JP4364068B2 - Signal distribution method and apparatus - Google Patents

Description

  The present invention relates to a signal distribution method and apparatus, and more particularly to a signal distribution method and apparatus for distributing a television signal using a synchronous network such as SONET / SDH (Synchronous Optical Network / Synchronous Digital Hierarchy).

  The distribution of television signals from a conventional CATV (CAble TeleVision) station or DTV (Digital TeleVision) station to a user is mainly performed by an analog method using a 64QAM (Quadrature Amplitude Modulation) method.

  FIG. 1 shows a block diagram of an example of a conventional television signal distribution system. In the figure, a television signal received from, for example, satellite broadcasting by a CATV headend station 10 is 64QAM modulated by an IRT (Integrated Receiver Transcoder) 11 and then frequency-converted to a high-frequency signal RF by a converter 12. And transmitted from the transmitter 14 to the network 15 in the form of an analog signal. The high-frequency signal RF in the form of an analog signal received from the network 15 by the receiving unit 16 is distributed to a plurality of systems by the distributing unit 17, amplified by the amplifier 18, and then distributed to each user through each coaxial cable 19.

  This analog system has an old system, and it cannot handle a large number of channels per line and cable telephone. In recent years, distribution from a CATV headend station is in a transitional period in which it is changed to a method of performing distribution by converting into a digital signal via a CODEC device.

  FIG. 2 is a block diagram showing another example of a conventional television signal distribution system. In the figure, a television signal received from a satellite broadcast, for example, by a CATV headend station 20 is 64QAM modulated by an IRT 21 and supplied to a modem unit 23. Also, the modulation / demodulation transmission unit 23 is supplied with a 64QAM modulated television signal of another channel from the video switch 22.

  The modulation / demodulation transmission unit 23 encodes and digitizes the 64QAM modulated signal for each channel, multiplexes it, and performs electrical / optical conversion to obtain an optical signal having a transmission rate of 2.38 Gbps, for example. This optical signal is further optically multiplexed by the optical multiplexing unit 24 and sent to the optical transmission line 25.

  The optical signal from the optical transmission line 25 is separated for each wavelength by the optical demultiplexing unit 26, optical / electrically converted by the modulation / demodulation receiving unit 27, demultiplexed into each channel, decoded for each channel, and analog 64QAM modulated. Signal. The 64QAM modulated signal is frequency-converted to a high-frequency signal RF by a converter 28, and the high-frequency signal RF is distributed to a plurality of systems by a distribution unit 29, amplified by an amplifier 30, and then distributed to each user through each coaxial cable 31.

  Here, the television signal is not compressed and is directly used as a 64QAM modulated signal using a band of 155.52 Mbps per channel, and the modulation / demodulation transmission unit 23 multiplexes the signal and bundles it to 2.388 Gbps for further multiplexing. Are distributed at N × 2.388 Gbps (N is an arbitrary integer).

  Since this method does not compress television signals, it requires a bandwidth of 155 Mbps per channel, and since the transmission rate is different from the signal transmission rate of SONET / SDH, the compatibility with SONET / SDH equipment is poor. I couldn't get phone or other services.

  In order to solve this problem, there is a system using a CODEC device and a SONET / SDH transmission device. FIG. 3 shows a block diagram of another example of a conventional television signal distribution system.

  In FIG. 3, a television signal received from, for example, a satellite broadcast by the CATV head end station 40 is 64QAM modulated by an IRT 41 and supplied to the modem unit 43. The modulation / demodulation transmission unit 43 is supplied with a 64QAM-modulated television signal of another channel from the video switch 42.

  The modulation / demodulation transmission unit 43 encodes and digitizes the 64QAM modulated signal for each channel, multiplexes it, converts it to electrical / optical conversion, maps it to a SONET / SDH path STS-xx at 155 Mbps per channel, and transmits SONET / SDH. To the optical transmission line 45 as a SONET / SDH communication line OC-xx (Optical Carrier-xx).

  The optical signal from the optical transmission line 45 is received by the SONET / SDH receiving unit 46, and an electrical signal mapped to the SONET / SDH path STS-xx is obtained. This electrical signal is demultiplexed into each channel by the modulation / demodulation receiving unit 47, decoded for each channel, and converted into an analog 64QAM modulated signal. The 64QAM modulated signal is frequency-converted into a high-frequency signal RF by a converter 48, and the high-frequency signal RF is distributed to a plurality of systems by a distribution unit 49 and distributed to each user.

  This method is very expensive as compared with the conventional analog transmission method, and the control of the entire system becomes management of the CODEC device and management of the SONET / SDH dedicated device, which is double management and is not complicated. It was.

In order to solve this problem, MPEG-2 Moving Transport Exports Group (MPEG-2 Transport Frame Group) MPEG-2 TS (Transport Transport) standard MPEGB Transport Amplification (DVB-ASI) Digital Video Broadcasting A Synchronous Interface (European Digital Broadcasting Standard) transmission format is used. Is considered to be transmitted to the SONET / SDH transmission network. Further, as a method similar to this, for example, there is a transmission method described in Patent Document 1.
JP-A-10-190767

  With the DVB-ASI transmission format, MPEG-2TS packets can be transmitted over the SONET / SDH transmission network with a maximum compression of about 3.75 Mbps per television channel, so the DVB- of the SONET / SDH transmission apparatus A maximum of 72 channels can be received per ASI reception port, and distribution to the SONET / SDH network is possible.

  However, in this case, since the CATV station distributes several hundreds of channels of 3.75 Mbps MPEG-2 TS packets to the DVB-ASI interface of the SONET / SDH transmission apparatus, the DVB-ASI interface has several ports. It will be. However, not all DVB-ASI receiving ports are delivered with 72ch (3.75Mbps x 72ch = 270Mbps, DVB-ASI maximum received data rate = 270Mbps) of MPEG-2TS packets of 3.75Mbps, but DVB-ASI interface There may be a case where only a few channels are distributed to a certain port.

  Normally, when allocating the maximum receiving rate of 270 Mbps for DVB-ASI to the bandwidth of the SONET / SDH network, STS-1-6v (311.04 Mbps) is assigned for SONET, and STM-1 (311.04 Mbps) is assigned for SDH. ing.

  At this time, in order for the customer side to allocate this port to the SONET / SDH transmission network by assigning a bandwidth, it is desired to make a contract with a bandwidth less than STS-1-6v instead of STS-1-6v (311.04 Mbps) It should be. However, there has been a problem that there is no optimal method for flexibly allocating and operating the SONET / SDH bandwidth according to customer requirements.

  In addition, even when the narrow-band MPEG-2TS packet can be transmitted on the CATV station side SONET / SDH transmission apparatus side, the MPEG-2TS packet is extracted from the reception-side SONET / SDH signal and distributed. Since there is no data at the full rate, some correction processing is necessary to match the data rate (270 Mbps) of the DVB-ASI on the output side with the DVB-ASI interface. There was a problem that it was not.

  The present invention has been made in view of the above points, and has as its general object to provide a signal distribution method and apparatus capable of flexibly allocating and operating a synchronous network band according to customer requirements.

The invention according to claim 1 is a signal distribution method in which a transport packet of a television signal multiplexed with a plurality of channels is supplied in a transmission format of a digital broadcasting standard, and is transmitted and distributed over a synchronous network.
By setting the transmission rate in the synchronous network according to the number of multiplexed channels for each customer, the synchronous network bandwidth can be flexibly allocated and operated in accordance with customer requirements.

The invention as set forth in claim 2 is a transmission device for supplying a transport signal of a television signal in which a plurality of channels are multiplexed in a transmission format of a digital broadcasting standard and sending it to a synchronous network.
By having transmission rate setting means for setting the transmission rate in the synchronous network according to the number of multiplexed channels for each customer, the bandwidth of the synchronous network can be flexibly allocated according to customer requirements.

The invention according to claim 3 is the transmission apparatus according to claim 2,
By having a packet discard means for discarding the transport packet to be supplied when the transport packet supplied for each customer exceeds the transmission rate in the synchronous network set according to the number of multiplexed channels for each customer, Input data that exceeds the contract bandwidth can be discarded.

The invention according to claim 4 is the transmission apparatus according to claim 3,
If the transport packet accumulated in the buffer is greater than or equal to a predetermined number of bytes, the transport packet having the predetermined number of bytes is converted into a super block, and if the transport packet is less than the predetermined number of bytes, the super block is only for a predetermined time. If the transport packet is again less than the predetermined number of bytes, a transport control packet having the predetermined number of bytes is converted to the super block by adding a pad control code if the transport packet is less than the predetermined number of bytes. By having GFP mapping means for mapping blocks to GFP frames, the bandwidth of the synchronous network can be used effectively.

According to a fifth aspect of the present invention, a transport packet of a television signal in which a plurality of channels are multiplexed in a digital broadcast standard transmission format is received from a synchronous network with a transmission rate corresponding to the number of multiplexed channels for each customer. A receiving device,
By having output rate control means for controlling the output rate by embedding a space code between transport packets extracted from the received signal, the transmission rate can be adjusted.

The invention according to claim 6 is the receiving apparatus according to claim 5,
A read wait time for uniformly reading each transport packet from the buffer during the next predetermined period is calculated from the number of packets of the transport packet accumulated in the buffer every predetermined period, and each transport packet is read from the buffer. Optimum transport packet transmission interval by having 8B10B encoding means for waiting for reading for each read wait time and performing 8B10B encoding of the transport packet read from the buffer to convert it into the transmission format DVB-ASI Can be

  According to the present invention, the bandwidth of the synchronous network can be flexibly allocated and operated according to customer requirements.

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

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

  FIG. 4 shows a block diagram of an embodiment of a transmission system to which the signal distribution method of the present invention is applied.

  In the figure, a television signal received from, for example, satellite broadcasting at a CATV headend station 50 is converted into a DVB-ASI signal in which a plurality of channels are multiplexed by an IRT 51 and supplied to a video switch 52 as a DVB-ASI signal of one customer. Is done. Further, DVB-ASI signals of other customers are supplied to the video switch 52, and DVB-ASI signals of a plurality of customers selected by the video switch 52 are respectively supplied to a plurality of input ports of the SONET / SDH transmission unit 53. Supplied.

  The SONET / SDH transmission unit 53 is a DVB-ASI signal obtained by multiplexing up to 72 channels (3.75 Mbps × 72 channels = 270 Mbps) of MPEG-2 TS packets of 3.75 Mbps per high-definition television channel per input port. The SONET / SDH transmission unit 53 replaces the DVB-ASI signal with the SONET / SDH format, performs STS switching, and transmits the signal to the optical transmission line 54.

  The optical signal from the optical transmission line 54 is received by the SONET / SDH receiving unit 55 of the local station, and after being subjected to STS switching, is converted into a DVB-ASI signal. This signal is supplied to the video switch and conversion unit 56, and the selected DVB-ASI signal is converted from the MPEG-2 format to the television signal format, and further 64QAM modulated to obtain a 64QAM modulated signal. The 64QAM modulated signal is frequency-converted into a high-frequency signal RF by a converter 57, and the high-frequency signal RF is distributed to a plurality of systems by a distribution unit 58 and distributed to each user.

FIG. 5 shows a block diagram of an embodiment of the SONET / SDH transmission unit 53. In the figure, DVB-ASI signals obtained by multiplexing a maximum of 72 channels of 3.75 Mbps MPEG-2 signals are input to input ports 60 _{1 to} 60 m, respectively. Each DVB-ASI signal is automatically waveform-equalized by equalization circuits 61 _{1 to} 61m, converted from a received signal clock to a clock inside the apparatus by clock recovery circuits 62 _{1 to} 62m, and then supplied to the 8B10B decoder 63. .

  The 8B10B decoder 63 converts the 10-bit code of each DVB-ASI signal into an 8-bit code, and supplies the 8-bit code to the transmission rate control unit 64 as a signal having a maximum actual character data transmission rate of 216 Mbps. The transmission rate control unit 64 maps this signal to a GFP frame while controlling the transmission rate.

The SONET mapping unit 65, based on a contract with a customer assigned to the input port ₆₀ 1 _~60m respectively, the GFP frame mapping the DVB-ASI signal inputted from the input port ₆₀ 1 _~60m by virtual concatenation These are mapped to paths STS-1-1v, STS-1-3v, STS-1-5v, and STS-1-6v, and further mapped to channels 1 to 48 of path STS-48 shown in FIG.

  Here, a case where a 270 Mbps DVB-ASI signal is mapped to STS-1-6v (311 Mbps) using six STS-1 (52 Mbps) units will be described. As shown in FIG. 6, the payload part of STS-1-6v is decomposed into six STS-1 # 0 to STS-1 # 5 for each column. Each of the six decomposed STS-1 # 0 to STS-1 # 5 stores the sequence number for each column in the H4 byte in the path overhead (POH).

  The H4 byte at the time of multi-frame will be described using FIG. The MFI (Multi Frame Indicator) is divided into lower 4 bits MFI1 and upper 8 bits MFI2, and MFI1 occupies bits 5 to 8 in the H4 byte and is incremented for each frame. MFI2 is represented by bits 1 to 4 when MFI1 = 0,1. When MFI1 = 0, the MSB of MFI2 is shown, and when MFI1 = 1, the LSB of MFI2 is shown. An 8-bit sequence number (SQ) is expressed by bits 1 to 4 when MFI1 = 14,15. When MFI1 = 14, the MSB of the sequence number is shown, and when MFI1 = 15, the LSB of the sequence number is shown.

The BWB interface 66 converts the 32-bit parallel STS-48 data shown in FIG. 8 into 4-bit parallel data of each 8-bit parallel STS-12 shown in FIG. 67. The numbers 1 to 48 in FIGS. 8 and 9 indicate channel numbers.
Data switched by the STS switch 67 is sent from the transmitter 68 to the optical transmission line 54. At this time, it is sent to the optical transmission line 54 at a transmission rate of STS-48 (2488 Mbps).

Here, the DVB-ASI signal whose format is shown in FIG. 10 (A) or FIG. 10 (B) is sent from the video switch 52 of the CATV headend station 50 to the input ports 60 ₁ to 60 m of the SONET / SDH transmission unit 53. Since several hundred channels are distributed, the DVB-ASI interface of the SONET / SDH transmission unit 53 has several ports (60 _{1 to} 60 m).

However, 72 channels (270 Mbps, DVB-ASI maximum received data rate = 270 Mbps) are not distributed to the input ports 60 ₁ to 60 m that receive all DVB-ASI signals. A certain input port may be distributed only for several channels.

  By the way, when the maximum reception rate of 270 Mbps of DVB-ASI is 8B10B decoded and then allocated to the bandwidth of the SONET network, it is allocated to STS-1-5v. However, on the customer side, as described above, the input port for which only a few channels are distributed does not use the bandwidth of the SONET / SDH transmission network as STS-1-5v, but is less than STS-1-5v, for example STS-1 It is necessary to make a contract in a low-cost band such as -1v (51.84 Mbps).

In the present invention, the SONET mapping unit 65, based on a contract with a customer assigned to the input port ₆₀ 1 _~60m respectively, the GFP frame mapping the DVB-ASI signal inputted from the input port ₆₀ 1 _~60m Since it is mapped to any of the paths STS-1-1v, STS-1-3v, STS-1-5v, and STS-1-6v by virtual concatenation, it is possible to perform bandwidth allocation in accordance with customer requirements. The bandwidth of the SONET / SDH transmission network can be used effectively.

FIG. 11 is a block diagram for explaining transmission rate control in the present invention. In the figure, each DVB-ASI signal converted to an 8-bit code supplied from the 8B10B decoder 63 for each of the input ports 60 _{1 to} 60 m is supplied to the packet extraction unit 71 to extract the MPEG-2TS packet, A K28.5 space code for synchronizing the clock provided at the packet delimiter is extracted. All the extracted MPEG-2 TS packets are written to the first buffer 72, but the K28.5 space code is removed when writing to the first buffer 72. However, at the time of reading the super block from the second buffer 74, the clock SO is synchronized with the opposite SONET / SDH receiving unit 55, so that a K28.5 space code of at least 2 bytes is left between the MPEG-2 TS packets.

  The MPEG-2TS packet read from the first buffer 72 is subjected to 64B / 65B frame conversion by the 64B / 65B conversion unit 73 as pre-processing before passing to the GFP mapping unit 75. This converted frame is called a super block.

  This super block is written into the second buffer 74. The super block of the second buffer 74 of each port is read by the round robin method and transferred to the GFP mapping unit 75. The GFP mapping unit 75 maps the supplied super block to a GFP frame having the format shown in FIG. At this time, the second buffer 74 of the port to be transferred notifies the state to the SONET mapping unit 65 via the GFP mapping unit 75 as a 3-bit signal TADD and waits for a response PTCA from the SONET mapping unit 65.

  Here, if the bandwidth of the SONET side is higher than the bandwidth of the MPEG-2 TS packet input to a certain port, that is, if the MGEP-2TS packet signal is input beyond the contract bandwidth, the GFP mapping section 75 The super block cannot be transmitted, and the super block is accumulated in the second buffer 74.

  For this reason, the second buffer 74 is set in advance with a first threshold value for prohibiting writing of the MPEG-2 TS packet to the first buffer 72 when the capacity of the second buffer exceeds a certain value. When the first threshold value is exceeded, the input data exceeding the contracted bandwidth is discarded by prohibiting the writing of the MPEG-2 TS packet to the first buffer 72.

  Also, when the MPEG-2 TS packet is discarded in the first buffer 72, the super block of the second buffer 74 is output as time elapses. A second threshold value (second threshold value <first threshold value) is provided so as to allow writing of the MPEG-2 TS packet. When the MPEG-2 TS packet value falls below the second threshold value, the MPEG-2 TS packet is read from the first buffer 72. Allow writing.

  By controlling the flow rate of the input data (MPEG-2TS packet) in accordance with the bandwidth on the SONET / SDH side in this way, even if an MPEG-2TS packet exceeding the SONET / SDH transmission bandwidth is input. It is possible to maintain the quality of data transmission by taking a certain period of protection without suddenly starting to discard the MPEG-2 TS packet.

  The 64B / 65B conversion performed by the 64B / 65B conversion unit 73 is ITU-T recommendation G.264. 7041 / Y. This is a method standardized at 1303. The MPEG2-TS packet is cut out in units of 8 bytes, and if there is a control code according to the conversion rule, the code is converted and rearranged. Eight 8-byte units are bundled, and a 1-byte reading flag LF, which is a control code presence / absence flag, is added to the 8 bytes to form a 65-byte super block as a whole. Therefore, 64-byte MPEG2-TS packet data is required to construct a super block.

  The MPEG2-TS packet is 188 bytes or 204 bytes long, and a plurality of super blocks are required to convert one packet (in this method, two K28.5 space codes are assigned per packet, The actual number of bytes required is 190 bytes or 206 bytes).

  If the MPEG2-TS packet is 188 bytes long, 3 super blocks are required. If it is 204 bytes long, 4 super blocks are required. If it is 188 bytes long, 2 bytes are free. If it is 204 bytes long, 50 bytes are free. appear. When there is a vacancy like this, it is common to insert a pad control code. This pad control code is discarded in the 64B / 65B decoding process on the receiving side.

  By the way, in the present invention, in order to effectively use the bandwidth of the SONET / SDH transmission network, super block conversion processing is performed without considering the packet boundary. FIG. 13 shows an outline of the super block conversion process. In the MPEG2-TS packet, unnecessary space codes (SC) other than the head of the packet are deleted and stored in the first buffer 72 shown in FIG. Superblocking is a method of processing MPEG2-TS packets stored in the first buffer 72 64 bytes at a time from the top without being aware of packet boundaries.

  Also, depending on the data rate of the MPEG2-TS packet, data of less than 64 bytes remains temporarily in the first buffer 72, and it is considered that there is insufficient superblocking. In this state, the pad control code is not inserted, and the super-blocking process is waited for a certain wait time, and the super-blocking process is resumed after data of 64 bytes or more is accumulated in the first buffer 72. This wait time is determined by factors such as the customer's MPEG-2TS rate and the SONET / SDH transmission line bandwidth.

  If the data accumulated in the first buffer 72 after the above wait is less than 64 bytes, a pad control code is inserted to make a super block in order to reduce the packet delivery delay.

  A series of these operations will be described with reference to FIGS. FIG. 14A shows a case where MPEG2-TS packet data of 64 bytes or more is accumulated in the first buffer 72. The 64B / 65B conversion unit 73 reads out 64 bytes of data from the head and performs superblocking.

  FIG. 14B shows a case where only MPEG2-TS packet data of less than 64 bytes remains, and the superblocking procedure is stopped for the set wait time, and waiting for the accumulation of data of 64 bytes or more is awaited.

  FIG. 14C shows a case in which only MPEG2-TS packet data less than 64 bytes is accumulated even after a certain wait time has elapsed. In this case, in order to reduce the data transmission delay, the pad control code is immediately set. The added 64 bytes are transmitted to the 64B / 65B conversion unit 73 which performs super-blocking.

  FIG. 15 shows a configuration of the 64B / 65B conversion unit 73, and FIG. 16 shows a processing flowchart of the 64B / 65B conversion unit 73. In FIG. 15, the 64B / 65B conversion unit 73 includes a conversion processing unit 73a, a read control unit 73b, and a pad addition unit 73c. A wait time supplied from the outside is set in the read control unit 73b.

  In FIG. 16, the read controller 73a monitors the first buffer 72 in step S10, and determines whether or not MPEG2-TS packets are accumulated in the first buffer 72 in 64 bytes in step S12. If 64 bytes or more are accumulated, the packet is read from the first buffer 72 in step S14, and after the 64B / 65B conversion process of the conversion processing unit 73a in step S16, the write process to the second buffer 74 is performed in step S18. Do.

  If the MPEG2-TS packet accumulated in the first buffer 72 is less than 64 bytes in step S12, after waiting for the wait time in step S20, the first buffer 72 is monitored again in steps S22 and S24. At this time, if the packet is accumulated by 64 bytes or more, the process proceeds to step S14, the packet is read from the first buffer 72, and the write process to the second buffer 74 is performed after the 64B / 65B conversion process in steps S16, S18. .

  If the packet is less than 64 bytes in step S24, data less than 64 bytes is read from the first buffer 72 in step S26, and the process proceeds to step S28 where a pad control code is added to the above data in the pad adding unit 73c and the byte length Then, the process proceeds to step S16 to perform 64B / 65B conversion processing.

  In this way, the bandwidth of the SONET / SDH transmission network can be effectively used.

  FIG. 17 shows a block diagram of an embodiment of the SONET / SDH receiving unit 55. In the figure, the signal received from the optical transmission line 54 by the transmission unit 81 is supplied to the STS switch 82 and is switched. Then, the BWB interface 83 converts the serial data from 4 bits of the 8-bit parallel STS-12 shown in FIG. It is converted into system parallel data, and further converted into 32-bit parallel STS-48 data shown in FIG. 8 and supplied to the SONET demapping unit 84.

  The SONET demapping unit 84 demaps the path STS-48 to each of the paths STS-1-1v, STS-1-3v, STS-1-5v, and STS-1-6v of the virtual concatenation, and further, a GFP frame To the output rate control unit 85.

  Here, when assembling six STS-1 # 0 to STS-1 # 5 to STS-1-6v shown in FIG. 7, frames having the same MFI are decomposed according to sequence numbers from STS-1 to STS. -1-6v is assembled. Of course, if the frame arrival timing shifts and the MFIs do not match, assembly becomes impossible. Therefore, a buffer is provided, and a plurality of frames are stored in the buffer for assembly work.

  The output rate control unit 85 performs demapping of the GFP frame, controls the output rate for each output port, and supplies it to the 8B10B encoder 86. The 8B10B encoder 86 converts an 8-bit code into a 10-bit code in units of output ports, thereby converting the MPEG-2 signal into a DVB-ASI signal multiplexed by 72 channels at maximum.

Each DVB-ASI signal is transmitted from the output ports 89 ₁ to 89 m through the cable drivers 87 _{1 to} 87 m and the amplifiers 88 _{1 to} 88 m.

  FIG. 18 is a block diagram for explaining output rate control in the present invention. In the figure, the GFP frame output from the SONET demapping unit 84 is supplied to the GFP demapping unit 91 in the output rate control 85, and is demapped from the GFP frame to the super block.

The demapped super block is read by the round robin method and supplied to the 64B / 65B conversion unit 92 provided for each of the output ports 89 _{1 to} 89 m. Each 64B / 65B conversion section 92 performs 65B / 64B frame conversion of the super block and returns it to the original MPEG-2 TS packet. The MPEG-2 TS packet obtained here contains a K28.5 space code of at least 2 bytes.

  Thereafter, the MPEG-2 TS packet is extracted by the packet extraction unit 93 and stored in the third buffer 94. The MPEG-2 TS packet stored in the third buffer 94 is read out in parallel at each output port by the 8B10B encoder 86. The 8B10B encoder 86 performs 8B10B conversion of the read MPEG-2TS packet, converts it into a 10-bit code, and outputs it serially.

  Since the serial output transmission rate is 270 Mbps, the 8B10B encoder 86 embeds a K28.5 space code in order to adjust the transmission rate to the gap between the MPEG-2 TS packets (actual data).

  However, when the transmission output clock after the 8B10B encoder 86 is slightly earlier than the clock on the subsequent receiving apparatus side, data is not output little by little on the transmission side, and the MPEG-2TS packet is output to the third buffer 94 in the preceding stage of the 8B10B encoder 86. Will stay.

  At this time, if the MPEG-2 TS packet equal to or greater than the third threshold is accumulated in the third buffer 94, the MPEG-2 TS packet to be written next is discarded. When the MPEG-2 TS packet is discarded, the MPEG-2 TS packet in the third buffer 94 is released when time elapses, and the MPEG-2 TS packet is accumulated up to the fourth threshold value (fourth threshold value <third threshold value). When the value decreases, the writing of the MPEG-2 TS packet is permitted again.

  Conversely, when the clock on the receiving side is earlier than the clock on the transmitting side, there are no MPEG-2TS packets to be read from the third buffer 94, so transmission is performed by embedding a K28.5 space code so that there is no gap in the transmission data. By performing rate matching, buffer underrun can be prevented from occurring.

  Processing for optimizing the transmission interval of MPEG2-TS packet data in the 8B10B encoder 86 will be described. The MPEG2-TS packets extracted by the packet extraction unit 93 are stored in the third buffer 94 of FIG.

  As described so far, the space code is deleted on the transmission side and only necessary MPEG2-TS packets are mapped to SONET / SDH, so that there is no interval information between the packets. Since the SONET / SDH frame is transmitted at a period of 125 μsec, it is considered that the received data becomes bursty within an interval of 125 μsec on the DVB-ASI signal receiving apparatus (video switch and conversion unit 56 in FIG. 4) side. .

  In general, the buffer capacity on the DVB-ASI receiving device (video switch and conversion unit 56) side is as small as 512 bytes. When MPGE-2TS packets are transferred in bursts even in a short period of 125 μsec, the buffer on the receiving device side overflows. appear. A mechanism for causing this overflow will be described.

  19A and 19B show time (μsec) on the horizontal axis and the amount of transmission data (bytes) on the vertical axis, and the data transmission amount for 125 μsec, which is a SONET / SDH transmission unit. is there. The slope of the graph means the data transmission speed. When the DVB-ASI signal is at a full rate of 270 Mbps, the amount of data that can be transmitted is as follows for 8B / 10B conversion.

270 Mbps x 8/10 = 216 Mbps
The solid line in FIG. 19A and the broken line in FIG. 19B indicate the relationship between the time at the full rate and the data transmission amount. The slope of the graph is the data transmission speed at full rate. The alternate long and short dash line in FIG. 19B shows the relationship between the time at the transmission rate of 64 Mbps and the data transmission amount. A DVB-ASI transmitting apparatus (such as IRT51 in FIG. 4) set at a rate of 64 Mbps transmits data at the speed indicated by the one-dot chain line, and a DVB-ASI receiving apparatus (video switch and conversion unit 56) is also at the same speed. I expect data to be entered.

  In the method of mapping MPEG2-TS data to SONET / SDH in the present invention, there is no interval information between packets. For this reason, there is a bias in the arrangement of MPEG2-TS packets on the receiving side through the SONET / SDH network as a relay device. This bias becomes maximum at the full rate indicated by the broken line in FIG.

  That is, the MPEG2-TS packet is transmitted at a full rate for 37 μsec, and then the MPEG2-TS packet data is not transmitted until 125 μsec. In this case, the MPEG2-TS packet data that cannot be processed by the DVB-ASI receiver at 37 μsec and is stored in the TS buffer is a maximum of 704 bytes, which exceeds the buffer capacity of 512 bytes of a general DVB-ASI receiver. As a result, overflow occurs.

  In order to solve this, in the present embodiment, the packets stored in the third buffer 94 shown in FIG. 18 are read at intervals of 125 μsec, which is the SONET / SDH frame period. In order to output MPEG2-TS packets of the number of packets stored in the third buffer 94 evenly during the next 125 μsec, the number of space codes to be inserted between each packet is calculated, and that number of space codes is inserted.

  A series of these operations will be described with reference to FIG. A square mark shown as an input to the third buffer 94 and an output from the third buffer 94 represents one MPEG2-TS packet. PKT_CNT represents the number of packets accumulated in the third buffer 94. The 8B10B encoder 86 reads the PKT_CNT value every 125 μsec, and calculates the reading speed from the third buffer 94 from the number of accumulated packets.

  At time N, PKT_CNT = 0. When PKT_CNT = 0, the packet output is stopped until the next 125 μsec.

  At point N + 1, PKT_CNT = 5. In this case, the packet read wait time is calculated so that five packets can be transmitted uniformly over the next 125 μsec. Each time one packet is read, only the read wait time is calculated. Wait and insert space code. Also, when PKT_CNT is near or exceeds the number that can be transmitted at 125 μ, the read wait time is set to 0 and continuous transmission is performed.

  FIG. 21 shows the configuration of the 8B10B encoder 86. In the figure, the 8B10B encoder 86 includes an 8B10B conversion processing unit 86a, a read control unit 86b, a weight calculation unit 86c, and a packet count unit 86d. The packet count unit 86d counts the number of packets PKT_CNT accumulated in the third buffer 94 and notifies the weight calculation unit 86c.

  The weight calculation unit 86c monitors the PKT_CNT of the packet count unit 86d every 125 μsec, calculates the read wait time to send the packets uniformly, that is, at regular intervals, and notifies the read control unit 86b. The read control unit 86b makes a read request to the third buffer 94 so that the interval for outputting the MPEG2-TS packet becomes the read wait time. The MPEG2-TS packet read from the third buffer 94 is 8B10B converted by the 8B10B conversion processing unit 86a and output to the subsequent circuit.

  Note that the third buffer 94 can store packets supplied in the past 125 μsec, and there is a possibility of burst transfer of packets in 125 μsec, so the buffer needs to have a capacity to store at least twice as many packets in 125 μsec. It is.

  As a result, an MPEG2-TS packet having no inter-packet interval information can be transmitted to the destination DVB-ASI receiver without causing a reception buffer overflow.

  As described above, the DVB-ASI signal is mapped to the GFP frame and mapped to the SONET / SDH virtual concatenation path for transmission, so that the existing area from the CATV headend station to the local station of the distribution destination is transmitted. It is possible to construct a system that transmits at low cost using the SONET / SDH network. Further, by providing a path for the DVB-ASI signal to the SONET / SDH network according to the required bandwidth on the customer side, a fine service can be provided.

  In addition, since rate control is automatically performed in accordance with the set bandwidth of the SONET / SDH network, complicated control is not necessary, and the burden on the control system that controls the entire CATV headend station 50 can be reduced.

  A high-definition television signal can be compressed to 3.75 Mbps per channel with MPEG-2, and a normal television signal can be compressed to 1.5 to 2 Mbps per channel with MPEG-2. A DVB-ASI signal in which 5 to 2 Mbps MPEG-2 TS packets are multiplexed may be supplied to the video switch 52.

  In the above embodiment, SONET has been described as an example. However, this can be similarly applied to SDH, and the synchronous network is not limited to SONET.

The transmission rate control unit 64 corresponds to the transmission rate setting unit described in the claims, the 8B10B decoder 63 corresponds to the 8B10B decoding unit, the packet extraction unit 71 corresponds to the space code deletion unit, the first buffer 72 and the first buffer 72 2 buffer 74 corresponds to packet discarding means, GFP mapping section 75 corresponds to GFP mapping means, SONET mapping section 65 corresponds to synchronous network mapping means, output rate control section 85 corresponds to output rate control means, The SONET demapping unit 84 corresponds to the synchronous network demapping unit, the GFP demapping unit 91 corresponds to the GFP demapping unit, and the 8B10B encoder 86 corresponds to the 8B10B encoding unit.
(Supplementary note 1) In a signal distribution method in which a transport signal of a television signal multiplexed with a plurality of channels is supplied in a transmission format of a digital broadcasting standard, and transmitted and distributed over a synchronous network,
A signal distribution method characterized by setting a transmission rate in the synchronous network according to the number of multiplexed channels for each customer.
(Appendix 2) In the signal distribution method described in Appendix 1,
The signal distribution method according to claim 1, wherein the transport packet is an MPEG-2TS packet and is supplied in a transmission format DVB-ASI, and the synchronous network is a SONET or SDH network.
(Supplementary note 3) In the signal distribution method according to supplementary note 2,
A signal delivery method, wherein a space code other than a space code of a predetermined number of bytes between the MPEG-2 TS packets is deleted and transmitted to the synchronous network.
(Supplementary note 4) In the signal distribution method according to supplementary note 1,
A signal distribution method for discarding a transport packet supplied when the transport packet supplied for each customer exceeds a transmission rate in a synchronous network set in accordance with the number of multiplexed channels for each customer. .
(Supplementary Note 5) In a transmission device that supplies a transport signal of a television signal in which a plurality of channels are multiplexed in a transmission format of a digital broadcasting standard and sends it to a synchronous network,
A transmission apparatus comprising transmission rate setting means for setting a transmission rate in the synchronous network according to the number of multiplexed channels for each customer.
(Supplementary note 6) In the transmission device according to supplementary note 5,
The transmission apparatus, wherein the transport packet is an MPEG-2TS packet and is supplied in a transmission format DVB-ASI, and the synchronous network is a SONET or SDH network.
(Supplementary note 7) In the transmission device according to supplementary note 6,
8. A transmission apparatus comprising 8B10B decoding means for performing 8B10B decoding of a signal supplied in the transmission format DVB-ASI.
(Supplementary note 8) In the transmission device according to supplementary note 6,
A transmitter comprising space code deleting means for deleting a space code other than a space code having a predetermined number of bytes between the MPEG-2 TS packets.
(Supplementary note 9) In the transmission device according to supplementary note 5 or 8,
Packet transport means for discarding transport packets to be supplied when transport packets supplied for each customer exceed a transmission rate in a synchronous network set according to the number of multiplexed channels for each customer. A transmitting device.
(Supplementary note 10) In the transmission device according to supplementary note 9,
A transmission apparatus comprising GFP mapping means for mapping a supplied transport packet to a GFP frame.
(Supplementary note 11) In the transmission device according to supplementary note 3,
If the transport packet accumulated in the buffer is greater than or equal to a predetermined number of bytes, the transport packet having the predetermined number of bytes is converted into a super block, and if the transport packet is less than the predetermined number of bytes, the super block is only for a predetermined time. If the transport packet is again less than the predetermined number of bytes, a transport control packet having the predetermined number of bytes is converted to the super block by adding a pad control code if the transport packet is less than the predetermined number of bytes. A transmission apparatus comprising GFP mapping means for mapping a block to a GFP frame.
(Supplementary note 12) In the transmission device according to supplementary note 10,
A transmission apparatus comprising: a synchronous network mapping means for mapping the GFP frame to a path having a different capacity by virtual concatenation according to the number of multiplexed channels for each customer and transmitting the path to the SONET or SDH network.
(Supplementary note 13) A receiving apparatus that receives a signal from a synchronous network, in which a transport packet of a television signal in which a plurality of channels are multiplexed in a digital broadcast standard transmission format has a transmission rate corresponding to the number of multiplexed channels for each customer. And
A receiving apparatus comprising output rate control means for controlling an output rate by embedding a space code between transport packets extracted from a received signal.
(Supplementary note 14) In the reception apparatus according to supplementary note 13,
The receiving apparatus according to claim 1, wherein the transport packet is an MPEG-2TS packet, the transmission format is DVB-ASI, and the synchronous network is a SONET or SDH network.
(Supplementary note 15) In the reception device according to supplementary note 14,
A receiving apparatus, comprising: synchronous network demapping means for demapping a path received from the SONET or SDH network into a GFP frame.
(Supplementary note 16) In the reception device according to supplementary note 15,
A receiving apparatus comprising GFP demapping means for demapping the GFP frame to the transport packet.
(Supplementary note 17) In the reception device according to supplementary note 16,
8. A receiving apparatus comprising 8B10B encoding means for performing 8B10B encoding of the transport packet and converting the transport packet into the transmission format DVB-ASI.
(Supplementary note 18) In the reception device according to supplementary note 13,
A read wait time for uniformly reading each transport packet from the buffer during the next predetermined period is calculated from the number of packets of the transport packet accumulated in the buffer every predetermined period, and each transport packet is read from the buffer. A receiving apparatus comprising: 8B10B encoding means for waiting for reading for each reading wait time each time, performing 8B10B encoding of a transport packet read from the buffer, and converting the transport packet into a transmission format DVB-ASI.

It is a block diagram of an example of the conventional television signal delivery system. It is a block diagram of another example of the conventional television signal delivery system. It is a block diagram of another example of the conventional television signal delivery system. It is a block diagram of one Embodiment of the transmission system to which the signal delivery method of this invention is applied. 4 is a block diagram of an embodiment of a SONET / SDH transmission unit 53. FIG. It is a figure for demonstrating the case where a DVB-ASI signal is mapped by STS-1-6v. It is a figure for demonstrating the H4 byte at the time of a multi-frame. It is a figure which shows the data of STS-48. It is a figure which shows the structure of 4-system parallel data of STS-12. It is a figure which shows the format of a DVB-ASI signal. It is a block diagram for demonstrating the transmission rate control in this invention. It is a figure which shows a GFP frame format. It is a figure which shows the outline | summary of a super block conversion process. It is a figure for demonstrating superblocking. It is a figure which shows the structure of a 64B / 65B conversion part. It is a process flowchart of a 64B / 65B conversion part. It is a block diagram of one Embodiment of a SONET / SDH receiving part. It is a block diagram for demonstrating output rate control in this invention. It is a figure which shows the data transmission amount for 125 microseconds which is a transmission unit of SONET / SDH. It is a figure for demonstrating the operation | movement which outputs a packet equally from a 3rd buffer. It is a figure which shows the structure of 8B10B encoder.

Explanation of symbols

50 headend station 52 video switch 53 SONET / SDH transmission unit 54 the optical transmission line 55 SONET / SDH reception unit 56 the video switch and the conversion unit 57 converter 58 the distribution unit 60 ₁ ～60M input port 61 ₁ ～61M equalizer 62 ₁ - 62m clock recovery circuit 63 8B10B decoder 64 transmission rate control unit 65 SONET mapping unit 66, 83 BWB interface 67 STS switch 68 transmission unit 71 packet extraction unit 72 first buffer 73 64B / 65B conversion unit 74 second buffer 75 GFP mapping unit 81 transmission unit 82 STS switch 84 SONET demapping unit 85 outputs the rate control unit 86 8B10B encoder 87 ₁ ~87m cable driver 88 ₁ ~88m amplifier 89 ₁ ~89m Power port 91 GFP demapper 92 64B / 65B converting section 93 packet extracting unit 94 third buffer

Claims (6)

In a signal distribution method in which a transport signal of a television signal multiplexed with a plurality of channels is supplied in a digital broadcast standard transmission format, and transmitted and distributed over a synchronous network,
A signal distribution method characterized by setting a transmission rate in the synchronous network according to the number of multiplexed channels for each customer. In a transmission apparatus for supplying a transport signal of a television signal multiplexed with a plurality of channels in a transmission format of a digital broadcasting standard and sending it to a synchronous network,
A transmission apparatus comprising transmission rate setting means for setting a transmission rate in the synchronous network according to the number of multiplexed channels for each customer. The transmission device according to claim 2, wherein
Packet transport means for discarding transport packets to be supplied when transport packets supplied for each customer exceed a transmission rate in a synchronous network set according to the number of multiplexed channels for each customer. A transmitting device. The transmission device according to claim 3, wherein
If the transport packet accumulated in the buffer is greater than or equal to a predetermined number of bytes, the transport packet having the predetermined number of bytes is converted into a super block, and if the transport packet is less than the predetermined number of bytes, the super block is only for a predetermined time. If the transport packet is again less than the predetermined number of bytes, a transport control packet having the predetermined number of bytes is converted to the super block by adding a pad control code if the transport packet is less than the predetermined number of bytes. A transmission apparatus comprising GFP mapping means for mapping a block to a GFP frame. A receiver for receiving from a synchronous network a signal in which a transport packet of a television signal in which a plurality of channels are multiplexed in a digital broadcast standard transmission format has a transmission rate corresponding to the number of multiplexed channels for each customer,
A receiving apparatus comprising output rate control means for controlling an output rate by embedding a space code between transport packets extracted from a received signal. The receiving device according to claim 5, wherein
A read wait time for uniformly reading each transport packet from the buffer during the next predetermined period is calculated from the number of packets of the transport packet accumulated in the buffer every predetermined period, and each transport packet is read from the buffer. A receiving apparatus comprising: 8B10B encoding means for waiting for reading for each reading wait time each time, performing 8B10B encoding of a transport packet read from the buffer, and converting the transport packet into a transmission format DVB-ASI.

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