PRIORITY

This application is a National Phase Entry of PCT International Application No. PCT/KR2012/004032, which was filed on May 22, 2012, and claims priority to Chinese Patent Application No. 201110157650.3, which was filed in the State Intellectual Property Office of the People's Republic of China on May 31, 2011, and Chinese Patent Application No. 201110234895.1, which was filed in the State Intellectual Property Office of the People's Republic of China on Aug. 15, 2011, the content of each of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to wireless communication system techniques, and more particularly, to a method and apparatus for transmitting ACK/NACK information.

BACKGROUND ART

Long Term Evolution (LTE) system supports two working modes including Frequency Division Duplex (FDD) and Time Division Duplex (TDD).FIG. 1is a schematic diagram illustrating a frame structure of a TDD system. Each radio frame is of length of 10 ms, divided into two 5 ms half-frames equally. Each half-frame includes eight 0.5 ms slots and 3 special fields, i.e. a Downlink Pilot Slot (DwPTS), a Guard Period (GP) and an Uplink Pilot Slot (UpPTS). The total length of the three special fields is 1 ms. Each sub-frame consists of two consecutive slots, i.e. the kth sub-frame consists of slot2kand slot2k+1. The TDD system supports 7 kinds of uplink-downlink configurations, as shown in table 1. In table 1, D denotes downlink sub-frames, U denotes uplink sub-frames, and S denotes the special sub-frames including the above 3 special fields.

TABLE 1UL/DLSwitchingConfigu-pointSub-frame numberrationperiod012345678905 msDSUUUDSUUU15 msDSUUDDSUUD25 msDSUDDDSUDD310 msDSUUUDDDDD410 msDSUUDDDDDD510 msDSUDDDDDDD65 msDSUUUDSUUD

In order to increase transmission rate of users, an LTE-Advanced (LTE-A) system is proposed. In the LTE-A system, multiple Component Carriers (CCs) are aggregated to obtain a larger working bandwidth, which is referred to as Carrier Aggregation (CA). Such constructed downlink and uplink links can support higher transmission rates. For example, in order to support a 100 MHz bandwidth, it is possible to aggregate five 20 MHz CCs. Herein, each CC is called a Cell. As to a UE, a NodeB may be configured to work on multiple CCs, wherein one is primary CC (PCC or Pcell), others are Secondary CCs (SCC or Scell).

It is defined in the LTE-A TDD system that, multiple CCs aggregated must adopt the same uplink-downlink configuration, as shown inFIG. 2.

FIG. 2shows a CA including 3 CCs, respectively is PCC, SCC1and SCC2.

Each CC adopts the same uplink-downlink configuration. In this example, sub-frames0,1,3-6,8and9in each radio frame are configured as downlink sub-frames, and sub-frames2and7are configured as uplink sub-frames.

As to data received from downlink sub-frames, the UE needs to transmit an ACK or NACK to the NodeB through an uplink sub-frame to acknowledge positively or negatively. Thus, a certain number of downlink sub-frames are divided into an ACK/NACK bundling window. ACK/NACK information of the downlink sub-frames belonging to the same ACK/NACK bundling window will be transmitted on the same uplink sub-frame, which will be described hereinafter with reference toFIG. 2.

InFIG. 2, sub-frames0,1,3and sub-frame9of a previous radio frame shown by small rectangles belong to the same ACK/NACK bundling window. The ACK/NACK information of each sub-frame in this ACK/NACK bundling window is transmitted on sub-frame7of the current radio frame. Content “N” in the rectangle corresponding to each sub-frame denotes that the ACK/NACK information of the sub-frame will be transmitted on the Nth sub-frame counting from this sub-frame. For example, the content in the rectangle corresponding to sub-frame0is 7. The seventh sub-frame counting from the sub-frame0is sub-frame7in the current radio frame. Therefore, the ACK/NACK information of sub-frame0will be transmitted on sub-frame7of the current radio frame. For another example, the content in the rectangle corresponding to the sub-frame9is 8, and the eighth sub-frame counting from the sub-frame9is sub-frame7in the next radio frame. Thus, the ACK/NACK information of the sub-frame9will be transmitted on sub-frame7of the next radio frame.

InFIG. 2, sub-frames4,5,6,8shown by rectangles filled with biases belong to the same ACK/NACK bundling window. The ACK/NACK information of each sub-frame in this ACK/NACK bundling window is transmitted on sub-frame2of the next radio frame. As described above, the content “N” in the rectangle corresponding to each sub-frame denotes that the ACK/NACK information of the sub-frame will be transmitted on the Nth sub-frame counting from this sub-frame. For example, the content in the rectangle corresponding to sub-frame8is 4. The fourth sub-frame counting from the sub-frame8is sub-frame2in the next radio frame. Therefore, the ACK/NACK information of sub-frame8will be transmitted on sub-frame2of the next radio frame. For another example, the content in the rectangle corresponding to the sub-frame5is 7, and the 7th sub-frame counting from the sub-frame5is sub-frame2in the next radio frame. Thus, the ACK/NACK information of the sub-frame5will be transmitted on sub-frame2of the next radio frame.

There may be following modes for the UE to return the ACK/NACK information: mode1, mode2, mode a and mode b.

Among them, mode1and mode2support at most 5 CCs, whereas mode a and mode b support at most 2 CCs.

In mode1and mode a, bits for transmitting the ACK/NACK information are not bundled, i.e., no matter how many downlink sub-frames are scheduled, the number of bits used for transmitting the ACK/NACK information is equal to the number of downlink sub-frames being scheduled.

In mode2and mode b, in order to ensure performance of the ACK/NACK information of edge UE, the length of the ACK/NACK information needs to be compressed (referred to as ACK/NACK bundling), the length after bundling is a fixed value. Each CC occupies 2 bits. Thus, it is required to map the ACK/NACK information before bundling to the ACK/NACK information actually transmitted.

Prior art provides mapping tables for bundling the ACK/NACK information of different lengths into 2-bit ACK/NACK information. Each mapping table is actually corresponding to a mapping manner under the number of elements, M, of the bundled ACK/NACK information. Hereinafter, the mapping table under mode b is taken as an example. The difference between mode2and mode b mostly relies in that they support different numbers of CCs. Therefore, the mapping under mode2may be implemented by referring to the mapping table under mode b.

If the number of elements of the bundled ACK/NACK information of each CC is 2, the mapping table shown in table 2 may be adopted to map the ACK/NACK information to the actually transmitted ACK/NACK information.

TABLE 2HARQ-ACK(j)HARQ-HARQ-AHARQ-ACK(0)ACK(1)HARQ-ACK(2)ACK(3)4The firstThe secondThe firstThe secondsub-frame ofsub-frame ofsub-frame ofsub-frame ofPrimary cellPrimary cellSecondary cellSecondary cell

According to table 2, there are 4 bits of ACK/NACK information to be transmitted actually. Bit0corresponds to the first downlink sub-frame scheduled in the PCC. Bit1corresponds to the second downlink sub-frame scheduled in the PCC. Bit2corresponds to the first downlink sub-frame scheduled in the SCC. And bit3corresponds to the second downlink sub-frame scheduled in the SCC. The value “1” of the bit denotes “ACK” and value “0” of the bit denotes “NACK”.

If the number of elements of the bundled ACK/NACK information of each CC is 3, a following table 3 may be adopted to map the ACK/NACK information to the actually transmitted ACK/NACK information.

TABLE 3PCCSCCHARQ-ACK(0),HARQ-ACK(0),HARQ-ACK(1),HARQ-ACK(1),resourceconstellationRM code input bitsHARQ-ACK(2)HARQ-ACK(2)nPUCCH(1)b(0), b(1)o(0), o(1), o(2), o(3)ACK, ACK, ACKACK, ACK,nPUCCH,1(1)1, 11, 1, 1, 1ACKACK, ACK, NACK/DTXACK, ACK,nPUCCH,1(1)0, 01, 0, 1, 1ACKACK, NACK/DTX, anyACK, ACK,nPUCCH,3(1)1, 10, 1, 1, 1ACKNACK/DTX, any, anyACK, ACK,nPUCCH,3(1)0, 10, 0, 1, 1ACKACK, ACK, ACKACK, ACK,nPUCCH,0(1)1, 01, 1, 1, 0NACK/DTXACK, ACK, NACK/DTXACK, ACK,nPUCCH,3(1)1, 01, 0, 1, 0NACK/DTXACK, NACK/DTX, anyACK, ACK,nPUCCH,0(1)0, 10, 1, 1, 0NACK/DTXNACK/DTX, any, anyACK, ACK,nPUCCH,3(1)0, 00, 0, 1, 0NACK/DTXACK, ACK, ACKACK,nPUCCH,2(1)1, 11, 1, 0, 1NACK/DTX,anyACK, ACK, NACK/DTXACK,nPUCCH,2(1)0, 11, 0, 0, 1NACK/DTX,anyACK, NACK/DTX, anyACK,nPUCCH,2(1)1, 00, 1, 0, 1NACK/DTX,anyNACK/DTX, any, anyACK,nPUCCH,2(1)0, 00, 0, 0, 1NACK/DTX,anyACK, ACK, ACKNACK/DTX,nPUCCH,1(1)1, 01, 1, 0, 0any, anyACK, ACK, NACK/DTXNACK/DTX,nPUCCH,1(1)0, 11, 0, 0, 0any, anyACK, NACK/DTX, anyNACK/DTX,nPUCCH,0(1)1, 10, 1, 0, 0any, anyNACK, any, anyNACK/DTX,nPUCCH,0(1)0, 00, 0, 0, 0any, anyDTX, any, anyNACK/DTX,No0,00, 0, 0, 0any, anyTransmission

If the number of elements of the bundled ACK/NACK information of each CC is 4, a following table 4 to 6 may be adopted to map the ACK/NACK information to the actually transmitted ACK/NACK information.

TABLE 4PCCSCCHARQ-ACK(0),HARQ-ACK(0),HARQ-ACK(1),HARQ-ACK(1),HARQ-ACK(2),HARQ-ACK(2),resourceconstellationRM code input bitsHARQ-ACK(3)HARQ-ACK(3)nPUCCH(1)b(0), b(1)o(0), o(1), o(2), o(3)ACK, ACK,ACK, ACK,nPUCCH,1(1)1, 11, 1, 1, 1ACK,ACK,NACK/DTXNACK/DTXACK, ACK,ACK, ACK,nPUCCH,1(1)0, 01, 0, 1, 1NACK/DTX,ACK,anyNACK/DTXACK, DTX,ACK, ACK,nPUCCH,3(1)1, 10, 1, 1, 1DTX, DTXACK,NACK/DTXACK, ACK,ACK, ACK,nPUCCH,3(1)1, 10, 1, 1, 1ACK, ACKACK,NACK/DTXNACK/DTX,ACK, ACK,nPUCCH,3(1)0, 10, 0, 1, 1any, any, anyACK,NACK/DTX(ACK,ACK, ACK,nPUCCH,3(1)0, 10, 0, 1, 1NACK/DTX,ACK,any, any), exceptNACK/DTXfor (ACK, DTX,DTX, DTX)ACK, ACK,ACK, ACK,nPUCCH,0(1)1, 01, 1, 1, 0ACK,NACK/DTX,NACK/DTXanyACK, ACK,ACK, ACK,nPUCCH,3(1)1, 01, 0, 1, 0NACK/DTX,NACK/DTX,anyanyACK, DTX,ACK, ACK,nPUCCH,0(1)0, 10, 1, 1, 0DTX, DTXNACK/DTX,anyACK, ACK,ACK, ACK,nPUCCH,0(1)0, 10, 1, 1, 0ACK, ACKNACK/DTX,anyNACK/DTX,ACK, ACK,nPUCCH,3(1)0, 00, 0, 1, 0any, any, anyNACK/DTX,any(ACK,ACK, ACK,nPUCCH,3(1)0, 00, 0, 1, 0NACK/DTX,NACK/DTX,any, any), exceptanyfor (ACK, DTX,DTX, DTX)ACK, ACK,ACK, DTX,nPUCCH,2(1)1, 11, 1, 0, 1ACK,DTX, DTXNACK/DTX

TABLE 5ACK, ACK,ACK, ACK,nPUCCH,2(1)1, 11, 1, 0, 1ACK,ACK, ACKNACK/DTXACK, ACK,ACK, DTX,nPUCCH,2(1)0, 11, 0, 0, 1NACK/DTX,DTX, DTXanyACK, ACK,ACK, ACK,nPUCCH,2(1)0, 11, 0, 0, 1NACK/DTX,ACK, ACKanyACK, DTX,ACK, DTX,nPUCCH,2(1)1, 00, 1, 0, 1DTX, DTXDTX, DTXACK, DTX,ACK, ACK,nPUCCH,2(1)1, 00, 1, 0, 1DTX, DTXACK, ACKACK, ACK,ACK, DTX,nPUCCH,2(1)1, 00, 1, 0, 1ACK, ACKDTX, DTXACK, ACK,ACK, ACK,nPUCCH,2(1)1, 00, 1, 0, 1ACK, ACKACK, ACKNACK/DTX,ACK, DTX,nPUCCH,2(1)0, 00, 0, 0, 1any, any, anyDTX, DTXNACK/DTX,ACK, ACK,nPUCCH,2(1)0, 00, 0, 0, 1any, any, anyACK, ACK(ACK,ACK, DTX,nPUCCH,2(1)0, 00, 0, 0, 1NACK/DTX,DTX, DTXany, any), exceptfor (ACK, DTX,DTX, DTX)(ACK,ACK, ACK,nPUCCH,2(1)0, 00, 0, 0, 1NACK/DTX,ACK, ACKany, any), exceptfor (ACK, DTX,DTX, DTX)ACK, ACK,NACK/DTX,nPUCCH,1(1)1, 01, 1, 0, 0ACK,any, any, anyNACK/DTXACK, ACK,(ACK,nPUCCH,1(1)1, 01, 1, 0, 0ACK,NACK/DTX,NACK/DTXany, any), exceptfor (ACK, DTX,DTX, DTX)ACK, ACK,NACK/DTX,nPUCCH,1(1)0, 11, 0, 0, 0NACK/DTX,any, any, anyanyACK, ACK,(ACK,nPUCCH,1(1)0, 11, 0, 0, 0NACK/DTX,NACK/DTX,anyany, any), exceptfor (ACK, DTX,DTX, DTX)

TABLE 6ACK, DTX,NACK/DTX,nPUCCH,0(1)1, 10, 1, 0, 0DTX, DTXany, any, anyACK, DTX,(ACK,nPUCCH,0(1)1, 10, 1, 0, 0DTX, DTXNACK/DTX,any, any), exceptfor (ACK, DTX,DTX, DTX)ACK, ACK,NACK/DTX,nPUCCH,0(1)1, 10, 1, 0, 0ACK, ACKany, any, anyACK, ACK,(ACK,nPUCCH,0(1)1, 10, 1, 0, 0ACK, ACKNACK/DTX,any, any), exceptfor (ACK, DTX,DTX, DTX)NACK, any,NACK/DTX,nPUCCH,0(1)0, 00, 0, 0, 0any, anyany, any, anyNACK, any,(ACK,nPUCCH,0(1)0, 00, 0, 0, 0any, anyNACK/DTX,any, any), exceptfor (ACK, DTX,DTX, DTX)(ACK,NACK/DTX,nPUCCH,0(1)0, 00, 0, 0, 0NACK/DTX,any, any, anyany, any),except for(ACK, DTX,DTX, DTX)(ACK,(ACK,nPUCCH,0(1)0, 00, 0, 0, 0NACK/DTX,NACK/DTX,any, any),any, any), exceptexcept forfor (ACK, DTX,(ACK, DTX,DTX, DTX)DTX, DTX)DTX, any, any,NACK/DTX,No0, 0, 0, 0anyany, any, anyTransmissionDTX, any, any,(ACK,No0, 0, 0, 0anyNACK/DTX,Transmissionany, any), exceptfor (ACK, DTX,DTX, DTX)

The above describes the mapping of the ACK/NACK bundling of mode b. With respect to the ACK/NACK bundling of mode2, the bundling method of each CC is the same as the above, only the number of CCs of mode2is greater than 2.

The NodeB transmits a UL grant on a Physical Downlink Control Channel (PDCCH) to schedule Physical Uplink Shared Channel (PUSCH) resources for the UE. The UL grant is transmitted on the last sub-frame of the ACK/NACK bundling window.

With respect to each CC not participating in the CA, a UL Downlink Assignment Index (DAI) in the UL grant in used for indicating the number of sub-frames scheduled in the current ACK/NACK bundling window. In the LTE-A TDD system configured with CA, since all CCs belonging to the same CA adopt the same uplink-downlink configuration, the UL DAI values in the UL grant of the CCs belonging to the same CA are the same. In this situation, what is indicated by the UL DAI is the number of sub-frames scheduled on the CC which has the most sub-frames scheduled in the ACK/NACK bundling window among all the CCs, i.e. the maximum number sub-frames scheduled.

After receiving the UL grant, the UE obtains the UL DAI value and determines how to transmit ACK/NACK information to the NodeB according to the UL DAI value. There are two possible usages of the UL DAI value.

The first usage: the UL DAI value may be used for determining the number of bits to be occupied for transmitting the ACK/NACK information, i.e. for determining the length of the ACK/NACK information. Hereinafter, suppose the UL DAI value is M, the description is based onFIG. 2. In this situation, the UE will adopt 3*M bits to transmit the ACK/NACK information to the NodeB. From the first bit, each M bits belong to a group. The 3*M bits are divided into three groups. Each group corresponds to a sub-frame scheduled in one CC. In the above example, suppose the working modes of the 3 CCs are all Sing Input and Multiple Output (SIMO). As to a CC whose working mode is Multiple Input and Multiple Output (MIMO), the ACK/NACK information of the CC requires M*2 bits.

The second usage: the UL DAI value may be used for determining the number of elements of the ACK/NACK bundling. Hereinafter, suppose the UL DAI value is M. The description is based onFIG. 2. In this situation, the UE will respectively transmit 2 bits ACK/NACK information mapped according to the mapping table when the number of elements of the ACK/NACK bundling M=2, 3 and 4 on PCC, SCC1and SCC2. When M=1, if the working mode of the CC is SIMO, 1 bit ACK/NACK information is transmitted. If the working mode of the CC is MIMO, 2 bits ACK/NACK information is transmitted to the NodeB, wherein the 2 bits ACK/NACK information is mapped according to the mapping table when the number of elements of the ACK/NACK bundling M=2.

DISCLOSURE OF INVENTION

Technical Problem

Actually, when frequency distance between the CCs of the CA is larger enough, the CCs can adopt different uplink-downlink configurations without being interrupted each other. In addition, in some situations, some CCs may be configured with different uplink-downlink configurations (e.g. neighbor frequencies are different TD-SCDMA configurations). At this time, if the same uplink-downlink configuration is adopted for these CCs, serious adjacent-frequency interference will be aroused. Therefore, in recent research of LTE-A, one important issue is how to effectively support different uplink-downlink configurations of multiple CCs of the CA. For example, when the uplink-downlink configurations of the CCs of the CA are different, how does the UE to determine the number of bits of ACK/NACK information and the number of elements of the ACK/NACK bundling.

Solution to Problem

Embodiments of the present invention provide a method for transmitting ACK/NACK information, so as to determine, when uplink-downlink configurations of multiple Component Carriers (CCs) of a Carrier Aggregation (CA) are different, number of bits of ACK/NACK information or number of elements of the ACK/NACK bundling.

According to an embodiment of the present invention, a method for transmitting ACK/NACK information is provided. The method is applicable for a situation that uplink-downlink configurations of multiple CCs of a CA are different, the method includes:

receiving, by a UE, a UL grant to a UE, the UL grant includes a UL Downlink Assignment Index (DAI) from a Node B;

obtaining, by the UE, the UL DAI in the UL grant; and

transmitting, by the UE, ACK/NACK information on a Physical Uplink Shared Channel (PUSCH),

wherein the length of the ACK/NACK information or the number of elements of the ACK/NACK bundling is determined according to the UL DAI value of a CC that the PUSCH belongs to.

It can be seen from the above that, in the method provided by embodiments of the present invention, the length of the ACK/NACK information or the number of elements of the ACK/NACK bundling is determined according to the UL DAI value of the CC that the PUSCH transmitting the ACK/NACK information belongs to. Thus, the ACK/NACK information can be transmitted correctly in the CA system with different uplink-downlink configurations on different CCs. Accordingly, the situation that the multiple CCs have different uplink-downlink configurations can be effectively supported, and the requirement of uplink-downlink configuration of the CC under different scenarios are met.

