JP3022865B1 - Dual frequency network system and its transmitter. - Google Patents

Abstract

The present invention provides a two-frequency network system in which a diversity effect can be easily obtained in an OFDM frequency diversity system, an inexpensive receiver can be manufactured, and a decrease in frequency use efficiency is suppressed. SOLUTION: Transmission stations A, B, C, and D are frequency bands f1,
Each of the SFNs is constituted by f2. Frequency band f1,
Of the information transmitted by f2, information requiring high reception quality is transmitted by both f1 and f2, and the reception point R receives diversity at frequencies f1 and f2. In each transmitting station, the transmission power of f1 and f2 is made different, so that f
1, the correlation value of the received signal of f2 is reduced, and effective diversity reception is enabled. As for f1 and f2, only a part of the information transmitted using those frequency bands is the same, so that it is possible to reduce the reduction in the frequency use efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-frequency network system used for digital broadcasting or digital communication using an OFDM (Orthogonal Frequency Division Multiplexing) system, and more particularly to a method for constructing a network capable of receiving frequency diversity. .

[0002]

2. Description of the Related Art The OFDM system is one of the multi-carrier systems, and since the modulation speed of each carrier is lower than that of a single carrier, a redundant period on a time axis called a guard interval is provided. Thereby, resistance to multipath can be provided. This allows
It is said that the OFDM system has a possibility of constructing a broadcast network with a single frequency.

FIG. 7A shows an example of a single frequency network. In this single frequency network, as shown in FIG. 7A, each transmitting station (station A, station B, station C, station D) performs transmission using the same frequency band f1. However, for example, when the receiving point R is located at the center of each station as shown in FIG. 7A, the period on the frequency axis depends on the delay time difference of the radio wave from each station due to the synthesis of the radio waves from each station. Ripple is generated, and the received power is reduced in a carrier that becomes a dip. As a result, C
Due to the decrease in / N, errors are concentrated, and the overall reception quality is degraded. Although the OFDM system has resistance to multipath, it can only avoid inter-symbol interference and does not have resistance to ripple on the frequency axis.

For this reason, a two-frequency network has been proposed in which a network is constructed using two frequency bands f1 and f2 shown in FIG. 7 (B). However, the dual-frequency network has a disadvantage that the use of two frequency bands basically results in poor frequency utilization efficiency. In particular, it is difficult to secure a frequency during a transition period from the current analog broadcasting to digital broadcasting (a period during which both analog broadcasting and digital broadcasting are performed). In addition, when receiving at a mobile object, there is a disadvantage that the receiving frequency must be changed with the movement.

On the other hand, diversity reception is known as a method for improving reception quality in mobile reception. In particular, since the OFDM system is a multi-carrier system, diversity reception can be performed for each carrier.

Here, in diversity reception,
In order to enhance the effect of diversity, it is necessary that the correlation between a plurality of received signals to be diversity-received is low, and it is considered that frequency diversity and route diversity have a higher effect of diversity than antenna diversity. However, in order to perform such diversity reception, a reception high-frequency unit and an FFT are required for each frequency band, and there is a problem that a reception device becomes expensive.

[0007]

As described above, in a single frequency network, there is a problem that the reception quality is degraded due to interference of radio waves from a plurality of transmitting stations. Further, in the conventional two-frequency network, it is difficult to secure a frequency during a transition period from the current analog broadcasting to the digital broadcasting (a period during which both the analog broadcasting and the digital broadcasting are performed), and two frequency bands are used. Therefore, there is a problem that the frequency use efficiency is poor. In addition, there is a problem that it is necessary to change the reception frequency with the movement. In addition, when performing diversity reception, there is a problem that a reception high-frequency unit and an FFT are required for each frequency band, and the reception device becomes expensive.

Accordingly, the present invention solves the above problems, improves the frequency use efficiency, further eliminates the need to change the reception frequency in mobile reception, and reduces the cost of the receiver by diversity reception. It is an object of the present invention to provide a frequency network system and a transmission device thereof.

[0009]

In order to achieve the above object, the present invention has the following characteristic configuration.

(1) A two-frequency network system used for digital broadcasting or digital communication using an OFDM (Orthogonal Frequency Division Multiplexing) system, wherein the same contents are transmitted using the first frequency band. Using the first group of (2 or more integer) stations and a second frequency band different from the first frequency band, the same contents as the contents transmitted by the first group of transmission stations are transmitted. A second transmission station group of M (an integer of 1 or more and less than N) stations, wherein at least one of the second transmission station groups is any one of the first transmission station groups. The transmission station is installed in the same or near the station as the station, and the second station is located within the transmission area of the first frequency band.
The transmission area is partially formed by the above frequency band.

(2) A two-frequency network system used for digital broadcasting or digital communication using the OFDM system, wherein the same contents are transmitted using the first frequency band N (an integer of 1 or more) M (1 or more) that transmits a part of the same content as the content transmitted by the first transmitting station group using a first transmitting station group of the station and a second frequency band different from the first frequency band. Of the second group of transmission stations, and at least one of the stations of the second group of transmission stations.
Is the same as any station in the first transmitting station group.
Alternatively, the transmission area is installed in a nearby transmission station, and a transmission area of the second frequency band is formed in a transmission area of the first frequency band.

[0012]

( 3 ) A two-frequency network system used for digital broadcasting or digital communication using the OFDM system, wherein the same contents are transmitted using the first frequency band.
Using the first group of (2 or more integer) stations and a second frequency band different from the first frequency band, the same contents as the contents transmitted by the first group of transmission stations are transmitted. M (2
And a second transmission station group of the above (integer) stations, and the transmission stations of the first transmission station group and the second transmission station group are installed in the same or nearby transmission station buildings, respectively. Alternatively, the first transmission station and the second transmission station installed in nearby transmission stations transmit at different powers.

( 4 ) A two-frequency network system used for digital broadcasting or digital communication using the OFDM system, wherein the same contents are transmitted using the first frequency band.
(Integer of 2 or more) Using a first transmitting station group of stations and a second frequency band different from the first frequency band, transmitting partially the same contents as the transmitting contents by the first transmitting station group. Do M
(Integer of 2 or more) and a second group of transmitting stations.
Each of the transmitting stations of the first transmitting station group and the second transmitting station group is installed in the same or nearby transmitting station building, and the first transmitting station and the first transmitting station installed in the same or nearby transmitting station building are respectively provided. 2
And transmitting power with mutually different powers.

( 5 ) In any one of the above (2) and (4) , different transmission contents between the transmission contents of the first transmission station group and the transmission contents of the second transmission station group may be different. It is a voice, and the same transmission content is an image or data.

( 6 ) In any one of the constitutions (2) and (4) , different transmission contents between the transmission contents of the first transmission station group and the transmission contents of the second transmission station group. It is characterized in that at least one of the high-definition information is video information source hierarchical coding and the same transmission content is video information source hierarchical coding basic information.

( 7 ) In any one of the above constitutions (2) and ( 4 ), different transmission contents between the transmission contents of the first transmission station group and the transmission contents of the second transmission station group. At least one is video information, and the same transmission content is the same material as the video information, and the video information has a smaller amount of information than the video information.

( 8 ) In any one of the constitutions (1) to ( 4 ), an adjacent frequency band including a guard band is used as the first and second frequency bands. I do.

( 9 ) A transmitting device used in the dual frequency network system according to any one of (1) to ( 4 ), wherein the first and second transmitting devices are installed in the same or nearby transmitting stations. It is shared as a transmission station, and the transmission signals of the first and second frequency bands are simultaneously amplified by an amplifier circuit of the same system.

That is, the dual-frequency network system according to the present invention can construct a network that can receive a service even in the reception of a single frequency band, and that enables high-quality reception when performing frequency diversity reception. When performing diversity reception in the receiving device,
It is also possible to process signals of a plurality of frequencies as one high-frequency signal.

As means for this, (A) transmission in the second frequency band is added to a single frequency network in the first frequency band to enable frequency diversity reception. (B) Only information requiring high-quality reception is transmitted at a plurality of frequencies to enable frequency diversity reception. (C) Stations and transmission power that enhance the effect of diversity reception. (D) Two frequency bands to be used are set to adjacent frequencies, so that the configuration of the receiving apparatus can be simplified.

In the case (A), it is considered difficult to secure a frequency for constructing a two-frequency network during the transition period from analog broadcasting to digital broadcasting. , And the transmission by the second frequency band is started after the transition is completed, thereby enabling reception by frequency diversity. At this time, a place where the reception quality deteriorates due to interference by a plurality of transmitting stations using the first frequency band is different from a place where the reception quality deteriorates due to interference by a plurality of transmitting stations using the second frequency band. In this way, the correlation between the received signals in each frequency band is reduced, and the effect of diversity reception is enhanced.

In the case of the above (B), information that can be serviced even if the reception quality is not so good such as voice is transmitted in a single frequency band, and high reception quality such as data is obtained. The required information is transmitted in a plurality of frequency bands, and only the latter can be received by frequency diversity. This also makes it possible to suppress a decrease in frequency use efficiency.

In the case of the above (C), station or transmission power is made different in each frequency band,
As a result, reception points where the reception quality in each frequency band deteriorates are set to different places, and the effect of diversity reception is enhanced.

In the case of the above (D), the two frequency bands to be used are adjacent frequency bands including a case where a guard band is interposed, so that signals in the two frequency bands can be converted into one high-frequency signal for frequency conversion or It is possible to perform the FFT processing and to manufacture an inexpensive diversity receiver.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, a first embodiment according to the present invention will be described.

FIG. 1 shows a conceptual configuration of a broadcast network using a dual frequency network system according to the present invention as a first embodiment. In FIG. 1, transmitting stations A, B, C, and D all form the single frequency network by transmitting the same content using the first frequency band f1. this house,
The stations A and C constitute a group of transmitting stations that transmit the same content as the content transmitted in the first frequency band f1 using a second frequency band f2 different from the first frequency band f1. FIG. 1 shows a case of a broadcast network for mobiles, in which transmitting stations A, B,
C and D are arranged, for example, along a highway.

Next, the operation of the broadcasting network having the above configuration will be described.

In FIG. 1, a single frequency network is constructed by transmitting stations A, B, C and D using the frequency band f1. However, in the case of a single frequency network, a plurality of radio waves of the same frequency are received at the same time. Therefore, when the radio waves from the respective stations have opposite phases, they cancel each other out, and the received electric field strength decreases. On the other hand, when the radio waves from the respective stations have the same phase, they are added and the received electric field strength increases.

If there is a time difference between arrivals of radio waves from the respective stations, a canceling frequency and a compensating frequency are generated, so that a ripple occurs in the reception frequency band.
The period of the ripple depends on the delay time difference between the signals from the stations. In the case of digital transmission by OFDM, many errors occur in data transmitted on a carrier of a frequency with a reduced received electric field strength, thereby deteriorating the transmission quality of the entire band.

For example, when receiving two signals,
When the amplitudes of the two signals are equal, the deterioration of the transmission quality is maximized. In FIG. 1, when the transmission powers of the frequency bands f1 are equal to each other, the reception quality is reduced most at the center between the transmitting stations indicated by R. On the other hand, considering the transmitting stations A and C using the frequency band f2, the receiving point R is not at the center of the transmitting stations A and C, so that the drop of the ripple is small. Therefore, the correlation between the frequency band f1 and the frequency band f2 is low,
Good reception quality can be obtained even at the reception point R by the diversity reception.

The two-frequency network described above uses the frequency band f1
Since only a single-frequency network is considered when considering only, the reception quality is lower than that of a two-frequency network, but reception in only the frequency band f1 is possible. Therefore, when the service is started, the service is performed only in the frequency band f1, and the transmission in the frequency band f2 is started when the transmission in the frequency band f2 is economical and the radio wave can be allocated, thereby improving the reception quality. Can also.

In FIG. 1, the frequency bands f1, f2
Is transmitted from different radio towers, it is also possible to transmit from the same radio tower, and the same transmitting device amplifies and transmits signals in frequency bands f1 and f2 simultaneously. It is also possible.

Next, a second embodiment according to the present invention will be described.

FIG. 2 shows, as a second embodiment, a conceptual configuration of a broadcasting network using another dual frequency network system of the present invention. In FIG. 2, transmitting stations A, B, C, D
Are to form a single frequency network by transmitting the same content using the first frequency band f1, but using a second frequency band f2 different from the first frequency band f1. A transmission station group that transmits the same content as the content transmitted in the first frequency band f1 is configured.

Here, in each of the transmitting stations A, B, C and D, the transmission power of the first frequency band f1 and the transmission power of the second frequency band f2 are different from each other. Note that the circumference of the ellipse in FIG. 2 indicates a place where the intensity of radio waves from each transmitting station is equal.

Next, the operation of the broadcasting network having the above configuration will be described.

In FIG. 2, when considering only the frequency band f1, the transmitting stations A, B, C, and D using the frequency band f1 are considered.
Thus, a single frequency network is constructed. Similarly, considering only the frequency band f2, a single frequency network is constructed by the transmitting stations A, B, C, and D using the frequency band f2.

Here, in each of the transmitting stations A, B, C, and D, the transmission power of the frequency band f1 and the transmission power of the frequency band f2 are different from each other. Radio waves from the transmitting station interfere
The point where the reception quality is lowered is different from the point where the reception quality is similarly lowered for the frequency band f2.
Therefore, when diversity reception is performed between the frequency bands f1 and f2, the frequency bands f1 and f2
, A good diversity effect can be expected.

For example, at the receiving point R, the frequency band f1
It is expected that a large ripple will be generated in the received signal of FIG. 5, but the radio wave from the transmitting station B is dominant at the frequency f2, and the difference in the received power from the radio wave from the transmitting station C is large. Will not occur. Therefore,
At the receiving point R, good diversity reception can be performed by receiving a carrier in the frequency band f2 in which the same information as that transmitted in a carrier that causes a large dip in the frequency band f1 is transmitted.

FIG. 2 shows a case where signals in the frequency bands f1 and f2 are transmitted from different radio towers, as in the first embodiment shown in FIG. It is also possible to transmit from a tower, and it is also possible to simultaneously amplify and transmit signals in frequency bands f1 and f2 by the same transmitting device.

Although the case where two frequency bands f1 and f2 are used has been described above, it is apparent that a broadcast network can be similarly constructed using three or more frequencies.

Next, with respect to the second embodiment, an example relating to transmission contents will be described with reference to FIG.

The embodiment shown in FIG. 3 is an example in digital terrestrial television broadcasting. The broadcasting system of digital terrestrial television broadcasting in Japan has a segment structure in which a broadcasting band of about 5.6 MHz is divided into 13 segments, and one central segment of the 13 segments can be partially received to receive only that segment. It is expected to be a method. This central one segment can be used for independent audio broadcasting and data broadcasting.

FIG. 3A shows two broadcast channels 1 and 2 of 13-segment approximately 5.6 MHz frequency bands f1 and f2, and one segment at the center of each of which is capable of partial reception. 3 and 4 are shown. FIG.
(B) is a segment capable of partial reception, which is obtained by frequency-converting one segment 3 or 4 at the center of two broadcast channels f1 and f2, which can be partially received, with different local oscillation frequencies and rearranging them on the frequency axis. Is shown.

In FIG. 3B, voice and data are assigned to each segment. That is, the segment 3 is composed of a part 5 to which audio is allocated and a part 7 to which data is allocated, and the segment 4 is composed of a part 6 to which audio is allocated and a part 8 to which data is allocated. At this time, for the audio, the segments are audio 1 and audio 2, which are different programs, and the data are the same.
As a result, frequency diversity reception becomes possible for the portion where data is transmitted.

This figure is an image diagram. Since frequency interleaving is actually performed, parts 5 and 6 where sound is transmitted on the frequency axis and parts 7 and 8 where data are transmitted on the frequency axis as shown in the figure. Although voice and data are not clearly separated as shown in the figure, since voice and data are transmitted by different carrier groups, diversity reception becomes possible.

In the embodiment shown in FIG. 3, the segments 3 and 4 are frequency-converted by different local oscillation frequencies.
Since the signals are rearranged on the frequency axis, the OFDM demodulation of the information of the segments 3 and 4 can be collectively processed by one FFT circuit, and the diversity is converted to the information of each carrier by the FFT processing. The receiving process is performed. Details of the configuration of diversity reception will be described later.

In the above, the case where independent audio broadcasting and data broadcasting are performed has been described.
The video is transmitted in two segments, and the video is converted into a quasi-moving image or a still image, or the resolution is reduced to reduce the amount of information and transmitted in one central segment. By transmitting the same data for the center segment of the group of segments of the other broadcast channels, frequency diversity reception is enabled for the center segment and hierarchical transmission can be performed. . Hierarchical transmission here means that a normal image is received when the reception condition is good, and a quasi-moving image or a still image is received when the reception condition is bad.

Similarly, when performing information source hierarchical coding, high-definition information is transmitted in 12 segments excluding the central one segment, and the central one of a plurality of segment groups is transmitted.
Broadcasting basic information using segments can also enable frequency diversity reception of basic information. In this case, similarly to the above example, a high-definition image is received when the reception condition is good, and an image based on only the basic information is received when the reception condition is bad.

Next, another embodiment relating to the transmission contents of the second embodiment will be described with reference to FIG.

The embodiment shown in FIG. 4 is an example in digital terrestrial audio broadcasting. The broadcasting system of digital terrestrial audio broadcasting in Japan is based on a segment having a frequency bandwidth of about 429 kHz, and is expected to be a system capable of broadcasting only one segment or a segment group of three segments. In the case of a three-segment structure, as in the case of the television, it is expected that the central one segment will be a system capable of partial reception of receiving only that segment.

FIG. 4A shows an example in which the segments 9, 10 of about 429 kHz in the frequency bands f1 and f2 are arranged adjacent to each other, as shown in FIG. 4B. Voice and data are assigned to each segment. That is, the segment 9 is composed of a part 11 to which audio is allocated and a part 13 to which data is allocated, and the segment 10 is composed of a part 12 to which audio is allocated and a part 14 to which data is allocated. At this time, for the audio, the segments are audio 1 and audio 2, which are different programs, and the data are the same. As a result, frequency diversity reception becomes possible for a portion where data is transmitted.

As in the previous embodiment, this diagram is an image diagram. Since frequency interleaving is actually performed, portions 11 and 12 where sound is transmitted on the frequency axis as shown in FIG. The portions 13 and 14 through which data is transmitted are not clearly separated.

Also, in the embodiment shown above, 2
One segment can collectively process OFDM demodulation by one FFT circuit. The configuration of a receiving apparatus that performs OFDM demodulation collectively will be described below.

FIG. 5 shows an example of the configuration of various diversity receivers.

FIG. 5A shows an example of the configuration of antenna diversity by RF combining. After the high-frequency signals received by the two antennas 20 and 21 are amplified and frequency-converted by the reception high-frequency units 22 and 23, respectively. , An adder / synthesizer 24, an OFDM demodulation by an FFT 25, a demodulation for each carrier by a demodulator 27, and an error correction process by an error correction circuit 28.

FIG. 5B shows an example of a configuration of antenna diversity by combining after FFT. High-frequency signals received by two antennas 20 and 21 are amplified and frequency-converted by respective high-frequency receiving units 22 and 23. After the OFDM demodulation by the FFTs 25 and 26, addition or selective synthesis is performed by the synthesizer 29, demodulation for each carrier by the demodulator 27, and error correction processing by the error correction circuit 28 are performed.

FIG. 5C shows an example of the configuration of a diversity receiver which collectively processes signals transmitted by frequency diversity by one system of FFT, and shows a high frequency signal transmitted by frequency diversity received by antenna 20. After the signals are collectively amplified and frequency-converted by the reception high-frequency unit 22, the signals are collectively OFF by the FFT
The DM is demodulated, added or selected by the combiner 29, demodulated for each carrier by the demodulator 27, and error-corrected by the error correction circuit 28.

As can be seen by comparing the above configurations (A), (B) and (C), in the case of frequency diversity, the reception high frequency section and the FFT can be integrated into one system, and the circuit configuration is Because of simplicity, the receiving device can be provided at low cost.

Next, a third embodiment of the present invention will be described in detail with reference to FIG.

The embodiment shown in FIG. 6 is a transmitting apparatus used in the dual-frequency network system, in which transmitting signals of two frequency bands are simultaneously amplified by the same system of amplifying circuit. The form is shown. Referring to FIG. 6, according to a third embodiment of the present invention, program 1 and program 2 transmitted at two frequencies are transmitted through error correction circuits 31, 32.
Are input to mapping circuits 33 and 34, and their outputs are input to an input terminal 3 of an IFFT (inverse Fourier transform circuit) 37.
5 and 36, and are collectively converted to signals on the time axis in the IFFT 37. Its output is a quadrature modulation circuit 3
At 8, the signal is orthogonally modulated and becomes an OFDM signal. This signal is converted to a required frequency by the frequency conversion circuit 39, power-amplified by the amplification circuit 40, and transmitted from the antenna 41.

Next, the processing contents of the transmitting apparatus having the above configuration will be described. The program 1 and the program 2 in FIG. 6 each include audio and data. The voice has different contents of voice 1 and voice 2, and data has the same content. This enables diversity reception of data. These programs 1 and 2 are added with redundancy for error correction in error correction circuits 31 and 32 and input to mapping circuits 33 and 34, respectively.

In the mapping circuits 33 and 34, for example, Q
By performing mapping according to the PSK constellation, modulation of each carrier forming the OFDM signal is performed. The output of the mapping circuits 33 and 34 is OFD
The power of each signal of the carriers forming the M signal and transmitted from the antenna 41 which is the final output can be controlled by the amplitude of the output of the mapping circuits 33 and 34. Therefore, when the transmission power of the program 1 and the transmission power of the program 2 are set to different powers, the mapping circuits 33 and 34 can multiply the amplitude of the output by a constant multiplier. Further, it can also be performed by mapping to a position multiplied by a constant power in advance.

The input terminals 35 and 36 of the IFFT 37
Since the signal corresponding to the carrier of each frequency is supplied,
By arranging and inputting the outputs of the mapping circuits 33 and 34 to the input of the IFFT 37, the program 1 and the program 2 can be frequency division multiplexed. The output of the IFFT 37 is the frequency band in which the program 1 is transmitted and the program 2 are transmitted. And the frequency band to be added is a signal on the time axis. The output of the IFFT 37 is quadrature-modulated by a quadrature modulation circuit 38, and OFD 37
After being converted into an M signal, the signal is converted into a transmission frequency by a frequency conversion circuit 39, power-amplified by an amplifier circuit 40, and then transmitted from an antenna 41.

In the case where the same content is transmitted in two frequency bands, if the output of the mapping circuit 33 is input in parallel to the input terminals 35 and 36 of the IFFT 37 in FIG. It becomes possible to transmit programs of the same content. Also, it is clear that a transmitter that amplifies signals in three or more frequency bands simultaneously can be realized.

[0068]

A first effect of the present invention is to realize a two-frequency network that effectively performs diversity.

A second effect of the present invention is that a two-frequency network capable of effectively utilizing a frequency while securing necessary reception quality is realized by performing frequency diversity only for a portion requiring high-quality reception. Is to do.

A third effect of the present invention is to realize a two-frequency network in which a high-frequency circuit and an FFT circuit necessary for receiving an OFDM signal by frequency diversity can be constituted by one high-frequency circuit and one FFT circuit, respectively. is there.

The fourth effect of the present invention is that, in the transmitting apparatus used in the above-mentioned dual frequency network system, the transmitting signals of the first and second frequency bands are simultaneously amplified by the same system of amplifying circuit. Thus, the first and second transmission stations installed in the same or nearby transmission station buildings can be shared.

As described above, according to the present invention, a two-frequency network which improves the frequency use efficiency, further eliminates the need to change the reception frequency in mobile reception, and reduces the cost of the reception apparatus by diversity reception. A method and a transmission device thereof can be provided.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a broadcast network according to a first embodiment of a dual frequency network system according to the present invention.

FIG. 2 is a conceptual diagram showing a configuration of a broadcast network according to a second embodiment of the dual-frequency network system according to the present invention.

FIG. 3 is a diagram showing an example of transmission contents according to the second embodiment.

FIG. 4 is a diagram showing another example regarding the transmission contents of the second embodiment.

FIG. 5 is a block diagram showing a plurality of configuration examples of a diversity receiver that can be used in the dual frequency network system according to the present invention.

FIG. 6 is a block diagram showing a configuration example of a transmitting device used in the dual frequency network system as a third embodiment according to the present invention.

FIG. 7 illustrates a single frequency network and a conventional dual frequency network.

[Explanation of symbols]

 1, 2, broadcast channel 3, 4, segment 5, 6, voice allocation portion 7, 8, data allocation portion 9, 10, segment 11, 12, voice allocation portion 13, 14, data allocation portion 20, 21, antenna 22 .., 23... A receiving high-frequency unit 24... A synthesizer 25, 26,... An FFT 27, a demodulator 28, an error correction circuit 29, a synthesizer 30, an FFT 31, 32, an error correction circuit 33, 34. Input terminal 37 IFFT 38 Quadrature modulation circuit 39 Frequency conversion circuit 40 Amplification circuit 41 Antenna

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tohru Hoshina 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) Reference “Digital Terrestrial Broadcasting by OFDM-Dual Frequency Broadcasting Wave Relay (DFN) -", Proceedings of the 1995 IEICE General Conference, Communication 2, p363" A Study of Digital Terrestrial Broadcasting Networks for Mobile Devices ", Technical Report of the Institute of Image Information and Television Engineers, vol. 23, No. 7, pp. 35-40, “Study of Broadcasting Network for Mobile Using Hierarchical Multiplexing Modulation”, Technical Report of the Institute of Image Information and Television Engineers, vol. 22, No. 64, p. 65-72 (58) Fields surveyed (Int. Cl. ⁷ , DB name) H04J 11/00

Claims (9)

(57) [Claims] 1. A two-frequency network system used for digital broadcasting or digital communication using an OFDM (Orthogonal Frequency Division Multiplexing) system, wherein N (the same content is transmitted using a first frequency band). M) that transmits the same content as the content transmitted by the first transmitting station group using a first transmitting station group of (2 or more integer) stations and a second frequency band different from the first frequency band.
(An integer greater than or equal to 1 and less than N) stations, and at least one of the second transmission station groups is any of the first transmission station groups. A two-frequency network system, which is installed in a transmission station building that is the same as or close to the transmission station, and in which a transmission area based on the second frequency band is partially formed in a transmission area based on the first frequency band. 2. A two-frequency network system used for digital broadcasting or digital communication using the OFDM system, wherein N (an integer of 1 or more) stations transmitting the same contents to each other using a first frequency band. And M (1 or more) that partially transmits the same content as the transmission content by the first transmission station group using a first transmission station group and a second frequency band different from the first frequency band. Integer) stations and a second group of stations, wherein at least one of the stations in the second group of stations is
Same as or near any station in the first transmitting station group
Of being placed in the transmitting station building, the first two-frequency network system, wherein a transmission area according to the second frequency band to the transmission area according to the frequency band is formed. 3. A two-frequency network system used for digital broadcasting or digital communication using the OFDM system, wherein the same content is transmitted using a first frequency band.
Using the first transmission station group of the above (integer) stations and a second frequency band different from the first frequency band, transmission of the same content as that transmitted by the first transmission station group is performed by M ( A second transmission station group of 2 or more integer) stations, wherein the transmission stations of the first transmission station group and the second transmission station group are respectively installed in the same or nearby transmission station buildings, A two-frequency network system in which a first transmitting station and a second transmitting station installed in the same or nearby transmitting stations transmit at different powers. 4. A two-frequency network system used for digital broadcasting or digital communication using the OFDM system, wherein N (2) which transmits the same contents using a first frequency band.
Using the first transmission station group of the above (integer) stations and a second frequency band different from the first frequency band, the transmission contents partially the same as the transmission contents of the first transmission station group are transmitted. M (2
The above-mentioned integer) stations, and the second transmission station group of the first transmission station group, and the transmission stations of the first transmission station group and the second transmission station group are respectively installed in the same or nearby transmission station buildings, Alternatively, a two-frequency network system in which a first transmitting station and a second transmitting station installed in nearby transmitting stations transmit at different powers. 5. A different transmission content between the transmission content of the first transmission station group and the transmission content of the second transmission station group is voice, and the same transmission content is an image or data. dual frequency network system according to claim 2, 4, characterized in. 6. The high-definition information obtained by transmitting at least one of different transmission contents between the transmission contents of the first transmission station group and the transmission contents of the second transmission station group by information source hierarchical coding of video. , and the claim 2, 4 dual frequency network system according to any one of the same transmission content is characterized in that it is a Basic information by the information source hierarchical encoding of the video. 7. At least one of the different transmission contents between the transmission contents of the first transmission station group and the transmission contents of the second transmission station group is video information, and the same transmission contents are the same. claim 2, 4 dual frequency network system according to any one of, wherein the amount of information than is and the image information of the same material as the video information is less video information. Wherein said first, as the second frequency band, dual frequency network system according to any one of claims 1 to 4, characterized by using the adjacent frequency band including when sandwiching the guard band. 9. A transmission apparatus for use in a two-frequency network system according to any one of claims 1 to 4, first, as the second transmission station installed in the transmitting station building of the same or adjacent A transmission apparatus which is shared and simultaneously amplifies transmission signals of the first and second frequency bands by an amplifier circuit of the same system.