JPH04196792A - Catv subscriber system transmission method - Google Patents

Abstract

PURPOSE:To simplify a configuration by receiving only a signal of a channel having a reception request and applying frequency multiplex between an incoming signal being a reception request from each subscriber to an off-premise device and an outgoing signal being an information signal from the off-premise device to each subscriber device. CONSTITUTION:A reception section 15 of an off-premise device 10 receiving incoming signal frequency bands f01-f0n receives an incoming signal from a subscriber device 30-1 as a signal of the frequency f01 and a control section 17 sends a control signal 19-1 to a demodulation section 11-1, which is controlled. The demodulation section 11-1 tunes with a signal of a channel subject to reception request by the subscriber device 30-1 and demodulates the signal and outputs the result to a modulation section 13-1. The modulation section 13-1 modulates the signal of a channel subject to reception request by the subscriber device 30-1 by using a frequency f1, an output of the modulation section 13-1 is subjected to frequency multiplex at a multiplexer section 14 together with outputs of other modulation sections 13-2 to 13-N, and the result is sent to a transmission line 20 as an outgoing signal and received by the subscriber device 30-1. Thus, the configuration is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a CATV subscriber transmission method, particularly to frequency multiplexing transmission.

Conventional technology The conventional subscriber transmission method for CATV is
For example, there is a method using off-premises equipment as shown in the block diagram in Figure 5. What is off-premises equipment?
This is a device that implements the function of a receiving converter used in CATV for fishing boats outdoors.It is a device that selects the signal of the channel that has been requested to be received and transmits only the signal of that channel indoors. This technology has been adopted as an effective means to prevent this, and there are two types of off-premises equipment: one off-premises device that handles one subscriber, and one off-premises equipment that handles multiple subscribers (in the present invention). The target is the latter off-premise equipment. In Figure 5, 2 is an all-channel signal 40 in which all the signals sent from the CATV center station are multiplexed.
is an off-premise group [60-1 to 60-N are N subscriber devices (N is an integer) connected to the off-premise device 40 @ 50-1 to 50-N are the subscriber devices from the off-premise device 40 Downlink signals u to 60-1 to 60-N 55-1 to 55-N are the subscriber devices 60-1 to 60-N.
FIG. 6 is a block diagram of the off-premises device 40 shown to explain the functions of the off-premises device 40 in more detail. In Fig. 6, numeral 11 is a demodulator that demultiplexes all channel signals 2 and demodulates them into signals for each channel, and the output signal formats are baseband, AM, FM,
12 selects N channel signals from the output of the demodulator 11, allowing overlap, and outputs the selectors 41-1 to 41-N, which output the selected signals ( It is a transmitting unit for transmitting downlink signals 50-1 to 5O-N), and when the output signal form of the selection unit 12 and the signal form receivable by the subscriber devices 60-1 to 60-N are different, It also performs signal conversion. 42-1 to 42-N
is a reception K that receives the upstream signals 55-1 to 55-N.
Reference numeral 16 designates the selection unit 12 so that the signal of the channel requested by each subscriber unit can be transmitted to the subscriber unit 60-1 to 60-N by the signal from the reception unit 42-1 to 42-N. In the conventional CATV subscriber system transmission method configured as described above, in which the control unit controls the connection relationship between the In the off-premises device 40, the receiving section 42-1 receives the upstream signal 55-1 and transmits the information to the control section 16.
The control section 16 controls the selection section 12 based on the control section 16.
When the selection unit 12 receives the signal from the control unit 16, it selects the signal of the channel that the subscriber device 60-1 requests to receive from among the demodulated signals of all channels.
Output to the transmitter 41-1 The transmitter 41-1! :
& The channel that the subscriber device 60-1 requests to receive.
The operation is explained for the case of the subscriber apparatus 60-1, and the same is true for other subscriber apparatuses. However, in the case of the above configuration, in order to connect the off-premise device 40 and each subscriber device 60-1 to 69-N, two independent cables are required. Transmission volume total 2N
A real transmission line is required, and off-premise equipment 40
requires N transmitting units 41-1 to 41-N, and the demodulating unit must demodulate all channel signals from all channel signals 2, regardless of whether they are necessary or not (~ In the case of the conventional example, the structure was complicated, but the present invention was made in view of this point, and handles only the signals of the necessary channels (＼ Also, each subscriber It is an object of the present invention to provide a CATV subscriber system transmission method that can allocate downlink signals and uplink signals to equipment by frequency multiplexing and connect off-premise equipment and all subscriber equipment with a single transmission path. Means for solving the problem Table 4 of the present invention In response to a request to receive a channel as an uplink signal from each subscriber device, the signals of those channels are selected from among the signals of all the channels, and the signals of those channels are sent down to each subscriber device. It consists of an off-premises device that transmits signals, and a plurality of subscriber devices connected to the off-premises device through a single bus-type transmission line, and each subscriber device uses a different frequency band for upstream and downstream signals. The present invention is a CATV subscriber-based transmission method characterized by assigning By frequency multiplexing the upstream signal, which is a reception request to the device, and the downlink signal, which is the information signal from the off-premises device to each subscriber device, the off-premises device and all the subscribers can be connected to each other through one transmission path. Devices can be connected.

Embodiment FIG. 1 is a block diagram showing the configuration for realizing the CATV subscriber system transmission method in the first embodiment of the present invention. In FIG. 1, 1 indicates all signals sent from the CATV center station. 10 is off-blemise equipment! 20 is transmission i
30-1 to 30-N are N subscriber devices connected to the off-premise device 10 via the transmission line 20. 4 FIG. 2 is shown to explain the functions of the off-premise device 10 in more detail. 4 is a block diagram of the off-premises device 10. In FIG. 2, 11-1 to 11-N are demodulators that tune and extract and demodulate the signal of one designated channel among all the channel signals 1; The output signal form is a baseband or intermediate frequency signal, and 4 13-1 to 13-N are signals selected to be transmitted to each subscriber device, that is, the demodulators 11-1 to 11-
It is a modulation section that modulates the outputs of N for frequency multiplexing, and the signal format of the output of the demodulation sections 11-1 to 11-N and the signal format that can be received by the subscriber devices 60-1 to 60-N are If different, the signal conversion is also performed. 14 frequency-multiplexes the outputs of the modulation units 13-1 to 13-N to form a transmission line 20.
The multiplexer 15 that outputs to the subscriber devices 30-1 to 30
-N receives the upstream signal from the subscriber devices 30-1 to 30-N in response to the signal from the receiver 15.
-N is a control unit that controls the tuning state of the demodulation units 11-1 to 11-N so that the signal of the channel that each subscriber device requests to receive can be transmitted to N, and 19-1 to 19-N are respectively FIG. 3 shows the frequency spectrum of the signal on the transmission line 20, and 4f+ to fx are the control signals output from the control unit 17 for controlling the demodulation units 11-1 to 11-N. Each subscriber device 30-1 to 30
The frequencies fs+ to fs+i for downlink signals (from the off-premise device to the subscriber device) respectively assigned to the subscriber devices 30-1 to 30-N are respectively assigned to the upstream signals (from the subscriber device to the off-premise device The condition for these signals is that they are frequency multiplexed, and it does not depend on how the signals of each frequency are modulated.
3-N will output modulated signals in the frequency bands assigned to each. On the other hand, each subscriber device 30-1 to 30-N transmits and receives only signals in the frequency band assigned to itself.As for uplink signals, the occupation time is short and it is not necessarily necessary to assign a fixed frequency; A multi-channel access method that dynamically allocates frequencies depending on the frequency may also be used (-The operation of this embodiment configured as described above will be explained below.) , the uplink signal for the reception request is sent to the off-premise device 10 via the transmission path 20 using the assigned frequency f@t. f1
~f@- (receives the upstream signal from the subscriber device 30-1 as a signal of the frequency f-1, transmits the information to the control unit 17, and the control unit 17 Based on this, the control signal 19-1 is sent to the demodulation section 11-1 for control.When the demodulation section 11-1 receives the control signal 19-1 from the control section 17, the all-channel signal 1 Among the subscriber devices 30-
The modulating section 13-1 tunes and demodulates the signal of the channel that 1 is requesting to receive and outputs it to the modulating section 13-1 in the form of a baseband signal or intermediate frequency signal.
i;L The signal of the channel that the subscriber device 30-1 requests to receive is modulated using the frequency f+ assigned to the subscriber device 30-1.4 The output of the modulator 13-1 is It is frequency-multiplexed in the multiplexer 14 together with the outputs of the other modulators 13-2 to 13-N, is transmitted to the transmission path 20 as a downlink signal, and is received by the subscriber device 30-1. The subscriber device 30-1 selects a channel and is unable to receive the desired signal. The case of off-premise equipment 1 is exactly the same as described above.
0, the signal of a desired channel is once demodulated from the all-channel signal 1, and then modulated.

Any combination of FM, FSX, PSK, etc. can be realized.Also, with the above configuration, if the human output signal is a general AM-FDM signal, a TV tuner can be used as the demodulator and a TV modulator can be used as the modulator. FIG. 4 is a block diagram of an off-premises device according to a second embodiment of the present invention.The overall configuration is the same as that in FIG. Although it has the same function as the off-premises device 10 in FIG. 1, the same number in FIGS. 2 and 4 represents the same function. In FIG. 4, 18-1 to 18-N are conversion units that extract the signal of one specified channel from all the channel signals 1 and convert the frequency to the frequency assigned to each. It is.

The operation of this embodiment configured as above will be described below.

For example, when the subscriber device 30-1 wants to receive a signal on a certain channel, the transmission path 20-1 uses the frequency f.
In the off-premise device 100, the receiving unit 15 receiving the uplink signal frequency bands f1 to fax receives the uplink signal from the subscriber device 30-1. It receives the signal of the frequency f1 and transmits the information to the control section 17, and the control section 17 receives the control signal 1 based on the information.
9-1 to the conversion section 18-1 for control.The conversion section 18-1 receives the control signal 19 from the control section 17.
-1, the subscriber device 30-1 tunes to the signal of the channel that the subscriber device 30-1 requests to receive from among all the channel signals 1, and the frequency of that signal is assigned to the subscriber device 30-1. Specifically, a sine wave signal having a frequency that is the difference between the frequency of the signal of the desired channel and the assigned frequency f+ is mixed with the all-channel signal 1 by a mixer, and its output is converted to the frequency f1. The above conversion function can be realized by extracting a signal from the frequency f1 using a bandpass filter set to the frequency f1, which is a so-called down-conversion or up-conversion function. In this case, the function of the control section 17 is to control the frequency of the sine wave.
The output of -1 is frequency-multiplexed with the outputs of the other converters 18-2 to 18-N in the multiplexer 14, and is transmitted to the transmission path 20 as a downlink signal to the subscriber device 3.
In this way, the subscriber device 30-1 selects a channel and is unable to receive the desired signal. The operation of the force fork whose operation was explained is exactly the same for other subscriber equipment.

As described above, according to this embodiment (L off-blemish device 1
In 00, only the frequency conversion of the signal is performed, so the configuration is simple, and there is almost no signal deterioration due to complicated signal processing.
It is assumed that the modulation method between the input and output signals is the same.

In the configuration of the present invention, it is important to be able to multiplex signals corresponding to uplink signals as part of downlink signals.
Full-duplex transmission like telephone is also possible.

As described in detail, the present invention has the advantage that the overall configuration is simplified because the off-premise device receives and handles only the signals of the channels that are requested to receive.
Ma? = By frequency multiplexing the upstream signal, which is a reception request from each subscriber device to the off-premises device, and the downlink signal, which is the information signal from the off-premises device to each subscriber device, the off-premises device and everything connected to it are subscriber equipment can be connected with one transmission path, shortening the overall transmission path length, and only one transmitter is required on the off-premises equipment side (~ Also, bidirectional signals can be frequency multiplexed) Therefore, it is easy to add subscriber equipment as long as there is enough frequency band, and there are no restrictions on the location where it can be connected to the transmission line. It is also possible to use a commercially available receiver as is, and its practical effectiveness is very low.

[Brief explanation of the drawing]

FIG. 1 is a CA of the first and second embodiments of the present invention.
FIG. 2 is a block diagram showing the configuration for realizing the TV subscriber system transmission method. FIG. 3 is a block diagram of the off-premise equipment in the first embodiment. FIG. FIG. 4 is a block diagram of an off-premise device in the second embodiment. FIG. 5 is a block diagram showing a configuration for realizing a conventional CATV subscriber transmission method. FIG. 6 is a block diagram of a conventional off-premise device. a 1.2...All channel signals q 10,100...
・Off-blemise family fi, 11...Demodulation ff1L
111 to 11-N...Demodulation star 12...Selection 13-1 to 13-N...Modulation B, 14...
・Multiplex unit 15... Reception 16.17... Control unit 18-1 to 18-N... Conversion @ 19-1
~19-N...Control signal 20...Transmission line 30
-1 to 30-N...Subscriber equipment 40...Off-premises group @ 501 to 50-N...Downlink signal
55-1 to 55-N...Uplink signal q 60-1 to 6
0-N...Subscriber equipment 41-1 to 41-N...
Sending clothes 42-1 to 42-N... Name of the receiving agent Patent attorney Akira Kokaji and two others Figure 1 30-1 30-z 30-s:
to-N Fig. 2 [Fig. 3 14 Fig. QQ / Fig. 5 6θ-2

Claims (2)

[Claims] (1) A signal in which signals of multiple channels are frequency multiplexed (
The FDM signal (hereinafter referred to as FDM signal) is received from the center station, and the FD
an off-premises device that selects the signal of the requested channel from among the M signals and transmits it to each of the subscriber devices; and a plurality of subscribers connected to the off-premises device by one bus-type transmission path. CAT consisting of
In the V subscriber system, different frequency bands for downlink signals are fixedly assigned to all of the connected subscriber devices, and the off-premise device uses tuning and demodulation functions to select the received FDM signal from among the FDM signals. Select each requested channel signal in the form of a baseband signal or intermediate frequency signal, modulate and frequency multiplex the selected channel signal with the frequency band assigned to each, and issue a reception request. transmitting the signal to the subscriber device as a downlink signal to the transmission path, while each subscriber device receives the signal of the channel it has requested to receive by receiving the signal of the frequency band assigned to each subscriber device; Further, each of the subscriber devices transmits a channel reception request signal to the off-premises device via the transmission path, using an uplink signal frequency band that is fixed or assigned to each subscriber device as necessary. A CATV subscriber system transmission method, characterized in that the device receives a channel reception request signal by receiving signals in all frequency bands for uplink signals. (2) A signal in which signals of multiple channels are frequency multiplexed (
The FDM signal (hereinafter referred to as FDM signal) is received from the center station, and the FDM
an off-premises device that selects the signal of the requested channel from among the signals and transmits it to each of the subscriber devices; and a plurality of subscribers connected to the off-premises device by one bus-type transmission path. CATV consisting of equipment
In the subscriber system, different downlink signal frequency bands are fixedly assigned to all of the connected subscriber devices, and the off-premise device receives the signal of the requested channel from among the FDM signals. selectively up-convert or down-convert to the frequency band assigned to each subscriber device, then frequency multiplex and transmit it to the transmission path as a downstream signal to the subscriber device that has issued a reception request, On the other hand, each subscriber device receives the signal of the channel it has requested to receive by receiving the signal of the frequency band assigned to each subscriber device, and each subscriber device receives the signal of the channel that it has requested to receive. A channel reception request signal is transmitted to the off-premises device via the transmission path using the frequency band for uplink signals allocated according to the frequency band, and the off-premises device receives the signals of all the frequency bands for uplink signals. 1. A CATV subscriber system transmission method, characterized in that a channel reception request signal is received by doing so.