Data transmission method, terminal, and computer program product

Abstract

Embodiments of the present disclosure provide a data transmission method, a terminal, and a computer program product. When a first sending end determines to discard a service data unit (SDU), a second sending end receives first discard indication information from the first sending end; and the second sending end performs data transmission on the basis of the first discard indication information.

Description

Data transmission methods, terminals and computer program products

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to Chinese patent application CN202510106124.6, filed on January 22, 2025, entitled “Data Transmission Method, Terminal and Computer Program Product”, and incorporates the entire contents of that patent application by reference. Technical Field

[0003] This disclosure relates to the field of communications, and more specifically, to a data transmission method, a terminal, and a computer program product. Background Technology

[0004] In wireless communication systems, when the Packet Data Convergence Protocol (PDCP) layer detects packet loss and starts a reordering timer, if the timer expires, the PDCP layer will abandon the waiting PDCP Service Data Units (SDUs) and update its internal state to continue subsequent data processing. However, in traditional technologies, this discarding behavior is not effectively propagated to the Radio Link Control (RLC) layer. This means the RLC layer may still be waiting for these lost or abandoned packets, which not only wastes resources but may also block transmission and degrade the overall system performance.

[0005] Furthermore, the impact of the PDCP layer's decision to discard certain SDUs on the RLC layer also needs to be considered. In existing technologies, the PDCP layer's behavior of discarding SDUs may create sequence number (SN) holes in the RLC layer, i.e., discontinuous sequence numbers. This can interfere with the normal functions of the RLC layer, such as packet assembly and reassembly window management.

[0006] In summary, the relevant technologies suffer from the problem that the PDCP layer's discard decision cannot be communicated to the RLC layer in a timely and accurate manner, leading to resource waste and transmission congestion in the RLC layer. Summary of the Invention

[0007] This disclosure provides a data transmission method, a terminal, and a computer program product.

[0008] According to one embodiment of this disclosure, a data transmission method is provided, comprising: when a first sending end determines that a service data packet (SDU) is to be discarded, a second sending end receives first discard indication information from the first sending end; and the second sending end performs data transmission based on the first discard indication information.

[0009] According to another embodiment of this disclosure, a data transmission method is provided, comprising: a second receiving end receiving second discard indication information from a first receiving end; and the second receiving end performing data transmission based on the second discard indication information.

[0010] According to another embodiment of this disclosure, a data transmission method is provided, comprising: when a reordering timer at a first receiving end times out, a second receiving end receives timeout indication information from the first receiving end; and the second receiving end performs data transmission based on the timeout indication information.

[0011] According to yet another embodiment of this disclosure, a terminal is provided, the terminal including a receiver, a transmitter, and a processor, the receiver being configured to receive configuration signaling, the configuration signaling being configured to instruct at least one of the receiver, the transmitter, and the processor to perform the steps in any of the above method embodiments.

[0012] According to yet another embodiment of this disclosure, a computer-readable storage medium is also provided, wherein a computer program is stored therein, wherein the computer program is configured to perform the steps in any of the above method embodiments when it is run.

[0013] According to yet another embodiment of this disclosure, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0014] According to yet another embodiment of this disclosure, a computer program product is also provided, including a computer program that, when executed by a processor, implements the steps in any of the above method embodiments. Attached Figure Description

[0015] Figure 1 is a flowchart of a data transmission method according to an embodiment of the present disclosure;

[0016] Figure 2 is another flowchart of a data transmission method according to an embodiment of the present disclosure;

[0017] Figure 3 is another flowchart of the data transmission method according to an embodiment of the present disclosure;

[0018] Figure 4 is a structural block diagram of a terminal according to an embodiment of this disclosure. Detailed Implementation

[0019] The embodiments of this disclosure will be described in detail below with reference to the accompanying drawings and examples.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of the embodiments of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0021] In related technologies, the PDCP layer includes a PDCP transmitter and a PDCP receiver. The PDCP transmitter's actions include: receiving a PDCP SDU from the upper layer and associating a COUNT value with the received PDCP SDU. The COUNT value contains two parts: the Hyper Frame Number (HFN) and the PDCP SN. The PDCP SN is the least significant bit of the COUNT, and the HFN is the most significant bit. Based on the associated COUNT value, the PDCP receiver may perform header compression, integrity protection, and ciphering operations on the PDCP SDU. The PDCP receiver constructs the corresponding PDCP PDU. This PDCP PDU includes the PDCP SDU, its protocol header, and the PDCP SN within the PDCP header.

[0022] In related technologies, if a PDCP discard timer is configured, the PDCP transmitter starts a discard timer for each PDCP SDU received from the upper layer. When the PDCP transmitter receives a PDCP status report, or the lower layer confirms that the PDCP SDU has been successfully received, the timer is stopped. If the timer expires, the PDCP transmitter discards the PDCP SDU and its corresponding PDCP PDU, or all PDCP SDUs and their corresponding PDCP PDUs belonging to the same PDCP set as the PDCP SDU.

[0023] The variable maintained by the PDCP transmitter is TX_NEXT: This variable is the COUNT value of the next PDCP SDU to be sent. Except for setting the SRB for the continued use of the variable, the initial value of this variable is 0.

[0024] In related technologies, the behavior of a PDCP receiver includes: receiving an RLC SDU (i.e., a PDCP PDU) delivered from its lower-layer protocol (RLC layer); determining the COUNT value associated with the PDCP PDU based on its PDCP SN; decrypting and verifying the integrity of the PDCP PDU based on the COUNT value if it is encrypted or protected for integrity; determining whether the PDCP PDU has been received before based on the COUNT value, discarding it if so, and placing it in the receive buffer if not; and reordering the received PDCP SDUs based on the COUNT value, delivering them to the upper layer in order according to their associated COUNT values ​​if out-of-order delivery is not configured or in-order delivery is configured. When PDCP detects a missing PDCP SDU, for example when the COUNT value of the received PDCP SDU is not continuous, PDCP can start a reordering timer to wait for the missing PDCP SDU. When the reordering timer times out, the PDCP layer gives up waiting for the missing PDCP SDU.

[0025] In related technologies, the PDCP receiver maintains the following variables, including but not limited to:

[0026] RX_DELIV is the COUNT value of the first PDCP SDU that has not been delivered to the upper layer but is still waiting to be received; that is, the COUNT value of the next PDCP SDU that is delivered to the upper layer in order. In addition to the sidelink broadcast channel, the configuration variables continue to specify the Signaling Radio Bearer (SRB) and the MBS Radio Bearer (MRB), with an initial value of 0.

[0027] RX_NEXT is the next COUNT value after the maximum COUNT value in the PDCP SDU in the PDCP receive buffer, i.e., the COUNT value of the next PDCP SDU expected to be received.

[0028] RCVD_COUNT is the COUNT value of the currently received PDCP SDU.

[0029] RX_REORD is the next COUNT value of the PDCP data PDU that triggered the reordering timer.

[0030] In related technologies, the reordering and in-order delivery behavior of the PDCP receiver includes: setting RX_DELIv to the COUNT value of the first PDCP SDU that has not been delivered to the upper layer. If RCVD_COUNT = RX_DELIV, then PDCP SDUs in the receive buffer with consecutive COUNT values ​​starting from RX_RCVD and greater than or equal to RX_DELIV are delivered to the upper layer. If RX_NEXT is greater than RX_DELIV, then a reordering timer is started, and the value of RX_REORD is set to RX_NEXT. If the reordering timer is running and RX_DELIV is greater than or equal to RC_REORD, then the reordering timer is stopped. If the reordering timer times out, then PDCP SDUs with a COUNT value less than RX_REORD in the buffer are delivered to their upper layer, and consecutive PDCP SDUs with a COUNT value starting from RX_REORD are delivered to their upper layer. The value of RX_DELIV is then updated. If RX_DELIV < RX_NEXT, then start the reordering timer (at this time there are still PDCP SDUs that have not been received / lost).

[0031] In related technologies, the RLC sublayer is located below the PDCP layer and above the Medium Access Control (MAC) layer in the protocol stack. A UE can be configured with multiple RLC transmitters and receivers. Each RLC is used to carry data for a radio bearer, including the Data Radio Bearer (DRB) and the Signaling Radio Bearer (SRB). A PDCP entity may be associated with one or more RLC entities.

[0032] In related technologies, the behavior of the RLC transmitter includes: receiving PDCP PDUs (i.e., RLC SDUs) sent by PDCP; constructing RLC PDUs based on the received RLC SDUs; and constructing RLC PDUs, which may involve segmenting the RLC SDUs. Segmentation involves dividing an RLC SDU into several segments and constructing an RLC PDU for each segment. The size of an RLC segment matches the size of the RLC PDU indicated by its underlying protocol; for example, the size of the RLC PDU constructed after segmentation is less than or equal to the size of the RLC PDU indicated by the MAC layer. An RLC PDU may contain a complete RLC SDU or a segment of an RLC SDU. AM RLC PDUs contain an RLC header, which includes an RLC sequence number (RLC SN). UM RLC determines whether to include an RLC SN based on whether the RLC PDU contains segments of an RLC SDU. Finally, the RLC PDU is sent to its underlying protocol, the MAC layer.

[0033] In related technologies, the Acknowledged Mode (AM) RLC transmitter maintains an RLC transmission window. The AM RLC transmitter maintains the following variables:

[0034] TX_Next_ACK: The RLC SN of the next RLC SDU waiting for successful reception confirmation within the RLC transmission window, with an initial value of 0.

[0035] TX_Next: This variable is the value of the RLC SN for the next RLC SDU, and its initial value is 0.

[0036] The RLC transmission window range is the interval: [TX_Next_ACK, TX_Next_ACK + AM transmission window size]. The RLC transmitter will not transmit RLC SDUs exceeding the transmission window range. When the RLC transmitter receives an RLC status report, it updates the value of TX_Next_ACK according to the acknowledged RLC SN indicated in the report and moves the RLC transmission window. In other words, the RLC transmission window moves based on the acknowledged RLC SDUs received by the receiver. The UM RLC transmitter maintains the following variables:

[0037] TX_Next: This variable is the value of the RLC SN for the next RLC SDU.

[0038] In related technologies, the functions of an RLC receiver include: receiving an RLC PDU from a MAC address; reassembling the received RLC PDU into an RLC SDU; determining the RLC SN associated with the reassembled RLC SDU, which is the RLC SN carried in the header of the RLC PDU; and maintaining the RLC receiving window in the AM RLC.

[0039] In related technologies, the AM RLC receiver maintains the following variables:

[0040] RX_NEXT is the next RLC SN after the SN of the last fully received RLC SDU, or the smallest RLC SN among the unreceived RLC SDUs. It is also the lower edge of the receive window, and its initial value is 0.

[0041] RX_Next_Highest is the maximum value of the RLC SN in the received RLC SDU plus 1.

[0042] RX_Next_Status_Trigger: This variable represents the next RLC SN of the RLC SDU that triggers the reassembly timer. RX_Highest_Status: This variable represents the highest possible RLC SN that can be indicated as the ACK SN field when building the status report; its initial value is 0. The RLC receive window ranges from the RLC SN interval [RX_Next, RX_Next+AM] (receive window size).

[0043] In related technologies, when the SN of a received RLC PDU is not within the RLC receive window, the RLC discards the RLC PDU. When the RLC receiver detects a lost RLC SDU or RLC SDU fragment, for example, when there is a gap between RX_Next and RX_Next_Highest where no RLC SDU or RLC fragment has been received, the RLC receiver starts a reassembly timer and sets the value of RX_Next_Status_Trigger to RX_Next_Highest. If all RLC SDUs before RX_Next_Status_Trigger at the start of the reassembly timer have been successfully received, or there is no RLC fragment gap, or due to the movement of the RLC receive window, RX_Next_Status_Trigger falls outside the receive window and is not equal to the receive window size of RX_Next+AM, then the reassembly timer stops. When the reassembly timer times out, update the value of RX_Highest_Status to SN, which is greater than or equal to the SN of the first RLC SDU that was not fully received by RX_Next_Status_Trigger. If there is an unreceived RLCSDU or RLC fragment hole between RX_Highest_Status and RX_Next_Highest, start the reassembly timer and update the value of RX_Next_Status_Trigger to RX_Next_Highest.

[0044] In related technologies, the Unacknowledged Mode (UM) RLC receiver maintains an RLC reassemble window. UM RLC maintains the following variables:

[0045] RX_Next_Reassembly: This variable represents the earliest RLC SN that has not yet been successfully assembled within the reassembly window. Its initial value is 0.

[0046] RX_Timer_Trigger: This variable is the next RLC SN that triggers the recombination timer.

[0047] RX_Next_Highest: This variable is the next RLC SN after the highest RLC SN of the received RLC PDU. This variable is also the upper edge of the recombination window. Its initial value is 0.

[0048] This disclosure provides a data transmission method. Figure 1 is a flowchart of the data transmission method according to this disclosure. As shown in Figure 1, the process includes the following steps:

[0049] In step S102, if the first sending end determines that the service data packet SDU has been dropped, the second sending end receives the first drop indication information from the first sending end.

[0050] In one exemplary embodiment, the first transmitting end is located at the Packet Data Convergence Protocol (PDCP) layer, and the second transmitting end is located at the Radio Link Control (RLC) layer.

[0051] In one exemplary embodiment, the first transmitting end and the second transmitting end are the same or different network devices, wherein the type of network device includes at least one of the following: access network element; base station; user terminal UE.

[0052] In one exemplary embodiment, the first discard indication information includes at least one of the following: a Packet Data Convergence Protocol Sequence Number (PDCP SN) associated with one or more discarded Packet Data Convergence Protocol Service Data Packets (PDCP SDUs); or a Sequence Count Value (COUNT) associated with one or more discarded PDCP SDUs.

[0053] In step S104, the second sending end transmits data based on the first discard indication information.

[0054] In one exemplary embodiment, the second transmitting end performs data transmission based on the first discard indication information, including: in response to the service data packet sequence number (SDU SN) of a discarded Radio Link Control Service Data Packet (RLC SDU) being equal to a first variable, the second transmitting end updates the value of the first variable to the SDU SN of the next RLC SDU that has not been discarded and has not been acknowledged for reception based on the first discard indication information, wherein the first variable is the TX_Next_Ack variable.

[0055] In one exemplary embodiment, the second transmitter performs data transmission based on the first discard indication information, including: the second transmitter adjusts the size of the transmission window based on the first discard indication information, wherein the size of the transmission window does not include discarded RLC SDUs.

[0056] Figure 2 is another flowchart of the data transmission method according to an embodiment of the present disclosure. As shown in Figure 2, the process includes the following steps:

[0057] In step S202, the second receiving end receives the second discard indication information from the first receiving end.

[0058] In one exemplary embodiment, the first receiving end is located at the Packet Data Convergence Protocol (PDCP) layer, and the second receiving end is located at the Radio Link Control (RLC) layer.

[0059] In one exemplary embodiment, the first receiving end and the second receiving end are the same or different network devices, wherein the type of network device includes at least one of the following: access network element; base station; user terminal UE.

[0060] In one exemplary embodiment, the second discard indication information includes at least one of the following: the Packet Data Convergence Protocol Service Data Packet (PDCP SDU) associated with the Packet Data Convergence Protocol Service Data Packet (PDCP SDU) discarded by the first receiver; the sequence count value (COUNT) associated with the PDCP SDU discarded by the first receiver; and a second variable updated by the first receiver.

[0061] In step S204, the second receiving end transmits data based on the second discard indication information.

[0062] In one exemplary embodiment, the second receiving end performs data transmission based on the second discard indication information, including: the second receiving end discarding the Radio Link Control Service Data Packet (RLC SDU) or a fragment of the RLC SDU corresponding to the second discard indication information; or, the second receiving end updating the third variable corresponding to the RLC SDU or the fragment of the RLC SDU.

[0063] In an exemplary embodiment, in response to the second receiving end being in acknowledgment mode, the second receiving end performs data transmission based on the second discard indication information, including: the second receiving end sets the value of the variable RX_Next to the variable reception sequence number RX_DELIV of the first receiving end, or sets the value of the variable RX_Next to the SDU SN of the RLC SDU corresponding to the PDCP SDU associated with RX_DELIV; or, in response to the second receiving end's variable RX_Next being equal to the SDU SN of a discarded RLC SDU, updating RX_Next to the SDU SN of the next RLC SDU that has not been discarded and has not been successfully received after RX_Next; or, in response to the second receiving end's variable RX_Next_Highest being less than the maximum value among the SDU SNs associated with the discarded RLC SDUs, setting the value of RX_Next_Highest to the maximum value among the SDU SNs of the discarded RLC SDUs plus 1; or, setting the upper limit of the second receiving end's receiving window to RX_Next, and setting the length of the receiving window to the number of discarded RLCs included in the receiving window. The sum of the number of SDUs; or, in response to the second receiver configuring a reassembly timer, the reassembly timer being run, and the value of the second receiver variable RX_Next_Status_Trigger being less than or equal to RX_Next, stop and reset the reassembly timer; or, in response to the second receiver configuring a reassembly timer, the reassembly timer being run, and the value of the second receiver variable RX_Next_Status_Trigger being less than or equal to RX_Next, stop and reset the reassembly timer, and reset the variable RX_Highest_Status; or, in response to the second receiver configuring a reassembly timer, and the reassembly timer not being run, check for the existence of missing RLC SDUs or RLC SDU fragments, and if missing RLC SDUs or RLC SDU fragments exist, start the reassembly timer.

[0064] In an exemplary embodiment, in response to the second receiving end being in unacknowledged mode, the second receiving end performs data transmission based on the second discard indication information, including: in response to the second receiving end's variable RX_Next_Reassembly being equal to the SDU SN of a discarded RLC SDU, updating RX_Next_Reassembly to the SDU SN of the next RLC SDU that has not been discarded and has not been successfully received after the current RX_Next_Reassembly; or, in response to the second receiving end's variable RX_Next_Highest being less than the maximum value among the SDU SNs associated with the discarded RLC SDU, setting the value of RX_Next_Highest to the maximum value among the SDU SNs of the discarded RLC SDU plus 1; or, setting the lower limit of the second receiving end's receiving window to RX_Next_Highest minus the set length of the receiving window minus the number of discarded RLCs included in the receiving window. The value of the number of SDUs; or, if the second receiver has a reassembly timer configured and the reassembly timer is running, and the value of the RLC variable RX_Time_Trigger is less than or equal to RX_Next_Reassembly, then stop and reset the reassembly timer; or, if the second receiver has a reassembly timer configured and the reassembly timer is not running, check whether there is a missing RLC SDU or RLC SDU fragment between RX_Next_Reassembly and RX_Next_Highest, and if there is a missing RLC SDU or RLC SDU fragment, start the reassembly timer.

[0065] Figure 3 is another flowchart of the data transmission method according to an embodiment of the present disclosure. As shown in Figure 3, the process includes the following steps:

[0066] In step S302, if the reordering timer of the first receiving end times out, the second receiving end receives timeout indication information from the first receiving end.

[0067] In one exemplary embodiment, the timeout indication information includes at least one of the following: the value of RX_DELIV after the reordering timer expires; the Packet Data Convergence Protocol Sequence Number (PDCP SN) corresponding to RX_DELIV after the reordering timer expires; the sequence count value COUNT corresponding to RX_DELIV after the reordering timer expires; RX_REORD before the reordering timer expires; the PDCP SN corresponding to RX_REORD before the reordering timer expires; the COUNT corresponding to RX_REORD before the reordering timer expires; and the maximum PDCP SN or maximum COUNT corresponding to the Packet Data Convergence Protocol Service Data Packet (PDCPSDU) that the second receiver needs to discard.

[0068] In step S304, the second receiving end transmits data based on the timeout indication information.

[0069] In an exemplary embodiment, in response to the second receiving end being in acknowledgment mode, the second receiving end performs data transmission based on timeout indication information, including: the second receiving end setting the value of RX_Next to the value of RX_DELIV, or the Radio Link Control Sequence Number (SDU SN) of the Radio Link Control Service Data Packet (RLC SDU) corresponding to the PDCP SDU corresponding to RX_DELIV; or, the second receiving end discarding the RLC SDU or a fragment of the RLC SDU corresponding to the timeout indication information; or, in response to the second receiving end configuring a reassembly timer, and the reassembly timer being running, and the value of the RX_Next_Status_Trigger variable of the second receiving end being less than or equal to RX_Next, stopping and resetting the reassembly timer, and resetting the RX_Highest_Status variable; or, the second receiving end sending an RLC status report to the second sending end, wherein the second sending end is located at the RLC layer, and the RLC status report includes information on abandoned RLC SDUs.

[0070] In one exemplary embodiment, in response to the second receiving end being in unacknowledged mode, the second receiving end performs data transmission based on timeout indication information, including: the second receiving end setting the value of RX_Next_Reassembly to the value of RX_DELIV, or the SDU SN of the RLC SDU corresponding to the PDCP SDU corresponding to RX_DELIV; or, the second receiving end discarding the RLC SDU or RLC SDU fragment corresponding to the timeout indication information; or, in response to the second receiving end configuring a reassembly timer, and the reassembly timer being running, and in response to the value of the RX_Timer_Trigger variable of the second receiving end being less than or equal to RX_Next, stopping and resetting the reassembly timer.

[0071] Through the above steps, a data transmission method is provided. When a first sending end determines that a service data packet (SDU) should be discarded, a second sending end receives first discard indication information from the first sending end; the second sending end then performs data transmission based on the first discard indication information. This embodiment of the present disclosure solves the problem in related technologies where the PDCP layer's discard decision cannot be promptly and accurately communicated to the RLC layer, leading to RLC layer resource waste and transmission congestion. It achieves the effect of timely and accurate communication of the discard decision to the RLC layer, avoiding RLC layer resource waste and transmission congestion.

[0072] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solutions of the embodiments of this disclosure, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the embodiments of this disclosure.

[0073] This disclosure also provides a terminal. FIG4 is a structural block diagram of the terminal according to an embodiment of this disclosure. As shown in FIG4, the terminal 40 includes a receiver 410, a transmitter 420 and a processor 430. The receiver 410 is used to receive configuration signaling. The configuration signaling is used to instruct at least one of the receiver 410, the transmitter 420 and the processor 430 to perform the steps of the above method embodiment.

[0074] This embodiment also provides a data transmission device for implementing the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0075] In this embodiment, the data transmission device may include different modules, and the naming and functional division of the modules may be selected in different ways according to the actual situation, as long as the steps of the data transmission method in the above embodiment can be implemented, and no specific limitations are made here.

[0076] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0077] This disclosure also provides a computer-readable storage medium storing a computer program configured to perform the steps in any of the above method embodiments when executed.

[0078] In one exemplary embodiment, the aforementioned computer-readable storage medium may include, but is not limited to, various media capable of storing computer programs, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard disk, magnetic disk, or optical disk.

[0079] This disclosure also provides an electronic device including a memory and a processor, the memory storing a computer program and the processor being configured to run the computer program to perform the steps in any of the above method embodiments.

[0080] In one exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor and the input / output device is connected to the processor.

[0081] This disclosure also provides a computer program product, including a computer program that, when executed by a processor, implements the steps in any of the above method embodiments.

[0082] In one exemplary embodiment, the computer program product described above includes a non-volatile computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the methods described in various embodiments of this application.

[0083] Specific examples in this embodiment can be found in the examples described in the above embodiments and exemplary implementations, and will not be repeated here.

[0084] Obviously, those skilled in the art should understand that the modules or steps of the embodiments of this disclosure described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the embodiments of this disclosure are not limited to any particular combination of hardware and software.

[0085] To enable those skilled in the art to better understand the technical solutions of the embodiments of this disclosure, the following description is provided in conjunction with different embodiments.

[0086] Example 1

[0087] In this embodiment of the disclosure, the PDCP transmitter is the first transmitter in the above embodiment, the RLC transmitter is the second transmitter in the above embodiment, the PDCP receiver is the first receiver in the above embodiment, and the RLC receiver is the second receiver in the above embodiment.

[0088] In this embodiment, when the PDCP transmitter discards an SDU, it instructs the RLC transmitter to update its maintained variables based on the discarded PDCP SDU (i.e., RLC SDU), such as the sequence number (RX_Next_Ack) of the next RLC SDU awaiting acknowledgment. One consequence of updating this variable is that the transmission window shifts, allowing the RLC transmitter to send new data packets. Furthermore, discarded RLC SDUs are not considered when determining the transmission window, thus eliminating their impact on the transmission window. The PDCP receiver instructs the RLC receiver on the information of the discarded SDU, and the RLC receiver can perform corresponding processing, including discarding the RLC SDU discarded by the PDCP layer, updating the variables maintained by the RLC, resetting the reassembly timer, and adjusting the receive window or reassembly window.

[0089] In this embodiment of the disclosure, when the PDCP transmitter discards the PDCP SDU, it sends a first discard indication message to the associated RLC transmitter.

[0090] In one embodiment, the first discard indication information includes: the PDCP SN associated with one or more discarded PDCP SDUs, or the COUNT value.

[0091] In this embodiment of the disclosure, the RLC transmitter confirms the SDU SN of the RLC SDU corresponding to the discarded PDCP SDU, i.e., the SDU SN of the discarded RLC SDU. The SDU SN can be the PDCP SN associated with the PDCP SDU, or COUNT, or the lower part of COUNT. The SDU SN of an RLC SDU may be the RLC SN of the RLC SDU.

[0092] In this embodiment of the disclosure, the behavior of the RLC transmitter further includes one of the following:

[0093] The corresponding RLC SDU is considered "acknowledged receipt".

[0094] If the SDU SN of a dropped RLC SDU is equal to TX_Next_Ack, set the value of TX_Next_Ack to: among the RLC SDUs that have not been dropped and have not been acknowledged, the SDU SN value is greater than or equal to the minimum value in TX_Next_Ack, that is, update TX_Next_Ack to the SDU SN of the next RLC SDU that has not been dropped and has not been acknowledged (the SDU SN value is greater than the current TX_NEXT_Ack).

[0095] If the (updated) TX_Next_Ack is less than or equal to the maximum SDU SN in the dropped RLC SDUs, then the higher edge of the RLC transmission window is set to: TX_Next_Ack + the set transmission window length + the number of dropped RLC SDUs contained in the transmission window. That is, the length of the RLC transmission window does not take into account the dropped RLC SDUs, and the number of RLC SDUs contained in the transmission window minus the number of dropped RLC SDUs is equal to the set transmission window length.

[0096] In this embodiment of the disclosure, the PDCP receiver receives information about discarded PDCP SDUs indicated by the PDCP transmitter. For example, the PDCP transmitter sends a PDCP SN gap report to the PDCP receiver to indicate the information about discarded PDCP SDUs. Based on the information about the discarded PDCP SDUs, the PDCP receiver updates the variables it maintains, such as the values ​​of the PDCP variables RX_DELIV and / or RX_REORD.

[0097] In this embodiment of the disclosure, the RLC receiver receives second discard indication information from the PDCP receiver. The second discard indication information includes at least one of the following: information about the discarded PDCP SDU, such as the PDCP SN or COUNT value associated with the discarded PDCP SDU; and updated variables of the PDCP receiver, such as the values ​​of RX_DELIV and / or RX_REORD.

[0098] In this embodiment of the disclosure, the RLC receiver determines the SDU SN of the RLC SDU (i.e., the discarded RLC SDU) corresponding to the discarded PDCP SDU. The SDU SN may be the PDCP SN associated with the corresponding PDCP SDU, or COUNT, or the lower part of COUNT, or the RLC SN of the corresponding RLC SDU.

[0099] In this embodiment of the disclosure, the RLC receiver performs at least one of the following:

[0100] a. The RLC receiver discards the received RLC SDU or fragments of the RLC SDU.

[0101] b. The RLC receiver will treat a discarded RLC SDU as either "discarded" or "successfully received" and update the variables it maintains.

[0102] In this embodiment of the disclosure, the behavior of the AM RLC receiver further includes one of the following:

[0103] a. Set the value of the RLC receiver variable RX_Next to the PDCP variable RX_DELIV, or the SDU SN of the RLC SDU corresponding to the PDCP SDU associated with RX_DELIV.

[0104] b. If the RLC receiver variable RX_Next is equal to the SDU SN of a discarded RLC SDU, then: set the value of RX_Next to the SDU SN of the first RLC SDU that is greater than RX_Next, and has not been considered discarded or successfully received, and is not already successfully received, that is, update RX_Next to the SDU SN of the next RLC SDU that has not been discarded and has not been successfully received after RX_Next.

[0105] c. If the value of the RLC variable RX_Next_Highest is less than the maximum value in the SDU SN associated with the discarded RLC SDU, then set the value of RX_Next_Highest to the maximum value in the SDU SN of the discarded RLC SDU plus 1.

[0106] d. Set the upper edge of the RLC receive window to RX_Next + the length of the receive window + the number of discarded RLC SDUs contained in the receive window. That is, discarded RLC SDUs are not counted in the length of the receive window.

[0107] e. If a rebuild timer is configured and is running, and the value of the RLC variable RX_Next_Status_Trigger is less than or equal to RX_Next, then stop and reset the rebuild timer. Optionally, reset the variable RX_Highest_Status, for example, to the value of RX_Next.

[0108] f. If a reassembly timer is configured but not running, test whether the reassembly timer needs to be started. This involves checking for missing RLC SDUs or RLC SDU fragments. If any exist, start the reassembly timer. For example, the following method:

[0109] If RX_Next_Highest > RX_Next+1; or if RX_Next_Highest = RX_Next+1, and there is at least one missing fragment of this RLC SDU before the last byte of all received fragments of this RLC SDU: start the reassembly timer; set RX_Next_Status_Trigger to RX_Next_Highest.

[0110] In this embodiment of the disclosure, the behavior of the UM RLC receiver further includes:

[0111] a. If the RLC receiver variable RX_Next_Reassembly is equal to the SDU SN of a discarded RLC SDU, then: set the value of RX_Next_Reassembly to the SDU SN of the first RLC SDU that is greater than RX_Next_Reassembly, and has not been considered discarded or successfully received, and is not already successfully received, that is, update RX_Next_Reassembly to the SDU SN of the next RLC SDU that has not been discarded and has not been successfully received after the current RX_Next_Reassembly.

[0112] b. If the value of the RLC variable RX_Next_Highest is less than the maximum value in the SDU SN associated with the discarded RLC SDU, then set the value of RX_Next_Highest to the maximum value in the SDU SN of the discarded RLC SDU plus 1.

[0113] c. Set the lower edge of the RLC receive window to RX_Next_Highest - the length of the receive window - the number of discarded RLC SDUs contained in the receive window, that is, discarded RLC SDUs are not counted in the length of the receive window.

[0114] e. If a reassembly timer is configured and is running, and the value of the RLC variable RX_Time_Trigger is less than or equal to RX_Next_Reassembly, then stop and reset the reassembly timer.

[0115] f. If a reassembly timer is configured but not running, test whether the reassembly timer needs to be started. Specifically, check if there is a missing RLC SDU or RLC SDU fragment between RX_Next_Reassembly and RX_Next_Highest. If so, start the reassembly timer. For example, the following method:

[0116] If RX_Next_Highest > RX_Next_Reassembly + 1; or, if RX_Next_Highest = RX_Next_Reassembly + 1, and there is at least one missing fragment of this RLC SDU before the last byte of all received fragments of this RLC SDU: start the reassembly timer; set RX_Time_Trigger to RX_Next_Highest.

[0117] The method in this embodiment applies to a method for setting up an RLC SN based on a PDCP SN, such as reusing the PDCP SN value. In this case, when the PDCP discards the SDU, a gap may occur in the RLC SN at the RLC layer, meaning the RLC SN is discontinuous at the radio interface, which may cause RLC transmission to be blocked.

[0118] In this embodiment, the PDCP layer indicates the information of SDUs that have been discarded by the RLC layer. The RLC layer regards these discarded SDUs as either discarded or successfully sent / received, in order to prevent the possibility of RLC layer transmission being blocked, thereby realizing the function of PDCP discarding SDUs.

[0119] Example 2

[0120] In this embodiment of the disclosure, the PDCP transmitter is the first transmitter in the above embodiment, the RLC transmitter is the second transmitter in the above embodiment, the PDCP receiver is the first receiver in the above embodiment, and the RLC receiver is the second receiver in the above embodiment.

[0121] In related technologies, when the reordering timer at the PDCP receiver times out, the PDCP abandons waiting for the missing PDCP SDU and updates its maintained variables. In one embodiment, this may include: submitting PDCP SDUs with stored COUNT values ​​less than RX_REORD to its upper layer; or, submitting stored PDCP SDUs with consecutive COUNT values ​​starting from RX_REORD to its upper layer, where the consecutive COUNT values ​​include received PDCP SDUs and COUNT values ​​of PDCP SDUs considered discarded, i.e., discarded PDCP SDUs are also part of the consecutive PDCP SDUs; or, updating the value of RX_DELIV to the COUNT value of the next PDCP SDU to be submitted to the upper layer, for example, setting it to a COUNT value greater than or equal to RX_REORD, and a COUNT value for which neither received nor considered discarded PDCP SDUs are present. Alternatively, if there are still PDCP SDUs that are not missing, such as RX_DELIV < RX_NEXT, then restart the reordering timer and set the value of RX_REORD to RX_NEXT.

[0122] In this embodiment of the disclosure, the PDCP receiver instructs the RLC receiver to at least one of the following via timeout indication information:

[0123] a. The value of the PDCP variable RX_DELIV after the above reordering timer timeout process, or the PDCP SN or COUNT value associated with the corresponding PDCP SDU.

[0124] b. The value of the variable RX_REORD before the reordering timer expires, or the PDCP SN or COUNT value associated with the corresponding PDCP SDU.

[0125] c. Information about PDCP SDUs that the RLC receiver needs to discard, such as the maximum COUNT value of the PDCP SDU that needs to be discarded, or the maximum SDU SN value in the RLC SDU.

[0126] In this embodiment of the disclosure, the AM mode RLC receiver performs one of the following operations:

[0127] a. Set the value of the RLC receiver variable RX_Next to the value of the PDCP variable RX_DELIV mentioned above, or the SDU SN of the RLC SDU corresponding to the PDCP SDU associated with RX_DELIV.

[0128] b. Discard RLC SDUs or RLC SDU fragments whose SDU SN stored at the RLC receiver is less than the RLC variable RX_Next.

[0129] c. Based on the PDCP SDU information indicating which PDCP SDUs need to be discarded, discard the corresponding RLC SDU or RLC SDU fragments.

[0130] d. If the RLC receiver has a reassembly timer configured, and the reassembly timer is running, and the value of the RLC variable RX_Next_Status_Trigger is less than or equal to RX_Next, then stop and reset the reassembly timer. Optionally, reset the variable RX_Highest_Status, for example, by setting it to the value of RX_Next.

[0131] f. If the RLC receiver has a reassembly timer configured, and the reassembly timer is not running, test whether the reassembly timer needs to be started. Specifically, check if there is a missing RLC SDU or an RLC SDU fragment between RX_Next and RX_Next_Highest. If so, start the reassembly timer. For example, the following method:

[0132] If RX_Next_Highest > RX_Next+1; or, if RX_Next_Highest = RX_Next+1, and there is at least one missing fragment of this RLC SDU before the last byte of all received fragments of this RLC SDU: start the reassembly timer; set RX_Next_Status_Trigger to RX_Next_Highest.

[0133] e. The RLC receiver indicates information about RLC SDUs that were discarded by the RLC transmitter. In one embodiment, the RLC receiver may construct an RLC status report and send it to the RLC transmitter. The RLC status report indicates the RLC SN or SDU SN of the discarded RLC SDU, or the discarded RLC SDU is indicated in the RLC status report as successfully received. The RLC transmitter updates its RLC receiver variables and transmission window based on the information of the discarded RLC SDUs.

[0134] In this embodiment of the disclosure, the RLC receiver in UM mode performs one of the following operations:

[0135] a. Set the value of the RLC receiver variable RX_Next_Reassembly to the value of the PDCP variable RX_DELIV mentioned above, or the SDU SN of the RLC SDU corresponding to the PDCP SDU associated with RX_DELIV.

[0136] b. Discard RLC SDUs or RLC SDU fragments whose SDU SN is less than RX_Next_Reassembly stored at the RLC receiver.

[0137] c. If the RLC receiver has a reassembly timer configured and the reassembly timer is running, and the value of the RLC variable RX_Timer_Trigger is less than or equal to RX_Next, then stop and reset the reassembly timer.

[0138] e. If the RLC receiver has a reassembly timer configured, and the reassembly timer is not running, test whether the reassembly timer needs to be started. Specifically, check if there is a missing RLC SDU or an RLC SDU fragment between RX_Next_Reassembly and RX_Next_Highest. If so, start the reassembly timer. For example, the following method:

[0139] If RX_Next_Highest > RX_Next_Reassembly + 1; or, if RX_Next_Highest = RX_Next_Reassembly + 1, and there is at least one missing fragment of this RLC SDU before the last byte of all received fragments of this RLC SDU: start the reassembly timer; set the value of RX_Time_Trigger to the value of RX_Next_Highest.

[0140] In this embodiment of the disclosure, the aforementioned SDU SN may be the RLC SN of the associated RLC SDU, or the PDCP SN of the PDCP SDU corresponding to the RCL SDU, or its COUNT value, or the lower part of its COUNT value.

[0141] In this embodiment, when the PDCP receiver times out and abandons waiting for unreceived PDCP SDUs, it instructs its associated RLC receiver to abandon waiting for the corresponding RLC SDUs that have not yet been successfully reassembled. This includes discarding fragments of the already received RLC SDUs, updating variables maintained by the RLC receiver, and adjusting the AM RLC's receive window and the UM RLC's reassembly window. This method facilitates coordinating the behavior of the PDCP and RLC receivers in waiting for data packets. For example, for UM mode RLC, a reassembly timer does not need to be configured; the PDCP reordering timer timeout method can replace the RLC reassembly timer function, saving processing resources. On the other hand, when the PDCP receiver abandons waiting for certain PDCP SDUs due to the reordering timer timeout and adjusts the AM RLC's receive window and the UM RLC's reassembly window, the process of the RLC receiver abandoning waiting for the corresponding RLC SDUs can be accelerated, preparing for the reception of subsequent RLC SDUs.

[0142] The data transmission method provided in this disclosure requires specific conditions to be used. These conditions may include: the network indicating whether to apply the data transmission method provided in this disclosure through configuration; or, the RLC receiver does not have a reassembly timer configured, and the UE applies the data transmission method provided in this disclosure.

[0143] The above description is merely a preferred embodiment of this disclosure and is not intended to limit the scope of this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A data transmission method, comprising: If the first sending end determines that the service data packet SDU should be dropped, the second sending end receives the first drop indication information from the first sending end; The second sending end transmits data based on the first discard indication information.

2. The method according to claim 1, wherein, The first transmitter is located at the Packet Data Convergence Protocol (PDCP) layer, and the second transmitter is located at the Radio Link Control (RLC) layer.

3. The method according to claim 2, wherein, The first transmitter and the second transmitter are the same or different network devices, wherein the type of the network device includes at least one of the following: Access network element; base station; user terminal (UE).

4. The method according to claim 1, wherein, The first discard indication information includes at least one of the following: The Packet Data Convergence Protocol Service (PDCP) Sequence Number (PDCP SN) associated with one or more discarded Packet Data Convergence Protocol Service (PDCP) SDUs; One or more discarded sequence count values ​​(COUNT) associated with the PDCP SDU.

5. The method according to claim 1, wherein, The second sending end transmits data based on the first discard indication information, including: In response to a dropped Radio Link Control Service Packet (RLC SDU) with the Service Packet Sequence Number (SDU SN) equal to a first variable, the second sender updates the value of the first variable to the SDU SN of the next RLC SDU that has not been dropped and has not been acknowledged, based on the first drop indication information, wherein the first variable is the TX_Next_Ack variable.

6. The method according to claim 5, wherein, The second sending end transmits data based on the first discard indication information, including: The second transmitter adjusts the size of the transmission window based on the first discard indication information, wherein the size of the transmission window does not include the discarded RLC SDU.

7. A data transmission method, comprising: The second receiving end receives the second discard indication information from the first receiving end; The second receiving end transmits data based on the second discard indication information.

8. The method according to claim 7, wherein, The first receiving end is located at the Packet Data Convergence Protocol (PDCP) layer, and the second receiving end is located at the Radio Link Control (RLC) layer.

9. The method according to claim 8, wherein, The first receiving end and the second receiving end are the same or different network devices, wherein the type of the network device includes at least one of the following: Access network element; base station; user terminal (UE).

10. The method according to claim 7, wherein, The second discard instruction information includes at least one of the following: The Packet Data Convergence Protocol Service Data Packet (PDCP SDU) associated with the first receiving end is the Packet Data Convergence Protocol Sequence Number (PDCP SN). The first receiving end discards the sequence count value COUNT associated with the PDCP SDU; The second variable updated by the first receiving end.

11. The method according to claim 7, wherein, The second receiving end performs data transmission based on the second discard indication information, including: The second receiving end discards the Radio Link Control Service Data Packet (RLC SDU) or fragments of the RLC SDU corresponding to the second discard indication information; Alternatively, the second receiving end updates the third variable corresponding to the RLC SDU or the fragment of the RLC SDU.

12. The method according to claim 7, wherein, In response to the second receiving end being in acknowledgment mode, the second receiving end performs data transmission based on the second discard indication information, including: The second receiving end sets the value of the variable RX_Next to the value of the variable RX_DELIV of the first receiving end, or sets the value of the variable RX_Next to the SDU SN of the RLC SDU corresponding to the PDCP SDU associated with RX_DELIV; Alternatively, in response to the second receiver's variable RX_Next being equal to the SDU SN of a discarded RLC SDU, RX_Next is updated to the SDU SN of the next RLC SDU that was not discarded and was not successfully received after RX_Next; Alternatively, in response to the second receiver's variable RX_Next_Highest being less than the maximum value in the SDU SN associated with the discarded RLC SDU, the value of RX_Next_Highest is set to the maximum value in the SDU SN of the discarded RLC SDU plus 1: Alternatively, the upper limit of the receiving window of the second receiving end can be set to RX_Next, and the length of the receiving window can be set to the sum of the number of discarded RLC SDUs contained in the receiving window; Alternatively, in response to the second receiver configuring a recombination timer, the recombination timer being run, and the value of the second receiver variable RX_Next_Status_Trigger being less than or equal to RX_Next, the recombination timer is stopped and reset; Alternatively, in response to the second receiver configuring a reassembly timer, the reassembly timer being run, and the value of the second receiver variable RX_Next_Status_Trigger being less than or equal to RX_Next, the reassembly timer is stopped and reset, and the variable RX_Highest_Status is reset; Alternatively, in response to the second receiving end configuring a reassembly timer, and the reassembly timer not being run, check whether there is a missing RLC SDU or RLC SDU fragment. If there is a missing RLC SDU or RLC SDU fragment, start the reassembly timer.

13. The method according to claim 7, wherein, In response to the second receiving end being in unacknowledged mode, the second receiving end performs data transmission based on the second discard indication information, including: In response to the second receiver's variable RX_Next_Reassembly being equal to the SDU SN of a discarded RLC SDU, RX_Next_Reassembly is updated to the SDU SN of the next RLC SDU that has not been discarded and has not been successfully received after the current RX_Next_Reassembly. Alternatively, in response to the second receiver's variable RX_Next_Highest being less than the maximum value in the SDU SN associated with the discarded RLC SDU, the value of RX_Next_Highest is set to the maximum value in the SDU SN of the discarded RLC SDU plus 1: Alternatively, the lower limit of the receiving window of the second receiving end can be set to RX_Next_Highest minus the set length of the receiving window and then minus the number of discarded RLC SDUs contained in the receiving window; Alternatively, if the second receiving end is configured with a reassembly timer, and the reassembly timer is running, and the value of the RLC variable RX_Time_Trigger is less than or equal to RX_Next_Reassembly, then the reassembly timer is stopped and reset. Alternatively, if the second receiving end is configured with a reassembly timer and the reassembly timer is not running, check whether there is a missing RLC SDU or RLC SDU fragment between RX_Next_Reassembly and RX_Next_Highest. If there is a missing RLC SDU or RLC SDU fragment, start the reassembly timer.

14. A data transmission method, comprising: If the reordering timer at the first receiving end times out, the second receiving end receives timeout indication information from the first receiving end; The second receiving end transmits data based on the timeout indication information.

15. The method according to claim 14, wherein, The timeout indication information includes at least one of the following: The value of RX_DELIV after the reordering timer times out; The packet data aggregation protocol sequence number (PDCP SN) corresponding to RX_DELIV after the reordering timer expires; The sequence count value COUNT corresponding to RX_DELIV after the reordering timer times out; The RX_REORD before the reordering timer times out; The PDCP SN corresponding to RX_REORD before the reordering timer times out; The COUNT corresponding to RX_REORD before the reordering timer times out; The second receiving end needs to discard the maximum PDCPSN or maximum COUNT corresponding to the Packet Data Convergence Protocol Service (PDCP) SDU.

16. The method according to claim 15, wherein, In response to the second receiving end being in acknowledgment mode, the second receiving end performs data transmission based on the timeout indication information, including: The second receiving end sets the value of RX_Next to the value of RX_DELIV, or the radio link control sequence number SDU SN of the radio link control service data packet RLC SDU corresponding to the PDCP SDU of RX_DELIV; Alternatively, the second receiving end may discard the RLC SDU or RLC SDU fragment corresponding to the timeout indication information; Alternatively, in response to the second receiver configuring a reassembly timer, the reassembly timer being run, and the value of the RX_Next_Status_Trigger variable of the second receiver being less than or equal to RX_Next, the reassembly timer is stopped and reset; Alternatively, in response to the second receiver configuring a reassembly timer, the reassembly timer being run, and the value of the RX_Next_Status_Trigger variable of the second receiver being less than or equal to RX_Next, the reassembly timer is stopped and reset, and the RX_Highest_Status variable is reset; Alternatively, the second receiving end sends an RLC status report to the second sending end, wherein the second sending end is located at the RLC layer, and the RLC status report includes abandoned RLC SDU information.

17. The method according to claim 15, wherein, In response to the second receiving end being in unacknowledged mode, the second receiving end performs data transmission based on the timeout indication information, including: The second receiving end sets the value of RX_Next_Reassembly to the value of RX_DELIV, or the SDU SN of the RLC SDU corresponding to the PDCP SDU corresponding to the RX_DELIV switch; Alternatively, the second receiving end may discard the RLC SDU or RLC SDU fragment corresponding to the timeout indication information; Alternatively, in response to the second receiver configuring a reassembly timer and the reassembly timer being run, and in response to the value of the RX_Timer_Trigger variable of the second receiver being less than or equal to RX_Next, the reassembly timer is stopped and reset.

18. A terminal comprising a receiver, a transmitter, and a processor, the receiver being configured to receive configuration signaling, the configuration signaling being configured to instruct at least one of the receiver, the transmitter, and the processor to perform the steps of the method according to any one of claims 1 to 17.

19. A computer-readable storage medium storing a computer program, wherein, When the computer program is executed by a processor, it implements the steps of the method described in any one of claims 1 to 17.

20. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, performs the steps of the method of any one of claims 1 to 17.

21. A computer program product comprising a computer program that, when executed by a processor, implements the steps of the method described in any one of claims 1 to 17.

Images