Indicating discarding of transmitted data unit

Abstract

Example embodiments of the present disclosure are directed to indicating discarding of a transmitted data unit A method includes sending at least one data unit of a first protocol layer towards a second apparatus via a lower second protocol layer of a first apparatus; sending, to the second apparatus, a first indication of the lower second protocol layer that a data unit of the at least one data unit of the first protocol layer has been discarded by the first apparatus; receiving, from the second apparatus, an acknowledgement for acknowledging the discarded data unit of the first protocol layer, indicating that the data unit of the first protocol layer is possible to have been abandoned on a corresponding lower second protocol layer of the second apparatus; and in response to the receiving, sending, to the second apparatus, a report of the first protocol layer, the report of the first protocol indicating that the acknowledged data unit has been discarded.

Description

INDICATING DISCARDING OF TRANSMITTED DATA UNITFIELDS

[0001] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to apparatuses, methods and computer readable storage medium for indicating discarding of a transmitted data unit.BACKGROUND

[0002] A packet data convergence protocol sequence number (PDCP SN) gap report is introduced for extended reality (XR) enhancements of New Radio (NR) in the third -generation partnership project (3GPP) Release 18 (Rel-18). The PDCP SN gap report is a PDCP control protocol data unit (PDU) with which a transmitting PDCP entity may inform a receiving PDCP entity of PDCP COUNT values of discarded PDCP service data units (SDUs). The PDCP COUNT is a 32-bit running sequence number assigned to PCDP SDUs. With the PDCP SN gap report, the receiving PDCP entity may know which PDCP SDUs it should not expect to receive, thereby expediting delivery of received PDCP SDUs to upper layers when the receiving PDCP entity delivers the received PDCP SDUs to the upper layers in an increasing order of PDCP COUNT values.SUMMARY

[0003] In a first aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus (110) at least to: send (202, 330, 1010) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); send (228, 340, 1020), to the second apparatus (120), a first indication (229, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110); receive (234), from the second apparatus (120), an acknowledgement (233) for acknowledging the discarded data unit (331) of the first protocol layer (305), indicating that the data unit (331) of the first protocol layer (305) is possible to have been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and in response to the receiving (234), send (236, 362, 1040), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol (305) indicating that the acknowledged data unit (331) has been discarded.

[0004] In a second aspect of the present disclosure, there is provided a second apparatus (120) for wireless communication. The second apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus (120) at least to: receive (230, 340, 1120), from a first apparatus (110), a first indication (229, 341) of a lower second protocol layer that a data unit (331) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110); in response to the receiving (230, 340, 1120), send (232, 1130), to the firstapparatus (110), an acknowledgement (233) for acknowledging the data unit (331) of the first protocol layer (305), to indicate that retransmission of the data unit (331) is no longer required; and receive (238, 364, 1140), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the acknowledged data unit (331) has been discarded.

[0005] In a third aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes means for sending (202, 330, 1010) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); means for sending (228, 340, 1020), to the second apparatus (120), a first indication (229, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110); means for receiving (234), from the second apparatus (120), an acknowledgement (233) for acknowledging the discarded data unit (331) of the first protocol layer (305), indicating that the data unit (331) of the first protocol layer (305) is possible to have been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and means for in response to the receiving (234), sending (236, 362, 1040), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol (305) indicating that the acknowledged data unit (331) has been discarded.

[0006] In a fourth aspect of the present disclosure, there is provided a second apparatus (120) for wireless communication. The second apparatus includes means for receiving (230, 340, 1120), from a first apparatus (110), a first indication (229, 341) of a lower second protocol layer that a data unit (331) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110); means for in response to the receiving (230, 340, 1120), sending (232, 1130), to the first apparatus (110), an acknowledgement (233) for acknowledging the data unit (331) of the first protocol layer (305), to indicate that retransmission of the data unit (331) is no longer required; and means for receiving (238, 364, 1140), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the acknowledged data unit (331) has been discarded.

[0007] In a fifth aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus (110) at least to: send (202, 330, 332, 610) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); receive (222, 620), from the second apparatus (120), a second indication (221) that a data unit (331) of the at least one data unit has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and in response to receiving (222, 620) the second indication (221), send (236, 362, 630), to the second apparatus (120), a report (237, 363) of the first protocol layer (305) to indicate the abandoned data unit (331).

[0008] In a sixth aspect of the present disclosure, there is provided a second apparatus (120) for wireless communication. The second apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus (120) at least to: send (220, 710), to a first apparatus (110), a second indication (221) that a data unit (331) from at least one data unit (203, 331, 333) of a first protocol layer (305) of the first apparatus (110) sent via a lower second protocol layer (310) of the first apparatus (110) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and receive (238, 364, 720), a report (237, 363) of the first protocol layer (305) from the first apparatus (110), the report (237, 363) of the first protocol layer indicating that the abandoned data unit (331) has been discarded.

[0009] In a seventh aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes means for sending (202, 330, 332, 610) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); means for receiving (222, 620), from the second apparatus (120), a second indication (221) that a data unit (331) of the at least one data unit has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and means for in response to receiving (222, 620) the second indication (221), send (236, 362, 630), to the second apparatus (120), a report (237, 363) of the first protocol layer (305) to indicate that the abandoned data unit (331) has been discarded.

[0010] In an eighth aspect of the present disclosure, there is provided a second apparatus (120) for wireless communication. The second apparatus includes means for sending (220, 710), to a first apparatus (110), a second indication (221) that a data unit (331) from at least one data unit (203, 331, 333) of a first protocol layer (305) of the first apparatus (110) sent via a lower second protocol layer (310) of the first apparatus (110) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and means for receiving (238, 364, 720), a report (237, 363) of the first protocol layer (305) from the first apparatus (110), the report (237, 363) of the first protocol layer indicating that the abandoned data unit (331) has been discarded.

[0011] In a ninth aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus (110) at least to: send (202, 330, 410) at least one data unit (203, 331, 333) of a first protocol layer (305) to a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); determine (206, 360, 420) that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and send (236, 362, 430), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the abandoned data unit (331) has been discarded.

[0012] In a tenth aspect of the present disclosure, there is provided a second apparatus (120)for wireless communication. The second apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus (120) at least to: receive (340, 510), from a first apparatus (110), a first indication (341) of a lower second protocol layer (310) that a data unit (311) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110), the at least one data unit (203, 331, 333) of the first protocol layer (305) having been sent via the lower second protocol layer (310) of the first apparatus (110) towards the second apparatus (120); send (350, 520), to the first apparatus (110), a confirmation (351) for the discarding of the data unit (331) of the first protocol layer (305); and receive (238, 364, 530), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report of the first protocol layer indicating that the abandoned data unit (311) has been discarded.

[0013] In an eleventh aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes means for sending (202, 330, 410) at least one data unit (203, 331, 333) of a first protocol layer (305) to a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); means for determining (206, 360, 420) that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and means for sending (236, 362, 430), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the abandoned data unit (331) has been discarded.

[0014] In a twelfth aspect of the present disclosure, there is provided a second apparatus (120) for wireless communication. The second apparatus includes means for receiving (340, 510), from a first apparatus (110), a first indication (341) of a lower second protocol layer (310) that a data unit (311) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110), the at least one data unit (203, 331, 333) of the first protocol layer (305) having been sent via the lower second protocol layer (310) of the first apparatus (110) towards the second apparatus (120); means for sending (350, 520), to the first apparatus (110), a confirmation (351) for the discarding of the data unit (331) of the first protocol layer (305); and means for receiving (238, 364, 530), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report of the first protocol layer indicating that the abandoned data unit (311) has been discarded.

[0015] In a thirteenth aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus (110) at least to: send (202, 330, 810) at least one data unit (203, 331, 333) of a first protocol layer (305) to a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); send (210, 340, 820), to the second apparatus (120), a first indication (211, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110); receive (222, 830), from the second apparatus (120), a second indication (221) that the data unit (331) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and send (236, 362, 630), tothe second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the abandoned data unit (331) has been discarded.

[0016] In a fourteenth aspect of the present disclosure, there is provided a second apparatus (120) for wireless communication. The second apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus (120) at least to: receive (214, 340, 910), from a first apparatus (110), a first indication (211, 341) of a lower second protocol layer that a data unit (331) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110), the at least one data unit (203, 331, 333) of the first protocol layer (305) having been sent via the lower second protocol layer (310) of the first apparatus (110) towards the second apparatus (120); send (220, 920), to the first apparatus (110), a second indication (221) that the data unit (311) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and receive (238, 362, 930), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer indicating that the abandoned data unit (311) has been discarded.

[0017] In a fifteenth aspect of the present disclosure, there is provided a first apparatus (110) for wireless communication. The first apparatus includes means for sending (202, 330, 810) at least one data unit (203, 331, 333) of a first protocol layer (305) to a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); means for sending (210, 340, 820), to the second apparatus (120), a first indication (211, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110); means for receiving (222, 830), from the second apparatus (120), a second indication (221) that the data unit (331) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and means for sending (236, 362, 630), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the abandoned data unit (331) has been discarded.

[0018] In a sixteenth aspect of the present disclosure, there is provided a second apparatus (120) for wireless communication. The second apparatus includes means for receiving (214, 340, 910), from a first apparatus (110), a first indication (211, 341) of a lower second protocol layer that a data unit (331) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110), the at least one data unit (203, 331, 333) of the first protocol layer (305) having been sent via the lower second protocol layer (310) of the first apparatus (110) towards the second apparatus (120); means for sending (220, 920), to the first apparatus (110), a second indication (221) that the data unit (311) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and means for receiving (238, 362, 930), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer indicating that the abandoned data unit (311) has been discarded.

[0019] It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0021] FIG. 1 illustrates an example communication environment in which example embodiments of the present disclosure may be implemented;

[0022] FIG. 2 illustrates a signaling diagram for indicating discarding of a transmitted data unit according to some example embodiments of the present disclosure;

[0023] FIG. 3 illustrates a signaling diagram for indicating discarding of a transmitted data unit according to some example embodiments of the present disclosure;

[0024] FIG. 4 illustrates a flowchart of a method implemented at a first apparatus according to some example embodiments of the present disclosure;

[0025] FIG. 5 illustrates a flowchart of a method implemented at a second apparatus according to some example embodiments of the present disclosure;

[0026] FIG. 6 illustrates a flowchart of another method implemented at a first apparatus according to some example embodiments of the present disclosure;

[0027] FIG. 7 illustrates a flowchart of another method implemented at a second apparatus according to some example embodiments of the present disclosure;

[0028] FIG. 8 illustrates a flowchart of another method implemented at a first apparatus according to some other example embodiments of the present disclosure;

[0029] FIG. 9 illustrates a flowchart of another method implemented at a second apparatus according to some other example embodiments of the present disclosure;

[0030] FIG. 10 illustrates a flowchart of yet another method implemented at a first apparatus according to some other example embodiments of the present disclosure;

[0031] FIG. 11 illustrates a flowchart of yet another method implemented at a second apparatus according to some other example embodiments of the present disclosure;

[0032] FIG. 12 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0033] FIG. 13 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0034] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0035] Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein may be implemented in various manners other than the ones described below.

[0036] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0037] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0038] It shall be understood that although the terms “first,” “second” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0039] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0040] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step has to be performed immediately after “A” occurs and one or more intervening steps may be included.

[0041] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0042] As used in this application, the term “circuitry” may refer to one or more or all ofthe following:(a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0043] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0044] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0045] As used herein, the term “network device” or “network access device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture includes a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IABnode includes a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

[0046] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0047] As described above, a PDCP SN gap report is introduced in 3GPP Rel-18 for XR enhancements. For example, transmitting and receiving operations of the PDCP SN gap report are specified in the 3GPP standards. Regarding the transmitting operation, for Unacknowledged mode (UM) data radio bearers (DRBs) and Acknowledged mode (AM) DRBs configured by upper layers to send the PDCP SN gap report in uplink, the transmitting PDCP entity may trigger the PDCP SN gap report when some conditions are met. For example, if the PDCP SDU(s) are discarded, there is at least one stored PDCP SDU(s) which is associated with a COUNT value larger than the COUNT value associated to the discarded PDCP SDU(s), and the discarded PDCP SDU(s) have not been submitted by radio link control (RLC) to lower layers, then the PDCP SN gap report may be sent.

[0048] If a PDCP SN gap report is triggered, the transmitting PDCP entity may compile the PDCP SN gap report and submit the PDCP SN gap report to lower layers for Uu interface. Furthermore, the transmitting PDCP entity may compile the PDCP SN gap report. For example, the transmitting PDCP entity may set the first discarded COUNT (FDC) field to the smallest COUNT value among those associated with the discarded PDCP SDUs. If more than one PDCP SDUs is discarded, the transmitting PDCP entity may allocate a Discard Bitmap field of length in bits equal to the number of COUNT values from and not including the first discarded PDCP SDU up to and including the last discarded PDCP SDU. This length may be rounded up to the next multiple of 8, or up to and including a PDCP SDU for which the resulting PDCP Control PDU size is equal to 9000 bytes, whichever comes first. For example, the transmitting PDCP entity may set in the discard bitmap field as ‘0’ for all PDCP SDUs that have not been discardedand set in the discard bitmap field as ‘ 1’ for all PDCP SDUs that have been discarded. It is to be noted that it is up to UE implementation how to limit the frequency of the PDCP SN gap reporting.

[0049] Upon reception of a PDCP SN gap report from lower layers, the receiving PDCP entity may consider each PDCP SDU with the bit in the discard bitmap set to ‘ 1 ’ or with the associated COUNT value equal to the value FDC field as discarded. If RX DELIV is less than or equal to the largest COUNT value associated with the discarded PDCP SDUs, and if RX_NEXT is less than or equal to COUNT value associated with the last discarded PDCP SDU indicated in the PDCP SN gap report, the receiving PDCP entity may update the RX NEXT to the largest COUNT value associated with the discarded PDCP SDU plus one. RX DELIV represents the COUNT value of the first PDCP SDU that has not been delivered to the upper layers but is still awaited. RX_NEXT represents the COUNT value of the next PDCP SDU that the receiving PDCP entity expects to receive.

[0050] If RX DELIV is equal to any COUNT value associated with the discarded PDCP SDU(s), then after performing header decompression if not decompressed before, the receiving PDCP entity may deliver all stored PDCP SDUs with consecutively associated COUNT values starting from RX_DELIV + 1 to upper layers in an ascending order of the associated COUNT value. Consecutively associated COUNT value(s) include COUNT value(s) of both the stored PDCP SDU(s) and PDCP SDU(s) which are considered as discarded. Then, the receiving PDCP entity may update the RX DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers and is not considered as discarded, with COUNT value greater than RX DELIV.

[0051] If a reordering timer, referring to the t-Reordering, is running and if RX_DELIV is greater than or equal to RX REORD, the receiving PDCP entity may stop and reset the t- Reordering. If the t-Reordering is not running and RX_DELIV is less than RX_NEXT, the receiving PDCP entity may update RX REORD to be RX NEXT and start t-Reordering. RX REORD represents the COUNT value following the COUNT value associated with the PDCP SDU which triggered the t-Reordering.

[0052] In the 3GPP Release 19 (Rel-19) continuation, RLC Acknowledged Mode (AM) may be improved to be better suited for XR applications. To avoid unnecessary retransmissions in RLC AM, enhancements for RLC AM may be adopted in either a transmitter (Tx) initiated approach or a receiver (Rx) initiated approach. In the Tx initiated approach, a transmitting side of a RLC AM entity may notify a receiving side of the RLC AM entity about obsolete SDUs. The transmitting side of the RLC AM entity may stop retransmitting those obsolete SDUs. Moreover, the receiving side of the RLC AM entity may update its state variables according to information received from the transmitting side of the RLC AM entity. In the Rx initiated approach, for proper advancing of a transmitting window, the RLC AM may be enhanced to allow the receiving side of the RLC AM entity to indicate abandoned SDUs to the transmitting side of the RLC AM entity. The transmitting side of the RLC AM entity may process the status report. It is for further study how the receiving side of the RLC AM entity determines that an SDU should be abandoned.

[0053] Thus, regardless of whether the Tx initiated approach or Rx initiated approach is adopted, the RLC AM may be enhanced with a way for the receiving side of the RLC AM entity to indicate abandoned SDUs to the transmitting side of the RLC AM entity. However, the form of this indication from the receiving side of the RLC AM entity to the transmitting side of the RLC AM entity has not been decided yet.

[0054] As mentioned above, the transmitting PDCP entity may trigger the PDCP SN gap report when certain conditions are met. One of these conditions is that the discarded PDCP SDU(s) have not been submitted by a RLC layer to lower layers. This implies that once an SDU has been transmitted by the RLC layer to lower layers, that is, after the initial transmission over the radio interface, the transmitting PDCP entity may not indicate to the receiving PDCP entity that the SDU has been discarded.

[0055] For RLC AM in 3GPP Rel-18, there is no mechanism to abandon the transmission of a given RLC SDU, even if it has become obsolete from application-layer requirements point of view. From this aspect, the above trigger condition is justified since, once RLC AM has started transmitting a given PDCP SDU, it is expected to successfully complete the transmission sooner or later, unless a radio-link failure occurs, in which case a memory of an RLC-AM entity may be flushed.

[0056] However, the ongoing Rel-19 work on avoiding unnecessary retransmissions is about to change this RLC-AM property. With this change, the previously mentioned trigger condition may become restrictive. If the receiving side of the RLC-AM entity ceases operations to expect reception of a given PDCP SDU, then the receiving side of the RLC-AM entity will no longer deliver an SDU to the receiving PDCP entity even if the SDU is received, given an operation of a receiving window in RLC AM. As mentioned above, when the transmitting side of the RLC AM entity has submitted the PDCP SDU to the lower layer, the PDCP SN gap report may not be triggered. In this case, the receiving PDCP entity without receiving the PDCP SN gap report may unnecessarily wait for the SDU, thereby delaying delivery of the received higher- numbered SDUs to an upper layer.

[0057] Example embodiments of the present disclosure propose a solution for indicating a discarding of a transmitted data unit. In this solution, after at least one data unit of a first protocol layer (such as a PDCP SDU) has been sent via a lower second protocol layer (such as an RLC layer) of a first apparatus towards a second apparatus, discarding of a data unit of the at least one data unit of the first protocol layer is allowed to be indicated based on an indication from the second apparatus that this data unit of the first protocol layer has been abandoned on a corresponding lower second protocol layer of the second apparatus. This indication may be an explicit indication or an implicit indication.

[0058] This solution allows indicating a discarding, when needed, of a data unit that has been delivered from a higher protocol layer to a lower protocol layer. In this way, a receiving entity may stop waiting for the discarded data unit and deliver higher-numbered data units to the upper layer, thereby reducing data transmission delay.

[0059] FIG. 1 illustrates an example communication environment 100 in which exampleembodiments of the present disclosure may be implemented. The communication environment 100 includes a plurality of apparatuses including a first apparatus 110 and a second apparatus 120 that may communicate with each other. During the communication, one of the first apparatus 110 and the second apparatus 120 may operate as a transmitting (Tx) entity, and the other of the first apparatus 110 and the second apparatus 120 may operate as a receiving (Rx) entity. In the following, for the purpose of illustration, some example embodiments are described with the first apparatus 110 operating as a Tx entity and the second apparatus 120 operating as a Rx entity.

[0060] It is to be understood that the numbers and types of apparatuses are illustrated in FIG. 1 only for the purpose of illustration without suggesting any limitations. The communication environment 100 may include any suitable numbers and types of apparatuses for implementing embodiments of the present disclosure.

[0061] In the example embodiments where one of the first apparatus 110 and the second apparatus 120 operates as a terminal device and the other operates a network device, a transmission direction from the network device to the terminal device may be referred to as a downlink (DL), and a direction from the terminal device to the network device may be referred to as an uplink (UL). In the example embodiments where both the first apparatus 110 and the second apparatus 120 operates as terminal devices, a link between the first apparatus 110 and the second apparatus 120 may be referred to as a sidelink (SL).

[0062] Communications in the communication environment 100 may be implemented according to any proper communication protocol(s), including, but not limited to, cellular communication protocols of the first generation (1G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation (5G), the sixth generation (6G), and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, including but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple- Input Multiple -Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0063] In the environment 100, the first apparatus 110 and the second apparatus 120 may establish a radio bearer for sending data unit(s) in RLC AM. During transmission of data units (e.g. PDCP SDUs) from the first apparatus 110 towards the second apparatus 120, discarding of a data unit that has been submitted from a first protocol layer of the first apparatus 110 to a lower second protocol layer of the first apparatus 110 may be indicated when needed. Some example implementations will be described below with reference to FIGS. 2 to 3.

[0064] FIG. 2 shows a signaling diagram of communications between the first apparatus 110 and the second apparatus 120 for indicating discarding of a transmitted data unit according to some example embodiments of the present disclosure.

[0065] As shown in FIG. 2, the first apparatus 110 may send (202) at least one data unit (203) of a first protocol layer towards the second apparatus 120 via a lower second protocol layer of the first apparatus 110. In some example embodiments, the at least one data unit of the first protocol layer (203) may be submitted from the first protocol layer of the first apparatus 110 to the lower second protocol layer of the first apparatus 110.

[0066] The first and second protocol layers may be any suitable protocol layer within the first apparatus 110. In some example embodiments, the first protocol layer may include a PDCP layer, and the second protocol layer may include a RLC layer. In some example embodiments, the data unit of the first protocol layer may include a PDCP SDU. For example, a PDCP entity of the first apparatus 110 may deliver a PDCP SDU to an RLC entity of the first apparatus 110. Then, the RLC entity of the first apparatus 110 may deliver the PDCP SDU to a lower layer of the first apparatus 110.

[0067] The at least one data unit of the first protocol layer may or may not be successfully received (204) by the second apparatus 120. If the transmission of the data unit of the first protocol layer is successful, this data unit may be received on a corresponding lower second protocol (e.g. an RLC layer) of the second apparatus 120. For example, an RLC entity of the second apparatus 120 may receive this data unit from a lower layer of the second apparatus 120.

[0068] According to some example embodiments of the present disclosure, illustrated to as Option 1 in FIG. 2, the first apparatus 110 may determine (206) that a data unit of the at least one data unit of the first protocol layer has been abandoned on the second protocol layer of the second apparatus 120. The abandoning of the data unit of the first protocol layer on the second protocol layer of the second apparatus 120 may be determined (206) by the first apparatus 110 in any suitable way.

[0069] In some example embodiments, the first apparatus 110 may make the determination (206) based on a confirmation from the second apparatus 120 after sending, to the second apparatus 120, a first indication of the second protocol layer that the data unit has been discarded by the first apparatus 110. In some other example embodiments, the first apparatus 110 may make the determination (206) based on an explicit or implicit indication from the second apparatus 120 indicating that the data unit has been abandoned on the second protocol layer of the second apparatus 120. Some example embodiments will be further detailed in the following paragraphs.

[0070] Based on the determination (206), the first apparatus 110 may send (236), to the second apparatus 120, a report (237) of the first protocol layer to indicate that the abandoned data unit has been discarded. Correspondingly, the second apparatus 120 may receive (238) this report from the first apparatus 110. In some example embodiments, the report (237) of the first protocol layer may be submitted from the first protocol layer of the first apparatus 110 to the second protocol layer of the first apparatus 110.

[0071] In some example embodiments, the report (237) of the first protocol layer may include a PDCP SN gap report which may indicate one or more sequence numbers (SNs) of discarded data units. For example, the PDCP entity of the first apparatus 110 (e.g. on the firstprotocol layer) may indicate the discarded SDU in a PDCP SN gap report based on an indication from the RLC entity of the first apparatus 110 (e.g. on the second protocol layer) indicating that the SDU has been abandoned by the RLC entity of the second apparatus 120. The PDCP SN gap report may be sent by the RLC entity of the first apparatus 110 to the RLC entity of the second apparatus 120. In one example, the PDCP entity of the first apparatus 110 may submit the PDCP SN gap report to the RLC entity of the first apparatus 110. Correspondingly, the RLC entity of the second apparatus 120 may relay the PDCP SN gap report to the PDCP entity of the second apparatus 110.

[0072] Based on this report, the second apparatus 120 may know the situation that a data unit of the first protocol layer has been discarded. Accordingly, the second apparatus 120 may stop waiting for the discarded data unit, and therefore the data transmission efficiency may be improved.

[0073] According to some other example embodiments of the present disclosure, illustrated as Option 2 in FIG. 2, the second apparatus 120 may indicate an abandoned data unit to the first apparatus 110 using an explicit indication. As shown in FIG. 2, the second apparatus 120 may send (220), to the first apparatus 110, a second indication (221) that a data unit of the at least one data unit (203) of the first protocol layer sent (202) by the first apparatus 110 has been abandoned on the second protocol layer of the second apparatus 120. For example, the RLC entity of the second apparatus 120 (e.g. on the second protocol layer) may indicate to the RLC entity of the first apparatus 110 an abandoned SDU (e.g. originating from the first protocol layer).

[0074] After the first apparatus 110 receives (222) the second indication (221) from the second apparatus 120, the first apparatus 110 may send (236), to the second apparatus 120, the report of the first protocol layer to indicate that the abandoned data unit has been discarded. In some example embodiments, the second indication (221) may be relayed from the second protocol layer of the first apparatus 110 to the higher first protocol layer of the first apparatus 110. For example, upon reception (222) of the second indication, the RLC entity of the first apparatus 110 may relay the second indication to the PDCP entity of the first apparatus 110. In response to the second indication, the PDCP entity of the first apparatus 110 may indicate the discarded SDU in the PDCP SN gap report (as an example of the report of the first protocol layer).

[0075] The second indication (221) may be carried in a same message as or a different message separate from a message (such as an acknowledgement message) carrying an acknowledgment (ACK) that is configured to indicate that a remaining of the at least one data unit (203) of the first protocol layer has been successfully received by the second apparatus 120 from the first apparatus 110. In some example embodiments, as shown in FIG. 2, separate from the second indication (221), the second apparatus 120 may send (216) an acknowledgment (217) to the first apparatus 110. Correspondingly, the first apparatus 110 may receive (218) the acknowledgment message (217) from the second apparatus 120.

[0076] In an example, the RLC entity of the second apparatus 120 may indicate, to the RLC entity of the first apparatus 110, an abandoned SDU using an explicit indication separate fromACK for the received data unit where the explicit indication and the ACK may be contained in a same message or in different messages. For example, the second indication may be contained in an RLC status PDU, in the same message as RLC ACKs.

[0077] In some example embodiments, the first apparatus 110 may send (212), to the second apparatus 120, the first indication (211) of the second protocol layer that a data unit of the at least one data unit (203) of the first protocol layer has been discarded by the first apparatus 110. In response to receiving (214) the first indication (211) of the second protocol layer from the first apparatus 110, the second apparatus 120 may send (220), to the first apparatus 110, the second indication (221) that the data unit has been abandoned on the second protocol layer of the second apparatus 120. Then, the first apparatus 110 may send (236), to the second apparatus 120, the report (237) of the first protocol layer to indicate that the abandoned or discarded data unit has been discarded.

[0078] According to some other example embodiments of the present disclosure, illustrated as Option 3 in FIG. 2, the second apparatus 120 may indicate to the first apparatus 110 an abandoned data unit by reusing an ACK for a data unit of the at least one data unit (203) of the first protocol layer. As shown in FIG. 2, the first apparatus 110 may send (228), to the second apparatus 120, the first indication (229) of the second protocol layer that a data unit of the at least one data unit (203) of the first protocol layer sent (202) by the first apparatus 110 has been discarded by the first apparatus 110. After the second apparatus 120 receives (230) the first indication (229) from the first apparatus 110, the second apparatus 120 may send (232), to the first apparatus 110, an acknowledgement to indicate that the data unit of the first protocol layer no longer requires retransmission from the second protocol layer of the first apparatus 110. In response to receiving (234) the acknowledgement (233) from the second apparatus 120, the first apparatus 110 may send (236), to the second apparatus 120, the report (237) of the first protocol layer to indicate that the acknowledged data unit has been discarded. In some example embodiments, the acknowledgement (233) may be relayed from the second protocol layer of the first apparatus 110 to the higher first protocol layer of the first apparatus 110.

[0079] In an example, the RLC entity of the second apparatus 120 (e.g. on the second protocol layer) may indicate an RLC ACK for an abandoned SDU to the RLC entity of the first apparatus 110. The RLC ACK may indicate either successful delivery of the SDU or the SDU having been abandoned. Upon reception of the RLC ACK, the RLC entity of the first apparatus 110 (on the second protocol layer) may relay it to the PDCP entity of the first apparatus 110 (e.g. on the first protocol layer). Since the RLC entity of the first apparatus 110 has previously sent to the RLC entity of the second apparatus 120 the first indication for discarding the SDU, the PDCP entity of the first apparatus 110 may determine that the RLC ACK may indicate the SDU having been abandoned. In response to the RLC ACK, the PDCP entity of the first apparatus 110 may indicate the discarded SDU in a PDCP SN gap report (as an example of the report of the first protocol layer). An example implementation of discarding a transmitted data unit will be discussed below by taking 3GPP TS 38,323 as an example.

[0080] An example process of discarding a transmitted data unit will be described below with reference to FIG. 3. In this example, a PDCP layer is an example of the first protocol layer, and an RLC layer is an example of the second protocol layer. The first apparatus 110, operating as a Tx entity, may include a transmitting PDCP 305 and a transmitting side of a first RLC AM entity 310. The second apparatus 120, operating as a Rx entity, may include a receiving side of a second RLC AM entity 315 and a receiving PDCP 320.

[0081] As shown in FIG. 3, at 322, the transmitting PDCP 305 may receive a SDU (denoted by SDU #1) from an upper layer and may start a discard timer (e.g. discardTimer) for SDU #1 331. At 330, the transmitting PDCP 305 may submit PDCP SDU #1 331 to the transmitting side of the first RLC AM entity 310. At 332, the transmitting PDCP 305 may also submitanother SDU (denoted by PDCP SDU #2 333) to the transmitting side of the first RLC AM entity 310. However, the initial transmission of SDU #1 331 and SDU #2 333 from the transmitting side of the first RUC AM entity 310 to the receiving side of the second RUC AM entity 315 are failed.

[0082] At 334, the discard timer for SDU #1 expires, which means that SDU #1 should be discarded. At 336, the transmitting side of the first RUC AM entity 310 may retransmit SDU #1 331, still without success. At 340, the transmitting PDCP 305 may send an indication 341 for discarding of SDU #1 via the transmitting side of the first RUC AM entity 310 towards the receiving side of the second RUC AM entity 315.

[0083] At 342, the transmitting PDCP 305 has not received a discard confirmation from the transmitting side of the first RUC AM entity 310, and thus no PDCP SN gap report is transmitted. At 344, the transmitting side of the first RUC AM entity 310 successfully retransmits SDU #2 333 to the receiving side of the second RUC AM entity 315 which delivers it to the receiving PDCP 320. At 346, the receiving PDCP 320 may start t-Reordering Timer for waiting for SDU #1 and hold the delivery of SDU #2 to an upper layer.

[0084] At 350, in response to the indication 341 of discarding of SDU #1 received from the transmitting side of the first RUC AM 310, the receiving side of the second RUC AM entity 315 may send, to the transmitting side of the first RLC AM entity 310, a confirmation 351 for the abandoning of SDU #1. At 352, the transmitting side of the first RLC AM entity 310 may relay the confirmation 351 for the abandoning of SDU #1 to the transmitting PDCP 305. The confirmation (351) may be implemented by an explicit indication or an ACK, as described above.

[0085] At 360, in response to receiving confirmation for the abandoning of SDU #1, the transmitting PDCP 305 may treat SDU #1, despite it having been submitted by the transmitting side of the first RLC AM entity 310 to lower layers, as eligible for reporting in a PDCP SN gap report sent. Additionally, it may optionally trigger a PDCP SN gap report. At 362, a PDCP SN gap report 363 may be sent from the transmitting PDCP 305 via the transmitting side of the first RLC AM entity 310 and the receiving side of the second RLC AM entity 315 towards the receiving PDCP entity 320, indicating SDU #1 as discarded. There may be no impact on the currently existing format of the PDCP SN gap report. At 368, in response to receiving the PDCP SN gap report indicating SDU #1 as discarded, the receiving PDCP entity 320 may stop waiting for SDU #1 and be able to immediately deliver SDU #2 to the upper layer.

[0086] In such a process as shown in FIG. 3, the transmitting PDCP entity 305 may indicate the SDUs that have been submitted to the lower layer by RLC in a PDCP SN gap report. Consequently, the delay at the receiving PDCP entity 320 in delivering higher-numbered SDUs to the upper layer may be reduced.

[0087] FIG. 4 shows a flowchart of an example method 400 implemented at a first apparatus for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0088] At block 410, the first apparatus 110 sends (202, 330, 410) at least one data unit (203, 331, 333) of a first protocol layer (305) to a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110).

[0089] At block 420, the first apparatus 110 determines (206, 360, 420) that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120).

[0090] At block 430, the first apparatus 110 sends (236, 362, 430), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the abandoned data unit (331) has been discarded.

[0091] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) is submitted (330) from the first protocol layer (305) of the first apparatus (110) to the lower second protocol layer (310) of the first apparatus (110).

[0092] In some example embodiments, the report (237, 363) of the first protocol layer (305) is submitted (362) from the first protocol layer (305) of the first apparatus (110) to the lower second protocol layer (310) of the first apparatus (110).

[0093] In some example embodiments, the first apparatus 110 sends (340), to the second apparatus (120), a first indication (341) of the lower second protocol layer (310) that the data unit (311) of the first protocol layer (305) has been discarded by the first apparatus (110); and receives (350), from the second apparatus (120), a confirmation (351) for the discarding of the data unit (311) of the first protocol layer (305). The determining (206, 360, 420) that the data unit (311) of the first protocol layer (305) has been abandoned on the lower second protocol layer (315) of the second apparatus (120) is based on receiving (350) the confirmation (351).

[0094] In some example embodiments, the confirmation (351) is relayed from the lower second protocol layer (310) of the first apparatus (110) to the first protocol layer (305) of the first apparatus (310).

[0095] In some example embodiments, the report (237, 363) of the first protocol layer (305) includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0096] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol (305) includes a packet data convergence protocol service data unit (PDCP SDU).

[0097] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0098] FIG. 5 shows a flowchart of an example method 500 implemented at a second apparatus for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0099] At block 510, the second apparatus 120 receives (340, 510), from a first apparatus (110), a first indication (341) of a lower second protocol layer (310) that a data unit (311) of atleast one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110). The at least one data unit (203, 331, 333) of the first protocol layer (305) has been sent via a lower second protocol layer (310) of the first apparatus (110) towards the second apparatus (120).

[0100] At block 520, the second apparatus 120 sends (350, 520), to the first apparatus (110), a confirmation (351) for the discarding of the data unit (331) of the first protocol layer (305).

[0101] At block 530, the second apparatus 120 receives (238, 364, 530), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report of the first protocol layer indicating that the abandoned data unit (311) has been discarded.

[0102] In some example embodiments, the report (237, 363) of the first protocol layer (305) includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0103] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) includes a packet data convergence protocol service data unit, (PDCP SDU).

[0104] In some example embodiments, the confirmation (351) is sent (350) from the lower second protocol layer (315) of the second apparatus (120).

[0105] In some example embodiments, the report (237, 363) of the first protocol layer (305) is relayed (366) from the lower second protocol layer (315) of the second apparatus (120) to a corresponding first protocol layer (320) of the second apparatus (120).

[0106] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0107] FIG. 6 shows a flowchart of an example method 600 implemented at a first apparatus for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0108] At block 610, the first apparatus 110 sends (202, 330, 332, 610) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110).

[0109] At block 620, the first apparatus 110 receives (222, 620), from the second apparatus (120), a second indication (221) that a data unit (331) of the at least one data unit has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120).

[0110] At block 630, in response to receiving (222, 620) the second indication (221), the first apparatus 110 sends (236, 362, 630), to the second apparatus (120), a report (237, 363) of the first protocol layer (305) to indicate that the abandoned data unit (331) has been discarded.

[0111] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) is submitted from the first protocol layer (305) of the first apparatus (110)to the lower second protocol layer (310) of the first apparatus (110) for transmission to the second apparatus (120).

[0112] In some example embodiments, the second indication (221) is relayed (352) from the lower second protocol layer (310) of the first apparatus to the first protocol layer (305) of the first apparatus.

[0113] In some example embodiments, the report (237, 363) of the first protocol layer is submitted from the first protocol layer (305) of the first apparatus to the second protocol layer (310) of the first apparatus.

[0114] In some example embodiments, the second indication (221) is carried in a same message as or a different message separate from a message carrying an acknowledgment (217), and the acknowledgment (217) is configured to indicate that a remaining of the at least one data unit (203, 333) of the first protocol layer (305) has been successfully received by the second apparatus (120) from the first apparatus (110).

[0115] In some example embodiments, the report (237, 363) of the first protocol layer includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0116] In some example embodiments, the at least one data unit (203, 331, 333) includes a packet data convergence protocol service data unit (PDCP SDU).

[0117] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0118] FIG. 7 shows a flowchart of an example method 700 implemented at a second apparatus 120 for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0119] At block 710, the second apparatus 120 sends (220, 710), to a first apparatus (110), a second indication (221) that a data unit (331) from at least one data unit (203, 331, 333) of a first protocol layer (305) of the first apparatus (110) sent via a lower second protocol layer (310) of the first apparatus (110) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120).

[0120] At block 720, the second apparatus 120 receives (238, 364, 720), a report (237, 363) of the first protocol layer (305) from the first apparatus (110), the report (237, 363) of the first protocol layer indicating that the abandoned data unit (331) has been discarded.

[0121] In some example embodiments, the second indication (221) is carried in a same message as or a different message separate from a message carrying an acknowledgment (217), and the acknowledgment (217) is configured to indicate that a remaining of the at least one data unit (203, 333) of the first protocol layer (305) has been successfully received by the second apparatus (120) from the first apparatus.

[0122] In some example embodiments, the report (237, 363) of the first protocol layerincludes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0123] In some example embodiments, the at least one data unit (203, 331, 333) includes a packet data convergence protocol service data unit (PDCP SDU).

[0124] In some example embodiments, the second indication (221) is sent from the lower second protocol layer (315) of the second apparatus (120).

[0125] In some example embodiments, the report (237, 363) of the first protocol layer is relayed from the lower second protocol layer (315) of the second apparatus (120) to a corresponding first protocol layer (320) of the second apparatus (120).

[0126] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the corresponding lower second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0127] FIG. 8 shows a flowchart of an example method 800 implemented at a first apparatus for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0128] At block 810, the first apparatus 110 sends (202, 330, 810) at least one data unit (203, 331, 333) of a first protocol layer (305) to a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110).

[0129] At block 820, the first apparatus 110 sends (210, 340, 820), to the second apparatus (120), a first indication (211, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110).

[0130] At block 830, the first apparatus 110 receives (222, 830), from the second apparatus (120), a second indication (221) that the data unit (331) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120).

[0131] At block 840, the first apparatus 110 sends (236, 362, 630), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the abandoned data unit (331) has been discarded.

[0132] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) is submitted (330) from the first protocol layer (305) of the first apparatus (110) to the lower second protocol layer (310) of the first apparatus (110).

[0133] In some example embodiments, the second indication (221) is relayed from the lower second protocol layer (310) of the first apparatus (110) to the first protocol layer (305) of the first apparatus (110).

[0134] In some example embodiments, the report (237, 363) of the first protocol layer (305) is submitted (362) from the first protocol layer (305) of the first apparatus (110) to the lowersecond protocol layer (310) of the first apparatus (305).

[0135] In some example embodiments, the second indication (221) is carried in a same message as or a different message separate from a message carrying an acknowledgment (217), and the acknowledgment (217) is configured to indicate that a remaining of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been successfully received by the second apparatus (120) from the first apparatus (110).

[0136] In some example embodiments, the report (237, 363) of the first protocol layer (305) includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0137] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) includes a packet data convergence protocol service data unit (PDCP SDU).

[0138] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0139] FIG. 9 shows a flowchart of an example method 900 implemented at a second apparatus for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 900 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0140] At block 910, the second apparatus 120 receives (214, 340, 910), from a first apparatus (110), a first indication (211, 341) of a lower second protocol layer that a data unit (331) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110). The at least one data unit (203, 331, 333) of the first protocol layer (305) has been sent via the lower second protocol layer (310) of the first apparatus (110) towards the second apparatus (120).

[0141] At block 920, the second apparatus 120 sends (220, 920), to the first apparatus (110), a second indication (221) that the data unit (311) of the first protocol layer (305) has been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120).

[0142] At block 930, the second apparatus 120 receives (238, 362, 930), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer indicating that the abandoned data unit (311) has been discarded.

[0143] In some example embodiments, the second indication (221) is carried in a same message as or a different message separate from a message carrying an acknowledgment (217), and the acknowledgement (217) is configured to indicate that a remaining of the at least one data unit (203, 331, 333) of the first protocol layer has been successfully received by the second apparatus (120) from the first apparatus (110).

[0144] In some example embodiments, the report (237, 363) of the first protocol layer (305) includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0145] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) includes a packet data convergence protocol service data unit (PDCP SDU).

[0146] In some example embodiments, the second indication (221) is sent from the lower second protocol layer (315) of the second apparatus (120).

[0147] In some example embodiments, the report (237, 363) of the first protocol layer (305) is relayed (366) from the lower second protocol layer (315) of the second apparatus (120) to a corresponding first protocol layer (320) of the second apparatus (120).

[0148] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0149] FIG. 10 shows a flowchart of an example method 1000 implemented at a first apparatus for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0150] At block 1010, the first apparatus 110 sends (202, 330, 1010) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110).

[0151] At block 1020, the first apparatus 110 sends (228, 340, 1020), to the second apparatus (120), a first indication (229, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110).

[0152] At block 1030, the first apparatus 110 receives (234), from the second apparatus (120), an acknowledgement (233) for acknowledging the discarded data unit (331) of the first protocol layer (305), indicating that the data unit (331) of the first protocol layer (305) is possible to have been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120).

[0153] At block 1040, in response to the receiving (234), sending (236, 362, 1040), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol (305) indicating that the acknowledged data unit (331) has been discarded.

[0154] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) is submitted (330) from the first protocol layer (305) of the first apparatus (110) to the lower second protocol layer (310) of the first apparatus (110).

[0155] In some example embodiments, the acknowledgement (233) is relayed from the lower second protocol layer (310) of the first apparatus (110) to the first protocol layer (305) of the first apparatus (110).

[0156] In some example embodiments, the report (237, 363) of the first protocol layer (305) is submitted (362) from the first protocol layer (305) of the first apparatus (110) to the lower second protocol layer (310) of the first apparatus (310).

[0157] In some example embodiments, the report (237, 363) of the first protocol (305)includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0158] In some example embodiments, the at least one data unit (203, 331, 333) includes a packet data convergence protocol service data unit (PDCP SDU).

[0159] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0160] FIG. 11 shows a flowchart of an example method 1100 implemented at a second apparatus for wireless communication in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1100 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0161] At block 1120, the second apparatus 120 receives (230, 340, 1120), from a first apparatus (110), a first indication (229, 341) of a lower second protocol layer that a data unit (331) of at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110).

[0162] At block 1130, in response to the receiving (230, 340, 1120), the second apparatus 120 sends (232, 1130), to the first apparatus (110), an acknowledgement (233) for acknowledging the data unit (331) of the first protocol layer (305), to indicate that retransmission of the data unit (331) is no longer required.

[0163] At block 1140, the second apparatus 120 receives (238, 364, 1140), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the acknowledged data unit (331) has been discarded.

[0164] In some example embodiments, the report (237, 363) of the first protocol layer (305) includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0165] In some example embodiments, the at least one data unit (203, 331, 333) includes a packet data convergence protocol service data unit (PDCP SDU).

[0166] In some example embodiments, the acknowledgement (233) is sent (232, 1130) from the lower second protocol layer (315) of the second apparatus (120).

[0167] In some example embodiments, the report (237, 363) of the first protocol layer (305) is relayed (366) from the lower second protocol layer (315) of the second apparatus (120) to a corresponding first protocol layer (320) of the second apparatus (120).

[0168] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0169] In some example embodiments, the first apparatus 110 and the second apparatus 120 may include means for performing the respective operations of the methods 400 to 1100. The means may be implemented in any suitable form. For example, the means may be implementedin a circuitry or software module.

[0170] FIG. 12 is a simplified block diagram of a device 1200 that is suitable for implementing example embodiments of the present disclosure. The device 1200 may be provided to implement a communication device, for example, the first apparatus 110 or the second apparatus 120 as shown in FIG. 1. As shown, the device 1200 includes one or more processors 1210, one or more memories 1220 coupled to the processor 1210, and one or more communication modules 1240 coupled to the processor 1210.

[0171] The communication module 1240 is for bidirectional communications. The communication module 1240 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 1240 may include at least one antenna.

[0172] The processor 1210 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1200 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0173] The memory 1220 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 1224, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), an optical disk, a laser disk, and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random-access memory (RAM) 1222 and other volatile memories that will not last in the power-down duration.

[0174] A computer program 1230 includes computer executable instructions that are executed by the associated processor 1210. The instructions of the program 1230 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 1230 may be stored in the memory, e.g., the ROM 1224. The processor 1210 may perform any suitable actions and processing by loading the program 1230 into the RAM 1222.

[0175] The example embodiments of the present disclosure may be implemented by means of the program 1230 so that the device 1200 may perform any process of the disclosure as discussed with reference to FIG. 1 to FIG. 7. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0176] In some example embodiments, the program 1230 may be tangibly contained in a computer readable medium which may be included in the device 1200 (such as in the memory 1220) or other storage devices that are accessible by the device 1200. The device 1200 may load the program 1230 from the computer readable medium to the RAM 1222 for execution.In some example embodiments, the computer readable medium may include any types of non- transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0177] FIG. 13 shows an example of the computer readable medium 1300 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 1300 has the program 1230 stored thereon.

[0178] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0179] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non- transitory computer readable medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0180] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general-purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0181] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0182] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (RAM), a readonly memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0183] Further, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, although several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separately or in any suitable sub -combination.

[0184] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

[0185] Various example embodiments of the techniques have been described. In addition to or as an alternative to the above, the following examples are described. The features described in any of the following examples may be utilized with any of the other examples described herein.

[0186] In an aspect, a first apparatus (110) for wireless communication includes: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus (110) at least to: send (202, 330, 1010) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); send (228, 340, 1020), to the second apparatus (120), a first indication (229, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110); receive (234), from the second apparatus (120), an acknowledgement (233) for acknowledging the discarded data unit (331) of the first protocol layer (305), indicating that the data unit (331) of the first protocol layer (305) is possible to have been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and in response to the receiving (234), send (236, 362, 1040), to the secondapparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol (305) indicating that the acknowledged data unit (331) has been discarded.

[0187] In some example embodiments, the at least one data unit (203, 331, 333) of the first protocol layer (305) is submitted (330) from the first protocol layer (305) of the first apparatus (110) to the lower second protocol layer (310) of the first apparatus (110).

[0188] In some example embodiments, the acknowledgement (233) is relayed from the lower second protocol layer (310) of the first apparatus (110) to the first protocol layer (305) of the first apparatus (110).

[0189] In some example embodiments, the report (237, 363) of the first protocol layer (305) is submitted (362) from the first protocol layer (305) of the first apparatus (110) to the lower second protocol layer (310) of the first apparatus (310).

[0190] In some example embodiments, the report (237, 363) of the first protocol (305) includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0191] In some example embodiments, the at least one data unit (203, 331, 333) includes a packet data convergence protocol service data unit (PDCP SDU).

[0192] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0193] In an aspect, a second apparatus (120) for wireless communication includes: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus (120) at least to: receive (230, 340, 1120), from the first apparatus (110), a first indication (229, 341) of a lower second protocol layer that a data unit (331) of at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by a first apparatus (110); in response to the receiving (230, 340, 1120), send (232, 1130), to the first apparatus (110), an acknowledgement (233) for acknowledging the data unit (331) of the first protocol layer (305), to indicate that retransmission of the data unit (331) is no longer required; and receive (238, 364, 1140), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the acknowledged data unit (331) has been discarded.

[0194] In some example embodiments, the report (237, 363) of the first protocol layer (305) includes a packet data convergence protocol sequence number (PDCP SN) gap report.

[0195] In some example embodiments, the at least one data unit (203, 331, 333) includes a packet data convergence protocol service data unit (PDCP SDU).

[0196] In some example embodiments, the acknowledgement (233) is sent (232, 1130) from the lower second protocol layer (315) of the second apparatus (120).

[0197] In some example embodiments, the report (237, 363) of the first protocol layer (305) is relayed (366) from the lower second protocol layer (315) of the second apparatus (120) to a corresponding first protocol layer (320) of the second apparatus (120).

[0198] In some example embodiments, the first protocol layer (305, 320) includes a packet data convergence protocol (PDCP) layer, and the second protocol layer (310, 315) includes a radio link control (RLC) layer.

[0199] In an aspect, a first apparatus (110) for wireless communication includes: means for sending (202, 330, 1010) at least one data unit (203, 331, 333) of a first protocol layer (305) towards a second apparatus (120) via a lower second protocol layer (310) of the first apparatus (110); means for sending (228, 340, 1020), to the second apparatus (120), a first indication (229, 341) of the lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of the first protocol layer (305) has been discarded by the first apparatus (110); means for receiving (234), from the second apparatus (120), an acknowledge (233) for acknowledging the discarded data unit (331) of the first protocol layer (305), to indicate that the data unit (331) of the first protocol layer (305) is possible to have been abandoned on a corresponding lower second protocol layer (315) of the second apparatus (120); and means for in response to the receiving (234), sending (236, 362, 1040), to the second apparatus (120), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol (305) indicating that the acknowledged data unit (331) has been discarded.

[0200] In an aspect, a second apparatus (120) for wireless communication includes: means for receiving (230, 340, 1120), from the first apparatus (110), a first indication (229, 341) of a lower second protocol layer that a data unit (331) of the at least one data unit (203, 331, 333) of a first protocol layer (305) has been discarded by the first apparatus (110); means for sending (232, 1130), to the first apparatus (110), an acknowledge (233) for acknowledging the data unit (331) of the first protocol layer (305), to indicate that retransmission of the data unit (331) is no longer required; and means for receiving (238, 364, 1140), from the first apparatus (110), a report (237, 363) of the first protocol layer (305), the report (237, 363) of the first protocol layer (305) indicating that the acknowledged data unit (331) has been discarded.

Claims

WHAT IS CLAIMED IS:

1. A first apparatus for wireless communication comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: send at least one data unit of a first protocol layer towards a second apparatus via a lower second protocol layer of the first apparatus; send, to the second apparatus, a first indication of the lower second protocol that a data unit of the at least one data unit of the first protocol layer has been discarded by the first apparatus; receive, from the second apparatus, an acknowledgement for acknowledging the discarded data unit of the first protocol layer, indicating that the data unit of the first protocol layer is possible to have been abandoned on a corresponding lower second protocol layer of the second apparatus; and in response to the receiving, send, to the second apparatus, a report of the first protocol layer, the report of the first protocol indicating that the acknowledged data unit has been discarded.

2. The first apparatus of claim 1, wherein the at least one data unit of the first protocol layer is submitted from the first protocol layer of the first apparatus to the lower second protocol layer of the first apparatus.

3. The first apparatus of claim 1 or 2, wherein the acknowledgement is relayed from the lower second protocol layer of the first apparatus to the first protocol layer of the first apparatus.

4. The first apparatus of any of claims 1 to 3, wherein the report of the first protocol layer is submitted from the first protocol layer of the first apparatus to the lower second protocol layer of the first apparatus.

5. The first apparatus of any of claims 1 to 4, wherein the report of the first protocol comprises a packet data convergence protocol sequence number (PDCP SN) gap report.

6. The first apparatus of any of claims 1 to 5, wherein the at least one data unit comprises a packet data convergence protocol service data unit (PDCP SDU).

7. The first apparatus of any of claims 1 to 6, wherein the first protocol layer comprises a packet data convergence protocol (PDCP) layer, and the second protocol layer comprises a radio link control (RLC) layer.

8. A second apparatus for wireless communication comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: receive, from a first apparatus, a first indication of a lower second protocol that a data unit of at least one data unit of a first protocol layer has been discarded by the first apparatus; in response to the receiving, send, to the first apparatus, an acknowledgement for acknowledging the data unit of the first protocol layer, to indicate that retransmission of the data unit is no longer required; and receive, from the first apparatus, a report of the first protocol layer, the report of the first protocol layer indicating that the acknowledged data unit has been discarded.

9. The second apparatus of claim 8, wherein the report of the first protocol layer comprises a packet data convergence protocol sequence number (PDCP SN) gap report.

10. The second apparatus of claim 8 or 9, wherein the at least one data unit comprises a packet data convergence protocol service data unit (PDCP SDU).

11. The second apparatus of any of claims 8 to 10, wherein the acknowledgement is sent from the lower second protocol layer of the second apparatus.

12. The second apparatus of any of claims 8 to 11, wherein the report of the first protocol layer is relayed from the lower second protocol layer of the second apparatus to a corresponding first protocol layer of the second apparatus.

13. The second apparatus of any of claims 8 to 12, wherein the first protocol layer comprises a packet data convergence protocol (PDCP) layer, and the second protocol layer comprises a radio link control (RLC) layer.

14. A first apparatus for wireless communication, comprising: means for sending at least one data unit of a first protocol layer towards a second apparatus via a lower second protocol layer of the first apparatus;means for sending, to the second apparatus, a first indication of the lower second protocol that a data unit of the at least one data unit of the first protocol layer has been discarded by the first apparatus; means for receiving, from the second apparatus, an acknowledgement for acknowledging the discarded data unit of the first protocol layer, indicating that the data unit of the first protocol layer is possible to have been abandoned on a corresponding lower second protocol layer of the second apparatus; and means for in response to the receiving, sending, to the second apparatus, a report of the first protocol layer, the report of the first protocol indicating that the acknowledged data unit has been discarded.

15. A second apparatus for wireless communication, comprising: means for receiving, from the first apparatus, a first indication of a lower second protocol layer that a data unit of at least one data unit of a first protocol layer has been discarded by the first apparatus; means for in response to the receiving, sending, to the first apparatus, an acknowledgement for acknowledging the data unit of the first protocol layer, to indicate that retransmission of the data unit is no longer required; and means for receiving, from the first apparatus, a report of the first protocol layer, the report of the first protocol layer indicating that the acknowledged data unit has been discarded.

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