WO2009045048A2

WO2009045048A2 - Method and apparatus for transmission of uplink control channel acknowledgement channel for downlink control channel in ofdma mobile communication system

Info

Publication number: WO2009045048A2
Application number: PCT/KR2008/005782
Authority: WO
Inventors: Jae-Chon Yu; Jun-Young Lee; Yeon-Ju Lim; Dae-Gyun Kim; Joon-Young Cho; Hwan-Joon Kwon; Ju-Ho Lee; Youn-Hyoung Heo
Original assignee: Samsung Electronics Co., Ltd.; Kim, Dong-Hee
Priority date: 2007-10-02
Filing date: 2008-10-01
Publication date: 2009-04-09
Also published as: WO2009045048A3; KR20090034254A; KR101455858B1

Abstract

Disclosed is a method and an apparatus for transmitting an uplink control channel acknowledgement channel for a downlink control channel in a mobile communication system of an OFDMA scheme. By the method and apparatus, it is possible to achieve efficient use of uplink resource in an OFDMA mobile communication system.

Description

METHOP ANB APPARATUS FOR TRANSMISSION OF UPLINK

CONTROL CHANNELACKNOWLEDGEMENT CHANNEL FOR

DOWNLINK CONTROL CHANNEL IN OFDMA MOBILE

COMMUNICATION SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus for transmitting an uplink control channel acknowledgement channel for a downlink control channel in a mobile communication system of an Orthogonal Frequency Division Multiple Access (OFDMA) scheme.

2. Description of the Related Art

Recently, for mobile communication systems, many studies have been and are being conducted on using an Orthogonal Frequency Division Multiplexing (OFDM) scheme as a scheme for high-speed data transmission over wired/wireless channels. The OFDM scheme, which transmits data using multiple carriers, is a special type of a Multiple Carrier Modulation (MCM) scheme in which a serial symbol sequence is converted into parallel symbol sequences and the parallel symbol sequences are modulated with a plurality of mutually orthogonal subcarriers (or subcarrier channels) before being transmitted.

The first MCM systems appeared in the late 1950's for military high frequency (HF) radio communication, and the OFDM scheme for overlapping orthogonal subcarriers was initially developed in the 1970's. However, as it was very difficult to implement orthogonal modulation between multiple carriers, the OFDM scheme had limitations in actual implementation. In 1971, Weinstein, et al. proposed that OFDM modulation/demodulation can be efficiently performed using Discrete Fourier Transform (DFT), which was a driving force behind the rapid development of the OFDM scheme. Also, the introduction of a guard interval and a cyclic prefix as the guard interval further mitigates adverse effects of multipath propagation and delay spread on systems.

Owing to such technical development, the OFDM scheme has been widely used for digital data communication technologies such as digital audio broadcasting (DAB), digital TV broadcasting, wireless local area network (WLAN), and wireless asynchronous transfer mode (WATM). That is to say, although hardware complexity was an obstacle to widespread implementation of the OFDM scheme, recent advances in digital signal processing technology including fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) have enabled implementation of the OFDM scheme. The OFDM scheme, similar to an existing Frequency Division Multiplexing (FDM) scheme, boasts of optimum transmission efficiency in high-speed data transmission because it transmits data on subcarriers, while maintaining orthogonality among them. The optimum transmission efficiency is further attributed to good frequency use efficiency and robustness against multipath fading in the OFDM scheme.

More specifically, overlapping frequency spectrums used in the OFDM scheme lead to efficient frequency use and robustness against frequency selective fading and multipath fading. The OFDM scheme reduces effects of intersystem interference (ISI) by use of guard intervals and enables design of a simple equalizer hardware structure. Furthermore, because the OFDM scheme is robust against impulse noise, it is increasingly popular in communication systems.

A Hybrid Automatic Repeat reQuest (HARQ) scheme is one of important techniques used in order to improve data throughput and reliability of data transmission in a packet-based mobile communication system. The HARQ corresponds to a combination of the techniques of Automatic Retransmission Request (ARQ) and Forward Error Correction (FEC). According to the ARQ, which is being widely used in a wire/wireless data communication system, a transmitter transmits data packets with sequence numbers attached to the data packets according to a pre-promised scheme, and a receiver requests retransmission of a missing packet from among the received packets by using the sequence numbers, thereby achieving reliable data transmission. Further, according to the FEC, each data packet is transmitted together with a redundant bit added thereto according to a predetermined rule, such as convolutional encoding or turbo encoding, so that the originally-transmitted data can be demodulated without noise or fading, which may occur during the data transmission/reception. In a system using the HARQ, that is, a combination of the above-mentioned two techniques, the receiver performs a Cyclic Redundancy Check (CRC) for data demodulated through a predetermined inverse FEC process, in order to determine if the data has an error. As a result of the CRC, when the data has no error, the system using the HARQ feeds back an Acknowledgement (ACK) to the transmitter, so that the transmitter transmits a next data packet. However, when the CRC check shows that the data has an error, the HARQ system feeds back a Non-Acknowledgement (NACK) to the transmitter, so that the transmitter retransmits the previously transmitted data packet.

FIG. 1 illustrates an example of a typical HARQ. In FIG. 1, the horizontal axis corresponds to a time axis.

Reference numeral 101 indicates initial transmission. The data channel in FIG. 1 refers to a channel through which data are actually transmitted. A receiver having received a data packet transmitted by the initial transmission 101 demodulates the received data packet and performs a CRC so as to determine if the received data packet has an error during the demodulation. When the receiver determines that the transmitted data has not been correctly demodulated, the receiver feeds back an NACK to the transmitter in step 102. Upon receiving the NACK 102, the data channel transmitter performs first retransmission 103 in relation to the initial transmission 101. Therefore, the initial transmission 101 and the first retransmission 103 carry the same information. Here, it should be noted that, even when the initial transmission 101 and the first retransmission 103 carry the same information, the same information may have different redundancies.

As used herein, the same data packet transmitted in steps 101, 103 and 105 is called a "sub-packet." Upon receiving the data packet by the first retransmission 103, the receiver combines the data packet of the first retransmission 103 with the data packet of the initial transmission 101 according to a predetermined rule and then demodulates the data channel by using the combined result. Through a CRC of the data channel during the demodulation, when the receiver determines that the transmitted data has not been correctly demodulated, the receiver feeds back an NACK 104 to the transmitter.

Upon receiving the NACK 104, the data channel transmitter performs second retransmission 105 after passage of a predetermined time interval from the time point of the first retransmission 103.

Therefore, the data channels of the initial transmission 101, the first retransmission 103, and the second retransmission 105 carry the same information. Upon receiving the data packet transmitted by the second retransmission 105, the receiver combines the data of the initial transmission 101, the data of the first retransmission 103, and the data of the second retransmission 105 with each other according to a predetermined rule, and then demodulates the data channel by using the combined data. Through this process, when the receiver determines, by CRC for the data channel, that the transmitted data has been correctly demodulated, the receiver feeds back an ACK 106 to the transmitter. After receiving the ACK 106, the transmitter transmits a sub-packet of an initial transmission 107 for next data information together with a control channel. The initial transmission 107 may be performed either immediately after the ACK 106 is received or after passage of a predetermined time interval from the reception of the ACK 106, based on a result of a predetermined scheduling.

In order to support the HARQ as described above, the data receiver must feeds back an ACK/NACK. Here, a channel for transmission of the ACK/NACK is called an ACKCH.

FIG. 2 illustrates a structure of a Physical Downlink Control Channel (PDCCH) and a relation between a Physical Uplink Control Channel (PUCCH) and the PDCCH. The PDCCHs include a plurality of Control Channel Elements (CCEs) 201, and each PDCCH can use one CCE or multiple CCEs. As shown in FIG. 2, each PDCCH can be used for Downlink grant (DL grant). That is, the PDCCH can be used for resource allocation of a Physical Downlink Shared Channel (PDSCH). A User Equipment (UE) having been allocated resources of the PDSCH through the PDCCH transmits ACK/NACK information through an acknowledgement channel (ACKCH) resource 206 mapped to the first CC3 of each PDCCH for the transmitted data. The ACKCH resource allocated in the manner described above is transmitted to a Physical Uplink Acknowledgement Channel (PUACKCH) 208, which is used as an ACK/NACK of the PDSCH. In order to transmit an ACK/NACK of the PUACKCH, an On/Off Keying (OOK) may be used, wherein the ACK may be set to transmit a signal while the NACK is set to make no signal transmission. A Node B uses Non Coherent Detection for signal reception. Since the PDCCH has one CCE or multiple CCEs, it is possible to transmit information having different lengths according to the attribute of the DL grant. Use of different lengths can yield improvement in efficiency of the downlink resources. However, based on an assumption that the ACKCH resource is allocated to each CCE of the PDCCH in transmitting uplink ACK/NACK, it is required to allocate the same number of ACKCH resources as the CCEs. However, if the PDCCH has multiple CCEs, a part of the uplink ACKCH resources mapped to the CCEs may be unused, which may degrade the efficiency in use of the resources.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve the above- mentioned problems occurring in the prior art, and the present invention provides a method and an apparatus for efficient use of uplink resource in a mobile communication system of an Orthogonal Frequency Division Multiple Access (OFDMA) scheme.

Also, the present invention provides a method and an apparatus for transmitting an uplink control channel acknowledgement channel for a downlink control channel in a mobile communication system of an OFDMA scheme.

In accordance with an aspect of the present invention, there is provided a method of transmitting an uplink control channel acknowledgement channel for a downlink control channel in a mobile communication system of an Orthogonal Frequency Division Multiple Access (OFDMA) scheme, the method including the steps of: determining how many control channel elements the downlink control channel includes or how many resource blocks a downlink shared channel includes; demodulating the downlink control channel and the downlink shared channel and determining if demodulation of the downlink control channel and the downlink shared channel is successful; and transmitting information on a success in demodulation of the downlink control channel through an uplink control channel acknowledgement channel by using acknowledgement channel resources mapped in advance to the resource blocks or the control channel elements, depending on success or failure in demodulation of the downlink control channel and the downlink shared channel and depending on if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks.

In accordance with another aspect of the present invention, there is provided an apparatus for transmitting an uplink control channel acknowledgement channel for a downlink control channel in a mobile communication system of an OFDMA scheme, the apparatus including: a control unit for determining how many control channel elements the downlink control channel includes or how many resource blocks a downlink shared channel includes, demodulating the downlink control channel and the downlink shared channel, and determining if demodulation of the downlink control channel and the downlink shared channel is successful; and a transmitter for transmitting information on a success in demodulation of the downlink control channel through an uplink control channel acknowledgement channel by using acknowledgement channel resources mapped in advance to the resource blocks or the control channel elements, depending on success or failure in demodulation of the downlink control channel and the downlink shared channel and depending on if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks.

In accordance with another aspect of the present invention, there is provided a method of receiving an uplink control channel acknowledgement channel in a mobile communication system of an OFDMA scheme, the method including the steps of: determining if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks; and when the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks, determining whether to transmit a next packet, based on if a PUCACKCH and/or PUACKCH is an ACK.

In accordance with another aspect of the present invention, there is provided an apparatus for receiving an uplink control channel acknowledgement channel in a mobile communication system of an OFDMA scheme, the apparatus including: a control unit for determining if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks; and an HARQ controller for, when the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks, determining whether to transmit a next packet, based on if a PUCACKCH and/or PUACKCH is an ACK.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an example of a typical HARQ;

FIG. 2 illustrates a structure of a PDCCH and a relation between a PUCCH and the PDCCH;

FIG. 3A illustrates a method for transmitting a Physical Uplink Control Channel Acknowledgement Channel (PUCACKCH) according to an embodiment of the present invention;

FIG. 3B illustrates a method for transmitting a physical uplink control channel acknowledgement channel according to another embodiment of the present invention;

FIG. 4 illustrates an operation of a UE based on success or failure in demodulation of a PDSCH and a PDCCH according to an embodiment of the present invention;

FIG. 5 is a block diagram of an apparatus for transmitting a PUACKCH and a PUCACKCH in a UE transmitter according to an embodiment of the present invention;

FIG. 6 is a flow chart illustrating a control when a UE transmitter transmits a PUCACKCH and a PUACKCH according to an embodiment of the present invention;

FIG. 7 is a block diagram of an apparatus for receiving a PUACKCH and a PUCACKCH in a Node B receiver according to an embodiment of the present invention; and

FIG. 8 is a flow chart illustrating a control when a Node B receiver receives a PUCACKCH and a PUACKCH according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, 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. Further, various specific definitions found in the following description are provided only to help general understanding of the present invention, and it is apparent to those skilled in the art that the present invention can be implemented without such definitions.

FIG. 3A illustrates a method for transmitting a Physical Uplink Control Channel Acknowledgement Channel (PUCACKCH) according to an embodiment of the present invention.

Referring to FIG. 3A, from among the uplink ACKCHs (PUCACKCHs) allocated based on downlink CCEs, the other ACKCH resources except for Physical Uplink Acknowledgement Channel (PUACKCH) resources used as ACKCH for the PDSCH are used as ACKCHs of the PDCCH. The uplink ACKCHs are indicated by reference numerals 301 to 310. From among the uplink ACKCHs 301 to 310, ACK/NACKs for the PDSCHs are transmitted through PUACKCHl to PUACKCH6 311, 312, 314, 315, 317, and 320 by using ACKCHl 301, ACKCH2 302, ACKCH4 304, ACKCH5 305, ACKCH7 307, and ACKCHlO 310. Further, from among the resources that are not used for the PUACKCH, ACKCH3 313, ACKCH6 316, ACKCH8 318, and ACKCH9 319, which are connected to the CCEs included in the PDCCH, are used as PUCACKCHs 313, 316, 318, and 319.

In the embodiment shown in FIG. 3A₅ the PDCCHl 323 uses a single CCE, that is, CCEl 321, and ACKCHl, which is an uplink ACKCH mapped to CCEl 321, is used as PUACKCHl for the PDSCH. Since there is no other ACKCH mapped to the PDCCHl, it is impossible to use the PUCACKCH for the PDCCH. In contrast, the PDCCH2 324 also uses CCE2 and CCE3, which are mapped to the uplink ACKCH2 and ACKCH3, respectively. ACK/NACK information for the PDSCH2 of downlink, which is not shown in the drawings, is transmitted to the ACKCH2 302 through the PUACKCH2 312, and ACK/NACK information for the PDCH is transmitted to the ACKCH3 303 through the PUCACKCH2 313. A UE may transmit only one of the two channels, including the PUACKCH and the PUCACKCH, while implicitly transmitting a value of the other channel, instead of transmitting both of the two channels. This will be described below in more detail. If two or more ACKCH resources are left after the ACKCHs are used as the PUACKCHs, either an ACKCH using the smallest index or the largest index may be used as the ACK/NACK for the PDCCH or the same information may be sent to all the remaining resources. That is, since control information for the PDCCH5 is transmitted by using CCE7, CCE8, and CCE9, ACK/NACK information for the PDSCH may be transmitted to the ACKCH7 through the PUACKCH5, and ACK/NACK information for the PDCCH may be transmitted by using either one of or both of the ACKCH8 and the ACKCH9. The same method can be applied to a case of using a PUCACKCH in an RB-based ACKCH, which will be described below with reference to FIG. 3B.

FIG. 3B illustrates a method for transmitting a physical uplink control channel acknowledgement channel according to another embodiment of the present invention.

The method according to the embodiment shown in FIG. 3B corresponds to a PUSACKCH resource allocation method in a case of configuring uplink ACKCHs based on Resource Blocks (RBs) of the PDSCH allocated from the PDCCH. Each PDSCH includes one or more RBs, which have ACKCH resources 905 to 914 mapped to an uplink, respectively. ACK/NACK for the PDSCH is transmitted through the PUACKCHl ~ PUACKCH6 by using the ACKCHl 905, ACKCH2 906, ACKCH4 908, ACKCH5 909, ACKCH7 911, and ACKCHlO 914. Further, from among the resources, which are not used as the PUACKCH, the ACKCH3 907, ACKCH6 910, ACKCH8 912, and ACKCH9 913, which are connected to the RBs included in the PDSCH, are used as PUCACKCHs. In the embodiment shown in FIG. 3B, since the PDSCHl 902 includes a single RB, which is RBl, and ACKCHl 905, which is a mapped uplink ACKCH, is used as a PUACKCHl 915 without another ACKCH mapped to the PDSCHl 902, it is impossible to use the PUCACKCH. In contrast, the PDSCH2 903 has RB2 and RB3, which are mapped to uplink ACKCH2 and ACKCH3, respectively. ACK/NACK information for the PDSCH2 of a downlink is transmitted to the ACKCH2 906 through the PUACKCH2 916, and ACK/NACK information for the PDCCH, which is not shown in the drawings, is transmitted to the ACKCH3 907 through the PUCACKCH2 917. The RB-based mapping as described above is not limited to each RB, and each uplink ACKCH resource may be mapped to an RB group including one or more RBs. The following description is based on ACKCH resource allocation to each RB.

FIG. 4 illustrates an operation of a UE based on success or failure in demodulation of a PDSCH and a PDCCH according to an embodiment of the present invention.

The PUACKCH and the PUCACKCH are control channels for transmitting ACK/NACK information of the PDSCH and the PDCCH, respectively, which may use Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), On Off Keying (OOK), etc. as a modulation/demodulation scheme. In the case of using the BPSK or QPSK as the modulation/demodulation scheme, a NACK of the PDSCH, which is ACK/NACK information for the PDSCH, is mapped to one modulation symbol according to a modulation scheme, which implies that demodulation of the PDCCH results in a success while demodulation of the PDSCH results in a failure. In this case, since ACK/NACK information for the PDSCH includes information on success or failure in demodulation of the PDCCH, a separate PUCACKCH having ACK/NACK information for the PDCCH is unnecessary. However, when the OOK modulation/demodulation scheme is used for ACK/NACK transmission of the PDSCH and NACK information of the PDSCH has been mapped to "OFF," which does not send a signal, a Node B receiving the ACK/NACK of the PDSCH cannot identify if it has failed in receiving the PDSCH due to failure in normal demodulation of the PDCCH or if it has failed in demodulation of the PDSCH in spite of a success in normal demodulation of the PDCCH. Therefore, a PUCACKCH having ACK/NACK information for the PDCCH can transmit information on success or failure in demodulation of the PDCCH, so as to enhance the reliability for the PDCCH sent from the Node B. As a result, it is possible to facilitate resource collection of the PDSCH indicated by the PDCCH in the case of PDCCH transmission failure, and reduce power consumption for initial transmission of the PDCCH.

Hereinafter, an operation of a UE according to the value of the PUACKCH and the PUCACKCH in the case of using the OOK modulation/demodulation scheme will be described with reference to FIG. 4. At the time of initial transmission or retransmission, a Node B transmits a DL GRANT by using a PDCCH 401 and simultaneously transmits data through the PDSCH 402. Upon receiving the PDCH and the PDSCH, a UE determines, according to the OOK scheme based on success or failure in demodulation of the PDCCH and the PDSCH, whether to transmit the PUACKCH/PUCACKCH 403, as noted from Table 1 below.

Table 1

In the first case in which demodulation of the PDSCH has failed, which means the PUACKCH is NACK, and demodulation of the PDCCH has failed, which means the PUCACKCH is NACK, the OOK modulation/demodulation scheme does not allow transmission of anything. In the second case in which demodulation of the PDSCH has failed and demodulation of the PDCCH is successful, the UE transmits only an ACK for the PUCACKCH, so as to report the success in demodulation of the PDCCH and the failure in demodulation of the PDSCH and request retransmission. In the third case in which demodulation of the PDSCH is successful and demodulation of the PDCCH has failed, the UE does not perform any operation. That is, the third case is equal to the first case, because the UE cannot receive a DL GRANT transmitted through the PDCCH due to failure in demodulation of the PDCCH. In the fourth case in which both demodulation of the PDSCH and demodulation of the PDCCH are successful, the UE sends a PUACKCH, which is an ACK for the PDSCH, thereby notifying the Node B of the success in demodulation of both the PDCCH and the PDSCH. That is, the success in demodulation of the PDSCH implies success in demodulation of the PDCCH, and it is unnecessary to additionally transmit ACK/NACK information for the PDCCH. In review of the four cases as described above, there is no case of simultaneously transmitting both the PUACKCH and the PUCACKCH. Since there is no simultaneous transmission of the two channels, it is possible to maintain the single carrier characteristic in an uplink, and to enhance the reliability of the control channel by using an ACK/NACK for the PDSCH and the PDCCH.

FIG. 5 is a block diagram of an apparatus for transmitting a PUACKCH and a PUCACKCH in a UE transmitter according to an embodiment of the present invention.

Information on success or failure in demodulation of the PDCCH is transmitted through the PUCACKCH to a PUCCH transmitter 501, and information on success or failure in demodulation of the PDSCH is transmitted through the PUACKCH to a PUSCH transmitter 507. These two types of information are delivered, together with information on if the PDCCH includes multiple CCEs or if the PDSCH includes multiple RBs₅ to a control unit 506. Then, by using the delivered information, the control unit 506 controls selection between transmission of the PUACKCH and the PUCACKCH by a selection unit 502. The control information of the control unit 506 will be described later in more detail with reference to FIG. 6. The selected ACK/NACK information is input, together with a signal generated from data of the PUSCH by a PUSCH transmitter 508, to an Inverse Fast Fourier Transform (IFFT) unit 503. Then, a Cyclic Prefix (CP) is inserted in the IFFTed signal by a CP inserter 504, and is then transmitted by a transmission unit 505.

FIG. 6 is a flow chart illustrating a control when a UE transmitter transmits a PUCACKCH and a PUACKCH according to an embodiment of the present invention.

First, a UE identifies success or failure in demodulation of the PDCCH in step 601. If the demodulation is not proved to be a success, the UE proceeds to step 607, in which the UE does not send any acknowledgment signal, and then terminates the process. If the demodulation is successful, the UE proceeds to step 602, in which the UE determines if the PDCCH includes multiple CCEs or if the PDSCH includes multiple RBs. As a result of in step 602, when the PDCCH does not include multiple CCEs or the PDSCH does not include multiple RBs, the UE proceeds to step 604, in which the UE determines if demodulation of the PDSCH is successful or has failed. When demodulation of the PDSCH is proved to have failed in step 604, the UE proceeds to step 607, in which the UE does not send any acknowledgment signal, and then terminates the process. When demodulation of the PDSCH is proved to be a success in step 604, the UE proceeds to step 605, in which the UE transmits an ACK signal through a PUACKCH. As a result of in step 602, when the PDCCH includes multiple CCEs or the PDSCH includes multiple RBs, the UE proceeds to step 603, in which the UE determines if demodulation of the PDSCH is successful or has failed. When demodulation of the PDSCH is proved to be a success in step 603, the UE proceeds to step 605, in which the UE transmits an ACK signal through a PUACKCH, and then terminates the process. When demodulation of the PDSCH is proved to have failed in step 603, the UE proceeds to step 606, in which the UE transmits an ACK signal through a PUCACKCH, and then terminates the process.

FIG. 7 is a block diagram of an apparatus for receiving a PUACKCH and a PUCACKCH in a Node B receiver according to an embodiment of the present invention.

An RF receiver 701 down-converts a transmitted RF signal and then outputs the down-converted signal. Then, a CP remover 702 removes a CP from the signal output from the RF receiver 701, and the CP-removed signal is transmitted through an Fast Fourier Transform (FFT) unit 703 to a PUCACKCH receiver 704, a PUACKCH receiver 705, and/or a PUSCH receiver 708. A Node B transmits size information of the PDCCH related to the ACK/NACK information at the current reception time point, that is, information on the number of CCEs in the PDCCH or the number of PvBs in the PDSCH, to a control unit 709, and the control unit 709 controls a selection unit 706 by using this information. Under the control of the control unit 709, the selection unit 706 selects an incoming signal of a PUCACKCH receiver 704 or a PUACKCH receiver 705, and then transmits the selected signal to an HARQ controller 707. The information selected by the selection unit 706 is used in supporting the HARQ operation by the HARQ controller 707. The control operation of the control unit 709 will be described below in detail with reference to FIG. 8.

A Node B brings size information of a PDCCH from system information in step 801. That is, the Node B identifies information on the number of RBs of the PDSCH or the number of CCEs of the PDCCH related to the ACK/NACK information at the current receiving time point. In step 802, the Node B determines if the PDCCH includes multiple CCEs or if the PDSCH includes multiple RBs. As a result of the determination in step 802, when the PDCCH does not include multiple CCEs or the PDSCH does not include multiple RBs, the Node B proceeds to step 805, in which the Node B determines if the PUACKCH is an ACK. When the PUACKCH is not an ACK, the Node B proceeds to step 806, in which the Node B transmits a next sub-packet of the current packet through a PDSCH. When the PUACKCH is an ACK, the Node B proceeds to step 807, in which the Node B transmits a new packet through a PDSCH. As a result of the determination in step 802, when the PDCCH includes multiple CCEs or the PDSCH includes multiple RBs, the Node B proceeds to step 803, in which the Node B determines if the PUACKCH is an ACK. When the PUACKCH is an ACK, the Node B proceeds to step 807, in which the Node B transmits a new packet through a PDSCH. As a result of the determination in step 803, when the PUACKCH is not an ACK, the Node B proceeds to step 804, in which the Node B determines if the PUCACKCH is an ACK. As a result of the determination in step 804, when the PUCACKCH is an ACK, the Node B proceeds to step 806, in which the Node B transmits a next sub-packet of the current packet through a PDSCH. When the PUCACKCH is not an ACK, the Node B proceeds to step 807, in which the Node B transmits a new packet through a PDSCH. The transmission of a new packet in step 807 is not required to be necessarily continuously performed, but can be performed with a predetermined time interval depending on a scheduling result by a Node B.

In an OFDMA mobile communication system according to the present invention, ACK/NACK information for the PDCCH is transmitted depending on the number of RBs allocated to a PDSCH or the number of CCEs used in transmission of one PDCCH. Therefore, the present invention can enhance downlink power efficiency through low power consumption at the time of initial PDCCH transmission, and can enhance downlink resource use efficiency through transmission of a new packet at the time of failure in transmission of the PDCCH.

While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method of transmitting an uplink control channel acknowledgement channel for a downlink control channel in a mobile communication system of an Orthogonal Frequency Division Multiple Access (OFDMA) scheme, the method comprising the steps of: determining how many control channel elements the downlink control channel includes or how many resource blocks a downlink shared channel includes; demodulating the downlink control channel and the downlink shared channel and determining if demodulation of the downlink control channel and the downlink shared channel is successful; and transmitting information on a success in demodulation of the downlink control channel through an uplink control channel acknowledgement channel by using acknowledgement channel resources mapped in advance to the resource blocks or the control channel elements, depending on success or failure in demodulation of the downlink control channel and the downlink shared channel and depending on if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks.

2. The method of claim I₃ wherein, when the demodulation of the downlink control channel is proved to be successful and the demodulation of the v downlink shared channel is proved to have failed, a UE transmits an acknowledgement signal (ACK) of a Physical Uplink Control Channel Acknowledgement Channel (PUCACKCH).

3. The method of claim 1, wherein, when the demodulation of the downlink control channel is proved to have failed and the demodulation of the downlink shared channel is proved to be a success, a UE does not operate.

4. The method of claim 1, wherein, when both the demodulation of the downlink control channel and the demodulation of the downlink shared channel have failed, a UE transmits neither of them.

5. The method of claim 1, wherein, when both the demodulation of the downlink control channel and the demodulation of the downlink shared channel are successful, a UE transmits an ACK of a Physical Uplink Channel Acknowledgement Channel (PUACKCH).

6. An apparatus for transmitting an uplink control channel acknowledgement channel for a downlink control channel in a mobile communication system of an OFDMA scheme, the apparatus comprising: a control unit for determining how many control channel elements the downlink control channel includes or how many resource blocks a downlink shared channel includes, demodulating the downlink control channel and the downlink shared channel, and determining if demodulation of the downlink control channel and the downlink shared channel is successful; and a transmitter for transmitting information on a success in demodulation of the downlink control channel through an uplink control channel acknowledgement channel by using acknowledgement channel resources mapped in advance to the resource blocks or the control channel elements, depending on success or failure in demodulation of the downlink control channel and the downlink shared channel and depending on if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks.

7. The apparatus of claim 6, wherein, when the demodulation of the downlink control channel is proved to be successful and the demodulation of the downlink shared channel is proved to have failed, a UE transmits an acknowledgement signal (ACK) of a Physical Uplink Control Channel Acknowledgement Channel (PUCACKCH).

8. The apparatus of claim 6, wherein, when the demodulation of the downlink control channel is proved to have failed and the demodulation of the downlink shared channel is proved to be a success, a UE does not operate.

9. The apparatus of claim 6, wherein, when both the demodulation of the downlink control channel and the demodulation of the downlink shared channel have failed, a UE transmits neither of them.

10. The apparatus of claim 6, wherein, when both the demodulation of the downlink control channel and the demodulation of the downlink shared channel are successful, a UE transmits an ACK of a Physical Uplink Channel Acknowledgement Channel (PUACKCH).

11. A method of receiving an uplink control channel acknowledgement channel in a mobile communication system of an OFDMA scheme, the method comprising the steps of: determining if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks; and when the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks, determining whether to transmit a next packet, based on if a PUCACKCH and/or PUACKCH is an ACK.

12. An apparatus for receiving an uplink control channel acknowledgement channel in a mobile communication system of an OFDMA scheme, the apparatus comprising: a control unit for determining if the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks; and an HARQ controller for, when the downlink control channel includes multiple control channel elements or if the downlink shared channel includes multiple resource blocks, determining whether to transmit a next packet, based on if a PUCACKCH and/or PUACKCH is an ACK.