Method for performing retransmission based on a discard indicator in a wireless communication system and apparatus for the same

Abstract

The present disclosure relates to a method performed by a User Equipment (UE) in a wireless communication system. In particular, the method comprises the step of submitting one or more service data units (SDUs) to a medium access control (MAC) entity of the UE by a radio link control (RLC) entity of the UE, wherein a poll retransmission timer is started based on one of the one or more RLC SDUs being submitted with a poll; the step of receiving a discard indication for at least one of the submitted RLC SDUs from a Packet Data Convergence Protocol (PDCP) entity of the UE by the RLC entity; and the step of selecting an RLC SDU for retransmission from among the one or more submitted RLC SDUs, excluding the at least one RLC SDU indicated by the discard indication, based on the expiration of the poll retransmission timer by the RLC entity. and includes the step of submitting the RLC SDU selected for retransmission to the MAC entity by the RLC entity.

Description

Technology Field

[0001] The present disclosure relates to a wireless communication system, in particular to a method for performing retransmission based on a discard indicator in a wireless communication system, and an apparatus for doing the same. Background Technology

[0002] With the introduction of new wireless communication technologies, not only is the number of UEs that a base station must service within a given resource area increasing, but the volume of data and control information transmitted and received by the base station with the UEs it services is also increasing. Since the amount of wireless resources available to a base station for communication with UE(s) is finite, new methods are required for the base station to efficiently receive and transmit uplink / downlink data and / or uplink / downlink control information from and to UE(s) using these finite wireless resources. In particular, there is an increasing number of applications whose performance is critically dependent on delay. Therefore, measures to reduce delay compared to existing systems are required. The problem to be solved

[0003] The object of the present invention is to provide a method for performing retransmission based on a discard indicator in a wireless communication system and an apparatus for doing so. means of solving the problem

[0004] The object of the present invention is achieved by a method for operations performed by a UE (user equipment), the method comprising the step of submitting one or more RLC SDUs (service data units) to a MAC (medium access control) entity of the UE by an RLC (radio link control) entity of the UE, wherein a poll retransmission timer is started based on one of the one or more RLC SDUs being submitted with a poll; the step of receiving a discard indication for at least one of the one or more submitted RLC SDUs from a PDCP (Packet Data Convergence Protocol) entity of the UE by the RLC entity; and the step of selecting an RLC SDU for retransmission from among the one or more submitted RLC SDUs, excluding the at least one RLC SDU indicated by the discard indication, based on the expiration of the poll retransmission timer by the RLC entity. and includes the step of submitting the RLC SDU selected for retransmission to the MAC entity by the RLC entity.

[0005] Additionally, a user equipment (UE) in a wireless communication system is proposed, wherein the UE comprises at least one processor; and at least one computer memory storing instructions that cause the UE to perform operations when executed by the at least one processor, the operations comprising: submitting one or more service data units (SDUs) from the radio link control (RLC) entity of the UE to the medium access control (MAC) entity of the UE, wherein a poll retransmission timer is started based on the fact that one of the one or more RLC SDUs is submitted with a poll; and receiving a discard indication for at least one of the submitted RLC SDUs from the Packet Data Convergence Protocol (PDCP) entity of the UE by the RLC entity. Based on the expiration of the pole retransmission timer, the method includes the step of selecting an RLC SDU for retransmission from among one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the discard indicator, by the RLC entity; and the step of submitting the RLC SDU selected for retransmission to the MAC entity by the RLC entity.

[0006] Preferably, the RLC SDU for retransmission is selected from among one or more submitted RLC SDUs that are not indicated by the discard indicator and have not yet received a positive response.

[0007] Preferably, the RLC SDU for retransmission is selected based on the fact that both the transmission buffer and the retransmission buffer are empty, or based on the fact that a new RLC SDU or a new RLC SDU segment cannot be transmitted due to window stalling.

[0008] Preferably, the step of selecting the RLC SDU for retransmission includes the step of submitting the RLC SDU for retransmission together with the pole; and the step of restarting the pole retransmission timer.

[0009] Preferably, the step of selecting the RLC SDU for retransmission includes selecting an RLC SDU having a minimum remaining time until disposal from among the one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the disposal indicator.

[0010] Preferably, the step of selecting the RLC SDU for retransmission includes selecting, from among the one or more submitted RLC SDUs excluding at least one RLC SDU indicated by the discard indicator, the RLC SDU indicated by the delay critical indication for retransmission from the upper layer.

[0011] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below. Effects of the invention

[0012] According to the present disclosure, when a poll retransmission timer expires, the UE can select an RLC SDU for retransmission based on the remaining time or a discard indication received from an upper layer. Thus, the user experience for XR services can be improved by preventing unnecessary retransmission of old data and enabling urgent XR data to be transmitted to the network at an appropriate time. Additionally, this can prevent the waste of wireless resources.

[0013] The effects obtainable from the present invention may not be limited to those described above. Furthermore, other unmentioned effects can be clearly understood by those skilled in the art from the following description. Brief explanation of the drawing

[0014] To further aid in understanding the present invention, the accompanying drawings illustrate embodiments of the present invention and explain the principles of the present invention together with the detailed description: FIG. 1 illustrates an example of a communication system to which the implementations of the present specification are applied; FIG. 2 is a block diagram illustrating examples of communication devices capable of performing the method according to the present specification; FIG. 3 illustrates an example of a frame structure in a 3GPP-based wireless communication system; Figure 4 illustrates examples of protocol stacks in a 3GPP (third generation partnership project) based wireless communication system; FIG. 5 illustrates an example of a data flow in a 3GPP NR (new radio) system; FIG. 6 illustrates an example of PDSCH time domain resource allocation by PDCCH and an example of PUSCH time resource allocation by PDCCH; FIG. 7 illustrates an example of physical layer processing at the transmitting side; FIG. 8 illustrates an example of physical layer processing at the receiving end; FIG. 9 is a first example of performing retransmission according to the present disclosure; FIG. 10 is a second example of performing retransmission according to the present disclosure; FIG. 11 is a third example of performing retransmission according to the present disclosure; FIG. 12 is a flowchart for performing an operation according to the present disclosure. Specific details for implementing the invention

[0015] Exemplary implementations of this specification are described in detail with reference to the accompanying drawings. The detailed description provided below, together with the accompanying drawings, is intended to describe exemplary implementations of this specification and is not intended to represent the only forms of implementation that may be carried out according to this specification. The following detailed description includes specific details to provide a complete understanding of this specification. However, it will be apparent to those skilled in the art that this specification may be practiced without such specific details.

[0016] The following technologies can be used in various wireless communication systems such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA can be implemented using wireless technologies such as UTRA (universal terrestrial radio access) or CDMA2000. TDMA can be implemented using wireless technologies such as GSM (global system for mobile communications), GPRS (general packet radio service), and EDGE (enhanced data rates for GSM evolution). OFDMA can be implemented using wireless technologies such as IEEE (institute of electrical and electronics engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (evolved UTRA). IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of UMTS (universal mobile telecommunications system). 3GPP (3rd generation partnership project) LTE (long term evolution) is part of E-UMTS (evolved UMTS) which uses E-UTRA (evolved-UMTS terrestrial radio access), employing OFDMA in the downlink and SC-FDMA in the uplink.LTE-A (advanced) is an evolution of 3GPP LTE.

[0017] For the sake of convenience of explanation, implementations of this specification are described primarily with respect to 3GPP-based wireless communication systems. However, the technical features of this specification are not limited thereto. For example, the following detailed description is based on mobile communication systems corresponding to 3GPP-based wireless communication systems, but aspects of this specification that are not limited to 3GPP-based wireless communication systems may be applied to other mobile communication systems. For terms and technologies used in this specification that are not specifically mentioned, reference may be made to wireless communication standard documents prior to the publication of this specification. For example, the following documents may be referenced.

[0018] 3GPP LTE

[0019] - 3GPP TS 36.211: Physical channels and modulation

[0020] - 3GPP TS 36.212: Multiplexing and channel coding

[0021] - 3GPP TS 36.213: Physical layer procedures

[0022] - 3GPP TS 36.214: Physical layer; Measurements

[0023] - 3GPP TS 36.300: Overall description

[0024] - 3GPP TS 36.304: User Equipment (UE) procedures in idle mode

[0025] - 3GPP TS 36.314: Layer 2 - Measurements

[0026] - 3GPP TS 36.321: Medium Access Control (MAC) protocol

[0027] - 3GPP TS 36.322: Radio Link Control (RLC) protocol

[0028] - 3GPP TS 36.323: Packet Data Convergence Protocol (PDCP)

[0029] - 3GPP TS 36.331: Radio Resource Control (RRC) protocol

[0030] 3GPP NR

[0031] - 3GPP TS 38.211: Physical channels and modulation

[0032] - 3GPP TS 38.212: Multiplexing and channel coding

[0033] - 3GPP TS 38.213: Physical layer procedures for control

[0034] - 3GPP TS 38.214: Physical layer procedures for data

[0035] - 3GPP TS 38.215: Physical layer measurements

[0036] - 3GPP TS 38.300: Overall description

[0037] - 3GPP TS 38.304: User Equipment (UE) procedures in idle mode and in RRC inactive state

[0038] - 3GPP TS 38.321: Medium Access Control (MAC) protocol

[0039] - 3GPP TS 38.322: Radio Link Control (RLC) protocol

[0040] - 3GPP TS 38.323: Packet Data Convergence Protocol (PDCP)

[0041] - 3GPP TS 38.331: Radio Resource Control (RRC) protocol

[0042] - 3GPP TS 37.324: Service Data Adaptation Protocol (SDAP)

[0043] - 3GPP TS 37.340: Multi-connectivity; Overall description

[0044] In this specification, UEs may be fixed or mobile and include various devices that communicate with a base station (BS) to transmit and receive user data and / or various control information. A UE may be referred to as Terminal Equipment, Mobile Station (MS), Mobile Terminal (MT), User Terminal (UT), Subscribe Station (SS), wireless device, Personal Digital Assistant (PDA), wireless modem, handheld device, etc. Additionally, in this specification, a BS generally refers to a fixed station that communicates with a UE and / or other BSs and exchanges various data and control information by communicating with a UE and other BSs. A BS may be referred to by other terms such as Advanced Base Station (ABS), Node-B (NB), eNB (evolved-NodeB), Base Transceiver System (BTS), Access Point, Processing Server (PS), etc. In particular, the BS of UMTS is called NB, the BS of EPC / LTE is called eNB, and the BS of the NR (new radio) system is called gNB.

[0045] In this specification, a node refers to a fixed point capable of transmitting or receiving wireless signals by communicating with a UE. Various types of eNBs may be used as nodes regardless of their designation. For example, a BS, NB, eNB, pico-cell eNB (PeNB), home eNB (HeNB), relay, repeater, etc., may serve as nodes. Additionally, a node does not have to be an eNB. For example, it may be a radio remote head (RRH) or a radio remote unit (RRU). RRHs, RRUs, etc. generally have a power level lower than that of an eNB. Since RRHs or RRUs (or RRH / RRUs) are generally connected to the eNB via a dedicated line such as an optical cable, cooperative communication between an RRH / RRU and an eNB can be performed more smoothly compared to cooperative communication between eNBs connected via wireless lines. At least one antenna is installed at each node. The antenna may refer to a physical antenna, an antenna port, a virtual antenna, or an antenna group.

[0046] In this specification, the term “cell” may refer to a geographic area where one or more nodes provide a communication system, or to a radio resource. A “cell” in a geographic area may be understood as coverage where a node can provide service using a carrier, and a “cell” as a radio resource (e.g., time-frequency resource) is associated with a bandwidth (BW), which is a frequency range configured by the carrier. A “cell” associated with a radio resource is defined by a combination of downlink resources and uplink resources, e.g., a combination of a downlink (DL) component carrier (CC) and an uplink (UL) CC. A cell may be configured by a downlink resource alone or by both a downlink resource and an uplink resource. Since downlink coverage, which is the range where a node can transmit a valid signal, and uplink coverage, which is the range where a valid signal can be received from a UE, depend on the carrier carrying the signal, the node’s coverage may also be associated with the coverage of the “cell” of the radio resources used by the node. Therefore, the term "cell" may sometimes be used to refer to the coverage of a service by a node, sometimes to wireless resources, and sometimes to the range where signals using said wireless resources can be reached with effective strength.

[0047] In this specification, the physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH) respectively refer to a set of time-frequency resources or resource elements (REs) carrying downlink control information (DCI) and a set of time-frequency resources or REs carrying downlink data. Additionally, the physical uplink control channel (PUCCH), the physical uplink shared channel (PUSCH), and the physical random access channel (PRACH) respectively refer to a set of time-frequency resources or REs carrying uplink control information (UCI), a set of time-frequency resources or REs carrying uplink data, and a set of time-frequency resources or REs carrying random access signals.

[0048] In Carrier Aggregation (CA), two or more CCs are aggregated. Depending on its capabilities, the UE can receive or transmit one or more CCs simultaneously. CA is supported for both continuous and non-continuous CCs. When CA is configured, only the UE has a single Radio Resource Control (RRC) connection with the network. During RRC connection establishment / re-establishment / handover, one serving cell provides non-access stratum (NAS) mobility information, and during RRC connection re-establishment / handover, one serving cell provides secure input. This cell is called the primary cell (PCell). The PCell is a cell operating on the primary frequency, where the UE performs the initial connection establishment procedure or initiates the connection re-establishment procedure. Depending on the UE's capabilities, a secondary cell (SCell) may be configured to form a set of serving cells together with the PCell. The SCell is a cell that provides additional radio resources in addition to the specialized cell. Therefore, the serving cell set configured for a UE always consists of one PCell and one or more SCells. For dual connectivity operation, the term special cell (SpCell) refers to a PCell of the master cell group (MCG) or a PSCell of the secondary cell group (SCG). SpCells support PUCCH transmission and contention-based random access and are always active. The MCG is a serving cell group associated with the master node and includes a SpCell (PCell) and optionally one or more SCells. The SCG is a subset of serving cells associated with the secondary node and consists of a PSCell and zero or more SCells for a UE configured for dual connectivity (DC).For UEs with RRC_CONNECTED not configured as CA / DC, there is only one serving cell consisting of PCells. For UEs with RRC_CONNECTED configured as CA / DC, the term "serving cell" is used to refer to a set of cells consisting of SpCell(s) and all SCells.

[0049] The MCG is a group of serving cells associated with a master BS that terminates at least the S1-MME, and the SCG is a group of serving cells associated with a secondary BS that provides additional radio resources for the UE but is not the master BS. The SCG consists of a primary SCell (PSCell) and optionally one or more SCells. At the DC, two MAC entities are established in the UE: a MAC entity for the MCG and a MAC entity for the SCG. Each MAC entity is established by the RRC as a serving cell that supports PUCCH transmission and contention-based random access. In this specification, the term SpCell refers to such a cell, while the term SCell refers to other serving cells. The term SpCell refers to the PCell of the MCG or the PSCell of the SCG, depending on whether the MAC entity is associated with the MCG or the SCG, respectively.

[0050] In this specification, channel monitoring refers to an attempt to decode a channel. For example, PDCCH monitoring refers to an attempt to decode a PDCCH(s) (or PDCCH candidates).

[0051] In this specification, "C-RNTI" refers to a cell RNTI, "SI-RNTI" refers to a system information RNTI, "P-RNTI" refers to a paging RNTI, "RA-RNTI" refers to a random access RNTI, "SC-RNTI" refers to a single cell RNTI, "SL-RNTI" refers to a sidelink RNTI, "SPS C-RNTI" refers to a semi-persistent scheduling C-RNTI, and "CS-RNTI" refers to a configured scheduling RNTI.

[0052] FIG. 1 illustrates a communication system to which the present invention is applied.

[0053] The three major requirement areas of 5G include (1) the Enhanced Mobile Broadband (eMBB) area, (2) the Massive Machine Type Communication (mMTC) area, and (3) the Ultra-reliable and Low Latency Communications (URLC) area.

[0054] Some use cases may require multiple domains for optimization, while others may focus on only a single Key Performance Indicator (KPI). 5G supports these diverse use cases in a flexible and reliable way.

[0055] eMBB goes far beyond basic mobile internet access, covering media and entertainment applications in rich interactive tasks, the cloud, or augmented reality. Data is one of the core drivers of 5G, and dedicated voice services may not be seen for the first time in the 5G era. In 5G, voice is expected to be processed simply as an application using the data connection provided by the communication system. The main causes for the increased traffic volume are the increase in content size and the growing number of applications requiring high data transfer rates. Streaming services (audio and video), interactive video, and mobile internet connectivity will become more widely used as more devices connect to the internet. Many of these applications require always-on connectivity to push real-time information and notifications to users. Cloud storage and applications are growing rapidly on mobile communication platforms, and this can be applied to both work and entertainment. Furthermore, cloud storage is a specific use case driving the growth of uplink data transfer rates. 5G is also used for remote work in the cloud, requiring much lower end-to-end latency to maintain an excellent user experience when haptic interfaces are used. Entertainment, for example, cloud gaming and video streaming, is another key factor increasing the demand for mobile broadband capabilities. Entertainment is essential on smartphones and tablets anywhere, including in highly mobile environments such as trains, cars, and airplanes. Other use cases include augmented reality for entertainment and information retrieval. Here, augmented reality requires very low latency and instantaneous data volumes.

[0056] Furthermore, one of the most anticipated use cases for 5G concerns mMTC, the ability to seamlessly connect embedded sensors across all fields. The number of potential IoT devices is projected to reach 20.4 billion by 2020. Industrial IoT is one of the areas where 5G plays a key role in enabling smart cities, asset tracking, smart utilities, agriculture, and security infrastructure.

[0057] URLLC includes new services that will transform industries through ultra-reliable / available low-latency links, such as remote control of critical infrastructure and self-driving vehicles. Levels of reliability and latency are essential for smart grid control, industrial automation, robotics, and drone control and coordination.

[0058] 5G can complement FTTH (fiber-to-the-home) and cable-based broadband (or DOCSIS) as a means of providing streams rated at hundreds of megabits per second to gigabits per second. These high speeds are required for virtual and augmented reality, as well as for delivering TV at resolutions of 4K and above (6K, 8K, and higher). VR (Virtual Reality) and AR ( Augmented Reality) applications include near-immersive sports matches. Certain applications may require special network configurations. For example, in the case of VR games, game companies may need to integrate core servers with the network operator's edge network servers to minimize latency.

[0059] The automotive sector is expected to become a significant new driving force for 5G, with numerous use cases for mobile communication within vehicles. For example, passenger entertainment requires high-capacity and high-mobility mobile broadband simultaneously. This is because future users will continue to expect high-quality connectivity regardless of their location or speed. Another application in the automotive sector is the augmented reality dashboard. This displays information overlaid onto what the driver is looking through the windshield, allowing them to identify objects in the dark and providing the driver with information about the objects' distances and movements. In the future, wireless modules will enable communication between vehicles, information exchange between vehicles and supporting infrastructure, and information exchange between vehicles and other connected devices (e.g., devices accompanying pedestrians). Safety systems will allow drivers to drive more safely by guiding them to alternative courses of action, thereby reducing the risk of accidents. The next step will be remotely controlled or self-driven vehicles. This requires highly reliable and very fast communication between different self-driven vehicles and between vehicles and infrastructure. In the future, self-driving vehicles will perform all driving activities, allowing drivers to focus solely on traffic anomalies that the vehicle itself cannot identify. The technical requirements for self-driving vehicles demand ultra-low latency and ultra-high reliability to increase traffic safety to a level unattainable by humans.

[0060] Smart cities and smart homes, referred to as a smart society, will be embedded with high-density wireless sensor networks. Distributed networks of intelligent sensors will identify conditions for maintaining the cost-effective and energy-efficient maintenance of the city or home. A similar setup can be implemented for each household. Temperature sensors, window and heating controllers, burglar alarms, and home appliances are all wirelessly connected. Many of these sensors typically feature low data transfer rates, low power consumption, and low cost. However, for example, real-time HD video may be required for certain types of devices for surveillance.

[0061] The consumption and distribution of energy, including heat or gas, are becoming highly decentralized, requiring automated control of distributed sensor networks. Smart grids interconnect these sensors using digital information and communication technologies to collect information and act accordingly. Since this information may include the behavior of suppliers and consumers, smart grids can improve efficiency, reliability, economic viability, production sustainability, and the automated distribution of fuels such as electricity. A smart grid can also be viewed as another sensor network with low latency.

[0062] Mission-critical applications (e.g., e-health) are one of the 5G usage scenarios. The health sector possesses many applications that can benefit from mobile communications. Communication systems can support telemedicine, providing clinical care in remote locations. This helps reduce distance barriers and improves access to medical services that are not consistently available in remote rural areas. It is also used to save lives in critical medical care and emergency situations. Mobile communication-based wireless sensor networks can provide remote monitoring and sensors for parameters such as heart rate and blood pressure.

[0063] Wireless and mobile communications are becoming increasingly important in industrial applications. Wiring is expensive to install and maintain. Therefore, the potential to replace cables with reconfigurable wireless links presents an attractive opportunity in many industries. However, achieving this requires wireless connections to operate with latency, reliability, and capacity comparable to cables, while also simplifying their management. Low latency and a very low probability of error are new requirements that 5G needs to meet.

[0064] Logistics and freight tracking are important use cases for mobile communications that use location-based information systems to enable the tracking of inventory and packages anywhere. Use cases for logistics and freight tracking typically require low data rates but necessitate wide coverage and reliable location information.

[0065] Referring to FIG. 1, a communication system (1) includes a wireless device, a base station (BS), and a network. Although FIG. 1 illustrates a 5G network as an example of the network of the communication system (1), implementations of the present specification are not limited to 5G systems and can be applied to next-generation communication systems beyond 5G systems.

[0066] The BS and network can be implemented as wireless devices, and a specific wireless device (200a) can operate as a BS / network node for other wireless devices.

[0067] A wireless device refers to a device that performs communication using radon access technology (RAT) (e.g., 5G NR (new RAT), LTE) and may be referred to as a communication / wireless / 5G device. Although not limited thereto, a wireless device may include a robot (100a), a vehicle (100b-1, 100b-2), an extended reality (XR) device (100c), a hand-held device (100d), a home appliance (100e), an Internet of Things (IoT) device (100f), and an artificial intelligence (AI) device / server (400). For example, a vehicle may include a vehicle equipped with wireless communication capabilities, an autonomous vehicle, and a vehicle capable of performing communication between vehicles. Here, a vehicle may include an unmanned aerial vehicle (UAV) (e.g., a drone). XR devices may include augmented reality (AR), virtual reality (VR), and mixed reality (MR) devices, and may be implemented in the form of a head-mounted display (HMD), a head-up display (HUD) equipped in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance, digital signage, a vehicle, a robot, etc. Portable devices may include smartphones, smartpads, wearable devices (e.g., smartwatches, smart glasses), and computers (e.g., laptops). Home appliances may include TVs, refrigerators, and washing machines. IoT devices may include sensors and smart meters.

[0068] In this specification, wireless devices (100a to 100f) may be referred to as UEs. A UE may include, for example, a mobile phone, a smartphone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation device, a slate PC, a tablet PC, an ultrabook, a vehicle, a vehicle equipped with autonomous driving capabilities, a connected car, a UAV, an AI module, a robot, an AR device, a VR device, an MR device, a holographic device, a public safety device, an MTC device, an IoT device, a medical device, a fintech device (or financial device), a security device, a climate / environment device, a device related to 5G services, or a device related to the field of the Fourth Industrial Revolution. A UAV may be, for example, an aircraft that flies by means of wireless control signals without a person on board. A VR device may include, for example, a device that implements objects or backgrounds of a virtual world. An AR device may include, for example, a device that implements objects or backgrounds of a virtual world by connecting objects or backgrounds of a real world. MR devices may include, for example, devices implemented by fusing objects or backgrounds of a virtual world with objects or backgrounds of a real world. Holographic devices may include, for example, devices that realize 360-degree stereoscopic images by recording and playing back stereoscopic information using the phenomenon of light interference generated when two laser beams meet, known as holography. Public safety devices may include, for example, video relay devices or video devices wearable on a user's body. MTC devices and IoT devices may be, for example, devices that do not require direct human intervention or operation. For example, MTC devices and IoT devices may include smart meters, vending machines, thermometers, smart light bulbs, door locks, or various sensors.Medical devices may be devices used for the purpose of diagnosing, treating, alleviating, managing, or preventing diseases, for example. For example, medical devices may be devices used for the purpose of diagnosing, treating, alleviating, or correcting injuries or disabilities. For example, medical devices may be devices used for the purpose of examining, replacing, or modifying structures or functions. For example, medical devices may be devices used for the purpose of controlling pregnancy. For example, medical devices may include medical devices, surgical devices, (in vitro) diagnostic devices, hearing aids, or procedural devices. Security devices may be devices installed to prevent potential risks and maintain safety, for example. For example, security devices may be cameras, CCTVs, recorders, or black boxes. Fintech devices may be devices capable of providing financial services, such as mobile payments, for example. For example, fintech devices may include payment devices or POS (point of sales) systems. Climate / environment devices may include devices that monitor or predict climate / environment conditions, for example.

[0069] Wireless devices (100a to 100f) can be connected to a network (300) via a BS (200). AI technology may be applied to the wireless devices (100a to 100f), and the wireless devices (100a to 100f) can be connected to an AI server (400) via the network (300). The network (300) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, and a Beyond 5G network. The wireless devices (100a to 100f) may communicate with each other via the BS (200) / network (300), but they may also communicate directly (e.g., sidelink communication) without using the BS / network. For example, vehicles (100b-1, 100b-2) can communicate directly (e.g., V2V (vehicle-to-vehicle) / V2X (vehicle-to-everything) communication). Also, IoT devices (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

[0070] Wireless communication / connection (150a, 150b) can be established between wireless devices (100a~100f) / BS (200) and BS (200). Here, wireless communication / connection can be established through various RATs (e.g., 5G NR), such as uplink / downlink communication (150a) and sidelink communication (150b) (or D2D communication). Through wireless communication / connection (150a, 150b), wireless devices and BS / wireless devices can transmit / receive wireless signals to / from each other. For example, wireless communication / connection (150a, 150b) can transmit / receive signals through various physical channels. To this end, based on the various proposals of this specification, at least some of the processes for configuring various configuration information for the transmission / reception of wireless signals, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, and resource mapping / demapping), and resource allocation processes may be performed.

[0071] FIG. 2 is a block diagram illustrating examples of communication devices capable of performing the method according to the present specification.

[0072] Referring to FIG. 2, the first wireless device (100) and the second wireless device (200) can transmit / receive wireless signals to / from an external device via various RATs (e.g., LTE, NR). In FIG. 2, the {first wireless device (100) and the second wireless device (200)} may correspond to the {wireless devices (100a~100f) and BS (200)} of FIG. 1 and / or the {wireless devices (100a~100f) and wireless devices (100a~100f)}.

[0073] The first wireless device (100) includes one or more processors (102) and one or more memories (104), and may additionally include one or more transceivers (106) and / or one or more antennas (108). The processor(s) (102) control the memory(s) (104) and / or transceivers(s) (106) and may be configured to implement the functions, procedures and / or methods described in this specification. For example, the processor(s) (102) may process information within the memory(s) (104) to generate first information / signals and then transmit wireless signals containing the first information / signals through the transceivers(s) (106). Additionally, the processor(s) (102) may receive wireless signals containing second information / signals through the transceiver (106) and then process the second information / signals to obtain information, which can then be stored in the memory(s) (104). The memory(s) (104) may be connected to the processor(s) (102) and may store various information related to the operation of the processor(s) (102). For example, the memory(s) (104) may store software code containing instructions for performing some or all of the processes controlled by the processor(s) (102) or for performing the procedures and / or methods described in this specification. Here, the processor(s) (102) and the memory(s) (104) may be part of a communication modem / circuit / chip designed to implement a RAT (e.g., LTE, NR). Transceiver(s) (106) may be connected to processor(s) (102) and may transmit and / or receive wireless signals through one or more antennas (108). Each of the transceiver(s) (106) may include a transmitter and / or receiver. The transceiver(s) (106) may be interchangeable with radio frequency (RF) unit(s). In the present invention, a wireless device may refer to a communication modem / circuit / chip.

[0074] The second wireless device (200) includes one or more processors (202) and one or more memories (204), and may additionally include one or more transceivers (206) and / or one or more antennas (208). The processor(s) (202) may control the memory(s) (204) and / or transceivers(s) (206) and may be configured to implement the functions, procedures and / or methods described in this specification. For example, the processor(s) (202) may process information within the memory(s) (204) to generate third information / signals and then transmit wireless signals containing the third information / signals through the transceivers(s) (206). Additionally, the processor(s) (202) may receive wireless signals containing fourth information / signals through the transceiver(s) (206), process the fourth information / signals, and store the obtained information in the memory(s) (204). The memory(s) (204) may be connected to the processor(s) (202) and may store various information related to the operation of the processor(s) (202). For example, the memory(s) (204) may store software code containing instructions for performing some or all of the processes controlled by the processor(s) (202) or for performing the procedures and / or methods described in this specification. Here, the processor(s) (202) and the memory(s) (204) may be part of a communication modem / circuit / chip designed to implement a RAT (e.g., LTE, NR). Transceiver(s) (206) may be connected to processor(s) (202) and may transmit and / or receive wireless signals through one or more antennas (208). Each of the transceiver(s) (206) may include a transmitter and / or receiver. The transceiver(s) (206) may be interchangeable with RF units. In the present invention, a wireless device may refer to a communication modem / circuit / chip.

[0075] Hereinafter, hardware elements of the wireless device (100, 200) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) layer, and a service data adaptation protocol (SDAP) layer). One or more processors (102, 202) may generate one or more protocol data units (PDU) and / or one or more service data units (SDU) according to the functions, procedures, proposals and / or methods disclosed in this specification. One or more processors (102, 202) may generate messages, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this specification. One or more processors (102, 202) may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this specification and provide them to one or more transceivers (106, 206).One or more processors (102, 202) can receive signals (e.g., baseband signals) from one or more transceivers (106, 206) and can obtain PDU, SDU, message, control information, data or information according to the functions, procedures, proposals and / or methods disclosed in this specification.

[0076] One or more processors (102, 202) may be referred to as a controller, microcontroller, microprocessor, or microcomputer. One or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more application-specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in one or more processors (102, 202). The functions, procedures, proposals, and / or methods disclosed in this specification may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, or functions. Firmware or software configured to perform the functions, procedures, proposals and / or methods disclosed in this specification may be included in one or more processors (102, 202) or stored in one or more memories (104, 204) and driven by one or more processors (102, 202). The functions, procedures, proposals and / or methods disclosed in this specification may be implemented using firmware or software in the form of code, instructions and / or sets of instructions.

[0077] One or more memories (104, 204) may be connected to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, code, instructions, and / or commands. One or more memories (104, 204) may be composed of ROM (read-only memory), RAM (random access memory), EPROM (Electrically erasable programmable read-only memory), flash memory, hard drive, register, cache memory, computer read storage media, and / or combinations thereof. One or more memories (104, 204) may be located inside and / or outside of one or more processors (102, 202). Additionally, one or more memories (104, 204) may be connected to one or more processors (102, 202) through various technologies such as wired or wireless connections.

[0078] One or more transceivers (106, 206) may transmit user data, control information, and / or wireless signals / channels mentioned in the methods and / or operation flowcharts of this specification to one or more other devices. One or more transceivers (106, 206) may receive user data, control information, and / or wireless signals / channels mentioned in the functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this specification from one or more other devices. For example, one or more transceivers (106, 206) may be connected to one or more processors (102, 202) and may transmit and / or receive wireless signals. For example, one or more processors (102, 202) may control one or more transceivers (106, 206) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (106, 206) may be connected to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and / or receive user data, control information, and / or wireless signals / channels mentioned in the functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this specification through one or more antennas (108, 208). In this specification, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (106, 206) can convert received wireless signals / channels, etc. from RF band signals into baseband signals in order to process received user data, control information, wireless signals / channels, etc. using one or more processors (102, 202).One or more transceivers (106, 206) can convert user data, control information, wireless signals / channels, etc., processed using one or more processors (102, 202) from baseband signals to RF band signals. To this end, one or more transceivers (106, 206) may include (analog) oscillators and / or filters. For example, the transceiver (106, 206) can upconvert OFDM baseband signals to a carrier frequency by the (analog) oscillators and / or filters of the transceiver under the control of the processor (102, 202), and transmit the OFDM signals upconverted from the carrier frequency. The transceiver (106, 206) receives OFDM signals at a carrier frequency and can down-convert the OFDM signals into OFDM baseband signals by the (analog) oscillators and / or filters of the transceiver under the control of the transceiver (102, 202).

[0079] In implementations of this specification, the UE may operate as a transmitting device in the uplink and as a receiving device in the downlink. In implementations of this specification, the BS may operate as a receiving device in the uplink and as a transmitting device in the downlink. For convenience of explanation, unless otherwise noted or described, it is generally assumed that the first wireless device (100) operates as the UE and the second wireless device (200) operates as the BS. For example, the processor(s) (102) connected to, mounted on, or launched in the first wireless device (100) may be configured to perform UE operations according to the implementation of this specification or configured to control the transceiver (106) to perform UE operations according to the implementation of this specification. A processor(s) (202) connected to, mounted on, or launched in the second wireless device (200) may be configured to perform a BS operation according to the implementation of the present specification or configured to control a transceiver(s) (206) to perform a BS operation according to the implementation of the present specification.

[0080] In this specification, at least one memory (e.g., 104 or 204) may store instructions or programs that, when executed, cause at least one processor operably connected thereto to perform operations according to some embodiments or implementations of this specification.

[0081] In this specification, a computer-readable storage medium stores at least one instruction or computer program that, when executed by at least one processor, causes at least one processor to perform an operation according to some embodiments or implementations of this specification.

[0082] In this specification, a processing device or device may include at least one processor and at least one computer memory connectable to at least one processor and, when executed, storing instructions that cause at least one processor to perform operations according to some embodiments or implementations of this specification.

[0083] Figure 3 illustrates an example of a frame structure in a 3GPP-based wireless communication system.

[0084] The structure of the frame in FIG. 3 is merely an example, and the number of subframes, slots, and / or symbols in the frame may vary. In a 3GPP-based wireless communication system, OFDM numerology (e.g., subcarrier spacing (SCS), transmission time interval (TTI) intervals) may be set differently among multiple cells aggregated for a single UE. For example, if the UE is set to different SCS for the cells aggregated for the cell, the (absolute time) intervals of time resources (e.g., subframes, slots, or TTI) consisting of the same number of symbols may differ between the aggregated cells. Here, the symbols may include OFDM symbols (or CP-OFDM symbols) or SC-FDMA symbols (or DFT-s-OFDM (discrete Fourier transform-spread-OFDM) symbols).

[0085] Referring to Fig. 3, uplink and downlink transmissions are organized into frames. Each frame is T f = It has a 10ms interval and is divided into two half-frames, each with a 5ms interval. Each half-frame consists of 5 subframes, and the interval of each subframe (T sf ) is 1ms. Each subframe is divided into slots, and the number of slots within a subframe depends on the subcarrier spacing. Each slot consists of 14 or 12 OFDM symbols based on a cyclic prefix (CP). In a normal CP, each slot consists of 14 OFDM symbols, while in an extended CP, each slot consists of 12 OFDM symbols. Numerology is an exponentially scalable subcarrier spacing (βf = 2 u* It is based on 15 kHz). The following table shows the subcarrier spacing (βf = 2 u*According to 15 kHz, the number of OFDM symbols per slot, the number of slots per frame, and the number of slots per subframe are shown for a general CP.

[0086] u N slot symb N frame,u slot N subframe,u slot 0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

[0087] The following table shows the number of OFDM symbols per slot, the number of slots per frame, and the number of slots per subframe for extended CP according to the subcarrier spacing (βf = 2u*15 kHz).

[0088] u N slot symb N frame,u slot N subframe,u slot 2 12 40 4

[0089] A slot contains multiple (e.g., 14 or 12) symbols in the time domain. For each numerology (e.g., subcarrier interval) and carrier, a common resource block (CRB) indicated by upper-layer signaling (e.g., RRC (radio resource control) signaling) N start,u grid Starting from, N size,u grid,x * N RB sc 2 subcarriers and N subframe,u symb A resource grid of OFDM symbols is defined. Here N size,u grid,x is the number of resource blocks (RB) in the resource grid, and the subscript x is DL for downlinks and UL for uplinks. N RB sc is the number of subcarriers per RB. In 3GPP-based wireless communication systems, N RB sc is generally 12. Given antenna port ( p ), subcarrier interval setting (configuration)(u One resource grid exists for ) and transmission direction (DL or UL). Subcarrier spacing setting ( u Carrier bandwidth for ) N size,u grid ) is given by upper-layer parameters (e.g., RRC parameters). Antenna port ( p ) and subcarrier spacing settings( u Each element within the resource grid for ) is referred to as a resource element (RE), and one complex symbol can be mapped to each resource element. Each resource element within the resource grid is an index in the frequency domain ( k An index indicating the symbol position relative to a reference point in the ) and time domains( l It is uniquely identified by ). In 3GPP-based radio communication systems, an RB is defined by 12 consecutive subcarriers in the frequency domain. In 3GPP NR systems, RBs are classified into Common Resource Blocks (CRBs) and Physical Resource Blocks (PRBs). CRBs are defined by subcarrier spacing settings ( u Numbering is performed in the frequency domain for ) in an increasing direction starting from 0. Subcarrier spacing setting ( u The center of the subcarrier 0 of CRB 0 for ) coincides with 'Point A', the common reference point for the resource block grid. In the 3GPP NR system, the PRB is defined within the bandwidth part (BWP), and from 0 to N size BWP,i Numbered up to -1. Here, i is the number of the above bandwidth part. Physical resource block (n) within the bandwidth part (i). PRB ) and, common resource block(n CRB The relationship between ) is as follows: n PRB = n CRB + N sizeBWP,i . Here N size BWP,i is a common resource block in which the above bandwidth part starts for CRB 0. A BWP includes multiple consecutive RBs in the frequency domain. A carrier may include up to N (e.g., 5) BWPs. A UE may be configured with one or more BWPs on a given configuration carrier. Among the BWPs configured for a UE, only one BWP may be active at a time. The active BWP defines the operating bandwidth of the UE within the operating bandwidth of the cell.

[0090] NR frequency bands are defined as two types of frequency ranges, FR1 and FR2. FR2 is also called millimeter wave (mmW). The frequency ranges in which NR can operate are distinguished as described in Table 3.

[0091] Frequency Range designation Corresponding frequency range Subcarrier Spacing FR1 450MHz - 7125MHz 15, 30, 60kHz FR2 24250MHz - 52600MHz 60, 120, 240kHz

[0092] Figure 4 illustrates an example of a protocol stack in a 3GPP-based wireless communication system.

[0093] In particular, FIG. 4(a) illustrates a wireless interface user plane protocol stack between a terminal (UE) and a base station (BS), and FIG. 4(b) illustrates a wireless interface control plane protocol stack between a UE and a BS. The control plane refers to a channel through which control messages used by the UE and the network to manage a call are transmitted. The user plane refers to a channel through which data generated at the application layer, such as voice data or Internet packet data, is transmitted. Referring to FIG. 4(a), the user plane protocol stack can be divided into a first layer (Layer 1) (i.e., the physical (PHY) layer) and a second layer (Layer 2). Referring to Fig. 4(b), the control plane protocol stack can be divided into Layer 1 (i.e., the PHY layer), Layer 2, Layer 3 (e.g., the RRC (radio resource control) layer and the non-access stratum (NAS) layer). Layers 1, 2, and 3 are referred to as the access stratum (AS).

[0094] The NAS control protocol terminates at the network-side access management function (AMF) and performs authentication, mobility management, and security control.

[0095] In the 3GPP LTE system, Layer 2 is divided into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP). In the 3GPP NR (New Radio) system, Layer 2 is divided into the following sublayers: MAC, RLC, PDCP, and Service Data Adaptation Protocol (SDAP). The PHY layer provides a transport channel to the MAC sublayer, the MAC sublayer provides a logical channel to the RLC sublayer, the RLC sublayer provides an RLC channel to the PDCP sublayer, and the PDCP sublayer provides a radio bearer to the SDAP sublayer. The SDAP sublayer provides QoS flow to the 5G core network.

[0096] In 3GPP NR systems, the main services and functions of SDAP include: mapping between QoS flows and data radio bearers; marking of QoS flow IDs (QoS flow ID, QFI) in both DL and UL packets. A single protocol entity of SDAP is established for each individual PDU session.

[0097] In 3GPP NR systems, the key services and functions of the RRC sublayer include: broadcasting of system information related to AS and NAS; paging initiated by 5GC or NG-RAN; establishment, maintenance, and release of RRC connections between the UE and NG-RAN; security functions including key management; establishment, setup, maintenance, and release of signaling radio bearers (SRBs) and data radio bearers (DRBs); mobility functions (including handover and context delivery; control of UE cell selection and reselection and cell selection and reselection; and mobility between RATs); QoS management functions, control of UE measurement reporting and reporting; detection of radio link failures and recovery from radio link failures; and delivery of NAS messages from the UE to the NAS and from the NAS to the UE.

[0098] In 3GPP NR systems, the key services and functions of the PDCP sublayer for the user plane include: sequence numbering; header compression and decompression (only for robust header compression (ROHC)); user data delivery; reordering and duplicate detection; sequential transmission; PDCP PDU routing (for split bearer); retransmission of PDCP SDUs; ciphering, deciphering, and integrity protection; PDCP SDU discarding; PDCP re-establishment and data recovery for RLC AM; PDCH status reporting for RLC AM; duplication of PDCP PDUs and instructions to discard duplicates to lower layers. The key services and functions of the PDCP sublayer for the control plane include: sequence numbering; ciphering, deciphering, and integrity protection; control plane data delivery; reordering and duplicate detection; sequential transmission; PDCP PDU replication and deletion instructions for replication to lower layers.

[0099] In 3GPP NR systems, the RLC sublayer supports three transport modes: transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). RLC configuration can be applied per logical channel, independent of the numerology and / or the transmission interval. In 3GPP NR systems, the key services and functions of the RLC sublayer depend on the transport mode and include: delivery of upper-layer PDUs; sequence numbering independent of PDCP numbering (for UM and AM); error correction via ARQ (automatic repeat request) (for AM only); segmentation (for UM and AM) and re-segmentation (for AM only) of RLC SDUs; reassembly of SDUs (for UM and AM); discarding of RLC SDUs (for UM and AM); and RLC re-establishment. Includes protocol error detection (only for AM).

[0100] In 3GPP NR systems, the key services and functions of the MAC sublayer include: mapping between logical channels and transport channels; multiplexing / demultiplexing of MAC SDUs belonging to one or different logical channels from / to transport blocks (TBs) transmitted to / from the PHY layer via the transport channel; reporting of scheduling information; error correction via HARQ (hybrid automatic repeat request) (one HARQ entity per cell in the case of CA); priority handling between UEs using dynamic scheduling; priority handling between logical channels of a single UE using logical channel priorities; and padding. A single MAC entity can support multiple numerologies, transport timings, and cells. Mapping constraints in logical channel priorities control which numerology(s), cell(s), and transport timing(s) a logical channel can use. Different types of data transport services are provided by the MAC. To accommodate different types of data transmission services, multiple logical channel types are defined, each supporting the transmission of a specific type of information. Each logical channel type is defined by the type of information being transmitted. Logical channels are classified into two groups: control channels and traffic channels. Control channels are used to transmit only control plane information, while traffic control channels are used to transmit only user plane information.The Broadcast Control Channel (BCCH) is a downlink logical channel for broadcasting system control information; the Paging Control Channel (PCCH) is a downlink logical channel for transmitting paging information, notifications of system information changes, and instructions for ongoing PWS broadcasts; the Common Control Channel (CCCH) is a logical channel for transmitting control information between the UE and the network, used for UEs that do not have an RRC connection with the network; and the Dedicated Control Channel (DCCH) is a point-to-point bidirectional logical channel for transmitting dedicated control information between the UE and the network, used by UEs that have an RRC connection. The Dedicated Traffic Channel (DTCH) is a point-to-point logical channel dedicated to a single UE for transmitting user information. The DTCH can exist in both the uplink and downlink. In the downlink, the connection between the logical channel and the transport channel is as follows: The BCCH can be mapped to the BCH; BCCH can be mapped to the downlink shared channel (DL-SCH); PCCH can be mapped to PCH; CCCH can be mapped to DL-SCH; DCCH can be mapped to DL-SCH; DTCH can be mapped to DL-SCH. In the uplink, the connections between the logical channel and the transport channel are as follows: CCCH can be mapped to the uplink shared channel (UL-SCH); DCCH can be mapped to UL-SCH; DTCH can be mapped to UL-SCH.

[0101] Figure 5 illustrates an example of a data flow in a 3GPP NR system.

[0102] In Figure 5, "RB" represents a radio bearer, and "H" represents a header. Radio bearers are classified into two groups: data radio bearers (DRBs) for user plane data and signaling radio bearers (SRBs) for control plane data. MAC PDUs are transmitted and received with external devices through the PHY layer using radio resources. MAC PDUs reach the PHY layer in the form of transport blocks.

[0103] At the PHY layer, the uplink transport channels UL-SCH and RACH are mapped to PUSCH and PRACH, respectively, and the downlink transport channels DL-SCH, BCH, and PCH are mapped to PDSCH, the physical broadcast channel (PBCH), and PDSCH, respectively. At the PHY layer, uplink control information (UCI) is mapped to PUCCH, and downlink control information (DCI) is mapped to PDCCH. MAC PDUs associated with UL-SCH are transmitted by the UE via PUSCH based on uplink grants, and MAC PDUs associated with DL-SCH are transmitted by the BS via PDSCH based on downlink assignments.

[0104] To transmit the data unit(s) of this specification over UL-SCH, the UE must have uplink resources available to the UE. To receive the data unit(s) of this specification over DL-SCH, the UE must have downlink resources available to the UE. Resource allocation includes time domain resource allocation and frequency domain resource allocation. In this specification, uplink resource allocation is also referred to as uplink grant, and downlink resource allocation is also referred to as downlink assignment. Uplink grant is dynamically received by the UE over PDCCH within a random connection response or is semi-continuously established to the UE by RRC. Downlink assignment is dynamically received by the UE over PDCCH or is semi-continuously established to the UE by RRC signaling from the BS.

[0105] In the uplink, the BS can dynamically allocate resources to the UE via the cell radio network temporary identifier (C-RNTI) on the PDCCH(s). The UE constantly monitors the PDCCH(s) to find available grants for uplink transmission when the UE's downlink reception is enabled (an activity controlled by discontinuous reception (DRX) at the time of configuration). Additionally, using the configured grants, the BS can allocate uplink resources to the UE for the initial HARQ transmission. Two types of configured uplink grants are defined: namely, Type 1 and Type 2. For Type 1, the RRC directly provides the configured uplink grant (including the period). For Type 2, the RRC defines the period of the configured uplink grant while the PDCCH addressed to the configured scheduling RNTI (CS-RNTI) is capable of signaling, enabling, or deactivating the configured uplink grant. In other words, the PDCCH addressed in CS-RNTI indicates that the uplink grant can be implicitly reused according to the period defined by the RRC until the uplink grant is deactivated.

[0106] In the downlink, the BS can dynamically allocate resources to the UE via C-RNTI on the PDCCH(s). The UE constantly monitors the PDCCH(s) to find available grants when the UE's downlink listening is enabled (an activity controlled by the DRX at configuration). Additionally, using semi-persistent scheduling (SPS), the BS can allocate downlink resources to the UE for the initial HARQ transmission. The RRC defines the period of the configured downlink assignment while the PDCCH addressed in the CS-RNTI can signal and enable or disable the configured downlink assignment. In other words, the PDCCH addressed in the CS-RNTI indicates that the downlink assignment may be implicitly reused according to the period defined by the RRC until the downlink assignment is disabled.

[0107] <PDCCH에 의한 자원 할당(즉, DCI에 의한 자원 할당)>

[0108] A PDCCH can be used to schedule downlink transmissions on a PDSCH and uplink transmissions on a PUSCH, wherein the DCI on the PDCCH includes: a downlink assignment associated with a DL-SCH that includes at least modulation and coding formats (e.g., modulation and coding scheme (MCS) index (IMCS)), resource allocation, and hybrid ARQ information; or an uplink scheduling grant associated with a UL-SCH that includes modulation and coding formats, resource allocation, and hybrid ARQ information. The size and use of the DCI carried by a single PDCCH depend on the DCI format. For example, in a 3GPP NR system, DCI format 0_0 or DCI format 0_1 ​​is used for scheduling PUSCH in a cell, and DCI format 1_0 or DCI format 1_1 is used for scheduling PDSCH in a cell.

[0109] Figure 6 illustrates an example of PDSCH time domain resource allocation by PDCCH and an example of PUSCH time resource allocation by PDCCH.

[0110] The DCI carried by PDCCH to schedule PDSCH or PUSCH contains the value m for row index m+1 for the allocation table for PDSCH or PUSCH. A predefined default PDSCH time domain allocation A, B, or C is applied as the allocation table for PDSCH, or a pdsch-TimeDomainAllocationList with RRC configured is applied as the allocation table for PDSCH. A predefined default PUSCH time domain allocation A is applied as the allocation table for PUSCH, or a pusch-TimeDomainAllocationList with RRC configured is applied as the allocation table for PUSCH. Which PDSCH time domain resource allocation settings to apply and which PUSCH time domain resource allocation tables to apply are determined according to fixed / predefined rules (e.g., Table 5.1.2.1.1-1 of 3GPP TS 38.214 v15.3.0, Table 6.1.2.1.1-1 of 3GPP TS 38.214 v15.3.0).

[0111] In the PDSCH time domain allocation configuration, each indexed row defines the slot offset K0, the start and length indicator SLIV or directly the start symbol S and allocation length L, and the PDSCH mapping type to be assumed in the PDSCH reception. In the PUSCH time domain allocation configuration, each indexed row defines the slot offset K2, the start and length indicator SLIV or directly the start symbol S and allocation length L, and the PUSCH mapping type to be assumed in the PUSCH reception. K0 for PDSCH or K2 for PUSCH is the timing difference between the slot containing PDSCH and the slot containing the PDSCH or PUSCH corresponding to PDSCH. SLIV is a joint indicator of the start symbol S for the start of the slot containing PDSCH or PUSCH and the number L of consecutive symbols counted from symbol S. For PDSCH / PUSCH mapping types, there are two mapping types: one is mapping type A, in which the demodulation reference signal (DMRS) is located in the 3rd or 4th symbol of the slot according to the mapping RRC signaling, and the other is mapping type B, in which the DMRS is located in the first assigned symbol.

[0112] The scheduling DCI includes a frequency domain resource allocation field that provides allocation information regarding resource blocks used for PDSCH or PUSCH. For example, the frequency domain resource allocation field may provide the UE with information regarding cells for PDSCH or PUSCH transmission, information regarding bandwidth parts for PDSCH or PUSCH transmission, and information regarding resource blocks for PDSCH or PUSCH transmission.

[0113] Resource Allocation by RRC

[0114] As previously mentioned, on the uplink, there are two types of transmissions without dynamic grants: configured grant type 1 and configured grant type 2. In the case of configured grant type 1, the uplink grant is provided by the RRC and stored as a configured grant. In the case of configured grant type 2, the uplink grant is provided by the PDCCH and is stored or cleared as a configured uplink grant based on L1 signaling indicating the activation or deactivation of the configured uplink grant. Types 1 and 2 are configured by RRC signaling per serving cell and per BWP. Multiple configurations can be simultaneously activated only on different serving cells. In the case of type 2, activation and deactivation are independent between serving cells. For the same serving cell, the MAC entity is configured as either type 1 or type 2.

[0115] When the configured Grant Type 1 is configured, the UE receives at least the following parameters from the BS via RRC signaling:

[0116] - CS-RNTI for retransmission, cs-RNTI;

[0117] - periododicity providing the configured grant type 1 period;

[0118] - timeDomainOffset representing the offset of a resource for system frame number (SFN) = 0 in the time domain;

[0119] - timeDomainAllocation value m providing row index m+1 that represents the allocation table, indicating a combination of start symbol S, length L, and PUSCH mapping type;

[0120] - frequencyDomainAllocation providing frequency domain resource allocation; and

[0121] - mcsAndTBS providing an IMCS indicating modulation order, target code rate, and transport block size. When a grant type 1 is set for a serving cell by the RRC, the UE stores the uplink grant provided by the RRC as the uplink grant set for the indicated serving cell, and initializes or re-initializes the uplink grant set to start and periodically re-emerge at the symbol according to timeDomainOffset and S (derived from SLIV). After the uplink grant is set for Grant Type 1, the UE considers the uplink grant to recur in association with each symbol satisfying the following: [(SFN * numberOfSlotsPerFrame (numberOfSymbolsPerSlot) + (slot number in the frame Х numberOfSymbolsPerSlot) + symbol number in the slot] = (timeDomainOffset * numberOfSymbolsPerSlot + S + N * periodicity) modulo (1024 * numberOfSlotsPerFrame * numberOfSymbolsPerSlot), for all N >= 0.

[0122] When the configured Grant Type 2 is configured, the UE receives at least the following parameters from the BS via RRC signaling:

[0123] - CS-RNTI for activation, deactivation, and retransmission, which is cs-RNTI; and

[0124] -Perodicity providing the configured grant type 2 period. The actual uplink grant is provided to the UE by the PDCCH (addressed as CS-RNTI). After an uplink grant is established for a set grant type 2, the UE considers the uplink grant to recur in association with each symbol satisfying the following: [(SFN * numberOfSlotsPerFrame * numberOfSymbolsPerSlot) + (slot number in the frame * numberOfSymbolsPerSlot) + symbol number in the slot] = [(SFNstart time * numberOfSlotsPerFrame * numberOfSymbolsPerSlot + slotstart time * numberOfSymbolsPerSlot + symbolstart time) + N * periodicity] modulo (1024 Х numberOfSlotsPerFrame * numberOfSymbolsPerSlot), for all N >= 0, where SFNstart time, slotstart time, and symbolstart time represent the SFN, slot, and symbol, respectively, of the first transmission opportunity of PUSCH when the established grant is (re)initialized. numberOfSlotsPerFrame and numberOfSymbolsPerSlot represent the number of consecutive slots per frame and the number of consecutive OFDM symbols per slot, respectively.

[0125] For a configured uplink grant, the HARQ process ID associated with the first symbol of the uplink transmission is derived from the following formula:

[0126] HARQ Process ID = [floor(CURRENT_symbol / periodicity)] modulo nrofHARQ-Processes

[0127] Here, CURRENT_symbol = (SFN Х numberOfSlotsPerFrame Х numberOfSymbolsPerSlot + slot number in the frame Х numberOfSymbolsPerSlot + symbol number in the slot), where numberOfSlotsPerFrame and numberOfSymbolsPerSlot represent the number of consecutive slots per frame and the number of consecutive symbols per slot, respectively, as specified in TS 38.211. CURRENT_symbol represents the symbol index of the first transmission opportunity of an occurring repeating bundle. A HARQ process is configured for the configured uplink grant if the configured uplink grant is enabled, and the associated HARQ process ID is less than nrofHARQ-Processes.

[0128] For downlinks, the UE can be configured with SPS per serving cell and per BWP via RRC signaling from the BS. Multiple configurations can be active simultaneously on different serving cells. The activation or deactivation of downlink SPS is independent between serving cells. For downlink SPS, downlink assignments are provided to the UE via PDCCH and are saved or removed based on L1 signaling indicating SPS activation or deactivation. When an SPS is configured, the UE receives the following parameters from the BS via RRC signaling:

[0129] - CS-RNTI for activation, deactivation, and retransmission, cs-RNTI;

[0130] - nrofHARQ-Processes, which provides the number of configured HARQ processes for SPS;

[0131] - Periodicity providing the configured downlink assignment cycle for SPS.

[0132] If SPS is released by the upper layer, all corresponding settings must be released.

[0133] After a downlink assignment is established for the SPS, the UE can assume that the Nth downlink assignment occurs sequentially in a slot satisfying the following: (numberOfSlotsPerFrame * SFN + slot number in the frame) = [(numberOfSlotsPerFrame * SFN start time + slot start time ) + N * periodicity * numberOfSlotsPerFrame / 10] modulo(1024 * numberOfSlotsPerFrame), where SFN start time and slot start time Indicates the SFN, slot, and symbol of the first transmission of the PDSCH, where the configured downlink assignment has been (re)initialized, respectively.

[0134] For a configured downlink assignment, the HARQ process ID associated with the slot where the downlink transmission starts is derived from the following formula:

[0135] HARQ Process ID = [floor (CURRENT_slot Х 10 / (numberOfSlotsPerFrame Х periodicity))] modulo nrofHARQ-Processes

[0136] Here, CURRENT_slot = [(SFN Х numberOfSlotsPerFrame) + slot number in the frame] and numberOfSlotsPerFrame represents the number of consecutive slots per frame as specified in TS 38.211.

[0137] If the cyclic redundancy check (CRC) of the DCI format is scrambled with the CS-RNTI provided by the RRC parameter cs-RNTI and the new data indicator field for the enabled transport block is set to 0, the UE confirms that the downlink SPS assigned PDCCH or the configured uplink grant type 2 PDCCH is valid for scheduling enable or unscheduling. If all fields for the DCI format are set according to Table 4 or Table 5, the validation of the DCI format is achieved. Table 4 exemplifies specific fields for validating the downlink SPS and uplink grant type 2 scheduling enable PDCCH, and Table 5 exemplifies specific fields for validating the downlink SPS and uplink grant type 2 scheduling unscheduled PDCCH.

[0138] DCI format 0_0 / 0_1 DCI format 1_0 DCI format 1_1 HARQ process number set to all '0's set to all '0's set to all '0's Redundancy version set to '00' set to '00' For the enabled transport block: set to '00'

[0139] DCI format 0_0 DCI format 1_0 HARQ process number set to all '0's set to all '0's Redundancy version set to '00' set to '00' Modulation and coding scheme set to all '1's set to all '1's Resource block assignment set to all '1's set to all '1's

[0140] The actual downlink assignment and the actual uplink grant, and the corresponding modulation and coding scheme, are provided by resource assignment fields within the DCI format carried by the downlink SPS or uplink grant type 2 scheduling enable PDCCH (e.g., a time domain resource assignment field providing a time domain assignment value m, a frequency domain resource assignment field providing a frequency resource block assignment, and a modulation and coding scheme field). When a valid confirmation is achieved, the UE considers the information within the DCI format to be a valid enable or valid release of the downlink SPS or the configured uplink grant type 2.

[0141] In the case of an uplink, the processor(s) (102) of this specification may transmit (or control the transceiver(s) (106) to transmit) a data unit of this specification based on an uplink grant available to the UE. The processor(s) (202) of this specification may receive (or control the transceiver(s) (206) to receive) a data unit of this specification based on an uplink grant available to the UE.

[0142] In the case of a downlink, the processor(s) (102) of this specification may receive (or control the transceiver(s) (106) to receive) downlink data of this specification based on the downlink assignment available to the UE. The processor(s) (202) of this specification may transmit (or control the transceiver(s) (206) to transmit) downlink data of this specification based on the downlink assignment available to the UE.

[0143] Physical layer processing is performed at the transmitting side of the data unit(s) of the present invention before they are transmitted through a wireless interface, and physical layer processing is performed at the receiving side of the wireless signals carrying the data unit(s) of the present invention. For example, physical layer processing can be performed on a MAC PDU including a PDCP PDU according to the present specification as follows.

[0144] Figure 7 illustrates an example of physical layer processing at the transmitting side.

[0145] The following tables show the mapping of transport channels (TrCH) and control information to the corresponding physical channels. Specifically, Table 6 shows the mapping of uplink transport channels to the corresponding physical channels, Table 7 shows the mapping of uplink control channel information to the corresponding physical channels, Table 8 shows the mapping of downlink transport channels to the corresponding physical channels, and Table 9 shows the mapping of downlink control channel information to the corresponding physical channels.

[0146] TrCH Physical Channel UL-SCH PUSCH RACH PRACH

[0147] Control information Physical Channel UCI PUCCH, PUSCH

[0148] TrCH Physical Channel DL-SCH PDSCH BCH PBCH PCH PDSCH

[0149] Control information Physical Channel DCI PDCCH

[0150] Encoding

[0151] Data and control streams from / to the MAC layer are encoded to provide transport and control services over the wireless transmission link at the PHY layer. For example, transport blocks from the MAC layer are encoded into codewords at the transmitting end. Channel coding schemes are combinations of error detection, error correction, rate matching, interleaving, and transport channel or control information that are mapped to or split from the physical channel.

[0152] In 3GPP NR systems, the following channel coding schemes are used for different types of TrCH and different types of control information.

[0153] TrCH Coding scheme UL-SCH LDPC DL-SCH PCH BCH Polar code

[0154] Control Information Coding scheme DCI Polar code UCI Block code Polar code

[0155] For the transmission of downlink transport blocks (i.e., DL MAC PDUs) or uplink transport blocks (i.e., UL MAC PDUs), a transport block CRC sequence is attached to provide error detection for the receiving end. In 3GPP NR systems, communication devices use low-density parity check (LDPC) codes when encoding / decoding UL-SCH and DL-SCH. 3GPP NR systems support two LDPC base graphs (i.e., two LDPC base matrices): LDPC base graph 1, optimized for small transport blocks, and LDPC base graph 2, optimized for larger transport blocks. LDPC base graph 1 or 2 is selected based on the size of the transport block and the coding rate R. The coding rate R is indicated by the MCS index (IMCS). The MCS index is dynamically provided to the UE by a PDCCH that schedules a PUSCH or PDSCH, which is provided to the UE by a PDCCH that enables or (re)initializes an uplink-configured Grant 2 or downlink SPS, or by RRC signaling associated with an uplink-configured Grant Type 1. If the CRC-attached transport block is larger than the maximum code block size for the selected LDPC base graph, the CRC-attached transport block may be split into code blocks, with an additional CRC sequence attached to each code block. The maximum code block sizes for LDPC base graph 1 and LDPC base graph 2 are 8448 bits and 3480 bits, respectively. If the CRC-attached transport block is not larger than the maximum code block size for the selected LDPC base graph, the CRC-attached transport block is encoded using the selected LDPC base graph. Each code block of the transport block is encoded using the selected LDPC base graph. Then, the LDPC-coded blocks are rate-matched individually.Code block concatenation is performed to generate codewords for transmission on the PDSCH or PUSCH. In the case of the PDSCH, up to two codewords (i.e., up to two transmission blocks) can be transmitted simultaneously on the PDSCH. The PUSCH can be used for the transmission of UL-SCH data and Layer 1 / 2 control information. Although not shown in FIG. 7, Layer 1 / 2 control information can be multiplexed with the codewords for the UL-SCH data.

[0156] Scrambling and Modulation

[0157] The bits of the codeword are scrambled and modulated to generate blocks of complex value modulation symbols.

[0158] Layer Mapping

[0159] The complex value modulation symbols of a codeword are mapped to one or more multiple input multiple output MIMO layers. A codeword can be mapped to up to four layers. Since PDSCH can transmit two codewords, PDSCH can support up to 8-layer transmission. Since PUSCH supports a single codeword, PUSCH can support up to 4-layer transmission.

[0160] Transform Precoding

[0161] The downlink transmission waveform is conventional OFDM using a cyclic prefix (CP). For the downlink, transform precoding (i.e., the Discrete Fourier Transform (DFT)) is not applied.

[0162] The uplink transmission waveform is conventional OFDM using CP with a transform precoding function that performs DFT spreading, which can be disabled or enabled. In 3GPP NR systems, for the uplink, transform precoding can be applied optionally when enabled. Transform precoding spreads uplink data in a specific way to reduce the waveform's peak-to-average power ratio (PAPR). Transform precoding is a form of DFT. In other words, 3GPP NR systems support two options for the uplink waveform: one is CP-OFDM (identical to the downlink waveform), and the other is DFT-s-OFDM. Whether the UE should use CP-OFDM or DFT-s-OFDM is set by the BS via the RRC parameter.

[0163] Subcarrier Mapping

[0164] Layers are mapped to antenna ports. In the downlink, a transparent (non-codebook-based) mapping method is supported for layer-to-antenna port mapping, and how beamforming or MIMO precoding is performed is transparent to the UE. In the uplink, both non-codebook-based and codebook-based mappings are supported for layer-to-antenna port mapping.

[0165] For each antenna port (i.e., layer) used for transmission on a physical channel (e.g., PDSCH, PUSCH), complex value modulation symbols are mapped to subcarriers in resource blocks allocated to the physical channel.

[0166] OFDM Modulation

[0167] The communication device at the transmitting side generates a time-continuous OFDM baseband signal for OFDM symbol l at antenna port p and subcarrier spacing setting u for the OFDM symbol l in the TTI for the physical channel by adding a CP and performing an inverse fast Fourier transform (IFFT). For example, for each OFDM symbol, the communication device at the transmitting side may perform an IFFT on the complex value modulation symbol mapped to the resource block in the corresponding OFDM symbol, and generate an OFDM baseband signal by adding a CP to the IFFT signal.

[0168] Up-conversion

[0169] The communication device at the transmitting side upconverts the OFDM baseband signal for antenna port p, subcarrier spacing setting u, and OFDM symbol l to the carrier frequency f0 of the cell to which the physical channel is assigned.

[0170] In FIG. 2, the processor (102, 202) can be configured to perform encoding, scrambling, modulation, hierarchical mapping, convert precoding (for uplink), subcarrier mapping, and OFDM modulation. The processor (102, 202) can control a transceiver (106, 206) connected to the processor (102, 202) to upconvert an OFDM baseband signal to a carrier frequency to generate a radio frequency (RF) signal. The radio frequency signal is transmitted to an external device via an antenna (108, 208).

[0171] Figure 8 illustrates an example of physical layer processing at the receiving end.

[0172] Physical layer processing at the receiving end is essentially the reverse of physical layer processing at the transmitting end.

[0173] Frequency Down-Conversion

[0174] A communication device at the receiving end receives an RF signal at a carrier frequency through an antenna. A transceiver (106, 206) that receives an RF signal at a carrier frequency down-converts the carrier frequency of the RF signal to a baseband to obtain an OFDM baseband signal.

[0175] < OFDM Demodulation >

[0176] The communication device at the receiving end obtains complex value modulation symbols through CP detachment and FFT. For example, for each OFDM symbol, the communication device at the receiving end removes the CP from the OFDM baseband signal and performs an FFT on the CP-removed OFDM baseband signal to obtain complex value modulation symbols for antenna port p, subcarrier spacing u, and OFDM symbol l.

[0177] Subcarrier Demapping

[0178] Subcarrier demapping is performed on the complex value modulation symbols to obtain the complex value modulation symbols of the corresponding physical channel. For example, the processor(s) (102) can obtain complex value modulation symbols that are mapped to subcarriers belonging to PDSCH among the complex value modulation symbols received from the BWP. As another example, the processor(s) (202) can obtain complex value modulation symbols that are mapped to subcarriers belonging to PUSCH among the complex value modulation symbols received from the BWP.

[0179] <Conversion Deprecoding>

[0180] Transform deprecoding (e.g., IDFT) is performed on complex value modulation symbols of the uplink physical channel when transform precoding is enabled for the uplink physical channel. Transform deprecoding is not performed for the downlink physical channel and for the uplink physical channel when transform precoding is disabled.

[0181] Layer Demapping

[0182] Complex value modulation symbols are demapped into one or two codewords.

[0183] <Decomposition and Descramming>

[0184] The complex value modulation symbols of the codeword are demodulated into the bits of the codeword and descrambled.

[0185] Decoding

[0186] The codeword is decoded into a transport block. For UL-SCH and DL-SCH, LDPC base graph 1 or 2 is selected based on the size of the transport block and the coding rate R. The codeword may include one or more coded blocks. Each coded block is decoded into a CRC-attached code block or a CRC-attached transport block using the selected LDPC base graph. When code block splitting is performed on a CRC-attached transport block at the transmitting side, the CRC sequence is removed from each of the CRC-attached code blocks to obtain the code blocks. The code blocks are concatenated into a CRC-attached transport block. The transport block CRC sequence is removed from the CRC-attached transport block to obtain the transport block. The transport block is passed to the MAC layer.

[0187] In the physical layer processing at the transmitting and receiving sides described above, time and frequency domain resources (e.g., OFDM symbols, subcarriers, carrier frequencies) related to subcarrier mapping, OFDM modulation, and frequency up / down conversion can be determined based on resource allocation (e.g., uplink grants, downlink assignments).

[0188] For uplink data transmission, the processor(s) (102) of the present specification may transmit the data unit wirelessly by applying the aforementioned physical layer processing at the transmitting side to the data unit of the present specification (or controlling the transceiver(s) (106) to apply it). For downlink data reception, the processor(s) (102) of the present specification may acquire the data unit of the present specification by applying the aforementioned physical layer processing at the receiving side to the received wireless signals (or controlling the transceiver(s) (106) to apply it).

[0189] For downlink data transmission, the processor(s) (202) of the present specification may transmit the data unit wirelessly by applying the aforementioned physical layer processing at the transmitting side to the data unit of the present specification (or controlling the transceiver(s) (206) to apply it). For uplink data reception, the processor(s) (202) of the present specification may acquire the data unit of the present specification by applying the aforementioned physical layer processing at the receiving side to the received wireless signals (or controlling the transceiver(s) (206) to apply it).

[0190] Retransmission based on discard indicators>

[0191] According to Release 17 of the 3GPP standard (TS38.322) for the RLC layer, when an RLC PDU containing an RLC SDU is submitted to a lower layer, the RLC entity may include a poll bit in the RLC PDU to request a status report from a peer RLC entity and start a poll retransmission timer.

[0192] Even if an RLC SDU submitted to a lower layer is indicated by a discard indication from the PDCP, this RLC SDU is not discarded, and the RLC entity maintains transmission of this RLC SDU until it receives a status report containing information related to the RLC SDU from a peer RLC entity or until a wireless link failure occurs (i.e., the maximum number of retransmissions of the RLC SDU is reached). If the poll retransmission timer expires, the RLC entity includes a poll in the RLC PDU according to the polling procedure. Under these conditions, if both the new transmission buffer and the retransmission buffer are empty or the transmission window is stalled (i.e., there is no room for a new transmission within the transmission window), the RLC entity selects the RLC SDU with the highest SN (sequence number) within the transmission window or any RLC SDU that has not yet received a positively acknowledged for retransmission.

[0193] On the other hand, in 3GPP Standard Release 18 regarding XR technology, PDU-set based discard was introduced to discard all related PDUs within a set when the discard timer of one PDU within that set expires. Additionally, PSI-based discard enhancement was introduced to discard PDUs of low importance earlier than PDUs of high importance, as the discard timer value for PDUs of low importance is smaller than that for PDUs of high importance.

[0194] The problem arising from this operational situation is when, as the poll retransmission timer expires and the transmission window stalls or both transmission buffers are empty, the RLC entity selects the RLC SDU with the highest SN within the transmission window or any RLC SDU that has not yet received a positive acknowledgment as a retransmission target, without considering the remaining time of the RLC SDU and / or discard instructions from the PDCP. In this case, RLC SDUs with a remaining time shorter than the threshold may not be retransmitted promptly, or RLC SDUs that have already received discard instructions from the PDCP may be retransmitted unnecessarily. This causes unnecessary data discarding by PDU set-based or PSI-based discard procedures and degrades XR service quality.

[0195] Therefore, considering that a delay status report based on the remaining time of data was introduced in 3GPP Standard Release 18, it is very important to meet the delay requirements for each data, especially for high-importance data, and the delay information and discard status of each data must be taken into account when an RLC entity selects an RLC SDU for retransmission.

[0196] According to the present disclosure, when the poll retransmission timer expires, if both the transmission buffer and the retransmission buffer are empty or new data (or new data segment) cannot be transmitted, it is suggested that the UE consider the data with the highest SN among the data submitted to the lower layer for retransmission or any data that has not yet received a positive acknowledgment. The UE then includes a poll for the data selected for retransmission.

[0197] In particular, data indicated by a discard indication from the upper layer is excluded from consideration for retransmission.

[0198] Alternatively, data with a remaining time lower than the threshold is considered for retransmission, data with the shortest remaining time is considered for retransmission, or the highest SN among data with a remaining time lower than the threshold is considered for retransmission.

[0199] The UE has multiple layers (e.g., PDCP, RLC, and MAC layers), and each layer has a unique function. Below, PDCP, RLC, and MAC layers are described using a layer concept, but this is not limited to this, and the names of each layer may be changed.

[0200] The PDCP entity can be set to a delay threshold used to determine delay-critical PDCP SDUs (i.e., PDCP SDUs with a remaining time lower than the delay threshold). When a PDCP SDU becomes a delay-critical PDCP SDU, the PDCP entity provides a delay-critical instruction for that PDCP SDU to the lower layer. If the PDCP entity is set to PDU-set based discard, when the discard timer for a PDCP SDU expires, the PDCP entity discards all PDCP SDUs belonging to that PDU set. Otherwise, if the PDCP entity is not set to PDU-set based discard, when the discard timer for a PDCP SDU expires, the PDCP entity discards that PDCP SDU along with its corresponding PDCP SDU.

[0201] If a PDCP entity is set to a discard timer value for low-importance PDCP SDUs and PSI (i.e., PDU set importance)-based discarding is enabled, the PDCP entity starts the discard timer with the value for low-importance PDCP SDUs when receiving low-importance PDCP SDUs, but starts the discard timer with a value other than for low-importance PDCP SDUs when receiving PDCP SDUs other than low-importance PDCP SDUs (i.e., high-importance PDCP SDUs or general PDCP SDUs). If PSI-based discarding is not enabled, a single discard timer value is used for all PDCP SDUs. Low-importance PDCP SDUs may belong to the low-importance PDU set, and high-importance PDCP SDUs may belong to the high-importance PDU set.

[0202] The RLC entity can be set to SN, at least one pole retransmission timer value, at least one pole PDU threshold, and at least one pole byte threshold. If the RLC transmission window size can be determined by subtracting 1 from SN (e.g., if a 5-bit SN is set), the RLC transmission window size can be 16.

[0203] When an RLC entity receives an RLC SDU from an upper layer, the RLC entity may associate an SN with the received RLC SDU and store the RLC SDUs in a transmission buffer for a new transmission. The lower layer instructs the RLC entity on the total size of the RLC PDU(s) at a specific transmission time after the UE receives an uplink grant. The RLC entity submits at least one RLC PDU containing RLC SDUs or segments of RLC SDUs up to the instructed total size, and the submitted RLC SDU may be located within the transmission window. The UE or the lower layer generates a MAC PDU containing at least one RLC PDU and then transmits the MAC PDU using the uplink grant.

[0204] The RLC entity counts the number of RLC PDUs submitted to the lower layer and the number of bytes of data in the upper layer.

[0205] An RLC entity includes a poll bit in the RLC PDU when one of the following conditions 1) through 4) is satisfied:

[0206] 1) The counted number of RLC PDUs submitted to the lower layer is greater than or equal to at least one poll PDU threshold;

[0207] 2) The counted number of bytes of upper-layer data submitted to the lower layer is greater than or equal to at least one poll byte threshold;

[0208] 3) After the transmission of the submitted RLC PDU, both the transmission buffer and the retransmission buffer become empty;

[0209] 4) A new RLC SDU cannot be transmitted after the transmission of a submitted RLC PDU.

[0210] If at least one RLC PDU contains a poll bit, both counters for the number of RLC PDUs and the number of upper-layer data bytes are set to 0. While an RLC PDU containing a poll bit is being submitted to the lower layer, the RLC entity stores or updates a specific poll SN parameter with the SN of the RLC PDU with the highest SN among all RLC PDUs submitted to the lower layer, and then starts a poll retransmission timer with the set value.

[0211] When the RLC entity receives a status report, it can determine whether the submitted RLC SDU has been successfully transmitted. If at least one submitted RLC SDU or RLC SDU segment is negatively acknowledged by the status report, the RLC entity may consider the negatively acknowledged RLC SDU or RLC SDU segment as a retransmission target and store this RLC SDU or RLC SDU segment in the retransmission buffer for retransmission. When the RLC entity retransmits an RLC SDU, the RLC entity increments the retransmission counter associated with that RLC SDU. The retransmission counter is set to 0 when the first retransmission for the RLC SDU is performed. When the retransmission counter reaches a specific value set by the upper layer, the RLC entity may indicate a radio link problem (i.e., an RLC failure problem) to the upper layer.

[0212] When the poll retransmission timer expires, the RLC entity includes a poll bit in the submitted RLC PDU. If both the transmit buffer and the retransmission buffer are empty and / or a new RLC SDU or RLC SDU segment cannot be transmitted, the RLC entity selects one of the RLC SDUs within the transmit window for retransmission.

[0213] When selecting an RLC SDU for retransmission, the RLC entity considers the RLC SDU with the highest SN among the RLC SDUs submitted to the lower layer, or any RLC SDU that has not yet received a positive acknowledgment for retransmission.

[0214] In particular, the RLC entity additionally considers one or more of the following conditions i) through vii) to select an RLC SDU for retransmission.

[0215] i) When the RLC SDU has not yet been indicated by a discard indication from the upper layer. That is, if the RLC SDU has been indicated by a discard indication from the upper layer, the RLC entity may not select the RLC SDU indicated by that discard indication.

[0216] ii) The RLC SDU has a remaining time that is less than or equal to a delay threshold that can be set in the RLC or PDCP.

[0217] iii) When the RLC SDU is indicated by a delay critical indication from a higher layer. That is, it is an RLC SDU associated with a delay critical PDCP SDU.

[0218] iv) When the RLC SDU has the shortest remaining time within the transmission window.

[0219] v) When an RLC SDU is associated with a high-importance PDCP SDU or a set of high-importance PDUs. That is, when it is not associated with a low-importance PDCP SDU or a set of low-importance PDUs.

[0220] vi) When the RLC SDU is associated with the PDCP control PDU.

[0221] vii) When an RLC SDU has the highest maximum retransmission counter value among the RLC SDUs submitted to the lower layer (i.e., RLC SDUs within the transmission window).

[0222] Alternatively, if a new RLC SDU or RLC SDU segment cannot be transmitted, the RLC entity may submit / transmit a new RLC SDU or RLC SDU segment after discarding at least one RLC SDU indicated by a discard indication from the upper layer among the RLC SDUs submitted to the lower layer.

[0223] Alternatively, if a new RLC SDU or RLC SDU segment cannot be transmitted, the RLC entity may submit / transmit a new RLC SDU or RLC SDU segment associated with a high-importance PDCP SDU or a high-importance PDU set after discarding at least one RLC SDU associated with a low-importance PDCP SDU or a low-importance PDU set among the RLC SDUs submitted to the lower layer. The RLC entity may report information regarding the discarded RLC SDUs within the transmitting window, i.e., information on RLC SDUs removed from the transmitting window, to the peer RLC entity.

[0224] After receiving the uplink grant, the UE or lower layer generates a MAC PDU containing the selected RLC SDU along with a poll bit for retransmission, and then transmits the MAC PDU using the uplink grant.

[0225] When the network receives an RLC PDU containing a poll bit, the network generates a status report containing RLC SDU reception information up to the SN of the next unreceived RLC SDU that was not reported as missing, and then transmits the status report to the UE.

[0226] FIG. 9 is a first example of performing retransmission according to the present disclosure.

[0227] In Fig. 9, it is assumed that SN is 4 bits and the transmission window size is 8. RLC SDUs with SN 1, SN 2, SN 3, and SN 5 have already been positively acknowledged. The peer RLC entity successfully receives RLC SDUs with SN 1, SN 2, SN 3, and SN 5. Additionally, it is assumed that the RLC SDU with SN 4 is associated with a PDCP SDU of low importance, and the RLC SDUs with SN 6, SN 7, and SN 8 are associated with a PDCP SDU of high importance. The set delay threshold is 5ms.

[0228] At T1, after receiving the uplink grant, the RLC entity submits RLC SDUs with SN 6, SN 7, and SN 8 to the MAC layer, includes a poll bit in the RLC PDU with RLC SDU 8, and starts the poll retransmission timer. However, the MAC PDU containing the RLC SDUs with SN 6, SN 7, and SN 8 is not successfully transmitted, and the peer receiving RLC entity does not receive this MAC PDU.

[0229] At T2, the pole retransmission timer expires and the transmission window stalls (i.e., no new RLC SDU or new RLC SDU segment can be transmitted). The remaining times of the RLC SDUs with SN 4, SN 6, SN 7, and SN 8 are 3ms, 4ms, 5ms, and 9ms, respectively.

[0230] At T3, after receiving the uplink grant, the RLC entity selects the RLC SDU with SN 6 for retransmission, even though the RLC SDU with SN 4 has the shortest remaining time of 3ms. This is because the RLC SDU has not yet been affirmed, is not associated with a PDCP SDU of low importance, and the remaining time of this RLC SDU with SN 6 is lower than the delay threshold and is the shortest remaining time among the RLC SDUs submitted to the lower layer.

[0231] The RLC entity submits an RLC SDU with SN 6 to the MAC layer for retransmission, includes a poll bit in the RLC PDU containing the RLC SDU with SN 6, and then starts the poll retransmission timer.

[0232] FIG. 10 is a second example of performing retransmission according to the present disclosure.

[0233] In Fig. 10, it is assumed that SN is 4 bits and the transmission window size is 8. RLC SDUs with SN 1, SN 2, SN 3, and SN 5 have already been positively acknowledged. The peer RLC entity successfully receives RLC SDUs with SN 1, SN 2, SN 3, and SN 5. Additionally, it is assumed that the RLC SDU with SN 4 is associated with a PDCP SDU of low importance, and the RLC SDUs with SN 6, SN 7, and SN 8 are associated with a PDCP SDU of high importance. The set delay threshold is 5ms.

[0234] At T1, after receiving the uplink grant, the RLC entity submits RLC SDUs with SN 6, SN 7, and SN 8 to the MAC layer, includes a poll bit in the RLC PDU containing the RLC SDU with SN 8, and starts the poll retransmission timer. However, the MAC PDU containing the RLC SDUs with SN 6, SN 7, and SN 8 is not successfully transmitted, and the peer receiving RLC entity does not receive this MAC PDU.

[0235] At T2, the pole retransmission timer expires and the transmission window stalls (i.e., no new RLC SDU or RLC SDU segment can be transmitted). The remaining times of the RLC SDUs with SN 4, SN 6, SN 7, and SN 8 are 3ms, 4ms, 5ms, and 9ms, respectively.

[0236] At T3, after receiving the uplink grant, the RLC entity removes the RLC SDU with SN 4 from the transmission window because the transmission window has stalled and this RLC SDU is associated with a PDCP SDU of low importance. Then, the RLC entity submits the RLC SDU with SN 9 to the MAC layer for a new transmission, includes a pole bit in the RLC PDU containing the RLC SDU with SN 9, and starts the pole retransmission timer.

[0237] FIG. 11 is a third example of performing retransmission according to the present disclosure.

[0238] In Fig. 11, it is assumed that SN is 4 bits and the transmission window size is 8. It is assumed that RLC SDUs with SN 1 and SN 5 have already been positively acknowledged. It is assumed that the peer RLC entity has successfully received RLC SDUs with SN 1 and SN 5.

[0239] At T1, after receiving the uplink grant, the RLC entity submits RLC SDUs with SN 6, SN 7, and SN 8 to the MAC layer, includes a poll bit in the RLC PDU containing the RLC SDU with SN 8, and starts the poll retransmission timer.

[0240] However, a MAC PDU containing RLC SDUs with SN 6, SN 7, and SN 8 is not successfully transmitted, and the peer receiving RLC entity does not receive this MAC PDU. When the RLC entity submits RLC SDUs with SN 7 and SN 8, these two RLC SDUs are not indicated by a discard indication from the upper layer.

[0241] At T2, the poll retransmission timer expires and the transmission window stalls (i.e., no new RLC SDU or RLC SDU segment can be transmitted). RLC SDUs with SN 7 and SN 8 are indicated by discard indicators from the upper layer.

[0242] At T3, after receiving the uplink grant, the RLC entity selects an RLC SDU with SN 6 for retransmission. This is because the RLC SDU has not yet been acknowledged and has not yet been discarded by a discard indicator from the upper layer. The RLC entity submits the RLC SDU with SN 6 to the MAC layer for retransmission, includes a poll bit in the RLC PDU containing the RLC SDU with SN 6, and restarts the poll retransmission timer.

[0243] FIG. 12 is a flowchart for performing an operation according to the present disclosure.

[0244] Referring to FIG. 12, in A01, the RLC entity of the UE submits one or more RLC SDUs (service data units) to the MAC entity of the UE. Preferably, when any one of the one or more RLC SDUs is submitted with a poll, a poll retransmission timer is started.

[0245] Next, in A02, the RLC entity receives a discard indication for at least one of the one or more RLC SDUs submitted by the UE's PDCP (Packet Data Convergence Protocol) entity.

[0246] When the poll retransmission timer expires, the RLC entity in A03 selects an RLC SDU for retransmission from the remainder of the one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the discard indicator.

[0247] Preferably, the RLC entity selects an RLC SDU for retransmission from among one or more submitted RLC SDUs that are not indicated by a discard indicator and have not yet been positively acknowledged.

[0248] Alternatively, the RLC entity selects for retransmission the RLC SDU with the shortest remaining time until discard among one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the discard indicator.

[0249] Alternatively, the RLC entity selects for retransmission the RLC SDU indicated by the delay critical indication from among the one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the discard indicator.

[0250] Of course, as with conventional technology, the procedure for selecting an RLC SDU for retransmission is performed when both the transmission buffer and the retransmission buffer are empty, or when a new RLC SDU or RLC SDU segment cannot be transmitted due to window stalling.

[0251] Finally, in A04, the RLC entity submits the RLC SDU selected for retransmission to the MAC entity. Preferably, the RLC SDU selected for retransmission is submitted along with the poll. Thus, the poll retransmission timer restarts when the RLC SDU selected for retransmission is submitted.

[0252] According to the present disclosure, when a poll retransmission timer expires, the UE can select an RLC SDU for retransmission based on the remaining time or a discard indication received from an upper layer. Thus, the user experience for XR services can be improved by preventing unnecessary retransmission of old data and enabling urgent XR data to be transmitted to the network at an appropriate time. Additionally, this can prevent the waste of wireless resources.

Claims

Claim 1 A step of submitting one or more RLC SDUs (service data units) to a MAC (medium access control) entity of a UE (user equipment) by an RLC (radio link control) entity of said UE, wherein a poll retransmission timer is started based on one of the one or more RLC SDUs being submitted with a poll; a step of receiving a discard indication for at least one of the one or more submitted RLC SDUs from a PDCP (Packet Data Convergence Protocol) entity of said UE by said RLC entity; and a step of selecting an RLC SDU for retransmission from among the one or more submitted RLC SDUs, excluding the at least one RLC SDU indicated by the discard indication, by said RLC entity, based on the expiration of the poll retransmission timer. A method comprising the step of submitting an RLC SDU selected for retransmission to the MAC entity by the RLC entity. Claim 2 A method according to claim 1, wherein the step of selecting the RLC SDU for retransmission comprises selecting the RLC SDU for retransmission from among one or more submitted RLC SDUs that are not indicated by the discard indicator and have not yet been positively acknowledged. Claim 3 A method according to claim 1, wherein the RLC SDU for retransmission is selected based on the fact that both the transmission buffer and the retransmission buffer are empty, or based on the fact that a new RLC SDU or a new RLC SDU segment cannot be transmitted due to window stalling. Claim 4 A method according to claim 1, wherein the step of selecting the RLC SDU for retransmission comprises: submitting the RLC SDU for retransmission together with the pole; and restarting the pole retransmission timer. Claim 5 A method according to claim 1, wherein the step of selecting an RLC SDU for retransmission comprises selecting an RLC SDU having a minimum remaining time until disposal from among one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the disposal indicator. Claim 6 A method according to claim 1, wherein the step of selecting an RLC SDU for retransmission comprises selecting an RLC SDU indicated by a delay critical indication for retransmission from an upper layer among one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the discard indicator. Claim 7 As a UE (User equipment), at least one processor; and includes at least one computer memory storing instructions that cause the UE to perform operations when executed by the at least one processor, said operations being: a step of submitting one or more RLC SDUs (service data units) to the UE's MAC (medium access control) entity by the UE's RLC (radio link control) entity, wherein a poll retransmission timer is started based on one of the one or more RLC SDUs being submitted with a poll; a step of receiving a discard indication for at least one of the submitted RLC SDUs from the UE's PDCP (Packet Data Convergence Protocol) entity by the RLC entity; and, based on the expiration of the poll retransmission timer, among the one or more submitted RLC SDUs, excluding the at least one RLC SDU indicated by the discard indication by the RLC entity A UE comprising the steps of: selecting an RLC SDU for retransmission; and submitting the RLC SDU selected for retransmission to the MAC entity by the RLC entity. Claim 8 In claim 7, the step of selecting the RLC SDU for retransmission comprises selecting the RLC SDU for retransmission from among one or more submitted RLC SDUs that are not indicated by the discard indicator and have not yet been positively acknowledged, UE. Claim 9 In claim 7, the RLC SDU for retransmission is selected based on the fact that both the transmission buffer and the retransmission buffer are empty, or based on the fact that a new RLC SDU or a new RLC SDU segment cannot be transmitted due to window stalling, in a UE. Claim 10 In claim 7, the step of selecting the RLC SDU for retransmission comprises: submitting the RLC SDU for retransmission together with the pole; and restarting the pole retransmission timer, UE. Claim 11 In claim 7, the step of selecting the RLC SDU for retransmission comprises selecting an RLC SDU having a minimum remaining time until disposal from among the one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the disposal indicator, UE. Claim 12 In claim 7, the step of selecting the RLC SDU for retransmission comprises selecting the RLC SDU indicated by the delay critical indication for retransmission from the upper layer among the one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the discard indicator, UE. Claim 13 In a device for UE (User Equipment), at least one processor; and includes at least one computer memory storing instructions that cause the UE to perform operations when executed by the at least one processor, said operations being: a step of submitting one or more RLC SDUs (service data units) to the UE's MAC (medium access control) entity by the UE's RLC (radio link control) entity, wherein a poll retransmission timer is started based on one of the one or more RLC SDUs being submitted with a poll; a step of receiving a discard indication for at least one of the submitted RLC SDUs from the UE's PDCP (Packet Data Convergence Protocol) entity by the RLC entity; and, based on the expiration of the poll retransmission timer, among the one or more submitted RLC SDUs, excluding the at least one RLC SDU indicated by the discard indication by the RLC entity A device comprising: a step of selecting an RLC SDU for retransmission; and a step of submitting the RLC SDU selected for retransmission to the MAC entity by the RLC entity. Claim 14 In a computer-readable storage medium, the storage medium comprises program instructions that cause a User Equipment (UE) to perform operations when performed by a processor, said operations comprising: submitting one or more RLC service data units (service data units) by the radio link control (RLC) entity of the UE to the medium access control (MAC) entity of the UE, wherein a poll retransmission timer is started based on one of the one or more RLC SDUs being submitted with a poll; receiving a discard indication for at least one of the submitted RLC SDUs from the Packet Data Convergence Protocol (PDCP) entity of the UE by the RLC entity; and, based on the expiration of the poll retransmission timer, among the one or more submitted RLC SDUs, excluding at least one RLC SDU indicated by the discard indication A storage medium comprising: a step of selecting an RLC SDU for retransmission; and a step of submitting the RLC SDU selected for retransmission to the MAC entity by the RLC entity.

Images