WO2021062880A1 - Harq for long propagation delay - Google Patents

Harq for long propagation delay Download PDF

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Publication number
WO2021062880A1
WO2021062880A1 PCT/CN2019/109831 CN2019109831W WO2021062880A1 WO 2021062880 A1 WO2021062880 A1 WO 2021062880A1 CN 2019109831 W CN2019109831 W CN 2019109831W WO 2021062880 A1 WO2021062880 A1 WO 2021062880A1
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WO
WIPO (PCT)
Prior art keywords
slot
harq
user equipment
erf
decoding
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PCT/CN2019/109831
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English (en)
French (fr)
Inventor
Tzu-Chung Frank Hsieh
Pingping Wen
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Nokia Shanghai Bell Co., Ltd.
Nokia Solutions And Networks Oy
Nokia Technologies Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Nokia Shanghai Bell Co., Ltd., Nokia Solutions And Networks Oy, Nokia Technologies Oy filed Critical Nokia Shanghai Bell Co., Ltd.
Priority to CN201980101049.7A priority Critical patent/CN114503642B/zh
Priority to PCT/CN2019/109831 priority patent/WO2021062880A1/en
Publication of WO2021062880A1 publication Critical patent/WO2021062880A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
    • H04L5/0057—Physical resource allocation for CQI
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851—Systems using a satellite or space-based relay
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0026—Transmission of channel quality indication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
    • H04L1/1819—Hybrid protocols; Hybrid automatic repeat request [HARQ] with retransmission of additional or different redundancy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1822—Automatic repetition systems, e.g. Van Duuren systems involving configuration of automatic repeat request [ARQ] with parallel processes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1825—Adaptation of specific ARQ protocol parameters according to transmission conditions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • H04L5/0051—Allocation of pilot signals, i.e. of signals known to the receiver of dedicated pilots, i.e. pilots destined for a single user or terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0091—Signaling for the administration of the divided path
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/08—Testing, supervising or monitoring using real traffic
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports

Definitions

  • Certain embodiments may relate to communication systems. For example, some embodiments may relate to random access procedures.
  • 3rd Generation Partnership Project (3GPP) release (Rel) -16 includes a study item on how fifth generation (5G) new radio (NR) standards may support non-terrestrial network (NTN) deployments using satellites and high altitude platform stations (HAPS) to provide connectivity across a wide service area.
  • 5G fifth generation
  • NR new radio
  • NTN non-terrestrial network
  • HAPS high altitude platform stations
  • the round trip signal propagation time may be considerably longer compared to ordinary cellular networks intended for NR interfaces.
  • these longer propagation delays may pose a challenge to hybrid automatic repeat request (HARQ) protocols in the physical layer for retransmission of erroneous packets.
  • HARQ hybrid automatic repeat request
  • One objective of the study item for the physical layer of NR is to enhance HARQ for NTN operations, which continues to be studied in 3GPP RAN1 and RAN2 meetings.
  • a method may include transmitting, by a user equipment, at least one indication of a fixed change of channel quality indicator (CQI) .
  • the method may further include measuring, by the user equipment, at least one CQI change rate.
  • the method may further include transmitting, by the user equipment, at least one downlink channel gain correlation time indication.
  • the method may further include transmitting, by the user equipment, at least one sounding reference signal.
  • CQI channel quality indicator
  • an apparatus may include means for transmitting at least one indication of a fixed change of channel quality indicator (CQI) .
  • the apparatus may further include means for measuring at least one CQI change rate.
  • the apparatus may further include means for transmitting at least one downlink channel gain correlation time indication.
  • the apparatus may further include means for transmitting at least one sounding reference signal.
  • CQI channel quality indicator
  • an apparatus may include at least one processor and at least one memory including computer program code.
  • the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus to at least transmit at least one indication of a fixed change of channel quality indicator (CQI) .
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least measure.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least transmit at least one downlink channel gain correlation time indication.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least transmit at least one sounding reference signal.
  • a non-transitory computer readable medium can be encoded with instructions that may, when executed in hardware, perform a method.
  • the method may include transmitting at least one indication of a fixed change of channel quality indicator (CQI) .
  • the method may further include measuring at least one CQI change rate.
  • the method may further include transmitting at least one downlink channel gain correlation time indication.
  • the method may further include transmitting at least one sounding reference signal.
  • CQI channel quality indicator
  • a computer program product may perform a method.
  • the method may include transmitting at least one indication of a fixed change of channel quality indicator (CQI) .
  • the method may further include measuring at least one CQI change rate.
  • the method may further include transmitting at least one downlink channel gain correlation time indication.
  • the method may further include transmitting at least one sounding reference signal.
  • CQI channel quality indicator
  • an apparatus may include circuitry configured to transmit at least one indication of a fixed change of channel quality indicator (CQI) .
  • the circuitry may further be configured to measure at least one CQI change rate.
  • the circuitry may further be configured to transmit at least one downlink channel gain correlation time indication.
  • the circuitry may further be configured to transmit at least one sounding reference signal.
  • CQI channel quality indicator
  • the method may further include identifying, by the network entity, at least one HARQ process transmitting within interval between slot t′and slot t′+T C -1.
  • the method may further include determining, by the network entity, at least one HARQ process P i whose number of transmissions is less than or equal to m.
  • the method may further include scheduling, by the network entity, P i for retransmission.
  • the apparatus may further include means for identifying at least one HARQ process transmitting within interval between slot t′and slot t′+T C -1.
  • the apparatus may further include means for determining at least one HARQ process P i whose number of transmissions is less than or equal to m.
  • the apparatus may further include means for scheduling P i for retransmission.
  • an apparatus may include at least one processor and at least one memory including computer program code.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least identify at least one HARQ process transmitting within interval between slot t′and slot t′+T C -1.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least determine at least one HARQ process P i whose number of transmissions is less than or equal to m.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least schedule P i for retransmission.
  • a non-transitory computer readable medium can be encoded with instructions that may, when executed in hardware, perform a method.
  • the method may further include identifying at least one HARQ process transmitting within interval between slot t′and slot t′+T C -1.
  • the method may further include determining at least one HARQ process P i whose number of transmissions is less than or equal to m.
  • the method may further include scheduling P i for retransmission.
  • a computer program product may perform a method.
  • the method may further include identifying at least one HARQ process transmitting within interval between slot t′and slot t′+T C -1.
  • the method may further include determining at least one HARQ process P i whose number of transmissions is less than or equal to m.
  • the method may further include scheduling P i for retransmission.
  • the circuitry may further be configured to identify at least one HARQ process transmitting within interval between slot t′and slot t′+T C -1.
  • the circuitry may further be configured to determine at least one HARQ process P i whose number of transmissions is less than or equal to m.
  • the circuitry may further be configured to schedule P i for retransmission.
  • a method may include decoding, by a user equipment, at least one DCI of slot i.
  • the method may further include determining, by the user equipment, whether at least one allocated ERF starts from slot i.
  • the method may further include, upon determining that no allocated ERF starts from slot i, determining, by the user equipment, whether at least one allocated asynchronous HARQ is associated with slot i.
  • the method may further include, upon determining that at least one allocated ERF starts from slot i, processing, by the user equipment, soft combining and decoding for N slots of the ERF.
  • the method may further include, upon determining that at least one allocated asynchronous HARQ is associated with slot i, processing, by the user equipment, soft combining and decoding for at least one current slot.
  • an apparatus may include means for decoding at least one DCI of slot i.
  • the apparatus may further include means for determining whether at least one allocated ERF starts from slot i.
  • the apparatus may further include means for, upon determining that no allocated ERF starts from slot i, determining whether at least one allocated asynchronous HARQ is associated with slot i.
  • the apparatus may further include means for, upon determining that at least one allocated ERF starts from slot i, processing soft combining and decoding for N slots of the ERF.
  • the apparatus may further include means for, upon determining that at least one allocated asynchronous HARQ is associated with slot i, processing soft combining and decoding for at least one current slot.
  • an apparatus may include at least one processor and at least one memory including computer program code.
  • the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus to at least decode at least one DCI of slot i.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least determine whether at least one allocated ERF starts from slot i.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least, upon determining that no allocated ERF starts from slot i, determine whether at least one allocated asynchronous HARQ is associated with slot i.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least, upon determining that at least one allocated ERF starts from slot i, process soft combining and decoding for N slots of the ERF.
  • the at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least, upon determining that at least one allocated asynchronous HARQ is associated with slot i, process soft combining and decoding for at least one current slot.
  • a non-transitory computer readable medium can be encoded with instructions that may, when executed in hardware, perform a method.
  • the method may include decoding at least one DCI of slot i.
  • the method may further include determining whether at least one allocated ERF starts from slot i.
  • the method may further include, upon determining that no allocated ERF starts from slot i, determining whether at least one allocated asynchronous HARQ is associated with slot i.
  • the method may further include, upon determining that at least one allocated ERF starts from slot i, processing soft combining and decoding for N slots of the ERF.
  • the method may further include, upon determining that at least one allocated asynchronous HARQ is associated with slot i, processing soft combining and decoding for at least one current slot.
  • a computer program product may perform a method.
  • the method may include decoding at least one DCI of slot i.
  • the method may further include determining whether at least one allocated ERF starts from slot i.
  • the method may further include, upon determining that no allocated ERF starts from slot i, determining whether at least one allocated asynchronous HARQ is associated with slot i.
  • the method may further include, upon determining that at least one allocated ERF starts from slot i, processing soft combining and decoding for N slots of the ERF.
  • the method may further include, upon determining that at least one allocated asynchronous HARQ is associated with slot i, processing soft combining and decoding for at least one current slot.
  • an apparatus may include circuitry configured to decode at least one DCI of slot i.
  • the circuitry may further be configured to determine whether at least one allocated ERF starts from slot i.
  • the circuitry may further be configured to, upon determining that no allocated ERF starts from slot i, determine whether at least one allocated asynchronous HARQ is associated with slot i.
  • the circuitry may further be configured to, upon determining that at least one allocated ERF starts from slot i, process soft combining and decoding for N slots of the ERF.
  • the circuitry may further be configured to, upon determining that at least one allocated asynchronous HARQ is associated with slot i, process soft combining and decoding for at least one current slot.
  • FIG. 1 illustrates a table showing round trip signal propagation delay for typical GEO and LEO satellite deployments.
  • FIG. 2 illustrates a chart of channel gain variation in a fast fading channel.
  • FIG. 3 illustrates a channel gain variation in a slow fading channel.
  • FIG. 4 illustrates an example of a method performed by a user equipment according to certain embodiments.
  • FIG. 5 (a) illustrates an example of determination of repetition factor k for early retransmission.
  • FIG. 5 (b) illustrates an example of an early retransmission frame.
  • FIG. 6 (a) illustrates an example of slots for asynchronous HARQ inserted between two early retransmission frames.
  • FIG. 6 (b) illustrates an example of multiple transmissions of the same packet between two early retransmission frames for determination of ERF repetition factor.
  • FIG. 7 illustrates an example of cross-process retransmission when a NACK bit is received.
  • FIG. 8 illustrates an example of a method performed by a network entity according to certain embodiments.
  • FIG. 9 illustrates an example of a method performed by a user equipment according to certain embodiments.
  • FIG. 10 illustrates an example of a system according to certain embodiments.
  • Hybrid automatic repeat request is a physical layer retransmission mechanism to reliably transport encoded packets.
  • Each HARQ process employs a stop-and-wait protocol, and receives feedback including acknowledgement (ACK) and non-acknowledgement (NACK) bits from the receiver.
  • ACK acknowledgement
  • NACK non-acknowledgement
  • the transmitter waits for feedback, and transmits a subsequent new packet when an ACK bit is received indicating the successfully decoding of the previously transmitted packet.
  • HARQ adaptive modulation and coding rate
  • the long distance between a satellite and a UE near the near the Earth’s surface may result in a much longer round trip time between the transmitter sending a packet and receiving the feedback for a HARQ process.
  • a packet error does occur, for example, when the receiver fails to decode an encoded packet, another RTT is required in reattempting to decode the encoded packet.
  • the CQI report and SRS from the UE may take longer to be received by the network entity, resulting in the AMC link adaptation being less responsive to channel condition changes and leading to a higher likelihood of packet errors occurring.
  • data services may have a much longer latency period for NTN.
  • TTI is the interval for transmitting one packet.
  • TTI is the interval for transmitting one packet.
  • TTI is the interval for transmitting one packet.
  • the first transmission may be made more reliable to reduce the probability of HARQ retransmissions. For example, this may be accomplished by lowering target BLER in AMC, such as from 10%to 1%, and/or selecting a lower MCS.
  • target BLER in AMC such as from 10%to 1%
  • MCS Mobility Management Function
  • Another technique for reducing latency may be through the use of blind retransmission, where the transmitter always sends redundant versions of the packet before a NACK bit is received.
  • This may be implemented by NR’s asynchronous HARQ by the network entity, with DCI carrying HARQ-related information, such as NDI, process ID, and RV.
  • RRC protocol may allow slot segregation to be configured semi-statically, wherein consecutive slots may be used to transmit one transport block (TB) with different RVs.
  • TB transport block
  • these two approaches may reduce latency, but at the expense of wasted network resources.
  • conventional HARQ may be spectrally efficient, there are significant drawbacks from associated large latencies.
  • Certain embodiments described herein may improve data service latency in a long distance communication link with more efficient utilization of resources. For example, various embodiments discussed below may reduce data service latencies, provide for the efficient use of resources during data delivery, reduce signalling overhead required for HARQ, and/or may reduce the required soft buffer size for the receiver. Certain embodiments are, therefore, directed to improvements in computer-related technology, specifically, by conserving network resources and reducing power consumption of network entities and/or user equipment located within the network.
  • a signaling mechanism may be employed to determine a channel correlation time that may be used to configure HARQ transmissions of data packets, and a frame structure with a build-in early retransmission pattern may be adapted to the channel variation.
  • This may further include low overhead HARQ signalling for multiple slots of the early retransmission frame, as well as cross-process asynchronous HARQ retransmissions which may be based on a single NACK and/or the channel correlation time.
  • UE reports its CQI measurement using a 4-bit codeword.
  • DL channel gain correlation time may be reported by the UE, while UL channel gain correlation time measurements may be performed by the network entity.
  • the rate of change of the channel gain may be determined. For example, when the change rate is small, as illustrated in FIG. 3, a relatively long period of time may be required for the channel to experience a fixed small variation of gain. In contrast, when the change rate is relatively large, as shown in FIG. 2, the same amount of channel variation may occur in a much shorter time span.
  • the small amount of channel gain variation may be represented by a fixed small change of short-term (or instantaneous) CQI, denoted as ⁇ CQI.
  • FIG. 4 illustrates an example of a signalling diagram according to some embodiments.
  • User equipment (UE) 410 may be similar to UE 1010, and network entity (NE) 420 may be similar to NE 1020, both illustrated in FIG. 10. Although only a single UE and NE are illustrated, a communications network may contain one or more of each of these entities.
  • UE User equipment
  • NE network entity
  • NE 420 may transmit to UE 410 at least one ⁇ CQI, wherein ⁇ CQI denotes the fixed change of short-term (or instantaneous) CQI.
  • ⁇ CQI denotes the fixed change of short-term (or instantaneous) CQI.
  • the value of ⁇ CQI may be predetermined so that, within this range of channel variation, decoding outcome of packets of the same MCS (i.e., transport format) may be correlated above a predetermined threshold.
  • the time period for the channel to have a variation ⁇ CQI may have a correlation time, denoted as T C , for packet detection to have the same outcome.
  • NE 420 may configure UE 410 according to at least one criteria to report at least one DL correlation time T c , such as one or more of at least one threshold for CQI variation ⁇ CQI and at least one SRS configuration, such as the time-frequency allocation of SRS, for at least one UL correlation time T c according to RRC signalling.
  • UE 410 may measure at least one CQI change rate. If the correlation time corresponding to the measured at least one CQI change rate is below at least one predetermined threshold, such as one or two slots, slot aggregation or blind retransmission may be applied to reduce service latency. However, if the correlation time corresponding to the measured at least one CQI change rate is at or above at least one predetermined threshold, latency and resource efficiency may be improved from these measurements.
  • at least one predetermined threshold such as one or two slots
  • slot aggregation or blind retransmission may be applied to reduce service latency.
  • latency and resource efficiency may be improved from these measurements.
  • UE 410 may transmit to NE 420 at least one downlink (DL) channel gain correlation time indication (T c ) , which may associated with at least one CSI/CQI measurement.
  • the DL T c measurement may be made on one or more of at least one SSB and at least one CSI-RS signal.
  • the at least one DL T c may be sent back in the unit of slot time corresponding to the ⁇ CQI on PUCCH and/or PUSCH.
  • correlation time T c may change over time.
  • NE 420 may request UE 410 to report downlink T c periodically, and/or when the difference from the previously reported value is greater than a predetermined number of slots. Additionally or alternatively, NE 420 may update UL T c from the channel estimation of at least one uplink signal.
  • UE 410 may transmit at least one SRS to NE 420 according to the configuration in step 401 as the reference signal for UL T c measurement.
  • NE 420 may perform at least one uplink (UL) channel gain correlation time measurement (T c ) , which may be performed on one or more of at least one SRS and at least one other UL signal associated with UE 410.
  • UL uplink
  • T c channel gain correlation time measurement
  • the NE may transmit at least one packet in repetition in consecutive slots before HARQ feedback is received. For example, this may be performed in an “Early Retransmission Frame” (ERF) over a period of T c slots where channel variation is expected to be small.
  • ERF Error Retransmission Frame
  • all slots may use fixed MCS, repetition factor k, and the same set of redundant versions. Consecutive slots may then be allocated for the transmission of the same packet allowing the NE to know if the packet has been decoded correctly after k times of transmission.
  • Each packet may be assigned a separate HARQ process for soft combining. If a packet may be successfully decoded before the end of the consecutive k slots, the memory used by the process in the soft buffer may be flushed, thus reducing the soft buffer size requirement when the RTT is long.
  • the number of HARQ processes in an ERF may be estimated from the repetition factor k so that the total number of slots is close to the measured correlation time T c . Since the HARQ related information, such as MCS and RV, is the same, it may be signaled in the DCI of the first slot of the frame. After the DCI is decoded, the HARQ process ID and RV of each slot may follow a predictable pattern.
  • the receiver may operate the same way as in a synchronous HARQ within the frame, but HARQ-related fields in the DCI of an individual slot may no longer be needed, reducing L1 control overhead.
  • the required DCI fields in the first slot may contain at least one ERF ID, a number of HARQ processes in the frame, repetition factor k, redundancy versions for k transmissions, MCS level, and/or allocated PRBs, as shown in FIG. 5 (b) .
  • the redundant versions for different retransmissions may alternatively be pre-configured in RRC to reduce the signaling bits.
  • the operation of UL ERF may be similar to DL, wherein DCI may indicate the structure of UL synchronous HARQ during the ERF with the same timing offset for the first slot of ERF as the rest of the UL transmission.
  • one or more slots may be scheduled for the retransmissions of previously transmitted packet which may not have been received correctly, as illustrated in FIG. 6 (a) .
  • retransmission in these slots may be asynchronous (without a specific order of HARQ processes) using the DCI of each slot to indicate the HARQ process of the transmission.
  • another set of new packets may be scheduled in the next ERF.
  • multiple transmissions of the same packet may also be inserted, as illustrated in FIG. 6 (b) , for an estimation of ERF repetition factors from the corresponding HARQ feedback.
  • a network entity may schedule retransmission in an asynchronous HARQ slot after an ERF, as shown in FIG. 6 (a) .
  • the network entity may determine if other processes need retransmission with its knowledge of the correlation time T c , and proactively schedule retransmission for those processes even before their HARQ feedback has been received.
  • the received NACK for slot t’ may be used to infer the outcome of packets sent in the interval between slot t′and slot t′+T C -1, as well as the processes in these slots which may need retransmission.
  • slot t’ is the m th transmission of a packet
  • the processes in the interval [t′, t′+T C -1] whose number of transmissions is less or equal to m may be expected to receive a NACK; thus, retransmission for those processes may be scheduled.
  • the number of transmissions of a packet may be directly compared in the retransmission decision without considering MCS since the MCS is not expected to charge much in an interval of T c .
  • the network entity may schedule the asynchronous HARQ slots in a similar manner directly based on the transport block decoding failures instead of NACK feedback.
  • FIG. 8 illustrates an example of a method performed by a network entity, such as network entity 1020 in FIG. 10.
  • the NE may identify one or more processes (P 1 , P 2 , ..., P n ) transmitting in the interval between slot t′and slot t′+T C -1.
  • the NE may determine at least one process P i whose number of transmissions is less than or equal to m.
  • the NE may schedule the process P i for retransmission.
  • the UE operation of this HARQ enhancement is shown in FIG. 9.
  • the action of the UE may be driven by DCI, which may perform soft combining and packet decoding either in synchronous mode of HARQ during an ERF or in an asynchronous mode based on per-slot HARQ information in the DCI.
  • an ACK/NACK bit is transmitted at every decoding attempt as the conventional HARQ.
  • the techniques described herein may be applied when the channel gain varies slowly, which may be used with NTN due to the required LOS condition and/or the use of directional antenna.
  • the ERF with its duration and repetition factor determined by the channel condition may reduce packet delivery delay with a more efficient user of resource compared to traditional blind retransmissions.
  • the retransmission patterns in ERF may minimize the soft buffer size requirement for the receiver.
  • some embodiments may further ensure robustness of the link.
  • FIG. 9 illustrates an example of a method performed by a user equipment, such as UE 1010 in FIG. 10.
  • the NE may control at least one HARQ process configured to schedule both uplink and downlink transmissions.
  • the NE may schedule retransmissions of a packet before a HARQ feedback is received in case of DL, and/or before a scheduled packet is decoded in case of UL.
  • the UE may decode at least one DCI of slot i.
  • the UE may determine whether at least one allocated ERF starts from slot i.
  • the UE may determine whether at least one allocated asynchronous HARQ is associated with slot i.
  • the UE may process soft combining and decoding for N slots of the ERF.
  • the UE may process soft combining and decoding for at least one current slot.
  • FIG. 10 illustrates an example of a system according to certain embodiments.
  • a system may include multiple devices, such as, for example, user equipment 1010 and/or network entity 1020.
  • User equipment 1010 may include one or more of a mobile device, such as a mobile phone, smart phone, personal digital assistant (PDA) , tablet, or portable media player, digital camera, pocket video camera, video game console, navigation unit, such as a global positioning system (GPS) device, desktop or laptop computer, single-location device, such as a sensor or smart meter, or any combination thereof.
  • a mobile device such as a mobile phone, smart phone, personal digital assistant (PDA) , tablet, or portable media player, digital camera, pocket video camera, video game console, navigation unit, such as a global positioning system (GPS) device, desktop or laptop computer, single-location device, such as a sensor or smart meter, or any combination thereof.
  • GPS global positioning system
  • Network entity 1020 may be one or more of a base station, such as a mmWave antenna, an evolved node B (eNB) or 5G or New Radio node B (gNB) , a serving gateway, a server, and/or any other access node or combination thereof.
  • a base station such as a mmWave antenna, an evolved node B (eNB) or 5G or New Radio node B (gNB) , a serving gateway, a server, and/or any other access node or combination thereof.
  • eNB evolved node B
  • gNB New Radio node B
  • processors 1011 and 1021 may be embodied by any computational or data processing device, such as a central processing unit (CPU) , application specific integrated circuit (ASIC) , or comparable device.
  • the processors may be implemented as a single controller, or a plurality of controllers or processors.
  • At least one memory may be provided in one or more of devices indicated at 1012 and 1022.
  • the memory may be fixed or removable.
  • the memory may include computer program instructions or computer code contained therein.
  • Memories 1012 and 1022 may independently be any suitable storage device, such as a non-transitory computer-readable medium.
  • a hard disk drive (HDD) random access memory (RAM) , flash memory, or other suitable memory may be used.
  • the memories may be combined on a single integrated circuit as the processor, or may be separate from the one or more processors.
  • the computer program instructions stored in the memory and which may be processed by the processors may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language.
  • Memory may be removable or non-removable.
  • Processors 1011 and 1021 and memories 1012 and 1022 or a subset thereof may be configured to provide means corresponding to the various blocks of FIGS. 1-9.
  • the devices may also include positioning hardware, such as GPS or micro electrical mechanical system (MEMS) hardware, which may be used to determine a location of the device.
  • MEMS micro electrical mechanical system
  • Other sensors are also permitted and may be included to determine location, elevation, orientation, and so forth, such as barometers, compasses, and the like.
  • transceivers 1013 and 1023 may be provided, and one or more devices may also include at least one antenna, respectively illustrated as 1014 and 1024.
  • the device may have many antennas, such as an array of antennas configured for multiple input multiple output (MIMO) communications, or multiple antennas for multiple radio access technologies. Other configurations of these devices, for example, may be provided.
  • Transceivers 1013 and 1023 may be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception.
  • the memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as user equipment to perform any of the processes described below (see, for example, FIGS. 1-9) . Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, certain embodiments may be performed entirely in hardware.
  • an apparatus may include circuitry configured to perform any of the processes or functions illustrated in FIGS. 1-9.
  • circuitry may be hardware-only circuit implementations, such as analog and/or digital circuitry.
  • circuitry may be a combination of hardware circuits and software, such as a combination of analog and/or digital hardware circuit (s) with software or firmware, and/or any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and at least one memory that work together to cause an apparatus to perform various processes or functions.
  • circuitry may be hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that include software, such as firmware for operation.
  • Software in circuitry may not be present when it is not needed for the operation of the hardware.
  • E-UTRAN Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network

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