WO2014073654A1

WO2014073654A1 - Transmission system and reception device

Info

Publication number: WO2014073654A1
Application number: PCT/JP2013/080299
Authority: WO
Inventors: 拓也蔀; 研一村山; 慎悟朝倉; 澁谷　一彦
Original assignee: 日本放送協会
Priority date: 2012-11-12
Filing date: 2013-11-08
Publication date: 2014-05-15
Also published as: JP2014112832A; JP6184012B2

Abstract

A transmission system equipped with a first transmission device having two transmitting antennas and a second transmission device having two transmitting antennas, wherein the first transmission device transmits transmit signals which correspond to first series data A and second series data A obtained by encoding series data which has been divided in two, and the second transmission device transmits transmit signals which correspond to first series data B and second series data B obtained by encoding the series data which has been divided in two. The first series data A is encoded using a different conversion matrix from that used for the first series data B, and the second series data A is encoded using a different encoding method from that used for the second series data B. Alternatively, the transmit signal corresponding to the first series data A is transmitted using a different polarized wave from that used for the transmit signal corresponding to the first series data B, and the transmit signal corresponding to the second series data A is transmitted using a different polarized wave from that used for the transmit signal corresponding to the second series data B.

Description

Transmission system and receiver

The present invention relates to a transmission system and a receiving device.

In the field of wireless transmission, there is a growing demand for expansion of transmission capacity in order to enable large-volume content services. As a technology that meets such a demand, there is a technology called SDM (Space Division Multiplexing) that uses a plurality of modulated waves in the same frequency band and spatially multiplexes and transmits different information. In the case of a 2 × 2 MIMO (Multiple Input Multiple Output) transmission system composed of two transmit antennas and two receive antennas, the transmission capacity is doubled by transmitting uncorrelated modulated signals from the two transmit antennas. It becomes.

On the other hand, STC (Space Time Coding) is known as a transmission diversity technique for the purpose of improving transmission characteristics. In STC using two transmitting antennas, Alamouti space-time block coding (STBC) is widely known. Two systems of signals encoded with Alamouti STBC are combined by a receiving apparatus. In Alamouti STBC, the same information is sent from two transmission antennas, so that the effect of transmission diversity is obtained and transmission characteristics are improved.

In a MIMO transmission system to which SDM is applied, the transmission capacity increases, but signals in the same frequency band become interference waves with each other, so that transmission characteristics deteriorate. In a MIMO transmission system to which STC is applied, transmission characteristics are improved, but transmission capacity is not expanded.

The Alamouti STBC can be applied only to a two-transmission system, but Patent Document 1 discloses a method of applying this Alamouti STBC to four transmissions. By using four transmissions, the transmission characteristics are further improved as compared with the case of two transmissions, but the transmission capacity does not increase. If the transmission rate of a SISO (Single Input Single Output) transmission system is 1 (1 symbol is transmitted in 1 unit time), the transmission rate of Patent Document 1 is also 1 (4 symbols are transmitted in 4 unit time).

In response to a request to improve transmission characteristics while increasing transmission capacity, there is a document on a spatial multiplexing transmission system that combines SDM and STBC (Non-Patent Document 1). Non-Patent Document 1 discloses a MIMO transmission system with four transmission antennas and two reception antennas. In the case of Non-Patent Document 1, the transmission rate is increased to 2 (4 symbols in 2 unit times) by application of SDM, and the transmission characteristics are improved by application of STBC.

In the current digital terrestrial television broadcasting, SFN (Single Frequency Network) is being constructed from the viewpoint of effective use of frequency, but the received power of the SFN desired wave and the SFN interference wave are equal, that is, D / U (Desired). In the SFN interference area where the “Undesired signal ratio” is close to 0 dB, there is a problem that transmission characteristics deteriorate. FIG. 27 is a comparison of reception spectrums depending on the presence or absence of SFN interference waves at the time of SFN construction. When constructing an SFN, the same signal is transmitted at the same frequency from a plurality of transmission apparatuses. For this reason, the spectrum of the received signal is distorted as shown on the left side in FIG. 27 due to the SFN interference wave, so that the transmission characteristics deteriorate. When constructing SFN by applying STC, distortions as shown on the left side in FIG. 27 are also observed in the SFN interference area where D / U is close to 0 dB because different signals are transmitted from a plurality of transmission apparatuses at the same frequency. It does not occur and the deterioration of transmission characteristics can be reduced.

Generally, antennas that receive radio waves are classified into omnidirectional antennas and directional antennas. When receiving radio waves such as terrestrial digital broadcasting, directional antennas are often used. Directional antennas have excellent characteristics such as gain and cross polarization discrimination (XPD) for radio waves coming from the main lobe direction, but the characteristics in the side lobe direction are generally not guaranteed. It is.

Here, for example, the number of transmitting stations (also referred to as transmitting systems) is two, and the transmitting stations are called A station and B station. Stations A and B are often installed at physically separated positions, but need not be separated. The signal from station A is called the desired wave, and the signal from station B is called the SFN interference wave. Consider the case where the signal from station B comes from the side lobe direction with the main lobe of the directional antenna directed toward station A in order to receive the signal from station A. Since the radio wave arriving from the B station is received by the side lobe of the receiving antenna, the transmission characteristic is deteriorated.

Special table 2010-519844

A first feature is a transmission system including a first transmission device having two transmission antennas and a second transmission device having two transmission antennas, wherein the first transmission device is configured to divide sequence data to obtain a first transmission device. A first serial-to-parallel converter that outputs one-sequence data and second-sequence data; and first sequence data A is generated by encoding the first-sequence data by space-time coding according to a first rule; A first encoding unit that generates second sequence data A by encoding the two sequence data by space-time encoding of the second rule, and the second transmission device divides the sequence data by dividing the sequence data A second serial-to-parallel converter that outputs the first series data and the second series data; and encoding the first series data by space-time coding according to the first rule. A second encoding unit that generates sequence data B, and generates the second sequence data B by encoding the second sequence data by space-time encoding according to the second rule, and the first sequence data A is encoded by a different transformation matrix from the first sequence data B, and the second sequence data A is encoded by a different encoding method from the second sequence data B, or The transmission signal corresponding to the first sequence data A is transmitted by a polarization different from that of the transmission signal corresponding to the first sequence data B, and the transmission signal corresponding to the second sequence data A is the second sequence data The gist is that the signal is transmitted with a polarization different from that of the transmission signal corresponding to B.

The second feature is a method of performing space-time coding using a plurality of antennas provided in different transmission apparatuses and performing space division multiplexing using a plurality of antennas provided in each of the plurality of transmission apparatuses. The first sequence data A is a reception device used in a transmission system including the first transmission device and the second transmission device, and obtained by encoding two series of sequence data obtained by dividing the sequence data. And the first sequence data B and the second sequence obtained by receiving the transmission signal corresponding to the second sequence data A from the first transmission device and encoding two series of sequence data obtained by dividing the sequence data A reception processing unit that receives a transmission signal corresponding to data B from the second transmission device; and the first sequence data A is the first sequence data And the second sequence data A is encoded by a different encoding method than the second sequence data B, or a transmission signal corresponding to the first sequence data A Is transmitted with a polarization different from that of the transmission signal corresponding to the first sequence data B, and the transmission signal corresponding to the second sequence data A is different from the transmission signal corresponding to the second sequence data B. The gist is that it is transmitted by waves.

FIG. 1 is a schematic block diagram showing the configuration of a transmission system common to the embodiments. FIG. 2 is a schematic block diagram illustrating a configuration of a transmission system common to the embodiments. FIG. 3 is a diagram comparing the encoding methods among the transmission systems of the respective embodiments. FIG. 4 is an equivalent conceptual diagram of the transmission system in the first embodiment. FIG. 5 is an equivalent conceptual diagram of the transmission system in the second embodiment. FIG. 6 is an equivalent conceptual diagram of the transmission system in the third embodiment. FIG. 7 is an equivalent conceptual diagram of the transmission system in the fourth embodiment. FIG. 8 shows the bit error rate characteristics when the radio wave of station B is received without rotating the polarization (rotation angle 0 °). FIG. 9 shows the bit error rate characteristics when the radio wave of station B is received with 90 ° polarization rotation. FIG. 10 is an equivalent conceptual diagram of the transmission system in the fifth embodiment. FIG. 11 is an equivalent conceptual diagram of the transmission system in the sixth embodiment. FIG. 12 is an equivalent conceptual diagram of the transmission system in the seventh embodiment. FIG. 13 is an equivalent conceptual diagram of the transmission system in the eighth embodiment. FIG. 14 is an equivalent conceptual diagram of the transmission system in the ninth embodiment. FIG. 15 is an equivalent conceptual diagram of the transmission system in the tenth embodiment. FIG. 16 is a schematic block diagram illustrating a configuration of a receiving apparatus common to the embodiments. FIG. 17 is a 4 × 2 MIMO transmission model for explaining the transmission system. FIG. 18 is a diagram for explaining a transmission path response matrix of an ideal transmission path and a transmission path response matrix of a transmission path having a 90 ° polarization rotation counterclockwise. FIG. 19 is a table showing the result of determining whether the rank of the transmission line response matrix H has dropped or not by changing the transmission line response matrix H _B of the B station when the transmission line response matrix H _A of the A station is ideal. It is. FIG. 20 is a system diagram of computer simulation. FIG. 21 shows transmission parameters in the computer simulation. FIG. 22 shows a simulation result of bit error rate characteristics in a high D / U environment. FIG. 23 is a simulation result of the relationship between the delay time of the received signal of station B and the required C / N in a low D / U environment. FIG. 24 is a simulation result of the relationship between the received power difference between polarized waves of the received signal of the station B and the required C / N in a low D / U environment. FIG. 25 shows the result of a simulation of the relationship between the angle φ formed by both polarizations of the received signal of station B and the required C / N in a low D / U environment. FIG. 26 is a simulation result of the relationship between the rotation angle χ of the polarization of the received signal of station B and the required C / N in a low D / U environment. FIG. 27 is a comparison of received spectrums depending on the presence / absence of an SFN interference wave at the time of SFN construction. FIG. 28 is a schematic block diagram illustrating a configuration of the transmission device disclosed in Non-Patent Document 1.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic block diagram showing a configuration of a transmission system 5 common to the embodiments. The transmission system 5 includes a transmission system 4 and a reception device 30. Here, the transmission system 4 includes a first transmission device 10 and a second transmission device 20. The first transmission device 10 and the second transmission device 20 are placed at different positions. The first transmission apparatus 10 and the second transmission apparatus 20 transmit different transmission signals obtained by encoding the same data with different encoding matrices, respectively, by space division multiplexing. The receiving device 30 receives the transmission signals transmitted by the first transmitting device 10 and the second transmitting device 20, and decodes the received transmission signals.

FIG. 2 is a schematic block diagram showing the configuration of the transmission system 4 common to the embodiments. The first transmission device 10 and the second transmission device 20 receive the same data. The first transmission device 10 includes an error correction encoding unit 11, a mapping unit (hereinafter also referred to as a mapping unit) 12, a serial / parallel conversion unit (hereinafter also referred to as an S / P unit) 13, an encoding unit 14, and an OFDM

frame Configuration units

151 and 152, an inverse Fourier transform unit 16, a transmission unit 17, a first transmission antenna 181, and a second transmission antenna 182 are provided. Here, the encoding unit 14 includes a first conversion unit 141 and a second conversion unit 142. The transmission unit 17 includes

GI addition units

171 and 172. The inverse Fourier transform unit 16 includes IFFT

units

161 and 162.

The error correction encoding unit 11 performs error correction encoding (for example, LDPC (Low-Density Parity-Check) encoding) on data input from the outside. The error correction encoding unit 11 outputs the signal after error correction encoding to the mapping unit 12.

For example, the mapping unit 12 maps the signal input from the error correction encoding unit 11 on the I / Q plane by QAM (Quadrature Amplitude Modulation) mapping. The mapping unit 12 outputs the symbol series data obtained by mapping to the serial / parallel conversion unit 13.

Note that the mapping in the mapping unit 12 is not limited to QAM, and other mappings may be used. The mapping unit 12 may map the data according to a predetermined rule.

The serial-to-parallel converter 13 converts the symbol series data input from the mapping section 12 into parallel series data in which symbols are parallel. Specifically, for example, the serial-to-parallel converter 13 alternately divides symbols included in the symbol sequence data input from the mapping unit 12 into first sequence data and second sequence data, Convert to parallel series data. The serial-to-parallel converter 13 converts one series of parallel series data obtained by the conversion to the first converter 141 of the encoder 14, and the other series data to the second converter of the encoder 14. 142 to output.

The encoding unit 14 uses an encoding process (for example, an encoding matrix) different from the encoding unit 24 of the second transmission device 20 for the parallel sequence data obtained by the conversion by the serial / parallel conversion unit 13. Process). Specifically, for example, the first conversion unit 141 converts one series of parallel series data according to the first rule. The second conversion unit 142 converts the other series data of the parallel series data according to the second rule. The details of the conversion differ for each embodiment described later, and will be described later for each embodiment. First conversion section 141 outputs the converted signal to OFDM frame configuration section 151. Second conversion section 142 outputs the converted signal to OFDM frame configuration section 152.

The OFDM frame configuration unit 151 generates an OFDM (Orthogonal Frequency-Division Multiplexing) symbol using the encoded signal input from the first conversion unit 141 and the pilot signal held by itself. To do. The OFDM frame configuration unit 151 outputs the generated OFDM symbol to the IFFT unit 161.

The OFDM frame configuration unit 152 generates an OFDM symbol using the encoded signal input from the second conversion unit 142 and the pilot signal held by itself. The OFDM frame configuration unit 152 outputs the generated OFDM symbol to the IFFT unit 162.

The IFFT unit 161 performs inverse Fourier transform on the OFDM symbol input from the OFDM frame configuration unit 151 and outputs a signal obtained by performing inverse Fourier transform to the GI adding unit 171. Moreover, IFFT section 162 performs inverse Fourier transform on the OFDM symbol input from OFDM frame configuration section 152 and outputs a signal obtained by performing inverse Fourier transform to GI adding section 172. In this manner, the inverse Fourier transform unit 16 performs inverse Fourier transform on each of the encoded symbol sequences obtained by the encoding unit 14.

GI adding section 171 adds a GI (Guard Interval: guard interval) to the signal input from IFFT section 161 and transmits the added transmission signal from first transmitting antenna 181. GI adding section 172 adds a GI to the signal input from IFFT section 162 and transmits the added transmission signal from second transmission antenna 182. In this way, the transmission unit 17 transmits one of the transmission signals after the inverse Fourier transform by the inverse Fourier transform unit 16 from the first transmission antenna 181 and the other from the second transmission antenna 182.

The first transmission antenna 181 wirelessly transmits a transmission signal with the first polarization (in this embodiment, horizontal polarization as an example). The second transmission antenna 182 wirelessly transmits a transmission signal with a second polarization different from the first polarization (in this embodiment, a vertical polarization as an example).

The second transmission apparatus 20 includes an error correction encoding unit 21, a mapping unit 22, a serial / parallel conversion unit 23, an encoding unit 24, OFDM

frame configuration units

251, 252, an inverse Fourier transform unit 26, a

transmission unit

27, 3 transmission antennas 281 and a fourth transmission antenna 282. Here, the encoding unit 24 includes a third conversion unit 241 and a fourth conversion unit 242. The transmission unit 27 includes

GI addition units

271 and 272. The inverse Fourier transform unit 26 includes IFFT

units

261 and 262.

The error correction encoding unit 21 performs the same processing as the error correction encoding unit 11. The mapping unit 22 performs the same process as the mapping unit 12. The serial / parallel converter 23 performs the same processing as the serial / parallel converter 13. The encoding unit 24 uses an encoding process (for example, an encoding matrix) that is different from the encoding unit 14 of the first transmission device 10 for the parallel sequence data obtained by the conversion from the serial / parallel conversion unit 23. Process).

Specifically, for example, the third conversion unit 241 converts one series data of the parallel series data according to the third rule. The fourth conversion unit 242 converts the other series data among the parallel series data according to the fourth rule. The details of the conversion differ for each embodiment described later, and will be described later for each embodiment. The third conversion unit 241 outputs the converted signal to the OFDM frame configuration unit 251. The fourth conversion unit 242 outputs the converted signal to the OFDM frame configuration unit 252.

The OFDM

frame configuration units

251 and 252 perform the same processing as the OFDM

frame configuration units

151 and 152, respectively. The

GI adding units

271 and 272 perform the same processing as the

GI adding units

171 and 172, respectively.

The third transmission antenna 281 wirelessly transmits a transmission signal with the first polarization (in this embodiment, horizontal polarization as an example). The fourth transmission antenna 282 wirelessly transmits a transmission signal with a second polarization different from the first polarization (in this embodiment, a vertical polarization as an example).

Hereinafter, the first transmitter 10 is also referred to as A station, and the second transmitter 20 is also referred to as B station. The first transmission antenna 181 is also referred to as antenna 0, the second transmission antenna 182 is also referred to as antenna 1, the third transmission antenna 281 is also referred to as antenna 2, and the fourth transmission antenna 282 is also referred to as antenna 3.

Also, hereinafter, as an example, PDM (Polarization Division Multiplexing) that performs multiplexed transmission of data using orthogonal polarizations is assumed. As an example of orthogonal polarization, a PDM using horizontal polarization and vertical polarization is assumed as an example. In station A, antenna 0 transmits with horizontal polarization, and antenna 1 transmits with vertical polarization. In the station B, the antenna 2 transmits the signal with horizontal polarization, and the antenna 3 transmits the signal with vertical polarization.

FIG. 3 is a diagram comparing the encoding methods among the transmission systems of the respective embodiments. The “encoded pair” in the figure is a set of transmission signals after encoding the same data. “Transmission with the same polarization” means that two transmission signals constituting the encoded pair are transmitted with the same polarization. “Transmission with cross polarization” means that two transmission signals constituting an encoded pair are transmitted with polarizations orthogonal to each other. In addition, it is shown whether or not there is a code inversion in a space-time block coding matrix of one coding matrix (for example, either STBC0 or STBC1) described later.

Also, each embodiment is divided into STBC (Space Time Block Coding) and SFBC (Space Frequency Block Code) as encoding rules used in the transmission system. In each column, a pair of the number of the embodiment and the STBC0 encoding matrix used in the embodiment and the STBC1 encoding matrix used in the embodiment are shown below the embodiment number. ing.

Examples 1 to 4 are examples in which Alamouti STBC is applied at least partially. Examples 5 to 8 are examples in which at least a part of Modified Alamouti STBC is applied. In the case of MISO transmission, this modified Alamouti is standardized in the European terrestrial digital broadcasting transmission system DVB-T2.

In Alamouti STBC, encoding is performed using matrix J in equation (1), so that complex conjugate processing occurs in the signal at time t + 1 of the A station and B station of the transmitting station. In Modified Alamouti, the A station of the transmitting station No signal inversion is performed on the signal transmitted from No. 1, and sign inversion is applied only to the signal of station B. As a result, when there is an A station that has already started the service, the A station transmits a conventional signal, and the modulator provided in the B station newly constructed in the service area supports the encoding of Modified Alamouti. It is also possible to make it.

Examples 9 and 10 are cases of SFBC in which Alamouti STBC is applied in the frequency direction. A method for applying the above-mentioned Modified Alamouti to SFBC is standardized by the communication standard LTE (Long Term Evolution). The description of Example 11 in the figure is omitted, but the results of evaluating the transmission characteristics will be described with reference to FIGS. In the figure, the description of “omission” is omitted.

Further, in the embodiment of the hatched region, as will be described later, even if there is a polarization rotation in the propagation path from one transmission device to the reception device 30, the observation equation described later does not overlap. The transmission signal can be calculated from the reception signal. As a result, in the embodiment of the hatched area, there is an advantage that the transmission characteristics are not deteriorated even if there is a polarization rotation in the propagation path from the one transmission apparatus to the reception apparatus 30.

Subsequently, the configuration of the transmission system in Non-Patent Document 1 will be described for comparison with examples described later. FIG. 28 is a schematic block diagram illustrating a configuration of the transmission device disclosed in Non-Patent Document 1. In the transmission system of the figure, STBC0 and STBC1 encode symbol sequence data in accordance with, for example, the matrix J in equation (1).

Here, the matrix J in Equation (1) is an Alamouti space-time block coding matrix. A row of the matrix J corresponds to a transmission antenna number, and the matrix J is used when signals are transmitted by two transmission antennas. The column of the matrix J corresponds to the transmission time.

In the example of FIG. 28, STBC0 converts the symbol “S0, S2” to “S0” at time t and “−S2 ^* ” at time t + 1. The IFFT unit performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 0. In the example of FIG. 28, STBC0 converts the symbol “S0, S2” to “S2” at time t and “S0 ^* ” at time t + 1. The IFFT unit performs inverse Fourier transform (IFFT) on the converted signal and transmits the signal after IFFT from the antenna 1.

In the example of FIG. 28, the STBC 1 converts the symbol “S1, S3” to “S1” at time t and “−S3 ^* ” at time t + 1. The IFFT unit performs inverse Fourier transform (IFFT) on the converted signal and transmits the signal after IFFT from the antenna 2. In the example of FIG. 28, STBC1 converts the symbol “S1, S3” to “S3” at time t and “S1 ^* ” at time t + 1. The IFFT unit performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 3.

[Example 1]
FIG. 4 is an equivalent conceptual diagram of the transmission system in the first embodiment. The figure is a conceptual diagram for comparison that makes it easy to understand the difference from the transmission system of Non-Patent Document 1, and is different from the actual configuration of the transmission system. STBC0 and STBC1 are virtual configurations, and such a member does not exist in the transmission system 4. Further, the mapping unit and the S / P unit are described so as to be common to the first transmission device 10 and the second transmission device 20, but the transmission system 4 is not common as an example. Hereinafter, the same points are different from the configuration of the transmission system 4 in the other embodiments.

Non-Patent Document 1 presents the transmission device of FIG. 28, but does not define the physical arrangement of antennas 0 to 3. In the first embodiment, the antennas 0 to 3 are arranged as shown in FIG. 4 so that data encoded by STBC is transmitted from the A station and the B station. In the figure, H represents transmission with horizontal polarization, and V represents transmission with vertical polarization. The same applies to the following figures. In FIG. 4, in STBC0 and STBC1, for example, symbol series data is encoded in accordance with matrix J in equation (1). Specifically, for example, the STBC0 and STBC1 convert the series data of the symbol “S0, S2” into two series data “S0, −S2 ^* ” and “S2, S0 ^* ”.

In the actual configuration of the first embodiment, the first converter 141 converts, for example, the symbol “S0, S2” into series data in which “S0” is assigned at time t and “−S2 ^* ” is assigned at time t + 1. IFFT section 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 0. The third conversion unit 241 converts, for example, the symbol “S0, S2” into series data in which “S2” is assigned to time t and “S0 ^* ” is assigned to time t + 1. IFFT section 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 2.

The second conversion unit 142 converts, for example, the symbols “S1, S3” into series data in which “S1” is assigned at time t and “−S3 ^* ” is assigned at time t + 1. IFFT section 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 1. The fourth conversion unit 242 converts, for example, the symbols “S1, S3” into series data in which “S3” is assigned to time t and “S1 ^* ” is assigned to time t + 1. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 3.

Therefore, the encoding unit 14 and the encoding unit 24 encode each of the parallel series data obtained by conversion by the serial / parallel conversion unit (13 or 23) for each block. At that time, the encoding unit 14 and the encoding unit 24 are encoded signals obtained by encoding the same symbol by the other transmission apparatus used in the transmission system 4 that encodes the symbol sequence data. The sequence data of the symbol is encoded so that encoded signals having different allocated times and complex conjugate relations can be obtained.

In the first embodiment, the transmission characteristics deteriorate due to the 90-degree polarization rotation in the propagation path of the B station. However, the transmission characteristics do not deteriorate without the 90-degree polarization rotation (see FIGS. 8 and 9 to be described later). ). In Non-Patent Document 1, assuming that the antenna 2 and the antenna 3 are installed in the B station, if the signal from the B station cannot be received at all, the receiving apparatus can receive S0 and S2, but S1 And S3 cannot be received, so that all data could not be restored.

On the other hand, in the first embodiment, even when the signal from the station B cannot be received at all (for example, when the station B is broken), the station A is assigned to all symbols (for example, S0, S1, S2, S3). Since the base signal can be transmitted, the receiving device 30 receiving the signal has an advantage that all data can be restored.

[Example 1 ']
The transmission system 4 in Embodiment 1 ′ performs the same processing as that in Embodiment 1, but differs from Embodiment 1 in the following points. In Example 1 ′, STBC0 and STBC1 encode symbol series data according to a matrix K different from that in Example 1. The matrix K is expressed by the following equation (2).

Here, the matrix K is different from the matrix J in that the sign of the element in the first row and the second column is plus and the sign of the element in the second row and the second column is minus. That is, the sign of the second column is inverted.

[Example 2]
FIG. 5 is an equivalent conceptual diagram of the transmission system in the second embodiment. The STBC 0 encodes the symbol series data in accordance with, for example, the matrix J in the equation (1). On the other hand, the STBC 1 encodes the symbol series data according to, for example, the matrix K in Expression (2).

In an actual configuration, the first conversion unit 141 converts, for example, the symbol “S0, S2” into series data in which “S0” is assigned at time t and “−S2 ^* ” is assigned at time t + 1. The IFFT unit 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 0 in, for example, horizontal polarization. The third conversion unit 241 converts, for example, the symbol “S0, S2” into series data in which “S2” is assigned to time t and “S0 ^* ” is assigned to time t + 1. The IFFT unit 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 2 in, for example, horizontal polarization.

The second conversion unit 142 converts, for example, the symbols “S1, S3” into series data in which “S1” is assigned at time t and “S3 ^* ” is assigned at time t + 1. The IFFT unit 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 1 with, for example, vertical polarization. Further, the fourth conversion unit 242 converts, for example, the symbols “S1, S3” into series data in which “S3” is assigned at time t and “−S1 ^* ” is assigned at time t + 1. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 3 by, for example, vertical polarization.

In STBC1, the sign of the second column of the matrix K is inverted from the sign of the second column of the matrix J. At time t + 1, the encoded symbol “−S2 ^* ” for transmission through antenna 0 and the encoded symbol “S3 ^* ” for transmission through antenna 1 have different codes. Also, the encoded symbol “S0 ^* ” for transmission through the antenna 2 of the B station and the encoded symbol “−S1 ^* ” for transmission through the antenna 3 of the B station have different codes.

As described above, in the second embodiment, the code of each component in the second column of the matrix K used for STBC encoding is different from the code of the corresponding component in the second column of the matrix J. If the viewpoint is changed, the encoding unit 14 and the encoding unit 24 perform encoding for each block, and at one time in the block (for example, time t + 1), the transmission apparatus has the same polarization. The codes of the encoded symbols to be transmitted are different from each other, and at one time (for example, time t + 1), the encoded code of one of the parallel sequence data is the code of the other sequence data. Encoding is performed differently from the encoded code. Further, at that time, the encoding unit 14 and the encoding unit 24 are the encoded signals obtained by encoding the same symbol by the other transmitting apparatus used in the transmission system 4 as in the first embodiment. , Encoding is performed so that encoded signals having different allocation times and complex conjugate relations can be obtained. Thereby, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the observation equation described later does not overlap, so that the receiving device 30 can calculate the transmission signal from the received signal. As a result, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the transmission characteristics do not deteriorate, which is an advantage over the first embodiment.

[Example 2 ']
The transmission system 4 in the second embodiment performs processing similar to that in the second embodiment, but differs from the second embodiment in the following points. In the second embodiment, contrary to the second embodiment, the STBC 0 encodes the symbol sequence data according to the matrix K. The STBC 1 encodes the symbol sequence data according to the matrix J.

[Example 3]
FIG. 6 is an equivalent conceptual diagram of the transmission system 4 in the third embodiment. In the transmission system 4 in the figure, both STBC0 and STBC1 realize STBC by the matrix J of Expression (1). The transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 through the antenna 0 of the A station and the antenna 3 of the B station, respectively. As an example, the antenna 0 transmits a transmission signal with horizontal polarization, and the antenna 3 transmits a transmission signal with vertical polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0, using different transmission apparatuses and different polarizations.

Further, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 by the antenna 1 of the A station and the antenna 2 of the B station, respectively. As an example, the antenna 1 transmits a transmission signal with vertical polarization, and the antenna 2 transmits a transmission signal with horizontal polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from different transmission apparatuses and with different polarizations.

Note that the antenna 0 and the antenna 2 may transmit a transmission signal with vertical polarization, and the antenna 1 and the antenna 3 may transmit a transmission signal with horizontal polarization.

In an actual configuration, the first conversion unit 141 converts, for example, the symbol “S0, S2” into series data in which “S0” is assigned at time t and “−S2 ^* ” is assigned at time t + 1. IFFT section 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 0. The third conversion unit 241 converts, for example, the symbol “S0, S2” into series data in which “S2” is assigned to time t and “S0 ^* ” is assigned to time t + 1. IFFT section 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 3.

The second conversion unit 142 converts, for example, the symbols “S1, S3” into series data in which “S1” is assigned at time t and “−S3 ^* ” is assigned at time t + 1. IFFT section 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 1. The fourth conversion unit 242 converts, for example, the symbols “S1, S3” into series data in which “S3” is assigned to time t and “S1 ^* ” is assigned to time t + 1. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 2.

As described above, in the third embodiment, the transmission system 4 transmits two transmission signals obtained by STBC encoding the same information from different transmission apparatuses and with different polarizations. When the viewpoint is changed, when one transmission apparatus transmits a transmission signal derived from the same information as another transmission signal transmitted by the other transmission apparatus, the other transmission apparatus transmits the other transmission signal. A transmission signal is transmitted with a polarization different from the polarization. In addition, the encoding unit 14 and the encoding unit 24 perform encoding for each block, and at one time (for example, time t + 1), the code after encoding one of the parallel sequence data. Is encoded to be the same as the encoded code of the other sequence data. In addition, at that time, the encoding unit 14 and the encoding unit 24 have the encoded code transmitted with the same polarization as that of the other transmitting apparatuses at the one time (for example, time t + 1). Encoding is performed differently from the symbol code. Thereby, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the observation equation described later does not overlap, so that the receiving device 30 can calculate the transmission signal from the received signal. As a result, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the transmission characteristics do not deteriorate, which is an advantage over the first embodiment.

[Example 3 ']
The transmission system 4 in the third embodiment performs processing similar to that in the third embodiment, but differs from the third embodiment in the following points. In the third embodiment, STBC0 and STBC1 encode the symbol series data according to a matrix K different from that of the third embodiment.

[Example 4]
FIG. 7 is an equivalent conceptual diagram of the transmission system 4 in the fourth embodiment. In the transmission system 4 in the figure, STBC0 implements STBC using the matrix J of Equation (1), and STBC1 implements STBC using the matrix K of Equation (2). The transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 from the antenna 0 of the A station and the antenna 3 of the B station, respectively. Here, the antenna 0 transmits a transmission signal with horizontal polarization, and the antenna 3 transmits a transmission signal with vertical polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 from different transmission apparatuses and with different polarizations.

Also, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from the antenna 1 of the A station and the antenna 2 of the B station, respectively. Here, the antenna 1 transmits a transmission signal with vertical polarization, and the antenna 2 transmits a transmission signal with horizontal polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from different transmission apparatuses and with different polarizations.

In an actual configuration, the first conversion unit 141 converts, for example, the symbol “S0, S2” into series data in which “S0” is assigned at time t and “−S2 ^* ” is assigned at time t + 1. IFFT section 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 0. The third conversion unit 241 converts, for example, the symbol “S0, S2” into series data assigned to “S2” at time t and “S0 ^* ” at time t + 1. IFFT section 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 3.

The second conversion unit 142 converts, for example, the symbols “S1, S3” into series data in which “S1” is assigned at time t and “S3 ^* ” is assigned at time t + 1. IFFT section 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 1. Further, the fourth conversion unit 242 converts, for example, the symbols “S1, S3” into series data in which “S3” is assigned at time t and “−S1 ^* ” is assigned at time t + 1. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 2.

As described above, in the fourth embodiment, the transmission system 4 transmits two transmission signals obtained by STBC encoding the same information from different transmission apparatuses and with different polarizations. Also, the code of each component in the second column of the matrix K used for STBC encoding is different from the code of each component in the second column of the matrix J. When changing the viewpoint, when the transmission unit of one transmission device transmits a transmission signal derived from the same information as the other transmission signal transmitted by the other transmission device, the transmission unit transmits the polarized wave transmitted by the other transmission device. Transmit with different polarizations. That is, the first transmission device transmits a transmission signal from a transmission antenna that transmits with a polarization different from the polarization transmitted by the other transmission device, out of the first transmission antenna 181 or the second transmission antenna 182.

In addition, the encoding unit 14 and the encoding unit 24 encode each block, and at one time (for example, time t + 1), after one of the parallel sequence data is encoded. Encoding is performed so that the code is different from the encoded code of the other sequence data. In addition, at that time, the encoding unit 14 and the encoding unit 24 have the encoded code transmitted with the same polarization as that of the other transmitting apparatuses at the one time (for example, time t + 1). Encode to be the same as the symbol code. At that time, as in the first embodiment, the encoding unit 14 and the encoding unit 24 are encoded signals obtained by encoding the same symbol by the other transmission device used in the transmission system. Encoding is performed so that encoded signals having different time allocations and complex conjugate relations can be obtained.

Subsequently, simulation results of characteristics when the radio wave of the A station is received by the main lobe of the receiving antenna and the radio wave of the B station is received by the side lobe will be described with reference to FIGS. As simulation conditions, the modulation multi-level number is 1024QAM, and the FFT size is 8k. Further, C / N (Carrier to Noise Ratio) is defined by the ratio of the noise power to the received power of the A station under the condition that the received power of the A station and the B station is the same, that is, D / U is 0 dB. This simulation result is a result of measuring the bit error rate (BER) at that time.

FIG. 8 shows the bit error rate characteristics when the radio wave of station B is received without rotating the polarization (rotation angle 0 °). The vertical axis represents the bit error rate (BER), and the horizontal axis represents the average received C / N of each polarization. In the figure, both the first embodiment and the third embodiment show substantially the same bit error rate characteristics. In either case, the C / N at which the bit error rate is 1.0 × 10 ⁻⁷ is about 23 dB.

FIG. 9 shows the bit error rate characteristics when the radio wave of station B is received with 90 ° polarization rotation. The vertical axis represents the bit error rate (BER), and the horizontal axis represents the average received C / N of each polarization. In the figure, the bit error rate characteristic of the third embodiment is almost the same as the bit error rate characteristic of the third embodiment in FIG. The C / N at which the bit error rate is 1.0 × 10 ⁻⁷ is about 23 dB. On the other hand, in Example 1, the bit error rate remains high even when C / N is increased.

8 and 9, in the first embodiment, the transmission characteristic when the received signal of the B station has a 90 ° polarization rotation is deteriorated as compared with the case where the received signal of the B station has no polarization rotation. On the other hand, in the third embodiment, the transmission characteristics when the received signal of the B station has a 90 ° polarization rotation are not deteriorated compared to the transmission characteristics when the received signal of the B station has no polarization rotation. Since Example 2 shows the same characteristics as Example 3, it is omitted. As described above, in the second and third embodiments, the transmission system 5 does not deteriorate the transmission characteristics even if the received signal of the B station has a 90 ° polarization rotation.

[Example 4 ']
The transmission system 4 in the fourth embodiment performs processing similar to that of the fourth embodiment, but differs from the fourth embodiment in the following points. In the fourth embodiment, contrary to the fourth embodiment, the STBC 0 encodes the symbol sequence data according to the matrix K. The STBC 1 encodes the symbol sequence data according to the matrix J.

[Example 5]
FIG. 10 is an equivalent conceptual diagram of the transmission system 4 in the fifth embodiment. In the transmission system 4 in the figure, the STBC0 and STBC1 encode the symbol series data, for example, according to the matrix L in Expression (3). Here, the matrix L in Expression (3) is a partially modified Alamouti space-time block coding matrix J (Modified Alamouti).

The row of the matrix L corresponds to the antenna number, and the column corresponds to the transmission time. The transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 by the antenna 0 of the A station and the antenna 2 of the B station, respectively. Here, antenna 0 transmits a transmission signal with horizontal polarization, and antenna 2 transmits a transmission signal with horizontal polarization. That is, the transmission system 4 transmits each of two transmission signals obtained by STBC encoding with STBC0 from different transmission apparatuses with the same polarization (same polarization).

Also, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from the antenna 1 of the A station and the antenna 3 of the B station, respectively. Here, the antenna 1 transmits a transmission signal with vertical polarization, and the antenna 3 transmits a transmission signal with vertical polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from different transmission apparatuses with the same polarization (same polarization).

In an actual configuration, the first conversion unit 141 outputs, for example, series data in which “S0” is assigned at time t and “S2” is assigned at time t + 1 without converting the symbols “S0, S2”. IFFT section 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 0. The third conversion unit 241, for example, the symbol "S0, S2 'to the time t" -S2 ^* "is converted to time t + 1" S0 ^* "in the allocated sequence data. IFFT section 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 2.

For example, the second conversion unit 142 outputs series data in which “S1” is assigned to time t and “S3” is assigned to time t + 1 without converting “S1, S3”. IFFT section 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 1. The fourth conversion unit 242, "-S3 ^*", for example, "S1, S3" time t, is converted to time t + 1 "S1 ^*" in the allocated sequence data. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 3.

As described above, in the fifth embodiment, the encoding unit 14 in the first transmission device (A station) 10 outputs the symbol sequence as it is without changing the input symbol sequence. The encoding unit 24 in the second transmission device (B station) 20 changes the input symbol sequence. As a result, when there is an A station that has already started the service, the encoding unit 24 provided in the B station to be newly constructed in the service area while the A station transmits a conventional signal, the encoding of Modified Alamouti Therefore, the construction cost of the broadcasting network can be reduced.

[Example 5 ']
The transmission system 4 in the fifth embodiment performs the same processing as the fifth embodiment, but differs from the fifth embodiment in the following points. In Example 5 ′, STBC0 and STBC1 encode symbol series data according to a matrix M different from Example 5, respectively. The matrix M is expressed by the following equation (4).

Compared with the matrix L, the sign of each component in the second row is inverted in the matrix M.

[Example 6]
Example 6 is an example in the case where there is a code inversion of the modified Alamouti space-time block coding matrix in STBC1. FIG. 11 is an equivalent conceptual diagram of the transmission system in the sixth embodiment. The STBC 0 performs STBC on the symbol series data using the matrix L in the equation (3). On the other hand, STBC 1 applies STBC to the symbol series data using matrix M shown in Equation (4).

The transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 from the antenna 0 of the A station and the antenna 2 of the B station, respectively. Here, antenna 0 transmits a transmission signal with horizontal polarization, and antenna 2 transmits a transmission signal with horizontal polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 from different transmission apparatuses and with the same polarization (same polarization).

Also, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from the antenna 1 of the A station and the antenna 3 of the B station, respectively. Here, the antenna 1 transmits a transmission signal with vertical polarization, and the antenna 3 transmits a transmission signal with vertical polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from different transmission apparatuses and with the same polarization (same polarization).

In the actual configuration, the first conversion unit 141 outputs, for example, sequence data in which “S0” is assigned at time t and “S2” is assigned at time t + 1 without converting the symbols “S0, S2”. IFFT section 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 0. The third conversion unit 241, for example, the symbol "S0, S2 'to the time t" -S2 ^* "is converted to time t + 1" S0 ^* "in the allocated sequence data. IFFT section 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 2.

For example, the second conversion unit 142 outputs series data in which “S1” is assigned to time t and “S3” is assigned to time t + 1 without converting the symbols “S1, S3”. IFFT section 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 1. The fourth conversion unit 242, "S3 ^*" for example the symbol "S1, S3" time t, is converted to time t + 1 "-S1 ^*" in the allocated sequence data. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 3.

From this, the encoding unit 24 encodes each of the parallel sequence data for each block, and at each time in the block, after encoding one of the parallel sequence data, Encoding is performed so that the code is different from the encoded code of the other sequence data. Also, at that time, the encoding unit 24 refers to an encoded signal obtained by encoding the same symbol by the first transmission device 10 which is the other transmission device used in the transmission system 4. Are encoded so that encoded signals having different complex conjugate relations can be obtained.

As described above, in the sixth embodiment, the antenna 2 in the B station transmits “−S2 ^* , S0 ^* ”, and the antenna 3 transmits “S3 ^* , −S1 ^* ”. The sign of the signal after encoding at the respective times differs between the antenna 2 and the antenna 3. In the fifth embodiment, since the antenna 3 transmits “−S3 ^* , S1 ^* ”, the sign of the signal transmitted by the antenna 3 is reversed before and after the fifth embodiment. Thereby, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the observation equation described later does not overlap, so that the receiving device 30 can calculate the transmission signal from the received signal. As a result, the transmission characteristics do not deteriorate even if the polarization rotation of the B station is present, which is an advantage over the fifth embodiment.

[Example 6 ']
The transmission system 4 in the sixth embodiment performs processing similar to that of the sixth embodiment, but differs from the sixth embodiment in the following points. In the sixth embodiment, contrary to the sixth embodiment, the STBC 0 encodes the symbol sequence data according to the matrix M. The STBC 1 encodes the symbol sequence data according to the matrix L.

[Example 7]
FIG. 12 is an equivalent conceptual diagram of the transmission system 4 in the seventh embodiment. In the transmission system 4 in the figure, both STBC0 and STBC1 perform STBC encoding using the matrix L of Equation (3). The transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 through the antenna 0 of the A station and the antenna 3 of the B station, respectively. Here, the antenna 0 transmits a transmission signal with horizontal polarization, and the antenna 3 transmits a transmission signal with vertical polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 using different transmission apparatuses and different polarizations (cross polarizations).

Further, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 by the antenna 1 of the A station and the antenna 2 of the B station, respectively. Here, the antenna 1 transmits a transmission signal with vertical polarization, and the antenna 2 transmits a transmission signal with horizontal polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from different transmission apparatuses and with different polarizations (cross polarizations).

As described above, in the seventh embodiment, the transmission system 4 transmits each of two transmission signals obtained by STBC encoding from different transmission apparatuses and with different polarizations. When the viewpoint is changed, the transmission unit 17 of the first transmission device 10 transmits the transmission signal derived from the same information as the other transmission signals transmitted by the second transmission device 20 when the first transmission antenna is transmitted. Among the transmission antennas 181 or 182, the transmission signal is transmitted from a transmission antenna that transmits a transmission signal with a polarization different from the polarization with which another transmission apparatus transmits another transmission signal. Thereby, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the observation equation described later does not overlap, so that the receiving device 30 can calculate the transmission signal from the received signal. As a result, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the transmission characteristics are not deteriorated, which is an advantage over the fifth embodiment.

[Example 7 ']
The transmission system 4 in the embodiment 7 ′ performs the same processing as that in the embodiment 7, but differs from the embodiment 7 in the following points. In Example 7 ′, STBC0 and STBC1 encode symbol series data according to a matrix M different from Example 7, respectively.

[Example 8]
FIG. 13 is an equivalent conceptual diagram of the transmission system 4 in the eighth embodiment. In the transmission system 4 shown in the figure, STBC0 implements STBC using the matrix L of Equation (3), and STBC1 implements STBC using the matrix M of Equation (4). The transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 from the antenna 0 of the A station and the antenna 3 of the B station, respectively. Here, the antenna 0 transmits a transmission signal with horizontal polarization, and the antenna 3 transmits a transmission signal with vertical polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with STBC0 from different transmission apparatuses and with different polarizations (cross polarization).

Also, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from the antenna 1 of the A station and the antenna 2 of the B station, respectively. Here, the antenna 1 transmits a transmission signal with vertical polarization, and the antenna 2 transmits a transmission signal with horizontal polarization. That is, the transmission system 4 transmits two transmission signals obtained by STBC encoding with the STBC 1 from different transmission apparatuses and with different polarizations (cross polarizations).

In an actual configuration, the first conversion unit 141 outputs, for example, series data in which “S0” is assigned at time t and “S2” is assigned at time t + 1 without converting the symbols “S0, S2”. IFFT section 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 0. The third conversion unit 241, for example, the symbol "S0, S2 'to the time t" -S2 ^* "is converted to time t + 1" S0 ^* "in the allocated sequence data. IFFT section 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 3.

The second conversion unit 142 outputs, for example, the series “S1” at time t and “S3” at time t + 1 without converting the symbols “S1, S3”. IFFT section 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 1. The fourth conversion unit 242, "S3 ^*" for example the symbol "S1, S3" time t, is converted to time t + 1 "-S1 ^*" in the allocated sequence data. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 2.

As described above, in the eighth embodiment, the transmission system 4 transmits each of two transmission signals obtained by STBC encoding from different transmission apparatuses and with different polarizations. In the transmission system 4, STBC0 implements STBC using the matrix L of Equation (3), and STBC1 implements STBC using the matrix M of Equation (4).

[Example 8 ']
The transmission system 4 in the eighth embodiment performs the same processing as the eighth embodiment, but differs from the eighth embodiment in the following points. In the eighth embodiment, contrary to the eighth embodiment, STBC0 encodes the symbol sequence data according to the matrix M. The STBC 1 encodes the symbol sequence data according to the matrix L.

[Example 9]
Next, the ninth embodiment shows a case of SFBC in which Alamouti STBC is applied in the frequency direction. FIG. 14 is an equivalent conceptual diagram of the transmission system in the ninth embodiment. SFBC0 and SFBC1 implement SFBC encoding using the matrix J of Equation (1). At this time, the rows of the matrix J correspond to antenna numbers, and the columns correspond to frequencies (or carrier numbers for multicarrier transmission in OFDM transmission). The transmission system 4 transmits two transmission signals obtained by SFBC encoding with SFBC0 from the antenna 0 of the A station and the antenna 2 of the B station, respectively. Here, as an example, both antenna 0 and antenna 2 transmit transmission signals with horizontal polarization. That is, the transmission system 4 transmits two transmission signals obtained by performing SFBC encoding with SFBC0 from different transmission apparatuses and with the same polarization (same polarization).

The transmission system 4 transmits two transmission signals obtained by SFBC encoding with SFBC 1 from the antenna 1 of the A station and the antenna 3 of the B station, respectively. Here, as an example, both the antenna 1 and the antenna 3 transmit transmission signals with vertical polarization. That is, the transmission system 4 transmits each of two transmission signals obtained by performing SFBC encoding with SFBC1 from different transmission apparatuses and with the same polarization (same polarization).

In an actual configuration, the first conversion unit 141 converts, for example, “S0, S2” into sequence data in which “S0” is assigned to the frequency f and “−S2 ^* ” is assigned to the frequency f + 1. IFFT section 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 0. The third conversion unit 241 converts, for example, “S0, S2” into sequence data in which “S2” is assigned to the frequency f and “S0 ^* ” is assigned to the frequency f + 1. IFFT section 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 2.

The second conversion unit 142 converts, for example, “S1, S3” into sequence data in which “S1” is assigned to the frequency f and “−S3 ^* ” is assigned to the frequency f + 1. IFFT section 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from antenna 1. Further, the fourth conversion unit 242 converts, for example, “S1, S3” into sequence data in which “S3” is assigned to the frequency f and “S1 ^* ” is assigned to the frequency f + 1. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 3.

Therefore, the encoding unit 14 and the encoding unit 24 encode each of the parallel series data obtained by conversion by the serial / parallel conversion unit (13 or 23) for each block. At that time, the encoding unit 14 and the encoding unit 24 are encoded signals obtained by encoding the same symbol by the other transmission apparatus used in the transmission system 4 that encodes the symbol sequence data. The sequence data of the symbols are encoded so that the assigned frequencies are different and are in a complex conjugate relationship with each other.

As described above, in the ninth embodiment, the transmission system 4 transmits each of two transmission signals obtained by SFBC encoding from different transmission apparatuses with the same polarization (same polarization). In Non-Patent Document 1, if the signal from the B station cannot be received at all, the receiving device can receive S0 and S2, but cannot receive S1 and S3, and therefore cannot restore all data. It was.

On the other hand, in the ninth embodiment, even when the signal from the B station cannot be received at all (for example, when the B station crashes), the A station has all symbols (for example, S0, S1, S2, S3). Since the base signal can be transmitted, the receiving device that receives the signal has the advantage that all data can be recovered.

[Example 9 ']
The transmission system 4 in the ninth embodiment performs the same processing as that of the ninth embodiment, but differs from the ninth embodiment in the following points. In the ninth embodiment, SFBC0 and SFBC1 each encode the symbol series data according to a matrix K different from the ninth embodiment.

[Example 10]
FIG. 15 is an equivalent conceptual diagram of the transmission system in the tenth embodiment. SFBC0 encodes the symbol series data in accordance with, for example, the matrix J in equation (1). On the other hand, SFBC1 encodes the symbol series data according to, for example, the matrix K shown in Expression (2). The transmission system 4 transmits two transmission signals obtained by SFBC encoding with SFBC0 using the antenna 0 of the A station and the antenna 2 of the B station, respectively. Here, as an example, both antenna 0 and antenna 2 transmit transmission signals with horizontal polarization. That is, the transmission system 4 transmits two transmission signals obtained by performing SFBC coding with SFBC0, using different transmission apparatuses and the same polarization (same polarization).

Also, the transmission system 4 transmits two transmission signals obtained by performing SFBC encoding with SFBC 1 through the antenna 1 of the A station and the antenna 3 of the B station, respectively. As an example, the antenna 1 transmits a transmission signal with vertical polarization, and the antenna 3 also transmits a transmission signal with vertical polarization. That is, the transmission system 4 transmits two transmission signals obtained by performing SFBC encoding with SFBC1 from different transmission apparatuses and using the same polarization (same polarization).

In an actual configuration, the first conversion unit 141 converts, for example, “S0, S2” into sequence data in which “S0” is assigned to the frequency f and “−S2 ^* ” is assigned to the frequency f + 1. The IFFT unit 161 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 0 in, for example, horizontal polarization. The third conversion unit 241 converts, for example, “S0, S2” into sequence data in which “S2” is assigned to the frequency f and “S0 ^* ” is assigned to the frequency f + 1. The IFFT unit 261 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 2 in, for example, horizontal polarization.

For example, the second conversion unit 142 converts “S1, S3” into sequence data in which “S1” is assigned to the frequency f and “S3 ^* ” is assigned to the frequency f + 1. The IFFT unit 162 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 1 with, for example, vertical polarization. Further, the fourth conversion unit 242 converts, for example, “S1, S3” into sequence data in which “S3” is assigned to the frequency f and “−S1 ^* ” is assigned to the frequency f + 1. The IFFT unit 262 performs inverse Fourier transform (IFFT) on the converted signal, and transmits the signal after IFFT from the antenna 3 by, for example, vertical polarization.

As described above, in the tenth embodiment, the code of each component in the second column of the matrix K used for SFBC encoding is different from the code of the corresponding component in the second column of the matrix J. If the viewpoint is changed, the encoding unit 14 and the encoding unit 24 perform encoding for each block, and the same polarization between the transmission apparatuses at one frequency (for example, frequency f + 1) in the block. In the one frequency (for example, frequency f + 1), the code after encoding of one of the parallel sequence data is different from the code of the other sequence data. Encoding is performed differently from the encoded code. Thereby, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the observation equation described later does not overlap, so that the receiving device 30 can calculate the transmission signal from the received signal. As a result, even if there is a polarization rotation in the propagation path from the B station to the receiving device 30, the transmission characteristics are not deteriorated, which is an advantage over the ninth embodiment.

[Example 10 ']
The transmission system 4 in the embodiment 10 ′ performs the same processing as that in the embodiment 10, but differs from the embodiment 10 in the following points. In the second embodiment, contrary to the second embodiment, SFBC0 encodes the symbol series data according to the matrix K. The SFBC 1 encodes the symbol series data according to the matrix J.

Subsequently, the receiving device 30 will be described. FIG. 16 is a schematic block diagram illustrating the configuration of the receiving device 30 common to the embodiments. The receiving device 30 includes a first receiving antenna 311, a second receiving antenna 312,

GI removal units

321 and 322, a Fourier transform unit 33, a transmission path response estimation unit 34, a transmission signal detection unit 35, a parallel / serial conversion unit 36, A carrier demodulation unit 37 and an error correction code decoding unit 38 are provided. The Fourier transform unit 33 includes an FFT unit 331 and an FFT unit 332.

The first receiving antenna 311 is an antenna that receives a horizontally polarized signal as an example. The first receiving antenna 311 is also referred to as Rx0 (horizontal). The first reception antenna 311 receives a horizontally polarized signal among the signals transmitted from the first transmission device 10 and the second transmission device 20, and outputs the received reception signal to the GI removal unit 321.

The second receiving antenna 312 is an antenna that receives a vertically polarized signal as an example. The second receiving antenna 312 is also referred to as Rx1 (vertical). The second reception antenna 312 receives a vertically polarized signal among the signals transmitted from the first transmission device 10 and the second transmission device 20, and outputs the received signal to the GI removal unit 322.

Note that the first receiving antenna 311 may receive a vertically polarized signal, and the second receiving antenna 312 may receive a horizontally polarized signal. In addition, it is desirable that the angle formed by the polarization of the signal received by the first receiving antenna 311 and the polarization of the signal received by the second receiving antenna 312 be orthogonal, but they may not be orthogonal. Good.

The GI removal unit 321 removes the GI from the reception signal input from the first reception antenna 311 and outputs the signal after removal to the FFT unit 331.

Similarly, the GI removal unit 322 removes the GI from the reception signal input from the second reception antenna 312 and outputs the signal after removal to the FFT unit 332.

The FFT unit 331 performs Fourier transformation on the signal input from the GI removal unit 321 and outputs the signal after Fourier transformation to the transmission path response estimation unit 34.

The FFT unit 332 performs Fourier transformation on the signal input from the GI removal unit 322 and outputs the signal after Fourier transformation to the transmission path response estimation unit 34.

The transmission path response estimation unit 34 extracts a first signal derived from a known pilot signal from the signal input from the FFT unit 331. Similarly, the transmission path response estimation unit 34 extracts a second signal derived from a known pilot signal from the signal input from the FFT unit 332. The transmission path response estimation unit 34 estimates the transmission path response with reference to the extracted first signal and second signal. The transmission path response estimation unit 34 outputs the calculated transmission path response to the transmission signal detection unit 35.

The transmission signal detection unit 35 is obtained by performing the Fourier transform on the encoding rule in the first transmission device 10 and the second transmission device 20, the transmission channel response calculated by the transmission channel response estimation unit 34, and the Fourier transform unit 33. The symbols transmitted by the first transmitter 10 and the second transmitter 20 are estimated with reference to the received signals (however, excluding signals derived from pilot signals). Detailed processing of the transmission signal detector 35 will be described later. The transmission signal detection unit 35 uses the symbol obtained by the estimation as, for example, parallel series data, and outputs the parallel series data to the parallel-serial conversion unit 36.

The parallel / serial converter 36 converts the parallel series data input from the transmission signal detector 35 into serial series data, and outputs the converted series data to the carrier demodulator 37.

The carrier demodulation unit 37 performs a demodulation process on the series data input from the parallel / serial conversion unit 36. Specifically, for example, the carrier demodulation unit 37 calculates an LLR (log likelihood ratio) from the input sequence data. Then, the carrier demodulation unit 37 outputs the sequence data obtained as a result of the carrier demodulation to the error correction code decoding unit 38.

The error correction code decoding unit 38 performs decoding processing of, for example, LDPC (Low-Density Parity-Check) code using the sequence data input from the carrier demodulation unit 37, and corrects a bit error generated in the transmission path. .

FIG. 17 is a 4 × 2 MIMO transmission model for explaining the transmission system. In the figure, y ₀ and y ₁ are horizontal polarization and vertical polarization reception signals, respectively. x ₀ , x ₁ , x ₂ , x ₃ are transmission symbols (signals to be obtained). h ₀₀ , h ₁₀ , h ₀₁ , h ₁₁ , h ₀₂ , h ₁₂ , h ₀₃ , and h ₁₃ are transmission path responses estimated using pilot signals. h ₀₀ is a channel response of the antenna 0 (horizontal) Rx0 to (horizontal). h ₁₀ is a transmission path response from the antenna 0 (horizontal) to Rx1 (vertical). h ₀₁ is a transmission path response from the antenna 1 (vertical) to Rx0 (horizontal). h ₁₁ is a transmission line response from the antenna 1 (vertical) to Rx1 (vertical). h ₀₂ is a channel response of the antenna 2 from (horizontal) Rx0 to (horizontal). h ₁₂ is a transmission path response from the antenna 2 (horizontal) to Rx1 (vertical). h ₀₃ is a transmission path response from the antenna 3 (vertical) to Rx0 (horizontal). h ₁₃ is a transmission line response from the antenna 3 (vertical) to Rx1 (vertical).

FIG. 18 is a diagram for explaining a transmission path response matrix of an ideal transmission path and a transmission path response matrix of a transmission path having a 90 ° polarization rotation counterclockwise. In the figure, there is shown a set of a schematic diagram C181 showing a transmission path response matrix H _ideal of an ideal transmission path without polarization rotation and a polarization state of a signal after being transmitted through the ideal transmission path. ing. It is assumed that the horizontal polarization H represents a positive value on the X axis, and the vertical polarization V represents a positive value on the Y axis. Here, each component of the transmission line response matrix H _ideal is g _ij (i is 0 or 1, j is 0 or 1). In an environment where transmission is performed through an ideal transmission path, g ₀₀ and g ₁₁ are 1, g ₀₁ is 0, and g ₁₀ is 0.

In the figure, the transmission line response matrix H ₉₀ of a transmission line having a 90 ° polarization rotation counterclockwise and the signal bias after being transmitted through the transmission line having a 90 ° polarization rotation counterclockwise. A set of schematic diagram C182 showing the state of the wave is shown. Here, each component of the transmission path response matrix H ₉₀ is assumed to be g ′ _ij (i is 0 or 1, j is 0 or 1). In the figure, since the polarization is rotated 90 degrees counterclockwise, the vertically polarized wave V is directed in the negative direction of the X axis, so g ′ ₀₁ is −1. Further, by rotating 90 degrees counterclockwise, the horizontally polarized wave H is directed in the positive direction of the Y axis, so g ′ ₁₀ is 1. Also, g ′ ₀₀ is 0 and g ′ ₁₁ is 0.

Subsequently, with respect to Embodiments 1 to 10, the processing (alignment method) of the receiving device 30 will be described under the following Condition 1 or Condition 2. Condition 1 is a transmission path response matrix H _A = H _ideal for the _A station and a transmission path response matrix H _B = H _ideal for the B station. Condition 2 is a transmission path response matrix H _A = H _ideal of the _A station, and a transmission path response matrix H _B = H ₉₀ of the B station.

[Example 1]
Processing of the transmission path response estimation unit 34 and the transmission signal detection unit 35 in the first embodiment will be described. In STBC, a received signal at time t and time t + 1 is paired for a certain frequency f. The relational expression at time t is expressed by the following expression (5).

The relational expression at time t + 1 is expressed by the following expression (6).

In this example, the encoded symbols transmitted by the first transmission device 10 are [x ₀ , x ₁ ] in Equation (5) and [−x ₂ ^* , −x ₃ ^* ] in Equation (6). is there. In this example, the encoded symbols transmitted by the second transmitter 20 are [x ₂ , x ₃ ] in Equation (5) and [x ₀ ^* , x ₁ ^* ] in Equation (6). is there.

When the expressions (5) and (6) are aligned, the following expression (7) is obtained as an alignment result.

Here, the leftmost matrix on the right side is a transmission line response matrix H having each transmission line response as a component. The transmission line response matrix H is estimated using a known pilot signal.

Subsequently, the transmission signal detection unit 35, for example, the transmission path responses h ₀₀ , h ₁₀ , h ₀₁ , h ₁₁ , h ₀₂ , h ₁₂ , h ₀₃ , h calculated by the transmission path response estimation unit 34 in Expression (7). ₁₃ and symbols y ₀ (t), y ₁ (t), y ₀ (t + 1), and y ₁ (t + 1) obtained by receiving each transmission signal and receiving by the receiving device 30 are substituted. Thereby, the transmission signal detection unit 35 calculates the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ .

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). In Condition 1, Expression (7) is expressed by the following Expression (7-1).

Since there is no rank drop in the transmission line response matrix H of Equation (7-1), there is no overlap in the four observation equations of Equation (7-1), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, in Condition 2, Expression (7) is expressed by the following Expression (7-2).

The row vector of the first row and the row vector of the fourth row of the transmission line response matrix H of the equation (7-2) are equal, and the row vectors of the second row and the third row are obtained by inverting the signs. Therefore, there is a rank drop in the transmission line response matrix H of Expression (7-2). In equation (7-2), there are two observation equations, but there are four unknown variables included in the observation equation. Therefore, the transmission path response estimation unit 34 cannot solve the observation equation. Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is not possible to correctly calculate the _2, _{x 3.}

The transmission line response is not limited to the condition that the received signal of the B station has a 90 ° polarization rotation counterclockwise, but also the condition that the received signal of the B station has a 270 ° polarization rotation counterclockwise. The estimation unit 34 cannot solve the observation equation. For this reason, the transmission signal detection unit 35 cannot correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ . On the other hand, under the condition that the received signal of station B has a polarization rotation other than 90 ° and 270 ° counterclockwise, the observation equation does not overlap, so that the transmission line response estimation unit 34 can solve the observation equation. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ .

[Example 1 ']
Subsequently, whether or not the transmission line response estimation unit 34 can solve the observation equation under the condition 1 and the condition 2 in the embodiment 1 ′ will be described. The relational expression at time t, the relational expression at time t + 1, and the alignment result are expressed by the following expressions (5) ′, (6) ′, and (7) ′, respectively.

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). In Condition 1, Expression (7) ′ is expressed by the following Expression (7-1) ′.

Since there is no rank drop in the transmission line response matrix H of Expression (7-1) ′, the transmission line response estimation unit 34 can solve the observation equation. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, under condition 2, the expression (7) ′ is expressed by the following expression (7-2) ′.

There is a rank drop in the transmission line response matrix H of Expression (7-2) ′. In equation (7-2) ′, there are two observation equations, but there are four unknown variables included in the observation equation, so the transmission line response estimation unit 34 cannot solve the observation equation. Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is not possible to correctly calculate the _2, _{x 3.}

[Example 2]
Subsequently, processing of the transmission signal detection unit 35 in the second embodiment will be described. The received signal at time t is expressed by the above-described equation (5). The received signal at time t + 1 is expressed by the following equation (8).

Aligning Equation (5) and Equation (8) yields the following Equation (9) as the alignment result.

Here, the transmission path response estimation unit 34 uses the known pilot signals in the same manner as in the first embodiment to transmit the transmission path responses h ₀₀ , h ₁₀ , h ₀₁ , h ₁₁ , h ₀₂ , h ₁₂ , h ₀₃ , h _13. Is estimated. Then, the transmission signal detection unit 35 calculates the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ by the same processing as in the first embodiment.

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). In Condition 1, Expression (9) is expressed by the following Expression (9-1).

Since there is no rank drop in the transmission line response matrix H of Equation (9-1), there is no overlap in the four observation equations of Equation (9-1), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, in Condition 2, Expression (9) is expressed by the following Expression (9-2).

Since there is no rank drop in the transmission line response matrix H of Equation (9-2), there is no overlap in the four observation equations of Equation (9-2), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is possible to correctly calculate the _2, _{x 3.}

[Example 2 ']
Subsequently, whether or not the transmission line response estimation unit 34 can solve the observation equation under the condition 1 and the condition 2 in the embodiment 2 ′ will be described. The relational expression at time t is assumed to be expression (5). The relational expression and the alignment result at time t + 1 are expressed by the following expressions (8) ′ and (9) ′, respectively.

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). In Condition 1, Expression (9) ′ is expressed by the following Expression (9-1) ′.

Since there is no rank drop in the transmission line response matrix H of Expression (9-1) ′, there is no overlap in the four observation equations of Expression (9-1) ′, and the transmission line response estimation unit 34 solves the observation equation. be able to. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, under condition 2, the expression (9) ′ is expressed by the following expression (9-2) ′.

Since there is no rank drop in the transmission line response matrix H of Expression (9-2) ′, there is no overlap in the four observation equations of Expression (9-2) ′, and the transmission line response estimation unit 34 solves the observation equation. be able to. Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is possible to correctly calculate the _2, _{x 3.}

[Example 3]
Subsequently, processing of the transmission signal detection unit 35 in the third embodiment will be described. If the received signal at time t is expressed by equation (5), the received signal at time t + 1 is expressed by equation (10) below. Here, _{x 3} in FIG. 17 corresponds to step S2 of FIG. 6, _{x 2} corresponds to S3.

Aligning Expression (5) and Expression (10) yields the following Expression (11) as an alignment result.

Here, the transmission path response estimation unit 34 calculates the transmission path responses h ₀₀ , h ₁₀ , h ₀₁ , h ₁₁ , h ₀₂ , h ₁₂ , h ₀₃ , and h ₁₃ by the same processing as in the first embodiment. Then, the transmission signal detection unit 35 calculates the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ by the same processing as in the first embodiment.

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). Under condition 1, equation (11) becomes the following equation (11-1).

Since there is no rank drop in the transmission line response matrix H of Equation (11-1), there is no duplication in the observation equations in each row of Equation (11-1), and the transmission line response estimation unit 34 determines these four observation equations. Can be solved. Therefore, the transmission signal detector 35 can calculate the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ under the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, in Condition 2, Expression (11) is expressed by the following Expression (11-2).

Since there is no rank drop in the transmission line response matrix H of Expression (11-2), there is no overlap in the four observation equations of Expression (11-2), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is possible to correctly calculate the _2, _{x 3.}

[Example 3 ']
Subsequently, whether or not the transmission line response estimation unit 34 can solve the observation equation under the condition 1 and the condition 2 in the embodiment 3 ′ will be described. The relational expression at time t is assumed to be expression (5). The relational expression and the alignment result at time t + 1 are expressed by the following expressions (10) ′ and (11) ′, respectively.

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). In Condition 1, Expression (11) ′ is expressed by the following Expression (11-1) ′.

Since there is no rank drop in the transmission line response matrix H of Expression (11-1) ′, there is no overlap in the four observation equations of Expression (11-1) ′, and the transmission line response estimation unit 34 solves the observation equation. be able to. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, under condition 2, the expression (11) ′ is expressed by the following expression (11-2) ′.

Since there is no rank drop in the transmission line response matrix H of Expression (11-2) ′, there is no overlap in the four observation equations of Expression (11-2) ′, and the transmission line response estimation unit 34 solves the observation equation. be able to. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

[Example 4]
Subsequently, processing of the transmission signal detection unit 35 in the fourth embodiment will be described. If the received signal at time t is Equation (5), the received signal at time t + 1 is represented by the following Equation (12).

Further, by aligning the equations (5) and (12), the following equation (13) is obtained as an alignment result.

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). Under condition 1, equation (13) becomes the following equation (13-1).

Since there is a rank drop in the transmission line response matrix H of the equation (13-1), the four observation equations of the equation (13-1) overlap, and the transmission line response estimation unit 34 cannot solve the observation equation. . Therefore, the transmission signal detector 35 cannot correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ under the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, in Condition 2, Expression (13) is expressed by the following Expression (13-2).

Since there is no rank drop in the transmission line response matrix H of Expression (13-2), there is no overlap in the four observation equations of Expression (13-2), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is possible to correctly calculate the _2, _{x 3.}

[Example 4 ']
Subsequently, whether or not the transmission line response estimation unit 34 can solve the observation equation under the condition 1 and the condition 2 in the embodiment 4 ′ will be described. The relational expression at time t is assumed to be expression (5). The relational expression and alignment result at time t + 1 are expressed by the following expressions (12) ′ and (13) ′, respectively.

Here, it is assumed that there is no time variation in the transmission path response h _ij (i is 0 or 1, j is an integer of 0 to 3), and h _ij (t) = h _ij (t + 1). In Condition 1, Expression (13) ′ is expressed by the following Expression (13-1) ′.

Since there is a rank drop in the transmission line response matrix H of the equation (13-1) ′, the four observation equations of the equation (13-1) ′ are overlapped, and the transmission line response estimation unit 34 solves the observation equation. I can't. Therefore, the transmission signal detector 35 cannot correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ under the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, under condition 2, the expression (13) ′ is expressed by the following expression (13-2) ′.

Since there is no rank drop in the transmission line response matrix H of Expression (13-2) ′, there is no overlap in the four observation equations of Expression (13-2) ′, and the transmission line response estimation unit 34 solves the observation equation. be able to. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

[Example 5]
Subsequently, processing of the transmission signal detection unit 35 in the fifth embodiment will be described. A relational expression at time t is expressed by Expression (5). The relational expression and alignment result at time t + 1 are expressed by the following expressions (14) and (15), respectively. Here, x ₀ , x ₁ , x ₂ , and x ₃ correspond to S 0, S 1, −S 2 ^* , and −S 3 ^* in FIG. 10, respectively.

Here, equation (15) matches equation (7). For this reason, the result is the same as in the first embodiment, and the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ under the condition that there is no polarization rotation in the transmission paths of both the A station and the B station. It can be calculated correctly. On the other hand, under the condition that there is no polarization rotation in the transmission path of the A station, but there is a 90 ° polarization rotation counterclockwise in the transmission path of the B station, the transmission signal detection unit 35 transmits the transmission symbols x ₀ , x ₁ , x it is not possible to correctly calculate the _2, _{x 3.}

The transmission path response estimation unit 34 calculates the transmission path responses h ₀₀ , h ₁₀ , h ₀₁ , h ₁₁ , h ₀₂ , h ₁₂ , h ₀₃ , and h ₁₃ by the same processing as in the first embodiment. Then, the transmission signal detection unit 35 calculates the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ by the same processing as in the first embodiment.

[Example 5 ']
Subsequently, whether or not the transmission line response estimation unit 34 can solve the observation equation under the

conditions

1 and 2 in the embodiment 5 ′ will be described. The relational expression at time t is expressed by Expression (5). The relational expression and the alignment result at time t + 1 are expressed by the following expressions (14) ′ and (15) ′, respectively.

Here, the expression (15) ′ matches the expression (7) ′. For this reason, the result is the same as in the first embodiment, and the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x ₂ , x _{3 under the} condition that there is no polarization rotation in the transmission paths of both the A station and the B station. Can be calculated correctly. On the other hand, under the condition that there is no polarization rotation in the transmission path of the A station, but there is a 90 ° polarization rotation counterclockwise in the transmission path of the B station, the transmission signal detection unit 35 transmits the transmission symbols x ₀ , x ₁ , x it is not possible to correctly calculate the _2, _{x 3.}

[Example 6]
Subsequently, processing of the transmission signal detection unit 35 in the sixth embodiment will be described. The received signal at time t is expressed by equation (5). The relational expression and the alignment result at time t + 1 are expressed by the following expressions (16) and (17), respectively. Here, x ₀ , x ₁ , x ₂ , and x ₃ correspond to S 0, S 1, −S 2 ^* , and S 3 ^* in FIG. 11, respectively.

Here, equation (17) matches equation (9). For this reason, the result is the same as that of the second embodiment, and the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ under the condition that there is no polarization rotation in the transmission paths of both the A station and the B station. It can be calculated correctly. Further, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x even under the condition that there is no polarization rotation in the transmission path of the A station but there is a 90 ° polarization rotation counterclockwise in the transmission path of the B station. it is possible to correctly calculate the _2, _{x 3.}

Also, since Example 6 'gives the same result as Example 2', the description thereof is omitted.

[Example 7]
Subsequently, processing of the transmission signal detection unit 35 in the seventh embodiment will be described. The received signal at time t is expressed by equation (5). The relational expression and the alignment result at time t + 1 are expressed by the following expressions (18) and (19), respectively. Here, x ₀ , x ₁ , x ₂ , and x ₃ correspond to S 0, S 1, −S 3 ^* , and −S 2 ^* in FIG. 12, respectively.

Here, equation (19) coincides with equation (11). For this reason, the result is the same as in the third embodiment, and the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ under the condition that there is no polarization rotation in the transmission paths of both the A station and the B station. Can be calculated. Further, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x even under the condition that there is no polarization rotation in the transmission path of the A station but there is a 90 ° polarization rotation counterclockwise in the transmission path of the B station. it is possible to correctly calculate the _2, _{x 3.}

Further, since Example 7 'has the same result as Example 3', the description thereof is omitted.

[Example 8]
Subsequently, processing of the transmission signal detection unit 35 in the eighth embodiment will be described. The received signal at time t is expressed by equation (5). The relational expression and the alignment result at time t + 1 are expressed by the following expressions (20) and (21), respectively. Here, x ₀ , x ₁ , x ₂ , and x ₃ correspond to S 0, S 1, S 3 ^* , and −S 2 ^* in FIG. 13, respectively.

Here, equation (21) coincides with equation (13). For this reason, the result is the same as that of the fourth embodiment, and the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ under the condition that there is no polarization rotation in the transmission paths of both the A station and the B station. It cannot be calculated correctly. On the other hand, under the condition that there is no polarization rotation in the transmission path of the A station, but there is a 90 ° polarization rotation counterclockwise in the transmission path of the B station, the transmission signal detection unit 35 transmits the transmission symbols x ₀ , x ₁ , x it is possible to correctly calculate the _2, _{x 3.}

In addition, since Example 8 'has the same result as Example 4', its description is omitted.

[Example 9]
Subsequently, processing of the transmission path response estimation unit 34 and the transmission signal detection unit 35 in the ninth embodiment will be described. In the ninth embodiment, since the reception signal is SFBC-encoded, the reception device 30 makes a pair of reception signals of frequency f and frequency f + 1 at a certain time t. The relational expression of the frequency f is expressed by the following expression (22).

The relational expression of the frequency f + 1 is expressed by the following expression (23).

Aligning Expression (22) and Expression (23) yields the following Expression (24) as an alignment result.

Here, it is assumed that the transmission line response estimation unit 34 estimates the transmission line response matrix H using a known pilot signal.

Subsequently, the transmission signal detection unit 35, for example, the transmission path responses h ₀₀ , h ₁₀ , h ₀₁ , h ₁₁ , h ₀₂ , h ₁₂ , h ₀₃ , h calculated by the transmission path response estimation unit 34 in Expression (24). ₁₃ and symbols y ₀ (f), y ₁ (f), y ₀ (f + 1), and y ₁ (f + 1) obtained by transmitting each transmission signal and receiving by the receiving device 30 are substituted. Thereby, the transmission signal detection unit 35 calculates the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ .

Here, it is assumed that the transmission line response h _ij (i is 0 or 1, j is an integer of 0 to 3) does not change in the frequency direction, and h _ij (f) = h _ij (f + 1). Under condition 1, equation (24) becomes the following equation (24-1).

Since there is no rank drop in the transmission line response matrix H of Equation (24-1), there is no overlap in the four observation equations of Equation (24-1), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, in Condition 2, Expression (24) is expressed by the following Expression (24-2).

Since there is a rank drop in the transmission line response matrix H of Expression (24-2), the four observation equations of Expression (24-2) are duplicated, and the transmission line response estimation unit 34 cannot solve the observation equation. . Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is not possible to correctly calculate the _2, _{x 3.}

Note that the transmission path response is not limited to the condition in which the transmission path of the B station has a 90 ° polarization rotation counterclockwise, but also in the condition in which the B station transmission path has a 270 ° polarization rotation counterclockwise. The estimation unit 34 cannot solve the observation equation. For this reason, the transmission signal detection unit 35 cannot correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ . On the other hand, under the condition where the transmission path of the B station has polarization rotations other than 90 ° and 270 °, the observation equations do not overlap, so the transmission channel response estimation unit 34 can solve the observation equations. Therefore, the transmission signal detecting unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ .

In addition, since Example 9 'has the same result as Example 9, its description is omitted.

[Example 10]
Subsequently, processing of the transmission signal detection unit 35 in the tenth embodiment will be described. The received signal of frequency f is expressed by the above-described equation (24). The relational expression and the alignment result at time f + 1 are represented by the following expressions (25) and (26), respectively.

The transmission path response estimation unit 34 calculates transmission path responses h ₀₀ , h ₁₀ , h ₀₁ , h ₁₁ , h ₀₂ , h ₁₂ , h ₀₃ , and h ₁₃ by the same processing as in the ninth embodiment. Then, the transmission signal detection unit 35 calculates transmission symbols x ₀ , x ₁ , x ₂ , x ₃ by the same processing as in the ninth embodiment.

Here, it is assumed that the transmission line response h _ij (i is 0 or 1, j is an integer of 0 to 3) does not change in the frequency direction, and h _ij (f) = h _ij (f + 1). Under condition 1, equation (26) becomes the following equation (26-1).

Since there is no rank drop in the transmission line response matrix H of Equation (26-1), there is no overlap in the four observation equations of Equation (26-1), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, the transmission signal detection unit 35 can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , and x ₃ on the condition that there is no polarization rotation in the transmission paths of both the A station and the B station.

Next, in Condition 2, Expression (26) is expressed by the following Expression (26-2).

Since there is no rank drop in the transmission line response matrix H of Equation (26-2), there is no overlap in the four observation equations of Equation (26-2), and the transmission line response estimation unit 34 can solve the observation equation. it can. Therefore, under the condition that there is no polarization rotation in the transmission path of the station A but there is a 90 ° polarization rotation in the counterclockwise direction in the transmission path of the station B, the transmission signal detector 35 transmits the transmission symbols x ₀ , x ₁ , x it is possible to correctly calculate the _2, _{x 3.}

In addition, since Example 10 'has the same result as Example 10, the description is abbreviate | omitted.

The above description will be summarized with reference to FIG. FIG. 19 is a table showing the result of determining whether the rank of the transmission line response matrix H has dropped or not by changing the transmission line response matrix H _B of the B station when the transmission line response matrix H _A of the A station is ideal. It is. In the figure, when the transmission path of station B is in an ideal environment, it rotates 90 ° counterclockwise, rotates 180 ° counterclockwise, rotates 270 ° counterclockwise, The case where there is a rank drop is shown. In the case of the counterclockwise rotation of 180 ° and 270 °, only the result is shown in FIG.

As shown in the figure, in the case of Examples 2, 2 ′, 3, 3 ′, 6, 6 ′, 7, 7 ′, 10, 10 ′, the polarization rotation angle of the transmission path of station B is changed. However, the rank of the transmission line response matrix H does not drop. Therefore, in the case of

Embodiments

2, 2 ′, 3, 3 ′, 6, 6 ′, 7, 7 ′, 10, 10 ′, even if there is polarization rotation in the transmission path of the B station, the transmission signal detection unit 35 Can correctly calculate the transmission symbols x ₀ , x ₁ , x ₂ , x ₃ .

Next, the results of evaluating the transmission characteristics of each example will be described. STBC (same polarization) of Example 1, STBC (cross polarization) of Example 3, SFBC (same polarization) of Example 9, and SFBC of Example 11 (see FIG. 3) with detailed description omitted ( The transmission characteristics of the STC-SDM system to which (cross polarization) is applied were evaluated using the system shown in FIG. For comparison, the case where STC was not applied was similarly evaluated.

FIG. 20 is a system diagram of computer simulation. In the figure, station A and station B functioning as a MIMO-OFDM modulator receive the PN code generated by the PN code generator. Stations A and B each generate a transmission signal from the received PN code. The A station transmits a horizontally polarized wave (H) transmission signal (hereinafter, “A station horizontally polarized signal”) and a vertically polarized wave (V) transmission signal (hereinafter, “A station vertically polarized signal”). The B station transmits a horizontally polarized wave (H) transmission signal (hereinafter referred to as B station horizontally polarized signal) and a vertically polarized wave (V) transmission signal (hereinafter referred to as B station vertically polarized signal). Addition of delay (Delay), change of received signal power (ATT), phase shift (Phase Shift), reception between polarized waves for B station horizontal polarization signal and B station vertical polarization signal transmitted by B station A series of processes of power change processing (ATT / Amp) and polarization rotation (Polarization Rotation) are performed. The B-station horizontal polarization signal after this series of processing is added to the A-station horizontal polarization signal transmitted from the A station, and a reception horizontal polarization signal is generated. Similarly, the B-station vertical polarization signal after the series of processing is added to the A-station vertical polarization signal transmitted from the A station, and a reception vertical polarization signal is generated. Thereafter, noise is added to the received horizontal polarization signal and the received vertical polarization signal. Then, the receiving device 30 as a MIMO-OFDM demodulator demodulates the received horizontal polarization signal and the reception vertical polarization signal after the noise is added. Then, the bit error rate measuring unit measures the bit error rate for the data obtained by demodulation.

Here, it is assumed that the ratio of the average received power between the polarizations of the A station and the B station is D / U [dB], and the received signals from the A station have the same horizontal and vertical polarization received power. For the B station signal, the delay time τ [μsec] in which the B station transmission signal is delayed with respect to the A station signal during reception, and the B station transmission signal shifts with respect to the A station signal during reception. Phase shift amount θ = 90 [°], received power difference δ [dB] between polarizations, angle φ [°] formed by both polarizations during reception, and rotation angle χ at which both polarizations rotate from transmission to reception [°] was set as a parameter. The reception C / N [dB] is defined as the noise power with respect to the reception power of the signal of the station A. Assuming an environment in which the signals of the B station are received by the side lobes of the first receiving antenna 311 and the second receiving antenna 312, the reception characteristics of the signals of the B station are changed, and the transmission characteristics are verified.

FIG. 21 shows transmission parameters in computer simulation. The bandwidth, FFT size, GI ratio, and pilot signal ratio were compliant with ISDB-T, which is ISDB (Integrated Services Digital Broadcasting) for terrestrial digital broadcasting.

(1) Bit error rate characteristics in high D / U environment

As a high D / U SFN environment, the bit error rate (BER: Bit Error Rate) with respect to the received C / N was evaluated in an environment (D / U = ∞) in which only the signal from the A station can be received. FIG. 22 shows a simulation result of bit error rate characteristics in a high D / U environment. This figure is a simulation result in an AWGN (Additive White Gaussian Noise) environment. Here, a C / N with a bit error rate of 1 × 10 ⁻⁷ or less is defined as a required C / N. With or without STC, the required C / N is about 26 dB. In a high D / U SFN environment, the transmission characteristics are almost equal regardless of the presence or absence of STC.

(2) Delay time characteristics of low D / U environment

As a low D / U SFN environment, the required C / N for the delay time τ of the B station was evaluated in an environment where the received power of the A station and the B station were equal (D / U = 0). FIG. 23 is a simulation result of the relationship between the delay time of the received signal of station B and the required C / N in a low D / U environment. Here, as simulation conditions, the received power difference between polarized waves δ = 0, the angle φ = 90 formed by both polarized waves during reception, and the rotation angle χ = 0. When the delay time τ = 0, the required C / N is about 23 dB in the STC-SDM system, which is an improvement of 3 dB compared to the case of D / U = ∞ in (1) described above. On the other hand, when STC is not applied, the signals received from the A station and the B station are the same signal, and frequency selective fading occurs, so that the required C / N is larger than 26 dB. As the delay time τ increases, the difference in the transmission channel response between adjacent carriers increases, so the SFBC-SDM system (STBC (same polarization) or STBC (cross polarization)) that pairs with adjacent carriers. These characteristics are slightly deteriorated compared with the STBC-SDM system (SFBC (same polarization) or SFBC (cross polarization)).

(3) Received power difference characteristics between polarized waves in low D / U environment

In D / U = 0, the required C / N with respect to the received power difference δ between the polarizations of the B station was evaluated. FIG. 24 is a simulation result of the relationship between the received power difference δ between polarized waves of the received signal of station B and the required C / N in a low D / U environment. Here, delay time τ = 60, angle φ = 90 formed by both polarized waves at the time of reception, and rotation angle χ = 0. The figure shows the result when the received power of the vertically polarized wave is larger than the received power of the horizontally polarized wave by the received power difference δ between the polarized waves. The figure shows that the STC-SDM scheme requires lower C / N for all received power differences δ between polarizations compared to the case where STC is not applied. Therefore, the same bit error rate can be achieved with a smaller C / N than in the case where the STC-SDM scheme does not apply STC.

In addition, when the received power difference δ between the polarizations becomes larger, the required C / N of the STBC (cross polarization) of the third embodiment increases than the STBC (same polarization) of the first embodiment. ing. This means that the condition of the MIMO transmission path is deteriorated and the transmission characteristics are deteriorated. Similarly, when the received power difference δ between the polarizations becomes larger, the required C / N is higher in SFBC (cross polarization) than in SFBC (same polarization) in the ninth embodiment. This means that the condition of the MIMO transmission path is deteriorated and the transmission characteristics are deteriorated. Therefore, the received power difference δ between the polarizations becomes large, and the same polarization is more effective than the cross polarization, so the same polarization is desirable.

FIG. 24 shows the result when the received power of the vertically polarized wave is larger than the received power of the horizontally polarized wave by the received power difference δ between the polarized waves. Similar results are obtained when the power is greater than the power.

(4) Polarization collapse characteristics of polarization in low D / U environment

In D / U = 0, the required C / N with respect to the angle φ formed by the polarization of the B station was evaluated. FIG. 25 is a simulation result of a relationship between an angle φ formed by both polarizations of the received signal of the station B and the required C / N in a low D / U environment. Here, the simulation conditions are delay time τ = 60, received power difference δ between polarized waves δ = 0, and rotation angle χ = 0. In addition, orthogonal rotation is caused by applying polarization rotation only to vertical polarization. The figure shows that the STC-SDM system has a lower required C / N at the angle φ formed by both polarizations at the time of reception than in the case where STC is not applied. Therefore, the same bit error rate can be achieved with a smaller C / N than in the case where the STC-SDM scheme does not apply STC.

Also, if the orthogonality of both polarizations collapses, the required C / N increases as the angle φ formed by both polarizations decreases. This means that the condition of the MIMO transmission path is deteriorated and the transmission characteristics are deteriorated. When the angle φ formed by both polarizations during reception is other than 0 ° and 90 °, STBC (cross polarization) achieves the same bit error rate with smaller C / N than STBC (same polarization). be able to. Similarly, SFBC (cross polarization) has the same bit error rate with smaller C / N than SFBC (same polarization) when the angle φ between the two polarizations at the time of reception is other than 0 degrees and 90 degrees. Can be achieved. Therefore, when the angle φ between the two polarized waves at the time of reception is other than 0 degrees and 90 degrees, the cross polarized waves have better transmission characteristics than the same polarized waves. desirable.

Note that FIG. 25 shows a result in the case where the orthogonal rotation is generated by applying the polarization rotation only to the vertical polarization, but the same result can be obtained when the polarization rotation is applied only to the horizontal polarization.

(5) Polarization rotation characteristics in low D / U environment

In D / U = 0, the angle C formed by the polarization of the B station was set to 90, and the required C / N with respect to the polarization rotation angle χ was evaluated. FIG. 26 is a simulation result of the relationship between the rotation angle χ of the polarization of the received signal of station B and the required C / N in a low D / U environment. Here, the simulation conditions are delay time τ = 60 and received power difference δ = 0 between polarizations. In the figure, in STBC (same polarization) and SFBC (same polarization), the required C / N increases as the polarization rotation angle increases as the polarization rotation angle increases from 0 degrees to 90 degrees. . Further, in STBC (same polarization) and SFBC (same polarization), the required C / N increases as the rotation angle of the polarization decreases from 180 degrees to 90 degrees. Then, the required C / N of STBC (same polarization) and SFBC (same polarization) takes the maximum value at the rotation angle χ = 90 of the polarization, and the required C / N becomes larger than the case where STC is not applied. ing. This is because the polarization rotation angle χ = 90, rank drop occurs in the transmission line response matrix H of the STBC (same polarization) and SFBC (same polarization) MIMO transmission lines, and transmission symbols cannot be calculated correctly. This means that the condition is bad and the transmission characteristics are greatly deteriorated.

On the other hand, in STBC (cross polarization) and SFBC (cross polarization), the required C / N does not change even when the polarization rotation angle χ changes. The required C / N is smaller than in the case of no application. That is, STBC (cross polarization) and SFBC (cross polarization) are robust to polarization rotation. In addition, the polarization rotation angle χ is an angle other than 0 degrees and 180 degrees, and STBC (cross polarization) and SFBC (cross polarization) are required more than STBC (same polarization) and SFBC (same polarization). C / N is small. Therefore, in an environment in which polarization rotation occurs in the propagation path (except when the polarization rotation angle is 180 degrees), cross polarization is more preferable than the same polarization. In STBC (same polarization) and SFBC (same polarization), the required C / N is smaller when the rotation angle χ of the polarization is in the range of 0 to about 60 or about 120 to 180 than when STC is not applied. Good transmission characteristics.

As described above, when the polarization rotation angle χ is in a predetermined range, the transmission characteristic is better when coded by any one of the STC-SDM systems than when STC is not applied. That is, in all the embodiments described above, if the polarization rotation angle χ is, for example, in the range of 0 to about 60 or about 120 to 180 in an environment where radio waves arriving from the A station and the B station are received, the STC It is possible to reduce the deterioration of the transmission characteristics compared to the case where is not applied.

In addition, compared to STBC (same polarization) and STBC (same polarization), STBC (cross polarization) and SFBC (cross polarization) do not deteriorate transmission characteristics even if polarization rotation occurs in the propagation path. Has the advantage. In addition, STBC has an advantage that transmission characteristics are less likely to deteriorate even in an environment where delay time τ is longer than SFBC. In addition, transmission using the same polarization has an advantage that transmission characteristics are less likely to deteriorate even in an environment where the received power difference between polarized waves is larger than transmission using cross polarization. Moreover, compared to transmission using the same polarization, cross-polarization transmission has the advantage that the transmission characteristics are less likely to deteriorate even when the angle φ formed by both polarizations during reception collapses from 90 degrees to other angles. Have.

Each transmission device includes two transmission antennas, but is not limited thereto, and may be three or more. For example, each transmission device includes a transmission antenna that wirelessly transmits a transmission signal with a first polarization, and a transmission antenna that wirelessly transmits a transmission signal with a second polarization different from the first polarization. It is sufficient to provide at least one each.

As described above, in the present embodiment, each transmission device is two transmission devices placed at different positions, and different transmission signals obtained by encoding symbols derived from the same data with different conversions are respectively used. It is used in a transmission system 4 including two transmission devices that perform space division multiplexing.

Also, the following processing is performed in each transmitting device. The encoding unit (14 or 24) is configured so that other transmission devices included in the transmission system 4 have the symbols included in the parallel sequence data obtained by dividing the symbol sequence data obtained by mapping the data into two. A conversion different from the conversion performed on the same symbol is performed, and the converted symbol obtained by performing the conversion is assigned to a different time or a different frequency from the converted symbol obtained by conversion by the other transmission device. . The inverse Fourier transform unit (16 or 26) performs inverse Fourier transform on each of the encoded symbol sequences obtained by encoding by the encoding unit (14 or 24). Each transmission device includes a first transmission antenna that wirelessly transmits one of two transmission signals obtained by the inverse Fourier transform of the inverse Fourier transform unit (16 or 26) using the first polarization, and the two transmission signals. At least one second transmission antenna that wirelessly transmits the other with a second polarization different from the first polarization is provided.

As a result, even when a signal from one transmitter cannot be received at all with respect to the technique of Non-Patent Document 1, the other transmitter can transmit a signal based on all symbols, so that the signal is received. The receiving device 30 has an advantageous effect that all data can be restored.

For example, in the configuration of the first embodiment, a new problem has been discovered in which transmission characteristics deteriorate when polarization rotation occurs in the transmission path from the other transmission apparatus. Therefore, each transmission device can further prevent deterioration of transmission characteristics even when polarization rotation occurs in the transmission path from the other transmission device by taking one of the following four configurations. it can.

As a first configuration, in FIG. 3, when an encoding pair is transmitted with cross polarization, the code is not inverted with one encoding matrix, and STBC or SFBC based on the Alamouti encoding matrix is used ( For example, in the case of SFBC corresponding to Example 3 or Example 3 ′), each transmission device has the following configuration. The encoding unit (14 or 24) encodes each parallel series data obtained by conversion by the serial-to-parallel conversion unit (13 or 23) for each block. Complex symbols are taken for two different symbols to be assigned to different frequencies, and the two symbols have the same code, but have different codes from the encoded symbols after the other transmitters have encoded. Convert to The transmission unit (17 or 27) transmits a transmission signal derived from the same information as another transmission signal transmitted by another transmission device, from the first transmission antenna or the second transmission antenna. The transmitting apparatus transmits from a transmitting antenna that transmits with a polarization different from the polarization that transmits the other transmission signal.

As a second configuration, in FIG. 3, when the encoding pair is transmitted with cross polarization, the code is not inverted with one encoding matrix, and STBC or SFBC based on the Modified Alamouti encoding matrix is used. For example (in the case of SFBC corresponding to Example 7 or Example 7 ′), the second transmission device 20 includes the following configuration. The encoding unit 24 encodes each of the parallel series data obtained by the conversion by the serial / parallel conversion unit 23 for each block, and each of the symbols included in the series data of the parallel series data. The complex conjugate is taken, and both the two symbols assigned to one time (for example, time t in FIG. 12) or one frequency in the block are multiplied by minus. The transmission unit 27 transmits a transmission signal derived from the same information as the other transmission signals transmitted by the first transmission device 10 out of the first transmission antenna or the second transmission antenna. The apparatus 10 transmits from a transmission antenna that transmits with a polarization different from the polarization with which the other transmission signal is transmitted.

As a third configuration, in FIG. 3, when the encoded pair is transmitted with the same polarization, the code is inverted with one encoding matrix, and STBC or SFBC based on the Alamouti encoding matrix is used (for example, In Example 2, Example 2 ′, Example 10 or Example 10 ′), each transmission device has the following configuration. The encoding unit (14 or 24) encodes each of the parallel series data obtained by conversion by the serial / parallel conversion unit (13 or 23) for each block, and one time (for example, In FIG. 5, time t + 1) or two different symbols assigned to one frequency are each complex conjugate, and one of the two symbols is multiplied by minus. The transmission unit (17 or 27) transmits a transmission signal derived from the same information as another transmission signal transmitted by another transmission device, from the first transmission antenna or the second transmission antenna. The transmission apparatus transmits the transmission signal from a transmission antenna that transmits the same polarization as that of the other transmission signal.

As a fourth configuration, in FIG. 3, when the encoded pair is transmitted with the same polarization, the code is inverted with one encoding matrix, and STBC or SFBC based on the modified Alamouti encoding matrix is used ( For example, in the case of SFBC corresponding to Example 6 or Example 6 ′), the second transmission device 20 includes the following configuration. The encoding unit 24 encodes each of the parallel series data obtained by the conversion by the serial / parallel conversion unit 23 for each block, and each of the symbols included in the series data of the parallel series data. A symbol that is complex conjugate and is assigned to the first time (for example, time t in FIG. 11) or the first frequency included in one of the series data is multiplied by minus, and the second time included in the other series data. (For example, time t + 1 in FIG. 11) or a symbol assigned to the second frequency is multiplied by minus. The transmission unit 27 transmits a transmission signal derived from the same information as another transmission signal transmitted by the first transmission device 10 out of the first transmission antenna or the second transmission antenna. 10 transmits from the transmitting antenna that transmits the same polarized wave as the other transmitting signal.

As described above, the transmission device 10 and the transmission device 20 perform space-time coding using a plurality of antennas provided in different transmission devices, and use a plurality of antennas provided in each of the plurality of transmission devices. This is a transmission device used in a transmission system that employs a method of performing space division multiplexing.

The transmitting apparatus 10 divides the series data to output the first series data and the second series data, and outputs the first series data to the first rule. First encoding for generating first sequence data A by encoding by space-time encoding and generating second sequence data A by encoding second sequence data by space-time encoding of the second rule (Encoding unit 14 described above). The transmission device 20 divides the series data to output the first series data and the second series data, and outputs the first series data and the second series data. Second encoding for generating first sequence data B by encoding by space-time encoding and generating second sequence data B by encoding second sequence data by space-time encoding of the second rule (Encoding unit 14 described above).

Under such a premise, the first sequence data A is encoded by a transform matrix different from that of the first sequence data B, and the second sequence data A is encoded by an encoding method different from that of the second sequence data B. Alternatively, the transmission signal corresponding to the first sequence data A is transmitted with a different polarization from the transmission signal corresponding to the first sequence data B, and the transmission signal corresponding to the second sequence data A is It is transmitted with a polarization different from the transmission signal corresponding to the second series data B.

Specifically, in the case described above, the transformation matrices applied to the first series data A and the first series data B are different, and the transformation matrices applied to the second series data A and the second series data B are different. The transmission signals corresponding to the first sequence data A and the first sequence data B have the same polarization, and the transmission signals corresponding to the second sequence data A and the second sequence data B have the same polarization ( For example,

Embodiments

2, 2 ′, 6, 6 ′, 10, 10 ′) shown in FIG. 3 can be considered.

Alternatively, in the case described above, the transformation matrix applied to the first series data A and the first series data B is the same, and the transformation matrix applied to the second series data A and the second series data B is the same. Yes, the transmission signals corresponding to the first sequence data A and the first sequence data B have different polarizations, and the transmission signals corresponding to the second sequence data A and the second sequence data B have different polarizations. (For example, Examples 3, 3 ′, 7, 7 ′, and 11 shown in FIG. 3) are conceivable.

In the present embodiment, the receiving device 30 is two transmitting devices placed at different positions, and space-division-multiplexes different transmission signals obtained by encoding the same data with different conversions. The transmission signals transmitted by the first transmission device 10 and the second transmission device 20 that transmit are received. In the receiving device, the first receiving antenna 311 receives a first polarized signal. The second receiving antenna 312 receives a signal having a second polarization different from the first polarization. The Fourier transform unit 33 Fourier transforms the signal received by the first receiving antenna 311 and Fourier transforms the signal received by the second receiving antenna 312. The transmission path response estimation unit 34 uses a known pilot signal transmitted from the first transmission device 10 and a known pilot signal transmitted from the transmission device 20 out of signals obtained by the Fourier transform performed by the Fourier transform unit 33. Estimate the channel response. The transmission signal detection unit 35 refers to the transmission path response calculated by the transmission path response estimation unit 34 and the signal obtained by the Fourier transform of the Fourier transform unit, and the first transmission device and the second transmission unit 35 The signal transmitted by the transmitter is estimated.

As described above, the receiving device 30 receives, from the first transmitting device, transmission signals corresponding to the first sequence data A and the second sequence data A obtained by encoding the two series of sequence data obtained by dividing the sequence data. In addition, a reception processing unit (for example, receiving a transmission signal corresponding to the first sequence data B and the second sequence data B obtained by encoding two series of sequence data obtained by dividing the sequence data from the second transmission device (for example, , The transmission signal detection unit 35, the parallel-serial conversion unit 36, the carrier demodulation unit 37, and the like shown in FIG. As described above, the first sequence data A is encoded by a different transformation matrix from the first sequence data B, and the second sequence data A is encoded by a different encoding method from the second sequence data B. Alternatively, the transmission signal corresponding to the first sequence data A is transmitted by a different polarization from the transmission signal corresponding to the first sequence data B, and the transmission signal corresponding to the second sequence data A is the second It is transmitted by a polarization different from the transmission signal corresponding to the sequence data B.

Also, a program for executing each process of each transmitting apparatus and each receiving apparatus of the present embodiment is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. By doing so, the above-described various processes relating to each transmission device and each reception device may be performed.

Note that the “computer system” referred to here may include an OS and hardware such as peripheral devices. Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used. The “computer-readable recording medium” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a CD-ROM, a hard disk built in a computer system, etc. This is a storage device.

Further, the “computer-readable recording medium” refers to a volatile memory (for example, DRAM (Dynamic) in a computer system serving as a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. Random Access Memory)), etc. that hold a program for a certain period of time. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, a concrete structure is not restricted to this embodiment. Each configuration in each embodiment, a combination thereof, and the like are examples, and the addition, omission, replacement, and other changes of the configuration can be made without departing from the spirit of the present invention. Further, the present invention is not limited by the embodiments, and is limited only by the scope of the claims.

Note that the entire content of Japanese Patent Application No. 2012-248786 (filed on November 12, 2012) is incorporated herein by reference.

According to one aspect of the present invention, in an environment in which radio waves arriving from two stations are received, even if reception characteristics of radio waves arriving from one station are deteriorated, deterioration of transmission characteristics can be reduced.

Claims

A transmission system comprising a first transmission device having two transmission antennas and a second transmission device having two transmission antennas,
The first transmitter is
A first serial / parallel converter that outputs the first series data and the second series data by dividing the series data;
First sequence data A is generated by encoding the first sequence data by a first rule space-time encoding, and the second sequence data is encoded by a second rule space-time encoding. A first encoding unit for generating two-sequence data A,
The second transmitter is
A second serial-to-parallel converter that outputs the first series data and the second series data by dividing the series data;
Encoding the first sequence data by space-time encoding of the first rule to generate first sequence data B, and encoding the second sequence data by space-time encoding of the second rule And a second encoding unit for generating the second series data B by
The first sequence data A is encoded by a transformation matrix different from that of the first sequence data B, and the second sequence data A is encoded by an encoding method different from that of the second sequence data B. Alternatively, the transmission signal corresponding to the first sequence data A is transmitted with a different polarization from the transmission signal corresponding to the first sequence data B, and the transmission signal corresponding to the second sequence data A is The transmission system, wherein the transmission signal is transmitted with a polarization different from that of the transmission signal corresponding to the second sequence data B.
Of the transmission signal corresponding to the first symbol sequence A and the transmission signal corresponding to the second symbol sequence A, one transmission signal is transmitted by the first polarization, and the other transmission signal is the second polarization. Sent by
Of the transmission signal corresponding to the first symbol sequence B and the transmission signal corresponding to the second symbol sequence B, one transmission signal is transmitted by the first polarization, and the other transmission signal is the second polarization. The transmission system according to claim 1, wherein the transmission system is transmitted by:
In the first rule space-time coding and the second rule space-time coding, the first symbol and the second symbol are coded for each block constituted by the first symbol and the second symbol. Spatial coding,
The transformation matrix used in the first rule space-time coding is different from the transformation matrix used in the second rule space-time coding;
The polarization of the transmission signal corresponding to the first symbol sequence A is the same as the polarization of the transmission signal corresponding to the first symbol sequence B;
The transmission system according to claim 1, wherein the transmission signal corresponding to the second symbol sequence A has the same polarization as the transmission signal corresponding to the second symbol sequence B.
In the first rule space-time coding and the second rule space-time coding, the first symbol and the second symbol are coded for each block constituted by the first symbol and the second symbol. Spatial coding,
The transformation matrix used in the first rule space-time coding is the same as the transformation matrix used in the second rule space-time coding;
The polarization of the transmission signal corresponding to the first symbol sequence A is different from the polarization of the transmission signal corresponding to the first symbol sequence B;
2. The transmission system according to claim 1, wherein a polarization of a transmission signal corresponding to the second symbol sequence A is different from a polarization of a transmission signal corresponding to the second symbol sequence B. 3.
The first rule space-time coding and the second rule space-time coding are performed for each block constituted by the first symbol P 0 and the second symbol P 1 for each of the first symbol P 0 and the second rule. is a space-time coding to encode the symbols P 1,
The transformation matrix used in the space-time coding of the first rule and the space-time coding of the second rule is a transformation matrix selected from the transformation matrix J and the transformation matrix K, or the transformation matrix L and the transformation matrix M. A transformation matrix selected from
The transformation matrix J to the transformation matrix M are:

The transmission system according to claim 3, wherein:
The first rule space-time coding and the second rule space-time coding are performed for each block constituted by the first symbol P 0 and the second symbol P 1 for each of the first symbol P 0 and the second rule. is a space-time coding to encode the symbols P 1,
The transformation matrix used in the space-time coding of the first rule and the space-time coding of the second rule is a transformation matrix selected from the transformation matrix J and the transformation matrix K, or the transformation matrix L and the transformation matrix M. A transformation matrix selected from
The transformation matrix J to the transformation matrix M are:

The transmission system according to claim 4, wherein:
A method of performing space-time coding using a plurality of antennas provided in different transmission apparatuses and performing space division multiplexing using a plurality of antennas provided in each of the plurality of transmission apparatuses is employed. A reception device used in a transmission system including one transmission device and a second transmission device,
The transmission signal corresponding to the first sequence data A and the second sequence data A obtained by encoding the two series of sequence data obtained by dividing the sequence data is received from the first transmission device, and the sequence data is divided A reception processing unit that receives transmission signals corresponding to the first sequence data B and the second sequence data B obtained by encoding the two series of sequence data obtained by the second transmission device,
The first sequence data A is encoded by a transformation matrix different from that of the first sequence data B, and the second sequence data A is encoded by an encoding method different from that of the second sequence data B. Alternatively, the transmission signal corresponding to the first sequence data A is transmitted with a different polarization from the transmission signal corresponding to the first sequence data B, and the transmission signal corresponding to the second sequence data A is The receiving apparatus, wherein the transmitting signal is transmitted by a polarization different from that of the transmission signal corresponding to the second series data B.