CN114503642A

CN114503642A - HARQ for long propagation delay

Info

Publication number: CN114503642A
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: 2022-05-13
Anticipated expiration: 2039-10-04
Also published as: CN114503642B; WO2021062880A1

Abstract

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

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

Background

Third generation partnership project (3GPP) release (Rel) -16 includes a research project (HAPS) on how the fifth generation (5G) New Radio (NR) standard supports non-terrestrial network (NTN) deployments using satellites and High Altitude Platform Stations (HAPS) to provide connectivity over a wide service area. In many NTN deployment scenarios, the round-trip signal propagation time may be much longer than for ordinary cellular networks intended for NR interfaces. Therefore, 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 research project for NR is to enhance HARQ for NTN operation, which will be studied further 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 also include measuring, by the user equipment, at least one rate of change of CQI. The method may also 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 Channel Quality Indicator (CQI). The apparatus may also include means for measuring at least one rate of change of CQI. 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 also include measuring at least one rate of change of CQI. 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 Channel Quality Indicator (CQI). The method may also include measuring at least one rate of change of CQI. 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.

In accordance with 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 also be configured to measure at least one rate of change of CQI. The circuitry may also be configured to transmit at least one downlink channel gain-related time indication. The circuitry may also be 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 a packet reception failure after m transmissions of a HARQ process for the time slot t' -t-RTT. The method may also include identifying, by the network entity, that the time slot T 'is at time slot T' + T_C-1 at least one HARQ process transmitted in the interval between. The method may also include 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, by the network entity, the P_iFor retransmission.

According to some embodiments, an apparatus may comprise at least one processor configured to receive, at a slot t, a packet reception failure after m transmissions of a HARQ process for the slot t' ═ t-RTTThe identified components. The apparatus may also include means for identifying between time slot T 'and time slot T' + T_C-means for at least one HARQ process transmitted in the interval between 1. The apparatus may also include at least one HARQ process P for determining that a number of transmissions is less than or equal to m_iThe component (2). The apparatus may also include means for scheduling P_iFor 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 to receive at least one acknowledgement of packet reception failure after m transmissions of a HARQ process for a slot t ═ t-RTT at 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 least a time slot T 'and a time slot T' + T_C-1 at least one HARQ process transmitted in the interval between. 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 with 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_iFor 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 include receiving at least one acknowledgement of packet reception failure after m transmissions of the HARQ process for a slot t' -t-RTT at a slot t. The method may also include identifying a time slot T 'and a time slot T' + T_C-1 at least one HARQ process transmitted in the interval between. The method may also 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_iFor retransmission.

According to some embodiments, a computer program product may perform a method. TheThe method may include receiving at least one acknowledgement of packet reception failure after m transmissions of the HARQ process for a slot t' -t-RTT at a slot t. The method may also include identifying a time slot T 'and a time slot T' + T_C-1 at least one HARQ process transmitted in the interval between. The method may also 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_iFor retransmission.

According to some embodiments, an apparatus may include circuitry configured to receive, at a slot t, at least one acknowledgement of a packet reception failure after m transmissions of a HARQ process for the slot t' ═ t-RTT. The circuitry may also be configured to identify a time slot T 'and a time slot T' + T_C-1 at least one HARQ process transmitted in the interval between. 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_iFor retransmission.

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

According to some embodiments, a computer program product may perform a method. The method may include decoding at least one DCI for slot i. The method may also include determining whether at least one assigned ERF begins from 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 the at least one allocated ERF starts from slot i. The method may also 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 no allocated asynchronous HARQ is associated with slot i; setting i ═ i + N after decoding N slots of the ERF; or after decoding at least one current slot, setting i to i +1, and re-decoding the DCI of the slot i.

According to some embodiments, an apparatus may include circuitry configured to decode at least one DCI for a time slot i. The circuitry may be further configured to determine whether at least one assigned ERF begins from time slot i. The circuitry may be further configured to determine whether at least one allocated asynchronous HARQ is associated with slot i after determining that no allocated ERF begins with slot i. The circuitry may be further configured to process 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 circuitry may be further configured to process soft combining and decoding for at least one current slot after determining that at least one assigned 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 the ERF; or after decoding at least one current slot, setting i to i +1, and re-decoding the DCI of the 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 the round trip signal propagation delay for a typical GEO and LEO satellite deployment.

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 equipment according to some embodiments.

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

Fig. 5(b) illustrates an example of early retransmission of a 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 retransmitted frames for determining an ERF repetition factor.

Fig. 7 illustrates an example of a cross-hop retransmission when a NACK bit is 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 equipment 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 including 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 is received indicating successful decoding of the previously transmitted packet.

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

In an NTN scenario, the long distance between the satellite and the UEs near the surface of the earth may cause a longer round trip time between the transmitter sending the packet and receiving feedback for the HARQ process. When a packet error does occur, e.g., when the receiver fails to decode the encoded packet, another RTT is needed in re-attempting to decode the encoded packet. Furthermore, the CQI reports and SRS from the UE may take longer to be received by the network entity, causing the AMC link adaptation to be less responsive to changes in channel conditions and a higher probability of packet errors occurring. Thus, for NTN, the data service may have a longer delay period.

Another challenge for HARQ when applied with long RTT scenarios is that a large number of processes are required to continuously send data. Since RTT includes both propagation delay and data processing time, the number of processes required is RTT/Transmission Time Interval (TTI), which is the time interval for transmitting one packet. For example, in the example of a 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 the NR. A long RTT may increase the soft buffer size requirement for operation of HARQ.

To avoid excessive delays in links with long propagation times, the first transmission can 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 complicated when the propagation time is even longer, since additional margin may need to be added in the MCS selection for the inaccuracy of the CQI due to feedback delay.

Another technique for reducing latency may be by using blind retransmission, where the transmitter always sends a redundancy version of the packet before the NACK bit is received. This may be achieved by asynchronous HARQ by the network entity through NR, where the DCI carries HARQ related information such as NDI, process ID and RV. Alternatively, the RRC protocol may allow for semi-statically configuring 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 methods can reduce latency, but at the cost of wasting network resources. Thus, while conventional HARQ may be spectrally efficient, there are significant drawbacks of the associated large delay.

Certain embodiments described herein may improve data service latency in long-range communication links by more efficient utilization of resources. For example, 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 a receiver. Accordingly, certain embodiments are directed to improvements in computer-related technology, particularly by conserving network resources and reducing power consumption of network entities and/or user equipment located within a network.

Described herein are techniques to provide extended propagation delay for HARQ. In particular, signaling mechanisms may be employed to determine channel correlation times that may be used to configure HARQ transmissions of data packets, and frame structures with built-in early retransmission modes may adapt to channel variations. This may also include low overhead HARQ signaling for early retransmission of multiple slots of a frame, and cross-hop asynchronous HARQ retransmissions that may be based on a single NACK and/or channel correlation time. Currently in NR, the UE reports its CQI measurement using a 4-bit codeword. However, the granularity of the reported CQI is not sufficient to determine the correlation time T_C(ii) a 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 the decoding results between consecutive slots are correlated, the rate of change of the channel gain may be determined. For example, where the rate of change is small, as shown in fig. 3, the channel may require a relatively long period of time to experience a fixed small gain change. In contrast, when the rate of change is relatively large, as shown in fig. 2, the same amount of channel change may occur in a shorter time span. A small amount of channel gain variation can be represented by a fixed small variation of the short-term (or instantaneous) CQI, denoted as delta CQI.

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 delta CQI to UE 410, where the delta CQI represents a fixed change in short-term (or instantaneous) CQI. In various embodiments, the value of Δ CQI may be predetermined such that within this range of channel variations, the solution of packets of the same MCS (i.e., transmit format)The code results may be correlated above a predetermined threshold. As shown in FIG. 2, the time period during which the channel has a variation Δ CQI may have an associated time, denoted T_CThe same result is used for packet detection.

In various embodiments, when at least one connection between UE 410 and NE 420 is established, a time T is associated for at least one UL according to RRC signaling_CNE 420 may configure UE 410 to report at least one DL-related time T according to at least one criterion_CSuch as one or more of at least one threshold for CQI change Δ CQI 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 change rate. If the correlation time corresponding to the measured at least one rate of change of CQI 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 rate of change of CQI is at or above at least one predetermined threshold, the latency and resource efficiency may be improved from these measurements.

In step 405, UE 410 may transmit 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_CThe 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_CMay be sent back in units of slots corresponding to delta CQI on PUCCH and/or PUSCH.

In various embodiments, the correlation time T_CMay change over time. For example, NE 420 may request UE 410 to periodically report downlink T_CAnd/or after a time slot that differs from a previously reported value by more than a predetermined number. Additionally or alternatively, NE 420 may update the UL T based on a channel estimate of at least one uplink signal_C。

In step 407, UE 410 may transmit at least one SRS to NE 420 as for UL according to the configuration in step 401T_CA 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 at least one SRS and at least one other UL signal associated with the UE 410.

For early retransmissions, the repetition factor k may be determined, e.g. by the NE, how many transmissions should be made for the packet. In some embodiments, this determination may be performed by scheduling consecutive slots for multiple Redundancy Versions (RVs) of the same packet and repeating k according to the HARQ feedback settings for these slots. For example, in the illustration of fig. 5(a), the same packet may be transmitted 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 current channel conditions requires three transmissions to successfully decode, 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 the HARQ feedback. This may be, for example, at T where channel variation is expected to be small_CIs performed in an "early retransmission frame" (ERF) within the period of a slot. During one ERF frame, all slots may use a fixed MCS, a repetition factor k, and the same set of redundancy versions. Consecutive time slots can 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 flushed, thereby reducing the soft buffer size requirement for RTT long.

As an example, the downlink ERF structure of fig. 5(b) illustrates six packets transmitted with a repetition factor k of 3 in six separate HARQ processes, resulting in a frame spanning a period of 3 × 6-18 slots. The number of HARQ processes in the ERF may be estimated from the repetition factor k such that the total number of slots is close to the measured correlation time T_C. Since HARQ-related information (such as MCS and RV) is the same, it is possible to reduce the amount of HARQ-related information (such as MCS and RV)May be signaled in the DCI for 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-frame synchronous HARQ, but may no longer require HARQ related fields in DCI for individual slots, thereby reducing L1 control overhead. For the ERF, the DCI field required in the first slot may contain at least one ERF ID, multiple HARQ processes in the frame, a repetition factor k, a redundancy version for k transmissions, an MCS level, and/or allocated PRBs, as shown in fig. 5 (b). The redundancy versions for the different retransmissions may alternatively be preconfigured in RRC to reduce the signaling bits. The operation of the UL ERF may be similar to the DL, where the DCI may indicate the structure of UL synchronous HARQ during the ERF, where the timing offset for the first slot of the ERF is the same as the rest of the UL transmission.

After the ERF, one or more 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 (without a specific order of HARQ processes), with the DCI for each slot being used to indicate the HARQ process of the transmission. Once these asynchronous retransmissions are complete, 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 from the corresponding HARQ feedback.

If a NACK bit for DL transmission is received and/or an UL packet cannot be decoded, the network entity may schedule a retransmission in an asynchronous HARQ slot following the ERF, as shown in fig. 6 (a). Unlike conventional HARQ, where packet retransmissions are sent in the same process of NACK, the network entity may utilize its correlation time T_CTo determine whether other processes need retransmissions, and to proactively 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 slot t, a DL packet transmitted at slot t' -t-RTT is acknowledged. Since the decoding result may be at time T_CInner correlation, so that the received NACK for slot t' can be usedAfter deducing the time slot T 'and the time slot T' + T_C-the result of the packets sent in the interval between 1, and the process of possible need for retransmission in these slots. In some embodiments, if slot T ' is the mth transmission of a packet, then the interval [ T ', T ' + T_C-1]Can be expected to receive a NACK, separated by [ T ', T' + T_C-1]Is less than or equal to m; thus, retransmissions for those processes may be scheduled. For example, if a second transmission is sent in time slot T ', for which a NACK is subsequently received in time slot T, then T ' and T ' + T_cAll processes between-1 (whose most recent transmission is the first or second time) should be scheduled for retransmission. Thus, the number of transmissions of a packet may be directly compared in the retransmission decision, regardless of the MCS, since the MCS is not expected at T_CToo much is charged in the interval.

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

The process of scheduling retransmissions in asynchronous time slots and indicating DL NACK bit 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 an 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) transmitted in the interval between 1₁，P₂，......，P_n). In step 805, the NE may determine at least one procedure P whose number of transmissions is less than or equal to m_i. At step 807, the NE may schedule process P_iFor 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 a synchronous mode of HARQ during ERF or in an asynchronous mode based on per-slot HARQ information in the DCI. In any case, the ACK/NACK bits are sent as conventional HARQ at each decoding attempt. The techniques described herein may be applied when the channel gain is slowly varying, which may be used with NTN due to 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 delivery delay by more efficient resource users compared to conventional blind retransmissions. The retransmission mode in the ERF may minimize the soft buffer size requirements of the receiver. In addition to the ERF, some embodiments may also ensure the robustness of the link.

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 packets before HARQ feedback is received in the case of DL and/or before scheduled packets are decoded in the case of UL.

In step 901, the UE may decode at least one DCI for 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 no allocated asynchronous HARQ is associated with slot i, at step 911; setting i ═ i + N after decoding N slots of the 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 multiple devices, such as, for example, user equipment 1010 and/or a network entity 1020.

The user devices 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 computer or portable media player, a digital camera, a pocket 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.

The 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 equipment 1010 and/or the network entity 1020 may be one or more of a citizen broadband radio service device (CBSD).

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

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. The 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 non-transitory computer-readable media. A Hard Disk Drive (HDD), Random Access Memory (RAM), flash memory, or other suitable memory may be used. The memory may be combined on a single integrated circuit as the processor or may be separate from the one or more processors. Furthermore, the computer program instructions stored in the memory and processable by the processor may be computer program code in any suitable form, such as 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 various blocks of fig. 1-9. Although not shown, the device may also include positioning hardware, such as GPS or micro-electro-mechanical systems (MEMS) hardware, which may be used to determine the location of the device. Other sensors are also permissible and may be included to determine position, altitude, direction, etc., such as barometers, compasses, etc.

As shown in fig. 10,

transceivers

1013 and 1023 may be provided, and one or more of the devices may further 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) communications, 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, 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 equipment, 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 purely hardware circuit implementations, 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 circuitry(s) and software or firmware, and/or any portion of 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), that includes software for operation, such as firmware. Software in the circuitry may not be present when the operation of the hardware does not require software.

The features, structures, or characteristics of certain embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, throughout this specification, the use of the phrases "certain embodiments," "some embodiments," "other embodiments," or other similar language, refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiments 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 throughout this 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.

One 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 configurations other than those 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. Therefore, to ascertain the metes and bounds of the invention, the appended claims should be referenced.

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

eNB evolved node B

ERF early retransmission frame

E-UTRAN evolved universal mobile telecommunications system terrestrial 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 near-ground orbit

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-terrestrial 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 (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 a Channel Quality Indicator (CQI);

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

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

transmitting, by the user equipment, at least one sounding reference signal.

2. A method, comprising:

receiving, by the network entity, at a time slot t, at least one acknowledgement of a packet reception failure after m transmissions of the HARQ process for the time slot t' ═ t-RTT;

identifying, by the network entity, at time slot T 'and time slot T' + T_C-1 at least one HARQ process transmitted in the interval between;

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(ii) a And

scheduling P by the network entity_iFor retransmission.

3. The method of claim 2, further comprising:

scheduling, by the network entity, at least one early retransmission frame based on at least one received downlink channel gain related time indication, wherein HARQ signaling is associated with first slot downlink control information, consecutive slots are used in the same process, and multiple processes are associated with synchronous HARQ reception.

4. A method, comprising:

decoding, by the user equipment, the at least one DCI of slot i;

determining, by the user equipment, whether at least one assigned ERF starts from a time slot i;

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;

processing, by the user equipment, soft combining and decoding of N slots for at least one assigned ERF after determining that the ERF starts from slot i;

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; and

after determining that no allocated asynchronous HARQ is associated with slot i, setting i ═ i + N after decoding N slots of the ERF; or after decoding the at least one current slot, setting i-i +1, and re-decoding the DCI of the slot i by the user equipment.

5. 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 processes of any of claims 1-4.

6. A non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform the process of any of claims 1-4.

7. An apparatus comprising means for performing a process according to any one of claims 1 to 4.

8. An apparatus comprising circuitry configured to cause the apparatus to perform the process of any of claims 1-4.

9. A computer program product encoded with instructions for performing a process according to any of claims 1-4.