KR20130071318A - Method and apparatus for power control of downlink in orthogonal frequency division multiplexing system - Google Patents

Abstract

The present invention relates to a method and apparatus for transmitting and receiving downlink power information. The method for transmitting downlink power information of a base station according to an embodiment of the present invention includes downlink power information of a general subframe instead of ABS (Almost Blank Suframe). Comprising a first configuration step, a second configuration step of configuring the downlink power information of the ABS and the downlink power information of the ABS and the downlink power information of the general subframe to the terminal. According to an embodiment of the present invention, when data of a terminal of a neighbor cell is received, neighbor cell interference between symbols is prevented to generate constant data interference in a subframe, and the feedback of the terminal uses a low power data channel using a power ratio. Enable scheduling of the receiving terminal.

Description

METHOD AND APPARATUS FOR POWER CONTROL OF DOWNLINK IN ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SYSTEM}

 The present invention relates to a power control method and apparatus for a downlink data channel in an orthogonal frequency division multiplexing (OFDM) system.

The mobile communication system has been developed to provide voice service while ensuring the user 's activity. However, mobile communication systems are gradually expanding to not only voice but also data services. Current mobile communication systems have evolved to the extent that they can provide high-speed data services. However, a shortage of resources is occurring in the mobile communication system where services are currently provided, and users are demanding higher speed services. Therefore, a more advanced mobile communication system is required.

In response to these demands, several next generation mobile communication systems have been developed. The 3rd Generation Partnership Project (3GPP) is working on specifications for the Long Term Evolution-Advanced (LTE-A) of next generation mobile communication systems. LTE-A is a technology for implementing high-speed packet-based communication having a transmission rate of up to about 1 Gbps. To this end, various measures are discussed. For example, a method of multiplexing the structure of a network so that several base stations overlap service in a specific region, and a method of increasing the number of frequency bands supported by one base station are discussed. In this case, interference increases between base stations. As a method for avoiding this, a cell interference control method using a time division method and a frequency division method has been discussed.

Frequency division method is applied to LTE system and time division method is added to LTE-Advanced. In the time division method, a base station having a high transmission power does not interfere with a neighboring base station terminal in a specific subframe. In this case, downlink transmission power control of a base station with high transmission power affects system performance and a technique for this is needed.

The present invention is a technique for scheduling with a very small power to a terminal connected to a base station with a high transmission power in a subframe region for controlling interference between base stations, so that the base station can effectively schedule the terminal even when there is a large difference in transmission power between subframes. Its purpose is to.

In order to achieve the above object, the method for transmitting downlink power information of a base station according to an embodiment of the present invention, the first configuration step of configuring the downlink power information of the general subframe, not ABS (Almost Blank Suframe), ABS A second configuration step of configuring the downlink power information of the and may include transmitting the downlink power information of the ABS and downlink power information of the general subframe to the terminal.

In order to achieve the above object, the base station for transmitting the downlink power information according to an embodiment of the present invention, configures the downlink power information of the general subframe, not the ABS (Almost Blank Suframe), the downlink power of the ABS The control unit constituting the information may include a downlink power information of the ABS and a downlink power information for transmitting the downlink power information of the general subframe to the terminal.

In order to achieve the above object, the method for receiving downlink power information of a terminal according to an embodiment of the present invention, when receiving the power information receiving step of attempting to receive the downlink power information of the ABS and downlink power information of the ABS And receiving a downlink channel at the same power corresponding to the downlink power information received for the symbol for transmitting the common reference signal (CRS) and the symbol for which the CRS is not transmitted.

In order to achieve the above object, the terminal receiving the downlink power information according to an embodiment of the present invention, the receiving unit attempts to receive the downlink power information of the ABS (Almost Blank Subframe) and receives the downlink power information of the ABS In one case, the control unit may receive a downlink channel with the same power corresponding to the downlink power information received for the symbol to which the common reference signal (CRS) is transmitted and the symbol for which the CRS is not transmitted.

According to an embodiment of the present invention, when data of a terminal of a neighbor cell is received, neighbor cell interference between symbols is prevented to generate constant data interference in a subframe, and the feedback of the terminal uses a low power data channel using a power ratio. Enable scheduling of the receiving terminal.

1 illustrates a downlink frame structure and a resource structure in an OFDM system.
2a is a diagram illustrating a radio frame structure of an LTE system.
2B shows the coverage of base stations in a general subframe.
2C shows the coverage of base stations in an ABS.
3 shows transmission power of a base station.
4 illustrates downlink power information transmitted to a terminal from a base station to a base station in a general subframe and an ABS subframe.
5 illustrates an operation of a base station according to an embodiment of the present invention.
6 illustrates an operation of a terminal according to the first embodiment of the present invention.
7 illustrates downlink power control according to a second embodiment of the present invention.
8 illustrates an operation of a terminal according to the second embodiment of the present invention.
9 illustrates downlink power control according to a fourth embodiment of the present invention.
FIG. 10 illustrates a power allocation and rate matching method for actual data transmission in the case of the ABS 933 and 945.
11 is a flowchart illustrating a method for transmitting a base station according to the fourth embodiment of the present invention.
12 is a flowchart illustrating a reception method of a terminal according to a fourth embodiment of the present invention.
13 is a block diagram of a base station transmitting apparatus according to an embodiment of the present invention.
14 is a block diagram of a receiving device of a terminal according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same components are denoted by the same reference numerals as possible in the accompanying drawings. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

In addition, the terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, the inventors should use the concept of terms in order to explain their own invention in the best way. It should be interpreted as meanings and concepts corresponding to the technical idea of the present invention based on the principle that it can be properly defined.

In the following description, although the LTE (Long Term Evolution) system and LTE-Advanced (LTE-A) TDD system have been described as an example, the present invention can be applied to other wireless TDD communication systems to which base station scheduling is applied.

The OFDM transmission method is a method of transmitting data using a multicarrier, that is, a multi-carrier. The OFDM transmission scheme parallelizes a serially input symbol string and modulates each of them into a plurality of multicarriers having a mutual orthogonal relationship, that is, a plurality of subcarrier channels. It is a kind of multi carrier modulation.

This multicarrier modulation system was first applied to military high frequency radios in the late 1950s. The OFDM scheme for superimposing a plurality of orthogonal subcarriers has been developed since the 1970s, but the implementation of orthogonal modulation between multi-carriers has been a difficult problem, so there is a limit to the practical system application. However, the technology for the OFDM scheme was rapidly developed in 1971 by Weinstein et al. That the modulation and demodulation using the OFDM scheme can be efficiently processed using a Discrete Fourier Transform (DFT). In addition, the use of guard intervals and the insertion of cyclic prefix (CP) symbols into the guard intervals are known, further reducing the negative effects of the system on multipath and delay spread.

Thanks to these technological advances, OFDM technology has been adopted for Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), Wireless Local Area Network (WLAN), and Wireless Asynchronous Transmission Mode (Wireless). It is widely applied to digital transfer technologies such as Asynchronous Transfer Mode (WATM). In other words, the OFDM method has not been widely used due to hardware complexity, but recently, various digital signal processing technologies including fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) have been used. It is made possible by the development.

The OFDM scheme is similar to the conventional Frequency Division Multiplexing (FDM) scheme, but most of all, the optimal transmission efficiency is obtained by maintaining orthogonality between a plurality of tones. In addition, the OFDM scheme has high frequency usage efficiency and strong characteristics in multi-path fading, thereby obtaining optimal transmission efficiency in high-speed data transmission.

Another advantage of the OFDM scheme is that the frequency spectrum is superimposed to use the frequency efficiently. The OFDM scheme is strong against frequency selective fading, multipath fading, and can reduce the effects of Inter Symbol Interference (ISI) using a guard interval, and it is hardware equalizer. It is possible to simply design the structure, and has the advantage of being resistant to impulsive noise, which is being actively used in communication systems.

The factors that hamper high-speed, high-quality data services in wireless communication are largely due to the channel environment. The channel environment of wireless communication is based on additive white Gaussian noise (AWGN) and fading due to fading phenomenon. Change frequently due to effects, interference from other users, and multi-path signals. Therefore, in order to support high-speed and high-quality data services in wireless communication, it is necessary to effectively overcome the above-mentioned obstacles in the channel environment.

In the OFDM scheme, a modulated signal is located in a two-dimensional resource composed of time and frequency. The resources on the time axis are divided into different OFDM symbols and they are orthogonal to each other. Resources on the frequency axis are divided into different tones and they are also orthogonal to each other. That is, in the OFDM scheme, if a specific OFDM symbol is designated on the time axis and a specific tone is designated on the frequency axis, it may indicate one minimum unit resource, which is called a resource element (RE). Different REs have orthogonality to each other even though they pass through a frequency selective channel, so that signals transmitted to different REs may be received at a receiving side without causing mutual interference.

A physical channel is a channel of a physical layer for transmitting a modulation symbol modulating one or more encoded bit streams. According to an Orthogonal Frequency Division Multiple Access (OFDMA) system, a transmitting device transmits modulation symbols by configuring a plurality of physical channels according to a purpose of a transmitting information string or a receiver. The rule that the transmitter and the receiver predetermine in which RE to arrange and transmit one physical channel is called mapping or mapping.

The present invention is applicable to both Long Term Evolution (LTE) and LTE-Advanced (LTE-A) systems, and in the following description, LTE includes both LTE and LTE-A systems. Hereinafter, the system after LTE release 11 is called a Rel 11 LTE system.

1 illustrates a downlink frame structure and a resource structure in an OFDM system.

In general, the overall downlink bandwidth 101 of the OFDM system is composed of a plurality of resource blocks (RBs) 103. Each physical resource block (PRB) 103 may be composed of 12 frequency tones or subcarriers arranged on the frequency axis and 14 OFDM symbols or 12 OFDM symbols arranged on the time axis. The PRB becomes a basic unit of resource allocation. The reference signal (RS) 115 is a signal transmitted by the base station to the terminal so that the terminal can perform channel estimation. The base station and the terminal promise a transmission scheme of the RS in advance. The RS of the LTE system is classified into a common reference signal (CRS) and a dedicated reference signal (DRS) 113. One subframe 105 on the time axis consists of two slots 107 0.5 milliseconds (msec) long.

2a is a diagram illustrating a radio frame structure of an LTE system. Referring to FIG. 2, the radio frame 201 includes a total of ten subframes 205. One subframe 205 is composed of two slots 203 as described above. One subframe 205 includes a control channel region and a data channel region. In terms of time, the control channel region 209 is transmitted first, followed by the data channel region 211. The control channel region 209 and the data channel region 211 appear in every subframe 205. In the LTE system, each channel is configured according to the distance between cells and the degree of interference, and is designed to ensure appropriate reception performance.

In the LTE-Advanced system, an overlapping system in which a base station with low transmission power is additionally installed in a cell region of an LTE system in which an existing cell-to-cell spacing is applied is applied. Accordingly, when all the base stations use the same frequency band, the amount of interference in the cell area is greatly increased compared to the LTE system. In order to reduce such interference, interference control technology within a cell region is used for a base station having a high transmit power in a specific subframe on the time axis, and the base station having a low transmit power schedules a terminal at a cell boundary in a corresponding subframe. Control techniques are applied. Such subframes are called ABS (almost blank subframe).

The base station with high transmit power does not transmit the power of all REs except the common reference signal (CRS) to the ABS or transmits very low power, so the interference to neighboring base stations is reduced to the ABS. However, the power of the common reference signal should be kept the same as the general subframe in the ABS. This is because the existing LTE terminal to which the ABS technology is not applied cannot know whether the ABS exists and the LTE terminal must acquire channel estimation information from the common reference signal of all subframes. When the power of the common reference signal of a specific subframe is changed, feedback of the UE becomes inaccurate and it is difficult for the base station to schedule. Therefore, information on which subframe is applied to the ABS in the radio frame is used to exchange information between base stations without informing the terminal.

2B shows the coverage of base stations in a general subframe.

2C shows the coverage of base stations in an ABS.

When the third, fourth, sixth, and seventh subframes of the radio frame 201 are configured by the ABS 215, information on the configuration of the ABS is transmitted to an adjacent base station. At this time, the base station 217 having a large transmission power and the base station 223 having a small transmission power schedule the base station based on the received ABS information. In the general subframe region 213 that does not correspond to the ABS, the base station 217 having a large transmission power schedules a terminal in its cell region 219. In the general subframe region 213, the base station 223 having a small transmission power schedules only the terminal 221 near the base station in consideration of interference due to a base station having a large transmission power. In the subframe 215 composed of ABS, the base station 217 having a large transmission power hardly serves a terminal because it uses little transmission power. In the ABS 215, the base station 223 having a small transmit power may also schedule the terminal 231 within a wider range.

If the base station 217 having a large transmission power does not schedule the UE in the ABS 215, it does not use the allocated frequency for a predetermined time. This is a factor that lowers the overall system capacity. Thus, to prevent this, ABS is applied simultaneously with cell range expansion (CRE). The CRE schedules, from the base station 223 having a low transmission power, terminals that can connect to the base station 223 having a low transmission power when there is no interference from the base station 217 among the terminals in the region of the base station 217 having a high transmission power. The technology that the system controls to receive. In addition, according to the CRE, such a terminal may schedule only the ABS 215 to increase the area of the base station 223 having a low transmission power, thereby increasing the capacity compared to the transmission power and increasing the total network capacity. That is, a plurality of base stations 223 having small transmission powers schedule a time during which the base station 217 having large transmission powers cannot be scheduled, thereby increasing the overall system capacity.

Since the ABS and the CRE technologies are composed of coordination between cells in the network, the terminal is not aware of the application of the technique, and the terminal is scheduled from the low base station 223 instead of the high base station 217 according to the command of the base station. . Even in the LTE-A terminal to which the corresponding technology can be applied, the base station does not inform the terminal of the presence of ABS. However, the base station distinguishes and informs two channel measurement resources for feedback of the LTE-A terminal and implements the ABS 215 to be included in any measurement resource. Accordingly, the base station may perform separate scheduling through two feedbacks of the terminal. Since the two channel measurement resources have information on channels experiencing different interference, the base station can schedule using these two channel measurement information.

3 shows transmission power of a base station. Referring to FIG. 3, the base station delivers three pieces of transmit power information to the terminal for downlink transmission. The three pieces of information are P _C , P _A , and P _B , respectively, and their definitions are shown in Equations 1, 2, and 3, respectively.

&Quot; (1) "

P _C = CRS power (cell specific), (value range: -60dBm to 50dBm)

&Quot; (2) "

P _A = ρ _A -δ _offset (ρ _A Value: -6dB, -4.77dB, -3dB, -1.77dB, 0dB, 1dB, 2dB, 3dB)

&Quot; (3) "

P _B = ρ _B / ρ _A

P _C 307 is a power of the CRS transmitted by the base station to one RE and is a value that is equally applied to all terminals in the cell. P _A is equal to ρ _A without considering δ _offset . ρ _A represents a ratio between the RE power 307 through which the CRS is transmitted and the power 309 through which the data RE is transmitted in the data symbol 311 without the CRS, as shown in Equation 4, and have a different value for each terminal.

&Quot; (4) "

ρ _A = P _{D_noCRS} / P _C

ρ _B represents the ratio of the RE power 307 through which the CRS is transmitted and the power 315 through which the data RE is transmitted in the data symbol 313 having the CRS, as shown in Equation 5 below.

&Quot; (5) "

ρ _B = P _{D_CRS} / P _C

P _B is the ratio of ρ _B and ρ _A as Equation 3, and means the power ratio of the data RE without the CRS and the data RE without the RE. P _B is transmitted as 2-bit information through higher signaling, and is defined as shown in Table 1 according to the number of ports of the CRE currently used by the base station.

P _B ρ _B / ρ _A Antenna port 1 Antenna port 2 or 4 0 One 5/4 One 4/5 One 2 3/5 3/4 3 2/5 1/2

The terminal uses these three pieces of information for two purposes.

First, the terminal uses this information as information for compensating for the power difference of the receiver caused by the power difference between a symbol having a CRS and a symbol not having a CRS during demodulation. This information is essential when received power affects demodulation much, such as quadrature amplitude modulation (16QAM) or 64QAM.

Second, the terminal uses this information to predict the performance difference caused by the power difference between the CRS and the data symbol. The channel estimation and reporting of the terminal is based on the CRS transmitted by the base station. Since there is a difference between the power of the CRS and the data symbol actually transmitted, the base station determines the power corresponding to the channel information reported by the terminal and the data symbol actually transmitted. The decoding and modulation technique suitable for the terminal is selected in consideration of the power difference of. Accordingly, in the absence of the above-described information, the base station cannot select a decoding and modulation suitable for the channel of the terminal, and the terminal cannot apply a modulation scheme having a high coding rate.

In the general subframe 301, the terminal performs reception and channel estimation using the information received from the base station. On the other hand, in the ABS (303, 305), the base station can perform two types of transmission. First, when the base station does not use any power except for the CRS (303), the power is zero in all data REs except for the CRS (317, 323). In this case, the terminal attempts to receive the control channel once as in the case of the general subframe 301, but since there is no channel actually transmitted, the terminal terminates the reception at the ABS without additional data channel reception.

When the base station transmits the actual data at very small power in the ABS (305), the terminal receives the data using the received P _C , P _A , P _B information. The actual transmit power 325 is very small and a value different from P _A is received. Since the actual transmit power P _{D_noCRS} 325 is different, a value different from the actual value is calculated even when the transmit power P _{D_CRS} 331 is calculated based on P _B. Therefore, when the base station transmits using QAM, the terminal generates a reception error. In addition, the base station transmits at a very low decoding rate because the base station does not know the decoding rate suitable for the terminal when transmitting at a low power (305). In addition, as described above, since the base station cannot use a modulation technique in which the ratio of power reception such as QAM is important, only the QPSK transmission can be used, and it is difficult to transmit at an accurate decoding rate. Therefore, it is very difficult to actually transmit a channel from the ABS to the terminal.

However, in a real environment, it is not necessary to perform scheduling in ABS in the same way to all terminals. In fact, even though several terminals are located in the same position from the cell, there are terminals in which a base station with a small transmission power is close according to the surrounding environment, and a terminal which does not exist. Therefore, the maximum performance should be transmitted using the highest decoding and modulation rate within each terminal as long as it does not interfere with neighboring cells as much as possible. Therefore, even if the base station transmits a data channel with a small power in the ABS, power control information for the terminal to receive with the same performance as the normal subframe should be transmitted from the base station to the terminal.

4 illustrates downlink power information transmitted to a terminal from a base station to a base station in a general subframe and an ABS subframe. According to the first embodiment of the present invention, the base station delivers the configuration of the ABS subframe to the terminal. In addition, the base station transmits the existing P _C 405, P _A , P _B to the terminal for compatibility of the existing system in the general subframe 401.

The terminal receives the data channels 407 and 411 and estimates the channel. The base station additionally transmits P _{A_R11} to control the data channel power in the ABS 403. P _{A_R11} means power of the data channel in the ABS subframe. In _practice, the transmission of P _{A_R11} may be transmitted in one of a function of a relative value of P _A transmitted in a general subframe, an absolute value of P _{A_R11} transmission power, or an offset value for CRE. It is _assumed that the terminal receives the data channels 415 and 419 using P _{A_R11} when receiving the data channel from the ABS 403 and P _B in the ABS is always 1. That is, in the _{ABS (403) P D_noCRS (417} ) and P _{D_CRS} (421) is always assumed to be the same power.

In the existing subframe 401, since the symbol 411 for transmitting the CRS is distinguished from the symbol 407 for which the CRS is not transmitted, information about P _B is required. In general, the power 405 used for the CRS is large. Therefore, in the case of the symbol 411 in which the CRS is transmitted, the remaining power 413 used in the CRS is used in the data RE, but in the case of the symbol 407 in which the CRS is not transmitted, the total power 409 of the base station is measured. Share everything. Therefore, the power of the data RE appears larger in the symbol 407 where the CRS is not transmitted.

However, since the ABS 403 sets the data power very low, there is no problem that the power is lowered than the symbol 417 without the CRS in the symbol 421 where the CRS exists due to insufficient power due to the CRS. In addition, each symbol to a terminal of a neighboring cell if the transmitted using a different power for each symbol as in the P _{D_noCRS} (409) and P _{D_CRS} (413) to act as interference to the ABS of the data symbol is smaller adjacent the base station end transmit power This interference changes.

In the case of applying the CRE, the small power of the base station may act as a large interference. However, if the power of the symbol 417 without the CRS and the symbol 419 with the CRS is the same as the proposed method, the demodulation performance of the receiver is further improved because there is no variation in interference felt by the UE in the neighboring cell. Performance will increase. Therefore, in the ABS 403 which transmits with little power without shortage of power, it is necessary to transmit without difference in power between symbols.

Table 2 shows an example of higher signaling when P _{A_R11} is transmitted with a relative value of P _A. This can be configured differently according to the transmission method transmitted.

- ASN1START

PDSCH-ConfigCommon :: = SEQUENCE {
referenceSignalPower INTEGER (-60..50),
pb INTEGER (0..3)
}

PDSCH-ConfigDedicated :: = SEQUENCE {
pa ENUMERATED {
dB-6, dB-4dot77, dB-3, dB-1dot77,
dB0, dB1, dB2, dB3}
}

PDSCH-ConfigDedicated-r11 :: = SEQUENCE {
pa-r11 ENUMERATED {
dB-INF, dB-12, dB-11, dB-10, dB-9, dB-7.23,
dB-6, dB-4.23, dB-3, FFS}
}
- ASN1STOP

5 illustrates an operation of a base station according to an embodiment of the present invention. 5 is a base station operation that can be equally applied to all embodiments of the present invention.

Referring to FIG. 5, in step 501, the base station configures downlink power control information for scheduling in the ABS in the R11 terminal. The power control information may include power control information as described with reference to FIGS. 3 and 4. Thereafter, in step 503, the base station transmits the power telegram configured in the R11 terminal to the terminal through higher signaling. Thereafter, in step 505, the base station performs downlink data channel scheduling to the terminal using the configured power information.

6 illustrates an operation of a terminal according to the first embodiment of the present invention. Referring to FIG. 6, in step 601, a terminal receives power control information for a downlink data channel through higher signaling from a base station. The power control information may include, for example, P _{A_R11} described above. In step 603, the UE separates and receives the power control information for the general subframe and the power control information for the ABS from the received power control information. In step 605, the UE demodulates using the received P _{A_R11} value to receive the data channel in the ABS and assumes that P _B for receiving the ABS is always 1 and demodulates.

7 illustrates downlink power control according to a second embodiment of the present invention. FIG. 7 illustrates an additional operation of the terminal when the downlink control information for the ABS described in the first embodiment is not configured.

According to the second embodiment of the present invention, the base station transmits configuration information of the ABS to the terminal, and the base station configures and transmits power control information for the ABS for each terminal. If the power control information for the ABS is configured for the terminal, the general subframe 701 transmits the existing P _C 707, P _A , P _B to the terminal for compatibility of the existing system. The terminal receives the data channels 709 and 713 and estimates the channel. The base station additionally transmits P _{A_R11} to control the data channel power in the ABS 703. P _{A_R11} refers to the power of the data channel in the ABS subframe. P _{A_R11} may be transmitted in any one of a function of a relative value of P _A transmitted in a general subframe, an absolute value of transmit power of P _{A_R11} , or an offset value for CRE. The terminal receives the data channels 717 and 721 using P _{A_R11} when the data channel is received by the ABS 703, and P _B in the ABS is always assumed to be 1.

On the other hand, if the power control information for the ABS is not configured for the terminal (705), in the general subframe 701 for the compatibility of the existing system through the existing data channel (P _C 707, P _A , P _B ) 709 and 713 are received and the channel is estimated. Assume that P _A in ABS has a negative infinity value 727 and P _B is always one.

In this way, the R11 terminal may or may not perform a reception operation in the ABS depending on whether power control information for ABS is configured. When the location of a specific terminal greatly affects the transmission to the neighboring terminal, the specific terminal may prevent interference by not configuring power control information for the ABS in the specific terminal. In addition, even though the terminal is not actually transmitted in the ABS as in the past, it is possible to prevent the demodulation operation to prevent data power consumption.

Table 3 shows an example of higher signaling according to whether power control information for ABS is configured. This can be configured differently according to the information transmission method.

- ASN1START

PDSCH-ConfigCommon :: = SEQUENCE {
referenceSignalPower INTEGER (-60..50),
pb INTEGER (0..3)
}

PDSCH-ConfigDedicated :: = SEQUENCE {
pa ENUMERATED {
dB-6, dB-4dot77, dB-3, dB-1dot77,
dB0, dB1, dB2, dB3}
}

PDSCH-ConfigDedicated-r11 :: = CHOICE {
Release NULL,
Setup SEQUENCE {
pa-r11 ENUMERATED {
dB-INF, dB-12, dB-11, dB-10, dB-9, dB-7.23,
dB-6, dB-4.23, dB-3, FFS}
}
}
- ASN1STOP

When the terminal does not have the power information configuration in the ABS, the following four examples of the operation of the terminal is possible. In the first method, the UE attempts to receive a data channel using power control information received in a general subframe in the ABS as in the conventional method. In the second method, the UE attempts reception only for the uplink control channel and the downlink response channel. This is because the base station can continue scheduling because the ABS does not exist. The third method is a method in which a UE attempts to receive a downlink response channel. This is because even though the ABS is configured, the transmission of the uplink actually occurs because in this case, the reception of the response channel is required even if the control channel is not transmitted. The fourth method is that the terminal does not perform any operation in the ABS when the power control information of the ABS is not configured. In this case, the terminal may reduce power consumption by not performing unnecessary operations.

When the base station attempts to schedule the terminal in the ABS based on the transmitted information, the base station should not only transmit power information to the corresponding terminal but also prevent interference with the terminal of the neighboring cell. As proposed in the present invention, while using the method of improving the performance of the terminal demodulator by setting the same power for each symbol, the base station must additionally adjust the amount of interference generated in the neighbor cell in the ABS. The amount of interference may be adjusted based on power control information that the base station notifies the terminal. The amount of such interference information should be transmitted to neighboring cells together with relative narrow TX power restrictions (RNTP) indicating the amount of interference occurring for each frequency in the existing general subframe. Therefore, the base station should inform the amount of interference generated in the ABS based on the ABS power control information together with the RNTP for each PRB. This may be performed by delivering a new RNTP applied to the ABS as in the past or transferring one representative value applied to the ABS to the neighboring base station together with the existing RNTP.

8 illustrates an operation of a terminal according to the second embodiment of the present invention. Referring to FIG. 8, in step 801, a terminal receives power control information of a downlink data channel through higher signaling from a base station. In step 803, the terminal extracts and receives power information for ABS reception from the received power information.

In step 805, the UE determines whether the ABS power information is configured, that is, whether the ABS power information has been successfully received. If the ABS power information has been configured, the process proceeds to step 807. In step 807, the UE receives the data channel from the ABS on the assumption that P _{A_R11} is used and P _B is 1 to receive the data channel from the ABS. If the terminal determines that power information for the ABS is not configured in step 805, the process proceeds to step 809. In step 809, the UE uses i) power information received for an existing general subframe to receive a data channel in the ABS, or ii) receives only an uplink control channel and a downlink response channel, or iii) a downlink response. Only channels can be received. In the case of the control channel and the response channel, only QPSK transmission and one decoding rate are available, so that it can be received with inaccurate power information.

According to the third embodiment of the present invention, the base station may configure power control information including two maximum transmit power values. One of the maximum transmit power values is the maximum transmit power used for the normal subframe and the other is the maximum transmit power used by the ABS. Also, based on this value, the base station configures two different values of P _A and P _B. If the P _B value is negative infinity (-INF), the base station does not transmit the CRS interference information of the neighbor cell to the terminal, and the terminal does not use the entire symbol for transmitting the CRS for data reception. If the P _B value is not negative infinity, the UE receives the CRS interference information of the neighbor cell and receives only the data symbols of the symbols from which the CRS is transmitted.

The reason why the base station configures power control information including two maximum transmit power values is as follows. The base station allocates power between REs in the form of a ratio of relative power to maximum power, which can only be lowered down to -6 dB. Thus, even if the base station tries to transmit with low power for the ABS, it cannot be lowered below -6dB. However, since the total power used by ABS is less than that of general subframe, the maximum transmit power used by ABS can be configured separately and the ABS can transmit with low transmit power. In addition, this information is transmitted to the terminal through P _{A_R11} and P _{B_R11} . In addition, it transmits information on the position of the symbol not used for reception for interference control of the terminal receiver. In other words, as shown in Table 5, P _{B_R11} , P _{A_R11} , and CRS_interferenceINFO information are transmitted. Each interpretation is as follows. First, P _{B_R11} is shown in Table 4 below. Compared with the conventional P _B , the negative infinity (-INF) value was added. When the base station configures a new maximum transmit power for the ABS, if the power is less than the maximum power used for the CRS, power cannot be allocated to the PDSCH data RE of the symbol where the CRS is transmitted. Thus, a value that means that the symbol to which the CRS is transmitted is not used is a negative infinity value. Therefore, interference information of the CRS by neighboring cells is also unnecessary.

P _B ρ _B / ρ _A Antenna port 1 Antenna port 2 or 4 0 One 5/4 One 4/5 One 2 3/5 3/4 3 2/5 1/2 4 1/5 1/3 5 -INF -INF

As _described in the first and second embodiments, P _{A_R11} may be either a relative value for P _A value or a relative value for CRS in a general subframe.

The CRS_interferenceINFO information represents CRS information of a neighbor cell which has strong interference to the UE. The CRS_interferenceINFO information is an offset value indicating the total number of CRS interferences, the number of antenna ports generating each CRS interference, and the actual CRS location. The offset value means +1 for 0, +2 for 1, and +1 and +2 for 2 based on the offset value used by the cell to which the cell is connected.

That is, the base station configures two P _A and P _B values. If the value of P _B for ABS is negative infinity, the base station does not transmit CRS interference information. If the value of P _B for ABS is not negative infinity, the base station transmits CRS interference information. This information includes CRS location information needed by the receiver to eliminate interference.

- ASN1START

PDSCH-ConfigCommon :: = SEQUENCE {
referenceSignalPower INTEGER (-60..50),
pb INTEGER (0..3)
pb-r11 INTEGER (0..5)

}

PDSCH-ConfigDedicated :: = SEQUENCE {
pa ENUMERATED {
dB-6, dB-4dot77, dB-3, dB-1dot77,
dB0, dB1, dB2, dB3}
}

PDSCH-ConfigDedicated-r11 :: = SEQUENCE {
pa-r11 ENUMERATED {
dB-INF, dB-12, dB-11, dB-10, dB-9, dB-7.23,
dB-6, dB-4.23, dB-3, FFS}
CRS_Interference CRS_interferenceINFO
}
CRS_interferenceINFO :: = SEQUENCE {// optional
NumberOfInterferer INTEGER (0..2)
NumberOfPort ENUMERATED {1, 2, 4}
Offset INTEGER (0..2)
}
- ASN1STOP

9 illustrates downlink power control according to a fourth embodiment of the present invention. Referring to FIG. 9, the base station schedules data by indicating a P _{B_R11} value or a data transmission mode among power information in the ABS. The base station instructs the terminal P _{A_R11} , which is a P _B value in ABS, to negative infinity (-INF) or transmits data by rate matching (rate matching) without using data RE of a symbol transmitted by RS in a data transmission mode. You can instruct the mode to be used. In this case, the UE calculates the entire data RE except for the data RE present in the symbol transmitted by the RS among the PRBs allocated when the data channel is received in the ABS and rate matching for receiving the TBS (Transport Block Set). for matching). Also, if the base station instructs the terminal P _{B_R11} , which is a P _B value in the ABS, to a value other than negative infinity (-INF) or does not instruct the data transmission mode very much, the terminal is allocated when receiving a data channel in the ABS. In the received PRB, the RS calculates the data RE of all symbols as all data REs regardless of transmission or not and receives the TBS.

Referring to FIG. 9, in the symbol 919 in which the CRS is transmitted, the transmit power of the CRS is P _C 913 and the data symbol power of the symbol 919 in which the CRS is transmitted is P _{D_CRS in the general subframe 921.} (915). In the symbol 917 where the CRS is not transmitted, the power of the data symbol is P _{D_noCRS} 911. At this time, the base station informs the UE of the power ratio of the data symbols for which the CRS is not transmitted to the CRS power to P _A , and informs the UE of the data symbol power ratio for the symbol with the CRS to the data symbol power for the symbol without the CRS to P _B. .

In the case of transmitting to the UE with low transmission power as in the ABS 933, the allocable power may be considered. In this case, as shown in FIG. 7, if the power is reduced by 1dB compared to the existing 46dBm transmission power, the base station transmits the total transmission power to 41dBm, and if the 5dB is decreased, the base station transmits 100% of its power to the power transmitted to the CRS in the symbol where the CRS is transmitted. No power is available for the data symbols. In this case, power may be allocated to a corresponding data symbol in a symbol in which the CRS is not transmitted, because the power used for the CRS may be used in the data channel. That is, a difference in power that can be allocated to the data RE occurs according to the presence of the CRS, and when the base station reduces the transmit power by 5 dB or more, the symbol to which the CRS is transmitted has no power allocated to the data symbol. Therefore, P _{A_R11} value for ABS should be informed to the UE as a low value, indicating that the transmit power is lowered, and P _{B_R11} value should indicate that there is no power of the data symbol in the symbol to which the CRS is transmitted. INF), the UE recognizes that power is not allocated to the data RE in the ball where the CRS is transmitted. Therefore, when the base station indicates P _{B_R11} as negative infinity (-INF), the symbols transmitted to the CRS cannot be used in the data channel. Therefore, it is necessary to transmit rate matching so that the corresponding resources are not included in the data transmission. It can increase. Therefore, when the terminal is _indicated as negative infinity (-INF) at P _{B_R11} , the terminal recognizes that the symbol to which the CRS is transmitted is not used for data transmission and determines that the base station transmits by rate matching. Receive. If the base station indicates P _{B_R11} to a value other than the negative infinity (-INF) value, the base station can transmit the data of the symbol to which the CRS is transmitted at a small power. It is advantageous in terms of transmission efficiency and performance. Accordingly, the terminal determines the total number of data REs included in the actual data transmission using the P _{B_R11} value indicated by the base station. The present invention includes that the UE can indicate a transmission method for whether the base station is used for data channel transmission of a symbol in which a CRS is transmitted during data transmission in ABS by using separate signaling instead of P _{B_R11} value. Table 7 shows an example of higher signaling indicating the corresponding information to the terminal using P _{A_R11} and P _{B_R11} . Table 8 shows how to interpret the value of P _{B_R11} and includes the negative infinity (-INF) value according to the number of antennas. Table 9 shows an example of indicating a data transmission method proposed by the present invention using a separate indicator other than P _{B_R11} . The table illustrated in the present invention is one of many examples included in the method proposed by the present invention, and other signaling methods for the same purpose are possible.

If operating as in the fourth embodiment of the present invention, the base station can be applied to the data transmission method of three cases in the ABS when the power is reduced and transmitted in the ABS. The ABS 933, 945, 957 in FIG. 9 are each it. Referring to FIG. 9, not the base station is in the ABS (933) notifies the P and P _{A_R11 B_R11} the terminal P _{B_R11} negative infinity (-INF) of. In this case, the base station transmits at a lower power than the case of the general subframe 917 in the symbol 929 in which the CRS is not transmitted, and informs the terminal of this in the form of P _{A_R11} . In addition, since the symbol 931 in which the CRS is transmitted allocates a large amount of power to the CRS 925, the power to be allocated to the data symbol is reduced, and P _{B_R11} is indicated by a small value to the data RE power 923 in the symbol without the CRS. Indicated by the power ratio to. On the other hand, when the base station indicates P _{B_R11} as negative infinity (-INF) (945), the data power 935 of the symbol without CRS is the data power 929 of the symbol without CRS in FIG. 933. Can be sent equal to or lower than However, the symbol 943 in which the CRS is present informs the UE through P _{B_R11} that there is no power for data RE. In addition, the terminal instructed thus determines that the corresponding symbol 943 is not used for data transmission but is rate-matched and demodulated. On the other hand, the base station may not perform scheduling in the ABS. In this case, the base station may not transmit regardless of the P _{A_R11} indicated by the base station. In this case, the terminal is not scheduled in the ABS by indicating P _{A_R11} as negative infinity (-INF). You can dictate that you are.

FIG. 10 illustrates a power allocation and rate matching method for actual data transmission in the case of the ABS 933 and 945. Reference numeral 1003 denotes a case where the base station instructs P _{B_R11} to a value other than negative infinity (-INF) when the base station transmits a data channel to the terminal with low transmission power in the ABS. Accordingly, the resource for data transmission is rate-matched so that both the symbol 1013 with CRS and the symbol 1011 without CRS are used, and the corresponding RE is utilized for a given data transmission. Therefore, the actual power is very low in the symbol with CRS as shown in 1031, and in the symbol without CRS as shown in 1011, the power used for the CRS is transmitted for data transmission and transmitted at a higher power. do. The terminal is used to receive data even when the power of the data symbol in the CRS is very low even during reception. On the other hand, when P _{B_R11} is _indicated as negative infinity (-INF), the base station transmits data by subtracting this resource and rate matching the data RE in the symbol with CRS as shown by reference numeral 1019. . Accordingly, the power transmits a symbol having a CRS as shown by reference numeral 1019 only CRS, and a data symbol as shown by reference numeral 1017 in a symbol without CRS. In the case of the reference numeral 1007, since P _{A_R11} can be set lower than the reference numeral 1003 and transmitted, it is necessary to use the method of the reference numeral 1003 in order to transmit at a very low power.

11 is a flowchart illustrating a method for transmitting a base station according to the fourth embodiment of the present invention. Referring to FIG. 11, in step 1101, the base station configures a general subframe and maximum transmission power information and downlink power control information used in the ABS to schedule the terminal in the ABS. In the next step 1103, the base station transmits power control information configured in the terminal to higher signaling or transmits a transmission method used in the ABS to higher signaling. The transmission method refers to an indicator for determining whether to transmit by matching any RE without including any RE. For convenience, the rate matching including the data RE to which the CRS is transmitted is called Method A, and the rate matching without including the data RE to which the CRS is transmitted is called Method B. In the next step 1105, the base station sets P _{B_R11} to a negative infinity (-INF) in the configured power control information and indicates whether to use the method B. In the configured power control information, P _{B_R11} is indicated by setting to negative infinity (-INF), or when using the method B, the base station performs rate matching except for the data RE of the symbol with the CRS when transmitting data from the ABS in step 1107. To transmit the data. Otherwise, the base station transmits data by rate matching including the data RE of the symbol with the CRS during data transmission in the ABS as shown in step 1109.

12 is a flowchart illustrating a reception method of a terminal according to a fourth embodiment of the present invention. Referring to FIG. 12, in step 1201, the terminal receives power control information or information on a transmission method for receiving a data channel in a normal subframe and an ABS from a base station through higher signaling. If P _{B_R11} received by the UE in step 120 is negative infinity (-INF) or configured using Method B, the UE performs rate matching except for data RE of the symbol with CRS when receiving data in ABS in step 1205. Otherwise, the terminal receives the data channel in the data channel region allocated by rate matching including the data RE of the symbol with the CRS.

Total eNB TX power (dBm) 46 45 44 43 42 41 a total CRS power (W) 12.61915 12.61915 12.61915 12.61915 12.61915 12.61915 b Total eNB TX power (W) 39.81072 31.62278 25.11886 19.95262 15.84893 12.58925 c Remainig TX power (W) (b-a) 27.19157 19.00363 12.49972 7.333476 3.229785 -0.02989 d Maximum PDSCH RE EPRE with CRS (dBm) 18.32374 16.76777 14.9484 12.6325 9.071136 -INF e CRS EPRE (dBm) 18 18 18 18 18 18 f Rho _B (dB) (d-e) 0.323743 -1.23223 -3.0516 -5.3675 -8.92886 -INF g Maximum PDSCH RE EPRE without CRS (dBm) 18.21849 17.21849 16.21849 15.21849 14.21849 13.21849 h Rho_A (dB) (g-e) 0.218487 -0.78151 -1.78151 -2.78151 -3.78151 -4.78151 i P_B (f-h) 0.105255 -0.45072 -1.27009 -2.58599 -5.14735 -INF j P_B (linear of i) 1.024532 0.901421 0.746434 0.551317 0.305678 -INF k P_A (dB) (g-e) 0.218487 -0.78151 -1.78151 -2.78151 -3.78151 -4.78151

- ASN1START

PDSCH-ConfigCommon :: = SEQUENCE {
referenceSignalPower INTEGER (-60..50),
pb INTEGER (0..3)
pb-r11 INTEGER (0..7)

}

PDSCH-ConfigDedicated :: = SEQUENCE {
pa ENUMERATED {
dB-6, dB-4dot77, dB-3, dB-1dot77,
dB0, dB1, dB2, dB3}
}

PDSCH-ConfigDedicated-r11 :: = SEQUENCE {
pa-r11 ENUMERATED {
dB-INF, dB-13, dB-12, dB-11, dB-10, dB-9,
dB-8, dB-7}
}
- ASN1STOP

P _B ρ _B / ρ _A Antenna port 1 Antenna port 2 or 4 0 One 5/4 One 4/5 One 2 3/5 3/4 3 2/5 1/2 4 1/5 1/3 5 -INF 1/4 6 RESERVED 1/8 7 RESERVED -INF

- ASN1START

PDSCH-ConfigCommon :: = SEQUENCE {
referenceSignalPower INTEGER (-60..50),
pb INTEGER (0..3)
RateMatching BOOLEAN

}

PDSCH-ConfigDedicated :: = SEQUENCE {
pa ENUMERATED {
dB-6, dB-4dot77, dB-3, dB-1dot77,
dB0, dB1, dB2, dB3}
}

PDSCH-ConfigDedicated-r11 :: = SEQUENCE {
pa-r11 ENUMERATED {
dB-INF, dB-13, dB-12, dB-11, dB-10, dB-9,
dB-8, dB-7}
}
- ASN1STOP

In order to adjust inter-cell interference in the ABS _including P _{A_R11} and P _{B_R11} described above, one base station can transmit downlink power information to another base station through inter-cell communication. At this time, P _{B_R11} value is configured for the P _{A_R11} value and each cell is configured for each mobile station to be transmitted along with the downlink power information used by existing regular subframe. The existing power control value P _A is included in the RNTP message and is transmitted to the neighbor cell together with P _B. The value of P and P _{A_R11 B_R11} proposed by the present invention are to be transmitted with a cell adjacent to the existing P _A and P _B. Therefore, P _{A_R11} consists of a new RNTP and should be transmitted together with P _{B_R11} . If P _{B_R11} of the neighbor cell is configured as 0, it means that the data symbol to which the CRS is transmitted is not used by the neighbor cell, and thus information that there is no interference by the neighbor cell is additionally transmitted. Therefore, transmitting P _{B_R11} is very important in ABS. This is because the scheduler can improve the data reception performance of the neighboring cell terminal by using the interference information on the symbol in an area sensitive to inter-cell interference such as ABS. Existing P _A is defined as in Equation 6 below.

&Quot; (6) "

That is, when the value of the RNTP indicated in units of PRB is 0, the neighboring cell indicates that the corresponding PRB does not exceed the indicated RNTP _threshold value. On the other hand, a PRB whose RNTP value is indicated as 1 means that it is transmitted without such a restriction.

P _{A_R11} may also be indicated in two ways through _RNTP . In the first method, as indicated by P _A , 0 indicates that the corresponding PRB does not exceed a specific transmission power. When 1 indicates that the PRB is transmitted without power limitation. See Equation 7.

&Quot; (7) "

Alternatively, as shown in Equation 8, when the RNTP value of the PRB of the ABS is 0, it means that the transmission does not exceed a specific power. Infinity of (-INF) means that no interference from the PRB. This is because in the case of ABS, most PRBs do not transmit power, and only a few PRBs transmit a low power to a neighboring cell, so that a specific PRB does not use power of a specific PRB at all, rather than being transmitted without power limitation. It is more informative. See Equation 8.

<Equation 8>

13 is a block diagram of a base station transmitting apparatus according to an embodiment of the present invention. Referring to FIG. 13, the base station controller 1309 controls the overall operation of the base station. The encoder 1301 encodes and transmits data for transmission to the modulator 1303. The modulator 1303 modulates the received data and transmits the modulated data to the mapper 1305. CRS 1307 is also passed to mapper 1305. The mapper 1305 allocates the data received from the modulator 1303 and the CRS 1307 to the physical region to be actually transmitted. In addition, the power allocator 1311 transmits power of a data channel transmitted based on downlink power control information transmitted to the terminal. The power amplifier 1313 amplifies the data channel, and the transmitter 1315 transmits the amplified data channel.

14 is a block diagram of a receiving device of a terminal according to an embodiment of the present invention. Referring to FIG. 14, the receiver 1401 receives a data channel and delivers it to the demapper 1403. The demapper 1403 extracts the channel assigned to it from the received channel. Channel estimator 1411 estimates the channel. The controller 1413 controls the gain controller 1405 to adjust the gain for each symbol together with the channel estimation information by using the received downlink power information. The gain controller 1405 adjusts the received downlink power information. The gain for each symbol is adjusted together with the channel estimation information. The adjusted signal is passed to demodulator 1407. The demodulator demodulates the received signal and delivers it to the decoder 1409. The decoder 1409 decodes the received signal.

Claims (14)

In the downlink power information transmission method of a base station,
A first configuration step of configuring downlink power information of a general subframe that is not ABS (Almost Blank Suframe);
A second configuration step of configuring downlink power information of the ABS; And
And transmitting downlink power information of the ABS and downlink power information of the general subframe to the terminal. The method of claim 1,
The second configuration step,
And configuring a relative value of the downlink power value of the ABS to the downlink power value of the general subframe as the downlink power information of the ABS. The method of claim 1,
The second configuration step,
And configuring the absolute value of the downlink power value of the ABS as the downlink power information of the ABS. The method of claim 1,
Transmitting relative narrow TX power restrictions (RNTP) of the general subframe and RNTP of ABS to an adjacent base station. A base station for transmitting downlink power information,
A control unit configured to configure downlink power information of a general subframe other than the ABS (Almost Blank Suframe), and configure downlink power information of the ABS; And
A base station comprising a transmitter for transmitting downlink power information of the ABS and downlink power information of the general subframe to the terminal. The method of claim 5,
The control unit,
And a relative value of the downlink power value of the ABS to the downlink power value of the general subframe as the downlink power information of the ABS. The method of claim 5,
The control unit,
And an absolute value of the downlink power value of the ABS is configured as downlink power information of the ABS. The method of claim 5,
The transmitter base station, characterized in that for transmitting the relative narrow TX power restrictions (RNTP) of the general subframe and the RNTP of the ABS to the adjacent base station. In the method for receiving downlink power information of a terminal,
A power information receiving step of attempting to receive downlink power information of an Almost Blank Subframe (ABS); And
In case of receiving downlink power information of the ABS, the downlink channel is received at the same power corresponding to the downlink power information received for the symbol to which the common reference signal (CRS) is transmitted and the symbol for which the CRS is not transmitted. Power information receiving method comprising the channel receiving step. 10. The method of claim 9,
And receiving only a downlink response channel in the ABS when the downlink power information of the ABS is not received. 10. The method of claim 9,
The downlink power information includes a relative value of the downlink power value of the ABS with respect to the downlink power value of the general subframe. A terminal for receiving downlink power information,
A receiver which attempts to receive downlink power information of an Almost Blank Subframe (ABS); And
In case of receiving downlink power information of the ABS, the downlink channel is received at the same power corresponding to the downlink power information received for the symbol to which the common reference signal (CRS) is transmitted and the symbol for which the CRS is not transmitted. Terminal comprising a control unit. The method of claim 12,
If the control unit does not receive the downlink power information of the ABS, characterized in that the terminal receives only the downlink response channel. The method of claim 12,
The downlink power information includes a relative value of the downlink power value of the ABS with respect to the downlink power value of the general subframe.

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