JP2001156762A - Unique word detection circuit and unique word detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of a conventional unique word detection method that cannot have coped with a change in channel quality because the number of permissible error bits is fixed in the detection of a unique word and have taken much time to estimate an accurate error rate because the conventional method uses data after demodulation to estimate the error rate. SOLUTION: The unique word detection circuit is provided with a C/N measurement unit 7 that measures a C/N of a satellite communication channel from a received signal, a permissible error bit number decision circuit 2 that has a relational table between the C/N and the number of permissible error bits, a comparator 6 that compares a unique word pattern stored in advance, the demodulated data and the permissible error bit number 21 from a permissible error bit number decision circuit 2 with each other and provides an output of unique word detection information 61 including the unique word denoting the result of comparison, and a unique word inspection circuit 8 that receives the unique word detection information 61 and provides an output of a permissible error deviation 81, and updates contents of the table on the basis of C/N data 71 from the C/N measurement unit 7 and the permissible error deviation 81 from the unique word inspection circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unique word detection circuit and a unique word detection method, and more particularly to a method for maintaining high reception efficiency and utilization efficiency in a satellite communication system in which C / N on a transmission path deteriorates. A unique word detection circuit and a unique word detection method.

[0002]

2. Description of the Related Art In a satellite communication system, an error correction code having a high coding gain and a high-efficiency speech coding technique are introduced in order to reduce required power or downsize an antenna. Also, the satellite communication system operates under a very low C / N. Therefore, in a satellite communication system to which a high-gain error correction code or a high-efficiency coding technique is applied, it is necessary to increase the reception efficiency even under extremely low C / N conditions, suppress retransmission requests, and increase the utilization efficiency. I have.

A preamble added to the head of burst data or a unique word periodically arranged in a frame is important for setting a reception frame reference and generating transmission frame timing for connection to a line network. Play a role. The unique word used for frame synchronization is also used for removing phase uncertainty and identifying a line.

In a satellite communication system, since occurrence of bit errors is unavoidable, a unique word must be detected even if a bit error occurs on a unique word pattern. Therefore, when detecting a unique word, the number of allowable error bits is determined in advance, and the unique word is detected when the number of error bits in the unique word pattern is equal to or less than the allowable error bit number.

[0005] As the bit error rate on the satellite communication line increases, the probability that a unique word will not be detected increases, but the probability that a unique word will not be detected decreases by increasing the number of allowable error bits.

However, when the allowable number of error bits is increased, the uniqueness of the unique word is lost, and even when there is no unique word, another bit string that is not a unique word is erroneously detected as a unique word, and a unique word detection signal is generated. Is output, and the erroneous detection rate of the unique word increases. This allowable number of error bits is determined for a specific line quality, and this value is used as a fixed value.

In such conventional detection of a unique word, the number of allowable error bits is a fixed value. Therefore, if the probability of a unique word being undetected due to a change in the quality of the satellite communication line changes, the number of allowable error bits is changed. There was a problem that the number was not optimal.

[0008]

As a solution to the conventional problem, Japanese Patent Application Laid-Open No. 3-78338 estimates an error rate by using data demodulated by a demodulator.
However, this requires time to estimate an accurate error rate, and since the length of a unique word is very short compared to the data length, an error rate using demodulated data is measured. However, there was a problem that the effect was small.

Due to the above problems, the reliability of a line may be significantly impaired in a transmission environment. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problem, and can control the allowable error bit number and improve the utilization efficiency of a satellite communication line even when the C / N of a received signal is low.

[0010]

According to an aspect of the present invention, there is provided a unique word detecting circuit for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system. A C / N measuring device for measuring the C / N of the satellite communication line from the received signal, and a table of a relationship between the C / N of the satellite communication line and the number of allowable error bits is determined. An allowable error bit number determination circuit, and unique word detection information including a unique word detected by comparing the allowable error bit number from the allowable error bit number determination circuit with the unique word pattern stored in advance and the demodulated data. A comparator for outputting the unique word detection information and outputting a permissible error deviation.
The table is updated based on the C / N data measured by the N measuring device and the allowable error deviation output by the unique word inspection circuit to detect a unique word.

A second aspect of the present invention is a unique word detection circuit for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system, and measuring a C / N of a satellite communication line from the received signal. A C / N measuring device, a C / N of the satellite communication line, an allowable error bit number determining circuit having a table of a relationship between the C / N and an allowable error bit number, A shift register that shifts bit by bit, a storage device that stores a unique word pattern in advance, an allowable error bit number from the allowable error bit number determination circuit, demodulated data from the shift register, and a unique word from the storage device A comparator for outputting unique word detection information including a unique word detected by comparing with a pattern; A unique word inspection circuit for inputting information and outputting an allowable error deviation, wherein the table is based on the C / N data measured by the C / N measuring device and the allowable error deviation sent by the unique word inspection circuit. Is updated to detect a unique word.

Further, the invention according to claim 3 is characterized in that the comparator uses a comparison function to compare the allowable error bit number, the demodulated data, and the unique word pattern.

Further, the invention according to claim 4 is characterized in that the unique word checking circuit includes a processing unit at the time of detection, a processing unit at the time of non-detection, a processing unit at the time of erroneous detection, and an allowable error deviation determination circuit, so that the unique word detection can be performed correctly. If performed, the number of error bits at the time of detection and the number of detected bursts are counted by the detection time processing unit and sent to the allowable error deviation determination circuit.If a unique word is not detected, The number of undetected bursts is counted by the non-detection processing section and sent to the allowable error deviation determining circuit. If a unique word is erroneously detected, the number of error bits at the time of erroneous detection and the number of erroneous detections are determined. The number of bursts is counted by the erroneous detection processing section and sent to the allowable error deviation determination circuit, and the allowable error deviation is determined by the allowable error deviation determination circuit.

Further, the invention according to claim 5 is characterized in that it can be applied to a data communication system or a radio communication system in the invention according to any one of claims 1, 2, 3, and 4.

Further, the invention of claim 6 is a unique word detection method for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system, and measuring a C / N of a satellite communication line from the received signal. A C / N measurement step, a C / N of the satellite communication line, and a permissible error bit number determining step of determining a permissible error bit number having a table of a relation between the C / N and the permissible error bit number; A comparison step of outputting unique word detection information including a unique word detected by comparing the allowable error bit number from the determination step with the demodulated data and a previously stored unique word pattern, and inputting the unique word detection information A unique word inspection step of outputting an allowable error deviation, wherein the C / N measured by the C / N measurement step is And detecting the unique word to update the table based on the allowable error deviation said the over data unique word test step was output.

Further, the invention according to claim 7 is a unique word detection method for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system, wherein a C / N of a satellite communication line is measured from the received signal. A C / N measurement step for determining the number of allowable error bits, a C / N of the satellite communication line and a table of a relation between the number of allowable error bits, and an allowable error bit number determining step. A shifting step of shifting bit by bit, a storing step of storing a unique word pattern in advance, an allowable error bit number from the allowable error bit number determining step, demodulated data from the shift step, and a unique word pattern from the storing step. The comparison step outputs unique word detection information including unique words detected by comparing When the Enter the unique word detection information and a unique word inspection step of outputting the allowable error deviation, the C / N measuring step is measured C
The unique word is detected by updating the table based on / N data and the allowable error deviation output by the unique word inspection step.

Further, the invention of claim 8 is characterized in that in the comparing step, a comparison function is used to compare the allowable error bit number, the demodulated data and the unique word pattern.

Further, the invention according to claim 9 is characterized in that the unique word checking step comprises a processing step at the time of detection, a processing step at the time of non-detection, a processing step at the time of erroneous detection, and a step of determining an allowable error deviation. If performed, the number of error bits at the time of detection and the number of detected bursts are counted in the detection processing step and sent to the allowable error deviation determination step, and if a unique word is not detected, The number of undetected bursts is counted in the non-detection processing step and sent to the allowable error deviation determination step. If a unique word is erroneously detected, the number of error bits at the time of erroneous detection and the number of erroneous detections are determined. The number of bursts is counted in the erroneous detection processing step and sent to the allowable error deviation determining step, Wherein the allowable error deviation is determined in a difference determination step.

Further, the invention of claim 10 is characterized in that it can be applied to a data communication system or a radio communication system in any one of the inventions of claims 6, 7, 8, and 9.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present invention, in the unique word detection circuit and the unique word detection method used in a satellite communication system, when the quality of the satellite communication line is deteriorated, the best non-detection rate and false positive rate of the unique word The number of allowable error bits used in detecting a unique word is determined based on the C / N (carrier-to-noise ratio) of the satellite communication line. A unique word detection circuit and a unique word detection method for updating the number of bits are provided. (Configuration of First Embodiment) FIG. 1 is a block diagram of a first embodiment, FIG. 2 is a block diagram of an allowable error bit number determination circuit, and FIG. 3 is a block diagram of a unique word inspection circuit. FIG. 4 shows a preamble PA (X bits).
This is a frame data format including N (N is a positive integer) burst data composed of a unique word portion UW (L bits) and a data portion.

In FIG. 1, 1 is a receiver, 2 is an allowable error bit number determining circuit, 3 is a demodulator, 4 is a shift register,
5 is a ROM (Read Only Memory), 6
Is a comparator, 7 is a C / N measuring device, 8 is a unique word inspection circuit, and 9 is a data processing unit.

The receiver 1 receives a high-frequency signal from an antenna system (not shown) and outputs it as a reception signal 11. The allowable error bit number determination circuit 2 determines the allowable error bit number 21 based on the C / N data 71 and the allowable error deviation 81. Demodulator 3 receives received signal 11 and receives demodulated data 31
Output as The shift register 4 shifts the demodulated data 31 bit by bit at a predetermined timing.
It has a width of L bits (the same as the unique word portion UW).
The ROM 5 stores a unique word pattern in advance. The comparator 6 compares the demodulated data 31 output from the shift register 4 and the set allowable error bit number 21 with a unique word pattern as a detection threshold. C /
The N measuring device 7 receives the received signal 11 and
/ N is measured and output as C / N data 71. The unique word inspection circuit 8 inputs the unique word detection information 61 including the unique word detected by the comparator 6, and determines the allowable error deviation 81 based on the detection (normal detection), erroneous detection, and non-detection of the unique word. . The data processing section 9 performs data processing of the data section (shown in FIG. 4) of the frame data format.

The received signal 11 received by the receiver 1
Is sent to the demodulator 3 and the C / N measuring device 7. Demodulated data 31 demodulated by demodulator 3 is sent to shift register 4. The demodulated data 31 sent to the shift register 4 is compared by the comparator 6 with a unique word pattern previously written in the ROM 5 to determine whether or not a unique word has been detected. Further, the C / N measuring device 7 measures the C / N data 71 of the satellite communication line from the received signal 11 and sends it to the allowable error bit number determining circuit 2.

The number of allowable error bits 21, which is one of the criteria for the unique word detection of the comparator 6, is determined by the C / N measuring device 7.
Is determined by the allowable error bit number determination circuit 2 on the basis of the C / N data 71 measured in step (1). The comparator 6 detects a unique word using the allowable error bit number 21 determined by the allowable error bit number determination circuit 2, and outputs unique word detection information 61 including the detected unique word.
When a unique word is detected, the data processing unit 9 performs processing of the demodulated data 31.

The received signal 11 is an analog signal of a predetermined frame data format. For example, a carrier is converted to a phase shift keying (PSK: Phase Shift Keyin) signal.
The modulated signal obtained by the modulation in step g), and the input received signal 11 are demodulated by the demodulator 3 into data of the frame data format shown in FIG. In FIG.
The frame data format has a fixed length and is composed of N burst data. Burst data 1
Each is composed of a preamble part PA, a unique word part UW, and a data part.

The preamble PA is a fixed pattern signal and has a length of X (X is a positive integer) bits.
Incidentally, the length of the preamble part PA is determined by the satellite system. The unique word portion UW is a fixed pattern signal of L (L is a positive integer) bits determined before and after the unique word and by the correlation of the unique word itself. A unique word pattern is written in the ROM 5 in advance.

The demodulated data 31 of the digital signal demodulated by the demodulator 3 is sent to the shift register 4. The demodulated data 31 sent to the shift register 4 is
Is compared with the unique word pattern stored in the ROM 5. Note that the comparison function f (t
n) (where n = 1,..., d) is represented by Equation 1 below. However, td indicates the time at which the unique word was detected in detection and erroneous detection, and is an arbitrary value (d ≧ X + 2) in non-detection.

[0028]

(Equation 1)

Where L = 1,..., L (L is the number of bits of the unique word portion UW) UW (i): a unique word pattern stored in the ROM 5 b (tn, i): at time tn , Shift register 4
Demodulated data 31 C (x, y): 0 when x = y 1 when x ≠ y The C / N data 71 measured by the C / N measuring device 7 is used as an allowable error bit number determining circuit. Send to 2. Incidentally, the table 201 in the allowable error bit number determination circuit 2 is C /
9 is a table in which the relationship between N and the number of allowable error bits ε0 is described.

The allowable error bit number ε0 and the comparison function f (t
As a result of comparing n) with the comparator 6, when the unique word is correctly detected, the detection-time processing unit 811
The number of erroneous bits at the time of detection is counted, and the number of detected bursts is counted to determine an allowable error deviation determining circuit 8.
14.

If the unique word is not normally detected and is not detected, the number of undetected bursts is counted by the non-detection processing section 812, and the allowable error deviation determination circuit 8
14.

If the unique word is not correctly detected and is erroneously detected, the erroneous detection processing section 813 counts the number of erroneous bits and the number of erroneous detection bursts when the erroneous detection is performed. Send out.

Based on the number of undetected bursts, the number of erroneous bits and the number of erroneously detected bursts, an allowable error deviation determining circuit 814
, An allowable error deviation 81 is determined. The determined allowable error deviation 81 is sent to the adder of the allowable error bit number determination circuit 2 and added to the allowable error bit number 21. Then, C
The table 201 describing the relationship between / N and the allowable error bit number ε0 is updated.

As described above, the C / N data 71 and the permissible error deviation 81 are input to the permissible error bit number determination circuit 2 to control the non-detection rate and the false detection rate of the unique word when the C / N is degraded. It becomes possible. Non-detection is
Since the allowable error bit number 21 is small, the data including the received error is not detected by the comparator 6. In addition, erroneous detection refers to a state in which received error-containing data is detected by the comparator 6 in a portion that is not a unique word because the allowable error bit number 21 is large. The portion that is not a unique word in FIG. 5 indicates a portion where the positions of the ROM 5 and the shift register 4 do not match the unique word portion UW. Therefore, if the number of allowable error bits is reduced, the non-detection rate increases,
Increasing the number of allowable error bits increases the false detection rate. (Unique Word Detecting Operation of First Embodiment) Next, a unique word detecting operation of the first embodiment will be described with reference to the operation diagram of the first embodiment of FIG. Now, the demodulated data 31 from the demodulator 3 is sent to the shift register 4 as digital data. The transmitted digital data corresponds to time t1 shown in FIG.
, The calculation of the comparison function f (tn) by the comparator 6 is started. Before time t1, the number of allowable error bits 21
Is determined.

At time tn shown in FIG. 5B, the comparator 6 calculates a comparison function f (tn),
Compare with ε0 which is 1. When f (tn)> ε0, it is determined that the unique word detection has failed. Assuming that n = n + 1, the comparator 6 obtains the comparison function f (tn + 1), and the unique word is detected by the operation of comparing with the allowable error bit number ε0. Repeat until it is done.

However, the comparator 6 first sets f (tn) ≦ ε
When it becomes 0, it is recognized that a unique word has been detected. Immediately after the first unique word is detected, the data section shown in FIG. 4 is recognized as data, and the data processing section 9 shown in FIG.
Starts data processing. By the way, d = X +
For the first time at 1 (X is the number of bits in the preamble part), f
If (td) ≦ ε0, it is determined that a unique word has been detected. If f (td) ≦ ε0 for the first time in d ≠ X, it is determined that an erroneous detection has been made. At this time, the allowable error deviation determination circuit 814 shown in FIG. 3 uses the allowable error deviation 81 (the larger the deviation, the smaller the unique word non-detection rate.
If this deviation is small, the unique word false detection rate is small. ) Is determined, and data describing the relationship between the C / N and the allowable error bit number ε0 in the table 201 shown in FIG. 2 is updated. (Other Embodiments) The present invention is not limited to the first embodiment. For example, instead of a C / N measuring instrument, rainfall, snowfall, temperature, Allowable error bit number ε from factors such as humidity
0 can be applied to an apparatus that controls and determines 0.

Further, since the present invention is an operation of only the unique word part, the present invention can be applied to any frame data format having a unique word.

Further, the present invention can be applied to an apparatus including one unit or an apparatus including a plurality of units, and can also be applied to a data communication system or a wireless communication system.

[0039]

As described above, according to the present invention, the allowable number of error bits ε0 is controlled by the C / N at the time of reception, so the conventionally used fixed number of allowable error bits ε0 is employed. Compared with the method described above, the erroneous detection rate and the non-detection rate of the unique word can be optimized.

In addition, by controlling the non-detection rate and the erroneous detection rate at the time of C / N deterioration, it is possible to reduce the number of data retransmission requests in the data processing unit that performs processing after detecting a unique word. Therefore, it has a feature that it greatly contributes to the improvement of the line use efficiency.

Further, the present invention measures the C / N to determine the allowable error bit number ε0 based on the detection rate of the unique word received after determining the allowable error bit number ε0.
Since a method for changing 0 is also provided at the same time, there is no need to create a strict table of C / N and the number of allowable error bits ε0. Therefore, the time required to create the table can be significantly reduced.

In addition, since the present invention counts the number of error bits and the detection status of the unique word, it is possible to determine a more optimal allowable error bit number ε0.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of a unique word detection circuit and a unique word detection method according to the present invention.

FIG. 2 is a block diagram of an allowable error bit number determining circuit according to a first embodiment of the unique word detecting circuit and the unique word detecting method according to the present invention;

FIG. 3 is a block diagram of a unique word detection circuit according to a first embodiment of the unique word detection circuit and the unique word detection method according to the present invention;

FIG. 4 is a frame data format according to a first embodiment of a unique word detection circuit and a unique word detection method according to the present invention;

FIG. 5 is an operation diagram of a first embodiment of a unique word detection circuit and a unique word detection method according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 receiver 11 received signal 2 allowable error bit number determination circuit 21 allowable error bit number 201 table 3 demodulator 31 demodulated data 4 shift register 5 ROM 6 comparator 61 unique word detection information 7 C / N measuring device 71 C / N data Reference Signs List 8 unique word inspection circuit 81 allowable error deviation 811 detection processing unit 812 non-detection processing unit 813 erroneous detection processing unit 9 data processing unit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (10)

[Claims] 1. A unique word detecting circuit for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system, comprising: a C / N measuring device for measuring a C / N of a satellite communication line from the received signal. An allowable error bit number determining circuit having a table of a relationship between the C / N of the satellite communication line and the allowable error bit number, and an allowable error bit from the allowable error bit number determining circuit; A comparator for outputting unique word detection information including a unique word detected by comparing the number with the demodulated data and a previously stored unique word pattern; and inputting the unique word detection information and outputting an allowable error deviation. A unique word inspection circuit, wherein the C / N data measured by the C / N measuring device and an allowable error deviation output by the unique word inspection circuit A unique word detection circuit that updates the table based on the data and detects a unique word. 2. A unique word detection circuit for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system, comprising: a C / N measuring device for measuring a C / N of a satellite communication line from the received signal. An allowable error bit number determining circuit having a table of a relationship between the C / N of the satellite communication line and the allowable error bit number, and a shift register for shifting the demodulated data one bit at a time. And a storage device storing a unique word pattern in advance, and comparing the allowable error bit number from the allowable error bit number determination circuit with the demodulated data from the shift register and the unique word pattern from the storage device. A comparator that outputs unique word detection information including the unique word detected, A unique word inspection circuit for outputting a deviation, wherein the table is updated based on the C / N data measured by the C / N measuring device and the permissible error deviation output by the unique word inspection circuit, and the unique word is updated. A unique word detection circuit characterized by detecting. 3. The unique word detection circuit according to claim 1, wherein the comparator uses a comparison function to compare the allowable error bit number, the demodulated data, and the unique word pattern. . 4. The unique word inspection circuit includes a processing unit at the time of detection, a processing unit at the time of non-detection, a processing unit at the time of erroneous detection, and an allowable error deviation determination circuit, and when the unique word is correctly detected, The number of error bits at the time of detection and the number of detected bursts are counted by the detection processing section and sent to the allowable error deviation determination circuit.If a unique word is not detected, the number of undetected bursts is calculated as The non-detection processing section counts and sends the counted value to the allowable error deviation determination circuit, and when a unique word is erroneously detected,
The number of erroneous bits and the number of erroneously detected bursts at the time of erroneous detection are counted by the erroneous detection processing section and sent to the allowable error deviation determining circuit, where the allowable error deviation is determined. 3. The unique word detection circuit according to claim 1, wherein: 5. The method according to claim 1, wherein the method is applicable to a data communication system or a wireless communication system.
3. The unique word detection circuit according to any one of items 3 and 4. 6. A unique word detection method for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system, comprising: a C / N measuring step of measuring a C / N of a satellite communication line from the received signal. An allowable error bit number determining step of determining an allowable error bit number by including a table of a relationship between a C / N of the satellite communication line and an allowable error bit number; and an allowable error bit from the allowable error bit number determining step. A comparison step of outputting unique word detection information including a unique word detected by comparing the number with the demodulated data and a previously stored unique word pattern, and inputting the unique word detection information and outputting an allowable error deviation A unique word inspection step, wherein the C / N data measured by the C / N measurement step and the unique word A unique word detection method, wherein the unique word is detected by updating the table based on the allowable error deviation output by the inspection step. 7. A unique word detection method for detecting a unique word from demodulated data obtained by demodulating a received signal of a satellite communication system, comprising: a C / N measuring step of measuring a C / N of a satellite communication line from the received signal. An allowable error bit number determining step of determining an allowable error bit number with a table of a relationship between a C / N of the satellite communication line and an allowable error bit number; and a shifting step of shifting the demodulated data one bit at a time. A storage step of storing a unique word pattern in advance, and a unique word pattern detected from a comparison between the allowable error bit number from the allowable error bit number determination step, the demodulated data from the shift step, and the unique word pattern from the storage step. A comparing step of outputting unique word detection information including a word; A unique word checking step of inputting the output information and outputting an allowable error deviation.
A unique word detection method, wherein the unique word is detected by updating the table based on the C / N data measured by the N measurement step and the allowable error deviation output by the unique word inspection step. 8. The unique word detecting method according to claim 6, wherein in the comparing step, a comparison function is used to compare the allowable error bit number, the demodulated data, and the unique word pattern. . 9. The unique word inspection step includes a detection processing step, a non-detection processing step, an erroneous detection processing step, and an allowable error deviation determination step, and when the unique word is correctly detected, The number of error bits at the time of detection and the number of detected bursts are counted in the processing step at the time of detection and sent to the allowable error deviation determination step.If a unique word is not detected, the number of undetected bursts is calculated as When the unique word is erroneously detected, the number of erroneous bits and the number of erroneously detected bursts are counted in the erroneous detection when the unique word is erroneously detected. The counting is performed in the processing step and sent to the allowable error deviation determining step. 8. The unique word detection method according to claim 6, wherein a deviation is determined. 10. The method according to claim 6, wherein the method is applicable to a data communication system or a wireless communication system.
The unique word detection method according to any one of 7, 8, and 9.