JP3047627B2 - Synchronization maintenance device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronization maintaining device used in a receiving section of a communication device used in a digital communication system.

[0002]

2. Description of the Related Art In recent years, in the field of communications, especially land mobile communications, a time division multiplex digital communication system has been adopted, and a time division signal is detected by detecting a unique word at a fixed time for each frame in a received signal. 2. Description of the Related Art There is known an apparatus for detecting a position of a group of slots (synchronization detection) and maintaining synchronization.

An example of the above-mentioned conventional synchronization maintaining device will be described with reference to the drawings. FIG. 2 is a block diagram showing a configuration of a conventional synchronization maintaining device. Reference numeral 101 denotes a unique word determination unit that detects a unique word from an input received baseband signal, performs a correlation between the received baseband signal and the unique word, and determines whether a correlation result is within a predetermined range. I do. Reference numeral 102 denotes a one-frame counter which stores the position of the unique word in one frame, and counts a clock synchronized with the received data. Reference numeral 103 denotes a synchronization protection counter for maintaining synchronization when the unique word determination unit makes an erroneous determination. Also, 104
Is a unique word determination unit 101, one frame counter 1
02, a synchronization control unit that determines whether the position of the unique word is the same as the past position based on the output of the synchronization protection counter 103, and controls the maintenance of synchronization.

Next, the operation of the above conventional example will be described. First, it is assumed that synchronization is established and the time at which the unique word exists in the relative time within one frame is already set by the one-frame counter 102. Since the one-frame counter 102 counts the clock synchronized with the received data, the time at which the next unique word exists can be predicted.

[0005] The unique word determining section 101 correlates the received baseband signal with the unique word, determines whether or not the correlation result is within a predetermined range, and outputs the result to the synchronization control section 104. The synchronization control unit 104 determines whether the unique word existence time predicted by the one-frame counter 102 matches the unique word existence time determined by the unique word determination unit 101. If the unique word existence time predicted by the one-frame counter 102 matches the unique word existence time determined by the unique word determination unit 101, the synchronization protection counter 1
Clear the counter value of 03 and wait for the next expected time of unique word existence. Unique word existence time estimated by one frame counter 102 and unique word determination unit 101
Does not match the unique word existence time determined by the unique word determination unit 101, and the unique word existence time determined by the unique word determination unit 101 is within a certain range with respect to the unique word existence time predicted by the one-frame counter 102. Clears the counter value of the synchronization protection counter 103, corrects the unique word existence position of the one-frame counter 102, and waits for the next expected unique word existence time. When the unique word determination unit 101 cannot determine the existence of the unique word, or the unique word existence time determined by the unique word determination unit 101 does not fall within a range having a difference from the unique word existence time predicted by the frame counter 102. In this case, the count value of the synchronization protection counter 103 is incremented, and the process waits for the next expected unique word existence time.

When the count value of the synchronization protection counter 103 is within a certain value, the synchronization control unit 104 interprets that the unique word determination unit 101 has made an erroneous determination and maintains the synchronization. If the value exceeds a certain value, it is determined that synchronization has been lost. In this way, synchronization is maintained by the unique word existence time.

[0007]

However, in the above-described conventional synchronization maintaining device, a clock synchronized with the received baseband signal is used, and one frame time can be managed with respect to a large deviation in a bit unit. However, when a synchronized clock cannot be used, there is a problem that one frame time cannot be managed and synchronization cannot be normally maintained. In particular, in the case of the time division multiplexing method, intermittent reception is performed, so that it may be difficult to reproduce the clock depending on the modulation method.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an excellent synchronization maintaining apparatus which can maintain synchronization even when using a clock which is not synchronized with a received baseband signal. I do.

[0009]

In order to achieve the above object, the present invention provides a sampling means for oversampling a received baseband signal containing a unique word and having one frame as a signal unit, A unique word determining means for correlating the received baseband signal with the unique word and generating a correlation output from the correlation result, a clock means for managing one frame time, a correlation output of the unique word determining means and a clock means. Synchronization control means for detecting synchronization deviation from output and maintaining synchronization, clock management means for smoothing the detected synchronization deviation and correcting deviation of clock means, and synchronization protection for preventing detection of erroneous loss of synchronization. Means.

[0010]

According to the present invention, according to the present invention, a received baseband signal is oversampled using a clock that is not synchronized with the received baseband signal, a correlation with a unique word is obtained, and a correlation between the received baseband signal and the unique word is obtained. By extending the time width in which the correlation can be obtained, there is an effect that the synchronization can be maintained based on the correlation output between the received baseband signal and the unique word even when a clock that is not synchronized with the received signal is used.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a synchronization maintaining apparatus according to an embodiment of the present invention. Reference numeral 1 denotes an oversampling unit (sampling means) for performing high-speed oversampling on an input received baseband signal; A unique word determining unit (corresponding to a unique word determining unit) for correlating a signal obtained from the unit 1 with a unique word and generating a correlation output from the correlation result
3 is a one-frame counter (clock means) that counts one frame time, and 4 is a unique word determination unit 2 or 1
A synchronization control unit (synchronization control means) that determines whether or not the synchronization is out of synchronization with the output of the frame counter 3 and generates a synchronization out-of-sync signal. 6 is a synchronization protection counter (synchronization protection means) for protecting the synchronization so as not to be discarded. Reference numeral 6 smoothes the synchronization shift signal output from the synchronization control unit 4, and uses the result to adjust and stabilize one frame time. It is a counter control unit (time management means) for performing the operation.

Next, the operation of the above embodiment will be described. First, the reception baseband signal a input to the oversampling unit 1 is oversampled by a fixed clock b higher than the expected maximum data rate of the signal, and a reception baseband signal c is generated.
This oversampling is performed to prevent reception data from being lost due to a shift in sampling frequency.

The received baseband signal c is correlated with the unique word in the unique word judging section 2. If the correlation result is correlated with a certain value, the correlation output of the unique word judging section 2 is obtained. The signal d is set to a high level, and if a certain value is not correlated, the correlation output signal d is set to a low level.

The correlation output signal d is compared with the estimated unique word existence time (relative time within one frame) signal e of the received baseband signal up to one frame before stored in the one frame counter 3 in the synchronization control unit 4. Then, the shift of the one-frame counter 3 is measured. The measurement of this deviation is based on the time when the estimated unique word existence time signal e indicates the estimated existence time of the unique word, and determines whether or not the high level signal of the correlation output signal d exists before and after this reference. Is determined. If there is, it is determined whether the high-level signal of the correlation output signal d is shifted in either the forward or backward direction based on the estimated unique word existence time signal e, and it is determined that the synchronization is maintained. The counter value of the synchronization protection counter 5 is deemed to be clear, and a synchronization shift notification signal f indicating information indicating in which direction the shift is before or after the high level signal is output to the counter control unit 6. If the high-level signal does not exist within a certain range, it is determined that synchronization may not be maintained, and the counter value of the synchronization protection counter 5 is incremented, and information indicating that the synchronization of the high-level signal is not deviated Is output to the counter control unit 6.

The synchronization protection counter 5 increments or clears the counter value in response to a control signal g from the synchronization control unit 4, and loses synchronization only when the counter value reaches a certain value. Unless the loss of synchronization is detected continuously by incrementing the counter value, erroneous loss of synchronization is prevented by detecting the loss of synchronization.

The counter control unit 6 has a counter therein and, based on the synchronization deviation notification signal f output from the synchronization control unit 4, increments or decrements the internal counter value, thereby smoothing the deviation of the unique word. Then, based on the result, the one-frame counter 3 is adjusted in clock units faster than the data rate of the received baseband signal, and the synchronization deviation is corrected. Adjustment of 1 frame counter 3 is faster than data rate of received baseband signal
By using a fixed clock and using a smoothed signal without directly using the control signal f, erroneous adjustment of the one-frame counter 3 can be reduced, and the maintenance of synchronization can be stabilized.

[0017]

As described above, the present invention provides a fixed data rate that is higher than the maximum data rate expected for a received baseband signal that includes a unique word and has one frame as a unit of signal format.
Sampling means for performing oversampling with a clock, unique word determination means for correlating an oversampled received baseband signal with a unique word and generating a correlation output from the correlation result, and clock means for managing one frame time Synchronization control means for detecting a synchronization shift from the correlation output of the unique word determination means and the output of the clock means to maintain synchronization, and clock management means for smoothing the detected synchronization shift and correcting the shift of the clock means When,
Since there is provided a synchronization protection means for preventing detection of erroneous loss of synchronization, even when a clock synchronized with the received baseband signal cannot be obtained, it is possible to continue to estimate the existence time of the unique word, This has the effect that synchronization can be maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a synchronization maintaining device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional synchronization maintaining device.

[Explanation of symbols]

 Reference Signs List 1 oversampling unit 2 unique word determination unit 3 1 frame counter 4 synchronization control unit 5 synchronization protection counter 6 counter control unit a received baseband signal b clock c oversampled received baseband signal d correlation output signal e estimated unique word existence Time signal f Synchronization error notification signal g Control signal

Claims (3)

(57) [Claims] Most expected in the received baseband signal to 1. A unit of a signal of one frame includes a unique word format
Sampling means for performing oversampling with a fixed clock faster than the large data rate, unique word determination means for correlating the oversampled received baseband signal with a unique word, and generating a correlation output from the correlation result, Clock means for managing one frame time, synchronization control means for detecting a synchronization shift from the correlation output of the unique word determination means and the output of the clock means to maintain synchronization, and smoothing the detected synchronization shift. A synchronization maintaining device comprising: clock management means for correcting a deviation of a clock means; and synchronization protection means for preventing detection of an erroneous loss of synchronization. 2. The synchronization maintaining device according to claim 1, wherein the synchronization control means detects whether or not the synchronization is out of synchronization, and outputs information only in the direction of the out of synchronization when the out of synchronization is detected. 3. The synchronization maintaining device according to claim 1, wherein the clock management means corrects the deviation of the clock means with a clock faster than the data rate of the received baseband signal.