KR20000047244A - Automatic channel selection apparatus in multimedia satellite communication system - Google Patents

Abstract

PURPOSE: An automatic channel selection apparatus in the multimedia satellite communication system is provided to automatically select a channel frequency for a return link which transmits data from a set top box to a central station. CONSTITUTION: An automatic channel selection apparatus(50) is comprised of a frequency down converter(51), a signal distributor(52), a frequency synthesizer(53), a channel selection processor(54) and a data storage unit(55). The frequency down converter(51) converts an intermediate frequency signal of 70 megahertz into a low intermediate frequency signal. The signal distributor(52) outputs inputted signals to a plurality of CDMA receiving unit. The frequency synthesizer(53) supplies a specific frequency signal to the frequency down converter(51) according to a required control signal. The channel selection processor(54) controls the whole operation of the automatic channel selection apparatus(50), based on a control signal supplied from a received data processing unit(26). The data storage unit(55) stores channel frequency information provided from the received data processing unit(26).

Description

Automatic Channel Selection Device in Multimedia Satellite Communication System

The present invention relates to a multimedia satellite communication system, and more particularly, to an automatic channel selection apparatus in a multimedia satellite communication system that is capable of automatically selecting a channel frequency for a return link transmitting data from a set-top box to a central station.

At present, a satellite communication system that enables ultra long-distance communication, such as communication between countries, without having a separate communication line, and a worldwide Internet network based on TCP / IP (Transport Control Protocol / Internet Protocol) In addition, multimedia satellite communication systems are being developed to connect the Internet network using satellites.

1 is a system configuration diagram showing an overall configuration of a general multimedia satellite communication system.

In the drawing, reference numeral 1 is connected to MSP (hereinafter referred to as MSP), DBS (Digital Broadcast Service) and the Internet to provide various multimedia services to terminal stations, and to provide overall network operation management and control functions. A central station antenna, 2 is a central station antenna, 3 is a terminal station antenna, 4 is a set top box as a terminal station providing multimedia service to a general subscriber, 5 is a communication terminal for a user to perform multimedia communication, 6 is a satellite.

That is, the multimedia satellite communication system generally includes a central station that is physically coupled to the Internet, and a set-top box that is physically coupled to the communication terminal, and the forward link from the central station to the set-top box uses a TDM method. Message and the return link from the set-top box to the central station is configured to accommodate multiple subscribers using CDMA.

On the other hand, Figure 2 shows the transponder configuration of the system, which has a frequency band f _A of 40 MHz for the forward link and a frequency band f _B of 40 MHz for the return link, for example. As (f _T ), for example, a bandwidth of 80 MHz and the return link is composed of a plurality of frequency channels f1 to fn with a bandwidth of approximately 1.5 MHz. For example, 64 CDMA codes are allocated to each of the frequency channels f1 to fn, and the central station 1 has a channel frequency for each set-top box 4 corresponding to each time the subscriber uses the Internet service. And a CDMA code are allocated to form a return link.

FIG. 2 is a block diagram showing the internal structure of the central station shown in FIG.

In the drawing, reference numeral 10 denotes an IP switch for switching an IP packet (Internet Protocol Packet), which includes a Domain Name System (DNS) server, an E-mail server, a Web (WEB) server, and a proxy ( Internet network such as proxy server and multimedia service provider will be combined.

In the figure, reference numeral 11 denotes a transmission data processing apparatus which processes transmission data input from the IP switch 10 to generate, for example, an MPEG-2 TS packet, and 12 denotes an output from the transmission data processing apparatus 11. A modulator for outputting an intermediate frequency signal of, for example, 70 MHz by performing quadrature phase shift keying (QPSK) modulation on TS packet data, and a 13 frequency upconverting and high output amplifying an intermediate frequency signal output from the modulator 12. It is an RF device for outputting to the antenna (2), the high-frequency signal received through the antenna (2) down-frequency conversion and low noise amplification output.

In the figure, reference numeral 14 denotes a demodulation device for demodulating an intermediate frequency signal input from the RF device 13, and 15 denotes CDMA demodulation of CDMA modulated data input by frequency demodulation in the demodulation device 14. A CDMA receiving device for outputting packet data, 16 is a receiving data processing device for processing data input from the CDMA receiving device 15, wherein the receiving data processing device 16 is an IP packet data from the set-top box (4) If the control message is received or converted to the data of the Ethernet frame is input to the IP switch 10. In addition, the reception data processing device 16 converts, for example, 100 baseT, that is, 100 Mbps data input from the CDMA reception device 15 into 10 baseT data and inputs the data to the IP switch 10.

In the drawing, reference numeral 17 denotes a central international language processor that controls the entire apparatus of the central station 1, and also assigns PIDs to the set-top box 4, transmit channel frequencies and transmit CDMA codes. 18 is a network management system for the system operator to operate and manage the entire satellite network, 19 is a PID, frequency data and CDMA code data that can be assigned to the set-top box 4, Database that stores billing information, etc.

That is, the central station is coupled to the Internet based on TCP / IP, and transmits and receives various data with the Internet through an IP packet (Internet Protocol Packet). In addition, for example, an MPEG-2 TS (Transport Stream) packet for a multimedia service is generated based on an IP packet for a subscriber received from the Internet, and the generated packet data is transmitted to the set-top box through a TDM scheme. Then, CDMA modulation data received from the set-top box is generated, and an IP packet is generated based on this, and the corresponding IP packet is transmitted to the Internet network.

In addition, the demodulator 14 of the central station includes a plurality of demodulators, and each demodulator demodulates a signal corresponding to a specific channel frequency and outputs it to the CDMA receiver 15.

The CDMA receiver includes a plurality of CDMA receivers, and each of the CDMA receivers is configured to accommodate a plurality of CDMA codes. For example, in case of 20 kinds of reception channel frequencies, 20 demodulators are provided. Eight CDMA receivers are combined for each demodulator, and each CDMA receiver can accommodate eight CDMA codes. That is, 64 CDMA codes are allocated to one channel frequency.

Meanwhile, in the conventional system, a channel selector is provided such that a fixed channel frequency is allocated to one demodulator. When a channel frequency of a channel selector provided corresponding to each of the plurality of demodulators is to be changed, There is a hassle that the system operator has to readjust the center channel frequency of the channel selector coupled to the demodulator to be changed.

Accordingly, the present invention has been made in view of the above circumstances, and the operation of the plurality of channel selectors is performed based on the control signal of the central international language processor, thereby reducing the node of the operator and ensuring the accuracy of channel selection. It is an object of the present invention to provide an automatic channel selection apparatus in a multimedia satellite communication system.

1 is a system schematic diagram for explaining a schematic configuration of a general multimedia satellite communication system.

2 is a diagram showing the configuration of a transponder of the multimedia satellite communication system shown in FIG.

3 is a block diagram showing the internal configuration of the central station shown in FIG.

4 is a block diagram showing an internal configuration of a receiving apparatus of a central station according to the present invention;

5 is a block diagram showing an internal configuration of the channel selector 50 shown in FIG.

6 is a detailed block diagram of the channel selector 50 shown in FIG.

*** Explanation of symbols for the main parts of the drawing ***

20: channel selector, 50: channel selector,

51: downlink frequency converter, 52: signal splitter,

53: frequency synthesizer, 54: channel selection processor,

55: data storage.

In order to achieve the above object, an automatic channel selection apparatus in a multimedia satellite communication system according to the present invention demodulates data received from a set-top box in a demodulator and applies it to a channel selector, and in the channel selector, a signal having an assigned channel frequency. Only the CDMA receiver sends the number of signals to the multiple CDMA receivers, and the CDMA demodulator processes the received signal using the CDMA code data allocated to the CDMA receiver and applies the received signal to the receiving data processing apparatus. A multimedia satellite communication system providing Internet and multimedia services to a subscriber on the basis of a signal, comprising: data storage means for storing channel frequency information applied from the reception data processing apparatus, and specified based on a predetermined control signal; Frequency synthesizing unit for synthesizing channel frequency, phase Down-frequency converting means for frequency down-converting the intermediate frequency signal for the information data applied from the set-top box based on the frequency selection signal applied from the frequency synthesizer; A signal distribution means for parallel output to the CDMA receiver and a channel frequency information applied from the reception data processing device when the system is initialized by being coupled to the reception data processing device through an I ² C bus and stored in the data storage means. And a channel selection processor for controlling to transmit predetermined channel frequency information to the frequency synthesizing means based on the channel frequency information stored in the data storing means.

That is, according to the present invention as described above, by automatically selecting the channel frequency of the channel selector according to the control of the central station, it is possible not only to reduce the operator's effort by changing the channel frequency of the channel selector, the channel of the channel selector The accuracy of the frequency change can be improved.

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

4 is a block diagram showing an internal configuration of a receiver in a central station for a multimedia satellite communication system according to an embodiment of the present invention.

In FIG. 4, the demodulator 14 is provided with a plurality of demodulators 14 _{1 to} 14n. Here, each of the demodulators 14 _{1 to} 14n corresponds to the respective channel frequencies f1 to fn in FIG. 2, and demodulates the corresponding channel frequency signals to the channel selector 20. Done.

On the other hand, the channel selection device (20 ₁ ~20n) is constituted by having a plurality of channel selectors (20 ₁ ~20n), each channel selector as being configured to correspond to each of the demodulator (14 ₁ ~14n), The signal applied from the demodulator converts the signal into a channel frequency signal having a specific channel frequency and outputs it to the CDMA receiver 15. In this case, the channel frequency is applied and set from the reception data processing device 26, respectively.

In addition, the CDMA receiver 15 includes a plurality of CDMA receivers 15 _{1 to} 15 n, and a predetermined number of CDMA receivers 15 are coupled to each of the channel selectors 20 _{1 to} 20 n. .

The signal output from the CDMA receivers 15 _{1 to} 15 m is applied to the reception data processing device 26, and the reception data processing device 26 is received from the CDMA receivers 15 _{1 to} 15 m. Data is sent to the IP switch 10.

In addition, the reception data processing apparatus 26 allocates the channel frequencies of the channel selectors 20 _{1 to} 20n based on a control signal applied from the central international language processor 17 through the IP switch 10.

That is, a channel frequency for the multiple CDMA receiver (15 ₁ ~15m) through the channel selector (20 ₁ ~20n) is to be set.

5 is a block diagram showing an internal configuration of a channel selection device 50 according to an embodiment of the present invention.

In the drawing, reference numeral 50 denotes a channel selection device for selecting a specific channel frequency, which is a downlink frequency converter for converting an input 70 MHz intermediate frequency signal (IF signal) into a low intermediate frequency signal (Low IF signal) of 4 MHz. (51), a signal divider (52) for outputting the input signal to the plurality of CDMA receivers, and a specific frequency signal to the downlink frequency converter (51) based on a predetermined control signal to select a specific frequency among the received signals. A channel selection processor 54 for controlling the overall operation of the channel selection device 50 on the basis of the control signal applied from the frequency synthesizer 53, the reception data processing device 16, and the reception data processing device 26 It is configured to include a data storage unit 55 for storing the channel frequency information applied from).

Further, reference numeral 15 denotes a CDMA receiver composed of a plurality of CDMA receivers 15 _{1 to} 15 m for performing CDMA demodulation on the intermediate frequency signal received from the channel selector 50, and 16 denotes from this CDMA receiver 15. A receiving data processing apparatus for converting, for example, 100baseT data into 10baseT data, and transmitting channel frequency information to the channel selection processor 54 based on a control signal applied from the central international language processor 17. It is a central international language processor which controls the overall operation and transmits the reception channel information to the reception data processing device 16.

On the other hand, Figure 4 is a configuration diagram showing the internal configuration of the channel selector 50 shown in FIG.

In the drawing, reference numeral 511 is a first attenuator for limiting the signal strength of the first mixer 513 to be described later by adjusting the input strength of the channel selector according to the setup state of the RF frequency down converter and the channel selection period. 512 is a first filter for removing an image signal while limiting an input frequency applied from the first attenuator 511 to a band of 52 to 88 MHz, 513 is an input applied from the first filter 512. The first mixer synthesizes the signal such that the output frequency becomes a specific frequency level, for example, 44 MHz, based on the first LO (Local Oscillator) signal applied from the PLL 532 to be described later.

On the other hand, reference numeral 514 is a second filter for selecting and outputting only the signal whose center frequency of the signal applied from the first mixer 513 is 44MHz, 515 is a predetermined band of the predetermined band applied from the second filter 514 A second mixer converts the signal into a frequency signal of a specific band, that is, a 3.6864 MHz frequency signal, based on the second LO signal applied from the DDS 531 to be described later.

Further, reference numeral 516 denotes a third filter for increasing impedance matching of the signal of about 3.6864 MHz frequency band applied from the second mixer 515, which outputs signals of all input bands.

Reference numeral 517 denotes a second attenuator for attenuating and outputting a signal applied from the third filter 516 to a set level, and reference numeral 52 denotes a plurality of CDMA signals applied from the second attenuator 517. It is a signal divider outputting in parallel to the receivers 15 _{1 to} 15m.

On the other hand, reference numeral 531 generates a predetermined reference frequency signal for selecting the corresponding CDMA receiver on the basis of the control signal applied from the channel selection processor 541 described later, the PLL (532) and the second to be described later As a DDS (Direct Digital Synthesizer: hereinafter referred to as DDS) output to the mixer 515, the DDS 531 is a reference control oscillator (Phase Lock Loop) to be described later based on the reference frequency signal of the channel selection processor 541. PLL) 532 provides a corresponding synthesized channel frequency for selecting a channel frequency, and provides a second LO signal to the second mixer 515.

On the other hand, reference numeral 532 is a reference control oscillator (PLL) for generating a first LO signal for selecting a CDMA channel by dividing the synthesized frequency signal applied from the DDS 531 by a predetermined multiplier, which is, for example, 10 The multiplication is performed to generate the first LO1 signal.

In addition, reference numeral 533 is a lock detection unit for detecting the LOCK signal of the reference control oscillator (PLL), 541 is a channel selection processor for controlling the operation of the overall channel selector 50, which is particularly described later I2C bus By storing the channel frequency information applied from the combiner 542 in the data storage unit 55 to be described later, the channel frequency of the channel selector 50 is allocated.

On the other hand, reference numeral 542 is an I2C bus coupling unit for performing data communication between the reception data processing apparatus 16 and the channel selector 50, and 55 is a data storage unit for storing channel frequency information.

Next, the operation of the channel selector 50 having the above-described configuration will be described.

There is no channel frequency assigned to the channel selector at system initialization, and when the channel selector is initialized, the channel frequency information allocated to the corresponding channel selector is received together with the channel selector initialization information from the reception data processing apparatus 16. The channel selection processor 54 of 50 stores the channel frequency information received from the reception data processing device 16 in the data storage unit 55.

Subsequently, the channel selection processor 54 transmits the corresponding information to the DDS 531 and the PLL 532 based on the channel frequency information stored in the data storage unit 55, and thus the DDS 531 and the PLL 531. It is possible to select only a signal having a corresponding channel frequency by the first LO signal and the second LO signal transmitted through).

That is, the intermediate frequency signal IF applied to the downlink frequency converter 51 of the channel selector 50 outputs the IF signal selected by the LO1 signal and the LO2 signal to the signal splitter 52. 52), the received IF signal is sent in parallel to the plurality of CDMA receivers 15 _{1 to} 15n. The CDMA receivers 15 _{1 to} 15n mix the corresponding CDMA codes with signals having the received channel frequency. Only the signal having the same CDMA code as the CDMA code is outputted to the reception data processing device 26.

That is, in the above configuration, the channel selector is initialized based on the initialization information received from the reception data processing apparatus, and the channel frequency assigned to the channel selector is received from the reception day processing apparatus and stored in a predetermined memory. Since it is possible to easily change the channel frequency of the channel selector.

Accordingly, according to the present invention, the channel frequency of the channel selector for processing data received from the set-top box is automatically selected according to the control of the central station during data communication between the central station and the set-top box, thereby causing the operator to change the channel frequency of the channel selector. In addition to reducing the effort, the channel selector can change the channel frequency more accurately.

In addition, this invention is not limited to the said Example, It can variously deform and implement within the range which does not deviate from the technical scope of this invention.

As described above, according to the present invention, by automatically selecting the channel frequency of the channel selector under the control of the central station, it is possible not only to reduce the operator's effort due to the channel frequency change of the channel selector, but also to change the channel frequency of the channel selector. Can increase the accuracy.

Claims (1)

Data received from the set-top box is demodulated by the demodulator and applied to the channel selector, and the channel selector sends only signals having the assigned channel frequency to the plurality of CDMA receivers, and the CDMA receiver uses the CDMA code data allocated thereto. In the multimedia satellite communication system for providing the Internet and multimedia services to the subscriber based on the signal received from the reception data processing device by the CDMA demodulation process and applying the received signal to the receiving data processing device , Data storage means for storing channel frequency information applied from said received data processing apparatus; A frequency synthesizer for synthesizing a specific channel frequency based on a predetermined control signal; A downlink frequency converting means for frequency downconverting the intermediate frequency signal for the information data applied from the set-top box based on the frequency selection signal applied from the frequency synthesizing unit; Signal distribution means for distributing frequency signals applied from the downlink frequency converting means and outputting them in parallel to a plurality of CDMA receivers; The channel data stored in the data storage means is stored in the data storage means when the system is coupled to the receiving data processing device through an I ² C bus and is initialized in the system initialization. And a channel selection processor for controlling to transmit predetermined channel frequency information to the frequency synthesizing means.