Cable television system or similar communication system

FIELD: cable television.

SUBSTANCE: system is made with possible reversed transfer of signals to local networks, included in system, back to main station of system in preset range of carrying frequencies, system has means for controlling interference, which include detection means, which are made with possible comparison of signals power level to one preset control level, and with possible generation of logic signals, memory devices, and also means in main station of system, using which information stored in memory means of local networks can be queried for transfer to main station for estimating this information at main station.

EFFECT: higher efficiency, broader functional capabilities.

10 cl, 3 dwg

 

The present invention relates to a cable television system or other similar communication system.

More specifically the invention relates to such a system of this type, which allows the transmission of signals in the reverse direction from local networks are included in the system, the head station of the specified system within a predetermined range of the carrier frequencies used for transmitting signals in a specified direction, and which includes control means interference in the system within a specified range of carrier frequencies.

Cable TV systems of this type are designed not only to distribute television signals and radio signals from the head-end station system to the subscribers connected to different local networks, but also for the bidirectional transmission of signals between subscribers and head station system.

In such cable television systems in the band of carrier frequencies used for transmitting signals in the opposite direction, there may be strong interference due to noise penetrating into the local network via the subscriber conclusions or lines associated with these conclusions, and cumulative with successive passage of signals through the system to the head-end station. That's why it was proposed to provide a system of this type special the remedies control interference occur within a specified band of frequencies.

In known systems, this control is based, or accuracy of measurement in the headend of the amplitudes and frequencies of all signals within the range of carrier frequencies coming into the head-end station or on the measurement of the amplitudes of the signals appearing within some specified time intervals by sampling. In practice, however, both alternatives are unsatisfactory and do not allow an easy way to define the local network, which is the source of the interference in the specified frequency range.

Therefore, the aim of the invention is to provide an improved communication system, initially designed to facilitate the detection of interference occurring within the frequency range return path, as well as to identify the local network from which the interference received.

According to the invention the system is proposed to achieve this goal, is distinguished primarily by the fact that these controls include interference detection means, installed in each local network that compare the power level of signals appearing within a specified range of carrier frequencies, at least one predetermined reference level and based on this comparison, generates logic signals, and remember what e means, located within each local network and are used to remember information about the time intervals during which the specified power level exceeds the reference level, based on the values of these logical signals at different points in time.

The invention makes it possible to continuously detect within each local network signals frequency range return path, which appear in this network and have a power level above the reference level, and to remember information corresponding to the nature of these signals, for subsequent evaluation, if required. As a result, when there is interference within the specified frequency range, it is easier to identify the local network from which come these obstacles.

In order from the head-end station system to determine which local network receives interference control interference may also contain any of the funds in the head-end station system by which the information stored in said storage means of local networks may be requested to transmit to the head station to the evaluation of this information in the head-end station.

These storage means may store the information about the specified time intervals in the form of information about the starting point and the length of each is a separate interval.

To reduce the total amount of information that must be stored in these storage media, these tools can be made with the possibility, at least for some periods of time, to store information about these time intervals in the form of statistical data relating to the number of such intervals occurring during the specified periods of time.

The specified reference level, which must be below the lowest level of the message signal transmitted to the head station of the system may be made adjustable, preferably under the control of the headend system. In this case, these storage means may be configured to store information of the specified reference level.

For receiving and storing information about the slope of the leading edge of the signals appearing within the specified range of carrier frequencies, these detection means may be configured to compare the power level of these signals at least two different reference levels.

For very careful control system specified detection can be made with the possibility of exercising comparison and produce logic signals depending on the result of this CPA is the means separately for each of the many different areas of the specified frequency range, and storage means may be configured to store information derived from the analysis of the logical signals, separately for each of these areas.

In this case, each local network can include multiple bandpass filters that divide the specified range of the carrier frequencies for the appropriate number of sub-bands and corresponding number of detection means, each of which serves for comparison of the signals appearing within one of these sub-bands, with a control level or levels, respectively.

Additionally, alternative, each local network can contain one band-pass filter having a predetermined bandwidth, which is only part of the full width of the specified range of carrier frequencies, and the only means of detecting, United with the specified filter; in this case the frequency spectrum range of the carrier frequencies can be controlled manner shifted relative to the bandwidth of the band pass filter, resulting in within the specified bandwidth of the filter are different areas of the range of carrier frequencies.

In the latter case can cycle to view different areas of the range of carrier frequencies cyclically placing them within the bandwidth of the passband of the filter.

P is compared using a set of bandpass filters and a corresponding set of detection using a single bandpass filter and some means of detection, and means for the controlled displacement of the frequency spectrum range of the carrier frequencies can reduce the cost of the equipment required for each local network, and at the same time to divide the considered range of carrier frequencies to a greater number of areas of smaller size.

Below the invention is described with reference to the drawings, where:

figure 1 is a schematic diagram of the local cable television network, a component part of the CATV system made according to one example implementation of the present invention and containing a number of such local networks

figure 2 shows the structural diagram of the control unit included in the specified local network and forming part of the equipment for control of this system in respect of noise transmitted in the opposite direction from different local networks, and

figure 3 shows a block diagram of the control unit, is performed according to alternative implementation of the present invention.

The cable network, shown in figure 1 and indicated generally by item 10, represents the local network, forming part of the CATV system, which contains the parent station 11, performing the functions of the communication node with which the network 10 is connected through a schematically shows a regional network 12 and Magistral the ing network 13, in the last of which is the parent station 11.

The network 10 includes multiple branches 14 which through a bi-directional amplifier 16 and diplexing filter 17 connected with the joint input/output 15 network 10, which, in turn, connected to the network 12. In each leg 14 has a variety of subscriber outlet boxes 18, each of which contains three different conclusion: conclusion 19 for connecting the TV antenna, the output 20 to connect the antenna 20 of radio and conclusion 21 for connecting the target device data.

In the illustrated television system to transmit different types of signals in different directions between the parent station 11 and outlet boxes 18 are used, in a known manner, the various strips of the carrier frequencies. Below, it is assumed that the system uses the first lower band b1 of the carrier frequencies, for example 15-65 MHz for transmission of data signals in the opposite direction, i.e. to transmit data signals from the terminals 22 of the data connected with the pins 21, the parent station 11; the second, higher frequency, the bandwidth b2 of the carrier frequencies, for example 120-127 MHz for transmission of data signals in a forward direction, i.e. from the headend 11 to target devices 22 data; and two lanes of b3 and b4 of the carrier frequencies, for example 88-108 and 130-860 MHz respectively teleperedachi signals radio and television signals from the headend to the subscriber conclusions.

To control network 10 in relation to the noise within the bandwidth b1 of the carrier frequencies, that is, within a band of carrier frequencies used for transmission of data signals in the opposite direction, from the local network to the network 12 through the combined inlet and outlet 15, the network 10 has a special unit 23 of the control of noise, the construction of which is shown in more detail in figure 2.

The input 24 of the unit 23 is connected with diplexer filter 17 and is designed to receive signals within a strip S of the carrier frequencies received in the specified filter from lines 14. Unit 23 contains a line 25, which is one of its end connected to the input 24 and contains a control circuit 26 of the lock. From line 25 of the signals received at input 24, if they are allowed to pass through the circuit 26 of the lock, can be transferred to the output 27 of the block 23 connected to the filter 17, then through the specified filter and amplifier 16 to go in the opposite direction to the output 15 of the network 10 and then to the parent station 11.

Figure 2 positions 28, 29, 30 and 31 are four bandpass filter connected to the input 24, which are different from each other bandwidth that follow one another, and are designed to separate the signals received through the inlet 24 into four sub-bands, and together these filters cover the entire band b1 frequency. In addition, positions 32, 33, 34 and 35 indicated four sensors, each of Kotor is x connected to the output of one of these filters and is designed to compare the power level of the output signal, coming from the matching filter, at least one predetermined reference level and for supplying logic signals depending on the result of this comparison, in block 36.

The unit 36 includes a storage means for storing, separately for each of these sub-bands, information about the time intervals during which the specified power level exceeds the reference level; this information is based on the values of the specified logical signal at different points in time. For the formation of the reference levels and submit them to the various sensors include a generator 37 reference level.

Unit 36, which may contain a processor for processing the incoming logic signals can store in its memory the information about the specified time intervals in the form of information about the starting point and the length of each of these intervals. However, the block 36 may also be configured to store said information in any other form, preferably in the form of statistical data relating to the number of time intervals of the aforementioned type that occur during certain periods of time. Using tools available in the parent station 11, the information stored in the block 36 at any desired time can be isplace the a and transferred to the head station for further analysis. These means may include the computer 11', which is located at the head-end station and with the help of which you can give a request for transmission of information in the head-end station, as well as to carry out its analysis.

In addition, the block 36 may serve as a control block diagram 26 of the lock. As described in the patent application Sweden No. 99 04589-0, unit 36 may be configured to determine whether the received logical signals to certain conditions, pre-recorded in the specified block, and with the possibility feed line 42, shown dash-dotted in scheme 26 lock control signal to stop transmission of signals through the specified schema from the inlet 24 to the outlet 27 only when the logic signals received at block 36, satisfy the specified conditions. In this case, the block 23 plays a role of block noise reduction, built-in local network.

The width of the bandwidth of the bandpass filters 32-35 in the preferred case, can be chosen such that expected on the basis of the available experience, the level of interference power for different bandwidths would be approximately the same. This means that the filters that allow lower frequencies, typically will have a lower bandwidth than the filters that allow the higher frequencies.

In order from the head-end station 11 was odat request for delivery information stored in the block 36, to reprogram the processor contained in this block, set the value of the reference level generated by the generator 37, or make a temporary mandatory locking or temporary closed transmission path of signals through the circuit 26 of the lock, a demodulator 38, in which the head-end station 11 can be submitted control commands transmitted in the band b2 frequencies through the inlet 39 connected to the connecting line between the amplifier 16 and diplexer filter 17, and through the band-pass filter 40 connected to this input. From block 36, the information stored in this block may be transferred to the output 27 by means of the modulator 43, in which this information is modulated carrier, the frequency of which may lie between the two frequency bands b1 and b2.

The work discussed above block 23 noise reduction can be generally described as follows. Using four filters 28-31 signal band b1 entering the block noise reduction through the inlet 24, is divided into four different sub-bands. Part of the signal that falls within a respective subrange, enters the sensor 32, 33, 34 or 35, respectively, connected with the corresponding filter. The sensor compares the power level of the received signal with at least one reference level and gives an output of logic is ignal, depending on the result of this comparison, in block 36. In the processor, available in block 36, the logic signals coming from different sensors are required processing to obtain the desired information, which is then stored in memory available in the specified block.

When the headend 11 through the inlet 39, the filter 40 and the demodulator 38 in block 36 receives a corresponding control command, the above information may be transmitted to the host station through the modulator 43 and the outlet 27. In the head-end station incoming information can then be evaluated to determine any required parameters. If this evaluation shows that the network 10 generates unacceptably large interference, you may submit from the head station command on the implementation of the push block by circuit 26 of the lock, thereby preventing any transfer of signals from the network 10 within the range b1 of the carrier frequencies until, until you fix the cause of the occurrence of such interference.

Above it was assumed that each detector 32, 33, 34 and 35, respectively, compares the power level of the signal received at the detector from the corresponding filter 28, 29, 30 or 31, respectively, with one of the control level. However, each detector may be configured to compare the specified power level with two times the ranks reference levels, thereby making it possible to determine the slope of the leading edge of each signal received by the detector, and remember relevant information in block 36.

In addition, the block 36 may carry out some assessment information, which it remembers. For example, he may initiate sending an emergency signal to the head station, when this evaluation shows that the network 10 there was clearly an unacceptable situation.

Figure 3 components of the block 23, which correspond to the components option of carrying out the invention shown in figure 2, are denoted by the same positions as in figure 2.

An embodiment of the invention, is shown in figure 3, differs from the variant shown in figure 2, primarily because instead of different bandpass filters 28, 29, 30 and 31 and the detectors 32, 33, 34 and 35 associated with these filters, it contains one band-pass filter 44 and a single detector 45 is connected to the output of the specified filter. Between the input 24 and the bandpass filter 44 includes a mixer 46, which is also connected to the generator 47, the feed to the mixer signal of adjustable frequency. Therefore, the filter 44 may receive a signal corresponding to the signal at the input 24, but having the frequency spectrum, which is shifted relative to the spectrum of the input signal 24 depending on the frequency of the output signal generator 47. Set the th output frequency of the generator can be controlled from the headend 11 CATV system through the inlet 39, the filter 40 and the demodulator 38. The bandwidth of the filter 44 should be only a small part of the full width of the range b1 of the carrier frequencies; for example, if the range b1 occupies the frequency range 15-65 MHz, then the bandwidth of the filter 44 may be 5 MHz.

With this design of unit 23, the driving frequency of the output signal generator 47, to shift the frequency spectrum band b1 of the carrier frequencies relative to the bandwidth of the band pass filter 44 that limits the bandwidth of this filter will get various areas of the specified frequency range. Thus, different areas of the range b1 of the carrier frequencies can be cyclically scanned by successive cyclic premises within the bandwidth of the filter 44. However, when this is desirable, such a periodic scanning may temporarily suspend, for a more detailed investigation of the nature of the signals in any particular area of the specified frequency range.

One of the feasible ways of identification that represents the signal within the range of the b1 frequency of the communication signal or the signal interference is to verify that the signal of the corresponding header. However, in this case, it is necessary that the means of detection available in local networks, had a rather high speed./p>

The invention is not limited to a variant implementation, which is described above and shown in the drawings. There are other numerous ways of its implementation in the framework of the present invention, the scope of which is defined by the claims.

1. The cable television system or other similar communication system configured to transmit signals in the opposite direction from the local network (10), are included in this system, in the head-end station (11) system in a predetermined range of carrier frequencies that is intended for transmitting signals in a specified reverse direction, and containing means (11', 23) control of interference appearing in the system within a specified range of carrier frequencies, characterized in that the said means (11', 23) control of interference include means (32-35; 45) detection available each local network (10)that is arranged to compare the power level of signals appearing within a specified range of carrier frequencies, at least one predetermined reference level and to generate a logical signal depending on the result of this comparison, a storage means (36)available in each local network (10) and executed with the ability to store information about the time intervals during which the specified power level to exceed the control level, obtained from the values of the specified logical signals at different points in time, and means (11') in the head-end station (11) system, through which information stored in said storage means (36) the local network (10), may be requested for transmission to the head station (11) to evaluate this information in the head-end station.

2. The system according to claim 1, characterized in that the said storage means (36) is arranged to store information about the specified time intervals in the form of information about the starting point and the length of each individual interval.

3. The system according to claim 1 or 2, characterized in that the said storage means (36) is arranged to store information about the specified time intervals, at least for some periods of time, in the form of statistical data relating to the number of occurrences of such intervals during the specified periods of time.

4. System according to any one of the preceding paragraphs, characterized in that the reference level is adjustable and management preferably is carried out from the head-end station (11) of the system.

5. The system according to claim 4, characterized in that the said storage means (36) is made with the possibility of storing information on the amount of the established reference level.

6. System according to any one of radiusy points, characterized in that the said means (32-35; 45) detection made with the possibility to compare the specified power level of at least two different reference levels.

7. System according to any one of the preceding paragraphs, characterized in that the means (32-35; 45) detection is made with the ability to make this comparison, and generating a logical signal depending on its result, individually for each of the many different areas of the specified frequency range, and a storage means (36) is made with the ability to store individual information obtained on the basis of these signals, for each of these areas.

8. The system according to claim 7, wherein each local network (10) includes a number of bandpass filters (28-31), which divide the range of the carrier frequencies for the appropriate number of sub-bands, and also includes a corresponding variety of tools (32-35) detection, each of which is intended for comparison of the signals appearing within one of these sub-bands, with a control level or levels, respectively.

9. The system according to claim 7, wherein each local network (10) includes a single band-pass filter (44) with a given bandwidth, which constitutes only part of the full width of the specified range of bearing h is the frequency, and the only means (45) detection, United with the specified filter, it is also possible in a controlled manner to shift the range of range of carrier frequencies relative to the bandwidth of the band pass filter (44) so that different areas of the range of carrier frequencies fall in the specified bandwidth bandpass filter.

10. The system according to claim 9, characterized in that the range of carrier frequencies is divided into several areas, cyclically placed in the specified bandwidth bandpass filter (44).



 

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