JP7788940B2 - Relay device and relay method - Google Patents

Description

Embodiments of the present invention relate to a wireless signal relay device and relay method.

The relay device receives the signal transmitted from the transmitting device, processes the received signal, and transmits the processed signal to the receiving device.

In recent years, in order to improve frequency utilization efficiency, a Layered Division Multiplexing (LDM) system has been proposed, which transmits two different signals simultaneously in the same band by transmitting a layered multiplexed signal in which two different signals are added together at different power levels. In this specification, a layered multiplexed signal may also be simply referred to as a multiplexed signal.

Conventional repeater devices do not take the LDM method into consideration, so they are unable to correctly demodulate multiplexed signals and are therefore unable to relay them.

Japanese Patent Application Laid-Open No. 2006-67123 Japanese Patent Application Laid-Open No. 2021-72614

The object of the present invention is to provide a relay device and relay method for relaying multiplexed signals.

A relay device according to an embodiment includes a receiving unit that receives a multiplexed signal including a first modulated signal at a first power level and a second modulated signal at a second power level different from the first power level, a demodulating unit that demodulates the multiplexed signal, a decoding unit that decodes the output of the demodulating unit, a coding unit that encodes the output of the decoding unit, a modulating unit that modulates the output of the coding unit, a canceling unit that cancels the output of the modulating unit from the output of the demodulating unit, a first transmitting unit that transmits the output signal of the canceling unit, an amplifying unit that amplifies the multiplexed signal, and a second transmitting unit that transmits the output signal of the amplifying unit .

FIG. 1 is a conceptual diagram illustrating an example of a system according to a first embodiment. FIG. 2 is a block diagram illustrating an example of a repeater according to the first embodiment. FIG. 3 is a block diagram illustrating an example of an output unit of the repeater according to the first embodiment. FIG. 2 is a diagram showing an example of a time waveform of a signal modulated by the ASK method according to the first embodiment. FIG. 10 is a diagram showing another example of the time waveform of a signal modulated by the ASK method according to the first embodiment. FIG. 2 is a block diagram for explaining an example of hierarchical multiplexing of an LDM system according to the first embodiment. FIG. 2 is a diagram for explaining an example of a hierarchical multiplexed signal according to the first embodiment. FIG. 3 is a diagram for explaining an example of a first signal and a second signal according to the first embodiment. 5A and 5B are diagrams for explaining an example of a received signal after amplitude adjustment in a demodulation unit of the repeater according to the first embodiment. 5A and 5B are diagrams showing examples of signals processed by each unit of a transmitter, a repeater, and a receiver in the first embodiment and a comparative example. FIG. 10 is a block diagram illustrating an example of a repeater according to a second embodiment. FIG. 11 is a block diagram illustrating an example of a repeater according to a third embodiment. FIG. 2 is a diagram for explaining an example of one OFDM segment transmitted by the transmitter according to the first embodiment. FIG. 10 is a block diagram illustrating an example of a repeater according to a fourth embodiment. FIG. 13 is a block diagram illustrating an example of a repeater according to a fifth embodiment. FIG. 13 is a diagram showing a constellation map in a repeater according to the fifth embodiment. FIG. 13 is a diagram for explaining an example of the operation of a likelihood operation unit 134 according to the fifth embodiment.

Embodiments will be described below with reference to the drawings. The following description exemplifies devices and methods embodying the technical concepts of the embodiments. The technical concepts of the embodiments are not limited to the structure, shape, arrangement, materials, etc. of the components described below. Modifications that can be readily conceived by those skilled in the art are naturally within the scope of the disclosure. For clarity of explanation, the drawings may show schematic representations of the size, thickness, planar dimensions, or shape of each element, modified from the actual embodiment. Elements with different dimensional relationships or ratios may be included in multiple drawings. Corresponding elements may be designated by the same reference numerals in multiple drawings, and redundant description may be omitted. Some elements may be designated by multiple names, but these names are merely examples and do not exclude the use of other names for these elements. Furthermore, elements that do not have multiple names may also be designated by other names. Note that in the following description, "connection" may include not only direct connection but also connection via other elements.

This embodiment will be described in detail below with reference to the drawings.

[First embodiment]
1 is a conceptual diagram illustrating an example of a system according to a first embodiment. The system includes a transmitter 12, a repeater 14, and a receiver 16. The transmitter 12 transmits an encoded transmission signal. The repeater 14 receives the transmission signal transmitted by the transmitter 12, processes the received signal, generates a transmission signal, and transmits the transmission signal. The transmission signal is at least a part of a hierarchical multiplexed signal. The receiver 16 receives the signal transmitted by the repeater 14.

The signal transmitted by transmitter 12 is a radio signal. This radio signal is a hierarchical multiplexed signal consisting of a first signal and a second signal having a different power level from the first signal. For example, the power level of the first signal is greater than the power level of the second signal.

Multiple repeaters 14 may be placed between the transmitter 12 and the receiver 16. A signal transmitted by one repeater 14 may be received by another repeater 14.

Figure 2 is a block diagram illustrating a repeater 14a, which is an example of the repeater 14 according to the first embodiment. The repeater 14a includes a receiving antenna 22, a demodulation unit 24, a decoding unit 26, an encoding/modulation unit 28, a cancellation unit 30, and an output unit 32. The encoding/demodulation unit 28 may be separated into an encoding unit and a demodulation unit.

The demodulation unit 24 demodulates the radio signal input from the receiving antenna 22. The demodulation unit 24 includes multiple units, such as a filter unit that removes out-of-band radio signals, an amplifier unit that amplifies the level of the radio signal, a downconversion unit that converts the radio signal into an analog signal at baseband frequency, an A/D conversion unit that converts the analog signal at baseband frequency into a digital signal, and a timing synchronization processing unit that adjusts the sample timing or symbol timing. The processing of the multiple units may be performed in the order listed, or in a different order than listed.

The demodulation unit 24 demodulates the hierarchical multiplexed signal and outputs the demodulated signal (e.g., the output signal of the timing synchronization processing unit) to the decoding unit 26. The demodulation unit 24 outputs the demodulated signal (e.g., the output signal of the timing synchronization processing unit) to the cancellation unit 30. The demodulation unit 24 may also output a signal in the middle of demodulation processing (e.g., the output signal of the A/D conversion unit) to the cancellation unit 30.

The decoding unit 26 inputs the signal output from the demodulation unit 24, decodes the input signal using a decoding method corresponding to the encoding of the first signal, and outputs the decoded signal to the encoding/modulation unit 28.

The encoding/modulation unit 28 encodes the input signal using the first signal encoding method, modulates the encoded signal using the first signal modulation method, and outputs the modulated encoded signal to the cancellation unit 30. Because the power level of the first signal is sufficiently greater than the power level of the second signal, when demodulating and decoding the first signal, regardless of the content of the second signal, the second signal can be demodulated and decoded while being largely ignored, just like noise, and the output of the encoding/modulation unit 28 is the first signal.

The cancellation unit 30 cancels the signal corresponding to the first signal input from the encoding/modulation unit 28 from the hierarchical multiplexed signal input from the demodulation unit 24. To extract the signal corresponding to the second signal from the hierarchical multiplexed signal through this cancellation, the level of the first signal input from the encoding/modulation unit 28 to the cancellation unit 30 may be adjusted (×β, as described later in Figure 6) or the timing between the input signals may be adjusted using a buffer included in the cancellation unit 30. The output of the second signal from the demodulation unit 24 to the cancellation unit can be achieved in one clock period. However, the first signal is decoded by the decoding unit 26 and encoded and modulated by the encoding/modulation unit 28. This process requires several clock periods. The timing of the second signal input from the demodulation unit 24 to the cancellation unit must be adjusted accordingly. The timing synchronization process of the demodulation unit 24 refers to sample timing synchronization, which oversamples the received signal and finds the optimal sample timing from the oversampled signal. In other embodiments, this may refer to symbol timing synchronization, which finds symbol timing from a signal with a GI, or frame timing synchronization, which finds the beginning of a frame. The cancellation unit 30 supplies a signal corresponding to the second signal obtained by cancellation to the output unit 32.

The output unit 32 transmits a signal corresponding to the second signal output by the cancellation unit 30 as a wireless signal or an optical signal. The signal transmitted by the repeater 14a is a wireless signal or an optical signal.

Figure 3 is a block diagram illustrating an example of the output unit 32 of the repeater 14a according to the first embodiment.

The output unit 32a shown in FIG. 3(a) includes a modulation unit 40 and a transmission antenna 42. The modulation unit 40 includes multiple units, such as a D/A conversion unit, an up-conversion unit that converts analog baseband signals to RF frequencies, a filter unit that removes out-of-band signals, and an amplifier unit that amplifies the level of the radio signal. The transmission antenna 42 emits a radio signal. The frequency of the radio signal transmitted by the repeater 14a may be the same as or different from the frequency of the radio signal transmitted by the transmitter 12.

The output unit 32b shown in Figure 3(b) includes a decoding unit 46 and an optical signal output unit 48. The decoding unit 46 decodes the signal output by the cancellation unit 30 using a decoding method corresponding to the encoding of the second signal. The optical signal output unit 48 converts the signal output by the decoding unit 46 into an optical signal and outputs it. In this way, when the repeater 14a demodulates and decodes the received signal before repeating it, there is no need for demodulation and decoding by the receiver 16. When the repeater 14a includes the output unit 32b, the repeater 14a and other repeaters 14a, or the repeater 14a and receiver 16, are connected by optical fiber. When signals are transmitted via optical fiber, there is almost no degradation in signal transmission quality.

(Operation of repeater 14a)
The specific operation of the repeater 14a will be described below, assuming that the modulation method used by the transmitter 12 is amplitude shift keying.

Figure 4 shows an example of the time waveform of a signal modulated using the ASK method according to the first embodiment. Figure 4(a) shows an example of the time waveform of a signal with an amplitude value of 1. Figure 4(b) shows an example of the time waveform of a signal with an amplitude value of 0. The symbol length is assumed to be ts. Figure 4(a) represents the waveform of a binary 1 (0b1), and Figure 4(b) represents the waveform of a binary 0 (0b0). Figure 4 shows an example where the amplitude values are two values, 0 and 1, and the number of bits transmitted per symbol is 1. The modulation method for the first signal and the second signal may be the same (both ASK), or they may be different modulation methods.

Figure 5 shows another example of the time waveform of a signal modulated using the ASK method according to the first embodiment. Figure 5 shows an example in which the amplitude values are four values: 0, 0.33, 0.67, and 1, and the number of bits transmitted per symbol is two. Figure 5(a) represents the waveform of binary 11 (0b11), Figure 5(b) represents the waveform of binary 10 (0b10), Figure 5(c) represents the waveform of binary 00 (0b00), and Figure 5(d) represents the waveform of binary 01 (0b01). The encoding method shown in Figure 5 is also known as Gray code.

Figure 6 is a block diagram illustrating an example of hierarchical multiplexing using the LDM method according to the first embodiment. Hierarchical multiplexing is performed by a first signal generation unit 52, a first power adjustment unit 54, a second signal generation unit 62, a second power adjustment unit 64, and an adder unit 56. The first signal generation unit 52 generates a first signal and outputs it to the first power adjustment unit 54. The first power adjustment unit 54 adjusts the power level of the input first signal and outputs the adjusted first signal to the adder unit 56. The second signal generation unit 62 generates a second signal and outputs it to the second power adjustment unit 64. The second power adjustment unit 64 adjusts the power level of the input second signal and outputs the adjusted second signal to the adder unit 56. The adder unit 56 adds the two input signals and outputs a hierarchical multiplexing signal indicating the addition result. The first power adjustment unit 54 multiplies the input signal by β. The second power adjustment unit 64 multiplies the input signal by αβ. α is called a scaling coefficient, and β is called a normalization coefficient. Here, α<1, but this is not limited to this.

Figure 7 is a diagram illustrating an example of a hierarchical multiplexed signal according to the first embodiment. Because the second signal is multiplied by the scaling coefficient α, the signal level of the second signal is lower than the signal level of the first signal. Therefore, the first signal is also referred to as the upper layer signal, and the second signal is also referred to as the lower layer signal. The power level ratio of the two layer signals (the ratio of the power level of the first signal to the power level of the second signal) is referred to as the injection level. Examples of injection levels are 23 dB or 15 dB.

One application of LDM hierarchical multiplexing is being considered for the next-generation standard for the current terrestrial digital television broadcasting, known as Integrated Services Digital Broadcasting-Terrestrial (ISDB-T). By using the LDM method, it is possible for the next-generation standard to coexist with the current standard.

As an example, a hierarchical multiplexed signal is transmitted using a signal conforming to the ISDB-T standard (hereinafter referred to as the ISDB-T signal) as the first signal and a signal conforming to a next-generation terrestrial digital television broadcasting standard (e.g., the 4K8K standard or the Super Hi-Vision (SHV) standard) that is an advanced version of the ISDB-T standard (hereinafter referred to as the SHV signal) as the second signal. This allows the SHV signal to be transmitted without having to allocate a new frequency for it.

Note that signals are not limited to two hierarchical layers, but may be multiplexed with three or more hierarchical layers. They are not limited to multiple different signals, but may also be multiplexed with the same signals at different power levels. For example, a hierarchically multiplexed signal may not include ISDB-T signals, and SHV signals may be multiplexed in upper and lower hierarchical layers.

The encoding of the transmitter 12 will now be explained. One example of an encoding method is the repetition method. When 0b1 is repeated three times and encoded, the encoded signal becomes 0b111. When 0b0 is repeated three times and encoded, the encoded signal becomes 0b000. When 0b11 is repeated three times and encoded, the encoded signal becomes 0b111111. When 0b10 is repeated three times and encoded, the encoded signal becomes 0b111000. When 0b00 is repeated three times and encoded, the encoded signal becomes 0b000000. When 0b01 is repeated three times and encoded, the encoded signal becomes 0b000111.

When decoding an encoded signal at the repeater 14a or receiver 16, decoding may be performed by majority decision. For example, if the encoded signal 0b001 is received, the encoded signal 0b001 is decoded as 0b0 because there are more 0b0 bits than 0b1 bits.

Figure 8 is a diagram illustrating an example of a first signal and a second signal according to the first embodiment. Figure 8(a) shows an example of a time waveform generated by the first signal generator 52. The first signal is encoded using a three-time repetition method. Figure 8(a) shows a case where the signal generator 52 modulates a signal using ASK, where the first signal before encoding is 0b101... and the first signal after encoding is 0b111000111.... Figure 8(b) is a diagram illustrating an example of a time waveform generated by the second signal generator 62. The second signal is encoded using a five-time repetition method. Figure 8(b) shows a case where the second signal before encoding is 0b10... and the second signal after encoding is 0b1111100000.... Figure 8(c) is a diagram illustrating an example of a time waveform of a signal in which the first signal and the second signal are hierarchically multiplexed. The hierarchical multiplexing in Figure 8(c) is achieved when the scaling coefficient α = 0.1 (amplitude is 0.1 times) and the normalization coefficient β = 1. Since the amplitude value of the first signal after power adjustment is 0.0 or 1.0 and the amplitude value of the second signal after power adjustment is 0.0 or 0.1, the amplitude value of the ASK modulated signal (Figure 8(c)) after hierarchical multiplexing is 0.0, 0.1, 1.0, or 1.1. Transmitter 12 transmits the hierarchical multiplexed signal shown in Figure 8(c).

Figure 9 is a diagram illustrating an example of a received signal whose amplitude has been adjusted by the demodulation unit 24 of the repeater 14a according to the first embodiment. Figure 9 shows a signal whose amplitude has been adjusted by the amplifier unit of the demodulation unit 24. Amplitude adjustment involves adjusting the power level of the received signal. The radio signal includes a pilot signal, which will be described later. The pilot signal is a known signal. The amplifier unit adjusts the power level of the received signal so that the power level of the pilot signal included in the received signal matches the power level of the known signal. Alternatively, assuming that 0b0 and 0b1 occur with equal probability in the transmitter 12, adjustment may be made so that the average value of the values of the multiple received symbols is 0.55.

The signal transmitted by the transmitter 12 may not be received correctly by the repeater 14a due to attenuation caused by propagation loss, the effects of multipath in the transmission path, or the effects of additive white guisian noise (AWGN) generated by the repeater 14a. The amplitudes of the transmitted signal shown in Figure 8(c) are 1.1, 1.1, 1.1, 0.1, 0.1, 0.0, 1.0, ... starting from the first symbol. The amplitudes of the signal after amplitude adjustment by the demodulation unit 24 of the repeater 14 shown in Figure 9 are 1.1, 1.1, 1.1, 0.6, 0.1, 0.0, 1.0, ... starting from the first symbol. The amplitude of 0.6 of the fourth symbol (3ts < t < 4ts) of the signal in Figure 9 changes from the amplitude of 0.1 of the fourth symbol of the transmitted signal (Figure 8(c)).

The decoding unit 26 determines (hard decision) the amplitude of the signal after timing synchronization processing by the demodulation unit 24 to be a value closer to either 0 or 1. As shown in Figure 9, the amplitude of the signal after timing synchronization processing is 1.1, 1.1, 1.1, 0.6, 0.1, 0.0, 1.0, ... starting from the first symbol, so the hard decision results are 1, 1, 1, 1, 0, 0, 1, ... starting from the first symbol. The decoding unit 26 further decodes this decision result every three symbols by majority decision. The decoded result is 0b10....

The encoding/modulation unit 28 encodes the output of the decoding unit 26 using the repetition method. The encoded signal is 0b111000.... The hard decision result 1, 1, 1, 0, 0, 1,... and the encoded signal 1, 1, 1, 0, 0, 0, 1,... differ in the bit of the fourth symbol. Bit 1 of the fourth symbol of the hard decision result is changed to bit 0 in the encoded signal. The encoding/modulation unit 28 modulates this encoded signal using the ASK method. The modulation result is a radio signal with an amplitude of 1.0, 1.0, 1.0, 0.0, 0.0, 0.0,.... The modulation result is a signal corresponding to the first signal.

The cancellation unit 30 cancels the modulation result from the encoding/modulation unit 28 from the signal after amplification by the demodulation unit 24 (Figure 9), obtaining an ASK-modulated signal with amplitudes of 0.1, 0.1, 0.1, 0.6, 0.1, 0.0, ... This signal corresponds to the second signal.

The output unit 32 transmits this modulated signal as a radio signal or an optical signal.

The amplitudes of the signal transmitted by the output unit 32 are 0.1, 0.1, 0.1, 0.6, 0.1, 0.0, .... Because the amplitudes of the second signal are 0.0 and 0.1, the receiver 16 decodes using 0.05, the intermediate value, as a reference. The decoding result by the receiver 16 is 1, 1, 1, 1, 1, 0, 0, .... Therefore, the receiver 16 can generate the second signal based on the signal transmitted from the repeater 14a according to the first embodiment. In this way, the repeater 14a can correct (compensate) for changes in the amplitude of the modulated signal contained in the received signal (deterioration of signal quality) by decoding, encoding, and demodulating the received signal. The output unit 32 may also amplify and transmit the amplitude input from the cancellation unit. For example, the amplitude may be amplified by 10 times, and an amplitude of 0.1 may be transmitted as an amplitude of 1.0, and an amplitude of 0.0 may be transmitted as an amplitude of 0.0.

(Comparative Example)
As a comparative example, a repeater that does not perform decoding processing and performs only modulation processing instead of encoding and modulation is assumed. In the repeater of the comparative example, the decoding unit 26 of the repeater 14a is omitted, and a modulation unit is provided instead of the encoding and modulation unit 28. Furthermore, the demodulation unit 28 includes a hard decision processing unit that performs hard decision processing. In the comparative example, the demodulation result is modulated, and this modulation result is canceled from the demodulation result of the demodulation unit 24.

The signal after hard decision of the amplitude-adjusted signal (Figure 9) after amplification by the demodulation unit 24 in the comparative example is 1, 1, 1, 1, 0, 0, 1, ... starting from the first symbol. The modulation unit modulates the hard decision result using the ASK method. The modulation result is a signal with amplitudes of 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, ....

The cancellation unit 30 cancels the signal resulting from modulation by the modulation unit from the signal amplified by the demodulation unit 24 (Figure 9), obtaining an ASK-modulated signal with an amplitude of 0.1, 0.1, 0.1, 0.0, 0.1, 0.0, .... The fourth symbol of this ASK-modulated signal is 0.6 - 1.0 = -0.4, but since there are no negative amplitudes, it is set to 0.0. Since the amplitude of the signal output from the cancellation unit 30 is 0.0 and 0.1, if the intermediate value of 0.05 is used as the decoding standard, an ASK-modulated signal with an amplitude of 0.1, 0.1, 0.1, 0.0, 0.1, 0.0, ... is likely to be decoded as 1, 1, 1, 0, 1, 0, ... by the receiver 16. Because the signal transmitted by the repeater already contains errors, the reception performance of the receiver 16 is degraded.

Figure 10 shows an example of signals processed by each section of the transmitter, repeater, and receiver in the first embodiment and the comparative example.

In the repeater 14a according to the first embodiment, the cancellation unit 30 cancels the signal corresponding to the first signal from the hierarchical multiplexed signal, thereby enabling the signal corresponding to the second signal to be generated with high accuracy. The decoding unit 26 decodes only the signal corresponding to the first signal before generating it. According to the repeater 14a according to the first embodiment, the time required for relaying can be shortened compared to when both the signal corresponding to the first signal and the signal corresponding to the second signal are decoded before generation. If the decoding unit 26 and the encoding/modulation unit 28 were omitted from the repeater 14a, the relaying time would be further shortened, but the accuracy of the signal corresponding to the second signal output by the cancellation unit 30 would be lower.

The repeater 14a according to the first embodiment can relay lower layer signals within a hierarchical multiplexed signal with high quality.

Second Embodiment
11 is a block diagram showing an example of a repeater 14b according to the second embodiment. The repeater 14b differs from the repeater 14a in that an amplifier unit 102 and an output unit 32a are added.

The hierarchical multiplexed signal received by the receiving antenna 22 is output to the demodulator 24 and amplifier 102. The amplifier 102 amplifies the power level of the hierarchical multiplexed signal and outputs it to the output unit 32a. The output unit 32a transmits the amplified hierarchical multiplexed signal as a radio signal.

By relaying the hierarchical multiplexed signal via the amplifier unit 102, the repeater 14b can perform low-latency relaying, eliminating the delays that occur in the demodulator 24, decoder 26, encoder/modulator 28, and cancellation unit 30. Furthermore, because the relaying is low-latency, the receiver 16 can receive the hierarchical multiplexed signal with low delay.

The amplifier unit 102 amplifies the power level, allowing the receiver 16 to receive the hierarchical multiplexed signal at a relatively high power level. The receiver 16 can obtain the first signal from the hierarchical multiplexed signal. Because the first signal has a much higher power level than the second signal, there is almost no degradation in signal quality compared to the second signal.

Repeater 14b, like repeater 14a, transmits a signal corresponding to the second signal from output unit 32, allowing receiver 16 to obtain the second signal without degradation in signal quality.

The receiver 16 can almost simultaneously receive the hierarchical multiplexed signal (direct signal) transmitted by the transmitter 12 without going through the repeater 14b, and the hierarchical multiplexed signal (relayed signal) transmitted by the transmitter 12 via the repeater 14b. Almost simultaneously means that, if the time difference between the two signals is Δt, Δt < ts (symbol length). The receiver 16 can receive the same information (hierarchical multiplexed signal) from both the transmitter 12 and the repeater 14b at the same time. In other words, improved reception performance of the receiver 16 can be expected.

However, depending on the location of the receiver 16, it may be possible that only the transmission signal from repeater 14b can be received, and that the first signal can be correctly demodulated but the second signal cannot be correctly demodulated due to attenuation in radio wave propagation and white noise (AWGN). In such a case, if the output unit 32 of repeater 14b transmits the output signal of the cancellation unit 30 at a frequency different from that of the first signal, the receiver 16 can receive the second signal. Alternatively, if the output unit 32 of repeater 14b transmits the output signal of the cancellation unit 30 to the receiver 16 via optical fiber, the receiver 16 can receive the second signal. Note that if the frequencies of the transmission signal from repeater 14b received by the receiver and the transmission signal from transmitter 12 are different, there will be no interference even if the time difference between them exceeds the symbol length.

The repeater 14b according to the second embodiment can relay lower layer signals with high quality and can relay the above layer signals with low latency.

[Third embodiment]
12 is a block diagram showing an example of a repeater 14c according to the third embodiment. The repeater 14c differs from the repeater 14a in that a determination unit 106 and a selection unit 108 are added.

The cancellation unit 30 outputs a signal corresponding to the second signal (lower layer signal) to the determination unit 106 and the selection unit 108. The determination unit 106 includes a hard decision unit 112 and a soft decision unit 114. The determination unit 106 determines whether the amplitude of the signal corresponding to the second signal is 0 or 1 by hard decision or soft decision. The selection unit 108 selects either the hard decision unit 112 or the soft decision unit 114. The determination unit 106 outputs the determination result to the output unit 32.

When the amplitude of the signal corresponding to the first signal changes, the amplitude of the signal corresponding to the second signal deviates significantly from the correct amplitude. Rather than relaying the signal corresponding to the second signal with a significantly deviated amplitude, determining the signal corresponding to the second signal using soft or hard decision and then relaying it is expected to improve reception performance at receiver 16 that receives the relayed signal.

Note that if the output unit 32 and receiver 16 are connected via optical fiber, the determination unit 106 can be omitted. Since the receiver 16 is equipped with a determination unit, if there is no degradation in communication quality due to optical fiber transmission, similar determination results can be expected whether the determination is made by the determination unit of the repeater or the receiver.

Transmitter 12 applies error correction coding to the first signal. Transmitter 12 may or may not apply error correction coding to the second signal.

If the second signal is not error-correction coded, the reception performance at the receiver 16 is better when the decision unit 106 determines the amplitude using hard decision rather than soft decision. The signal received by the receiver 16 is affected by both noise and distortion that occurs between the transmitter 12 and repeater 14c and noise and distortion that occurs between the repeater 14c and the receiver 16. Hard decision can reduce the effects of this noise and distortion. However, soft decision can also reduce this noise; it is just that the degree of reduction is greater with hard decision than with soft decision.

On the other hand, if the second signal is error-correction coded, determining the amplitude by the decision unit 106 using soft decision may result in better reception performance at the receiver 16 than determining the amplitude using hard decision. If the repeater 14c determines the amplitude using soft decision, an error may occur, but the receiver 16 can correct the error during the decoding process. If the repeater 14c determines the amplitude using hard decision, there is a possibility that the value may be determined (misjudged) to be different from the true value (the value transmitted by the transmitter 12). A misjudgment occurs when the decision boundary is exceeded. In the case of the ASK modulation method, the transmitter and receiver agree in advance that an amplitude of 0 is 0b0 and an amplitude of 1 is 0b1. On the receiver side, due to the influence of factors such as AWGN, the amplitude value may take on values other than amplitude 0 and amplitude 1, such as 0.1, 0.45, 0.55, and 1.1. It is determined whether each amplitude value is 0b0 or 0b1. In normal judgment, the boundary is 0.5, which is halfway between 0 and 1, and if it is less than 0.5 it is judged as 0b0, otherwise it is judged as 0b1. Without processing such as decoding, the receiving side cannot tell whether the judged 0b0 or 0b1 is correct or an incorrect judgment. If a signal that was judged as 0b0 (amplitude 0) on the transmitting side is received on the receiving side and exceeds the boundary of 0.5, it is judged as 0b1, resulting in an incorrect judgment. Soft judgment reduces the adverse effects of incorrect judgment when the judgment boundary is exceeded. By reducing the effects of incorrect judgment using soft judgment and performing error correction decoding in the receiver 16, it is possible to obtain a correct signal.

The selection unit 108 determines whether the second signal has been error-correction coded based on the output signal of the cancellation unit 30. The selection unit 108 selects either the hard decision unit 112 or the soft decision unit 114 depending on the result of the determination. The selection unit 108 may perform the necessary processing to obtain flag information indicating whether the second signal has been error-correction coded. As another example, the flag indicating whether the second signal has been error-correction coded may be obtained from the first signal, or may be obtained by other means.

The transmitter 12 can transmit a flag in the multiplexed signal indicating whether the second signal has been error-correction coded.

The transmitter 12 uses Orthogonal Frequency Division Multiplexing (OFDM) modulation as an example of a signal modulation method. Figure 13 is a diagram illustrating an example of one OFDM segment transmitted by the transmitter 12 according to the third embodiment. In the example of Figure 13, one OFDM segment includes 432 carriers. The number of carriers in an OFDM segment is not limited to this example, and it may include 108 or 216 carriers. The 432 carriers are collectively referred to as a symbol group. 13 consecutive OFDM segments in the frequency direction are referred to as one OFDM symbol. In other words, one OFDM symbol contains 5616 (= 13 x 432) carriers. 204 consecutive OFDM symbols in the time direction are referred to as an OFDM frame.

The transmitter 12 inserts a pilot signal into the OFDM segment (a portion of the 432 carriers is used as the pilot signal). The pilot signal is a known signal. By inserting the pilot signal into the OFDM segment, the receiving device can estimate the frequency characteristics of the propagation path by comparing the received pilot signal with the known signal. The receiving device can compensate for degradation of the frequency characteristics of the propagation path by correcting the frequency characteristics of the propagation path based on the estimation results. Degradation of the frequency characteristics of the propagation path can result in errors in the transmitted data. Compensating for degradation of the frequency characteristics of the propagation path can reduce transmission errors.

Pilot signals include scattered pilot signals (also called SP signals), which are inserted in a dispersed manner in the frequency direction (carrier direction), and continual pilot signals (also called continuous pilot signals, or CP signals), which are inserted continuously in the time direction at frequencies within the transmission band outside of the OFDM segment. Note that SP signals may also be inserted in a dispersed manner in the time direction (symbol direction).

When CP signals are used, one OFDM symbol consists of 5617 carriers. Si,j (i = 0 to 383, j = 0 to 203) represents carriers excluding SP signals, etc.

When SP signals are used, the transmitter 12 inserts one SP signal into the OFDM segment for every 12 carriers. The insertion period of the SP signals in the frequency direction is the first period (12 carriers). The transmitter 12 inserts one SP signal into every four carriers in the time (symbol number) direction. The insertion period of the SP signals in the time direction is the second period (4 carriers).

Note that the carrier numbers of the carriers into which the SP signal is inserted may be the same for every few symbol groups. For example, for the symbol group with symbol number 4, the SP signal is inserted into carriers with carrier numbers 0, 12, etc., just as in the symbol group with symbol number 0.

The transmitter 12 also inserts a TMCC (Transmission and Multiplexing Configuration Control) signal and an AC (Auxiliary Channel) signal into the OFDM segment.

TMCC signals are signals used to transmit control information. Control signals are information that assists the demodulation and decoding operations of the receiving device, such as the hierarchical structure and transmission parameters of OFDM segments. Control information includes system identification, a transmission parameter switching indicator, a start control signal (start flag for emergency alert broadcasts), current information, next information, etc. Current information indicates the current transmission parameters of each hierarchical signal, and next information indicates the transmission parameters of each hierarchical signal after switching. Next information can be set or changed at any time before the switching countdown, but cannot be changed during the countdown.

The transmission parameter information for each layer signal included in the current/next information indicates the carrier modulation mapping method. For example, transmission parameter information "001" indicates the QPSK method, transmission parameter information "010" indicates the 16QAM method, transmission parameter information "011" indicates the 64QAM method, and transmission parameter information "111" indicates that the layer in question is unused or that no next information exists. The transmitting device may transmit the transmission parameter information to the relay device by including it in a signal other than the TMCC signal, such as an AC signal, or by including it in any control information other than the pilot signal for channel estimation.

The AC signal is an extension signal for transmitting additional information related to broadcasting. The additional information is additional information related to the transmission control of modulated waves, or earthquake warning information. The transmitter 12 includes an encoding flag in the AC signal that indicates whether the second signal is error correction encoded. The transmitting device may include the encoding flag in a signal other than the AC signal, such as a TMCC signal, or in any control information other than the pilot signal for channel estimation.

The carriers of the TMCC signal and AC signal are randomly arranged in the frequency direction to reduce the effects of periodic distortion in the propagation path characteristics due to multipath.

The selection unit 108 demodulates the OFDM frame output from the cancellation unit 30, decodes the demodulated signal, and detects the coding flag. The selection unit 108 selects either the hard decision unit 112 or the soft decision unit 114 based on the detected coding flag.

The selection unit 108 may include a memory that stores selection information for selecting the hard decision unit 112 or the soft decision unit 114 according to arbitrary criteria, rather than based on information contained in the output signal of the cancellation unit 30, and may determine the selection of the hard decision unit 112 or the soft decision unit 114 based on the selection information. The repeater 14c may include an input unit for writing the selection information to the memory, and the user of the repeater 14c may rewrite the selection information.

In the repeater 14c according to the third embodiment, the determination unit 106 makes a hard or soft decision on the signal corresponding to the lower layer signal obtained by the cancellation unit 30 depending on whether the lower layer signal is error-correction coded, and the output unit 32 transmits a signal indicating the decision result, thereby enabling the lower layer signal to be relayed with high quality.

[Fourth embodiment]
14 is a block diagram showing an example of a repeater 14d according to the fourth embodiment. The repeater 14d differs from the repeater 14c in that a multiplexing section 122 is added.

The determination unit 106 outputs the determination result of the signal corresponding to the second signal (lower layer signal) to the multiplexing unit 122. The encoding/modulation unit 28 outputs a signal corresponding to the modulated first signal to the cancellation unit 30 and also to the multiplexing unit 122. The multiplexing unit 122 multiplexes the signal corresponding to the input first signal with the signal corresponding to the determined second signal. The multiplexing unit 122 outputs a multiplexed signal of the signal corresponding to the first signal and the signal corresponding to the second signal to the output unit 32. The output unit 32 transmits the multiplexed signal wirelessly or as an optical signal.

The multiplexing unit 122 may include a buffer for storing the signal corresponding to the first signal and a buffer for storing the signal corresponding to the second signal in order to align the timing of the signal corresponding to the first signal and the signal corresponding to the second signal. The demodulation unit 24 adds the same indicator to the signal output to the cancellation unit 30 and the signal output to the decoding unit 26. The multiplexing unit 122 adjusts the timing of multiplexing the two signals based on the indicator added to the signal corresponding to the input first signal and the indicator added to the signal corresponding to the input second signal.

The multiplexing unit 122 may have a level adjustment function to adjust the levels of the signal corresponding to the first signal and the signal corresponding to the second signal. For example, if the determination unit 106 normalizes the output after determination and the encoding/modulation unit 28 normalizes the output after modulation, the input from the determination unit 106 may be power-adjusted by a circuit similar to the first power adjustment unit 54 in Figure 6, and the input from the encoding/modulation unit 28 may be power-adjusted by a circuit similar to the second power adjustment unit 64 in Figure 6, and then multiplexed.

The values of the scaling coefficient α and normalization coefficient β used by the multiplexer 122 for power adjustment may be different from the values of the scaling coefficient α used by the second power adjustment unit 64 of the transmitter 12 and the normalization coefficient β used by the first power adjustment unit 54. For example, if the geographical range of the receiver 16 receiving via the repeater 14d is limited and the signal-to-noise ratio (SNR) of the signal passing through the repeater 14d is expected to be relatively high, the receiver 16 is expected to be able to receive the first signal with high quality. In this case, the scaling coefficient α of the repeater 14d may be set larger (the injection level may be smaller) than the scaling coefficient α of the transmitter 12. This increases the possibility of receiving the second signal while maintaining the communication quality of the first signal at a certain level or higher.

The repeater 14d according to the fourth embodiment is equipped with a multiplexing unit 122, and is therefore able to relay a high-quality hierarchical multiplexed signal generated from a received hierarchical multiplexed signal.

Fifth Embodiment
15 is a block diagram showing an example of a repeater 14e according to the fifth embodiment. The repeater 14e differs from the repeater 14d in that the functional blocks included in the determination unit 106 are explicitly shown, the selection unit 108 is included in the determination unit 106b, and a signal is additionally transmitted from the demodulation unit 24a to the signal quality measurement unit 146 included in the determination unit 106b.

The demodulation unit 24a demodulates the radio signal input from the receiving antenna 22. The demodulation unit 24a may be the same as the demodulation unit 24, but here it is assumed to be different from the demodulation unit 24. The demodulation unit 24a includes multiple units, such as a filter unit that removes out-of-band radio signals, an amplifier unit that amplifies the level of the radio signal, a quadrature demodulation unit that converts the radio signal into I-channel and Q-channel signals at baseband frequencies, an A/D conversion unit that converts analog signals at baseband frequencies into digital signals, a timing synchronization processing unit that adjusts symbol timing, an FFT unit that converts time-domain signals into frequency-domain signals, and an equalization unit that corrects distortion in the transmission path.

The determination unit 106b includes a likelihood calculation unit 132, a likelihood manipulation unit 134, a bit probability calculation unit 136, a symbol probability calculation unit 138, a soft replica generation unit 140, a noise power calculation unit 144, and a signal quality measurement unit 146.

The demodulation unit 24a demodulates the hierarchical multiplexed signal and outputs the demodulated signal (e.g., the output signal of the equalization unit) to the decoding unit 26 and the cancellation unit 30.

As explained with reference to Figure 13, a pilot signal is inserted into the OFDM segment. The equalization unit of the demodulation unit 24a extracts the pilot signal from the OFDM segment, estimates the frequency characteristics of the propagation path by comparing the extracted pilot signal with a known signal, processes the received signal according to the estimated frequency characteristics, and corrects distortion in the transmission path. The equalization unit supplies the estimated frequency characteristics to the signal quality measurement unit 146.

The cancellation unit 30 outputs a signal corresponding to the second signal (lower layer signal) obtained by canceling the output of the encoding/modulation unit 28 from the output of the demodulation unit 24a to the likelihood calculation unit 132 and the noise power calculation unit 144.

The noise power calculation unit 144 calculates the noise power contained in the signal corresponding to the second signal and outputs the calculated noise power to the likelihood calculation unit 132 and the signal quality measurement unit 146.

The likelihood calculation unit 132 receives a signal corresponding to the second signal from the cancellation unit 30, receives noise power from the noise power calculation unit 144, and calculates the log-likelihood ratio (LLR) for each bit. The likelihood calculation unit 132 outputs the calculated LLR to the likelihood operation unit 134.

The signal quality measurement unit 146 measures the signal quality of the second signal based on the noise power input from the noise power calculation unit 144 and the frequency characteristic information input from the demodulation unit 24a. The signal quality measurement unit 146 outputs the measured signal quality to the likelihood operation unit 134.

The likelihood manipulation unit 134 inputs the LLRs from the likelihood calculation unit 132 and the signal quality from the signal quality measurement unit 146. The likelihood manipulation unit 134 selects one likelihood manipulation function from among multiple pre-stored likelihood manipulation functions based on the signal quality. The likelihood manipulation unit 134 changes the LLRs using the selected likelihood manipulation function and outputs the new LLRs for each bit after the change.

The bit probability calculation unit 136 inputs the LLRs from the likelihood operation unit 134, calculates the bit probability for each bit, and outputs the bit probability.

The symbol probability calculation unit 138 inputs the bit probabilities from the bit probability calculation unit 136, calculates the probabilities of signal points preset on the constellation map, and calculates the symbol probability by aggregating the probabilities for each signal point. The symbol probability calculation unit 138 outputs the calculated symbol probabilities to the soft replica generation unit 140.

The soft replica generation unit 140 inputs the symbol probability, generates a soft replica, which is a signal corresponding to the second signal, and outputs it to the multiplexing unit 122.

The multiplexing unit 122 inputs the soft replica and a signal corresponding to the modulated first signal from the encoding/modulation unit 28. The multiplexing unit 122 multiplexes the signal corresponding to the input first signal with the soft replica (signal corresponding to the second signal) and outputs the result.

When the signal quality measured by the signal quality measurement unit 146 is worse than a certain reference quality, the likelihood manipulation unit 134 selects a likelihood manipulation function that causes the decision unit 106b to perform soft decision processing or processing similar to this.

On the other hand, if the signal quality is better than the reference quality, the likelihood manipulation unit 134 selects a likelihood manipulation function that causes the decision unit 106b to perform hard decision processing or processing similar to this. In this specification, replicas generated by hard decisions are also referred to as soft replicas.

As a result, when the signal quality is poor, the likelihood manipulation unit 134 changes the LLR calculated by the likelihood calculation unit 132 to an LLR calculated from a signal that is superimposed as is, with the effects of noise and the like largely removed. On the other hand, when the signal quality is good, the likelihood manipulation unit 134 changes the LLR calculated by the likelihood calculation unit 132 to an LLR calculated from a signal from which the effects of noise and the like have been largely removed.

A signal corresponding to the second signal generated based on the LLRs changed in this way and a signal corresponding to the first signal modulated by the encoding/modulation unit 28 are hierarchically multiplexed in the multiplexing unit 122 and transmitted. The receiver 16 can receive a high-quality hierarchically multiplexed signal.

(Specific Operation of Repeater 14e)
The operation of repeater 14e will be specifically described assuming that the primary modulation method of the first signal transmitted by transmitter 12 is QPSK (Quadrature Phase Shift Keying), the primary modulation method of the second signal is 16QAM (Quadrature Amplitude Modulation), and the secondary modulation method of the first signal and the second signal is OFDM (Orthogonal Frequency Division Multiplexing).

Figure 16(a) is a constellation map showing the arrangement of signal points when the first signal is modulated using the QPSK method. Figure 16(b) is a constellation map showing the arrangement of signal points when the second signal is modulated using 16QAM. Figure 16(c) is a constellation map showing the arrangement of signal points for a signal obtained by hierarchically multiplexing the first and second signals. The hierarchical multiplexing method may be the same as that shown in Figure 6.

The transmitter 12 performs serial/parallel conversion on the hierarchically multiplexed signal, performs IFFT processing, adds a guard interval (GI), and generates and transmits a signal that has been secondarily modulated using OFDM.

The noise power calculation unit 144 calculates the noise power contained in the signal corresponding to the input second signal. If the second signal is modulated using 16QAM, it calculates the square of the distance between the signal point of the input symbol and the signal point on the constellation map that is closest to the input symbol signal point. This squared value is the noise power. The noise power calculation unit 144 may also calculate the average value of multiple noise powers calculated from multiple input symbol signal points as the noise power.

The likelihood calculation unit 132 calculates the LLR for each bit using the signal corresponding to the second signal and noise power. Assume that one symbol transmits multiple bits of data. The likelihood calculation unit 132 calculates the LLR of the k-th bit of one symbol using Equation 1.

Here, _yI and _yQ indicate the I and Q components of the kth bit of the received symbol. _xj,I and _yj,Q indicate the I and Q components of the jth transmitted symbol. ^σ2 is the noise variance estimated by the repeater 14e. _Jk,0 is a set of signal points on the constellation map where the kth bit is 0. _Jk,1 is a set of signal points on the constellation map where the kth bit is 1.

The signal quality measurement unit 146 inputs noise power and frequency characteristic information. The frequency characteristic information is a value (complex number) representing the frequency characteristic of the transmission path of each subcarrier estimated by pilot subcarriers, etc. The larger the absolute value of the value representing the frequency characteristic of the transmission path of each subcarrier, the higher the reliability of that subcarrier. If the frequency characteristic (complex number) of the transmission path of the nth subcarrier is _fn , the signal quality measurement unit 146 measures the signal quality Q as shown in Equation 2.

Q=(|f _n | ² )/σ2 Equation 2
The signal quality measurement unit 146 outputs the measured signal quality to the likelihood operation unit 134 .

The likelihood manipulation unit 134 receives the LLR from the likelihood calculation unit 132 and the signal quality from the signal quality measurement unit 146. The likelihood manipulation unit 134 compares the received signal quality with a preset threshold, and if the threshold is higher, selects a likelihood manipulation function g ₁ (x) that causes the decision unit 106b to perform soft decision processing or processing similar thereto. The likelihood manipulation unit 134 compares the received signal quality with a preset threshold, and if the signal quality is higher, selects a likelihood manipulation function g ₂ (x) that causes the decision unit 106b to perform hard decision processing or processing similar thereto.

The likelihood manipulation unit 134 receives the LLR as input x, and outputs the value obtained by the likelihood manipulation function g ₁ (x) or g ₂ (x) as a new LLR after modification.

Fig. 17 is a diagram illustrating an example of the operation of the likelihood manipulation unit 134 according to the fifth embodiment. Fig. 17(a) is a diagram illustrating an example of the likelihood manipulation function g ₁ (x). The likelihood manipulation function g ₁ (x) is a function that limits the lower limit of the LLR to -a (limiter processing) and limits the upper limit of the LLR to +a. The likelihood manipulation function g ₁ (x) outputs the input x as is (g ₁ (x) = x) when -a≦x≦+a, fixes the output to -a (g ₁ (x) = -a) when x<-a, and fixes the output to +a (g ₁ (x) = a) when x>+a.

17(b) is a diagram illustrating an example of the likelihood manipulation function g ₂ (x). When -b≦x≦+b, the likelihood manipulation function g ₂ (x) outputs a value obtained by multiplying the input x by the gradient a/b (g ₂ (x) = (a/b)x), when x<-b, the output is fixed to -a (g ₂ (x) = -a), and when x>+b, the output is fixed to +a (g ₂ (x) = a), where 0<b<a.

The k-th bit probabilities _Pk (0) and _Pk (1) are _Pk (0) + _Pk (1) = 1. The bit probability calculation unit 136 calculates the bit probabilities _Pk (0) and _Pk (1) according to Equations 3 and 4 using the LLR _k changed by the likelihood manipulation function.

P _k (0)=exp(LLR _k )/(1+exp(LLR _k )) Equation 3
P _k (1) = 1/((1+exp(LLR _k )) Equation 4
The symbol probability calculation unit 138 calculates the symbol probability according to the bit sequence represented by the symbol using Equation 5.

Here, v denotes the number of bits represented by one symbol, and b _j (k) denotes the k-th bit of the bit sequence represented by an arbitrary signal point x _j .

The soft replica generation unit 140 calculates the position (I coordinate, Q coordinate) of the soft replica according to Equations 6 and 7 using the symbol probability Q(x _j ).

The degree of judgment in the likelihood manipulation function is referred to as the judgment rate. The judgment rate is higher as the judgment approaches a hard decision. For example, if the slope of the likelihood manipulation function g1(x) in the range of -a<x<+a in FIG. 17(a) or the slope of the likelihood manipulation function g2(x) in the range of -b<x<+b in FIG. 17(b) is c, the value of c may be used as the judgment rate. Alternatively, if the width of the range of x that is not limited is d, the value of 1/d may be used as the judgment rate. For example, in the case of FIG. 17(a), the width of the range of x that is not limited is 2a (-a<x<+a), so 1/d = 1/(2a). Similarly, in the case of FIG. 17(b), the width of the range of x that is not limited is 2b (-b<x<+b), so 1/d = 1/(2b).

The likelihood manipulation function can be changed depending on the signal quality, allowing for a decision rate that corresponds to the signal quality. As a result, improved reception performance at the receiver 16 can be expected.

The repeater 14e according to the fifth embodiment performs hard or soft decision on the signal corresponding to the lower layer signal obtained by the cancellation unit 30 depending on the signal quality of the lower layer signal, and hierarchically multiplexes the signal indicating the decision result with the signal corresponding to the higher layer signal, thereby relaying the hierarchically multiplexed signal with high quality.

The repeater 14d according to the fourth embodiment and the repeater 14e according to the fifth embodiment are equipped with a multiplexing unit 122, and when relaying a signal to another repeater 14, they transmit a hierarchical multiplexed signal. When relaying a signal to the receiver 16, the repeaters 14d and 14e may transmit a hierarchical multiplexed signal or a signal corresponding to a lower layer signal.

The present invention is not limited to the above-described embodiments, and can be embodied by modifying the components within the scope of the spirit of the invention when implemented. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined.

12...Transmitter, 14...Repeater, 16...Receiver, 22...Receiving antenna, 24...Demodulation unit, 26...Decoding unit, 28...Encoding/modulation unit, 30...Cancellation unit, 32...Output unit, 40...Modulation unit, 44...Demodulation unit, 46...Decoding unit, 48...Optical signal output unit

Claims (15)

a receiving unit that receives a multiplexed signal including a first modulated signal at a first power level and a second modulated signal at a second power level different from the first power level;
a demodulation unit that demodulates the multiplexed signal;
a decoding unit that decodes the output of the demodulation unit;
a modulation unit that encodes the output of the decoding unit and modulates the encoded signal;
a canceller that cancels the output of the modulator from the output of the demodulator;
a first transmitting unit that transmits an output signal of the canceling unit;
an amplifier that amplifies the multiplexed signal;
a second transmitting unit that transmits the output signal of the amplifying unit . a receiving unit that receives a multiplexed signal including a first modulated signal at a first power level and a second modulated signal at a second power level different from the first power level;
a demodulation unit that demodulates the multiplexed signal;
a decoding unit that decodes the output of the demodulation unit;
a modulation unit that encodes the output of the decoding unit and modulates the encoded signal;
a canceller that cancels the output of the modulator from the output of the demodulator;
a determination unit that determines a value of the output of the cancellation unit;
a multiplexing unit that multiplexes a signal indicating the determination result of the determination unit and an output signal of the modulation unit;
a first transmitter that transmits a signal indicating a multiplexing result of the multiplexer;
Equipped with
the multiplexing unit multiplexes the signal indicating the determination result of the determination unit and the output signal of the modulation unit at different power levels;
a power level of the signal indicating the determination result is different from a power level of the second modulated signal;
a relay device, wherein the power level of the output signal of the modulation unit is different from the power level of the first modulated signal; a receiving unit that receives a multiplexed signal including a first modulated signal at a first power level and a second modulated signal at a second power level different from the first power level;
a demodulation unit that demodulates the multiplexed signal;
a decoding unit that decodes the output of the demodulation unit;
a modulation unit that encodes the output of the decoding unit and modulates the encoded signal;
a canceller that cancels the output of the modulator from the output of the demodulator;
a determination unit that determines a value of the output of the cancellation unit by hard decision or soft decision;
a first transmitting unit that transmits a signal indicating a determination result of the determining unit;
Equipped with
The determination unit
If the second modulated signal is error correction coded, determining the value by the soft decision;
If the second modulated signal is not error-correction coded, the relay device determines the value by hard decision. The relay device according to claim 1 , wherein the output signal of said modulation unit is a signal corresponding to said first modulated signal. an amplifier that amplifies the multiplexed signal;
4. The relay device according to claim 2, further comprising: a second transmitting unit that transmits the output signal of the amplifying unit. a determination unit that determines a value of the output of the cancellation unit;
The relay device according to claim 1 , wherein the first transmission unit transmits a signal indicating a determination result of the determination unit. a multiplexing unit that multiplexes a signal indicating the determination result of the determination unit and an output signal of the modulation unit;
The relay device according to claim 6 , wherein the first transmitting section transmits a signal indicating a multiplexing result of the multiplexing section. the multiplexing unit multiplexes the signal indicating the determination result of the determination unit and the output signal of the modulation unit at different power levels;
a power level of the signal indicating the determination result is different from a power level of the second modulated signal;
The relay device according to claim 7 , wherein a power level of the output signal of said modulation section and a power level of said first modulated signal are different. The relay device according to claim 2 , wherein the decision unit decides the value by hard decision or soft decision. The determination unit
If the second modulated signal is error correction coded, determining the value by the soft decision;
The relay device according to claim 9 , wherein when the second modulated signal is not error-correction coded, the value is determined by the hard decision. 11. The relay device according to claim 10, wherein the multiplexed signal includes a flag indicating whether the second modulated signal is encoded using error correction coding. further comprising a quality measurement unit for measuring a signal quality of at least a part of the multiplexed signal;
The determination unit
When the signal quality of at least a part of the multiplexed signal is worse than a first quality, the value is determined by the soft decision;
The relay device according to claim 9 , wherein when the signal quality of at least the part of the multiplexed signals is better than the first quality, the value is determined by the hard decision. receiving a multiplexed signal including a first modulated signal at a first power level and a second modulated signal at a second power level different from the first power level;
demodulating the multiplexed signal;
decoding the demodulation result;
encoding the decoding result and modulating the encoded signal;
canceling the modulation result from the demodulation result;
Sending the cancellation result;
amplifying the multiplexed signal;
and transmitting the amplified result. receiving a multiplexed signal including a first modulated signal at a first power level and a second modulated signal at a second power level different from the first power level;
demodulating the multiplexed signal;
decoding the demodulation result;
encoding the decoding result and modulating the encoded signal;
canceling a modulation result from the demodulation result;
determining a cancellation result value;
multiplexing a signal indicating the determination result and the modulation result;
transmitting a signal indicating the multiplexed result;
Equipped with
The multiplexing step multiplexes the signal indicating the determination result and the modulation result at different power levels,
a power level of the signal indicating the determination result is different from a power level of the second modulated signal;
A relay method, wherein the power level of the modulation result is different from the power level of the first modulated signal. receiving a multiplexed signal including a first modulated signal at a first power level and a second modulated signal at a second power level different from the first power level;
demodulating the multiplexed signal;
decoding the demodulation result;
encoding the decoding result and modulating the encoded signal;
canceling a modulation result from the demodulation result;
determining the value of the cancellation result by hard decision or soft decision;
transmitting a signal indicative of the determination result;
Equipped with
The determining step comprises:
If the second modulated signal is error correction coded, determining the value by the soft decision;
If the second modulated signal is not error-correction coded, the value is determined by hard decision.