WO2018021819A1

WO2018021819A1 - Apparatus and method for retransmission in wireless communication system

Info

Publication number: WO2018021819A1
Application number: PCT/KR2017/008043
Authority: WO
Inventors: Chen QIAN; Bin Yu; Qi XIONG; Jingxing Fu
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2016-07-27
Filing date: 2017-07-26
Publication date: 2018-02-01

Abstract

The present disclosure relates to a pre-5^th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4^th-Generation (4G) communication system such as Long Term Evolution (LTE). A method for operating a base station in a wireless communication system includes receiving, from a terminal, a signal based a grant-free transmission, and if a decoding of the signal is successful, transmitting an acknowledge (ACK) for the signal and information indicating the terminal that is identified from the signal.

Description

APPARATUS AND METHOD FOR RETRANSMISSION IN WIRELESS COMMUNICATION SYSTEM

The present disclosure relates to a wireless communication system, and in particular to a method and an apparatus for retransmission in the wireless communication system.

To meet the demand for wireless data traffic having increased since deployment of 4^th generation (4G) communication systems, efforts have been made to develop an improved 5^th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a 'Beyond 4G Network' or a 'Post Long Term Evolution (LTE) System'.

The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.

In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.

Based on the above description, the present disclosure provides an apparatus and method for effectively performing retransmissions in a wireless communication system.

Further, the present disclosure provides an apparatus and method for allowing to avoid the problem that an error occurs during detecting an acknowledgement (ACK)/negative-ACK (NACK) signal by a terminal due to a collision in a wireless communication system.

Further, the present disclosure provides an apparatus and method for performing retransmissions with consideration for a grant-free transmission based on the non-orthogonal multiple access technologies.

In accordance with an aspect of the present disclosure, a method for operating a base station in a wireless communication system includes receiving, from a terminal, a signal based a grant-free transmission, and if a decoding of the signal is successful, transmitting an acknowledge (ACK) for the signal and information indicating the terminal that is identified from the signal.

In accordance with an aspect of the present disclosure, a method for operating a terminal in a wireless communication system includes, transmitting, to a base station, a signal based a grant-free transmission, and if a decoding of the signal is successful at the base station, receiving an ACK for the signal and information indicating the terminal that is identified from the signal.

In accordance with an aspect of the present disclosure, a base station in a wireless communication system includes, a transceiver configured to receive, from a terminal, a signal based a grant-free transmission, and if a decoding of the signal is successful, transmit an ACK for the signal and information indicating the terminal that is identified from the signal.

In accordance with an aspect of the present disclosure, a terminal in a wireless communication system includes a transceiver configured to transmit a signal based a grant-free transmission to a base station, and if a decoding of the signal is successful at the base station, receiving an ACK for the signal and information indicating the terminal that is identified from the signal.

Further, the present disclosure adopts the following technical solutions.

A Hybrid Automatic Repeat Request (HARQ) transmission method is provided, comprising the following steps of:

by a base station, receiving a signal transmitted by a terminal and performing signal detection, decoding and Cyclic Redundancy Check (CRC);

determining terminal identifier information according to terminal information carried in the signal, and transmitting acknowledgement (ACK) information and the terminal identifier information, if the CRC check is successful; and

transmitting non-acknowledgement (NACK) information, or not transmitting HARQ information, if the CRC check is failed.

Preferably, the terminal identifier information is carried in an HARQ indication channel, a downlink control channel or a downlink shared channel.

Preferably, if the terminal identifier information is carried in the HARQ indication channel, during transmitting the NACK information, redundancy information having the same length as the terminal identifier information is added after the NACK information.

Preferably, the terminal identifier information is a Cell Radio Network Temporary Identifier (C-RNTI), a Serving-Temporary Mobile Subscriber Identity (S-TMSI), a terminal identifier generated according to the C-RNTI or the S-TMSI, token information allocated by the base station, or partial uplink data transmitted by the terminal.

Preferably, the number of bits of the token information is

, wherein

represents rounding up, M_max is the maximum number of terminals allocated with the same uplink transmission resources, and the uplink transmission resources comprise demodulation reference signals (DMRSs), multiple access signatures and/or time-frequency resources;

and/or, the terminal identifier information is randomly generated according to the C-RNTI or the S-TMSI, wherein the number of bits of the terminal identifier information is:

where,

is the probability of discriminating an NACK as an ACK according to the system performance requirement.

Preferably, the randomly generating the terminal identifier information comprises: generating the terminal identifier information with the aid of a pseudorandom sequence.

Preferably, the generating the terminal identifier information with the aid of a pseudorandom sequence comprises:

according to a set generator polynomial for generating an m-sequence, using the C-RNTI, or the S-TMSI, or a partial bit sequence of the C-RNTI, or a partial bit sequence of the S-TMSI as an initial state to generate the m-sequence; and clipping partial bits from the generated m-sequence to serve as the terminal identifier information;

or

according to a set generator polynomial for generating a first m-sequence, using the C-RNTI, or the S-TMSI, or a partial bit sequence of the C-RNTI, or a partial bit sequence of the S-TMSI as an initial state to generate the first m-sequence; generating a Gold sequence according to the first m-sequence and a set second m-sequence; and clipping partial bits from the generated Gold sequence to serve as the terminal identifier information;

or, according to a set generator polynomial for generating a first m-sequence, using the C-RNTI, or the S-TMSI, or a partial bit sequence of the C-RNTI, or a partial bit sequence of the S-TMSI as an initial state to generate the first m-sequence; according to a set generator polynomial for generating a second m-sequence, using the C-RNTI, or the S-TMSI, or a partial bit sequence of the C-RNTI, or a partial bit sequence of the S-TMSI as an initial state to generate the second m-sequence; generating a Gold sequence according to the first m-sequence and a set second m-sequence; and clipping partial bits from the generated Gold sequence to serve as the terminal identifier information.

Preferably, prior to the signal detection, the method comprises: performing collision detection of DMRSs; and

when the result of the collision detection of DMRSs shows that there is a collision, and if the signal does not pass the CRC check, the method comprises: by the base station, clearing a buffer of the corresponding signal, and transmitting a collision indication or a new transmission indication; when the result of the collision detection of DMRSs shows that there is no collision, and if the signal does not pass the CRC check, the method comprises: by the base station, storing the result of detection into a buffer of the corresponding signal, and transmitting a non-collision indication or a retransmission indication.

Preferably, before receiving an uplink signal transmitted by the terminal, the method comprises:

by the base station, configuring DMRSs and multiple access signatures, which are used for transmitting the uplink signal of the terminal, for the terminal through a signaling of a downlink control channel or a system high-layer signaling;

or, by the base station, configuring a resource pool used for transmitting the uplink signal of the terminal for the terminal, wherein the resource pool comprises DMRSs, multiple access signatures and/or time-frequency resources.

Preferably, the base station determines DRMSs and multiple access signatures configured to the terminal according to the monitored network load condition.

Preferably, the determining DRMSs and multiple access signatures configured to the terminal comprises:

by the base station, increasing the number of terminals configured with the same multiple access signatures and/or DMRSs, when the network load exceeds a set threshold;

and/or, in accordance with a preset lookup table, determining DMRSs and multiple access signatures configured to the terminal according to the network load condition and the corresponding multiple access signatures and/or DMRSs having the same configuration.

Preferably, before transmitting the ACK information or the NACK information, the method comprises: according to the position of a time-frequency resource bearing the signal, a multiple access signature used by the signal and a DMRS feature of the signal, determining a time-frequency resource corresponding to the HARQ indication channel of the signal; and

on the determined time-frequency resource of the HARQ indication channel, transmitting the ACK information or the NACK information.

Preferably, the time-frequency resource of the HARQ indication channel is a time-frequency resource determined by an index group

, wherein

is an HARQ indication channel group index,

is an intra-group sequence index, and the index group

is determined according to the position of the time-frequency resource bearing the signal, the multiple access signature used by the signal and the DMRS feature of the signal.

Preferably, when there is no mapping relation between DMRSs and multiple access signatures or when there is a one-to-multiple mapping relation between DMRSs and multiple access signatures, a way of determining the index group

comprises:

,

;

or,

,

;

where, I_PRB _{_RA} is an index of the time-frequency resource bearing the signal; N_MA' is the total number of available multiple access signatures on a time-frequency resource corresponding to I_PRB _{_RA} when there is no mapping relation between DMRSs and multiple access signatures, or N_MA' is the total number of multiple access signatures having a mapping relation with the same DMRS when there is a one-to-multiple mapping relation between DMRSs and multiple access signatures; n_MA' is an index of the multiple access signature used by the signal among the N_MA' multiple access signatures; N_DMRS is the number of available DMRSs on the time-frequency resource corresponding to I_{PRB_RA}; n_DMRS is a DMRS index of the DMRS used by the signal among the N_DMRS DMRSs; and

is the number of HARQ indication channel groups;

and/or,

when there is a multiple-to-one mapping relation between DMRSs and multiple access signatures, a way of determining the index group

comprises:

,

;

or,

,

;

where, I_PRB _{_RA} is an index of the time-frequency resource bearing the signal; N_MA is the total number of available multiple access signatures on a time-frequency resource corresponding to I_PRB _{_RA}; n_MA is an index of the multiple access signature used by the signal among the N_MA multiple access signatures; N_DMRS' is the number of available DMRSs corresponding to the multiple access signature used by the signal; n_DMRS' is an index of the DMRS used by the signal among the N_DMRS' DMRSs; and

is the number of HARQ indication channel groups;

and/or

when there is a one-to-one mapping relation between DMRSs and multiple access signatures, a way of determining the index group

comprises:

,

;

or,

,

;

where, I_PRB _{_RA} is an index of the time-frequency resource bearing the signal; N_MA is the total number of available multiple access signatures on a time-frequency resource corresponding to I_PRB _{_RA}; n_MA is an index of the multiple access signature used by the signal among the N_MA multiple access signatures; N_DMRS is the number of available DMRSs on the time-frequency resource corresponding to I_PRB _{_RA}; n_DMRS is a DMRS index of the DMRS used by the signal among the N_DMRS DMRSs; and

is the number of HARQ indication channel groups.

Preferably, the performing signal detection comprises:

by the base station, performing DMRS activation detection according to the signal, and detecting the signal by a multiple access signature corresponding to a DMRS which is determined to be activated.

Preferably, the DMRS activation detection comprises: performing correlation energy detection on all possible DMRSs, and determining a DMRS having the result of detection greater than a set energy detection threshold to be activated.

Preferably, if determining that the signal is retransmitted data according to the result of the signal detection, after detecting the signal and before decoding the signal, the method comprises: according to a multiple access signature corresponding to the activated DMRS, by using a mapping relation between a resource pool for new transmission and a resource pool for retransmission, determining previously-transmitted data corresponding to the retransmitted data, and combining the retransmitted data and the previously-transmitted data for decoding during the decoding process.

Preferably, for a DMRS determined to be non-activated, the base station does not transmit information on all HARQ indication channels corresponding to the non-activated DMRS, or the base station transmits NACK information on all HARQ indication channels corresponding to the non-activated DMRS;

or, for a DMRS determined to be activated, if the CRC check is failed, the base station transmits NACK information on all HARQ indication channels corresponding to the activated DMRS and transmits a retransmission indication; and, for a DMRS determined to be non-activated, the base station transmits NACK information on all HARQ indication channels corresponding to the non-activated DMRS and transmits a new transmission indication.

by a first terminal, transmitting an uplink signal to a base station;

by the first terminal, receiving HARQ information corresponding to the uplink signal on a time-frequency resource of an HARQ indication channel;

when the received HARQ information is ACK information, by the first terminal, extracting, from the information transmitted by the base station, terminal identifier information corresponding to the HARQ information; determining that the uplink signal is received correctly if the identifier information is consistent with identifier information of the first terminal; and, terminating this transmission and transmitting the uplink signal for the first time again if the identifier information is inconsistent with the identifier information of the first terminal; and

when the received HARQ information is NACK information, retransmitting the uplink signal or transmitting the uplink signal for the first time again.

Preferably, the determining that the uplink signal is received correctly comprises: delivering ACK information to a high layer, and ending this transmission;

and/or,

the transmitting the uplink signal for the first time again comprises: delivering NACK information and a new transmission request to a high layer.

Preferably, when the first terminal does not receive the HARQ information on the time-frequency resource of the HARQ indication channel, the first terminal determines the HARQ information as NACK information.

Preferably, when the received HARQ information is NACK information, the retransmitting the uplink signal or transmitting the uplink signal for the first time again comprises: detecting a collision indication or a retransmission/new transmission indication; delivering NACK information and a retransmission request to the high layer until the maximum number of transmissions is reached, if the collision indication indicates no collision or the retransmission/new transmission indication is a retransmission indication; and, delivering NACK information and a new transmission request to the high layer for indicating the high layer to transmit the uplink signal for the first time again, if the collision indication indicates a collision or the retransmission/new transmission indication is a new transmission indication;

or, when the received HARQ information is NACK information, the retransmitting the uplink signal or transmitting the uplink signal for the first time again comprises: delivering NACK information to the high layer.

Preferably, the retransmission request or the new transmission request is carried by an HARQ_RE in an HARQ process corresponding to the uplink signal.

Preferably, the transmitting, by a first terminal, an uplink signal to a base station comprises:

when there is newly-transmitted data, by an HARQ entity in the first terminal, establishing a corresponding HARQ process for the newly-transmitted data and allocating time-frequency resources, DMRSs and multiple access signatures for the HARQ process, and transmitting the allocated resources and the newly-transmitted data to the HARQ process, the HARQ process storing the allocated time-frequency resources, DMRSs and multiple access signatures; and

within each Transmission Time Interval (TTI), for each time-frequency resource for grant-free transmission, by the HARQ entity, determining an HARQ process corresponding to the time-frequency resource, transmitting the received HARQ information corresponding to the HARQ process or newly-transmitted data to a corresponding HARQ process, and indicating the corresponding HARQ process to perform retransmission or new transmission, wherein the DMRSs and multiple access signatures stored by the HARQ process are used for distinguishing whether the HARQ information transmitted to the HARQ process by the HARQ entity belongs to the HARQ process, and the HARQ entity is used for maintaining multiple of parallel HARQ processes.

Preferably, the allocating time-frequency resources, DMRSs and multiple access signatures for the HARQ process comprises: according to the configuration of a command of the downlink control channel or a system high-layer signaling, determining DMRSs and multiple access signatures allocated for the first terminal, and using the DMRSs and multiple access signatures as DMRSs and multiple access signatures for transmitting the uplink signal, and randomly selecting time-frequency resources from available time-frequency resources in a time-frequency resource pool set for the first terminal by the base station; or, randomly selecting multiple access signatures and DMRSs from available resources in a resource pool configured for the first terminal by the base station in an equal probability manner, and randomly selecting time-frequency resources from available resources in the configured resource pool;

and/or

the transmitting, by the HARQ entity, the HARQ information or newly-transmitted data to a HARQ process and indicating the corresponding HARQ process to perform retransmission or new transmission comprises: according to a mapping relation between new transmission resources and retransmission resources, determining whether each time-frequency resource belongs to a new transmission time-frequency resource or a retransmission time-frequency resource of the HARQ process; if it is determined that the each time-frequency resource belongs to a retransmission time-frequency resource, selecting retransmission resources for the corresponding HARQ process according to the mapping relation, transmitting the selected resource and HARQ information to the HARQ process, and indicating the corresponding HARQ process to initiate retransmission; and, if it is determined that the each time-frequency resource belongs to a new transmission time-frequency resource of the HARQ process, transmitting the newly-transmitted data to the HARQ process, and indicating the HARQ process to use the stored resources to initiate new transmission.

Preferably, the selecting retransmission resources for the HARQ process according to the mapping relation comprises: selecting time-frequency resources for retransmission for the HARQ process according to the mapping relation; and, using the stored DMRSs and multiple access signatures and the received time-frequency resources for retransmission when the HARQ process initiates data retransmission;

or, the selecting retransmission resources for the HARQ process according to the mapping relation comprises: selecting time-frequency resources for retransmission, DMRSs and multiple access signatures for the HARQ process according to the mapping relation; and using the received time-frequency resources for retransmission, DMRSs and multiple access signatures when the HARQ process initiates data retransmission.

Preferably, the available resources are time-frequency resources, DMRSs and multiple access signatures, which are not used for newly transmitting and retransmitting data by the HARQ entity;

and/or, the available time-frequency resources are time-frequency resources which are not used for newly transmitting and retransmitting data by the HARQ entity.

Preferably, when the retransmission indication received by the HARQ entity shows that no retransmission is needed or the maximum number of retransmissions has been reached, the HARQ entity extracts data in a data buffer from the corresponding HARQ process, releases the resources allocated for the HARQ process, and resets the HARQ process.

Preferably, a way of determining a time-frequency resource of the HARQ indication channel comprises: according to the position of a time-frequency resource bearing the signal, a multiple access signature used by the signal and a DMRS feature of the signal, determining a time-frequency resource corresponding to the HARQ indication channel of the signal.

, wherein

is an HARQ indication channel group index,

is an intra-group sequence index, and the index group

comprises:

, ;

or,

,

;

where, I_PRB _{_RA}is an index of the time-frequency resource bearing the signal; N_MA' is the total number of available multiple access signatures on a time-frequency resource corresponding to I_PRB _{_RA} when there is no mapping relation between DMRSs and multiple access signatures, or N_MA' is the total number of multiple access signatures having a mapping relation with the same DMRS when there is a one-to-multiple mapping relation between DMRSs and multiple access signatures; n_MA' is an index of the multiple access signature used by the signal among the N_MA' multiple access signatures; N_DMRS is the number of available DMRSs on the time-frequency resource corresponding to I_PRB _{_RA}; n_DMRS is a DMRS index of the DMRS used by the signal among the N_DMRS DMRSs; and

is the number of HARQ indication channel groups;

and/or,

comprises:

,

;

or,

,

;

is the number of HARQ indication channel groups;

and/or,

comprises:

,

;

or,

,

;

is the number of HARQ indication channel groups.

A Hybrid Automatic Repeat Request (HARQ) transmission apparatus is provided, comprising: a signal detection unit and a transmitting unit;

the signal detection unit is configured to receive a signal transmitted by a terminal and perform signal detection, decoding and CRC check; and

the transmitting unit is configured to determine terminal identifier information according to terminal information carried in the signal and transmit acknowledgement (ACK) information and the terminal identifier information when the signal detection unit determines that the CRC check is successful; and further configured to transmit non-acknowledgement (NACK) information or not transmit HARQ information when the signal detection unit determines that the CRC check is failed.

A Hybrid Automatic Repeat Request (HARQ) transmission apparatus is provided, comprising: a transmitting unit and a receiving unit;

the transmitting unit is configured to transmit an uplink signal to a base station; and

the receiving unit is configured to receive HARQ information corresponding to the uplink signal on a time-frequency resource of an HARQ indication channel; extract, from the information transmitted by the base station, terminal identifier information corresponding to the HARQ information when the received HARQ information is ACK information; determine that the uplink signal is received correctly if the identifier information is consistent with identifier information of the first terminal; terminate this transmission and transmit the uplink signal for the first time again if the identifier information is inconsistent with the identifier information of the first terminal; and, retransmit the uplink signal or transmit the uplink signal for the first time again when the received HARQ information is NACK information.

It can be seen from the above technical solutions that, in the present application, the base station also transmits the terminal identifier information while transmitting the ACK information; upon receiving the ACK information, the terminal extracts the terminal identifier information; if the extracted identifier information is consistent with the identifier information of this terminal, it is determined that the data is received correctly, or the uplink signal transmitted previously will be transmitted for the first time again. In this way, by transmitting the ID information of the terminal while transmitting the ACK signal, the problem that an error occurs during detecting an ACK/NACK signal by a terminal due to a collision can be avoided; in addition, after the terminal has received the ACK signal and has found that the ID information of the terminal is not matched, a new transmission will be directly initiated, so that the problem that the retransmission cannot improve the reliability of data transmission in this case is avoided.

In addition, preferably, when the base station and the terminal determine the position of an HARQ indication channel according to the position of the time-frequency resource bearing the uplink signal, the multiple access signature used by the uplink signal and the DMRS feature of the uplink signal; in comparison to the existing way of determining the position of the HARQ indication channel according to the lowest index of the uplink resource blocks and the cyclic shift of the used DMR, the same uplink physical resource block can be corresponding to positions of more HARQ indication channels, so more users can multiplex the same physical resource block.

An apparatus and method according to various embodiments of the present disclosure enables effectively support retransmission for a grant-free transmission by transmitting acknowledgement (ACK)/negative-ACK (NACK) information with an identifier of a terminal.

The effects obtainable by the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned herein will be clearly understood by those skilled in the art from the following description.

FIG. 1 illustrates a wireless communication system according to various embodiments of the present disclosure;

FIG. 2 illustrates a configuration of a base station in a wireless communication system according to various embodiments of the present disclosure;

FIG. 3 illustrates a configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure;

FIG. 4 illustrates a coding process of hybrid automatic repeat request (HARQ) indication information according to various embodiments of the present disclosure;

FIG. 5 illustrates examples of mapping of a physical HARQ indicator channel (PHICH) time-frequency resource according to various embodiments of the present disclosure;

FIG. 6 illustrates a mapping relation between a resource pool for new transmission and a resource pool for retransmission according to various embodiments of the present disclosure;

FIG. 7 illustrates a uplink transmission data structure according to various embodiments of the present disclosure;

FIG. 8 illustrates a flowchart of an HARQ transmission method according to various embodiments of the present disclosure;

FIG. 9 illustrates information bits of an HARQ indication channel according to various embodiments of the present disclosure;

FIG. 10 illustrates a flow of information processing of an HARQ indication channel according to various embodiments of the present disclosure;

FIGS. 11A and 11B illustrate allocation modes of time-frequency resource indexes according to various embodiments of the present disclosure;

FIG. 12 illustrates a token bit allocation mode according to various embodiments of the present disclosure;

FIG. 13 illustrates determining a terminal identifier by using an m-sequence according to various embodiments of the present disclosure;

FIG. 14 illustrates generating a terminal identifier by using a Gold sequence according to various embodiments of the present disclosure;

FIG. 15 illustrates a collision detection threshold and a energy detection threshold according to various embodiments of the present disclosure;

FIG. 16 illustrates a flowchart of a terminal according to various embodiments of the present disclosure;

FIG. 17 illustrates another flowchart of another terminal according to various embodiments of the present disclosure;

FIG. 18 illustrates a structure of a HARQ transmission apparatus according to various embodiments of the present disclosure; and

FIG. 19 illustrates another structure of a HARQ transmission apparatus according to various embodiments of the present disclosure.

The terms used in the present disclosure are only used to describe specific embodiments, and are not intended to limit the present disclosure. As used herein, singular forms may include plural forms as well unless the context clearly indicates otherwise. Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meanings as those commonly understood by a person skilled in the art to which the present disclosure pertains. Such terms as those defined in a generally used dictionary may be interpreted as having the meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted as having ideal or excessively formal meanings unless clearly defined in the present disclosure. In some cases, even terms defined in the present disclosure should not be interpreted as excluding embodiments of the present disclosure.

Hereinafter, various embodiments of the present disclosure will be described from the perspective of hardware. However, various embodiments of the present disclosure include a technology that uses both hardware and software, and thus the various embodiments of the present disclosure may not exclude the perspective of software.

Hereinafter, the present disclosure relates to an apparatus and method for retransmission in a wireless communication system. Specifically, the present disclosure describes a technique for performing a retransmission for a grant-free transmission in a wireless communication system.

Terms used in the following descriptions, such as a term referring to a signal, a term referring to a channel, a term referring to control information, a term referring to resources, a term referring to network entities, and a term referring to an element of a device, are used for convenience of explanation. Accordingly, the present disclosure is not limited to the following terms, and other terms having an equivalent technical meaning may be used.

Further, the present disclosure describes various embodiments using terms used in some communication standards (e.g., 3rd Generation Partnership Project (3GPP)), but this merely corresponds to an example for explanation. Various embodiments of the present disclosure may be easily modified and applied to other communication systems as well.

FIG. 1 illustrates a wireless communication system according to various embodiments of the present disclosure. FIG. 1 illustrates a base station 110, a terminal 120, and a terminal 130, as a part of nodes using a wireless channel in a wireless communication system. FIG. 1 illustrates only one base station, but may further include another base station that is identical or similar to the base station 110.

The base station 110 is a network infrastructure that provides the

terminals

120 and 130 with wireless access. The base station 110 has a coverage defined by a predetermined geographic area based on the distance over which a signal may be transmitted. The base station 110 may be referred to as an "access point (AP)", an "eNodeB (eNB)", a "5th generation node (5G node)", a "wireless point", a "transmission/reception point (TRP)", or other terms having an equivalent technical meaning.

Each of the terminal 120 and the terminal 130 is an apparatus used by a user, and performs communication with the base station 110 through a wireless channel. In some cases, at least one of the terminal 120 and the terminal 130 may be operated without user involvement. That is, at least one of the terminal 120 and the terminal 130 is an apparatus that performs machine-type communication (MTC), and may not be carried by a user. Each of the terminal 120 and the terminal 130 may be referred to as a "user equipment (UE)", a "mobile station", a "subscriber station", a "remote terminal", a "wireless terminal", a "user device", or other terms having an equivalent technical meaning.

The base station 110, the terminal 120, and the terminal 130 may transmit and receive a radio signal in a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, or 60 GHz). At this time, in order to improve a channel gain, the base station 110, the terminal 120, and the terminal 130 may perform beamforming. Here, the beamforming may include transmission beamforming and reception beamforming. That is, the base station 110, the terminal 120, and the terminal 130 may assign directivity to a transmission signal or a reception signal. To this end, the base station 110 and the

terminals

120 and 130 may select serving

beams

112, 113, 121, and 131 through a beam search or a beam management procedure. After the serving

beams

112, 113, 121, and 131 are selected, subsequent communication may be performed through a resource in a quasi co-located (QCL) relationship with a resource for transmission of the serving

beams

112, 113, 121, and 131.

FIG. 2 illustrates a configuration of a base station in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 2 may be understood as a configuration of the base station 110. The terms "... unit", "... device", etc. used below refer to a unit for processing at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Referring to FIG. 2, the base station may include a wireless communication unit 210, a backhaul communication unit 220, a storage unit 120, and a control unit 240.

The wireless communication unit 210 performs functions for transmitting or receiving a signal through a wireless channel. For example, the wireless communication unit 210 performs conversion between a baseband signal and a bit string according to the physical layer standard of the system. For example, when data is transmitted, the wireless communication unit 210 generates complex symbols by encoding and modulating a transmission bit string. Further, when data is received, the wireless communication unit 210 restores a reception bit string by demodulating and decoding a baseband signal. In addition, the wireless communication unit 210 up-converts a baseband signal to a radio frequency (RF) band signal, transmits the up-converted signal through an antenna, and down-converts an RF band signal received through the antenna to a baseband signal.

To this end, the wireless communication unit 210 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like. In addition, the wireless communication unit 210 may include a plurality of transmission/reception paths. Further, the wireless communication unit 210 may include at least one antenna array including a plurality of antenna elements. In terms of hardware, the wireless communication unit 210 may include a digital unit and an analog unit, and the analog unit may include a plurality of sub-units according to an operation power, an operation frequency, and the like.

As described above, the wireless communication unit 210 transmits and receives a signal. Accordingly, all or a part of the wireless communication unit 210 may be referred to as a "transmitter", a "receiver", or a "transceiver". In addition, in the following description, the meaning of transmission and reception performed through a wireless channel includes performing of processing, such as that described above, by the wireless communication unit 210.

The backhaul communication unit 220 provides an interface for performing communication with other nodes within a network. That is, the backhaul communication unit 220 converts a bit string transmitted from the base station to another node, for example, another access node, another base station, an upper node, a core network, etc., into a physical signal, and converts a physical signal received from another node into a bit string.

The storage unit 230 stores data, such as a basic program for operation of the base station, an application program, and configuration information. The storage unit 230 may include a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. Further, the storage unit 230 provides stored data in response to a request from the control unit 240.

The control unit 240 controls the overall operation of the base station. For example, the control unit 240 transmits and receives a signal through the wireless communication unit 210 or through the backhaul communication unit 220. In addition, the control unit 240 records data in the storage unit 230 and reads the data. Further, the control unit 240 may perform functions of a protocol stack required by the communication standard. To this end, the control unit 240 may include at least one processor.

According to various embodiments, the control unit 240 supports retransmissions for a terminal performing a grant-free transmission. For example, the control unit 240 controls to receive, from a terminal, a signal based a grant-free transmission, and if a decoding of the signal is successful, transmit an acknowledge (ACK) for the signal and information indicating the terminal that is identified from the signal. For example, the control unit 240 may control the base station to perform operations according to various embodiments described below.

FIG. 3 illustrates a configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 3 may be understood as a configuration of the terminal 120. The terms "... unit", "... device", etc. used below refer to a unit for processing at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Referring to FIG. 3, the terminal includes a communication unit 310, a storage unit 320, and a control unit 330.

The communication unit 310 performs functions for transmitting or receiving a signal through a wireless channel. For example, the communication unit 310 performs conversion between a baseband signal and a bit string according to the physical layer standard of the system. For example, when data is transmitted, the communication unit 310 generates complex symbols by encoding and modulating a transmission bit string. Further, when data is received, the communication unit 310 restores a reception bit string by demodulating and decoding a baseband signal. In addition, the communication unit 310 up-converts a baseband signal to an RF band signal, transmits the up-converted signal through an antenna, and down-converts an RF band signal received through the antenna to a baseband signal. For example, the communication unit 310 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like.

In addition, the communication unit 310 may include a plurality of transmission/reception paths. Further, the communication unit 310 may include at least one antenna array including a plurality of antenna elements. In terms of hardware, the communication unit 310 may include a digital circuit and an analog circuit (e.g., a radio frequency integrated circuit (RFIC)). Here, the digital circuit and the analog circuit may be implemented as a single package. In addition, the communication unit 310 may include a plurality of RF chains. Furthermore, the communication unit 310 may perform beamforming.

As described above, the communication unit 310 transmits and receives a signal. Accordingly, all or a part of the communication unit 310 may be referred to as a "transmitter", a "receiver", or a "transceiver". In addition, in the following description, the meaning of transmission and reception performed through a wireless channel includes performing of processing, such as that described above, by the communication unit 310.

The storage unit 320 stores data, such as a basic program for operation of the terminal, an application program, and configuration information. The storage unit 320 may include a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. Further, the storage unit 320 provides stored data in response to a request from the control unit 330.

The control unit 330 controls the overall operation of the terminal. For example, the control unit 330 transmits and receives a signal through the communication unit 310. In addition, the control unit 330 records data in the storage unit 320 and reads the data. Further, the control unit 330 may perform functions of a protocol stack required by the communication standard. To this end, the control unit 330 may include at least one processor or a microprocessor, or may be part of a processor. Further, the control unit 330 and a part of the communication unit 310 may be referred to as a communication processor (CP).

According to various embodiments, the control unit 330 may control to perform a grant-free transmission, and perform a retransmission for the grant-free transmission. The control unit 330 may control to transmit, to a base station, a signal based a grant-free transmission, and if a decoding of the signal is successful at the base station, receive an ACK for the signal and information indicating the terminal that is identified from the signal. For example, the control unit 330 may control the terminal to perform operations according to various embodiments described below.

The rapid development of information industry, particularly the increasing demand from the mobile Internet and the Internet of Things (IoT), brings about unprecedented challenges in the future mobile communications technology. According to the ITU-R M.[IMT. BEYOND 2020. TRAFFIC] issued by the International Telecommunication Union (ITU), it may be expected that, by 2020, mobile services traffic will grow nearly 1,000 times as compared with that in 2010 (4G era), and the number of user device connections will also be over 17 billion, and with a vast number of IoT devices gradually expand into the mobile communication network, the number of connected devices will be even more astonishing. In response to this unprecedented challenge, the communications industry and academia have prepared for 2020s by launching an extensive study of the fifth-generation mobile communications technology (5G). Currently, in ITU-R M.[IMT.VISION] from ITU, the framework and overall objectives of the future 5G have been discussed, where the demands outlook, application scenarios and various important performance indexes of 5G have been described in detail. In terms of new demands in 5G, the ITU-R M.[IMT. FUTURE TECHNOLOGY TRENDS] from ITU provides information related to the 5G technology trends, which is intended to address prominent issues such as significant improvement on system throughput, consistency of the user experience, scalability to support IoT, time delay, energy efficiency, cost, network flexibility, support for emerging services and flexible spectrum utilization, etc.

The demand of supporting massive Machine-Type Communication (mMTC) is proposed for 5G. The connection density will reach millions of connections per square kilometer, considerably higher than the link density supported by the existing standards. The existing orthogonal multiple access modes, for example, orthogonal frequency division multiple access (OFDMA), cannot satisfy the demand of millions of connections to be achieved by mMTC in 5G. To improve the capacity of the multiple access technology, some non-orthogonal multiple access (NoMA) technologies have been proposed, and discussed as the potential 5G key technologies in the 3GPP standard conferences. Among those technologies, CDMA-based access modes such as Sparse code multiple access (SCMA), pattern defined multiple access (PDMA) and multi-user shared access (MUSA), and interleaving-based access modes such as interleave division multiple access (IDMA) and interleave-grid multiple access (IGMA), are included. When compared with the orthogonal multiple access modes, by using non-orthogonal access resources, for example, non-orthogonal codebooks, interleaved sequences or more, those access technologies may allow more users to access on the limited time-frequency resources, so that the number of apparatuses connected in a unit area is significantly increased, and the demands of massive scenarios in 5G are satisfied.

To reduce the signaling overhead in the mMTC scenarios, the grant-free transmission becomes an importance part of the 5G researches. During the grant-free transmission, original scheduling requests (SRs) of the LTE or even the random access process may be skipped. When a user needs to transmit data, the uplink data is transmitted directly on a specified time-frequency resource using a random or system-configured multiple access signature. This transmission mode may effectively reduce the signaling overhead, but may cause collisions. In other words, different users select a same multiple access signature or a reference signal for data transmission, so that the BER performance of the uplink data is degraded.

The hybrid automatic repeat request (HARQ) is an important means for ensuring the reliability of data transmission in the LTE. During the grant-free transmission, the HARQ may also be used for improving the reliability of data transmission when a resource collision occurs. The HARQ feedback in the LTE-A is transmitted by a Physical Hybrid ARQ Channel (PHICH), and the transmission content is an ACK or non-ACK (NACK) indication transmitted by the uplink data. The HARQ information is indicated by 1-bit data, where 0 may represent ACK and 1 may represent NACK. The coding process of the HARQ indication information is as shown in FIG. 4. FIG. 4 illustrates a coding process of HARQ indication information. Referring FIG. 4, the 1-bit data 402 is modulated by a BPSK modulation mode and is repeated for three times. Each of repeated BPSK symbols 404 is spread by a Walsh spreading code having a length of 4 so as to obtain symbol data 406 having a length of 12.

Considering that there are eight manually orthogonal sequences which may be generated by multiple of Walsh spread sequences each having a length of 4 is 8, there are eight users who may be multiplexed on PHICHs on the same time-frequency resources. To reduce the inter-cell interference, scrambling based on cell IDs is performed on the symbol sequence having a length of 12. FIG. 5 illustrates examples of mapping of a PHICH time-frequency resource. Referring FIG. 5, the PHICH channel may occupy one to three OFDM symbols in the downlink subframe.

Through the spreading of the orthogonal Walsh sequence, multiple of PHICHs may be multiplexed on the same time-frequency resources to form a PHICH group, and different PHICHs in the PHICH group are distinguished by PHICH indexes. In the LTE, the PHICH group and the PHICH indexes are determined by the lowest index of resource blocks of a corresponding physical uplink shared channel and the cyclic shift of a demodulation reference signal (DMRS). According to the lowest index of the resource blocks of the physical uplink shared channel allocated to a user and the cyclic shift of the used DMRS, the user calculates a PHICH group and an intra-group PHICH index corresponding to this uplink transmission, so as to determine the physical time-frequency resource of the PHICH and the used spreading code. Accordingly, the ACK/NACK information of this uplink transmission is obtained by decoding, and retransmission is authorized or the next transmission of uplink data is started according to the uplink data transmission.

For the grant-free transmission based on the non-orthogonal multiple access technologies, the HARQ transmission mode in the existing LTE-A cannot effectively solve the problem of retransmission indication. First, for a massive access scenario in 5G, as the number of access users borne on a same time-frequency resource is greater than that in a typical scenario in the LTE-A, the ACK/NACK information of more terminals needs to be multiplexed on the same physical resource blocks, and the mapping mode of the PHICH in the LTE-A needs to be further enhanced; second, for the grant-free transmission, as the transmission mode of the HARQ and the resource mapping mode in the LTE-A are still used in the possible case of DMRSs collision with multiple access signatures, a user using the same multiple access signature and DMRS cannot distinguish whether the ACK or NACK signal corresponds to the uplink resource transmission of this user, so that the retransmission efficiency is reduced or even the reliability of data transmission of the user is reduced; finally, in the case of a resource collision, it is difficult to combine retransmitted and received data of different redundancy versions.

As aforementioned, existing HARQ transmission methods have many problems on the grant-free transmission based on non-orthogonal multiple access technologies. On this basis, the present disclosure provides an HARQ transmission method, which may allow more users to be multiplexed on the same uplink physical resource blocks. The HARQ transmission method is suitable for various existing transmission scenarios, for example, LTE, LTE-A and etc., and also is suitable for massive connection scenarios, for example, 5G scenarios. The HARQ transmission method is particularly suitable for the grant-free transmission based on non-orthogonal multiple access technologies. The HARQ transmission method provided by the present disclosure will be described below by taking a grant-free transmission scenario as an example.

The grant-free transmission will be described first. In accordance with the allocation and selection mode of resources, the grant-free transmission may be classified into the following two categories.

First, a base station configures multiple access signatures and/or DMRSs of a terminal and/or time-frequency resources for transmission through a signaling in a downlink control channel or a system high-layer signaling, and the terminal uses the configured multiple access signatures, DMRSs and/or time-frequency resources to directly transmit data when the terminal needs to transmit data, without requesting an unlink grant.

Wherein, preferably, the base station may configure multiple access signatures and DMRSs for the terminal through a signaling, and set time-frequency resources for grant-free transmission. When the terminal needs to transmit data, the terminal selects a grant-free time-frequency resource for this transmission from the set time-frequency resources and uses the configured multiple access signatures and DMRSs on the selected time-frequency resource for transmitting data.

In this way, the terminal has already completed uplink synchronization and access through random access or other processes, has obtained the terminal ID or other information, and is now in an RRC connected state. After the uplink synchronization and access have been completed, the base station allocates multiple access signatures and/or DMRSs for the terminal through the signaling in the downlink control channel or the system high-layer signaling. The base station may allocate the same multiple access signatures and/or DMRSs for different terminals. After the resources have been allocated, the terminal will continuously use the allocated multiple access signatures and DMRSs on the specified time-frequency resource to transmit uplink data. If the terminal has completed the transmission of uplink data and entered an idle state from the RRC connected state, the terminal informs the base station through an uplink control channel or an uplink shared channel, and then the base station releases the multiple access signatures and DMRSs allocated to the terminal.

The base station may also allocate periodic time-frequency resources for the terminal. When the terminal needs to transmit data, that is, when the terminal transmits the data for the first time, that is, as an initialization transmission, the terminal randomly selects from the time-frequency resources allocated by the base station and then transmits the data. For the retransmission of data, the time-frequency resources allocated to the terminal may be classified into time-frequency resources for new transmission and time-frequency resources for retransmission, and then a mapping relation is established between the time-frequency resources for new transmission and the time-frequency resources for retransmission. During allocating the time-frequency resources for retransmission, a time-frequency resource for this retransmission is selected from the time-frequency resources allocated by the base station according to the mapping relation.

The base station continuously monitors the network load condition. For the DMRSs and multiple access signatures configured to the terminal by the base station, the base station may adjust the allocation of the multiple access signatures and the allocation of the DMRSs according to the monitored network load condition. For example, if the base station finds that the network load becomes high, the same multiple access signatures and DMRSs may be allocated to more users; and if the base station finds that the network load becomes low, the same multiple access signatures and DMRSs may be allocated to fewer users. In other words, preferably, if the network load is high, the same multiple access signatures and/or DMRSs may be allocated to more terminals. The base station may change the allocated multiple access signatures and DMRSs according to the change in the network load condition, and then inform the terminal of the change condition of the allocated resources through the downlink control channel or the high-layer signaling; subsequently, the terminal monitors the notification of the downlink control channel or the high-layer signaling, then releases the original resources when the allocated resources change, and uses new resources for transmission.

In this way, the base station may control the probability of terminal collision, and adjust the probability of terminal collision according to the network load condition. Preferably, when the network load exceeds a set threshold, the base station may increase the number of terminals allocated with the same multiple access signatures and/or DMRSs; and, in accordance with a preset lookup table, the base station may also determine DMRSs and multiple access signatures configured for a terminal according to the network load condition and the corresponding multiple access signatures and/or DMRSs having the same configuration. For example, if the network load is high, the probability of terminal collision may be increased through resource allocation, so that the number of the support terminals is ensured. If the network load is low, the probability of terminal collision may be decreased through resource allocation, so that the quality of data transmission of loads in the network is ensured.

Second, a base station allocates a resource pool for the grant-free transmission. Wherein, the resource pool includes multiple access signatures, DMRSs and time-frequency resources. When a terminal needs to transmit data, the terminal randomly selects multiple access signatures and DMRSs from the resource pool in an equal probability manner, and then randomly selects a time-frequency resource for transmitting uplink data.

In this case, the base station configures a resource pool for the terminal for grant-free transmission, and informs the terminal through a broadcast channel, system information in a downlink control channel or a high-layer signaling. The resources in the resource pool include, but are not limited to, time-frequency resources, multiple access signatures and DMRS resources. When the terminal transmits uplink data, the terminal randomly selects uplink transmission resources (including time-frequency resources, multiple access signatures and DMRSs) from the resource pool configured by the base station in an equal probability manner, then processes the uplink transmission data on the selected time-frequency resource according to the selected multiple access signatures, and then inserts the selected DMRSs for transmitting the uplink data. This way is suitable for a terminal which is in the idle state or has completed the uplink access and is now in the RRC connected state. In other words, no matter whether the terminal has completed the uplink access, the uplink data may be transmitted as long as the terminal has completed downlink synchronization and obtained part of system information.

To distinguish newly-transmitted data from retransmitted data and establish a relation between the newly-transmitted data and the retransmitted data, it is also possible to distinguish a resource pool for the newly-transmitted data and a resource pool for the retransmitted data and meanwhile establish a mapping relation between corresponding resources, as shown in FIG. 6.

FIG. 6 illustrates a mapping relation between a resource pool for new transmission and a resource pool for retransmission according to various embodiments of the present disclosure. Referring FIG. 6, each of the resource pools 610, 620-1 to 620-K is divided into N_max sub resource pools which are not interacted with each other and separately used for the newly-transmitted data and the retransmitted data. Wherein, the N_max is the maximum number of transmissions. There is a mapping relation between resources in each of resource pools 610, 620-1 to 620-K. In the example shown in FIG. 6, the number of resources in each of the resource pools 610, 620-1 to 620-K for each transmission is the same, and there is a one-to-one mapping relation between the resources in the resource pool for each transmission. If the terminal selects resource k in the resource pool 610 for new transmission during the first time of data transmission and if it is required to perform retransmission, the terminal will select, from the corresponding resource pool 620-1 for retransmission, a corresponding resource k' having the one-one-one mapping relation with the resource k. Wherein, the resources include multiple access signatures, DMRSs and/or time-frequency resources.

The mapping mode between the resource pool 610 for the newly-transmitted data and the resource pool 620-1 for the retransmitted data is not limited to the one-to-one mapping mode shown in FIG. 6. For example, there may be a one-to-multiple mapping or multiple-to-multiple mapping between the resource pools, the classification of new transmission resources and retransmission resources of a user may also be realized, but it is required to ensure that a retransmission resource for the n^th retransmission may find a unique corresponding resource for the previous transmission.

For the grant-free transmission, the base station does not transmit an uplink grant for the terminal and also does not allocate any time-frequency resource for the uplink transmission. Therefore it is unable to realize distinguishing of the source of uplink data with respect to the allocated time-frequency resources, as realized in the LTE-A by authorization. To be convenient for the base station to determine the source of the uplink data, the terminal may attach the terminal ID information in the data while transmitting the uplink data. A possible data structure for grant-free uplink transmission is as shown in FIG. 7.

FIG. 7 illustrates a uplink transmission data structure according to various embodiments of the present disclosure. Referring FIG. 7, the terminal identifier (ID) information 710 is inserted prior to the uplink data 720. The terminal ID information 710 may also be inserted behind the uplink data 720 or in the middle of the uplink data 720. If the uplink data 720, which has experienced detection and decoding, passes the CRC check, the base station may know which terminal the uplink data is from, through the terminal ID information710.

In addition, there may be or not be a mapping relation between DMRSs and multiple access signatures in the system. If there is a mapping relation between DMRSs and multiple access signatures, a selection range of the multiple access signatures may be determined by selecting the DMRSs. For example, if there is a one-to-one mapping relation between the DMRSs and the multiple access signatures, the selection of the DMRSs is equivalent to the selection of corresponding multiple access signatures, and the base station may also know the use of the multiple access signatures by detecting the DMRSs. When there is a multiple-to-one mapping relation between the DMRSs and the multiple access signatures, that is, different DMRSs may be mapped to a same multiple access signature, the base station may also know the use of the multiple access signatures by detecting the DMRSs. This way is usually used for a scenario where there are many DMRS resources and there are more DMRS resources than multiple access signatures. When there is a one-to-multiple mapping relation between the DMRSs and the multiple access signatures, that is, a same DMRS may be mapped to different multiple access signatures, the base station may know a range of the multiple access signatures by detecting the DMRSs. This way is usually used for a scenario where there are many multiple access signatures and there are more multiple access signatures than DMRSs.

Next, the HARQ transmission method provided by the present disclosure will be described. The HARQ transmission method provided by the present invention includes two types: one is processing on the base station side, while the other is processing on the terminal side. For ease of description, the processing on the base station side and the processing on the terminal side will be described together below.

FIG. 8 illustrates a flowchart of an HARQ transmission method according to various embodiments of the present disclosure.

Referring FIG. 8, at step 801, a terminal transmits an uplink signal to a base station. In this step, the terminal may transmit the uplink signal in the grant-free transmission manner as described above. Specifically, multiple access signatures and/or DMRSs are randomly selected in an equal probability manner according to a resource pool configured by the base station; or, the terminal may also transmit uplink data according to the multiple access signatures and/or DMRSs configured by the base station through a signaling in a downlink control channel or a system high-layer signaling. Wherein, the transmitted uplink data contains terminal ID information.

At step 802, the base station receives the uplink signal, and performs signal detection, decoding and CRC check on the uplink signal.

At step 803, the base station determines terminal identifier information according to the terminal information carried in the uplink signal, and ACK information and the terminal identifier information are transmitted on a time-frequency resource of an HARQ indication channel corresponding to the uplink signal, if the CRC check is successful. In the present disclosure, after the CRC check is successful, it is determined that the data is received correctly. Considering that different terminals may use the same uplink resources, the identifier (ID) information of the terminal is also fed back to the terminal while feeding back the ACK information. Wherein, the terminal identifier information may be determined according to the terminal information carried in the uplink signal.

At step 804, NACK information is transmitted on the time-frequency resource of the HARQ indication channel corresponding to the uplink signal, or no HARQ information is transmitted, if the CRC check is failed.

At step 805, the terminal receives HARQ information corresponding to the uplink signal on the time-frequency resource of the HARQ indication channel, at step 806 will be executed when the received information is ACK information, and at step 807 will be executed when the received information is NACK information.

At step 806, the terminal extracts the terminal identifier information corresponding to the HARQ information from the information transmitted by the base station; it is determined that the uplink signal is received correctly if the identifier information is consistent with the identifier information of this terminal; or, this transmission is ended, and the uplink signal is transmitted for the first time again. When the transmission mode is grant-free transmission, if the terminal detects the ACK and the terminal ID information on the time-frequency resource or carried in the downlink control channel or downlink shared channel is matched with the ID information of this terminal, it is indicated that the base station correctly receives the uplink data information, and this uplink data transmission is completed correctly. If the ACK is detected and the terminal ID information on the time-frequency resource or carried in the downlink control channel or downlink shared channel is not matched with the ID information of this terminal, it is indicated that a resource or DMRS collision occurs during this uplink data transmission, so that the terminal reselects uplink resources (it is possible to reselect multiple access signatures, DMRSs and time-frequency resources, or it is also possible to reselect time-frequency resource only) to initiate the transmission of uplink data (i.e., transmit the uplink data for the first time again).

At step 807, the terminal retransmits the uplink signal or transmits the uplink signal for the first time again. If the terminal detects the NACK, the terminal may adopt an existing processing mode, i.e., use a new redundancy version (RV) and the specified multiple access signatures and DMRSs for retransmission, and count the number of retransmissions. If the number of retransmissions is greater than the maximum number of retransmission set by the system, this uplink transmission is failed, and the terminal will return the count of the number of retransmissions to zero, reselect multiple access signatures and DMRSs, and re-initiate the transmission of uplink data.

So far, the basic HARQ transmission flow shown in FIG. 8 in the present disclosure ends. Wherein, steps 801, 805, 806 and 807 constitute the HARQ transmission method on the terminal side in the present disclosure, while

steps

802, 803 and 804 constitute the HARQ transmission method on the base station side in the present disclosure. By the basic HARQ transmission method, when multiple of terminals share the same uplink resources for grant-free transmission, a terminal corresponding to the ACK information still may be distinguished, so that the retransmission efficiency and the reliability of data transmission of users are improved.

Based on the basic transmission method as aforementioned, preferably, the base station and the terminal may perform the following processing.

First, before transmitting the ACK information or the NACK information, by the base station, the position of the HARQ indication channel corresponding to the uplink signal is determined according to the position of a time-frequency resource bearing the uplink signal, a multiple access signature used by the uplink signal and a DMRS feature, and the ACK information or NACK information determined according to the result of the CRC check is transmitted at the determined position.

In the present disclosure, the position of the HARQ indication channel is determined according to the position of the time-frequency resource bearing the uplink signal, the multiple access signature used by the signal and the DMRS feature. In comparison with the existing way of determining the position of the PHICH according to an index of a time-frequency resource and a cyclic shift of a DMRS, the way in the present disclosure may give more combinations to determine the position of the HARQ indication channel. Particularly, there may be more combinations of multiple access signatures and DMRSs corresponding to the same time-frequency resource, so that more users may be supported. Accordingly, more users are allowed to be multiplexed on the same uplink physical resources.

Second, during determining the position of an HARQ indication channel, by the terminal, the position of the HARQ indication channel corresponding to the uplink signal is determined according to the position of the time-frequency resource bearing the uplink signal, the multiple access signature used by the uplink signal and the DMRS feature, and HARQ (ACK/NACK) information is detected at the determined position of the HARQ indication channel. Wherein, the way of determining the position of the HARQ indication channel by the terminal is the same as that of the base station and will not be repeated here.

The solutions provided by the present invention will be specifically described below by specific embodiments.

Embodiment 1

In this embodiment, a resource mapping method based on the HARO transmission solution provided by the present invention will be described, which is specifically corresponding to the way of determining an HARQ indication channel on the base station side and the terminal side. For the grant-free transmission mode based on the non-orthogonal multiple access technologies, the position of a time-frequency resource of the HARQ indication channel is determined jointly by the position of a time-frequency resource for uplink transmission, a DMRS feature used by the uplink transmission (for example, a cyclic shift of the DMRS , an Orthogonal Cover Code (OCC) used by the DMRS, a comb structure used by the DMRS and etc.) and a multiple access signature used by the uplink transmission (for example, an interleaved sequence, a codebook and etc.).

The transmission of HARQ information on an HARO indication channel will be described first. In the present disclosure, if the transmission mode is grant-free transmission, the transmission content of the HARQ indication channel may include: 1-bit ACK information+ terminal ID information, or 1-bit ACK information, or 1-bit NACK information.

Wherein, the terminal ID information may be a 16-bit Cell Network Temporary Identifier (C-RNTI) allocated to the terminal by the base station; or a unique 48-bit Serving-Temporary Mobile Subscriber Identity (S-TMSI) of the terminal; or a short terminal-specific identifier generated according to the C-RNTI or the S-TMSI; or token bits allocated to the terminal by the base station; or part of the uplink data transmitted by the terminal (for example, part or all of bits in the CRC check bits).

An example of the HARQ information is shown at FIG. 0. FIG. 9 illustrates information bits of an HARQ indication channel according to various embodiments of the present disclosure. When the terminal ID information 910, together with the ACK information, is transmitted in the HARQ indication channel, to ensure the length of the HARQ indication information is the same during transmitting an ACK signal and during transmitting an NACK signal, redundancy information 920 having the same length as the terminal ID information 910 may be added after the 1-bit NACK signal. The redundancy information 920 may be a sequence of full zeros, or a repetition of the NACK signal.

The terminal ID information may also be transmitted in another transmission mode. Specifically, only the 1-bit ACK/NACK information is transmitted in the HARQ indication channel, while the terminal ID information is transmitted in a downlink control channel or a downlink shared channel. In this case, the information bit in the HARQ indication channel is only 1 bit.

After the information bit of the HARQ indication channel is obtained, the information bit of the HARQ indication channel is processed as FIG. 10 and transmitted. FIG. 10 illustrates a flow of information processing of an HARQ indication channel according to various embodiments of the present disclosure. Referring FIG. 10, constellation modulation is performed on the sequence of the information bit at block 1010, the modulated symbols are coded repeatedly at block 1020, spreading is performed by using a spreading factor for

at block 1030, and resource mapping is performed on the symbol stream at block 1040.

Wherein, to ensure the reliability of detection of the HARQ indication channel, the constellation modulation is low-order modulation, for example, BPSK or QPSK modulation; the spreading applies orthogonal sequences, for example, the spreading code is a complex orthogonal Walsh sequences, and

orthogonal spread sequences may be generated when the length is

. In this embodiment, it is assumed that the spreading is performed using the complex orthogonal Walsh sequences during subsequent operations. HARQ indication channels on the same time-frequency resources are multiplexed to form HARQ indication channel groups, and the HARQ indication channels in a group are distinguished by indexes of the orthogonal sequences. The HARQ indication channels in different HARQ indication channels groups are distinguished from one another by time-frequency resources. The number of HARQ groups transmitted on a same downlink subframe is

, whose value is determined by the number of resources allocated by the downlink control channel and the number of resources occupied by the HARQ indication channels. In addition, during determining the group number

and the multiplexed HARQ indication channels in a group

, it is required to ensure the product

is the same as the number of available resources on grant-free resources mapped to this subframe.

The resource allocation process of an HARQ indication channel, i.e., the process of determining the position of the HARQ indication channel on the base station side and on the terminal side, will be described below.

For the uplink transmission data transmitted on a subframe n, the terminal should determine corresponding HARQ indication channels on a subframe n+k_PHICH. Wherein, the parameter k_PHICH has a different value according to different frame structures. For example, for a Frequency Division Duplex (FDD) mode, k_PHICH is a fixed value, for example, k_PHICH=4; however, for a Time Division Duplex (TDD) mode, k_PHICH is determined by different uplink/downlink configurations. For example, for an unlink/downlink configuration in the LTE-A, the following configuration mode as <Table 1> may be adopted. <Table 1> exemplifies values of k_PHICH in the TDD mode.

In the table, the position with a numeral represents an uplink transmission symbol, while the position without any numeral represents a downlink transmission symbol or a special time slot.

For a self-contained TDD frame structure possibly used in 5G, k_PHICH is determined according to the length of symbols (i.e., an interval between subcarriers) and the processing capacity of the base station, and k_PHICH may be a positive integer.

The time-frequency resource of an HARQ indication channel is determined by an index group

, where

is an index of the HARQ indication channel group, and

is an intra-group sequence index. The index group is determined by the selected time-frequency resource, the selected DMRS and the selected multiple access signature during transmitting the uplink data by the terminal. According to different selection ways, the way of determining the index group is also different. Possible ways will be enumerated below.

Way 1: When there is no mapping relation between DMRSs and multiple access signatures or when there is a one-to-multiple mapping relation between DMRSs and multiple access signatures (that is, one DMRS corresponds to multiple of multiple access signatures), a way of determining the index group

is as <equation 1> or <equation 2> below.

where, I_PRB _{_RA}is an index of the time-frequency resource selected during transmitting the uplink data by the terminal, and

is the number of HARQ indication channel groups. FIGS. 11A and 11B show possible ways of allocating time-frequency resource indexes.

FIGS. 11A and 11B illustrate allocation modes of time-frequency resource indexes according to various embodiments of the present disclosure. In accordance with the way of classifying time-frequency resources allocated to a grant-free transmission terminal, FIGS. 11A and 11B show several possible ways of allocating time-frequency resource indexes.

In FIGS. 11A and 11B, time-frequency resources allocated for the grant-free transmission are discretely distributed on the whole frequency band. FIGS. 11A and 11B merely show resources allocated for grant-free transmission, referred to as grant-free resource sub-blocks 1110 to 1112, 1120 to 1123 herein. A way of selecting time-frequency resources is as follows: after a terminal selects a certain grant-free resource sub-block, this time-frequency resource will be fully occupied for transmitting data; and, multiple of terminals may select a same resource sub-block for transmitting data. In FIG. 11A, time-frequency resource indexes are classified in a frequency classification manner, and grant-free resource sub-blocks 1110 to 1112 located on a same time slot are numbered according to the frequency and then used as time-frequency resource indexes. For example, the grant-free resource sub-blocks 1110 to 1112 are sorted according to the frequency, the index of a grant-free resource sub-block 1110 having the lowest frequency is set as 0, and then the grant-

free resource sub-blocks

1111, 1112 are numbered successively, as shown in FIG. 11A. In FIG. 11B, grant-free resource sub-blocks 1120 to 1123 are numbered according to the frequency and the subframe number, and then used as time-frequency resource indexes. For example, the index of a grant-free resource sub-block 1120 having the lowest frequency and a minimum subframe number is set as 0, and the grant-free resource sub-blocks 1120 to 1123 are numbered according to the frequency and the time, as shown in FIG. 11B. The number is an index of this grant-free resource sub-block.

The way of determining grant-free resources is also suitable for the case where multiple of grant-free resource sub-blocks are successive in the time or frequency.

In the case where there is no mapping relation between DMRSs and multiple access signatures, the parameter N_MA' is the number of available multiple access signatures on the time-frequency resource having an index of I_{PRB_RA}; while in the case where there is a one-to-multiple mapping relation between DMRSs and multiple access signatures, the parameter N_MA' is the number of multiple access signatures having the mapping relation with the same DMRS. The parameter n_MA' is an index of a multiple access signature selected from N_MA' multiple access signatures for the uplink data, and is informed to the terminal through a high-layer configuration and by a downlink control channel or shared channel.

The parameter N_DMRS is the number of available DMRSs on the time-frequency resource having an index of I_PRB _{_RA}. The parameter n_DMRS is an index of a DMRS selected from N_DMRS DMRSs for the uplink data, and is informed to the terminal through a high-layer configuration and by a downlink control channel or shared channel. Considering that different DMRSs may multiplex the same time-frequency resource through a cyclic shift, an orthogonal cover code and a comb structure, the parameters N_DMRS and n_DMRS representing the number of DMRSs may be expressed by <equation 3> below.

where, N_CS, N_OCC, N_comb are the number of available cyclic shifts, the number of available orthogonal cover codes and the number of available comb structures, respectively; n_CS is an index of a cyclic shift; n_OCC is an index of an orthogonal cover code; and n_comb is an index of comb structure. The corresponding index definition way is appointed by the base station and the terminal.

Way 2: When there is a multiple-to-one mapping relation between DMRSs and multiple access signatures (that is, one multiple access signature corresponds to multiple of DMRSs), a way of determining the index group

is as <equation 4> or <equation 5> below.

where, I_PRB _{_RA} is an index of the time-frequency resource selected during transmitting the uplink data by the terminal. The parameter N_DMRS' is the number of DMRSs having the mapping relation with a same multiple access signature, and the parameter n_DMRS' is an index of the DMRS selected from N_DMRS' DMRSs for the uplink data and is informed to the terminal through a high-layer configuration and by a downlink control channel or shared channel. The parameter N_MA is the number of available multiple access signatures on the time-frequency resource having an index of N_MA, and the parameter n_MA is an index of the multiple access signature selected from N_MA multiple access signatures for the unlink data and is informed to the terminal through a high-layer configuration and by a downlink control channel or shared channel.

Way 3: When there is a one-to-one mapping relation between DMRSs and multiple access signatures, that is, when a unique multiple resource may be determined by a DMRS and a unique DMRS is determined by a multiple access signature, N_DMRS=N_MA, and a way of determining an inter-group index and an intra-group index may be simplified, i.e., by using an DMRS index only or an multiple access signature index only.

When the inter-group index and the intra-group index are determined by using a DRMS index only, the formulae are as <equation 6> below.

In the formulae, the parameters are defined as above.

When the inter-group index and the intra-group index are determined by using a multiple access signature index only, the formulae are as <equation 7> below.

In the formulae, the parameters are defined as above. In addition, the positions of the index parameters may be exchanged in the formulae.

In the solutions, the position of an HARQ indication channel is determined by the position of the grant-free time-frequency resource, the DMRS feature and the used multiple access signature. When there is only one sub-band for grant-free transmission on a time slot, a simpler way is that the position of the time-frequency resource of the HARQ indication channel is determined only by using a DMRS related feature and the used multiple access signature.

Specifically, after the terminal transmits uplink data on corresponding grant-free resources in a subframe n, an HARQ indication channel will be detected on n+k_PHICH downlink subframes. Wherein, k_PHICH is a preset parameter which is known by both the base station and the terminal, or a parameter configured by a high-layer signaling. The specific time-frequency position of a corresponding HARQ indication channel on this subframe is determined by the used uplink resources. The uplink resources include a DMRS feature and a multiple access signature. In this case, multiple of HARQ indication channels still may be mapped to a same time-frequency resource, that is, the positions of HARQ indication channels still may be determined by an index group

, where,

is an inter-group index representing an index of an HARQ indication channel group which may be supported on this time slot, and

is an intra-group index representing an index of an HARQ indication channel multiplexed in one group, i.e., an index for distinguishing different HARQ indication channels multiplexed on the same time-frequency resource.

The way of determining of the index group

is similar to the forgoing description, but it is required to set the parameter I_PRB _{_RA} in the forgoing formulae as 0. A simple example is as follows: when there is a one-to-multiple mapping relation between DMRSs and multiple access signatures, the index group may be determined in the following <equation 8>.

In the formulae, the HARQ indication channel group is determined by available DMRS resources and available multiple access signatures, and the inter-group index is determined by the multiple access signatures. The way of determining the index group will be described below in a simple example.

There are four available DMRSs each corresponding to eight multiple access signatures, so there are total 32 available resources. If there are four HARQ indication channel groups and there are eight HARQ indication channels multiplexing the same-frequency resource in each group, the way of determining the index group is as <equation 9> below.

where, the value of n_DMRS is from 0 to 3, and the value of n_MA' is from 0 to 7.

The following table shows index group values corresponding to different DMRS indexes and MA indexes. <table 2> exemplifies index group values

corresponding to different DMRS indexes n_DMRS and MA indexes n_MA'.

It may be seen from the example that the obtained values of the HARQ indication channel index groups are different due to different indexes of the DMRSs and multiple access signatures, so it is indicated that terminals, which perform transmission on a same time-frequency resource but use different DMRSs and multiple access signatures, will use different HARQ indication channels. Therefore, the HARQ indication channels may be distinguished in the above way.

In the example of determining the position of an HARQ indication channel by using DMRSs and multiple access signatures only, the way of determining the index group may also be expressed by <equation 10> below.

It is still assumed that there are four available DMRSs each corresponding to eight multiple access signatures, so there are total 32 available resources. If there are four HARQ indication channel groups, there are eight HARQ indication channels multiplexing the same-frequency resource in each group. The above formulae should be expressed by <equation 11> below.

where, the value of n_DMRS is from 0 to 3, and the value of n_MA is from 0 to 7.

The indexes of HARQ indication channels corresponding to different DMRS and multiple access indexes are obtained according to the following <table 3>. <table 3> exemplifies another index group values

corresponding to different DMRS indexes n_DMRS and MA indexes n_MA'.

As may be seen, after the DMRS indexes and the multiple access signature indexes are replaced, the values of HARQ indication channel index groups obtained by different DMRS indexes and multiple access signature indexes are still different, so it is indicated that the position of an HARQ indication channel of a terminal using a particular DMRS and a particular multiple access signature may be determined according to the above formulae.

In addition, it is to be noted that, the HARQ indication channel in this embodiment may be an actual physical channel, for example, a PHICH in the LTE-A, or may also be a domain in a downlink control channel or a downlink shared channel; the base station determines the position of corresponding HARQ indication information according to the time-frequency resource, DMRSs and multiple access signatures used for the unlink transmission; and the terminal searches HARQ information transmitted to this terminal from the domain through the index group.

Embodiment 2

Hereinafter, a specific flow of uplink data transmission on the terminal side according to the present disclosure will be described. This embodiment mainly relates to a flow of performing data transmission for the first time and performing subsequent data transmission according to the received HARQ information in a Media Access Control (MAC) layer according to the present disclosure, which is corresponding to at step 801 in the flow of FIG. 8. This embodiment will be described in two parts, i.e., an HARQ entity or an HARQ process.

1. HARQ entity

For the grant-free transmission, on the UE side, there are HARQ entities for maintaining multiple of parallel HARQ processes, so that the terminal may continuously transmit data while waiting for the HARQ feedback of the previous transmission.

The maximum number of parallel HARQ processes supported by each HARQ entity is determined according to the Round-Trip Time (RTT) of transmitting data by the terminal and the temporal period of resources allocated for the grant-free transmission. For example, if grant-free transmission resources are continuously distributed in time and the RTT of transmitting data by the terminal is 8 symbols, the maximum number of parallel HARQs is 8.

Within each Transmission Time Interval (TTI), for each given time-frequency resource for grant-free transmission, an HARQ entity determines an HARQ process for transmission on this time-frequency resource. For the determined HARQ process, the HARQ entity is also used for determining transmitting sources used by this HARQ process, delivering the received HARQ feedback information or newly-transmitted data to a corresponding HARQ process, and instructing the corresponding HARQ process to perform retransmission or new transmission.

For the grant-free transmission, new data transmission is triggered by a data generation unit (configured to generate or package data), and a data transmission request is transmitted to the HARQ entity. Upon receiving the data transmission request, the HARQ entity establishes an HARQ process and allocates, to this HARQ process, time-frequency resourced, DMRSs and multiple access signatures for unlink transmission. Then, the HARQ process stores the allocated resources for new data transmission. Wherein, the DMRSs and multiple access signatures stored by the HARQ process are used for distinguishing whether the HARQ information transmitted to the HARQ process by the HARQ entity belongs to this HARQ process.

The data transmission of retransmission corresponds to a same HARQ process as the first data transmission. The HARQ entity allocates time-frequency resources, DMRSs and multiple access signatures to this retransmission of this HARQ process, and transmits them to a corresponding HARQ process.

Similar to the above-described way of allocating resources in the grant-free transmission, a way of allocating uplink transmission resources for an HARQ process by an HARQ entity may include the following two ways.

1) For the transmission of new data, transmission resources may be selected from available grant-free transmission resources (including time-frequency resources, DMRSs and multiple access signatures) in the resource pool allocated to the terminal by the base station in an equal probability manner, and then allocated to this HARQ process. The available grant-free transmission resources refer to time-frequency resources, DMRSs and multiple access signatures, which are not used for newly transmitting data and retransmitting data by the HARQ entity, so that no resource collision will occur when the HARQ entity (i.e., the terminal) transmits newly-transmitted data and retransmitted data.

For an HARQ entity needing to perform retransmission, if the retransmission indication shows that no retransmission is needed or the maximum number of retransmissions has been reached, data in a data buffer is extracted from the corresponding HARQ process, the resources allocated to this HARQ process are released, and the HARQ process is reset. Subsequently, transmission resources are reselected from the available grant-free transmission resources in an equal probability and then allocated to this HARQ process for waiting for retransmission of data.

For an HARQ entity needing to perform retransmission, if the retransmission indication shows that a retransmission is needed and the maximum number of retransmissions have not been reached, resources for this retransmission are determined according to the mapping relation between resources in a resource pool for new transmission and in a resource pool for retransmission. These resources include time-frequency resources, DMRSs and multiple access signatures.

2) For the transmission of new data, through an indication of the signaling in the downlink control channel or the system high-layer signaling, the HARQ entity selects DMRSs and multiple access signatures indicated for the terminal by the signaling to serve as DMRSs and multiple access signatures of the HARQ process, and selects time-frequency resources from the available time-frequency resources allocated to the terminal by the base station in an equal probability way and then allocates the selected time-frequency resources to this process.

For an HARQ entity needing to perform retransmission, if the retransmission indication shows that a retransmission is needed and the maximum number of retransmissions has not been reached, DMRSs and multiple access signatures indicated for the terminal by the signaling are selected as DMRSs and multiple access signatures of the HARQ process, and a time-frequency resource for this retransmission is determined according to the mapping relation between time-frequency resources for new transmission and time-frequency resources for retransmission.

Specifically, the specific processing flow within each TTI includes the following.

For a given time-frequency resource A for grant-free transmission, an HARQ entity determines an HARQ process corresponding to this time-frequency resource, and determines resources for this transmission by the corresponding HARQ process in the following ways.

If the given grant-free time-frequency resource A is applied to retransmission of a certain HARQ process according to the mapping relation between new transmission resources and retransmission resources and the retransmission indication of this HARQ process shows that a retransmission is needed, resources for this retransmission are selected according to the mapping relation between the new transmission resources and the retransmission resources, the HARQ information containing the selected resources is transferred to a corresponding HARQ process, and this process is instructed to initiate retransmission; the HARQ process receives and stores the selected resources and initiates retransmission; wherein, it may be seen from the above general description of the resource allocation, the mapping relation between new transmission resources and retransmission resources may include DMRSs, multiple access signatures and time-frequency resources, and accordingly, during selecting the resources for retransmission, the DMRSs, multiple access signatures and a time-frequency resource (i.e., A) are selected according to the time-frequency resource A and the mapping relation; or, the mapping relation between new transmission resources and retransmission resources may include time-frequency resources only, and accordingly, during selecting the resources for retransmission, i.e., during selecting the time-frequency resource A, the DMRSs and multiple access signatures stored by a corresponding HARQ are used as retransmission resources.

If the given grant-free time-frequency resource is applied to new transmission of a certain HARQ process according to the resource selection condition, data from a data generation unit is correspondingly transmitted to this process, and this process is instructed to initiate new transmission, and the HARQ process uses the stored resources as transmission resources for this new data transmission.

2. HARQ process

Each HARQ process is associated to a HARQ buffer. The buffer is used for storing uplink data which is being transmitted currently.

Each HARQ process maintains a state variable CURRENT_TX_NB, which indicates the number of transmissions in the current buffer, and a state variable HARQ_FEEDBACK, which indicates ACK/NACK feedback of the data in the current buffer, and maintains a state variable HARQ_RE, which indicates whether the data in the current buffer needs to be retransmitted, wherein it is indicated that a retransmission is needed if the variable is 1, or otherwise, it is indicated that no retransmission is needed. When an HARQ is established, CURRENT_TX_NB shall be initialized to be 0.

The sequence of a redundancy version is determined in advance and known by both the base station and the terminal. One possible sequence of redundancy version is 0,2,3,1. The variable CURRENT_IRV is an index into the sequence of redundancy version. This variable is updated modulo V, where V is the length of the redundancy version sequence.

Resources used by both new transmission and retransmission of the data are determined by an HARQ entity and then transferred to the HARQ process.

The maximum number of transmissions of the HARQ is determined by a high-layer signaling, and expressed by maxHARQ-Tx.

The operation description of the HARQ process is as follows:

When HARQ feedback is received for a certain transmission data block, the HARQ process sets HARQ_FEEDBACK to received value and also sets HARQ_RE to received value.

If the HARQ entity requests anew transmission (including that the retransmission indication is 0), the HARQ process shall:

set CURRENT_TX_NB to 0;

set CURRENT_IRV to 0;

store uplink data to be transmitted into a corresponding HARQ buffer;

set HARQ_FEEDBACK to NACK;

set HARQ_RE to 0;

store data transmission resources allocated by the HARQ entity, including time-frequency resources, DMRSs and multiple access signatures;

instruct physical layer to generate transmission according to the stored data transmission resources and according to the redundancy version determined by the CURRENT_IRV; and

increment CURRENT_IRV by 1.

If the HARQ entity requests one retransmission, the HARQ process shall:

Increment CURRENT_TX_NB by 1;

instruct a physical layer to generate transmission according to the stored data transmission resources and according to the redundancy version determined by the CURRENT_IRV; and

increment CURRENT_IRV by 1.

After performing above operations, the HARQ process then shall:

flushing the HARQ buffer if CURRENT_TX_NB=the maximum number of transmissions-1.

Embodiment 3

In this embodiment, the HARQ transmission method on the base station side provided by the present invention will be described.

For the grant-free transmission, the processing on the base station side may be briefly described as below.

1. By a base station, uplink signal is transmitted to a terminal, and blind detection is performed.

2. By the base station, it is determined whether the received data is newly transmitted or retransmitted according to the result of the blind detection and the classification and mapping relation between new transmission resources and retransmission resources.

During decoding, the newly-transmitted data is decoded directly by using soft information output from a multi-user detector; while for the retransmitted data, after detection ends according to the mapping relation between new transmission resources and retransmission resources, and previously-decoded data is extracted from a corresponding buffer and then combined with the retransmitted data for decoding.

3. If it is detected that the decoded data passes the CRC check, the terminal ID information is read from the detected data, the position of an HARQ indication channel is determined according to the position of the time-frequency resource for transmitting the uplink signal, the multiple resources and the DMRSs, and the ACK and the terminal ID information are transmitted.

If it is detected that the decoded data fails to pass the CRC check, the position of an HARQ indication channel is determined according to the position of the corresponding time-frequency resource, the multiple resources and the DMRSs, NACK information is transmitted, and the soft information for this decoding is stored in a corresponding buffer for use in the combining and decoding of the subsequent retransmission. If the number of retransmissions has exceeded the maximum number of retransmissions, the buffer is cleared.

If there is a one-to-one mapping relation between DMRSs and multiple access signatures or there is a multiple-to-one mapping relation between DMRSs and multiple access signatures, the condition of the selected multiple access signatures may be known through the DMRSs, and the blind detection on the base station side may be completed by detecting the DMRSs. Specifically, upon receiving data on a certain time-frequency resource block, the base station performs activation detection on DMRSs to determine which DMRSs are used for transmitting the data on this time-frequency resource block. One possible detection way is as follows: performing correlation energy detection on all possible DMRSs, setting an energy detection threshold, and determining all DMRS having the result of the correlation energy detection greater than the set energy detection threshold to be activated.

Since the used multiple access signatures may be determined through the activation of the DMRSs, multiple access signatures participating in the multi-user detection may be obtained after the DMRS detection, so that the blind detection process is greatly simplified. Meanwhile, the multiple access signatures participating in the multi-user detection are obtained, the previously-transmitted data corresponding to the retransmitted data may be determined according to the mapping relation between the resource pool for new transmission and the resource pool for retransmission so that it is convenient to read data from the buffer and combine the retransmitted data and the previously-transmitted data for decoding.

If there is a one-to-multiple mapping relation between DMRSs and multiple access signatures, one DMRS may correspond to multiple of multiple access signatures, so the used multiple access signatures cannot be determined through the activation of DMRSs. However, the range of the blind detection still may be narrowed, and the complexity of the blind detection may be reduced.

If the activation detection of the DMRSs indicates that a certain DMRS is non-activated, the base station may not transmit information on all corresponding HARQ indication channels, or may transmit NACK information on all corresponding HARQ indication channels. In the case where one DMRS corresponds to multiple of multiple access signatures, if a certain DMRS fails to pass the activation detection, information should be not transmitted on all HARQ indication channels corresponding to the corresponding multiple access signatures, or an NACK signal should be transmitted on all HARQ indication channels.

As a collision may occur during the grant-free transmission, for example, if different terminals select the same DMRS and multiple access signatures for transmission on the same time-frequency resource, when the base station performs multi-user blind detection, there may be a case where the data from two terminals is detected successfully or a case where the data from one of the terminals is detected successfully. In the first case, the terminal transmits NACK signals in corresponding HARQ indication channels. However, in the second case, in addition to transmitting ACK signals, the terminal also needs to inform the terminal ID information which is detected and decoded correctly, to avoid a data transmission error because a correctly detected and decoded terminal mistakenly thinks that the ACK signals have been received.

The terminal ID information in the present disclosure may include the following forms:

1. C-RNTI: the information is an identifier allocated to the terminal by the base station for distinguishing from a terminal in a connected state, and has a length of 16 bits;

2. S-TMSI: the information is a unique identifier of the terminal, and has a length of 48 bits;

3. a terminal identifier generated according to the C-RNTI or the S-TMSI: the terminal identifier is generated according to the C-RNTI or the S-TMSI in accordance with some preset rules, and may be regarded as a compressed identifier, so that the overhead in HARQ indication channels is reduced by increasing by a certain terminal identifier collision probability;

4. token information: the information is allocated by the base station and used for distinguishing terminals allocated with the same DMRSs and/or multiple access signatures; and

5. part of uplink data: for example, the information may be part or all of CRC check bits of the uplink data.

The way of generating the terminal ID information will be briefly described below according to the way of selecting resources.

If the terminal is in a connected state, the base station allocates multiple access signatures and DMRSs to the terminal. In this case, a preferred solution is that the base station also allocates token bits to the terminal. The allocation rule of token bits is as follows: allocating different token bits for terminals allocated with the same multiple access signatures and DMRSs. FIG. 12 shows a token bit allocation way.

FIG. 12 illustrates a token bit allocation mode according to various embodiments of the present disclosure. In FIG. 12, the resources include DMRSs, multiple access signatures and/or time-frequency resources. The same resources are allocated for four terminals, and the terminals allocated with the same resources obtain different token bits 1200 to 1203 in order to distinguish the four terminals. Considering that there are four token bits 1200 to 1203, it is desirable to represent the token bits 1200 to 1203 by 2bits. Generally, the size of token bits 1200 to 1203 is related to the maximum number of terminals allocated with the same resources. If the maximum number of terminals allocated with the same resources is M_max, the number of bits of the token information is

, where

represents rounding up.

When the base station transmits an ACK/NACK signal, one preferred way is transmitting ACK plus token bits and NACK plus zero-padding bits/random bits. Wherein, the length of the zero-padding bits/random bits is the same as that of the token bits. In this case, the length of information bits in the HARQ indication channel is

. When there are fewer token bits, a high-order modulation mode (for example, QPSK, 8PSK or more) may be adopted for modulation, the modulated symbols are coded repeatedly and spread, the position of the HARQ indication channel is determined according to the position of the used time-frequency resources, the used DMRSs and the used multiple access signatures, and resource mapping and signal transmission are performed.

Another way of transmitting an ACK/NACK signal is as follows: transmitting only 1 bit of ACK/NACK information in the HARQ indication channel, and transmitting token information in a downlink control channel or a downlink shared channel. Specifically, the position of the HARQ indication channel is determined according to the time-frequency resources, DMRSs and multiple access signatures, and corresponding ACK/NACK information is transmitted. If the ACK information is transmitted, the position of the corresponding token information is determined according to the time-frequency resources, DMRSs and multiple access signatures, and then transmitted through a downlink control channel or a downlink shared channel.

If the terminal does not complete uplink synchronization and the base station does not allocate the C-RNTI used for identifying the terminal to the terminal, a way of informing the terminal of correct detection is as follows: transmitting a terminal unique identifier carried in the correct detection data while transmitting the ACK information, where the identifier is S-TMSI. If the detection is failed, it is required to transmit an NACK signal, and zero-padding is performed or random bits are added after the NACK signal, where the number of supplemented bits is consistent with the number of bits of the S-TMSI. The position of the HARQ indication channel is determined according to the used time-frequency resources, DMRSs and multiple access signatures, and corresponding ACK/NACK information and the terminal ID information are transmitted.

Similar to the previous case, the 1-bit ACK/NACK signal and the S-TMSI representing the terminal ID information may be transmitted separately. The S-TMSI is transmitted in a downlink control channel or a downlink shared channel, and the position of the S-TMSI is determined by the used time-frequency resources, DMRSs and multiple access signatures.

If the terminal is in the connected state, but the base station does not allocate access resources including DMRSs and multiple access signatures to the terminal or the base station has allocated the access resources but does not allocate corresponding token information, the terminal ID information may be identified by the C-RNTI allocated by the base station when the terminal accesses to the network. If the detection is failed, it is required to transmit an NACK signal, and zero-padding is performed or random bits are added after the NACK signal, where the number of supplemented bits is consistent with the number of bits of the C-RNTI. The position of the HARQ indication channel is determined according to the used time-frequency resources, DMRSs and multiple access signatures, and the corresponding ACK/NACK information and the terminal ID information are transmitted.

Similar to the above-mentioned way, the 1-bit ACK/NACK signal and the C-RNTI may be transmitted separately. The C-RNTI is transmitted in a downlink control channel or a downlink shared channel, and the position of the C-RNTI is determined by the used time-frequency resources, DMRSs and multiple access signatures.

Considering that the length of the S-TMSI is 48 bits and the length of the C-RNTI is 16 bits in the existing standards, although the direct transmission of the S-TMSI and C-RNTI may help the terminal to accurately distinguish the ACK/NACK information, a high signaling overhead will be brought to the downlink transmission channel. As one feasible solution, a short terminal identifier is generated according to the S-TMSI or C-RNTI to serve as the terminal ID information, and the terminal identifier is transmitted in an HARQ indication channel or a downlink control channel/downlink shared channel. Wherein, preferably, the terminal ID information may be randomly generated according to the C-RNTI or the S-TMSI.

Although the terminal identifier is short, terminal identifiers of different terminals may still collision. If the number of bits of a terminal identifier is b, the number of possible terminal identifiers is 2^b. If two terminals select terminal identifiers in an equal probability manner, the probability of collision is 1/2^2b. The number of bits is selected as b, and it is ensured that the probability is less than the probability

of determining the NACK as ACK in the system performance requirements. Hence, the selection rule of the number b of bits is <equation 12> below.

In other words, the minimum number b of bits is selected so that the probability of the terminal identifier collision is not greater than the probability of determining NACK as ACK. Taking the requirements in the LTE-A as an example, the probability of determining NACK as ACK is required to be less than

=10^-4. In this case, when b=7 may be calculated according to the formula, the probability of the terminal identifier collision is about 6*10^-5, which is less than

. The system requirements may be met only if 7 bits of terminal identifiers are needed and the overhead resulted from the transmission of the terminal ID information is greatly reduced.

A way of generating a terminal identifier is as follows: generating the terminal identifier with the aid of a pseudorandom sequence. For example, the terminal identifier is generated through an m-sequence. The base station specifies a generator polynomial for generating the m-sequence, and different terminals use the C-RNTI or the S-TMSI or a partial bit sequence of the identifier as an initial state to generate successive pseudorandom sequences. Then, a clip position of the terminal identifier in the pseudorandom sequence is determined according to the C-RNTI or the S-TMSI or the partial bit sequence of the identifier.

The way of generating a terminal identifier according to the m-sequence will be described in the following example. FIG. 13 illustrates determining a terminal identifier by using an m-sequence according to various embodiments of the present disclosure. Taking the C-RNTI as an example, considering that the length of the C-RNTI is 16 bits, the initial state is determined by 8 high-order bits 1310, and the clip position is determined by 8 low-order bits 1320. The m-sequence is generated by a generator polynomial having the maximum number of times of 8, the 8 high-order bits 1310 (i.e., c₁₅, ... , c₈) of the C-RNTI are used as the initial state, and 8 low-order bits 1320 determine an initial clip position, i.e.,

,where, c_i is the i^th bit data in the C-RNTI, and p_f is a fixed value not less than zero. The clip position means that, taking p_clip output by the m-sequence as a starting point, successive b bits are selected as the terminal identifier.

The terminal identifier may also be generated by other sequences. For example, a Gold sequence is used, two m-sequence generator polynomials for generating the Gold sequence are fixed, and the initial state of one m-sequence is fixed. The initial state of another m-sequence is determined by the C-RNTI or the S-TMSI or a partial bit sequence of the identifier, and a clip position of the terminal identifier in the pseudorandom sequence is determined according to the C-RNTI or the S-TMSI or the partial bit sequence of the identifier.

In another way, two m-sequence generator polynomials for generating the Gold sequence are fixed, and the initial states of two m-sequences are determined by the C-RNTI or the S-TMSI or a partial bit sequence of the identifier; and a clip position of the terminal identifier in the pseudorandom sequence is determined according to the C-RNTI or the S-TMSI or the partial bit sequence of the identifier.

The implementation of this way will be described in the following example.

FIG. 14 illustrates generating a terminal identifier by using a Gold sequence according to various embodiments of the present disclosure. A Gold sequence having a period of 31 is adopted, where the degree of generator polynomials for m-sequences is 5. Considering that the length of the C-RNTI is 16 bits, 5 high-order bits 1410 are used for determining the initial state of the first m-sequence, 5 following bits 1420 are used for determining the initial state of the second m-sequence, and 6 low-order bits 1430 are used for determining the clip position of the Gold sequence. Specifically, the initial state of the first m-sequence is c₁₅, ... , c₁₁, the initial state of the second m-sequence is c₁₀, ..., c₆, and the clip position is

. Wherein, c_i is the i^th bit data in the C-RNTI, and p_f is a fixed value not less than zero. The clip position means that, taking p_clip output by the m-sequences as a starting point, successive b bits are selected as the terminal identifier.

The method for generating the terminal identifier based on a sequence is also applicable to the S-TMSI. Considering that the length of the S-TMSI is greater than that of the C-RNTI, a partial S-TMSI may be clipped for generating a terminal identifier. For example, in the above two examples, the terminal identifier may also be generated by replacing the C-RNTI with a low 16-bit S-TMSI.

In addition to the way of generating the terminal ID information based on the C-RNTI or the S-TMSI, the terminal ID information may also be represented by the transmitted uplink data. As one feasible way, b-bit CRC check bits are added to the uplink transmission data which has passed the CRC check, and the check bits serving as the terminal ID information are transmitted in an HARQ indication channel or a downlink control channel/shared channel. To ensure higher reliability and lower collision probability, 8-bit CRC check or 16-bit CRC check may be selected, and the 8-bit CRC check or 16-bit CRC check as the terminal ID information is transmitted to the terminal together with the ACK information.

If the base station may perform collision detection of DMRSs through DMRS energy detection or more, the result of collision detection may be attached to the NACK signal. Specifically:

1. The base station receives a reception signal on a certain time-frequency resource block, performs activation detection and collision detection on DMRSs, determines the range of multiple access signatures to be performed with blind detection according to the activated DMRs, and determines whether the corresponding uplink data is newly-transmitted data or retransmitted data according to the DMRSs and the multiple access signatures.

2. The base station performs multi-user detection according to the range of the multi-resource detection and the corresponding channel estimation to obtain the result of uplink data detection.

3. If the result of uplink data detection obtained through the multiple access signature detection passes the CRC check, it is indicated that the detection is successful, and the base station acquires terminal ID information from the uplink data and then transmits ACK and the terminal ID information on a corresponding HARQ indication channel or a downlink control channel or a downlink shared channel.

If the result of uplink data detection obtained through the multiple access signature detection fails to pass the CRC check and the DMRS collision detection corresponding to the uplink data indicates that there is no collision, the base station transmits NACK and a non-collision indication in a corresponding HARQ indication channel or a downlink control channel or a downlink shared channel, and stores the result of this detection into a corresponding buffer.

If the result of uplink data detection obtained through the multiple access signature detection fails to pass the CRC check and the DMRS collision detection corresponding to the uplink data indicates that there is a collision, the base station transmits NACK and a collision indication in a corresponding HARQ indication channel or a downlink control channel or a downlink shared channel, and clears the corresponding buffer.

Both the collision detection and the DMRS activation detection on the base station side may adopt correlation energy detection. FIG. 15 illustrates a collision detection threshold and a energy detection threshold according to various embodiments of the present disclosure. Specifically, an energy detection threshold 1510 and a collision detection threshold 1520 greater than the energy detection threshold 1510 are set according to the DMRS correlation and the open-loop power control parameters of the terminal. The base station first performs the correlation energy detection on a DMRS. If the result of detection is less than the energy detection threshold 1510, it is indicated that the DMRS is not activated; if the result of detection is greater than the energy detection threshold 1510 but less than the collision detection threshold 1520, it is indicated that the DMRS is activated and there is no collision; and, if the result of detection is greater than the collision detection threshold 1520, it is indicated that the DMRS is activated and there is a collision.

If there is no collision in the DMRS, a detection failure is possibly because of poor channel condition or high interference from other terminals, and retransmission may effectively improve the reliability of transmitting data. If there is a collision in the DMRS, the detection failure is possibly because different channels cannot be distinguished from each other due to the DMRS collision. In this case, the retransmission has a limited effect on the reliability of transmitting data, and the terminal should reselect resources to try to transmit data.

Some DMRSs are likely to be not used during the transmission of the uplink data. In this case, by performing activation detection on DMRSs, the base station may find activated DMRSs, and transmit NACK or not transmit data in all corresponding HARQ indication channels through the unused DMRSs. However, when the transmission channel condition of the terminal is poor, it is possible that the terminal has transmitted data but corresponding DMRSs are not detected through the DMRS activation detection on the base station side, so that the base station deems that the DMRSs and corresponding multiple resources are not used for data transmission and data in a corresponding buffer is not transmitted. In this case, the base station will transmit an NACK signal or not transmits data in a corresponding DMRS indication channel. In both cases, the terminal deems that the previous transmission is failed, and then initiates retransmission. During retransmission, as the base station does not store the previously transmitted data, the combining for decoding cannot improve the probability of successful detection, even resulting in the case where more times of decoding leads to more errors. In this case, a preferred processing way for the terminal is initiating transmission for the first time again, rather than initiating retransmission.

As one possible solution, a retransmission/new transmission indication is transmitted while transmitting the NACK signal. If the activation of a DMRS is detected, but the result of detection fails to pass the CRC check, the NACK and a retransmission indication are transmitted in a corresponding HARQ indication channel; and if no activation of a DMRS is detected, the NACK and a new transmission indication are transmitted in a corresponding HARQ indication channel. In addition, the retransmission indication and the new transmission indication may be combined with a collision detection indication. In other words, the retransmission indication represents a non-collision indication, while the new transmission indication represents a collision indication. In addition, the retransmission/new transmission indication and the NACK signal may be transmitted separately. In other words, the ACK/NACK signal is transmitted in an HARQ indication channel, while the retransmission/new transmission indication is transmitted in a downlink control channel or a downlink shared channel.

Embodiment 4

In this embodiment, the detection of the HARQ information in the HARQ transmission method on the terminal side provided by the present invention, i.e., the processing of

steps

806 and 807 in FIG. 8 will be described.

After one uplink grant-free transmission ends, on a time-frequency resource of the HARQ indication channel, the terminal detects the HARQ indication channel for this transmission. If the transmission content in the HARQ indication channel is the ACK and the terminal ID information, the processing on the terminal side is as follows.

The terminal detects the content in the HARQ indication channel; if the ACK is decoded, the terminal further tries to decode the terminal ID information in the HARQ indication channel; and, if the terminal ID information in the HARQ indication channel is matched with the ID information of this terminal, ACK for that transport block shall be delivered to the high layer. In this case, it is indicated that the uplink transmission corresponding to the HARQ indication channel is correctly received by the base station. The terminal may initiate new transmission or complete the uplink transmission, and then enter a waiting state or a dormant state.

The terminal detects the content in the HARQ indication channel; if the ACK is decoded, the terminal further tries to decode terminal ID information in the HARQ indication channel; if the terminal ID information in the HARQ indication channel is not matched with the ID information of this terminal, the terminal transfers information about ending this transmission to the high layer and initiates a request for retransmitting the uplink transmission content corresponding to the HARQ indication channel. In this case, it is indicated that the uplink transmission corresponding to the HARQ indication channel occurs a resource collision on the base station side, the data transmitted by the terminal is not decoded correctly, but the data transmitted by other terminals collision with this terminal and using the same resources is decoded correctly. In this case, the continuous retransmission of this terminal cannot improve the transmission reliability, so the terminal ends this transmission and reselects resources from the resource pool for transmitting the uplink data (it is equivalent that the uplink data transmitted unsuccessfully is transmitted newly).

The terminal detects the content in the HARQ indication channel; and, if the NACK is decode, NACK for that transmit block shall be delivered to the high layer. In this case, the uplink data transmitted by the terminal is not decoded successfully, and retransmission will facilitate the improvement of the reliability of data transmission, so the terminal will initiate retransmission by using a new redundancy version if the maximum number of transmissions has not been reached; or, the terminal will terminate this transmission and select new resources to try to transmit the uplink data.

The processing on the terminal side may be described in FIG. 16. In the processing on the terminal side, the terminal ID information includes a C-RNTI allocated by the base station, or a unique S-TMSI of the terminal, or a terminal-specific identifier generated according to the C-RNTI or the S-TMSI, or token bits allocated by the base station.

If only the ACK/NACK information is transmitted in the HARQ indication channel and the terminal ID information is transmitted on a particular time-frequency resource of the downlink control channel or the downlink shared channel, the operation on the terminal side is as follows.

FIG. 16 illustrates a flowchart of a terminal according to various embodiments of the present disclosure.

Referring FIG. 16, at step 1601, the terminal detects the content in the HARQ indication channel; if the ACK is decoded, at step 1603, the terminal decodes terminal ID information at a specified position of the downlink control channel or the downlink shared channel according to the time-frequency resources, multiple access signatures and DMRSs used for the uplink transmission; and if the detected terminal ID information is matched with the ID information of this terminal, at step 1605, ACK for that transmit block shall be delivered to the high layer. In this case, it is indicated that the uplink transmission corresponding to the HARQ indication channel is correctly received by the base station. The terminal may initiate new transmission or complete the uplink transmission, and then enter a waiting state or a dormant state.

At step 1601, the terminal detects the content in the HARQ indication channel; if the ACK is decoded, at step 1603, the terminal detects terminal ID information at a specified position of the downlink control channel or the downlink shared channel according to the time-frequency resources, multiple access signatures and DMRSs used for the uplink transmission; and if the detected terminal ID information is not matched with the ID information of this terminal, at step 1607, NACK and new transmission request for that transmit block shall be delivered to the high layer, informs the high layer of information about terminating this transmission and requests for retransmitting the uplink transmission content corresponding to the HARQ indication channel. In this case, it is indicated that the uplink transmission corresponding to the HARQ indication channel occurs a resource collision on the base station, the data transmitted by the terminal is not decoded correctly, but the data transmitted by other terminals collision with this terminal and using the same resources is decoded correctly. In this case, the continuous retransmission of this terminal cannot improve the transmission reliability, so the terminal ends this transmission and reselects resources from the resource pool for transmitting the uplink data (it is equivalent that the uplink data transmitted unsuccessfully is transmitted newly).

The terminal detects the content in the HARQ indication channel, and if NACK is decoded, NACK for that transmit block shall be delivered to the high layer. In this case, the uplink data transmitted by the terminal is not decoded successfully, and retransmission will facilitate the improvement of the reliability of data transmission, so the terminal will initiate retransmission by using a new redundancy version if the maximum number of transmissions has not been reached. Accordingly, at step 1609, the terminal determines whether the maximum number of transmissions has been reached. If the maximum number of transmissions has not been reached, at step 1611, the terminal performs the retransmission by using the new redundancy version. If the maximum number of transmissions has been reached, at step 1613, the terminal will end this transmission and select new resources to try to transmit the uplink data.

In the operations on the terminal side, the terminal ID information includes a C-RNTI allocated by the base station, or a unique S-TMSI of the terminal, or a terminal-specific identifier generated according to the C-RNTI or the S-TMSI, or token bits allocated by the base station.

If the content transmitted in the HARQ indication channel is ACK + terminal ID information, and NACK + retransmission indication information, the operation on the terminal side is described as follows.

FIG. 17 illustrates another flowchart of another terminal according to various embodiments of the present disclosure.

Referring FIG. 17, at step 1701, the terminal detects the content in the HARQ indication channel, and at step 1703, further detects the terminal ID information in the HARQ indication channel if ACK is decoded; at step 1703, ACK shall be delivered to high layer if the terminal ID information in the HARQ indication channel is matched with the terminal ID information. In this case, it is indicated that the uplink transmission corresponding to the HARQ indication channel is received by the base station correctly. The terminal may initiate new transmission or complete the uplink transmission, and then enter the waiting state or IDLE state.

The terminal detects the content in the HARQ indication channel, and further detects the terminal ID information in the HARQ indication channel if ACK is decoded; and if the terminal ID information in the HARQ indication channel is not matched with the terminal ID information, at step 1707, NACK and new transmission request for that transmit block shall be delivered to high layer, informs the high layer to terminate information of this transmission, and requests for retransmitting the uplink transmission content corresponding to the HARQ indication channel. In this case, it is indicated that, with respect to the uplink transmission corresponding to the HARQ indication channel, a resource collision occurs on the base station side, and that the data transmitted by the terminal is not decoded correctly while the data transmitted by the same resource of another terminal collision with this terminal is decoded correctly. In this case, the reliability of transmission will not be improved if the terminal continues to perform retransmission. Therefore, the terminal will terminate this transmission, and reselect resources from the resource pool to transmit the uplink data (it is equivalent that the uplink data transmitted unsuccessfully is transmitted newly).

The terminal detects the content in the HARQ indication channel, and at step 1709, further detects a retransmission indication if NACK is decoded. If detected information indicates that retransmission is required, NACK is delivered to high layers. In this case, it is indicated that the base station finds that no collision occurs by the collision detection of the DMRS. However, because of channel condition or more, the uplink data of the user is not decoded successfully. In this case, data of other redundancy versions is transmitted. Decoding the data by combining by the base station may increase the success rate of detection. Accordingly, at step 1711, the terminal determines whether the maximum number of transmissions has been reached. If the maximum number of transmissions has not been reached, at step 1713, the terminal performs the retransmission by using the new redundancy version. If the maximum number of transmissions has been reached, at step 1715, the terminal ends this transmission and selects new resources to try to transmit the uplink data.

The terminal detects the content in the HARQ indication channel, and further detects a retransmission indication if NACK is decoded. If detecting no information indicating that retransmission is required, at step 117, the terminal transfers information of terminating this transmission to the high layer, initiates a request for retransmitting the uplink transmission content corresponding to the HARQ indication channel. In this case, it is indicated that the base station finds that the DMRSs inserted for uplink transmission of the terminal collision with DMRSs used by other terminals, by the collision detection of the DMRS, and that data from the collision terminal is all decoded successfully. In this case, improving the reliability of detection of the base station by retransmission is limited. Therefore, the terminal will terminate this transmission, and reselect resources from the resource pool to transmit the uplink data which is not transmitted successfully.

In the operation on the terminal side, the terminal ID information includes C-RNTI allocated by the base station, or the unique S-TMSI of the terminal, or the terminal-specific identifier generated according to the C-RNTI or the S-TMSI, or the token bits allocated by the base station. The retransmission indication information may indicate whether to retransmit by 1-bit information, and may represent whether to retransmit by 1-bit collision information. For example, 1 indicates that a collision occurs and the terminal initiates new transmission instead of performing retransmission; and 0indicates that no collision occurs and the terminal uses a new redundancy version to retransmit the uplink data.

In a case where only ACK/NACK information is transmitted in the HARQ indication channel and the terminal ID information and the retransmission indication information are transmitted in a downlink control channel or a downlink shared channel, the operation on the terminal side is similar to that described above. The difference lies in that: the terminal further reads the corresponding terminal ID information from the downlink control channel or the downlink shared channel according to the used multiple access signatures and DMRSs, if detecting an ACK signal; and the terminal further reads the corresponding retransmission indication information from the downlink control channel or the downlink shared channel according to the used DMRSs and/or multiple access signatures, if detecting an NACK signal.

It is to be noted that, the HARQ indication channel in this embodiment may be an actual physical channel; or may be a domain in a downlink control channel, for transmitting ACK/NACK information, and terminal ID information and/or retransmission indication information; or may be a domain in a downlink shared channel, for transmitting ACK/NACK information, and terminal ID information and/or retransmission indication information.

The above description is the specific implementation of the HARQ transmission method in the present disclosure. In the above description, description is made by taking grant-free transmission based on the non-orthogonal multiple access technologies as an example. Indeed, the HARQ transmission method may also be applicable to other transmission modes.

Corresponding to the HARQ transmission on the base station side, the present disclosure further provides an HARQ transmission apparatus, which may be located in a base station. FIG. 18 illustrates a structure of a HARQ transmission apparatus according to various embodiments of the present disclosure. As shown in FIG. 18, the apparatus includes: a signal detection unit 1810 and a transmitting unit 1820.

Wherein, the signal detection unit 1810 is configured to receive a signal transmitted by a terminal and perform signal detection, decoding and CRC check. The transmitting unit 1820 is configured to determine terminal identifier information according to terminal information carried in the signal and transmit acknowledgement (ACK) information and the terminal identifier information when the signal detection unit 1810 determines that the CRC check is successful; and further configured to transmit non-acknowledgement (NACK) information or not transmit HARQ information when the signal detection unit 1810 determines that the CRC check is failed.

Corresponding to the HARQ transmission on the terminal side, the present disclosure further provides an HARQ transmission apparatus, which may be located in a terminal. FIG. 19 illustrates another structure of a HARQ transmission apparatus according to various embodiments of the present disclosure. As shown in FIG. 19, the apparatus includes: a transmitting unit 1910 and a receiving unit 1920.

Wherein, the transmitting unit 1910 is configured to transmit an uplink signal to a base station. The receiving unit 1920 is configured to receive HARQ information of the uplink signal on a time-frequency resource of an HARQ indication channel; extract, from the information transmitted by the base station, terminal identifier information corresponding to the HARQ information when the received HARQ information is ACK information; determine that the uplink signal is received correctly if the identifier information is consistent with identifier information of the first terminal; terminate this transmission and transmit the uplink signal for the first time again if the identifier information is inconsistent with the identifier information of the first terminal; and, retransmit the uplink signal or transmit the uplink signal for the first time again when the received HARQ information is NACK information.

As described above, the present disclosure provides an HARQ transmission solution. By transmitting the ID information of the terminal while transmitting the ACK signal, the problem that an error occurs during detecting an ACK/NACK signal by a terminal due to a collision may be avoided; in addition, after the terminal has received the ACK signal and has found that the ID information of the terminal is not matched, a new transmission will be directly initiated, so that the problem that the retransmission cannot improve the reliability of data transmission in this case is avoided. Preferably, the position of an HARQ indication channel is determined according to the position of the time-frequency resource bearing the uplink signal, the multiple access signature used by the uplink signal and the DMRS feature of the uplink signal, so that more users may be allowed to be multiplexed on the same physical resource blocks.

In conclusion, the HARQ transmission solution provided by the present disclosure may improve the reliability and stability of the grant-free transmission system.

Methods according to embodiments stated in claims and/or specifications of the present disclosure may be implemented in hardware, software, or a combination of hardware and software.

When the methods are implemented by software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium may be configured for execution by one or more processors within the electronic device. The at least one program may include instructions that cause the electronic device to perform the methods according to various embodiments of the present disclosure as defined by the appended claims and/or disclosed herein.

The programs (software modules or software) may be stored in non-volatile memories including a random access memory and a flash memory, a Read Only Memory (ROM), an Electrically Erasable Programmable Read Only Memory (EEPROM), a magnetic disc storage device, a Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other type optical storage devices, or a magnetic cassette. Alternatively, any combination of some or all of the may form a memory in which the program is stored. Further, a plurality of such memories may be included in the electronic device.

In addition, the programs may be stored in an attachable storage device which is accessible through communication networks such as the Internet, Intranet, local area network (LAN), wide area network (WAN), and storage area network (SAN), or a combination thereof. Such a storage device may access the electronic device via an external port. Further, a separate storage device on the communication network may access a portable electronic device.

In the above-described detailed embodiments of the present disclosure, a component included in the present disclosure is expressed in the singular or the plural according to a presented detailed embodiment. However, the singular form or plural form is selected for convenience of description suitable for the presented situation, and various embodiments of the present disclosure are not limited to a single element or multiple elements thereof. Further, either multiple elements expressed in the description may be configured into a single element or a single element in the description may be configured into multiple elements.

While the present disclosure has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be defined as being limited to the embodiments, but should be defined by the appended claims and equivalents thereof.

Claims

A method for operating a base station in a wireless communication system, the method comprising:

receiving, from a terminal, a signal based a grant-free transmission; and

if a decoding of the signal is successful, transmitting an acknowledge (ACK) for the signal and information indicating the terminal that is identified from the signal.
The method of claim 1, further comprising:

If the decoding of the signal is failed, transmitting a negative-ACK (NACK) for the signal and redundancy information having a same length as the information indicating the terminal.
The method of claim 1, further comprising:

transmitting information regarding a configuration for at least one reference signal, at least one signature, or at least one time-frequency resource to transmit the signal.
The method of claim 1, further comprising:

detecting a collision between at least one reference signal from the terminal and an least one different reference signal from another terminal; and

transmitting information indication the collision or information indicating a new transmission.
A method for operating a terminal in a wireless communication system, the method comprising:

transmitting, to a base station, a signal based a grant-free transmission; and

if a decoding of the signal is successful at the base station, receiving an acknowledge (ACK) for the signal and information indicating the terminal that is identified from the signal.
The method of claim 5, further comprising:

if the decoding of the signal is failed at the base station, receiving a negative-ACK (NACK) for the signal and redundancy information having a same length as the information indicating the terminal.
The method of claim 5, further comprising:

receiving information regarding a configuration for at least one reference signal, at least one signature, or at least one time-frequency resource to transmit the signal.
The method of claim 5, further comprising:

if detecting a collision between at least one reference signal from the terminal and an least one different reference signal from another terminal, receiving information indication the collision or information indicating a new transmission.
A base station in a wireless communication system, the base station comprising:

a transceiver configured to:

receive, from a terminal, a signal based a grant-free transmission, and

if a decoding of the signal is successful, transmit an acknowledge (ACK) for the signal and information indicating the terminal that is identified from the signal.
The base station of claim 9, wherein the transceiver is further configured to, if the decoding of the signal is failed, transmit a negative-ACK (NACK) for the signal and redundancy information having a same length as the information indicating the terminal.
The base station of claim 9, wherein the transceiver is further configured to transmit information regarding a configuration for at least one reference signal, at least one signature, or at least one time-frequency resource to transmit the signal.
A terminal in a wireless communication system, the terminal comprising:

a transceiver configured to transmit:

a signal based a grant-free transmission to a base station, and

if a decoding of the signal is successful at the base station, receiving an acknowledge (ACK) for the signal and information indicating the terminal that is identified from the signal.
The terminal of claim 12, wherein the transceiver is further configured to, if the decoding of the signal is failed at the base station, receive a negative-ACK (NACK) for the signal and redundancy information having a same length as the information indicating the terminal.
The terminal of claim 12, wherein the transceiver is further configured to receive information regarding a configuration for at least one reference signal, at least one signature, or at least one time-frequency resource to transmit the signal.
The method of claim 1, the method of claim 5, the base station of claim 9 or the terminal of claim 12, wherein the ACK is transmitted on a resource that is determined based on a configuration of the signal.