KR101119112B1 - Communication method according to ARQ scheme in communication system - Google Patents

Abstract

The present invention relates to a communication method according to an automatic retransmission request scheme in a communication system. The communication method according to the automatic retransmission request scheme according to the present invention is a communication method according to the automatic retransmission request scheme in a mobile communication system, comprising: a first packet associated with a first packet transmitted in a frame group including a plurality of consecutive frames; Transmitting a retransmission packet at regular intervals for a negative acknowledgment signal (NACK) of the terminal; and retransmitting the packet aperiodically for a negative acknowledgment signal (NACK) of a second terminal associated with a second packet transmitted in the frame group. Characterized in that it comprises a step of transmitting.

Auto retransmit, ACK, NACK, ARQ, HARQ

Description

Communication method according to ARQ scheme in communication system

1 is a view for explaining the HARQ scheme according to the prior art.

2 is a view for explaining a preferred embodiment of the present invention.

The present invention relates to a communication system, and more particularly, to a communication method according to an automatic retransmission request scheme in a communication system.

In general, an automatic repeat request (ARQ) method detects data transmission errors occurring on a transmission channel and corrects data errors by requesting retransmission on the transmission side if a data transmission error occurs. to be. Therefore, the purpose of the automatic retransmission request (ARQ) scheme is to improve reliability by requiring retransmission of the same data until it is transmitted without error if a data transmission error occurs.

Hybrid ARQ (HARQ) method combines automatic retransmission request (ARQ) method with Forward Error Correction (FEC) method which uses error correcting code to correct errors caused by channel environment. In this way, reliability and data throughput in data transmission in a communication system can be improved by the HARQ method. In particular, by performing the HARQ scheme between the physical layer of the transmitting side and the receiving side, it is possible to reduce the packet transmission delay and increase the transmission efficiency.

1 is a view for explaining the HARQ scheme according to the prior art. Referring to FIG. 1, the base station determines downlink control information including the transmission format by determining a terminal to receive a packet and a transmission format (coding rate, modulation scheme, data amount, etc.) applied to the packet to be transmitted to the terminal. The terminal transmits the data packet to the terminal through the channel [S11], and transmits the corresponding data packet to the terminal at the time associated with the terminal [S12]. Here, the term 'transmission format' refers to transmission parameters used by a base station or a terminal to transmit data (for example, the number of data bits included in one frame, modulation scheme, channel coding rate, channel coding scheme, etc.). ) Means a combination of at least two or more. In addition, the transport format set is a set including a plurality of different transport formats, and the transport format index is an identification number assigned to identify each transport format in the transport format set.

The terminal receives the downlink control channel to know the transmission format and the transmission time of the packet to be transmitted to it, and can receive the packet through this. After the packet is received, the packet data is decoded. If the terminal fails to decode the packet, the terminal transmits a negative acknowledgment signal (NACK) to the base station [S13]. Upon receiving the NACK signal, the base station detects that the packet transmission to the terminal has failed, transmits control information for the retransmission packet to the terminal [S14], and then transmits the retransmission packet at a proper time point. S15]. The retransmission packet may be transmitted in the same transmission format or a new transmission format as the packet transmitted in step S12.

When the terminal receives the retransmission packet and successfully decrypts the terminal, the terminal transmits an acknowledgment signal (ACK) to the base station [S16], and the base station receiving the ACK signal indicates that the packet transmission to the terminal was successful. Can detect and perform the next packet transfer operation. In this case, the terminal attempts to decode again by combining the packet that has previously received the retransmission packet but failed to decode with a chase combining or incremental redundancy (IR) combination.

In order to provide a high-capacity high-speed data service and simplify the channel structure in a wireless communication system, models that can perform packet communication and voice communication through one channel have been developed. In this case, the packet data and the voice data have different characteristics from each other. That is, since the voice data generates a relatively small amount of data relatively periodically and at a low speed compared to the packet data, the occurrence statistics are close to the circuit (circuit). Therefore, there is a need to develop a new technique considering each feature in applying the HARQ technique to packet data and voice data transmitted through one channel.

The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to provide an automatic retransmission request scheme for each service characteristic in providing a packet service and a voice service through one channel. It is to provide a communication method according to.

Another object of the present invention is to provide a communication method according to an automatic retransmission request scheme that can reduce the amount of control information required for applying an automatic retransmission scheme in a communication system.

In one aspect of the present invention, a communication method according to an automatic retransmission request scheme according to the present invention is a communication method according to an automatic retransmission request scheme in a mobile communication system, and is transmitted within a frame group including a plurality of consecutive frames. Transmitting a retransmission packet at regular intervals to a negative response signal (NACK) of a first terminal associated with a first packet; and a negative response signal (NACK) of a second terminal associated with a second packet transmitted in the frame group. It characterized in that it comprises a step for transmitting a retransmission packet aperiodic for the.

In another aspect of the present invention, a communication method according to the automatic retransmission request scheme according to the present invention is a communication method according to the automatic retransmission request scheme in a mobile communication system, comprising: at least one in a frame group including a plurality of consecutive frames Transmitting retransmission packets periodically or aperiodically to a negative acknowledgment signal (NACK) of a receiver related to a packet transmitted to a first subgroup including the frame, and other than the first subgroup within the frame group. A retransmission packet is aperiodically transmitted to a negative acknowledgment signal (NACK) of a receiver related to a packet transmitted in a frame.

As another aspect of the present invention, a communication method according to the automatic retransmission request scheme according to the present invention is a communication method according to the automatic retransmission request scheme in a mobile communication system, which is received within a frame group consisting of a plurality of consecutive frames. Transmitting a negative acknowledgment signal (NACK) for the received first packet to the base station, transmitting a negative acknowledgment signal (NACK) for the second packet received in the frame group to the base station, and a predetermined period has elapsed. Receiving a retransmission packet for the first packet, receiving control information for the retransmission packet of the second packet, and receiving a retransmission packet of the second packet using the control information. Characterized in that configured to include.

In another aspect of the present invention, a communication method according to the automatic retransmission request scheme according to the present invention comprises the steps of: transmitting a packet to a receiving side; receiving a negative acknowledgment signal (NACK) for the packet from the receiving side; In the communication method according to the automatic retransmission request method comprising the step of transmitting a retransmission packet to the receiving side, Retransmission at a predetermined period for at least one frame in a frame group consisting of a plurality of consecutive frames The packet is transmitted, and a retransmission packet is aperiodically transmitted to a negative acknowledgment signal (NACK) of a receiver for at least one or more other frames in the frame group.

The construction, operation, and other features of the present invention will be readily understood by the preferred embodiments of the present invention described below with reference to the accompanying drawings. Embodiments described below are examples in which the technical features of the present invention are applied to a 3GPP High Speed Downlink Packet Access (HSDPA) system.

HSDPA improves the performance of the existing downlink shared channel (DSCH) to provide a high-speed data transmission service of up to 10 Mbps over the downlink. Representative radio access technologies adopted in the physical layer of the HSDPA system include a link adaptation (LA) technique and an HARQ technique as an automatic retransmission request scheme. The link adaptation (LA) method is a method of using an appropriate modulation and coding scheme (MCS) suitable for a channel state for every packet (or subpacket) transmission. The physical layer channel of the HSDPA includes a HSDPA Physical DSCH (HS-PDSCH) and a Shared Physical Control Channel (HS-SCCH). The HS-PDSCH is a physical channel for transmitting data transmitted through the HS-DSCH, and the HS-SCCH is a channel for transmitting control information for supporting the HS-PDSCH.

The HARQ scheme can be roughly divided into synchronous HARQ and asynchronous HARQ according to a scheme of defining a relationship between a packet retransmission time point and a previous transmission time point.

In the synchronous HARQ scheme, a time point for retransmission of a specific packet is generally fixed as a time interval relative to a previous time point for transmission. For example, if it is defined that retransmission is allowed once every 6 frames, when the transmission of a particular packet fails, the retransmission of the packet is made after 5 frames. In this case, when transmission of a specific packet to a specific terminal fails, five frames must be waited to transmit a retransmission packet to the terminal. Therefore, to transmit another packet to the terminal within frames waiting for retransmission, the terminals are different. Six HARQ processes should be able to operate independently. That is, the terminal fails to receive the first transmission of the first packet and can receive the first transmission of another packet even in a state of waiting for the retransmission of the first packet. In the synchronous HARQ scheme, a plurality of HARQ processes are periodically repeated in the same order. The advantage of the synchronous HARQ scheme is that, if the packet format and the transmission format of the retransmission are determined in advance according to the number of retransmissions, the base station knows the predetermined retransmission time of the packets when the reception of a packet fails. There is no need for downlink control channel transmissions that indicate the transmission format of the packet.

In the asynchronous HARQ scheme, the base station may perform packet retransmission at a time irrelevant to a previous transmission time of the packet. When the UE fails to receive a packet, the BS does not know when the BS transmits the retransmission packet. Thus, even when the BS transmits the retransmission packet, the BS informs the downlink control channel of information indicating that the retransmission packet is the retransmission packet for the terminal. Should give In the asynchronous HARQ scheme, the base station can freely determine a packet retransmission time point for a plurality of terminals, thereby maximizing scheduling freedom, thereby maximizing scheduling gain.

HARQ scheme basically adopted in HSDPA system transmits data asynchronously in downlink, and response information is transmitted synchronously. That is, each downlink data may be transmitted at any time according to the scheduler's decision, and the response signal may be transmitted uplink within a predetermined time.

2 is a view for explaining a preferred embodiment of the present invention. In the embodiment of FIG. 2, six consecutive frames transmitted through the HS-PDSCH are defined as one frame group, and in the first frame (frame # 1), a packet is transmitted by a synchronous HARQ scheme. In the remaining frames, a packet is transmitted by an asynchronous HARQ scheme. That is, the retransmission packet for the packet transmitted in the first frame of the frame group is periodically transmitted. In the second to sixth frames, the transmission time of the retransmission packet is freely determined according to the scheduling of the base station. In the following, it will be described in more detail.

The base station transmits control information (control information # 1) for the first packet (packet # 1) to the terminal through the HS-SCCH [S21]. The control information includes an identifier (UE ID) of a terminal that is a destination of the first packet and an identifier of a transmission format to be applied when the first packet is transmitted. In addition, the control information may include HARQ process identification information, 'New Data Indicator', 'Redundancy Version' and the like. The HARQ identification information is information on which of the HARQ processes the base station transmits data using. 'New Data Indicator' is an indicator indicating that the first packet is the first transport packet. 'Redundancy Version' is information for identifying 'Redundancy' of coding data additionally transmitted in the HARQ scheme. Particularly, given that the synchronous HARQ scheme is mainly a relatively small amount of data such as a voice service and does not require various transmission formats, all of the information constituting the control information for all the frames operating in the synchronous HARQ scheme are all. Alternatively, the control information transmitted for the first packet can be simplified by making some of them in common. For example, the first frame of each frame group is preset to use one or a few transmission formats, and the terminal transmits information related to this by presuming the one or a few transmission formats and attempting decoding thereof. Can be omitted. As another method, it is also possible to reduce the number of bits of identification information of the transmission format by simplifying the transmission format of the frame to which the synchronous HARQ scheme is applied than the transmission format of the frame to which the asynchronous HARQ scheme is applied.

The terminal corresponding to the terminal identifier knows that the packet is to be transmitted to the user through the control information, and information necessary for receiving the first packet such as a transmission format to be applied to the packet to be transmitted, HARQ process identification information, and a 'New Data Indicator' Get The base station transmits an initial transport packet (packet # 1) on the first frame of the first frame group on the downlink physical channel HS-PDSCH. Here, the first transmission packet means that the base station transmits to the terminal for the first time with respect to a certain packet and is distinguished from a retransmission packet transmitted after receiving a negative acknowledgment signal (NACK) from the terminal.

The base station transmits the packet # 1 to the terminal through the first frame of the first frame group [S22]. The terminal receives the packet # 1 and decodes it. If decoding fails due to an error in the packet # 1, a NACK is transmitted to the base station [S23]. The base station receiving the NACK for the packet # 1 from the terminal transmits the retransmission packet of the packet # 1 to the terminal [S29]. Since the first frame (frame # 1) of each frame group is designated to use the synchronous HARQ technique, the retransmission packet of the packet # 1 is transmitted in the first frame of the next frame group, the second frame group. Since the UE knows that the synchronous HARQ scheme is applied to the first frame of each frame group, it can prepare in advance by knowing that the retransmission packet of the packet # 1 is received in the first frame (frame # 1) of the second frame group. have. Therefore, HARQ process identification information, 'Redundancy Version', the transmission format for retransmission packet transmission, etc. are determined in advance according to the number of retransmissions, thereby significantly reducing the control information to be transmitted through the HS-SCCH for the transmission of the retransmission packet. I can not do HS-SCCH transmission itself.

In FIG. 2, it is set to apply an asynchronous HARQ technique to the remaining frames except the first frame of each frame group. Accordingly, when the base station transmits the retransmission packet in the remaining frames, the base station transmits the retransmission packet according to scheduling of the base station scheduler regardless of the transmission time of the packet before the retransmission packet. In this case, since the UE cannot know the transmission time of the retransmission packet transmitted in the remaining frames, the base station transmits the control information for the retransmission packet transmitted through the HS-SCCH even when the retransmission packet is transmitted in the remaining frames. Must be sent to the terminal. In FIG. 2, the base station controls control information (control information # 2 and packet # 2 and packet # 3) in a third frame (frame # 3) and a fourth frame (frame # 4) of the first frame group on the HS-PDSCH. Control information # 3) is transmitted through the HS-SCCH [S23, S25], and then the packet # 2 and the packet # 3 are transmitted through the HS-PDSCH, respectively [S24, S26].

The terminal receives the packet # 2 and the packet # 3 according to the control information # 2 and the control information # 3 received from the base station. When the terminal receives the packet # 2 and the packet # 3 and decodes the packet # 2 and the packet # 3, the NACK is transmitted to the base station in response to the packet # 2 and the packet # 3, respectively. [S27, S28]. When the base station receives a NACK in response to the packet # 2 and the packet # 3, it should transmit a retransmission packet for each. At this time, the transmission time of the retransmission packet for the packet # 2 and the packet # 3 is determined according to the downlink scheduling of the scheduler of the base station. In FIG. 2, the retransmission packet for the packet # 2 is determined to be transmitted in the fifth frame of the second frame group (frame # 5), and the retransmission packet for the packet # 3 is in the third of the second frame group. It was determined to be transmitted in frame (frame # 3).

The base station transmits control information # 2 and control information # 3, which are control information, through the HS-SCCH before transmitting the retransmission packets of the packet # 2 and the packet # 3. The control information # 2 and the control information # 3 are identifiers of terminals to which retransmission packets of the packets # 2 and # 3 are to be transmitted, indication information indicating that the retransmission packets are retransmission packets of the packets # 2 and # 3, and It may include an identifier of a transmission format applied to the retransmission packet, HARQ process identification information, 'New Data Indicator', 'Redundancy Version' and the like.

In the embodiment of Figure 2, the frame to apply the synchronous HARQ and the frame to apply the asynchronous HARQ in one frame group can be determined by the base station, which frame is applied to the synchronous HARQ or which frame is applied to the asynchronous HARQ Information on whether the information is informed to the terminal through uplink signaling. To this end, in the case of the HSDPA system, by applying the same length of the frame group and the starting point of the frame group to all the terminals in order to efficiently arrange the frame for the synchronous HARQ operation of a plurality of terminals frame identification number in each frame group ( It is desirable to create an indicator. A system frame number (SFN) may be used to generate the frame identification number.

When determining the frame to apply the synchronous HARQ in the frame group to determine in common for all terminals that are currently connected to the base station (connection), or for each terminal group including at least two or more terminals, or for each terminal It is possible to decide individually. In other words, it is possible to determine that the synchronous HARQ technique is applied to at least one or more frames in the frame group for all terminals currently connected to the base station, and to determine to use different frames synchronously for each UE group. In addition, it may be determined to apply a synchronous HARQ scheme to a different frame for each terminal. For example, in FIG. 2, the first frame of each frame group is allocated by applying a synchronous HARQ technique to provide a voice service to a first terminal, and the remaining frames (frames # 2 to # 6) are allocated to a base station. In order to provide packet services to other terminals in the network, it may be allocated by applying an asynchronous HARQ scheme.

In another preferred embodiment of the present invention, within the frame group on the HS-PDSCH, a first subgroup applying the synchronous HARQ scheme and a second subgroup applying the asynchronous HARQ scheme are distinguished from each other and used in the second subgroup. Only the asynchronous HARQ operation is allowed for the first subgroup and the synchronous HARQ operation or the asynchronous HARQ operation can be configured according to the selection of the base station scheduler. For example, in the example of FIG. 2, the asynchronous HARQ operation is performed from the second frame (frame # 2) to the sixth frame (frame # 6) within each frame group, and the first frame (frame # 1) of the base station. Optionally, to perform a synchronous HARQ operation or an asynchronous HARQ operation. In this case, it is preferable to limit the reception complexity of the terminal so that one terminal does not simultaneously perform a synchronous HARQ operation and an asynchronous HARQ operation on a frame belonging to the first subgroup.

In the second embodiment, since the UE does not know whether the BS scheduler performs a synchronous HARQ operation or an asynchronous HARQ operation in the frames included in the first subgroup, a method of distinguishing the MSs should be considered. For example, through the control information transmitted through the HS-SCCH, distinguished through the transmission format of the received HS-SCCH, or Orthogonal Variable Spreading Function (OVSF) code used for the HS-SCCH or HS-PDSCH Can be distinguished by channel code. For example, when a specific OVSF code is used in the HS-SCCH or HS-PDSCH, a packet transmitted in a corresponding frame performs a synchronous HARQ operation, and when a different channel code is used, the terminal is configured to perform an asynchronous HARQ operation. It is possible to distinguish whether to perform a synchronous HARQ operation or an asynchronous HARQ operation on the frames included in the first subgroup.

Although the above embodiments are examples of the HSDPA system using the HARQ technique, it is obvious to those skilled in the art that the technical features of the present invention can be applied to other communication systems using various kinds of automatic retransmission request (ARQ) techniques. . In addition, the term packet as used herein may be replaced with a 'subpacket' in some cases. In other words, when the HARQ scheme is applied, one 'subpacket' may be configured as a plurality of 'subpackets', and each 'subpacket' may be transmitted as a retransmission packet when retransmission is performed according to the NACK of the receiver. .

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

According to the present invention has the following effects.

First, when the voice service and the packet service are provided through one channel, an automatic retransmission request scheme for each feature can be applied.

Second, while reducing the complexity of the terminal, it is possible to obtain the advantages of the asynchronous HARQ scheme and the advantages of the synchronous HARQ scheme.

Third, the amount of control information required to apply the automatic retransmission scheme in a communication system can be reduced.

Claims (21)

In a communication method according to a hybrid automatic retransmission request (HARQ) method in a mobile communication system, Transmitting a retransmission packet at regular intervals of the same time interval in a synchronous HARQ scheme for a negative acknowledgment signal (NACK) of a first terminal associated with a first packet transmitted in a frame group consisting of a plurality of consecutive frames; And And transmitting a retransmission packet aperiodically in an asynchronous HARQ manner with respect to a negative acknowledgment signal (NACK) of a second terminal associated with a second packet transmitted in the frame group. The method of claim 1, And transmitting control information for the second packet and the retransmission packet to the second terminal, respectively, before transmitting the second packet and the retransmission packet. 3. The method of claim 2, And the control information includes an identifier of the second terminal and a transmission format of the second packet and its retransmission packet. The method of claim 1 The control method according to the automatic retransmission request method, characterized in that for transmitting the control information for the first packet to the first terminal before the transmission of the first packet. The method of claim 1, The communication method according to the automatic retransmission request scheme, characterized in that the terminal is informed of the identification information (indicator) of the frame to be transmitted periodically and the frame to be transmitted aperiodically within the frame group. The method of claim 5, The identification information is a communication method according to the automatic retransmission request method characterized in that the higher layer from the upper layer than the physical layer signaling (signaling). The method of claim 5, The frame according to the automatic retransmission request method characterized in that the frame to be retransmitted packet periodically and the frame to be transmitted aperiod in the frame group are designated for each terminal. The method of claim 5, The frame according to the automatic retransmission request scheme, characterized in that the frame to be retransmitted packet periodically and the frame to be transmitted aperiod in the frame group are commonly specified for all terminals to which the current connection (connection) is established. The method of claim 5, The frame according to the automatic retransmission request scheme, characterized in that the frame to be retransmitted packet periodically and the frame to be transmitted aperiod within the frame group is assigned to a certain group of all the terminals to which the current connection is established. The method of claim 1, The predetermined period is the communication method according to the automatic retransmission request scheme, characterized in that the same as the length of the frame group. The method of claim 1, The first terminal and the second terminal is a communication method according to the automatic retransmission request method, characterized in that the same entity (entity). delete In a communication method according to a hybrid automatic retransmission request (HARQ) method in a mobile communication system, Constant periods of equal time intervals in a synchronous HARQ scheme for a negative acknowledgment signal (NACK) of a receiver related to a packet transmitted to a first subgroup including at least one frame in a frame group consisting of a plurality of consecutive frames. Retransmitted packets are sent aperiodically in a periodic or asynchronous HARQ manner every time, Retransmitted packets aperiodically for a negative acknowledgment signal (NACK) of a receiver related to a packet transmitted in a frame other than the first subgroup in the frame group, Whether retransmission packets are periodically transmitted or aperiodically transmitted in the first subgroup is classified according to a transmission format of control information for the first transmission packet. delete The method of claim 13, According to the automatic retransmission request scheme, whether the retransmission packet is periodically transmitted or aperiodically transmitted in the first subgroup is distinguished by the channel code used for the transmission channel of the control information for the first transmission packet. Communication method. The method of claim 13, Method according to the automatic retransmission request method characterized in that the retransmission packet is periodically transmitted or aperiodic in the first subgroup by the channel code used for the transmission channel of the first transmission packet. The method of claim 13, The communication method according to the automatic retransmission request scheme, characterized in that it informs the receiving side of the identification information on whether the retransmission packet is periodically transmitted or aperiodically transmitted in the first subgroup. In a communication method according to a hybrid automatic retransmission request (HARQ) method in a mobile communication system, Transmitting a negative acknowledgment signal (NACK) to a base station for a first packet received in a frame group consisting of a plurality of consecutive frames; Transmitting a negative acknowledgment signal (NACK) for a second packet received in the frame group to the base station; Receiving a retransmission packet for the first packet at a certain period of time in a synchronous HARQ scheme; Receiving control information for a retransmission packet of the second packet; And Receiving a retransmission packet of the second packet which is retransmitted aperiodically in an asynchronous HARQ scheme using the control information, And the control information includes a terminal identifier and a transmission format of a retransmission packet for the second packet. The method of claim 18, The first packet is a communication method according to the automatic retransmission request method, characterized in that the packet for voice communication. delete Transmitting a packet to a receiving side; Receiving a negative acknowledgment signal (NACK) for the packet from the receiving side; And In the communication method according to a hybrid automatic retransmission request (HARQ) method comprising the step of transmitting a retransmission packet (retransmission packet) to the receiving side, A retransmission packet is transmitted at regular intervals of the same time interval in a synchronous HARQ scheme for at least one or more frames in a frame group consisting of a plurality of consecutive frames, and is negated by the receiver for at least one or more other frames in the frame group. A method according to an automatic retransmission request method, characterized in that a retransmission packet is aperiodically transmitted in an asynchronous HARQ scheme with respect to a response signal (NACK).

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