WO2019071463A1

WO2019071463A1 - Grant-free hybrid automatic repeat request

Info

Publication number: WO2019071463A1
Application number: PCT/CN2017/105665
Authority: WO
Inventors: Yuantao Zhang; Yanji Zhang; Yi Zhang; Nan HAO
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2017-10-11
Filing date: 2017-10-11
Publication date: 2019-04-18
Also published as: CN111213335A

Abstract

Various communication systems may benefit from improved retransmission of data packets in a grant-free environment. For example certain communication systems may benefit from an enhanced grant-free hybrid automatic repeat request. A method, in certain embodiments, may include receiving at a network entity a grant-free transmission from a user equipment. The transmission may comprise a plurality of transport blocks each associated with a logic identification, and the logic identification may be included within, or received along with, the received transport blocks. The method may also include determining at the network entity that one of the plurality of transport blocks is missing based on the logic identification. In addition, the method may include scheduling retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.

Description

GRANT-FREE HYBRID AUTOMATIC REPEAT REQUEST

BACKGROUND： Field：

Various communication systems may benefit from improved retransmission of data packets in a grant-free environment. For example， certain communication systems may benefit from enhanced hybrid automatic repeat request in a grant-free environment.

Description of the Related Art：

Third Generation Partnership Project (3GPP) Fifth Generation (5G) or New Radio (NR) technology are designed to allow for ultra-reliable low latency communications (URLLC) . URLLC provide for stringent latency， reliability， and availability requirements for data transmission. Latency refers to time delay between data being generated and correctly transmitted from one device to another. Reliability relates to a guaranteeing of a successful message transmission within a defined latency period， while availability refers to the ability of URLLC to endure outages.

To meet the stringent delay requirements of 5G URLLC， certain communication systems may use an uplink grant-free transmission. In uplink grant-free transmissions， the user equipment can send data immediately when the data is received in the user equipment buffer without having to wait for an uplink grant from the network. The user equipment therefore does not have to send a scheduling request and wait for a reply that includes an uplink grant， as needed in a traditional grant-based transmission. Rather， the user equipment can utilize a grant-free transmission to send data immediately upon the arrival of the data at the user equipment buffer. To further improve reliability of the grant-free URLLC transmissions， a repeated K number of transmissions can occur.

SUMMARY

According to certain embodiments， an apparatus may include at least one memory including computer program code， and at least one processor. The at least one memory and the computer program code may be configured， with the at least one processor， to cause the apparatus at least to receive at a network entity a grant-free transmission from a user equipment. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or received along with， the received transport blocks. The at least one memory and the computer program code may also be configured， with the at least one processor， to cause the apparatus at least to determine at the network entity that one of the plurality of transport blocks is missing based on the logic identification. In addition， the at least one memory and the computer program code may be configured， with the at least one processor， to cause the apparatus at least to schedule retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.

A method， in certain embodiments， may include receiving at a network entity a grant-free transmission from a user equipment. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or received along with， the received transport blocks. The method may also include determining at the network entity that one of the plurality of transport blocks is missing based on the logic identification. In addition， the method may include scheduling retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.

An apparatus， in certain embodiments， may include means for receiving at a network entity a grant-free transmission from a user equipment. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or received along with， the received transport blocks. The apparatus may also include means for determining at the network entity that one of the plurality of transport blocks is missing based on the logic identification. In addition， the apparatus may include scheduling retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.

According to certain embodiments， a non-transitory computer-readable medium encoding instructions that， when executed in hardware， perform a process. The process may include receiving at a network entity a grant-free transmission from a user equipment. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or received along with， the received transport blocks. The process may also include determining at the network entity that one of the plurality of transport blocks is missing based on the logic identification. In addition， the process may include scheduling retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.

According to certain other embodiments， a computer program product may encode instructions for performing a process. The process may include receiving at a network entity a grant-free transmission from a user equipment. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or received along with， the received transport blocks. The process may also include determining at the network entity that one of the plurality of transport blocks is missing based on the logic identification. In addition， the process may include scheduling retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.

According to certain embodiments， an apparatus may include at least one memory including computer program code， and at least one processor. The at least one memory and the computer program code may be configured， with the at least one processor， to cause the apparatus at least to transmit a grant-free transmission from a user equipment to a network entity. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or transmitted along with， the transport blocks. The at least one memory and the computer program code may also be configured， with the at least one processor， to cause the apparatus at least to receive a request to retransmit a missing one of the plurality of transport blocks to the network entity. The request may be based on the logic identification. In addition， the at least one memory and the computer program code may be configured， with the at least one processor， to cause the apparatus at least to retransmit the missing one of the plurality of transport blocks from the user equipment to the network entity.

A method， in certain embodiments， may include transmitting a grant-free transmission from a user equipment to a network entity. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification is included within， or transmitted along with， the transport blocks. The method may also include receiving a request to retransmit a missing one of the plurality of transport blocks to the network entity. The request may be based on the logic identification. In addition， the method may include retransmitting the missing one of the plurality of transport blocks from the user equipment to the network entity.

An apparatus， in certain embodiments， may include means for transmitting a grant-free transmission from a user equipment to a network entity. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or transmitted along with， the transport blocks. The apparatus may also include means for receiving a request to retransmit a missing one of the plurality of transport blocks to the network entity. The request may be based on the logic identification. In addition， the apparatus may include means for retransmitting the missing one of the plurality of transport blocks from the user equipment to the network entity.

According to certain embodiments， a non-transitory computer-readable medium encoding instructions that， when executed in hardware， perform a process. The process may include transmitting a grant-free transmission from a user equipment to a network entity. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or transmitted along with， the transport blocks. The process may also comprise receiving a request to retransmit a missing one of the plurality of transport blocks to the network entity. The request may be based on the logic identification. In addition， the process may comprise retransmitting the missing one of the plurality of transport blocks from the user equipment to the network entity.

According to certain other embodiments， a computer program product may encode instructions for performing a process. The process may include transmitting a grant-free transmission from a user equipment to a network entity. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or transmitted along with， the transport blocks. The process may also comprise receiving a request to retransmit a missing one of the plurality of transport blocks to the network entity. The request may be based on the logic identification. In addition， the process may comprise retransmitting the missing one of the plurality of transport blocks from the user equipment to the network entity.

BRIEF DESCRIPTION OF THE DRAWINGS：

For proper understanding of the invention， reference should be made to the accompanying drawings， wherein：

Figure 1 illustrates an example of a hybrid automatic repeat request according to certain embodiments.

Figure 2 illustrates an example of a hybrid automatic repeat request according to certain embodiments.

Figure 3 illustrates an example of a flow diagram according to certain embodiments.

Figure 4 illustrates an example of a flow diagram according to certain embodiments.

Figure 5 illustrates an example of a system according to certain embodiments.

DETAILED DESCRIPTION：

In certain embodiments that utilize grant-free transmissions， one or more hybrid automatic repeat request (HARQ) processes may be used to allow for consecutive transmission of transport blocks. HARQ may be a combination of high-rate forward error-correcting coding and automatic repeat request (ARQ) error-control. The use of one or more HARQ processes may help to reduce the retransmission latency of the transport blocks from the user equipment to a network entity， such as a 5G/NR NodeB (gNB) . The number of HARQ processes for grant-free transmissions may be configured by the gNB. As will be seen in the embodiments of Figures 1 and 2， the gNB may configure three HARQ processes.

Given that some embodiment may utilize multiple HARQ processes， there should be a way for the network entity and/or the user equipment to determine an identification for each of the transport blocks. The identification， for example， may be an HARQ process identification. Using the identification of the transport block， the network entity may transmit an indication， such as an acknowledgement， to indicate that a transport block corresponding to a HARQ process is correctly detected. The indication may also include an uplink grant to the user equipment for retransmission of the grant-free transport block.

The identification， such as an HARQ process identification， may be associated with a slot index. If the network entity， for example a gNB， detects a user equipment transmission from a slot， it may implicitly know the identification associated with the slot. In certain embodiment， this identification may be known as an absolute identification or an absolute HARQ process identification.

Figure 1 illustrates an example of a hybrid automatic repeat request according to certain embodiments. In particular， Figure 1 illustrates an association between the HARQ identification 110 and slot index 120. If the network entity detects a user equipment transmission from a slot， it may know that the identification implicitly. As shown in the example of Figure 1， the network entity， for example a gNB， may configured three HARQ processes for grant-free transmission. This means that three different grant-free transmissions may be retransmitted using HARQ if needed. In other words， the identification or HARQ processes identification may have a value or number of 1， 2， or 3. The configured slots for grant-free transmissions may be represented by m， m+N， m+2N， ...， and m+7N， where m represents the first slot， and N represents the configured periodicity for grant-free transmission.

In Figure 1， a data packet may be received by or may come to a buffer of the user equipment between slots m and m+N. In a grant-free environment， the user equipment may start the transmission of the data packet in slot m+N upon its receipt in the buffer. The network entity may then use the HARQ process identity {2， 3， 1 } to identify grant-free transport block {1， 2， 3} ， respectively. Figure 1 illustrates that another data packet is received by or comes to the buffer of the user equipment between m+4N and m+5N. The user equipment then transmits two transport blocks， at slot m+5N and m+6N， having the associated

HARQ identifications

3 and 1， respectively.

As can be seen in the example shown in Figure 1， the HARQ process that corresponds to the grant-free transport block is variable. As such， in certain embodiments in which the first one or more transport blocks are not detected by the network entity， the network entity does not immediately know that is missed a. transport block. The higher layer may camp in the network entity. In certain embodiments， the transport block may have been missed by the network entity due to a high inter-cell interference that caused the data sent within the transport block to be incorrectly received.

Traditional radio link control (RLC) retransmission may not meet the strict user plane latency requirements of URLLC. Performing retransmission in URLLC may therefore rely on a high layer application， such as the application layer， to perform the retransmission， which means an even higher latency for retransmission. In some embodiments， the user equipment can retransmit that the transport block using grant-free transmissions after a predefined backoff time. Waiting until after the predefined backoff time， however， may translate to an even high latency. In other embodiments， retransmission may be based on scheduling from which grant-free transmissions may be excluded.

Certain embodiments therefore help to reduce the latency of a grant-free retransmission. In doing so， two different identifiers associated with the same grant-free transport block may be associated. As discussed above， the first identifier may be an absolute identifier， also known as an absolute identification， for example an absolute HARQ process identifier. The absolute identifier may be associated with the slot index， as shown in Figure 1， and may be determined by a slot， a mini-slot， or a subframe index. The second identifier may be a logic identifier， also known as a logic identification， for example a logic HARQ process identifier. The logic identifier may be associated with the grant-free transport block index of the incoming packet. The logic identifier may therefore be included in， or sent along with， the transmission received by the network entity from the user equipment.

Based on the logic identifier received or detected by the network entity and/or the absolute identifier， the network entity may determine or decide whether there are one or more transport blocks that were missed in a previous time slot. A missed transport block may mean that the network entity failed to receive a data packet that was transmitted from the user equipment in the transport block. If the network entity determines that one or more transport blocks were missed， the network entity may schedule a retransmission of the one or more missed transport blocks without having to rely on higher layer checking or a timer.

In certain embodiments， the absolute identifier may be included in the downlink control information transmitted to the user equipment. The user equipment may then use the absolute identifier to identify the transport block that needs to be retransmitted. The absolute identity may be included in downlink control information sent from the network entity to the user equipment. Because the absolute identification may be known to both the user equipment and the network node through the slot index， the absolute identification may not be transmitted by the user equipment， unlike the logic identification.

The network entity may configure a single number or a single value of grant-free HARQ processes that applies to both kind of HARQ processes. For example， the network entity， such as a gNB， may configure a HARQ process number or value for grant-free transmissions， and this number may apply to both absolute HARQ process and logic HARQ process. The logic HARQ process may be associated with the logic identification. In the embodiments shown in Figure 2， the network entity may configure three HARQ processes for both absolute and logic processes. Each grant-free HARQ process may be associated with a particular absolute and/or logic identifier. As discussed above， the logic identifier may be included in， or transmitted along or together with， the associated transport block. When a new packet is received or comes to the user equipment buffer， the user equipment transmits the first transport block with the first logic identifier from the nearest available slot. The next transport block may then be transmitted along with the second logic identifier from the next available slot. In certain embodiments， one data packet may be divided into multiple transport blocks.

The logic identifier may be transmitted from the user equipment to the network entity in various ways. For example， the logic identification may be included as part of a medium access control (MAC) protocol data unit (PDU) . A new MAC control element (MAC CE) may be defined in the MAC PDU to indicate the logic identification. In another example， the logic identification may be included in a MAC subheader that corresponding to a medium access control service data unit (SDU) . In yet another example， the logic identification may be transmitted from the user equipment to the network entity as part of the uplink control information.

Figure 2 illustrates an example of a hybrid automatic repeat request according to certain embodiments. Unlike the example shown in Figure 1， the example in Figure 2 employs both an absolute identification 220 and a logic identification 210. In Figure 2， the network entity may configure three HARQ processes for a grant-free transmission. The configured slots for a grant-free transmission， also known as slot index 230， may be m， m+N， m+2N， ...， m+7N. When a data packet may come to the user equipment buffer between slot m and m+N， the user equipment may start the transmission from slot m+N. The logic identification for the three grant-free transport blocks may be {1， 2， 3 } ， while the absolute HARQ for the three grant-flee transport blocks may be {2， 3， 1} . The absolute HARQ process identification may be determined by a slot， a mini-slot， and/or a subframe index. The logic identification may be included in the transport block as one MAC CE in the MAC PDU and/or in the MAC subheader corresponding to the MAC SDU.

In the example of Figure 2， the network entity， such as the gNB， may not detect the first grant-free transport block， for example transport block in m+N， but may detect the remaining two transport blocks in m+2N and m+3N. In certain embodiments， the failure to detect the first grant-free transport block may be caused by a high inter-cell interference suffered in slot m+N， while m+2N and m+3N experience a lower level of interference.

Once the network entity detects the second transport block， m+2N， the network entity may also receive logic identification 2. In other words， the transport block received by the network entity may be associated with an absolute identification of 3， but a logic identification of 2. Based on the logic identification of the first received transport block not having a value of 1， the network entity may then determine or know that there is one previous transport block that has been missed. In other words， the determining by the network entity that one of the plurality of transport blocks is missing may occur when a value of the logic identification received at the network entity is not lower than an available value. The value is a first value， a last value， or a middle value falling between the first value and the last value. When the value is a first value of the logic identification received at the network entity， the network entity may determine that one of the plurality of transport blocks is missing when the first value is not the minimum available value.

For example， in Figure 2 the logic identification may not be 1， based on which the network entity may determine that a transport block has been missed. In another example， the value of the logic identification may be 3. If the network entity does not receive a logic identification of 2 before receiving a logic identification of 3， and the logic identification of 2 is an available value， then the network entity may determine that one of the plurality of transport blocks is missing.

The network entity may then schedule the retransmission of the missed transport block between slot m+2N and m+3N. The above example allows the network entity to schedule the transport block retransmission without having to use a higher layer checking and signaling. This may allow for a much lower latency.

Figure 3 illustrates a flow diagram according to certain embodiments. In particular， Figure 3 illustrates an embodiment of a method performed by a network entity， such as a gNB. In step 310， the network entity receives a grant-free transmission from the user equipment. The transmission may comprise a plurality of transport blocks each associated with a logic identification， and the logic identification may be included within， or received along with， the received transport blocks. For example， the logic identification is included as part of a medium access control protocol data unit. Specifically， the logic identification is included as part of a medium access control protocol data unit. In another example， the logic identification may be included in a medium access control subheader corresponding to a medium access control service data unit. In yet another example， the logic identification is transmitted as part of the uplink control information.

In step 320， the network entity may determine that one of the plurality of transport blocks is missing based on the logic identification. In certain other embodiments， the network entity may determine that one of the plurality of the transport blocks is missing based on an absolute identification associated with a slot index of the transport blocks. The absolute identification may be determined by a slot， a mini-slot， or a subframe index of the transport blocks. The absolute identification may be included in downlink control information sent from the network entity to the user equipment. The absolute identification may be known to both the user equipment and the network node through the slot index， as shown in Figures 1 and 2. In certain embodiments， the network entity may configure a single value of a HARQ process number that may apply to both an absolute HARQ process and a logic HARQ process. The logic HARQ process may be associated with the logic identification.

In certain embodiments， the determining by the network entity that one of the plurality of transport blocks is missing occurs when a value of the logic identification received at the network entity is not lower than an available value. The value may be a first value， a last value， or a middle value falling between the first value and the last value. For example， the logic identification may not be 1. For example， as can be seen in Figure 2， the network entity may receive a first transport block with a logic identification of 2. Based on both the logic identification and the absolute identification， the user equipment may determine a missing transmitting block.

In another embodiment， the network entity may determine the missing of the latter transport blocks by the received logic identification and/or the buffer status. In the example of Figure 2， the network entity， such as the gNB， may not detect the last grant-free transport block， for example transport block in m+3N， but may detect the first two transport blocks in m+N and m+2N. The network entity may determine that the last grant-free transport block is missing when the received buffer status in m+2N is not an empty value. In other words， the determining by the network entity that one of the plurality of transport blocks is missing may occur when a last value of the logic identification received at the network entity is not a maximum available value， and the received buffer status is not empty.

In step 330， the network entity may schedule retransmission of the missing one of the plurality of transport blocks from the user equipment. In step 340， the network entity may receive the retransmission including the missing one of the plurality of transport blocks.

Figure 4 illustrates a flow diagram according to certain embodiments. In particular， Figure 4 illustrates an embodiment of a method performed by a user equipment. The embodiment of the user equipment shown in Figure 4 may receive and/or transmit grant-free transmissions and retransmission requests from the network entity shown in Figure 3. In step 410， the user equipment may transmit a grant-free transmission to a network entity. The transmission may comprise the data packet. The transmission may comprise a plurality of transport blocks each associated with a logic identification. The logic identification may be included within， or transmitted along with， the transport blocks.

In step 420， the user equipment may receive a request to retransmit a missing one of the plurality of transport blocks to the network entity. The request may be based on the logic identification. The received request may be a hybrid automatic repeat request. In another embodiment， the request may be determined to an absolute identification associated with a slot index of the transport blocks. The absolute identification may be determined by a slot， a mini-slot， or a subframe index of the transport blocks. In step 430， the user equipment may retransmit the missing one of the plurality of transport blocks to the network entity. The transmitting of the grant-free transmission occurs upon the arrival of a data packet at a buffer of the user equipment.

Figure 5 illustrates a system according to certain embodiments. It should be understood that each signal or block in Figures 1-4 may be implemented by various means or their combinations， such as hardware， software， firmware， one or more processors and/or circuitry. In one embodiment， a system may include several devices， such as， for example， a network entity 520 or a user equipment (UE) 510. The system may include more than one UE 510 and more one network entity 520， although only one access node shown for the purposes of illustration. The network entity may be a network node， an access node， a base station， a 5G/NR NodeB (gNB) ， server， host， or any of the other access or network node discussed herein.

Each of these devices may include at least one processor or control unit or module， respectively indicated as 511 and 521. At least one memory may be provided in each device， and indicated as 512 and 522， respectively. The memory may include computer program instructions or computer code contained therein. One or

more transceiver

513 and 523 may be provided， and each device may also include an antenna， respectively illustrated as 514 and 524. Although only one antenna each is shown， many antennas and multiple antenna elements may be provided to each of the devices. Higher category UEs generally include multiple antenna panels. Other configurations of these devices， for example， may be provided. For example， network entity 520 and UE 510 may be additionally configured for wired communication， in addition to wireless communication， and in such a

case antennas

514 and 524 may illustrate any form of communication hardware， without being limited to merely an antenna.

Transceivers

513 and 523 may each， independently， 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. In other embodiments， the UAVs or the network entity may have at least one separate receiver or transmitter. The transmitter and/or receiver (as far as radio parts are concerned) may also be implemented as a remote radio head which is not located in the device itself， but in a mast， for example. The operations and functionalities may be performed in different entities， such as nodes， hosts or servers， in a flexible manner. In other words， division of labor may vary case by case. One possible use is to make a network node deliver local content. One or more functionalities may also be implemented as virtual application (s) in software that can run on a server. A beamformer may be a type of transceiver.

Auser device or user equipment 510 may be a mobile station (MS) such as a mobile phone or smart phone or multimedia device， a computer， such as a tablet， provided with wireless communication capabilities， personal data or digital assistant (PDA) provided with wireless communication capabilities， portable media player， digital camera， pocket video camera， navigation unit provided with wireless communication capabilities or any combinations thereof. In other embodiments， the UE may be a machine type communication (MTC) device， which may not require human interaction， such as a sensor， a meter， or an actuator.

In some embodiments， an apparatus， such as a network entity， may include means for carrying out embodiments described above in relation to Figures 1-4. In certain embodiments， at least one memory including computer program code can be configured to， with the at least one processor， cause the apparatus at least to perform any of the processes described herein.

Processors

511 and 521 may be embodied by any computational or data processing device， such as a central processing unit (CPU) ， digital signal processor (DSP) ， application specific integrated circuit (ASIC) ， programmable logic devices (PLDs) ， field programmable gate arrays (FPGAs) ， digitally enhanced circuits， or comparable device or a combination thereof. The processors may be implemented as a single controller， or a plurality of controllers or processors.

For firmware or software， the implementation may include modules or unit of at least one chip set (for example， procedures， functions， and so on) .

Memories

512 and 522 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 therefrom. Furthermore， the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code， for example， a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal but may also be external or a combination thereof， such as in the case when additional memory capacity is obtained from a service provider. The memory may be fixed or removable.

The memory and the computer program instructions may be configured， with the processor for the particular device， to cause a hardware apparatus such as network entity 520 or UE 510， to perform any of the processes described above (see， for example， Figures 1-4) . Therefore， in certain embodiments， a non-transitory computer-readable medium may be encoded with computer instructions or one or more computer program (such as added or updated software routine， applet or macro) that， when executed in hardware， may perform a process such as one of the processes described herein. Computer programs may be coded by a programming language， which may be a high-level programming language， such as objective-C， C， C++， C#， Java， etc.， or a low-level programming language， such as a machine language， or assembler. Alternatively， certain embodiments may be performed entirely in hardware.

Furthermore， although Figure 5 illustrates a system including a network entity 520 and UE 510， certain embodiments may be applicable to other configurations， and configurations involving additional elements， as illustrated and discussed herein. For example， multiple user equipment devices and multiple network entities may be present， or other nodes providing similar functionality， such as nodes that combine the functionality of a user equipment and an network entity， such as a relay node. The UE 510 may likewise be provided with a variety of configurations for communication other than communication network entity 1020. For example， the UE 510 may be configured for device-to-device or machine-to-machine transmission.

The above embodiments may provide for significant improvements to the functioning of a network and/or to the functioning of the network entities within the network. Specifically， certain embodiments may allow for a low latency grant-free retransmission based on the logic identification and/or the absolute identification. The logic identification may be transmitted either with the grant-free transmission or along with the grant-free transmission. The logic identification may be associated with the grant-free transport block of the incoming packet. By lowering the latency of the retransmission， both the HARQ processes of the network may be made more efficient.

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， the usage of the phrases “certain embodiments， ” “some embodiments， ” “other embodiments， ” or other similar language， throughout this specification refers to the fact that a particular feature， structure， or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. Thus， appearance of the phrases “in certain embodiments， ” “in some embodiments， ” “in other embodiments， ” or other similar language， throughout this specification does 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 having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order， and/or with hardware elements in configurations which are different than those which are disclosed. Therefore， although the invention has been described based upon these preferred embodiments， it would be apparent to those of skill in the art that certain modifications， variations， and alternative constructions would be apparent， while remaining within the spirit and scope of the invention.

Partial Glossary

3GPP Third Generation Partnership Project

5G Fifth Generation

NR New Radio

LTE Long Term Evolution

gNB NR Node B

UE User Equipment

URLLC Ultra-reliable and low latency communication

DL Downlink

UL Uplink

TB Transport block

HARQ Hybrid automatic repeat request

MAC Media access control

CE Control element

Claims

A method comprising：

receiving at a network entity a grant-free transmission from a user equipment， wherein the transmission comprises a plurality of transport blocks each associated with a logic identification， and wherein the logic identification is included within， or received along with， the received transport blocks；

determining at the network entity that one of the plurality of transport blocks is missing based on the logic identification； and

scheduling retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.
The method according to claim 1， further comprising：

receiving at the network entity the retransmission comprising the missing one of the plurality of transport blocks.
The method according to claim 1， wherein the logic identification is included as part of a medium access control protocol data unit.
The method according to claim 3， wherein the logic identification is defined using a medium access control control element.
The method according to claim 1， wherein the logic identification is included in a medium access control subheader corresponding to a medium access control service data unit.
The method according to claim 1， wherein the logic identification is transmitted as part of uplink control information.
The method according to claim 1， wherein the network entity determines that one of the plurality of the transport blocks is missing based on an absolute identification associated with a slot index of the transport blocks.
The method according to claim 7， wherein the absolute identification is included in downlink control information sent from the network entity to the user equipment.
The method according to claim 7， wherein the absolute identification is determined by a slot， a mini-slot， or a subframe index of the transport blocks.
The method according to claim 1， wherein the determining by the network entity that one of the plurality of transport blocks is missing occurs when a value of the logic identification received at the network entity is not lower than an available value， wherein the value is a first value， a last value， or a middle value falling between the first value and the last value.
The method according to claim 1， wherein the determining by the network entity that one of the plurality of transport blocks is missing occurs when a last value of the logic identification received at the network entity is not a maximum available value， and when a received buffer status is not empty.
The method according to claim l， wherein the network entity configures a single value of a hybrid automatic repeat request process number that applies to both an absolute hybrid automatic repeat request process and a logic hybrid automatic repeat request process， associated with the logic identification.
A method comprising：

transmitting a grant-free transmission from a user equipment to a network entity， wherein the transmission comprises a plurality of transport blocks each associated with a logic identification， and wherein the logic identification is included within， or transmitted along with， the transport blocks；

receiving at the user equipment a request to retransmit a missing one of the plurality of transport blocks to the network entity， wherein the request is based on the logic identification； and

retransmitting the missing one of the plurality of transport blocks from the user equipment to the network entity.
The method according to claim 13， wherein the transmitting of the grant-free transmission occurs upon the arrival of a data packet at a buffer of the user equipment， wherein the transmission comprises the data packet.
The method according to claim 13， wherein the logic identification is included as part of a medium access control protocol data unit.
The method according to claim 15， wherein the logic identification is defined using a medium access control control element.
The method according to claim 13， wherein the logic identification is included in a medium access control subheader corresponding to a medium access control service data unit.
The method according to claim 13， wherein the logic identification is transmitted as part of uplink control information.
The method according to claim 13， wherein the request is determined to an absolute identification associated with a slot index of the transport blocks.
The method according to claim 19， wherein the absolute identification is determined by a slot， a mini-slot， or a subframe index of the transport blocks.
The method according to claim 19， wherein the absolute identity is included in downlink control information sent from the network entity to the user equipment.
The method according to claim 13， wherein the determining by the network entity that one of the plurality of transport blocks is missing occurs when a value of the logic identification received at the network entity is not lower than an available value， wherein the value is a first value， a last value， or a middle value falling between the first value and the last value.
The method according to claim 13， wherein the determining by the network entity that one of the plurality of transport blocks is missing occurs when a last value of the logic identification received at the network entity is not a maximum available value， and when a received buffer status is not empty.
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 at least to：

receive at a network entity a grant-free transmission from a user equipment， wherein the transmission comprises a plurality of transport blocks each associated with a logic identification， and wherein the logic identification is included within， or received along with， the received transport blocks；

determine at the network entity that one of the plurality of transport blocks is missing based on the logic identification； and

schedule retransmission of the missing one of the plurality of transport blocks from the user equipment to the network entity.
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 at least to：

transmit a grant-free transmission from a user equipment to a network entity， wherein the transmission comprises a plurality of transport blocks each associated with a logic identification， and wherein the logic identification is included within， or transmitted along with， the transport blocks；

receive a request to retransmit a missing one of the plurality of transport blocks to the network entity， wherein the request is based on the logic identification；

retransmit the missing one of the plurality of transport blocks from the user equipment to the network entity.
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 at least to perform a process， the process including the method according to any of claims 2-12 and 14-23.
A non-transitory computer-readable medium encoding instructions that， when executed in hardware， perform a process， the process including the method according to any of claims 1-23.
An apparatus comprising means for performing a process， the process including the method according to any of claims 1-23.
A computer program product encoding instructions for performing a process， the process including the method according to any of claims 1-23.
A computer program product embodied in a non-transitory computer-readable medium and encoding instructions that， when executed in hardware， perform a process， the process including the method according to any of claims 1-23.