WO2011083761A1

WO2011083761A1 - Wireless transmission device and reference signal transmission method

Info

Publication number: WO2011083761A1
Application number: PCT/JP2011/000020
Authority: WO
Inventors: 中尾正悟; 福岡将
Original assignee: パナソニック株式会社
Priority date: 2010-01-07
Filing date: 2011-01-06
Publication date: 2011-07-14

Abstract

Disclosed are a wireless transmission device and a reference signal transmission method that minimize data error characteristic degradation upon a first wireless receiver device even when data sent to the first wireless receiver device is overwritten by a reference signal intended for a second wireless receiver device with the reference signal intended for the second wireless receiver device being positioned upon resources that are allocated to the data sent to the first wireless receiver device. In a base station (100), a signal processing unit for terminals (101-a) positions a first reference signal and a second reference signal for a second terminal (herein referred to as a terminal (200)) upon a first resource element and a second resource element that are included within a common SFBC resource group and that are adjacent in the frequency direction. The first reference signal matches a complex conjugate of the result of rotating the second reference signal upon a complex plane by an angle θ, where 0 ≤ θ < 2π[rad].

Description

Wireless transmission apparatus and reference signal transmission method

The present invention relates to a wireless transmission device and a reference signal transmission method.

In wireless communication systems such as cellular systems, reference signals for obtaining various indicators of propagation paths or transmission signals are introduced. For example, a reference signal (RS) is also used in LTE (Long Term Evolution) of the next generation communication system established by 3GPP (3rd Generation Partnership Project) which is an international standardization organization for mobile communication. . In downlink communication from a base station to a terminal, reference signals transmitted from a transmitting apparatus (base station) to a receiving apparatus (terminal) mainly include (1) channel estimation for demodulation and (2) frequency scheduling and adaptive MCS. (Modulation and Coding 品質 Scheme) Used for quality measurement for control. In LTE, a reference signal is transmitted in units of predetermined radio resources in a multi-antenna system for applying MIMO (Multiple 信号 Input Multiple Output).

Further, for example, the LTE frame has a configuration as shown in FIG. In LTE, the minimum unit of frequency scheduling and adaptive MCS control (that is, control of coding rate and multi-level modulation number) is called a resource block (RB) (hereinafter also referred to as RB). In the configuration shown in FIG. 1, in one RB, a control signal and a reference signal RS are arranged from the beginning of the time axis, and then data is arranged. Here, 1 RB is a group of 12 subcarriers in the frequency direction and 14 OFDM symbols in the time direction. Reference signal RS is arranged on a specific subcarrier in a specific OFDM symbol in 1 RB. A unit specified by one OFDM symbol and one subcarrier is called a resource element (RE: Resource ： Element, hereinafter also referred to as RE). That is, since 1 RB includes 12 subcarriers and 14 OFDM symbols, 168 REs are included.

Here, as shown in Non-Patent Document 1, when there are a plurality of LTE base station antennas, SFBC (Space-Frequency Block Coding) as shown in FIG. 2 is applied to downlink data. However, FIG. 2 shows a conceptual diagram when the number of antennas of the base station is two.

As shown in FIG. 2, in the LTE base station, an SFBC result unit (hereinafter referred to as “SFBC group”) obtained by performing SFBC on the block code processing unit of SFBC (the whole of S1 and S2 in FIG. 2). 2, S1, S2, -S2 *, S1 * constitute an SFBC group) and are mapped to one resource group (hereinafter referred to as "SFBC resource group") in the resource block. That is, the SFBC resource group is a resource unit to which the SFBC result unit is mapped, and one SFBC resource group is composed of two REs adjacent on the frequency axis. For example, one SFBC resource group is transmitted from both antenna 1 and antenna 2, and S1 and S2 are arranged in the first RE and second RE of the SFBC resource group transmitted from antenna 1, respectively, while antenna 2 -S2 * and S1 * are arranged in the first RE and the second RE of the SFBC resource group to be transmitted, respectively. However, S2 * and S1 * represent the complex conjugate of S2 and S1. As described above, the diversity gain is obtained by transmitting the frame in which the SFBC group is mapped to the SFBC resource group. When receiving downlink data encoded by SFBC, the LTE terminal collectively receives the SFBC resource group, and combines the signal components received by the SFBC resource group by a known decoding method, so that S1 , S2.

In LTE-Advanced (hereinafter referred to as LTE-A), which is a communication system that further advances LTE, introduction of higher-order MIMO (for example, eight transmission antennas) and coordinated multipoint transmission / reception (CoMP) has been introduced in order to further improve the level of sophistication. It is being considered. For this reason, in addition to the reference signal (first reference signal) studied in LTE, an additional reference signal (second reference signal) is required for LTE-A, and its transmission method is discussed. .

For example, as shown in Non-Patent Document 2, in LTE-A, two types of reference signals are examined for the above-mentioned uses.

(1) Demodulation RS (DM RS): A reference signal for demodulating PDSCH (Physical downlink shared channel). The same number of layers as PDSCH is applied, and precoding is also applied. This is a UE-specific reference signal for a terminal (User Equipment: UE).

(2) CSI-RS: A reference signal for CSI (Channel state information) observation. Precoding is not applied. It is a cell-specific reference signal. The CSI includes CQI (channel （quality indicator), PMI (precoding matrix indicator), RI (rank indicator), and the like.

Basically, the DM RS is inserted only in the RB that allocates data to the LTE-A terminal so that the LTE-A terminal can demodulate the downlink signal. Accordingly, the terminal cannot know in advance which RB and which subframe the DM RS is inserted into. In contrast, CSI-RS is by all LTE-A terminal connected to a base station, have been recognized for whether it is inserted in advance which RB, in which sub-frame. Therefore, the LTE-A terminal can receive the CSI-RS based on the CSI-RS arrangement information, and feeds back the CSI to the base station. That is, the CSI-RS is always inserted regardless of whether data is assigned to the LTE-A terminal in any RB or any subframe. That is, the CSI-RS is transmitted even when no resource is allocated to the transmission data sequence for the LTE-A terminal. However, the use of CSI-RS is not regarded as an exclusive position. Specifically, the discussion is proceeding on the assumption that CSI-RS may be used for the application (1).

Examples of CSI-RS transmission methods for LTE-A terminals are disclosed in Non-Patent Documents 3 and 4, for example. 3 and 4 are diagrams illustrating a CSI-RS transmission method corresponding to the LTE-A terminal. In the example illustrated in FIGS. 3 and 4, CSI-RSs are arranged for OFDM symbols that are not used for any of RSs for LTE, control channels, and DMRSs.

3, CSI-RS is arranged in the 11th OFDM symbol in the resource block shown in FIG. 3, and CSI-RS is arranged in the 10th and 11th OFDM symbols in the resource block shown in FIG. 4. Using these CSI-RSs, the LTE-A terminal can measure the quality of the channel from the base station to its own device. Here, in the example of FIG. 3, the CSI-RS is transmitted from the four antennas of the LTE-A base station arranged in different REs (that is, by FDM). On the other hand, in the example of FIG. 4, CSI-RS is the same from one antenna pair of LTE-A base station (that is, one set in which four antennas of LTE-A base station are divided into two). Placed in RE and transmitted. However, CSI-RS transmitted from two antennas constituting an antenna pair is transmitted by CDM (that is, code-multiplexed). Between the two antenna pairs, the CSI-RS is frequency-multiplexed (FDM) and transmitted as in the case of FIG. In FIGS. 3 and 4, the difference in hatching representing CSI-RS represents the difference in antenna to be transmitted. The same notation is adopted in the drawings described below.

By the way, the above-mentioned CSI-RS is also transmitted in an RB to which downlink data for LTE terminals is assigned. In this case, the CSI-RS overwrites downlink data for the LTE terminal. That is, significant data for the LTE terminal is overwritten by CSI-RS that does not make sense for the LTE terminal. Here, the LTE terminal cannot know the existence of the CSI-RS. Therefore, the LTE terminal performs the decoding process on the assumption that significant information addressed to the terminal itself is also included in the RE in which the CSI-RS is arranged. Since convolutional coding is applied to downlink data in LTE, even if a part of RE is overwritten by CSI-RS, in general, decoding can be performed without error. However, when downlink data for LTE terminals is overwritten by CSI-RS, “SNR (SignalＮＲto Noise Ratio) vs. BLER (Block Error rate) characteristics” relating to downlink data for LTE terminals, that is, error rate Characteristics deteriorate.

For example, FIG. 5 shows a conceptual diagram in which the CSI-RS shown in FIG. 2 overwrites data for the LTE terminal. In FIG. 5, a part of REs constituting the 11th OFDM symbol is overwritten by CSI-RS.

In this way, when it becomes necessary to transmit CSI-RS in the RB to which downlink data is allocated to the LTE terminal, the LTE-A base station sets an MCS that is more resistant to noise to the LTE terminal. Then, control is performed so that the LTE terminal can receive downlink data without error.

However, if an MCS that is more resistant to noise is set, the amount of time / frequency resources required when transmitting information of the same size to the LTE terminal increases. Therefore, even when downlink data for LTE terminals is overwritten by CSI-RS, the MCS setting does not have to be greatly shifted to the high noise tolerance side, that is, the degradation of error rate characteristics of downlink data is minimized. A CSI-RS transmission method that can be suppressed to the limit is desired.

An object of the present invention is to arrange a reference signal for the second wireless reception device in a resource allocated to data to the first wireless reception device, so that the data to the first wireless reception device is the first. By providing a wireless transmission device and a reference signal transmission method that minimize deterioration of error characteristics of data to the first wireless reception device even when overwritten by a reference signal for the second wireless reception device is there.

The radio transmission apparatus of the present invention performs spatial frequency block coding (SFBC) on a transmission data sequence for the first type reception apparatus in units of block code processing, and forms an SFBC group that is a code result for each block code processing unit. A frequency block encoding unit; and an arrangement unit that arranges the SFBC group or the first reference signal and the second reference signal for the second type receiving apparatus in a resource group including a plurality of resource elements; The first reference signal and the second reference signal are in a complex conjugate relationship with each other.

In the reference signal transmission method of the present invention, a transmission data sequence for the first type receiver is subjected to spatial frequency block coding (SFBC) in block code processing units, and an SFBC group as a code result for each block code processing unit is formed. A forming step, and an arrangement step of arranging the SFBC group or the first reference signal and the second reference signal for the second type receiving apparatus in a resource group composed of a plurality of resource elements. The first reference signal and the second reference signal are in a complex conjugate relationship with each other.

According to the present invention, the reference signal for the second wireless reception device is arranged in the resource allocated to the data to the first wireless reception device, so that the data to the first wireless reception device is the first. To provide a wireless transmission device and a reference signal transmission method that minimizes deterioration of error characteristics of data to the first wireless reception device even when overwritten by a reference signal for the second wireless reception device. it can.

The figure which shows the structure of the flame | frame of LTE Diagram for explaining examples of arrangement of SFBC result units in SFBC (Space-Frequency Block Coding) and LTE The figure which shows the transmission method of CSI-RS corresponding to a LTE-A terminal The figure which shows the transmission method of CSI-RS corresponding to a LTE-A terminal The figure explaining the overwriting to the data for LTE terminals by CSI-RS The block diagram which shows the structure of the base station which concerns on one embodiment of this invention The block diagram which shows the structure of the terminal 200 which concerns on one embodiment of this invention. The figure which uses for description of the example of arrangement | positioning of CSI-RS with respect to the SFBC resource group by the base station which concerns on this Embodiment The figure which shows the simulation result at the time of maintaining the relationship of Formula (1) with respect to the pair of CSI-RS which overwrites a SFBC resource group (when a 1st type terminal carries out QPSK demodulation) The figure which shows the simulation result in case the process of a complex conjugate is not accompanied with respect to the pair of CSI-RS which overwrites a SFBC resource group The figure which shows the simulation result at the time of maintaining the relationship of Formula (1) with respect to the pair of CSI-RS which overwrites a SFBC resource group (when a 1st type terminal carries out 16QAM demodulation) The figure which shows the simulation result at the time of maintaining the relationship of Formula (1) with respect to the pair of CSI-RS which overwrites a SFBC resource group (when a 1st type terminal carries out 64QAM demodulation)

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[System Overview]
In the following description, an example is shown in which the wireless communication apparatus according to the present invention is applied to a cellular system for mobile communication such as a mobile phone.

The wireless communication system according to the present embodiment includes a base station 100, which will be described later, which is a wireless communication device, a first type terminal compatible with the first type system, and a terminal 200 that is a second terminal compatible with the second type system. Have. For example, the base station 100 is an LTE-A base station corresponding to the LTE-A system (and LTE system), the first type terminal is an LTE terminal corresponding to the LTE system, and the second type terminal is LTE. -A terminal. Base station 100 transmits a signal to a first type terminal or a second type terminal via a plurality of antennas. For this transmission, for example, OFDM is used. Base station 100 transmits an OFDM signal obtained by performing serial-parallel conversion and IFFT on a serial transmission signal in units of OFDM symbols. That is, base station 100 transmits a “spatial multiplexed resource block” to a receiving terminal by transmitting resource blocks defined by a plurality of OFDM symbols and a plurality of subcarriers from a plurality of antennas.

Since the second type system follows the first type system, the base station 100 can also communicate with the first type terminal. The first type terminal cannot know the existence of the second type system, but can communicate with the base station 100 by performing the same operation as the communication with the base station compatible with the first type system. . On the other hand, the type 2 terminal includes a base station classified into the type 1 system (that is, a type 1 base station) and a base station classified into the type 2 system (that is, the base station 100 corresponding to the second type). Seed base stations) and appropriate communication can be performed with each base station.

The base station 100 also transmits a second reference signal (for example, CSI-RS) for the LTE-A system in addition to the first reference signal for the first type system. These reference signals are inserted into a predetermined RE in the RB. The second reference signal is mainly used by the type 2 terminal to generate feedback information necessary for frequency scheduling and adaptive MCS control.

In addition, the base station 100 divides, in the RB, the RE group that can be allocated to the downlink data to the first type terminal into an RE group composed of a predetermined number of REs. This RE group is a resource unit to which the SFBC result unit is mapped, and corresponds to the above-described SFBC resource group. Here, this RE group is composed of two REs that are adjacent on the frequency axis, like the SFBC resource group.

Hereinafter, a case where the base station 100 is an LTE-A base station, the terminal 200 is an LTE-A terminal, and the first type terminal is an LTE terminal will be described as an example.

[Base station configuration]
FIG. 6 is a block diagram showing a configuration of base station 100 according to the present embodiment. In FIG. 6, the base station 100 includes a plurality of terminal signal processing units 101-a and 101b, a plurality of transmission RF units 103-1 to m, a plurality of antennas 104-1 to m, a scheduling unit 105, Second reference signal arrangement setting unit 106, second reference signal generation unit 107, complex conjugate processing unit 114, first reference signal generation unit 108, reception RF unit 109, separation unit 110, demodulation / decoding unit 111, a CRC checker 112, and a feedback information demodulator 113. Of antennas 104-1 to m, antennas 104-1 to n are used to transmit transmission data for the LTE terminal, the first reference signal, transmission data for the LTE-A terminal, and CSI-RS. . On the other hand, the antennas 104-n + 1 to m are not used for transmitting transmission data for the LTE terminal and the first reference signal, but are used for transmission of transmission data for the LTE-A terminal and CSI-RS.

The terminal signal processing unit 101-a includes an encoding / modulation unit 121-1, a precoding processing unit 123-1, and a data overwriting unit 124. The terminal signal processing unit 101-b includes an encoding / modulation unit 121-2, a second reference signal mapping unit 122, and a precoding processing unit 123-2.

The signal transmitted from the terminal 200 or the first type terminal is input to the reception RF unit 109 via the antenna 104-1.

The reception RF unit 109 performs predetermined radio reception processing (down-conversion, A / D conversion, etc.) on the reception signal, and then outputs the reception signal after the radio reception processing to the separation unit 110.

Separation section 110 separates the received signal received from reception RF section 109 into a feedback signal and a data signal, outputs the feedback signal to feedback information demodulation section 113, and outputs the data signal to demodulation / decoding section 111.

The demodulation / decoding unit 111 obtains received data by demodulating and decoding the data signal. The CRC checker 112 performs error detection processing by CRC check on the received data output from the demodulator / decoder 111 to determine whether the received data contains an error. Then, the reception data is output from the CRC inspection unit 112.

The feedback information demodulation unit 113 demodulates the feedback signal and outputs the demodulation result to the scheduling unit 105. The feedback signal includes channel quality information (CSI) or Ack / Nack information. The channel quality information indicates the channel quality measured by the terminal 200 based on the first type reference signal transmitted from the base station 100.

Scheduling section 105 performs transmission signal scheduling based on channel quality information and CSI-RS arrangement information. Specifically, the scheduling unit 105 performs at least one of frequency scheduling and adaptive MCS control based on channel quality information transmitted from a terminal that receives a reference signal. In addition, the scheduling unit 105 refers to the CSI-RS arrangement information, and with respect to the data for the LTE-A terminal, the scheduling unit 105 transmits the transmission data (ie, the downlink) to the RE excluding the RE in which the CSI-RS is arranged. Data). In addition, regarding data for LTE terminals, scheduling section 105 assigns transmission data to REs based on mapping rules recognized by LTE terminals, regardless of whether or not CSI-RS is arranged. However, when the transmission data for the LTE terminal is allocated to an arbitrary RB where the CSI-RS is allocated, the scheduling unit 105 overwrites a part of the transmission data for the LTE terminal with the CSI-RS. Considering this, a slightly more robust MCS is set than the MCS in the RB where the CSI-RS is not arranged.

The scheduling information determined by the scheduling unit 105 (including at least one of the frequency scheduling result and the determined MCS) is output to the terminal signal processing units 101-a and 101b.

The second reference signal arrangement setting unit 106 outputs CSI-RS arrangement information to the scheduling unit 105 and the second reference signal generation unit 107. Further, the arrangement information of CSI-RS is also notified separately to the second type terminal.

The second reference signal generation unit 107 includes m / 2 types of CSI-RS (that is, CSI-RS that is half the number of antennas to which CSI-RS is to be transmitted. Part or all may be the same series) and output to the complex conjugate processing unit 114.

The complex conjugate processing unit 114 performs a complex conjugate operation on each of m / 2 types of CSI-RSs input from the second reference signal generation unit 107, and further adds θ rotation on the complex plane (0 ≦ θ <2π [rad]) is generated as a CSI-RS that should correspond to the remaining m / 2 antennas. In other words, the complex conjugate processing unit 114 generates m / 2 pairs of CSI-RS pairs that are in a complex conjugate (+ rotation) relationship (that is, CSI-RSs corresponding to m antennas).

Further, the complex conjugate processing unit 114 generates CSI-RSs transmitted from the transmission antennas 104-1 to m at the timing of forming resource blocks in which transmission data for LTE-A terminals is arranged, and is used for terminals. Output to the signal processing unit 101-b.

Further, when transmitting CSI-RS in a resource block in which transmission data for LTE terminals is arranged, complex conjugate processing section 114 generates CSI-RS transmitted from transmitting antennas 104-1 to 104-n, respectively. To the terminal signal processing unit 101-a.

The terminal signal processing unit 101-a forms a resource block in which transmission data for LTE terminals is arranged. Specifically, the terminal signal processing unit 101-a performs spatial frequency block coding (SFBC) on a transmission data sequence for LTE terminals in block code processing units, and an SFBC group that is a code result for each block code processing unit. Form. Then, the terminal signal processing unit 101-a arranges the formed SFBC group in an SFBC resource group composed of a plurality of resource elements assigned to the transmission data sequence. Then, the terminal signal processing unit 101-a arranges CSI-RS pairs having a complex conjugate (+ rotation) relationship with each other in a predetermined SFBC resource group. Then, one CSI-RS constituting the CSI-RS pair is transmitted from the first antenna, and the other CSI-RS is transmitted from the second antenna. That is, the CSI-RS is arranged in some SFBC resource groups among the SFBC resource groups included in the RB.

That is, terminal signal processing section 101-a is connected to the first resource element and the second resource element included in the same SFBC resource group (here, particularly adjacent in the frequency direction) for LTE-A terminals. “First CSI-RS” and “second CSI-RS in which the complex conjugate of the first CSI-RS is rotated by an angle θ (0 ≦ θ <2π [rad])” are arranged. The first CSI-RS and the second CSI-RS constitute a CSI-RS pair.

Specifically, in the terminal signal processing unit 101-a, the encoding / modulation unit 121-1 performs spatial frequency block coding (SFBC) on the transmission data sequence for LTE terminals in block code processing units, and performs block code processing units. An SFBC group which is a code result of each is formed. Note that the encoding / modulation unit 121-1 also performs multiplexing processing of a control signal, rate matching processing, interleaving processing, modulation processing, and the like.

The precoding processing unit 123-1 forms n parallel streams corresponding to the antennas 104-1 to 104-n from the SFBC group group received from the encoding / modulation unit 121-1. The precoding processing unit 123-1 forms a plurality of parallel streams by dividing the SFBC group. Each stream obtained by the precoding processing unit 123-1 is serially output in units of OFDM symbols.

The data overwriting unit 124 overwrites the configuration data corresponding to the resource element in which the CSI-RS is to be arranged in the configuration data group that configures the plurality of parallel streams with the CSI-RS, and the obtained plurality of parallel streams. Output to transmission RF sections 103-1 to n. Reference signals for LTE terminals generated by the first reference signal generation unit 108 are inserted into the plurality of parallel streams. However, in the plurality of parallel streams, the data is arranged avoiding the RE in which the reference signal for the LTE terminal is inserted, so that the data is not overwritten by the first reference signal.

The arrangement of the CSI-RS with respect to the second reference signal generation unit 107, the complex conjugate processing unit 114, and the SFBC resource group will be described in detail later.

The terminal signal processing unit 101-b forms a resource block in which transmission data for the LTE-A terminal is arranged.

Specifically, in the terminal signal processing unit 101-b, the encoding / modulation unit 121-2 performs spatial frequency block coding (SFBC) on the block data processing unit for the transmission data sequence for the LTE-A terminal, and blocks An SFBC group that is a code result for each code processing unit is formed.

The encoding / modulation unit 121-2 also performs control signal multiplexing processing, rate matching processing, interleaving processing, modulation processing, and the like. Second reference signal mapping section 122 receives CSI-RSs transmitted from transmission antennas 104-1 to m received from second reference signal generation section 107, and divides CSI-RS for each antenna and performs precoding processing in parallel. To the unit 123-2. Note that the encoding / modulation unit 121-2 also performs multiplexing processing of a control signal, rate matching processing, interleaving processing, modulation processing, and the like.

The precoding processing unit 123-2 receives m parallels corresponding to the antennas 104-n + 1 to m from the SFBC group group received from the encoding / modulation unit 121-1 and the CSI-RS received from the second reference signal generation unit 107. Form a stream. Each stream obtained by the precoding processing unit 123-2 is serially output in units of OFDM symbols. In the OFDM symbol unit stream, the SFBC group configuration data and CSI-RS correspond to the SFBC group configuration data and CSI-RS to be allocated in the resource block transmitted from the antenna corresponding to the stream. It is arranged at the position to do.

The transmission RF units 103-1 to 103-m receive the OFDM symbol unit stream, perform serial-parallel conversion and IFFT processing, and form an OFDM signal. The OFDM signals formed by the transmission RF units 103-1 to l are transmitted from the antennas 104-1 to l, respectively.

[Terminal configuration]
FIG. 7 is a block diagram showing a configuration of terminal 200 according to the present embodiment. In FIG. 7, terminal 200 includes a plurality of antennas 211-1 to 211-1, a plurality of reception RF units 212-1 to 212-1, a CSI-RS sequence generation unit 223, a complex conjugate processing unit 224, and a channel estimation unit 213. A CSI measuring unit 214, a MIMO demodulating unit 215, a decoding unit 216, a CRC checking unit 217, a feedback information generating unit 218, an encoding unit 219, a multiplexing unit 220, a transmission RF unit 221, and a control A signal demodulator 222. Here, as described above, terminal 200 is described as an LTE-A terminal.

The spatially multiplexed OFDM signal obtained by spatially multiplexing the OFDM signal transmitted from the base station 100 is received by the antennas 211-1 to 211-1.

The reception RF units 212-1 to 212-l perform radio reception processing (down-conversion, A / D conversion, etc.) and OFDM demodulation processing (Fourier transform, parallel) on the received OFDM signals received via the antennas 211-1-l. / Serial conversion etc.) to obtain serial received signals. This received signal is output to channel estimation section 213, MIMO demodulation section 215, and control signal demodulation section 222.

The CSI-RS sequence generation unit 223 is a type corresponding to half of the number of antennas to which the base station 100 that is the channel quality report target transmits CSI-RS (that is, m / 2 types. However, m / 2 types of CSI- A part or all of the RSs may be the same series), and is output to the complex conjugate processing unit 224.

The complex conjugate processing unit 224 performs a complex conjugate operation on the input m / 2 types of CSI-RSs, and further rotates the angle θ (0 ≦ θ <2π [rad]) on the complex plane. The complex conjugate processing unit 224 outputs the input m / 2 types of CSI-RS and the m / 2 types of CSI-RS subjected to the complex conjugate arithmetic processing and the rotation processing to the channel estimation unit 213. . That is, complex conjugate processing section 224 generates a total of m types of CSI-RS sequences (that is, m / 2 sets of CSI-RS pairs) and outputs them to channel estimation section 213.

The channel estimation unit 213 estimates a channel from a channel quality measurement reference signal included in the received signal based on the CSI-RS sequence input from the complex conjugate processing unit 224, and calculates a channel estimation value. The position of the channel quality measurement reference signal is notified separately from the base station 100. Specifically, the channel estimation unit 213 receives CSI-RS arrangement information as resource information for the second reference signal and a CSI-RS sequence as inputs. And the channel estimation part 213 specifies the frequency position in the resource block to which CSI-RS which is a reference signal for channel quality measurement is allocated based on CSI-RS arrangement information, and the resource block. Channel estimation section 213 performs channel estimation based on the channel quality measurement reference signal included in the frequency position and the CSI-RS sequence received from complex conjugate processing section 224. However, the CSI-RS arrangement information is separately notified from the base station 100. The channel estimation value calculated by channel estimation section 213 is output to CSI measurement section 214 and MIMO demodulation section 215.

The control signal demodulator 222 demodulates the control signal transmitted from the base station 100. Then, the control signal demodulator 222 extracts control information such as a transmission parameter including MCS information such as a modulation scheme or a coding rate of the transmission signal from the demodulated control signal. At this time, the control signal demodulator 222 receives and demodulates the CSI-RS arrangement information in advance and holds the CSI-RS arrangement information.

The CSI measurement unit 214 uses the channel estimation value calculated by the channel estimation unit 213 to calculate CSI as channel quality (reception quality) and outputs the CSI to the feedback information generation unit 218. At this time, the CSI measurement unit 214 receives the CSI-RS arrangement information as in the channel estimation unit 213, and acquires information on the resource element to which the CSI-RS that is a reference signal for channel quality measurement is assigned. Then, the CSI measurement unit 214 calculates channel quality information by averaging the channel estimation values for each resource element indicated by the information regarding the resource element. Furthermore, the CSI measurement unit 214 also calculates channel quality information of resource elements in which no CSI-RS is arranged by performing an interpolation process using the average channel estimation value. As specific channel quality information, CSI corresponding to a combination of a predetermined modulation scheme and coding rate, PMI for selecting a precoding matrix corresponding to the current channel condition from a predetermined codebook, and the desired number of transmission streams And the like.

The MIMO demodulator 215 uses the channel estimation value received from the channel estimation unit 213 and a channel estimation value based on a data signal demodulation reference signal (DM RS) (not shown) to perform a MIMO demodulation process (for example, SFBC). Reception processing), and outputs the demodulated signal to the decoding unit 216. The MIMO demodulator 215 also performs deinterleaving processing, rate dematching processing, likelihood combining processing, and the like.

The decoding unit 216 obtains received data by performing error correction decoding on the signal after MIMO separation.

The CRC checker 217 checks the received data CRC (Cyclic Redundancy Check) obtained by the decoder 216, and outputs data error presence / absence information indicating whether or not the received data includes an error to the feedback information generator 218. . When the CRC checking unit 217 determines that there is no error, the CRC checking unit 217 outputs the received data to the subsequent function unit.

The feedback information generation unit 218 generates feedback information including the channel quality information (CQI, PMI, RI, etc.) calculated by the CSI measurement unit 214. Further, the feedback information generation unit 218 generates Ack / Nack information based on the error detection result in the CRC check unit 217. Here, if the error detection result in the CRC checking unit 217 indicates “no error”, the feedback information generation unit 218 generates an ACK (Acknowledgement). If the error detection result indicates “error present”, the Nack ( Generate Negative (Acknowledgement).

The encoding unit 219 decodes the transmission data and outputs the decoding result to the multiplexing unit 220.

The multiplexing unit 220 multiplexes transmission signals including feedback information and encoded transmission data. Then, multiplexing section 220 performs rate matching (Rate-Maching) processing, interleaving processing, modulation processing, and the like that adaptively sets the modulation multi-level number or coding rate, and outputs the result to transmission RF section 221.

The transmission RF unit 221 performs OFDM modulation processing (serial / parallel conversion, inverse Fourier transform, etc.) and radio transmission processing (up-conversion, D / A conversion, amplification, etc.) on the multiplexed signal received from the multiplexing unit 220, and the antenna 211- 1 to send.

[Details of CSI-RS generation and arrangement by base station 100]
For example, the base station 100 generates a CSI-RS sequence based on the cell ID of the own station, and arranges it in each RE. Specifically, as described above, the base station 100 transmits the “first CSI-RS” for the LTE-A terminal to the first resource element and the second resource element included in the SFBC resource group in the LTE system. And “second CSI-RS in which the complex conjugate of the first CSI-RS is rotated by an angle θ (0 ≦ θ <2π [rad])”.

That is, two CSI-RSs arranged in a certain SFBC resource group (these may be transmitted from the same antenna, or may be transmitted from different antennas respectively. FIG. 8 shows a certain SFBC. the in and) shows an example in which two CSI-RS is arranged in the resource group is transmitted from always different antennas, respectively when p ₁ and p _2, between p ₁ and p _2, the following The relationship of the formula (1) is established.

At this time, the relative relationship between CSI-RSs arranged in different SFBC resource groups may be an arbitrary relationship. That is, for example, in FIG. 8, the relative relationship between the _two CSI-RSs (p ₁ , p ₂ ) arranged in the SFBC resource group 1 is expressed by Expression (1). Similarly, two CSI-RSs (p ₃ , p ₄ ) arranged in the SFBC resource group 2 are expressed by Expression (2).

On the other hand, the relative relationship between p ₁ and p ₃ is not limited, and for example, an arbitrary independent sequence is set. In this way, m types of CSI-RSs are generated and transmitted.

[Generation of CSI-RS by terminal 200]
The second type system compatible terminal 200 generates m types of CSI-RS sequences corresponding to m antennas from which the base station 100 transmits CSI-RS. That is, the same m types of CSI-RS sequences generated in base station 100 are generated. Specifically, the first CSI-RS sequence and the complex conjugate of the first CSI-RS sequence include a second CSI-RS sequence rotated by an angle θ (0 ≦ θ <2π [rad]). M / 2 types of CSI-RS pairs are generated. The m types of CSI-RS sequences are used as reference signals in channel estimation.

That is, for two CSI-RSs arranged in a certain SFBC resource group, terminal 200 assigns one CSI-RS sequence (p ₁ ) based on a predetermined rule (for example, for base station 100 Generate based on Cell ID. Terminal 200 generates the other CSI-RS sequence (p ₂ ) arranged in the same SFBC resource group using the relationship of equation (1).

[Effects of CSI-RS on type 1 terminal reception]
Here, a case where the first type terminal performs a reception operation corresponding to SFBC in the first type system will be described.

When the first type terminal receives a signal subjected to SFBC as shown in FIG. 2 from the base station 100, the signals r ₁ and r ₂ received by the REs ₁ and ₂ in the SFBC group are expressed by Equation (3). expressed.

However, the influence of noise is not taken into consideration here, h ₁ is a channel corresponding to the propagation path from the first transmitting antenna of the base station 100 to the receiving antenna of the first type terminal, and h ₂ is the base It is a channel corresponding to the propagation path from the second transmitting antenna of the station to the receiving antenna of the first type terminal.

The first type terminal estimates the channels h ₁ and h ₂ from the reference signal for the first type system that is separately transmitted. Then, the first type terminal demodulates the signals s ₁ and s ₂ transmitted from the base station 100 by a process corresponding to Equation (4). Hereinafter, this operation is referred to as “SFBC demodulation”. However, for the sake of convenience, it is assumed that the terminal can perform ideal channel estimation, and the same h ₁ , h ₂ (and s1, s2) are used for both Equation (3) and Equation (4) (ie, These equations do not take into account demodulation errors due to noise or channel estimation errors, and the same applies to the following equations.)

Here, as described above, the base station 100 uses the CSI-RS for the second type system for the first type system in the two REs forming the SFBC resource group with respect to a predetermined part of the resource group. The operation of overwriting the significant data is performed. That is, for example, the base station 100 overwrites the data for the first type system with the CSI-RS (p ₁ ) for the second type system transmitted from the first transmission antenna in the RE1 configuring the SFBC resource group. On the other hand, in RE2, the data for the first type system is overwritten with the CSI-RS (p ₂ ) for the second type system from the second transmission antenna. The p ₁ and p ₂ satisfy the relational expression (1) described above.

At this time, the signals r ₁ and r ₂ received by the first type terminal at the REs ₁ and ₂ are expressed by Expression (5).

By substituting Equation (5) into Equation (4), the CSI-RS demodulation result by the first type terminal can be obtained, and is represented by Equation (6). However, s _csi1 and s _csi2 are recognized as data for the first type system in the first type terminal, and error correction decoding taking these demodulation results into consideration is performed on the first type terminal side. In general, in error correction decoding, a demodulation result with high power is more strongly trusted (ie, the likelihood is recognized as high), and a demodulation result with low power is not reliable (ie, the likelihood is recognized as low). Is done). That is, a CSI-RS demodulation result that does not make sense for a type 1 terminal is recognized as having a low likelihood on the type 1 terminal side (that is, a case that is not considered important during error correction decoding). The adverse effect on the error correction decoding operation in the type 1 terminal is small and considered to be preferable.

For example, if θ = 0, Equation (6) can be transformed as Equation (7).

If θ = π, equation (6) can be transformed into equation (8).

Here, the following relationship (9) is established.

Therefore, it can be seen that the power (and amplitude) of the SFSI demodulation result of the CSI-RS recognized on the first type terminal side is smaller in the formula (8) than in the formula (7). That is, when the relative relationship between p ₁ and p ₂ is defined as θ = π in Equation (1), the likelihood of the demodulation result in the RE in which the CSI-RS is arranged is treated as the smallest, so the CSI-RS It can be seen that the effect of the insertion on the error correction decoding result of the first type terminal is also minimized.

9 and 10 show the results of simulation regarding these. FIG. 9 is a simulation result in the case where the relationship of Expression (1) is maintained for the CSI-RS pair overwriting the SFBC resource group. On the other hand, FIG. 10 shows a simulation result in the case where the complex conjugate processing is not performed for the CSI-RS pair overwriting the SFBC resource group, that is, the relationship of the following formula (10) is maintained. In both of FIGS. 9 and 10, a transmission signal formed by a type 1 terminal is overwritten with transmission data for a type 1 terminal modulated by QPSK and applied with SFBC by a CSI-RS. BLER (Block error rate) in the case of reception is shown.

As can be seen from FIGS. 9 and 10, the CSI-RS pair included in the SFBC resource group in the first type system and arranged in the first resource element and the second resource element adjacent in the frequency direction is represented by the formula (1). When the relationship is maintained and θ = π, the most adverse effect on the first type terminal can be reduced.

In other words, when the CSI-RS pair that overwrites the first resource element and the second resource element in the SFBC resource group satisfies the relationship of Equation (10), the reception performance of QPSK (that is, according to CSI-RS) The degree of deterioration due to overwriting) is almost constant regardless of the value of θ. On the other hand, when the CSI-RS pair satisfies the relationship of equation (1), the QPSK of the first type terminal depends on θ. It can be seen that the reception performance changes greatly.

This is due to the following reason. That is, when the CSI-RS pair maintains the relationship of the equation (10), the equation (6) is transformed into the following equation (11). Therefore, the influence of the interference component received by each of the first resource element and the second resource element is substantially constant regardless of θ.

In other words, as described above, the CSI-RS pair that overwrites the resource elements that form the SFBC resource group has the relationship of Equation (1), and the angle θ in Equation (1) is set to an appropriate angle. By doing so, it is possible to minimize the reception performance degradation of the first type terminal.

As described above, according to the present embodiment, in the base station 100, the terminal signal processing section 101-a includes the first resource element and the second resource element that are included in the same SFBC resource group and are adjacent in the frequency direction. A first reference signal and a second reference signal for the second type terminal (here, the terminal 200) are arranged in the resource element. The first reference signal matches the complex conjugate resulting from rotating the second reference signal on the complex plane by an angle θ (0 ≦ θ <2π [rad]).

By doing so, it is possible to suppress the reception performance deterioration of the first type terminal as described above.

In the above description, it has been shown that the optimum θ is π for the SFBC process shown in the equation (2). On the other hand, when the SFBC process is expressed by, for example, the following formula (12), the optimum θ is 0.

This is because the equations (4) and (6) are transformed into the following equations (13) and (14).

In the above description, the influence on the QPSK demodulation of the first type terminal has been described. Not limited to this, when the first type terminal demodulates the 16QAM or 64QAM signal, as shown in FIGS. 11 and 12, θ in the equation (1) is around 2π / 3 [rad] (120 degrees). In this case, the performance degradation is the smallest.

In the above description, the antenna is described. However, the present invention can be similarly applied to an antenna port.

An antenna port refers to a logical antenna composed of one or more physical antennas. That is, the antenna port does not necessarily indicate one physical antenna, but may indicate an array antenna composed of a plurality of antennas.

For example, in 3GPP LTE, it is not specified how many physical antennas an antenna port is composed of, but it is specified as a minimum unit in which a base station can transmit different reference signals (Reference signal).

Also, the antenna port may be defined as a minimum unit for multiplying the weight of a precoding vector (Precoding vector).

In the above description, the case where the present invention is configured by hardware has been described as an example, but the present invention can also be realized by software.

Further, each functional block used in the above description is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. Although referred to as LSI here, it may be referred to as IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Further, the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

Furthermore, if integrated circuit technology that replaces LSI emerges as a result of advances in semiconductor technology or other derived technology, it is naturally also possible to integrate functional blocks using this technology. Biotechnology can be applied.

The disclosure of the specification, drawings and abstract contained in the Japanese application of Japanese Patent Application No. 2010-001812 filed on Jan. 7, 2010 is incorporated herein by reference.

According to the wireless transmission device and the reference signal transmission method of the present invention, the reference signal for the second wireless reception device is arranged in the resource allocated to the data to the first wireless reception device, so that the first wireless Even when the data to the receiving device is overwritten by the reference signal for the second wireless receiving device, it is useful for minimizing the deterioration of the error characteristics of the data to the first wireless receiving device.

DESCRIPTION OF SYMBOLS 100 Base station 101 Signal processing part for terminals 103 Transmission RF part 104, 211 Antenna 105 Scheduling part 106 Second reference signal arrangement setting part 107 Second reference signal generation part 108 First reference signal generation part 109, 212 Reception RF part 110 Separation Unit 111 demodulation /

decoding unit

112, 217 CRC checking unit 113 feedback

information demodulation unit

114, 224 complex conjugate processing unit 121 encoding / modulation unit 122 second reference signal mapping unit 123 precoding processing unit 124 data overwriting unit 200 terminal 213 channel Estimation unit 214 CSI measurement unit 215 MIMO demodulation unit 216 Decoding unit 218 Feedback information generation unit 219 Encoding unit 220 Multiplexing unit 222 Control signal demodulation unit 223 CSI-RS sequence generation unit

Claims

Spatial frequency block coding means for performing a spatial frequency block coding (SFBC) on a block code processing unit for a transmission data sequence for the first type receiver, and forming an SFBC group as a code result for each block code processing unit;
Arrangement means for arranging the SFBC group or the first reference signal and the second reference signal for the second type receiving apparatus in a resource group composed of a plurality of resource elements;
Comprising
The first reference signal and the second reference signal are in a complex conjugate relationship with each other.
Wireless transmission device.
A plurality of resource elements constituting the SFBC group are adjacent to each other in the frequency direction.
The wireless transmission device according to claim 1.
The first reference signal and the second reference signal are transmitted from different antennas, respectively.
The wireless transmission device according to claim 1.
Spatial frequency block coding means for performing a spatial frequency block coding (SFBC) on a block code processing unit for a transmission data sequence for the first type receiver, and forming an SFBC group as a code result for each block code processing unit;
Arrangement means for arranging the SFBC group or the first reference signal and the second reference signal for the second type receiving apparatus in a resource group composed of a plurality of resource elements;
Comprising
The first reference signal is a wireless transmission device obtained by rotating a complex conjugate of the second reference signal by an angle θ (0 ≦ θ <2π [rad]).
A plurality of resource elements constituting the SFBC group are adjacent to each other in the frequency direction.
The wireless transmission device according to claim 4.
The first reference signal and the second reference signal are transmitted from different antennas, respectively.
The wireless transmission device according to claim 4.
The angle θ is 2π / 3 [rad] or π [rad].
The wireless transmission device according to claim 4.
A modulation unit that is provided on an input side of the spatial frequency block encoding unit and modulates the transmission data sequence input to the spatial frequency block encoding unit;
The angle θ is π [rad] when the modulation method of the modulation means is QPSK.
The wireless transmission device according to claim 4.
A modulation unit that is provided on an input side of the spatial frequency block encoding unit and modulates the transmission data sequence input to the spatial frequency block encoding unit;
The angle θ is 2π / 3 [rad] when the modulation method of the modulation means is quadrature amplitude modulation.
The wireless transmission device according to claim 4.
A step of forming a SFBC group that is a code result of each block code processing unit by performing spatial frequency block coding (SFBC) on a block code processing unit on a transmission data sequence for the first type receiving device;
An arrangement step of arranging the first reference signal and the second reference signal for the SFBC group or the second type reception apparatus in a resource group including a plurality of resource elements;
Comprising
The first reference signal and the second reference signal are in a complex conjugate relationship with each other.
Reference signal transmission method.