JP2002247005A - Digital transmitter/receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set up a guard interval length corresponding to the delay quantity of a multi-pass. SOLUTION: A receiver 2 is provided with a status data generator 208 for generating status system data and a status system data transmission means for transmitting the status system data in the reverse direction against main line system data and a transmitter 1 is provided with a status system data demodulation means for demodulating the status system data and a status data extractor 109 for extracting the status system data to select one of a plurality of guard interval length on the basis of the status system data. The status system data transmission means is constituted of a power amplifier 209, filters 212, 213 and 210, a frequency converter 211, an orthogonal modulator 214, an OFDM modulation circuit 215, and a transmission line encoder 216 and the status system data demodulation means is constituted of a transmission line decoder 110, an OFDM demodulation circuit 111, an orthogonal demodulator 112, filters 113, 114 and 116, and a frequency converter 115.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM (Orthogonal) used for digital broadcasting, for example.
Frequency Division Multip
The present invention relates to a transmission / reception apparatus that employs a lexing (orthogonal frequency division multiplexing) method, and particularly to selection of a guard interval length used for an OFDM method.

[0002]

2. Description of the Related Art Generally, in the OFDM system, the existence of a guard interval is cited as one factor of the multipath resistance, and the longer the guard interval length, the more resistant to a ghost with a large delay. However, there is a trade-off between the guard interval length and the information bit rate, and the longer the guard interval length, the lower the information bit rate.

When the condition of the transmission path changes every moment as in the case of mobile transmission, it is important for the operation side to improve the multipath resistance, but a decrease in the information bit rate causes a decrease in video quality. This is also an important factor, and the selection of various circuit parameters must be carefully performed, and it is necessary to conduct sufficient tests accordingly.

[0004]

As described above, in the conventional OFDM transmission system, the relationship between the guard interval length and the information bit rate is not taken into account, and the multipath resistance is reduced and the information throughput is reduced. Or declined.

[0005] The present invention solves the above-mentioned problems and provides OFDM.
It is an object of the present invention to provide a digital transmission / reception device that sets a guard interval length so as to improve signal transmission efficiency.

[0006]

In order to achieve the above object, the present invention according to a first aspect of the present invention relates to a transmitting apparatus including main line data transmitting means for transmitting main line data such as digital broadcasting and the like. A digital transmission / reception device including a reception device including main line data demodulation means for demodulating main line data, wherein the reception device generates status system data from the main data and transmission system status data. A status data transmission means for transmitting the status data in a direction opposite to the main data, wherein the transmission device demodulates the status data, and a status data demodulation means for demodulating the status data. Status data extraction means for extracting, the main data transmission means and the main data demodulation means, And selects a plurality of guard interval length based on status system data.

[0007] The invention according to claim 2 of the present invention provides:
2. The status data according to claim 1, wherein the status data is data obtained by coding a multipath delay amount generated in a transmission path and a data error detection signal obtained from a transmission path decoder provided in the main line data demodulation means. There is a feature.

Further, according to a third aspect of the present invention, when the delay amount calculated from the status data according to the first aspect is larger than the length of the guard interval length, the main data transmission is performed. O prepared for the means
The circuit parameters of the OFDM demodulation circuit provided in the FDM modulation circuit and the main line data demodulation means are updated so that the guard interval length is further increased.

Further, according to a fourth aspect of the present invention, in the first aspect, the status-related data transmission means includes a power amplifier, a filter, a frequency converter, a quadrature modulator, an OFDM modulation circuit, and a transmission line code. And a status-system data demodulation means including a transmission line decoder, an OFDM demodulation circuit, a quadrature demodulator, and a filter frequency converter.

Further, in the invention according to claim 5 of the present invention, the plurality of guard interval lengths according to claim 1 are represented by a first guard interval length represented by logic 0 and a logic 1. It is the second guard interval length.

Further, in the invention according to claim 6 of the present invention, the status-related data extracting means according to claim 1 is characterized in that the guard interval length set as a default value when the power of the transmitting device is turned on. And outputting the guard interval length information set as a default value when the power of the receiving device is turned on.

Further, in the invention according to claim 7 of the present invention, the status-related data generating means according to claim 1 determines the time difference between a direct wave and a delayed wave generated when a multipath exists on a transmission line. It is characterized by having a counter for calculating.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Next, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a transmitting apparatus 1 of a digital transmitting / receiving apparatus according to the present invention, FIG. 2 is a block diagram of a receiving apparatus of the digital transmitting / receiving apparatus of the present invention, and FIG. It is a conceptual diagram of a data signal.

Referring to FIG. 1, the transmission apparatus 1 includes a main line data transmission unit, a status data demodulation unit, and a status data extractor 109. From the transmission path encoder 101 to the power amplifier 108 (transmission path encoder 1)
01, the OFDM modulation circuit 102, the quadrature modulator 103, the filters 104 and 105, the frequency converter 106, the filter 107, and the power amplifier 108) are main data transmission means for digital broadcasting or the like. In FIG. 1, the filter 10
4 and 105 are separated, but need not be separated. Also, the filter 116
(The transmission path decoder 110, the OFDM demodulation circuit 111, the quadrature demodulator 112, the filters 113 and 114, the frequency converter 115, and the filter 116) are status data demodulation means transmitted from the receiving device 2. In FIG.
Although the filters 113 and 114 are separated, they need not be separated.

The input digital data is subjected to energy spreading, outer error correction coding, and outer interleaving processing in a transmission path encoder 101, and is output to an OFDM modulation circuit 102. In the OFDM modulation circuit 102, inner error correction,
OFDM framing, inner interleaving, IFFT
A series of basic processing of OFDM modulation, such as conversion and addition of a guard interval, is performed.
The signal is down-converted to one IF signal. The signal modulated in the IF band is subjected to band limitation and unnecessary wave removal by a filter 104 and input to a filter 105. Filter 105
Is provided to separate the IF signal of the status data. After passing through the filter 105, it is up-converted to the designated RF frequency F1 by the frequency converter 106, and R
The signal becomes an F signal, and after unnecessary wave removal by the filter 107 and amplification by the power amplifier 108, the signal is output via the antenna system.

Referring to FIG. 2, the receiving apparatus 2 includes a main line data demodulation unit, a status data transmission unit, and a status data generator 208. From the filter 201 to the transmission path decoder 207 (filter 201, frequency converter 202, filters 203 and 204, quadrature demodulator 205, OFDM demodulation circuit 206, transmission path decoder 20
Up to 7) are main line data demodulation means. In FIG. 2, the filters 203 and 204 are separated, but need not be separated. Further, the power amplifier 209 transmits the signal to the transmission path encoder 216 (the power amplifier 209, the filter 210, the frequency converter 211, the filters 212 and 213, the quadrature modulator 214, the OFDM modulation circuit 215, the transmission path encoder 2).
Up to 16) are the stator data transmission means. In FIG. 2, the filters 212 and 213 are separated, but need not be separated.

The demodulation of the main line data will be described with reference to the receiver 2 shown in FIG. Received RF frequency F1
Of the RF signal is obtained only in the desired frequency component by the filter 201, and is down-converted by the frequency converter 202 into an IF signal of the center frequency f1. The filter 203 is for removing unnecessary frequency components. Filter 204
Are also provided for the same purpose. Filters 203 and 204
The IF signal after passing through is converted by a quadrature demodulator 205 into a baseband digital signal,
Is input to First, the OFDM demodulation circuit 206
The synchronization of the DM frame is detected, and the OFD shown in FIG.
The processing opposite to that of the M modulation circuit 102 is performed. The demodulated digital data is processed by the transmission path decoder 207 in the order of outer interleaving, outer error correction decoding, and inverse energy spreading.

Next, transmission of status data will be described with reference to FIG. A status data generator 208 (which generates status-related data obtained by encoding the multipath delay amount information generated in the transmission path and the data error detection signal obtained from the transmission path decoder 207, which can be output from the OFDM demodulation circuit 206. The output data of the status-system data generation means) is output to the main-line OFDM demodulation circuit 20.
6 to control various circuit parameters related to the guard interval length.

On the other hand, the status data is subjected to energy spreading, outer error correction coding, and outer interleaving processing in a transmission path encoder 216 to perform an OFDM modulation circuit 215.
Output to Thereafter, the OFDM modulation circuit 215, the quadrature modulator 214, the filters 213 and 212, the frequency converter 21
1, a filter 210, a power amplifier 209, a filter 116, a frequency converter 115, and a filter 11 shown in FIG.
4, 113, quadrature demodulator 112, OFDM demodulation circuit 11
The configurations up to 1 are the same as those of the main line data except for the RF center frequency F2 and the IF center frequency f2, and therefore, will not be described.

The status data transmission line decoder 110 shown in FIG. 1 can restore the status data transmitted from the receiving device 2,
(Status data extraction means) extracts the coded status data, and controls various circuit parameters related to the guard interval length of the main line OFDM modulation circuit 102 by the status data.

Next, the operation of the embodiment of the present invention will be described with reference to the drawings. 1 and 2 will be described mainly with respect to the status data extractor 109 in FIG. 1 and the status data generator 208 in FIG. The other configuration is a function used in a general OFDM digital transmitting / receiving apparatus.

First, it is assumed that when the power of the transmitting apparatus 1 is turned on, data of logic 0 corresponding to, for example, a guard interval length A (see FIG. 3) is output from the status data extractor 109 shown in FIG. OFDM modulation circuit 102
Receives this information (data of logic 0) and operates with various circuit parameters according to the guard interval length A. As will be described later, a data error detection signal is transmitted from the status data generator 208 of the receiver 2 shown in FIG. 2 in addition to the data having the guard interval length information. As a result, the status data extractor 109 receives these two pieces of information. However, when the power of the transmitting apparatus 1 is turned on,
The status data extractor 109 ignores (masks) both the guard interval length information and the data error detection signal and outputs the guard interval length information of logic 0 set as a default value. Thereafter, after a lapse of a predetermined time, the mask is released, and monitoring of guard interval length information is started.

When the logic 1 corresponding to the guard interval length B (see FIG. 3) is extracted, the status data extractor 109 operates the OFDM modulation circuit 102 with various circuit parameters corresponding to the guard interval length B. Give instructions. Note that the transmission line decoder 110 always outputs a data error detection signal of the status data line to the status data extractor 109, and when a data error is detected, the guard interval length information to the OFDM modulation circuit 102 is not changed. It works.

On the other hand, the receiver 2 also outputs data of logic 0 corresponding to the guard interval length A from the status data generator 208 at the time of default (such as when power is turned on), and the OFDM demodulation circuit 206 outputs the guard interval length. It operates with various circuit parameters according to A. At the same time, this information is given to the transmission path encoder 216, and finally demodulated by the receiving apparatus 2. Hereinafter, the transmitting device 1
Similarly to the above, it is assumed that the information (guard interval length information) input from the OFDM demodulation circuit 206 after a certain time has elapsed is valid, and the operation for monitoring this information (guard interval length information) is started.

As described above, when the power of both the transmitting apparatus 1 and the receiving apparatus 2 is turned on, the circuit operates according to the guard interval length A. Since the line for transmitting the status data is an important line that governs the control of various circuit parameters of the transmission device 1, the error correction method includes, for example, convolution, a coding rate of 1/2, and a guard interval length. It is important to select various circuit parameters that are sufficiently resistant to fluctuations in the transmission path.

The status data generator 208 shown in FIG.
The operation of is described in detail. The main line OFDM demodulation circuit 206 includes a frame synchronization circuit and a frame counter for synchronizing a normal OFDM frame. As an example, there is known a method of correlating with a synchronization symbol inserted in advance on the transmission side. Have been. In this method, when a multipath exists on the transmission path, it is possible to detect the correlation peak corresponding to each of the direct wave and the delayed wave.
The peak detection signal and the frame pulse are output from the FDM demodulation circuit 206 and input to the status data generator 208.

Further, the status data generator 208
The data error detection signal output from the transmission path decoder 207 is also input. The status data generator 208 includes a counter for calculating the time difference between the direct wave and the delayed wave, and the counter is reset by a frame pulse. The counting of the counter is started with the occurrence of the peak corresponding to the direct wave as a trigger, and stopped when the peak corresponding to the delayed wave occurs. The amount of delay actually occurring in the transmission path can be calculated from the count value during this time. Thereafter, a counter reset is performed by a frame pulse, and the same operation is repeated.

When the calculated delay amount is larger than the set guard interval length A, the logic 1 corresponding to the guard interval length B (A <B) is output, and the OFDM modulation circuit 102 shown in FIG. OF shown in FIG.
The setting of various circuit parameters of the DM demodulation circuit 206 is updated. Here, in the OFDM system, there is a background that if a delayed wave within the guard interval length is present, there is almost no influence on a data error. That is, in the OFDM system, a transmission symbol to which a replica of a transmission signal called a guard interval is added is created, and for a multipath shorter than the guard interval length, the influence of the multipath can be removed.

(Second Embodiment) A second embodiment of the present invention will be described. In the first embodiment, two guard interval lengths A and B are described. However, even in the case of two or more guard intervals, the number of guard interval length information bits can be easily increased.

In addition to the automatic selection of the guard interval length, if a data error detection signal is employed in place of the guard interval length information as information of the criterion in the status data generator 208, the coding rate of error correction (for example, , Coding rate 1/2, coding rate 1/3, coding rate 5
/ 8, etc.).

[0031]

An effect of the present invention is to provide a digital transmission / reception apparatus capable of monitoring the occurrence of multipath on a transmission line and automatically selecting various circuit parameters relating to an optimum guard interval length at all times. Usually, in the case of a mobile transmission such as a marathon, the operator repeats the test many times to investigate the state of occurrence of the delay wave and try to eliminate the line disconnection due to the multipath, but this also leads to a reduction in labor.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmission device of a digital transmission / reception device of the present invention.

FIG. 2 is a block diagram of a receiving device of the digital transmitting / receiving device of the present invention.

FIG. 3 is a conceptual diagram of a main line data signal to which a guard interval is added in the digital transmitting / receiving apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transmitting apparatus 101 Transmission path encoder 102 OFDM modulation circuit 103 Quadrature modulator 104, 105, 107, 113, 114, 116
Filters 106, 115 Frequency converter 108 Power amplifier 109 Status data extractor 110 Transmission line decoder 111 OFDM demodulation circuit 112 Quadrature demodulator 2 Receiver 201, 203, 204, 210, 212, 213
Filter 202, 211 Frequency converter 205 Quadrature demodulator 206 OFDM demodulation circuit 207 Transmission line decoder 208 Status data generator 209 Power amplifier 214 Quadrature modulator 215 OFDM modulation circuit 216 Transmission line encoder

Claims (7)

[Claims] 1. A digital transmitting / receiving apparatus comprising: a transmitting device including main line data transmitting means for transmitting main line data such as digital broadcasting; and a receiving device including main line data demodulating means for demodulating the main line data. A receiving system, the status data generating means for generating status data of a transmission path from the main data, and a status data transmitting means for transmitting the status data in a direction opposite to the main data. Wherein the transmitting device comprises: status data demodulating means for demodulating the status data; and status data extracting means for extracting the status data. The main data transmitting means and the main data demodulating means. Select a plurality of guard interval lengths based on the status data. Digital transceiver. 2. The status data is coded data of a multipath delay amount generated in a transmission path and a data error detection signal obtained from a transmission path decoder provided in the main line data demodulation means. The digital transmitting / receiving apparatus according to claim 1, wherein: 3. When the delay amount calculated from the status data is larger than the length of the guard interval length, the OFDM modulation circuit provided in the main data transmission means and the main data demodulation means provided in the main data transmission means. OFDM
2. The digital transmitting / receiving apparatus according to claim 1, wherein the setting of the circuit parameter of the demodulation circuit is updated so that the length of the guard interval length is further increased. 4. The status-related data transmission means includes a power amplifier, a filter, a frequency converter, a quadrature modulator, and an OF.
A DM modulator and a transmission path encoder, wherein the status-related data demodulation means includes a transmission path decoder and an OF.
2. The digital transmitting / receiving apparatus according to claim 1, further comprising a DM demodulation circuit, a quadrature demodulator, and a filter frequency converter. 5. The method according to claim 1, wherein the plurality of guard interval lengths are a first guard interval length indicated by logic 0,
2. The digital transmitting / receiving apparatus according to claim 1, wherein the length is a second guard interval length displayed by logic 1. 6. The status-related data extracting means outputs guard interval length information set as a default value when the transmitting device is powered on,
2. The digital transmission / reception apparatus according to claim 1, wherein the status data generation unit outputs the guard interval length information set as a default value when the power of the reception apparatus is turned on. 7. The status data generator according to claim 1, further comprising a counter for calculating a time difference between a direct wave and a delayed wave generated when a multipath exists on a transmission path. A digital transmitting / receiving device according to claim 1.