JPH1032557A - Relay system, transmitter and repeater used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relay system in which a distance between a transmitter and a repeater is extended or a period of a guard interval being a redundant period is reduced so as to increase transmission capacity and a transmitter and a repeater used for the same. SOLUTION: The time required for information to be transmitted from a transmitter 1 is a sum of a propagation time of a radio wave 21 between the transmitter 1 and a repeater 11 and a time required for signal processing by the repeater 11. A hierarchy modulation circuit 3 assigns a high-order 2-bit (lower-order bits (receptible even at a low C/N)) to a receiver signal (a) and assigns a low-order 2-bit (hingher-order bits (reception disable at a low C/N)) to the receiver signal (a) and the result is subjected to a hierarchical processing and an OFDM(orthogonal frequency division multiplex modulation). The repeater 11 uses a hierarchical demodulation circuit 14 to conduct OFDM demodulation and outputs only the repeater signal assigned to the high-order bits.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay system and a transmitting apparatus and a relay apparatus used for the same, and more particularly to a relay system in which a receiver receives an orthogonal frequency division multiplexed signal from one or both of the transmitting apparatus and the relay apparatus. The present invention relates to a transmission device and a relay device used for the communication device.

[0002]

2. Description of the Related Art As a modulation method for digital terrestrial broadcasting,
An orthogonal frequency division multiplexing (OFDM) scheme is being studied. In the OFDM system, a redundant period called a guard interval can be provided, and a ghost (multipath) of a delay time in the guard interval period is much smaller than that of the digital broadcasting system of the single carrier system. Has strong resistance. For this reason, relaying on a single frequency called a single frequency network (SFN) becomes possible, and the receiver can receive the same frequency and the same orthogonal frequency division multiplexed signal from one or both of the transmitting device and the relay device. it can.

[0003] Further, utilizing this fact, a stable transmission state is established by a repeater (retransmitter) using the same frequency called a gap filler for transmission and reception in a place where the electric field strength is reduced such as a building shadow. It is also possible to maintain.

[0004]

However, when relaying is performed using a single frequency, the relay device provided at the relay point receives the radio wave of the transmitter provided at the transmission point,
Because it is amplified and retransmitted, the signal to be retransmitted is
There is a delay in the radio wave propagation time between the transmission point and the relay point and a delay in the time required for signal processing (amplification) of the relay device itself, and the radio wave transmitted from the transmission device and the retransmission from the relay device are retransmitted. As a result, a ghost (multipath) delay time difference at the receiving point increases.

At the receiving point, the delay time difference between the radio wave transmitted from the transmitting device and the radio wave retransmitted from the relay device becomes largest because the receiving point is located on a straight line connecting the transmitting device and the relay device. This is a case where the receiving point is located in a direction opposite to the relay device when viewed from the transmitting device. In this case, the delay time difference is obtained by adding a time required for signal processing (amplification) of the relay device itself to twice the radio wave propagation time between the transmitting device and the relay device.

In order to suppress such a delay time difference within a guard interval period of an OFDM signal, conventionally, it is necessary to shorten the distance between the transmitting device and the relay device or to lengthen the guard interval period. Further, in the above-described conventional relay system, when there is a ghost (multipath) having a delay time exceeding the guard interval, the transmission quality is rapidly deteriorated. On the other hand, the guard interval is a redundant period, and increasing this period causes a decrease in transmission capacity.

On the other hand, a dual frequency network (DFN) using two frequency bands has been proposed (Aiichiro Tsutake, et al., "Digital Terrestrial Broadcasting by OFDM-Dual Frequency Broadcasting Relay (DFN)", Proceedings of the 1995 Annual Conference of the Institute of Television Engineers of Japan, pp. 277-278).
Since the DFN is a method in which two frequencies are alternately and repeatedly used for one program, the adoption of the DFN reduces a decrease in transmission quality due to a ghost.

However, since this DFN uses two frequency bands, the frequency utilization efficiency is lower than SFN, and it is difficult to use the two frequency bands when relaying program material. Furthermore, DFN requires the receiver to select and receive two frequency bands according to the receiving point, which is not suitable for mobile reception.

[0009] The present invention has been made in view of the above points,
In an SFN in which a transmission device and a relay device use the same frequency, a relay method and a transmission device used for the relay method that can reduce a delay time difference between reception points of a radio wave transmitted from the transmission device and a radio wave retransmitted from the relay device. An object is to provide a relay device.

Another object of the present invention is to provide a relay system capable of increasing the transmission capacity by lengthening the distance between a transmitting device and a relay device or shortening a guard interval which is a redundant period. An object of the present invention is to provide a transmitting device and a relay device used.

[0011]

In order to achieve the above object, a relay system according to the present invention modulates information to be transmitted by a transmitting device by a predetermined modulation method, transmits the information at a predetermined frequency, and transmits the information by the relay device. After receiving and demodulating the radio wave transmitted by the device, re-modulate and transmit the information to be transmitted again using the same frequency as the transmitting device, and the receiver transmits the radio wave from one or both of the transmitting device and the relay device. In the relay system for receiving, the transmitting apparatus superimposes a signal for the relay apparatus for retransmission by the relay apparatus and a signal for the receiver for direct transmission to the receiver by layering, and performs the first orthogonal frequency division. The relay apparatus modulates and transmits the multiplexed signal. The relay apparatus receives the radio wave transmitted by the transmitting apparatus, separates and demodulates the signal for the relay apparatus, modulates again, and retransmits the signal as a second orthogonal frequency division multiplexed signal. Feature To.

In the present invention, since the signal for the relay device directed to the relay device is superimposed on the signal for the receiver directed from the transmission device to the receiver, the same transmission unit in the transmission device relays the signal to the receiver. Each signal can be transmitted simultaneously to both devices.

[0013] In order to achieve the above object, the transmitting apparatus of the present invention corresponds to the sum of the radio wave propagation time from the transmission point to the relay point and the signal processing time of the relay apparatus. A delay circuit that outputs a signal for a receiver with a time delay, and information to be transmitted, which is input to the delay circuit, together with a signal for the receiver, is input as a signal for the relay device, and the signal for the receiver and the signal for the relay device are input. And a hierarchical modulation circuit that performs hierarchical frequency division multiplexing modulation by allocating the signals to different bits, and a transmission unit that converts an output modulated signal of the hierarchical modulation circuit into a predetermined frequency band and transmits the signal.

[0014] Of the signals transmitted from the transmitting device, the signal for the receiver directed directly to the receiving point without passing through the relay device is different from the signal for the relay device transmitted from the transmitting device to the relay device with the transmitting point. This is information delayed by a delay circuit by a time obtained by adding a time required for signal processing (amplification, demodulation, re-modulation) of the relay device itself to a radio wave propagation time between the points. Therefore, according to the present invention, the transmission timing of the signal retransmitted from the relay device to the receiver and the transmission timing of the signal for the receiver transmitted from the transmission device to the receiver can be substantially matched, and these signals can be transmitted by the transmission device. And the relay device always have the same information content.

As a result, even when the delay time difference between the radio wave transmitted from the transmitting device and the radio wave retransmitted from the relay device becomes the largest in the receiver, the delay time difference between the transmitting device and the relay device becomes larger. Does not exceed the radio wave propagation time. Therefore, compared to the conventional relay system,
The delay time difference between the radio wave transmitted from the transmitting device and the radio wave retransmitted from the relay device in the receiver is less than half.

Further, in the present invention, when there are a plurality of relay devices, the transmitting device transmits information to be transmitted to a plurality of relay devices located at each relay point at each radio wave propagation time from the transmission point to each of the plurality of relay points. Of the time obtained by adding the signal processing time of the relay device, the maximum time is set as a delay time in the delay circuit, and the relay device makes the transmission time of the transmission device substantially equal to the time of transmission by the own device. Since the delay circuit is provided on the input side or the output side of the hierarchical demodulation circuit, a signal retransmitted from a plurality of relay devices to the receiver,
The transmission timings of the receiver signal transmitted from the transmission device to the receiver can be made substantially the same.

Further, according to the present invention, the hierarchical modulation circuit is configured to hierarchically modulate the signal for the receiver to the lower order and the signal for the relay to the higher order, so that the C / N required for reception in the relay is less. Although higher, a relay device that can be installed in a place with a good reception environment such as the roof of a building can receive radio waves from a transmission device with a higher C / N than a general receiver.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a relay system according to a first embodiment of the present invention, and a transmitting apparatus and a relay apparatus used therein. The relay system according to this embodiment includes a transmitting device 1
And the relay device 11 transmit an OFDM signal of the same content at the same frequency, and the receiver 25 receives the OFDM signal. The transmitting device 1 has the hierarchical modulation circuit 3, and the relay device 11 has the hierarchical demodulation circuit. It has a feature in having 14.

The transmitting apparatus 1 receives a delay circuit 2 for delaying information to be transmitted, an output signal of the delay circuit 2 as a signal a for a receiver, and information to be transmitted as a signal b for a relay apparatus. And these signals are hierarchized and OF
It comprises a hierarchical modulation circuit 3 for performing DM modulation, and a transmission high frequency section 4 for amplifying and frequency-converting an output signal of the hierarchical modulation circuit 3 into a high-frequency transmission band and transmitting the converted signal via an antenna 5. In the hierarchical modulation circuit 3, the signal a for the receiver is on the low-order side (reception is possible even at a low carrier power-to-noise power ratio (C / N)), and the signal b for the relay apparatus is the high-order (low C / N). (Sometimes reception is not possible). The hierarchical modulation circuit 3 includes, for example, a mapping circuit 6 as shown in the block diagram of FIG.
It comprises an inverse fast Fourier transform (IFFT) circuit 7 and a quadrature modulation circuit 8.

The relay device 11 receives the radio wave 2 from the transmitting device 1.
1, a reception high-frequency unit 13 for extracting and amplifying a signal in a required frequency band from a reception signal from the antenna 12, and a reception high-frequency signal from the reception high-frequency unit 13.
Hierarchical demodulation circuit 1 that performs FDM demodulation, separates the hierarchized signal, and further obtains relay apparatus signal c that is a higher-order signal.
4 and a modulation circuit 1 for OFDM-modulating the relay device signal c
5, a transmission high frequency unit 16 for amplifying and converting the output OFDM signal of the modulation circuit 15 into a high frequency band, and a transmission high frequency unit 1
Antenna 1 transmitting the output high-frequency signal of 6 as radio wave 23
7 is comprised. The hierarchical demodulation circuit 14 includes, for example, a quadrature demodulator 18, a fast Fourier transform (FFT) circuit 19, and a discrimination circuit 20, as shown in the block diagram of FIG.

The radio wave 23 transmitted from the antenna 17
Is the same frequency as the radio waves 21 and 22 from the transmitting apparatus 1. In addition, the receiver 25 includes the radio wave 22 transmitted from the transmission device 1 and the radio wave 2 transmitted from the relay device 11.
3 is demodulated after being received by the antenna 24.

Next, the operation of this embodiment will be described in detail with reference to FIGS. FIG. 4 (A)
Is a diagram showing a positional relationship between a transmission point 31 at which the transmission device 1 is installed, a relay point 32 at which the relay device 11 is installed, and a reception point 33 which is the position of the receiver 25, and t1, t2 and t4 indicate transmissions, respectively. The delay time required for radio wave propagation between the point 31 and the reception point 33, between the transmission point 31 and the relay point 32, and between the relay point 32 and the reception point 33 is shown. 11 shows a processing time, that is, a delay time required for retransmission.

At the receiving point 33, a radio wave 34 transmitted from the transmission point 31 and a radio wave 36 transmitted from the relay point 32 are simultaneously received. Now, assuming that the relay device 11 installed at the relay point 32 simply amplifies and retransmits the radio wave 35 transmitted from the transmission point 31, the radio wave transmitted from the transmission point 31 is received at the reception point 33. 34 and relay point 32
(T2 + t3 + t4)
−t1).

FIG. 4B shows the signal 3 of the radio wave 34 at this time.
FIG. 7 is a diagram showing a time relationship between a signal 7 and a signal 38 of a radio wave 36 at a reception point 33. The signals 37 and 38 have the same contents, but have a delay time difference t5. The delay time difference t5 is the delay time difference (t2 + t3 + t4-t1). Each of the signals 37 and 38 forms one symbol from the information d1 and the guard interval d2. OF
For the DM demodulation, a period having a length corresponding to the information d1 portion is extracted from an arbitrary period within this one symbol period.

In FIG. 4B, the demodulation section t6 corresponds to this. However, when the delay time difference t5 between the signal 37 and the signal 38 is large and the signal 37 and the signal 38 are combined, an inter-symbol interference section t7 occurs. In the inter-symbol interference section t7, since symbols having different information are combined, an error occurs in the original information after demodulation.
That is, when the delay time difference t5 is longer than the guard interval d2, an intersymbol interference section t7 corresponding to at least the time difference is generated, and an error occurs.

The purpose of the present embodiment is to prevent the occurrence of the inter-symbol interference section.
FIG. 4 (A) shows (t2 + t
By compensating the delay time corresponding to 3), the delay time difference t5 is set to (t4−t1). FIG.
(C) shows the time relationship between the signal 37 of the radio wave 34 and the signal 38 of the radio wave 36 at the receiving point 33 at this time.
As shown in the figure, the delay time difference t5 is shorter than the guard interval d2, and no symbol interference section occurs.

Next, hierarchical modulation will be described with reference to FIG. FIG. 5A shows a constellation of non-uniform 16QAM (quadrature amplitude modulation), and a four-digit number in the figure indicates a 4-bit code assigned to each signal point. The upper two bits of each number correspond to the quadrant in which each signal point is located, and the lower two bits correspond to the position of the signal point in each quadrant. For the upper 2 bits, the distance between each code is large and transmission at low C / N is possible.
For the lower 2 bits, the distance between each code is smaller and the upper 2 bits are smaller.
A higher C / N is required compared to bits. Therefore, by assigning the information of the lower order (receivable also at the time of low C / N) to the upper 2 bits and the information of the higher order (impossible to receive at the time of low C / N) to the lower 2 bits, hierarchical modulation is achieved. It becomes possible.

The upper 2 bits are shown in FIG.
The same numbers as those of the constellation of QPSK (four-phase modulation) shown in (B) are assigned. Therefore, FIG.
In the case where only the low-order (receivable even at low C / N) signals among the non-uniform 16QAM signals shown in (A) need to be received, the non-uniform 16QAM signals are shown in FIG. Processing can be performed as a QPSK signal.

FIG. 5C shows a non-uniform 16DAP.
It shows a constellation of SK (differential amplitude phase modulation). The four-digit numbers in the figure indicate 4-bit codes assigned to each signal point. Also in this case, as in the non-uniform 16QAM, the upper two bits correspond to the quadrant where each signal point is located, and the lower two bits correspond to the position of the signal point in each quadrant. Therefore, similarly, when it is only necessary to be able to receive only the low-order (reception is possible even at low C / N) side, it is possible to process the non-uniform 16 DAPSK signal as the QPSK signal shown in FIG. 5B. it can.

Returning to FIG. 1, the operation will be described again. In the transmitting apparatus 1, information to be transmitted is divided into two parts, one of which is delayed by a delay circuit 2 for a predetermined time. This delay time is caused by the transmission of the radio wave 2 between the transmitting device 1 and the relay device 11.
1 (t2 in FIG. 4A), the relay device 1
The time required for the signal processing (1 in FIG. 4A) (t3 in FIG. 4A) is the sum of the times. Therefore, in the example shown in FIG.
This delay time is set to (t2 + t3), and the delay time difference t5 is set to (t4-t1). The signal delayed by the delay circuit 2 becomes a receiver signal a. By setting the delay time of the delay circuit 2 in this way, the transmitting device 1 and the relay device 11 can transmit information at the same timing.

The other of the two pieces of information to be transmitted is directly supplied to the hierarchical modulation circuit 3 as a relay device signal b. The hierarchical modulation circuit 3 receives the above-mentioned signal b for the relay device and the signal a for the receiver from the delay circuit 3 as input signals, hierarchizes these, and performs OFDM modulation. That is,
The hierarchical modulation circuit 3 is configured as shown in the block diagram of FIG. 2, and the data is allocated to each carrier constituting the OFDM signal in the mapping circuit 6 by the input receiver signal a and relay apparatus signal b. And (A) of FIG.
Alternatively, on a complex plane including the I and Q axes shown in FIG.
The signal a for the receiver and the signal b for the relay device are respectively lower-order sides,
By being arranged on the higher order side, it is hierarchized.

Here, the non-uniform 16QAM of the constellation shown in FIG. 5A and the non-uniform 16DAPSK of the constellation shown in FIG. Assigns the upper 2 bits (lower order (reception is possible even at low C / N)) and the lower 2 bits (higher order (low C / N)
When N, reception is not possible). As a result, the information directed to the receiver 25 (that is, the signal a for the receiver) is:
Reception is possible even at low C / N.

In FIG. 2, the IFFT circuit 7 is an OFDM circuit.
FIG. 5 (A) or FIG. 5 (A) which has a number of complex signal input units (real number input unit and imaginary number input unit) corresponding to the number of a large number of carriers constituting the signal, and is output from the mapping circuit 6. A signal corresponding to coordinates on a complex plane including the I and Q axes shown in FIG. (C) is input to a corresponding input unit and subjected to a complex inverse Fourier transform to convert an input signal on the frequency axis into time. It is converted to an on-axis complex signal (data symbol sequence). The complex signal is supplied to the quadrature modulator 8 and quadrature-modulated, so that a high-frequency OFDM signal is obtained.

OFDM extracted from hierarchical modulation circuit 3
The signal is amplified and frequency-converted into a transmission frequency band by the transmission high-frequency unit 4 shown in FIG. 1, and then transmitted as radio waves 21 and 22 from the antenna 5 to the relay device 11 and the receiver 25.

In the repeater 11, the radio wave 21 from the transmitter 1 is received by the antenna 12, and
After extracting and amplifying the signal of the required frequency band in step 3, the signal is OFDM-demodulated by the layer demodulation circuit 14 to separate the layered signal. That is, the hierarchical demodulation circuit 14 has the configuration shown in the block diagram of FIG.
8 to obtain a complex signal on the time axis and supply the complex signal to the FFT circuit 19 to perform a complex fast Fourier transform, thereby outputting a received signal on the frequency axis. The digital signal is supplied to the discriminating circuit 20 and sequentially compared with the threshold value to demodulate and output a digital signal corresponding to the I and Q axes.

When demodulating the non-uniform 16 QAM signal in the repeater 11, the non-uniform 16
If the constellation of QAM is a subset of the constellation of 64QAM, the discriminating circuit 20 determines that the constellation is 64QAM, that is, it takes eight values at equal intervals in each of the I and Q axes. It can be determined by the same threshold value as that of the 64QAM signal.

In the repeater 11, only the information of the signal b for the higher-order relay device out of the hierarchically modulated non-uniform 16QAM information is necessary for retransmission, and the information for the lower-order receiver is not necessary. Since the information of the signal a is unnecessary,
Of the results of discriminating the non-uniform 16QAM signal, the quadrant information (upper two bits shown in FIG. 5A) is discarded, and only the information in the quadrant (lower two bits shown in FIG. 5A) is deleted. The output is supplied to the modulation circuit 15 of FIG.

That is, the hierarchical demodulation circuit 14
Only the signal for the relay device assigned to the higher order (reception is impossible at the time of low C / N) by the hierarchical modulation circuit 3 is output. Since the relay device 11 can be installed in a place having a good reception environment such as the roof of a building or the top of a mountain, it is necessary to receive the radio wave 21 from the transmission device 1 with a higher C / N than a general receiver. Can be obtained, so that higher order (low C / N
Even a signal assigned to the (sometimes unreceivable) side can be demodulated sufficiently without error.

The output signal of the hierarchical demodulation circuit 14, that is, the signal c for the relay device is supplied to the modulation circuit 15, where the QPS
After being OFDM-modulated by K, the signal is converted to the same frequency as the radio wave 21 from the transmitting device 1 by the transmitting high-frequency unit 16,
The radio wave 23 is transmitted from the antenna 17 to the receiver 25.

In the receiver 25, the radio wave 22 transmitted from the transmission device 1 and the radio wave 22 transmitted from the relay device 11
3 is received by the antenna 24. Radio wave 22 transmitted from transmitting device 1 is an OFDM signal in which each carrier is modulated by non-uniform 16QAM or non-uniform 16DAPSK including information for the relay device, while radio wave 23 transmitted from relay device 11 is QPSK. Are OFDM signals in which each carrier is modulated, and have different modulation schemes. However, in the receiver 25, the lower order (low C) of the radio waves 22 and 23 is used.
/ N), it is only necessary to receive the signal on the side.
Also, as described above, the non-uniform 1
6QAM signal or non-uniform 16DAP
Since the SK signal can be processed as the same QPSK signal as the radio wave 23, the receiver 25 can simultaneously receive the two radio waves and demodulate the combined signal as a QPSK signal.

As described above, according to this embodiment, it is possible to match the timing of information transmission between the transmitting device 1 and the relay device 11, so that the same guard interval period as in the conventional case is used. The distance between the transmission device 1 and the relay device 11 can be increased, and the service area can be expanded. Further, when the distance between the transmission device 1 and the relay device 11 is the same as that in the related art, it is possible to shorten the guard interval period, which is a redundant period, and thereby increase the amount of information to be transmitted.

Also, since the hierarchically modulated information is transmitted to the relay device 11, the information directed to the relay device 11 can be superimposed on the signal transmitted from the transmission device 1 to the reception device 25. Line is unnecessary.

Next, a description will be given of a second embodiment of the relay apparatus according to the present invention. FIG. 6A shows a block diagram of a second embodiment of the relay device according to the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The relay device 41 according to the second embodiment shown in FIG. 6A is different from the relay device 11 shown in FIG.
Is added to enable use when there are a plurality of relay points.

That is, although the first embodiment shown in FIG. 1 is an example in which each of the transmission point and the relay point is one, a plurality of relay points may be requested. In FIG. 6C, the relay points are denoted by 52 and 53, and the
The positional relationship provided at each location is shown. In this case, the transmission point 51
The delay time required for radio wave propagation between the relay point 52 and the relay point 52 is t8
The delay time required for radio wave propagation between the transmission point 51 and the relay point 53 is t9, the delay times t8 and t9 are not equal, and their distances are not equal.

In such a case, the delay time of the delay circuit 2 shown in FIG. 1 cannot be uniquely determined. Therefore, the relay device 41 of the second embodiment is a relay device that can uniquely determine the delay time of the delay circuit 2 shown in FIG. 1 in such a case. FIG.
In using the relay device 41 shown in (A), the delay time of the delay circuit 2 shown in FIG. 1 is set to the delay time required for radio wave propagation between the relay point and the transmission point. It is adjusted to the delay time of the relay device that maximizes the total delay time including the delay time due to the processing. As a result, a relay device other than the relay device having the longest delay time transmits a signal at a timing earlier than the transmission point.

In the repeater 41 shown in FIG. 6A, a delay circuit 43 is provided at the output of the hierarchical demodulation circuit 14 to prevent the timing shift, and the output demodulation signal of the hierarchical demodulation circuit 14 is delayed. To the modulation circuit 15. The delay time of the delay circuit 43 is equal to the total delay time obtained by adding the delay time required for radio wave propagation between the relay point where the relay device is located and the transmission point, and the delay time due to the signal processing of the relay device. This is set to the difference between the delay times of the delay circuits 2 provided in all the transmission devices. As a result, the timing of the transmission point coincides with the timing of each relay point.

For example, in FIG. 6C, t9> t8
In addition, assuming that time t3 is required for the relay processing at each of the relay points 52 and 53, the delay time of the delay circuit 2 in the transmission device 1 arranged at the transmission point 51 is set to (t9 + t3). Then, the information is transmitted from the relay device at the relay point 53 and the transmission device 1 at the transmission point 51 at substantially the same timing.

Further, in this case, the relay device 4 of the relay point 52
The delay time of the delay circuit 43 in 1 is set to (t9-t8). As a result, the transmission timing of the transmission device 1 disposed at the transmission point 51 and the transmission timing of the relay device 41 disposed at each of the relay points 52 and 53 substantially match. In addition, as the relay device disposed at the relay point 53, any of the relay device shown in FIG. 1 and the relay device 41 shown in FIG. 6A can be used. The delay time of the circuit 43 is set to zero.

Since the delay circuit 43 is a circuit for delaying a digital signal, digital processing is possible. Specifically, a memory can be used, and the delay time can be determined by the difference between the write address and the read address. Therefore, it is possible to easily change the setting of the delay time.

Next, a description will be given of a third embodiment of the relay apparatus according to the present invention. FIG. 6B is a block diagram of a third embodiment of the relay device according to the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The relay device 45 according to the third embodiment shown in FIG. 6B is different from the relay device 11 shown in FIG.
Is added, as in the second embodiment, and can be used when there are a plurality of relay points. However, in the second embodiment, the delay circuit 43 is provided on the output side of the hierarchical demodulation circuit 14. However, in the relay device 45 of the third embodiment, as shown in FIG. Circuit 4
7 is provided on the input side of the hierarchical demodulation circuit 14.

The delay time and the operation of the delay circuit 47 are the same as those of the delay circuit 43 of the second embodiment, and the description is omitted. The delay circuit 47 can be constituted by either analog or digital. In the case of digital processing, similarly to the second embodiment, the delay time can be determined by controlling the address of writing and reading of the memory. In the case of analog processing, since processing in a high frequency band is possible, a delay line using a known SAW (surface acoustic wave) element can be used. In this case, the setting of the delay time is performed. Although the degree of freedom is low, miniaturization is possible.

The relay system using the relay devices 41 and 45 of the second and third embodiments has the same features as the first embodiment and is applicable to a relay system having a plurality of relay points. It has the feature that it is possible.

[0054]

As described above, according to the present invention,
Since each signal can be simultaneously transmitted from the same transmitting unit in the transmitting device to both the receiver and the relay device, a line for the relay device can be eliminated.

According to the present invention, the transmission timing of the signal retransmitted from the relay apparatus to the receiver and the transmission timing of the signal for the receiver transmitted from the transmission apparatus to the receiver are substantially matched, so that these signals are transmitted. Since the transmission device and the relay device always have the same information content, the delay time difference between the radio wave transmitted from the transmission device and the radio wave retransmitted from the relay device in the receiver is 2 minutes compared to the conventional relay system. Therefore, in the case of the same guard interval period as in the conventional relay system, the distance between the transmitting apparatus and the relay apparatus can be increased, and the service area can be expanded.

Further, according to the present invention, when the distance between the transmitting device and the relay device is the same as that of the conventional relay system, the length of the guard interval, which is a redundant period, can be reduced. It can be increased more than before.

Further, according to the present invention, when there are a plurality of relay devices, the transmitting device arranges information to be transmitted at each relay point in each radio wave propagation time from the transmission point to each of the plurality of relay points. The delay time is set in the delay circuit as the maximum time among the times obtained by adding the signal processing times of the plurality of relay devices, and the relay device almost keeps the transmission time of the transmission device and the transmission time of the own device. A delay circuit for matching is provided on an input side or an output side of the hierarchical demodulation circuit, and a signal transmitted from a plurality of relay apparatuses to a receiver and a signal transmitted from a transmission apparatus to a receiver are transmitted. Since the timings are substantially matched, it is possible to construct a system that does not impair the above effects even in a relay system in which a plurality of relay devices exist.

Further, according to the present invention, a relay apparatus which can be installed in a place having a good reception environment such as a building roof receives radio waves from a transmission apparatus with a higher C / N than a general receiver. Because the signal for the receiver can be
The signal for the relay device is hierarchically modulated to a higher order side, so that both the signal for the receiver and the signal for the relay device can be received and demodulated without a sufficient error.

Furthermore, since the present invention is basically SFN, it has better frequency use efficiency than DFN and is suitable for mobile reception.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of an example of a hierarchical modulation circuit in FIG.

FIG. 3 is a block diagram illustrating an example of a hierarchical demodulation circuit in FIG. 1;

FIG. 4 is an explanatory diagram of a positional relationship between a transmission point, a relay point, and a reception point and a time relationship between signals in a relay system.

FIG. 5 is a constellation diagram illustrating the hierarchical modulation circuit in FIG. 1;

FIG. 6 is a block diagram of the second and third embodiments of the relay device of the present invention, and an explanatory diagram of radio wave propagation time between a transmission point and a relay point.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitting apparatus 2 Delay circuit 3 Hierarchical modulation circuit 4 Transmission high frequency part 6 Mapping circuit 7 Inverse fast Fourier transform (IFFT) circuit 8 Quadrature modulator 11, 41, 45 Repeater 13 Reception high frequency part 14 Hierarchical demodulation circuit 15 Modulation circuit 16 Transmission High frequency section 18 Quadrature demodulator 19 Fast Fourier transform (FFT) circuit 20 Discrimination circuit 21 to 23 Radio wave 25 Receiver 31, 51 Transmission point 32, 52, 53 Relay point 33 Receiving point 43, 47 Delay circuit a Receiver signal b , C Relay device signal d1 information d2 guard interval

Claims (8)

[Claims] 1. A transmitting apparatus modulates information to be transmitted by a predetermined modulation method, transmits the information at a predetermined frequency, and a relay apparatus receives and demodulates a radio wave transmitted by the transmitting apparatus, modulates the radio wave again, and performs the transmission. The information to be transmitted is retransmitted using the same frequency as the transmitting device, and in a relay system in which a receiver receives a transmission radio wave from one or both of the transmitting device and the relay device, the transmitting device includes the relay device. A relay device signal for retransmission and a receiver signal for direct transmission to the receiver are superimposed by hierarchization and modulated to a first orthogonal frequency division multiplexed signal for transmission; Is a method of receiving a radio wave transmitted by the transmitting apparatus, separating and demodulating the signal for the relay apparatus, modulating the signal again, and retransmitting the signal as a second orthogonal frequency division multiplexed signal. 2. A delay circuit for delaying information to be transmitted by a time corresponding to a sum of a radio wave propagation time from a transmission point to a relay point and a signal processing time of the relay device, and outputting a signal for a receiver. The information to be transmitted, which is input to the delay circuit, together with the signal for the receiver, is input as a signal for a relay device, and the receiver signal and the signal for the relay device are assigned to different bits, and are hierarchized and orthogonalized. 2. A hierarchical modulation circuit for performing frequency division multiplex modulation, and a transmission unit for converting an output modulated signal of the hierarchical modulation circuit into a predetermined frequency band and transmitting the converted signal.
A transmission device used for the relay system described in the above. 3. When there are a plurality of relay devices, information to be transmitted is transmitted to each of the plurality of relay devices at each relay point during a radio wave propagation time from a transmission point to each of the plurality of relay points. 3. The transmission device according to claim 2, wherein a maximum time among the times obtained by adding the signal processing time is set as the delay time in the delay circuit. 4. The transmission according to claim 2, wherein the hierarchical modulation circuit hierarchizes the signal for the receiver on a lower-order side and the signal for the relay apparatus on a higher-order side. apparatus. 5. The non-uniform 16QAM or non-uniform 16DAPSK layering circuit, wherein each of a plurality of carriers is a non-uniform 16QAM or non-uniform 16DAPSK.
The transmitting apparatus according to claim 2, wherein the transmitting apparatus outputs an orthogonal frequency division multiplexed signal modulated by: 6. A receiving section for receiving a radio wave transmitted by the transmitting apparatus, a hierarchical demodulation circuit for demodulating the signal for the relay apparatus from a signal received by the receiving section, and a demodulating circuit for demodulating the demodulated signal for the relay apparatus. A modulation circuit for outputting an orthogonal frequency division multiplexed signal modulated by the modulation method, and a transmission unit for converting an output signal of the modulation circuit into the same frequency band as the transmission device and transmitting the same. 2. A relay device used in the relay system according to 1. 7. A delay circuit for making the transmission time of the transmission device substantially equal to the transmission time of the transmission device is provided on the input side or the output side of the hierarchical demodulation circuit. 7. The relay device according to 6. 8. The relay device according to claim 5, wherein the modulation circuit generates and outputs orthogonal frequency division multiplexing in which each of the plurality of carrier waves is QPSK-modulated by the signal for the relay device.