CN114503642B

CN114503642B - HARQ for long propagation delay

Info

Publication number: CN114503642B
Application number: CN201980101049.7A
Authority: CN
Inventors: T-C·F·谢; 温萍萍
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2019-10-04
Filing date: 2019-10-04
Publication date: 2023-05-30
Anticipated expiration: 2039-10-04
Also published as: WO2021062880A1; CN114503642A

Abstract

According to some embodiments, a method comprises transmitting, by a user equipment, at least one indication of a fixed change in channel quality indicator, CQI. The method also includes measuring, by the user equipment, at least one CQI rate of change. The method also includes transmitting, by the user equipment, at least one downlink channel gain related time indication. The method also includes transmitting, by the user equipment, at least one sounding reference signal.

Description

HARQ for long propagation delay

Technical Field

Some embodiments may relate to a communication system. For example, some embodiments may relate to a random access procedure.

Background

Third generation partnership project (3 GPP) release (Rel) -16 includes a research project (HAPS) on how the fifth generation (5G) New Radio (NR) standard supports non-terrestrial network (NTN) deployment using satellites and High Altitude Platforms (HAPS) to provide connectivity over a wide service area. In many NTN deployment scenarios, the round-trip signal propagation time may be much longer compared to a common cellular network intended for the NR interface. Thus, these longer propagation delays may pose challenges to the hybrid automatic repeat request (HARQ) protocol in the physical layer for retransmission of erroneous packets. One goal of the physical layer study item for NR is to enhance HARQ for NTN operation, which will continue to be studied in the 3gpp RAN1 and RAN2 conference.

Disclosure of Invention

According to some embodiments, a method may include transmitting, by a user equipment, at least one indication of a fixed change in a Channel Quality Indicator (CQI). The method may further include measuring, by the user equipment, at least one CQI rate of change. The method may further include transmitting, by the user equipment, at least one downlink channel gain related time indication. The method may also include transmitting, by the user equipment, at least one sounding reference signal.

According to some embodiments, an apparatus may include means for transmitting at least one indication of a fixed change in a Channel Quality Indicator (CQI). The apparatus may also include means for measuring at least one CQI rate of change. The apparatus also includes means for transmitting at least one downlink channel gain related time indication. The apparatus may also include means for transmitting at least one sounding reference signal.

According to some embodiments, 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 may be configured to, with the at least one processor, cause the apparatus at least to transmit at least one indication of a fixed change in a Channel Quality Indicator (CQI). The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to measure. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to transmit at least one downlink channel gain-related time indication. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to transmit at least one sounding reference signal.

According to some embodiments, a non-transitory computer-readable medium may be encoded with instructions that, when executed in hardware, may perform a method. The method may include transmitting at least one indication of a fixed change in Channel Quality Indicator (CQI). The method may further include measuring at least one CQI rate of change. The method may also include transmitting at least one downlink channel gain related time indication. The method may also include transmitting at least one sounding reference signal.

According to some embodiments, a computer program product may perform a method. The method may include transmitting at least one indication of a fixed change in a Channel Quality Indicator (CQI). The method may further include measuring at least one CQI rate of change. The method may also include transmitting at least one downlink channel gain related time indication. The method may also include transmitting at least one sounding reference signal.

According to some embodiments, an apparatus may include circuitry configured to transmit at least one indication of a fixed change in a Channel Quality Indicator (CQI). The circuitry may be further configured to measure at least one CQI rate of change. The circuitry may be further configured to transmit at least one downlink channel gain related time indication. The circuitry may be further configured to transmit at least one sounding reference signal.

According to some embodiments, a method may include receiving, by a network entity, at a time slot t, at least one acknowledgement of packet reception failure after m transmissions of a HARQ process for time slot t' =t-RTT. The method may further include identifying, by the network entity, between time slot T 'and time slot T' +t _C -at least one HARQ process transmitted in the interval between-1. The method may further comprise determining, by the network entity, at least one HARQ process P for which the number of transmissions is less than or equal to m _i . The method may also include scheduling P by the network entity _i For retransmission.

According to some embodiments, an apparatus may include means for receiving at least one acknowledgement of packet reception failure after m transmissions of a HARQ process for time slot t' =t-RTT at time slot t. The apparatus may further include means for identifying the time slot T 'and the time slot T' +T _C -means of at least one HARQ process transmitted in the interval between-1. The apparatus may further include means for determining at least one HARQ process P for which the number of transmissions is less than or equal to m _i Is a component of (a). The apparatus may also include means for scheduling P _i For retransmission.

According to some embodiments, 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 may be configured to, with the at least one processor, cause the apparatus at least toAt least one acknowledgement of packet reception failure after m transmissions of the HARQ process for time slot t' =t-RTT is received at time slot t. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to identify at time slot T 'and time slot T' +t _C -at least one HARQ process transmitted in the interval between-1. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to determine at least one HARQ process P having a number of transmissions less than or equal to m _i . The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to schedule P _i For retransmission.

According to some embodiments, a non-transitory computer-readable medium may be encoded with instructions that, when executed in hardware, may perform a method. The method may comprise receiving at least one acknowledgement of packet reception failure at time slot t after m transmissions of the HARQ process for time slot t' =t-RTT. The method may further include identifying the time slot T 'and the time slot T' +T _C -at least one HARQ process transmitted in the interval between-1. The method may further include determining at least one HARQ process P for which the number of transmissions is less than or equal to m _i . The method may also include scheduling P _i For retransmission.

According to some embodiments, a computer program product may perform a method. The method may comprise receiving at least one acknowledgement of packet reception failure at time slot t after m transmissions of the HARQ process for time slot t' =t-RTT. The method may further include identifying the time slot T 'and the time slot T' +T _C -at least one HARQ process transmitted in the interval between-1. The method may further include determining at least one HARQ process P for which the number of transmissions is less than or equal to m _i . The method may also include scheduling P _i For retransmission.

According to some embodiments, an apparatus may include circuitry configured to receive, at a time slot t, a packet reception failure after m transmissions of a HARQ process for time slot t' =t-RTTAt least one acknowledgement. The circuitry may also be configured to identify the time slot T 'and the time slot T' +t _C -at least one HARQ process transmitted in the interval between-1. The circuitry may be further configured to determine at least one HARQ process P for which the number of transmissions is less than or equal to m _i . The circuitry may also be configured to schedule P _i For retransmission.

According to some embodiments, a method may include decoding, by a user equipment, at least one DCI of a slot i. The method may further comprise determining, by the user equipment, whether at least one allocated ERF starts from time slot i. The method may further comprise determining, by the user equipment, whether at least one allocated asynchronous HARQ is associated with slot i after determining that no allocated ERF starts from slot i. The method may further comprise processing, by the user equipment, soft combining and decoding of the N time slots for the ERF after determining that the at least one allocated ERF starts from time slot i. The method may further include processing, by the user equipment, soft combining and decoding for at least one current slot after determining that at least one allocated asynchronous HARQ is associated with slot i. The method may further include, after determining that the unassigned asynchronous HARQ is associated with slot i; setting i=i+n after decoding N slots of ERF; or setting i=i+1 after decoding at least one current slot, and re-decoding DCI of slot i by the user equipment.

According to some embodiments, an apparatus may include means for decoding at least one DCI for a slot i. The apparatus may also include means for determining whether at least one allocated ERF begins at time slot i. The apparatus may also include means for determining whether at least one allocated asynchronous HARQ is associated with slot i after determining that no allocated ERF starts from slot i. The apparatus may further include means for processing soft combining and decoding of the N slots for the ERF after determining that the at least one allocated ERF starts from slot i. The apparatus may also include means for processing soft combining and decoding for at least one current slot after determining that at least one allocated asynchronous HARQ is associated with slot i. The apparatus may further comprise means for: after determining that the unassigned asynchronous HARQ is associated with slot i; setting i=i+n after decoding N slots of ERF; or setting i=i+1 after decoding at least one current slot, and re-decoding DCI of slot i.

According to some embodiments, 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 may be configured to, with the at least one processor, cause the apparatus at least to decode at least one DCI of time slot i. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to determine, after determining that no allocated ERF starts from slot i, whether at least one allocated asynchronous HARQ is associated with slot i. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to process soft combining and decoding of N time slots of an ERF after determining that the at least one allocated ERF starts from time slot i. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to process soft combining and decoding for at least one current time slot after determining that the at least one allocated asynchronous HARQ is associated with time slot i. The at least one memory and the computer program code may also be configured to, with the at least one processor, cause the apparatus at least to, after determining that the unassigned asynchronous HARQ is associated with slot i; setting i=i+n when decoding N slots of ERF; or setting i=i+1 after decoding at least one current slot, and re-decoding DCI of slot i.

According to some embodiments, a non-transitory computer-readable medium may be encoded with instructions that, when executed in hardware, may perform a method. The method may include decoding at least one DCI of a slot i. The method may further include determining whether at least one allocated ERF starts at time slot i. The method may further include determining whether at least one allocated asynchronous HARQ is associated with slot i after determining that no allocated ERF starts from slot i. The method may further include processing soft combining and decoding of the N slots for the ERF after determining that at least one allocated ERF starts from slot i. The method may further include processing soft combining and decoding for at least one current slot after determining that at least one allocated asynchronous HARQ is associated with slot i. The method may further include, after determining that the unassigned asynchronous HARQ is associated with slot i; setting i=i+n after decoding N slots of ERF; or setting i=i+1 after decoding at least one current slot, and re-decoding DCI of slot i.

According to some embodiments, a computer program product may perform a method. The method may include decoding at least one DCI of a slot i. The method may further include determining whether at least one allocated ERF starts at time slot i. The method may further include determining whether at least one allocated asynchronous HARQ is associated with slot i after determining that no allocated ERF starts from slot i. The method may further include processing soft combining and decoding of the N slots for the ERF after determining that at least one allocated ERF starts from slot i. The method may further include processing soft combining and decoding for at least one current slot after determining that at least one allocated asynchronous HARQ is associated with slot i. The method may further include, after determining that the unassigned asynchronous HARQ is associated with slot i; setting i=i+n after decoding N slots of ERF; or setting i=i+1 after decoding at least one current slot, and re-decoding DCI of slot i.

According to some embodiments, an apparatus may include circuitry configured to decode at least one DCI for a slot i. The circuitry may be further configured to determine whether at least one allocated ERF starts at slot i. The circuitry may be further configured to determine, after determining that no allocated ERF starts from slot i, whether at least one allocated asynchronous HARQ is associated with slot i. The circuitry may be further configured to process soft combining and decoding of the N time slots for the ERF after determining that the at least one allocated ERF starts from time slot i. The circuitry may be further configured to process soft combining and decoding for the at least one current slot after determining that the at least one allocated asynchronous HARQ is associated with slot i. The circuitry may be further configured to, after determining that no allocated asynchronous HARQ is associated with slot i; setting i=i+n after decoding N slots of ERF; or setting i=i+1 after decoding at least one current slot, and re-decoding DCI of slot i.

Drawings

For a proper understanding of the present disclosure, reference should be made to the accompanying drawings, in which:

fig. 1 illustrates a table showing round-trip signal propagation delays for typical GEO and LEO satellite deployments.

Fig. 2 illustrates a graph of channel gain variation in a fast fading channel.

Fig. 3 illustrates channel gain variation in a slow fading channel.

Fig. 4 illustrates an example of a method performed by a user device in accordance with certain embodiments.

Fig. 5 (a) illustrates an example of determining the repetition factor k for early retransmissions.

Fig. 5 (b) illustrates an example of an early retransmission frame.

Fig. 6 (a) illustrates an example of a slot for asynchronous HARQ inserted between two early retransmission frames.

Fig. 6 (b) illustrates an example of transmitting the same packet multiple times between two early retransmission frames for determining the ERF repetition factor.

Fig. 7 illustrates an example of a cross-process retransmission when NACK bits are received.

Fig. 8 illustrates an example of a method performed by a network entity in accordance with certain embodiments.

Fig. 9 illustrates an example of a method performed by a user device in accordance with certain embodiments.

Fig. 10 illustrates an example of a system according to some embodiments.

Detailed Description

Hybrid automatic repeat request (HARQ) is a physical layer retransmission mechanism for reliably transmitting encoded packets. Each HARQ process employs a stop-and-wait protocol and receives feedback from the receiver that includes Acknowledgement (ACK) and non-acknowledgement (NACK) bits. After the encoded packet is transmitted, the transmitter waits for feedback and transmits a subsequent new packet when an ACK bit indicating successful decoding of the previously transmitted packet is received.

In contrast, when NACK bits are received by the transmitter, the transmitter will transmit a redundancy version of the encoded packet, which can be soft-combined by the receiver with previously received encoded bits for decoding of the packet. Multiple HARQ processes may need to run in parallel so that data may be sent consecutively by the available processes while other processes are decoding the packet or waiting for feedback. In fast fading channels, HARQ is an effective technique for minimizing errors and inaccuracy of adaptive modulation and coding rate (AMC) selection.

In NTN scenarios, the long distance between the satellite and the UE near the surface of the earth may cause a longer round trip time between the transmitter sending the packet and receiving the feedback for the HARQ process. When a packet error does occur, for example, when the receiver fails to decode the encoded packet, another RTT is required in retrying to decode the encoded packet. Furthermore, CQI reports and SRS from the UE may take longer to be received by the network entity, resulting in poorer responsiveness of AMC link adaptation to channel condition changes and a higher probability of occurrence of packet errors. Thus, for NTN, the data service may have a longer latency period.

Another challenge for HARQ when applied with long RTT scenarios is that a large number of processes are required to continuously transmit data. Since RTT includes both propagation delay and data processing time, the number of required procedures is RTT/Transmission Time Interval (TTI), which is a time interval for transmitting one packet. For example, in the example of transparent GEO shown in the table of fig. 1, a 1ms TTI using a 15KHz SCS OFDM waveform requires more than 540 processes, which is much higher than the maximum number of 16 HARQ processes for NR. A long RTT may increase the soft buffer size requirements for operation of HARQ.

To avoid excessive delays in links with long transmission times, the first transmission may be made more reliable to reduce the probability of HARQ retransmissions. This may be achieved, for example, by lowering the target BLER in AMC, such as from 10% to 1%, and/or selecting a lower MCS. However, seeking such high reliability in a single transmission may reduce spectral efficiency. This problem may be more complex when the propagation time is even longer, as additional margin may need to be added in the MCS selection for inaccuracy of the CQI due to feedback delay.

Another technique for reducing latency may be through the use of blind retransmissions, where the transmitter always transmits a redundancy version of the packet before the NACK bits are received. This may be achieved by the network entity by asynchronous HARQ of NR, where DCI carries HARQ related information such as NDI, process ID and RV. Alternatively, the RRC protocol may allow for semi-statically configured slot isolation, where consecutive slots may be used to transmit one Transport Block (TB) with a different RV. For systems involving long-range service links, such as NTN, both of these approaches may reduce latency, but at the cost of wasting network resources. Thus, while conventional HARQ may be spectrally efficient, there is a significant disadvantage of the associated large latency.

Certain embodiments described herein may improve data service latency in long-range communication links by more efficient utilization of resources. For example, the various embodiments discussed below may reduce data service latency, provide efficient use of resources during data transfer, reduce signaling overhead required for HARQ, and/or may reduce the soft buffer size required for the receiver. Accordingly, certain embodiments are directed to improvements in computer-related technology, particularly by conserving network resources and reducing power consumption by network entities and/or user equipment located within a network.

Described herein are techniques to provide extended propagation delay to HARQ. In particular, a signaling mechanism may be employed to determine channel related times that may be used to configure HARQ transmissions of data packets, and a frame structure with built-in early retransmission modes may accommodate channel variations. This may also include low overhead HARQ signaling for multiple slots of an early retransmission frame, and may be based on single NACK and/or cross-process asynchronous HARQ retransmissions of the channel dependent time. Currently in NRThe UE reports its CQI measurements using a 4-bit codeword. However, the granularity of the reported CQI is not sufficient to determine the correlation time T _C The method comprises the steps of carrying out a first treatment on the surface of the Thus, in the following embodiments, DL channel gain related time may be reported by the UE, while UL channel gain related time measurements may be performed by the network entity.

To determine whether decoding results between consecutive time slots are correlated, a rate of change of channel gain may be determined. For example, in the case of a small rate of change, the channel may require a relatively long period of time to experience a fixed small gain change, as shown in fig. 3. In contrast, when the rate of change is relatively large, as shown in fig. 2, the same amount of channel variation may occur in a shorter time span. The smaller amount of channel gain variation may be represented by a fixed small variation in short-term (or instantaneous) CQI, denoted Δcqi.

Fig. 4 illustrates an example of a signaling diagram in accordance with some embodiments. User Equipment (UE) 410 may be similar to UE 1010 and Network Entity (NE) 420 may be similar to NE 1020, both shown in fig. 10. Although only a single UE and NE are shown, the communication network may contain one or more of each of these entities.

In step 401, NE 420 may send at least one Δcqi to UE 410, where Δcqi represents a fixed change in short term (or instantaneous) CQI. In various embodiments, the value of Δcqi may be predetermined such that the decoding results of packets of the same MCS (i.e., transmission format) may be correlated above a predetermined threshold within this range of channel variations. As shown in fig. 2, the time period in which the channel has a varying Δcqi may have a correlation time, denoted as T _C The same results are used for packet detection.

In various embodiments, when at least one connection between UE 410 and NE 420 is established, at least one UL related time T according to RRC signaling is targeted _C NE 420 may configure UE 410 to report at least one DL-related time T according to at least one criterion _C Such as one or more of at least one threshold for CQI variation Δcqi and at least one SRS configuration (such as time-frequency allocation of SRS).

In step 403, the UE 410 may measure at least one CQI rate of change. If the correlation time corresponding to the measured at least one CQI rate of change is below at least one predetermined threshold, such as one or two time slots, then time slot aggregation or blind retransmission may be applied to reduce service latency. However, delay and resource efficiency may be improved from these measurements if the correlation time corresponding to the measured at least one CQI rate of change is at or above at least one predetermined threshold.

In step 405, UE 410 may send at least one Downlink (DL) channel gain related time indication (T) to NE 420 _C ) Which may be associated with at least one CSI/CQI measurement. In certain embodiments, DL T _C The measurements may be made on one or more of the at least one SSB and the at least one CSI-RS signal. In some embodiments, at least one DL T _C May be transmitted back in units of slots corresponding to Δcqi on PUCCH and/or PUSCH.

In various embodiments, the correlation time T _C May change over time. For example, NE 420 may request UE 410 to periodically report downlink T _C And/or after a time slot having a difference from a previously reported value of greater than a predetermined number. Additionally or alternatively, NE 420 may update UL T based on channel estimates of at least one uplink signal _C 。

In step 407, UE 410 may send at least one SRS to NE 420 as for UL T according to the configuration in step 401 _C A measured reference signal. In step 409, NE 420 may perform at least one Uplink (UL) channel gain related time measurement (T _C ) Which may be performed on one or more of the at least one SRS and the at least one other UL signal associated with the UE 410.

For early retransmissions, the repetition factor k may be determined, for example, by the NE how many transmissions should be made for the packet. In some embodiments, this determination may be performed by scheduling consecutive time slots for multiple Redundancy Versions (RVs) of the same packet and repeating k according to the HARQ feedback settings for those time slots. For example, in the illustration of fig. 5 (a), the same packet may be sent in 4 slots with different RV and HARQ feedback, including two NACK bits and two ACK bits. The NE may then assume that if a packet under the current channel conditions requires three transmissions to decode successfully, then the appropriate repetition factor may be k=3.

After determining the repetition factor k, the NE may repeatedly transmit at least one packet in consecutive slots before receiving HARQ feedback. This may be, for example, T when channel variations are expected to be small _C Is performed in an "early retransmission frame" (ERF) within the segment of the slot. During one ERF frame, all slots may use a fixed MCS, repetition factor k and the same redundancy version set. Consecutive time slots may then be allocated for transmission of the same packet, allowing the NE to know after k transmissions whether the packet has been decoded correctly. Each packet may be assigned a separate HARQ process for soft combining. If the packet can be successfully decoded before the end of the consecutive k slots, the memory used by the process in the soft buffer can be refreshed, thus reducing the demands on the soft buffer size for RTT length.

As an example, the downlink ERF structure of fig. 5 (b) illustrates six packets transmitted with a repetition factor k=3 in six separate HARQ processes, resulting in a frame spanning a period of 3×6=18 slots. The number of HARQ processes in ERF may be estimated from the repetition factor k such that the total number of time slots is close to the measured correlation time T _C . Since HARQ related information (such as MCS and RV) is the same, it may be signaled in DCI of the first slot of a frame. After the DCI is decoded, the HARQ process ID and RV of each slot may follow a predictable pattern. For example, the receiver may operate in the same manner as intra-synchronous HARQ, but may no longer need HARQ related fields in DCI of a separate slot, thereby reducing L1 control overhead. For ERF, the DCI field required in the first slot may contain at least one ERF ID, a plurality of HARQ processes in the frame, a repetition factor k, redundancy versions for k transmissions, MCS levels, and/or allocated PRBs, as shown in fig. 5 (b). Redundancy versions for different retransmissions may alternatively be preconfigured in RRC to reduce signaling bits. The operation of UL ERF may be similar to DL, where DThe CI may indicate a structure of UL synchronous HARQ during ERF, where the timing offset for the first slot of the ERF is the same as the rest of the UL transmission.

After ERF, one or more time slots may be scheduled for retransmission of previously transmitted packets that may not be received correctly, as shown in fig. 6 (a). For example, retransmissions in these slots may be asynchronous (no particular order of HARQ processes), with DCI for each slot indicating the transmitted HARQ process. Once these asynchronous retransmissions are completed, another new set of packets may be scheduled in the next ERF. Between two ERFs, multiple transmissions of the same packet may also be inserted, as shown in fig. 6 (b), for estimation of the ERF repetition factor according to the corresponding HARQ feedback.

If NACK bits for DL transmission are received and/or UL packets cannot be decoded, the network entity may schedule retransmission in an asynchronous HARQ slot after ERF, as shown in fig. 6 (a). Unlike conventional HARQ, in which packet retransmissions are sent in the same process as NACK, the network entity can utilize its associated time T _C To determine if other processes need retransmissions and to actively schedule retransmissions for those processes even before their HARQ feedback has been received.

As shown in fig. 7, where a NACK bit is received at time slot t, a DL packet transmitted at time slot t' =t-RTT is acknowledged. As the decoding result may be at time T _C Inner correlation, and thus the received NACK for slot T ' can be used to infer the correlation between slot T ' and slot T ' +T _C The result of the packets sent in the interval between-1 and the procedure in which retransmissions may be required in these time slots. In some embodiments, if the time slot T ' is the mth transmission of the packet, then the interval [ T ', T ' +T _C -1]May be expected to receive a NACK, interval T ', T' +t _C -1]The number of transmissions of (2) is less than or equal to m; thus, retransmissions for those procedures may be scheduled. For example, if the second transmission is sent at time slot T ', for which a NACK is subsequently received at time slot T, then T ' and T ' +T _c All procedures between-1 (the most recent transmission of which is the first or second time) should be scheduled for re-transmissionsAnd (5) transmitting. Thus, the number of transmissions of a packet can be directly compared in the retransmission decision without regard to the MCS, since the MCS is not expected at T _C Too much charge is made in the interval of (2).

For UL transmissions, the network entity may schedule asynchronous HARQ slots in a similar manner directly based on transport block decoding failure rather than NACK feedback.

A procedure of scheduling retransmissions in asynchronous slots and indicating DL NACK bits or UL packet errors is illustrated in fig. 8. Fig. 8 illustrates an example of a method performed by a network entity, such as network entity 1020 in fig. 10. In step 801, the NE may receive HARQ feedback for the mth transmission from the UE in at least one process of time slot t' =t-RTT, which may be similar to UE 1010 in fig. 10. In step 803, the NE may identify the time slot T 'and the time slot T' +t _C One or more procedures (P ₁ ，P ₂ ，......，P _n ). In step 805, the NE may determine at least one process P whose number of transmissions is less than or equal to m _i . In step 807, the NE can schedule procedure P _i For retransmission.

The HARQ enhanced UE operation is shown in fig. 9. Thus, the actions of the UE may be driven by DCI, which may perform soft combining and packet decoding in synchronous mode of HARQ during ERF or in asynchronous mode based on per-slot HARQ information in DCI. In any case, the ACK/NACK bits are transmitted as conventional HARQ at each decoding attempt. When the channel gain is slowly varying, the techniques described herein may be applied, which may be used with NTN due to the desired LOS conditions and/or the use of directional antennas. An ERF with a duration and repetition factor determined by channel conditions may reduce packet transfer delay by more efficient resource users than conventional blind retransmissions. Retransmission modes in ERF may minimize the soft buffer size requirements of the receiver. In addition to ERF, some embodiments may also ensure link robustness.

Fig. 9 illustrates an example of a method performed by a user equipment, such as UE 1010 in fig. 10. In some embodiments, the NE may control at least one HARQ process configured to schedule both uplink and downlink transmissions. To reduce HARQ latency, the NE may schedule retransmission of the packet before HARQ feedback is received in the case of DL and/or before the scheduled packet is decoded in the case of UL.

In step 901, the UE may decode at least one DCI of slot i. In step 903, the ue may determine whether at least one allocated ERF starts from slot i. In step 905, after determining that no allocated ERF starts from slot i, the UE may determine whether at least one allocated asynchronous HARQ is associated with slot i. In step 907, after determining that at least one allocated ERF starts from slot i, the UE may process soft combining and decoding for N slots of the ERF. In step 909, after determining that at least one allocated asynchronous HARQ is associated with slot i, the UE may process soft combining and decoding for at least one current slot. After determining that the unassigned asynchronous HARQ is associated with slot i, step 911; setting i=i+n after decoding N slots of ERF; or set i=i+1 after decoding at least one current slot, the ue may re-decode the DCI for slot i.

Fig. 10 illustrates an example of a system according to some embodiments. In one embodiment, the system may include a plurality of devices, such as, for example, user device 1010 and/or network entity 1020.

The user device 1010 may include one or more of a mobile device, such as a mobile phone, a smart phone, a Personal Digital Assistant (PDA), a tablet or portable media player, a digital camera, a pocket video camera, a video game console, a navigation unit, such as a Global Positioning System (GPS) device, a desktop or laptop computer, a single location device, such as a sensor or smart meter, or any combination thereof.

Network entity 1020 may be a base station such as a millimeter wave 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. Further, the user device 1010 and/or the network entity 1020 may be one or more of a national broadband radio service device (CBSD).

One or more of these devices may include at least one processor, indicated as 1011 and 1021, respectively. The

processors

1011 and 1021 may be implemented by any computing or data processing device, such as a Central Processing Unit (CPU), application Specific Integrated Circuit (ASIC), or similar device. A processor may be implemented as a single controller or as multiple controllers or processors.

At least one memory may be provided in one or more of the devices indicated at 1012 and 1022. The memory may be fixed or removable. The memory may include computer program instructions or computer code embodied 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 memory may be combined as a processor on a single integrated circuit or may be separate from one or more processors. Furthermore, the computer program instructions stored in the memory and processable by the processor may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. The memory may be removable or non-removable.

The

processors

1011 and 1021 and

memories

1012 and 1022 or a subset thereof may be configured to provide components corresponding to the respective blocks of fig. 1 through 9. Although not shown, the device may also include positioning hardware, such as GPS or microelectromechanical system (MEMS) hardware, which may be used to determine the location of the device. Other sensors are also permissible and may be included to determine location, altitude, orientation, etc., such as barometers, compass, etc.

As shown in fig. 10,

transceivers

1013 and 1023 may be provided, and one or more devices may also include at least one antenna, illustrated as 1014 and 1024, respectively. A device may have many antennas, such as an antenna array configured for multiple-input multiple-output (MIMO) communication, or multiple antennas for multiple radio access technologies. For example, other configurations of these devices may be provided.

Transceivers

1013 and 1023 may be transmitters, receivers, or both transmitters and receivers, or may be units or devices configured for transmission and reception.

The memory and computer program instructions may be configured, with the processor for a particular device, to cause a hardware apparatus, such as a user device, to perform any of the processes described below (see, e.g., fig. 1-9). Thus, 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, some embodiments may be implemented entirely in hardware.

In some embodiments, an apparatus may include circuitry configured to perform any of the processes or functions shown in fig. 1-9. For example, the circuitry may be a pure hardware circuit implementation, such as analog and/or digital circuitry. In another example, the circuitry may be a combination of hardware circuitry and software, such as a combination of analog and/or digital hardware circuit(s) and software or firmware, and/or any portion of a hardware processor(s) with software, including digital signal processor(s), software, and at least one memory that work together to cause the apparatus to perform various processes or functions. In yet another example, the circuitry may be hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), including software for operation, such as firmware. When the operation of the hardware does not require software, the software in the circuitry may not be present.

The particular features, structures, or characteristics of some embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the use of the phrases "certain embodiments," "some embodiments," "other embodiments," or other similar language throughout this specification may, for example, refer to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the present invention. Thus, appearances of the phrases "in certain embodiments," "in some embodiments," "in other embodiments," or other similar language in the specification do not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Those of ordinary skill in the art will readily appreciate that certain embodiments discussed above may be practiced with steps in a different order and/or with hardware elements in a different configuration than that disclosed. Accordingly, certain modifications, variations, and alternative constructions will be apparent to those skilled in the art while remaining within the spirit and scope of the invention. Accordingly, reference should be made to the appended claims for determining the metes and bounds of the invention.

Part glossary

3GPP third Generation partnership project

5G fifth generation wireless system

ACK acknowledgement

AMC adaptive modulation and coding

BLER block error Rate

CQI channel quality indicator

CSI channel state information

CSI-RS channel state information reference signal

DCI downlink control information

DL downlink

Emtc enhanced machine type communication

eNBs evolved node B

ERF early retransmission frame

E-UTRAN evolution type universal mobile telecommunication system land radio access network

GEO geostationary orbit

HAPS high altitude platform station

HARQ hybrid automatic repeat request

IoT (Internet of things)

gNB next generation node B

LEO (LEO) ground-near track

LOS line of sight

LTE long term evolution

MCS modulation and coding scheme

Earth orbit in MEO

MME mobility management entity

NACK negative acknowledgement

NAS non-access stratum

NDI new data indicator

NE network entity

NLOS non-line-of-sight

NR new radio (5G)

NTN non-land network

OFDM orthogonal frequency division multiplexing

PRB physical resource block

PDSCH physical downlink data channel

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

RRC radio resource control

Round trip time of RTT

RV redundancy version

SCS subcarrier spacing

SRS sounding reference signal

SSB synchronization signal block

TB transport block

TTI transmission time interval

UL uplink

UE user equipment

Claims

1. A method, comprising:

receiving, by a user equipment, at least one indication of a fixed change in channel quality indicator, CQI;

measuring, by the user equipment, at least one CQI rate of change;

transmitting, by the user equipment, at least one downlink channel gain related time indication; and

at least one sounding reference signal is transmitted by the user equipment.

2. An apparatus comprising at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to perform the method of claim 1.

3. A non-transitory computer readable medium encoding instructions that, when executed in hardware, perform the method of claim 1.

4. An apparatus comprising means for performing the method of claim 1.

5. An apparatus comprising circuitry configured to cause the apparatus to perform the method of claim 1.