WO2012169815A2

WO2012169815A2 - Method and apparatus for transmitting an uplink signal in a tdd-based wireless communication system

Info

Publication number: WO2012169815A2
Application number: PCT/KR2012/004515
Authority: WO
Inventors: 박성호; 천진영; 김기태; 김수남; 강지원; 임빈철
Original assignee: 엘지전자 주식회사
Priority date: 2011-06-08
Filing date: 2012-06-08
Publication date: 2012-12-13
Also published as: WO2012169815A3; JP2014520449A; JP5680255B2

Abstract

Provided are a method and apparatus for transmitting an uplink signal by a terminal. The method comprises: a step of receiving uplink subframe-type information from a first base station; a step of configuring an uplink subframe having one of a plurality of predetermined subframe structures on the basis of the uplink subframe-type information; and a step of transmitting an uplink signal from the thus-configured uplink subframe to the first base station. The uplink subframe is a subframe which overlaps, in a time domain, with a downlink subframe for transmitting a downlink control signal from a second base station adjacent to the first base station. The plurality of subframe structures each have different reference-signal locations.

Description

Method and apparatus for transmitting uplink signal in TDD based wireless communication system

The present invention relates to wireless communication, and more particularly, to a method and apparatus for transmitting an uplink signal in a time division duplex (TDD) based wireless communication system.

The wireless communication system may use a frequency division duplex (FDD) scheme or a time division duplex (TDD) scheme. In the FDD scheme, a downlink transmission in which a base station transmits a signal to a terminal and an uplink transmission in which a terminal transmits a signal to a base station are performed in different frequency bands. The FDD scheme is very efficient where a wide frequency band is guaranteed, and can dynamically handle the asymmetry of downlink / uplink transmission. In the TDD scheme, downlink transmission and uplink transmission are performed at different times in the same frequency band. The TDD scheme may be utilized even when there is a limitation in the frequency band, and is advantageous in the case of mainly using traffic such as voice over internet protocol (VoIP). However, the TDD scheme has a relatively small cell coverage compared to the FDD scheme due to the limitation of the round trip time (RTT) and also requires a guard period when switching between downlink and uplink transmissions.

In a TDD system using a TDD scheme, various downlink / uplink subframe configurations (hereinafter, referred to as subframe configurations) are provided. Subframe setting means setting each subframe as an uplink subframe, a downlink subframe, or a special subframe in a radio frame. However, subframe configuration may be limited in the base station unit of the TDD system. For example, in 3GPP LTE, one network may not have different subframe configuration. That is, the base stations in the same network are all limited to have the same subframe configuration. Such a TDD system is called a symmetric TDD system. If the influence of the data burden on each base station is not considered in the symmetric TDD system, the inter-cell interference (ICI) in each cell will be constant. In this case, each base station may assume a constant ICI in the time domain, thereby easily performing link-adaptation, power control, etc. with respect to the target SINR.

However, in recent years, since the above limitation impedes the efficient use of radio resources and does not properly reflect the data burden characteristics of the base stations, it is considered to use different subframe settings between base stations. That is, each base station may perform different link transmission and reception at the same time according to different subframe settings. Such a TDD system is called an asymmetric TDD system. In an asymmetric TDD system, a terminal at a cell coverage boundary of a specific base station is interfered by a signal transmitted by another base station or another terminal. In particular, the downlink control channel is particularly sensitive to interference in that it contains system control information. In order to solve this problem, there is a method of reducing the transmission power of a terminal transmitting an uplink signal in a time interval in which another terminal receives a downlink control signal in a subframe, and resetting the transmission power in the remaining time intervals. . However, if the transmission power is changed in the subframe like this, there is a problem in that phase discontinuity of the transmission signal occurs. As a result, there is a problem that the base station cannot properly receive the uplink signal transmitted by the terminal.

Accordingly, there is a need for an uplink signal transmission method and apparatus that can solve an interference problem in an asymmetric TDD system.

An object of the present invention is to provide an uplink signal transmission method and apparatus in a TDD (Time Division Duplex) based wireless communication system.

In one aspect, a method of transmitting an uplink signal of a terminal is provided. The method is

Receiving uplink subframe type information from a first base station; Configuring an uplink subframe having one of a plurality of predetermined subframe structures according to the uplink subframe type information; And transmitting an uplink signal to the first base station in the configured uplink subframe, wherein the uplink subframe transmits a downlink control signal from a second base station adjacent to the first base station. The subframes overlap each other in the frame and time domain, and the plurality of subframe structures are subframe structures having different reference signal positions.

When the number of orthogonal frequency division multiplexing (OFDM) symbols for transmitting a downlink control signal in the second base station is N (N is a natural number of 1 or more and 4 or less),

The terminal may transmit an uplink signal by lowering the transmit power of the remaining OFDM symbols in the first N OFDM symbols of the uplink subframe.

When N is 2, a reference signal may be transmitted in any one OFDM symbol, the fourth OFDM symbol, and the eleventh OFDM symbol of the first two OFDM symbols of the uplink subframe.

When N is 3, a reference signal may be transmitted in any one OFDM symbol and the 11th OFDM symbol of the first three OFDM symbols of the uplink subframe.

When N is 3, a reference signal may be transmitted in any one OFDM symbol and the eighth OFDM symbol of the first three OFDM symbols of the uplink subframe.

When N is 4, a reference signal may be transmitted in 4th, 7th, and 11th OFDM symbols of the uplink subframe.

When N is 4, a reference signal may be transmitted in 3rd, 7th, and 11th OFDM symbols of the uplink subframe.

The uplink subframe type information may be received through an uplink grant scheduling the uplink subframe.

The uplink subframe type information may be received through an upper layer signal.

In another aspect, a terminal includes a radio frequency (RF) unit for transmitting and receiving a radio signal; And a processor connected to the RF unit, wherein the processor receives uplink subframe type information from a first base station, and has one structure among a plurality of predetermined subframe structures according to the uplink subframe type information. And configures an uplink subframe having an uplink subframe, and transmits an uplink signal to the first base station in the configured uplink subframe, wherein the uplink subframe is a downlink control signal at a second base station adjacent to the first base station. A subframe overlapping in a time domain with a downlink subframe for transmitting a Tx subframe structure, wherein the plurality of subframe structures are subframe structures having different reference signal positions.

In a time division duplex (TDD) system using different subframe configurations, interference to a downlink control signal transmitted by a base station can be mitigated. Therefore, the downlink control signal reception performance of the terminal is improved.

1 shows a structure of a radio frame.

2 shows a structure of a TDD radio frame.

3 shows an example of a resource grid for one downlink slot.

4 shows a downlink subframe structure.

5 shows a structure of an uplink subframe.

6 illustrates inter-cell interference when different UL-DL configurations are used in adjacent cells.

7 shows a case where cell A is an interference cell and cell B is an interference cell.

8 illustrates a case where cell B is an interference cell and cell A is an interference cell.

9 shows a conventional uplink subframe structure.

10 shows a subframe structure that can be applied when the first OFDM symbol of the uplink subframe overlaps with the PDCCH transmission OFDM symbol of the neighboring base station.

FIG. 11 illustrates a case where the first two OFDM symbols of an uplink subframe overlap with PDCCH transmission OFDM symbols of a neighbor base station.

FIG. 12 shows a subframe structure applicable to the situation as shown in FIG. 11.

FIG. 13 illustrates a case where the first three OFDM symbols of an uplink subframe overlap with PDCCH transmission OFDM symbols of a neighbor base station.

FIG. 14 shows a subframe structure applicable to the situation as shown in FIG. 13.

15 shows an example of changing a reference signal position of a second slot of an uplink subframe.

16 shows an example of a subframe structure that can be applied when the resource allocation scheme applied to the terminal is a slot hopping scheme.

FIG. 17 illustrates a case where the first four OFDM symbols of an uplink subframe overlap with PDCCH transmission OFDM symbols of a neighbor base station.

FIG. 18 shows a subframe structure applicable to the situation as shown in FIG. 17.

19 shows an uplink transmission method of a terminal according to an embodiment of the present invention.

20 is a block diagram illustrating a wireless device in which an embodiment of the present invention is implemented.

The user equipment (UE) may be fixed or mobile, and may include a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a personal digital assistant (PDA). It may be called other terms such as digital assistant, wireless modem, handheld device.

A base station generally refers to a fixed station communicating with a terminal, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), and an access point.

The communication from the base station to the terminal is called downlink (DL), and the communication from the terminal to the base station is called uplink (UL). The wireless communication system including the base station and the terminal may be a time division duplex (TDD) system or a frequency division duplex (FDD) system. The TDD system is a wireless communication system that performs uplink and downlink transmission and reception using different times in the same frequency band. The FDD system is a wireless communication system capable of transmitting and receiving uplink and downlink simultaneously using different frequency bands. The wireless communication system can perform communication using a radio frame.

1 shows a structure of a radio frame.

A radio frame includes 10 subframes, and one subframe includes two consecutive slots. Slots included in the radio frame are indexed from 0 to 19. The time taken for one subframe to be transmitted is called a transmission time interval (TTI), and the TTI may be a minimum scheduling unit. For example, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

2 shows a structure of a TDD radio frame.

Referring to FIG. 2, a subframe having an index # 1 and an index # 6 is called a special subframe, and includes a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UPPTS). ). DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. GP is a section for removing interference caused in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink. The TDD radio frame is a downlink subframe, an uplink subframe, or a special sub for each subframe according to an uplink / downlink configuration (UL / DL configuration) transmitted in an upper layer signal such as an RRC message. Set to a frame.

3 shows an example of a resource grid for one downlink slot.

Referring to FIG. 3, the downlink slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain and N _RB resource blocks (RBs) in the frequency domain. The RB includes one slot in the time domain and a plurality of consecutive subcarriers in the frequency domain in resource allocation units. The number N _RB of resource blocks included in the downlink slot depends on the downlink transmission bandwidth N ^DL configured in the cell. For example, in the LTE system, N _RB may be any one of 6 to 110. The structure of the uplink slot may also be the same as that of the downlink slot.

Each element on the resource grid is called a resource element (RE). Resource elements on the resource grid may be identified by an index pair (k, l) in the slot. Where k (k = 0, ..., N _RB × 12-1) is the subcarrier index in the frequency domain, and l (l = 0, ..., 6) is the OFDM symbol index in the time domain.

In FIG. 3, one resource block includes 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain to include 7 × 12 resource elements, but the number of OFDM symbols and the number of subcarriers in the resource block is exemplarily described. It is not limited to this. The number of OFDM symbols and the number of subcarriers can be variously changed according to the length of the CP, frequency spacing, and the like. The number of subcarriers in one OFDM symbol may be selected and used among 128, 256, 512, 1024, 1536 and 2048.

4 shows a downlink subframe structure.

Referring to FIG. 4, a downlink (DL) subframe is divided into a control region and a data region in the time domain. The control region includes the first up to four OFDM symbols of the first slot in the subframe, but the number of OFDM symbols included in the control region may be changed. A physical downlink control channel (PDCCH) and another control channel are allocated to the control region, and a physical downlink shared channel (PDSCH) is allocated to the data region.

In the control region, control channels such as a physical control format indicator channel (PCFICH), a physical hybrid-ARQ indicator channel (PHICH), and a physical downlink control channel (PDCCH) are transmitted.

The PCFICH transmitted in the first OFDM symbol of the subframe carries a control format indicator (CFI) regarding the number of OFDM symbols (that is, the size of time of the control region) used for transmission of control channels in the subframe. The terminal first receives the CFI on the PCFICH, and then monitors the PDCCH. Unlike the PDCCH, the PCFICH does not use blind decoding and is transmitted on a fixed PCFICH resource of a subframe.

The PHICH carries a positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for an uplink hybrid automatic repeat request (HARQ). An ACK / NACK signal for uplink (UL) data on a physical uplink shared channel (PUSCH) transmitted by a terminal is transmitted on a PHICH.

Control information transmitted through the PDCCH is called downlink control information (DCI). DCI is a resource allocation of PDSCH (also called DL grant), a PUSCH resource allocation (also called UL grant), a set of transmit power control commands for individual UEs in any UE group. And / or activation of Voice over Internet Protocol (VoIP).

5 shows a structure of an uplink subframe.

Referring to FIG. 5, an uplink subframe is allocated a control region in which a physical uplink control channel (PUCCH) carrying uplink control information is allocated in a frequency domain and a physical uplink shared channel (PUSCH) carrying user data. It can be divided into data areas.

PUCCH is allocated to an RB pair in a subframe. RBs belonging to the RB pair occupy different subcarriers in each of the first slot and the second slot. RB pairs have the same resource block index m.

In the PUSCH, user data and / or uplink control information are transmitted.

Now, an asymmetric TDD system will be described.

In TDD, a downlink (DL) subframe and an uplink (UL) subframe coexist in one radio frame. Table 1 shows an example of a UL-DL configuration of a radio frame.

TABLE 1

In Table 1, 'D' represents a DL subframe, 'U' represents a UL subframe, and 'S' represents a special subframe. Upon receiving the UL-DL configuration from the base station, the terminal may know whether each subframe is a DL subframe or a UL subframe in a radio frame. Hereinafter, the UL-DL configuration N (N is any one of 0 to 6) may refer to Table 1 above.

Conventionally, in the TDD system using the TDD scheme, the same UL-DL configuration is used in base stations (or cells) constituting one network. However, in the future, base stations configuring the same network may support using different UL-DL settings. In this case, for example, a case where a first base station uses a first subframe as a DL subframe and a second base station uses a first subframe as a UL subframe may have a different transmission direction.

Cells A and B are cells adjacent to each other and use different UL-DL configurations. Assume that a terminal of cell A is a first terminal and a terminal of cell B is a second terminal. Referring to FIG. 6A, the subframe 61 of cell A is set to a DL subframe, and the subframe 62 of cell B is set to a UL subframe. In this case, when the second terminal transmits the uplink signal in the subframe 62 of the cell B, the first terminal receiving the downlink signal in the subframe 61 of the cell A is subjected to interference. That is, cell A is a interfered cell and cell B is an interfering cell.

Alternatively, referring to FIG. 6B, the subframe 63 of the cell A is set to the DL subframe, and the subframe 64 of the cell B is set to the UL subframe. In this case, the downlink signal transmitted in the subframe 63 of the cell A interferes with the uplink signal transmitted in the subframe 64 of the cell B.

6 (a) and 6 (b), the amount of interference received by each cell will be described in detail in relation to the interfering cell and the interfering cell.

Referring to FIG. 7, in cell A,

subframe sections

71 and 72 are DL subframes, and subframe section 73 is UL subframes. In cell B, the subframe periods 71 are DL subframes, and the

subframe periods

72 and 73 are UL subframes. In this case, the subframe section 71 performs downlink transmission in the same manner in cell A and cell B. Such a subframe section having the same transmission direction is called a homogeneous subframe. If the transmission direction is the same as downlink transmission, it is called a downlink homogeneous subframe (for example, 71). If the uplink transmission is the same, the uplink homogeneous subframe (for example, 73) is called. Each subframe section 72 has a different transmission direction of each cell. Such a subframe section is called a heterogeneous subframe. The interfering cell performs downlink transmission, but the interfering cell performs downlink heterogeneous subframe, and the interfering cell performs uplink transmission. The interfering cell performs downlink transmission. In this case, it is called an uplink heterogeneous subframe.

The first terminal 77 of the cell A is subjected to inter-cell interference (ICI) by the downlink transmission of the second base station 80 of the cell B in the subframe period 71, the cell in the subframe period 72 Inter-cell interference is caused by an uplink signal transmitted by the second terminal 78 of B. FIG. That is, although the

subframe sections

71 and 72 of the cell A are all composed of downlink subframes, interference between cells having different characteristics is caused. In particular, the inter-cell interference in the subframe period 72 may act as a stronger interference when the distance to the second terminal 78 is close.

Referring to FIG. 8, in contrast to FIG. 7, cell B is an interference cell and cell A is an interference cell. Downlink transmission for the second terminal 78 belonging to the cell B is performed in the subframe period 71. At this time, the downlink transmission for the first terminal 77 belonging to the cell A is also performed in the subframe section 71. Accordingly, inter-cell interference may be assumed as in the existing TDD system.

Uplink transmission of the second terminal 78 belonging to the cell B is performed in the

subframe periods

72 and 73. On the other hand, uplink transmission of the first terminal 77 belonging to the cell A is performed only in the subframe period 73. In this case, although the

subframe periods

72 and 73 of the cell B are all composed of uplink subframes, interference between cells having different characteristics is caused. The terminal performs power control based on noise and interference (NI). If such interference is changed between cells, power control performance cannot be guaranteed.

In the asymmetric TDD system as described above, interference occurs in homogeneous subframes having the same transmission direction in adjacent cells, but interference occurs in heterogeneous subframes having different transmission directions in adjacent cells. In particular, inter-cell interference in heterogeneous subframes is a very important factor for deterioration of data reception performance. This is because, in a heterogeneous subframe, a case in which a specific terminal needs to receive a downlink control signal having a great influence on data reception occurs.

One solution for solving the inter-cell interference problem in the heterogeneous subframe is to alleviate the inter-cell interference by performing a proper power control by the terminal transmitting the uplink signal. For example, assume a specific subframe configured as a downlink subframe for the first terminal and an uplink subframe for the second terminal. In the specific subframe, in the OFDM symbols in which the first terminal receives the downlink control signal, the second terminal can lower the inter-cell interference for the first terminal by transmitting a PUSCH by lowering transmission power or allocating zero power. have. As a result, the second terminal transmits the PUSCH / PUCCH at a low transmission power in some OFDM symbols in one subframe and transmits the PUSCH / PUCCH at the original transmission power in the remaining OFDM symbols.

However, changing the transmission power in this continuous time domain may cause discontinuity in the channel phase. In general, due to the cost problem among the linear power amplifier and the nonlinear power amplifier, the terminal uses a low performance but low cost nonlinear power amplifier. In the case of a nonlinear power amplifier, changing the uplink transmission power in a continuous time domain is accompanied by discontinuity in phase.

Therefore, the above solution affects uplink signal transmission of the second terminal. In other words, it is difficult for the base station to properly receive / decode the uplink signal of the second terminal.

In order to solve this problem, the present invention proposes a method for transmitting an uplink signal using a new subframe structure in an uplink heterogeneous subframe, and a terminal using the method.

First, a conventional uplink subframe structure will be described.

9 shows a conventional uplink subframe structure.

Referring to FIG. 9, an uplink subframe includes two slots including seven OFDM symbols in a normal cyclic prefix (CP). In the fourth OFDM symbol of each slot, a UE-specific reference signal (hereinafter, abbreviated as reference signal) for uplink signal demodulation is transmitted (the reference signal is a signal previously known to the base station and the terminal). That is, reference signals are transmitted in the fourth and eleventh OFDM symbols of the subframe. The base station may perform channel estimation and data demodulation in units of slots or units of subframes using the reference signal.

If the uplink subframe is an uplink heterogeneous subframe, the first specific number of OFDM symbols (up to four) of the uplink subframe may be reduced in transmission power to mitigate interference on reception of downlink control signals from other terminals. Allocate zero power.

As such, when it is necessary to allocate different transmission powers in an uplink subframe or an uplink slot, that is, an uplink subframe in which a part overlapping with OFDM symbols in which another base station transmits a downlink control signal occurs A new subframe structure can be used for uplink channel estimation and / or data demodulation.

Referring to FIG. 10, when only the first one OFDM symbol of an uplink subframe overlaps the PDCCH region of a neighboring base station, the UE allocates a transmission power of the first one OFDM symbol to zero and original transmission in the remaining OFDM symbols. It transmits an uplink signal with power. That is, while using the same uplink subframe structure, the OFDM symbol overlapping the PDCCH region of the neighboring base station is transmitted by muting. This is because, when the overlapping region is one OFDM symbol, it is not easy to insert a separate reference signal in the overlapping region because of SC-FDMA characteristics.

FIG. 11 illustrates a case where the first two OFDM symbols of an uplink subframe overlap with PDCCH transmission OFDM symbols of an adjacent base station, and FIG. 12 illustrates a subframe structure applicable to the situation shown in FIG. 11.

Referring to FIG. 11, first two OFDM symbols of an uplink subframe overlap with an area in which a neighbor base station transmits a PDCCH. In FIG. 11, a region indicated by 111 of the PUSCH region indicates an area in which subcarriers can be allocated in pairs, such as space time block coding (STBC).

In the situation as shown in FIG. 11, as shown in FIG. 12, one reference signal is further allocated to the overlapping area. That is, an additional reference signal 123 is inserted into the first OFDM symbol or the second OFDM symbol of the uplink subframe for channel estimation and data demodulation for the PUSCH.

In the region indicated by 122 in FIG. 12, a multi input multi output (MIMO) technique such as frequency selection transmit diversity (FSTD), beamforming, and antenna selection may be used. In the region indicated by 121, subcarriers can be allocated in pairs as in STBC.

When the UE transmits an uplink signal using the subframe structure as shown in FIG. 12, the BS may perform separate channel estimation and data demodulation using an additional reference signal 123 for the PUSCH overlapping with the PDCCH region of the neighbor BS. In other areas, channel estimation and data demodulation are possible using the existing reference signal 124.

FIG. 13 illustrates a case where the first three OFDM symbols of an uplink subframe overlap with PDCCH transmission OFDM symbols of an adjacent base station, and FIG. 14 illustrates a subframe structure applicable to the situation shown in FIG. 13.

When three OFDM symbols overlap with the PDCCH transmission region as shown in FIG. 13, when an additional reference signal is inserted into the first or second OFDM symbol in the overlapping region 131, the performance of the PUSCH transmitted in the overlapping region 131 may be secured. If transmit diversity is used in the remaining region, transmit diversity performance is deteriorated.

Accordingly, the position of the existing reference signal of the first slot in the subframe may be changed without inserting an additional reference signal as shown in FIG. 14 (a) or (b). That is, in the conventional uplink subframe structure, the reference signal of the first slot is located in the fourth OFDM symbol. In this embodiment, the position of the reference signal located in the first slot of the uplink subframe corresponds to the PDCCH transmission region of the neighboring base station. It is to move to one OFDM symbol of the three OFDM symbols.

In this case, channel estimation / data demodulation performance for the fast UE may be somewhat degraded in the remaining regions except for the first three OFDM symbols of the uplink subframe, but the resource allocation efficiency may be maintained without additional reference signal overhead. There is this.

In FIG. 14, only the reference signal position in the first slot of the uplink subframe is changed, but this is not a limitation. That is, the reference signal position in the second slot can also be changed.

Referring to FIG. 15, while the reference signal of the first slot of the uplink subframe is located in one of the OFDM symbols corresponding to the PDCCH region of the neighboring base station, the reference signal of the second slot is replaced by the fourth OFDM symbol of the second slot. Rather, it is located in the first OFDM symbol.

The uplink subframe structure illustrated in FIGS. 14 and 15 may be applied when the base station performs channel estimation / data demodulation in units of subframes. If the resource allocation scheme applied to the UE is hopped on a slot basis, it may be difficult to demodulate data in a region that does not overlap the PDCCH transmission region of the neighboring base station in the first slot.

To solve this problem, the following subframe structure can be used.

Referring to FIG. 16, reference signals are inserted into third and seventh OFDM symbols in a first slot. That is, in the first slot, one reference signal is inserted in an area overlapping with the PDCCH transmission area of the neighboring base station, and one reference signal is inserted in the remaining area of the first slot to ensure data demodulation and channel estimation performance.

FIG. 17 illustrates a case where the first four OFDM symbols of an uplink subframe overlap with PDCCH transmission OFDM symbols of an adjacent base station, and FIG. 18 illustrates a subframe structure applicable to the situation shown in FIG. 17.

When the first four OFDM symbols of the uplink subframe overlap with the PDCCH transmission OFDM symbols of the neighboring base station as shown in FIG. 17, when the transmission diversity is used in the non-overlapping region, resource allocation cannot be performed in units of symbol pairs, thereby degrading performance. May occur. In addition, when resource allocation is performed in units of slots, channel estimation and data demodulation may be difficult in the first slot. Therefore, an additional reference signal can be inserted for data demodulation and channel estimation of OFDM symbols that do not overlap the PDCCH transmission region in the first slot. That is, as shown in FIG. 18, the reference signal may be additionally inserted into the seventh OFDM symbol in addition to the fourth OFDM symbol of the first slot. In this case, resource allocation is possible in units of symbol pairs, and channel estimation and data demodulation are possible even when resource allocation is performed in slot units.

In the methods described with reference to FIGS. 9 to 18, the number of OFDM symbols constituting the PDCCH transmission region of a neighboring base station is the same as the maximum number of OFDM symbols allocated for transmitting the PDCCH by N (N is a natural number of 1 or more). Or can be many. In addition, in the subframe structure proposed in the present invention, any MIMO transmission diversity scheme may be used in addition to STBC in OFDM symbols except for an OFDM symbol to which a reference signal is allocated.

Referring to FIG. 19, the base station transmits uplink subframe type information to the terminal (S110). The uplink subframe type information may be information indicating which subframe structure to use among the subframe structures described with reference to FIGS. 9 to 18. The plurality of subframe structures may be subframe structures having different reference signal positions. The uplink subframe type information may be included in the UL grant and transmitted or may be transmitted through an upper layer signal such as an RRC message. When transmitted through a higher layer signal, uplink subframe type information for a plurality of uplink subframes may be delivered by one-time RRC message information transmission. For example, the base station may inform what type of subframe structure to use for a plurality of subframes in a bitmap format.

The base station may transmit the uplink subframe type information when the transmission power of the terminal needs to be changed in one subframe, such as a case where a heterogeneous uplink subframe is generated due to different UL / DL configuration from neighboring base stations.

After configuring the uplink subframe according to the uplink subframe type information (S120), the UE transmits an uplink signal according to the configured uplink subframe structure (S130).

According to the above-described method, in the asymmetric TDD system having different transmission directions in the same time interval, the interference on the downlink control signal transmission of the neighboring base station can be alleviated, and the uplink signal transmission of the terminal can be reliably.

The base station 100 includes a processor 110, a memory 120, and an RF unit 130. The processor 110 implements the proposed functions, processes and / or methods. For example, the processor 110 may transmit uplink subframe type information to the terminal through a physical layer signal such as a UL grant or a higher layer signal such as an RRC message. In addition, the PUSCH according to the subframe structure indicated by the uplink subframe type information may be received and decoded from the UE. The memory 120 is connected to the processor 110 and stores various information for driving the processor 110. The RF unit 130 is connected to the processor 110 and transmits and / or receives a radio signal.

The terminal 200 includes a processor 210, a memory 220, and an RF unit 230. The processor 210 implements the proposed functions, processes and / or methods. For example, the processor 210 receives uplink subframe type information from a base station and configures an uplink subframe having one of a plurality of predetermined subframe structures according to the uplink subframe type information. . The subframe structure has been described with reference to FIGS. 9 to 18. The processor 210 transmits an uplink signal to the base station in the configured uplink subframe. As described above, the uplink subframe is a downlink subframe in which a downlink control signal is transmitted from an adjacent base station and a subframe overlapping in a time domain. It may be a subframe to be transmitted. The memory 220 is connected to the processor 210 and stores various information for driving the processor 210. The RF unit 230 is connected to the processor 210 to transmit and / or receive a radio signal.

Processors

110 and 210 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, data processing devices, and / or converters for interconverting baseband signals and wireless signals. The

memory

120, 220 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and / or other storage device. The

RF unit

130 and 230 may include one or more antennas for transmitting and / or receiving a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in the

memories

120 and 220 and executed by the

processors

110 and 210. The

memories

120 and 220 may be inside or outside the

processors

110 and 210, and may be connected to the

processors

110 and 210 by various well-known means.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

Claims

In the uplink signal transmission method of the terminal,
Receiving uplink subframe type information from a first base station;
Configuring an uplink subframe having one of a plurality of predetermined subframe structures according to the uplink subframe type information; And
Transmitting an uplink signal to the first base station in the configured uplink subframe,
The uplink subframe overlaps a downlink subframe in which a downlink control signal is transmitted by a second base station adjacent to the first base station in a time domain, and the plurality of subframe structures have different positions of reference signals. And a subframe structure.
The method of claim 1, wherein the number of orthogonal frequency division multiplexing (OFDM) symbols for transmitting a downlink control signal in the second base station is N (N is a natural number of 1 or more and 4 or less).
The terminal transmits an uplink signal by lowering the transmit power of the remaining OFDM symbols in the first N OFDM symbols of the uplink subframe.
The method of claim 2, wherein when N is 2,
And transmitting a reference signal in any one of the first two OFDM symbols, the fourth OFDM symbol, and the eleventh OFDM symbol of the uplink subframe.
The method of claim 2, wherein when N is 3,
And transmitting a reference signal in one of the first three OFDM symbols and the 11th OFDM symbol of the uplink subframe.
The method of claim 2, wherein when N is 3,
And transmitting a reference signal in any one OFDM symbol and an eighth OFDM symbol of the first three OFDM symbols of the uplink subframe.
The method of claim 2, wherein when N is 4,
And transmitting a reference signal in 4th, 7th, and 11th OFDM symbols of the uplink subframe.
The method of claim 2, wherein when N is 4,
And transmitting a reference signal in 3rd, 7th, and 11th OFDM symbols of the uplink subframe.
The method of claim 1, wherein the uplink subframe type information is received through an uplink grant scheduling the uplink subframe.
The method of claim 1, wherein the uplink subframe type information is received through a higher layer signal.
A radio frequency (RF) unit for transmitting and receiving a radio signal; And
Including a processor connected to the RF unit,
The processor receives uplink subframe type information from a first base station, configures an uplink subframe having one of a plurality of predetermined subframe structures according to the uplink subframe type information, and In the configured uplink subframe, an uplink signal is transmitted to the first base station,
The uplink subframe overlaps a downlink subframe in which a downlink control signal is transmitted by a second base station adjacent to the first base station in a time domain, and the plurality of subframe structures have different positions of reference signals. Terminal characterized in that the subframe structure.