KR20210037952A - Method and apparatus for performing wireless communication in non-terrestrial network - Google Patents

Abstract

The present embodiments relate to a method and an apparatus for performing wireless communication in a non-terrestrial network, and an embodiment provided a method that includes the steps of checking round-trip propagation delay information for a specific node, determining whether the number of HARQ processes per transport block of data calculated based on round-trip propagation delay information exceeds the number of HARQ processes configured for a specific node, initially transmitting data, and retransmitting the same retransmission data as the data consecutively N times based on the determination result. Efficient HARQ (Hybrid Automatic Repeat Request) process can be controlled.

Description

Method and apparatus for performing wireless communication in a non-terrestrial network {METHOD AND APPARATUS FOR PERFORMING WIRELESS COMMUNICATION IN NON-TERRESTRIAL NETWORK}

The present embodiments propose a method and apparatus for performing wireless communication in a non-terrestrial network in a next-generation radio access network (hereinafter, referred to as “New Radio”).

3GPP recently approved "Study on New Radio Access Technology", a study item for research on next-generation radio access technology (that is, 5G radio access technology), and based on this, RAN WG1 for each NR (New Radio) Design for a frame structure, channel coding & modulation, waveform & multiple access scheme, etc. is in progress. NR is required to be designed to satisfy various QoS requirements required for each subdivided and detailed usage scenario as well as an improved data rate compared to LTE.

As representative usage scenarios of NR, eMBB (enhancement mobile broadband), mMTC (massive machine type communication), and URLLC (Ultra Reliable and Low Latency Communications) are defined, and a frame structure that is flexible compared to LTE in order to satisfy the needs of each usage scenario Design is in demand.

Since each usage scenario has different requirements for data rates, latency, reliability, coverage, etc., the frequency band constituting an arbitrary NR system is used. Based on different numerology (e.g., subcarrier spacing, subframe, TTI (Transmission Time Interval), etc.) as a method to efficiently satisfy the needs of each usage scenario There is a need for a method of efficiently multiplexing a radio resource unit of a device.

As part of this aspect, when the round-trip propagation delay is large in NR, for example, in an environment such as a non-terrestrial network, a design for performing wireless communication is required.

The present embodiments can provide a method and apparatus for performing wireless communication in a non-terrestrial network capable of efficiently controlling a hybrid automatic repeat request (HARQ) process in a case of a large round trip propagation delay.

In one aspect, the present embodiments confirm the round-trip propagation delay information for a specific node, the number of HARQ processes per transport block of data calculated based on the round-trip propagation delay information for the node. It is possible to provide a method including determining whether the number of configured HARQ processes is exceeded, initially transmitting data, and continuously retransmitting the same retransmission data N times based on the determination result.

In another aspect, the present embodiments confirm round-trip propagation delay information for a specific node, and the number of HARQ processes per transport block of data calculated based on the round-trip propagation delay information is configured for the node. It is possible to provide an apparatus including a control unit for determining whether the number of HARQ processes is exceeded, and a transmission unit for initially transmitting data and continuously retransmitting the same retransmission data N times based on the determination result.

According to the present embodiments, it is possible to provide a method and apparatus for performing wireless communication in a non-terrestrial network capable of efficiently controlling a hybrid automatic repeat request (HARQ) process in the case of a large round trip propagation delay.

In addition, according to the present embodiments, when the round-trip propagation delay is large, the reliability and accuracy of data transmission can be further improved by performing blind retransmission in which retransmission is performed without separate signaling according to each HARQ process.

1 is a diagram schematically showing the structure of an NR wireless communication system to which the present embodiment can be applied.
2 is a diagram for explaining a frame structure in an NR system to which the present embodiment can be applied.
3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.
4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.
5 is a diagram exemplarily showing a synchronization signal block in a wireless access technology to which the present embodiment can be applied.
6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.
7 is a diagram for explaining CORESET.
8 is a diagram illustrating an example of symbol level alignment in different subcarrier spacing (SCS) to which the present embodiment can be applied.
9 is a diagram schematically showing an NR MAC structure to which this embodiment can be applied.
10 is a diagram illustrating an example of a non-terrestrial network to which the present embodiment can be applied.
11 is a diagram illustrating a procedure for performing a blind retransmission operation of data based on round trip propagation delay information according to an embodiment.
12 is a diagram illustrating a procedure for performing a blind reception operation of data based on round trip propagation delay information according to an embodiment.
13 is a diagram for describing an operation of blind retransmission of data according to an exemplary embodiment.
14 is a diagram showing a configuration of a base station according to another embodiment.
15 is a diagram showing a configuration of a user terminal according to another embodiment.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to elements of each drawing, the same elements may have the same numerals as possible even if they are indicated on different drawings. In addition, in describing the embodiments, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present technical idea, a detailed description thereof may be omitted. When "include", "have", "consists of" and the like mentioned in the present specification are used, other parts may be added unless "only" is used. In the case of expressing the constituent elements in the singular, the case including the plural may be included unless there is a specific explicit description.

In addition, in describing the constituent elements of the present disclosure, terms such as first, second, A, B, (a) and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, order, or number of the component is not limited by the term.

In the description of the positional relationship of components, when two or more components are described as being "connected", "coupled" or "connected", the two or more components are directly "connected", "coupled" or "connected" "It may be, but it should be understood that two or more components and other components may be further "interposed" to be "connected", "coupled" or "connected". Here, the other components may be included in one or more of two or more components "connected", "coupled" or "connected" to each other.

In the description of the temporal flow relationship related to the components, the operation method or the manufacturing method, for example, the temporal precedence relationship such as "after", "after", "after", "before", etc. Alternatively, a case where a flow forward and backward relationship is described may also include a case that is not continuous unless “directly” or “directly” is used.

On the other hand, when a numerical value for a component or its corresponding information (e.g., level, etc.) is mentioned, the numerical value or its corresponding information is related to various factors (e.g., process factors, internal or external impacts, etc.) It can be interpreted as including an error range that can be caused by noise, etc.).

The wireless communication system in the present specification refers to a system for providing various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

The embodiments disclosed below can be applied to a wireless communication system using various wireless access technologies. For example, the present embodiments include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA). Alternatively, it may be applied to various various wireless access technologies such as non-orthogonal multiple access (NOMA). In addition, the wireless access technology may mean not only a specific access technology, but also a communication technology for each generation established by various communication consultation organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with a radio technology such as global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented with 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 a system based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) that uses evolved-UMTSterrestrial radio access (E-UTRA), and employs OFDMA in downlink and SC- Adopt FDMA. As described above, the present embodiments may be applied to a wireless access technology currently disclosed or commercialized, and may be applied to a wireless access technology currently being developed or developed in the future.

Meanwhile, the terminal in the present specification is a generic concept that refers to a device including a wireless communication module that performs communication with a base station in a wireless communication system, and in WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or New Radio), etc. It should be interpreted as a concept including all of the user equipment (UE) of the, as well as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device in GSM. In addition, the terminal may be a user's portable device such as a smart phone according to the usage type, and in the V2X communication system, it may mean a vehicle, a device including a wireless communication module in the vehicle, and the like. In addition, in the case of a machine type communication system, it may mean an MTC terminal, an M2M terminal, a URLLC terminal, etc. equipped with a communication module to perform machine type communication.

The base station or cell of the present specification refers to the end of communication with the terminal in terms of the network, and Node-B (Node-B), eNB (evolved Node-B), gNB (gNode-B), LPN (Low Power Node), Sector, Site, various types of antennas, BTS (Base Transceiver System), Access Point, Point (e.g., transmission point, reception point, transmission/reception point), relay node ), a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, a remote radio head (RRH), a radio unit (RU), and a small cell. In addition, the cell may mean including a bandwidth part (BWP) in the frequency domain. For example, the serving cell may mean an activation BWP of the terminal.

In the various cells listed above, since there is a base station controlling one or more cells, the base station can be interpreted in two meanings. 1) In relation to the radio area, the device itself may provide a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, and a small cell, or 2) the radio area itself may be indicated. In 1), devices providing a predetermined wireless area are controlled by the same entity, or all devices interacting to form a wireless area in collaboration are instructed to the base station. Depending on the configuration method of the wireless area, a point, a transmission/reception point, a transmission point, a reception point, etc. become an embodiment of the base station. In 2), it is also possible to instruct the base station to the radio region itself that receives or transmits a signal from the viewpoint of the user terminal or from the viewpoint of a neighboring base station.

In this specification, a cell refers to a component carrier having coverage of a signal transmitted from a transmission/reception point or a coverage of a signal transmitted from a transmission/reception point, and the transmission/reception point itself. I can.

Uplink (Uplink, UL, or uplink) refers to a method of transmitting and receiving data to a base station by a terminal, and downlink (Downlink, DL, or downlink) refers to a method of transmitting and receiving data to a mobile station by a base station. do. Downlink may refer to a communication or communication path from multiple transmission/reception points to a terminal, and uplink may refer to a communication or communication path from a terminal to multiple transmission/reception points. In this case, in the downlink, the transmitter may be a part of multiple transmission/reception points, and the receiver may be a part of the terminal. In addition, in the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of the multiple transmission/reception points.

Uplink and downlink transmit and receive control information through control channels such as Physical Downlink Control CHannel (PDCCH), Physical Uplink Control CHannel (PUCCH), and the like, and The same data channel is configured to transmit and receive data. Hereinafter, a situation in which signals are transmitted and received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH is expressed in the form of ``transmitting and receiving PUCCH, PUSCH, PDCCH, and PDSCH''. do.

For clarity, in the following description, the present technical idea is mainly described in the 3GPP LTE/LTE-Ack/NackR (New RAT) communication system, but the present technical feature is not limited to the corresponding communication system.

3GPP develops 5G (5th-Generation) communication technology to meet the requirements of ITU-R's next-generation wireless access technology after research on 4G (4th-Generation) communication technology. Specifically, 3GPP develops a new NR communication technology separate from 4G communication technology and LTE-A pro, which has improved LTE-Advanced technology as a 5G communication technology according to the requirements of ITU-R. Both LTE-A pro and NR refer to 5G communication technology, and hereinafter, 5G communication technology will be described centering on NR when a specific communication technology is not specified.

The operation scenario in NR defined various operation scenarios by adding considerations to satellites, automobiles, and new verticals from the existing 4G LTE scenario.In terms of service, eMBB (Enhanced Mobile Broadband) scenario, high terminal density, but wide It is deployed in the range and supports the mMTC (Massive Machine Communication) scenario that requires a low data rate and asynchronous connection, and the URLLC (Ultra Reliability and Low Latency) scenario that requires high responsiveness and reliability and supports high-speed mobility. .

To satisfy this scenario, NR discloses a wireless communication system to which a new waveform and frame structure technology, a low latency technology, a mmWave support technology, and a forward compatible provision technology are applied. In particular, in the NR system, various technical changes are proposed in terms of flexibility in order to provide forward compatibility. The main technical features of the NR will be described below with reference to the drawings.

<NR system general>

1 is a diagram schematically showing the structure of an NR system to which the present embodiment can be applied.

Referring to FIG. 1, the NR system is divided into 5GC (5G Core Network) and NR-RAN parts, and NG-RAN controls the user plane (SDAP/PDCP/RLC/MAC/PHY) and UE (User Equipment). It consists of gNB and ng-eNB that provide plane (RRC) protocol termination. The gNB or gNB and ng-eNB are interconnected through an Xn interface. The gNB and ng-eNB are each connected to 5GC through the NG interface. The 5GC may include an Access and Mobility Management Function (AMF) in charge of a control plane such as a terminal access and mobility control function, and a User Plane Function (UPF) in charge of a control function for user data. NR includes support for both frequency bands below 6GHz (FR1, Frequency Range 1) and frequency bands above 6GHz (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to a terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to a terminal. The base station described in this specification should be understood to encompass gNB and ng-eNB, and may be used as a meaning to distinguish between gNB or ng-eNB as needed.

<NR wave form, numer roller and frame structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with MIMO (Multiple Input Multiple Output), and has the advantage of being able to use a receiver of low complexity with high frequency efficiency.

Meanwhile, in NR, since the requirements for data rate, delay rate, coverage, etc. are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through the frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing a plurality of different numerology-based radio resources has been proposed.

Specifically, the NR transmission neuron is determined based on sub-carrier spacing and CP (cyclic prefix), and the value of μ is used as an exponential value of 2 based on 15 kHz as shown in Table 1 below. Is changed to.

μ Subcarrier spacing Cyclic prefix Supported for data Supported for synch 0 15 Normal Yes Yes One 30 Normal Yes Yes 2 60 Normal, Extended Yes No 3 120 Normal Yes Yes 4 240 Normal No Yes

As shown in Table 1 above, the NR neuron can be classified into 5 types according to the subcarrier spacing. This is different from LTE, one of 4G communication technologies, where the subcarrier spacing is fixed at 15 kHz. Specifically, subcarrier intervals used for data transmission in NR are 15, 30, 60, and 120kHz, and subcarrier intervals used for synchronization signal transmission are 15, 30, 120, and 240kHz. In addition, the extended CP is applied only to the 60kHz subcarrier interval. Meanwhile, a frame structure in NR is defined as a frame having a length of 10 ms consisting of 10 subframes having the same length of 1 ms. One frame can be divided into 5 ms half frames, and each half frame includes 5 subframes. In the case of a 15 kHz subcarrier interval, one subframe consists of 1 slot, and each slot consists of 14 OFDM symbols.

2 is a diagram for explaining a frame structure in an NR system to which the present embodiment can be applied.

Referring to FIG. 2, in the case of a normal CP, a slot is fixedly composed of 14 OFDM symbols, but the length in the time domain of the slot may vary according to the subcarrier interval. For example, in the case of a newer roller with a 15 kHz subcarrier spacing, a slot is 1 ms long and has the same length as the subframe. In contrast, in the case of a newer roller with a 30 kHz subcarrier interval, a slot consists of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5 ms. That is, the subframe and the frame are defined with a fixed time length, and the slot is defined by the number of symbols, and the time length may vary according to the subcarrier interval.

Meanwhile, NR defines a basic unit of scheduling as a slot, and a mini-slot (or sub-slot or non-slot based schedule) is also introduced in order to reduce the transmission delay of the radio section. If a wide subcarrier spacing is used, the length of one slot is shortened in inverse proportion, so that transmission delay in the radio section can be reduced. Mini-slots (or sub-slots) are for efficient support for URLLC scenarios and can be scheduled in units of 2, 4, or 7 symbols.

In addition, unlike LTE, NR defines uplink and downlink resource allocation as a symbol level within one slot. In order to reduce HARQ delay, a slot structure capable of transmitting HARQ ACK/NACK directly within a transmission slot has been defined, and this slot structure is named and described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported through a combination of various slots. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which a downlink symbol and an uplink symbol are combined are supported. In addition, NR supports that data transmission is distributed and scheduled in one or more slots. Accordingly, the base station may inform the UE of whether the slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI). The base station can indicate the slot format by indicating the index of the table configured through UE-specific RRC signaling using SFI, and dynamically indicates through Downlink Control Information (DCI) or statically or through RRC. It can also be quasi-static.

<NR physical resource>

In relation to the physical resource in NR, an antenna port, a resource grid, a resource element, a resource block, a bandwidth part, etc. are considered. do.

The antenna port is defined so that a channel carrying a symbol on an antenna port can be inferred from a channel carrying another symbol on the same antenna port. When the large-scale property of a channel carrying a symbol on one antenna port can be inferred from a channel carrying a symbol on another antenna port, the two antenna ports are QC/QCL (quasi co-located or quasi co-location) relationship. Here, the wide-range characteristic includes one or more of delay spread, Doppler spread, frequency shift, average received power, and received timing.

3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.

Referring to FIG. 3, in a resource grid, since NR supports a plurality of neurons in the same carrier, a resource grid may exist according to each neuron. In addition, the resource grid may exist according to an antenna port, a subcarrier spacing, and a transmission direction.

A resource block consists of 12 subcarriers, and is defined only in the frequency domain. In addition, a resource element consists of one OFDM symbol and one subcarrier. Accordingly, as shown in FIG. 3, the size of one resource block may vary according to the subcarrier interval. In addition, NR defines “Point A” that serves as a common reference point for the resource block grid, a common resource block, and a virtual resource block.

4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

In NR, unlike LTE in which the carrier bandwidth is fixed at 20Mhz, the maximum carrier bandwidth is set from 50Mhz to 400Mhz for each subcarrier interval. Therefore, it is not assumed that all terminals use all of these carrier bandwidths. Accordingly, in the NR, as shown in FIG. 4, a bandwidth part (BWP) can be designated within the carrier bandwidth and used by the terminal. In addition, the bandwidth part is associated with one neurology and is composed of a subset of consecutive common resource blocks, and can be dynamically activated over time. The terminal is configured with up to four bandwidth parts, respectively, in uplink and downlink, and data is transmitted/received using the active bandwidth part at a given time.

In the case of a paired spectrum, the uplink and downlink bandwidth parts are set independently, and in the case of an unpaired spectrum, unnecessary frequency re-tuning between downlink and uplink operations is prevented. For this purpose, the downlink and uplink bandwidth parts are set in pairs to share the center frequency.

<NR initial connection>

In NR, the terminal accesses the base station and performs cell search and random access procedures to perform communication.

Cell search is a procedure in which a terminal synchronizes with a cell of a corresponding base station, obtains a physical layer cell ID, and obtains system information using a synchronization signal block (SSB) transmitted by a base station.

5 is a diagram exemplarily showing a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

Referring to FIG. 5, the SSB is composed of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) occupying 1 symbol and 127 subcarriers, respectively, and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

The terminal receives the SSB by monitoring the SSB in the time and frequency domain.

SSB can be transmitted up to 64 times in 5ms. A plurality of SSBs are transmitted in different transmission beams within 5 ms time, and the UE performs detection on the assumption that SSBs are transmitted every 20 ms period based on one specific beam used for transmission. The number of beams that can be used for SSB transmission within 5 ms time may increase as the frequency band increases. For example, under 3GHz, up to 4 SSB beams can be transmitted, in a frequency band of 3 to 6GHz, up to 8, and in a frequency band of 6GHz or higher, SSBs can be transmitted using up to 64 different beams.

Two SSBs are included in one slot, and the start symbol and the number of repetitions in the slot are determined according to the subcarrier interval as follows.

On the other hand, the SSB is not transmitted at the center frequency of the carrier bandwidth unlike the conventional LTE SS. That is, the SSB may be transmitted even in a place other than the center of the system band, and when supporting broadband operation, a plurality of SSBs may be transmitted in the frequency domain. Accordingly, the UE monitors the SSB by using a synchronization raster, which is a candidate frequency location for monitoring the SSB. The carrier raster and synchronization raster, which are information on the center frequency of the channel for initial access, have been newly defined in NR, and the synchronization raster has a wider frequency interval than the carrier raster, thus supporting fast SSB search of the terminal. I can.

The UE can acquire the MIB through the PBCH of the SSB. The MIB (Master Information Block) includes minimum information for the terminal to receive remaining system information (RMSI, Remaining Minimum System Information) broadcast by the network. In addition, PBCH is information on the location of the first DM-RS symbol in the time domain, information for the UE to monitor SIB1 (e.g., SIB1 neurology information, information related to SIB1 CORESET, search space information, PDCCH Related parameter information, etc.), offset information between the common resource block and the SSB (the position of the absolute SSB in the carrier is transmitted through SIB1), and the like. Here, the SIB1 neurology information is equally applied to some messages used in the random access procedure for accessing the base station after the terminal completes the cell search procedure. For example, the neurology information of SIB1 may be applied to at least one of messages 1 to 4 for a random access procedure.

The aforementioned RMSI may mean SIB1 (System Information Block 1), and SIB1 is periodically broadcast (ex, 160 ms) in a cell. SIB1 includes information necessary for the UE to perform an initial random access procedure, and is periodically transmitted through the PDSCH. In order for the UE to receive SIB1, it is necessary to receive newer roller information used for SIB1 transmission and CORESET (Control Resource Set) information used for SIB1 scheduling through the PBCH. The UE checks scheduling information for SIB1 using SI-RNTI in CORESET, and acquires SIB1 on the PDSCH according to the scheduling information. SIBs other than SIB1 may be periodically transmitted or may be transmitted according to the request of the terminal.

6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 6, when the cell search is completed, the UE transmits a random access preamble for random access to the base station. The random access preamble is transmitted through the PRACH. Specifically, the random access preamble is transmitted to the base station through a PRACH consisting of consecutive radio resources in a specific slot that is periodically repeated. In general, when a terminal initially accesses a cell, a contention-based random access procedure is performed, and when a random access is performed for beam failure recovery (BFR), a contention-free random access procedure is performed.

The terminal receives a random access response to the transmitted random access preamble. The random access response may include a random access preamble identifier (ID), a UL Grant (uplink radio resource), a temporary C-RNTI (Temporary Cell-Radio Network Temporary Identifier), and a TAC (Time Alignment Command). Since one random access response may include random access response information for one or more terminals, the random access preamble identifier may be included to inform which terminal the included UL Grant, temporary C-RNTI, and TAC are valid. The random access preamble identifier may be an identifier for the random access preamble received by the base station. TAC may be included as information for the UE to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, that is, a Random Access-Radio Network Temporary Identifier (RA-RNTI).

Upon receiving the valid random access response, the terminal processes the information included in the random access response and performs scheduled transmission to the base station. For example, the terminal applies TAC and stores a temporary C-RNTI. In addition, by using UL Grant, data stored in the buffer of the terminal or newly generated data is transmitted to the base station. In this case, information for identifying the terminal should be included.

Finally, the terminal receives a downlink message for resolving contention.

<NR CORESET>

The downlink control channel in NR is transmitted in CORESET (Control Resource Set) having a length of 1 to 3 symbols, and transmits uplink/downlink scheduling information, SFI (Slot Format Index), and TPC (Transmit Power Control) information. .

In this way, NR introduced the concept of CORESET to secure system flexibility. CORESET (Control Resource Set) refers to a time-frequency resource for a downlink control signal. The terminal may decode the control channel candidate using one or more search spaces in the CORESET time-frequency resource. A QCL (Quasi CoLocation) assumption for each CORESET is set, and this is used to inform the characteristics of the analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay, which are characteristics assumed by conventional QCL.

7 is a diagram for explaining CORESET.

Referring to FIG. 7, CORESET may exist in various forms within a carrier bandwidth within one slot, and CORESET may consist of up to three OFDM symbols in the time domain. In addition, CORESET is defined as a multiple of 6 resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated through the MIB as part of the initial bandwidth part configuration so that additional configuration information and system information can be received from the network. After connection establishment with the base station, the terminal may receive and configure one or more CORESET information through RRC signaling.

In this specification, frequencies, frames, subframes, resources, resource blocks, regions, bands, subbands, control channels, data channels, synchronization signals, various reference signals, various signals, or various messages related to NR (New Radio) May be interpreted as a meaning used in the past or present or a variety of meanings used in the future.

New Radio (NR)

NR progressed in 3GPP is a radio access technology capable of satisfying various QoS requirements required for each segmented and specified usage scenario, as well as an improved data rate compared to LTE. In particular, eMBB (enhancement mobile broadband), mMTC (massive MTC), and URLLC (Ultra Reliable and Low Latency Communications) were defined as representative usage scenarios of NR. In contrast, a flexible frame structure is provided. The frame structure of NR supports a frame structure based on multiple subcarriers. The basic SCS is 15kHz, and a total of 5 SCS types are supported at ^{15kHz*2 μ.}

8 shows an example of symbol level alignment for different SCSs. As shown in FIG. 8, it can be seen that the length of the slot varies according to the numerology. That is, it can be seen that the shorter the slot length, the larger the SCS. In addition, in the case of a normal cyclic prefix (CP), the number of OFDM symbols constituting a slot in the NR, y, was determined to have a value of y=14 regardless of the SCS value. Accordingly, a random slot consists of 14 symbols, and all symbols are used for downlink transmission or all symbols are used for uplink transmission according to the transmission direction of the corresponding slot. ), or may be used in the form of a downlink portion + a gap + an uplink portion (UL portion). In addition, a mini-slot composed of fewer symbols than the slots in an arbitrary neuron (or SCS) is defined, and based on this, a short time domain scheduling interval for uplink/downlink data transmission/reception is defined. -domain scheduling interval) may be set, or a long time-domain scheduling interval for transmitting/receiving uplink/downlink data may be configured through slot aggregation. In particular, in the case of transmission and reception of latency critical data such as URLLC, scheduling in slot units based on 1 ms (14 symbols) defined in a newer roller frame structure with a small SCS value such as 15 kHz. In this case, since it may be difficult to satisfy the latency requirement, for this purpose, a mini-slot composed of fewer OFDM symbols than the corresponding slot is defined, and based on this, latency critical data such as the corresponding URLLC. It can be defined so that scheduling is performed.

In NR, the following structure is supported in the time axis. Here, the difference from existing LTE is that in NR, the basic scheduling unit is changed to a slot. Also, regardless of subcarrier spacing, a slot consists of 14 OFDM symbols. On the other hand, it supports a non-slot structure composed of 2, 4, and 7 OFDM symbols, which are smaller scheduling units. The non-slot structure can be used as a scheduling unit for URLLC service.

NR HARQ (Hybrid ARQ)

The MAC protocol performs an error correction function through HARQ. 9 shows an example of a MAC structure. NR is supported by Asynchronous Incremental Redundancy Hybrid ARQ (HARQ) in downlink transmission. The base station may provide the HARQ-ACK feedback timing to the terminal dynamically within the downlink control information (DCI) or semi-statically in the RRC configuration. The MAC entity includes one HARQ entity for each serving cell, and each HARQ entity maintains 16 downlink HARQ processes. NR supports asynchronous incremental redundancy hybrid ARQ (HARQ) in uplink transmission. The base station schedules uplink transmission and retransmission using an uplink grant on DCI. The MAC entity includes one HARQ entity for each serving cell, and each HARQ entity maintains 16 uplink HARQ processes.

Non-Terrestrial Network (NTN)

A non-terrestrial network represents a network or a segment of a network that uses RF resources mounted on a satellite (or an Unmanned Aircraft System platform (UAS)). FIG. 10 shows an example of a typical NTN scenario.

NTN can be implemented in various ways as follows.

Scenario A: Transparent GEO (Geostationary orbit) (NTN beam foot print fixed on earth)

Scenario B: Regenerative GEO (NTN beam foot print fixed on earth)

Scenario C1: Transparent LEO (Low Earth Orbit) (NTN beam foot print fixed on earth)

Scenario C2: Transparent LEO (NTN beam foot print moving on earth)

Scenario D1: Regenerative LEO (NTN beam foot print fixed on earth)

Scenario D2: Regenerative LEO (NTN beam foot print moving on earth)

Here, a transparent payload or regenerative payload is defined as follows.

Transparent payload: Radio frequency filtering, frequency conversion and amplification. Therefore, the waveform signal repeated by the transparent payload is not changed. (Radio Frequency filtering, Frequency conversion and amplification. Hence, the waveform signal repeated by the payload is un-changed)

Regenerative payload: demodulation/decoding, switch and/or routing, coding/modulation, as well as radio frequency filtering, frequency conversion and amplification. This is substantially the same as having all or part of the base station functions (e.g. gNB) on the satellite (or UAS platform) board. (Radio Frequency filtering, Frequency conversion and amplification as well as demodulation/decoding, switch and/or routing, coding/modulation.This is effectively equivalent to having all or part of base station functions (eg gNB) on board the satellite (or UAS platform))

The satellite (or UAS platform) generate beams typically generate several beams over a given service area. bounded by its field of view.) The beam's footprint is typically elliptical. Table 2 shows the types of NTN platforms and the footprint size of typical beams.

Due to the distance between the terminal and the satellite, when the NTN provides the HARQ procedure of the NR as it is, for example, when the HARQ operation is performed through 16 parallel HARQ processes provided by the NR, the packet is transmitted in the error correction process through HARQ. May be delayed (HARQ stalling). However, in order to increase the number of HARQ processes, it is difficult to increase the number of HARQ processes because an additional cost is required for the terminal. In addition, the base station transmits the HARQ process ID to the terminal through the DCI. In order to distinguish the increased HARQ process ID, more bits must be allocated to the DCI to distinguish the HARQ process ID.

Accordingly, in the present disclosure, a method and apparatus for efficiently providing HARQ operation through a non-terrestrial network is proposed. Hereinafter, description is made on the premise that wireless communication is performed in a non-terrestrial network, but is not limited thereto. In a wireless communication system, if the radio wave round trip time between nodes is longer than a predetermined time and thus a larger number of HARQ processes than the number of HARQ processes implemented for the same data is required, the same can be applied to a terrestrial network.

11 is a diagram illustrating a procedure for performing a blind retransmission operation of data based on round trip propagation delay information according to an embodiment.

Referring to FIG. 11, in a non-terrestrial network, a node may check round-trip propagation delay information for a specific node (S1100).

In the present disclosure, one node and a specific node may correspond to a satellite base station or a terminal in a non-terrestrial network. That is, in the case of data transmission in downlink, one node may correspond to a satellite base station as a non-terrestrial network node, and a specific node may correspond to a terminal. In the case of data transmission in uplink, one node may correspond to a terminal and a specific node may correspond to a satellite base station. Hereinafter, for convenience of description, the case of data transmission in the downlink is mainly described, but the same may be applied to the case of uplink.

According to an example, the satellite base station may estimate round trip propagation delay information for the terminal through the RACH signal transmitted from the terminal. However, this is an example, and is not limited thereto, and other signals may be used as long as round trip propagation delay information can be estimated for a terminal to which data is to be transmitted.

Referring back to FIG. 11, a node may determine whether the number of HARQ processes per transmission block of data calculated based on the round trip propagation delay information exceeds the number of HARQ processes configured for a specific node (S1110).

According to an example, the HARQ process per transmission block of data considering the propagation delay may be calculated by Equation 1 below.

Here, T _p is a propagation delay, reflected as _{2T p in consideration of RTT, and T slot} is a slot transmission time. In addition, T _UEP is the UE data processing time after PDCCH and PDSCH reception after PDCCH and PDSCH reception, T _ack is the Ack/Nack feedback transmission time (Transmission time of Ack/Nack), and T _gNBP is It corresponds to the data processing time (gNB data processing time after Ack/Nack reception) of the base station after Ack/Nack reception.

Referring to Equation 1, it can be seen that as the propagation delay time increases, the number of HARQ processes required for the same data transmission increases. However, since the number of HARQ processes configured for the terminal, which is a specific node, is determined by the number of soft buffers implemented in the terminal, it may be smaller than the number of HARQ processes increased according to propagation delay.

For example, if the terminal has 8 soft buffers, the number of HARQ processes configured for the terminal is 8. In this case, it is assumed that the number of HARQ processes required according to the propagation delay between the satellite base station and the terminal is calculated as 32. According to this example, since 24 HARQ processes cannot be accommodated in a corresponding terminal, transmission of new data cannot be performed for slots corresponding to 24 HARQ processes.

In this case, the satellite base station as one node may determine that the number of HARQ processes per transmission block of data calculated based on the round-trip propagation delay information exceeds the number of HARQ processes configured for a terminal as a specific node.

Referring back to FIG. 11, a node may initially transmit data to a specific node (S1120), and may continuously retransmit N times the same retransmission data as the initially transmitted data based on the determination result (S1130).

The satellite base station, which is one node, may transmit downlink data to the terminal, which is a specific node. Thereafter, the satellite base station may retransmit N times the same retransmission data as the successively transmitted data. According to an example, the value of N, which is the number of retransmissions of data, may be determined by a preset function taking as factors the number of HARQ processes per transport block of data and the number of HARQ processes configured for the terminal.

According to the above example, it is assumed that the number of HARQ processes required according to the propagation delay is 32, and the number of HARQ processes configured for the terminal is 8. In this case, since new data may be transmitted through 8 HARQ processes in a section corresponding to 32 HARQ processes, the number of retransmissions may be determined as 3 for each data. That is, since the same data is initially transmitted once and retransmitted 3 times, a total of 4 transmissions are performed for the same data, and thus data transmission can be performed without blank intervals for a total of 32 intervals.

According to an example, the satellite base station may perform a data retransmission operation without separate signaling or setting of data retransmission. That is, in consideration of propagation delay, data retransmission may be performed N times without separate signaling. In the present disclosure, such retransmission may be referred to as blind retransmission.

In this case, initially transmitted data and retransmission data may be transmitted according to the same HARQ process among each HARQ process according to the number of HARQ processes configured for the terminal. That is, the downlink control information (DCI) included in the initial transmission data and the retransmission data, respectively, includes the index of the HARQ process, and the index of the same HARQ process may be indicated for the same data.

In addition, the downlink control information may include a new data indicator (NDI) field for distinguishing initially transmitted data from retransmission data. According to an example, the field may be implemented with 1 bit. In this case, when the value of the corresponding bit is 1, initial transmitted data may be indicated, and when the value of the corresponding bit is 0, retransmitted data may be indicated.

Accordingly, it is possible to provide a method and apparatus for performing wireless communication in a non-terrestrial network capable of efficiently controlling the HARQ process in the case of a large round trip propagation delay. In addition, when the round trip propagation delay is large, the reliability and accuracy of data transmission can be further improved by performing blind retransmission in which retransmission is performed without separate signaling according to each HARQ process.

12 is a diagram illustrating a procedure for performing a blind reception operation of data based on round trip propagation delay information according to an embodiment.

Referring to FIG. 12, a terminal, which is a specific node, may determine whether the number of HARQ processes per transmission block of data calculated based on round trip propagation delay information exceeds the number of HARQ processes configured for the node (S1200).

In order to receive retransmission data according to blind retransmission performed by the satellite base station, the terminal must be able to know whether the same data is continuously transmitted without additional signaling information provided by the satellite base station. To this end, the terminal estimates the propagation delay time with the satellite base station, assumes that data can be continuously transmitted in the form of blind retransmission, and may perform data reception.

According to the example described above in FIG. 11, it is assumed that the number of HARQ processes required according to the propagation delay is 32, and the number of HARQ processes configured for the terminal is 8. In this case, the terminal may determine that the number of HARQ processes per transport block of data calculated based on the round trip propagation delay information exceeds the number of HARQ processes configured for the terminal.

Referring back to FIG. 12, the terminal may continuously receive initial transmission data and retransmission data based on the determination result (S1210).

In the above-described example, since the terminal needs to operate up to 8 parallel HARQ transmissions per single TB, it can be assumed that the same data is transmitted in 4 consecutive slots based on blind retransmission. That is, the terminal may assume that data retransmission is made in consecutive slots without Ack/Nack feedback. Accordingly, the terminal can receive data for four consecutive slots.

The terminal may check a value of a new data indicator (NDI) field in downlink control information included in the received initial transmission data and retransmission data. When the value of the corresponding field is 1, the terminal may determine that it is initially transmitted data, and when the value of the corresponding field is 0, it may determine that the data is retransmitted. The terminal may perform soft combining of data received through all N slots in which retransmission has been performed, irrespective of success in data reception.

Referring back to FIG. 12, the terminal may transmit HARQ feedback information to the satellite base station (S1220).

According to an example, the transmission timing of HARQ feedback information for initially transmitted data and retransmission data may be indicated by preset downlink control information among downlink control information included in each of the initially transmitted data and retransmission data. .

After receiving data in the first slot, even if a Nack is detected, if an Ack is detected through soft value combining after receiving the retransmission data in the next consecutive slot, the terminal can finally transmit the Ack. . If Nack is still detected even after performing soft value combining for N times of retransmission data, the UE can finally transmit Nack.

In this case, the UE may feed back the final Ack/Nack based on the Ack/Nack timing field of the received first DCI. That is, even if Nack is detected after receiving the PDSCH in the first slot, if an Ack is detected through soft value combining after receiving the PDSCH in the next slot, the terminal finally transmits the Ack, but in the first slot. In the detected DCI, HARQ feedback information may be transmitted according to the timing indicated by the PDSCH-to-HARQ_feedback timing indicator.

Alternatively, a final Ack/Nack may be fed back based on the Ack/Nack timing field of the last DCI received by the UE. That is, even if Nack is detected after receiving the PDSCH in the first slot, if an Ack is detected through soft value combining after receiving the PDSCH in the next slot, the UE finally transmits the Ack, but in the last slot. In the detected DCI, ARQ feedback information may be transmitted according to the timing indicated by the PDSCH-to-HARQ_feedback timing indicator.

According to another example, Ack/Nack timing may be referred to as higher layer signaling irrespective of the aforementioned Ack/Nack timing. In this case, the UE may transmit the final Ack/Nack at a predetermined time regardless of the Ack/Nack timing in the DCI field of the received PDSCH data. That is, the higher layer setting value is followed regardless of the value of the PDSCH-to-HARQ_feedback timing indicator field in the DCI including data scheduling information.

Alternatively, according to another example, when the transmission timing of HARQ feedback information for initially transmitted data and retransmission data is not specified, a detection window for detecting HARQ feedback information for each of the initially transmitted data and the retransmission data is provided. Can be set.

For example, the terminal may be configured to transmit an Ack/Nack feedback for each retransmitted data between consecutive slots transmitted by a satellite base station. It can be assumed that the satellite base station can transmit 1:1 Ack/Nack feedback for all slots regardless of the blind reception procedure when the terminal transmits Ack/Nack. The base station performs Ack/Nack detection in the form of a window for a section in which the corresponding Ack/Nack can be transmitted.

If the terminal transmits Ack/Nack for all slots/subframes irrespective of retransmission data, the base station may determine whether the final transmission/reception is successful based on the last detected Ack/Nack.

Accordingly, it is possible to provide a method and apparatus for performing wireless communication in a non-terrestrial network capable of efficiently controlling the HARQ process in the case of a large round trip propagation delay. In addition, when the round trip propagation delay is large, the reliability and accuracy of data transmission can be further improved by performing blind retransmission in which retransmission is performed without separate signaling according to each HARQ process.

Hereinafter, each embodiment of performing a blind retransmission operation when transmitting data according to an HARQ process in a non-terrestrial network will be described in detail with reference to the related drawings.

Hereinafter, a method of controlling HARQ based on NR radio access technology will be described. However, this is for convenience of description, and embodiments according to the present disclosure may be applied to any radio access technology as long as it does not contradict the technical idea. In addition, the present disclosure describes a HARQ control method through a non-terrestrial network, but, unless contradictory to the technical idea, the implementation according to the present disclosure for HARQ control on a terrestrial network or through an interface between a terminal and a terminal (eg PC5). Examples can be applied. The embodiments described in the present disclosure include the contents of information elements and operations specified in TS 38.321, which is an NR MAC standard, and TS 38.213, which is an NR physical layer control standard. Even if the contents of the terminal operation related to the definition of the information element are not included in the present disclosure, the corresponding contents specified in the standard specification, which is a known technology, may be included in the present disclosure. In addition, the embodiments provided below may be implemented individually or by arbitrarily combining or combining each of the embodiments.

As described above, due to the limited number of HARQ processes, the application of HARQ becomes difficult as the distance between the terminal and the satellite increases, such as a geostationary orbit (GEO) or a medium earth orbit (MEO). Therefore, it is possible to disable the HARQ process. For convenience of description, not operating the HARQ process is indicated as HARQ turn off. This is for convenience of description, and may be replaced with an arbitrary name that may mean that HARQ is not operated, such as HARQ disable, HARQ deactivation, no Uplink HARQ feedback, and HARQ feedback disable in the terminal for downlink transmission.

On the other hand, in the case of an unmanned aircraft system (UAS) platform or low earth orbit (LEO), the HARQ delay may not be significant. In addition, since the HARQ process has an advantage of a soft combining gain, there is a case where it is desirable to operate the HARQ process (enable/turn on/Uplink HARQ feedback) even in the case of NTN.

Accordingly, it is necessary for the base station to configure HARQ turn off/turn on in the terminal, and it is necessary to additionally define a terminal operation corresponding thereto.

In this regard, network deactivation of HARQ may be supported through RRC configuration, and dynamic deactivation of HARQ by gNB may be supported. In addition, when HARQ is activated, depending on the effect of satellite round-trip time (Satellite RTT), if the number of HARQ processes is greater than 16, DCI size and HARQ soft buffer size should be considered.

In the present disclosure, embodiments of the case where it is impossible to increase the soft buffer of the terminal for the increase in the number of HARQ processes currently considered by the NR NTN, or when the corresponding system changes are not accommodated by the terminal will be described.

Currently, NR is conducting simulation considering various satellite orbits, and among them, as shown in Table 3 below, specific simulation parameters have been defined for three cases.

_{A method of deriving the number of HARQ processes} N HARQ in the existing LTE/NR is as in Equation 1 above. In Equation 1, T _p is a propagation delay and is reflected as _{2T p in consideration of RTT, and T slot} is a slot transmission time, for example, 1 ms based on 15 kHz. . In addition, T _UEP is UE data processing time after PDCCH and PDSCH reception after PDCCH and PDSCH reception, T _ack is Ack/Nack feedback transmission time (Transmission time of Ack/Nack), and T _gNBP is It corresponds to the data processing time (gNB data processing time after Ack/Nack reception) of the base station after Ack/Nack reception.

Accordingly, when the LTE/NR subcarrier spacing (SCS) is 15 kHz, the following values can be derived by default. If the distance between the terminal and the base station is negligibly small or falls within the CP, the propagation delay T _p becomes zero. In addition, in LTE/NR, a single subframe/slot is 1 ms, and the processing time of the terminal and the base station is generally reflected as 3 ms or less. In addition, if it is assumed that PUCCH for Ack/Nack transmission is also transmitted in a slot unit, it is 1 ms. Therefore, when the HARQ process number is derived based on SCS=15kHz LTE/NR for each transport block (TB), it is as shown in Equation 2 below.

That is, since the number of HARQ processes is 8, a 3-bit field for each TB is included in the DCI to indicate the number of each HARQ process. Using the same principle, if the propagation delay between the satellite and the terminal located in the satellite orbits LEO-600, LEO-1200, and GEO is calculated, it becomes 2ms, 4ms, and 120ms, respectively, and the number of HARQ processes in each case is calculated as follows.

In this way, the number of HARQ processes required can be derived through a delay according to the satellite orbit of the terminal. Therefore, when considering the propagation delay between satellites and terminals, the number of HARQ processes needs to be increased by more than a specific bit from 16 per existing TB (in this case, 4 bits are required) based on NR. In this case, since HARQ cannot be applied to the number of HARQ processes having a size that is too large, it may be assumed that the HARQ on/off technique is applied. However, as in the case of LEO-600,1200, it is possible to expand and operate the HARQ chain sufficiently by adding relatively few'N' bits.

However, when it is impossible to configure an additional HARQ process due to limitations in the implementation of the terminal, the existing 16 HARQ processes per TB are maintained. In this case, a retransmission procedure may be applied to a slot corresponding to a blank in a 16 HARQ-based slot configuration. Hereinafter, description is made on the premise of a non-terrestrial network, but if the number of HARQ processes greater than the number of HARQ processes implemented in the terminal is required because the radio wave round trip time is longer than a predetermined criterion, the following description is not limited to a specific case, and It can be applied in the same way.

Embodiment 1. In an NTN, a blind retransmission-based data transmission procedure may be applied in an inter-data transmission delay period caused by a propagation delay between a satellite and a terminal.

According to an embodiment of the present disclosure, blind retransmission may be performed for a section in which the number of HARQ processes increases in consideration of propagation delay between satellites and terminals. Here, blind retransmission refers to performing a data retransmission operation without special signaling and configuration between the terminal and the base station. However, the term is not limited thereto as an example, and may be replaced with another term.

_{For example, it is assumed that N HARQ, which} is the number of HARQ processes taking into account the propagation delay between satellites and terminals described above, is 32 per transport block (TB). In this case, 32 HARQ parallel processes are required, but since the soft buffer of the terminal itself is maintained, data for slots or subframes corresponding to 16 HARQ processes other than 16 HARQ processes configured in the terminal You cannot perform the transfer.

Accordingly, according to an embodiment, such a blank section may be used for data retransmission. However, since there is no separate signaling for the corresponding retransmission between the base station and the terminal, the terminal may perform data detection assuming that the corresponding data channel PDSCH is continuously retransmitted without performing Ack/Nack feedback.

Referring to FIG. 13, for example, a case in which a total of 4 transmissions are performed and 3 retransmission intervals are set is shown in FIG. 13. For the same TB (transmission data), transmission is performed in a total of 4 consecutive slots including initial transmission and 3 retransmissions. In this case, downlink control information (DCI) is transmitted during initial transmission and retransmission, respectively, and the terminal may determine whether or not the corresponding data is retransmitted through a new data indicator (NDI) field included in the DCI. That is, when the value of the NDI field is 1, the UE determines that data transmission through the corresponding PDSCH is the initial transmission of new data, and when the value of the NDI field is 0, it is determined as retransmission data identical to the initially transmitted data. can do.

Since the HARQ process applied during initial transmission and retransmission is the same, the same HARQ process index is allocated in the DCI. Accordingly, the terminal may perform soft value combining with previously transmitted data. That is, the terminal performs an operation for detecting individual data for each slot as it is, and the base station can perform retransmission between consecutive slots/subframes.

In FIG. 13, although illustrated on the premise of a downlink procedure, embodiments according to the present disclosure may be substantially equally applied to uplink PUSCH transmission. In this case, the terminal may perform blind retransmission in consideration of the propagation delay, and the base station may receive initial transmission and retransmitted data in consideration of the propagation delay.

Hereinafter, for convenience of description, it is assumed that the maximum number of parallel HARQ processes that can be implemented in the terminal is 8, and specific embodiments will be described. However, this is an example and is not limited thereto, and the number of parallel HARQ processes may be 16 in NR.

Example 1-1. The satellite base station applies the blind retransmission procedure of data in proportion to the propagation delay value between the satellite and the terminal.

According to an embodiment, the satellite base station may estimate the propagation delay with the terminal and set the continuous slot/subframe repetitive transmission proportional to the corresponding delay time. According to an example, the base station may estimate the corresponding propagation delay through the RACH signal transmitted from the terminal. Based on the estimated propagation delay, the terminal may calculate the number of HARQ processes described above.

For example, if the one-way propagation delay is 4 ms, the number of HARQ processes per TB is 16. That is, from the standpoint of a base station that must implement up to 8 parallel HARQ transmissions per single TB, data cannot be allocated to 8 slots corresponding to 8 HARQ process intervals, which are blank intervals. Accordingly, the same data is transmitted in two consecutive slots based on blind retransmission, and since the UE must perform an existing operation of detecting PDCCH in each of two consecutive slots, it is different from conventional repetitive transmission. Another base station operation is to be performed.

Example 1-2. The terminal may apply a blind reception procedure of data in proportion to the propagation delay value between the satellite and the terminal.

According to the present embodiment, the existing operation of first performing PDCCH detection and then performing scheduled PDSCH/PUSCH detection through the acquired DCI is not excluded. However, the terminal may improve the reception accuracy and improve performance through an additional procedure capable of detecting data transmitted in the form of blind retransmission from the base station. For this, it is necessary to know whether the same data is currently continuously transmitted without additional signaling information provided by the base station. To this end, the terminal may perform data reception on the assumption that the base station can continuously transmit data in the form of blind retransmission in consideration of at least the base station-to-terminal propagation delay time.

For example, as described above, if the one-way propagation delay is 4 ms, the number of HARQ processes per TB is 16. That is, since the UE needs to operate up to 8 parallel HARQ transmissions per single TB, it can be assumed that the same data is transmitted in two consecutive slots based on blind retransmission. That is, the UE assumes that data retransmission is made in consecutive slots without Ack/Nack feedback.

In this case, the UE may perform a soft combining operation of PDSCH data received through all N slots in which retransmission has been performed regardless of success of data reception.

Embodiment 2. In applying the blind retransmission procedure in NTN, the Ack/Nack transmission timing may follow a set value.

In this embodiment, when a blind retransmission procedure for retransmitting the same data between consecutive slots is applied, a method of feeding back Ack/Nack is described.

As described above, the blind retransmission procedure refers to a procedure in which the same data is transmitted between consecutive slots/subframes without Ack/Nack. Therefore, after receiving the same data, the terminal needs to finally feed back Ack/Nack whether or not the corresponding data has been successfully detected to the base station. At this time, since the same data is continuously transmitted, ambiguity about the time of Ack/Nack transmission may occur. For example, the Ack/Nack timing may be indicated in the PDSCH PDSCH-to-HARQ_feedback field included in the DCI. However, if the Ack/Nack timings for the same data are different from each other or are concentrated at the same time point, it may be difficult for the base station to determine whether or not the same data is accurately received because the Nack and Ack are simultaneously fed back at a specific time point from the base station point of view.

To this end, the base station may refer to feedback on a specific Ack/Nack time point to the terminal.

Example 2-1. In NTN, when the UE receives blind retransmission-based data, it instructs to follow HARQ feedback timing in DCI (PDCCH) used for transmission of the first data.

According to an embodiment, the UE may feed back the final Ack/Nack based on the Ack/Nack timing field of the received first DCI. That is, even if the terminal receives the PDSCH in the first slot and then Nack is detected, if an Ack is detected through soft value combining after receiving the PDSCH in the next slot, the terminal finally transmits the Ack, but the first The PDSCH-to-HARQ_feedback timing indicator may be referred to in the DCI detected in the slot.

Example 2-2. In NTN, when the UE receives blind retransmission-based data, it may instruct to follow HARQ feedback timing in DCI (PDCCH) used for transmission of the last data.

According to an embodiment, all processes are the same as those of the above-described embodiment 2-1, but the final Ack/Nack may be fed back based on the Ack/Nack timing field of the last DCI received by the terminal. That is, even if the UE receives the PDSCH in the first slot and Nack is detected, if an Ack is detected through soft value combining after receiving the PDSCH in the next slot, the UE finally transmits the Ack, but the last slot The PDSCH-to-HARQ_feedback timing indicator may be referred to in the DCI detected at.

Example 2-3. When performing blind retransmission, the base station may set a specific Ack/Nack feedback time to the terminal as higher layer signaling.

According to an embodiment, the Ack/Nack timing may be referred to as higher layer signaling irrespective of the aforementioned Ack/Nack timing. In this case, the UE may transmit the final Ack/Nack at a predetermined time regardless of the Ack/Nack timing in the DCI field of the PDSCH data received by the UE. That is, the higher layer setting value is followed regardless of the value of the PDSCH-to-HARQ_feedback timing indicator field in the DCI including data scheduling information.

Example 2-4. If the base station does not assume the time point of the specified Ack/Nack feedback of the terminal, the base station may set an Ack/Nack detection window section and perform detection of PUCCH/PUSCH resources within the corresponding section.

In this regard, regardless of whether the terminal receives blind retransmission data, the base station describes a processing method for the Ack/Nack fed back by the terminal.

According to an example, in extreme cases, the terminal may transmit Ack/Nack feedback for each retransmitted data between consecutive slots transmitted by the base station. This corresponds to the existing operation of the terminal. Including this case, the time point at which the Ack/Nack feedback is transmitted for the same data to the terminal to which the blind reception procedure is applied may be ambiguous.

At this time, it may be assumed that the base station can transmit 1:1 Ack/Nack feedback for all slots regardless of the blind reception procedure when the terminal transmits Ack/Nack. The base station may perform Ack/Nack detection in the form of a window for a continuous PUCCH/PUSCH interval in which the corresponding Ack/Nack can be transmitted.

If the terminal transmits Ack/Nack for all slots/subframes irrespective of retransmission data, the base station may determine whether the final transmission/reception is successful based on the last detected Ack/Nack.

Here, basically, it is assumed that the base station detects the Ack/Nack transmitted on the PUCCH/PUSCH in proportion to the number of N retransmissions caused by the propagation delay between the satellite and the terminal. Therefore, the base station performs Ack/Nack feedback detection in a window form proportional to at least the number of retransmissions N, and the corresponding value can be directly known by the base station when obtaining a timing advance (TA) value through an uplink RACH.

Accordingly, by applying a specific operation according to the HARQ turn off instruction to a terminal serviced through a non-terrestrial network, it is possible to solve the ambiguity of the operation and reduce the loss during transmission.

Hereinafter, configurations of a terminal and a base station capable of performing some or all of the embodiments described with reference to FIGS. 1 to 13 will be described with reference to the drawings.

14 is a diagram showing a configuration of a base station 1400 according to another embodiment.

Referring to FIG. 14, a base station 1400 according to another embodiment includes a control unit 1410, a transmission unit 1420, and a reception unit 1430.

The controller 1410 controls the overall operation of the base station 1400 according to the method of controlling the HARQ process in the non-terrestrial network required for carrying out the above-described present invention.

The transmitting unit 1420 and the receiving unit 1430 are used to transmit and receive signals, messages, and data necessary for carrying out the above-described present invention to and from the terminal.

The controller 1410 may check round-trip propagation delay information for a specific node in a non-terrestrial network. According to an example, the controller 1410 may estimate round-trip propagation delay information for the terminal through the RACH signal transmitted from the terminal. However, this is an example, and is not limited thereto, and other signals may be used as long as round trip propagation delay information can be estimated for a terminal to which data is to be transmitted.

The controller 1410 may determine whether the number of HARQ processes per transport block of data calculated based on the round trip propagation delay information exceeds the number of HARQ processes configured for a specific node. As described above, it can be seen that as the propagation delay time increases, the number of HARQ processes required for the same data transmission increases. However, since the number of HARQ processes configured for the terminal, which is a specific node, is determined by the number of soft buffers implemented in the terminal, it may be smaller than the number of HARQ processes increased according to propagation delay.

For example, if the terminal has 8 soft buffers, the number of HARQ processes configured for the terminal is 8. In this case, it is assumed that the number of HARQ processes required according to the propagation delay between the satellite base station and the terminal is calculated as 32. According to this example, since 24 HARQ processes cannot be accommodated in a corresponding terminal, transmission of new data cannot be performed for slots corresponding to 24 HARQ processes.

In this case, the control unit 1410 may determine that the number of HARQ processes per transmission block of data calculated based on the round trip propagation delay information exceeds the number of HARQ processes configured for a terminal that is a specific node.

The transmitter 1420 may initially transmit data to a specific node, and may continuously retransmit N times of retransmission data identical to the initially transmitted data based on the determination result. The transmitter 1420 may transmit downlink data to a terminal that is a specific node. Thereafter, the transmitter 1420 may retransmit the same retransmission data N times as the successively transmitted data. According to an example, the value of N, which is the number of retransmissions of data, may be determined by a preset function taking as factors the number of HARQ processes per transport block of data and the number of HARQ processes configured for the terminal.

According to an example, the satellite base station may perform a data retransmission operation without separate signaling or setting of data retransmission. That is, in consideration of propagation delay, data retransmission may be performed N times without separate signaling.

In this case, initially transmitted data and retransmission data may be transmitted according to the same HARQ process among each HARQ process according to the number of HARQ processes configured for the terminal. That is, the downlink control information (DCI) included in the initial transmission data and the retransmission data, respectively, includes the index of the HARQ process, and the index of the same HARQ process may be indicated for the same data.

In addition, the downlink control information may include a new data indicator (NDI) field for distinguishing initially transmitted data from retransmission data. According to an example, the field may be implemented with 1 bit. In this case, when the value of the corresponding bit is 1, initial transmitted data may be indicated, and when the value of the corresponding bit is 0, retransmitted data may be indicated.

Accordingly, it is possible to provide a method and apparatus for performing wireless communication in a non-terrestrial network capable of efficiently controlling the HARQ process in the case of a large round trip propagation delay. In addition, when the round trip propagation delay is large, the reliability and accuracy of data transmission can be further improved by performing blind retransmission in which retransmission is performed without separate signaling according to each HARQ process.

15 is a diagram showing a configuration of a user terminal 1500 according to another embodiment.

Referring to FIG. 15, a user terminal 1500 according to another embodiment includes a control unit 1510, a transmission unit 1520, and a reception unit 1530.

The receiver 1530 receives downlink control information, data, and a message from the base station through a corresponding channel.

In addition, the control unit 1510 controls the overall operation of the user terminal 1500 according to the method of controlling the HARQ process in the non-ground network required to perform the above-described present invention.

The transmitter 1520 transmits uplink control information, data, and a message to the base station through a corresponding channel.

The controller 1510 may determine whether the number of HARQ processes per transport block of data calculated based on the round trip propagation delay information exceeds the number of HARQ processes configured for a node. In order to receive retransmission data according to blind retransmission performed by the satellite base station, the terminal must be able to know whether the same data is continuously transmitted without additional signaling information provided by the satellite base station. To this end, the controller 1510 estimates a propagation delay time with the satellite base station, assumes that data can be continuously transmitted in the form of blind retransmission, and may perform data reception.

According to the above example, it is assumed that the number of HARQ processes required according to the propagation delay is 32, and the number of HARQ processes configured for the terminal is 8. In this case, the controller 1510 may determine that the number of HARQ processes per transmission block of data calculated based on the round trip propagation delay information exceeds the number of HARQ processes configured for the terminal.

The receiver 1530 may continuously receive initial transmission data and retransmission data based on the determination result. In the above-described example, since the controller 1510 needs to operate up to 8 parallel HARQ transmissions per single TB, it may be assumed that the same data is transmitted in 4 consecutive slots based on blind retransmission. That is, the control unit 1510 may assume that data retransmission is performed in consecutive slots without Ack/Nack feedback. Accordingly, the receiver 1530 may receive data for four consecutive slots.

The controller 1510 may check a value of a new data indicator (NDI) field in downlink control information included in the received initial transmission data and retransmission data. When the value of the corresponding field is 1, the controller 1510 may determine that the data is initially transmitted, and when the value of the corresponding field is 0, the controller 1510 may determine that the data is retransmitted. The control unit 1510 may perform soft combining of data received through all N slots in which retransmission has been performed regardless of success in data reception.

The transmitter 1520 may transmit HARQ feedback information to a satellite base station. According to an example, the transmission timing of HARQ feedback information for initially transmitted data and retransmission data may be indicated by preset downlink control information among downlink control information included in each of the initially transmitted data and retransmission data. .

Even if Nack is detected after receiving data in the first slot, if an Ack is detected through soft value combining after receiving retransmission data in the next consecutive slot, the transmitter 1520 can finally transmit the Ack. have. If Nack is still detected even after performing soft value combining for N times of retransmission data, the transmitter 1520 may finally transmit Nack.

In this case, the transmitter 1520 may feed back the final Ack/Nack based on the Ack/Nack timing field of the received first DCI. That is, even if Nack is detected after receiving the PDSCH in the first slot, if an Ack is detected through soft value combining after receiving the PDSCH in the next slot, the transmitter 1520 finally transmits the Ack, In the DCI detected in the first slot, HARQ feedback information may be transmitted according to the timing indicated by the PDSCH-to-HARQ_feedback timing indicator.

Alternatively, the transmitter 1520 may feed back the final Ack/Nack based on the Ack/Nack timing field of the received last DCI. That is, even if Nack is detected after receiving the PDSCH in the first slot, if an Ack is detected through soft value combining after receiving the PDSCH in the next slot, the transmitter 1520 finally transmits the Ack, In the DCI detected in the last slot, ARQ feedback information may be transmitted according to the timing indicated by the PDSCH-to-HARQ_feedback timing indicator.

According to another example, Ack/Nack timing may be referred to as higher layer signaling irrespective of the aforementioned Ack/Nack timing. In this case, the transmitter 1520 may transmit the final Ack/Nack at a predetermined time regardless of the Ack/Nack timing in the DCI field of the received PDSCH data.

Alternatively, according to another example, when the transmission timing of HARQ feedback information for initially transmitted data and retransmission data is not specified, a detection window for detecting HARQ feedback information for each of the initially transmitted data and the retransmission data is provided. Can be set. For example, the transmitter 1520 may be configured to transmit an Ack/Nack feedback for each retransmitted data between consecutive slots transmitted by a satellite base station. It can be assumed that the satellite base station can transmit 1:1 Ack/Nack feedback for all slots regardless of the blind reception procedure when the terminal transmits Ack/Nack. The base station may perform Ack/Nack detection in the form of a window for a section in which the corresponding Ack/Nack can be transmitted.

If the transmitter 1520 transmits Ack/Nack for all slots/subframes irrespective of retransmission data, the base station may determine whether the final transmission/reception is successful based on the last detected Ack/Nack.

Accordingly, it is possible to provide a method and apparatus for performing wireless communication in a non-terrestrial network capable of efficiently controlling the HARQ process in the case of a large round trip propagation delay. In addition, when the round trip propagation delay is large, the reliability and accuracy of data transmission can be further improved by performing blind retransmission in which retransmission is performed without separate signaling according to each HARQ process.

The above-described embodiments may be supported by standard documents disclosed in at least one of IEEE 802, 3GPP and 3GPP2 wireless access systems. That is, steps, configurations, and parts not described in order to clearly reveal the present technical idea among the embodiments may be supported by the above-described standard documents. In addition, all terms disclosed in this specification can be described by the standard documents disclosed above.

The above-described embodiments can be implemented through various means. For example, the present embodiments may be implemented by hardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to the embodiments includes one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), and FPGAs. (Field Programmable Gate Arrays), a processor, a controller, a microcontroller, or a microprocessor.

In the case of implementation by firmware or software, the method according to the embodiments may be implemented in the form of an apparatus, procedure, or function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor through various known means.

In addition, terms such as "system", "processor", "controller", "component", "module", "interface", "model", or "unit" described above generally refer to computer-related entity hardware, hardware and software. It may mean a combination of, software, or running software. For example, the above-described components may be, but are not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, an execution thread, a program, and/or a computer. For example, both the controller or processor and the application running on the controller or processor can be components. One or more components may be within a process and/or thread of execution, and the components may be located on a single device (eg, a system, a computing device, etc.) or distributed across two or more devices.

The above description is merely illustrative of the technical idea of the present disclosure, and those of ordinary skill in the technical field to which the present disclosure pertains will be able to make various modifications and variations without departing from the essential characteristics of the technical idea. In addition, the present embodiments are not intended to limit the technical idea of the present disclosure, but to describe the present disclosure, and thus the scope of the present technical idea is not limited by these embodiments. The scope of protection of the present disclosure should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present disclosure.

Claims (14)

Checking round-trip propagation delay information for a specific node;
Determining whether the number of HARQ processes per transport block of data calculated based on the round trip propagation delay information exceeds the number of HARQ processes configured for the node;
Initially transmitting the data; And
And continuously retransmitting the retransmission data identical to the data N times based on the determination result. The method of claim 1,
The N value is,
A method determined by a preset function taking as factors the number of HARQ processes per transmission block of the data and the number of HARQ processes configured for the node. The method of claim 1,
The initial transmitted data and the retransmitted data,
Method transmitted according to one of the same HARQ process among each HARQ process according to the number of HARQ processes configured for the node. The method of claim 1,
The initial transmitted data and the retransmitted data,
Each method including downlink control information (DCI). The method of claim 4,
The downlink control information,
A method including a new data indicator (NDI) field for discriminating between the initially transmitted data and the retransmitted data. The method of claim 1,
Transmission timing of the initial transmitted data and HARQ feedback information for the retransmission data,
A method in which the initially transmitted data and the retransmitted data are indicated by preset downlink control information from among downlink control information respectively included in the retransmission data, or are set to higher layer signaling. The method of claim 1,
When the transmission timing of the initially transmitted data and the HARQ feedback information for the retransmission data is not specified, a detection window for detecting the HARQ feedback information for each of the initially transmitted data and the retransmission data is set. Check round-trip propagation delay information for a specific node, and the number of HARQ processes per transport block of data calculated based on the round-trip propagation delay information exceeds the number of HARQ processes configured for the node. A control unit that determines whether or not; And
And a transmitter configured to initially transmit the data and continuously retransmit the same retransmission data as the data N times based on a result of the determination. The method of claim 8,
The N value is,
An apparatus that is determined by a preset function taking as factors the number of HARQ processes per transmission block of the data and the number of HARQ processes configured for the node. The method of claim 8,
The initial transmitted data and the retransmitted data,
An apparatus that is transmitted according to the same HARQ process among each HARQ process according to the number of HARQ processes configured for the node. The method of claim 8,
The initial transmitted data and the retransmitted data,
Devices each including downlink control information (DCI). The method of claim 11,
The downlink control information,
An apparatus including a new data indicator (NDI) field for distinguishing between the initially transmitted data and the retransmitted data. The method of claim 8,
Transmission timing of the initial transmitted data and HARQ feedback information for the retransmission data,
A device that is indicated by preset downlink control information from among downlink control information included in the initially transmitted data and the retransmitted data, or is set to higher layer signaling. The method of claim 8,
When the transmission timing of the initially transmitted data and the HARQ feedback information for the retransmission data is not specified, a detection window for detecting the HARQ feedback information for each of the initially transmitted data and the retransmission data is set.

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