JP4856119B2 - Packet transmission system - Google Patents

Description

  The present invention uses a free frequency band such as a VHF (Very High Frequency) band in a video / audio distribution system that transmits an optical fiber by an RF (Radio Frequency) system, and an occupied bandwidth per carrier is 6 MHz. The present invention relates to a packet transmission system that has the above bandwidth, modulates a plurality of carriers with an Ethernet (registered trademark) MAC (Media Access Control) packet or the like, performs SCM (Subcarrier Multiplexing) together with other video / audio signals, and allows simultaneous transmission.

  An FM (Frequency Modulation) batch conversion system has been put to practical use as a multi-channel (up to 100 ch) video / audio signal distribution system using optical fibers. In this method, the optical carrier is used for the RF carrier signal that is SCM 90-2100 MHz, and the optical carrier is FM converted into an electrical signal centered on 3 GHz, which is converted into an intensity modulation method. It is a system that transmits in an optical fiber, and is more resistant to noise and reflection than a video / audio distribution system using an IM (Intensity Modulation) system that does not use the FM batch conversion system, and can transmit over a long distance (for example, (Refer nonpatent literature 1.).

  In addition, since the output interface from the optical terminal network (V-ONU: Video-Optical Network Unit) through which the FM batch conversion modulation video / audio signals are transmitted is a coaxial interface, it is used in most houses. The existing coaxial infrastructure for receiving broadcast signals can be used as it is, and all channels of multi-channel broadcasting can be distributed to a TV (television) receiver.

  CATV (Cable Television) multi-channel video and audio distribution by SCM in Japan occupies a bandwidth of 6 MHz per carrier. Therefore, in the Japanese CATV standard, modulation is performed on a video / audio signal by using a 64QAM (Quadrature Amplitude Modulation) method. In this case, the transmission capacity per carrier is 31.644 Mbps (for example, see Non-Patent Document 2). .

  In CATV, there is a standard for transmitting a data signal such as an IP (Internet Protocol) packet using such an RF signal carrier. US Cable Labs. Is a standard called DOCSIS (Data Over Cable Service Specifications), and in Japan, CATV operators have started a service for transmitting IP packet signals as a cable internet using DOCSIS.

  DOCSIS assumes that the occupied bandwidth per RF carrier is 6 MHz. This is mainly due to the existing CATV video / audio signal distribution, in which the occupied bandwidth per 1 RF carrier of the video / audio signal is 6 MHz, so that it is consistent with it. DOCSIS defines an MPEG2-TS (Moving Picture Expert Group 2-Transport Stream) layer on an RF carrier, and further defines a special link layer called DOCSIS MAC in an upper layer thereof. DOCSIS MAC corresponds to the MAC layer of IEEE 802.3 (the Institute of Electrical and Electronics Engineers. Inc.) Ethernet (registered trademark). Therefore, the network layer IP or transport layer RTP (Real-time Transport Protocol) / UDP (User Diagram Control Protocol) / TCP (Transmission Protocol Control), etc., in the OSI (Open Source Initiative) reference layer above the DOCSIS MAC. Are stacked, and the application layer is stacked as the top layer. The construction of the transmission mechanism based on MPEG2-TS is a major feature of DOCSIS.

  The latest DOCSIS version 3.0 specification (hereinafter referred to as DOCSIS3.0) is a channel that uses multiple bundles of RF carriers used for data transfer compared to the previous 1.0 version and 2.0 version specifications. A new bonding mechanism has been added. This was specified based on the reason for bundling a plurality of RF carriers to transmit a large-capacity signal because a large-capacity signal cannot be transmitted by a 1 RF carrier having an occupied bandwidth of 6 MHz. That is, if the physical layer carrier modulation scheme is the 64QAM scheme used in normal CATV, the capacity that can be transmitted with one RF carrier is 31.644 Mbps, and the reality is that the capacity of information and the speed of the Internet have increased in recent years. High-speed signal transmission requested by Therefore, a technique has been born in which a large capacity is transmitted by bundling a plurality of RF carriers and handling them integrally. However, currently, only up to four carrier bundles (= about 120 Mbps) are realized, and signals that require a transmission rate of about 120 Mbps or more cannot be distributed (see, for example, Non-Patent Document 3). ).

  Furthermore, in the four carrier bundles of DOCSIS, the bundled carriers must be within 60 MHz. In addition, it is necessary to adjust the skew between the carriers. Therefore, as the number of carriers increases, these adjustments become difficult, and so far, only up to four channel bondings have been realized. That is, only signal transmission up to about 120 Mbps can be realized. However, since DOCSIS is a specification related to the CATV Internet, an existing coaxial infrastructure can be used. For this reason, it is advantageous in that it can be used in most houses where coaxial infrastructure has been developed.

  By the way, among the RF carrier frequencies of each SCM video / audio signal, the VHF band from 90 to 220 MHz is the VHF-low band of 90 to 108 MHz, the VHF-mid band of 108 to 170 MHz, and the VHF-hi band of 170 to 222 MHz. It is divided into. Among them, the analog television broadcast is currently distributed in the VHF-low band and the VHF-hi band, and the CATV provider uses it for program distribution in the VHF-mid band.

  The analog television broadcast currently distributed in the VHF band is determined to stop in 2011, and the television broadcast is unified into a broadcast in the UHF (Ultra High Frequency) band. Therefore, an empty band is generated in the VHF band where analog television broadcasting has been distributed. Currently, the use of the VHF band has been discussed mainly by the Ministry of Internal Affairs and Communications, which has jurisdiction, but the use has not yet been officially determined.

  The above is the current state of packet signal distribution method using the RF carrier and the VHF band utilization, but so-called IP communication using IP (Internet Protocol) packets as a signal distribution method by another method has been widely spread. Yes. As described above, in the RF form with an occupied bandwidth of 6 MHz, in the 64QAM system, only 31.644 Mbps signal transmission can be performed, but 100 Mbps has already been widely introduced on a commercial basis in IP communication called optical internet access. 1 Gbps is also being introduced. The IP packet signal by the optical internet access is provided by the GE-PON (Gigabit Ethernet (registered trademark) -Passive Optical Network) system in the optical access network. The GE-PON system realizes 1 Gbps IP packet communication when the optical fiber topology is a PON configuration. At this time, the IP packet signal is transmitted through the optical fiber as an optical pulse signal through 8B / 10B encoding. Then, it is output as 100 Mbps 100Base-TX in a line termination device GE-ONU (Gigabit Ethernet (registered trademark) Optical Network Unit).

  In order to receive the IP packet signal at the terminal, the 100Base-TX output from the GE-ONU must be connected to the terminal. In reality, there are many examples in which connection to the terminal, that is, connection to the terminal with a category 5 or higher cable or an optical fiber cable is not easy. The number of households with category 5 or higher Ethernet (registered trademark) cables and fiber optic cables in both residential and residential buildings is increasing mainly in new buildings, but in most buildings Most of them are coaxial cables and telephone wiring infrastructures, and category 5 or higher Ethernet (registered trademark) cables and optical fiber cables are not installed, and the user performs additional wiring at a high cost as necessary . Therefore, in an existing premises system of an apartment house, a line termination device for an optical access network is installed in an MDF (Main Distribution Frame) room in the apartment house, and a VDSL (Very) that uses a telephone line wired to each house. In many cases, IP packet signals are transmitted to and received from each house via a high-speed digital subscriber line) device. In that case, the upper limit of the transmission rate is 100 Mbps. In addition, there is a wireless LAN (Local Area Network), but the signal transmission speed of the wireless LAN in the 5 GHz band is as low as about 50 Mbps at the maximum, and there is a problem that it can only be used between lines of sight.

  In this way, considering that an IP packet signal of 100 Mbps or higher is to be received by a terminal, there are actually some problems, and there is an environment in which all households want to enjoy a broadband access service of 100 Mbps or higher. Not progressing. That is, although there is no problem in transmission speed in IP packet communication using GE-PON, it is difficult to receive a service of 100 Mbps or more because the wiring of the home / premises infrastructure has not progressed, and IP by DOCSIS using an RF carrier is used. In packet communication, there is no problem in the maintenance of home / premises infrastructure, but a service of 120 Mbps or higher cannot be received due to the limitation of the number of RF carriers used for channel bonding.

The present invention was developed for the purpose of providing a high-speed packet transmission method that could not be realized in DOCSIS 3.0 by focusing on the RF transmission method using a coaxial infrastructure that has already been established as a home / premises infrastructure. .
ITU-T J.I. 185, “Transmission equipment for transfer multi-channel television signals over optical access network by FM conversion” JCTEA STD-007-4.2. , "Digital cable television receiver" Cable Labs. , “Data over cable service interface specifications DOCSIS3.0”

  If you can receive IP packet signals of 100 Mbps or higher using coaxial infrastructure that is widely maintained in existing detached houses and apartment buildings, you can enjoy a broadband environment without additional costs corresponding to in-home and on-premises infrastructure. Is possible. For this purpose, there is a method of distributing by RF form using the DOCSIS 3.0 standard of CATV that uses a coaxial infrastructure. However, in DOCSIS 3.0, the occupied bandwidth of 1 RF carrier is 6 MHz, and channel bonding can only be performed up to 4 carriers. Therefore, in the case of the 64QAM system widely used in CATV as a carrier modulation system, a signal can be transmitted only at a maximum of about 120 Mbps. As shown in the DOCSIS protocol stack diagram of FIG. 1A, DOCSIS defines DOCSIS MAC as a link layer on MPEG2-TS. Therefore, it is necessary to once divide the IP packet signal into MPEG2-TS, which is a packet stream having a size of one packet of 188 bytes. Considering that the MAC length of Ethernet (registered trademark) that is normally used is about 1500 bytes, it is complicated to divide into MPEG2-TS with a small packet size, assign, and transmit a signal. There was a problem of poor efficiency.

  Therefore, the present invention utilizes a video / audio distribution system of an FM batch conversion optical transmission system that can use the coaxial wiring infrastructure on the receiving side and transmits an RF signal, and converts a high-speed and large-capacity packet signal into video / audio. It is intended to be transmitted simultaneously with the signal.

  In order to solve the above-mentioned problem, a packet transmission system according to the present invention is a video / audio distribution system of the FM batch conversion optical transmission method, wherein a plurality of packet signals having an occupied bandwidth of 6 MHz or more are used in the VHF band. The SCM signal obtained by assigning the audio signal to a frequency band higher than the VHF band and frequency-multiplexed is FM-converted and optically transmitted.

  In the present invention, as described above, after analog television broadcasting was stopped in 2011, in addition to using the site of the 90 to 220 MHz VHF band for packet signal distribution, it is used in ordinary CATV. An occupied bandwidth wider than 6 MHz per carrier, for example, a wide occupied bandwidth such as 32 MHz is used. By using such a VHF band for packet signals, a coaxial infrastructure such as an existing apartment house can be used as it is, and a VHF Super Hi / UHF to BS / CS (Broadcast Satellite / Communication Satellite) band (220 to 2100 MHz). In addition to receiving terrestrial digital television broadcasts and multi-channel broadcasts distributed as in (1), high-speed signals of 120 Mbps or higher, which are difficult to achieve with the DOCSIS 3.0 specification, can be distributed.

  Further, by assigning an Ethernet (registered trademark) MAC packet signal directly to an RF carrier without using MPEG2-TS with a small packet size such as DOCSIS 3.0 and DOCSIS MAC located in the upper layer thereof, allocation of the signal to the RF carrier is possible. Processing can be simplified, and the apparatus can be simplified.

Specifically, the packet transmission system according to the present invention has an RF (Radio Frequency) with an occupied bandwidth of 6 MHz or more in which a data signal packetized on the frequency axis of the VHF (Very High Frequency) band is SCM (Subcarrier Multiplexing). ) RF signal multiplexes the signal and video / audio broadcast signal existing in a frequency band higher than the VHF band, FM batch conversion and transmission, and signal from the transmission unit is received as FM batch conversion signal A receiving unit that separates the RF signal and receives the RF signal and the video / audio broadcast signal, wherein the transmitting unit packetizes the data signal; and The signal from the packet processing unit is divided and changed for each carrier frequency to be loaded later. A modulation unit, an RF processing unit that places a signal from the modulation unit on each carrier frequency, and an RF signal multiplexing unit that frequency-multiplexes the signal from the RF processing unit, and the reception unit includes the RF An RF signal demultiplexing unit that demultiplexes the frequency-multiplexed signal of the signal multiplexing unit for each carrier frequency, a demodulating unit that demodulates the signal from the RF signal demultiplexing unit for each carrier frequency, and a skew between signals from each of the demodulating units An inter-carrier skew adjustment unit that performs adjustment, and a packet processing unit that reproduces a packet of a signal from the inter-carrier skew adjustment unit, wherein the packet processing unit of the transmission unit performs physical processing in packetization of the data signal. A physical layer processing unit for performing layer processing, and a MAC (Media Access C) for packetizing the signal from the physical layer processing unit a MAC layer processing unit that performs Ntrol) layer processing, characterized in that it and a MAC data allocation unit for allocating a carrier frequency a predetermined signal from the MAC layer processing section.

In the packet transmission system according to the present invention, the modulation unit includes the error correction code unit that encodes a signal from the packet processing unit with an error correction code, and the error correction code according to a conversion table that defines a correspondence between the symbol and the modulation data. And a digital modulation unit that digitally modulates a signal from the unit .

In the packet transmission system according to the present invention, the RF processing unit includes a multiplier that puts a signal from the modulation unit on a carrier wave of a carrier frequency, and a bandpass that passes the carrier of the carrier frequency among the signals from the multiplier It is preferable to include a filter and an amplifier that amplifies the signal from the bandpass filter to a voltage level necessary for RF output .

Packet transmission system according to the present invention, VHF (Very High Frequency) band of the packetized data signals on the frequency axis and SCM (Subcarrier Multiplexing) has been occupied bandwidth 6MHz or an RF (Radio Frequency) signal An RF signal multiplexes a video / audio broadcast signal existing in a frequency band higher than the VHF band, performs FM batch conversion and transmits the signal, receives a signal from the transmission unit as an FM batch conversion signal, and receives an RF signal. A packet transmission system comprising: a receiving unit that separates and receives the RF signal and the video / audio broadcast signal, wherein the transmitting unit packetizes a data signal; and the packet processing unit Modulator that divides and modulates the signal from each carrier frequency to be loaded later An RF processing unit that puts the signal from the modulation unit on each carrier frequency, and an RF signal multiplexing unit that frequency-multiplexes the signal from the RF processing unit, and the receiving unit is a part of the RF signal multiplexing unit. An RF signal separation unit that separates frequency-multiplexed signals for each carrier frequency, a demodulation unit that demodulates signals from the RF signal separation unit for each carrier frequency, and a carrier that performs skew adjustment between signals from the demodulation units. An inter-skew adjustment unit, and a packet processing unit that reproduces a packet of a signal from the inter-carrier skew adjustment unit, wherein the packet processing unit of the reception unit restores the original signal from the inter-carrier skew adjustment unit. MAC data allocating unit to reproduce into one data signal, and MAC layer processing for processing in the MAC layer of the signal from the MAC data allocating unit And a physical layer processing unit that performs processing in the physical layer of a signal from the MAC layer processing unit .

  In the packet transmission system according to the present invention, the demodulation unit includes a BP (Bandpass) signal processing unit that performs bandpass processing at a carrier frequency of the signal from the RF signal separation unit, and a signal from the BP signal processing unit. A phase rotation control unit that performs phase rotation control, a digital modulation unit that digitally demodulates a signal from the phase rotation control unit according to a conversion table that defines the correspondence between symbols and demodulated data, and a signal from the digital modulation unit. And an error correction code decoding unit for decoding the error correction code.

  In the packet transmission system according to the present invention, the BP signal processing unit passes a signal of a predetermined carrier frequency only, and downconverts the signal from the bandpass filter to an IF (Intermediate Frequency) frequency. A local oscillator, a low-pass filter that removes unnecessary high-frequency components from the signal down-converted by the local oscillator, an equalizer that smoothes the signal from the low-pass filter, and a signal from the equalizer is converted to a digital signal It is preferable to include an AD (Analog to Digital) converter and a Nyquist filter that suppresses a signal component in a frequency band larger than half of the Nyquist frequency among signals from the AD converter.

  In the packet transmission system according to the present invention, the phase rotation control unit includes a phase rotation control circuit that performs phase rotation control of a signal from the BP signal processing unit, and an equalizer that smoothes a signal from the phase rotation control circuit; A phase error detection circuit for detecting a phase error of a signal from the equalizer, an APC (Automatic Phase Control) loop filter for outputting the phase error detected by the phase error detection circuit, and a phase error from the APC loop filter. Based on a numerically controlled oscillation circuit that performs phase rotation control of the signal from the BP signal processing unit, a clock recovery circuit that recovers a clock signal based on the signal from the phase rotation control circuit, and a signal from the clock recovery circuit Based on the oscillation circuit that oscillates the clock and the signal amplitude from the phase rotation control circuit It is preferable that an AGC (Automatic Gain Control) circuit that increases or decreases an amplification factor of a signal from the low-pass filter in the BP signal processing unit is provided.

  In the packet transmission system according to the present invention, the packet processing unit includes a MAC data allocating unit that regenerates a signal from the inter-carrier skew adjusting unit into an original data signal, and a MAC of the signal from the MAC data allocating unit. It is preferable to include a MAC layer processing unit that performs processing in a layer and a physical layer processing unit that performs processing in a physical layer of a signal from the MAC layer processing unit.

  According to the present invention, a high-speed and large-capacity packet signal can be transmitted simultaneously with a video / audio signal by using an FM batch conversion optical transmission video / audio distribution system that can use a coaxial wiring infrastructure on the receiving side. it can. Further, since a high-speed and large-capacity packet signal can be transmitted without being divided into MPEG2-TS packets, packet transmission processing can be reduced.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.

  FIG. 2 shows an example of VHF band channel allocation required for the packet transmission system of the present invention. (A) shows a case where the occupied bandwidth per carrier is 32 MHz, and (b) shows the occupied bandwidth per carrier. The case of 64 MHz is shown. In this example, the occupied bandwidth per carrier is 32 MHz in (a) and 64 MHz in (b). However, if the total bandwidth is within 220 MHz-90 MHz = 130 MHz, the occupied bandwidth per carrier can be freely determined. Good. For example, in the case of 64 MHz, if the modulation method is 64QAM, a transmission rate of 384 Mbps per carrier can be realized theoretically. Similarly, 192 Mbps can be realized at 32 MHz. Further, if a plurality of carriers are bundled, a higher transmission speed can be realized. If two 64 MHz band carriers are bundled, 768 Mbps can be realized. If two 32 MHz band carriers are bundled, 384 Mbps can be realized and if four bundles are bundled, 768 Mbps can be realized. In this way, not only can a high-speed signal be transmitted by using a VHF band that is an empty frequency band and a carrier with an occupied bandwidth of 6 MHz or more, but SCM is also performed in the VHF Super Hi / UHF to BS / CS band. Ordinary video / audio signals can be transmitted at the same time without any change.

  FIG. 3 is a schematic configuration diagram illustrating an example of a packet transmission system according to the present embodiment. The packet transmission system includes a transmission unit 10 and a reception unit 30. The transmitter 10 performs RF signal multiplexing of an RF signal having an occupied bandwidth of 6 MHz or more in which a data signal is SCMed on the frequency axis of the VHF band and a video / audio broadcast signal in a frequency band higher than the VHF band, and multiplexed. The signal is FM converted and transmitted. For example, the transmission unit 10 includes a packet processing unit 11, a modulation unit 12, an RF processing unit 13, an RF signal multiplexing unit 14, a video / audio signal modulation unit 15, and an RF processing unit 16.

  The packet processing unit 11 packetizes the data signal. For example, processing is performed to convert a packet data signal of Gigabit Ethernet (registered trademark) from a server or the like into a data string of a packet to be placed on one or a plurality of RF carriers having an occupied bandwidth of 6 MHz or more. The modulation unit 12 modulates the signal from the packet processing unit 11 for each carrier frequency. For example, encoding of an error correction code and digital modulation processing such as 64QAM are performed for each carrier. Each modulated signal is loaded on each carrier frequency in the VHF band by the RF processing unit 13. In parallel with the process of placing the packet signal on the carrier, the normal video / audio signal is modulated by the video / audio signal modulation unit 15 and becomes a carrier having a normal 6 MHz occupied bandwidth in the VHF Super Hi / UHF to BS / CS band. The processing to be mounted is performed by the RF processing unit 16. There are several tens to several hundreds of channels of the video / audio signals. The data signal and video / audio signal from the RF processing unit 13 placed on each carrier frequency are subjected to SCM in the RF signal multiplexing unit 14. At this time, voltage level adjustment and frequency fine adjustment are performed so as not to cause distortion of each carrier. The adjusted signal is input to the FM batch transmission unit 17 and introduced into the optical fiber network as an optical signal. The FM batch conversion system signal propagated through the optical fiber network is input to the FM batch receiver 21.

  The FM batch reception unit 21 receives a signal from the transmission unit as an FM batch conversion signal, and the RF signal separation unit 22 separates the RF signal to receive the RF signal and the video / audio broadcast signal. For example, the reception unit 30 includes an RF signal separation unit 22, a demodulation unit 23, an intercarrier skew adjustment unit 24, and a packet processing unit 25.

  A signal demodulated into an SCM signal before FM batch conversion by the FM batch receiving unit 21 and input to the receiving unit 30 enters the RF signal separating unit 22 as an SCM signal. The RF signal separation unit 22 separates the frequency multiplexed signal of the RF signal multiplexing unit 14 for each carrier frequency. For example, the data signal and the video / audio signal carried on each carrier frequency are filtered. The demodulator 23 demodulates the signal from the RF signal separator 22 for each carrier frequency. The inter-carrier skew adjustment unit 24 performs skew adjustment between signals from the demodulation units 23. The packet processing unit 25 reproduces the signal packet from the inter-carrier skew adjustment unit 24.

  A normal video / audio signal is filtered at a desired carrier frequency by a tuner 26 such as an STB (Set Top Box) or a TV receiver, and input to a video / audio signal demodulator 27 for video / audio reproduction. The video / audio signal demodulator 27 demodulates 64QAM or the like, decodes an error correction code, and the like, and outputs it to a decoding portion (not shown) of a video / audio signal in the subsequent stage to decode MPEG2 or the like.

  On the other hand, the packet data signal passes through an RF signal separation unit 22 such as a bandpass filter for filtering the carrier of the frequency on which the packet data signal is carried, and the demodulation unit 23 performs AD conversion, phase rotation control, demodulation, and the like. Is called. In the case of signal transmission by multi-carrier, the skew adjustment between the carriers is performed by the inter-carrier skew adjustment unit 24 and input to the packet processing unit 25 for packet reproduction.

  Here, in the demodulator 23, although the occupied bandwidth is as wide as 6 MHz or more, for example, 32 MHz, the characteristics can be made to function flatly over a wide band. In addition, when the QAM method is used, carrier amplitude information and phase information are used. Therefore, it is necessary to keep the carrier amplitude flat over the occupied bandwidth. In the 64QAM system, the amplitude fluctuation must be suppressed within 0.4 to 1 dB, but the amplitude fluctuation within 0.4 to 1 dB can be realized by the equalizer.

  4 and 5 are schematic diagrams of a configuration for directly allocating IP packet signals to carriers in the VHF band. Here, FIG. 4 shows the case where the input signal is 1000Base-X, and FIG. 5 shows the case where the input packet signal is 1000Base-T.

  First, the case of 1000Base-X shown in FIG. 4 will be described. In the case of 1000Base-X, since 8B / 10B encoding is performed as a physical layer signal, a bit string of 1.25 Gbps is input to the transmission unit. The bit sequence of the data signal input to the transmission unit is subjected to physical layer processing in packetization of the data signal by the 1 Gbps physical layer processing unit 11-1. The processed data string is serial / parallel converted by an S / P (Serial / Parallel) unit 11-2 and input to the MAC layer processing unit 11-3. The data string is subjected to MAC layer processing by the MAC layer processing unit 11-3, and then parallel / serial conversion and interframe gap adjustment are performed by the MAC data allocating unit 11-4 to allocate to each carrier frequency. Is done. And it inputs into the modulation part 12 of each carrier.

  In order to increase the error tolerance on the transmission path by the error correction code unit 12-1, the signal from the packet processing unit 11 is encoded with the error correction code. The signal is input to the digital modulation unit 12-3 via the S / P unit 12-2. The digital modulation unit 12-3 digitally modulates the signal from the error correction coding unit 12-1 according to a conversion table 12-4 that defines the correspondence between symbols and modulation data.

  Here, the digital modulation unit 12-3 preferably uses a 64QAM system as a digital modulation system. This is because the existing CATV is based on the 64QAM system, but the QPSK (Quadrature Phase Shift Keying) system used in the satellite system, the 8PSK system, or the 256QAM system may be used. In this way, there is no need to divide and assign an IP packet signal such as DOCSIS once from DOCSIS MAC to MPEG2-TS and then assign it to the QAM carrier, and the process is simplified because the MAC packet is directly assigned to the QAM carrier. . Accordingly, it is possible to realize a reduction in processing delay, a reduction in the size of the apparatus, and a reduction in power consumption.

  As described above, the occupied bandwidth of the carrier may be set in any manner as long as it is within 130 MHz. When multi-carrier transmission is performed, skew adjustment on the receiving side is necessary, and the processing becomes more complicated as the number of carriers increases. On the other hand, if the occupied bandwidth is increased, the transmission capacity per carrier increases, but the sampling rate necessary for AD conversion in the receiving unit increases, and the processing on the receiving side becomes complicated. Therefore, both are in a trade-off relationship. Here, an example in which the occupied bandwidth per carrier is 32 MHz and four carriers are bundled and used for data transmission is shown.

  When signal transmission is performed using four multicarriers, the MAC data allocating unit 11-4 of the packet processing unit 11 needs to allocate and transmit data to each carrier, and thus includes four modulating units 12. Needless to say, each modulation section 12 performs the same processing. The modulation signal output from the modulation unit 12 is sent to the subsequent RF processing unit 13.

  When the input packet signal shown in FIG. 5 is transmitted with 1000Base-T, since it is 8B1Q4 code, the physical layer processing of 1 Gbps in the packet processing unit 11 is different from the case of 1000Base-X. In this case, the interface to the MAC layer processing unit 11-3 is GMII (Gigabit Media Independent Interface). Processing subsequent to the MAC layer processing unit 11-3 is the same as that in the case of 1000Base-X.

  FIG. 6 shows a configuration example of the RF processing unit. The modulation signal transmitted from the modulation unit 12 is loaded on the carrier wave of the oscillator 13-1 oscillated at each carrier frequency by the multiplier 13-2 and filtered by the bandpass filter 13-3 corresponding to the carrier frequency. . Here, the carrier frequency of each carrier wave is predetermined. Thereafter, the amplifier 13-4 amplifies the electrical signal to a voltage level necessary for RF output so as not to generate a good CNR (Carrier to Noise Ratio) or distortion, and outputs it as an RF signal. The output RF signal is multiplexed with the carrier frequency corresponding to the transmission carrier by the RF signal multiplexer 14.

  7 and 8 are schematic configuration diagrams showing an example of processing from the RF signal separation unit 22 to the packet processing unit 25 in the case of 1000Base-X and 1000Base-T, respectively. The RF signal that has been SCM is separated by the RF signal separation unit 22 into the frequency of each carrier. The separated RF signal is input to a BP (band pass) signal processing unit 23-1 of the demodulation unit 23. The phase rotation control unit 23-2 performs phase rotation control processing on the signal subjected to band pass signal processing at each carrier frequency by the BP signal processing unit 23-1 in order to minimize the influence of phase noise during transmission. Thereafter, the digital demodulation unit 23-3 performs digital demodulation processing with reference to the conversion table 23-4 that defines the correspondence between the symbol and the demodulated data, and the parallel / serial conversion is performed by the P / S (Parallel / Serial) unit 23-5. Thereafter, the error correction code is decoded by the error correction decoding unit 23-6. After the error correction code decoding process is performed, the skew adjustment for matching the skew between the carriers is performed by the inter-carrier skew adjustment unit 24. When signal transmission is performed with an occupied bandwidth of 32 MHz per carrier, the skew is adjusted between four carriers. The skew adjustment between the four carriers can be realized without any problem since it is also realized in DOCSIS 3.0. Skew adjustment becomes difficult if the occupied bandwidth per carrier is reduced and the number of carriers is increased. A skew adjustment of about 4 carriers is realistic. The packet signal is subjected to packet reproduction processing by the packet processing unit 25 for the data signal subjected to skew adjustment.

  In the case of 1000Base-X shown in FIG. 7, each data signal transmitted by a plurality of carriers is restored to one original data signal by the MAC data allocation unit 25-1. Thereafter, the MAC layer processing unit 25-2 performs MAC layer processing, and the P / S unit 25-3 performs parallel / serial conversion, and then outputs it as an 8B / 10B encoded bit string. In the case of 1000Base-T shown in FIG. 8, since the P / S unit 25-3 subsequent to the MAC layer processing unit 25-2 is not required, data is passed through the GMII interface, and the physical layer processing unit 25-4 performs physical processing. Layer processing is performed. After the physical layer processing is performed, it is output as a 1000Base-T signal encoded by 8B1Q4. Similar to the transmission side, MPEG2-TS conversion processing such as DOCSIS is unnecessary, and the Ethernet (registered trademark) MAC is directly restored from the QAM carrier, so that the processing can be simplified.

FIG. 9 is a schematic diagram showing the demodulator 23 in the receiver 30 in some detail. The signal separated into each carrier signal by the RF signal separation unit 22 first passes through a BPF (band pass filter) 23-11 that can pass only a signal having a preset carrier frequency f ₁ (MHz). . Here, the bandwidth of the bandpass filter 23-11 is Δf (MHz). Δf is determined by the occupied bandwidth per carrier. The signal filtered by the BPF 23-11 is mixed with the signal from the local oscillator 23-18 having the frequency f _local (MHz) and down-converted to the IF frequency band. The IF band data signal is removed by a 2Δf (MHz) LPF (Low Pass Filter) 23-12 to remove high frequency components and sent to an AGC-controlled AMP (amplifier) 23-13. The signal amplified by the AMP 23-13 is equalized and smoothed by an EQ (equalizer) 23-14 as necessary, and sent to an AD converter 23-15 for analog / digital conversion processing.

  The signal subjected to AD conversion processing by the AD converter 23-15 is then separated into an I component and a Q component whose phase is shifted by 90 ° from the I component, and a signal component in a frequency band larger than half of the Nyquist frequency. Is input to the phase rotation control circuit 23-21. The phase rotation control circuit 23-21 performs phase rotation control of the signal from the BP signal processing unit 23-1 in order to minimize the influence of phase noise. The signal subjected to the phase rotation control process passes through an EQ (equalizer) 23-22 that smoothes the signal from the phase rotation control circuit 23-21, and a digital demodulation process such as 64QAM is performed by the digital demodulation unit 23-3. . Thereafter, parallel / serial conversion is performed by the P / S unit 23-5, and the error correction code decoding process is performed by the error correction decoding unit 23-6, and the subsequent inter-carrier skew adjustment unit (reference numeral 24 in FIG. 7). Sent.

  In order to suppress distortion of the I component and Q component signals from the Nyquist filter 23-16, a phase error detection circuit 23-24, an APC loop filter 23-25, a numerically controlled oscillation circuit 23-26, and clock recovery It is preferable to include a circuit 23-23, an oscillation circuit 23-29, and an AGC circuit 23-27. The phase error detection circuit 23-24 detects the phase error of the signal from the EQ 23-22. The APC loop filter 23-25 outputs the phase error detected by the phase error detection circuit 23-24. The numerically controlled oscillation circuit 23-26 controls the phase rotation of the signal from the BP signal processing unit based on the phase error from the APC loop filter. The clock recovery circuit 23-23 recovers the clock signal based on the signal from the phase rotation control circuit 23-21. The oscillation circuit 23-29 oscillates based on the signal from the clock recovery circuit 23-23. The AGC circuit 23-27 increases or decreases the amplification factor of the signal from the LPF 23-12 in the BP signal processing unit based on the signal amplitude from the phase rotation control circuit 23-21.

  In FIG. 9, the APF control from the AFC control loop filter 23-17 is performed on the BPF 23-11. This processing is necessary when a bandpass filter having a variable bandpass band is used. This is not necessary when the bandwidth of the path is fixed. Further, the clock necessary for AD conversion in the ADC 23-15 is extracted from the signal after the phase rotation control processing is performed in the clock recovery circuit 23-23 provided in the subsequent phase rotation control unit 23-2, and provided. Is done. By doing in this way, sampling processing is performed more accurately.

  If the present invention eliminates the need for dividing and assigning MPEG2-TS packets having a small packet size, such as DOCSIS 3.0, and only reducing packet transmission processing by directly assigning Ethernet (registered trademark) MAC packets to carriers. However, by setting the occupied bandwidth to 6 MHz or more, for example, 32 MHz, a high-speed packet signal that cannot be transmitted by DOCSIS 3.0 can be transmitted. In addition, by utilizing the available frequency band of the VHF band in the future, large-capacity IP packet signals can be provided at the same time as existing video / audio signals without changing the infrastructure, even in buildings where only coaxial wiring infrastructure is available. It becomes like this. As a result, the broadband environment advances and it is possible to easily develop attractive services.

FIG. 10 shows an example of the packet transmission system according to this embodiment. An example in which communication data signals and video / audio signals are provided via an optical access network is shown, and a packet signal can be transmitted even in a broadcast network using an RF carrier.
First, transmission / reception of packet signals provided via the communication network 101 will be described. For ease of explanation, a VOD (Video on Demand) service is taken as an example. A normal VOD service is provided in response to a request from a user's PC 55 via a communication network 101 such as the Internet from a provider's VOD server 51 connected to the Internet. On the other hand, the control packet signal from the user's PC 55 is input to the GE-ONU 53 which is a line terminating device for communication service via a LAN such as Ethernet (registered trademark) in the user's home, and passes through the WDM optical access network. Then, it enters a GE-OLT (Gigabit Ethernet (registered trademark) -Optical Line Terminal) 52 which is a station side transmission apparatus. Thereafter, the control packet signal reaches the VOD server 51 which is a provider facility via the communication network 101. On the contrary, the video / audio packet signal corresponding to the request for the control packet signal reaches the user's PC 55 via the communication network 101. The above is provided by the normal communication network 101. Conventionally, this method is also provided.

  Next, reception of a packet signal or the like provided via the broadcast network 102 will be described. Video / audio signals are received by antennas installed in HE (Head End) 66 facilities, and terrestrial digital television broadcasts and BS / CS broadcasts provided in the UHF band are pre-determined for each carrier in the 220-2100 MHz band. SCM is carried by the transmission device 67 on the frequency of the frequency and then transmitted via a broadcast network 102 such as a channel video / audio distribution network. These video / audio signals are input from the V-OLT 62 installed in the accommodation station via the WDM optical access network 103 to the V-ONU 63 which is a line terminating device of the broadcasting network 102 such as a multi-channel video distribution network. Is done. Since it is output from the V-ONU 63 to the coaxial cable, the video / audio signal is transmitted as it is on the infrastructure in the existing building, and reaches the conventional TV receiver 65 connected to the coaxial cable via the distributor 64. . Thereby, the terrestrial digital television broadcast and the BS / CS broadcast can be viewed on the TV receiver 65.

  On the other hand, a video / audio server 61 for packet distribution is connected to the HE 66. The packet signal from the video / audio server 61 is placed in the VHF band free frequency region by the method described so far in the transmission device 67 of the HE 66. Since the VHF band is used, the packet signal can be transmitted without any change to the conventional coaxial infrastructure. That is, the output by the coaxial cable from the V-ONU 63 is branched by the distributor 64 and input to the packet signal transmission device 70 in the VHF band. The packet signal transmission signal is demodulated by the receiving unit 30 of the packet signal transmission device 70, converted into an Ethernet (registered trademark) packet form by the IP packet multiplexing / SW unit 31, and output to the Ethernet (registered trademark) interface 50. The The packet signal output from the Ethernet (registered trademark) interface 50 is subjected to processing such as reception and reproduction of the packet signal by the TV receiver 71 corresponding to STB or Ethernet (registered trademark).

  As described above, for example, when a signal is transmitted by the 64QAM system, signal transmission of 700 Mbps or more is possible. Such high-speed signal transmission is not possible with DOCSIS 3.0. Therefore, the transmitted packet signal can be stored in the user's hard disk or the like, and the user can view it with a time shift. In the accumulation, unlike the case of recording the RF signal, a demodulator / recorder for the carrier for simultaneous recording becomes unnecessary. It is also possible to provide very high-definition video and audio signals of 120 Mbps or higher via the coaxial infrastructure using the VHF band data packet transmission method, and can be viewed if the STB 71 supports high-definition video and audio viewing. Become.

  In this way, communication such as VOD can be provided using the communication network 101, and broadcast-type data distribution targeting a large number of users at once can be provided using the packet transmission method of the present invention that can use the coaxial infrastructure as it is. Therefore, it is very advantageous for service development.

  FIG. 11 shows an example of wiring when the packet transmission method according to the present embodiment is used in an existing apartment house. An example in the case of receiving a signal by an Ethernet (registered trademark) packet of 100 Mbps or higher is shown. The communication system is provided from the optical access network by the GE-PON system, and the line is terminated by the GE-ONU 53. The terminated signal is connected to the VDSL modem installed in each house using the existing telephone line from the main unit 56 of the VDSL apparatus installed in the MDF room of the apartment house. As already mentioned, VDSL can only flow up to 100 Mbps. Therefore, packet signals of 100 Mbps or higher cannot be exchanged from the communication network.

  On the other hand, an RF signal is output from the V-ONU 63, which is a terminal device of a broadcasting network such as a multi-channel video / audio distribution network, through the coaxial interface 60. The coaxial interface 60 has a data signal superimposed on the VHF band from 90 to 220 MHz and a digital terrestrial television broadcast or BS / CS video superimposed on the VHF Super Hi / UHF to BS / CS band from 220 to 2100 MHz.・ Audio signal is flowing. Booster amplifiers and inline amplifiers are installed in the coaxial infrastructure in apartment buildings, but if an amplifier corresponding to this frequency band is installed, all of the above video and audio signals will travel on the coaxial infrastructure. Can be passed. The signal that has passed through the coaxial infrastructure is branched by the distributor 64 and reaches each door.

  Here, let us consider the usage forms classified into three as A, B, and C in FIG. A is a case where the STB 72 with the Ethernet (registered trademark) interface is connected to both the communication network and the broadcast network, and the output is connected to the conventional TV receiver 65. In this case, for example, a service such as VOD is provided via a communication network via VDSL.

  On the other hand, multi-channel video / audio signals based on Ethernet (registered trademark) packet signals are provided from a broadcast network via a coaxial infrastructure. Ordinary RF multi-channel video / audio signals are also input to the STB via the coaxial infrastructure and can be viewed on an existing TV receiver. Furthermore, very high-definition video / audio signals of 100 Mbps or more per channel are also provided as packet signals superimposed on the VHF band via the coaxial infrastructure, and can be viewed on a TV monitor if playback processing is performed on the STB.

  B shows a case where a TV receiver 71 with an Ethernet (registered trademark) interface is directly connected to a communication network such as a coaxial interface and VDSL. Since the STB function indicated by A is incorporated in the TV receiver, the viewing mode is equivalent to the case where the STB 72 function indicated by A is incorporated in the TV receiver 71, and thus the viewing mode is the same as A. .

  C is a case where an existing service is received, that is, a data signal up to 100 Mbps is received by a communication network via VDSL, and only a video / audio service is received by a broadcast network via a coaxial interface. is there. Since the user C cannot reproduce the data signal superimposed in the VHF band, only the multi-channel video / audio signals from VHF Super Hi / UHF to BS / CS are received. This is considered to correspond to the case immediately after the 2011 analog broadcasting is stopped.

  As described above, reception of new video / audio and data services including existing services can be realized without changing the existing infrastructure. In addition, it is possible to transmit high-speed signals that cannot be transmitted with DOCSIS 3.0.

  FIG. 12 shows an example of viewing video / audio content using the packet transmission method according to the present embodiment. FIG. 12A is a schematic diagram of a network when receiving the content service. (B) shows the flow of control signals and video / audio signals when viewing the VOD service among the video / audio content services, and (c) shows the multi-channel video / audio signals stored in the home server in the house in real time. This is a flow of switching between normal broadcast content viewing and stored video / audio viewing provided. As described above, the communication service is provided by the GE-PON system, and the multi-channel video / audio service and the packet distribution service are provided by the video / audio service using the broadcast network 102 of this system. Accordingly, as shown in FIG. 12A, the respective networks are terminated by the respective line termination devices, and are passed through the packet signal transmission device 70 to the home server 73 and the TV receiver 71 with an Ethernet (registered trademark) interface. It is connected.

  As shown in FIG. 12B, it is assumed that a viewing request for content 1 is transmitted from the TV receiver 71 corresponding to Ethernet (registered trademark) to the VOD server 51. Since the VOD server needs a conversation with the terminal device, it is more efficient to perform it via the communication network 101. The VOD server 51 transmits the content 1 in response to a request from the TV receiver 71. When performing trick play or the like with the TV receiver 71, the control signal packet is transmitted to the VOD server 51 via the communication network 101. In accordance with the request signal, the VOD server transmits a video / audio signal of the location where trick play of the content 1 is performed. After that, when a content 1 viewing stop request is transmitted from the TV receiver 71, the transmission of the content 1 from the VOD server ends.

  On the other hand, FIG. 12C shows a case where content is distributed using a packet signal in the VHF band. Regardless of whether the user views the TV receiver 71 or not, video / audio content is always stored in the home server 73. Storage in units of video / audio contents is possible, but here, an example of storage in units of channels (carrier units) is shown. When a user makes a channel A viewing request to the home server 73 from a TV receiver 71 corresponding to Ethernet (registered trademark), the content of the channel A stored in the home server 73 is distributed from the home server 73. A request to stop viewing channel A is also sent to the home server 73.

  Next, it is assumed that the user makes a viewing request for the channel α distributed in real time through a remote controller or the like. Since all channels distributed in real time are distributed to the TV receiver 71 compatible with Ethernet (registered trademark), only the carrier on which the channel α to be viewed on the TV receiver 71 side is superimposed is selected by the tuner. Then, it can be viewed by performing the reproduction process. If you want to view the stored video / sound of the home server 73 during viewing, you can select the video / sound of the home server 73 from the TV receiver 71, or if you want to watch VOD, from the TV receiver 71 to the communication network 101. Enter and access the VOD server 51 of the provider.

  In this way, it is possible not only to receive different services seamlessly from the TV receiver 71, but also to provide these services without changing the existing coaxial infrastructure and communication infrastructure. In addition, since the signal transmission speed for accumulation becomes a large speed of 120 Mbps or more by setting the carrier occupied bandwidth to 6 MHz or more, for example, 32 MHz or 64 MHz, accumulation is performed in a shorter time than that using DOCSIS 3.0. This also improves the convenience of reducing stress on the waiting time of the user.

  The present invention can be used for an IP packet distribution service using an RF multi-channel video / audio distribution network.

It is a block diagram which shows a protocol stack typically, (a) shows an example of a DOCSIS system, (b) shows an example of the packet transmission system of this invention. It is an example of channel allocation of the VHF band necessary for the packet transmission system according to the present invention, where (a) is an occupied bandwidth per carrier of 32 MHz, and (b) is an occupied bandwidth per carrier of 64 MHz. Show the case. It is a schematic structure figure showing an example of a packet transmission system concerning this embodiment. It is a schematic block diagram which shows an example of a transmission part in case an input signal is 1000Base-X. It is a schematic block diagram which shows an example of a transmission part in case an input signal is 1000Base-T. It is a structural example of RF processing part. It is a schematic block diagram which shows an example of the process from the demodulation part 22 to the packet process part 25 in case an output signal is 1000Base-X. It is a schematic block diagram which shows an example of the process from the demodulation part 22 to the packet process part 25 in case an output signal is 1000Base-T. 3 is a schematic diagram showing a demodulator 23 in the receiver 30 in some detail. FIG. The Example of the packet transmission system which concerns on this embodiment is shown. It is an example of wiring at the time of using the packet transmission system of this invention in the existing apartment house. An example in the case of viewing video / audio content using the packet transmission method according to the present embodiment is shown, (a) is a schematic diagram of a network when receiving the content service, (b) is a video / audio content. This is a flow of control signals and video / audio signals when viewing a VOD service among audio content services, and (c) is a normal broadcast in which multi-channel video / audio signals are stored in a home server in the house and provided in real time. This is a flow of switching between content viewing and stored video / audio viewing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transmission part 11 Packet processing part 11-1 Physical layer processing part 11-2 S / P part 11-3 MAC layer processing part 11-4 MAC data allocation part 12 Modulation part 12-1 Error correction encoding part 12-2 S / P section 12-3 Digital modulation section 12-4 Conversion table 13 RF processing section 13-1 Oscillator 13-2 Multiplier 13-3 Bandpass filter 13-4 Amplifier 14 RF signal multiplexing section 15 Video / audio signal modulation section 16 RF Processing unit 17 FM batch transmission unit 21 FM batch reception unit 22 RF signal separation unit 23 Demodulation unit 23-1 BP signal processing unit 23-11 BPF
23-12 LPF
23-13 AMP
23-14 EQ
23-15 AD Converter 23-16 Nyquist Filter 23-17 AFC Loop Filter 23-18 Oscillator 23-2 Phase Rotation Control Unit 23-21 Phase Rotation Control Circuit 23-22 EQ
23-23 Clock recovery circuit 23-24 Phase error detection circuit 23-25 APC loop filter 23-26 Numerically controlled oscillation circuit 23-27 AGC
23-28 π / 2 phase shifter 23-29 oscillator 23-3 digital demodulation unit 23-4 conversion table 23-5 P / S unit 23-6 error correction code decoding unit 24 inter-carrier skew adjustment unit 25 packet processing unit 25 -1 MAC data allocation unit 25-2 MAC layer processing unit 25-3 P / S unit 25-4 physical layer processing unit 26 tuner 27 video / audio signal demodulation unit 30 receiving unit 31 IP packet multiplexing / SW unit 50 Ethernet (registration) Trademark) Interface 51 VOD Server 52 GE-OLT
53 GE-ONU
54 HUB
55 PC
56 Base unit of VDSL device 60 Coaxial interface 61 Video / audio server 62 V-OLT
63 V-ONU
64 Distributor 65 TV (Television) receiver 66 HE
67 Transmitter 68 AV-IF
69 Hearing apparatus 70 Packet signal transmission apparatus 71 TV receiver compatible with Ethernet (registered trademark) 72 STB
73 Home Server 101 Communication Network 102 Broadcast Network 103 Optical Access Network

Claims (7)

An RF (Radio Frequency) signal having an occupied bandwidth of 6 MHz or more in which a data signal packetized on the frequency axis of the VHF (Very High Frequency) band is subjected to SCM (Subcarrier Multiplexing) and a frequency band higher than the VHF band exists. A transmission unit that multiplexes the video / audio broadcast signal with the RF signal, converts the FM signal, and transmits it;
Receiving a signal from the transmission unit as an FM batch conversion signal, separating the RF signal, and receiving the RF signal and the video / audio broadcast signal;
A packet transmission system comprising:
The transmitter is
A packet processing unit for packetizing the data signal;
A modulation unit that divides and modulates a signal from the packet processing unit for each carrier frequency to be loaded later;
An RF processing unit for placing a signal from the modulation unit on each carrier frequency;
An RF signal multiplexing unit that frequency-multiplexes signals from the RF processing unit,
The receiver is
An RF signal separator for separating the frequency-multiplexed signal of the RF signal multiplexer for each carrier frequency;
A demodulator that demodulates the signal from the RF signal separator for each carrier frequency;
An inter-carrier skew adjustment unit that performs skew adjustment between signals from each of the demodulation units;
A packet processing unit for reproducing a packet of a signal from the inter-carrier skew adjustment unit;
With
The packet processor of the transmitter is
A physical layer processing unit for performing physical layer processing in packetization of the data signal;
A MAC layer processing unit that performs MAC (Media Access Control) layer processing in packetization on the signal from the physical layer processing unit;
A MAC data allocation unit that allocates a signal from the MAC layer processing unit to a predetermined carrier frequency;
A packet transmission system comprising: The modulator is
An error correction code unit for encoding a signal from the packet processing unit with an error correction code;
A digital modulation unit that digitally modulates a signal from the error correction code unit according to a conversion table that defines a correspondence between the symbol and the modulation data;
The packet transmission system according to claim 1 , further comprising: The RF processing unit
A multiplier for placing a signal from the modulation unit on a carrier wave of a carrier frequency;
A bandpass filter that passes a carrier of the carrier frequency among signals from the multiplier;
An amplifier that amplifies the signal from the bandpass filter to a voltage level required for RF output;
The packet transmission system according to claim 1, further comprising: An RF (Radio Frequency) signal having an occupied bandwidth of 6 MHz or more in which a data signal packetized on the frequency axis of the VHF (Very High Frequency) band is subjected to SCM (Subcarrier Multiplexing) and a frequency band higher than the VHF band exists. A transmission unit that multiplexes the video / audio broadcast signal with the RF signal, converts the FM signal, and transmits it;
Receiving a signal from the transmission unit as an FM batch conversion signal, separating the RF signal, and receiving the RF signal and the video / audio broadcast signal;
A packet transmission system comprising:
The transmitter is
A packet processing unit for packetizing the data signal;
A modulation unit that divides and modulates a signal from the packet processing unit for each carrier frequency to be loaded later;
An RF processing unit for placing a signal from the modulation unit on each carrier frequency;
An RF signal multiplexing unit that frequency-multiplexes signals from the RF processing unit,
The receiver is
An RF signal separator for separating the frequency-multiplexed signal of the RF signal multiplexer for each carrier frequency;
A demodulator that demodulates the signal from the RF signal separator for each carrier frequency;
An inter-carrier skew adjustment unit that performs skew adjustment between signals from each of the demodulation units;
A packet processing unit for reproducing a packet of a signal from the inter-carrier skew adjustment unit;
With
The packet processor of the receiver is
A MAC data allocating unit that reproduces a signal from the inter-carrier skew adjusting unit into one original data signal;
A MAC layer processing unit that performs processing in the MAC layer of a signal from the MAC data allocation unit;
A physical layer processing unit that performs processing in a physical layer of a signal from the MAC layer processing unit;
A packet transmission system comprising: The demodulator
A BP (Bandpass) signal processing unit that performs bandpass processing at a carrier frequency of the signal from the RF signal separation unit;
A phase rotation control unit that performs phase rotation control of a signal from the BP signal processing unit;
A digital demodulator that digitally demodulates the signal from the phase rotation controller in accordance with a conversion table that defines the correspondence between the symbol and the demodulated data;
An error correction code decoding unit for decoding the error correction code encoded in the signal from the digital modulation unit;
The packet transmission system according to claim 4 , further comprising: The BP signal processor is
A band-pass filter that passes only a signal of a predetermined carrier frequency;
A local oscillator that down-converts the signal from the bandpass filter to an IF (Intermediate Frequency) frequency;
A low-pass filter for removing unnecessary high-frequency components from the signal down-converted by the local oscillator;
An equalizer for smoothing the signal from the low-pass filter;
An AD (Analog to Digital) converter that converts a signal from the equalizer into a digital signal;
A Nyquist filter that suppresses signal components in a frequency band larger than half of the Nyquist frequency among signals from the AD converter;
The packet transmission system according to claim 5 , further comprising: The phase rotation controller is
A phase rotation control circuit for performing phase rotation control of a signal from the BP signal processing unit;
An equalizer for smoothing a signal from the phase rotation control circuit;
A phase error detection circuit for detecting a phase error of a signal from the equalizer;
An APC (Automatic Phase Control) loop filter that outputs the phase error detected by the phase error detection circuit;
A numerically controlled oscillation circuit that performs phase rotation control of a signal from the BP signal processing unit based on a phase error from the APC loop filter;
A clock recovery circuit for recovering a clock signal based on the signal from the phase rotation control circuit;
An oscillation circuit that oscillates a clock based on a signal from the clock recovery circuit;
An AGC (Automatic Gain Control) circuit that increases or decreases the amplification factor of the signal from the low-pass filter in the BP signal processing unit based on the signal amplitude from the phase rotation control circuit;
The packet transmission system according to claim 6 , further comprising:

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