JP2005006035A - Fpu device and operation control method for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an FPU device capable of conducting an orderwire function while leaving the compression encoding of a video bit stream behind. <P>SOLUTION: In the FPU device for performing OFDM modulation of an MPEG2-TS (transport stream) signal obtained by encoding and multiplexing a video signal and a sound signal as an OFDM frame construction and transmitting it as a high frequency signal, voice phone signals from an orderwire line are encoded, assigned to parts other than those which encoding data of the video signal and the sound signal of a data symbol of the OFDM frame construction are assigned to, and transmitted. In the FPU device of a transmission destination, by extracting an orderwire encoding signal from the OFDM frame construction and decoding it, it becomes possible to conduct the orderwire function to realize the voice phone among the FPUs without lowering the bit rate of the video data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an FPU (Field Pick-Up Unit) apparatus, and more particularly to an 800 MHz digital FPU apparatus that uses voice call signals from an order wire line for mobile relay communication.
[0002]
[Prior art]
In a conventional 800 MHz digital FPU device (hereinafter referred to as a digital FPU device), when a voice call via an order wire line is required between a transmitter and a receiver, the systems on the transmission side and the reception side are shown in FIGS. 10 is configured.
[0003]
FIG. 9 is a block diagram on the transmission side, and FIG. 10 is a block diagram on the reception side. Referring to FIG. 9, in the encoder 1, the video signal is encoded by the video encoding unit 11, and in addition to the 2-channel audio signal (including L / R), the 1-channel audio call signal is further encoded by audio encoding. Encoded by the unit 12. Further, the data is encoded by the data encoding unit 13. The video bit stream, the audio bit stream, and the data bit stream by each of the encoding units 11 to 13 are multiplexed by the multiplexing unit 14, and MPEG2-TS (transport stream) is generated and supplied to the transmitter 2.
[0004]
The MPEG2-TS input to the transmitter 2 is converted into an IF (intermediate frequency) signal (intermediate frequency division multiplex) (IF) signal 213 in the transmission control unit 21 via a transmission path encoder 211, a framing circuit 212, and an OFDM (Orthogonal Frequency Division Multiplex) modulator 213. 130 MHz) and supplied to the frequency conversion / power amplifier 22 constituting the transmission high-frequency unit. In this transmission high-frequency unit, the IF signal (130 MHz) is frequency-converted into a high-frequency signal in the 800 MHz band, amplified, and transmitted via the transmission antenna 3.
[0005]
Next, referring to FIG. 10, the high frequency signal from the transmission side received by the reception antenna 4 is supplied to the receiver 5. In the frequency converter 51 constituting the reception high-frequency unit, the 800 MHz band high-frequency signal received by the reception antenna 4 is frequency-converted to an IF signal (130 MHz) and supplied to the reception control unit 52.
[0006]
In this reception control unit 52, an IF signal (130 MHz) is input, demodulated via an OFDM demodulator 521, a deframing circuit 522, and a transmission path decoder 523, and supplied to the decoder 6 as MPEG2-TS. In this decoder 6, the video signal, audio signal, data signal, and voice call signal from the order wire line are separated by the separation unit 6, respectively, and the video decoding unit 62, the audio decoding unit 63, and the data decoding unit are separated. Each of the parts 64 is decoded. Note that the voice call signal is output to the order wire line, thereby enabling a call on the order wire.
[0007]
Patent Document 1 discloses a technique for performing channel switching of an FPU device without using a special voice call channel. In this technique, the channel designation information is converted into voice band information by disconnecting normal transmission voice and transmitted to the partner FPU device via the voice modulator, and the receiving FPU device receives the channel designation information. By demodulating and identifying and controlling the local oscillator, automatic switching to the designated channel is performed.
[0008]
[Patent Document 1]
JP-A-8-317355 (Pages 2, 3 and 1)
[0009]
[Problems to be solved by the invention]
The parameters of the digital FPU device described above are described in ARIB (Association of Radio Industries and Businesses) standard STD-B13, and the permissible transmission bit rate between transmission and reception is theoretically determined to be 16.13054726 Mbps. As a result, the allowable bit rate of MPEG2-TS that can be transmitted between the codec and the digital FPU device is also determined.
[0010]
In a conventional digital FPU device, when performing a voice call (the audio bit stream by digital audio encoding is a fixed bit rate), the number of audio channels is increased by one more, and the bit rate of MPEG2-TS is the same as before. Then, since the video bit stream to be digital video encoded has a variable bit rate, the video bit stream must be compressed and encoded more than ever.
[0011]
In other words, if the video bitstream is compressed and encoded more than ever, the amount of information of the video signal input to the encoder is reduced, so that the resolution of the video signal is greatly degraded compared to the previous decoded video. There is. In Patent Document 1, channel switching information is transmitted with the normal transmission sound cut off, which affects normal transmission.
[0012]
Therefore, the present invention eliminates the above-mentioned problems and uses the OFDM frame structure in order to enable transmission on the order wire line, so that the compression coding of the video bitstream remains as it is. An object of the present invention is to provide an FPU device capable of performing the above.
[0013]
[Means for Solving the Problems]
An FPU apparatus according to the present invention is an FPU apparatus that transmits at least a video signal and an audio signal by encoding and multiplexing a TS (transport stream) signal as an OFDM frame structure, and transmitting the modulated signal from an order wire line. Transmission control means for encoding the voice communication signal and controlling to allocate the data symbol of the OFDM frame structure to the portion other than the allocated encoded data of the video signal and the audio signal.
[0014]
An operation control method according to the present invention is an operation control method in an FPU apparatus in which a TS (transport stream) signal obtained by encoding and multiplexing at least a video signal and an audio signal is OFDM-modulated and transmitted as an OFDM frame configuration. And a transmission control step of controlling to encode a voice call signal from an order wire line and assign it to a portion of the data symbol of the OFDM frame configuration other than where the encoded data of the video signal and voice signal is allocated. It is characterized by.
[0015]
The operation of the present invention will be described. In an FPU apparatus in which an MPEG2-TS (transport stream) signal obtained by encoding and multiplexing a video signal and an audio signal is OFDM-modulated as an OFDM frame structure and transmitted as a high-frequency signal, a voice call signal from an order wire line is transmitted. It is encoded and transmitted so as to be allocated to portions other than those where the encoded data of the video signal and audio signal of the data symbol of the OFDM frame configuration is allocated. The receiving-side FPU apparatus extracts and decodes the encoded data of the voice call signal from the OFDM frame configuration, and thereby performs an order wire function for making a voice call between the FPUs without reducing the bit rate of the video data. Is feasible.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 show the configuration of a digital FPU apparatus according to an embodiment of the present invention. FIG. 1 is a block diagram on the transmission side, and FIG. 2 is a block diagram on the reception side. 1 and 2, the same parts as those in FIGS. 9 and 10 are denoted by the same reference numerals.
[0017]
First, referring to FIG. 1, in the encoder 1, the video encoding unit 11 encodes the video signal, the audio encoding unit 12 encodes the audio signal, and the data encoding unit 13 encodes the data signal. To do. The multiplexing unit 14 multiplexes these encoded outputs and supplies them to the transmitter 2 as MPEG2-TS.
[0018]
The MPEG2-TS input to the transmitter 2 is subjected to energy spreading, error correction coding (outer code), outer interleaving, and error correction coding (inner code) by the transmission path encoder 211 in the transmission control unit 21. And supplied to the framing circuit 212. In addition, error correction coding (inner code) uses a convolutional code, and includes five modes including coding rate 1/2, 2/3, 3/4, 7/8 and the case of not coding. It shall have.
[0019]
On the other hand, the voice call input through the order wire line is input to the order wire encoder 214 in the transmission control unit 21, subjected to ADPCM encoding and error correction encoding, and supplied to the framing circuit 212. . In this framing circuit 212, the TS encoded signal output from the transmission line encoder 211 and the order wire encoded signal output from the order wire encoder 214 are multiplexed and multiplexed using the OFDM frame structure. Frame (framing) is performed.
[0020]
The framed OFDM frame data is modulated by the OFDM modulator 213, output as an IF signal (130 MHz), and supplied to the frequency conversion / power amplifier 22 constituting the transmission high-frequency unit. In this frequency conversion / power amplifier 22, the IF signal (130 MHz) is frequency-converted into a high-frequency signal in the 800 MHz band, amplified, and transmitted through the transmission antenna 3.
[0021]
Referring to FIG. 2, the signal from the transmission side received by the reception antenna 4 is input to the frequency converter 51 that constitutes the reception high frequency unit in the receiver 5, and the high frequency of the 800 MHz band is the IF signal (130 MHz). The frequency is converted and supplied to the reception control unit 52. In this reception control unit 52, an IF signal (130 MHz) is demodulated by an OFDM demodulator 521, and an MPEG2-TS signal, an order wire signal (voice call signal), and an MPEG2-TS signal are demultiplexed / demultiplexed by a deframing circuit 522. Is output.
[0022]
The deframed TS signal is decoded by the transmission path decoder 523 and supplied to the decoder 6 as MPEG2-TS, and is separated into a video signal, an audio signal, and a data signal by the separation unit 61. These separated signals are decoded and output by the video decoding unit 62, the audio decoding unit 63, and the data decoding unit 64, respectively.
[0023]
On the other hand, the order wire signal deframed by the deframing circuit 522 is input to the order wire decoder 524, subjected to error correction decoding and ADPCM decoding, and restored as a voice call signal to the order wire line. It is derived.
[0024]
FIG. 3 is a block diagram of the order wire encoder 214 shown in FIG. As shown in the figure, the order wire encoder 214 performs ADPCM encoding circuit 2141 for ADPCM code conversion of the voice call signal input from the order wire line, and convolutionally encodes the signal output from the ADPCM encoding circuit 2141. A clock (16 MHz) input from an error encoding circuit 2142 and a clock generator (not shown) in the transmission control unit 21 is divided by 400 to generate a clock (40 KHz), and an error is detected between the ADPCM encoding circuit 2141 and the error. And a clock frequency divider 2143 that supplies a clock to the encoding circuit 2142. Note that the error coding circuit 2142 uses only a coding rate of 1/2.
[0025]
FIG. 4 is a block diagram of the framing circuit 212 shown in FIG. The TS encoded signal output from the transmission line encoder 211 is sampled at 8 Mbps, while the order wire encoded signal output from the order wire encoder 214 is sampled at 40 Kbps, and is stored in the memory 2121. One frame is written in the memory 2122.
[0026]
The memory controller 2124 controls the writing / reading of these memories 2121 and 2122. The selector 2123 outputs read data of either the memory 2121 or 2122 under selection control by the memory control unit 2124.
[0027]
The number of data for which one frame of the TS encoded signal is written to the memory 2121 is 60.3 ms for the OFDM1 frame.
60.3 ms / 8 MHz (= 125 ns) = 482400
It becomes. On the other hand, the number of data in which the order wire encoded signal for one frame is written to the memory 2122 is:
60.3 ms / 40 KHz (= 25 μs) = 2412
It becomes.
[0028]
FIG. 5 shows an OFDM frame structure composed of synchronization symbols and data symbols. In order to transmit carrier data, the number of effective carriers of one symbol included in the data symbols is 544. The total number of symbols in one frame is 900. Among them, the number of synchronization symbols is 6. Therefore, the number of data symbols is 894 as shown in FIG.
[0029]
Therefore, the total number of effective carriers in one frame is
894 x 544 = 486336
It becomes. The number of data in which the TS encoded signal is written in one frame is small compared to the total number of effective carriers,
486336-482400 = 3936
(482400/544) + 6 = (886.7) + 6 = 892.7
The TS encoded signal after framing is allocated as carrier data up to the middle of the 893th symbol. Therefore, the order wire encoded signal can be sufficiently allocated to the carrier data in the OFDM frame structure, and the allocation of the carrier data is from the 894th symbol to the middle of the 898 symbol.
[0030]
The memory control unit 2124 that performs read control of the memories 2121 and 2122 and switching control of the selector 2123 performs multiplexing of the order wire encoded signal and TS encoded signal, and further framing, and the same 16 MHz as the FFT sampling clock. Sampled OFDM frame data is generated. This multiplexed and framed OFDM frame structure is shown in FIG.
[0031]
FIG. 7 is a block diagram of the deframing circuit 522 in FIG. As shown in the figure, the deframing circuit 522 is configured by memories 5221 and 5222 for writing OFDM demodulated OFDM frame data, and a memory control unit 5223 for controlling writing and reading of these memories. As a result, deframe processing and separation are performed, and the TS signal is output as 8 Mbps and the order wire signal is output as 40 Kbps.
[0032]
FIG. 8 is a block diagram of the order wire decoder 524 shown in FIG. As shown in the figure, the order wire decoder 524 includes an error correction decoding circuit 5241 that performs Viterbi decoding on the order wire demodulated signal separated from the deframing circuit 522, and a Viterbi decoded signal from the error correction decoding circuit 5241. An ADPCM decoding circuit 5242 that performs ADPCM decoding conversion, a clock (16 MHz) input from a clock generator in the reception control unit 52 is divided by 400 to generate a clock (40 KHz), and an error correction decoding circuit 5241 And a clock frequency divider 5243 for supplying a clock to the ADPCM decoding circuit 5242.
[0033]
With the configuration described above, an order wire function that enables voice communication by simply adding an order wire encoder 214 and decoder 524, a framing circuit 212, and a deframing circuit 522 to a conventional digital FPU device. Is feasible.
[0034]
【The invention's effect】
As described above, according to the present invention, by using the frame structure of OFDM, the compression coding of the video bitstream is kept as it is, and the voice communication by the order wire at the transmitter and receiver of the digital FPU device. There is an effect that becomes possible. In addition, since the processing time required for encoding and decoding on the codec side is eliminated by incorporating the order wire function in the digital FPU device, the amount of delay required for conventional calls is greatly reduced and the amount of delay is small. There is also an effect that voice call transmission can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram of a transmitting side of a digital FPU device according to an embodiment of the present invention.
FIG. 2 is a receiving side block diagram of a digital FPU device according to an embodiment of the present invention.
FIG. 3 is a block diagram of order wire encoder 214;
4 is a block diagram of a framing circuit 212. FIG.
FIG. 5 is an OFDM frame configuration diagram.
FIG. 6 is an OFDM frame configuration diagram in which order wire signals are multiplexed.
7 is a block diagram of a deframing circuit 522. FIG.
FIG. 8 is a block diagram of an order wire decoder 524.
FIG. 9 is a transmission side block diagram of a conventional digital FPU.
FIG. 10 is a reception side block diagram of a conventional digital FPU.
[Explanation of symbols]
1 Encoder 2 Transmitter 3 Transmitting antenna 4 Receiving antenna 5 Receiver 6 Decoder 11 Video encoding unit 12 Audio encoding unit 13 Data encoding unit 14 Multiplexing unit 21 Transmission control unit 22 Frequency conversion / power amplifier 51 Frequency converter 52 Reception control unit 61 Separation unit 62 Video decoding unit 63 Audio decoding unit 64 Data decoding unit 211 Transmission path encoder 212 Framing circuit 213 OFDM modulator 214 Order wire encoder 521 OFDM demodulator 522 Deframing circuit 523 Transmission path decoder 524 Order wire decoder

Claims (8)

An FPU device configured to transmit an OFDM-modulated TS (transport stream) signal obtained by encoding and multiplexing at least a video signal and an audio signal,
Including transmission control means for controlling to encode a voice call signal from an order wire line and assign it to a portion of the data symbol of the OFDM frame configuration other than where the encoded data of the video signal and voice signal is allocated. A featured FPU device. 2. The reception control unit according to claim 1, further comprising reception control means for performing control so as to demodulate a received signal into the OFDM frame structure and derive encoded data of the voice call signal allocated in the frame. FPU equipment. 3. The FPU apparatus according to claim 1, wherein the transmission control unit includes a framing unit that configures the TS signal and the encoded signal of the voice call signal as the OFDM frame configuration. 4. The FPU apparatus according to claim 3, wherein the reception control means includes deframing means for separating the TS signal and the encoded signal of the voice call signal from the OFDM frame configuration. An operation control method in an FPU device configured to perform OFDM modulation and transmit a TS (transport stream) signal obtained by encoding and multiplexing at least a video signal and an audio signal, as an OFDM frame configuration,
Including a transmission control step of encoding a voice call signal from an order wire line and controlling to encode the data symbol of the OFDM frame configuration to a portion other than the allocated encoded data of the video signal and the voice signal. A characteristic operation control method. 6. The reception control step further comprising: a reception control step of performing control so as to demodulate a received signal into the OFDM frame structure and derive encoded data of the voice call signal allocated in the frame. Operation control method. 7. The operation control method according to claim 5, wherein the transmission control step includes a framing step in which the TS signal and the encoded signal of the voice call signal are configured as the OFDM frame. 8. The operation control method according to claim 7, wherein the reception control step includes a deframing step of separating the TS signal and the encoded signal of the voice call signal from the OFDM frame configuration.

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