WO2016109978A1

WO2016109978A1 - Method and apparatus for performing data transmission

Info

Publication number: WO2016109978A1
Application number: PCT/CN2015/070450
Authority: WO
Inventors: Hongmei Liu; Lei Jiang; Zhennian SUN; Chuangxin JIANG; Gang Wang
Original assignee: Nec Corporation
Priority date: 2015-01-09
Filing date: 2015-01-09
Publication date: 2016-07-14

Abstract

Embodiments of the disclosure provide a method and apparatus for performing data transmission in a HARQ procedure. The method may comprise: transmitting first transmission of a data block to a receiver, wherein a data channel of the first transmission is carried on a first component carrier; in response to receiving from the receiver a negative acknowledge message indicating the first transmission is failed, determining a second component carrier for retransmission of the data block based on carrier availability; and performing the retransmission on the second component carrier.

Description

METHOD AND APPARATUS FOR PERFORMING DATA TRANSMISSION

FIELD OF THE INVENTION

Embodiments of the present invention generally relate to communication techniques. More particularly， embodiments of the present invention relate to a method and apparatus for performing data transmission in a Hybrid Automatic Repeat Request (HARQ) procedure.

BACKGROUND OF THE INVENTION

Automatic repeat request (ARQ) is simple error correction scheme in which a receiver， upon detecting an error， requests a retransmission of a data block. The receiver may explicitly acknowledge each data block， by transmitting an acknowledgment (ACK) if no errors are detected or a negative acknowledgment (NACK) if the data block was received with one or more errors.

Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination of high-rate forward error-correcting coding and ARQ error-control. In particular， HARQ with Chase combining and IR combining is an effective way to decrease the latency and provide time diversity gain for data transmission.

In recent years， for the purpose of improving user equipment (UE) ’s throughput， unlicensed carrier has been introduced to provide additional spectrum resource. However， the carrier availability is uncertain due to regulations and there is restriction on the maximum available time. As such， the component carrier that carries first transmission of a data block may be unavailable for carrying the retransmission of the data block due to the uncertain carrier availability.

Therefore， there is a need to develop a scheme for determining a component carrier for carrying the retransmission of the data block.

SUMMARY OF THE INVENTION

The present invention proposes a solution for data transmission in a HARQ procedure. Specifically， the present invention provides a method and apparatus for determining a component carrier for carrying the retransmission of the data block based on channel availability.

According to a first aspect of embodiments of the present invention， embodiments of the invention provide a method for performing data transmission in a HARQ procedure. The method may comprise： transmitting first transmission of a data block to a receiver， wherein a data channel of the first transmission is carried on a first component carrier； in response to receiving from the receiver a negative acknowledge message indicating the first transmission is failed， determining a second component carrier for retransmission of the data block based on carrier availability； and performing the retransmission on the second component carrier.

According to a second aspect of embodiments of the present invention， embodiments of the invention provide a method for performing data transmission in a HARQ procedure. The method may comprise： in response to that first transmission of a data block is failed， transmitting a negative acknowledge message to a transmitter， wherein a data channel of the first transmission is carried on a first component carrier； and receiving retransmission of the data block on a second component carrier， wherein the second component carrier is determined based on carrier availability.

According to a third aspect of embodiments of the present invention， embodiments of the invention provide an apparatus for performing data transmission in a HARQ procedure. The apparatus may comprise： a transmitting unit configured to transmit first transmission of a data block to a receiver， wherein a data channel of the first transmission is carried on a first component carrier； a determining unit configured to，in response to receiving from the receiver a negative acknowledge message indicating the first transmission is failed， determine a second component carrier for retransmission of the data block based on carrier availability； and a performing unit configured to perform the retransmission on the second component carrier.

According to a fourth aspect of embodiments of the present invention， embodiments of the invention provide an apparatus for performing data transmission in a HARQ procedure. The apparatus may comprise： a transmitting unit configured to， in response to that first transmission of a data block is failed， transmit a negative acknowledge message to a transmitter， wherein a data channel of the first transmission is carried on a first component carrier； and a receiving unit configured to receive retransmission of the data block on a second component carrier， wherein the second component carrier is determined based on carrier availability.

Compared with those existing solutions， the proposed solution is directed to a HARQ procedure， in which a component carrier for carrying retransmission of a data block can be determined based on channel availability.

Other features and advantages of the embodiments of the present invention will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings， which illustrate， by way of example， the principles of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are presented in the sense of examples and their advantages are explained in greater detail below， with reference to the accompanying drawings， where

FIG. 1 illustrates a flow chart of a method 100 for performing data transmission in a HARQ procedure at a transmitter according to embodiments of the invention；

FIG. 2 illustrates a flow chart of a method 200 for performing data transmission in a HARQ procedure at a transmitter according to embodiments of the invention；

FIG. 3 illustrates a flow chart of a method 300 for performing data transmission in a HARQ procedure at a transmitter according to further embodiments of the invention；

FIG. 4 illustrates a flow chart of a method 400 for performing data transmission in a HARQ procedure at a receiver according to further embodiments of the invention；

FIG. 5A illustrates a schematic diagram of a HARQ procedure 500 in a Time Division Duplex (TDD) system according to embodiments of the invention；

FIG. 5B illustrates a schematic diagram of a HARQ procedure 510 in a Frequency Division Duplex (FDD) system according to embodiments of the invention；

FIG. 6A illustrates a schematic diagram of a HARQ procedure 600 in a TDD system according to embodiments of the invention；

FIG. 6B illustrates a schematic diagram of a HARQ procedure 610 in a FDD system according to embodiments of the invention；

FIG. 7 illustrates a block diagram of an apparatus 700 for performing data transmission in a HARQ procedure according to embodiments of the invention； and

FIG. 8 illustrates a block diagram of an apparatus 800 for performing data transmission in a HARQ procedure according to embodiments of the invention.

Throughout the figures， same or similar reference numbers indicate same or similar elements.

DETAILED DESCRIPTION OF EMBODIMENTS

The subject matter described herein will now be discussed with reference to several example embodiments. It should be understood these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the subject matter described herein， rather than suggesting any limitations on the scope of the subject matter.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein， the singular forms “a， ” “an” and “the” are intended to include the plural forms as well， unless the context clearly indicates otherwise. It will be further understood that the terms “comprises， ” “comprising， ” “includes” and/or “including， ” when used herein， specify the presence of stated features， integers， steps， operations， elements and/or components， but do not preclude the presence or addition of one or more other features， integers， steps， operations， elements， components and/or groups thereof.

It should also be noted that in some alternative implementations， the functions/acts noted may occur out of the order noted in the figures. For example， two functions or acts shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order， depending upon the functionality/acts involved.

Embodiments of the present invention are directed to a solution for performing data transmission in a HARQ procedure. The solution may be carried out between a receiver and a transmitter. In particular，the transmitter transmits firsttransmission of a data block to a receiver by using a first component carrier. In response to receiving from the receiver a negative acknowledge message that indicates first transmission of a data block is failed，the transmitter determines based on carrier availabilitv a second component carrier for retransmission of the data block and performs the retransmission by using the second component carrier.

According to some embodiments of the present invention，the HARQ procedure may be used in downlink cellular transmission. In this case，the receiver may comprise user equipment (UE)， such as a terminal，a Mobile Terminal (MT) ， a Subscriber Station (SS)， a Portable Subscriber Station (PSS) ， Mobile Station (MS) ， or an Access Terminal (AT) . Meanwhile， the transmitter may comprise a base station (BS) ， such as a node B (NodeB or NB) ， or an evolved NodeB (eNodeB or eNB) .

According to some other embodiments of the present invention，the cross carrier HARQ procedure may be used in D2D transmission. In this case，the receiver may be a Device-to-Device (D2D) receiver and the transmitter may be a D2D transmitter.

Embodiments of the present invention may be applied in various communication systems，including but not limited to a Long Term Evolution (LTE) system or a Long Term Evolution Advanced (LTE-A) system. Given the rapid development in communications，there will of course also be future type wireless communication technologies and systems with which the present invention may be embodied. It should not be seen as limiting the scope of the invention to only the aforementioned system.

Referenee is first made to FIG. 1， which illustrates a flow chart of a method 100for performing data transmission in a HARQ procedure at a transmitter according to embodiments of the invention. The method 100 may be performed at a transmitter， sueh as a BS， a D2D transmitter， and other suitable device.

According to embodiments of the present invention， in the HARQ procedure， the transmitter transmits first transmission of a data block to a receiver by using a first component carrier. Upon a failure of the first transmission， the receiver may send a negative acknowledge message， for example NACK， to the transmitter to request retransmission. In response to the negative acknowledge message， the transmitter may retransmit the data block to the receiver by using a second component carrier.

The first transmission of the data block may comprise a data portion and a control portion. The data portion comprises the transmitted data block， which may be carried on a data channel of the first transmission， for example， Physical Downlink Shared Channel (PDSCH) . The control portion comprises control information of the first transmission， which may be carried on a control channel of the first transmission， for example， Physical Downlink Control Channel (PDCCH) . In addition， the retransmission of the data block may likewise comprise a data portion and a control portion.

The data channel and the control channel may be carried on the same component carrier， which may be called as “self-scheduling. ” As an alternative， the data channel and the control channel may be carried on different component carriers， which may be called as “cross carrier scheduling. ”

At step S 110， first transmission of a data block is transmitted to a receiver.

According to embodiments of the present invention， the first transmission may employ either self-scheduling or cross carrier scheduling. In both cases， the component carrier carrying the data channel of the first transmission may be called as “first component carrier” . The first component carrier may be a licensed carrier or an unlicensed carrier.

If the data block is received with one or more errors， the receiver may send a negative acknowledge message， for example NACK， to the transmitter to request retransmission. In response to the negative acknowledge message， the transmitter may retransmit the data block to the receiver.

The retransmission may be performed on the second component carrier that may be the same as the first component carrier or different from the first component carrier. Similar to the first transmission， the retransmission may employ either self-scheduling or cross carrier scheduling. If the self-scheduling is employed， the second component carrier may be used in carrying both the data channel (for example， PDSCH) and the control channel (for example， PDCCH) of the retransmission. Alternatively， if the cross carrier scheduling is employed， the second component carrier may be used in carrying the data channel of the retransmission.

According to embodiments of the present invention， both licensed carriers and unlicensed carriers may be employed by the retransmission. Since the carrier availability may be uncertain due to regulations， restrictions， occupations， and so on， there is a need to determine a component carrier for the retransmission before retransmitting the data block.

At step S 120， in response to receiving from the receiver a negative acknowledge message indicating the first transmission is failed， a second component carrier for retransmission of the data block is determined based on carrier availability.

According to embodiments of the present invention， the second component carrier may be determined in several ways. By way of example， in some embodiments， whether the first component carrier is available for the retransmission may be determined first. In response to that the first component carrier is available for the retransmission， the first component carrier may be determined as the second component carrier. In response to that the first component carrier is unavailable for the retransmission， the first component carrier may be determined as the second component carrier once the first component is available. Details of the embodiment will be described with reference to FIG. 2.

In some other embodiments， at least one candidate component carrier available for the retransmission may be determined first， and then the second component carrier may be determined based on the at least one candidate component carrier. According to embodiments of the present invention， one or more candidate component carriers may be determined as available for the retransmission by means of energy detection， carrier sensing， and so on. The second component carrier may be selected from the candidate component carriers based on load status or channel quality thereof. Details of the embodiment will be described with reference to FIG. 3.

At step S 130， the retransmission is performed on the second component carrier.

In some embodiments， the retransmission may employ the self-scheduling， thus both the data channel (for example， PDSCH) and the control channel (for example， PDCCH) of the retransmission may be carried on the determined second component carrier. In alternative embodiments， the retransmission may employ the cross carrier scheduling， and the data channel of the retransmission may be carried on the second component carrier.

FIG. 2 illustrates a flow chart of a method 200 for performing data transmission in a HARQ procedure at a transmitter according to embodiments of the invention. The method 200 may be considered as a specific implementation of the method 100 described above with reference to Fig. 1. According to embodiments illustrated with reference to FIG. 2， when the retransmission is to be performed， whether the first component carrier is available is determined. If the first component carrier is available， it is used in the retransmission； otherwise， the transmitter will wait until the first component carrier is available.

Method 200 starts at step S210， wherein first transmission of a data block is transmitted to a receiver， wherein a data channel of the first transmission is carried on a first component carrier.

This step is similar to the step S 110 of method 100. According to embodiments of the present invention， the first component carrier may be a licensed carrier or an unlicensed carrier.

If the data block is received with one or more errors， the receiver may send a negative acknowledge message， for example NACK， to the transmitter to request retransmission. In response to the negative acknowledge message， the transmitter may perform retransmission of the data block to the receiver. Before the retransmission， the transmitter may determine a component carrier for use in the retransmission.

At step S220， determining whether the first component carrier is available for the retransmission.

The carrier availability may be checked by determining whether a component carrier is available for the retransmission. According to embodiments of the present invention， whether the first component carrier is available for the retransmission may be determined in several ways， such as energy detection， carrier sensing， and so on. In some embodiments， strength of energy from a further transmitter may be measured on the first component carrier. The further transmitter may be a transmitter that may use the first component carrier and is different from the transmitter performing the method according to embodiments of the present invention. Ifthe energy strength is not strong， it may be determined that the first component carrier is idle. In this regard， the energy strength may be compared with a strength threshold. In response to that the measured strength is less than the strength threshold， the first component carrier may be determined as available for the retransmission. The strength threshold may be a predetermined threshold， which may be set according to system requirements， specifications， channel quality， and so on. According to embodiments of the present invention， the strength threshold may be set as a fixed value or a value that is changed dynamically.

It is to be understood that the above example embodiments are only for the purpose of illustration， without suggesting any limitations on the subject matter described herein. The strength threshold may be implemented in any other suitable ways.

Alternatively， the carrier availability may be detected based on carrier sensing. By way of example， a signalling from a further transmitter may be detected on the first component carrier. The further transmitter may be a transmitter that may use the first component carrier and is different from the transmitter performing the method according to embodiments of the present invention. The signalling may for example contain information about whether the further transmitter occupies the first component carrier， the corresponding occupation time period， and the like. Based on the signalling， whether the first component carrier is available for the retransmission may be determined. For instance， if the signalling contains information indicating that a further transmitter occupies the first component carrier， it may be determined that the first component carrier is unavailable for the retransmission.

It is to be noted although the above embodiments illustrate a further transmitter， there may be a plurality of further transmitters in a communication system according to embodiments of the present invention. In such embodiments， energy detection and carrier sensing may be performed with respect to the plurality of further transmitters.

At step S230， in response to that the first component carrier is available for the retransmission， determining the first component carrier as the second component carrier. In this way， the first component carrier can be used as the component carrier of the retransmission.

At step S240， in response to that the first component carrier is unavailable for the retransmission， the carrier availability of the first carrier is monitored until the first component carrier is available， and the first component carrier is determined as the second component carrier.

In embodiments with respect to FIG. 2， if the first component carrier is unavailable for the retransmission， the transmitter will not perform the retransmission immediately. In some embodiments， the transmitter may wait until the first component carrier becomes available. During the waiting period， the transmitter may continue monitoring the carrier availability of the first component carrier until the first component carrier is available. When the first component carrier becomes available， it may be determined as the second component carrier.

In some alternative embodiments， the transmitter may wait for a predetermined period and detect the carrier availability of the first component carrier in the predetermined period. Once the first component carrier becomes available in the predetermined period， the transmitter may determine the first component carrier as the second component carrier. The predetermined period may be set according to system requirements， specifications， and so on. According to embodiments of the present invention， the predetermined period may be set as a fixed value or a value that is changed dynamically. It is to be understood that the above examples are only for the purpose of illustration， without suggesting any limitations on the subject matter described herein. For example， the predetermined period may be implemented in any other suitable ways.

At step S250， the retransmission is performed on the second component carrier. This step is similar to the step S130 of method 100. As discussed， the retransmission may employ either the self-scheduling or the cross carrier scheduling by using the second component carrier.

FIG. 5A illustrates a schematic diagram of a HARQ procedure 500 in a TDD system according to embodiments of the invention. It is to be noted that although the embodiments of FIG. 5A illustrate one configuration designed for the TDD system， it is described for purpose of example， rather than limitation. In alternative embodiments， other configurations designed for the TDD system are applicable as well.

As shown in FIG. 5A， there are three frames， Frame 0， Frame 1 and Frame 2， and each frame comprises 10 subframes. There are 3 types of subframes， wherein “D” represents a downlink subframe， “U” represents an uplink subframe， and “S” represents a special subframe. Availability indicates whether the first component carrier is available at respective subframes. For example， at subframes 4 to 6 of Frame 0， the first component carrier is available； at subframes 6 to 9 of Frame 1， the first component carrier is unavailable； and at subframe 0 of Frame 2， the first component carrier becomes available.

In embodiments of FIG. 5A， the transmitter performs 501 first transmission of a data block to at subframe 4 of Frame 0. If the first transmission is failed， the receiver may send 502 NACK to the transmitter， at subframe 2 of Frame 1， to request retransmission. In response to NACK， the transmitter may perform retransmission of the data block to the receiver. Assuming the transmitter wants 503 to perform the retransmission at subframe 6 of Frame 1， since the first component carrier is unavailable at subframes 6-9 of Frame 1， the transmitter will monitoring the carrier availability of the first component carrier until the first component carrier becomes available， for example， at subframe 0 of Frame 2. At that time， the transmitter may determine 504 the first component carrier as the second component carrier of the retransmission and perform the retransmission on the second component carrier. In this way， the delay of the retransmission may be 4 subframes， for example， 4ms， and the Round-Trip Time (RTT) of the HARQ procedure 500 is 16ms.

It is to be noted that although the HARQ procedure 500 of FIG. 5A is illustrated with a TDD case， it is also applicable to a FDD case. FIG. 5B illustrates a schematic diagram of a HARQ procedure 510 in a FDD system according to embodiments of the invention.

As shown in FIG. 5B， at subframes 4 to 6 of Frame 0， the first component carrier is available； at subframes 2 to 5 of Frame 1， the first component carrier is unavailable； and at subframe 6 of Frame 1， the first component carrier becomes available.

In embodiments of FIG. 5B， the transmitter performs 511 first transmission of a data block to at subframe 4 of Frame 0. If the first transmission is failed， the receiver may send 512 NACK to the transmitter， at subframe 8 of Frame 0， to request retransmission. In response to NACK， the transmitter may perform retransmission of the data block to the receiver. Assuming the transmitter wants 513 to perform the retransmission at subframe 2 of Frame 1， since the first component carrier is unavailable at subframes 2-5 of Frame 1， the transmitter will monitoring the carrier availability of the first component carrier until the first component carrier becomes available， for example， at subframe 6 of Frame 1. At that time， the transmitter may determine 514 the first component carrier as the second component carrier of the retransmission and perform the retransmission on the second component carrier. In this way， the delay of the retransmission may be 4 subframes， for example 4ms， and the RTT of the HARQ procedure 510 is 12ms.

FIG. 3 illustrates a flow chart of a method 300 for performing data transmission in a HARQ procedure at a transmitter according to further embodiments of the invention. The method 300 may be considered as a specific implementation of the method 100 described above with reference to Fig. 1. According to embodiments illustrated with reference to FIG. 3， when the retransmission is to be performed， the second component carrier is determined from one or more candidate component carriers available for the retransmission， wherein the candidate component carriers may comprise the first component carrier available for the retransmission， and/or other licensed or unlicensed carrier available for the retransmission.

Method 300 starts at step S310， wherein first transmission of a data block is transmitted to a receiver， wherein a data channel of the first transmission is carried on a first component carrier.

At step S320， at least one candidate component carrier available for the retransmission is determined.

According to embodiments of the present invention， the candidate component carrier may be a licensed carrier or an unlicensed carrier. In some embodiments， at step S320， if the first component carrier is available， it may be determined as a candidate component carrier. Alternatively or additionally， the candidate component carrier may be any other licensed or unlicensed carrier that is available for the retransmission.

The candidate component carrier may be determined by means of energy detection， carrier sensing， and so on. In some embodiments， strength of energy from a further transmitter may be measured on a component carrier. In response to that the measured signal strength is less than a strength threshold， it may be determined that the energy strength is not strong and the component carrier is idle. As such， the component carrier may be determined as a candidate component carrier. According to embodiments of the present invention， the strength threshold may be a predetermined threshold， which may be set according to system requirements， specifications， channel quality， and so on. The strength threshold may be set as a fixed value or a value that is changed dynamically.

Alternatively， whether a candidate component carrier is available for the retransmission may be determined based on carrier sensing. By way of example， a signalling from a further transmitter may be detected on a component carrier and the at least one candidate component carrier may be determined based on the signalling. The further transmitter is a transmitter that is different from the transmitter performing the method according to embodiments of the present invention. The signalling sent from the further transmitter may for example contain infonnation about whether the further transmitter occupies a component carrier， the corresponding occupation time period， and the like. Based on the signalling， whether the component carrier is available for the retransmission may be determined. If the component carrier is available， it may be determined as a candidate component carrier.

Alternatively or additionally， candidate component carrier (s) may be determined as those available for the retransmission in a certain period. In some embodiments， a delay tolerance window of the retransmission may be obtained， and the at least one candidate component carrier available for the retransmission may be determined in the delay tolerance window. The delay tolerance window may be a period of time， which may be predefined according to system requirements， specifications， and so on. According to embodiments of the present invention， the delay tolerance window may be a fixed time period or a time period that is changed dynamically. Upon receiving the negative acknowledge message from the receiver， the transmitter may determine， as the candidate component carriers， one or more component carrier available for the retransmission during the delay tolerance window. In this way， a component carrier that is unavailable in the delay tolerance window but available later may be not considered as a candidate component carrier.

At step S330， the second component carrier is determined based on the at least one candidate component carrier.

According to embodiments of the present invention， there may be at least one candidate component carrier determined at step S320. The second component carrier may be selected from the at least one candidate component carrier based on load status or channel quality of the at least one candidate component carrier. By way of example， in some embodiments， the load status of each candidate component carrier may be obtained. The load status may comprise information indicating whether the load on a component carrier is light or heavy. Based on the load status， a candidate component carrier that has lighter load may be selected as the second component carrier.

Alternatively or additionally， the channel quality of each candidate component carrier may be obtained. The channel quality may comprise information indicating the quality of a component carrier， such as Signal Noise Ratio (SNR) ， Signal Interference Noise Ratio (SINR) ， and/or the like. Then， a candidate component carrier that has higher channel quality， such as higher SNR or SINR， may be selected as the second component carrier.

At step S340， the retransmission is performed on the second component carrier.

This step is similar to the step S130 of method 100. As discussed， the retransmission may employ either the self-scheduling or the cross carrier scheduling by using the second component carrier.

FIG. 6A illustrates a schematic diagram of a HARQ procedure 600 in a TDD system according to embodiments of the invention. It is to be noted that although the embodiments of FIG. 6A illustrate one configuration designed for the TDD system， it is described for purpose of example， rather than limitation. In alternative embodiments， other configurations designed for the TDD system are applicable as well.

As shown in FIG. 6A， there are three frames， Frame 0， Frame 1 and Frame 2， and each frame comprises 10 subframes. There are 3 types of subframes， wherein “D” represents a downlink subframe， “U” represents an uplink subframe， and “S” represents a special subframe. Availability indicates whether the first component carrier is available at respective subframes. For example， at subframes 4 to 6 of Frame 0， the first component carrier is available； at subframes 6 to 9 of Frame 1， the first component carrier is unavailable； and at subframe 0 of Frame 2， the first component carrier is available.

In embodiments of FIG. 6A， the transmitter performs 601 first transmission of a data block to at subframe 4 of Frame 0. If the first transmission is failed， the receiver may send 602 NACK to the transmitter， at subframe 2 of Frame 1， to request retransmission. In response to NACK， the transmitter may perform retransmission of the data block to the receiver. Assuming the transmitter wants 603 to perform the retransmission at subframe 6 of Frame 1， the transmitter may first determine one or more candidate component carriers which are available at subframe 6 of Frame 1. Since the first component carrier is unavailable at subframe 6 of Frame 1， the first component carrier will not be determined as a candidate component carrier. Then， the transmitter may select one from the one or more candidate component carriers as the second component carrier to perform the retransmission. As such， the retransmission may start at subframe 6 of Frame 1， and the delay of the retransmission may be removed. In this way， the RTT in the HARQ procedure 600 is 12ms， less than the 16ms in the HARQ procedure 500.

It is to be noted that although the HARQ procedure 600 of FIG. 6A is illustrated with a TDD case， it is also applicable to a FDD case. FIG. 6B illustrates a schematic diagram of a HARQ procedure 610 in a FDD system according to embodiments of the invention.

As shown in FIG. 6B， at subframes 4 to 6 of Frame 0， the first component carrier is available； at subframes 2 to 5 of Frame 1， the first component carrier is unavailable； and at subframe 6 of Frame 1， the first component carrier is available.

In embodiments of FIG. 6， the transmitter performs 611 first transmission of a data block to at subframe 4 of Frame 0. If the first transmission is failed， the receiver may send 612 NACK to the transmitter， at subframe 8 of Frame 0， to request retransmission. In response to NACK， the transmitter may perform retransmission of the data block to the receiver. Assuming the transmitter wants 613 to perform the retransmission at subframe 2 of Frame 1， the transmitter may first determine one or more candidate component carriers which are available at subframe 2 of Frame 1. Since the first component carrier is unavailable at subframe 2 of Frame 1， the first component carrier will not be determined as a candidate component carrier. Then， the transmitter may select one from the one or more candidate component carriers as the second component carrier to perform the retransmission. As such， the retransmission may start at subframe 2 of Frame 1， and the delay of the retransmission may be removed. In this way， the RTT in the HARQ procedure 610 is 8ms， less than the 12ms in the HARQ procedure 510.

FIG. 4 illustrates a flow chart of a method 400 for performing data transmission in a HARQ procedure at a receiver according to further embodiments of the invention. The method 400 may be performed at a receiver， such as a UE， a D2D receiver， and other suitable device.

At step S410， in response to that first transmission of a data block is failed， a negative acknowledge message is sent to a transmitter， wherein a data channel of the first transmission is carried on a first component carrier. At step S420， retransmission of the data block is received on a second component carrier， wherein the second component carrier is determined based on carrier availability.

According to embodiments of the present invention， the second component carrier may be determined as the first component carrier available for the retransmission. In some embodiments， the second component carrier may be determined by： determining whether the first component carrier is available for the retransmission； in response to that the first component carrier is available for the retransmission， determining the first component carrier as the second component carrier； and in response to that the first component carrier is unavailable for the retransmission， monitoring the carrier availability of the first carrier until the first component carrier is available， and determining the first component carrier as the second component carrier. Details may be found in embodiments described with reference to FIG. 2.

According to embodiments of the present invention， the second component carrier may be determined based on at least one candidate component carrier available for the retransmission. In some embodiments， the second component carrier may be selected from the at least one candidate component carrier based on load status or channel quality of the at least one candidate component carrier. Details may be found in embodiments described with reference to FIG. 3.

FIGs. 7 and 8 relate to block diagrams of apparatus for performing data transmission in a HARQ procedure according to embodiments of the invention， respectively.

Reference is now made to FIG. 7， which illustrates a b1ock diagram of an apparatus 700. In accordance with embodiments of the present invention， the apparatus 700 may be implemented at a transmitter， for example， a B S， a D2D transmitter or any other applicable device.

As shown，the apparatus 700 comprises： a transmitting unit 710 configured to transmit first transmission of a data block to a receiver， wherein a data channel of the first transmission is carried on a first component carrier； a determining unit 720 configured to， in response to receiving from the receiver a negative acknowledge message indicating the first transmission is failed，determine a second component carrier for retransmission of the data block based on carrier availability； and a performing unit 73 0 configured to perform the retransmission on the second component carrier.

According to embodiments of the present invention， the determining unit 720 may comprise： a first availability determining unit configured to determine whether the first component carrier is available for the retransmission. The deterinining unit may be further configured to， in response to that the first component carrier is available for the retransmission， determine the first component carrier as the second component carrier； and in response to that the first component carrier is unavailable for the retransmission， monitor the carrier availability of the first carrier until the first component carrier is available and determine the first component carrier as the second component carrier.

In some embodiments，the first availability determining unit may comprise： ameasuring unit configured to measure strength of energy from a further transmitter on the first component carrier， and wherein the first availability determining unit may be further configured to， in response to that the measured strength is less than a strength threshold， determine that the first component carrier is available for the retransmission.

In some embodiments， the first availability determining unit may comprise： a detecting unit configured to detect， on the first component carrier， a signalling from a further transmitter， and wherein the first availability determining unit may be further configured to determine whether the first component carrier is available for the retransmission based on the signalling.

According to embodiments of the present invention， the determining unit 720 may comprise： a second availability determining unit configured to determine at least one candidate component carrier available for the retransmission， and wherein the determining unit may be further configured to determine the second component carrier based on the at least one candidate component carrier.

In some embodiments， the second availability determining unit may comprise： an obtaining unit configured to obtain a delay tolerance window of the retransmission， and wherein the second availability determining unit may be further configured to determine， in the delay tolerance window， the at least one candidate component carrier available for the retransmission.

In some embodiments， the second availability determining unit may comprise： a measuring unit configured to measure strength of energy from a further transmitter on a component carrier， and wherein the second availability determining unit may be further configured to， in response to that the measured signal strength is less than a strength threshold， determine the component carrier as a candidate component carrier.

In some embodiments， the second availability determining unit may comprise： a detecting unit configured to detect， on a component carrier， a signalling from a further transmitter， and wherein the second availability determining unit may be further configured to determine the at least one candidate component carrier based on the signalling.

In some embodiments， the determining unit may comprise： a selecting unit configured to select the second component carrier from the at least one candidate component carrier based on load status or channel quality of the at least one candidate component carrier.

Reference is now made to FIG. 8， which illustrates a block diagram of an apparatus 800 for performing data transmission in a HARQ procedure according to embodiments of the invention. In accordance with embodiments of the present invention， the apparatus 800 may be implemented at a receiver， for example， a cellular UE， a D2D receiver or any other applicable device.

As shown， the apparatus 800 comprises： a sending unit 810 configured to， in response to that first transmission of a data block is failed， send a negative acknowledge message to a transmitter， wherein a data channel of the first transmission is carried on a first component carrier； and a receiving unit 820 configured to receive retransmission of the data block on a second component carrier， wherein the second component carrier is determined based on carrier availability.

According to embodiments of the present invention， the second component carrier may be determined by： determining whether the first component carrier is available for the retransmission； in response to that the first component carrier is available for the retransmission， determining the first component carrier as the second component carrier； and in response to that the first component carrier is unavailable for the retransmission， monitoring the carrier availability of the first carrier until the first component carrier is available， and determining the first component carrier as the second component carrier.

According to embodiments of the present invention， the second component carrier may be determined based on at least one candidate component carrier available for the retransmission.

In some embodiments， the second component carrier is selected from the at least one candidate component carrier based on load status or channel quality of the at least one candidate component carrier.

It is also to be noted that the

apparatuses

700 and 800 may be respectively implemented by any suitable technique either known at present or developed in the future. Further， a single device shown in FIG. 7 or FIG. 8 may be alternatively implemented in multiple devices separately， and multiple separated devices may be implemented in a single device. The scope of the present invention is not limited in these regards.

It is noted that the apparatus 700 may be configured to implement functionalities as described with reference to FIGs. 1-3， and the apparatus 800 may be configured to implement functionalities as described with reference to FIG. 4. Therefore， the features discussed with respect to any of methods 100-300 may apply to the conesponding components of the apparatus 700， and the features discussed with respect to the method 400 may apply to the corresponding components of the apparatus 800. It is further noted that the components of the

apparatus

700 or 800 may be embodied in hardware， software， firmware， and/or any combination thereof. For example， the components of the

apparatus

700 or 800 may be respectively implemented by a circuit， a processor or any other appropriate device. Those skilled in the art will appreciate that the aforesaid examples are only for illustration not limitation.

In some embodiment of the present disclosure， the

apparatus

700 or 800 may comprise at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include， by way of example， both general and special purpose processors already known or developed in the future. The

apparatus

700 or 800 may further comprise at least one memory. The at least one memory may include， for example， semiconductor memory devices， e.g.， RAM， ROM， EPROM， EEPROM， and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compliable or interpretable programming languages. In accordance with embodiments， the computer executable instructions may be configured， with the at least one processor， to cause the apparatus 700 to at least perform according to any of methods 100 to 300 as discussed above， or to cause the apparatus 800 to at least perform according to method 400 as discussed above.

Based on the above description， the skilled in the art would appreciate that the present disclosure may be embodied in an apparatus， a method， or a computer program product. In general， the various exemplary embodiments may be implemented in hardware or special purpose circuits， software， logic or any combination thereof. For example， some aspects may be implemented in hardware， while other aspects may be implemented in firmware or software which may be executed by a controller， microprocessor or other computing device， although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams， flowcharts， or using some other pictorial representation， it is well understood that these blocks， apparatus， systems， techniques or methods described herein may be implemented in， as non-limiting examples， hardware， software， firmware， special purpose circuits or logic， general purpose hardware or controller or other computing devices， or some combination thereof.

The various blocks shown in FIGs. 1-4 may be viewed as method steps， and/or as operations that result from operation of computer program code， and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function (s) . At least some aspects of the exemplary embodiments of the disclosures may be practiced in various components such as integrated circuit chips and modules， and that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit， FPGA or ASIC that is configurable to operate in accordance with the exemplary embodiments of the present disclosure.

While this specification contains many specific implementation details， these should not be construed as limitations on the scope of any disclosure or of what may be claimed， but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely， various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover， although features may be described above as acting in certain combinations and even initially claimed as such， one or more features from a claimed combination can in some cases be excised from the combination， and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

Similarly， while operations are depicted in the drawings in a particular order， this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order， or that all illustrated operations be performed， to achieve desirable results. In certain circumstances， multitasking and parallel processing may be advantageous. Moreover， the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments， and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

Various modifications， adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description， when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Furthermore， other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings.

Therefore， it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein， they are used in a generic and descriptive sense only and not for purpose of limitation.

Claims

A method of performing data transmission in a Hybrid Automatic Repeat Request (HARQ) procedure， comprising：

transmitting first transmission of a data block to a receiver， wherein a data channel of the first transmission is carried on a first component carrier；

in response to receiving from the receiver a negative acknowledge message indicating the first transmission is failed， determining a second component carrier for retransmission of the data block based on carrier availability； and

performing the retransmission on the second component carrier.
The method of Claim 1， wherein determining a second component carrier for retransmission of the data block based on carrier availability comprises：

determining whether the first component carrier is available for the retransmission；

in response to that the first component carrier is available for the retransmission， determining the first component carrier as the second component carrier； and

in response to that the first component carrier is unavailable for the retransmission，

monitoring the carrier availability of the first carrier until the first component carrier is available， and

determining the first component carrier as the second component carrier.
The method of Claim 2， wherein determining whether the first component carrier is available for the retransmission comprises：

measuring strength of energy from a further transmitter on the first component carrier； and

in response to that the measured strength is less than a strength threshold， determining that the first component carrier is available for the retransmission.
The method of Claim 2， wherein determining whether the first component carrier is available for the retransmission comprises：

detecting， on the first component carrier， a signalling from a further transmitter； and

determining whether the first component carrier is available for the retransmission based on the signalling.
The method of Claim 1， wherein determining a second component carrier for retransmission of the data block based on carrier availability comprises：

determining at least one candidate component carrier available for the retransmission； and

determining the second component carrier based on the at least one candidate component carrier.
The method of Claim 5， wherein determining at least one candidate component carrier available for the retransmission comprises：

obtaining a delay tolerance window of the retransmission； and

determining， in the delay tolerance window， the at least one candidate component carrier available for the retransmission.
The method of Claim 5， wherein determining at least one candidate component carrier available for the retransmission comprises：

measuring strength of energy from a further transmitter on a component carrier；and

in response to that the measured signal strength is less than a strength threshold， determining the component carrier as a candidate component carrier.
The method of Claim 5， wherein determining at least one candidate component carrier available for the retransmission comprises：

detecting， on a component carrier， a signalling from a further transmitter； and

determining the at least one candidate component carrier based on the signalling.
The method of Claim 5， wherein determining the second component carrier based on the at least one candidate component carrier comprises：

selecting the second component carrier from the at least one candidate component carrier based on load status or channel quality of the at least one candidate component carrier.
A method of performing data transmission in a Hybrid Automatic Repeat Request (HARQ) procedure， comprising：

in response to that first transmission of a data block is failed， transmitting a negative acknowledge message to a transmitter， wherein a data channel of the first transmission is carried on a first component carrier； and

receiving retransmission of the data block on a second component carrier， wherein the second component carrier is determined based on carrier availability.
The method of Claim 10， wherein the second component carrier is determined by：determining whether the first component carrier is available for the retransmission； in response to that the first component carrier is available for the retransmission， determining the first component carrier as the second component carrier； and in response to that the first component carrier is unavailable for the retransmission， monitoring the carrier availability of the first carrier until the first component carrier is available， and determining the first component carrier as the second component carrier.
The method of Claim 10， wherein the second component carrier is determined based on at least one candidate component carrier available for the retransmission.
The method of Claim 12， wherein the second component carrier is selected from the at least one candidate component carrier based on load status or channel quality of the at least one candidate component carrier.
An apparatus of performing data transmission in a Hybrid Automatic Repeat Request (HARQ) procedure， comprising：

a transmitting unit configured to transmit first transmission of a data block to a receiver， wherein a data channel of the first transmission is carried on a first component carrier；

a determining unit configured to， in response to receiving from the receiver a negative acknowledge message indicating the first transmission is failed， determine a second component carrier for retransmission of the data block based on carrier availability； and

a performing unit configured to perform the retransmission on the second component carrier.
The apparatus of Claim 14， wherein the determining unit comprises：

a first availability determining unit configured to determine whether the first component carrier is available for the retransmission， and

wherein the determining unit is further configured to，

in response to that the first component carrier is available for the retransmission， determine the first component carrier as the second component carrier； and

in response to that the first component carrier is unavailable for the retransmission，

monitor the carrier availability of the first carrier until the first component carrier is available， and

determine the first component carrier as the second component carrier.
The apparatus of Claim 15， wherein the first availability determining unit comprises：

a measuring unit configured to measure strength of energy from a further transmitter on the first component carrier， and

wherein the first availability determining unit is further configured to， in response to that the measured strength is less than a strength threshold， determine that the first component carrier is available for the retransmission.
The apparatus of Claim 15， wherein the first availability determining unit comprises：

a detecting unit configured to detect， on the first component carrier， a signalling from a further transmitter， and

wherein the first availability determining unit is further configured to determine whether the first component carrier is available for the retransmission based on the signalling.
The apparatus of Claim 14， wherein the determining unit comprises：

a second availability determining unit configured to determine at least one candidate component carrier available for the retransmission， and

wherein the determining unit is further configured to determine the second component carrier based on the at least one candidate component carrier.
The apparatus of Claim 18， wherein the second availability determining unit comprises：

an obtaining unit configured to obtain a delay tolerance window of the retransmission， and

wherein the second availability determining unit is further configured to determine， in the delay tolerance window， the at least one candidate component carrier available for the retransmission.
The apparatus of Claim 18， wherein the second availability determining unit comprises：

a measuring unit configured to measure strength of energy from a further transmitter on a component carrier， and

wherein the second availability determining unit is further configured to， in response to that the measured signal strength is less than a strength threshold， determine the component carrier as a candidate component carrier.
The apparatus of Claim 18， wherein the second availability determining unit comprises：

a detecting unit configured to detect， on a component carrier， a signalling from a further transmitter， and

wherein the second availability determining unit is further configured to determine the at least one candidate component carrier based on the signalling.
The apparatus of Claim 18， wherein the determining unit comprises：

a selecting unit configured to select the second component carrier from the at least one candidate component carrier based on load status or channel quality of the at least one candidate component carrier.
An apparatus of performing data transmission in a Hybrid Automatic Repeat Request (HARQ) procedure， comprising：

a sending unit configured to， in response to that first transmission of a data block is failed， send a negative acknowledge message to a transmitter， wherein a data channel of the first transmission is carried on a first component carrier； and

a receiving unit configured to receive retransmission of the data block on a second component carrier， wherein the second component carrier is determined based on carrier availability.
The apparatus of Claim 23， wherein the second component carrrier is determined by： determining whether the first component carrier is available for the retransmission； in response to that the first component carrier is available for the retransmission， determining the first component carrier as the second component carrier； and in response to that the first component carrier is unavailable for the retransmission， monitoring the carrier availability of the first carrier until the first component carrier is available， and determining the first component carrier as the second component carttier.
The apparatus of Claim 23， wherein the second component carrier is determined based on at least one candidate component carrier available for the retransmission.
The apparatus of Claim 25， wherein the second component carrier is selected from the at least one candidate component carrier based on load status or channelquality of the at least one candidate component carrier.