JP2001298392A - Method for capturing satellite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a satellite capturing method capable of efficiently capture processing in accordance with a noise level in a communication environment because appropriate capture of a satellite signal is not realized at a fixed threshold level under a fluctuating environment noise level. SOLUTION: In satellite capture processing in a satellite communication system, a reception processing part 5 is provided with a means for quantifying a signal/noise level ratio according to the number of receiving errors per unit time during the operation of continuously receiving a satellite signal after capturing the satellite, and efficient capture processing is realized by deciding a threshold level in a capture processing part 3 by using the quantified signal/noise level ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite capturing method for capturing a satellite in a satellite communication terminal that performs satellite communication using a satellite.

[0002]

2. Description of the Related Art In a satellite communication system, when starting communication between a satellite and a terminal on the ground, first, a satellite signal acquisition process for selectively detecting a satellite signal modulated by phase modulation or the like from other noise signals. Is required. 1 is a configuration diagram of a conventional satellite signal receiving unit, FIG. 2 is an explanatory diagram of a conventional satellite signal acquisition, FIG. 3 is a configuration diagram of a conventional acquisition processing unit, and FIG. 4 is a detection signal of a conventional detection time averaging unit. FIG. 6 is a diagram illustrating the relationship between the signal and the signal / noise ratio.

In FIG. 1, a signal from a satellite is sent to an analog receiving section 2 via an antenna 1, and at this time, a surrounding noise signal is input from the antenna 1 together with the satellite signal. The output of the analog receiving section 2 is
And the satellite signal is detected. The analog receiving section 2 performs filtering of a specific area in the entire receiving band by the acquisition frequency area designation signal from the acquisition processing section 3 and supplies the result to the acquisition processing section 3 (FIG. 2).

At this time, if a satellite signal exists in the acquisition frequency range, the acquisition processing unit 3 can acquire the satellite. In the acquisition processing unit 3, as shown in FIG. 3, a satellite signal is detected by the satellite signal detection unit 6. However, in general, since the satellite signal and noise enter the satellite signal detection unit at the same time, the detection signal (detection 1, ratio detection 0) itself varies in time. Therefore, the detection time averaging unit 7 performs time averaging of the detection signal. The satellite capture determination unit 8 is a processing unit that finally determines the capture of the satellite, and determines the satellite capture by comparing the average value output from the detection time averaging unit 7 with a predetermined threshold level. If the average value exceeds the threshold level, the acquisition is successful, and the acquisition completion signal is sent to the demodulation unit 4 together with the satellite signal (including noise). If the average value does not exceed the threshold level, acquisition is unsuccessful, and in this case, the acquisition frequency domain designation signal is changed, and acquisition in another frequency domain is attempted.

FIG. 4 specifically shows a temporal change of a detection signal in the detection time averaging unit 7. As shown in FIG. In case 1, six satellite signals are detected during 10 unit times, and the average value is set to 6. Case 2 is a case where the degree of noise is greater than case 1 and the average value is 1. Case 3 is a case where the degree of noise is smaller than that of Case 1 and has an average value of 9. In each case, if the threshold level is determined to be 6, cases 1 and 3
Is determined to be capture success, and in case 2, capture is not successful. The demodulation unit 4 shown in FIG.
Start demodulation of valid data from the satellite signal. However,
Some errors occur in demodulated data due to noise included in the signal. These are usually detected as packet errors by a parity check or the like performed in packet units. The reception processing unit 5 is a part that processes demodulated data and performs protocol processing with a satellite.

[0006]

In the conventional method, the threshold point for separating the noise signal level from the satellite signal level is fixed. Therefore, when the threshold is set high, the environment in which the noise level of the communication environment is high is set. If it is difficult to detect a satellite signal at a low speed, or if the noise signal is set low, there is a problem that it takes a long time to process the original satellite signal due to erroneous detection of a noise signal.

It is an object of the present invention to provide a satellite capturing method capable of performing an efficient capturing process according to the noise level of the communication environment.

[0008]

According to the present invention, in a satellite acquisition process in a satellite communication system, a signal / noise level ratio is determined by the number of reception errors per unit time during a continuous satellite signal reception operation after acquisition. By providing means for quantification and reflecting the quantified signal / noise level ratio on a threshold level in the next acquisition processing, efficient acquisition processing is realized.

With this configuration, it is possible to realize a satellite capturing method capable of performing efficient capturing processing according to the noise level of the communication environment.

[0010]

According to the first aspect of the present invention, in a satellite acquisition process in a satellite communication system, during a continuous satellite signal reception operation after acquisition, a signal / noise level is determined by the number of reception errors per unit time. Means for quantifying the ratio are provided, and by reflecting the quantified signal / noise level ratio on a threshold level in the next acquisition process, an efficient acquisition process is realized.

According to a second aspect of the present invention, in the first aspect, when quantifying a signal / noise level during a receiving operation, a temporary increase in the number of reception errors due to occlusion and almost stationary reception due to environmental noise. By having means for distinguishing the occurrence of an error according to the state of occurrence, only the latter steady-state error is used as a determinant of the threshold level,
This enables more appropriate capture processing excluding temporary noise.

According to the third aspect of the present invention, in the first aspect, a terminal position detecting means and a means for holding a past terminal position and a signal / noise level at the position are provided so that the current position can be set to a past position. If the position matches the recording position, the threshold is determined using the recorded signal / noise level, thereby realizing a more appropriate acquisition process at a stage before the continuous reception operation succeeds.

According to a fourth aspect of the present invention, in the first aspect, a signal / noise performed during a receiving operation is provided by having means for holding a threshold level correction value corresponding to a time zone or a satellite number in the past receiving. By correcting the threshold level based on the past reception history when quantifying the level, it is possible to capture statistical information that is difficult to quantify in a short reception operation and realize more appropriate capture processing I do.

According to a fifth aspect of the present invention, in the first aspect, at a high threshold level when the low noise state is determined, the environmental state suddenly changes to the high noise state, thereby making it difficult to capture the satellite signal. Since this may occur, a means for gradually lowering the threshold level from a high threshold level in accordance with the elapsed time of the capturing process realizes reliable capture of satellite signals even when the environment changes suddenly.

In the above configuration, efficient satellite acquisition is realized by switching the threshold point for separating the noise signal level from the satellite signal level according to the measured environmental noise level. Thus, in an environment with a low noise level, setting a high threshold level can prevent a delay in the capture processing time due to erroneous detection of a satellite signal due to noise.

In an environment where the noise level is high, setting a low threshold level makes it possible to capture a satellite signal which cannot be detected at all at a high threshold level, although the capture time is delayed due to erroneous detection. Further, even in an environment where the noise level is constant, when the target satellite moves in orbit, its elevation angle and altitude change, so that the intensity of the satellite signal received by the terminal itself changes accordingly. Even in such a situation, by appropriately switching the threshold level in the same manner as above, an appropriate acquisition process corresponding to each signal / noise level is realized.

(Embodiment 1) FIG. 1 is a block diagram of a satellite signal receiving section according to Embodiment 1 of the present invention, FIG. 2 is an explanatory diagram of capturing satellite signals in Embodiment 1 of the present invention, and FIG. FIG. 4 is a configuration diagram of the acquisition processing unit according to the first embodiment of the present invention, and FIG. 4 is a diagram illustrating a relationship between a detection signal and a signal / noise ratio of the detection time averaging unit according to the first embodiment of the present invention. 1 to 4 are the same as those in the related art, and the description thereof is omitted. FIG. 5 is a configuration diagram of a threshold level determination processing unit added to the reception processing unit according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating a change in the threshold level due to a change in the signal / noise level according to the first embodiment of the present invention. , According to the first aspect of the present invention.

In FIG. 5, the number of errors per unit time in demodulated data is measured by providing an error number counting section 9 in the reception processing section 5. This measurement result is sent to the threshold level determination unit 10 as error information. For example, assuming that one second of demodulated data is one frame,
It is assumed that each is composed of 50 packets whose errors can be detected by a checksum. In this case, the error number counting unit 9 sends the number of packet errors generated for each frame to the threshold level determining unit 10 as error information. When the noise level is sufficiently low, packet errors hardly occur, so that the error information also has a value close to 0. However, as the noise level increases, the frequency of occurrence of packet errors increases, and the error information also reaches the maximum value. Approaching 50.

The threshold level determining section 10 determines a threshold level based on the error information. In determining the threshold level, when the error information value is large, the noise level is determined to be large and the threshold level is set low. Conversely, when the error information value is small, the noise level is determined to be small and the threshold level is determined. The basic idea is to set high. In this example, the relationship between the error information and the threshold level is expressed as: threshold level = 10− (error information value /
5) Determine as.

Specifically, when the number of packet errors per second is 8, the error information value is 8, and the threshold level is 10− (8/5) = 9 (/ is an integer). division). This threshold level is sent to the satellite capture determining unit 8, and this value is used when the capture process is performed. In the example of FIG. 4, only the case 3 having a strong signal / noise ratio can be captured by the threshold level determination unit 10.

The time point of S1 in FIG. 6 corresponds to the acquisition processing at the high threshold level. In this state, the threshold level is set higher than the noise level, so that the satellite capture determination unit 8 does not generate an erroneous capture completion signal due to the noise signal. as a result,
Scanning of satellite signals in all reception bands can be performed quickly.

On the other hand, the number of packet errors per second is 3
In the case of six (error information value 38), the threshold level is 10- (38/5) = 3. This threshold level corresponds to a state where the noise level is large, and in the example of FIG. 4, cases 1 and 3 can be captured at this threshold level.

The point in time S2 in FIG. 6 corresponds to the acquisition processing at the low threshold level. Since the threshold level at this time is equal to or lower than the noise level, the satellite capture determination unit 8 generates an erroneous capture completion signal due to noise. In the case of an erroneous capture completion signal, stable reception is impossible, so that the capture process is started again, and the time required for these processes is a delay time (wasted time) of the capture process. However, to capture satellite signals that are likely to be buried in noise,
It is not possible to set the threshold level higher than that of the satellite signal, and even if time is used for scanning the satellite signal due to such a delay time, the satellite signal is surely set by setting the lower threshold level. It becomes possible to capture.

As described above, by estimating the signal / noise level from the number of packet errors of the demodulated data and setting an appropriate threshold level, when the signal / noise level is high, quick acquisition processing is enabled. When the noise level is low, the satellite signal is reliably acquired.

(Embodiment 2) In Embodiment 1,
When the number of packet errors is simply measured in quantifying the signal / noise level during the reception operation performed by the error number counting unit 9, the number of reception errors temporarily increases and the almost steady reception error due to environmental noise Cannot be distinguished from the occurrence of Even in an environment with a low noise level, when a terminal on the receiving side is in a moving state, a satellite signal is temporarily blocked by a building or the like, which may cause a packet error. In the determination of the threshold level, adding such a temporary error to the threshold level determining factor unnecessarily lowers the threshold level.

Therefore, it is desirable to use only the latter steady noise level as a determining factor. In the second embodiment, a more appropriate threshold level setting excluding temporary noise is realized by distinguishing between the two depending on the occurrence state of a packet error. FIG. 7 is a diagram illustrating an example of the operation of counting the number of errors according to the second embodiment of the present invention. In this example, packet errors that occur continuously for 10 or more packets are determined to be due to occlusion, and are excluded from the error information.

In Cases 1 and 2, since no more than 10 consecutive packet errors have occurred, the error information value is counted equal to the number of packet errors. In Case 3, 12 consecutive packet errors have occurred. ing.
For this reason, the error information value is simply 16 but this continuous portion is not counted as an error due to occlusion, and as a result, the error information is output as 4.

(Embodiment 3) The noise level tends to depend on the installation position of the terminal on the receiving side. In particular, when the terminal moves, if the current position of the terminal is known, an approximate signal / noise level at that point, that is, an error information value can be estimated. The third embodiment utilizes this point, and has means for detecting the position of the terminal according to the position of the terminal, and means for holding the past terminal position and the signal / noise level at that position. When the position coincides with the recording position, the threshold is determined using the recorded signal / noise level, thereby realizing a more appropriate acquisition process at a stage before the continuous reception operation succeeds.

FIG. 8 is a block diagram of the threshold level determination according to the third embodiment of the present invention. The position detector 11 detects the current position of the terminal. The error information holding unit 12 is a storage unit that holds a past reception history, and includes a set of terminal position information and corresponding error information. Error information holding unit 12
Is updated at appropriate times as the terminal position changes. The position comparison unit 13 is configured to store the current position of the position detection unit 11 and the error information holding unit only at a stage before the number of errors is counted by a continuous reception operation, such as the first acquisition operation after the terminal is powered on. The comparison with the position information of No. 12 is performed. If the comparison results match, the corresponding error information is read from the error information holding unit 12 in the error information selection unit 14 and sent to the threshold level determination unit 10. In this case, a more appropriate threshold level can be determined by using the error information estimated from the terminal position, even though there is no error information from the error number counting unit 9. On the other hand, if the position information does not match, a default error information value is sent to the threshold level determination unit 10. Further, in a situation where continuous reception is performed, the error information selecting unit 14 always outputs the error number counting unit 9.
Select error information from.

(Embodiment 4) Embodiment 4 quantifies a signal / noise level performed during a reception operation by holding threshold level correction values corresponding to time zones and satellite numbers in past reception. In the case of, the threshold level correction based on the past reception history is enabled, and statistical information that is difficult to quantify in a short reception operation is taken in,
This makes it possible to realize more appropriate capture processing.

FIG. 9 is a block diagram of the threshold level correction according to the fourth embodiment of the present invention. FIG. 9 shows an example of the correction function based on the time zone. The threshold level correction table unit 15 is a table that holds reception time zones (in this example, in units of four hours) and threshold value correction values corresponding thereto.
This threshold level correction table section is always referred to during the capturing process, and the threshold level correction value in the time zone corresponding to the reception time is read.

The read correction value is added to the threshold level before correction from the threshold level determination section 10 in the threshold level correction section 16 and sent to the satellite acquisition determination section 8 as a final threshold level. The correction based on the satellite number can be similarly realized by correcting / adding the information on the satellite number in the threshold level correction table section.

(Embodiment 5) At a high threshold level determined when it is determined to be in a low noise state, it may be difficult to capture a satellite signal due to a sudden change in the environmental state to a high noise state. . In order to solve this point, the fifth embodiment has a means for gradually decreasing the threshold level from a high threshold level according to the elapsed time of the acquisition process, so that the satellite signal can be reliably obtained even when the environment changes suddenly. This is to achieve an effective capture.

FIG. 10 is a block diagram of satellite acquisition according to a fifth embodiment of the present invention. The threshold level sent to the satellite acquisition determining unit 8 is supplied via a threshold reducing unit 17. The threshold reduction unit 17 measures the elapsed time from the start of the capturing operation,
If the acquisition completion signal has not been generated for a certain period of time, a value obtained by reducing the input threshold value by a certain value from the original threshold level value is supplied to the satellite acquisition determination unit 8. If the acquisition is not completed for a certain period of time even at the reduced threshold level, the threshold level is further reduced and this processing is repeated until the acquisition is finally completed or the reduced threshold level reaches the minimum value. It is.

[0035]

According to the present invention, an efficient satellite can be obtained by switching the threshold point for separating the noise signal level from the satellite signal level in the satellite acquisition processing according to the environmental noise level estimated from an error in the received data. Capture can be achieved. Therefore, in an environment with a low noise level, it is possible to prevent a delay in acquisition processing time due to erroneous detection of a satellite signal due to noise. Further, in an environment with a high noise level, it becomes possible to capture a satellite signal that cannot be detected at all at a high threshold.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a satellite signal receiving unit according to a conventional and a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of capturing a satellite signal according to the related art and the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a capture processing unit according to the related art and the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between a detection signal of a detection time averaging unit and a signal / noise ratio according to the related art and the first embodiment of the present invention.

FIG. 5 is a configuration diagram of a threshold level determination processing unit added to the reception processing unit according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a change in a threshold level due to a change in a signal / noise level according to the first embodiment of the present invention;

FIG. 7 is a diagram illustrating an example of an error number counting operation according to the second embodiment of the present invention;

FIG. 8 is a configuration diagram for determining a threshold level in Embodiment 3 of the present invention.

FIG. 9 is a configuration diagram of threshold level correction according to a fourth embodiment of the present invention.

FIG. 10 is a configuration diagram of satellite acquisition in Embodiment 5 of the present invention.

[Explanation of symbols]

 Reference Signs List 2 analog receiving unit 3 capturing processing unit 5 receiving processing unit 6 satellite signal detecting unit 7 detection time averaging unit 8 satellite capturing determining unit 9 error count counting unit 10 threshold level determining unit 11 position detecting unit 12 error information holding unit 13 position comparing unit 14 Error information selection unit 15 Threshold level correction table unit 16 Threshold level correction unit 17 Threshold reduction unit

Claims (5)

[Claims] In a satellite acquisition process in a satellite communication system, means is provided for quantifying a signal / noise level ratio by the number of reception errors per unit time during a continuous satellite signal reception operation after acquisition. A satellite acquisition method characterized by realizing an efficient acquisition process by reflecting a quantified signal / noise level ratio on a threshold level in a next acquisition process. 2. The method according to claim 1, wherein when quantifying the signal / noise level during the receiving operation, an increase in the number of temporary receiving errors due to occlusion and an almost steady occurrence of the receiving error due to environmental noise are performed. By having means for distinguishing according to the occurrence situation, only the latter steady error is used as a determinant of the threshold level, thereby enabling more appropriate capture processing excluding temporary noise. Satellite acquisition method. 3. The apparatus according to claim 1, further comprising means for detecting the position of the terminal and means for holding the past terminal position and the signal / noise level at that position, so that the current position matches the past recording position. A method of determining a threshold using a recorded signal / noise level to realize a more appropriate acquisition process before a continuous reception operation succeeds. 4. The method according to claim 1, further comprising means for holding a threshold level correction value corresponding to a time zone or a satellite number in a past reception, so as to quantify a signal / noise level performed during a reception operation. In addition, by correcting the threshold level based on the past reception history, statistical information that is difficult to quantify in a short reception operation is acquired, and more appropriate acquisition processing can be realized. Satellite acquisition method. 5. In the first aspect, at a high threshold level when it is determined to be in a low noise state, it may be difficult to capture a satellite signal due to a sudden change in an environmental state to a high noise state. A satellite acquisition method characterized by realizing reliable acquisition of a satellite signal even by a sudden change in environment by having means for gradually decreasing a threshold level from a high threshold level according to an elapsed time of an acquisition process. .