Methods and apparatuses for indication or detection of a discarded protocol data unit of a protocol data unit set

Abstract

A first apparatus and a first method, wherein the first method comprises detecting (302), by a terminal device, that a first uplink protocol data unit is discarded in the terminal device, sending (306), by the terminal device, a second uplink protocol data unit in the uplink, wherein the second uplink protocol data unit comprises an indication that the first uplink protocol data unit or a protocol data unit set that comprises the first uplink protocol data unit has been discarded. A second apparatus and a second method, wherein the second method comprises receiving (306) a first uplink protocol data unit in an uplink, wherein the first uplink protocol data unit comprises an indication that a second uplink protocol data unit is discarded, and detecting (308), depending on the indication, that the second uplink protocol data unit, or a protocol data unit set that comprises uplink protocol data units is discarded, or wherein the first uplink protocol data unit comprises an indication that a protocol data unit set that comprises uplink protocol data units is discarded, and wherein the method comprises detecting (308), depending on the indication, that the uplink protocol data unit set is discarded.

Description

[0001] Title : Methods and apparatuses for indication or detection of a discarded protocol data unit of a protocol data unit set

[0002] Specification

[0003] Field of the invention

[0004] Various example embodiments relate to methods and apparatuses for indication or detection of a discarded protocol data unit of a protocol data unit set .

[0005] Background

[0006] A protocol data unit , PDU, set enables a radio access network, RAN, to identi fy protocol data units that comprise interrelated content . User equipment , UE , may send PDUs of a PDU set in an uplink, UL, to a network entity, e . g . , a next generation node B, gNB .

[0007] Summary

[0008] A first method comprises detecting, by a terminal device , that a first uplink protocol data unit is discarded in the terminal device , sending, by the terminal device , a second uplink protocol data unit in the uplink, wherein the second uplink protocol data unit comprises an indication that the first uplink protocol data unit , or a protocol data unit set that comprises the first uplink protocol data unit has been discarded . According to some aspects of the first method, the first uplink protocol data unit and the second uplink protocol data unit are comprised in a protocol data unit set , or wherein the second uplink protocol data unit is , in particular a control protocol data unit , outside of a protocol data unit set that comprises the first uplink protocol data unit .

[0009] According to some aspects of the first method, the first uplink protocol data unit is associated with a position of the first uplink protocol data unit in the protocol data unit set , wherein the first method comprises determining the position, and determining the indication, wherein the indication comprises the position .

[0010] According to some aspects of the first method, the protocol data unit set comprises the first uplink protocol data unit , and the second uplink protocol data unit , and wherein the first method comprises determining a number of uplink protocol data units of the protocol data unit set , including the first uplink protocol data unit , that are discarded in the uplink, and determining the indication, wherein the indication comprises the number .

[0011] According to some aspects of the first method, the first method comprises determining a direction that indicates whether the uplink protocol data units of the protocol data unit set that are discarded precede , or follow the second uplink protocol data unit , and wherein the indication comprises the direction . According to some aspects of the first method, the first method comprises determining the second uplink protocol data unit , wherein the second uplink protocol data unit comprises a field that indicates the number, and a field that indicates the direction, or wherein the second uplink protocol data unit comprises a field that indicates the number of uplink protocol data units that are discarded, and precede the second uplink protocol data unit , and a field that indicates the number of uplink protocol data units that are discarded, and follow the second uplink protocol data unit .

[0012] According to some aspects of the first method, the first method comprises determining the second uplink protocol data unit , wherein the second uplink protocol data unit comprises at least one field that comprises the indication .

[0013] According to some aspects of the first method, the second uplink protocol data unit comprises a header, and the at least one field in the header .

[0014] According to some aspects of the first method, the second uplink protocol data unit comprises a field that indicates that the second uplink protocol data unit comprises the at least one field that comprises the indication .

[0015] According to some aspects of the first method, the second uplink protocol data unit comprises the header, and, in the header, the field that indicates that the second uplink protocol data unit comprises the at least one field . According to some aspects of the first method, the protocol data unit set of the first uplink protocol data unit has been discarded in the terminal device , and wherein the indication comprises a range of sequence numbers of protocol data units in the protocol data unit set .

[0016] According to some aspects of the first method, the indication further comprises a protocol data unit set sequence number of the discarded protocol data unit set .

[0017] According to some aspects of the first method, the indication comprises at least one information element indicating a number of protocol data unit sets subj ected to said discarding and at least one information element indicating a total number of protocol data unit sets .

[0018] According to some aspects of the first method, the indication further comprises a protocol data unit set sequence number of the last protocol data unit set covered by the indication .

[0019] According to some aspects of the first method, the first method comprises detecting that the first uplink protocol data unit is discarded due to congestion in the uplink, and not determining or not sending the second uplink protocol data unit upon detecting that the first uplink protocol data unit is discarded due to congestion .

[0020] A second method comprises receiving a first uplink protocol data unit in an uplink, wherein the first uplink protocol data unit comprises an indication that a second uplink protocol data unit is discarded, and detecting, depending on the indication, that the second uplink protocol data unit , or a protocol data unit set that comprises uplink protocol data units is discarded, or wherein the first uplink protocol data unit comprises an indication that a protocol data unit set that comprises uplink protocol data units is discarded, and wherein the method comprises detecting, depending on the indication, that the uplink protocol data unit set is discarded .

[0021] According to some aspects of the second method, the second method comprises determining a protocol data unit set error rate depending on the indication upon receipt of the indication .

[0022] A first apparatus comprises means for detecting that a first uplink protocol data unit is discarded, in the first apparatus , and means for sending, by the first apparatus , a second uplink protocol data unit in the uplink, wherein the second uplink protocol data unit comprises an indication that the first uplink protocol data unit of the has been discarded .

[0023] According to some aspects of the first apparatus , the first uplink protocol data unit and the second uplink protocol data unit are comprised in a protocol data unit set , or wherein the second uplink protocol data unit is , in particular a control protocol data unit , outside of a protocol data unit set of that comprises the first uplink protocol data unit . According to some aspects of the first apparatus , the first uplink protocol data unit is associated with a position of the first uplink protocol data unit in the protocol data unit set , wherein the first apparatus comprises means for determining the position, and means for determining the indication, wherein the indication comprises the position .

[0024] According to some aspects of the first apparatus , the protocol data unit set comprises the first uplink protocol data unit , and the second uplink protocol data unit , and wherein the first apparatus comprises means for determining a number of uplink protocol data units of the protocol data unit set , including the first uplink protocol data unit , that are discarded in the uplink, and means for determining the indication, wherein the indication comprises the number .

[0025] According to some aspects of the first apparatus , the first apparatus comprises determining a direction that indicates whether the uplink protocol data units of the protocol data unit set that are discarded precede , or follow the second uplink protocol data unit , and wherein the indication comprises the direction .

[0026] According to some aspects of the first apparatus , the first apparatus comprises means for determining the second uplink protocol data unit , wherein the second uplink protocol data unit comprises a field that indicates the number, and a field that indicates the direction, or wherein the second uplink protocol data unit comprises a field that indicates the number for uplink protocol data unit sets that are discarded, and precede the second uplink protocol data unit , and a field that indicates the number for uplink protocol data unit sets that are discarded, and follow the second uplink protocol data unit .

[0027] According to some aspects of the first apparatus , the first apparatus comprises means for determining the second uplink protocol data unit , wherein the second uplink protocol data unit comprises at least one field that comprises the indication .

[0028] According to some aspects of the first apparatus , the second uplink protocol data unit comprises a header, and the at least one field in the header .

[0029] According to some aspects of the first apparatus , the second uplink protocol data unit comprises a field that indicates that the second uplink protocol data unit comprises the at least one field that comprises the indication .

[0030] According to some aspects of the first apparatus , the second uplink protocol data unit comprises the header, and, in the header, the field that indicates that the second uplink protocol data unit comprises the at least one field .

[0031] According to some aspects of the first apparatus , the protocol data unit set of the first uplink protocol data unit has been discarded in the first apparatus , and wherein the indication comprises a range of sequence numbers of protocol data units in the protocol data unit set .

[0032] According to some aspects of the first apparatus , the indication comprises at least one information element indicating a number of protocol data unit sets subj ected to said discarding and at least one information element indicating a total number of protocol data unit sets .

[0033] According to some aspects of the first apparatus , the indication comprises at least one information element indicating a number of protocol data unit sets subj ected to said discarding and at least one information element indicating a total number of protocol data unit sets .

[0034] According to some aspects of the first apparatus , the indication further comprises a protocol data unit set sequence number of the last protocol data unit set covered by the indication .

[0035] According to some aspects of the first apparatus , the first apparatus comprises means for detecting that the first uplink protocol data unit is discarded due to congestion in the uplink, and means for not determining or not sending the second uplink protocol data unit upon detecting that the first uplink protocol data unit is discarded due to congestion . A second apparatus comprises means for receiving a first uplink protocol data unit in an uplink, wherein the first uplink protocol data unit comprises an indication that a second uplink protocol data unit is discarded, and means for detecting, depending on the indication, that the second uplink protocol data unit , or a protocol data unit set that comprises the second uplink protocol data unit is discarded, or wherein the first uplink protocol data unit comprises an indication that a protocol data unit set that comprises uplink protocol data units is discarded, wherein the second apparatus comprises means for detecting, depending on the indication, that the uplink protocol data unit set is discarded .

[0036] According to some aspects of the second apparatus , the second apparatus comprises means for determining a protocol data unit set error rate depending on the indication upon receipt of the indication .

[0037] An apparatus , wherein the apparatus comprises at least one processor and at least one memory storing instructions that , when executed by the at least one processor, cause the apparatus at least to perform the first method or the second method .

[0038] A computer program comprising instructions , which, when executed by an apparatus , cause the apparatus to at least perform the first method or the second method . Brief description of the figures

[0039] Fig. 1 schematically depicts a first apparatus,

[0040] Fig. 2 schematically depicts a second apparatus,

[0041] Fig. 3 depicts a sequence diagram,

[0042] Fig. 4 depicts an exemplary protocol data unit,

[0043] Fig. 5 depicts an exemplary protocol data unit,

[0044] Fig. 6 depicts an exemplary protocol data unit,

[0045] Fig. 7 depicts an exemplary protocol data unit,

[0046] Fig. 8 depicts an exemplary protocol data unit,

[0047] Fig. 9 depicts an exemplary protocol data unit,

[0048] Fig. 10 depicts an exemplary protocol data unit,

[0049] Fig. 11 depicts an exemplary protocol data unit,

[0050] Fig. 12 depicts an exemplary protocol data unit.

[0051] Description of the embodiments

[0052] Figure 1 schematically depicts a first apparatus 100.

[0053] The first apparatus 100 comprises means for detecting that a first uplink protocol data unit is discarded in an uplink .

[0054] The first apparatus 100 comprises means for determining a second uplink protocol data unit, wherein the second uplink protocol data unit comprises an indication that the first uplink protocol data unit of the protocol data unit set is discarded.

[0055] The first apparatus 100 comprises means for sending the second uplink protocol data unit in the uplink. For example , the first apparatus 100 comprises at least one processor 102 , and at least one memory 104 , and a sender 106 .

[0056] The at least one memory 104 of the first apparatus 100 may be configured for storing instructions that , when executed by the at least one processor 102 of the first apparatus 100 cause the first apparatus 100 at least to perform a first method .

[0057] Figure 2 schematically depicts a second apparatus 200 .

[0058] The second apparatus 200 comprises means for receiving a uplink protocol data unit in the uplink that comprises an indication that a uplink protocol data unit of a protocol data unit set is discarded .

[0059] The second apparatus 200 comprises means for detecting, depending on the indication, that the uplink protocol data unit of the protocol data unit set , or the protocol data unit set is discarded .

[0060] The second apparatus 200 may comprise means for determining a protocol data unit set error rate upon receipt of the indication .

[0061] For example , the second apparatus 200 comprises at least one processor 202 , and at least one memory 204 , and a receiver 206 .

[0062] The at least one memory 204 of the second apparatus 200 may be configured for storing instructions that , when executed by the at least one processor 202 the second apparatus 200 cause the second apparatus 200 at least to perform a second method .

[0063] Figure 3 depicts a sequence diagram with steps of the first method and the second method .

[0064] The first method comprises a step 302 . The step 302 comprises detecting that the first uplink protocol data unit is discarded in the uplink .

[0065] The first method may comprise detecting that the first uplink protocol data unit is discarded due to congestion in the uplink, and not determining or not sending the second uplink protocol data unit upon detecting that the first uplink protocol data unit is discarded due to congestion .

[0066] The first method comprises a step 304 . The step 304 comprises determining the indication . The step 304 comprises determining the second uplink protocol data unit . The first method may comprise determining the second uplink protocol data unit to comprise at least one field that comprises the indication .

[0067] The first method may comprise determining the second uplink protocol data unit to comprise a header, and the at least one field in the header .

[0068] The first method may comprise determining the second uplink protocol data unit to comprise a field that indicates that the second uplink protocol data unit comprises the at least one field that comprises the indication .

[0069] The first method may comprise determining the second uplink protocol data unit to comprise the header, and, in the header, the field that indicates that the second uplink protocol data unit comprises the at least one field .

[0070] The protocol data unit set may comprise the first uplink protocol data unit and the second uplink protocol data unit . The second uplink protocol data unit may be a control uplink protocol data unit , outside of a uplink protocol data set that comprises protocol data units .

[0071] According to an example , the first uplink protocol data unit is associated with a position of the first uplink protocol data unit in the protocol data unit set . The first method may comprise determining the position, and determining the indication to comprise the position .

[0072] According to an example , the protocol data unit set comprises the first packet data and the second packet data . The first method may comprise determining a number of uplink protocol data units of the protocol data unit set , including the first uplink protocol data unit , that are discarded in the uplink, and determining the indication to comprise the number .

[0073] The first method may further comprise determining a direction that indicates whether the uplink protocol data units of the protocol data unit set that are discarded precede , or follow the second uplink protocol data unit , and to determine the indication to comprise the direction .

[0074] The first method may comprise determining the second uplink protocol data unit to comprise a field that indicates the number, and a field that indicates the direction .

[0075] The first method may comprise determining the second uplink protocol data unit to comprise a field that indicates the number for protocol data unit sets that are discarded, and precede the second uplink protocol data unit , and a field that indicates the number for protocol data unit sets that are discarded, and follow the second uplink protocol data unit

[0076] The first method comprises a step 306 . The step 306 comprises sending the second uplink protocol data unit in the uplink .

[0077] The second method comprises receiving the second uplink protocol data unit in the step 306 in the uplink .

[0078] The second method comprises a step 308 .

[0079] The step 308 comprises detecting, depending on the indication, that the first uplink protocol data unit of the protocol data unit set is discarded, or detecting that the protocol data unit set is discarded . The step 308 may comprise determining a protocol data unit set error rate upon receipt of the indication.

[0080] The first apparatus 100 may be a UE . The second apparatus may be a network entity, e.g., an eNB or a gNB .

[0081] According to some examples, a timer, e.g., a packet data convergence protocol, PDCP, discard timer, is started, when the PDCP entity receives a service data unit (SDU) for transmission from upper layers. According to some examples, the PDU the UE intends to send, generated from the SDU, is discarded when the timer, e.g., the PDCP discard timer, expires .

[0082] According to some examples, the UE has knowledge of which PDUs belong to an UL PDU set and monitors the relative amount of transmitted PDU Sets versus PDU Sets that are discarded due to expiry of the timer.

[0083] With the first method, the UE for example informs the gNB in UL about a discarded PDU of a PDU set. Therefore, the gNB can track the protocol data unit set error rate, PSER, in UL.

[0084] According to some examples, the UE informs the gNB when it discards a PDU set, thus allowing gNB to count the discarded PDU sets.

[0085] PDCP Data PDU According to an example, the second uplink protocol data unit is a PDCP Data PDU. The PDCP Data PDU comprises a header. According to an example, the header of the PDCP Data PDU indicates how many PDUs with associated numbers immediately preceding this PDU are discarded, and therefore, the data-receiving PDCP entity, e.g., the second apparatus 200, should not expect to receive. For example, if PDUs with associated numbers 1 and 5 are transmitted but the PDUs with values 2, 3, and 4 are discarded, the indication in the header of PDU #5 indicates the value 3. According to some examples, the header of the PDCP Data PDU indicates the direction of the discarded PDUs, i.e., whether they precede or follow the current PDU. For example, if PDUs with associated numbers 1 and 2 are transmitted but the PDUs with values 3, 4 and 5 are known to be discarded already, e.g., due to a shorter discard timer, the indication in the header of PDU#2 indicates the value 3 along with the direction, e.g., a bit giving the direction .

[0086] Figure 4 depicts a first example 400 for the second uplink protocol data unit.

[0087] The second uplink protocol data unit according to the first example 400 is the PDCP Data PDU. According to the example, the PDCP Data PDU comprises N Octets 1, ..., N, wherein octet 1 comprises a D / C field indicating the type of the PDU, e.g., D / C=l for the PDCP Data PDU, the field for the indication of the Discarded PDUs, and a field for a first part of PDCP SN, octets 2 and 3 comprise a respective field for a continuation of PDCP SN, octets 4 to N-4 may comprise data, optional octets N-3 to N may comprise Message Authentication Code - Integrity, MAC-I.

[0088] The field for the indication in the header of the PDCP Data PDU for example comprises 3, 4 or 5 bits previously reserved. The number of reserved bits, R, may be determined depending on a radio-bearer type of a data radio bearer, DRB, and a configured sequence number, SN, length.

[0089] Figure 4 depicts the first example 400 with a PDCP Data PDU format for DRBs with 18 bits PDCP SN, where the R bits are replaced with a 5 bits field to signal the number of missing PDUs preceding the PDCP SN.

[0090] This provides a prompt and light mechanism for reporting discarded PDUs when the number of PDUs that should not be expected to receive does not exceed 23-l, 24-l or 25-l, i.e., 7, 15 and 31 respectively.

[0091] According to an example, one of the current reserved bits R indicates the presence of the field for the indication in a header octet. This allows up to 28PDUs, i.e., 256 PDUs, to be reported.

[0092] Figure 5 depicts a second example 500 for the second uplink protocol data unit. The second uplink protocol data unit according to the second example 500 is configured as described for the first example 400. According the second example 500, the second uplink protocol data unit has a PDCP Data PDU format for DRBs with 12 bits PDCP SN, where two R bits remain and one R bit is replaced by one M bit to signal the occurrence of an 8 bits field giving the indication, e.g., the number as number of discarded PDUs, preceding the PDCP SN. The 8 bit field replaces in the example the continuation of the PDCP SN in octet 3.

[0093] According to an example, one reserved bit R may be used to signal the direction and the remaining R bits may be used to indicate the number as number of PDUs discarded, i.e., allowing 22-l, 23-l or 24-l PDUs to be signaled as discarded in either direction, i.e., 3, 7 and 15 respectively.

[0094] Figure 6 depicts a third example 600 for the second uplink protocol data unit. The second uplink protocol data unit according to the third example 600 is configured as described for the first example 400. According the third example 600, the second uplink protocol data unit has a PDCP Data PDU format for DRBs with 18 bits PDCP SN, where the five R bits are replaced with the combination of one D bit indicating the direction and a 4 bits field to signal the number, i.e., the number of discarded PDUs either preceding or following the PDCP SN.

[0095] Figure 7 depicts a fourth example 700 for the second uplink protocol data unit. The second uplink protocol data unit according to the fourth example 700 is configured as described for the second example 500. According the fourth example 700, the second uplink protocol data unit has one of the reserved bits R replaced by the bit M indicating the presence of the field comprising the indication in the header in an octet, e.g., the octet 3, that comprises the direction, DIR, and the number, i.e., the number of discarded DPUs . This allows up to 27-l PDUs to be reported discarded in either direction, i.e., 127. According to an example, one of the remaining reserved bits, R, of the header may be used instead for indicating the direction. This allows up to 28-l PDUs to be reported discarded in either direction, i.e., 255.

[0096] Figure 7 depicts the fourth example 700 for the second uplink protocol data unit having a PDCP Data PDU format for DRBs with 12 bits PDCP SN, where the one M bit is introduced to signal the occurrence of an 8 bits field giving the direction, DIR, and the number, i.e., the number of discarded PDUs.

[0097] Figure 8 depicts a fifth example 800 for the second uplink protocol data unit for a case in which the PDUs are missing in both direction. The second uplink protocol data unit according to the fifth example 800 is configured as described for the first example 400, wherein the Data may be in octets 5 to N-3, the MAC-I optionally may be in octets N-2 to N. According to the fifth example 800, two R bits may be used to signal the presence of a header fields indicating the respective number, i.e., number of missing PDUs, in either direction. Figure 8 depicts an example with a PDCP Data PDU format for DRBs with 12 bits PDCP SN, where one F bit is introduced to signal the occurrence of an 8 bits field giving the number of missing PDUs forward, and one B bit is introduced to signal the occurrence of an 8 bits field giving the number of missing PDUs backward .

[0098] Figure 9 depicts a sixth example 900 for the second uplink protocol data unit . The second uplink protocol data unit according to the sixth example 900 is configured as described for the second example 500 , wherein an octet , e . g . , the octet 3 , of the header is split in two fields to report PDUs missing in both directions . Figure 9 depicts an example with a PDCP Data PDU format for DRBs with 12 bits PDCP SN, where one M bit is introduced to signal the occurrence of two 4 bits field giving the number of missing PDUs preceding the PDCP SN and following the PDCP SN .

[0099] PDCP control PDU

[0100] A PDCP control PDU may be used to report discarded PDU sets , albeit with increased overhead .

[0101] The PDCP control PDU is for example used where ranges of PDUs not expected to be received are signaled .

[0102] The PDCP control PDU is for example used to allow a receiver of the control PDU to infer the reported lost PDU sets .

[0103] The ranges may be organi zed per PDU set , i . e . , two ranges will correspond to two PDU sets . I f available , the PDU set SN may also be reported, e . g . , one per range .

[0104] For example , a triplet per PDU set is reported : { Discarded PDU-set SN, First SDU SN thereof , Last SDU SN thereof } .

[0105] According to some examples , the first uplink protocol data unit is comprised in a protocol data unit set , wherein protocol data units are associated with sequence numbers of protocol data units in the protocol data unit set .

[0106] According to some examples , wherein the protocol data unit set of the first uplink protocol data unit has been discarded, the indication comprises a range of sequence numbers of protocol data units in the protocol data unit set .

[0107] According to some examples , the indication comprises at least one information element indicating a number of protocol data unit sets subj ected to said discarding and at least one information element indicating a total number of protocol data unit sets .

[0108] According to some examples , the indication comprises at least one information element indicating a number of protocol data unit sets subj ected to said discarding and at least one information element indicating a total number of protocol data unit sets . According to some examples , the protocol data unit set is associated with a sequence number, wherein the indication further comprises a protocol data unit set sequence number of the last protocol data unit set covered by the indication .

[0109] Furthermore , in order to exclude PDUs and PDU sets lost due to congestion from PER / PSER calculation, the PDUs and PDU sets that were discarded when downlink signaling was used to trigger a discard mechanism to cope with congestion, may be flagged as such in the report .

[0110] Furthermore , in order to exclude PDUs and PDU sets lost due to congestion from PER / PSER calculation, the PDUs and PDU sets that were discarded when downlink signaling was used to trigger a discard mechanism to cope with congestion, may not be reported as discarded at all .

[0111] Although this downlink signaling may be in control of the network, the network may not know exactly from which PDU set it applies , which would distort PSER calculations at the gNB .

[0112] It might also be interesting for the gNB to know whether discard due to PS IHI occurred for a discarded PDU set . This may be signaled with one bit indication .

[0113] Figure 10 depicts a seventh example 1000 for the second uplink protocol data unit . The second uplink protocol data unit according to the seventh example 1000 is the PDCP Control PDU . According to the seventh example 1000 , the PDCP Control PDU comprises a plurality of octets , wherein octet 1 comprises a D / C field indicating the type of the PDU, e . g . , D / C=0 for the PDCP Control PDU, a field for a PDU Type , a reserved bit R, a field E for the indication of the Discarded PDUs , e . g . , the PDU set , and a field for a first part of a PDCP SN . Octet 2 comprises a continuation of the PDCP SN . Octet 3 comprise a field for a first SN . Octet 4 comprises a respective field for a continuation of the first SN and a part of a last SN . Octet 5 comprises a continuation of the last SN . The second uplink protocol data unit according to the seventh example 1000 comprises further octets that have the format of the octets 1 to 5 . The octets 6 to 10 in the example comprise the same format as octets 1 to 5 .

[0114] According to the seventh example 1000 , at least one of the values for the PDU Type is used to indicate that the Control PDU comprises the indication of discarded PDUs .

[0115] Figure 10 depicts the seventh example 1000 for with a PDU Set Sequence number, PSSN, defined as 10-bits long, and assuming 12 bits PDCP SN .

[0116] Figure 11 depicts an eight example 1100 of the second uplink protocol data unit . The eight example 1100 is configured as described for the seventh example 1000 , wherein alternatively to the E bit , the first bits after the PDU-Type field are used to signal how many PDU Sets are discarded . According to an example , in case more PDUs are discarded, than the field can report , another control PDU may be sent .

[0117] According to an example , for a 6 bits long PDU Sequence Number with a PDU set , PSN, a last PDCP SN may not be reported, i f the last PSN is discarded . This reduces an overhead, because the last PDCP SN = first PDCP SN + last PSN .

[0118] Figure 11 depicts the eight example 1100 as example of such a control PDU for an 18 bit PDCP SN, wherein PS IHI indicates whether the PDU set was discarded due to the PS IHI condition being met , i . e . , a loss of one PDU within the set triggered the discard of all other PDUs , and wherein CGT indicates whether the PDU set was discarded after receiving downlink signaling used to trigger discard mechanism to cope with congestion .

[0119] According to some examples , any combination of the principles outlined above is used :

[0120] 12 bits or 18 bits PDCP SN; using the E bit or indication of how many PDU Sets Number are reported; using last PDCP SN or last PSN; Using an indication per PDU Set of whether it has been discarded due to congestion as determined by the reception of a downlink signaling from the gNB ;

[0121] Using an indication per PDU set indicating whether the PDU set was discarded due to the PS IHI condition being met .

[0122] As for the use of the PDCP Data PDU, two di f ferent formats may be used for 12 bits and 18 bits PDCP SN due to di f ferences in number of bits to indicate at least the first of the SN .

[0123] One purpose of reporting discarded PDU sets is to allow the network to keep track of PSER, the network also needs to know how the discards relate to the total number of PDU sets . I f the UE only rarely reports isolated discarded PDU- set SNs , the network may not have a clear understanding on whether or how many times the PDU-set SN space has wrapped around between reports .

[0124] Therefore , discarded PDU sets may be reported in a PDCP control PDU indicating : the number of past PDU sets covered by the report ; the number of discarded PDU sets among the previous number ; and optionally, how these covered PDU sets map to the PDU-set SN space . For example, the report comprises a most recently assigned PDU set SN covered in the report, i.e., highest PDU set SN when not considering SN wrap-around.

[0125] The last, optional element above allows the network to resolve possible overlapping between consecutive reports.

[0126] This may be useful given that these reports may not have guaranteed delivery over the unacknowledged-mode RLC (radio link control protocol) channels envisioned to provide extended reality, XR, services. The indicated number of discarded PDU sets may well be 0 because also that is valuable information for the network to track PSER.

[0127] According to some examples, in particular to make sure that reporting of non-discarded PDU sets is not premature, a rule is introduced by which a PDU set is reported as nondiscarded only when, for all service data units, SDUs, making up the PDU set, the timer, e.g., the PDCP discard timer, has expired and the SDU has been submitted to lower layers for transmission, i.e., without resulting in actual discarding the PDU at the PDCP level.

[0128] Figure 12 depicts a ninth example 1200 of the second uplink protocol data unit. The second uplink protocol data unit according to the ninth example 1200 is a PDCP Control PDU. According to the ninth example 1200, the PDCP Control PDU comprises a plurality of octets, wherein octet 1 comprises a D / C field indicating the type of the PDU, e.g., D / C=0 for the PDCP Control PDU, a field for a PDU Type , and a field for a part of a Number of PDU Sets . An octet 2 comprises a field for a continuation of the number of PDU Sets , and a field for a part of the indication for discarded PDU Sets . Octets 3 comprises a field for a continuation of the indication of the discarded PDU sets . Octet 4 comprises a field for a last PDU Set SN, PSSN .

[0129] Octet 5 comprises a continuation of the last PSSN, and in particular six reserved bits R .

[0130] According to the ninth example 1200 , one of the values for the PDU Type is used to indicate that the control PDU comprises the indication of discarded PDUs . The control PDU report the numbers of PDU sets and of the discarded PDU sets thereof , as well as a PDU Set SN, e . g . , Last PSSN, to which the report maps .

[0131] According to the ninth example , 1200 , the lengths of the former two fields are chosen to equal the 10-bit PSSN, so that a single report will not span more than one PSSN space .

[0132] According to some examples , the field indicating Discarded PDU sets could be shorter than that indicating the ( total ) Number of PDU sets . According to some examples , it may be suf ficient information to the network i f , it is reported, that as much as 10% of the Number of PDU sets have been discarded . In this case , one code point of Discarded PDU Sets may cover anything above some maximum value . For example , in the above format the Discarded PDU Sets field could be only 8 bits long, with the highest value indicated by all bits set to ' 1 ' indicating anything greater than or equal to 256 . This makes the format of the uplink protocol data unit one octet shorter .

Claims

CLAIMS1 . A first method, wherein the first method comprises detecting ( 302 ) , by a terminal device , that a first uplink protocol data unit is discarded in the terminal device , sending ( 306 ) , by the terminal device , a second uplink protocol data unit in the uplink, wherein the second uplink protocol data unit comprises an indication that the first uplink protocol data unit or a protocol data unit set that comprises the first uplink protocol data unit has been discarded, and wherein the indication comprises a range of sequence numbers of protocol data units or protocol data unit sets that are discarded in the uplink .2 . The first method according to claim 1 , wherein the first method comprises determining ( 304 ) a number of uplink protocol data units with consecutive sequence numbers immediately next to a sequence number of the second protocol data unit , including the first uplink protocol data unit , that are discarded in the uplink, and determining the indication, wherein the indication comprises the number .3 . The first method according to claim 2 , wherein the first method comprises determining ( 304 ) a direction that indicates whether the sequence numbers of the uplink protocol data units that are discarded precede , or follow the sequence number of the second uplink protocol data unit , and wherein the indication comprises the direction .4 . The first method according to claim 3 , wherein the first method comprises determining ( 304 ) the second uplink protocol data unit , wherein the second uplink protocol data unit comprises a field that indicates the number, and a field that indicates the direction, or wherein the second uplink protocol data unit comprises a field that indicates the number of uplink protocol data units that are discarded, and precede the second uplink protocol data unit , or wherein the second uplink protocol data unit comprises a field that indicates the number of uplink protocol data units that are discarded, and follow the second uplink protocol data unit .5 . The first method according to one of the preceding claims , wherein the protocol data unit set of the first uplink protocol data unit has been discarded in the terminal device , and wherein the indication comprises a range of sequence numbers of protocol data units in the protocol data unit set .6 . The first method according to claim 5 , wherein the indication further comprises a protocol data unit set sequence number of the discarded protocol data unit set .7 . The first method according to any preceding claim, wherein the indication comprises at least one information element indicating a number of protocol data unit sets subj ected to said discarding and atleast one information element indicating a total number of protocol data unit sets .8 . The first method according to claim 7 , wherein the indication further comprises a protocol data unit set sequence number of the last protocol data unit set covered by the indication .9 . The first method according to one of the preceding claims , wherein the first method comprises detecting ( 302 ) that a third uplink protocol data unit is discarded due to congestion in the uplink, and not determining or not sending a fourth uplink protocol data unit comprising an indication that the third uplink protocol data unit has been discarded upon detecting that the first uplink protocol data unit is discarded due to congestion .10 . A second method, wherein the second method comprises receiving ( 306 ) a first uplink protocol data unit in an uplink, wherein the first uplink protocol data unit comprises an indication that a second uplink protocol data unit is discarded, and wherein the indication comprises a range of sequence numbers of protocol data units or protocol data unit sets that are discarded in the uplink, and detecting ( 308 ) , depending on the indication, that the second uplink protocol data unit , or a protocol data unit set that comprises uplink protocol data units is discarded, or wherein the first uplink protocol data unit comprises an indication that a protocol data unit set that comprises uplinkprotocol data units is discarded, and wherein the method comprises detecting ( 308 ) , depending on the indication, that the uplink protocol data unit set is discarded .11 . The second method according to claim 10 , wherein the second method comprises determining ( 308 ) a protocol data unit set error rate depending on the indication upon receipt of the indication .12 . A first apparatus ( 100 ) , wherein the first apparatus( 100 ) comprises means for detecting that a first uplink protocol data unit is discarded, in the first apparatus , and means for sending, by the first apparatus , a second uplink protocol data unit in the uplink, wherein the second uplink protocol data unit comprises an indication that the first uplink protocol data unit has been discarded, and wherein the indication comprises a range of sequence numbers of protocol data units or protocol data unit sets that are discarded in the uplink .13 . The first apparatus ( 100 ) according to claim 12 , wherein the protocol data unit set comprises the first uplink protocol data unit , and the second uplink protocol data unit , and wherein the first apparatus ( 100 ) comprises means for determining a number of uplink protocol data units of the protocol data unit set , including the first uplink protocol data unit , that are discarded in the uplink, and means fordetermining the indication, wherein the indication comprises the number .14 . The first apparatus ( 100 ) according to claim 13 , wherein the first apparatus ( 100 ) comprises determining a direction that indicates whether the uplink protocol data units of the protocol data unit set that are discarded precede , or follow the second uplink protocol data unit , and wherein the indication comprises the direction .15 . The first apparatus ( 100 ) according to claim 14 , wherein the first apparatus ( 100 ) comprises means for determining the second uplink protocol data unit , wherein the second uplink protocol data unit comprises a field that indicates the number, and a field that indicates the direction, or wherein the second uplink protocol data unit comprises a field that indicates the number for uplink protocol data unit sets that are discarded, and precede the second uplink protocol data unit , and a field that indicates the number for uplink protocol data unit sets that are discarded, and follow the second uplink protocol data unit .16 . The first apparatus ( 100 ) according to one of the claims 12 to 15 , wherein the protocol data unit set of the first uplink protocol data unit has been discarded in the first apparatus ( 100 ) , and wherein the indication comprises a range of sequence numbers of protocol data units in the protocol data unit set .17 . The first apparatus ( 100 ) according to one of the claims 12 to 15 , wherein the indication comprises at least one information element indicating a number of protocol data unit sets subj ected to said discarding and at least one information element indicating a total number of protocol data unit sets .18 . The first apparatus ( 100 ) according to claim 17 , wherein the indication further comprises a protocol data unit set sequence number of the last protocol data unit set covered by the indication .19 . The first apparatus ( 100 ) according to one of the claims 12 to 18 , wherein the first apparatus ( 100 ) comprises means for detecting that a third uplink protocol data unit is discarded due to congestion in the uplink, and means for not determining or not sending a fourth uplink protocol data unit comprising an indication that the third uplink protocol data unit has been discarded upon detecting that the first uplink protocol data unit is discarded due to congestion .20 . A second apparatus ( 200 ) , wherein the second apparatus( 200 ) comprises means for receiving a first uplink protocol data unit in an uplink, wherein the first uplink protocol data unit comprises an indication that a second uplink protocol data unit is discarded, and wherein the indication comprises a range of sequence numbers of protocol data units or protocol data unit sets that are discarded in the uplink, and means fordetecting, depending on the indication, that the second uplink protocol data unit, or a protocol data unit set that comprises the second uplink protocol data unit is discarded, or wherein the first uplink protocol data unit comprises an indication that a protocol data unit set that comprises uplink protocol data units is discarded, wherein the second apparatus comprises means for detecting, depending on the indication, that the uplink protocol data unit set is discarded .

21. The second apparatus (200) according to claim 20, wherein the second apparatus (200) comprises means for determining a protocol data unit set error rate depending on the indication upon receipt of the indication .

22. An apparatus (100, 200) , wherein the apparatus (100, 200) comprises at least one processor (102, 202) and at least one memory (104, 204) storing instructions that, when executed by the at least one processor (102, 202) , cause the apparatus at least to perform the method of any of claims 1 to 11.

23. A computer program comprising instructions, which, when executed by an apparatus (100, 200) , cause the apparatus (100, 200) to at least perform the method of any of claims 1 to 11.

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