The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting an uplink control signal by a relay station to a base station.
Standardization works of international mobile telecommunication (IMT)-advanced which is a next generation (i.e., post 3rd generation) mobile communication system are carried out in the international telecommunication union radio communication sector (ITU-R). The IMT-advanced aims at support of an Internet protocol (IP)-based multimedia service with a data transfer rate of 1 Gbps in a stationary or slowly moving state or 100 Mbps in a fast moving state.
3rd generation partnership project (3GPP) prepares a system standard satisfying requirements of the IMT-advanced, long term evolution (LTE)-advanced, which is an improved version of LTE based on orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission. The LTE-advanced is one of promising candidates for the IMT-advanced. Technology related to a relay station is one of main technologies for the LTE-advanced.
A relay station (RS) is a device for relaying a signal between a base station (BS) and a user equipment (UE), and is used for cell coverage extension and throughput enhancement of a wireless communication system.
The RS can transmit a control signal to the BS. Examples of the transmitted signal may include a hybrid automatic repeat request (HARQ) acknowledgement/negative acknowledgement (ACK/NACK), a channel quality indicator (CQI), a scheduling request (SR), etc. A mechanism of allocating a radio resource needs to be considered when the RS transmits the control signal to the BS.
In addition, the UE can also transmit the control signal to the BS in the wireless communication system including the RS. Therefore, it is not preferable if a method of transmitting the control signal by the RS to the BS has an effect on a procedure of transmitting the control signal by the UE to the BS. That is, it is preferable to maintain backward compatibility with the legacy UE.
Accordingly, there is a need for a method and apparatus for transmitting a control signal of an RS by considering the aforementioned aspects.
The present invention relates to a method and apparatus for transmitting a control signal of a relay station.
According to an aspect of the present invention, a method of transmitting a control signal of a relay station is provided. The method includes: receiving a control signal and data from a base station in a first subframe (i.e., sub-frame); and transmitting an acknowledgement/negative acknowledgement (ACK/NACK) signal for the data to the base station in a second subframe, wherein a radio resource for transmitting the ACK/NACK signal is determined by a radio resource to which the control signal received in the first subframe is allocated and by a logical physical uplink control channel (PUCCH) index received by using a higher layer signal.
According to another aspect of the present invention, an apparatus for wireless communication is provided. The apparatus includes: a signal generator for generating and transmitting a radio signal; and a processor coupled to the signal generator, wherein the processor receives a control signal and data from a base station in a first subframe, and transmits an ACK/NACK signal for the data to the base station in a second subframe, wherein the ACK/NACK signal is allocated to a radio resource determined by a radio resource to which the control signal received in the first subframe is allocated by a logical physical uplink control channel (PUCCH) index received by using a higher layer signal.
According to the present invention, a relay station can transmit a control signal without having an effect on transmission of an uplink control signal of a user equipment. Therefore, it is possible to maintain backward compatibility with a legacy system consisting of a base station and the user equipment.
Referring to
The RS 12 is a device for relaying a signal between the BS 11 and the UE 14, and is also referred to as another terminology such as a relay node (RN), a repeater, a relay, etc. A relay scheme used in the RS may be either amplify and forward (AF) or decode and forward (DF), and the technical features of the present invention are not limited thereto.
The UEs 13 and 14 may be fixed or mobile, and may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), a wireless modem, a handheld device, an access terminal (AT), etc. Hereinafter, a macro UE (or Ma UE) 13 denotes a UE that directly communicates with the BS 11, and a relay UE (or Re UE) 14 denotes a UE that communicates with the RS. Even if the Ma UE 13 exists in a cell of the BS 11, the Ma UE 13 can communicate with the BS 11 via the RS 12 to improve a data transfer rate depending on a diversity effect.
Hereinafter, a downlink (DL) denotes communication from the BS 11 to the Ma UE 13, and an uplink (UL) denotes communication from the Ma UE 13 to the BS 11. A backhaul DL denotes communication from the BS 11 to the RS 12. A backhaul UL denotes communication from the RS 12 to the BS 11.
The wireless communication system 10 employing the RS is a system supporting bidirectional communication. The bidirectional communication may be performed by using a time division duplex (TDD) mode, a frequency division duplex (FDD) mode, etc. When in the TDD mode, different time resources are used in UL transmission and DL transmission and in backhaul UL transmission and backhaul DL transmission. When in the FDD mode, different frequency resources are used in UL transmission and DL transmission and in backhaul UL transmission and backhaul DL transmission.
Referring to
Referring to
Each element on the resource grid is referred to as a resource element (RE). One RB includes 12×7 REs. The number NDL of RBs included in the DL slot depends on a DL transmission bandwidth configured in a cell.
The resource grid for one DL slot of
Referring to
The control region consists of a plurality of control channel elements (CCEs) that is a logical CCE stream. Hereinafter, the CCE stream denotes a set of all CCEs constituting the control region in one subframe. The CCE corresponds to a plurality of resource element groups (REGs). For example, the CCE may correspond to 9 REGs. The REG is used to define mapping of a control channel onto a resource element (RE). For example, one REG may consist of 4 REs. Therefore, one CCE may include 36 REs.
A plurality of PDCCHs may be transmitted in the control region. The PDCCH carries control information such as scheduling allocation. The PDCCH is transmitted on an aggregation of one or several consecutive CCEs. A PDCCH format and the number of available PDCCH bits are determined according to the number of CCEs constituting the CCE aggregation. Hereinafter, the number of CCEs used for PDCCH transmission is referred to as a CCE aggregation level. The CCE aggregation level is a CCE unit for searching for the PDCCH. A size of the CCE aggregation level is defined by the number of contiguous CCEs. For example, the CCE aggregation level may be an element of {1, 2, 4, 8}.
Table 1 below shows examples of the PDCCH format and the number of available PDCCH bits according to the CCE aggregation level.
Control information transmitted through the PDCCH is referred to as downlink control information (hereinafter, DCI). The DCI includes UL or DL scheduling information, a UL power control command, control information for paging, control information for indicating a random access channel (RACH) response, etc. Examples of a DCI format include a format 0 for scheduling of a physical uplink shared channel (PUSCH), a format 1 for scheduling of one physical downlink shared channel (PDSCH) codeword, a format 1A for compact scheduling of the one PDSCH codeword, a format 1B for simple scheduling for rank-1 transmission of a single codeword in a spatial multiplexing mode, a format 1C for significantly compact scheduling of a downlink shared channel (DL-SCH), a format 2 for scheduling of the PDSCH in a closed-loop spatial multiplexing mode, a format 2A for scheduling of the PDSCH in an open-loop spatial multiplexing mode, and formats 3 and 3A for transmission of a transmission power control (TPC) command for a UL channel.
Referring to
In the subframe, the PUCCH for one UE is allocated in a resource block (RB) pair. RBs belonging to the RB pair occupy different subcarriers in each of 1st and 2nd slots. This is called that the RB pair allocated to the PUCCH is frequency-hopped in a slot boundary. In
Examples of UL control information transmitted on the PUCCH include a hybrid automatic repeat request (HARQ) acknowledgement/negative acknowledgement (ACK/NACK), a channel quality indicator (CQI) indicating a DL channel state, a scheduling request (SR) as a request for UL radio resource allocation, etc.
The PUCCH can support multiple formats. That is, it is possible to transmit a UL control signal having a different number of bits per subframe according to a modulation scheme. Table 2 below shows an example of the number of bits per subframe and a modulation scheme based on a PUCCH format.
A PUCCH format 1 is used for transmission of an SR. A PUCCH format 1a or format 1b is used for transmission of an HARQ ACK/NACK signal. A PUCCH format 2 is used for transmission of a CQI. A PUCCH format 2a/2b is used for transmission of the CQI and the HARQ ACK/NACK signal.
When the HARQ ACK/NACK signal is transmitted alone in any subframe, the PUCCH format 1a or format 1b can be used, and when the SR is transmitted alone, the PUCCH format 1 can be used. The UE can transmit the HARQ ACK/NACK signal and the SR in the same subframe. For positive SR transmission, the UE can transmit the HARQ ACK/NACK signal by using a PUCCH resource allocated for the SR. For negative SR transmission, the UE can transmit the HARQ ACK/NACK signal by using a PUCCH resource allocated for the ACK/NACK.
A BS can allocate a band including K resource blocks to an RS 1 in a frequency domain. The BS can allocate a band including 2K resource blocks to an RS 2 and an RS 3 in the frequency domain. K can be any natural number, for example, may be 6.
A PDCCH on which the BS transmits a control signal to the RS is referred to an R-PDCCH for convenience of explanation. The BS can add a cyclic redundancy check (CRC) for error detection to a DCI to be transmitted to the RS. The CRC is masked with a unique identifier (referred to as a radio network temporary identifier (RNTI)) according to an owner or usage of the R-PDCCH. If the R-PDCCH is for a specific RS, a unique identifier (e.g., cell-RNTI (C-RNTI)) of the RS may be masked to the CRC. Alternatively, if the R-PDCCH is for a paging message transmitted through a paging channel (PCH), a paging indication identifier (e.g., paging-RNTI (P-RNTI)) may be masked to the CRC. If the R-PDCCH is for system information transmitted through a DL-SCH, a system information identifier (e.g., system information-RNTI (SI-RNTI)) may be masked to the CRC.
An R-PDCCH for the RS 1 can include one CCE, and an R-PDCCH for the RS 2 and the RS 3 can include two CCEs. One of the two CCEs may be for the RS 2, and the other may be for the RS 3.
Each RS can transmit a control signal to a Re UE in first n (e.g., 2) OFDM symbols of a subframe in a time domain. The RS requires a guard period since the RS has to perform switching for receiving the backhaul DL signal from a BS after transmitting the control signal to the Re UE. An OFDM symbol including the guard period can vary according to the number of symbols of the PDCCH to be transmitted by the BS to a Ma UE and the number of symbols of a PDCCH to be transmitted by the RS to the Re UE. In addition, the OFDM symbol including the guard period may have a different index according to whether a cyclic prefix (CP) in use is a normal CP or an extended CP. The R-PDCCH can be included in only one frequency band among a plurality of frequency bands allocated to respective RSs such as RSs #n and #m shown in
A plurality of R-PDCCHs can be transmitted from the viewpoint of the frequency domain of the subframe. The RS acquires a logical CCE stream by de-mapping a physical resource element (RE) constituting a control region to a CCE for an nth symbol of the subframe. The RS performs monitoring on R-PDCCHs in the CCE stream. Herein, monitoring is an operation performed by the RS to attempt to decode each R-PDCCH according to a DCI format. The BS may not provide the RS with information indicating a position where a corresponding R-PDCCH is located in the CCE stream. The RS searches for its R-PDCCH by monitoring a set of R-PDCCH candidates in the CCE stream. This is called blind decoding (or blind detection). For example, the RS detects its R-PDCCH when there is no CRC error detected through CRC checking after de-masking its C-RNTI in a unit of 3 resource blocks in an nth symbol of a subframe.
Hereinafter, an R-PUSCH denotes a PUSCH for transmitting backhaul UL data by an RS to a BS, and an R-PUSCH(k) denotes an R-PUSCH transmitted by an RS k (where k is any natural number) to the BS. An R-PUCCH denotes a PUCCH for transmitting backhaul UL control information by the RS to the BS, and an R-PUCCH(k) denotes an R-PUCCH transmitted by the RS k to the BS.
Referring to
Referring to
Meanwhile, referring to
Referring to
A transmission subframe of the HARQ ACK/NACK signal for the backhaul DL data can be predetermined according to a resource allocation or a transmission time of the backhaul DL data. For example, in a frequency division duplex (FDD) system, when an R-PDSCH is received through a subframe n-4, an HARQ ACK/NACK signal for the R-PDSCH can be transmitted through an R-PUCCH in a subframe n. However, the present invention is not limited thereto, and the transmission subframe of the HARQ ACK/NACK signal can be dynamically reported by the BS through signaling. Alternatively, the transmission subframe can be implicitly reported according to a subframe location or other information. Then, the RS can transmit the HARQ ACK/NACK after 4, 5, or 6 subframes. In this case, the HARQ ACK/NACK can be referred to as a dynamic ACK/NACK. Alternatively, a different transmission subframe of a HARQ ACK/NACK signal can be determined according to a predetermined radio frame period. The RS can determine an R-PUCCH resource index (i.e., a logical/physical R-PUCCH index) required for transmission of the HARQ ACK/NACK by using a CCE index of the R-PDCCH and a logical PUCCH index. Alternatively, the R-PUCCH resource can also be reserved in advance by using higher layer signaling rather than physical layer signaling. That is, the RS can transmit the HARQ ACK/NACK by using the R-PUCCH resource reserved by a higher layer signal such as a radio resource control (RRC) signal.
Hereinafter, a first or specific CCE index to which a corresponding DCI is allocated in the R-PDCCH is denoted by nR-CCE. n(1)PUCCH denotes a PUCCH resource index at which a Ma UE transmits UL control information according to the PUCCH format 1/1a/lb, and n(2)PUCCH denotes a PUCCH resource index at which the Ma UE transmits the UL control information according to the PUCCH format 2/2a/2b. n(1)R-PUCCH denotes an R-PUCCH resource index at which the RS transmits backhaul UL control information according to the PUCCH format 1/1a/1b, and n(2)R-PUCCH denotes an R-PUCCH resource index at which the RS transmits the backhaul UL control information according to the PUCCH format 2/2a/2b. A logical PUCCH index transmitted to the RS can be configured by a higher layer signal. The logical PUCCH index transmitted to the RS may be an offset value with respect to the logical PUCCH index transmitted to the Ma UE.
For example, the RS can acquire nR-CCE through the R-PDCCH received in the subframe n-4, and can determine an R-PUCCH resource index on the basis of the logical PUCCH index given by using the higher layer signal. This can be expressed by Equation 1 below.
n1)R-PUCCH=nR-CCE+N(1)R-PUCCH Equation 1
In Equation 1 above, nR-CCE may be a first CCE index of corresponding DCI reception in the R-PDCCH received by the RS in the subframe n-4. N(1)R-PUCCH denotes a logical PUCCH index, and can be configured by the higher layer signal. The R-PUCCH resource index can be used to determine a cyclic shift index and frequency used for transmission of a backhaul UL control signal. In addition, an orthogonal sequence index used to increase transmission capacity can also be determined by using the R-PUCCH resource index. That is, the RS can transmit the backhaul HARQ ACK/NACK in the subframe n by using n(1)R-PUCCH.
If the RS fails to receive the R-PDCCH in the subframe n-4 and receives the R-PDSCH, then the R-PUCCH resource index n(1)R-PUCCH used for R-PUCCH transmission (i.e., backhaul HARQ ACK/NACK transmission) in the subframe n can be determined by Table 3 below.
Referring to
The number of RBs that can be supported as a mixed RB in each slot is equal to or less than one. Different types of control information can be multiplexed in the mixed RB. The mixed RB of
For RBs to which the PUCCH or R-PUCCH is allocated, a logical PUCCH index can be logically allocated first to a PUCCH resource and then can be allocated to an R-PUCCH resource. In other words, the logical PUCCH index is allocated by separating the PUCCH resource allocated to the UE and the R-PUCCH resource allocated to the RS. Herein, the PUCCH resource is a resource used for transmission of a control signal by a Ma UE through the PUCCH. The R-PUCCH resource is a resource used by the RS for transmission of a backhaul UL control signal through the R-PUCCH. The PUCCH resource and the R-PUCCH resource can be identified by the logical PUCCH index. Herein, the same mapping as a physical PUCCH index can be used for the logical PUCCH index, or mapping considering an RB-based allocation can be used for the logical PUCCH index. That is, although a start point of the R-PUCCH is reported by using a logical index, it is also possible to allocate the logical index to a first point of the physical RB when mapping to the physical index. This is a case where mapping is performed by separating the R-PUCCH and the PUCCH based on not only the logical RB but also the physical RB. Of course, continuous allocation is also possible without separation.
Referring to
The BS can transmit N(1)R-PUCCH to an RS as the logical PUCCH index to indicate an R-PUCCH transmission resource capable of transmitting backhaul UL control information. The logical PUCCH index value N(1)R-PUCCH transmitted to the RS may indicate a first index of a physical RB which is the closest in location when a logical index is divided physically, or unlike this, in order to reduce resource waste, it can be mapped to consecutive PUCCH index resources irrespective of division of the physical RB. According to the logical PUCCH index allocation, a PUCCH resource allocated to the legacy UE and an R-PUCCH resource allocated to the RS are divided logically/physically when allocating the logical PUCCH index, and thus it is possible to allocate a backhaul UL control information resource of the RS without having an effect on the legacy LTE system or LTE UE. That is, backward compatibility with the legacy system can be maintained.
The example of
Referring to
A resource 151 for the SPS ACK/NACK and SR of the RS can be configured by a higher layer signal and can be reserved. The RS can determine a resource index of an R-PUCCH to be transmitted in a subframe n by using the index N(1)R-PUCCH and the CCE index of the R-PDCCH received in a subframe n-4. In this case, N(1)R-PUCCH can indicate a first resource index for the dynamic ACK/NACK.
The example of
Referring to
A BS can indicate a start position on a resource for the dynamic ACK/NACK by using the logical PUCCH index N(1)PUCCH transmitted to the Ma UE, and can indicate a start position on a resource for the dynamic ACK/NACK by using the logical PUCCH index N(1)R-PUCCH to be transmitted to the RS. The logical PUCCH index N(1)R-PUCCH to be transmitted to the RS directly indicates a location for the dynamic ACK/NACK in
RS s can be classified into two groups according to whether an HARQ ACK/NACK is an SPS ACK/NACK or a dynamic ACK/NACK. In
Such a method can be applied when an R-PUCCH resource index at which a backhaul UL ACK/NACK is transmitted is independent for each RS group. For example, assume that R-PUCCH resource indices 0 to 10 are reserved for the RS group A, R-PUCCH resource indices 0 to 20 are reserved for the RS group B, and R-PUCCH resource indices 0 to 15 are reserved for the RS group C. In this case, as shown in
The method of
A logical PUCCH index for each RS group has the same index gap Δ. As such, the logical PUCCH index can have the same index gap when a size of an R-PDCCH is equal to nR-CCE. In this case, a logical PUCCH index N(1)R-PUCCH can be given commonly to each RS group, and only an offset of the logical PUCCH index (i.e., the index gap Δ) can be optionally given for each RS group. Therefore, signaling overhead can be reduced.
In
A1 though N(1)R-PUCCH, Δ1, and Δ2 are expressed by a positive value in the description based on
In addition, although a method of allocating a logical PUCCH index for determining an R-PUCCH resource index for a dynamic ACK/NACK has been exemplified in the aforementioned description, the present invention is not limited thereto. That is, the present invention is also applicable when determining an R-PUCCH resource index for a case of an SPS ACK/NACK, an SR, and a CQI.
Referring to
Referring to
The signal generator 840 can generate a transmission signal based on an SC-FDMA scheme. For this, the signal generator 840 can include a discrete Fourier transform (DFT) unit 842 for performing DFT, a subcarrier mapper 844, and an inverse fast Fourier transform (IFFT) unit 846 for performing IFFT. The DFT unit 842 outputs a frequency-domain symbol by performing DFT on an input sequence. The subcarrier mapper 844 maps frequency-domain symbols to respective subcarriers. The IFFT unit 846 outputs a time-domain signal by performing IFFT on an input symbol. The time-domain signal is transmitted through the antenna 890 as a transmission signal. The time-domain signal generated by the signal generator 840 can be generated according to the SC-FDMA scheme.
While the present invention has been particularly shown and described with reference to 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. The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.
Number | Date | Country | Kind |
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10-2010-0019389 | Mar 2010 | KR | national |
This application is a reissue of U.S. Pat. No. 8,761,077 issued on Jun. 24, 2014, which is the National Phase of PCT/KR2010/001372 filed on Mar. 5, 2010, which claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Nos. 61/157,889, 61/158,415, 61/233,132 filed on Mar. 5, 2009, Mar. 9, 2009 and Aug. 12, 2009 respectively, and under 35 U.S.C. 119(a) to Patent Application No. KR 10-2010-0019389 filed in Republic of Korea on Mar. 4, 2010, all of which are hereby expressly incorporated by reference into the present application. Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 8,761,077. The reissue applications are application Ser. Nos. 14/598,004 (the present application) and 14/631,685 (continuation of the present application).
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/KR2010/001372 | 3/5/2010 | WO | 00 | 9/2/2011 |
Publishing Document | Publishing Date | Country | Kind |
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WO2010/101432 | 9/10/2010 | WO | A |
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61157889 | Mar 2009 | US | |
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Number | Date | Country | |
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Parent | 13254714 | Mar 2010 | US |
Child | 14598004 | US |