WO2010101433A2

WO2010101433A2 - Method and device for signal transmission on a multiple antenna system

Info

Publication number: WO2010101433A2
Application number: PCT/KR2010/001378
Authority: WO
Inventors: 고현수; 이문일; 정재훈; 한승희; 권영현
Original assignee: 엘지전자주식회사
Priority date: 2009-03-05
Filing date: 2010-03-05
Publication date: 2010-09-10
Also published as: WO2010101433A3

Abstract

A method for signal transmission on a multiple antenna system comprises the steps of: receiving power amplifier setting information from a base station; altering the setting between a multiple power amplifier and a multiple antenna in accordance with the power amplifier setting information; and transmitting a signal to the base station in accordance with the altered setting; and the power amplifier setting information controls a power amplifier connected to the multiple antenna.

Description

Signal transmission method and apparatus in multi-antenna system

The present invention relates to wireless communication, and more particularly, to a method for transmitting a signal in a multi-antenna system.

Recently, multiple input multiple output (MIMO) systems have attracted attention in order to maximize performance and communication capacity of a wireless communication system. MIMO technology is a method that can improve the transmission and reception data transmission efficiency by adopting multiple transmission antennas and multiple reception antennas, away from the use of one transmission antenna and one reception antenna. The MIMO system is also called a multiple antenna system. MIMO technology is an application of a technique of gathering and completing fragmented pieces of data received from multiple antennas without relying on a single antenna path to receive one entire message. As a result, it is possible to improve the data transfer rate in a specific range or increase the system range for a specific data transfer rate.

MIMO techniques include transmit diversity, spatial multiplexing, beamforming, and the like. Transmit diversity is a technique of increasing transmission reliability by transmitting the same data in multiple transmit antennas. Spatial multiplexing is a technology that allows high-speed data transmission without increasing the bandwidth of the system by simultaneously transmitting different data from multiple transmit antennas. Beamforming is used to increase the signal to interference plus noise ratio (SINR) of a signal by adding weights according to channel conditions in multiple antennas. In this case, the weight may be represented by a weight vector or a weight matrix, which is referred to as a precoding vector or a precoding matrix.

In a conventional multi-antenna system, a base station performs multi-antenna transmission using a plurality of power amplifiers, and a terminal is considered to perform multi-antenna transmission using a single power amplifier. The power amplifier of the terminal has a predetermined maximum output (for example, the maximum output of the terminal may be 23 dBm), and uplink power control is performed according to the maximum output.

However, subsequent terminals may perform multi-antenna transmission using a plurality of power amplifiers. When the terminal uses a plurality of power amplifiers, the mapping relationship between the physical antenna transmitting the signal and the power amplifier providing the output power should be considered.

There is a need for a method for effectively transmitting a signal from a terminal using a plurality of power amplifiers in a multi-antenna system.

An object of the present invention is to provide a method for effectively transmitting a signal in a multi-antenna system.

Signal transmission method in a multi-antenna system includes the steps of receiving power amplifier configuration information from a base station; Changing a setting between a multiple power amplifier and multiple antennas according to the power amplifier setting information; And transmitting a signal to the base station according to the changed setting, wherein the power amplifier setting information includes information indicating a power amplifier connected to the multiple antennas.

In a multiple antenna system, a terminal using a plurality of power amplifiers can effectively transmit an uplink signal.

1 is a block diagram illustrating a wireless communication system.

2 shows a structure of a radio frame.

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

4 is a block diagram showing the structure of a transmitter having multiple antennas.

5 illustrates a signal transmission method in a transmitter including multiple antennas and multiple power amplifiers.

6 illustrates an example of setting up multiple antennas and multiple power amplifiers.

7 is another example illustrating the configuration of multiple antennas and multiple power amplifiers.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice and packet data.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station 20 (BS). The terminal 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device. The base station 20 generally refers to a fixed station that communicates with the terminal 10, and in other terms, such as a Node-B, a Base Transceiver System, or an Access Point. Can be called. One or more cells may exist in one base station 20.

Hereinafter, downlink (DL) means communication from the base station 20 to the terminal 10, and uplink (UL) means communication from the terminal 10 to the base station 20. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20.

The wireless communication system may be an Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) based system. OFDM uses multiple orthogonal subcarriers. OFDM uses orthogonality between inverse fast fourier transforms (IFFTs) and fast fourier transforms (FFTs). The transmitter performs IFFT on the data and transmits it. The receiver recovers the original data by performing an FFT on the received signal. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

One of the main problems with OFDM / OFDMA systems is that the Peak-to-Average Power Ratio (PAPR) can be very large. The PAPR problem is caused by the fact that the peak amplitude of the transmitted signal is much larger than the average amplitude, due to the fact that the OFDM symbol is a superposition of N sinusoidal signals on different subcarriers. PAPR is a problem especially in terminals that are sensitive to power consumption in relation to the capacity of the battery. To reduce power consumption, it is necessary to lower the PAPR.

One system proposed to lower PAPR is Single Carrier-Frequency Division Multiple Access (SC-FDMA). SC-FDMA combines Frequency Division Multiple Access (FDMA) with Single Carrier-Frequency Division Equalization (SC-FDE). SC-FDMA has similar characteristics to OFDMA in that it modulates and demodulates data in time and frequency domain using Discrete Fourier Transform (DFT), but the PAPR of the transmission signal is low, which is advantageous in reducing transmission power. . In particular, it can be said that it is advantageous for the uplink to communicate with the base station from the terminal sensitive to the transmission power in relation to the use of the battery. In the SC-FDMA system, the symbols of each antenna path are DFT spreaded and the precoded symbols are mapped to subcarriers by localized mapping or interleaved mapping in order to maintain low PAPR. The OFDM symbol may be used in the same meaning as the SC-FDMA symbol.

When the terminal transmits data to the base station, an important point is that the bandwidth of the data to be transmitted is not large, but wide coverage that can concentrate power. SC-FDMA systems allow for small amounts of signal variation, resulting in broader coverage than other systems when using the same power amplifier.

On the other hand, unlike the SC-FDMA scheme, clustered DFT-S-OFDM allocates (or maps) an M (<N) symbol string to a contiguous subcarrier among the N-DFT spread N symbol strings, and the remaining NM symbol strings are M symbol strings. It allocates (or maps) to successive subcarriers spaced apart from the assigned (or mapped) subcarriers. When using clustered DFT-S-OFDM, there is an advantage that frequency selective scheduling can be performed.

The wireless communication system may be a multiple antenna system. The multiple antenna system may be a multiple-input multiple-output (MIMO) system. Alternatively, the multi-antenna system may be a multiple-input single-output (MISO) system or a single-input single-output (SISO) system or a single-input multiple-output (SIMO) system. May be a system. The MIMO system uses multiple transmit antennas and multiple receive antennas. The MISO system uses multiple transmit antennas and one receive antenna. The SISO system uses one transmit antenna and one receive antenna. The SIMO system uses one transmit antenna and multiple receive antennas.

Techniques using multiple antennas in a multi-antenna system include a space frequency block code (SFBC), a space-time coding (STC) such as space time block code (STBC), a cyclic delay diversity (CDD), and a frequency switched (FSTD) in rank 1. transmit diversity), time switched transmit diversity (TSTD), or the like may be used. In Rank 2 or higher, spatial multiplexing (SM), Generalized Cyclic Delay Diversity (GCDD), Selective Virtual Antenna Permutation (S-VAP), and the like may be used. SFBC is a technique that efficiently applies selectivity in the spatial domain and frequency domain to secure both diversity gain and multi-user scheduling gain in the corresponding dimension. STBC is a technique for applying selectivity in the space domain and the time domain. FSTD is a technique for dividing a signal transmitted through multiple antennas by frequency, and TSTD is a technique for dividing a signal transmitted through multiple antennas by time. Spatial multiplexing is a technique to increase the data rate by transmitting different data for each antenna. GCDD is a technique for applying selectivity in the time domain and the frequency domain. S-VAP is a technique using a single precoding matrix. Multi-codeword (MCW) S, which mixes multiple codewords between antennas in spatial diversity or spatial multiplexing, and Single Codeword (SCW) S using single codeword. There is a VAP.

2 shows a structure of a radio frame.

Referring to FIG. 2, a radio frame may consist of 10 subframes, and one subframe may consist of two slots. Slots in a radio frame are numbered slots 0 through 19. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). TTI may be referred to as a scheduling unit for data transmission. For example, one radio frame may have a length of 10 ms, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms. The structure of the radio frame is merely an example, and the number of subframes included in the radio frame or the number of slots included in the subframe may be variously changed.

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

Referring to FIG. 3, an uplink slot includes a plurality of SC-FDMA symbols in the time domain and includes a plurality of resource blocks in the frequency domain. Here, one uplink slot includes 7 SC-FDMA symbols, and one resource block includes 12 subcarriers as an example, but is not limited thereto.

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

Referring to FIG. 4, the transmitter 100 includes an encoder (110-1, ..., 110-K), a mapper (120-1, ..., 120-K), a layer mapper (layer mapper). 130, a precoder 140, a resource element mapper 150-1, ..., 150-K and a signal generator 160-1, ..., 160-K. . The transmitter 100 includes Nt transmit antennas 170-1,..., 170 -Nt.

The encoders 110-1, ..., 110-K encode the input data according to a predetermined coding scheme to form coded data (hereinafter, referred to as codewords). The mappers 120-1, ..., 120-K map the codewords to modulation symbols representing positions on the signal constellation. The modulation scheme is not limited and may be m-Phase Shift Keying (m-PSK) or m-Quadrature Amplitude Modulation (m-QAM). For example, m-PSK may be BPSK, QPSK or 8-PSK. m-QAM may be 16-QAM, 64-QAM or 256-QAM.

The hierarchical mapper 130 defines a hierarchy of modulation symbols so that the precoder 140 can distribute antenna-specific symbols to the path of each antenna. The layer may be defined as an information path input to the precoder 140. The information path before the precoder 140 may be referred to as a virtual antenna or a layer.

The precoder 140 outputs an antenna specific symbol by processing the modulation symbol by a MIMO scheme according to the multiple transmit antennas 170-1,..., 170 -Nt. The precoder 140 distributes the antenna specific symbol to the resource mappers 150-1,..., 150 -K of the path of the antenna. Each information path sent by the precoder 140 to one antenna is called a stream. This may be referred to as a physical antenna.

The resource mapper 150-1,..., 150 -K assigns an antenna specific symbol to an appropriate resource element and multiplexes according to a user. The signal generators 160-1, ..., 160-K modulate the antenna specific symbols by the OFDM scheme and output a transmission signal. The signal generators 160-1,..., 160 -K may generate transmission signals in various multiple access schemes, such as OFDMA or SC-FDMA schemes. The transmission signal is transmitted through each antenna port 170-1,..., 170-Nt.

An antenna power amplifier may be included in the signal generators 160-1, ..., 160-K. Alternatively, the antenna power amplifier may be provided as a separate device from the signal generators 160-1,..., 160 -K. Here, the antenna power amplifier may be composed of two types. One is a signal amplifier (SA) and the other is a power amplifier (PA). The signal amplifier amplifies the radio signal and provides the amplified radio signal to the connected antenna. The power amplifier provides the current required by the signal amplifier. Hereinafter, the antenna power amplifier refers to a signal amplifier and the antenna power amplifier will be abbreviated as a power amplifier for convenience. In the following description, a transmitter is a part of a terminal and a receiver is a part of a base station as an example, but this is not a limitation. That is, the transmitter may be part of the base station and the receiver may be part of the terminal. In addition, the transmitter and receiver may be part of a relay station. It is assumed that the transmitter has multiple antennas and multiple power amplifiers. The maximum power of each power amplifier may be the same or different. For example, all power amplifiers may have a maximum power of 23 dBm, or may have different maximum powers such that each power amplifier has any one of 23 dBm, 20 dBm, and 17 dBm. Alternatively, a transmitter can have one power amplifier twice the maximum power of another power amplifier to support single antenna transmission. The signal amplified by the power amplifier may be transmitted through any one of multiple antennas.

The transmitter may perform MIMO transmission. MIMO transmission includes, for example, spatial multiplexing, transmit diversity, beamforming, and the like. In addition, the transmitter may perform trun-off of antennas, transmission through only one antenna among multiple antennas (for example, precoding vector switching (PVS), small delay CDD, and virtualization scheme). SIMO transmission may be performed by using, for example).

For example, suppose a terminal including a transmitter capable of performing MIMO transmission enters a system in which only a single antenna transmission is allowed in uplink transmission. In this case, the terminal may need to perform uplink communication with the system only through a single antenna transmission.

When a terminal having a low maximum power amplifier (eg, having 20 dBm and 17 dBm) enters a communication system that allows only single antenna transmission, the terminal may perform rank 1 transmission to have the same effect as the single antenna transmission. Can be. For example, if signals of the same transmission power are transmitted in all transmission antennas using the precoding vector having rank 1, the base station may receive the multi-antenna transmission of the terminal as a single antenna transmission. In addition, to support single antenna transmission, the terminal may use PVS, small delay CDD, virtualization scheme, and the like.

When a terminal having at least one maximum power amplifier (eg, a power amplifier having 23 dBm) among a plurality of power amplifiers enters a communication system that allows only a single antenna transmission, the single antenna transmission may be performed using the maximum power amplifier. . The terminal may block other antennas except one antenna among multiple antennas and use one antenna.

If the available power is limited, the transmitter may attempt to transmit data using higher power within the maximum power of the power amplifier. However, there may be a case where a signal output from an antenna to which a higher transmission power is allocated is weakened or absorbed by an obstacle in front of the antenna. In such a case, the data to be transmitted may fall short of the required power level and transmission performance. In this case, although the transmitter uses maximum power, performance degradation may occur. The power amplifier setting change can be used to solve the problem of a weak transmission power of the transmitter. Changing the power amplifier settings means resetting the mapping between the power amplifier and the physical antenna.

The configuration signal may be given from the base station to the terminal, or may be given from the terminal to the base station. When the set signal is given from the terminal to the base station, a diversity mode may be added to obtain a maximum antenna selection gain. On the other hand, when the configuration signal is given from the base station to the terminal, the terminal should be able to receive each antenna configuration signal in the uplink sounding channel.

Referring to Figure 5, the terminal transmits a signal that can be used for channel measurement to the base station (S110). For example, the terminal may transmit a sounding reference signal (SRS). The sounding reference signal is a reference signal transmitted from the terminal to the base station to measure the uplink channel state. The sounding reference signal may be transmitted through the bandwidth of all or part of the system bandwidth. The sounding reference signal is only an example, and the proposed invention may transmit other uplink signals using all or part of the system bandwidth.

The base station measures the received signal (S120). The receiver included in the base station measures the received signal. The signal used at this time may be selected from various signals such as a data signal, a data demodulation signal, a control signal, and a sounding reference signal. For example, when the sounding reference signal is selected and used, the base station can know the state of the channel experienced by each transmit antenna through measurement of the received sounding reference signal.

The measurement method of the received signal may be performed by various methods such as signal to interference plus noise ratio (SINR) and block error rate (BLER).

The base station transmits the power amplifier setting information to the terminal when the channel state is not better than the required level as a result of the measurement of the received signal (S130). For example, when the SINR value measured by the received sounding reference signal is smaller than a preset threshold value, the base station may transmit power amplifier configuration information to the terminal (or measure by the received sounding reference signal). If the BLER value is larger than the preset threshold, the base station may transmit the power amplifier setting information to the terminal, that is, the power amplifier setting information may be transmitted to the terminal when it is larger or smaller than the threshold according to the measurement method.

Here, the power amplifier configuration information means information for controlling the configuration between the multiple antennas and the multiple power amplifiers included in the terminal (ie, the transmitter). The power amplifier setting information is 1) request the terminal to change the transmit power of all transmit antennas, 2) request to change the transmit power for each transmit antenna, 3) request to switch the mapping between the transmit antenna and the power amplifier or 4) An indicator and / or index requesting a change of a mapping rule between the transmit antenna and the power amplifier may be included. The power amplifier setting information may be transmitted as an L1 / L2 signal or a higher layer signal. For example, the power amplifier configuration information may be transmitted as a physical signal through a physical downlink control channel (PDCCH) or may be transmitted through a higher layer signal such as radio resource control (RRC). The setting between the multiple antenna and the multiple power amplifier according to the power amplifier setting information will be described later in detail.

The terminal changes the setting between the multi-antenna and the multi-power amplifier according to the received power amplifier setting information (S140), and transmits a signal to the base station according to the changed power amplifier setting (S150). At this time, the terminal may report or feed back the power amplifier setting change to the base station. The power amplifier setting change report may be sent as an L1 / L2 signal or a higher layer signal.

The mapping between the power amplifier and the physical antenna may be predefined. Table 1 below shows examples of mapping rules between two power amplifiers and four physical antennas. P1 and P2 are indexes of power amplifiers, and A1 to A4 are indexes of physical antennas. The index added to the power amplifier can be a physical or logical index.

Table 1

Table 2 below shows examples of mapping rules between four power amplifiers and four physical antennas.

TABLE 2

In Table 2, an index was added as P1 to P4 to distinguish four power amplifiers, and an index was added as A1 to A4 to distinguish a physical antenna.

The base station may include a mapping rule change indicator and / or a mapping rule index in the power amplifier configuration information. The UE may know whether the mapping rule between the power amplifier and the physical antenna is changed through the mapping rule change indicator. When the mapping rule is requested, the terminal may change the power amplifier configuration through the mapping rule index. The power amplifier setting information may designate a time interval to which the mapping rule is applied. The time interval may be, for example, a symbol unit, a slot unit, a subframe unit, or a radio frame unit. The mapping rule between the power amplifier and the physical antenna can be changed in various time interval units to achieve a better transmit diversity effect.

6 illustrates an example of setting up multiple antennas and multiple power amplifiers. Assume the transmitter has two power amplifiers and two physical antennas.

Referring to FIG. 6 (a), power amplifier 1 (power amp # 1, P1) is mapped to physical antenna 1 (A1), and power amplifier 2 (power amp # 2, P2) is assigned to physical antenna 2 (A2). Can be mapped. In the mapping of the power amplifier and the physical antenna, the mapping rule index may be '0000' according to Table 1.

Referring to FIG. 6 (b), power amplifier 1 (P1) may be mapped to physical antenna 2 (A2), and power amplifier 2 (P2) may be mapped to physical antenna 1 (A1). In the mapping of the power amplifier and the physical antenna, the mapping rule index may be '0011' according to Table 1. The mapping of FIG. 6 (b) is a switching form of the mapping of FIG. 6 (a).

The transmitter may select and use the mapping according to the mapping rule index '0000' and then change the mapping to the mapping rule mapping index '0011' when the mapping rule change indicator and / or the mapping rule index included in the power amplifier configuration information are received.

In FIG. 7A, the physical antenna mapped to power amplifier # 1 is antenna # 1, and in FIG. 7 (b), the physical antenna mapped to power amplifier # 1 is antenna # 2. That is, in FIGS. 7A and 7B, physical antennas mapped to power amplifier # 1 may be switched by power amplifier setting information. Alternatively, the power amplifier setting information may be regarded as turning off one or more power amplifiers among the power amplifiers. When the power amplifier setting information is given in the form of a power control message for each power amplifier, the power control message may include an output power value for each power amplifier. In this case, the output power value for the power amplifier to be blocked may be set to '0'.

The base station (receiver) sends a physical antenna to the terminal (transmitter) when the maximum output power is reached for at least one of the physical antennas or the output power of at least one of the physical antennas is less than or equal to a threshold in the power control process. May request switching. Then, the signal may be transmitted through the switched physical antenna. If the number of activated power amplifiers is smaller than the number of physical antennas, the number of physical antennas capable of transmitting signals may be limited to the number of activated power amplifiers.

The activated power amplifier may be a power amplifier having maximum power in a situation where a power limit is set. Alternatively, when low transmission power is used to reduce power consumption of the terminal, the activated power amplifier may be a power amplifier having a power lower than the maximum power.

In the above description, the terminal (ie, the transmitter) has been described as an example of changing the setting between the power amplifier and the physical antenna by the power amplifier setting information transmitted by the base station (ie, the receiver), but this is not a limitation. That is, the terminal (eg, Long Term Evolution-Advanced (LTE-A) terminal) may change the setting between the power amplifier and the physical antenna by its own decision. When the terminal changes the configuration by itself, the terminal may report the information on the configuration change to the base station. For example, the mapping rule change indicator and / or the changed mapping rule index may be transmitted to the base station.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

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 signal transmission method in a multi-antenna system,

Receiving power amplifier setting information from a base station;

Changing a setting between a multiple power amplifier and multiple antennas according to the power amplifier setting information; And

And transmitting a signal to the base station according to the changed setting, wherein the power amplifier setting information includes information indicating a power amplifier connected to the multiple antennas.
The method of claim 1, wherein the power amplifier setting information is

And a mapping rule index indicating a predetermined mapping relationship between the multiple power amplifier and the multiple antennas.
The method of claim 1, wherein the power amplifier setting information is

And output power information for each of the power amplifiers connected to one of the multiple antennas.
The method of claim 1, wherein before receiving the power amplifier setting information.

Transmitting a signal used for channel measurement to the base station.
The method of claim 4, wherein the power amplifier setting information is

And the base station is determined according to a result of measuring a signal used for measuring the channel.
5. The method of claim 4, wherein the signal used for channel measurement is a sounding reference signal.
The method of claim 1, wherein the power amplifier setting information is

Method transmitted through the physical downlink control channel (PDCCH) transmitted by the base station, or included in the radio resource control (RRC) signal.
The method of claim 1, wherein transmitting a signal to the base station according to the changed setting

And feeding back the modified setting to the base station.
The method of claim 8, wherein the information for feeding back the changed setting to the base station is transmitted through a control signal.
10. The method of claim 8, wherein the information for feeding back the changed setting to the base station comprises a mapping rule index indicating a predetermined mapping relationship between the multiple power amplifier and the multiple antenna.