the message may contain an indication (e.g. a flag or IE) indicating that the RRC re-establishment procedure is for the control plane only”; Mildh, page 23, lines 21-24 “if an indication from lower layers triggered the re-establishment and it indicates a control plane only re-establishment: 2> initiate transmission of the RRCCPReestablishmentRequest message in accordance with 5.3.7.4”).
Claim 7 recites its alternatives joined by at least one of, so the claim is satisfied when any one of them is satisfied. The alternative relied on is the recitation of an indicator indicative of whether a new radio resource control procedure in uplink is permitted during the failure of the first central unit, which is the limitation mapped above.
Regarding claim 8, Mildh discloses: (Currently Amended) A distributed unit, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the distributed unit at least to:, since Mildh explains that the network node of its method 1100 may be a distributed unit and that the apparatus in that network node comprises processing circuitry, one or more processors, and a memory containing instructions that the processing circuitry executes and that make the apparatus operable to determine that the control plane function is unavailable and to instruct the UE, whereby the distributed unit comprises at least one processor and at least one memory including computer program code configured to, with the processor, cause the distributed unit to carry out the operations that follow: (Mildh, page 17, lines 5-6 “The network node may comprise for example a distributed unit (DU) or any other suitable network node or function”; Mildh, page 27, lines 23-26 “Figure 15 is a schematic of an example of apparatus 1500 in a network node of instructing a User Equipment (UE) to perform a RRC re-establishment procedure. The apparatus 1500 comprises processing circuitry 1502 (e.g. one or more processors) and a memory 1504 in communication with the processing circuitry 1502”; Mildh, page 27, lines 32-35 “In one embodiment, the memory 1504 contains instructions executable by the processing circuitry 1502 such that the apparatus 1500 is operable to determine that a first base station control plane function associated with a UE is unavailable, and send an instruction to the UE to perform a RRC re-establishment procedure”).
Furthermore, Mildh discloses: when the distributed unit determines a failure of a first central unit, the first central unit being active and associated with the distributed unit; and, in that Mildh shows CU-CP1 currently serving the UE through the DU, and the DU determining that CU-CP1 has failed or become unavailable, for example from the lack of a response to SCTP keep alive requests or to F1-AP messages, with the result that the distributed unit determines a failure of a first central unit that was active and associated with the distributed unit: (Mildh, page 19, lines 28-30 “During normal conditions, in some examples, the CU-CP1 1206 that is currently serving the UE continuously or periodically stores or updates the UE context in a backup control plane function (CU-CP2 1208) or a UE context database 1210”; Mildh, page 18, lines 35-37 “In step 4), DU 1204 detects failure or unavailability of CU-CP1 1206. In step 5, DU 1204 triggers RRC re-establishment in the UE 1202, for example in accordance with steps 1002 and 1104 described above”; Mildh, page 19, lines 30-35 “The DU 1204 can detect unavailability of the control plane function CU-CP1 1206 in one of several ways, such as for example: - Lack of response to SCTP keep alive requests - Not receiving a response to F1-AP messages such as F1-AP context modification required within a given time”).
Although Mildh teaches the DU, on determining that the first control plane function serving the UE is unavailable, sending the UE an instruction to perform an RRC re-establishment toward a second control plane function: (Mildh, page 17, lines 9-12), Mildh does not expressly teach that the distributed unit is caused to send to the one or more user equipments, a central unit failure indication indicative of the failure of the first central unit, or to start buffering radio resource control messages received from one or more user equipments.
Nonetheless, Mildh in view of Tamura discloses send to the one or more user equipments, a central unit failure indication indicative of the failure of the first central unit. given that Tamura sets out the gNB-DU that has detected the failure of the gNB-CU-CP sending, to the UEs that have an RRC association with the failed gNB-CU-CP, an RRC message whose cause parameter tells them that re-establishment of the RRC connection is required, so that the distributed unit sends to the one or more user equipments a central unit failure indication indicative of the failure of the first central unit (Tamura, para [0044], “In case that the gNB-DU 6101 detects the failure of the gNB-CU-CP 62011, all resources related to the gNB-CU-CP 62011 may be locally released in the gNB-DU 6101”; Tamura, para [0044], “The gNB-DU 6101 optionally sends the RRC release message to the UEs which have an RRC association with the failed gNB-CU-CP 62011. The RRC release message to the UEs may include cause parameter indicating that Re-establishment of the RRC connection is required”).
Mildh does not expressly disclose that the distributed unit is caused to start buffering radio resource control messages received from one or more user equipments when it determines the failure.
However, Tamura does disclose the gNB-DU that has determined that the gNB-CU-CP has failed directing every F1AP message that was destined to the failed gNB-CU-CP to the backup gNB-CU-CP instead, using the UE contexts that were backed up there, and choosing the backup for a new RRC message that arrives from a UE after the failure (Tamura, para [0173], “If the gNB-DU 6101 determined that the gNB-CU-CP 62011 has failed based on the decision in step 2-1, the gNB-DU 6101 sends all F1AP messages to the gNB-CU-CP 62012, as a backup of gNB-CU-CP 62011, if the messages are destined to the gNB-CU-CP 62011”; Tamura, para [0173], “Note that UE contexts including gNB-CU UE F1AP ID, C-RNTI, gNB-CU UE F1AP ID for the gNB-CU-CP 62011 can be used with the gNB-CU-CP 62012 as they are backed up in step 0”; Tamura, para [0043], “In case that gNB-CU-CP 62011 fails, the gNB-CU-CP 62012 can be chosen by the gNB-DU 6101 when the gNB-DU 6101 receives new RRC initial message from the UE”).
Thus, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have the DU of Mildh send its UEs, on determining the failure of CU-CP1, the failure indication with its cause that Tamura’s gNB-DU sends, and to have that DU hold the RRC messages it receives from its UEs from the moment it determines the failure and deliver them to CU-CP2 once CU-CP2 has been selected and has taken over, that is, to send the central unit failure indication to the user equipments and to start buffering the RRC messages received from the user equipments when the DU determines the failure of the first central unit. Tamura’s gNB-DU, once it has determined the failure, sends every message that was destined to the failed gNB-CU-CP to the backup and directs a UE’s new RRC message to the backup, and Tamura’s stated purpose is that the existing RRC connections continue to be served; Mildh’s stated problem is the loss of synchronization between the UE and the network when a control plane function fails, and Mildh teaches that an RRC message directed to a failed control plane function does not arrive. A DU that has determined that CU-CP1 is unavailable and has not yet selected CU-CP2 has two options for an RRC message that arrives from a UE in the meantime, to discard it or to hold it for the backup, and holding it for delivery to the control plane function that takes over is the ordinary store and forward behavior of a DU that already encapsulates each uplink RRC message in an F1 message before transferring it, extended by the interval until the backup is available. The result, that the failure is signaled to the UEs and their RRC messages reach the control plane function that has taken over rather than being lost, is predictable, and one of ordinary skill would have had a reasonable expectation of success because the indication travels in the downlink message that Mildh’s DU already sends and the DU already has the memory in which it holds each RRC message while it builds the F1 message that carries it.
Regarding claim 9, which depends on claim 8, Mildh in view of Tamura discloses The distributed unit of Claim 8 wherein the distributed unit determines the failure of the first central unit based on: a standby central unit activation indication received from the first central unit or from a second central unit, the standby central unit activation indication being indicative of that the second central unit is to be activated and associated with the distributed unit; or a failure detection performed at the distributed unit for the first central unit., as Tamura further discloses the gNB-DU determining that gNB-CU-CP 62011 has failed on receiving from the backup gNB-CU-CP 62012 an F1AP message indicating that 62011 has failed and that 62012 takes over all of its processes, and, in the graceful removal variant, on receiving from gNB-CU-CP 62011 itself an ERROR INDICATION message whose new cause value says that 62011 is going to close its service, on which the gNB-DU sends its F1AP messages to the backup. The gNB-DU also determines the failure itself when the SCTP heartbeat acknowledgement from 62011 stays out, with the result that the distributed unit determines the failure of the first central unit based on a standby central unit activation indication received from the first central unit or from a second central unit, the indication being indicative of that the second central unit is to be activated and associated with the distributed unit, or on a failure detection performed at the distributed unit for the first central unit (Tamura, para [0157], “In case that the gNB-DU 6101 receives, from the gNB-CU-CP 62012, an F1AP message indicating that the gNB-CU-CP 62011 has failed and the gNB-CU-CP 62012 takes over all processes from the gNB-CU-CP 62011, the gNB-DU 6101 may determine that the gNB-CU-CP 62011 has failed”; Tamura, para [0179], “The step 2-1 is replaced with the ERROR INDICATION message from the gNB-CU-CP 62011 to the gNB-DU 6101 including new cause value and time information for closure of service. The new cause value indicates that the gNB-CU-CP 62011 is going to close the service”; Tamura, para [0179], “The time information indicates a remaining time to close the service. The time information can be absolute time or a remaining time period to close of the service. Once the gNB-DU 6101 receives the ERROR INDICATION message, the gNB-DU 6101 performs the step 3-1”; Tamura, para [0154], “If the gNB-DU 6101 does not receive the Heartbeat Acknowledgement chunk as a reply to the Heartbeat Request Chunk for pre-determined period from the gNB-CU-CP 62011, the gNB-DU 6101 may determine that the gNB-CU-CP 62011 has failed”).
Claim 9 recites its alternatives joined by or, so the claim is satisfied when either of them is satisfied. The alternative relied on is the recitation of a standby central unit activation indication received from the first central unit or from a second central unit, which is mapped above in both of its forms; the failure detection performed at the distributed unit is mapped above as well. Consequently, Mildh and Tamura are combined for the reasons set forth in the rejection of claim 8 above.
Regarding claim 10, which depends on claim 9, Mildh in view of Tamura discloses The distributed unit of Claim 9 wherein the standby central unit activation indication received from the first central unit or the second central unit includes at least one of: a time duration before the second central unit is activated; a first indication to extend timers for procedures associated with the one or more user equipments; a second indication to prevent from initiating a new procedure or retry of an existing procedure during the time duration; and a list of radio resource control messages that have been received at the first central unit or the second central unit., as Tamura further discloses the ERROR INDICATION message from gNB-CU-CP 62011 to the gNB-DU carrying, beside the new cause value, time information for the closure of service that gives the remaining time, as an absolute time or as a remaining time period, until 62011 closes its service, after which the gNB-DU stops contacting 62011 and works with the backup 62012 to which it has directed its F1AP messages, so that the standby central unit activation indication received from the first central unit includes a time duration before the second central unit is activated (Tamura, para [0179], “The step 2-1 is replaced with the ERROR INDICATION message from the gNB-CU-CP 62011 to the gNB-DU 6101 including new cause value and time information for closure of service. The new cause value indicates that the gNB-CU-CP 62011 is going to close the service”; Tamura, para [0179], “The time information indicates a remaining time to close the service. The time information can be absolute time or a remaining time period to close of the service. Once the gNB-DU 6101 receives the ERROR INDICATION message, the gNB-DU 6101 performs the step 3-1”; Tamura, para [0179], “For example, the gNB-DU 6101 stops contacting to the gNB-CU-CP 62011 after the indicated time by the time information elapsed”).
Claim 10 recites its alternatives joined by at least one of, so the claim is satisfied when any one of them is satisfied. The alternative relied on is the recitation of a time duration before the second central unit is activated, which is the limitation mapped above.
For these reasons, Mildh and Tamura are combined for the reasons set forth in the rejection of claim 8 above.
Regarding claim 11, which depends on claim 8, Mildh discloses The distributed unit of Claim 8 wherein the central unit failure indication is sent via a radio resource control message, a medium access control control element or a physical layer message., as Mildh further discloses the DU sending the instruction in a MAC control element, in downlink control information on the physical downlink control channel, in a flag in a system information block or in a broadcast message, or as an RRC message that the DU encrypts with an incorrect key and forwards to the UE, which means that the central unit failure indication is sent via a radio resource control message, a medium access control control element or a physical layer message (Mildh, page 17, lines 13-16 “The instruction may be sent in a MAC control element (CE), in Downlink Control Information (DCI) transmitted over a Physical Downlink Control Channel (PDCCH), in a flag in a System Information Block (SIB), or in a broadcast message in some examples”; Mildh, page 18, lines 14-16 “Sending the instruction to the UE in some examples comprises encrypting and RRC message with an incorrect encryption key, and forwarding the RRC message to the UE, e.g. similar to the procedure as described above”).
Claim 11 recites its alternatives joined by or, so the claim is satisfied when any one of them is satisfied. The alternatives relied on are the recitations of a radio resource control message and of a medium access control control element, both of which are mapped above.
Regarding claim 12, which depends on claim 11, Mildh discloses The distributed unit of Claim 11 wherein the radio resource control message carrying the central unit failure indication is encrypted with a common security key, the radio resource control message carrying the central unit failure indication has a dedicated packet data convergence protocol sequence number, and/or the radio resource control message carrying the central unit failure indication is sent with a flag over a common control channel., as Mildh further discloses the DU sending the instruction as a flag in a system information block, using system information block signaling or a broadcast message. A system information block is an RRC message that the cell broadcasts to all of its UEs on the broadcast control channel, a control channel that is common to the UEs of the cell rather than dedicated to one of them, such that the radio resource control message carrying the central unit failure indication is sent with a flag over a common control channel (Mildh, page 17, lines 13-16 “The instruction may be sent in a MAC control element (CE), in Downlink Control Information (DCI) transmitted over a Physical Downlink Control Channel (PDCCH), in a flag in a System Information Block (SIB), or in a broadcast message in some examples”; Mildh, page 21, lines 4-7 “the message that was used to trigger the re-establishment in step 5) may in some examples be sent from the DU 1204 using a lower layer signaling (e.g. MAC control element (CE), downlink control information (DCI), system information block (SIB) signaling, etc)”).
Claim 12 recites its alternatives joined by and/or, so the claim is satisfied when any one of them is satisfied. The alternative relied on is the recitation that the radio resource control message carrying the central unit failure indication is sent with a flag over a common control channel, which is the limitation mapped above.
Regarding claim 13, which depends on claim 8, Mildh discloses The distributed unit of Claim 8 wherein the central unit failure indication comprises at least one of: cause for the failure of the first central unit; a time duration of the failure; an indicator indicative of whether a new radio resource control procedure in uplink and/or retry of an existing radio resource control procedure in uplink is permitted during the failure of the first central unit or not; an identifier or address of the first central unit; and a list of radio resource control messages received from the user equipment buffered at the distributed unit., as Mildh further discloses that the RRC re-establishment is one of the procedures the UE initiates in the uplink, and that the instruction the DU sends carries an indication, a flag or information element, that a control plane only re-establishment is to be performed, on which the UE initiates transmission of the re-establishment request, whereby the central unit failure indication comprises an indicator indicative of whether a new radio resource control procedure in uplink is permitted during the failure of the first central unit (Mildh, page 4, lines 22-25 “Some RRC procedures are also initiated by the UE, such as: - Measurement reports (e.g. used for UE mobility) - RRC re-establishment in case of connection failure”; Mildh, page 17, lines 25-27 “the instruction sent to the UE comprises an instruction to perform a control-plane only re-establishment procedure, as suggested above in some examples”; Mildh, page 15, lines 23-25 “the message may contain an indication (e.g. a flag or IE) indicating that the RRC re-establishment procedure is for the control plane only”; Mildh, page 23, lines 21-24 “if an indication from lower layers triggered the re-establishment and it indicates a control plane only re-establishment: 2> initiate transmission of the RRCCPReestablishmentRequest message in accordance with 5.3.7.4”).
Claim 13 recites its alternatives joined by at least one of, so the claim is satisfied when any one of them is satisfied. The alternative relied on is the recitation of an indicator indicative of whether a new radio resource control procedure in uplink is permitted during the failure of the first central unit, which is the limitation mapped above.
Regarding claim 14, which depends on claim 8, Mildh does not expressly disclose The distributed unit of Claim 8 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the distributed unit at least to: receive from the first central unit or an operation administration and maintenance function, an encoded radio resource control message comprising the central unit failure indication before the distributed unit determines the failure of the first central unit.
However Mildh in view of Tamura discloses the system information that the gNB-DU broadcasts being generated and updated by the O&M, passed from the O&M to the gNB-CU-CP, and sent by the gNB-CU-CP to the gNB-DU in a GNB-CU CONFIGURATION UPDATE message, the gNB-DU storing the received system information and using it for broadcasting (Tamura, para [0062], “The O&M sends, to the UDSF-SI 7701, Nudsf_UnstructuredDataManagement_Update message including DU 6101 as the data identifier corresponding to the gNB-DU Identity and the updated system information for gNB-DU 6101 as the data”; Tamura, para [0067], “The gNB-CU-CP 62011 sends, to the gNB-DU 6101, GNB-CU CONFIGURATION UPDATE message including the received system information if the gNB-CU-CP 62011 decides to update the system information in the gNB-DU 6101”; Tamura, para [0069], “The gNB-DU 6101 updates the stored system information to the received system information in step 6, stores the received system information, and uses it, for example, for broadcasting the system information”).
Consequently, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have CU-CP1 of Mildh, while it is still serving the DU, provide the DU in advance with the encoded system information block that carries the flag by which Mildh instructs the UEs, in the GNB-CU CONFIGURATION UPDATE message by which Tamura’s gNB-CU-CP delivers to the gNB-DU the system information that the gNB-DU stores and broadcasts, so that the DU holds the encoded RRC message ready and broadcasts it when it determines that CU-CP1 has failed, that is, to receive from the first central unit an encoded radio resource control message comprising the central unit failure indication before the distributed unit determines the failure of the first central unit. Tamura’s configuration update carries ordinary system information and not the flag by which Mildh instructs the UEs, so neither reference alone shows the encoded message with the indication reaching the DU beforehand. Mildh assigns the generation of RRC messages to the control plane function and their forwarding to the DU, and it wants the DU to be able to send the instruction as a flag in a system information block at the moment the serving control plane function is no longer available to generate one; Tamura’s procedure is the ordinary way system information reaches a gNB-DU, from the O&M through the gNB-CU-CP in a configuration update that the gNB-DU stores until it broadcasts it. Providing the DU beforehand with the encoded system information block that carries the flag is therefore the predictable arrangement that lets Mildh’s system information block form of the instruction work when CU-CP1 fails, and one of ordinary skill would have had a reasonable expectation of success because the message is generated and delivered exactly as Tamura describes and the DU merely stores it, as Tamura’s gNB-DU already does, until it is needed.
Regarding claim 15, which depends on claim 8, Mildh discloses The distributed unit of Claim 8 wherein the central unit failure indication is encoded into a radio resource control message at the distributed unit before it is sent to the one or more user equipments., as Mildh further discloses the network node of method 1100, the DU, sending the instruction by encrypting an RRC message with an incorrect encryption key and forwarding it to the UE, the UE reading the resulting integrity verification failure as the instruction to re-establish, so that the central unit failure indication is encoded into a radio resource control message at the distributed unit before it is sent to the one or more user equipments (Mildh, page 18, lines 14-16 “Sending the instruction to the UE in some examples comprises encrypting and RRC message with an incorrect encryption key, and forwarding the RRC message to the UE, e.g. similar to the procedure as described above”; Mildh, page 16, lines 20-23 “the network node (or other node in the network) may intentionally perform encryption or integrity protection on the RRC message using an incorrect or alternate integrity protection key, and thus the message will fail integrity protection at the UE. This may trigger a RRC re-establishment procedure”).
Regarding claim 16, which depends on claim 8, Mildh discloses The distributed unit of Claim 8 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the distributed unit at least to: receive a standby central unit activation complete message from a second central unit, the standby central unit activation complete message being indicative of that the second central unit is activated and associated with the distributed unit; and, as Mildh further discloses CU-CP2 taking over responsibility for the UE and, having retrieved the UE context, sending the RRCReestablishment message for the UE, which the gNB-CU transfers to the gNB-DU in a DL RRC MESSAGE TRANSFER message for the DU to deliver, which means that the distributed unit receives from the second central unit a standby central unit activation complete message, the RRCReestablishment message transfer by which CU-CP2, now serving the UE through this DU, shows that it is activated and associated with the distributed unit (Mildh, page 19, lines 13-16 “In step 11), CU-CP2 1208, which receives the request, retrieves the UE context from UE context database 1210. CU-CP2 1208 then sends a RRCReestablishment message to the UE 1202 in step 12)”; Mildh, page 17, lines 20-23 “The second base station control plane function (e.g. a CU-CP) may therefore be a control plane function that takes over responsibility for serving the UE, and thus becomes associated with the UE, for example as a result of the re-establishment procedure”; Mildh, page 7, lines 7-9 “The gNB-CU includes RRCReestablishment message and transfers to the gNB-DU. If the UE requests to re-establish RRC connection in the last serving gNB-DU, the DL RRC MESSAGE TRANSFER message shall include old gNB-DU UE F1AP ID”; Mildh, page 7, lines 10-11 “The gNB-DU retrieves UE context based on old gNB-DU UE F1AP ID, replaces old C-RNTI/PCI with new C-RNTI/PCI. It sends RRCReestablishment message to UE”).
Mildh does not expressly disclose that the distributed unit is further caused to: send the buffered radio resource control messages to the second central unit. However, Tamura does disclose the gNB-DU that has determined the failure of gNB-CU-CP 62011 sending to the backup gNB-CU-CP 62012 all F1AP messages that were destined to 62011 (Tamura, para [0173], “If the gNB-DU 6101 determined that the gNB-CU-CP 62011 has failed based on the decision in step 2-1, the gNB-DU 6101 sends all F1AP messages to the gNB-CU-CP 62012, as a backup of gNB-CU-CP 62011, if the messages are destined to the gNB-CU-CP 62011”).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have the DU of Mildh, as modified in the rejection of claim 8 to buffer the RRC messages received from its UEs on determining the failure of CU-CP1, send the buffered RRC messages to CU-CP2, as Tamura’s gNB-DU sends to the backup every message that was meant for the failed unit, that is, to send the buffered radio resource control messages to the second central unit. Delivering the held messages to the control plane function that has taken over is the purpose of holding them, Tamura’s gNB-DU already directs to the backup every F1AP message destined to the failed gNB-CU-CP and Mildh’s DU already forwards to CU-CP2 the re-establishment request it receives from the UE after the failure, and the result, that the RRC messages of the UEs reach the control plane function that now serves them, is predictable, so one of ordinary skill would have had a reasonable expectation of success.
Regarding claim 17, which depends on claim 16, Mildh discloses The distributed unit of Claim 16 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the distributed unit at least to: transmit to the one or more user equipments, a central unit recovery indication in response to receiving the standby central unit activation complete message from the second central unit., as Mildh further discloses the gNB-DU, on receiving the DL RRC MESSAGE TRANSFER message that carries the RRCReestablishment message from the gNB-CU, sending the RRCReestablishment message to the UE, the message by which the UE learns that its control plane connection has been re-established with CU-CP2 and after which it resumes its signaling to CU-CP2, such that the distributed unit transmits to the user equipment a central unit recovery indication in response to receiving the standby central unit activation complete message from the second central unit (Mildh, page 7, lines 7-9 “The gNB-CU includes RRCReestablishment message and transfers to the gNB-DU. If the UE requests to re-establish RRC connection in the last serving gNB-DU, the DL RRC MESSAGE TRANSFER message shall include old gNB-DU UE F1AP ID”; Mildh, page 7, lines 10-11 “The gNB-DU retrieves UE context based on old gNB-DU UE F1AP ID, replaces old C-RNTI/PCI with new C-RNTI/PCI. It sends RRCReestablishment message to UE”; Mildh, page 19, lines 15-17 “CU-CP2 1208 then sends a RRCReestablishment message to the UE 1202 in step 12). In step 13), the UE 1202 replies to the CU-CP2 1208 with a RRCReestablishmentComplete message”; Mildh, page 6, lines 25-27 “Once the UE has received the RRCReestablishment message, restored some configurations (e.g. SRB1) and reestablished the connection, it will transmit the RRCReestablishmentComplete message to the network”).
Regarding claim 18, Mildh discloses: A second central unit, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the second central unit at least to:, since Mildh explains that its network includes a second control plane function CU-CP2 1208 beside the first control plane function CU-CP1 1206, and that the functions of its nodes are implemented with software programs and data run by one or more digital microprocessors, or embodied in a computer readable memory holding the instructions that cause a processor to carry them out. A node whose functions are carried out by a processor executing program instructions held in a memory has at least one processor and at least one memory including computer program code, whereby CU-CP2 is a second central unit comprising at least one processor and at least one memory including computer program code configured to, with the processor, cause the second central unit to carry out the operation that follows: (Mildh, page 18, lines 19-20 “The network includes a UE 1202, DU 1204, first control plane function CU-CP1 1206, second control plane function CU-CP2 1208”; Mildh, page 13, lines 3-6 “the functions described may be implemented in one or more nodes using hardware circuitry (e.g., analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc.) and/or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers”; Mildh, page 13, lines 8-11 “the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein”).
Although Mildh teaches the DU learning that a new control plane function has taken over responsibility from the unavailable CU-CP1 by an explicit indication from that new control plane function: (Mildh, page 19, lines 36-37), Mildh stops short of disclosing that the second central unit is caused to send to a distributed unit, a standby central unit activation indication indicative of that the second central unit is to be activated to replace a first central unit, the first central unit being active and associated with the distribute unit.
Nonetheless, Mildh in view of Tamura discloses send to a distributed unit, a standby central unit activation indication indicative of that the second central unit is to be activated to replace a first central unit, the first central unit being active and associated with the distribute unit. in that Tamura shows the backup gNB-CU-CP 62012, in which the UE contexts of the serving gNB-CU-CP 62011 are constantly backed up, sending the gNB-DU an F1AP message indicating that 62011 has failed and that 62012 takes over all of its processes, the backup taking over the role of the failed unit so that the existing RRC connections continue to be served, with the result that the second central unit sends to a distributed unit a standby central unit activation indication indicative of that the second central unit is to be activated to replace a first central unit that was active and associated with the distribute unit (Tamura, para [0150], “All UE context(s) to handle the UE in both RRC_INACTIVE state and RRC_CONNECTED state in the gNB-CU-CP 62011 are constantly backed up in the gNB-CU-CP 62012 by implementation specific technology”; Tamura, para [0157], “In case that the gNB-DU 6101 receives, from the gNB-CU-CP 62012, an F1AP message indicating that the gNB-CU-CP 62011 has failed and the gNB-CU-CP 62012 takes over all processes from the gNB-CU-CP 62011, the gNB-DU 6101 may determine that the gNB-CU-CP 62011 has failed”; Tamura, para [0073], “In a case where the gNB-CU-CP fails, one of the backup gNB-CU-CPs takes over the role of the failed gNB-CU-CP so that existing RRC connections can be continuously served”).
Thus, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have CU-CP2 of Mildh, on taking over responsibility for the UEs and DUs of the failed CU-CP1, send the DU the F1AP takeover message of Tamura’s backup gNB-CU-CP, indicating that CU-CP1 has failed and that CU-CP2 takes over its processes, that is, to send to the distributed unit a standby central unit activation indication indicative of that the second central unit is to be activated to replace the first central unit. Mildh already contemplates the DU receiving an explicit indication from the new control plane function that has taken over, without saying what it contains, and Tamura supplies the content of exactly that message and its purpose, that the DU knows which gNB-CU-CP now serves it so that the existing RRC connections continue to be served, without the UE and the network losing synchronization, which is the problem Mildh sets out to cure. The expected operation, a DU that on receiving the message directs its F1AP messages and the UE’s re-establishment request to CU-CP2, is what both references describe, and one of ordinary skill would have had a reasonable expectation of success because the message travels over the F1 interface that Mildh’s DU already has to the backup control plane function.
Regarding claim 19, which depends on claim 18, Mildh disclose The second central unit of Claim 18, wherein the standby central unit activation indication includes at least one of: a time duration before the second central unit is activated; a first indication to extend timers for procedures associated with user equipments served by the distributed unit; a second indication to prevent from initiating a new procedure or retry of an existing procedure at the distributed unit during the time duration; and a list of radio resource control messages that have been received at the second central unit from the distributed unit. CU-CP2 sending the DU the explicit indication that it has taken over responsibility from the unavailable CU-CP1, CU-CP1 writing the UE information to CU-CP2 during normal conditions, and Mildh’s resynchronization technique in which the receiving side reports the sequence number of the last RRC message it received so that the sender can verify which of its RRC messages were received (Mildh, page 19, lines 36-37 “Receiving an explicit indication from the failed CU-CP (upon re-start) or a new CU-CP that has taken over responsibility from the unavailable control plane function”; Mildh, page 18, lines 32-34 “In step 2), CU-CP1 writes UE information to CU-CP2 1208 and/or UE context database 1210. Thus for example UE context(s) may be stored or updated for the UE”; Mildh, page 21, lines 31-34 “the UE may in some examples include the PDCP sequence number (SN) of the last received RRC (e.g. SRB1) message, or the next expected PDCP SN. The network may therefore verify if the UE has received the latest RRC message that it has sent”).
Consequently, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to include in the F1AP takeover message with which CU-CP2 of Mildh, as modified in the rejection of claim 18, announces its takeover to the DU a list of the RRC messages that CU-CP2 has received from the DU, that is, to have the standby central unit activation indication include a list of radio resource control messages that have been received at the second central unit from the distributed unit. Tamura, which supplies the takeover message, says only that the message indicates the failure and the takeover and does not list its contents. Mildh’s aim after a control plane failure is to resynchronize the two sides of the connection, and its technique for doing so is to let one side report what it has received so that the other side knows what still has to be delivered. CU-CP2 holds, from the UE information that CU-CP1 wrote to it, the uplink RRC messages that reached the control plane before the failure, and the DU of Mildh, as modified in the rejection of claim 8, holds the RRC messages received since. Applying Mildh’s reporting technique on the interface between them, by having CU-CP2 list what it already has, lets the DU deliver only the missing messages and is the same known technique used in the same way for the same result. One of ordinary skill would have had a reasonable expectation of success because the list is one more information element in an indication that CU-CP2 already sends to the DU.
Regarding claim 20, which depends on claim 18, Mildh in view of Tamura discloses The second central unit of Claim 18 wherein the standby central unit activation indication is further sent to an access and mobility management function, neighboring radio access network nodes, a central unit user plane associated with the distributed unit, and other network nodes or functions having a direct interface with the first central unit., as Tamura further discloses the backup gNB-CU-CP 62012 sending the same indication, that 62011 has failed and that 62012 takes over its processes, in an NGAP message to the AMF, in an XnAP message to the gNB-CU-CP 62013 of a neighboring node and in an E1AP message to the gNB-CU-UP, and the gNB-CU-CP providing its backup related information to every node connected to it, the gNB-DUs, AMFs, gNB-CU-UPs and gNB-CU-CPs that have an interface with it, so that the standby central unit activation indication is further sent to an access and mobility management function, neighboring radio access network nodes, a central unit user plane associated with the distributed unit, and other network nodes or functions having a direct interface with the first central unit (Tamura, para [0167], “In case that the AMF 70 receives, from the gNB-CU-CP 62012, an NGAP message indicating that the gNB-CU-CP 62011 has failed and the gNB-CU-CP 62012 takes over all processes from the gNB-CU-CP 62011, the AMF 70 may determine that the gNB-CU-CP 62011 has failed”; Tamura, para [0172], “In case that the gNB-CU-CP 62013 receives, from the gNB-CU-CP 62012, an XnAP message indicating that the gNB-CU-CP 62011 has failed and the gNB-CU-CP 62012 takes over all processes from the gNB-CU-CP 62011, the gNB-CU-CP 62013 may determine that the gNB-CU-CP 62011 has failed”; Tamura, para [0162], “In case that the gNB-CU-UP 62021 receives, from the gNB-CU-CP 62012, an E1AP message indicating that the gNB-CU-CP 62011 has failed and the gNB-CU-CP 62012 takes over all processes from the gNB-CU-CP 62011, the gNB-CU-UP 62021 may determine that the gNB-CU-CP 62011 has failed”; Tamura, para [0075], “To deal with gNB-CU-CP failure, a gNB-CU-CP may optionally provide backup gNB-CU-CP related information to connected node(s), for example, gNB-DU(s), connected AMF(s), connected gNB-CU-UP(s) or connected gNB-CU-CP(s)”).
For these reasons, Mildh and Tamura are combined for the reasons set forth in the rejection of claim 18 above.
Regarding claim 22, the claim recites: A method implemented at a user equipment, comprising: receiving from a distributed unit, a central unit failure indication indicative of a failure of a first central unit associated with the distributed unit; and preventing the user equipment from transitioning into a radio resource control idle mode during the failure of the first central unit. Claim 22 is analogous to claim 1 and is rejected for the same reasons.
Claim 21 is rejected under 35 U.S.C. 103 as being unpatentable over Mildh (WO 2022/066071 A1) in view of Tamura (WO 2023/032528 A1) and further in view of Chandrashekar (WO 2023/274730 A2).
Regarding claim 21, which depends on claim 18, Mildh discloses send to the distributed unit, a standby central unit activation complete message when the second central unit is activated and associated with the distributed unit; and, as Mildh further discloses CU-CP2, having taken over responsibility for the UE and retrieved the UE context, sending the RRCReestablishment message, which the gNB-CU transfers to the gNB-DU in a DL RRC MESSAGE TRANSFER message for delivery to the UE, which means that the second central unit sends to the distributed unit a standby central unit activation complete message, the RRCReestablishment message transfer, when it is activated and associated with the distributed unit (Mildh, page 19, lines 13-16 “In step 11), CU-CP2 1208, which receives the request, retrieves the UE context from UE context database 1210. CU-CP2 1208 then sends a RRCReestablishment message to the UE 1202 in step 12)”; Mildh, page 7, lines 7-9 “The gNB-CU includes RRCReestablishment message and transfers to the gNB-DU. If the UE requests to re-establish RRC connection in the last serving gNB-DU, the DL RRC MESSAGE TRANSFER message shall include old gNB-DU UE F1AP ID”; Mildh, page 7, lines 10-11 “The gNB-DU retrieves UE context based on old gNB-DU UE F1AP ID, replaces old C-RNTI/PCI with new C-RNTI/PCI. It sends RRCReestablishment message to UE”; Mildh, page 17, lines 20-23 “The second base station control plane function (e.g. a CU-CP) may therefore be a control plane function that takes over responsibility for serving the UE, and thus becomes associated with the UE, for example as a result of the re-establishment procedure”).
Mildh does not expressly disclose that the second central unit is further caused to receive from the distributed unit, one or more uplink radio resource control messages buffered at the distributed unit before the second central unit is activated and associated with the distributed unit.
However, Mildh in view of Tamura does disclose the backup gNB-CU-CP 62012 receiving from the gNB-DU, once the gNB-DU has determined that gNB-CU-CP 62011 has failed, every F1AP message that was destined to 62011, handled with the UE contexts that were backed up in 62012 (Tamura, para [0173], “If the gNB-DU 6101 determined that the gNB-CU-CP 62011 has failed based on the decision in step 2-1, the gNB-DU 6101 sends all F1AP messages to the gNB-CU-CP 62012, as a backup of gNB-CU-CP 62011, if the messages are destined to the gNB-CU-CP 62011”; Tamura, para [0173], “Note that UE contexts including gNB-CU UE F1AP ID, C-RNTI, gNB-CU UE F1AP ID for the gNB-CU-CP 62011 can be used with the gNB-CU-CP 62012 as they are backed up in step 0”).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have CU-CP2 of Mildh receive from the DU, as modified in the rejection of claim 8 to buffer the RRC messages received from its UEs on determining the failure of CU-CP1, the uplink RRC messages that the DU buffered before CU-CP2 took over, that is, to receive from the distributed unit one or more uplink radio resource control messages buffered at the distributed unit before the second central unit is activated and associated with the distributed unit. Receiving them is the counterpart of the DU sending them, Tamura’s backup already receives from the gNB-DU every F1AP message that was meant for the failed gNB-CU-CP and handles it with the backed up UE contexts, and delivering the held messages to the control plane function that takes over is the purpose of holding them. The result, that the uplink RRC messages of the UEs reach the control plane function that now serves them, is predictable, and one of ordinary skill would have had a reasonable expectation of success because the buffered messages travel over the F1 interface on which the DU already transfers every uplink RRC message.
Even though Mildh in view of Tamura teaches CU-CP2 acting on being informed by the DU of the unavailability of CU-CP1, and the backup gNB-CU-CP announcing to the gNB-DU that it takes over the processes of the failed gNB-CU-CP: (Mildh, page 21, lines 7-9, Tamura, para [0157]), Mildh in view of Tamura does not explicitly disclose that the second central unit is caused to receive from the first central unit or an operation administration and maintenance function, a standby central unit activation request before sending the standby central unit activation indication to the distributed unit.
Nevertheless, Mildh in view of Tamura and further in view of Chandrashekar discloses The second central unit of Claim 18 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the second central unit at least to: receive from the first central unit or an operation administration and maintenance function, a standby central unit activation request before sending the standby central unit activation indication to the distributed unit; as Chandrashekar describes a stand-by central unit CU 120 that is told, by a management entity of the network that has determined that the CU-CP of CU 110 has failed, that the switchover to CU 120 needs to be performed, CU 120 then, in response to being so informed, triggering the switchover to itself, such that the second central unit receives from an operation administration and maintenance function a standby central unit activation request before sending the standby central unit activation indication to the distributed unit (Chandrashekar, para [0058], “management entity, for example, may determine that the CU-CP of CU 110 has failed and consequently that switchover to CU 120 needs to be performed. CU 120 is informed of this and, responsive to this, CU 120 in phase 480 triggers the switchover”).
Accordingly, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have CU-CP2 of Mildh, as modified by Tamura to announce its takeover to the DU, take over on a request from an operation administration and maintenance function that has determined the failure of CU-CP1, as Chandrashekar’s stand-by CU 120 does, before it sends the takeover indication to the DU, that is, to receive from an operation administration and maintenance function a standby central unit activation request before sending the standby central unit activation indication to the distributed unit. Chandrashekar’s reason is that the failure of a CU-CP can be determined by a management entity of the network as well as by the DU, and that a stand-by CU-CP which is informed of the failure and told to switch over, having already synchronized the control data and prepared its connections, restores control of the DU without establishing anything anew, so that the connections of the UE do not time out before connectivity is restored. Mildh’s backup CU-CP2 already holds the UE context written by CU-CP1 and already acts on being informed of the unavailability of CU-CP1 by another node, so an activation request from the operation administration and maintenance function is one more source of the same trigger, and the expected operation, CU-CP2 taking over on the request and then announcing the takeover to the DU, follows what the three references describe. One of ordinary skill would have had a reasonable expectation of success because the operation administration and maintenance function of a radio access network already manages its central units and the request reaches CU-CP2 over the management interface it already has.
Claim 21 recites its alternatives joined by or, so the claim is satisfied when either of them is satisfied. The alternative relied on is the recitation of an operation administration and maintenance function, which is the limitation mapped above.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to CHONGSUH (John) PARK whose telephone number is 408-918-7574. The examiner can normally be reached Monday - Friday 8:00-5:30 PST
Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice.
If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Avellino, Joseph can be reached at 571-272-3905 The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000.
/CHONGSUH PARK/Examiner, Art Unit 2478
/JOSEPH E AVELLINO/Supervisory Patent Examiner, Art Unit 2478
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