KR20000047241A - Method for generating access frames in multimedia satellite communication system - Google Patents

Abstract

PURPOSE: A method for generating access frames in the multimedia satellite communication system is provided to generate access frames by inserting the length of preamble data variably. CONSTITUTION: An RF unit(31) executes frequency down conversion for high frequency signals transmitted from a central station(1) and frequency up conversion for the intermediate frequency signals output from an intermediate frequency generation unit(39). A tuner(32) converts the high frequency signals output from the RF unit(31) into intermediate frequency signals. A demodulation unit(33) demodulates the intermediate frequency signals of the tuner(32). A demultiplexer(34) extracts a TS packet from the TS packet data output from the demodulation unit(33). A network interface card(35) executes interfacing with a personal computer(5). A transmitting frame generation unit(36) generates and outputs serial transmitting access frames. A CDMA channel transmitting unit(37) executes CDMA modulation, mixing CDMA codes supplied from a processor(43). A modulation unit(38) carries out QPSK modulation for the data output from the CDMA channel transmitting unit(37). The intermediate frequency generation unit(39) modulates the modulation signals output from the modulation unit(38) into intermediate frequency signals.

Description

Method and apparatus for generating access frame in multimedia satellite communication system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multimedia satellite communication system. In particular, in generating an access frame for transmitting data from a set-top box to a central station, the multimedia satellite communication system is configured to generate an access frame by variably inserting a preamble data length. A method and apparatus for generating an access frame are provided.

At present, with the rapid development of wireless communication technology, a wireless communication system that enables a subscriber to execute voice and data communication with the other party through a wireless network rather than a conventional wired network is rapidly spreading. The research on the communication system using satellite is being made rapidly because ultra long distance communication such as communication between countries is possible without the communication line.

In addition, as the communication method based on TCP / IP (Transport Control Protocol / Internet Protocol) has been established, a global Internet network is being established. A multimedia satellite communication system in which a general subscriber accesses the Internet network using a satellite communication system Is being developed.

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 (hereinafter referred to as DBS)) and the Internet to provide various multimedia services to terminal stations and to provide overall network operation. A central station that performs management and control functions, 2 is a central station antenna, 3 is a terminal station antenna, 4 is a set top box as a terminal station that provides multimedia services to subscribers, and 5 is a user to perform multimedia communication. The communication terminal 6 is a satellite.

In the above system, in the case of a forward link transmitted from the central station 1 to the set top box 4, a large amount of messages can be transmitted through the TDMA method, and the set top box 4 to the central station 1 are transmitted. In the case of a return link to be transmitted, by using a synchronous CDMA (Code Division Multiple Access) method to accommodate a plurality of subscribers, multimedia data can be transmitted to a plurality of subscribers at high speed.

In addition, in the above system, the set top box 4 generates a predetermined access frame and transmits the data to the central station when transmitting and receiving data with the central station. The access frame structure is shown in FIG.

That is, the preamble data for notifying that the access frame and the unique word data for notifying the start of the access data are added to the access data and transmitted. Here, the preamble data and the unique word data are fixedly assigned the access data and the length of the data. For example, the preamble data is set to "01001000 ... 10001" as 91 bit data, and the unique word data is 16 bits. The data is set to "0000111100011000".

Meanwhile, the length of the access frame transmitted to the central station is also fixed. Since the data lengths of the preamble data and the unique word data are fixed, the length of the access data transmitted through one access frame is always fixed. .

However, the preamble data is sync data indicating that the access frame is an access frame. The preamble data detects the preamble data and loses meaning. After the preamble data is detected, the preamble data is detected. do.

Therefore, since the preamble data is detected in the same part of the preamble data section in the access frame received after the preamble data is detected once, the transmission of the preamble data section after the preamble data is detected is performed. It is a factor that limits the transmission data length of access data in one access frame.

Accordingly, the present invention has been made in view of the above circumstances, and by varying the length of the preamble data of the access frame transmitted to the central station to transmit the access frame, it is possible to improve the transmission efficiency of the access frame. An object of the present invention is to provide a method and apparatus for generating an access frame in a multimedia satellite communication system.

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

Figure 2 is a block diagram showing the internal configuration of the set-top box 30 according to an embodiment of the present invention.

Figure 3 is a functional block diagram showing the functional separation of the internal configuration of the transmission frame generating unit 36 shown in FIG.

4 is a block diagram showing an internal configuration of a central station 50 according to an embodiment of the present invention.

FIG. 5 is a functional block diagram showing the internal structure of the reception data processing apparatus 54 shown in FIG.

6 is an operation flowchart for explaining the operation of the set-top box 30 shown in FIG.

FIG. 7 is an operation procedure for explaining the operation of the central station 50 shown in FIG.

8 shows a data format of a conventional access frame and an access frame according to an embodiment of the present invention.

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

30: set top box, 31: RF generator,

32: tuner, 33: demodulator,

34: demultiplexer (DMUX), 35: network interface card (NIC),

36: transmission frame generation unit, 37: CDMA channel transmitter,

38: modulator, 39: IF generator,

40: transmission timing generator, 41: data memory,

42: preamble information storage unit, 43: processor.

In the multimedia satellite communication system according to the first aspect of the present invention for realizing the above object, an access frame generation method generates a predetermined access frame for a central station, performs a call connection request, and transmits data received from the central station to a communication terminal. In the multimedia satellite communication system having a set-top box for transmitting to the network and a central station for providing the Internet or multimedia services based on the access frame received from the set-top box, generating the preamble detection information of the access frame received from the set-top box Preamble information generation step, preamble information transmission step of transmitting the preamble information generated in the preamble information generation step, and preamble information received by the set-top box in the preamble information transmission step Preamble information storage step, and the preamble information storage stage On the basis of the preamble information stored in the access, including the frame generation step of generating an access frame it is characterized in that configured.

In addition, an apparatus for generating an access frame in a multimedia satellite communication system according to a second aspect of the present invention for realizing the above object generates a predetermined access frame for a central station, performs a call connection request, and receives data received from the central station. In the multimedia satellite communication system having a set-top box for transmitting a communication to the communication terminal and a central station for providing the Internet or multimedia services based on the access frame received from the set-top box, the central station in the access frame received from the set-top box It detects the preamble data and sends the detection information to the set-top box, and the set-top box generates an access frame by varying the preamble data length based on the preamble data received from the central station. do.

That is, according to the present invention having the above-described configuration, by setting the length of the preamble data to be variable to generate an access frame, by increasing the access data length that can be transmitted in one access frame to improve the data transmission speed As a result, the quality of communication services can be improved.

Next, an embodiment according to the present invention will be described with reference to the accompanying drawings.

Figure 3 is a block diagram showing the internal configuration of the set-top box 30 of the multimedia satellite communication system according to an embodiment of the present invention.

In the figure, reference numeral 31 denotes a frequency down-conversion and low noise amplification of the high frequency signal transmitted from the central station 1, and a frequency up-change of the intermediate frequency signal output from the intermediate frequency generator 39 to be described later. An RF device for amplifying, 32 is a tuner for frequency-converting a high frequency signal output from the RF device 31 and outputting an intermediate frequency, and 33 is an intermediate frequency signal output from the tuner 32, that is, at the central station 1. A demodulator for demodulating a QPSK modulated signal.

In the drawing, reference numeral 34 denotes a demultiplexer for extracting a TS packet corresponding to the set-top box from the TS packet data output from the demodulator 33, which includes a register for storing PID information therein. The PID applied from the processor 43 to be described later is stored in the register. The TS packet including the PID stored in the register is extracted from the TS packets applied from the demodulator 33 and applied to the processor 43.

In the drawing, reference numeral 35 denotes a network interface card (NIC) that executes an interface with the personal computer 5, which converts Ethernet packets applied from the processor 43 into IP packets to convert the personal computer 5 into an IP packet. In addition to the above), the IP packet applied by the personal computer 5 is converted into an Ethernet packet and applied to the processor 43.

Further, reference numeral 36 generates a serial transmission access frame based on the preamble data, the unique word data, and the access data applied in parallel from the processor 43, and the transmission timing generation unit 40 to be described later. The transmission frame generation unit sequentially outputs the transmission access frame according to the transmission timing signal applied from the.

Reference numeral 37 denotes a CDMA channel transmitter for performing CDMA modulation by mixing the CDMA code applied from the processor 43 with respect to the transmission data output from the transmission frame generator 36. 38 denotes the CDMA channel transmitter. A modulator for modulating and outputting the data output from (37), for example, QPSK, 39 modulates the modulated signal output from the modulator 38 based on the frequency data applied from the processor 43 to a predetermined intermediate frequency signal. Intermediate frequency generator to convert.

In addition, 40 is a transmission timing generation part which produces | generates the transmission timing signal for the said transmission frame generation part 40 under control of the processor 43, 41 is control for allocating various data, especially from the central station 1 for control. A data memory in which a PID for traffic and a PID for traffic and a service information PID for receiving service information are stored.

In addition, 42 is a preamble information storage unit for storing variable preamble information added to an access frame to be transmitted to the central station, and 43 is a processor for controlling the overall operation of the set-top box 30, which is particularly a PC 5. It is controlled to apply the predetermined message and the unique word data and the preamble data stored in the variable preamble information storage unit 42 to the transmission frame generation unit 36.

4 is a functional block diagram showing an internal configuration of the transmission frame generation unit 36 shown in FIG.

In the figure, reference numeral 361 denotes a message generator for separating and transmitting data applied from the processor 43 to correspond to a preamble length to generate a predetermined message and transmitting the same in parallel, and 362 denotes a parallel message from the message generator 361. This is an access data generation unit that converts and outputs the message data applied to the serial.

Reference numeral 363 denotes a preamble generation unit that generates preamble data based on preamble information applied from the processor 43, and 364 generates unique word data based on a control signal applied from the processor 43. Is a unique word generator.

Reference numeral 365 denotes access data applied from the access data generation unit 362, preamble data applied from the preamble generation unit 363, and unique word data applied from the unique word generation unit 364. Is an access frame generation unit that generates access data by combining the data into a predetermined format, and the generated access data has an access frame structure shown in FIG.

5 is a block diagram showing an internal configuration of a central station 50 for receiving and processing an access frame generated from the set top box 30 shown in FIG.

In the figure, reference numeral 51 denotes an IP switch for switching an IP packet, which is connected to a server and a router for combining with an internet network or a multimedia network. In particular, the router performs connection processing between the main station and the Internet. In this case, the IP packet input from the Internet to the central station is converted into data of the Ethernet frame, and the Ethernet frame sent from the central station to the Internet is converted into the IP packet.

Further, reference numeral 52 denotes an MPEG-2 TS packet by processing the transmission data input from the IP switch 51, and modulating and outputting the generated TS packet data by QPSK, for example, into an intermediate frequency signal of 70 MHz, for example. A transmission data processing unit 53 is a frequency up-conversion and high-output amplified modulated signal output from the transmission data processing unit 52 to output to the antenna, the reception through the antenna is a frequency up-conversion and low-noise amplification output through the antenna RF device.

On the other hand, reference numeral 54 denotes a reception data processor for performing CDMA demodulation on the intermediate frequency signal input from the RF apparatus 53 to output original packet data, and receiving and processing the packet data, which is accessed from the set-top box 30. When the frame is received, it is converted into data of the Ethernet frame and input to the IP switch 51. In addition, the reception data processing unit 54 detects the preamble data and the unique word data and then outputs the subsequent access data to the IP switch 51 by performing CDMA demodulation processing. Referring to FIG. The internal structure of 54) is explained.

That is, the reception data processing unit 54 includes a preamble data detection unit 541 for detecting preamble data of an access frame applied from the RF device 53, and an access frame applied from the preamble data detection unit 541. From a unique word data detection unit 542 for detecting unique word data, a CDMA demodulation unit 543 for performing CDMA demodulation processing on data applied from the unique word data detection unit 542, and the preamble detection unit 541. And a reception control unit 544 for transmitting the preamble detection data and the access data applied from the CDMA demodulator 543 to the central international language processor 55.

In FIG. 4, reference numeral 55 denotes a central international language processor that controls the entire apparatus of the central station, and also allocates a PID to the set-top box 30, a transmission channel frequency and a CDMA code for transmission. In particular, it is controlled to calculate the length data of the preamble data based on the preamble data detection time of the data received from the set-top box 30 to store in the variable preamble information storage 56.

On the other hand, reference numeral 56 is a variable preamble information storage unit for storing the variable preamble data applied from the central international language processor 55, 57 is a network management system for the system operator to operate and manage the entire satellite network (Network Management System (NMS), 58 is a database that stores PID, frequency data and CDMA code data that can be assigned to the set-top box, and also stores billing information for the subscriber.

Next, the operation of the device having the above configuration will be described.

6 is an operation flowchart for explaining the operation of the set-top box 30 according to an embodiment of the present invention.

First, when the predetermined variable preamble data is received from the central station, the set top box 30 stores the received variable preamble data in the variable preamble information storage 42. When the call release request is received from the PC 5, the preamble information stored in the variable preamble information storage 42 is cleared.

On the other hand, when the set-top box 30 receives the predetermined access data from the PC 5 (ST1), the processor 43 of the set-top box 30 has data in the variable preamble information storage unit 42 It is checked whether or not it is (ST2, ST3).

When it is determined in step ST3 that the variable preamble data exists in the variable preamble information storage unit 42, the processor 43 reads the information data stored in the variable preamble information storage unit 42 and transmits the transmission frame generation unit ( In step ST4, the transmission frame generation unit 36 generates preamble data based on the received variable preamble information data, thereby accessing the data generation unit 362 in the transmission frame generation unit 36. To be applied.

Subsequently, the processor 43 transmits the unique word generation control signal to the transmission frame generation unit 36 (ST5), and the transmission frame generation unit 36 generates the unique word based on the received unique word generation control signal. The unit 484 is controlled to transmit the unique word data to the access frame generation unit 485.

In addition, the processor 43 transmits the access data received from the PC 5 to the transmission frame generation unit 36 (ST6), and the transmission frame generation unit 36 applies the preamble applied from the processor 43. On the basis of the information, the access data received from the PC 5 through the processor 43 is divided into predetermined lengths in the message generating unit 361 and transmitted in parallel to the access data generating unit 362, and the access data generating unit ( In operation 362, the message received from the message generator 361 is serially converted and transmitted to the access frame generator 365. In the access frame generation unit 365, the preamble data applied from the preamble generation unit 363, the unique word data applied from the unique word generation unit 364 and the access data generation unit 362 are applied. The combined access data is combined into an access frame as shown in FIG. 8 and sent to the CDMA channel transmitter 37. FIG.

Thereafter, the processor 43 performs a normal access data frame transmission control operation.

On the other hand, when the variable preamble data does not exist in step ST3 determining whether the variable preamble data exists in the variable preamble information storage unit 42, a preamble generation control signal and a unique word generation control signal are applied. The transmission frame generation unit 36 applies the preamble data and the unique word data that are fixedly set to the access frame generation unit 365 of the transmission frame generation unit 36 (ST8).

Then, the processor 43 applies the access data received from the PC 5 to the transmission frame generation unit 36 to perform steps ST6 and ST7 to generate and transmit a predetermined access data frame.

7 is an operation flowchart for explaining the control operation of the central station according to the embodiment of the present invention.

First, when a predetermined access frame is received from the set top box 30 through the RF apparatus 53 of the central station 50 by the receiving data processing apparatus 54, the receiving data processing apparatus 54 receives the received access frame. The preamble data and the unique word data are detected and the detection data is sent to the reception controller 544. The reception controller 544 uses the preamble detection information based on the preamble detection data and the unique word detection data. It is sent to the processor 55.

That is, the reception control unit 544 counts a counter (not shown) from the time point at which the preamble detection data is applied and terminates the counting operation of the counter when the unique word detection signal is applied. If the number of bits is 91 bits, the length of the unique word data is 16 bits, and the counter value is 67, the reception controller 544 provides information about the preamble detection point, that is, "40" ((91 + 16) -67 = 40). ) Is transmitted to the central international language processor 55.

On the other hand, the central international language processor 55 determines whether or not data is received from the reception data processing apparatus 54 (ST51). When predetermined data is received from the reception data processing apparatus 54, the received data is received. The central international language processor 55 determines whether or not the preamble information data is based on the message ID of the data received from the reception data processing apparatus 54.

Subsequently, when the received data is the preamble information data in step ST52 for checking whether the data received from the reception data processing apparatus 54 is the preamble information data, the central international language processor 55 receives the received preamble information data. It is sent to the set-top box 30 by using the control PID (ST53).

On the other hand, if the received data is the access data in step ST52 to check whether the data received from the receiving data processing device 54 is preamble information data is transmitted to the corresponding subsystem through the IP switch 51 ( ST54).

That is, the central station detects the preamble data in the data frame received upon the call connection request from the set top box, calculates the detection time point, and applies the calculated preamble information to the set top box.

In the set-top box, when the call connection request to the central station is requested, the set preamble data is generated to generate a predetermined access frame, and then the predetermined access frame is transmitted to the central station, and then the preamble information received from the central station is stored in a predetermined memory. When generating an access frame to be transmitted to the central station, the access frame is generated and transmitted by inserting only the length of the preamble data at the time of detection based on the preamble information stored in the predetermined memory. The configuration of the access frame is shown in FIG. .

That is, in the drawing, (A) shows a conventional access frame configuration, and (B) shows an access frame configuration in which variable preamble data is inserted according to an embodiment of the present invention. For example, the preamble data is 91 bits. In a data frame consisting of 16 bits of uniqueword data and 320 bits of access data and 427 bits in total, (A) can always transmit only 320 bits of access data in one access frame. When the information is 40, 327 bits of access data can be transmitted in one access frame.

Therefore, according to the present invention, by setting the length of the preamble data variably to generate an access frame, by increasing the length of the access data that can be transmitted in one access frame to improve the data transmission rate, as a result of the communication service You can improve the quality.

On the other hand, the present invention is not limited to the above embodiments and can be modified in various ways without departing from the technical spirit of the present invention.

In other words, the variable preamble data length may be configured to be actually set by increasing a predetermined bit from the bit at the time point at which the preamble data is detected.

Also, in the above embodiment, the preamble detection data is calculated only when the call is connected, and the preamble information is transmitted to the set-top box. In another embodiment, the central station to the set-top box is transmitted every time the access data is transmitted from the set-top box to the central station. By repeating the above-described preamble information sending operation, it is possible to prevent the occurrence of a data reception situation when the preamble detection information changes due to an increase in an error component due to bad weather or the like.

As described above, according to the present invention, by setting the length of the preamble data variably to generate an access frame, the access data length that can be transmitted in one access frame is increased to improve the data transmission rate. The quality of communication service can be improved.

Claims (6)

Creates a predetermined access frame for the central station to perform a call connection request, and provides a set-top box for transmitting data received from the central station to the communication terminal, and providing the Internet or multimedia service based on the access frame received from the set-top box. A method of generating an access frame in a multimedia satellite communication system having a central station, A preamble information generation step of generating preamble detection information of an access frame received from the set-top box; A preamble information sending step of sending the preamble information generated in the preamble information generating step to a set top box; A preamble information storing step of storing the preamble information received by the set top box in the preamble information transmitting step; And an access frame generation step of generating an access frame based on the preamble information stored in the preamble information storing step. The method of claim 1, And the preamble information is data bit information at the time point at which preamble data is detected. The method of claim 1, The preamble information is set by increasing by one or more bits from the time point at which the preamble data is detected. The method of claim 1, The preamble information generation step and the preamble information sending step are performed only for an access frame received when a call connection request from a set-top box is performed. The method of claim 1, The preamble information generating step and the preamble information sending step are performed repeatedly when the access data is transmitted from the set-top box to the central station. Creates a predetermined access frame for the central station to perform a call connection request, and provides a set-top box for transmitting data received from the central station to the communication terminal, and providing the Internet or multimedia service based on the access frame received from the set-top box. In a multimedia satellite communication system having a central station, The central station detects preamble data in an access frame received from the set top box, and transmits the detection information to the set top box. The set-top box generates an access frame by varying the length of the preamble data based on the preamble data received from the central station, and generates and outputs an access frame.