WO2010041868A2 - Method and apparatus for data transfer in multiple antenna systems - Google Patents

Abstract

This invention relates to a method and apparatus for transferring data through multiple antenna systems. An uplink grant is received from the station. Said uplink grant includes an MCS (Modulation and Coding Scheme) for multiple codes and the assignment of uplink resources. Uplink codes are created by said MCS, which are then transferred through radio resources presented by the uplink resource assignment.

Description

Method and device for data transmission in multi-antenna system

The present invention relates to wireless communication, and more particularly, to a control channel supporting multiple antennas and a data transmission using the same in a wireless communication system.

Wireless communication systems are widely deployed to provide various kinds of communication services such as voice and data. In general, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency (SC-FDMA). division multiple access) system.

The Multiple Input Multiple Output (MIMO) scheme increases the capacity of a system by simultaneously transmitting several data streams spatially by a base station and / or a terminal using two or more transmission antennas. Transmit diversity enables reliable data transmission on fast time-varying channels by transmitting the same data stream through multiple transmit antennas. Spatial multiplexing increases the capacity of a system by transmitting different data streams through a plurality of transmit antennas.

Spatial multiplexing for a single user is referred to as Single User-MIMO (SU-MIMO), and the channel capacity of the MIMO system increases in proportion to the minimum of the number of transmit antennas and the number of receive antennas. Spatial multiplexing for multiple users is called SDMA (Spatial Division Multiple Access) or MU-MIMO (MU-MIMO).

In spatial multiplexing, a single codeword (SCW) scheme is used to transmit N (N> 1) data streams simultaneously transmitted using one codeword, and M (M≤N) codewords for N data streams. There is a multiple codeword (MCW) method for transmitting using. Each codeword is generated through independent channel encoding to enable independent error detection.

Long-Term Evolution (LTE), working in the 3rd Generation Partnership Project (3GPP), is one of the latest standards in mobile communications technology. The wireless connection of LTE is called Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN). LTE supports multiple antennas and can support both SU-MIMO and MU-MIMO in downlink.

3GPP LTE does not support transmission using multiple antennas in uplink. Therefore, uplink resource allocation using SU-MIMO is not disclosed. However, there is a need for supporting SU-MIMO in uplink due to an increase in uplink transmission capacity. Therefore, a method for efficiently designing uplink resource allocation for SU-MIMO is needed.

The present invention is directed to an uplink resource allocation method and apparatus for supporting multiple antennas.

Another object of the present invention is to provide a method and apparatus for transmitting uplink data using uplink resource allocation supporting multiple antennas.

In one aspect, a method of transmitting a plurality of codewords via a multi-antenna system is provided. The method receives an uplink grant from a base station, the uplink grant includes an uplink resource allocation and one modulation and coding scheme (MCS) for a plurality of codewords, and the plurality of codes using the MCS. Generating a word and transmitting the plurality of codewords over a radio resource indicated by the uplink resource allocation.

The method may further comprise receiving one positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for the plurality of codewords from the base station. A resource used for transmitting the ACK / NACK signal may be determined from a radio resource used for transmitting one selected codeword among the plurality of codewords. Information about the selected one codeword may be obtained from the base station.

The uplink grant may further include one redundancy version (RV) for the plurality of codewords. The uplink grant may further include one new data indicator (NDI) for the plurality of codewords.

The uplink grant may further include a CS (cyclic shift) used to transmit reference signals used for demodulation of the plurality of codewords. CS of the reference signal for each antenna may be different. The position of the reference signal for each antenna in the subframe may be the same. The position of the reference signal for each antenna in the subframe may be different.

In another aspect, a terminal having multiple antennas includes a radio frequency (RF) unit for transmitting and receiving a radio signal, and a processor connected to the RF unit. The processor receives an uplink grant from a base station, wherein the uplink grant includes one modulation and coding scheme (MCS) for uplink resource allocation and a plurality of codewords and the plurality of codes using the MCS. Generates a word and transmits the plurality of codewords through a radio resource indicated by the uplink resource allocation.

Uplink SU-MIMO can be implemented in a multi-antenna system. SCW / MCW transmission is possible and efficient downlink control information transmission is possible without significantly changing the structure of the conventional single antenna system.

1 shows a wireless communication system.

2 shows a structure of a radio frame in 3GPP LTE.

3 is an exemplary diagram illustrating a resource grid for one downlink slot.

4 shows a structure of a downlink subframe.

5 is a flowchart showing the configuration of a PDCCH.

6 is an exemplary diagram illustrating transmission of uplink data.

7 is an exemplary diagram illustrating reception of downlink data.

8 shows a reference signal structure for a PDSCH in a normal CP.

9 shows a reference signal structure for a PDSCH in an extended CP.

10 shows uplink HARQ.

11 is a flowchart showing the configuration of a PHICH.

12 shows a transmitter supporting a multiple codeword (MCW) scheme.

13 shows codeword-layer mapping in 3GPP LTE.

14 shows an example of SCW transmission.

15 shows an example of MCW transmission.

16 is a block diagram illustrating a multiple antenna system in which an embodiment of the present invention is implemented.

1 shows a wireless communication system. The wireless communication system 10 includes at least one base station (BS) 11. Each base station 11 provides a communication service for a particular geographic area (generally called a cell) 15a, 15b, 15c. The cell can in turn be divided into a number of regions (called sectors). The user equipment (UE) 12 may be fixed or mobile, and may include a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), It may be called other terms such as a wireless modem and a handheld device. The base station 11 generally refers to a fixed station communicating with the terminal 12, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like. have.

Hereinafter, downlink means communication from the base station to the terminal, and uplink means communication from the terminal to the base station. In downlink, a transmitter may be part of a base station, and a receiver may be part of a terminal. In uplink, a transmitter may be part of a terminal, and a receiver may be part of a base station.

2 shows a structure of a radio frame in 3GPP LTE. A radio frame consists of 10 subframes, and one subframe consists of two slots. The time it takes for one subframe to be transmitted is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.

One slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain, and includes a plurality of resource blocks (RBs) in the frequency domain. The OFDM symbol is used to represent one symbol period since 3GPP LTE uses OFDMA in downlink, and may be referred to as an SC-FDMA symbol or a symbol period according to a multiple access scheme. The RB includes a plurality of consecutive subcarriers in one slot in resource allocation units.

The structure of the radio frame is only an example, and the number of subframes included in the radio frame or the number of slots included in the subframe and the number of OFDM symbols included in the slot may be variously changed.

3 is an exemplary diagram illustrating a resource grid for one downlink slot. The downlink slot includes a plurality of OFDM symbols in the time domain. Here, one downlink slot includes 7 OFDMA symbols and one resource block includes 12 subcarriers in a frequency domain, but is not limited thereto.

Each element on the resource grid is called a resource element, and one resource block includes 12 × 7 resource elements. The number N ^DL of resource blocks included in the downlink slot depends on the downlink transmission bandwidth set in the cell.

4 shows a structure of a downlink subframe. The subframe includes two slots in the time domain. Up to three OFDM symbols in the first slot of the subframe are control regions to which control channels are allocated, and the remaining OFDM symbols are data regions to which a Physical Downlink Shared Channel (PDSCH) is allocated.

Downlink control channels used in 3GPP LTE include a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and the like. The PCFICH transmitted in the first OFDM symbol of the subframe carries information about the number of OFDM symbols (that is, the size of the control region) used for transmission of control channels in the subframe. Control information transmitted through the PDCCH is called downlink control information (DCI). DCI indicates uplink resource allocation information, downlink resource allocation information, and uplink transmission power control command for arbitrary UE groups. The PHICH carries a positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for an uplink hybrid automatic repeat request (HARQ). That is, the ACK / NACK signal for the uplink data transmitted by the terminal is transmitted on the PHICH.

Now, a PDCCH which is a downlink physical channel will be described.

The PDCCH is a resource allocation and transmission format of PDSCH (also called downlink grant), resource allocation information of PUSCH (also called uplink grant), a set of transmit power control commands for individual UEs in any UE group, and VoIP (Voice over Internet Protocol) can be activated. A plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH consists of an aggregation of one or several consecutive control channel elements (CCEs). The PDCCH composed of one or several consecutive CCEs may be transmitted through the control region after subblock interleaving. CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

Control information transmitted through the PDCCH is called downlink control information (DCI). The following table shows DCI according to DCI format.

Table 1

DCI format 0 indicates uplink resource allocation information, DCI formats 1 to 2 indicate downlink resource allocation information, and DCI formats 3 and 3A indicate uplink transmit power control (TPC) commands for arbitrary UE groups. .

The following table shows information elements included in DCI format 0, which is uplink resource allocation information (or uplink grant). This can be found in section 5.3.3.1 of 3GPP TS 36.212 V8.3.0 (2008-05) "Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding (Release 8)". .

TABLE 2

5 is a flowchart showing the configuration of a PDCCH. In step S110, the base station determines the PDCCH format according to the DCI to be sent to the terminal, and attaches a CRC (Cyclic Redundancy Check) to the control information. The CRC is masked with a unique identifier (referred to as RNTI (Radio Network Temporary Identifier)) according to the owner or purpose of the PDCCH. If the PDCCH is for a specific terminal, a unique identifier of the terminal, for example, a C-RNTI (Cell-RNTI) may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier, for example, P-RNTI (P-RNTI), may be masked to the CRC. If it is a PDCCH for system information, a system information identifier and a system information-RNTI (SI-RNTI) may be masked to the CRC. A random access-RNTI (RA-RNTI) may be masked to the CRC to indicate a random access response that is a response to the transmission of the random access preamble of the UE. The following table shows examples of identifiers masked on the PDCCH.

TABLE 3

If the C-RNTI is used, the PDCCH carries control information for the corresponding specific terminal. If another RNTI is used, the PDCCH carries common control information received by all or a plurality of terminals in the cell.

In step S120, the DCI to which the CRC is added is subjected to channel coding to generate coded data. In step S130, rate mathing is performed according to the number of CCEs allocated to the PDCCH format. In step S140, the coded data is modulated to generate modulation symbols. In step S150, modulation symbols are mapped to physical resource elements.

A plurality of PDCCHs may be transmitted in one subframe. The UE monitors the plurality of PDCCHs in every subframe. Here, monitoring means that the UE attempts to decode each of the PDCCHs according to the monitored PDCCH format. In the control region allocated in the subframe, the base station does not provide the UE with information about where the corresponding PDCCH is. The UE finds its own PDCCH by monitoring a set of PDCCH candidates in a subframe. This is called blind decoding. For example, if the CRC error is not detected by demasking its C-RNTI in the corresponding PDCCH, the UE detects the PDCCH having its DCI.

In order to receive downlink data, the terminal first receives downlink resource allocation on the PDCCH. Upon successful detection of the PDCCH, the UE reads the DCI on the PDCCH. The downlink data on the PDSCH is received using the downlink resource allocation in the DCI. In addition, in order to transmit the uplink data, the terminal first receives the uplink resource allocation on the PDCCH. Upon successful detection of the PDCCH, the UE reads the DCI on the PDCCH. Uplink data is transmitted on the PUSCH by using uplink resource allocation in the DCI.

6 is an exemplary diagram illustrating transmission of uplink data. The UE monitors the PDCCH in a downlink subframe and receives the DCI format 0 601, which is an uplink resource allocation, on the PDCCH. The uplink data 602 is transmitted on the PUSCH configured based on the uplink resource allocation.

7 is an exemplary diagram illustrating reception of downlink data. The terminal receives downlink data on the PDSCH 652 indicated by the PDCCH 651. The UE monitors the PDCCH 651 in a downlink subframe and receives downlink resource allocation information on the PDCCH 651. The terminal receives downlink data on the PDSCH 652 indicated by the downlink resource allocation information.

Now, an uplink reference signal is described in 3GPP LTE. This is a demodulation reference signal (DM RS) for data demodulation.

8 shows a reference signal structure for a PDSCH in a normal CP. The subframe includes a first slot and a second slot, and each of the first slot and the second slot includes 7 OFDM symbols. 14 OFDM symbols in a subframe are symbol indexed from 0 to 13. The reference signal RS is transmitted through OFDM symbols having symbol indices of 3 and 10. Data is transmitted through the remaining OFDM symbols except for the OFDM symbol on which the reference signal is transmitted.

9 shows a reference signal structure for a PDSCH in an extended CP. The subframe includes a first slot and a second slot, and each of the first slot and the second slot includes 6 OFDM symbols. 12 OFDM symbols in a subframe are indexed from 0 to 11 symbols. The reference signal is transmitted through an OFDM symbol having symbol indexes 2 and 8. Data is transmitted through the remaining OFDM symbols except for the OFDM symbol on which the reference signal is transmitted.

3GPP LTE uses a cyclically shifted sequence as an uplink reference signal sequence. The cyclically shifted sequence is generated by cyclically shifting a base sequence by a specific cyclic shift amount.

The basic sequence may be represented by r _{u, v} (n). Where u ∈ {0,1, ..., 29} is a sequence group number, v is a base sequence number in the group, and n is an element index, 0≤n≤M -1, M is the length of the base sequence. The length M of the basic sequence may be equal to the number of subcarriers included in one demodulation reference signal symbol in a subframe. For example, if one resource block includes 12 subcarriers and three resource blocks are allocated for data transmission, the length M of the base sequence is 36.

The following equation shows an example of the basic sequence r _{u, v} (n).

Equation 1

Where x _q is a ZC sequence whose root index is q and N is the length of x _q . 'mod' stands for modulo operation. That is, the basic sequence r _{u, v} (n) has a form in which x _q is cyclically expanded. When one resource block includes 12 subcarriers, the length M of the base sequence may be 36 or more.

The ZC sequence x _q (m) having the raw index q may be defined as in the following equation.

Equation 2

Where N is the length of x _q (m) and m is 0 ≦ m ≦ N−1. N may be the largest prime number among natural numbers smaller than the length M of the base sequence. q is a natural number less than or equal to N, and q and N are relatively prime with each other. If N is a prime number, the number of raw indexes q is N-1.

When the length M of the base sequence is 12 or 24, an example of the base sequence r _{u, v} (n) may be expressed by the following equation.

Equation 3

Different base sequences are defined according to the group number u.

When M = 12, b (n) may be defined as shown in the following table.

Table 4

When M = 24, b (n) can be defined as shown in the following table.

Table 5

The base sequence r _{u, v} (n) may vary depending on the sequence group number u and the base sequence number v. The sequence group number u and the base sequence number v in the group may each change semi-statically or slot by slot. When the sequence group number u changes from slot to slot is called group hopping, and the basic sequence number v in a group changes from slot to slot is called sequence hopping. Each of group hopping and sequence hopping may be set by a higher layer of a physical layer. For example, the upper layer may be RRC (Radio Resource Control) which plays a role of controlling radio resources between the terminal and the network.

The configuration of uplink HARQ and PHICH will now be described.

10 shows uplink HARQ. The base station receiving the uplink data 101 on the PUSCH (Physical Uplink Shared Channel) from the terminal transmits an ACK (Acknowledgement) / NACK (Not-Acknowledgement) signal 102 on the PHICH after a predetermined subframe elapses. . The ACK / NACK signal 102 becomes an ACK signal when the uplink data 101 is successfully decoded, and becomes an NACK signal when the decoding of the uplink data 101 fails. When the NACK signal is received, the terminal may transmit retransmission data 111 for the uplink data 101 until ACK information is received or up to a maximum number of retransmissions. The base station may transmit the ACK / NACK signal 112 for the retransmission data 111 on the PHICH.

11 is a flowchart showing the configuration of a PHICH. This may be referred to Section 6.9 of 3GPP TS 36.211 V8.3.0 (2008-05).

Referring to FIG. 11, since the LTE system does not support SU-MIMO in uplink, the PHICH carries a 1-bit ACK / NACK signal corresponding to the PUSCH for one UE. In step S210, the 1-bit ACK / NACK signal performs channel coding using repetition coding at a code rate 1/3. In step S220, the ACK / NACK signal coded with a 3-bit codeword is mapped to three modulation symbols through Binary Phase Shift Keying (BPSK) modulation. In step S230, modulation symbols are spread using a Spreading Factor (SF) N ^PHICH _SF and an orthogonal sequence. The number of orthogonal sequences used for spreading is twice the N ^PHICH _SF to apply I / Q multiplexing. 2N _SF ^PHICH orthogonal 2N _SF ^PHICH of PHICH is spread by using the sequences are defined as one PHICH group. PHICHs belonging to the same PHICH group are distinguished through different orthogonal sequences. In step S240, the spread symbols are layer mapped according to rank. In step S250, the hierarchically mapped symbols are mapped to resource elements, respectively.

According to section 6.9 of 3GPP TS 36.211 V8.3.0 (2008-05), the PHICH resource corresponding to the PUSCH is the lowest physical resource block (PRB) index I ^lowest_index _{PRB_RA} of the resource used for the PUSCH and the data copy used for the PUSCH. It is defined using the cyclic shift n _DMRS of the quiet reference signal. The demodulation reference signal refers to a reference signal used for demodulation of data transmitted on the PUSCH. More specifically, PHICH resources are known by index pairs (n ^group _PHICH , n ^seq _PHICH ). n ^group _PHICH is a PHICH group number, n ^seq _PHICH is an orthogonal sequence index in the PHICH group, and is given as follows.

Equation 4

Where 'mod' represents a modulo operation.

n ^group _PHICH has a value between 0 and (N ^group _PHICH- 1), and the number of PHICH groups N ^group _PHICH is given as follows.

Equation 5

Here, N _g ∈ {1/6, 1/2, 1, 2} is given in the upper layer.

Orthogonal sequences used in the PHICH are shown in the following table.

Table 6

Now, a multiple antenna system will be described.

12 shows a transmitter supporting a multiple codeword (MCW) scheme.

Referring to FIG. 12, the transmitter 300 includes channel encoders 310-1 and 310-2, mappers 320-1 and 320-2, a layer mapping unit 340, and a precoder ( 350) and a signal generator (Signal Generator, 360-1, ..., 360-Nt). Nt is the number of antenna ports. The channel encoders 310-1 and 310-2 encode the input information bits according to a predetermined coding scheme to generate codewords (CW). The first channel encoder 310-1 generates a first codeword CW1, and the second channel encoder 310-2 generates a second codeword CW2.

The mappers 320-1 and 320-2 modulate each codeword according to a modulation scheme and map them to modulation symbols having a complex value. The first mapper 320-1 generates modulation symbols for the first codeword CW1, and the second mapper 320-2 generates modulation symbols for the second codeword CW2.

The layer mapping unit 340 maps modulation symbols of input codewords CW1 and CW2 to each layer according to the number of layers. The layer may be referred to as an information path input to the precoder 350 and corresponds to a rank value. The layer mapping unit 340 may determine the number of layers (ie, rank) and then map modulation symbols of each codeword to each layer. The precoder 350 processes the mapping symbols mapped to each layer by a MIMO scheme according to the plurality of antenna ports 390-1,..., 390 -Nt, and outputs antenna specific symbols. The signal generators 360-1, ..., 360-Nt convert the antenna specific symbols into transmission signals, and the transmission signals are transmitted through each antenna port 390-1, ..., 390-Nt. The signal generators 360-1,..., 160 -Nt may perform OFDM modulation and / or SC-FDMA modulation.

Although the transmitter 300 includes two channel encoders 310-1 and 310-2 and two mappers 320-1 and 320-2 to process two codewords, the transmitter 300 The number of channel encoders and the number of mappers included in the are not limited. The transmitter 300 may include at least one channel encoder and at least one mapper for processing at least one codeword.

13 shows codeword-layer mapping in 3GPP LTE. This may be referred to Section 6.3 of 3GPP TS 36.211 V8.3.0 (2008-05). If the rank is 1, one codeword CW1 is mapped to one layer. One layer is processed to be transmitted through four antenna ports by precoding. If the rank is 2, two codewords CW1 and CW2 are mapped to two layers and mapped to four antenna ports by a precoder. If the rank is 3, one codeword of two codewords (CW1, CW2) is mapped to two layers by a serial-to-parallel converter (S / P), so that a total of two codewords Mapped to layer When the rank is 4, each of the two code words CW1 and CW2 is mapped to two layers by the serial-to-parallel converter S / P, respectively. Since a transmitter having four antenna ports may have up to four layers, four independent codewords may be transmitted, but 3GPP LTE supports a maximum of two codewords. Therefore, when each codeword has an independent HARQ process, up to two independent HARQ processes may be performed.

Currently in 3GPP TS 36.212 V8.3.0 (2008-05), only DCI format 0 for uplink scheduling for the case of not using SU-MIMO in uplink is defined. Therefore, in order to schedule a PUSCH using SU-MIMO in uplink, a design of a new DCI format is required.

In addition, when using the SU-MIMO in the uplink, PUSCH transmission is possible in a single codeword (SCW) or multiple codeword (MCW) scheme, so that an appropriate DCI format design according to the MIMO capacity (number or rank of codes) is required. need.

Hereinafter, the design of the DCI format for uplink SU-MIMO will be described in more detail.

Hereinafter, DCI format X refers to a DCI format for supporting SCW of uplink SU-MIMO, and DCI format Y refers to a DCI format for supporting MCW of uplink SU-MIMO. It is clear that the DCI format X / Y may be replaced with any other name that refers to the DCI format of control information for PUSCH scheduling supporting SCW / MCW SU-MIMO. In the DCI format X / Y, the C-RNTI may be masked, but a separate identifier for the DCI format X / Y may be masked.

14 shows an example of SCW transmission. In step S1010, the base station sends an uplink grant, that is, DCI format X on the PDCCH to the terminal. In step S1020, the terminal sends the SCW on the PUSCH from the base station.

The DCI format X includes at least one of a flag for identifying the DCI format, MIMO information, a cyclic shift (CS) of the demodulation reference signal, and padding bits. The CS of the flag, MIMO information, and the demodulation reference signal may be replaced by some of the information elements of the DCI format 0 of Table 2 or a new information element is added. Accordingly, DCI format X may further include some of the information elements of DCI format 0 in Table 2.

The flag is a field defined to distinguish the DCI format X from other DCI formats having the same or similar payload size. The number of bits of the flag may be floor (log ₂ (1 + m)). floor (x) is a function representing the smallest integer greater than x. m is the number of other DCI formats that require differentiation due to the same or similar payload size as DCI format X. For example, when the number of other DCi formats that need to be distinguished from DCI format X is one, one bit flag may be used to distinguish DCI format X from another DCI format. If there is no other DCI format having the same or similar size as the payload of DCI format X, the flag field may not be included in DCI format X.

MIMO information is MIMO-related information used for uplink SU-MIMO. For example, MIMO information is the number of layers (or rank), precoding information (eg, precoding matrix index (PMI)) and / or pre- It may include a precoding confirmation. Precoding confirmation is information that the base station confirms the PMI requested by the terminal. The number of bits of each field included in the MIMO information may have a variable value depending on the number of transmit antennas. Alternatively, the combination of the number of layers, the precoding information, and the precoding confirmation may be represented as a table according to an antenna configuration and / or a transmission mode, and then MIMO information may be represented as an index of the table.

The CS for the reference signal is a field included in the DCI format X to distinguish the allocation of the downlink ACK / NACK channel, that is, the PHICH for the UE using the uplink MU-MIMO. The reference signal is a demodulation reference signal used for demodulation of PUSCH data and may be defined for each antenna port. In SU-MIMO, since one codeword is not transmitted through one antenna port and the number of layers and the number of physical antennas may be different from the number of codewords, a change is necessary in the CS field for an existing reference signal. .

The same or different CS may be defined depending on whether the reference signal for each antenna port is located in the same OFDM symbol or in another OFDM symbol. If the reference signal for each antenna port is located in the same OFDM symbol, different CSs for each antenna port may be allocated to the reference signal for each antenna port. For example, if the reference signal for each antenna is located at the same position as the example shown in FIG. 8, the first reference signal for the first antenna port is assigned the first CS and the second reference signal for the second antenna port. Is assigned a second CS. The number of bits required is n * floor (log ₂ k) bits. n is the number of bits required to represent one CS, k is the number of antenna ports. If the reference signal for each antenna port is located in different OFDM symbols, the same or different CS for each antenna port may be allocated to the reference signal for each antenna port. For example, in a subframe, the first reference signal for the first antenna port is located in the second OFDM symbol, the second reference signal for the second antenna port is located in the fourth OFDM symbol, and the first reference signal for the first antenna port is located. The first CS is allocated to the first reference signal, and the second CS is allocated to the second reference signal for the second antenna port. N bits are required if the CS of all antenna ports have the same value, and n * floor ((log ₂ k)) bits are required if the CS of each antenna port has a different value.

A plurality of antenna ports may be divided into at least one subset, and different CSs may be allocated to reference signals belonging to each subset. Reference signals belonging to each subset may be located in different OFDM symbols in a subframe (or in a slot).

The location of the reference signal for each antenna port may vary in every subframe (or every slot). Information on the position at which the reference signal is transmitted in the corresponding subframe may be additionally included in the DCI format X together with the CS allocation for the reference signal. In this case, the required number of bits is floor (log ₂ p), and p is the number of cases in which the reference signal can be located in a subframe. For example, when a subframe includes 14 OFDM symbols, p may be 14. The number p of cases in which the reference signal can be located may express the number of all cases, or the number of cases for the limited position among the cases where only a limited position for the reference signal is allowed to reduce the number of bits. have. In addition, according to the antenna configuration, various methods such as indicating the positions of the antenna ports and the reference signals in a table and informing the index of the table may be used.

Based on the CS of the reference signal for the first antenna port, the CS of the reference signal for the remaining antenna ports may be expressed as a difference value.

The padding bit is a bit added for discrimination when DCI format X and another DCI format have the same payload size. The size of the padding bit may be 0 to floor (log ₂ m). m needs to distinguish the payload size including the DCI format including the corresponding padding bit, but is the number of DCI formats. For example, if the number of different DCI formats requiring payload size is 1, the DCI format X and the other DCI formats may be distinguished by 1-bit padding. The padding bit may not be included when the payload size is not the same as other DCI formats.

15 shows an example of MCW transmission. In step S1110, the base station sends an uplink grant, that is, DCI format Y to the terminal on the PDCCH. In step S1120, the terminal sends the MCW on the PUSCH from the base station. The DCI format Y includes at least one of a flag for distinguishing the DCI format, MIMO information, a cyclic shift (CS) of the demodulation reference signal, and padding bits. Since the flag, the MIMO information, the CS and padding bits of the demodulation reference signal are the same as the contents of the field included in the DCI format X of the embodiment of FIG.

DCI format Y further includes codeword-specific information to support MCW SU-MIMO. Codeword specific information is control information applied only to a corresponding codeword.

The codeword specific information may include a modulation and coding scheme (MCS), a redundancy version (RV), and a new data indicator (NDI) for each codeword. The MCS represents the MCS of the corresponding codeword, the RV represents the RV of the corresponding codeword, and the NDI is a field transmitted to distinguish whether a block to be transmitted is retransmission or new data. MCS and RV are composed of one table, and can be expressed as an index of the table. For the MCW, the indices of the MCS and RV of the remaining codewords based on the indices of the MCS and RV of the first codeword may be represented by difference values.

MCS and / or RV is not given for each codeword, and only one may be given for all codewords. In the case of using MCW in uplink SU-MIMO, specific information for each codeword is basically required, but even codeword specific information can be used in common for all codewords to reduce the number of bits of DCI format Y. In particular, if the CQI between MCWs is averaged using a technique such as layer permutation, the MCW may experience the same channel as much as possible. Therefore, it may be more efficient to transmit the MCW using one MCS, such as SCW transmission, without giving the MCS for each codeword for the MCW.

When the MCW is transmitted using one MCS, only one downlink ACK / NACK may be transmitted to the MCW without transmitting downlink ACK / NACK for each codeword for MCW PUSCH transmission. In this case, RV and NDI may be commonly used for all codewords. In this case, the PHICH resource may be determined from a PUSCH resource for one codeword selected from a plurality of codewords. For example, the PHICH resource is determined from the PUSCH resource of the first codeword or the last codeword. This has the advantage that it can be applied without significantly changing the structure of the existing 3GPP LTE. The UE may implicitly determine which codeword of the plurality of codewords to determine the PHICH resource, or the base station may inform the UE through a part of system information, an RRC message and / or a PDCCH.

16 is a block diagram illustrating a multiple antenna system in which an embodiment of the present invention is implemented. The terminal 2400 and the base station 2450 may have multiple antennas and communicate through a wireless channel. The terminal 2400 includes a processor 2401 and a radio frequency (RF) unit 2402. The RF unit 2402 transmits and / or receives a radio signal. The processor 2401 is connected to the RF unit 2402 to implement SCW and / or MCW transmission. The processor 2401 monitors the PDCCH and receives an uplink grant on the PDCCH, that is, the DCI format X or Y. SCW or MCW is transmitted through the PUSCH indicated by the uplink grant.

The base station 2450 includes a processor 2451 and an RF unit 2452. The RF unit 2452 transmits and / or receives a radio signal. The processor 2251 is connected to the RF unit 2452, configures a DCI format, and transmits a DCI format on a PDCCH.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Claims (13)

In the method for transmitting a plurality of codewords through a multi-antenna system, Receive an uplink grant from a base station, the uplink grant includes an uplink resource allocation and one MCS (Modulation and coding scheme) for a plurality of codewords, Generating the plurality of codewords using the MCS, and And transmitting the plurality of codewords over a radio resource indicated by the uplink resource allocation. 2. The method of claim 1, further comprising receiving one positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for the plurality of codewords from the base station. The method of claim 2, wherein the resources used for transmission of the ACK / NACK signal are determined from radio resources used for transmission of one codeword selected from the plurality of codewords. 4. The method of claim 3, wherein the information about the selected one codeword is obtained from the base station. 2. The method of claim 1, wherein the uplink grant further comprises one redundancy version (RV) for the plurality of codewords. 6. The method of claim 5, wherein the uplink grant further comprises one new data indicator (NDI) for the plurality of codewords. The method of claim 1, wherein the uplink grant further comprises a CS (cyclic shift) used for transmission of reference signals used for demodulation of the plurality of codewords. 8. The method of claim 7, wherein the CS of the reference signal for each antenna is different. 9. The method of claim 8, wherein the positions of the reference signals for each antenna in the subframe are all the same. 8. The method of claim 7, wherein the position of the reference signal for each antenna in the subframe is different. In a terminal having multiple antennas, RF (radio frequency) unit for transmitting and receiving a radio signal; And Including a processor connected to the RF unit, wherein the processor Receive an uplink grant from a base station, the uplink grant includes an uplink resource allocation and one MCS (Modulation and coding scheme) for a plurality of codewords, Generating the plurality of codewords using the MCS, and A terminal for transmitting the plurality of code words through a radio resource indicated by the uplink resource allocation. The terminal of claim 11, wherein the processor receives one positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for the plurality of codewords from the base station. The terminal of claim 12, wherein the processor determines a resource used for transmitting the ACK / NACK signal from a radio resource used for transmitting one codeword selected from the plurality of codewords.

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