JP7723565B2 - Transmitting device, receiving device, and relay station - Google Patents

Description

This disclosure relates to a transmitting device, a receiving device, and a relay station.

In order to improve the quality and functionality of terrestrial digital broadcasting, studies are underway on a next-generation terrestrial broadcasting transmission system (advanced terrestrial broadcasting system) that inherits the features of the current ISDB-T system (Non-Patent Document 1). ISDB-T is an abbreviation for Integrated Services Digital Broadcasting - Terrestrial. It is expected that the advanced terrestrial broadcasting system will also build a broadcasting network equivalent to that of current terrestrial broadcasting.

Current terrestrial broadcasting in Japan uses a broadcasting network that uses the Orthogonal Frequency Division Multiplexing (OFDM) modulation method, which enables the creation of a Single Frequency Network (SFN), in which radio waves are emitted at a single frequency from the master station and relay stations (Non-Patent Document 2). SFN is an abbreviation for Single Frequency Network. OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. In an SFN, the same channel and content are transmitted in multiple areas, enabling efficient use of frequencies. The creation of a broadcasting network using the OFDM modulation method, which enables the creation of such an SFN, is also being considered for the advanced terrestrial broadcasting system. Furthermore, in ISDB-T, layers for fixed and mobile reception are multiplexed using Frequency Division Multiplexing (FDM). FDM is an abbreviation for Frequency Division Multiplexing.

On the other hand, ATSC 3.0, the transmission standard for terrestrial broadcasting in North America, uses signal multiplexing using time division multiplexing (TDM). ATSC stands for Advanced Television Systems Committee. TDM stands for Time Division Multiplexing. In the ATSC 3.0 system, transmitting stations can multiplex a TxID onto the preamble signal of a transmitted signal and transmit it (Non-Patent Document 3). A TxID is an identification ID assigned individually to each relay station. By receiving a signal with a TxID, the receiving side can determine which relay station the signal is from. Therefore, by demodulating the TxID, receiving points within the network can determine the delay with which radio waves from each relay station arrive. Note that in ATSC 3.0, TxID multiplexing is optional, and whether or not to multiplex is decided by the broadcaster.

NHK R&D, No.172, P.2-P.47, November 2018 ARIB STD-B31 Association of Radio Industries and Businesses ATSC 3.0 Standard: Physical Layer Protocol A/322:2020 P245-249, Internet〈https://www.atsc.org/wp-content/uploads/2020/01/A322-2020-Physical-Layer-Protocol.pdf〉

When relay stations are installed in an SFN, they are designed so that the arrival time difference between two stations in the reception area falls within the OFDM guard interval. In an SFN area where radio waves arrive from two relay stations, the receiver can determine that two waves are arriving by acquiring a delay profile. However, the receiver cannot determine which wave is the main wave, or, if there are multipath components, which relay station the multipath is from. Therefore, even in the advanced terrestrial broadcasting system, it is possible to multiplex and transmit a TxID assigned to each relay station, allowing the receiver to identify the source of the signal.

However, while ATSC 3.0 uses TDM, FDM transmission is being considered for the Advanced Terrestrial Broadcasting Standards, and the signal structures of the two are different. That is, ATSC 3.0 uses TDM, and the TxID is multiplexed into the preamble portion, but the Advanced Terrestrial Broadcasting Standards, which uses FDM, do not have a preamble. Therefore, the ATSC 3.0 method cannot be applied directly to the Advanced Terrestrial Broadcasting Standards.

The objective of this disclosure is to provide a transmitting device, a receiving device, and a relay station that are capable of multiplexing and transmitting or receiving TxIDs assigned to each relay station in a broadcasting system using FDM.

In one aspect of the present disclosure, a transmitting device in a broadcasting system that transmits broadcast signals using an FDM modulation method multiplexes identification information that identifies the device onto FDM subcarriers on the frequency axis of the broadcast signals and transmits the information.

In one embodiment, the transmitting device multiplexes the identification information onto control data related to the transmission method of the broadcast signal and transmits the same.

In one embodiment, the transmitting device multiplexes the identification information onto multiple symbols starting from the first symbol of the control data and transmits it.

In one embodiment, the transmitting device multiplexes the identification information onto at least one of the known signals, LLch and TMCC carrier, and transmits the control data.

In one embodiment, the transmitting device multiplexes the identification information onto a known signal, L0ch or L1ch, as the control data and transmits it.

In one embodiment, the transmitting device multiplexes the identification information onto the FDM subcarriers on the frequency axis of the broadcast signal and transmits it a number of times corresponding to the number of FFT samples used in the modulation/demodulation process.

In one aspect of the present disclosure, a transmitting device in a broadcasting system that transmits broadcast signals using an FDM modulation method multiplexes identification information that identifies the device onto FDM subcarriers on the time axis of the broadcast signals and transmits the information.

In one embodiment, the transmitting device multiplexes the identification information onto FDM subcarriers on the time axis of the broadcast signal and transmits it, so that the bandwidth for transmitting the identification information is equal to or less than the partial reception bandwidth.

In one embodiment, the receiving device receives the broadcast signal from the transmitting device, analyzes the received broadcast signal, and obtains the identification information.

In one embodiment, the relay station receives the broadcast signal from the transmitting device, removes noise from the received broadcast signal, assigns identification information that identifies the relay station to the noise-removed broadcast signal, and transmits the broadcast signal with the added identification information.

According to one embodiment of the present disclosure, it is possible to provide a transmitting device, a receiving device, and a relay station in a broadcasting system using FDM that are capable of multiplexing and transmitting or receiving TxIDs assigned to each relay station.

FIG. 2 is a diagram illustrating a configuration example of a modulator of a transmission device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the configuration of a BICM unit. FIG. 10 is a diagram illustrating a process of assigning a TxID to each OFDM frame. FIG. 2 is a diagram illustrating a configuration example of a TxID generation unit according to an embodiment of the present disclosure. FIG. 1 is a diagram illustrating a configuration example of a receiving device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a waveform of a received signal. FIG. 10 is a schematic diagram showing an example of a correlation between a received signal and a TxID. FIG. 10 is a diagram illustrating a configuration example of a relay station according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating a configuration example of a modulator of a transmission device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating a configuration example of a TxID generation unit according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example of the number of LLch carriers in one symbol. FIG. 10 is a diagram illustrating an example of the number of LLch carriers in one symbol. FIG. 1 is a diagram illustrating a configuration example of a receiving device according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating a configuration example of a relay station according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating a configuration example of a TxID generation unit according to an embodiment of the present disclosure. FIG. 1 is a diagram illustrating a configuration example of a receiving device according to an embodiment of the present disclosure.

One embodiment of the present disclosure will be described below with reference to the drawings. In each drawing, identical or corresponding parts are designated by the same reference numerals. In describing this embodiment, descriptions of identical or corresponding parts will be omitted or simplified as appropriate.

First Embodiment
(Transmitting device)
1A is a block diagram showing an example configuration of a modulator of a transmitting device 100 according to a first embodiment of the present disclosure. The block diagram of the modulator of the transmitting device 100 in FIG. 1A shows from a data input interface to an IF signal output. The transmitting device 100 multiplexes a TxID onto an OFDM signal on the time axis, thereby enabling multiplexing and transmission or reception of TxIDs assigned to each relay station.

The modulator of the transmitting device 100 includes an input I/F (Interface) 10, a BICM (Bit-Interleaved Coded Modulation) unit 11, a level adjustment unit 14, a system separation unit 15, a hierarchical synthesis unit 16, a band division unit 17, a time IL (Interleave) unit 18, a frequency IL unit 19, a band synthesis unit 20, a MISO (Multi-Input Single-Output) coding unit 21, a TMCC (Transmission and Multiplexing Configuration Control) information bit generation unit 22, a synchronization bit generation unit 23, a TMCC generation unit 24, a pilot generation unit 25, an OFDM frame construction unit 26, an IFFT (Inverse Fast Fourier Transform) unit 27, a GI (Guard Interval) addition unit 28, a TxID generation unit 40a, and an attenuator 41a. The modulator outputs, signal output 1 and IF signal output 2, undergo predetermined modulation processing and are then output from different transmission systems (antennas). If transmitter 100 is implemented using, for example, an FPGA (Field-Programmable Gate Array), each block of transmitter 100 operates on a common clock, making it possible to synchronize signals between blocks.

The input I/F (interface) 10 is an interface through which data to be transmitted is input, including image signal data and various types of data such as control data related to the transmission method. For example, the image signal data is divided into three layers, A, B, and C, as necessary, and output to the processing system of each layer. Furthermore, the control data is output, for example, as TMCC information or LLch (Low Latency Channel) data.

The BICM (Bit-Interleaved Coded Modulation) units 11 (11a, 11b, 11c) perform error correction coding and carrier symbol mapping on the data sequences of layers A, B, and C. Figure 1B shows the configuration of the BICM unit 11. The BICM unit 11 includes an energy dispersal unit 31, a BCH encoding unit 32, an LDPC encoding unit 33, and a mapping unit 34. The energy dispersal unit 31 converts data using a predetermined generating polynomial to reduce consecutive "0"s or "1"s, thereby performing signal processing to prevent specific frequency components of the modulated signal from increasing in magnitude. The BCH (Bose-Chaudhuri-Hocquenghem) encoding unit 32 performs BCH encoding on the data sequences of each layer that have undergone energy dispersal. The LDPC (Low-Density Parity-Check) encoding unit 33 performs LDPC encoding on the data sequences of each layer that have undergone BCH encoding. The mapping unit 34 maps the data onto the I-Q plane for each specified number of bits based on the modulation method of each layer of data, and performs carrier conversion. In other words, the mapping unit 34 converts the data into carrier symbols. The generated carrier symbols are output to the level adjustment unit 14.

Returning to the explanation of Figure 1A, the level adjustment units 14 (14a, 14b, 14c) adjust the levels of the carrier symbols for each layer. The adjusted carrier symbols are output to the system demultiplexing unit 15.

The system separation unit 15 (15a, 15b, 15c) is a demultiplexer that separates input carrier symbols into multiple systems (two systems in this example). This system separation unit 15 operates only when the transmission method for that layer is a spatial division multiplexing MIMO (Multi-Input Multi-Output) transmission method. One of the separated carrier symbols for each layer is output to a layer combiner 16-1 for a first system (hereinafter simply referred to as "system 1"), and the other is output to a layer combiner _16-2 for a second system (hereinafter simply referred to as "system ₂ "). When the transmission method for that layer is the MISO system, the system separation unit 15 outputs all carrier symbols to the layer combiner _16-1 for system 1. Note that when the MIMO transmission method is performed using three or more transmission systems, data is separated according to the number of transmission systems.

The layer combining units 16 ( ₁₆₁ , ₁₆₂ ) layer-combine the carrier symbols of layers A, B, and C input from the system separating units 15a, 15b, and 15c, respectively. The layer-combined carrier symbols are output to the band dividing unit 17 for each system.

The band dividing unit 17 ( ₁₇₁ , ₁₇₂ ) divides the hierarchically combined carrier symbols into each band. For example, it divides a part of the C layer data into adjustment bands as necessary. The band-divided carrier symbols are output to the time IL unit 18.

The time IL (interleave) units 18 ( ₁₈₁ , ₁₈₂ ) perform interleaving on the band-divided carrier symbols in the time direction (i.e., the direction in which the symbols are arranged in each carrier). The time-interleaved carrier symbols are output to the frequency IL unit 19.

The frequency IL (interleave) units 19 ( ₁₉₁ , ₁₉₂ ) perform interleaving in the carrier frequency direction. The frequency-interleaved carrier symbols are output to the band synthesis unit 20.

The band synthesis units 20 ( ₂₀₁ , ₂₀₂ ) synthesize carrier symbols of the frequency-interleaved partial reception band, non-partial reception band, and adjustment band to form a data segment. When a space division multiplexing MIMO system is adopted, the band synthesis unit ₂₀₁ for system 1 outputs a system 1 carrier symbol x1, and the band synthesis unit ₂₀₂ for system 2 outputs a system 2 carrier symbol x2 different from system 1.

The MISO encoding unit 21 performs space-time encoding (STBC (Space Time Block Code) encoding or SFBC (Space Frequency Block Code) encoding) on the data of the 1-system carrier symbol x1 to generate the 2-system carrier symbol x2. Note that STBC encoding (hereinafter sometimes simply referred to as "STBC") pairs two data symbols in the time direction and performs complex conjugation and sign inversion on the data carrier symbol. Note that SFBC encoding (hereinafter sometimes simply referred to as "SFBC") pairs two data symbols in the frequency direction and performs complex conjugation and sign inversion on the data carrier symbol.

A switch (selector) selects data based on the transmission method of each layer or segment, and outputs it as second-system carrier symbol x2. In the case of the MIMO method, the output from the second-system band combiner ₂₀₂ is output as second-system carrier symbol x2, and in the case of the MISO method, the output from the MISO encoder 21 is output as second-system carrier symbol x2. This switching is linked to the processing of the system separator 15. These carrier symbols x1 and x2 are output to the OFDM frame constructor 26.

The TMCC information (Transmission and Multiplexing Configuration Control Information) bit generator 22 receives TMCC information (various control information) from the input I/F 10, generates TMCC information bits, and outputs them to the TMCC generator 24.

The synchronization bit generator 23 generates a synchronization bit that becomes part of the TMCC and outputs it to the TMCC generator 24.

The TMCC generation unit 24 receives the TMCC information bits from the TMCC information bit generation unit 22, the synchronization bits from the synchronization bit generation unit 23, and FEC (Forward Error Correction) pointer information, and generates a TMCC. The generated TMCC is output to the OFDM frame configuration unit 26.

The pilot generation unit 25 generates pilot signals (e.g., SP (Scattered Pilot) signals, CP (Continual Pilot) signals) to be incorporated into OFDM frames. The generated pilot signals are output to the OFDM frame configuration unit 26.

The OFDM frame constructing units 26 ( ₂₆₁ , ₂₆₂ ) construct an OFDM frame by adding a TMCC, a pilot signal, and an LLch signal to the input carrier symbols (data segments). The OFDM frame constructing unit ₂₆₁ for system 1 generates an OFDM frame for system 1 based on the carrier symbol x1 for system 1, and the OFDM frame constructing unit ₂₆₂ for system 2 generates an OFDM frame for system 2 based on the carrier symbol x2 for system 2. The generated OFDM frames are each output to the IFFT unit 27.

The IFFT units 27 ( ₂₇₁ , ₂₇₂ ) perform IFFT (Inverse Fast Fourier Transform) processing on the input OFDM frame to generate an effective symbol signal. The generated effective symbol signal is output to the GI adding unit .

The GI adding units 28 (28 ₁ , 28 ₂ ) add a guard interval, which is a signal obtained by copying a portion of the end of the effective symbol signal, to the beginning of the effective symbol signal input from the IFFT unit 27. The guard interval is set so that the delay time of the multipath delay wave does not exceed the guard interval length. The signal of the first channel to which the guard interval has been added has a TxID added in an adder 42a and is output as signal output 1. The signal of the second channel to which the guard interval has been added is output as signal output 2. In this embodiment, the OFDM frame constructing unit 26, the IFFT unit 27, and the GI adding unit 28 may be collectively referred to as an "OFDM modulation unit."

In this embodiment, the adder 42a multiplexes the TxID output from the attenuator 41a onto the OFDM symbols of the main system (OFDM symbols containing data carriers) for each OFDM frame. Figure 2 is a diagram illustrating the process of assigning a TxID to each OFDM frame. As shown in Figure 2, the adder 42a assigns a TxID to the first few symbols of each OFDM frame. While Figure 2 illustrates an example in which a TxID is assigned once for each OFDM frame, the number of times a TxID is assigned is not limited to this. Generally, when multiplexing the first few symbols, the greater the number of symbols, the greater the impact of degradation of the reception characteristics of the main system. Therefore, for example, the adder 42a may assign a TxID every few frames rather than every frame. In this case, although it takes longer to detect the TxID, the impact on the main system can be reduced. Alternatively, depending on the application or purpose, the adder 42a may assign the TxID multiple times to one OFDM frame. In this case, the receiving side can receive the TxID signal multiple times in a short period of time, thereby improving the accuracy of detecting the TxID itself. Because the TxID is typically received as a low-level signal, the receiving side adds and averages multiple signals to improve the accuracy of detecting the TxID. Therefore, by transmitting and receiving the TxID multiple times in a short period of time, the receiving side can detect the TxID with high accuracy in a short period of time. Even when the communication characteristics of the transmission path fluctuate gradually over time, adding the TxID multiple times per OFDM frame enables more accurate detection of the TxID than the configuration in which the TxID is transmitted once per OFDM frame as shown in FIG. 2. Furthermore, by setting the IL (Interleave) time longer, the impact of TxID assignment on the main line signal can be mitigated. In this way, the transmitting device 100 assigns a TxID to the OFDM signal on the time axis to identify itself. As will be described later, relay station 300 also assigns a TxID to the OFDM signal on the time axis to identify itself. This allows the receiving side to identify the transmitting device 100 or relay station 300 that transmitted the received signal. This allows the receiving side to determine the signal delay time for each transmitting device 100 or relay station 300.

Returning to the description of FIG. 1A , the TxID generation unit 40a generates a TxID, which is identification information for identifying its own device (the transmitting device 100 in the example of FIG. 1A ). FIG. 3 is a diagram showing an example configuration of the TxID generation unit 40a. The TxID generation unit 40a generates a TxID based on a Gold sequence, but codes other than the Gold sequence that have excellent autocorrelation and cross-correlation values may also be used. As shown in FIG. 3 , the TxID generation unit 40a assigns a TxID using a 13-bit initial value from x ¹ to x ^13. Therefore, the TxID generation unit 40a can assign a unique TxID to each of a maximum of 8192 (=2 ¹³ ) transmitting devices 100 or relay stations 300. The period of the Gold sequence is 8191, and the generated 8191 sequence is BPSK (Binary Phase Shift Keying) modulated and output to the attenuator 41a. 3 shows an example in which the initial value is 13 bits, i.e., a 13th-order atomic polynomial is used, but a Gold sequence may be generated using an atomic polynomial of a higher order, thereby increasing the number of assignable TxIDs.

The clock rate of the TxID can be the same as that of the main line system (6.32 (512/81) MHz for the terrestrial broadcasting advanced standard). In this case, if band-limiting is performed using an ideal filter (roll-off rate α = 9), the bandwidth will be 3.16 MHz. Alternatively, by reducing the clock rate of only the TxID, band-limiting can be applied so that the bandwidth is equal to or less than the partial reception bandwidth (1.5 MHz). This reduces the impact on the main line system caused by assigning the TxID.

Returning to the explanation of Figure 1A, the attenuator 41a attenuates the signal level (signal power) of the TxID signal output from the TxID generation unit 40a. Because the TxID signal acts as an interference component for the main line signal, it is sufficiently attenuated before multiplexing. The attenuator 41a can attenuate the TxID signal to a sufficiently low level, such as 20 dB (1/100) compared to the signal power of the main line signal. This makes it possible to mitigate the impact of degradation of the main line signal caused by the assignment of the TxID. The TxID signal attenuated by the attenuator 41a is output to the adder 42a.

Signal outputs 1 and 2 undergo a predetermined modulation process and are then output from different antennas (transmission systems).

The modulator of the transmitting device 100 according to the first embodiment is configured in this manner. The transmitting device 100 according to this embodiment multiplexes an ID (TxID) specific to the transmitting station onto the OFDM signal on the time axis. Therefore, according to the configuration of this embodiment, it is possible to multiplex and transmit the TxID for identifying the device itself in a digital broadcasting system using FDM. Furthermore, as will be described later, the relay station 300 also multiplexes its own ID (TxID) (specific to the transmitting station) onto the OFDM signal on the time axis. Therefore, even when signal waves from multiple transmitting devices 100 or relay stations 300 are mixed, the receiving side can distinguish the arrival times of each signal wave from the transmitting device 100 and relay station 300 by correlating with the TxID.

(receiving device)
4 is a block diagram showing an example configuration of a receiving device 200 according to the first embodiment of the present disclosure. The receiving device 200 includes a receiving unit 51, a correlation calculation unit 52, and a TxID generation unit 53. The receiving unit 51 receives a signal transmitted by the transmitting device 100. The received signal received by the receiving unit 51 is output to the correlation calculation unit 52. The TxID generation unit 53 has a configuration similar to that of the TxID generation unit 40a included in the transmitting device 100, and generates a TxID. The generated TxID signal is output to the correlation calculation unit 52. The correlation calculation unit 52 correlates the received signal received by the receiving unit 51 with the TxID generated by the TxID generation unit 53, and identifies the TxID of the received signal received by the receiving unit 51.

Figure 5A shows the delay profile of a received signal. The delay profile can be obtained by performing an inverse Fourier transform (IFFT) on the transfer function of the frequency characteristics, and indicates the level and delay of each delayed wave relative to the main wave. The horizontal axis represents time, and the vertical axis represents level. While the delay profile (transmission delay characteristics) can be determined from the waveform of the delay profile, the delay profile alone cannot determine which transmitting device 100 or relay station 300 transmitted the radio wave. Therefore, the correlation calculation unit 52 of the receiving device 200 calculates the correlation between the received signal and the unique TxID generated by the TxID generation unit 53, and calculates the magnitude of the correlation and the position of the peak for each TxID. In other words, the TxID generation unit 53 sequentially generates 8,192 TxIDs, and the correlation calculation unit 52 calculates the correlation coefficient between the signal of each TxID generated by the TxID generation unit 53 and the received signal. The correlation calculation unit 52 identifies the signal with the TxID for which the calculated correlation coefficient exceeds a predetermined value as the TxID of that received signal. This makes it possible to identify the TxID of the received signal and identify the transmitting device 100 or relay station 300 that transmitted the received signal.

Figure 5B is a schematic diagram showing an example of the correlation between a received signal and a TxID. In Figure 5B, the horizontal axis represents time, and the vertical axis represents the correlation coefficient between the received signal and the unique TxID generated by the TxID generation unit 53. Figure 5B also shows a schematic example of a correlation coefficient calculated for a received signal that contains a mixture of signals from two transmitting devices 100 or relay stations 300. The first received signal exhibits a high correlation with the first TxID, Tx#1, and the second received signal exhibits a high correlation with the second TxID, Tx#2. Therefore, it can be seen that the first received signal is a signal transmitted from the transmitting device 100 or relay station 300 identified by Tx#1, and the second received signal is a signal transmitted from the transmitting device 100 or relay station 300 identified by Tx#2.

For example, if the FFT size is 8192 and the effective symbol length is 1296 μs, changing the number of samples to be moved from 0 to 800 corresponds to a delay of approximately 0 to 126 μs. Therefore, the FFT sample clock is 8192/1296 = 6.32 MHz, and the time required to calculate the correlation of 800 samples is 800/6.32 = 126.56 μs.

(Relay station)
6 is a diagram illustrating an example configuration of a relay station 300 according to an embodiment of the present disclosure. The relay station 300 includes a receiving unit 61, an FFT (Fast Fourier Transform) unit 62, a channel estimating unit 63, an equalization and symbol determining unit 64, an IFFT unit 65, a GI adding unit 66, a TxID generating unit 67, an attenuator 68, and an adder 69.

The receiving unit 61 receives signals transmitted by the transmitting device 100 or other relay stations 300. The signals received by the receiving unit 61 are output to the FFT unit 62.

The FFT unit 62 performs FFT (Fast Fourier Transform) processing on the signal input from the receiving unit 61. The FFT-transformed received signal becomes a frequency-domain OFDM signal. The FFT-transformed received signal is output to the transmission path estimation unit 63 and the equalization/symbol decision unit 64.

The transmission path estimation unit 63 estimates the transmission path characteristics (distortion of the transmission path) from the SP signal (known signal) in the OFDM frame output by the FFT unit 62.

The equalization and symbol determination unit 64 performs equalization and symbol determination. Equalization involves dividing the FFT output signal by a transmission channel estimate. This process removes distortion from the transmission channel. Symbol determination involves rearranging the equalized signal to the closest constellation point. This process removes noise added from the transmission channel. This equalization and symbol determination process deletes the TxID signal information of the parent station. The OFDM frame signal with added noise, etc. is output to the IFFT unit 65. The relay station 300 then adds a TxID to identify its own device to the OFDM signal after IFFT and GI addition.

The IFFT unit 65 performs IFFT (inverse fast Fourier transform) on the input OFDM frame to generate an effective symbol signal. The generated effective symbol signal is output to the GI addition unit 28.

The GI adding units 28 (28 ₁ , 28 ₂ ) add a guard interval, which is a signal obtained by copying a portion of the end of the effective symbol signal, to the beginning of the effective symbol signal input from the IFFT unit 27. The guard interval is set so that the delay time of the multipath delay wave does not exceed the guard interval length. The signal with the guard interval added has a TxID added in an adder 69, and is output as a signal output.

The TxID generation unit 67 generates a TxID, which is identification information for identifying the device itself (relay station 300). The generated TxID is BPSK modulated and output to the attenuator 68. The attenuator 68 attenuates the signal level (signal power) of the TxID signal output from the TxID generation unit 67. The functions and processing contents of the TxID generation unit 67, attenuator 68, and adder 69 are similar to those of the TxID generation unit 40a, attenuator 41a, and adder 42a of the transmitting device 100.

As described above, in a broadcasting system that transmits broadcast signals using the FDM modulation method, the transmitting device 100 and relay station 300 multiplex identification information that identifies their own device onto FDM subcarriers on the time axis of the broadcast signal and transmit it. Therefore, according to this embodiment, the receiver of the broadcast signal can identify the device that transmitted or relayed that broadcast signal.

In addition, the transmitting device 100 and relay station 300 multiplex and transmit the identification information onto FDM subcarriers on the time axis of the broadcast signal, ensuring that the bandwidth for transmitting the identification information is equal to or less than the partial reception bandwidth. Therefore, according to this embodiment, the impact on the main line system caused by assigning identification information can be reduced.

Furthermore, the receiving device 200 receives a broadcast signal from the transmitting device 100 or relay station 300, analyzes the received broadcast signal, and obtains identification information, thereby being able to identify the transmitting device 100 that transmitted the broadcast signal or the relay station 300 that relayed it. When receiving broadcast signals from multiple transmitting devices 100 or relay stations 300, the receiving device 200 determines the correlation between each broadcast signal and the signal of the identification information, thereby being able to identify the transmitting device 100 or relay station 300 that transmitted each signal and also determine the signal level and arrival time.

In addition, relay station 300 receives the broadcast signal transmitted from transmitting device 100 and corrects distortion in the transmission path from the received broadcast signal to remove noise, thereby also removing the identification information of transmitting device 100 that was added by transmitting device 100. It then adds identification information that identifies itself to the noise-removed broadcast signal and transmits the broadcast signal with the added identification information. Therefore, receiving device 200 that receives the broadcast signal relayed by this relay station 300 can identify the relay station 300 that relayed the broadcast signal using the identification information.

Second Embodiment
(Transmitting device)
FIG. 7 is a diagram showing an example of the configuration of a modulator in a transmitting device 101 that adds a TxID according to the second embodiment. In the second embodiment, the transmitting device 101 multiplexes the TxID onto an OFDM signal on the frequency axis. Furthermore, taking into consideration the impact on the data carrier, the transmitting device 101 multiplexes only onto an LLch (Low Latency Channel) carrier. The LLch corresponds to the AC (Auxiliary Channel) carrier of the current terrestrial broadcasting (ISDB-T). However, since the TxID signal acts as an interference component for the LLch signal, it is sufficiently attenuated before multiplexing. The LLch includes L0ch, a partial reception band, and L1ch, a non-partial reception band, and two types of content are transmitted via the LLch.

In Fig. 7, components similar to those in Fig. 1A are assigned the same reference numerals, and detailed description thereof will be omitted. The configuration of the BICM unit 11 is shown in Fig. 1B, similar to that of the transmitting device 100. In the configuration of Fig. 1A, the transmitting device 100 assigns a TxID to the output of the GI adding unit _28-1 . In contrast, the transmitting device 101 in Fig. 7 assigns a TxID to the LLch signal input to the input I/F unit 10.

The TxID generation unit 40b generates a TxID, which is identification information for identifying its own device (the transmitting device 101 in the example of FIG. 7). The TxID generated by the TxID generation unit 40b is BPSK modulated and output to an attenuator 41b. The attenuator 41b attenuates the signal level (signal power) of the TxID signal output from the TxID generation unit 40b. The attenuated TxID signal is added to the LLch by an adder 42b and output to the OFDM frame configuration units _26-1 and _26-2 .

Figure 8 shows a detailed example configuration of the TxID generation unit 40b. In the configuration of Figure 8, the TxID generation unit 40b includes a TxID signal generation unit 44, an error correction encoding unit 45, and a BPSK unit 46. The TxID signal generation unit 44 generates the TxID signal using individual bits rather than a code such as a Gold sequence. The error correction encoding unit 45 applies error correction encoding to the TxID signal. The BPSK unit 46 BPSK-modulates the error correction encoded TxID signal and outputs it to the attenuator 41b. The functions and processing contents of the attenuator 41b and the adder 42b are similar to those of the attenuator 41a and the adder 42a of the transmitting device 100.

In this embodiment, the TxID is multiplexed onto the LLch carrier of the first symbol of the OFDM frame. Because the LLch is differentially modulated in the symbol direction, the beginning of the OFDM frame is defined as a differential reference symbol (known signal). Therefore, the TxID is multiplexed onto the known signal.

Figures 9A and 9B show examples of the number of LLch carriers within one symbol. Figure 9A shows examples of the number of LLch carriers in compatible mode and normal mode when the FFT size is 8k (8192) points, 16k (16384) points, and 32k (32768) points. Figure 9B shows examples of the number of L0ch and L1ch carriers in compatible mode and normal mode when the FFT size is 8k (8192) points. There are a minimum of 66 LLch carriers within one symbol, and a BPSK-modulated TxID is added to these carriers. One possible use of the 66 carriers (66 bits) is to use 14 bits as TxID information bits, perform error correction coding on these 14 bits, and use the remaining 52 bits as parity bits. Additionally, since the number of carriers doubles in the case of 16k and 32k, the transmitting device 101 may transmit the 66-bit TxID two or four times. Additionally, the transmitting device 101 may multiplex the TxID onto only either L0ch or L1ch.

Although the method using the LLch carrier has been described here, multiplexing can also be performed on the TMCC carrier in the same manner. In this case, a TxID is assigned to the TMCC generated in the TMCC generation unit 24, and the TMCC to which the TxID has been assigned is output to the OFDM frame configuration units _26-1 and _26-2 .

The modulator of the transmitting device 101 according to the second embodiment is configured in this manner. With the transmitting device 101 according to this embodiment, the transmitting station's unique ID (TxID) is multiplexed onto the LL channel on the time axis rather than onto the mainline OFDM signal, so the TxID for identifying the device itself can be assigned to the signal without degrading the mainline signal. However, because the signal is multiplexed on the frequency axis, the receiving side cannot distinguish the delay time of each wave when signal waves from multiple stations are mixed. Furthermore, it is only possible to distinguish the TxID of the wave with the highest level.

(receiving device)
10 is a diagram showing an example of the configuration of a receiving device 201 according to the second embodiment. The receiving device 201 includes a receiving unit 71, an FFT unit 72, a transmission path estimation unit 73, an LL channel extraction unit 74, an equalization unit 75, an LL channel replica unit 76, an LL channel replica removal unit 77, a TxID signal demodulation unit 78, and a TxID signal error correction decoding unit 79.

The receiving unit 71 receives broadcast waves, extracts OFDM symbols, and outputs them to the FFT unit 72. The FFT unit 72 performs OFDM demodulation processing on the OFDM symbols using FFT. As a result, the received signal is converted into a frequency axis signal by FFT. The transmission path estimation unit 73 estimates the transmission path characteristics (transmission path distortion) from the SP signal (known signal) in the output signal of the FFT unit 72. The estimation result is output to the equalization unit 75. The LLch extraction unit 74 extracts the LLch signal from the output signal of the FFT unit 72. Since the LLch is assigned to the subcarrier of the first symbol of a specific OFDM frame, it can be extracted by referencing that subcarrier. The equalization unit 75 performs equalization processing by dividing the LLch signal included in the output signal of the FFT unit 72 by the transmission path estimation value estimated by the transmission path estimation unit 73. The divided LLch signal is output to the LLch replica removal unit 77 as an equalized LLch signal.

The LLch replica unit 76 generates the LLch of the first symbol of the OFDM frame. The LLch of the first symbol of the OFDM frame is a known signal. The LLch replica removal unit 77 removes the LLch replica by subtracting the LLch replica generated by the LLch replica unit 76 from the LLch signal equalized by the equalization unit 75. This extracts the TxID signal. The TxID signal demodulation unit 78 performs BPSK demodulation of the TxID extracted by the LLch replica removal unit 77. The TxID signal error correction decoding unit 79 performs error correction demodulation of the TxID.

(Relay station)
11 is a diagram showing an example of the configuration of a relay station 301 in the second embodiment. The relay station 301 includes a receiving unit 81, an FFT unit 82, a transmission channel estimating unit 83, an equalization/symbol determining unit 84, a TxID generating unit 85, an attenuator 86, an adder 87, an IFFT unit 88, and a GI adding unit 89. Similar to the relay station 300 described with reference to FIG. 6 , the relay station 301 performs equalization/symbol determining on the received signal to delete information on the TxID signal of the master station. Then, by multiplexing the TxID of the relay station 301 onto the LL channel carrier, it becomes possible to assign a TxID for identifying each relay station 301.

The receiver 81, FFT unit 82, transmission channel estimation unit 83, equalization/symbol decision unit 84, TxID generation unit 85, attenuator 86, adder 87, IFFT unit 88, and GI addition unit 89 have the same functions as the receiver 61, FFT unit 62, transmission channel estimation unit 63, equalization/symbol decision unit 64, TxID generation unit 67, attenuator 68, adder 69, IFFT unit 65, and GI addition unit 66 of the relay station 300. However, in the relay station 300 of FIG. 6, the IFFT unit 65 performs an inverse Fourier transform, and the GI addition unit 66 adds a TxID to the signal to which the GI has been added. In contrast, the relay station 301 of FIG. 11 adds a TxID to the symbol after the equalization decision in the equalization/symbol decision unit 84 and before the IFFT unit 88 performs an inverse Fourier transform.

As described above, the transmitting device 101 according to this embodiment, in a broadcasting system that transmits broadcast signals using the FDM modulation method, multiplexes and transmits identification information that identifies the device onto FDM subcarriers on the frequency axis of the broadcast signal. Specifically, the transmitting device 101 multiplexes and transmits the identification information onto control data related to the transmission method of the LL channel or broadcast signal, such as at least one of the LL channel and TMCC carrier, which are known signals. The relay station 301 also multiplexes and transmits its own identification information onto control data related to the transmission method of the LL channel or broadcast signal, such as at least one of the LL channel and TMCC carrier, which are known signals. Therefore, according to this embodiment, the identification information of the transmitting device 101 or relay station 301 can be transmitted without degrading the main line signal.

The transmitting device 101 and relay station 301 may multiplex the identification information onto the known signal L0ch or L1ch as control data and transmit it. The transmitting device 101 and relay station 301 may also multiplex the identification information onto FDM subcarriers on the frequency axis of the broadcast signal a number of times corresponding to the number of FFT samples used in the modulation/demodulation process and transmit it.

Also, as mentioned above, LLch includes L0ch, which is a partial reception band, and L1ch, which is a non-partial reception band. The transmitting device 101 and relay station 301 may multiplex TxID only onto L0ch. This allows the identification information of the transmitting device 101 or relay station 301 to be transmitted without degrading the signal of L1ch, which is not multiplexed with TxID. In this case, the transmitting device 101 and relay station 301 may apply a bandwidth limit by reducing the clock rate of only TxID so that the bandwidth is equal to or less than the partial reception bandwidth (1.5 MHz). This reduces the impact on L0ch caused by assigning TxID.

Third Embodiment
(Transmitting device)
The configuration of the transmitting device 101 according to the third embodiment is shown in FIG. 7 , similarly to the second embodiment. FIG. 12 is a diagram illustrating an example of the configuration of a TxID generator according to this embodiment. As described with reference to FIG. 8 , the TxID signal generator 44 of the TxID generator 40 b in the second embodiment generates a TxID signal using individual bits rather than a code such as a Gold sequence. In contrast, the TxID signal generator 44 of the TxID generator 40 c in the third embodiment generates a TxID signal using a code with excellent autocorrelation and cross-correlation values, such as a Gold sequence. Furthermore, in the transmitting device 101 according to the second embodiment, the TxID is multiplexed onto the LL channel carrier of the first symbol of the OFDM frame. In contrast, in the transmitting device 101 according to this embodiment, the TxID is multiplexed across multiple OFDM symbols. The BPSK unit 46 has the same function as the BPSK unit 46 described with reference to FIG. 8 .

As shown in FIG. 12, the TxID generation unit 40c includes a TxID signal generation unit 44 and a BPSK unit 46. The TxID is multiplexed onto several LLch carrier symbols, starting from the first symbol of the OFDM frame. The TxID is also multiplexed onto signals other than known LLch signals. The TxID signal generation unit 44 generates a highly autocorrelated code, such as the Gold sequence (8191 bits) shown in FIG. 3. For example, when using an 8kFFT in compatible mode, there are at least 66 LLch carriers within one symbol (see FIG. 9A). Therefore, the TxID signal generation unit 44 multiplexes 125 symbols from the beginning of the frame (8191/66 = 124.1...). The TxID signal generation unit 44 may multiplex the TxID onto only either L0ch or L1ch. The TxID signal generation unit 44 may also multiplex onto LLch symbols only within the partial reception band.

The modulator of the transmitting device 101 according to the third embodiment is configured as described above. According to the transmitting device 101 of this embodiment, the transmitting station's unique ID (TxID) is multiplexed onto the LL channel on the time axis, rather than onto the mainline OFDM signal. Similarly, the relay station 301 multiplexes its own ID (TxID) onto the LL channel on the time axis, rather than onto the mainline OFDM signal. Therefore, the TxID for identifying the device can be assigned to the signal without degrading the mainline signal. Furthermore, since this embodiment calculates correlation values across multiple symbols, even when signal waves from multiple transmitting devices 101 or relay stations 301 are mixed, it is possible to determine the TxIDs of the multiple arriving transmitting devices 101 or relay stations 301, as well as their individual signal levels and delay times. In other words, it is possible to distinguish not only the wave with the highest level, but also each of the multiple mixed signal waves, and to determine the signal level and delay time of each signal wave, as well as the transmitting device 101 or relay station 301 that output the signal wave.

(receiving device)
13 is a diagram showing an example of the configuration of a receiving device 202 according to this embodiment. The receiving device 202 includes a receiving unit 91, an FFT unit 92, a transmission channel estimating unit 93, an LL channel extracting unit 94, an equalizing unit 95, an LL channel demodulating/LL channel replica creating unit 96, an LL channel replica removing unit 97, a correlation calculating unit 98, a TxID generating unit 99, and a phase rotating unit 105. The receiving unit 91, the FFT unit 92, the transmission channel estimating unit 93, the LL channel extracting unit 94, and the equalizing unit 95 have the same functions as the receiving unit 71, the FFT unit 72, the transmission channel estimating unit 73, the LL channel extracting unit 74, and the equalizing unit 75 described with reference to FIG.

That is, the FFT unit 92 converts the received signal received by the receiver 91 into a frequency-domain signal. Next, the transmission path estimation unit 93 performs transmission path estimation processing using the SP carrier on the received signal converted into a frequency-domain signal. In parallel with this, the LLch extraction unit 94 extracts the LLch carrier from the received signal. The equalization unit 95 performs equalization processing by dividing the LLch carrier by the transmission path estimation value. The LLch demodulation/LLch replica creation unit 96 demodulates the LLch from the equalized signal to create an LLch replica. That is, the LLch demodulation/LLch replica creation unit 96 generates the LLch (known signal) of the first symbol of the OFDM frame. Furthermore, for symbols other than the first symbol, the LLch demodulation/LLch replica creation unit 96 performs BPSK demodulation. The LLch replica removal unit 97 removes this replica from the equalized signal to extract the TxID signal.

On the other hand, the TxID generation unit 99 generates a TxID using a code with excellent autocorrelation and cross-correlation values, such as the Gold sequence described with reference to Figure 3. Furthermore, the TxID generation unit 99 performs BPSK modulation on the generated TxID.

The phase rotation unit 105 rotates the phase of the TxID generated by the TxID generation unit. That is, the phase rotation unit 105 multiplies the TxID signal by e ^jθ to rotate the phase. Here, θ = 2πki/N, k is a variable (number of samples) that determines the rotation angle, i is the subcarrier number, and N is the FFT size. For example, if the FFT size is 8192 and the effective symbol length is 1296 μs, changing k from 0 to 800 corresponds to a delay of approximately 0 to 126 μs. This is because the FFT sample clock is 6.32... (= 8192/1296) [MHz], and for a sample count of 800, the delay is 800/6.32 = 126.56 [μs].

The correlation calculation unit 98 calculates a different correlation value for each TxID by calculating the correlation between the TxID signal extracted by the LLch replica removal unit 97 and the unique TxID generated by the TxID generation unit 99 while changing the phase of the TxID. The correlation is calculated by adding the product of the two signals. The difference in these correlation values indicates the level from the transmitting device 101 or relay station 301. Furthermore, the phase difference between the TxIDs for which correlation is detected corresponds to the delay time between the stations.

In a broadcasting system that transmits broadcast signals using the FDM modulation method, the transmitting device 101 of this embodiment multiplexes identification information that identifies the device onto FDM subcarriers on the frequency axis of the broadcast signal and transmits it. Specifically, the transmitting device 101 multiplexes its identification information onto multiple symbols, starting from the first symbol of control data related to the broadcast signal transmission method, and transmits it. The relay station 301 similarly multiplexes its identification information onto multiple symbols, starting from the first symbol of control data related to the broadcast signal transmission method, and transmits it. Therefore, according to this embodiment, it is possible to transmit identification information for the transmitting device 101 or relay station 301 without degrading the mainline signal. Furthermore, according to this embodiment, when multiple signals are transmitted from the transmitting device 101 and relay station 301, the receiving side can identify the transmitting device 101 and relay station 301 that transmitted each signal and also determine the signal level and arrival time.

Furthermore, relay station 301 receives the broadcast signal transmitted from transmitting device 101, removes noise from the received broadcast signal, assigns identification information that identifies the relay station to the noise-removed broadcast signal, and transmits the broadcast signal with the added identification information. Therefore, receiving devices 201 and 202 that receive the broadcast signal relayed by relay station 301 can identify relay station 301 that relayed the broadcast signal by the identification information.

The transmitting device 101 and relay station 301 may multiplex identification information onto the known signal L0ch or L1ch as control data and transmit it. The transmitting device 101 and relay station 301 may also multiplex identification information onto FDM subcarriers on the frequency axis of the broadcast signal a number of times corresponding to the number of FFT samples used in the modulation/demodulation process and transmit it. The configuration of this embodiment is applicable to digital broadcasting systems that use FDM, and can be applied to ISDB-T as well as advanced terrestrial broadcasting systems.

In each of the above embodiments, the transmitting devices 100, 101 and relay stations 300, 301 assign a TxID to identify themselves and multiplex it onto the transmission signal. With FDM, there is no preamble signal, and OFDM symbols containing data carriers are always transmitted. Therefore, in this embodiment, the TxID is multiplexed onto the first few symbols of the OFDM frame. Specifically, the TxID is multiplexed onto the time axis signal or the frequency axis signal. Therefore, in advanced terrestrial broadcasting systems that use FDM, the TxID can be used to determine from which transmitting device 100, 101 or relay station 300, 301 the received broadcast wave originated. Therefore, each embodiment is effective for investigating interference within a broadcast area.

The present disclosure is not limited to the above-described embodiments. For example, multiple blocks shown in the block diagrams may be integrated, or one block may be divided. Multiple steps shown in the flowcharts may be executed in parallel or in a different order, depending on the processing capabilities of the device executing each step, or as needed, instead of being executed chronologically as described. Other modifications are possible without departing from the spirit of the present disclosure.

10 Input I/F
11 BICM section 14 Level adjustment section 15 System separation section 16 Layer synthesis section 17 Band division section 18 Time IL section 19 Frequency IL section 20 Band synthesis section 21 MISO encoding section 22 TMCC information bit generation section 23 Synchronization bit generation section 24 TMCC generation section 25 Pilot generation section 26 OFDM frame construction section 27, 65, 88 IFFT section 28, 66, 89 GI addition section 31 Energy dispersal section 32 BCH encoding section 33 LDPC encoding section 34 Mapping section 40a, 40b, 67, 85, 99 TxID generation section 41a, 41b, 68, 86 Attenuator 42a, 42b, 69, 87 Adder 44 TxID signal generation section 45 Error correction encoding section 46 BPSK section 61, 71, 81, 91 Receivers 62, 72, 82, 92 FFT units 63, 73, 83, 93 Transmission path estimation units 64, 84 Equalization and symbol decision units 74, 94 LL channel extraction units 75, 95 Equalization unit 76 LL channel replica units 77, 97 LL channel replica removal unit 78 TxID signal demodulation unit 79 TxID signal error correction decoding unit 96 LL channel demodulation/LL channel replica creation unit 98 Correlation calculation units 100, 101 Transmitting device 105 Phase rotation units 200, 201, 202 Receiving devices 300, 301 Relay station

Claims (8)

In a broadcasting system that transmits broadcast signals using an FDM modulation method,
Identification information for identifying the device itself is control data relating to a transmission method of the broadcast signal in FDM subcarriers on the frequency axis of the broadcast signal, and is multiplexed onto at least one of LLch and TMCC carriers, which are known signals, and transmitted.
Transmitting device. The transmitting device according to claim 1 , wherein the identification information is multiplexed into a plurality of symbols starting from the first symbol of the control data and transmitted. 3. The transmitting device according to claim 1 , wherein the identification information is multiplexed onto a known signal, L0ch or L1ch, as the control data and transmitted. 4. The transmitting device according to claim 1 , wherein the identification information is multiplexed onto the FDM subcarriers on the frequency axis of the broadcast signal a number of times corresponding to the number of FFT samples used in modulation/demodulation processing and transmitted. In a broadcasting system that transmits broadcast signals using an FDM modulation method,
Identification information for identifying the device itself is control data relating to a transmission method of the broadcast signal in FDM subcarriers on the time axis of the broadcast signal, and is multiplexed onto at least one of LLch and TMCC carriers, which are known signals, and transmitted.
Transmitting device. 6. The transmitting device according to claim 5 , wherein the identification information is multiplexed onto FDM subcarriers on the time axis of the broadcast signal and transmitted so that the bandwidth for transmitting the identification information is equal to or less than a partial reception bandwidth. receiving the broadcast signal from the transmitting device according to any one of claims 1 to 6 ;
analyzing the received broadcast signal to obtain the identification information;
Receiving device. receiving the broadcast signal transmitted from the transmitting device according to any one of claims 1 to 6 ;
removing noise from the received broadcast signal;
control data relating to a transmission method of the broadcast signal in FDM subcarriers on a frequency axis or a time axis of the broadcast signal from which the noise has been removed, the control data being multiplexed and assigned to at least one of an LLch and a TMCC carrier, which are known signals, and identification information for identifying the device itself;
transmitting the broadcast signal to which the identification information is assigned;
Relay station.