KR970005601B1 - Method for recovering data in international maritime phase shift keying - Google Patents

Abstract

The method for restoring a data inversion phenomenon of a MODEM based on a binary phase shift keying in an international maritime satellite communication C(INMASAT-C) in receiving data through a use of the binary phase shift keying MODEM in its inversion phenomenon restoration method 17271, comprises a first step(N1) of checking whether among the received frame data it is user data and jumping to a data processing part if it is the user data; in case it is not the user data in the first step(N1), a second step(N2) of checking whether it is a first unique-word, and storing it as it is if the first unique-word; a third step(N3) of storing a second unique-word if it is not the first unique-word in the second step(N2); and a fourth step(N4) of synthesizing the first and second unique-words stored after an execution of the above three steps, comparing this synthesized value with a value of the unique-word previously noted when communicating this synthesized value, questioning whether the compared two values are same each other, and if same, acknowledging that there is no the inversion phenomenon of data, and finishing its program, and if not same, checking a bit synchronizing state and jumping to a part for changing a flag value.

Description

Data Reversal Recovery Method of Two-Phase Phase Modulation Modem in International Maritime Satellite Communications-C

1 is a flow chart illustrating a method for recovering the data reversal phenomenon of the present invention.

2 is a detailed flowchart of the data processing unit of FIG.

FIG. 3 is a detailed flowchart of the flag changer in the bit synchronization state with respect to FIG.

The present invention relates to a method for recovering data reversal of a two-phase phase modulation method modem in international maritime satellite communication-C, and a two-phase phase modulation method in international maritime satellite organization C (INMASAT-C). In case of communication using modem that adopts Phase Shift Keying: BPSK), it detects the inversion of frequently occurring data and inverts the data and restores it to the original data so that the data can be received correctly. The present invention relates to a method for recovering data inversion of a phase modulator modem.

In general, the two-phase phase modulation method modem used in the International Maritime Satellite Communication-C causes the bit synchronization to be reversed by 180 degrees according to the attenuation of the received radio frequency (RF) signal. That is, when the signal is weakened and the bit synchronization is lost, and the bit synchronization is held again, the bit synchronization is held in the inverted state by 180 degrees. In this case, the reverse data of the original data is received and the data must be processed separately. there was.

In view of the above-described problems, the present invention reuses a unique word used for frame synchronization to periodically detect data, and then restores the data to a normal state according to the detected result.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, a frame and a unique word used by a communication company will be described as follows.

In general, the received data of the International Maritime Satellite Communication-C has a transmission rate of 1200 [symbol / sec], one frame is composed of 8.64 seconds and 10368 symbols, and the 10368 symbols are used for 128 frame synchronization. The unique word is composed of 160 symbols of user data. The unique word is used with two 64 pieces per frame, and the value is shown in hexadecimal.

Unique Word Value: 7BA9 6917 32E9 B888 (Hexadecimal)

The unique words configured in this way are arranged between two 160 user data and used to monitor the status of the data. The unique words are always constant regardless of the bit synchronization status of the two-phase phase modulation type modem. It is used to process the data by determining the modem status of the system. Of course, if an error occurs in the received data, the receiver's de-scrambler and decoder (D-coder) will recover this error. Data reception can be achieved, and the program operated as described above will be described with reference to the drawings. As shown in FIG. 1, whether the user data is applied among the data of the received frame is jumped to the data processing unit. The first step (N1); A second step (N2) of inquiring whether the first unique word is requested if the user data is not user data in the first step (N1); A third step (N3) of storing a second unique word if it is not the first unique word in the second step (N2); After all the above steps, synthesize the stored first and second unique words, and compare the synthesized values with the known unique word values when communicating. Since there is no data reversal phenomenon, the program is terminated, and if it is not the same, a fourth step N4 is performed in which the state of bit synchronization is checked and a flag jumps to a flag for changing a flag value.

FIG. 2 is a flow chart illustrating the data processing unit jumped in the first step N1 of FIG. 1, and receives data and asks whether the data is normal. If the data is normal, the received data is stored as is and the program is terminated. The first step P1; If the data is not normal in the first step (P1) is a second step (P2) of inverting and storing the received data and ending the program, Figure 3 is a fourth step (N4) of FIG. Flowchart explaining the flag change unit of the jumped bit synch state. Whether the flag of the bit synch state is normal by receiving data, and if the flag of the bit synch state is normal, change the flag value of the bit synch state to abnormal. A first step Q1 to end; In the first step Q1, when the flag of the bit synchronization state is not normal, a second step Q2 of changing the flag value of the bit synchronization state to the normal state and ending the program is performed.

This operation is executed before the descrambler and decoder section of the receiver. The program is repeatedly executed every time data is received from the transmitter, so that even if the bit synchronization of the input data is inverted and inverted in phase, it is used for frame synchronization. By using a word to invert the data value again, the data can be received more accurately.

As described in detail above, the invention re-uses the unique word used for frame synchronization before inputting the input data to the descrambler and decoder unit, and checks whether the data is reversed. By recovering the signal, the data reception is possible even at the received high frequency signal level at which the bit-keeping circuit of the two-phase phase modulation mode modem cannot operate, thereby increasing the gain of the receiver.

Claims (3)

A method for receiving data using a two-phase phase modulation modem in International Maritime Satellite Communication-C, the method comprising: a step of jumping to a data processor in the case of user data asking whether user data is among the data of a received frame; N1) and a second step (N2) of storing the first unique word if it is the first unique word if it is not user data in the first step (N1); In the second step (N2), if the first unique word is not the third step (N3) for storing the second unique word, and after the steps are all synthesized, the first unique word and the second unique word is stored, and the synthesized value When communicating with other devices, compare the value with the known unique word and ask whether the two values are the same or not. If the data is the same, there is no data reversal. If not, terminate the program. A multi-phase data reversal phenomenon of a two-phase phase modulation method modem in International Maritime Satellite Communication-C, comprising a fourth step (N4) of jumping to a negative value changing value. The method of claim 1, wherein the data processing step jumped in the first step (N1) is a first step (P1) for receiving data and asking whether the data is normal or not, if the data is normal, storing the received data as it is and terminating the program (P1). )Wow ; If the data is not normal in the first step (P1), the two phases in the international maritime satellite communication-C characterized in that the sequential operation consisting of a second step (P2) to reverse and store the received data and to end the program A method for recovering data reversal in a phase modulated modem. The method of claim 1, wherein the step of changing the flag of the bit synchronization state jumped in the second step (N2) is performed by receiving data and asking whether the flag of the bit synchronization state is normal or not. A first step Q1 of changing the flag value of the bit synchronization state to abnormal and ending the program; In the first step (Q1), if the flag of the bit synchronization state is not normal, it is composed of a second step (Q2) to change the flag value of the bit synchronization state to normal and end the program to operate sequentially Data Reversal Recovery Method of Two-Phase Phase Modulation Modem in Satellite Communication-C.