KR101421253B1 - Apparatus and method for supporting synchronous hybrid automatic repeat request in a broadband wireless communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for supporting HARQ in a broadband wireless communication system. A method of operating a terminal according to the present invention includes the steps of receiving a control message including resource allocation information, decoding the control message, determining whether a previous control message is lost if the decoding is successful, And transmitting a null signal or a specific indicator through the response channel if the previous control message is lost.

HARQ (Hybrid Automatic Repeat reQuest), synchronous HARQ, control information, feedback

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates generally to a hybrid access control ("

The present invention relates to an apparatus and method for performing a Hybrid Automatic Repeat reQuest (HARQ) in a broadband wireless communication system, and more particularly to a system and method for performing HARQ in a broadband wireless communication system, And an apparatus and method for restoring the same.

Today, many wireless communication technologies are proposed as candidates for high-speed mobile communication. Of these, Orthogonal Frequency Division Multiplexing (OFDM) is recognized as the most promising next generation wireless communication technology. The OFDM technology is expected to be used in most wireless communication technologies in the future, and the WDM (Wireless Metropolitan Area Network) of the IEEE 802.16 series, which is called 3.5 generation technology, adopts the OFDM technology as a standard standard.

The OFDM scheme is a scheme for transmitting data using a multi-carrier. That is, it is possible to perform parallel conversion of symbol streams input in series and to modulate them into a plurality of mutually orthogonal sub-carriers, that is, a plurality of sub-channels, Modulation (MCM: Multi Carrier Modulation).

In recent years, a method of fixedly allocating radio resources to terminals in the OFDM-based broadband wireless communication system has been proposed. The persistent allocation scheme is a technique for reducing an overhead generated by transmitting resource allocation information (or a resource allocation message) to a mobile station for every frame (or subframe). That is, the base station periodically allocates a specific resource to a terminal having a service (e.g., VoIP service, etc.) in which traffic occurs periodically. Thereafter, the UE performs communication by continuously using fixedly allocated resources without confirming the resource allocation information until the change or release of the fixedly allocated resource occurs. In this case, the base station does not have to transmit the resource allocation information for the terminal every frame.

Meanwhile, most communication systems use a Hybrid Automatic Repeat reQuest (HARQ) scheme that combines an FEC (Forward Error Correction) technique and an ARQ (Automatic Repeat reQuest) technique in order to increase the reliability of data transmission. The HARQ scheme is a method for correcting an error through an error correction code for a received packet and determining whether to request a retransmission through an error detection code (e.g., a CRC code) of the error-corrected packet. Further, when a retransmission packet is received, additional gain (e.g., coding gain, SNR increase) can be obtained by combining and decoding the received packet and the previously received packet.

As described above, the connection to which HARQ is applied may continue to be retransmitted if the link performance is poor. Accordingly, studies are currently underway to allocate fixed resources to the HARQ scheme. Hereinafter, a technique combining a HARQ scheme and a fixed resource allocation scheme will be defined as a "synchronous HARQ scheme ".

The synchronous HARQ scheme is a scheme in which resources for a response signal and a retransmission packet are fixed according to resources used in initial transmission. That is, when using the synchronous HARQ scheme, the base station only allocates resources for initial transmission and does not allocate additional resources for the response signal and the retransmission packet. In this case, the base station does not need to transmit allocation information on resources for the retransmission packet and the response signal to the UE. However, if the resource allocation information of the initial transmission is not received, the receiving end can not receive a continuous retransmission packet.

In addition, it may happen that the position of a resource used for retransmission must be changed inevitably. In this case, the location of the changed resource should be informed to the corresponding terminal. However, if the UE fails to receive the resource change information, a serious problem may occur.

For example, in the downlink case, when the UE fails to receive the resource change information, the UE decodes the signal using a packet of a wrong resource location (Garbage Combine). In this case, the UE can not recover the signal or can not receive all retransmission packets that occur thereafter. In case of uplink, the UE transmits the uplink packet at the wrong resource location, so that the BS can not restore the signal of the corresponding UE. Also, the uplink packet transmitted from the wrong location acts as a fatal interference to other terminals.

As a result, if the UE does not receive the control information, it increases the probability of a residual packet error that is impossible to receive data even after the maximum retransmission, thereby degrading the overall transmission efficiency of the system. This problem occurs not only in the synchronous HAQR but also in a general HARQ (or Asynchronous HARQ).

Accordingly, it is an object of the present invention to provide an apparatus and a method for performing reliable HARQ in a broadband wireless communication system.

It is another object of the present invention to provide an apparatus and method for preventing performance degradation due to failure in receiving control information when performing HARQ in a broadband wireless communication system.

It is still another object of the present invention to provide an apparatus and method for detecting whether a base station receives control information of a terminal when performing HARQ in a broadband wireless communication system.

Yet another object of the present invention is to provide a method and apparatus for allocating resources for retransmission in a base station and transmitting resource allocation information for retransmission to a mobile station when HARQ is not received in a broadband wireless communication system And a method.

It is still another object of the present invention to provide an apparatus and method for transmitting an indicator for notifying a garbage packet to a base station when a terminal fails to receive control information when performing HARQ in a broadband wireless communication system .

It is still another object of the present invention to provide an apparatus and a method for performing decoding with a packet excluding a garbage packet according to information from a base station when a HARQ is performed in a broadband wireless communication system.

It is still another object of the present invention to provide an apparatus and method for reliably detecting a null signal received through an acknowledgment channel when performing HARQ in a wireless communication system.

It is still another object of the present invention to provide an apparatus and method for detecting a null signal by combining at least two response channel signals received during HARQ in a wireless communication system.

It is still another object of the present invention to provide an apparatus and method for a UE to determine whether a UE fails to receive previous control information when performing HARQ in a wireless communication system.
It is still another object of the present invention to provide an apparatus and method for transmitting a null or promised indicator to a base station when a terminal detects a failure in receiving previous control information in a broadband wireless communication system.
It is still another object of the present invention to provide an apparatus and method for determining whether to receive control information of a terminal by combining at least two response channel signals in a broadband wireless communication system.

According to one aspect of the present invention, there is provided a method of operating a terminal in a wireless communication system, the method comprising: receiving a control message including resource allocation information; decoding the control message; Determining whether the previous control message is lost if the previous control message is lost, and transmitting a null signal or a specific indicator through the response channel when the previous control message is lost.

Preferably, the method further comprises the step of receiving a control message for recovering the loss of the control message from the base station after transmitting the null signal or the specific indicator.

According to another aspect of the present invention, there is provided a method of operating a base station in a wireless communication system, comprising: determining whether a null signal has been received twice or more consecutively over a response channel; The method comprising the steps of: combining at least two response channel signals received; performing null decision using the combined value; and, if null, And determining that the message is lost.

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According to another aspect of the present invention, there is provided a base station apparatus in a wireless communication system, comprising: a feedback receiver for receiving a null signal twice or more times consecutively over a response channel; And combines the received at least two response channel signals and performs a null decision using the combined value. If it is determined to be null, it is determined that the previously transmitted control message is lost And a control unit for controlling the display unit.

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As described above, the present invention performs Hybrid Automatic Repeat reQuest (HARQ) in a broadband wireless communication system. There is an advantage that performance degradation caused by failure of the UE to receive the resource allocation information and the resource change information can be prevented. That is, there is an advantage that the overall transmission efficiency of the system can be increased by reducing the packet error rate caused by the terminal not receiving the control information.

Hereinafter, the operation principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a method for preventing degradation in performance due to failure of a UE to receive control information (resource allocation information, resource change information, etc.) when performing HARQ (Hybrid Automatic Repeat reQuest) in a broadband wireless communication system Let's take a look. More specifically, the present invention will be described in order to detect whether or not the control information of the terminal has been successfully received, and to recover the control information when it is determined that the control information has failed to be received. The present invention can be applied to a communication system using an HARQ scheme, and the following description will be made by way of example of a broadband wireless communication system based on IEEE 802.16m or IEEE802.16e.

The HARQ scheme is roughly classified into an asynchronous HARQ scheme and a synchronous HARQ scheme. Hereinafter, a synchronous HARQ scheme will be described as an example of the present invention. However, the present invention is applicable to asynchronous HARQ scheme as well as synchronous HARQ scheme. It will be obvious that it can be done.

In the case of the synchronous HARQ scheme, the BS transmits resource allocation information to the UE for the initial transmission HARQ packet, and then transmits the retransmission packet through the same resource without additional control information. Also, when the location of the resource is changed at the time of retransmission, the base station transmits the resource change information to the terminal, and after the change, the base station can transmit the retransmission packet through the changed resource without any additional control information.
In the following description, "control information", "MAP IE", "MAP information" and "resource allocation information" are used in the same meaning, and "control message" and "MAP message" are used in the same meaning .

FIG. 1 shows a frame structure of a broadband wireless communication system according to an embodiment of the present invention.

As shown, the frame structure according to the present invention includes a hierarchical structure such as a super-frame 120, a frame 110, and a sub-frame 130 . For example, a superframe 120 of 20 msec consists of four 5 msec frames 110, and each frame 110 may be composed of 8 subframes. Here, n subframes 130 in one frame 110 composed of K subframes 130 are used for downlink communication and Kn subframes 130 can be used for uplink communication have. The subframe 130 includes a plurality of OFDMA symbols 140.

A super frame header is transmitted for each super frame 120. The superframe header may include a preamble (or synchronization channel) and a broadcast channel (BCH) for system synchronization. Here, the preamble may be designed more than one OFDM symbol, and may be transmitted every super frame 120. The terminal can identify the system synchronization and the currently connected base station through the preamble. In addition, the broadcast information channel (BCH) may include control information having a short modification period, among DCD (Downlink Channel Descriptor) / UCD (Uplink Channel Descriptor) information used in an existing system (e.g., IEEE 802.16e). The period of the broadcast information channel may be determined according to the control information to be included in the broadcast channel information. In addition, a MAP message including resource allocation information is included in the DL subframe 130 and may be transmitted in one or more subframe periods.

In the case of using the frame having the structure as shown in FIG. 1, the resources used for the initial transmission and acknowledgment (ACK) / NACK (Non-ACK) transmission and retransmission according to the synchronous HARQ scheme are, for example, As shown.

2 (a) shows a case where the ratio of the downlink communication and the uplink communication is 4: 4, and FIG. 2 (b) shows the case where the ratio of the downlink communication and the uplink communication is 5: 2 (c) shows a case where the ratio of the downlink communication and the uplink communication is 6: 2. In FIGS. 2 (a), 2 (b), and 2 (c), the subframes indicated by the same number of points mean subframes that depend on initial transmission.

For example, in FIG. 2A, a response (ACK / NACK) for a packet initially transmitted in subframe 1-D1 is transmitted in subframe 1-U1. The retransmission packet for the initially transmitted packet is transmitted in the subframe 2-D1, and the ACK / NACK for the retransmission packet is transmitted in the subframe 2-U1. In the case of FIGS. 2B and 2C, since the subframes used for downlink communication and the subframes used for uplink communication are not the same, a plurality of downlink subframes are allocated to one uplink subframe Frame, and the corresponding rule may be determined according to the system design method.

Hereinafter, embodiments of the present invention will be described focusing on downlink communication. However, the present invention can be applied to the uplink communication in the same manner.

FIG. 3 illustrates a synchronous HARQ procedure in a broadband wireless communication system according to an embodiment of the present invention. In particular, FIG. 3 illustrates a method for the base station to recognize a control information reception failure of the UE using feedback information on a data packet, and to control the retransmission accordingly.

Referring to FIG. 3, in step 301, the BS allocates a resource for an initial transmission (first packet) (or a subpacket) and transmits resource allocation information to the MS. And transmits the initial transmission packet to the terminal through the allocated corresponding resource. At this time, it is assumed that the position of the resource allocated for the initial transmission packet is position 1 (POS 1: position 1).

In step 303, the UE decodes the resource allocation information (e.g., MAP IE) received from the BS. Here, it is assumed that the UE has failed to decode the resource allocation information. If the reception of the resource allocation information fails, the UE does not receive the data packet and does not transmit any feedback signal to the base station. That is, a null is transmitted through the response channel.

On the other hand, in step 305, the BS predicts whether or not to receive the resource allocation information of the MS using the feedback signal from the MS. If an ACK signal for a data packet is received from the terminal, the BS determines that the terminal normally received the packet and ends the retransmission procedure for the packet. On the other hand, when a NACK signal is received from the UE, the Node B considers that the UE has failed to decode the packet but successfully received the resource allocation information. In this case, the BS transmits a subsequent retransmission packet through a previously allocated resource (POS 1) after a specific point in time without additional control information.

3, if no feedback signal (ACK or NACK) is received from the UE (when a null is received), the BS considers that the UE has not successfully received the resource allocation information. As described above, in the case of the synchronous HARQ scheme, the uplink response channel (ACKCH) is automatically allocated according to the resource allocated to the data packet. That is, when the UE does not receive the resource allocation information for the data packet, the UE can not transmit the feedback response signal to the Node B because the corresponding response channel is unknown. Therefore, if the feedback signal for the corresponding data packet is not received, the terminal can regard it as not receiving the corresponding control information.

Therefore, in step 307, the BS allocates a resource for a retransmission packet after a predetermined time, and transmits resource allocation information to the MS. Also, the BS transmits a retransmission packet to the MS through the allocated resources. In this case, the position of the resource allocated for the retransmission packet is assumed to be POS 2 (POS 2: position 2), and the POSITION 1 and POSITION 2 may be the same or different.

In step 309, the UE decodes the resource allocation information received from the BS. Here, it is assumed that the UE has successfully received the resource allocation information. When the resource allocation information is successfully received, the UE can recognize the position of the retransmission packet, and receives and decodes the retransmission packet at the corresponding location. Then, the terminal transmits a feedback signal (ACK or NACK) according to the decoding result to the base station.

Thereafter, in step 311, the BS predicts whether or not to receive the resource allocation information of the MS using the feedback signal from the MS. At this time, since the feedback signal is received from the UE, the Node B considers that the UE has successfully received the resource allocation information, and determines whether or not to retransmit the UE according to the feedback signal.

The procedure of FIG. 3 described above takes into consideration a case where the UE does not feed back a response (ACK) to resource allocation information (e.g., MAP information). In the future, the system considers feedback of the resource allocation information to the base station by the UE, and the embodiment of the present invention will be described.

FIG. 4 illustrates a synchronous HARQ procedure in a broadband wireless communication system according to an embodiment of the present invention. In particular, FIG. 4 illustrates a scheme for the base station to recognize the failure to receive control information of the UE using the resource allocation information and the feedback information on the data packet, and to control the retransmission accordingly.

Referring to FIG. 4, in step 401, a BS allocates resources for an initial transmission packet (or a subpacket) and transmits resource allocation information to the MS. And transmits the initial transmission packet to the terminal through the allocated corresponding resource.

In step 403, the UE decodes the resource allocation information (e.g., MAP IE) received from the BS. Here, it is assumed that the UE has failed to decode the resource allocation information. If the reception of the resource allocation information fails, the terminal does not transmit any feedback signal to the base station. As shown, Null is transmitted on the MAP response channel (MAP ACKCH) and the data response channel (ACKCH). Here, the null indicates that there is no feedback signal.

In step 405, the BS estimates whether or not to receive resource allocation information of the MS using a feedback signal received through the MAP response channel (MAP ACKCH) and the data response channel (ACKCH). At this time, since a null is received through the MAP response channel (MAP ACKCH) and the data response channel (ACKCH), the BS considers that the UE has not successfully received the resource allocation information.

Accordingly, in step 407, the BS allocates a resource for a retransmission packet after a predetermined time, and transmits resource allocation information to the MS. Also, the BS transmits a retransmission packet to the MS through the allocated resources. Since the subsequent procedure is the same as that of FIG. 3, detailed description will be omitted.

As described above, the BS can receive an uplink ACKCH (uplink ACKCH) and feedback on ACK or NULL for the resource allocation information (MAP information) from the UE. Accordingly, the base station can predict whether or not to receive the control information of the UE by using a feedback signal (ACK or NACK) for the data packet and a feedback signal (ACK or NULL) for the control information. That is, the BS considers that the UE has not received the control information in the following cases.

A. If no feedback signal is received for the data packet

B. If no feedback signal is received for the corresponding control information

C. If both of the above cases have occurred

FIG. 5 shows a signaling procedure according to HARQ in a broadband wireless communication system according to an embodiment of the present invention.

As shown in the figure, when only a response channel (ACKCH) for a data packet is operated, the UE decodes a MAP message to determine whether resource allocation information has been received in step 501 (step 501).

If the resource allocation information is received, the UE receives and decodes a packet (DL Burst) at a location designated by the resource allocation information, and when there is an error in the packet as a result of decoding, the UE receives a NACK (ACKCH) To the base station (step 503). On the other hand, if there is no error in the packet as a result of decoding, the UE transmits an ACK to the BS through the response channel (step 505).

Meanwhile, when the MAP message decoding fails, the UE receives and decodes a packet (DL burst) at a pre-allocated location, and when there is an error in the packet as a result of decoding, transmits a NACK to the BS through the response channel (Step 507). On the other hand, if there is no decoding result error, ACK is transmitted to the BS through the response channel (step 509).

6 shows a signaling procedure according to HARQ in a broadband wireless communication system according to an embodiment of the present invention.

As shown in the figure, when a response channel for a data packet and a response channel for control information are operated together, the UE decodes a received MAP message to determine whether resource allocation information has been received, If the resource allocation information is received, ACK is transmitted to the BS through a MAP response channel (MAP ACKCH) (step 601). If decoding of the MAP message fails, no signal is transmitted through the MAP response channel. As shown, the DL-MAP message may include location information on the MAP response channel.

When the resource allocation information is received, the UE receives and decodes a packet (DL Burst) at a location specified by the resource allocation information, and when there is an error in the packet as a result of decoding, it performs a NACK through an ACKCH To the base station (step 603). On the other hand, if there is no error in the packet as a result of decoding, the UE transmits ACK to the BS through the response channel (step 605).

FIG. 7 illustrates a synchronous HARQ procedure in a broadband wireless communication system according to an embodiment of the present invention. In particular, FIG. 7 shows a method for transmitting indication information for controlling HARQ combining of a UE by recognizing failure of the UE to receive control information using feedback information from the UE.

Referring to FIG. 7, in step 701, the BS allocates resources for an initial transmission packet (or a subpacket) and transmits resource allocation information to the MS. And transmits the initial transmission packet to the terminal through the allocated corresponding resource. At this time, it is assumed that the position of the resource allocated for the initial transmission packet is position 1 (POS 1: position 1).

In step 703, the terminal decodes the resource allocation information received from the base station. Here, it is assumed that the UE successfully decodes the resource allocation information. Accordingly, the MS transmits an ACK to the BS through a MAP response channel (MAP ACKCH). In addition, the UE receives and decodes the initial transmission packet at a location (POS 1) specified by the resource allocation information, and transmits the feedback signal on a response channel (ACKCH) according to a decoding result. Herein, it is assumed that the UE has failed to decode the initial transport packet, and thus the UE transmits a NACK to the BS through the response channel.

Next, in step 705, the BS determines to retransmit the initial transport packet because an ACK is received on the MAP response channel and a NACK is received on the data response channel. At this time, it is determined that the resource change for the retransmission packet is necessary.

Accordingly, in step 707, the BS allocates resources for the retransmission packet and transmits resource allocation information to the MS. And transmits the retransmission packet to the terminal through the allocated corresponding resource. At this time, the position of the resource allocated for the retransmission packet is assumed to be position 2 (POS 2: position 2).

Then, in step 709, the terminal decodes the resource allocation information received from the base station. Here, it is assumed that the UE has failed to decode the resource allocation information. Therefore, Null is transmitted through the MAP response channel. In addition, since the UE can not know the location of the resource changed due to decoding failure of the resource allocation information, the UE receives and decodes the packet at a previously known location. At this time, since the terminal has HARQ combined and decoded the erroneous packet, decoding fails. Accordingly, the UE transmits a NACK to the BS through the previously allocated data response channel. As a result, a null is transmitted through the changed response channel.

In step 711, the BS estimates whether or not to receive the resource allocation information of the MS using the feedback signal received through the MAP response channel (MAP ACKCH) and the data response channel (ACKCH). At this time, since the null is received through the MAP response channel (MAP ACKCH) and the data response channel, the BS considers that the UE has not successfully received the resource allocation information.

Therefore, in step 713, the BS reallocates resources for the retransmission packet and transmits resource allocation information to the MS. At this time, the BS transmits a failure indicator (FI) to the MS indicating that the MS has received a garbage packet. And transmits the retransmission packet to the terminal through the allocated corresponding resource. At this time, the position of the resource allocated for the retransmission packet is assumed to be position 3 (POS 3: position 3).

On the other hand, the terminal receiving the failure indicator determines that the previously received packet is a garbage packet and decodes the remaining packets (the 1st sub-packet and the 3rd sub-packet) excluding the previously received packet.

The detailed operation of the present invention based on the above description will be described in detail as follows. Hereinafter, a downlink communication will be assumed.

FIG. 8 illustrates a synchronous HARQ procedure of a base station in a broadband wireless communication system according to an embodiment of the present invention. In particular, FIG. 8 illustrates an operation procedure for a case in which the MAP response channel (ACKCH) is not operated.

Referring to FIG. 8, if initial transmission or pre-allocated resource change is required, the base station configures resource allocation information (e.g., MAP IE) for the packet to be transmitted at step 801. In case of initial transmission, the resource allocation information includes resource information for an initial transmission packet. In case of a resource change, the resource allocation information may include changed resource information.

After configuring the resource allocation information, the BS transmits a MAP message including the resource allocation information through the MAP area in step 803, and transmits the corresponding packet at the corresponding location in the data area. At this time, the resource allocation information may be scrambled, masked, interleaved, or CRC encoded (or CRC masked) using a unique code for the corresponding terminal.

After transmitting the resource allocation information and the packet, the BS checks in step 805 whether a feedback signal is received from the UE. If the feedback signal is not received through the acknowledgment channel (ACKCH), the BS proceeds to step 807 to determine the retransmission of the packet and configure the resource allocation information for the retransmission packet. At this time, the BS may include a failure indicator (FI) indicating that the terminal has received a garbage packet in the resource allocation information.

In step 809, the BS transmits a MAP message including the configured resource allocation information through the MAP area, and transmits the retransmission packet at a corresponding location in the data area. Thereafter, the base station returns to step 805 to check the feedback reception, and then re-executes the following steps.

If the feedback signal is received through the response channel designated in step 805, the BS proceeds to step 811 to check whether the received feedback signal is ACK or NACK. If the feedback signal is a NACK (retransmission request), the BS proceeds to step 813 and transmits the retransmission packet through a pre-allocated resource (resource for synchronous HARQ), and then returns to step 805. On the other hand, if the feedback signal is ACK (successful reception), the BS proceeds to step 815 and terminates the retransmission procedure for the packet.

FIG. 9 illustrates a synchronous HARQ procedure of a base station in a broadband wireless communication system according to an embodiment of the present invention. In particular, FIG. 9 illustrates an operation procedure for operating a MAP response channel (ACKCH).

Referring to FIG. 9, when initial transmission or pre-allocated resource change is required, the base station configures resource allocation information for a packet to be transmitted at step 901. FIG. In case of initial transmission, the resource allocation information includes resource information for an initial transmission packet, and in case of a resource change, the resource allocation information includes changed resource information.

After configuring the resource allocation information, the BS transmits a MAP message including the resource allocation information through the MAP area in step 903, and transmits the corresponding packet at a corresponding location in the data area. At this time, it is assumed that the resource allocation information is scrambled, masked, interleaved, or CRC encoded (or CRC masked) by using a unique code for the corresponding UE.

After transmitting the resource allocation information and the packet, the BS determines whether a feedback signal is received from the MS on a MAP response channel (MAP ACKCH) designated in step 905. If the feedback signal is not received in the designated MAP response channel, the BS proceeds directly to step 909.

On the other hand, when ACK (MAP reception success) is received in the designated MAP response channel, the BS proceeds to step 907 and checks whether a feedback signal is received through a designated data response channel (ACKCH). If a feedback signal is not received through the data response channel, the BS proceeds to step 909 to determine a packet retransmission and configure resource allocation information for a retransmission packet. At this time, the BS may include a failure indicator (FI) indicating that the terminal has received a garbage packet in the resource allocation information.

In step 911, the BS transmits a MAP message including the configured resource allocation information through the MAP area, and transmits the retransmission packet at a corresponding location in the data area. Thereafter, the BS returns to step 905 to check the feedback on the MAP.

If the feedback signal is received through the response channel designated in step 907, the BS proceeds to step 913 to check whether the received feedback signal is ACK or NACK. If the feedback signal is a NACK (retransmission request), the BS proceeds to step 915 and transmits the retransmission packet through a pre-allocated resource (resource for synchronous HARQ), and then returns to step 907. [ On the other hand, if the feedback signal is ACK (successful reception), the BS proceeds to step 917 and terminates the retransmission procedure for the packet.

FIG. 10 illustrates a synchronous HARQ procedure of a terminal in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 10, in step 1001, a UE, which is performing synchronous HARQ for downlink communication, receives and decodes a MAP message for each subframe, and checks whether resource allocation information for itself is received.

If the resource allocation information is received, the terminal receives a downlink packet through a resource designated by the resource allocation information in step 1003, and proceeds to step 1007. [ If the MAP response channel (ACKCH) is operated, the UE can transmit an ACK to the BS through the MAP response channel. On the other hand, if the resource allocation information is not received (decoding of the MAP message fails), the MS proceeds to step 1005 and receives a downlink packet through a pre-allocated resource (resource for synchronous HARQ) The process proceeds to step 1007.

In step 1007, the MS determines whether a failure indicator (FI) is received from the BS. If the failure indicator is received, the UE proceeds to step 1009 and discards the immediately received packet, and then HARQ-combines the remaining packets (including the received packet). Generally, a UE performs HARQ combining and decoding every time a retransmission packet is received. At this time, if the decoding is successful, the HARQ combined packet is discarded. If the decoding fails, the HARQ combined packet is buffered. According to the present invention, when the failure indicator is operated, the UE must have both the first joint packet generated through the previous HARQ joint and the second joint packet generated through the previous HARQ joint. When a failure indicator is received from the base station, the terminal discards the first combined packet, and combines the second combined packet and the received packet to perform decoding. This is because the first combined packet is a packet in which a packet received incorrectly by the terminal (the immediately preceding received packet) is combined.

On the other hand, if the failure indicator is not received, the MS proceeds to step 1011 to HARQ combine all the previously received packets with the currently received packet. The terminal combines the first combined packet with the currently received packet when storing the first combined packet and the second combined packet.

As described above, when the HARQ combining is completed, the UE proceeds to step 1013 and decodes the HARQ combined packet. In step 1015, the UE checks the CRC with the decoding result and checks whether there is an error according to the CRC result. If the error does not exist (CRC success), the MS proceeds to step 1017 and transmits an ACK to the BS through a designated acknowledgment channel (ACKCH). On the other hand, if the error exists (CRC failure), the UE proceeds to step 1019 and transmits a NACK to the BS through the response channel.

The above-described embodiment is a case of detecting whether or not the control information of the terminal is received using one response channel signal. In another embodiment, it is possible to combine at least two response channel signals to detect the reception of the control information of the terminal in order to increase the detection reliability. Hereinafter, a method for detecting whether or not the UE has received previous control information using at least two consecutive acknowledgment channel signals received from the UE will be described.

The case where the UE transmits a null to the BS can be defined as follows.

(1) When the location of the acknowledgment channel (ACKCH) is not known due to the failure in receiving the control information

(2) When the terminal recognizes the failure to receive the previous control information

In the case of (2), when the control information is received from the base station, the UE determines whether the received control information is control information for an expected retransmission packet. If the control information is not control information for an expected retransmission packet, The failure of the information can be recognized. For example, if the retransmission packet index (or the number of retransmissions) expected by the terminal does not match the index in the control information received from the base station, the terminal can recognize the failure in receiving the previous control information. If the UE recognizes that the UE has successfully received the control information but failed to receive the previous control information, the UE transmits a null through the response channel to inform the Node B of the failure in receiving the previous control information. Alternatively, instead of the null, the terminal may feed back the previously promised indicator (or a specific sequence) through the response channel. In this case, the base station can determine failure in receiving the control information of the terminal by detecting the indicator.

Hereinafter, a method for detecting the case (2) will be described in detail with reference to the drawings.

FIG. 11 illustrates a signal exchange procedure for detecting whether or not to receive control information of a terminal when performing HARQ in the broadband wireless communication system according to the present invention.

11, in step 1101, a BS allocates a resource for an initial transmission or retransmission packet (or a subpacket), and transmits a control message 1 including resource allocation information to the MS ). Also, the packet is transmitted to the terminal through the allocated resource.

In step 1103, the UE decodes the control message 1 received from the BS. Here, it is assumed that the UE has failed to decode the control message. If the reception of the control message fails, the UE can not receive the data packet and can not know the response channel position, so that the UE can not transmit any signal through the response channel. That is, a null signal is transmitted through the response channel.

On the other hand, in step 1105, the BS detects a null through the response channel. If a null is detected, the base station considers the previous transmission as failed. Accordingly, in step 1107, the BS allocates a resource for retransmission and transmits a control message (control message 2) including resource allocation information to the MS. Also, the BS transmits a retransmission packet to the MS through the allocated resources. Here, in the case of synchronous HARQ, the control message 2 may not be transmitted.

In step 1109, the UE decodes the control message 2 received from the BS. Here, it is assumed that decoding of the control message (control message 2) is successful. At this time, the UE compares the expected retransmission packet index with the index in the control message (control message 2). If the two indices do not coincide with each other, the UE recognizes that the control message 1 has failed to be received. If it is determined that the previous control message has not been received, the UE transmits a null signal through the response channel. That is, no signal is transmitted through the response channel. As another example, a promised indicator (or a specific sequence) may be transmitted instead of a null signal.

In step 1111, the BS detects null on the acknowledgment channel. In this manner, when null is detected twice or more through power level detection, the base station detects whether or not the control information reception of the terminal has failed.

For example, whether or not the reception of the control information is failed can be detected as follows. The BS determines that the UE has not received the previous control message if the conditions of Equation (1) and Equation (2) are not satisfied.

In Equation (1), S _{i, NACK} denotes a sequence used for NACK transmission, S _{i, ACK} denotes a sequence for ACK transmission, and i denotes a bit index of a sequence. And R ₁ represents the signal received over the previous acknowledgment channel, and R ₂ represents the signal received over this acknowledgment channel. And TH is a reference value to be compared with the correlation value between the received signal and the sequence. For example, if the correlation value is larger than the reference value, the sequence can be regarded as being received.

Equation (1) represents an ACK test of R2. If the condition is satisfied, it is determined that an ACK is received through the response channel. Equation (2) shows the NACK test of R2. When the condition is satisfied, it is determined that NACK is received through the response channel.

If neither Equation (1) or Equation (2) is satisfied, the BS determines that the control message, which was previously transmitted, is not received by the UE. In this case, the BS may perform an error recovery procedure by transmitting the corresponding control information (or resource allocation information) to the MS. At this time, the BS may transmit a packet corresponding to the failed control information to the MS.

12 is a flowchart illustrating an HARQ procedure of a UE in a wireless communication system according to an embodiment of the present invention. In particular, FIG. 12 shows a procedure for the UE to recognize the failure in receiving the previous control information and inform the base station of the failure.

Referring to FIG. 12, in step 1201, the MS determines whether a control message (e.g., a MAP message) including HARQ related resource allocation information (or control information) is received from a base station. Upon receiving the control information, the terminal decodes the control information in step 1203. In step 1205, the terminal performs an error check on the decoded data, and checks whether decoding is successful using the error check result. If the control information decoding fails, the terminal proceeds to step 1211 and discards the received control information.

On the other hand, if the control information decoding is successful, the terminal compares the expected retransmission packet index (or the number of retransmission times) with the index included in the control information in step 1207, and determines whether or not the previous control information has failed to be received. If the two indices are different, the terminal determines that the previous control information has failed to be received (or lost).

If it is determined that the previous control information is not lost, the terminal proceeds to step 1213 and processes the received packet normally. On the other hand, if it is determined that the previous control information is lost, the UE proceeds to step 1209 and transmits a null signal through an acknowledgment channel (ACK channel) to notify the BS of loss of previous control information. As another example, the terminal may transmit an indicator or sequence indicating the loss of the previous control information to the base station through a response channel or another method (e.g., a message).

FIG. 13 illustrates a procedure of performing HARQ of a base station in a wireless communication system according to an embodiment of the present invention. In particular, FIG. 13 illustrates a procedure for the base station to detect loss of previous control information and to recover it.

Referring to FIG. 13, in step 1301, the BS determines whether a null is received through an HARQ channel (ACK channel). For example, the base station may determine whether a null is received by comparing a correlation value between a received signal and a sequence with a reference value. If it is determined that a null has been received, the base station checks in step 1303 whether a null is received from the corresponding terminal two or more times in succession.

If the null is received consecutively two or more times, the BS proceeds to step 1305 and combines the received at least two acknowledgment channel signals. For example, the combining may be performed according to Equation (1) and Equation (2).

In step 1307, the BS performs a null decision using the result of the combine. Here, when it is determined to be null, it is determined that the previously transmitted control information is lost. That is, the BS determines in step 1307 whether the previously transmitted control information is lost.

If the previously transmitted control information is lost, the base station proceeds to step 1309 and performs a recovery procedure according to loss of control information. For example, the base station may perform an error recovery procedure by transmitting loss control information corresponding to an initial null to a mobile station. At this time, the BS can transmit a packet corresponding to loss control information to the MS again.

FIG. 14 shows a configuration of a base station according to an embodiment of the present invention.

As illustrated, the base station includes a controller 1400, a message generator 1402, a traffic processor 1404, an encoder 1406, a modulator 1408, a resource mapper 1410, an OFDM modulator 1412, an RF (Radio Frequency) transmitter 1414 and a feedback receiver 1416. The feedback receiver 1416 is assumed to be a physical channel receiver for demodulating a fast feedback channel (ACKCH, CQICH, etc.).

Referring to FIG. 14, the controller 1400 performs resource scheduling and controls the corresponding component according to the scheduling result. In accordance with the present invention, the controller 1400 controls the overall operation according to HARQ performance. That is, the controller 1400 controls generation of various signaling according to the HARQ performance, and controls packet transmission according to the HARQ performance. The control unit 1400 predicts whether or not to receive the control information (e.g., MAP information) of the terminal using the feedback signal from the terminal, and when it is determined that the corresponding terminal does not receive the control information, Perform restoration procedure. For example, the control unit 1400 determines the loss of control information through null-receiving as shown in FIGS. 3, 4, and 7, and combines at least two response channel signals as shown in FIG. 11 It is possible to judge the loss of the control information.
The message generator 1402 generates various signaling messages under the control of the controller 1400. In accordance with the present invention, the message generator 1402 generates resource allocation information according to HARQ performance. At this time, in case of initial transmission, the resource allocation information includes resource information for an initial transmission packet, and in case of resource change, the resource allocation information may include changed resource information. In addition, when retransmitting a packet due to a failure in receiving resource allocation information of the UE, the corresponding resource allocation information may include a failure indicator (FI) indicating that the UE has received a garbage packet. Here, the resource allocation information may be scrambled, masked, interleaved, or CRC encoded (or CRC masked) using a unique code for the corresponding terminal.

The traffic processor 1404 configures the transmission data into a data burst (physical layer packet) according to a protocol and transmits the data burst to the encoder 1406.

The encoder 1406 of the physical layer encodes and outputs a signaling message from the message generator 1402 and a data packet from the traffic processor 1404 according to a modulation and coding scheme (MCS) level. The encoder 1406 may use a convolutional code (CC), a turbo code (TC), a convolutional turbo code (CTC), or a low density parity check (LDPC) code. When the HARQ is performed, the encoder 1406 buffers the encoded bits of the data packet in the HARQ buffer. When a retransmission request (NACK) is received from the receiver, the encoder 1406 performs HARQ (e.g., chase combining, IR, etc.) All or some of the buffered encoded data can be selected and retransmitted.

A modulator 1408 modulates the coded data from the encoder 1406 according to the MCS level to generate modulation symbols. For example, the modulator 1408 may use QPSK, 16QAM, 64QAM, or the like.

The resource mapper 1410 maps the data from the modulator 1408 to predetermined resources (or subcarriers) and outputs the data. When performing synchronous HARQ according to the present invention, the resource mapper 1410 maps an initial transmission packet and a retransmission packet to resources fixedly allocated for the synchronous HARQ.

The OFDM modulator 1412 OFDM-modulates the resource mapped data from the resource mapper 1410 to generate OFDM symbols. Here, the OFDM modulation includes an IFFT (Inverse Fast Fourier Transform) operation, a CP (Cyclic Prefix) addition, and the like. The RF transmitter 1414 converts the sample data from the OFDM modulator 1412 into an analog signal, converts the analog signal into a signal of a radio frequency (RF) band, and transmits the signal through an antenna.

The feedback receiver 1416 demodulates the feedback signal received via the fast feedback channel and provides the result to the controller 1400. The feedback receiver 1416 according to the present invention demodulates the feedback signal received via the acknowledgment channel (ACKCH) and provides the feedback signal to the controller 1400. Also, according to the present invention, the feedback receiver 1416 combines at least two response channel signals under the control of the controller 1400 to detect a null, and provides the result to the controller 1400. When the result of the combination is null, the controller 1400 determines that the previous control information is lost, and performs the restoration procedure by transmitting the lost control information to the corresponding terminal. The acknowledgment channel may include a response channel for the data packet and a response channel for the control information (MAP information).

FIG. 15 shows a configuration of a terminal according to an embodiment of the present invention.

As illustrated, the UE includes a radio frequency (RF) receiver 1500, an OFDM demodulator 1502, a resource demapper 1504, a demodulator 1506, a decoder 1508, a first buffer 1510, A buffer 1512, a CRC checker 1514, a message interpreter 1516, a traffic processor 1518, a controller 1520 and a feedback transmitter 1522. The feedback transmitter 1522 is assumed to be a physical channel transmitter for modulating a signal transmitted through a fast feedback channel (ACKCH, CQICH, etc.).

Referring to FIG. 15, the RF receiver 1500 converts an RF band signal received through an antenna into a baseband signal, and converts the baseband signal into digital sample data. The OFDM demodulator 1502 performs OFDM demodulation of the sample data from the RF receiver 1500 to output frequency-domain data. Here, the OFDM demodulation includes CP removal, fast Fourier transform (FFT), and the like.

The resource demapper 1504 extracts a burst (or packet) to be demodulated from the frequency-domain data from the OFDM demodulator 1502 and outputs the burst. When performing synchronous HARQ, the resource demapper 1504 extracts and outputs packets (initial transmission packet and retransmission packet) mapped to a fixed resource according to the synchronous HARQ.

The demodulator 1506 demodulates and outputs the packet from the resource demapper 1504. The decoder 1508 decodes the demodulated data from the demodulator 1506 and outputs the decoded data. At this time, if a retransmission packet according to the HARQ is received, the decoder 1508 HARQ-couples the previously received packet with the currently received packet, and decodes the HARQ combined packet.

The first buffer 1510 stores the first combined packet generated through the immediately preceding HARQ combining. The second buffer 1512 stores the second combined packet generated through the previous HARQ combination. When the failure indicator FI is received from the base station, the decoder 1508 discards the first combined packet and performs HARQ combining on the received second packet and the received packet to perform decoding. If the failure indicator FI is not received from the base station, the decoder 1508 may perform HARQ combining with the first combined packet and the received packet to decode the packet.

The CRC checker 1514 performs a CRC check on the decoded data from the decoder 1508 and provides the CRC check result to the decoder 1508 and the feedback transmitter 1522. Then, the decoder 1508 discards the corresponding HARQ combined packet according to the CRC check result, or stores the HARQ combined packet in the first buffer 1510 or the second buffer 1512.

Meanwhile, the feedback transmitter 1522 generates a feedback signal (ACK or NACK) according to the CRC result, modulates the feedback signal, and transmits the modulated feedback signal to the base station via a designated acknowledgment channel (ACKCH). Also, the feedback transmitter 1522 transmits a feedback signal (ACK) for control information (MAP information) to the base station through a designated MAP response channel.

If it is determined that there is no error as a result of the CRC check, the CRC checker 1514 transfers the decoded data to the MAC layer. At this time, if the decoded data is a signaling message, the corresponding signaling message is provided to the message interpreter 1516, and if the decoded data is traffic, the corresponding packet is provided to the traffic processor 1518.

The message interpreter 1516 interprets the received signaling message and provides the result to the controller 1520. The message analyzer 1516 decodes the MAP message to determine whether there is a resource allocation information (MAP IE) received from the MS, and if the resource allocation information is received, (1520). In case of initial transmission according to the synchronous HARQ, the resource allocation information includes resource information for an initial transmission packet, and in case of a resource change, the resource allocation information may include changed resource information. Also, in case of retransmission due to failure in receiving resource allocation information of the UE, the corresponding resource allocation information may include a failure indicator (FI) indicating that the UE has received the garbage packet. The resource allocation information may be scrambled, masked, interleaved, or CRC encoded (or CRC masked) using a unique code for the corresponding terminal. In this case, the terminal decodes a message received through the MAP region in units of IE using the scrambling code or the like. At this time, if there is an IE that is successfully decoded, the terminal can determine that its resource allocation information has been received.
The traffic processor 1518 processes the traffic from the CRC checker 1514 according to the corresponding protocol.

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The controller 1520 controls the overall operation of the terminal. When performing the synchronous HARQ, when the resource allocation information for the initial transmission is received, the controller 1520 sets the resource designated by the resource allocation information as a fixed resource, and then transmits the retransmission packet to the fixed resource And controls the operation. Also, the controller 1520 checks an acknowledgment channel corresponding to the fixed resource and controls an operation for transmitting a feedback signal on the acknowledgment channel. In addition, when resource allocation information for changing a fixed resource according to the synchronous HARQ is received, the controller 1520 controls an operation for receiving a retransmission packet from the changed resource, And controls an operation for transmitting a signal. In addition, when the failure indicator FI is received from the base station, the controller 1520 controls the decoder 1508 to discard the immediately previous received packet (first combining packet). If the expected retransmission packet index is different from the index in the received control information, the controller 1520 determines that the previous control information is lost and controls the operation to transmit null through the response channel do.

Although the above-described embodiment of the present invention describes downlink communication as an example, the present invention can be applied to uplink communication in the same manner.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

1 is a diagram showing a frame structure of a broadband wireless communication system according to the present invention;

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a method and apparatus for transmitting / receiving data in a broadband wireless communication system.

3 is a flowchart illustrating a synchronous HARQ procedure in a broadband wireless communication system according to an embodiment of the present invention.

4 is a flowchart illustrating a synchronous HARQ procedure in a broadband wireless communication system according to an embodiment of the present invention.

5 is a diagram illustrating a signaling procedure according to synchronous HARQ in a broadband wireless communication system according to an embodiment of the present invention.

6 is a diagram illustrating a signaling procedure according to synchronous HARQ in a broadband wireless communication system according to an embodiment of the present invention.

7 is a flowchart illustrating a synchronous HARQ procedure in a broadband wireless communication system according to an embodiment of the present invention.

8 is a flowchart illustrating a synchronous HARQ procedure of a base station in a broadband wireless communication system according to an embodiment of the present invention.

9 is a flowchart illustrating a synchronous HARQ procedure of a base station in a broadband wireless communication system according to an embodiment of the present invention.

10 is a diagram illustrating a procedure for performing a synchronous HARQ of a terminal in a broadband wireless communication system according to an embodiment of the present invention.

11 is a diagram illustrating a signal exchange procedure for detecting whether or not control information of a terminal is received when an HARQ is performed in a broadband wireless communication system according to the present invention.

12 is a flowchart illustrating a HARQ procedure of a UE in a wireless communication system according to an embodiment of the present invention.

13 is a flowchart illustrating a HARQ procedure of a base station in a wireless communication system according to an embodiment of the present invention.

14 is a diagram illustrating a configuration of a base station according to an embodiment of the present invention.

15 is a diagram illustrating a configuration of a terminal according to an embodiment of the present invention.

Claims (35)

A method of operating a terminal in a wireless communication system, Receiving a control message including resource allocation information; Decoding the control message, Determining if a previous control message is lost if the decoding is successful; And transmitting a null signal or a specific indicator through the response channel if the previous control message is lost. The method of claim 1, Comparing an expected retransmission packet index with an index in the control message; And determining that the previous control message is lost if the two indices are different. The method according to claim 1, Wherein the specific indicator is a specific sequence that represents a null. The method according to claim 1, Further comprising the step of receiving a control message for recovering the loss of the control message from the base station after transmitting the null signal or the specific indicator. The method according to claim 1, Receiving a data packet using the received resource allocation information if the previous control message is not lost; Decoding the received data packet; Transmitting an ACK signal through the response channel when the decoding is successful; And transmitting the NACK signal through the acknowledgment channel if the decoding fails. A method of operating a base station in a wireless communication system, Determining whether a null signal has been received twice or more consecutively through the response channel; Combining the received at least two acknowledgment channel signals when the null signal is received twice or more consecutively; Performing a null decision using the combined value, And determining that the previously transmitted control message is lost if it is determined to be null. The method according to claim 6, And performing a restoration procedure according to the loss of the control message if the previously transmitted control message is lost. 8. The method of claim 7, And transmitting the control information corresponding to the first null signal among the two or more consecutive null signals to the corresponding terminal. 7. The method of claim 6, Checking whether both of the following two expressions are satisfied, and if not, judging to be null. (Equation 1)

(Equation 2)

In the above formula, S _{i, NACK} denotes the sequence used for the NACK transmission, S _{i, ACK} denotes a sequence for the ACK transmission, i represents the bit index of the sequence, R ₁ is received on the previous acknowledgment channel And R2 represents the signal received via this response channel. A terminal apparatus in a wireless communication system, A receiver for receiving a control message including resource allocation information and decoding the control message; A control unit for determining whether a previous control message is lost if the decoding is successful, And a feedback transmitter for transmitting a null signal or a specific indicator through the response channel if the previous control message is lost. 11. The apparatus according to claim 10, Compares the expected retransmission packet index with the index in the control message, and determines that the previous control message is lost if the two indexes are different. 11. The method of claim 10, Wherein the specific indicator is a specific sequence of nulls. 11. The method of claim 10, After transmitting the null signal or the specific indicator, And receives a control message for recovering the loss of the control message from the base station. 11. The method of claim 10, If the previous control message is not lost, Receives the data packet using the received resource allocation information, and decodes the received data packet. A base station apparatus in a wireless communication system, A feedback receiver for determining whether a null signal is received twice or more consecutively through the response channel, And when the null signal is received consecutively two or more times, combining the received at least two acknowledgment channel signals, performing a null decision using the combined value, The control unit determines that the previously transmitted control message has been lost. 16. The apparatus of claim 15, And performs a restoration procedure according to a control message loss if the previously transmitted control message is lost. 16. The method of claim 15, Further comprising a transmitter for transmitting control information corresponding to the first null signal among the two or more consecutive null signals to the corresponding terminal for the restoration procedure. 16. The apparatus of claim 15, Checking whether both of the following two expressions are satisfied, and if not, judging to be null. (Equation 1)

(Equation 2)

In the above formula, S _{i, NACK} denotes the sequence used for the NACK transmission, S _{i, ACK} denotes a sequence for the ACK transmission, i represents the bit index of the sequence, R ₁ is received on the previous acknowledgment channel And R2 represents the signal received via this response channel. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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