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WO2008084927A1 - Method and apparatus for transmitting/receiving ack/nack signal in mobile communication system - Google Patents

Method and apparatus for transmitting/receiving ack/nack signal in mobile communication system Download PDF

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Publication number
WO2008084927A1
WO2008084927A1 PCT/KR2007/006837 KR2007006837W WO2008084927A1 WO 2008084927 A1 WO2008084927 A1 WO 2008084927A1 KR 2007006837 W KR2007006837 W KR 2007006837W WO 2008084927 A1 WO2008084927 A1 WO 2008084927A1
Authority
WO
WIPO (PCT)
Prior art keywords
ack
nack
control channel
data
cch
Prior art date
Application number
PCT/KR2007/006837
Other languages
French (fr)
Inventor
Young-Bum Kim
Ju-Ho Lee
Joon-Young Cho
Yong-Jun Kwak
Original Assignee
Samsung Electronics Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Samsung Electronics Co., Ltd. filed Critical Samsung Electronics Co., Ltd.
Publication of WO2008084927A1 publication Critical patent/WO2008084927A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signalling, i.e. of overhead other than pilot signals
    • H04L5/0055—Physical resource allocation for ACK/NACK
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/1607—Details of the supervisory signal
    • H04L1/1621—Group acknowledgement, i.e. the acknowledgement message defining a range of identifiers, e.g. of sequence numbers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1867—Arrangements specially adapted for the transmitter end
    • H04L1/1887—Scheduling and prioritising arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
    • H04L1/0004—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes applied to control information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
    • H04L1/001—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding applied to control information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/04—Error control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation

Definitions

  • the present invention relates to a method and apparatus for transmitting an acknowledgement (ACK)/non-acknowledgement (NACK) signal for transmitted data in a mobile communication system, and more particularly to a method and apparatus for informing a user equipment (UE) of a radio frequency (RF) resource over which to transmit an ACK/NACK signal for transmitted data, and transmitting/receiving the ACK/NACK signal over the informed RF resource in a mobile communication system.
  • ACK acknowledgement
  • NACK non-acknowledgement
  • OFDMA orthogonal frequency division multiple access
  • SC-FDMA single carrier- frequency division multiple access
  • the 3GPP (3 rd Generation Partnership Project) responsible for the standardization of asynchronous cellular mobile communication systems is currently discussing the LTE (Long Term Evolution) system as an evolved mobile communication system based on the above-mentioned multiple access scheme.
  • LTE Long Term Evolution
  • the OFDMA scheme as employed by the LTE system is characterized by allocating and managing time-frequency resources for carrying data or control information to respective users in such a manner as not to overlap each other, that is, in such a manner as to be orthogonal to each other, thereby distinguishing between data or control information according to the respective users.
  • FIG. 1 illustrates an example of data transmission/reception and ACK/NACK resource allocation in a typical LTE system.
  • a Node B 102 transmits data to each of UE#1 103 and UE#2 104 (this is the case of downlink).
  • the Node B 102 transmits control information to the UE#1 103 over a control channel 106, and transmits control signal to the UE#2 104 over a control channel 108.
  • the control information transmitted over each of the control channels 106, 108 includes various information, such as resource information for data to be transmitted to each UE 103, 104 by the Node B 102, a UE ID (Identifier) that is UE identification information, a data transmission format, HARQ (Hybrid Automatic Repeat Request)-related information, a resource and a transmission format for data to be transmitted by the UE, etc.
  • resource information for data to be transmitted to each UE 103, 104 by the Node B 102 a UE ID (Identifier) that is UE identification information, a data transmission format, HARQ (Hybrid Automatic Repeat Request)-related information, a resource and a transmission format for data to be transmitted by the UE, etc.
  • the Node B 102 When the control information is transmitted over each of the control channels 106, 108, the Node B 102 needs to inform the UE 103, 104 of information on a resource for transmitting an ACK/NCAK signal indicative of successful or erroneous data reception, as well as resource information for data to be transmitted.
  • the Node B 102 informs each UE 103, 104 of how to feed back an ACK/NACK signal for transmitted data to the Node B 102 and which resource to use for the ACK/NACK signal transmission, thereby distinguishing between ACKTNACK signals according to respective users.
  • the Node B 102 signals the UE#1 103 to use ACK/NACK resource #1, and signals the UE#2 to use ACK/NACK resource #2.
  • the Node B 102 transmits data to the UE#1 103 and the UE#2 104 over data channels 110, I r respectively.
  • Each of the UE#1 103 and the UE#2 104 acquires resource information necessary for decoding the data channel, a data transmission format, HARQ information, etc. by using the control information received over the control channel 106, 108, and decodes the received data by using the acquired information.
  • Each of the UE#1 103 and the UE#2 104 feeds back a result of the data decoding (whether or not the data decoding is successful or erroneous) to the Node B 102 by using an ACK/NACK signal, thereby enabling the Node B 102 to determine whether or not to retransmit the data.
  • the UE#1 103 transmits an ACK/NACK signal to the Node B 102 by using the ACK/NACK resource#l according to the information acquired from the control channel 106, as indicated by reference numeral "114"
  • the UE#2 104 transmits an ACK/NACK signal to the Node B 102 by using the ACK/NACK resource#2 according to the information acquired from the control channel 108, as indicated by reference numeral " 116".
  • the Node B 102 receives the ACK/NACK signal from each UE 103, 104, and retransmits the data in response to a NACK signal or transmits new data in response to an ACK signal.
  • the UE can improve data reception performance by combining the retransmitted data with the previously received data.
  • FIG. 2 illustrates the time-frequency domain transmission structure of a downlink data or control channel in a typical LTE system.
  • the abscissa axis represents the time domain
  • the ordinate axis represents the frequency domain.
  • the minimum transmission unit in the time domain is an OFDM symbol
  • an N symb number of OFDM symbols constitute one slot 206 with a length of 0.5ms
  • two slots constitute one sub-frame with a length of 1.0ms.
  • the minimum transmission unit in the frequency domain is a sub-carrier, and the overall system transmission band consists of an N B w number of sub- carriers 204 in total. That is, N BW is the number of sub-carriers constituting the overall system transmission band.
  • the basic unit of a resource in the time-frequency domain is a resource element (RE) 212 that may be defined using an OFDM symbol index and a sub- carrier index.
  • RE resource element
  • a resource block (RB) 208 is defined by an N symb number of consecutive OFDM symbols 202 in the time domain and an N RB number of consecutive sub- carriers 210 in the frequency domain. That is, N symb is the number of consecutive OFDM symbols constituting one RB, and N R8 is the number of consecutive sub-carriers constituting one RB. Thus, one RB 208 consists of an (N s y mb x N RB ) number of REs 212.
  • data or control information is transmitted at least in units of RBs.
  • the LTE system under consideration sets N symb to 7, sets N RB to 12, and sets N B w to a value in proportion to a system transmission band.
  • N BW is equal to 600
  • a Node B can simultaneously perform scheduling for a maximum of 50 UEs, and thus 50 ACK/NACK signals corresponding to such data transmission are also needed.
  • the present invention has been made to solve at least the above-mentioned problems occurring in the prior art, and the present invention provides a method and apparatus for transmitting/receiving an ACK/NACK signal in an evolved mobile communication system.
  • the present invention provides a method and apparatus for signaling an RF resource for an ACK/NACK signal and transmitting/receiving the ACK/NACK signal over the signaled RF resource.
  • the present invention provides a method and apparatus for grouping control channels into a plurality of groups corresponding one-to-one to all ACK/NACK channel groups, and informing a UE of information on the grouping and identifier information for identifying an ACK/NACK channel when informing the UE of an RF resource for transmitting/receiving an ACK/NACK signal for transmitted data over the ACK/NACK channel.
  • the present invention provides a method and apparatus for informing a UE of information on the number of control channel groups into which control channels are grouped, group information of the grouped control channels, such as information how many control channels are included in the respective control channel groups arid information on which control channel group includes a control channel to be received by the UE, and sequence information of the control channels in the corresponding control channel group through a defined signaling procedure, and informing the UE of ACK/NACK channel indicator information for identifying ACK/NACK channels according to UEs over the corresponding control channel when informing the UE of an RF resource for an ACK/NACK signal.
  • a method of receiving an ACK/NACK signal in a mobile communication system including the steps of: transmitting an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and receiving the ACK/NACK signal for data transmitted to the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
  • a method of transmitting an ACK/NACK signal in a mobile communication system including the steps of: receiving an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and transmitting the ACK/NACK signal for data transmitted to the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
  • an apparatus for receiving an ACK/NACK signal in a mobile communication system including: a control channel (CCH) generator for generating an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups through a control channel included in the allocated control channel group; a transmitter for transmitting the ACK/NACK channel indicator and control information over the control channel, and transmitting data over a data channel; and a receiver for receiving the ACK/NACK signal for data, transmitted to the UE, from the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
  • CCH control channel
  • an apparatus for transmitting an ACK/NACK signal in a mobile communication system including: a control channel receiver for receiving an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE, which is to receive data, from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and a transmitter for being informed of whether or not the data is erroneous, thereby generating an ACK/NACK signal accordingly, and transmitting the ACK/NACK signal over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
  • FIG. 1 is a view for explaining the concept of data transmission/reception and ACK/NACK signal transmission/reception in a typical LTE system
  • FIG. 2 is a view illustrating a time-frequency domain transmission structure in the typical LTE system
  • FIG. 3 a is a view for explaining an example of informing a UE of an RF resource for ACK/NACK signal transmission in the LTE system to which the present invention is applied;
  • FIG. 3b is a view for explaining an example of informing a UE of an RF resource for ACK/NACK signal transmission in accordance with an exemplary embodiment of the present invention
  • FIG 4 is a view for explaining the concept of grouping control channels (CCHs) and ACK/NACK channels (ACKCHs) in accordance with an exemplary embodiment of the present invention
  • FIG. 5 is a flowchart illustrating a procedure of informing a UE of an RF resource for ACK/NACK signal transmission by a Node B in accordance with an exemplary embodiment of the present invention
  • FIG 6 is a flowchart illustrating a procedure of transmitting an ACK/NACK signal by a UE in accordance with an exemplary embodiment of the present invention
  • FIG. 7 is a view illustrating the overall signal flow when an RF resource for ACK/NACK signal transmission and an ACK/NACK signal are transmitted/received between a Node B and a UE in accordance with an exemplary embodiment of the present invention
  • FIG. 8 is a block diagram illustrating an apparatus for informing a UE of an RF resource for ACK/NACK signal transmission in accordance with an exemplary embodiment of the present invention
  • FIG. 9 is a block diagram illustrating in detail a control channel generator in accordance with an exemplary embodiment of the present invention.
  • FIG 10 is a block diagram illustrating an ACK/NACK signal transmitter in accordance with an exemplary embodiment of the present invention.
  • the present invention to be described below relates to a mobile communication system, and more particularly provides a way for a data transmitter to inform a data receiver of an RF resource necessary for transmitting an ACK/NACK signal for transmitted data in an OFDMA- or SC-FDMA-based mobile communication system.
  • the present invention will explain how a Node B informs a UE of an RF resource necessary for transmitting ACK/NACK signal and manages such an RF resource when the Node B transmits downlink data and the UE transmits the ACK/NACK signal corresponding to the transmitted data.
  • the present invention is also applicable to uplink data transmission.
  • a UE in the case of the uplink data transmission, a UE not only may transmit data to a Node B, but also inform the Node B of an RF resource over which to transmit an ACK/NACK signal for the data, and the Node B may transmit the ACK/NACK signal corresponding to the data over the informed RF resource.
  • the present invention is not limited by a way to multiplex ACK/NACK signals between users.
  • the present invention is not limited to ACK/NACK signal transmission, and may extend to resource allocation information notification and signal transmission for managing the resource allocation information notification.
  • the present invention will be hereinafter described based on the LTE system that is currently under standardization by the 3GPP, but it is obvious that the present invention may also be applied to mobile communication systems employing other communication schemes. Also, for the convenience of the following description, downlink transmission will be exemplified.
  • FIG. 3a illustrates an example of informing a UE of an RF resource for ACK/NACK signal transmission in the LTE system to which the present invention is applied.
  • a Node B transmits data, and the UE transmits an ACK/NACK signal corresponding to the transmitted data.
  • the ACK/NACK signal is transmitted to the Node B over an ACK/NACK channel (ACKCH).
  • ACKCH ACK/NACK channel
  • the Node B may receive 16 ACK/NACK signals from a maximum of 16 UEs over the ACKCHs at the same point of time.
  • the ACKCHs correspond one-to-one to RF resources for ACK/NACK signal transmission (ACKCH transmission resources).
  • the ACKCH transmission resources may be time-frequency resources, code resources, or any combination thereof, and are maintained orthogonal to each other.
  • the present invention is described by exemplifying downlink transmission. That is, the Node B transmits data or control information, and the UE feeds back an ACK/NACK signal, which indicates whether or not the data or control information is erroneous, to the Node B over an ACKCH allocated thereto.
  • the UE transmits data or control information, and the Node B feeds back an ACK/NACK signal, which indicates whether or not the data or control information is erroneous, to the UE over an ACK/NACK transmission resource allocated to the UE.
  • FIG. 3b illustrates the concept of reducing the overhead of signaling for informing a UE of an ACKCH according to an exemplary embodiment of the present invention.
  • This embodiment as illustrated in FIG. 3b is characterized in that a Node B groups all allocable ACKCHs into ACKCH groups, and configures CCHs in such a manner as to correspond to the ACKCH groups. Also, the Node B inserts control information for informing the UE of a specific ACKCH within a corresponding ACKCH group into the CCH, and signals the inserted control information to the UE over the CCH.
  • the Node B groups for example, total 16 ACKCHs into 4 ACKCH groups, that is, ACKCH group A 312, ACKCH group B 314, ACKCH group C 316, and ACKCH group D 318.
  • the Node B also configures CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310 as 4 grouped CCHs corresponding one-to-one to the 4 respective ACKCH groups.
  • the Node B includes 2-bit control information in each of the identifiable CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310, and transmits the control information to the UE, thereby informing the UE of which ACKCH within the ACKCH group corresponding one-to-one to each of the CCHs is assigned thereto.
  • the Node B assigns an ACKCH to a corresponding UE in such a manner as to be identified by 2-bit control information, and informs the UE of the assigned ACKCH over each of the CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310.
  • Information on which ACKCH group includes the ACKCH over which to transmit an ACK/NACK signal from the UE to the Node B may be informed in advance, for example, through a call establishment procedure. It can be noted that this reduces the overhead of signaling for assigning the ACKCH from 4 bits to 2 bits, as compared to the example of FIG. 3a.
  • the Node B transmits 2-bit information to the UE over the CCH#A 304, and upon receiving the 2-bit information, the UE should select an ACKCH indicated by the 2-bit information within the ACKCH group A 312 corresponding one-to-one to the CCH#A 304 and transmit an ACK/NACK signal over the selected ACKCH.
  • the UE upon receiving the CCH#A 304, the UE detects from the 2-bit information which ACKCH among ACKCHs (ACKCH#1, ACKCH#2, ACKCH#3 and ACKCH#4) within the ACKCH group A 312 should be used for transmitting an ACK/NACK signal.
  • the Node B may inform the UE of which CCH or combination of CCHs is received from among the CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310 through prior signaling.
  • Group information of the CCHs 304, 306, 308, 310 such as information on which CCH among the CCHs is allocated to the UE, may be informed to the UE in the middle of performing, for example, a call establishment procedure between the Node B and the UE.
  • the UE uses the ACKCH, which has been used for previous ACK/NACK signal transmission, so as to transmit an ACK/NACK signal corresponding to the data.
  • FIG 4 illustrates the concept of reducing signaling overhead by grouping CCHs and ACKCHs according to an exemplary embodiment of the present invention.
  • a Node B configures a total (Li+L 2 H ( -L 0 ) number of CCHs to be used for transmitting control information to UEs that are under the control thereof.
  • the Node B also configures a total (Ki+K 2 -i HK G ) number of
  • ACKCHs 404 to be used for transmitting ACK/NACK signals by the UEs. That is, the CCHs are grouped into a G number of groups 406, 408,"-, 410, and "CCH group g (g is a number not less than 1 and not greater than G)" consists of an L g (g is a number not less than 1 and not greater than G) number of CCHs.
  • G denotes the maximum number of corresponding groups or channels
  • g denotes an index that indicates the consecutive number of a corresponding group or channel.
  • the Node B groups all the ACKCHs into a G number of groups 412, 414,--, 416, and configures "ACKCH group g (g is a number not less than 1 and not greater than G)" in such a manner as to include a K g (g is a number not less than 1 and not greater than G) number of ACKCHs.
  • "G" corresponding to the number of CCH groups is the same as "G" corresponding to the number of ACKCH groups.
  • the lth CCH within the CCH group g will be represented by "CCH (g, I)"
  • the kth ACKCH within the ACKCH group g will be represented by "ACKCH (g, k)”.
  • the CCH corresponds one-to-one to a CCH transmission resource
  • the ACKCH corresponds one-to-one to an ACKCH transmission resource.
  • the CCH transmission resource and the ACKCH transmission resource may be a time-frequency resource, a code resource, or any combination thereof.
  • the CCHs are orthogonal to each other, and the ACKCHs are orthogonal to each other.
  • the Node B transmits data to the UE, it transmits control information, including information necessary for decoding the data to be transmitted, an ACKCH indicator indicating an ACKCH over which to transmit an ACK/NACK signal for the data, etc., to the UE over the CCH.
  • an ACKCH indicator 436 included in and transmitted by the CCH (1, 1) 418 indicates an ACKCH which corresponds to the CCH (1, 1) from among ACKCHs included in "ACKCH group 1" 412 corresponding one-to-one to "CCH group 1" 406 including the CCH (1, 1) 418 and over which the UE is to transmit an ACK/NACK signal.
  • the ACKCH indicator represents which ACKCH included in an ACKCH group is indicated by each CCH included in a CCH group corresponding to the ACKCH group.
  • the ACKCH indicator included in the CCH (1, 1) indicates ACKCH (1, 2) 440.
  • the ACKCH indicator 436 may be expressed by bits, the number of which is ceil (LOg 2 K 1 ) in proportion to Ki that is the number of ACKCHs constituting the "ACKCH group 1" 412.
  • the ceiling function ceil (x) denotes a minimum integer greater than x.
  • the ACKCH indicator 436 indicates ACKCH (1, 1) 438 within the "ACKCH group 1" 412 corresponding one-to-one to the CCH (1, L 1 ) 422.
  • CCH search group In receiving the CCHs 418, 420, 422 according to the UEs, which CCH the UEs should search may be recognized mutually between the Node B and the UEs through prearrangement or prior signaling, so that complexity that may be caused by the UEs' CCH search can be reduced.
  • a CCH group to be searched by a UE will be referred to as a "CCH search group”.
  • the CCH search group there is no particular connection between the CCH search group and the CCH group.
  • a UE searches CCHs, it can find out whether or not a corresponding CCH includes information relevant thereto by comparing its own ID with an ID included in the CCH and checking if the two IDs are identical.
  • the UE when the transmission format of data or a data transmission resource used for data transmission is retained in its entirety after initial CCH transmission, the UE can acquire information necessary for data decoding from control information previously received over the CCH, even if the CCH transmission is omitted.
  • the Node B omits the CCH transmission, and transmits only data.
  • the ACKCH that the UE has used for previous ACK/NACK signal transmission is maintained as an ACKCH corresponding to the transmitted data, which additionally reduces overhead for the ACKCH indicator.
  • CCH group 2 corresponds one-to-one to "ACKCH group 2" 414, and more particularly CCH (2, 1) 424, CCH (2, 2) 426 and CCH (2, L 2 ) 428 within the "CCH group 2" 408 indicate ACKCH (2, 2) 446, ACKCH (2, 1) 444 and ACKCH (2, K 2 ) 448 respectively through the ACKCH indicator 436.
  • the ACKCH indicator 436 may be expressed by bits, the number of which is ceil (LOg 2 K 2 ) in proportion to K 2 that is the number of ACKCHs constituting the "ACKCH group 2" 414.
  • CCH group G” 410 corresponds one-to-one to "ACKCH group G” 416, and more particularly CCH (G, 1) 430, CCH (G, 2) 432 and CCH (G L G ) 434 within the "CCH group G” 410 indicate ACKCH (G, 1) 450, ACKCH (G, K 0 ) 454 and ACKCH (G, 2) 452 respectively through the ACKCH indicator 436.
  • the ACKCH indicator 436 may be expressed by bits, the number of which is ceil (LOg 2 Ko) in proportion to KQ that is the number of ACKCHs constituting the "ACKCH group G" 416.
  • the number of ACKCHs constituting each ACKCH group may be arbitrarily defined, but is preferably defined by the same number.
  • FIG. 5 illustrates a procedure of informing a UE of an ACKCH transmission resource by a Node B over a CCH according to an exemplary embodiment of the present invention.
  • step 500 the Node B determines to transmit data to the UE in consideration of a buffer status, a channel condition, priority, etc.
  • step 502 the Node B then determines prior to data transmission whether or not to transmit the CCH.
  • the CCH is transmitted along with the data transmission to thereby be used as information for decoding the data.
  • the Node B may omit the CCH transmission and perform only the data transmission.
  • the UE can acquire information necessary for data decoding from a previously received CCH, even if the CCH transmission is omitted.
  • signaling overhead is reduced by omitting the CCH transmission.
  • the Node B determines in step 504 if an RF resource for the CCH transmission or a specific CCH mapped to the resource is used. In next step 506, the Node B determines if an RF resource over which to transmit an ACK/NACK signal corresponding to the data transmission or a specific ACKCH mapped to the resource is used.
  • the Node B determines a CCH transmission format to thereby perform channel coding in step 508, and then transmits control information over the CCH by using the resource determined in step 504.
  • the CCH includes resource information for data to be transmitted to the UE, the ID of the UE, a data transmission format, HARQ-related information, resource information and the transmission format of data to be transmitted to the Node B by the UE, an ACKCH indicator, etc.
  • step 510 the Node B transmits the data to the UE. If the Node B determines in step 502 to omit the CCH transmission, it skips steps 504, 506 and 508, and transmits the data directly in step 510. In step 512, the Node B receives an ACK/NACK signal for the data transmitted in step 510 over the ACKCH transmission resource that has been informed over the CCH.
  • FIG. 6 illustrates a procedure of transmitting an ACK/NACK signal by a UE according to an exemplary embodiment of the present invention.
  • the procedure in FIG. 6 corresponds to a procedure of transmitting an ACK/NACK signal by a UE when data is transmitted irrespective of whether or not CCH transmission is performed by a Node B.
  • the UE searches CCHs so as to receive a CCH allocated thereto.
  • the Node B informs the UE in advance of a CCH search group to be searched by the UE, and thus the UE searches CCHs within the CCH search group.
  • the CCH search group is recognized mutually between the Node B and the UE through prearrangement, and is signaled to the UE.
  • the UE When the UE succeeds in searching the CCH in step 600, it acquires control information included in the CCH in step 602. In step 604, the UE receives data, and decodes the received data by using the control information, thereby determining if the data is erroneous.
  • step 606 when a result of the determination in step 604 shows that there is no error in the data decoding, the UE generates an ACK signal, but otherwise generates an NACK signal. Also, in step 606, the UE transmits the generated ACK or NACK signal over an ACKCH indicated by the ACKCH indicator within the CCH.
  • step 608 the UE acquires control information necessary for data decoding and ACKCH information for ACK/NACK signal transmission from a previously received CCH, and decodes the data received in step 604 by using the acquired control information.
  • step 606 the UE checks if the received data is erroneous, and according to whether or not the data is erroneous, transmits an ACK or NACK signal to the Node B over an ACKCH indicated by an ACKCH indicator included in the previously received CCH.
  • FIG. 6 does not allow for a case where the Node B transmits control information over the CCH, but the UE fails to receive the control information due to the occurrence of errors.
  • FIG. 7 illustrates the overall signal flow when an ACKCH transmission resource is allocated and an ACK/NACK signal is transmitted between a Node B and a UE according to an exemplary embodiment of the present invention.
  • the Node B 700 transmits control information to UE#1 702 and UE#2 704 over CCHs.
  • the Node B 700 transmits the control information to the UE#1 702 over CCH (1, 1).
  • the CCH (1, 1) transmitted in step 706 is a CCH belonging to CCH group 1, which informs the UE#1 702 that it should use ACKCH group 1 corresponding one-to-one to the CCH group 1 for ACKCH transmission.
  • step 708 the Node B 700 transmits the control information to the UE#2 over CCH (2, 2).
  • the CCH (2, 2) transmitted in step 708 is a CCH belonging to CCH group 2, which informs the UE#2 704 that it should use ACKCH group 2 corresponding one-to-one to the CCH group 2 for ACKCH transmission.
  • the Node B transmits data to the UE#1 702 and the UE#2 704 over data channels.
  • the Node B 700 transmits the data to the UE#1 702 over a data channel.
  • the data channel is transmitted according to a transmission format that is indicated by data-related control information included in the CCH (1, 1) in step 706.
  • the transmission format of the data channel transmitted from the Node B 700 to the UE#2 704 in step 712 follows a transmission format that is indicated by data-related control information included in the CCH (2, 2) in step 708.
  • the UE#1 702 and the UE#2 704 receive the data over the data channels respectively, determine if the received data are erroneous, and then generate ACK or NACK signals according to whether or not the data are erroneous.
  • the UE#1 702 transmits the generated ACK/NACK signal by using the second ACKCH within the ACKCH group 1, that is, the ACKCH (1, 2) that is informed from the CCH (1, 1) received in step 706, as designated by reference numeral "742".
  • the UE#2 704 transmits the generated ACK/NACK signal by using the third ACKCH within the ACKCH group 2, that is, the ACKCH (2, 3) that is informed from the CCH (2, 2) received in step 708, as designated by reference numeral "744".
  • the Node B 700 Upon receiving the ACK/NACK signals over the ACKCH (1, 2) and the ACKCH (2, 3) in steps 714 and 716, the Node B 700 determines whether or not to perform retransmission for the data transmitted over the data channels in steps 710 and 712.
  • the Node B 700 receives an NACK signal from any UE, and thus determines data retransmission, it transmits a CCH and data in the same manner as that described above. However, when the transmission format of the data to be retransmitted is maintained unchanged in comparison to the previous data transmission, the Node B may reduce additional signaling overhead by omitting the CCH transmission.
  • the Node B 700 omits the CCH transmission for the UE#1 702, as designated by reference numeral "718".
  • the UE#1 receives the retransmitted data over the data channel.
  • the UE#1 702 uses the ACKCH (1, 2), which has been informed from the CCH (1, 1) received in step 706, as an ACKCH over which to transmit an ACK/NACK signal for the data retransmitted over the data channel in step 722, as designated by reference numeral "746".
  • the UE#2 704 transmits an ACK/NACK signal by using ACKCH (1, 3) that is informed from the CCH (1, 1) in step 720, as designated by reference mineral "748".
  • CCHs may be grouped as follows:
  • Index i may vary at each point of time of transmission, and the maximum number of transmittable channels, I, is equal to or greater than (Li+L 2 H i-L G ) as described in FIG. 4.
  • the total number of CCH groups, G, and the maximum number of CCHs within each CCH group, Ll, L2,--, L 0 , are recognized mutually between the Node B and the UE through prearrangement or prior signaling.
  • the CCH (i) and the CCH (g, 1) are logical concepts that correspond one-to-one to time- frequency resources used for physical transmission.
  • Method 1 can be expressed by the following equation:
  • CCHs are mapped to CCH group g in such a manner as to sequentially map the CCHs to CCH groups in ascending order of index g, that is, in order from the lowest index to the highest index.
  • each CCH group g is configured as follows:
  • each CCH group g is configured as follows:
  • CCH groups are configured according to modulation and coding schemes (MCS) of CCHs.
  • MCS modulation and coding schemes
  • the MCS of a CCH may vary according to channel conditions. For example, UEs with good channel conditions may be improved in resource efficiency through a high-order modulation scheme, such as 16QAM, or coding with high coding rate. Contrarily, UEs with bas channel conditions may be set in such a manner as to maximize error correction capability through QPSK or coding with low coding rate.
  • CCHs with the same MSC or similar MSCs applied thereto constitute the same CCH group.
  • CCH groups are configured according to whether data to be transmitted are localized in order to acquire scheduling gain or are distributed in order to frequency diversity gain.
  • FIG. 8 illustrates a Node B apparatus 800 operating according to an exemplary embodiment of the present invention.
  • the Node B apparatus 800 includes a scheduler 810, a pilot generator 812, a data generator 814, a CCH generator 816, a multiplexer 817, a serial-to-parallel (S/P) converter 818, a mapper 820, an IFFT (Inverse Fast Fourier Transform) block 822, a parallel-to-serial (P/S) converter 824, a CP (Cyclic Prefix) adder 830, and a transmit antenna 832.
  • a scheduler 810 includes a scheduler 810, a pilot generator 812, a data generator 814, a CCH generator 816, a multiplexer 817, a serial-to-parallel (S/P) converter 818, a mapper 820, an IFFT (Inverse Fast Fourier Transform) block 822, a parallel-to-serial (P/S) converter 824, a CP (Cyclic Prefix) adder 830, and
  • the scheduler 810 controls the overall operation of the Node B apparatus, and determines whether or not to transmit data or control information, a resource mapping method, etc.
  • the scheduler 810 applies necessary control information to main blocks including the multiplexer 817, the mapper 820, the pilot generator 812, the data generator 814, the CCH generator 816, and the like.
  • the control information input into the pilot generator 812 includes a sequence index for generating an allocation pilot sequence, time domain cyclic shift information, etc.
  • the pilot is also referred to as an RS (Reference Signal), and is used for channel estimation and coherent demodulation on a receiving side.
  • RS Reference Signal
  • the multiplexer 817 receives timing information from the scheduler 810 so as to transmit a pilot, data, a CCH, etc. generated by the pilot generator 812, the data generator 814, and the CCH generator 816.
  • the scheduler 810 inputs timing information, frequency allocation information, etc, into the mapper 820 that maps the above information (pilot, data, CCH) to an actual frequency resource.
  • the CCHs as described in embodiments of the present invention are mapped to time-frequency resources allocated through the multiplexer 817 and the mapper 820.
  • An output signal from the multiplexer 817 is converted into a parallel signal by the S/P converter 818, and then is input into the mapper 820, in which the parallel signal is mapped to a frequency resource to actually carry it.
  • An output signal from the mapper 820 is converted into a time domain signal by the IFFT block 822, and is input into the P/S converter 824, in which the time domain signal is converted into a serial signal.
  • the CP adder 830 adds a cyclic prefix (CP) for preventing inter-symbol interference to the signal, and the signal with the CP added thereto is transmitted through the transmit antenna 832.
  • CP cyclic prefix
  • FIG. 9 illustrates the CCH generator 816 of FIG. 8 in more detail.
  • the scheduler 810 inputs data transmission-related control information, such as resource information for data to be transmitted from the Node B to the UE, the ID of the UE, a data transmission format, HARQ- related information, a resource and the transmission format of data to be transmitted by the UE, etc., into a control information generator 840, as designated by reference numeral "836", and the control information generator 840 then generates control information including the input information.
  • data transmission-related control information such as resource information for data to be transmitted from the Node B to the UE, the ID of the UE, a data transmission format, HARQ- related information, a resource and the transmission format of data to be transmitted by the UE, etc.
  • the scheduler 810 also inputs ACKCH-related control information, to be used for ACK/NACK transmission by the UE, into an ACKCH indicator generator 842, as designated by reference numeral "838", and the ACKCH generator 842 then generates an ACKCH indicator.
  • the ACKCH-related control information is information on which ACKCH group includes a corresponding ACKCH indicator to which a CCH to be used by the scheduler 810 is mapped, that is, information indicating an ACKCH to be used for ACK/NACK transmission by the UE.
  • a multiplexer 844 multiplexes signals generated by the control information generator 840 and the ACKCH indicator generator 842, and then outputs the multiplexed signal to an encoder 846.
  • the encoder 846 adds error correction capability to the signal input from the multiplexer 844, and outputs the signal with the error correction capability added thereto to the multiplexer 817.
  • FIG 10 illustrates a UE apparatus 1000 operating according to an exemplary embodiment of the present invention.
  • the UE apparatus 1000 includes a receive antenna 1010, a CP remover 1012, an S/P converter 1014, an FFT block 1016, a demapper 1018, a P/S converter 1022, a demultiplexer 1024, a controller 1026, a CCH receiver 1028, a channel estimator 1030, a data receiver 1032, an ACK/NACK generator 1034, a modulator 1036, a transmission part 1038, and a transmit antenna 1040.
  • the controller 1026 controls the overall operation of the UE apparatus 1000, and provides main blocks, such as the demultiplexer 1024, the demapper 1018, the CCH receiver 1028, the channel estimator 1030, the data receiver 1032, the ACK/NACK generator 1034, etc., with necessary control information.
  • the controller 1026 inputs CCH reception timing, data reception timing, and ACK/NACK transmission timing into the CCH receiver 1028, the data receiver 1032, and the ACK/NACK generator 1034 respectively.
  • the control information input into the channel estimator 1030 includes a sequence index for generating a pilot sequence allocated to a target UE for reception, time domain cyclic shift information, and so forth.
  • the demultiplexer 1024 receives timing information from the controller 1026 so as to divide an input signal into a CCH signal, data, a pilot, etc. to be input into the CCH receiver 1028, the data receiver 1032, and the channel estimator 1030.
  • the demapper 1018 for extracting the information from an actual frequency resource receives timing information, frequency allocation information, etc. from the controller 1026.
  • the controller 1026 has already received CCH search group information, that is, information on which time-frequency resource should be searched for CCH reception, through prior signaling.
  • the UE receives a signal from the Node B through the receive antenna 1010, the CP remover 1012 removes a CP from the received signal, the S/P converter 1014 converts the resultant signal into a parallel signal, and then the parallel signal is input into the FFT block 1016.
  • An output signal from the FFT block 1016 passes through the demapper 1018, and is converted into a serial signal by the P/S converter 1022.
  • the serial signal is divided into a CCH, a pilot and data by the demultiplexer 1024, and the divided CCH, pilot and data are input into the CCH receiver 1028, the channel estimator 1030, and the data receiver 1032 respectively.
  • the channel estimator 1030 acquires a channel estimate from the input pilot signal, and uses the acquired channel estimate for channel compensation of the CCH and data signals respectively.
  • the CCH receiver 1028 demodulates and decodes the input signal to thereby acquire resource information for the data and transmission format-related control information, and applies them to the data receiver 1032.
  • the Node B informs the UE of control information for the CCH transmission format through separate signaling, thereby enabling the UE to demodulate and decode the CCH.
  • the CCH receiver 1028 acquires an ACKCH indicator from the received CCH, and provides the ACK/NACK generator 1034 with ACKCH information for an ACKCH to be used by the UE.
  • the ACKCH information that has been used for previous ACK/NACK transmission is retained as ACKCH information to be used for ACK/NACK transmission by the UE.
  • the CCH receiver 1028 stores the previous ACKCH information in a memory (not illustrated), and subsequently provides the data receiver 1032 with the stored ACKCH information.
  • the controller 1026 controls the operation of the CCH receiver 1028 according to whether or not the CCH is received.
  • the data receiver 1032 acquires data resource information and data transmission format-related information from the CCH receiver 1028, and performs data demodulation and decoding by using the acquired information.
  • the ACK/NACL generator 1034 is informed from the data receiver 1032 of whether or not the received data is erroneous, generates an ACK signal in the case of no error, and generates an NACK signal when errors occur. Also, the ACK/NACK generator 1034 configures an ACKCH over which to transmit the generated ACK/NACK signal, based on the ACKCH information input from the CCH receiver 1028.
  • the controller 1026 controls transmission timing of the configured ACKCH.
  • the ACK/NACK signal generated by the ACJK/NACK generator 1034 is modulated by the modulator 1036, is subjected to signal processing by the transmission part 1038, and then is transmitted through the transmit antenna 1040.
  • signaling overhead for an ACK/NACK signal can be reduced by grouping ACK/NACK resources into ACK/NACK transmission resource groups, grouping CCHs for informing the receiving side of the ACK/NACK transmission resources into groups corresponding to the ACK/NACK transmission resource groups, and transmitting the CCHs while inserting control information for ACK/NACK transmission resource notification into the CCHs corresponding one-to-one to the grouped ACK/NACK transmission resources.

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Abstract

Disclosed is a method and apparatus for informing a UE of an RF resource for ACK/NACK transmission in order to transmit/receive an ACK/NACK signal for transmitted data in a mobile communication system. A method of receiving an ACK/NACK signal in a mobile communication system, includes the steps of: transmitting an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and receiving the ACK/NACK signal for data transmitted to the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.

Description

METHOD AND APPARATUS FOR TRANSMITTING/RECEIVING ACK/NACK SIGNAL IN MOBILE COMMUNICATION SYSTEM
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for transmitting an acknowledgement (ACK)/non-acknowledgement (NACK) signal for transmitted data in a mobile communication system, and more particularly to a method and apparatus for informing a user equipment (UE) of a radio frequency (RF) resource over which to transmit an ACK/NACK signal for transmitted data, and transmitting/receiving the ACK/NACK signal over the informed RF resource in a mobile communication system.
2. Description of the Related Art
In mobile communication systems, active research on an orthogonal frequency division multiple access (OFDMA) scheme or a single carrier- frequency division multiple access (SC-FDMA) scheme similar thereto has recently been conducted as a scheme useful for high-speed data transmission over an RF channel.
The 3GPP (3rd Generation Partnership Project) responsible for the standardization of asynchronous cellular mobile communication systems is currently discussing the LTE (Long Term Evolution) system as an evolved mobile communication system based on the above-mentioned multiple access scheme.
The OFDMA scheme as employed by the LTE system is characterized by allocating and managing time-frequency resources for carrying data or control information to respective users in such a manner as not to overlap each other, that is, in such a manner as to be orthogonal to each other, thereby distinguishing between data or control information according to the respective users.
FIG. 1 illustrates an example of data transmission/reception and ACK/NACK resource allocation in a typical LTE system. For the convenience of the following discussion, let us suppose that a Node B 102 transmits data to each of UE#1 103 and UE#2 104 (this is the case of downlink).
Referring to FIG. 1, at a point of time designated by reference numeral "118", the Node B 102 transmits control information to the UE#1 103 over a control channel 106, and transmits control signal to the UE#2 104 over a control channel 108.
The control information transmitted over each of the control channels 106, 108 includes various information, such as resource information for data to be transmitted to each UE 103, 104 by the Node B 102, a UE ID (Identifier) that is UE identification information, a data transmission format, HARQ (Hybrid Automatic Repeat Request)-related information, a resource and a transmission format for data to be transmitted by the UE, etc.
When the control information is transmitted over each of the control channels 106, 108, the Node B 102 needs to inform the UE 103, 104 of information on a resource for transmitting an ACK/NCAK signal indicative of successful or erroneous data reception, as well as resource information for data to be transmitted.
In other words, the Node B 102 informs each UE 103, 104 of how to feed back an ACK/NACK signal for transmitted data to the Node B 102 and which resource to use for the ACK/NACK signal transmission, thereby distinguishing between ACKTNACK signals according to respective users.
In FIG 1, at a point of time designated by reference numeral "118", the Node B 102 signals the UE#1 103 to use ACK/NACK resource #1, and signals the UE#2 to use ACK/NACK resource #2.
Also, at a point of time designated by reference numeral "120", the Node B 102 transmits data to the UE#1 103 and the UE#2 104 over data channels 110, I r respectively.
Each of the UE#1 103 and the UE#2 104 acquires resource information necessary for decoding the data channel, a data transmission format, HARQ information, etc. by using the control information received over the control channel 106, 108, and decodes the received data by using the acquired information.
Each of the UE#1 103 and the UE#2 104 feeds back a result of the data decoding (whether or not the data decoding is successful or erroneous) to the Node B 102 by using an ACK/NACK signal, thereby enabling the Node B 102 to determine whether or not to retransmit the data. That is, the UE#1 103 transmits an ACK/NACK signal to the Node B 102 by using the ACK/NACK resource#l according to the information acquired from the control channel 106, as indicated by reference numeral "114", and the UE#2 104 transmits an ACK/NACK signal to the Node B 102 by using the ACK/NACK resource#2 according to the information acquired from the control channel 108, as indicated by reference numeral " 116".
At a point of time designated by reference numeral "122", the Node B 102 receives the ACK/NACK signal from each UE 103, 104, and retransmits the data in response to a NACK signal or transmits new data in response to an ACK signal. The UE can improve data reception performance by combining the retransmitted data with the previously received data.
FIG. 2 illustrates the time-frequency domain transmission structure of a downlink data or control channel in a typical LTE system.
In FIG. 2, the abscissa axis represents the time domain, and the ordinate axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM symbol, an Nsymb number of OFDM symbols constitute one slot 206 with a length of 0.5ms, and two slots constitute one sub-frame with a length of 1.0ms.
The minimum transmission unit in the frequency domain is a sub-carrier, and the overall system transmission band consists of an NBw number of sub- carriers 204 in total. That is, NBW is the number of sub-carriers constituting the overall system transmission band.
The basic unit of a resource in the time-frequency domain is a resource element (RE) 212 that may be defined using an OFDM symbol index and a sub- carrier index.
A resource block (RB) 208 is defined by an Nsymb number of consecutive OFDM symbols 202 in the time domain and an NRB number of consecutive sub- carriers 210 in the frequency domain. That is, Nsymb is the number of consecutive OFDM symbols constituting one RB, and NR8 is the number of consecutive sub-carriers constituting one RB. Thus, one RB 208 consists of an (Nsymb x NRB) number of REs 212. In general, data or control information is transmitted at least in units of RBs. The LTE system under consideration sets Nsymb to 7, sets NRB to 12, and sets NBw to a value in proportion to a system transmission band.
For example, when the system transmission band has a value of 10 MHz, NBW is equal to 600, and the number of RBs is equal to 50 (600/12 = 50). In this example, since RB corresponds to the minimum transmission unit of data, a Node B can simultaneously perform scheduling for a maximum of 50 UEs, and thus 50 ACK/NACK signals corresponding to such data transmission are also needed. With regard to this, 6-bit signaling (Iog250 =* 6) is required to inform the UEs of ACK/NACK resources to be used for ACK/NACK signal transmission.
In other words, signaling overhead corresponding to 6 bits is imposed on total 50 ACK/NCAK signals for total 50 UEs.
However, such excessive signaling overhead leads to a decrease in system efficiency.
Therefore, there is an earnest need for a way to inform a data receiver of an RF resource over which to transmit an ACK/NACK signal corresponding to transmitted data to a data transmitter in an evolved mobile communication system, such as the LTE system. More specially, a way to inform a data receiver of an RF resource over which to transmit an ACK/NACK signal and a way to reduce signaling overhead of control information for the RF resource to be informed to the data receiver are all needed in the LTE system.
This also means that more efficient use of RF resources necessitates reducing signaling overhead that occurs in informing a data receiver of an RF resource over which to transmit an ACK/NACK signal.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made to solve at least the above-mentioned problems occurring in the prior art, and the present invention provides a method and apparatus for transmitting/receiving an ACK/NACK signal in an evolved mobile communication system.
Further, the present invention provides a method and apparatus for signaling an RF resource for an ACK/NACK signal and transmitting/receiving the ACK/NACK signal over the signaled RF resource.
Further, the present invention provides a method and apparatus for grouping control channels into a plurality of groups corresponding one-to-one to all ACK/NACK channel groups, and informing a UE of information on the grouping and identifier information for identifying an ACK/NACK channel when informing the UE of an RF resource for transmitting/receiving an ACK/NACK signal for transmitted data over the ACK/NACK channel.
Further, the present invention provides a method and apparatus for informing a UE of information on the number of control channel groups into which control channels are grouped, group information of the grouped control channels, such as information how many control channels are included in the respective control channel groups arid information on which control channel group includes a control channel to be received by the UE, and sequence information of the control channels in the corresponding control channel group through a defined signaling procedure, and informing the UE of ACK/NACK channel indicator information for identifying ACK/NACK channels according to UEs over the corresponding control channel when informing the UE of an RF resource for an ACK/NACK signal.
In accordance with an aspect of the present invention, there is provided a method of receiving an ACK/NACK signal in a mobile communication system, the method including the steps of: transmitting an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and receiving the ACK/NACK signal for data transmitted to the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
In accordance with another aspect of the present invention, there is provided a method of transmitting an ACK/NACK signal in a mobile communication system, the method including the steps of: receiving an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and transmitting the ACK/NACK signal for data transmitted to the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
In accordance with yet another aspect of the present invention, there is provided an apparatus for receiving an ACK/NACK signal in a mobile communication system, the apparatus including: a control channel (CCH) generator for generating an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups through a control channel included in the allocated control channel group; a transmitter for transmitting the ACK/NACK channel indicator and control information over the control channel, and transmitting data over a data channel; and a receiver for receiving the ACK/NACK signal for data, transmitted to the UE, from the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
In accordance with still yet another aspect of the present invention, there is provided an apparatus for transmitting an ACK/NACK signal in a mobile communication system, the apparatus including: a control channel receiver for receiving an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE, which is to receive data, from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and a transmitter for being informed of whether or not the data is erroneous, thereby generating an ACK/NACK signal accordingly, and transmitting the ACK/NACK signal over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
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 is a view for explaining the concept of data transmission/reception and ACK/NACK signal transmission/reception in a typical LTE system;
FIG. 2 is a view illustrating a time-frequency domain transmission structure in the typical LTE system;
FIG. 3 a is a view for explaining an example of informing a UE of an RF resource for ACK/NACK signal transmission in the LTE system to which the present invention is applied;
FIG. 3b is a view for explaining an example of informing a UE of an RF resource for ACK/NACK signal transmission in accordance with an exemplary embodiment of the present invention;
FIG 4 is a view for explaining the concept of grouping control channels (CCHs) and ACK/NACK channels (ACKCHs) in accordance with an exemplary embodiment of the present invention;
FIG. 5 is a flowchart illustrating a procedure of informing a UE of an RF resource for ACK/NACK signal transmission by a Node B in accordance with an exemplary embodiment of the present invention;
FIG 6 is a flowchart illustrating a procedure of transmitting an ACK/NACK signal by a UE in accordance with an exemplary embodiment of the present invention;
FIG. 7 is a view illustrating the overall signal flow when an RF resource for ACK/NACK signal transmission and an ACK/NACK signal are transmitted/received between a Node B and a UE in accordance with an exemplary embodiment of the present invention;
FIG. 8 is a block diagram illustrating an apparatus for informing a UE of an RF resource for ACK/NACK signal transmission in accordance with an exemplary embodiment of the present invention;
FIG. 9 is a block diagram illustrating in detail a control channel generator in accordance with an exemplary embodiment of the present invention; and
FIG 10 is a block diagram illustrating an ACK/NACK signal transmitter in accordance with an exemplary 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.
The present invention to be described below relates to a mobile communication system, and more particularly provides a way for a data transmitter to inform a data receiver of an RF resource necessary for transmitting an ACK/NACK signal for transmitted data in an OFDMA- or SC-FDMA-based mobile communication system.
More specially, the present invention will explain how a Node B informs a UE of an RF resource necessary for transmitting ACK/NACK signal and manages such an RF resource when the Node B transmits downlink data and the UE transmits the ACK/NACK signal corresponding to the transmitted data.
In addition to the downlink data transmission, the present invention is also applicable to uplink data transmission. For example, in the case of the uplink data transmission, a UE not only may transmit data to a Node B, but also inform the Node B of an RF resource over which to transmit an ACK/NACK signal for the data, and the Node B may transmit the ACK/NACK signal corresponding to the data over the informed RF resource.
Further, the present invention is not limited by a way to multiplex ACK/NACK signals between users.
Further, it will be apparent to those skilled in the art that the present invention is not limited to ACK/NACK signal transmission, and may extend to resource allocation information notification and signal transmission for managing the resource allocation information notification.
By way of example, the present invention will be hereinafter described based on the LTE system that is currently under standardization by the 3GPP, but it is obvious that the present invention may also be applied to mobile communication systems employing other communication schemes. Also, for the convenience of the following description, downlink transmission will be exemplified.
FIG. 3a illustrates an example of informing a UE of an RF resource for ACK/NACK signal transmission in the LTE system to which the present invention is applied.
Referring to FIG. 3 a, a Node B transmits data, and the UE transmits an ACK/NACK signal corresponding to the transmitted data. With regard to this, the ACK/NACK signal is transmitted to the Node B over an ACK/NACK channel (ACKCH).
As an example, let us suppose that total 16 ACKCHs exist in the system. Thus, the Node B may receive 16 ACK/NACK signals from a maximum of 16 UEs over the ACKCHs at the same point of time. The ACKCHs correspond one-to-one to RF resources for ACK/NACK signal transmission (ACKCH transmission resources). The ACKCH transmission resources may be time-frequency resources, code resources, or any combination thereof, and are maintained orthogonal to each other.
That is, in FIG. 3 a, the Node B transmits signaling information with a total length of 4 bits (Iog216 = 4) to the UE over a control channel (CCH) 302.
As mentioned above, the present invention is described by exemplifying downlink transmission. That is, the Node B transmits data or control information, and the UE feeds back an ACK/NACK signal, which indicates whether or not the data or control information is erroneous, to the Node B over an ACKCH allocated thereto.
Contrarily, in the case of uplink transmission, the UE transmits data or control information, and the Node B feeds back an ACK/NACK signal, which indicates whether or not the data or control information is erroneous, to the UE over an ACK/NACK transmission resource allocated to the UE.
FIG. 3b illustrates the concept of reducing the overhead of signaling for informing a UE of an ACKCH according to an exemplary embodiment of the present invention. This embodiment as illustrated in FIG. 3b is characterized in that a Node B groups all allocable ACKCHs into ACKCH groups, and configures CCHs in such a manner as to correspond to the ACKCH groups. Also, the Node B inserts control information for informing the UE of a specific ACKCH within a corresponding ACKCH group into the CCH, and signals the inserted control information to the UE over the CCH.
Referring to FIG. 3b, first of all, the Node B groups, for example, total 16 ACKCHs into 4 ACKCH groups, that is, ACKCH group A 312, ACKCH group B 314, ACKCH group C 316, and ACKCH group D 318.
The Node B also configures CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310 as 4 grouped CCHs corresponding one-to-one to the 4 respective ACKCH groups. With regard to this, the Node B includes 2-bit control information in each of the identifiable CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310, and transmits the control information to the UE, thereby informing the UE of which ACKCH within the ACKCH group corresponding one-to-one to each of the CCHs is assigned thereto.
That is, the Node B assigns an ACKCH to a corresponding UE in such a manner as to be identified by 2-bit control information, and informs the UE of the assigned ACKCH over each of the CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310. Information on which ACKCH group includes the ACKCH over which to transmit an ACK/NACK signal from the UE to the Node B may be informed in advance, for example, through a call establishment procedure. It can be noted that this reduces the overhead of signaling for assigning the ACKCH from 4 bits to 2 bits, as compared to the example of FIG. 3a.
In other words, in FIG. 3b, the Node B transmits 2-bit information to the UE over the CCH#A 304, and upon receiving the 2-bit information, the UE should select an ACKCH indicated by the 2-bit information within the ACKCH group A 312 corresponding one-to-one to the CCH#A 304 and transmit an ACK/NACK signal over the selected ACKCH.
More specially, upon receiving the CCH#A 304, the UE detects from the 2-bit information which ACKCH among ACKCHs (ACKCH#1, ACKCH#2, ACKCH#3 and ACKCH#4) within the ACKCH group A 312 should be used for transmitting an ACK/NACK signal.
Also, the Node B may inform the UE of which CCH or combination of CCHs is received from among the CCH#A 304, CCH#B 306, CCH#C 308 and CCH#D 310 through prior signaling. Group information of the CCHs 304, 306, 308, 310, such as information on which CCH among the CCHs is allocated to the UE, may be informed to the UE in the middle of performing, for example, a call establishment procedure between the Node B and the UE.
If the CCH transmission from the Node B for informing the UE of the ACKCH is omitted, and only data transmission occurs, the UE uses the ACKCH, which has been used for previous ACK/NACK signal transmission, so as to transmit an ACK/NACK signal corresponding to the data.
FIG 4 illustrates the concept of reducing signaling overhead by grouping CCHs and ACKCHs according to an exemplary embodiment of the present invention.
Referring to FIG. 4, a Node B configures a total (Li+L2H (-L0) number of CCHs to be used for transmitting control information to UEs that are under the control thereof. The Node B also configures a total (Ki+K2-i HKG) number of
ACKCHs 404 to be used for transmitting ACK/NACK signals by the UEs. That is, the CCHs are grouped into a G number of groups 406, 408,"-, 410, and "CCH group g (g is a number not less than 1 and not greater than G)" consists of an Lg (g is a number not less than 1 and not greater than G) number of CCHs. As used herein, the capital letter "G" denotes the maximum number of corresponding groups or channels, and the small letter "g" denotes an index that indicates the consecutive number of a corresponding group or channel.
In consideration of the UEs to be signaled by the Node B, the Node B groups all the ACKCHs into a G number of groups 412, 414,--, 416, and configures "ACKCH group g (g is a number not less than 1 and not greater than G)" in such a manner as to include a Kg (g is a number not less than 1 and not greater than G) number of ACKCHs. Here, "G" corresponding to the number of CCH groups is the same as "G" corresponding to the number of ACKCH groups. For the convenience of the following explanation, the lth CCH within the CCH group g will be represented by "CCH (g, I)", and the kth ACKCH within the ACKCH group g will be represented by "ACKCH (g, k)".
The CCH corresponds one-to-one to a CCH transmission resource, and the ACKCH corresponds one-to-one to an ACKCH transmission resource. The CCH transmission resource and the ACKCH transmission resource may be a time-frequency resource, a code resource, or any combination thereof. Thus, the CCHs are orthogonal to each other, and the ACKCHs are orthogonal to each other.
As mentioned above, before the Node B transmits data to the UE, it transmits control information, including information necessary for decoding the data to be transmitted, an ACKCH indicator indicating an ACKCH over which to transmit an ACK/NACK signal for the data, etc., to the UE over the CCH.
When the Node B transmits such control information to UE#1 over CCH (1, 1) 418, an ACKCH indicator 436 included in and transmitted by the CCH (1, 1) 418 indicates an ACKCH which corresponds to the CCH (1, 1) from among ACKCHs included in "ACKCH group 1" 412 corresponding one-to-one to "CCH group 1" 406 including the CCH (1, 1) 418 and over which the UE is to transmit an ACK/NACK signal. In FIG. 4, as designated by reference numeral "436" the ACKCH indicator represents which ACKCH included in an ACKCH group is indicated by each CCH included in a CCH group corresponding to the ACKCH group.
By way of example, in FIG 4, the ACKCH indicator included in the CCH (1, 1) indicates ACKCH (1, 2) 440. The ACKCH indicator 436 may be expressed by bits, the number of which is ceil (LOg2K1) in proportion to Ki that is the number of ACKCHs constituting the "ACKCH group 1" 412. Here, the ceiling function ceil (x) denotes a minimum integer greater than x. When the Node B transmits the control information to another UE, e.g., UE# 2 over CCH (1, 2) 420, the ACKCH indicator 436 indicates ACKCH (1, K1) 442 within the "ACKCH group 1" 412 corresponding one-to-one to the CCH (1, 2) 420.
When the Node B transmits the control information to yet another UE, e.g., UE# 3 over CCH (1, L1) 422, the ACKCH indicator 436 indicates ACKCH (1, 1) 438 within the "ACKCH group 1" 412 corresponding one-to-one to the CCH (1, L1) 422.
In receiving the CCHs 418, 420, 422 according to the UEs, which CCH the UEs should search may be recognized mutually between the Node B and the UEs through prearrangement or prior signaling, so that complexity that may be caused by the UEs' CCH search can be reduced. In the following description, a CCH group to be searched by a UE will be referred to as a "CCH search group".
In the present invention, there is no particular connection between the CCH search group and the CCH group. When a UE searches CCHs, it can find out whether or not a corresponding CCH includes information relevant thereto by comparing its own ID with an ID included in the CCH and checking if the two IDs are identical.
In addition, there may a case where the CCH transmission from the Node B is omitted, and only data transmission occurs.
For example, when the transmission format of data or a data transmission resource used for data transmission is retained in its entirety after initial CCH transmission, the UE can acquire information necessary for data decoding from control information previously received over the CCH, even if the CCH transmission is omitted. Thus, in order to reduce signaling overhead, the Node B omits the CCH transmission, and transmits only data. With regard to this, the ACKCH that the UE has used for previous ACK/NACK signal transmission is maintained as an ACKCH corresponding to the transmitted data, which additionally reduces overhead for the ACKCH indicator.
In FIG. 4, "CCH group 2" 408 corresponds one-to-one to "ACKCH group 2" 414, and more particularly CCH (2, 1) 424, CCH (2, 2) 426 and CCH (2, L2) 428 within the "CCH group 2" 408 indicate ACKCH (2, 2) 446, ACKCH (2, 1) 444 and ACKCH (2, K2) 448 respectively through the ACKCH indicator 436.
The ACKCH indicator 436 may be expressed by bits, the number of which is ceil (LOg2K2) in proportion to K2 that is the number of ACKCHs constituting the "ACKCH group 2" 414.
In the same way, "CCH group G" 410 corresponds one-to-one to "ACKCH group G" 416, and more particularly CCH (G, 1) 430, CCH (G, 2) 432 and CCH (G LG) 434 within the "CCH group G" 410 indicate ACKCH (G, 1) 450, ACKCH (G, K0) 454 and ACKCH (G, 2) 452 respectively through the ACKCH indicator 436. The ACKCH indicator 436 may be expressed by bits, the number of which is ceil (LOg2Ko) in proportion to KQ that is the number of ACKCHs constituting the "ACKCH group G" 416.
In general, the number of ACKCHs constituting each ACKCH group, that is, Kl, K2,..., K0, may be arbitrarily defined, but is preferably defined by the same number.
FIG. 5 illustrates a procedure of informing a UE of an ACKCH transmission resource by a Node B over a CCH according to an exemplary embodiment of the present invention.
Referring to FIG. 5, in step 500, the Node B determines to transmit data to the UE in consideration of a buffer status, a channel condition, priority, etc. In step 502, the Node B then determines prior to data transmission whether or not to transmit the CCH. In general, the CCH is transmitted along with the data transmission to thereby be used as information for decoding the data.
Contrarily, the Node B may omit the CCH transmission and perform only the data transmission. For example, when the transmission format of data or a data transmission resource used for data transmission is retained in its entirety after initial CCH transmission, the UE can acquire information necessary for data decoding from a previously received CCH, even if the CCH transmission is omitted. Thus, signaling overhead is reduced by omitting the CCH transmission.
When the Node B determines in step 503 to transmit the CCH, it determines in step 504 if an RF resource for the CCH transmission or a specific CCH mapped to the resource is used. In next step 506, the Node B determines if an RF resource over which to transmit an ACK/NACK signal corresponding to the data transmission or a specific ACKCH mapped to the resource is used.
Subsequently, the Node B determines a CCH transmission format to thereby perform channel coding in step 508, and then transmits control information over the CCH by using the resource determined in step 504. The CCH includes resource information for data to be transmitted to the UE, the ID of the UE, a data transmission format, HARQ-related information, resource information and the transmission format of data to be transmitted to the Node B by the UE, an ACKCH indicator, etc.
In step 510, the Node B transmits the data to the UE. If the Node B determines in step 502 to omit the CCH transmission, it skips steps 504, 506 and 508, and transmits the data directly in step 510. In step 512, the Node B receives an ACK/NACK signal for the data transmitted in step 510 over the ACKCH transmission resource that has been informed over the CCH.
FIG. 6 illustrates a procedure of transmitting an ACK/NACK signal by a UE according to an exemplary embodiment of the present invention. The procedure in FIG. 6 corresponds to a procedure of transmitting an ACK/NACK signal by a UE when data is transmitted irrespective of whether or not CCH transmission is performed by a Node B.
Referring to FIG. 6, in step 600, the UE searches CCHs so as to receive a CCH allocated thereto. With regard to this, the Node B informs the UE in advance of a CCH search group to be searched by the UE, and thus the UE searches CCHs within the CCH search group. The CCH search group is recognized mutually between the Node B and the UE through prearrangement, and is signaled to the UE.
When the UE succeeds in searching the CCH in step 600, it acquires control information included in the CCH in step 602. In step 604, the UE receives data, and decodes the received data by using the control information, thereby determining if the data is erroneous.
In step 606, when a result of the determination in step 604 shows that there is no error in the data decoding, the UE generates an ACK signal, but otherwise generates an NACK signal. Also, in step 606, the UE transmits the generated ACK or NACK signal over an ACKCH indicated by the ACKCH indicator within the CCH.
If the Node B transmits the data while omitting the CCH transmission, so the UE will fail in the CCH search in step 600. Then, in step 608, the UE acquires control information necessary for data decoding and ACKCH information for ACK/NACK signal transmission from a previously received CCH, and decodes the data received in step 604 by using the acquired control information.
In step 606, the UE checks if the received data is erroneous, and according to whether or not the data is erroneous, transmits an ACK or NACK signal to the Node B over an ACKCH indicated by an ACKCH indicator included in the previously received CCH.
In the convenience of explanation, FIG. 6 does not allow for a case where the Node B transmits control information over the CCH, but the UE fails to receive the control information due to the occurrence of errors. Reference will now be made to a concrete way to implement the present invention, with reference to an exemplary embodiment of the present invention, to be described below.
FIG. 7 illustrates the overall signal flow when an ACKCH transmission resource is allocated and an ACK/NACK signal is transmitted between a Node B and a UE according to an exemplary embodiment of the present invention.
Referring to FIG. 7, at a point of time designated by reference numeral "730", the Node B 700 transmits control information to UE#1 702 and UE#2 704 over CCHs. In step 706, the Node B 700 transmits the control information to the UE#1 702 over CCH (1, 1). The CCH (1, 1) transmitted in step 706 is a CCH belonging to CCH group 1, which informs the UE#1 702 that it should use ACKCH group 1 corresponding one-to-one to the CCH group 1 for ACKCH transmission. Additionally, the Node B 700 inserts "ACKCH indicator = 2" into the CCH (1, 1), thereby informing the UE#1 702 that an ACKCH to be used by the UE#1 702 is the second ACKCH within the ACKCH group 1, that is, ACKCH (1, 2), as designated by reference numeral "742".
In step 708 at the point of time designated by reference numeral "730", the Node B 700 transmits the control information to the UE#2 over CCH (2, 2). The CCH (2, 2) transmitted in step 708 is a CCH belonging to CCH group 2, which informs the UE#2 704 that it should use ACKCH group 2 corresponding one-to-one to the CCH group 2 for ACKCH transmission. Additionally, the Node B 700 inserts "ACKCH indicator = 3" into the CCH (2, 2), thereby informing the UE#2 704 that an ACKCH to be used by the UE#2 704 is the third ACKCH within the ACKCH group 2, that is, ACKCH (2, 3), as designated by reference numeral "744".
At a point of time designated by reference numeral "732", the Node B transmits data to the UE#1 702 and the UE#2 704 over data channels. In step 710, the Node B 700 transmits the data to the UE#1 702 over a data channel. The data channel is transmitted according to a transmission format that is indicated by data-related control information included in the CCH (1, 1) in step 706. The transmission format of the data channel transmitted from the Node B 700 to the UE#2 704 in step 712 follows a transmission format that is indicated by data-related control information included in the CCH (2, 2) in step 708.
In steps 710 and 712, the UE#1 702 and the UE#2 704 receive the data over the data channels respectively, determine if the received data are erroneous, and then generate ACK or NACK signals according to whether or not the data are erroneous.
In step 714, the UE#1 702 transmits the generated ACK/NACK signal by using the second ACKCH within the ACKCH group 1, that is, the ACKCH (1, 2) that is informed from the CCH (1, 1) received in step 706, as designated by reference numeral "742".
Also, in step 716, the UE#2 704 transmits the generated ACK/NACK signal by using the third ACKCH within the ACKCH group 2, that is, the ACKCH (2, 3) that is informed from the CCH (2, 2) received in step 708, as designated by reference numeral "744".
Upon receiving the ACK/NACK signals over the ACKCH (1, 2) and the ACKCH (2, 3) in steps 714 and 716, the Node B 700 determines whether or not to perform retransmission for the data transmitted over the data channels in steps 710 and 712.
If the Node B 700 receives an NACK signal from any UE, and thus determines data retransmission, it transmits a CCH and data in the same manner as that described above. However, when the transmission format of the data to be retransmitted is maintained unchanged in comparison to the previous data transmission, the Node B may reduce additional signaling overhead by omitting the CCH transmission.
For example, if the transmission format of the data to be retransmitted to the UE#1 702 is the same as that of the previously transmitted data, the Node B 700 omits the CCH transmission for the UE#1 702, as designated by reference numeral "718". In step 722, the UE#1 receives the retransmitted data over the data channel. In step 726, the UE#1 702 uses the ACKCH (1, 2), which has been informed from the CCH (1, 1) received in step 706, as an ACKCH over which to transmit an ACK/NACK signal for the data retransmitted over the data channel in step 722, as designated by reference numeral "746".
Contrarily, in step 728, the UE#2 704 transmits an ACK/NACK signal by using ACKCH (1, 3) that is informed from the CCH (1, 1) in step 720, as designated by reference mineral "748".
- Example of Grouping -
In the present invention operating as described above, CCHs may be grouped as follows:
In the following description, CCH (i) (i = 1, 2,— , I) denotes a CCH that the Node B transmits at a specific point of time. Index i may vary at each point of time of transmission, and the maximum number of transmittable channels, I, is equal to or greater than (Li+L2H i-LG) as described in FIG. 4.
Here, CCH (g, 1) (g - 1, 2,—, G; 1 = 1, 2, — , L0) denotes the lth CCH within CCH group g to which the CCH (i) is mapped according to methods as will be described below.
The total number of CCH groups, G, and the maximum number of CCHs within each CCH group, Ll, L2,--, L0, are recognized mutually between the Node B and the UE through prearrangement or prior signaling. Also, the CCH (i) and the CCH (g, 1) are logical concepts that correspond one-to-one to time- frequency resources used for physical transmission.
<Method 1>
Method 1 can be expressed by the following equation:
CCH _GROUP(g) = {CCH(g,l) =
Figure imgf000018_0001
l,2, -,Lg,i = \,2, -,Lg}, CCH_GROUP(g + \) = {CCH(g + l,l) = CCH(i)\l = l,2,-,Lg+1,i = Lg +l, Lg +2,-,Lg + Lg+l} (1)
In the Method 1, CCHs are mapped to CCH group g in such a manner as to sequentially map the CCHs to CCH groups in ascending order of index g, that is, in order from the lowest index to the highest index.
For example, when G is set to G = 4, Li, L2, L3 and L4 are set to Li = L2 = L3 = L4 = 2, and the Node B currently intends to transmit 5 CCHs from CCH (1) to CCH (5), each CCH group g is configured as follows:
CCH_GROUP(1) - {CCH (1, 1) = CCH (1), CCH (1, 2) = CCH (2)}, CCHGROUP(2) = {CCH (2, 1) = CCH(3), CCH (2, 2) - CCH (4)}, CCH_GROUP(3) = {CCH (3, 1) = CCH (5)}, CCH_GROUP (4) = { }
<Method 2>
Method 2 can be expressed by the following equation:
CCH_GROUP(g) = {CCH{g,l) =
Figure imgf000019_0001
= (g-l), (/ = l,2,-,/,g = l,2,-,G,/ = l,2,-,Zg}
In the Method 2, although the number of CCHs to be currently transmitted varies according to the passage of time, the number of CCHs mapped to each CCH group is maintained as similar as possible, so that the CCHs are prevented from being concentrated in a specific CCH group.
For example, when total 4 CCH groups are established, and the Node B currently intends to transmit 6 CCHs from CCH (1) to CCH (6), each CCH group g is configured as follows:
CCH_GROUP (1) = {CCH (1, 1) - CCH (1), CCH (1, 2) = CCH (5)}, CCH GROUP (2) = {CCH (2, 1) - CCH (2), CCH (2, 2) = CCH (6)}, CCH_GROUP (3) = {CCH (3, 1) = CCH (3)}, CCH_GROUP (4) - {CCH (4, 1) = CCH (4) }
<Method 3>
In Method 3, CCH groups are configured according to modulation and coding schemes (MCS) of CCHs.
The MCS of a CCH may vary according to channel conditions. For example, UEs with good channel conditions may be improved in resource efficiency through a high-order modulation scheme, such as 16QAM, or coding with high coding rate. Contrarily, UEs with bas channel conditions may be set in such a manner as to maximize error correction capability through QPSK or coding with low coding rate.
Thus, in the Method 3, CCHs with the same MSC or similar MSCs applied thereto constitute the same CCH group.
<Method 4> In Method 4, CCH groups are configured according to whether data to be transmitted are localized in order to acquire scheduling gain or are distributed in order to frequency diversity gain.
FIG. 8 illustrates a Node B apparatus 800 operating according to an exemplary embodiment of the present invention.
Referring to FIG. 8, the Node B apparatus 800 includes a scheduler 810, a pilot generator 812, a data generator 814, a CCH generator 816, a multiplexer 817, a serial-to-parallel (S/P) converter 818, a mapper 820, an IFFT (Inverse Fast Fourier Transform) block 822, a parallel-to-serial (P/S) converter 824, a CP (Cyclic Prefix) adder 830, and a transmit antenna 832.
The scheduler 810 controls the overall operation of the Node B apparatus, and determines whether or not to transmit data or control information, a resource mapping method, etc. The scheduler 810 applies necessary control information to main blocks including the multiplexer 817, the mapper 820, the pilot generator 812, the data generator 814, the CCH generator 816, and the like. The control information input into the pilot generator 812 includes a sequence index for generating an allocation pilot sequence, time domain cyclic shift information, etc. The pilot is also referred to as an RS (Reference Signal), and is used for channel estimation and coherent demodulation on a receiving side.
Various information related to whether or not to perform data transmission and CCH transmission, a transmission format, and so forth is input into the data generator 814 and the CCH generator 816.
The multiplexer 817 receives timing information from the scheduler 810 so as to transmit a pilot, data, a CCH, etc. generated by the pilot generator 812, the data generator 814, and the CCH generator 816. At the same time, the scheduler 810 inputs timing information, frequency allocation information, etc, into the mapper 820 that maps the above information (pilot, data, CCH) to an actual frequency resource. The CCHs as described in embodiments of the present invention are mapped to time-frequency resources allocated through the multiplexer 817 and the mapper 820.
An output signal from the multiplexer 817 is converted into a parallel signal by the S/P converter 818, and then is input into the mapper 820, in which the parallel signal is mapped to a frequency resource to actually carry it. An output signal from the mapper 820 is converted into a time domain signal by the IFFT block 822, and is input into the P/S converter 824, in which the time domain signal is converted into a serial signal. The CP adder 830 adds a cyclic prefix (CP) for preventing inter-symbol interference to the signal, and the signal with the CP added thereto is transmitted through the transmit antenna 832.
FIG. 9 illustrates the CCH generator 816 of FIG. 8 in more detail.
Referring to FIG. 9, the scheduler 810 inputs data transmission-related control information, such as resource information for data to be transmitted from the Node B to the UE, the ID of the UE, a data transmission format, HARQ- related information, a resource and the transmission format of data to be transmitted by the UE, etc., into a control information generator 840, as designated by reference numeral "836", and the control information generator 840 then generates control information including the input information.
The scheduler 810 also inputs ACKCH-related control information, to be used for ACK/NACK transmission by the UE, into an ACKCH indicator generator 842, as designated by reference numeral "838", and the ACKCH generator 842 then generates an ACKCH indicator. The ACKCH-related control information is information on which ACKCH group includes a corresponding ACKCH indicator to which a CCH to be used by the scheduler 810 is mapped, that is, information indicating an ACKCH to be used for ACK/NACK transmission by the UE.
A multiplexer 844 multiplexes signals generated by the control information generator 840 and the ACKCH indicator generator 842, and then outputs the multiplexed signal to an encoder 846.
The encoder 846 adds error correction capability to the signal input from the multiplexer 844, and outputs the signal with the error correction capability added thereto to the multiplexer 817.
FIG 10 illustrates a UE apparatus 1000 operating according to an exemplary embodiment of the present invention.
Referring to FIG. 10, the UE apparatus 1000 includes a receive antenna 1010, a CP remover 1012, an S/P converter 1014, an FFT block 1016, a demapper 1018, a P/S converter 1022, a demultiplexer 1024, a controller 1026, a CCH receiver 1028, a channel estimator 1030, a data receiver 1032, an ACK/NACK generator 1034, a modulator 1036, a transmission part 1038, and a transmit antenna 1040.
The controller 1026 controls the overall operation of the UE apparatus 1000, and provides main blocks, such as the demultiplexer 1024, the demapper 1018, the CCH receiver 1028, the channel estimator 1030, the data receiver 1032, the ACK/NACK generator 1034, etc., with necessary control information.
The controller 1026 inputs CCH reception timing, data reception timing, and ACK/NACK transmission timing into the CCH receiver 1028, the data receiver 1032, and the ACK/NACK generator 1034 respectively.
The control information input into the channel estimator 1030 includes a sequence index for generating a pilot sequence allocated to a target UE for reception, time domain cyclic shift information, and so forth.
The demultiplexer 1024 receives timing information from the controller 1026 so as to divide an input signal into a CCH signal, data, a pilot, etc. to be input into the CCH receiver 1028, the data receiver 1032, and the channel estimator 1030. To this end, the demapper 1018 for extracting the information from an actual frequency resource receives timing information, frequency allocation information, etc. from the controller 1026. With regard to this, the controller 1026 has already received CCH search group information, that is, information on which time-frequency resource should be searched for CCH reception, through prior signaling.
The UE receives a signal from the Node B through the receive antenna 1010, the CP remover 1012 removes a CP from the received signal, the S/P converter 1014 converts the resultant signal into a parallel signal, and then the parallel signal is input into the FFT block 1016. An output signal from the FFT block 1016 passes through the demapper 1018, and is converted into a serial signal by the P/S converter 1022. The serial signal is divided into a CCH, a pilot and data by the demultiplexer 1024, and the divided CCH, pilot and data are input into the CCH receiver 1028, the channel estimator 1030, and the data receiver 1032 respectively. The channel estimator 1030 acquires a channel estimate from the input pilot signal, and uses the acquired channel estimate for channel compensation of the CCH and data signals respectively.
In particular, the CCH receiver 1028 demodulates and decodes the input signal to thereby acquire resource information for the data and transmission format-related control information, and applies them to the data receiver 1032.
When the transmission format of the CCH, for example, a modulation scheme, coding rate, etc., is changed, the Node B informs the UE of control information for the CCH transmission format through separate signaling, thereby enabling the UE to demodulate and decode the CCH.
The CCH receiver 1028 acquires an ACKCH indicator from the received CCH, and provides the ACK/NACK generator 1034 with ACKCH information for an ACKCH to be used by the UE. When the UE receives only data without receiving the CCH, based on prearrangement between the Node B and the UE, the ACKCH information that has been used for previous ACK/NACK transmission is retained as ACKCH information to be used for ACK/NACK transmission by the UE. Thus, in order to provide for such a case, the CCH receiver 1028 stores the previous ACKCH information in a memory (not illustrated), and subsequently provides the data receiver 1032 with the stored ACKCH information.
The controller 1026 controls the operation of the CCH receiver 1028 according to whether or not the CCH is received.
The data receiver 1032 acquires data resource information and data transmission format-related information from the CCH receiver 1028, and performs data demodulation and decoding by using the acquired information.
The ACK/NACL generator 1034 is informed from the data receiver 1032 of whether or not the received data is erroneous, generates an ACK signal in the case of no error, and generates an NACK signal when errors occur. Also, the ACK/NACK generator 1034 configures an ACKCH over which to transmit the generated ACK/NACK signal, based on the ACKCH information input from the CCH receiver 1028.
The controller 1026 controls transmission timing of the configured ACKCH. The ACK/NACK signal generated by the ACJK/NACK generator 1034 is modulated by the modulator 1036, is subjected to signal processing by the transmission part 1038, and then is transmitted through the transmit antenna 1040.
According to the present invention as described above, in informing a receiving side of an ACK/NACK transmission resource by a transmitting side, signaling overhead for an ACK/NACK signal can be reduced by grouping ACK/NACK resources into ACK/NACK transmission resource groups, grouping CCHs for informing the receiving side of the ACK/NACK transmission resources into groups corresponding to the ACK/NACK transmission resource groups, and transmitting the CCHs while inserting control information for ACK/NACK transmission resource notification into the CCHs corresponding one-to-one to the grouped ACK/NACK transmission resources.
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 receiving an ACK/NACK signal in a mobile communication system, the method comprising the steps of: transmitting an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and receiving the ACK/NACK signal for data transmitted to the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
2. The method as claimed in claim 1, wherein the control channel groups are configured by mapping control channels thereto in ascending order of indexes, starting from the control channel group with the lowest index.
3. The method as claimed in claim 1, wherein the control channel groups are configured by including control channels, the number of which is as the same as possible, in the respective control channel groups.
4. The method as claimed in claim 1, wherein the control channel groups are configured by grouping control channels according to modulation and coding schemes thereof.
5. The method as claimed in claim 1, wherein the control channel groups are configured by grouping control channels, over which control information to be used for data demodulation is transmitted, according to whether the data to be transmitted is transmitted in a localized manner or a distributed manner.
6. The method as claimed in claim 1, wherein bit size of the ACK/NACK channel indicator comprises a minimum integer greater than a number that is calculated by taking logarithm of the total number of the ACK/NACK channels included in the ACK/NACK channel group corresponding to the UE, with 2 as a base of the logarithm.
7. A method of transmitting an ACK/NACK signal in a mobile communication system, the method comprising the steps of: receiving an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and transmitting the ACK/NACK signal for data transmitted to the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
8. The method as claimed in claim 7, wherein the control channel groups are configured by mapping control channels thereto in ascending order of indexes, starting from the control channel group with the lowest index.
9. The method as claimed in claim 7, wherein the control channel groups are configured by including control channels, the number of which is as the same as possible, in the respective control channel groups.
10. The method as claimed in claim 7, wherein the control channel groups are configured by grouping control channels according to modulation and coding schemes thereof.
11. The method as claimed in claim 7, wherein the control channel groups are configured by grouping control channels, over which control information to be used for data demodulation is transmitted, according to whether the data to be transmitted is transmitted in a localized manner or a distributed manner.
12. The method as claimed in claim 7, wherein bit size of the ACK/NACK channel indicator comprises a minimum integer greater than a number that is calculated by taking logarithm of the total number of the ACK/NACK channels included in the ACK/NACK channel group corresponding to the UE, with 2 as a base of the logarithm.
13. An apparatus for receiving an ACK/NACK signal in a mobile communication system, the apparatus comprising: a control channel (CCH) generator for generating an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE from among control channel groups through a control channel included in the allocated control channel group; a transmitter for transmitting the ACK/NACK channel indicator and control information over the control channel, and transmitting data over a data channel; and a receiver for receiving the ACK/NACK signal for data, transmitted to the UE, from the UE over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
14. The apparatus as claimed in claim 13, wherein the control channel groups are configured by mapping control channels thereto in ascending order of indexes, starting from the control channel group with the lowest index.
15. The apparatus as claimed in claim 13, wherein the control channel groups are configured by including control channels, the number of which is as the same as possible, in the respective control channel groups.
16. The apparatus as claimed in claim 13, wherein the control channel groups are configured by grouping control channels according to modulation and coding schemes thereof.
17. The apparatus as claimed in claim 13, wherein the control channel groups are configured by grouping control channels, over which control information to be used for data demodulation is transmitted, according to whether the data to be transmitted is transmitted in a localized manner or a distributed manner.
18. The apparatus as claimed in claim 13, wherein bit size of the ACK/NACK channel indicator comprises a minimum integer greater than a number that is calculated by taking logarithm of the total number of the ACK/NACK channels included in the ACK/NACK channel group corresponding to the UE, with 2 as a base of the logarithm.
19. An apparatus for transmitting an ACK/NACK signal in a mobile communication system, the apparatus comprising: a control channel receiver for receiving an ACK/NACK channel indicator that indicates one ACK/NACK channel belonging to an ACK/NACK channel group corresponding to a control channel group allocated to a UE, which is to receive data, from among control channel groups over a control channel included in the allocated control channel group, the control channel groups corresponding one-to-one to a given number of ACK/NACK channel groups, each of which includes a plurality of ACK/NACK channels; and a transmitter for being informed of whether or not the data is erroneous, thereby generating an ACK/NACK signal accordingly, and transmitting the ACK/NACK signal over the ACK/NACK channel indicated by the ACK/NACK channel indicator.
20. The apparatus as claimed in claim 19, wherein the control channel groups are configured by mapping control channels thereto in ascending order of indexes, starting from the control channel group with the lowest index.
21. The apparatus as claimed in claim 19, wherein the control channel groups are configured by including control channels, the number of which is as the same as possible, in the respective control channel groups.
22. The apparatus as claimed in claim 19, wherein the control channel groups are configured by grouping control channels according to modulation and coding schemes thereof.
23. The apparatus as claimed in claim 19, wherein the control channel groups are configured by grouping control channels, over which control information to be used for data demodulation is transmitted, according to whether the data to be transmitted is transmitted in a localized manner or a distributed manner.
24. The apparatus as claimed in claim 19, wherein bit size of the ACK/NACK channel indicator comprises a minimum integer greater than a number that is calculated by taking logarithm of the total number of the ACK/NACK channels included in the ACK/NACK channel group corresponding to the UE, with 2 as a base of the logarithm.
PCT/KR2007/006837 2007-01-12 2007-12-26 Method and apparatus for transmitting/receiving ack/nack signal in mobile communication system WO2008084927A1 (en)

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