PDCP Discard Instructions for XR

Abstract

A method, system, apparatus, and computer program product for notifying a Packet Data Convergence Protocol (PDCP) receiver of PDCP PDUs to be discarded. In one aspect, the method can include determining, by a PDCP transmitter, a set of PDCP PDUs to be discarded, generating, by the PDCP transmitter, discard markers in PDCP PDU headers that signal to the PDCP receiver that the determined PDCP PDUs should be discarded, and transmitting, by the PDCP transmitter, the generated PDCP PDUs to the PDCP receiver.

Description

[Background technology]

[0001] Wireless communication networks provide an integrated communications platform and telecommunications services to wireless user devices. Exemplary telecommunications services include telephony, data (e.g., voice, audio, and / or video data), messaging, Internet access, and / or other services. Wireless communication networks have radio access nodes that exchange wireless signals with wireless user devices using radio network protocols, such as those described in various telecommunications standards promulgated by the 3rd Generation Partnership Project (3GPP). Exemplary wireless communication networks include code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal frequency division multiple access (OFDMA) networks, long term evolution (LTE), and fifth generation new radio (5G NR). Wireless communication networks facilitate mobile broadband services using technologies such as OFDM, multiple input multiple output (MIMO), advanced channel coding, massive MIMO, beamforming, and / or other features. Summary of the Invention

[0002] In XR operation, Packet Data Convergence Protocol (PDCP) operation includes a packet discard option, and PDUs are discarded fairly regularly so that packet discards are no longer an unusual event. In traditional PDCP operation, discarding a PDCP SDU already associated with a PDCP SN causes a SN gap among multiple PDCP data PDUs being transmitted, which increases the PDCP reordering delay in the receiving PDCP entity. XR, on the other hand, requires low latency, and processing overhead and use of system resources (including memory in the PDCP receiver) should be minimized.

[0003] Previous systems had PDCP transmitters that suffered from the processing overhead of discarding PDCP packets, causing increased PDCP reordering delays at the PDCP receiver. However, the present disclosure provides systems and methods that can be employed to minimize the overhead at the PDCP receiver as a result of PDCP packet discarding at the PDCP transmitter by enhancing the functionality of the PDCP receiver. In some instances, as described in the co-pending application, a PDCP receiver can be employed to perform operations to discard PDCP PDU packets that the PDCP transmitter has marked for discard, thus avoiding the overhead of the PDCP transmitter performing the discard processing.

[0004] However, in order for a PDCP receiver to discard PDCP PDUs tagged for discard by a PDCP transmitter, the PDCP receiver must be notified as to which particular PDCP PDUs have been sent by the PDCP transmitter while being marked for discard by the PDCP transmitter. This disclosure provides multiple implementations for generating and transmitting to a PDCP receiver discard markers (also called discard indicators) that inform the PDCP receiver of PDCP PDUs that have been marked for discard and can be discarded by the PDCP receiver.

[0005] Thus, the discard markers of the present disclosure enable a PDCP transmitter to mitigate the need for a PDCP receiver to perform reordering operations (e.g., discarding PDCP PDUs marked for discard). Additionally, discarding PDCP PDUs by a PDCP transmitter may occur after the PDCP PDUs are encrypted or after the PDCP PDUs are transmitted to lower-level protocols, making discarding PDUs a computationally intensive task.

[0006] According to one innovative aspect of the present disclosure, a method for notifying a Packet Data Convergence Protocol (PDCP) receiver of PDCP PDUs to be discarded is disclosed. In one aspect, the method can include the actions of determining, by a PDCP transmitter, a set of PDCP PDUs to be discarded, generating, by the PDCP transmitter, discard markers in PDCP PDU headers that signal to the PDCP receiver that the determined PDCP PDUs should be discarded, and transmitting, by the PDCP transmitter, the generated PDCP PDUs to the PDCP receiver.

[0007] Other aspects include apparatuses, systems, and computer programs for performing the actions of the aforementioned methods.

[0008] This innovative method can include other optional features. For example, in some implementations, the generated discard marker is in the PDCP PDU header of the first PDCP PDU by sequence number in the determined set of PDCP PDUs to be discarded. In such implementations, the discard marker is a one-bit indication that (i) the first PDCP PDU by sequence number in the set of PDCP PDUs and (ii) subsequent PDCP PDUs should be discarded by the PDCP receiver.

[0009] In some implementations, the generated discard marker is in the PDCP PDU header of the last non-to-be-discarded nominal PDCP PDU by sequence number that precedes the first PDCP PDU by sequence number in the determined set of PDCP PDUs to be discarded. In such implementations, the discard marker is a one-bit indication that the following PDCP PDUs by sequence number in the set of PDCP PDUs should be discarded by the PDCP receiver.

[0010] In some implementations, the method may further include generating, for each particular PDCP PDU of the set of PDCP PDUs to be discarded, by the PDCP transmitter a one-bit discard marker in a PDCP PDU header of that particular PDCP PDU, the discard marker signaling to the PDCP receiver that that particular PDCP PDU should be discarded.

[0011] In some implementations, the discard marker is a one-bit discard marker that signals to the PDCP receiver that (i) the PDCP PDU containing the one-bit discard marker should be discarded, or (ii) the subsequent PDCP PDUs by sequence number should be discarded.

[0012] In some implementations, the discard marker indicates a PDCP PDU set identifier of a set of PDCP PDUs that are to be discarded.

[0013] In some implementations, the method may further include transmitting, by the PDCP transmitter, the set of PDCP PDUs to be discarded to the PDCP receiver.

[0014] In some implementations, the set of PDCP PDUs to be discarded have sequence numbers that are sequential.

[0015] In some implementations, the generated discard marker is in a PDCP PDU header of a first PDCP PDU and signals to the PDCP receiver the first PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded. In such implementations, the method can further include generating, by the PDCP transmitter, a second discard marker in a last PDCP PDU of the determined set of PDCP PDUs to be discarded, the second discard marker signaling to the PDCP receiver the last PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded.

[0016] In some implementations, the generated discard marker is in a PDCP PDU header of the first PDCP PDU, signaling to the PDCP receiver the first PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded. In such implementations, the generated discard marker is in a PDCP PDU header of the last nominal PDCP PDU that is not to be discarded, by sequence number, before the first PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded, signaling to the PDCP receiver that the subsequent PDCP PDU by sequence number is the first PDCP PDU of the determined set of PDCP PDUs to be discarded. In such implementations, the method can further include generating, by the PDCP transmitter, a second discard marker in the last PDCP PDU of the determined set of PDCP PDUs to be discarded, the second discard marker signaling to the PDCP receiver the last PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded.

[0017] In some implementations, the generated discard marker is in the PDCP PDU header of the first PDCP PDU by sequence number in the determined set of PDCP PDUs to be discarded, hi such implementations, the discard marker is a two-bit indication of (i) the sequence number of the first PDCP PDU in the set of PDCP PDUs to be discarded and (ii) the sequence number of the last PDCP PDU in the set of PDCP PDUs to be discarded.

[0018] In some implementations, the discard marker is a two-bit indication of (i) the sequence number of the first PDCP PDU in the set of PDCP PDUs to be discarded and (ii) the total number of subsequent PDCP PDUs to be discarded.

[0019] In some implementations, the PDCP PDU header is the header of a PDCP data PDU in the set of PDCP PDUs that is to be discarded.

[0020] In some implementations, the PDCP PDU header is the header of a PDCP PDU that is sent within a padded PDCP data PDU that contains no other content.

[0021] In some implementations, the discard marker includes a parameter that indicates to the PDCP receiver the number of discarded PDCP PDUs in flight.

[0022] According to another innovative aspect of the present disclosure, a method for notifying a Packet Data Convergence Protocol (PDCP) receiver of PDCP PDUs to be discarded is disclosed. In one aspect, the method can include the actions of determining, by a PDCP transmitter, a set of PDCP PDUs to be discarded, generating, by the PDCP transmitter, a PDCP control PDU including one or more parameters signaling to the PDCP receiver that the determined PDCP PDUs should be discarded, and transmitting, by the PDCP transmitter, the generated PDCP control PDU to the PDCP receiver.

[0023] Other aspects include apparatuses, systems, and computer programs for performing the actions of the aforementioned methods.

[0024] The innovative method may include other optional features. For example, in some implementations, the method may further include transmitting, by the PDCP transmitter, the set of PDCP PDUs to be discarded to the PDCP receiver.

[0025] In some implementations, the PDCP control PDU includes a parameter that indicates the identifier of the first PDCP PDU to be discarded, which in such implementations is a PDCP PDU sequence number.

[0026] In some implementations, the PDCP control PDU includes multiple parameters indicating (i) an identifier of the first PDCP PDU to be discarded and (ii) an identifier of the last PDCP PDU to be discarded, where the identifier of the first PDCP PDU to be discarded is the first PDCP PDU sequence number and the identifier of the last PDCP PDU to be discarded is a different PDCP PDU sequence number.

[0027] In some implementations, the PDCP control PDU includes multiple parameters indicating (i) the number of discarded PDCP PDUs in the set of PDCP PDUs to be discarded and (ii) an identifier of a reference PDCP PDU in the set of PDCP PDUs to be discarded. In such implementations, the identifier is a PDCP PDU sequence number, and the reference PDCP PDU indicates either (i) the PDCP PDU for which discarding should be initiated or (ii) the PDCP PDU for which discarding should be stopped.

[0028] In some implementations, the PDCP control PDU includes parameters signaling sets of PDCP PDUs to be discarded, and in such implementations, the parameters signaling sets of PDCP PDUs include ranges of PDCP PDU sequence numbers corresponding to sequences of PDCP PDU sequences to be discarded.

[0029] In some implementations, the PDCP control PDU includes a parameter indicating a PDCP PDU set identifier that identifies a set of PDCP PDUs to be discarded.

[0030] In some implementations, the PDCP control PDU includes a parameter that indicates the number of PDCP PDUs that should be discarded but are still in transit.

[0031] In some implementations, the method can further include generating, by the PDCP transmitter, a different PDCP control PDU that indicates the number of PDCP PDUs that should be discarded but are in transit.

[0032] In some implementations, the PDCP control PDU is an extension of the PDCP status PDU.

[0033] In some implementations, the set of PDCP PDUs to be discarded have sequence numbers that are sequential.

[0034] According to another innovative aspect of the present disclosure, a method for notifying a Packet Data Convergence Protocol (PDCP) receiver of PDCP PDUs to be discarded is disclosed. In one aspect, the method includes the actions of determining, by a PDCP transmitter, a set of PDCP PDUs including one or more PDCP PDUs to be discarded, generating, by the PDCP transmitter, a discard bitmap signaling to the PDCP receiver that the determined PDCP PDUs should be discarded, the discard bitmap including a bitmap field for each PDCP PDU of a set of PDUs and having a toggle bit for each PDCP PDU of the PDCP PDU set to be discarded, and transmitting, by the PDCP transmitter, the generated discard bitmap to the PDCP receiver.

[0035] Other aspects include apparatuses, systems, and computer programs for performing the actions of the aforementioned methods.

[0036] The innovative method may include other optional features, such as, in some implementations, the determined set of PDCP PDUs to be discarded includes PDCP PDUs with non-consecutive sequence numbers.

[0037] In some implementations, the toggle bit for each PDCP PDU in the set of PDCP PDUs to be discarded is an enabled bit.

[0038] In some implementations, the toggle bit for each PDCP PDU in the set of PDCP PDUs to be discarded is a disabled bit.

[0039] In some implementations, the generated discard bitmap is transmitted to the PDCP receiver as a field in a PDCP status report PDU.

[0040] In some implementations, the generated discard bitmap is transmitted to the PDCP receiver as a field in a PDCP control PDU.

[0041] According to another innovative aspect of the present disclosure, a method for generating a discard bitmap report is disclosed. In one aspect, the method includes the actions of determining, by a PDCP receiver, that a subset of essential PDCP PDUs has been received from a set of PDCP PDUs, generating, by the PDCP receiver, a PDCP status report that indicates to the PDCP transmitter that the PDCP transmitter may discard remaining PDCP PDUs in the set of PDCP PDUs, and transmitting, by the PDCP receiver, the PDCP status report to the PDCP transmitter.

[0042] Other aspects include apparatuses, systems, and computer programs for performing the actions of the aforementioned methods.

[0043] The innovative method may include other optional features, for example, in some implementations, the PDCP status report includes a discard bitmap signaling to the PDCP transmitter that the remaining PDCP PDUs in a set of PDCP PDUs should be discarded, the discard bitmap including a bitmap field for each PDCP PDU in the set of PDCP PDUs and having a toggle bit for each remaining PDCP PDU set to be discarded by the PDCP transmitter.

[0044] In some implementations, the set of remaining PDCP PDUs includes PDCP PDUs with non-consecutive sequence numbers.

[0045] In some implementations, the toggle bit for each remaining PDCP PDU in the set of PDCP PDUs to be discarded is an enabled bit.

[0046] In some implementations, the toggle bit for each remaining PDCP PDU in the set of PDCP PDUs to be discarded is a disabled bit.

[0047] According to another innovative aspect of the present disclosure, a method for generating a discard bitmap report is disclosed. In one aspect, the method can include the actions of: determining, by a PDCP receiver, a subset of PDCP PDUs from a set of PDCP PDUs that have been locally discarded by the PDCP receiver; generating, by the PDCP receiver, a PDCP status report to a PDCP transmitter, the PDCP status report indicating the subset of PDCP PDUs that have been locally discarded by the PDCP receiver; and transmitting, by the PDCP receiver, the PDCP status report to the PDCP transmitter.

[0048] Other aspects include apparatuses, systems, and computer programs for performing the actions of the aforementioned methods.

[0049] The innovative method may include other optional features, for example, in some implementations, the PDCP status report includes a discard bitmap signaling to the PDCP transmitter that a subset of PDCP PDs have been locally discarded, the discard bitmap including a bitmap field for each PDCP PDU of the set of PDCP PDUs that has been locally discarded, and having a toggle bit for each PDCP PDU that has been locally discarded by the PDCP receiver.

[0050] In some implementations, the subset of PDCP PDUs locally discarded by the PDCP receiver includes PDCP PDUs with non-consecutive sequence numbers.

[0051] In some implementations, the toggle bit for each PDCP PDU that is locally discarded by the PDCP receiver is an enabled bit.

[0052] In some implementations, the toggle bit for each remaining PDCP PDU that is locally discarded by the PDCP receiver is a disabled bit.

[0053] According to another innovative aspect of the present disclosure, a method for implicitly determining PDCP PDU packets marked for discard is disclosed. In one aspect, the method can include detecting, by a PDCP receiver, that a first PDCP PDU set signals a last sequence number earlier than expected, detecting, by the PDCP receiver, that a second PDU set signals a first sequence number, and determining, by the PDCP receiver, that PDCP PDUs having sequence numbers between the last sequence number of the first PDCP PDU set and the first sequence number of the second PDU set should be discarded.

[0054] Other aspects include apparatuses, systems, and computer programs for performing the actions of the aforementioned methods.

[0055] According to another innovative aspect of the present disclosure, a method for implicitly indicating a PDCP PDU packet for discard is disclosed. In one aspect, the method can include determining, by a PDCP transmitter, that remaining PDCP PDUs in a PDU set should be discarded, and setting, by the PDCP transmitter, a last sequence number in the PDCP PDU set to the last actual PDCP PDU to be processed.

[0056] Other aspects include apparatuses, systems, and computer programs for performing the actions of the aforementioned methods.

[0057] The details of one or more embodiments of these systems and methods are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of these systems and methods will be apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0058] [Figure 1] 1 illustrates a wireless network according to some implementations.

[0059] [Figure 2] 10 is a flowchart of a process for notifying a PDCP receiver of a set of PDCP PDUs to be discarded using discard markers in a PDCP data PDU header.

[0060] [Figure 3] A figure showing an example of a PDCP control PDU format for PDCP discard status reporting.

[0061] [Figure 4]10 is a flowchart of a process for notifying a PDCP receiver of a set of PDCP PDUs to be discarded using a discard marker in a PDCP control PDU.

[0062] [Figure 5] 10 is a flowchart of a process for notifying a PDCP receiver of a set of PDCP PDUs to be discarded using a PDCP discard bitmap.

[0063] [Figure 5A] FIG. 10 is a diagram illustrating the fields of a discard bitmap.

[0064] [Figure 6] 10 is a flowchart of a PDCP receiver's process of notifying a PDCP transmitter that, after processing an essential PDCP PDU from a set of PDCP PDUs, the remaining PDCP PDUs in the set of PDCP PDUs can be discarded.

[0065] [Figure 7] 10 is a flowchart of a process of a PDCP receiver notifying a PDCP transmitter that a subset of PDCP PDUs of a PDCP set have been locally discarded by the PDCP receiver.

[0066] [Figure 8] FIG. 10 illustrates a description of the fields of a discard bitmap report.

[0067] [Figure 9] A figure showing an example of another PDCP control PDU format for PDCP discard status reporting.

[0068] [Figure 10] FIG. 1 illustrates a user equipment (UE) according to some implementations.

[0069] [Figure 11]FIG. 1 illustrates an access node according to some implementations. DETAILED DESCRIPTION OF THE INVENTION

[0070] The present disclosure provides multiple implementations for generating and transmitting to a PDCP receiver a discard marker (also called a discard indicator) that informs the PDCP receiver of PDCP PDUs that have been marked for discard and can be discarded by the PDCP receiver.

[0071] Thus, the discard markers of the present disclosure enable a PDCP transmitter to mitigate the need for a PDCP receiver to perform reordering operations (e.g., discarding PDCP PDUs marked for discard). Furthermore, because discarding PDCP PDUs by a PDCP transmitter can occur after the PDCP PDUs are encrypted or after the PDCP PDUs are transmitted to lower-level protocols, discarding PDUs is a computationally intensive task.

[0072] Another implementation provided by the present disclosure enables a PDCP receiver to generate and send discard feedback reports to a PDCP transmitter, which can be discarded by the PDCP receiver or can inform the PDCP transmitter of PDCP PDUs that have already been locally discarded, thus alleviating additional overhead processing by the PDCP transmitter related to PDCP PDUs that should be discarded or that have been locally discarded.

[0073] 1 illustrates a wireless network 100 according to some implementations. The wireless network 100 includes a UE 102 and a base station 104 connected via one or more channels 106A, 106B over an air interface 108. The UE 102 and the base station 104 communicate using a system that supports control for managing access of the UE 102 to the network via the base station 104.

[0074] In some implementations, the wireless network 100 may be a non-standalone (NSA) network incorporating Long Term Evolution (LTE) and Fifth Generation (5G) New Radio (NR) communication standards defined by the 3rd Generation Partnership Project (3GPP) technical specifications. For example, the wireless network 100 may be an Evolved Universal Terrestrial Radio Access (E-UTRA)-NR Dual Connectivity (EN-DC) network or an NR-EUTRA Dual Connectivity (NE-DC) network. However, the wireless network 100 may also be a standalone (SA) network incorporating only 5G NR. Additionally, other types of communication standards are possible, including future 3GPP systems (e.g., sixth-generation (6G)) systems, Institute of Electrical and Electronics Engineers (IEEE) 802.11 technologies (e.g., IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11-2007, IEEE 802.11n, IEEE 802.11-2012, IEEE 802.11ac, or other current or future-developed IEEE 802.11 technologies), IEEE 802.16 protocols (e.g., WMAN, WiMAX, etc.), etc. Although aspects may be described herein using terminology generally associated with 5G NR, aspects of the present disclosure may apply to other systems, such as systems subsequent to 3G, 4G, and / or 5G (e.g., 6G).

[0075] In wireless network 100, UE 102 and any other UEs in the system may be, for example, laptop computers, smartphones, tablet computers, machine-type devices such as smart meters or dedicated devices for healthcare, intelligent transportation systems, or any other wireless devices with or without a user interface. In network 100, base stations 104 provide UE 102 with network connectivity to a wider network (not shown). This UE 102 connectivity is provided over an air interface 108 within a base station service area provided by base station 104. In some implementations, such a wider network may be a wide area network operated by a cellular network provider or may be the Internet. Each base station service area associated with a base station 104 is supported by an antenna integrated with the base station 104. The service area is divided into multiple sectors associated with specific antennas. Such sectors may be physically associated with fixed antennas or may be assigned to a physical area using adjustable antennas or antenna settings in a beamforming process used to direct signals to specific sectors.

[0076] The UE 102 includes a control circuit 110 coupled to a transmit circuit 112 and a receive circuit 114. The transmit circuit 112 and the receive circuit 114 may each be coupled to one or more antennas. The control circuit 110 may include various combinations of application-specific and baseband circuitry. The transmit circuit 112 and the receive circuit 114 may be adapted to transmit and receive data, respectively, and may include radio frequency (RF) circuitry or front-end module (FEM) circuitry.

[0077] In various implementations, aspects of the transmit circuitry 112, the receive circuitry 114, and the control circuitry 110 may be integrated in various ways to implement the operations described herein. The control circuitry 110 may be adapted or configured to perform various operations, such as those described elsewhere in this disclosure related to a UE. By way of example, when the UE 102 is a PDCP receiver, the control circuitry 110 may perform operations related to determining that all mandatory PDUs of a PDU set have been processed and generate a discard bitmap report that provides an indication of the remaining discardable PDCP PDUs of the PDU set to the PDCP transmitter. These operations may include, for example, one or more of operations 610, 620 of FIG. 6. Similarly, when the UE 102 is a PDCP receiver, the control circuitry 110 may perform operations related to determining a set of PDCP PDUs that have been locally discarded by the PDCP receiver and generate a discard feedback report that indicates to the PDCP transmitter the PDCP PDUs that have been locally discarded by the PDCP receiver. These operations may include, for example, operations 710, 720 of FIG. 7.

[0078] As a different example, when UE 102 is a PDCP transmitter, control circuitry 110 can perform operations 210 and 220 of Figure 2, which determine a set of PDCP PDUs to be discarded and generate a discard marker in a PDCP header that signals to a PDCP receiver that the determined PDCP PDUs should be discarded. Similarly, when a PDCP transmitter, control circuitry 110 of UE 102 can perform operations 410 and 420 of Figure 4 by determining a set of PDCP PDUs to be discarded and generating a PDCP control PDU that includes one or more parameters that signal to a PDCP receiver that the determined PDCP PDUs should be discarded. Similarly, when a PDCP transmitter, control circuitry 110 can also perform operations 510 and 520 of Figure 5, which determine a set of PDCP PDUs that includes one or more PDCP PDUs to be discarded and generate a discard bitmap that signals to a PDCP receiver that the determined PDCP PDUs should be discarded.

[0079] The transmit circuitry 112 may perform various operations described herein. For example, when the UE is a PDCP transmitter, the transmit circuitry 112 may transmit a generated PDCP data PDU including a discard marker to a PDCP receiver, transmit a generated PDCP control PDU to a PDCP receiver, or transmit a generated discard bitmap to a PDCP receiver, e.g., as described in operations 230, 430, and 530 in Figures 2, 4, and 5, respectively. Furthermore, the transmit circuitry 112 may transmit multiple multiplexed uplink physical channels. The multiple uplink physical channels may be multiplexed by time division multiplexing (TDM) or frequency division multiplexing (FDM) with carrier aggregation. The transmit circuitry 112 may be configured to receive block data from the control circuitry 110 for transmission over the air interface 108.

[0080] The receiving circuitry 114 may perform various operations described herein. For example, when the UE 102 is a PDCP receiver, the UE 102 may receive a discard marker transmitted by a PDCP transmitter using the receiving circuitry 114. Similarly, when the UE 102 is a PDCP transmitter, the UE 102 may receive a discard bitmap report and a discard feedback report from the PDCP receiver using the receiving circuitry 114. Furthermore, the receiving circuitry 114 may receive multiple multiplexed downlink physical channels from the air interface 108 and relay the physical channels to the control circuitry 110. The multiple downlink physical channels may be multiplexed by TDM or FDM with carrier aggregation. The transmitting circuitry 112 and the receiving circuitry 114 may transmit and receive both control data and content data (e.g., messages, images, videos, etc.) structured within data blocks carried by the physical channels.

[0081] 1 also shows a base station 104. In implementations, the base station 104 may be an NG Radio Access Network (RAN) or 5G RAN, an E-UTRAN, a non-terrestrial cell, or a legacy RAN such as UTRAN or GERAN. As used herein, terms such as "NG RAN" may refer to a base station 104 operating in an NR or 5G wireless network 100, and terms such as "E-UTRAN" may refer to a base station 104 operating in an LTE or 4G wireless network 100. The UE 102 utilizes connections (or channels) 106A, 106B, each of which includes a physical communication interface or layer.

[0082] The base station 104 circuitry may include control circuitry 116 coupled to transmit circuitry 118 and receive circuitry 120. The transmit circuitry 118 and receive circuitry 120 may each be coupled to one or more antennas that may be used to enable communication over the air interface 108. The transmit circuitry 118 and receive circuitry 120 may be adapted to transmit and receive data, respectively, to any UE connected to the base station 104. The transmit circuitry 118 may transmit a downlink physical channel including multiple downlink subframes. Furthermore, for example, when the base station 104 is a PDCP transmitter, the base station can use the transmit circuitry 118 to perform operations in the nature of a PDCP transmitter, e.g., operations 230 of FIG. 2, 430 of FIG. 4, and 530 of FIG. 5. Alternatively, when the base station is a PDCP receiver, the base station 104 can use the transmit circuitry 118 to perform operations in the nature of a PDCP receiver, e.g., operations 630 of FIG. 6 and 730 of FIG. 7. The base station 104 may use the receiver circuitry 120 to receive multiple uplink physical channels from various UEs, including the UE 102. Additionally, when the base station 104 is a PDCP receiver, the base station 104 may receive discard markers transmitted from a PDCP transmitter. Furthermore, when the base station 104 is a PDCP transmitter, the base station 104 may use the receiver circuitry 120 to receive discard bitmap reports and discard feedback reports transmitted by the PDCP receiver using operation 630 of FIG. 6 and operation 730 of FIG. 7, respectively. Furthermore, when the base station 104 is a PDCP receiver, the base station 104 may use the control circuitry 116 to perform operations 610 and 620 of FIG. 6 and operations 710 and 720 of FIG. 7. Similarly, when the base station 104 is a PDCP transmitter, the base station 104 may use the control circuitry 116 to perform operations 210 and 220 of FIG. 2, 410 and 420 of FIG. 4, and 510 and 520 of FIG. 5.

[0083] In FIG. 1 , one or more channels 106A, 106B are depicted as air interfaces enabling a communicative coupling and may conform to a cellular communication protocol such as a GSM protocol, a CDMA network protocol, a UMTS protocol, a 3GPP LTE protocol, an Advanced Long Term Evolution (LTE-A) protocol, an LTE-based access to unlicensed spectrum (LTE-U), a 5G protocol, an NR protocol, an NR-based access to unlicensed spectrum (NR-U) protocol, and / or any of the other communication protocols described herein. In implementations, the UE 102 may directly exchange communication data over the ProSe interface. The ProSe interface may alternatively be referred to as a sidelink (SL) interface and may include one or more logical channels, including, but not limited to, a physical sidelink control channel (PSCCH), a physical sidelink control channel (PSCCH), a physical sidelink downlink channel (PSDCH), and a physical sidelink broadcast channel (PSBCH).

[0084] Discard Marker for Dynamic Signaling of Discarded PDCP PDUs

[0085] In some implementations where the PDUs in a PDU set are contiguous and a discard condition triggers at a particular SN within a sequence of PDUs in the PDU set, the remaining PDUs in the PDU set (assumed to be contiguous) can be interpreted as being scheduled for discard, which is, for example, one option and is in line with the current assumptions made by SA2 and RAN2.

[0086] In some implementations, a PDCP transmitter can indicate a discard indication, referred to herein as a discard marker, to a PDCP receiver. In some implementations, the discard marker is associated with the sequence number (SN) of the PDU to be discarded (e.g., the first PDU in the sequence). In some implementations, the discard marker can be a one-bit indicator.

[0087] In some implementations, the discard marker can be signaled, for example, using one of the reserved bits (R bits) in the data PDU header. Since data PDUs are typically associated with an SN anyway, the receiver can identify PDUs that are intended to be discarded. In implementations, when a data PDU cannot be used, a separate SN may be included along with the discard marker (e.g., in a control PDU).

[0088] The discard indication can serve either as a discard command from the sender to the receiver or as an indication of a PDU that has already been discarded at the sender, so that the receiver can minimize reordering delays or take advantage of the knowledge of this indication to further optimize its processing.

[0089] Scenario when the PDCP receiver is aware of the remaining PDUs in the PDU set

[0090] In some implementations, when the PDCP receiver knows the number of remaining PDUs in the PDU set (or can be derived by the receiver, for example, based on the size of the PDU set or another description or indication provided for the PDU set), the discard marker can be implemented in several different ways.

[0091] In some implementations, for example, the transmitter may signal a one-bit indication on the first PDU in a PDU set to be discarded or on the last actual PDU to be transmitted, after which subsequent PDUs in the PDU set are intended to be discarded as well.

[0092] In some implementations, a one-bit discard marker can be provided for one or more PDUs in a PDU set. For example, if the first PDU to be discarded is associated with, say, SN=555 (and, say, the last nominal SN in the PDU set is at SN=750), a discard marker may be sent either at, say, SN=555 (the first PDU to be discarded) or at, say, SN=554 (the last actual PDU in the PDU set).

[0093] In some implementations, the 1-bit discard marker can be repeated several times, e.g., to avoid loss of discard information. For example, the discard marker can be set at, e.g., SN=554, 555, 556, or a later time.

[0094] Scenario when the PDCP receiver is aware of the remaining PDUs in the PDU set

[0095] In some implementations, when the PDCP receiver does not know the number of remaining PDUs in a PDU set, the transmitter can send an additional discard marker using the SN of the last nominal PDU in the PDU set. This can be implemented in several ways.

[0096] For example, in some implementations, there may be at least two discard markers, one on the first SN to be discarded, e.g., SN=554 (or SN=555), and one on the last SN to be discarded in the PDU set, e.g., SN=750. The two SNs (e.g., 555 and 750) may also be transmitted immediately after SN=554, for example.

[0097] In other implementations, two bits (e.g., two adjacent reserved bits in the PDU header) may be used to encode first and last discard markers, for example, associated with the first and last SNs to be discarded.

[0098] Alternatively, or in addition, the transmitter may indicate the "number of PDCP PDUs that should be discarded together" (for consecutive PDUs). Thus, for example, if SN=555 is to be discarded, the transmitter may further indicate, for example, "195", and thus everything between 555 and 555+195 (=750) should be discarded.

[0099] Since the actual application layer data should be discarded, a discard marker (when given on the PDU SN that is to be discarded) may be sent on another empty PDU (with a little padding or dummy data, or without any content). Alternatively, a discard marker can be given on a control PDU.

[0100] In some implementations, some form of dynamic (in-band) signaling may be available in the PDU header that can identify the last SN in the PDU set. Thus, when the remaining PDUs in a PDU set are to be discarded, the transmitter can simply set its last SN indication earlier, e.g., to the last actual SN in the PDU set (e.g., SN=554). This is called, for example, an implicit discard indication or early termination of the PDU set.

[0101] In some implementations, when the next SN (e.g., SN=555) no longer carries the first PDU of the next PDU set, an explicit discard marker may not be required and reordering delay is naturally minimized.

[0102] For example, when the nominal number of PDUs in a PDU set is known to the receiver in advance (e.g., from semi-static signaling or through an indication in the PDU set descriptor (P55803)), or when a general PDU set description is signaled at the beginning of a PDU set, the last PDU in the PDU set can be indicated earlier than expected using normal end-of-PDU-set signaling already on the last actual SN. For example, the nominal number of PDUs in a PDU set is indicated as, e.g., 500 PDUs, but the transmitter has already signaled the end of the PDU set after, e.g., 260 PDUs. The same method may be used when the nominal number of PDUs in a PDU set is not known in advance. Furthermore, the normal start-of-PDU-set signaling of the next PDU set can be used to identify the next SN. By using the parameters in the packet header that describe the PDU set, it is possible to identify both the last SN before the gap and the first SN after the gap, assuming that PDU set 1 (with PDU set end signaling) is followed by PDU set 2 (with PDU set start signaling).

[0103] The above options depend on the final distribution between semi-static and dynamic (in-band) parameters that will be available for that PDU set. In some cases, immediate termination of a PDU set may be challenging for UE / gNB implementations, since it would mean that PDCP PDUs already submitted to lower layers (e.g., SN=555, 556-590) would have to be discarded in the lower layer queue before the same PDCP SN can be associated with a different PDU set. Therefore, a discard marker (or another form of discard signaling) may be considered. For example, a discard marker could be used to terminate a PDU set, for example, at SN=554. To take into account the PDUs already submitted to lower layers, the next PDU set could start immediately with the next SN (e.g., SN=591 in the above example), or with an SN depending on whatever number of PDUs have already been submitted to lower layers.

[0104] In another option, the transmitter may inform the receiver of packets that have expired (e.g., identified as to be discarded) but will continue to send, e.g., by indicating a PDU that was already submitted to the lower layer due to the above constraints. This may be done in a separate discard marker (with a new combination of R bits when two R bits are used), or in a separate PDCP control PDU, or by extending the PDCP data / control PDU with parameters to indicate these special packets, or even in a new RLC control PDU (since the number of packets is available in the RLC) or in the MAC CE.

[0105] The number of packets submitted to the lower layer may be implementation specific (pre-processing) or may depend on the discard timing. Therefore, the transmitter can determine this number. Alternatively, there may be a fixed value or a configuration (from the NW for the UE or operator configuration for the gNB) for setting such expired PDUs. In this case, separate signaling is not necessarily required.

[0106] Discard markers signaled using the PDCP data PDU header

[0107] In some implementations, a discard marker can be implemented in the PDCP data PDU header. The PDCP data PDU header option for signaling a discard marker can be implemented in either the uplink (UL) or downlink (DL).

[0108] In some implementations, R bits are available for all types of data PDUs, and one or two R bits may be used to signal a discard marker in the PDCP data PDU header.

[0109] Some implementations use one or two R bits to signal a discard marker, plus an extra parameter (e.g., "195" in the example above) to indicate the number of discarded PDUs. This option can be useful, for example, when the PDUs have already been submitted to lower layers (pre-processing) or when the nominal number of PDUs in a PDU set is not known to the PDCP receiver.

[0110] In some implementations, if the PDCP receiver knows the "PDU set identifiers," the PDCP transmitter can indicate only the identifiers of the PDU sets that should be discarded all together (if applicable). Thus, one or two R bits can be used to signal a discard marker, and additional parameters can be used to signal one or more PDU set identifiers. In some implementations, this option can be combined with the above implementation that uses an extra parameter to indicate the number of discarded PDUs.

[0111] In some implementations, two R bits can be used for the discard marker, where one R bit combination is used to indicate a preset number of PDUs that are intended to be discarded but are in transit. No other parameters are required other than the two-bit combination that indicates the type of discard marker.

[0112] In some implementations, the above options are combined with an additional parameter to indicate the number of discarded PDUs in transit.

[0113] 2 is a flowchart of a process 200 for notifying a PDCP receiver of a set of PDCP PDUs to be discarded using discard markers in PDCP data PDU headers. Process 200 is described herein as being performed by a PDCP transmitter that transmits the PDCP discard markers. For purposes of this disclosure, a PDCP receiver can be a UE or a base station that receives the PDCP PDUs. Similarly, a PDCP transmitter can be a UE or a base station that transmits the PDCP PDUs. Thus, communication between the PDCP transmitter and the PDCP receiver can be UE-to-base station communication, base station-to-UE communication, or UE-to-UE communication.

[0114] The PDCP transmitter may begin execution of process 200 by determining 210 a set of PDCP PDUs to be discarded.

[0115] The PDCP transmitter may continue execution of process 200 by generating a discard marker in the PDCP PDU header that signals to the PDCP receiver that the determined multiple PDCP PDUs should be discarded (220).

[0116] The PDCP transmitter may continue execution of process 200 by transmitting the generated PDCP PDU to the PDCP receiver (230).

[0117] In some implementations, the generated discard marker is in the PDCP PDU header of the first PDCP PDU by sequence number in the determined set of PDCP PDUs to be discarded, and in such implementations, the discard marker is a one-bit indication that (i) the first PDCP PDU by sequence number in the set of PDCP PDUs and (ii) the subsequent PDCP PDUs should be discarded by the PDCP receiver.

[0118] In some implementations, the generated discard marker is in the PDCP PDU header of the last non-to-be-discarded nominal PDCP PDU by sequence number that precedes the first PDCP PDU by sequence number in the determined set of PDCP PDUs to be discarded. In such implementations, the discard marker is a one-bit indication that the following PDCP PDUs by sequence number in the set of PDCP PDUs should be discarded by the PDCP receiver.

[0119] In some implementations, for each particular PDCP PDU in the set of PDCP PDUs to be discarded, the PDCP transmitter may continue executing process 200 by generating a one-bit discard marker in the PDCP PDU header of the particular PDCP PDU, signaling to the PDCP receiver that the particular PDCP PDU should be discarded.

[0120] In some implementations, the discard marker is a one-bit discard marker that signals to the PDCP receiver that (i) the PDCP PDU containing the one-bit discard marker should be discarded, or (ii) the subsequent PDCP PDUs by sequence number should be discarded.

[0121] In some implementations, the discard marker indicates a PDCP PDU set identifier of a set of PDCP PDUs to be discarded, hi some implementations, the set of PDCP PDUs to be discarded have sequence numbers that are consecutive in order.

[0122] In some implementations, the PDCP transmitter may continue execution of process 200 by sending the set of PDCP PDUs to be discarded to the PDCP receiver.

[0123] In some implementations, the generated discard marker is in the PDCP PDU header of the first PDCP PDU, signaling to the PDCP receiver the first PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded. In such implementations, the PCDP transmitter can continue execution of process 200 by generating a second discard marker in the last PDCP PDU of the determined set of PDCP PDUs to be discarded, signaling to the PDCP receiver the last PDCP PDU by sequence number of the determined PDCP PDUs to be discarded.

[0124] In some implementations, the generated discard marker is in the PDCP PDU header of the first PDCP PDU, signaling to the PDCP receiver the first PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded. In such implementations, the generated discard marker is in the PDCP PDU header of the last nominal PDCP PDU that is not to be discarded, by sequence number, before the first PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded, signaling to the PDCP receiver that the subsequent PDCP PDU by sequence number is the first PDCP PDU of the determined set of PDCP PDUs to be discarded. In such implementations, the PDCP transmitter can continue execution of process 200 by generating a second discard marker in the last PDCP PDU of the determined set of PDCP PDUs to be discarded, signaling to the PDCP receiver the last PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded.

[0125] In some implementations, the generated discard marker is in the PDCP PDU header of the first PDCP PDU by sequence number in the determined set of PDCP PDUs to be discarded, hi such implementations, the discard marker is a two-bit indication of (i) the sequence number of the first PDCP PDU in the set of PDCP PDUs to be discarded and (ii) the sequence number of the last PDCP PDU in the set of PDCP PDUs to be discarded.

[0126] In some implementations, the discard marker is a two-bit indication of (i) the sequence number of the first PDCP PDU in the set of PDCP PDUs to be discarded and (ii) the total number of subsequent PDCP PDUs to be discarded.

[0127] In some implementations, the PDCP PDU header is the header of a PDCP data PDU in the set of PDCP PDUs that is to be discarded.

[0128] In some implementations, the PDCP PDU header is the header of a PDCP PDU that is sent within a padded PDCP data PDU that contains no other content.

[0129] In some implementations, the discard marker includes a parameter that informs the PDCP receiver of the number of discarded PDCP PDUs in transit.

[0130] New PDCP Control PDU Option for Signaling Discard Markers

[0131] In some implementations, a discard marker can be implemented in a PDCP control PDU, which can be used to signal a discard marker in either the uplink (UL) or downlink (DL).

[0132] In some implementations, a new control PDU is provided for use as a discard marker control PDU (or PDCP discard status report). An example of the new discard marker control PDU 300 is shown in FIG. 3. The discard marker control PDU 300 may include fields indicating the data necessary to provide the PDCP discard reporting status for a discard operation. In some implementations, the PDU type 310 in octet 1 may be a new PDU type indicating that the PDCP control PDU 300 is used as a discard marker. The fields in octets 2 through 5 may be used to indicate the first discard sequence number or count (FDC) of one or more PDCP sequence number ranges. Optionally, the new discard marker control PDU 300 may be extended to include optional fields 320 and 330 if the new discard marker control PDU 300 is used to report a discard bitmap, for example, as described with respect to 5, 6, and 7.

[0133] The new discard marker control PDU can contain several different parameter options, which are not mutually exclusive and can be combined.

[0134] In some implementations, only one parameter is included in the discard marker control PDU, which may indicate, for example, the count / SN of the first PDU to be discarded.

[0135] In some implementations, two parameters can be included in the discard marker control PDU. In some implementations, the two parameters can include, for example, a) the count or SN of the first PDU to be discarded, and b) the count / SN of the last PDU to be discarded. In other embodiments, the two parameters can include, for example, a) the number of discarded PDUs in the PDU set, and b) a reference SN / count (to indicate the start or stop of discarding).

[0136] In some implementations, a variable format with multiple sets of discarded SN / counts can be indicated, where each SN set is in order within itself but can indicate multiple blocks of SN / counts. This implementation can be based on any of the implementations described above related to the new discard marker control PDU.

[0137] In some implementations, any of the above / below options related to the new discard marker control PDU can be combined with a parameter to indicate one (or more) PDU set identifiers.

[0138] In some implementations, a separate discard marker control PDU can be used to indicate a pre-configured number of PDUs that are intended to be discarded but are in transit.

[0139] In some implementations, any of the above options for the discard marker control PDU can be combined with an additional parameter to indicate the number of discarded PDUs in transit.

[0140] In some implementations, an extension of the existing PDCP Status PDU (eg, using one of the implementations described above) can be used for the new Discard Marker Control PDU.

[0141] In some implementations, a discard marker control PDU can be used when PDUs are discarded consecutively or partially consecutively (in multiple blocks). In principle, a PDCP receiver considers the last PDU before the discard and the next PDU after the discard to be in order. Upon receiving discard marker signaling, the PDCP receiver can also eliminate the SN gap using one of the methods in solutions 2 or 3. The PDCP receiver can update the reordering window using the new parameters. If necessary, the PDCP receiver may use that information to update (existing) PDCP status variables accordingly.

[0142] 4 is a flowchart of a process 400 for notifying a PDCP receiver of a set of PDCP PDUs to be discarded using discard markers in a PDCP control PDU. Process 400 is described herein as being performed by a PDCP transmitter that transmits the PDCP discard markers. For purposes of this disclosure, a PDCP receiver can be a UE or a base station that receives the PDCP PDUs. Similarly, a PDCP transmitter can be a UE or a base station that transmits the PDCP PDUs. Thus, communication between the PDCP transmitter and the PDCP receiver can be UE-to-base station communication, base station-to-UE communication, or UE-to-UE communication.

[0143] The PDCP transmitter can perform process 400 by determining 410 a set of PDCP PDUs to be discarded.

[0144] The PDCP transmitter may continue execution of process 400 by generating 420 a PDCP control PDU that includes one or more parameters signaling to the PDCP receiver that the determined plurality of PDCP PDUs should be discarded.

[0145] The PDCP transmitter may continue execution of process 400 by transmitting the generated PDCP control PDU to the PDCP receiver (430).

[0146] In some implementations, the PDCP transmitter may continue execution of process 400 by sending the set of PDCP PDUs to be discarded to the PDCP receiver.

[0147] In some implementations, the PDCP control PDU may include a parameter indicating an identifier of the first PDCP PDU to be discarded, which, in such implementations, is a PDCP PDU sequence number.

[0148] In some implementations, the PDCP control PDU may include multiple parameters indicating (i) the identifier of the first PDCP PDU to be discarded and (ii) the identifier of the last PDCP PDU to be discarded, where the identifier of the first PDCP PDU to be discarded is the first PDCP PDU sequence number and the identifier of the last PDCP PDU to be discarded is a different PDCP PDU sequence number.

[0149] In some implementations, the PDCP control PDU may include multiple parameters indicating (i) the number of discarded PDCP PDUs in the set of PDCP PDUs to be discarded and (ii) an identifier of a reference PDCP PDU in the set of PDCP PDUs to be discarded. In such implementations, the identifier is a PDCP PDU sequence number, and the reference PDCP PDU indicates either (i) the PDCP PDU for which discarding should be initiated or (ii) the PDCP PDU for which discarding should be stopped.

[0150] In some implementations, a PDCP control PDU may include multiple parameters signaling multiple sets of PDCP PDU sets that are to be discarded.

[0151] In some implementations, the parameters signaling the sets of PDCP PDUs may include ranges of PDCP PDU sequence numbers corresponding to sequences of PDCP PDU sequences that are to be discarded.

[0152] In some implementations, the PDCP control PDCU may include a parameter indicating a PDCP PDU set identifier that identifies the PDCP PDU set that is to be discarded.

[0153] In some implementations, the PDCP control PDU may include a parameter that indicates the number of PDCP PDUs that should be discarded but are still in transit.

[0154] In some implementations, the PDCP transmitter can continue execution of process 400 by generating a different PDCP control PDU that indicates the number of PDCP PDUs that should be discarded but are still in transit.

[0155] In some implementations, the PDCP control PDU is an extension of the PDCP status PDU.

[0156] In some implementations, the set of PDCP PDUs to be discarded have sequence numbers that are sequential.

[0157] PDCP Discard Bitmap

[0158] There may be a mode in which a PDU set can be considered complete when a defined or configured amount (or percentage) of the PDUs in the PDU set are acknowledged as successfully transmitted on the lower layer (e.g., HARQ ACKed). When all such "required" PDUs / SNs have been received, the transmitter can notify the receiver using a PDCP status report (or PDCP discard report). The status report informs the receiver of the PDUs intended to be discarded at the transmitter. The receiver can use this information to minimize reordering delays.

[0159] Furthermore, the triggers for such discarding of PDUs are specific to XR, and several conditions can lead to the discarding of a PDU set or part of a PDU set.

[0160] However, in the above example, not all of the PDUs to be discarded are in order. To identify such "sparse" PDUs / SNs, a discard bitmap can be provided in the PDCP Status Report / PDCP Discard Report. The discard bitmap has a similar format to the existing bitmap in the PDCP Status Report, but uses, for example, a bitmap field to set (or not set) a bit for all discarded PDUs. An example of such a discard bitmap is shown in Figure 5.

[0161] In some implementations, using discard markers in PDCP data PDU headers or new PDCP control PDUs may not be optimal or applicable for minimizing reordering delay when discarded PDUs are out of order. Instead, a PDCP receiver can store a discard bitmap and selectively skip those discarded PDUs as part of the reordering process (by introducing no latency and considering all last PDUs before the discard and all next PDUs after the discard as in order). Such behavior is somewhat more complicated. PDCP receivers can handle this based on the implementation, but the protocol may still need to define a bitmap and have procedural text that indicates the receiver uses the discard bitmap to minimize reordering delay.

[0162] A discard bitmap, such as discard bitmap 500A of Figure 5A, can be used by a PDCP transmitter to inform a PDCP receiver of multiple discarded PDUs (including cases where the discarded PDUs are not necessarily in order). The discard bitmap can be a new field in a PDCP status report, such as one or more optional fields 320, 330 of PDCP control PDU 300. Alternatively, a separate PDCP status report (or control PDU) is used for discard reporting.

[0163] 3, the PDCP control PDU may have one or more First Discard Count (FDC) fields for the PDCP Status Report. In some implementations, each of the one or more FDC fields may have a length of 32 bits. Each FDC field may indicate a count value of the SN of the first discarded PDCP SDU in a PDU set at the PDCP transmitter.

[0164] Each discard bitmap, such as discard bitmap 500A in Figure 5A, can have a variable length. In some implementations, the length of the discard bitmap field can be zero.

[0165] Each field in the discard bitmap 500A indicates which SDUs are to be discarded and which SDUs are to be transmitted / processed correctly at the transmitting PDCP entity. The bit position of the Nth bit in the discard bitmap is N, i.e., the bit position of the first bit in the bitmap is 1. In some implementations, a bit corresponding to a PDCP PDU may be set or enabled when the bit is toggled to a value of "1." Otherwise, a bit corresponding to a PDCP PDU may not be set or disabled when the bit is toggled to a value of "0."

[0166] 5 is a flowchart of a process 500 for notifying a PDCP receiver of a set of PDCP PDUs to be discarded using a PDCP discard bitmap. Process 500 is described herein as being performed by a PDCP transmitter that transmits a PDCP discard marker. For purposes of this disclosure, a PDCP receiver can be a UE or a base station that receives a PDCP PDU. Similarly, a PDCP transmitter can be a UE or a base station that transmits a PDCP PDU. Thus, communication between a PDCP transmitter and a PDCP receiver can be UE-to-base station communication, base station-to-UE communication, or UE-to-UE communication.

[0167] The PDCP transmitter may begin execution of process 500 by determining 510 a set of PDCP PDUs that includes one or more PDCP PDUs to be discarded.

[0168] The PDCP transmitter may continue execution of process 500 by generating a discard bitmap signaling to the PDCP receiver that the determined PDCP PDUs should be discarded, the discard bitmap including a bitmap field for each PDCP PDU in a PDU set and having a toggle bit for each PDCP PDU in the PDCP PDU set that should be discarded (520).

[0169] The PDCP transmitter may continue execution of process 500 by transmitting the generated discard bitmap to the PDCP receiver (530).

[0170] In some implementations, the determined set of PDCP PDUs to be discarded includes PDCP PDUs with non-consecutive sequence numbers.

[0171] In some implementations, the toggle bit for each PDCP PDU in the set of PDCP PDUs to be discarded is an enabled bit.

[0172] In some implementations, the toggle bit for each PDCP PDU in the set of PDCP PDUs to be discarded is a disabled bit.

[0173] In some implementations, the generated discard bitmap is transmitted to the PDCP receiver as a field in a PDCP status report PDU.

[0174] In some implementations, the generated discard bitmap is transmitted to the PDCP receiver as a field in a PDCP control PDU.

[0175] PDCP discard bitmap reporting by a PDCP receiver after processing a mandatory PDCP PDU

[0176] In some implementations, there may be a mode in which a PDU set can be considered complete when a defined or set amount (or percentage) of PDUs in the PDU set have been received. Once all such "required" PDUs / SNs have been received, the receiver can notify the transmitter using a PDCP status report / PDCP discard report. The status report informs the receiver of the PDUs intended to be discarded at the transmitter. The PDCP transmitter may then discard the remaining PDUs in the PDU set. Note that not all PDUs to be discarded may be in order. A bitmap may also be provided in the PDCP status report to identify such "sparse" PDUs. In other words, this function may simply respond to an existing status report for acknowledgment. Such a status report is triggered once all "required" SNs have been received. Alternatively, a new PDCP discard status report may be used.

[0177] Note, however, that not all PDUs to be discarded may be in order. To identify such "sparse" PDUs, a bitmap may be provided in a PDCP status report, such as PDCP Control PDU 900. In other words, this function may simply respond to an existing status report for acknowledgment. Such a status report is triggered once all "required" SNs have been received. Alternatively, a new PDCP discard status report may be used.

[0178] More specifically, another example of a new discard marker control PDU 900 is shown in FIG. 9. The discard marker control PDU 900 may include fields indicating data necessary to provide the PDCP discard reporting status for a discard operation. In some implementations, the PDU type 910 in octet 1 may be a new PDU type indicating that the new PDCP control PDU 900 is used as a discard marker. The fields in octets 2 through 5 may be used for a count or SN of the first discarded PDCP PDU within a reordering window at the PDCP receiver. Optionally, the new discard marker control PDU 900 may be extended to include optional fields 920 and 930 if the new discard marker control PDU 900 is used to report a discard bitmap, for example, as described with respect to FIG. 6 or FIG. 7.

[0179] 9, a PDCP control PDU 900 can have one or more First Discard Count Reports (FDCRs). In some implementations, the FDCR field has a length of 32 bits. The FDCR field can indicate a count value of the first discarded PDCP SDUs within a reordering window at the receiver.

[0180] Each discard bitmap report 800 can have a variable length. In some implementations, the length of the discard bitmap field can be zero.

[0181] Each field in the discard bitmap report 800 indicates which SDUs are discarded and which are correctly received / processed at the receiving PDCP entity. The bit position of the Nth bit in the discard bitmap report 800 is N, i.e., the bit position of the first bit in the discard bitmap report is 1.

[0182] In some implementations, a discard bitmap report, such as discard bitmap report 800 of Figure 8, can be used by a PDCP receiver to notify a PDCP transmitter of multiple discarded PDUs (including cases where the discarded PDUs are not necessarily in order). Discard bitmap report 800 can be a new field within a PDCP status report, such as one or more optional fields 920, 930 of PDCP control PDU 900. Alternatively, a separate PDCP status report (or control PDU) is used for discard reporting.

[0183] 6 is a flowchart of a process 600 of a PDCP receiver that, after processing a mandatory PDCP PDU from a set of PDCP PDUs, notifies a PDCP transmitter that the remaining PDCP PDUs in the set of PDCP PDUs can be discarded. Process 600 is described herein as being performed by a PDCP receiver that sends a discard bitmap report. For purposes of this disclosure, a PDCP receiver can be a UE or a base station that receives PDCP PDUs. Similarly, a PDCP transmitter can be a UE or a base station that transmits PDCP PDUs.

[0184] A PDCP receiver may begin execution of process 600 by determining that a subset of essential PDCP PDUs has been received from a set of PDCP PDUs (610).

[0185] The PDCP receiver may continue execution of process 600 by generating a PDCP status report that indicates to the PDCP sender that the PDCP sender may discard the remaining PDCP PDUs in the set of PDCP PDUs (620).

[0186] The PDCP receiver may continue execution of process 600 by sending a PDCP status report to the PDCP transmitter (630).

[0187] In some implementations, the PDCP status report may include a discard bitmap signaling to the PDCP transmitter that the remaining PDCP PDUs in a set of PDCP PDUs should be discarded, the discard bitmap including a bitmap field for each PDCP PDU in the set of PDCP PDUs and having a toggle bit for each remaining PDCP PDU set that should be discarded by the PDCP transmitter.

[0188] In some implementations, the set of remaining PDCP PDUs includes PDCP PDUs with non-consecutive sequence numbers.

[0189] In some implementations, the toggle bit for each remaining PDCP PDU in the set of PDCP PDUs to be discarded is an enabled bit.

[0190] In some implementations, the toggle bit for each remaining PDCP PDU in the set of PDCP PDUs to be discarded is a disabled bit.

[0191] PDCP discard feedback reporting by a PDCP receiver to report locally discarded PDCP PDUs

[0192] In some implementations, if the PDCP receiver needs to inform the PDCP transmitter of any PDUs that have been discarded locally at the PDCP receiver, the PDCP receiver can send a feedback report to the PDCP transmitter.

[0193] For example, a PDCP receiver may generate and send such a discard feedback report to provide feedback as a result of dedicated discard rules that may be configured in the receiver or that may be dynamically applied. As another example, a PDCP receiver may generate and provide such a discard feedback report after reordering that involves PDU discarding. Alternatively, or additionally, a PDCP receiver may generate and send a discard feedback report when another layer (or the PDCP layer itself) requests the discarding of a complete PDU set or the discarding of remaining PDUs in a PDU set.

[0194] In some implementations, it is assumed that PDUs to be discarded may not be in order, and a discard bitmap may be provided in the PDCP status report / PDCP discard report to identify such "sparse" PDUs / SNs. In some implementations, the discard bitmap has a similar format to the existing bitmap in the PDCP status report, but uses a bitmap field to set (or not set) a bit for every discarded PDU, for example. An example of a bitmap report that can be used for discard feedback reporting is shown in Figure 8, and an example of a PDCP control PDU that can be used to send the bitmap feedback report is shown in Figure 9.

[0195] 7 is a flowchart of a process 700 of a PDCP receiver notifying a PDCP transmitter that a subset of PDCP PDUs of a PDCP set have been locally discarded by the PDCP receiver. Herein, process 700 is described as being performed by the PDCP receiver sending a discard feedback report. For purposes of this disclosure, a PDCP receiver can be a UE or a base station that receives PDCP PDUs. Similarly, a PDCP transmitter can be a UE or a base station that transmits PDCP PDUs.

[0196] The PDCP receiver may begin execution of process 700 by determining 710 a subset of PDCP PDUs from a set of PDCP PDUs that have been locally discarded by the PDCP receiver.

[0197] The PDCP receiver may continue execution of process 700 by generating a PDCP status report that indicates to the PDCP transmitter the subset of PDCP PDUs that were locally discarded by the PDCP receiver (720).

[0198] The PDCP receiver may continue execution of process 700 by sending a PDCP status report to the PDCP transmitter (730).

[0199] In some implementations, the PDCP status report may include a discard bitmap signaling to the PDCP transmitter that a subset of PDCP PDs have been locally discarded, the discard bitmap including a bitmap field for each PDCP PDU that has been locally discarded out of the set of PDCP PDUs, and having a toggle bit for each PDCP PDU that has been locally discarded by the PDCP receiver.

[0200] In some implementations, the subset of PDCP PDUs locally discarded by the PDCP receiver includes PDCP PDUs with non-consecutive sequence numbers.

[0201] In some implementations, the toggle bit for each PDCP PDU that is locally discarded by the PDCP receiver is an enabled bit.

[0202] In some implementations, the toggle bit for each remaining PDCP PDU that is locally discarded by the PDCP receiver is a disabled bit.

[0203] 10 illustrates a UE 1000 according to some implementations. The UE 1000 may be similar to and substantially interchangeable with the UE 102 of FIG.

[0204] The UE1000 may be any mobile or non-mobile computing device, such as a mobile phone, a computer, a tablet, an industrial wireless sensor (e.g., a microphone, a pressure sensor, a thermometer, a motion sensor, an accelerometer, an inventory sensor, a voltage / current meter, etc.), a video device (e.g., a camera, a video camera, etc.), a wearable device (e.g., a smart watch), a relaxed-IoT device, etc.

[0205] The UE 1000 may include a processor 1002, an RF interface circuit 1004, memory / storage 1006, a user interface 1008, sensors 1010, a driver circuit 1012, a power management integrated circuit (PMIC) 1014, an antenna structure 1016, and a battery 1018. The components of the UE 1000 may be implemented as an integrated circuit (IC), portions thereof, separate electronic devices or other modules, logic, hardware, software, firmware, or a combination thereof. The block diagram of FIG. 10 is intended to illustrate a high-level view of some of the components of the UE 1000. However, some of the components shown may be omitted, additional components may be present, and different arrangements of the components shown may occur in other embodiments.

[0206] The components of the UE 1000 may be coupled to various other components via one or more interconnects 1020, which may represent any type of interface, input / output, bus (local, system or expansion), transmission line, trace, optical connection, etc. that may allow various circuit components (on a common or different chips or chipsets) to interact with one another.

[0207] The processor 1002 may include processor circuitry such as, for example, a baseband processor circuit (BB) 1022A, a central processing unit circuit (CPU) 1022B, and a graphics processing unit circuit (GPU) 1022C. The processor 1002 may include any type of circuitry or processor circuitry that executes or otherwise operates computer-executable instructions, such as program code, software modules, or functional processes from memory / storage 1006 to cause the UE 1000 to perform the operations described herein.

[0208] In some implementations, the baseband processor circuit 1022A may access a communications protocol stack 1024 in the memory / storage 1006 to communicate over a 3GPP-compliant network. Generally, the baseband processor circuit 1022A may access the communications protocol stack to perform user plane functions at the physical (PHY) layer, medium access control (MAC) layer, radio link control (RLC) layer, packet data convergence protocol (PDCP) layer, service data adaptation protocol (SDAP) layer, and PDU layer, and control plane functions at the PHY layer, MAC layer, RLC layer, PDCP layer, RRC layer, and non-access layer. In some implementations, PHY layer operations may additionally or alternatively be performed by components of the RF interface circuit 1004. The baseband processor circuit 1022A may generate or process baseband signals or waveforms that carry information within a 3GPP-compliant network. In some implementations, waveforms for NR may be based on cyclic prefix orthogonal frequency division multiplexing (OFDM) "CP-OFDM" in the uplink or downlink and discrete Fourier transform spread OFDM "DFT-S-OFDM" in the uplink.

[0209] The memory / storage 1006 may include one or more non-transitory computer-readable media (e.g., communication protocol stack 1024) that include instructions that may be executed by one or more of the processors 1002 to cause the UE 1000 to perform various operations described herein. The memory / storage 1006 includes any type of volatile or non-volatile memory that may be distributed throughout the UE 1000. In some implementations, some of the memory / storage 1006 may be located within the processor 1002 itself (e.g., L1 and L2 caches), while other memory / storage 1006 is external to the processor 1002 but accessible via a memory interface. The memory / storage 1006 may include any suitable volatile or non-volatile memory, such as, but not limited to, dynamic random access memory (DRAM), static random access memory (SRAM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory, or any other type of memory device technology.

[0210] The RF interface circuitry 1004 may include transmit / receive circuitry and a radio frequency front end module (RFEM) that enable the UE 1000 to communicate with other devices over a radio access network. The RF interface circuitry 1004 may include various elements disposed in the transmit or receive paths. These elements may include, for example, switches, mixers, amplifiers, filters, combiner circuits, control circuits, etc.

[0211] In the receive path, the RFEM may receive a radiated signal from the air interface via the antenna structure 1016 and proceed to filter and amplify the signal (using a low noise amplifier). The signal may be provided to a receiver in the transceiver, which downconverts the RF signal to a baseband signal, which is provided to a baseband processor in the processor 1002.

[0212] In the transmit path, the transmitter of the transceiver upconverts baseband signals received from the baseband processor and provides an RF signal to the RFEM, which may amplify the RF signal through a power amplifier before the signal is radiated over the air interface via the antenna 1016. In various implementations, the RF interface circuitry 1004 may be configured to transmit and receive signals in a manner that is compliant with NR access technologies.

[0213] The antenna 1016 may include antenna elements that convert electrical signals into radio waves that travel through the air and convert received radio waves into electrical signals. The antenna elements may be arranged in one or more antenna panels. The antenna 1016 may have antenna panels that are omnidirectional, directional, or a combination thereof to enable beamforming and multiple-input, multiple-output communications. The antenna 1016 may include microstrip antennas, printed antennas fabricated on the surface of one or more printed circuit boards, patch antennas, phased array antennas, etc. The antenna 1016 may have one or more panels designed for a specific frequency band, including bands in FR1 or FR2.

[0214] User interface circuitry 1008 includes various input / output (I / O) devices designed to enable user interaction with UE 1000. User interface 1008 includes input device circuitry and output device circuitry. Input device circuitry includes any physical or virtual means for accepting input, including, among others, one or more physical or virtual buttons (e.g., a reset button), a physical keyboard, a keypad, a mouse, a touchpad, a touchscreen, a microphone, a scanner, a headset, etc. Output device circuitry includes any physical or virtual means for displaying or otherwise communicating information, such as sensor readings, actuator position(s), or other similar information. The output device circuitry may include any number or combination of audio or visual displays, including, among others, one or more simple visual outputs / indicators (e.g., binary status indicators such as light emitting diodes "LEDs" and multi-character visual outputs), or more complex outputs such as display devices or touch screens (e.g., liquid crystal displays "LCDs," LED displays, quantum dot displays, projectors, etc.), including text, graphics, multimedia objects, and the like, generated or created from operation of the UE1000.

[0215] The sensor 1010 may include a device, module, or subsystem intended to detect events or changes in its environment and transmit information about the detected events (sensor data) to some other device, module, subsystem, etc. Examples of such sensors include, among others, inertial measurement units including accelerometers, gyroscopes, or magnetometers, microelectromechanical or nanoelectromechanical systems including 3-axis accelerometers, 3-axis gyroscopes, or magnetometers, level sensors, temperature sensors (e.g., thermistors), pressure sensors, image capture devices (e.g., cameras or lensless apertures), light detection and ranging sensors; proximity sensors (e.g., infrared detectors, etc.); depth sensors; ambient light sensors; ultrasonic transceivers; microphones or other similar audio capture devices; and the like.

[0216] The driver circuit 1012 may include software and hardware elements that operate to control particular devices embedded in, attached to, or otherwise communicatively coupled to the UE 1000. The driver circuit 1012 may include individual drivers that enable other components to interact with or control various input / output (I / O) devices that may be present in or connected to the UE 1000. For example, the driver circuit 1012 may include a display driver that controls and enables access to a display device, a touchscreen driver that controls and enables access to a touchscreen interface, a sensor driver that obtains sensor readings of the sensor circuit 1010 and controls and enables access to the sensor circuit 1010, a driver that obtains actuator positions of or controls and enables access to electromechanical components, a camera driver that controls and enables access to an embedded image capture device, and an audio driver that controls and enables access to one or more audio devices.

[0217] The PMIC 1014 may manage the power provided to various components of the UE 1000. In particular, with respect to the processor 1002, the PMIC 1014 may control power source selection, voltage scaling, battery charging, or DC-DC conversion.

[0218] In some implementations, the PMIC 1014 may control or otherwise be a part of various power saving mechanisms of the UE 1000. The battery 1018 may power the UE 1000, although in some examples, the UE 1000 may be mounted and deployed at a fixed location and may have a power source coupled to an electrical grid. The battery 1018 may be a lithium-ion battery, a metal-air battery such as a zinc-air battery, an aluminum-air battery, a lithium-air battery, or the like. In some implementations, such as in vehicle-based applications, the battery 1018 may be a typical automotive lead-acid battery.

[0219] 11 illustrates an access node 1100 (e.g., a base station or a gNB) according to some implementations. The access node 1100 may be similar to, and substantially interchangeable with, the base station 104. The access node 1100 may include a processor 1102, RF interface circuitry 1104, a core network (CN) interface circuitry 1106, memory / storage circuitry 1108, and an antenna structure 1110.

[0220] The components of the access node 1100 may be coupled to various other components via one or more interconnects 1112. The processor 1102, RF interface circuitry 1104, memory / storage circuitry 1108 (including communication protocol stack 1114), antenna structure 1110, and interconnect 1112 may be similar to the like-named elements shown and described with respect to Figure 10. For example, the processor 1102 may include processor circuits such as a baseband processor circuit (BB) 1116A, a central processing unit circuit (CPU) 1116B, and a graphics processing unit circuit (GPU) 1116C.

[0221] The CN interface circuit 1106 may provide connectivity to a core network, e.g., a 5th Generation Core network (5GC), using a 5GC-compliant network interface protocol, such as a Carrier Ethernet protocol or some other suitable protocol. Network connectivity may be provided to / from the access node 1100 via optical fiber or wireless backhaul. The CN interface circuit 1106 may include one or more dedicated processors or FPGAs for communicating using one or more of the aforementioned protocols. In some implementations, the CN interface circuit 1106 may include multiple controllers to provide connectivity to other networks using the same or different protocols.

[0222] As used herein, terms such as “access node,” “access point,” and the like may describe equipment that provides wireless baseband functionality for data and / or voice connectivity between a network and one or more users. These access nodes may be referred to as BSs, gNBs, RAN nodes, eNBs, NodeBs, RSUs, TRxPs, or TRPs, and may include terrestrial stations (e.g., terrestrial access points) or satellite stations that provide coverage within a geographic area (e.g., a cell). As used herein, terms such as “NG RAN node” may refer to an access node 1100 operating in an NR or 5G system (e.g., gNB), and terms such as “E-UTRAN node” may refer to an access node 1100 operating in an LTE or 4G system (e.g., eNB). According to various implementations, the access node 1100 may be implemented as one or more of dedicated physical devices, such as a macrocell base station, and / or a low power (LP) base station for providing a femtocell, picocell, or other similar cell having a smaller coverage area, lower user capacity, or higher bandwidth compared to a macrocell.

[0223] In some implementations, all or a portion of the access node 1100 may be implemented as one or more software entities running on a server computer as part of a virtual network, which may be referred to as a CRAN and / or a virtual baseband unit pool (vBBUP). In a V2X scenario, the access node 1100 may be or operate as a “roadside unit.” The term “roadside unit” or “RSU” may refer to any transportation infrastructure entity used for V2X communications. An RSU may be implemented in or by an appropriate RAN node or a stationary (or relatively stationary) UE; an RSU implemented in or by a UE may be referred to as a “UE-type RSU,” an RSU implemented in or by an eNB may be referred to as an “eNB-type RSU,” an RSU implemented in or by a gNB may be referred to as a “gNB-type RSU,” etc.

[0224] In the description herein, for convenience, various components may be described as performing a task or tasks. Such descriptions should be construed to include the phrase "configured to." It is expressly intended that a description of a component being configured to perform one or more tasks does not invoke 35 U.S.C. 112(f) interpretation with respect to that component. Other embodiments

[0225] While certain embodiments of the present disclosure have been described, other embodiments are within the scope of the following claims. For example, the steps recited in the claims, or any of the processes described herein, can be combined, performed in a different order, or both, and still achieve desirable results.

Claims

1. 1. A method for notifying a Packet Data Convergence Protocol (PDCP) receiver of a PDCP PDU to be discarded, comprising: determining, by a PDCP transmitter, a set of PDCP PDUs to be discarded; generating, by the PDCP transmitter, discard markers in PDCP PDU headers that signal to a PDCP receiver that the determined PDCP PDUs should be discarded; transmitting the generated PDCP PDU by the PDCP transmitter to a PDCP receiver; A method comprising:

2. the generated discard marker is in a PDCP PDU header of a first PDCP PDU, determined by a sequence number, in the set of PDCP PDUs to be discarded; The method of claim 1.

3. the discard marker is a one-bit indication that (i) the first PDCP PDU and (ii) subsequent PDCP PDUs according to sequence numbers within the set of PDCP PDUs should be discarded by the PDCP receiver. The method of claim 2.

4. the generated discard marker is in a PDCP PDU header of a last nominal PDCP PDU that should not be discarded, based on a sequence number, before a first PDCP PDU, based on a sequence number, in the set of PDCP PDUs that have been determined to be discarded; The method of claim 1.

5. the discard marker is a one-bit indication that a subsequent PDCP PDU by that sequence number within the set of PDCP PDUs should be discarded by the PDCP receiver. The method of claim 4.

6. For each particular PDCP PDU of the set of PDCP PDUs to be discarded: generating, by the PDCP transmitter, a one-bit discard marker in a PDCP PDU header of the particular PDCP PDU, signaling to a PDCP receiver that the particular PDCP PDU should be discarded. The method of claim 1.

7. 2. The method of claim 1, wherein the discard marker is a one-bit discard marker that signals to a PDCP receiver that (i) a PDCP PDU containing the one-bit discard marker should be discarded, or (ii) subsequent PDCP PDUs by sequence number should be discarded.

8. The method of claim 1 , wherein the discard marker indicates a PDCP PDU set identifier of the set of PDCP PDUs to be discarded.

9. transmitting the set of PDCP PDUs to be discarded by the PDCP transmitter to the PDCP receiver. The method of claim 1.

10. The method of claim 1 , wherein the set of PDCP PDUs to be discarded have sequentially consecutive sequence numbers.

11. signaling to the PDCP receiver a first PDCP PDU by a sequence number of the determined set of PDCP PDUs to be discarded, the first PDCP PDU being in a PDCP PDU header of the first PDCP PDU; The method comprises: generating, by the PDCP transmitter, a second discard marker in a last PDCP PDU of the determined set of PDCP PDUs to be discarded, the second discard marker signaling to a PDCP receiver a last PDCP PDU by sequence number among the determined set of PDCP PDUs to be discarded. The method of claim 1.

12. signaling to the PDCP receiver a first PDCP PDU by a sequence number of the determined set of PDCP PDUs to be discarded, the first PDCP PDU being in a PDCP PDU header of the first PDCP PDU; signaling to a PDCP receiver that the generated discard marker is in a PDCP PDU header of a last nominal PDCP PDU with a sequence number that should not be discarded before a first PDCP PDU with a sequence number in the determined set of PDCP PDUs that should be discarded, and that a subsequent PDCP PDU with a sequence number is the first PDCP PDU in the determined set of PDCP PDUs that should be discarded; The method comprises: generating, by the PDCP transmitter, a second discard marker in a last PDCP PDU of the determined set of PDCP PDUs to be discarded, the second discard marker signaling to a PDCP receiver the last PDCP PDU by sequence number of the determined set of PDCP PDUs to be discarded. The method of claim 1.

13. the generated discard marker is in a PDCP PDU header of a first PDCP PDU, determined by a sequence number, in the set of PDCP PDUs to be discarded; the discard marker is a two-bit indication of (i) the sequence number of the first PDCP PDU of the set of PDCP PDUs to be discarded, and (ii) the sequence number of the last PDCP PDU of the set of PDCP PDUs to be discarded. The method of claim 1.

14. the discard marker is a two-bit indication of (i) the sequence number of the first PDCP PDU of the set of PDCP PDUs to be discarded, and (ii) the total number of subsequent PDCP PDUs to be discarded. The method of claim 1.

15. 2. The method of claim 1, wherein the PDCP PDU header is a header of a PDCP data PDU in the set of PDCP PDUs to be discarded.

16. 2. The method of claim 1, wherein the PDCP PDU header is a header of a PDCP PDU transmitted within a padded PDCP data PDU that does not contain other content.

17. 2. The method of claim 1, wherein the discard marker comprises a parameter that indicates to a PDCP receiver the number of discarded PDCP PDUs in transit.

18. One or more processors comprising circuitry for executing one or more instructions that, when executed, cause a PDCP transmitter device to perform the operations of method claims 1-17.

19. 20. The method of claim 18, wherein the PDCP transmitter device is a UE or a base station.

20. One or more computer-readable storage media storing instructions that, when executed by a PDCP transmitter device, cause the PDCP transmitter device to perform the operations of the method of any one of claims 1 to 17.

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