CN103986943A - Large-ring time delay measurement method of digital satellite television timing system - Google Patents

Abstract

The invention relates to a large-ring time delay measurement method of a digital satellite television timing system. The large-ring time delay measurement method includes the steps of signal synchronization, nanosecond-stage timestamp generation, large-ring time delay measurement and amendment. The transmitting-receiving time of special identification bits in television signals is marked, large-ring time delay is measured with the nanosecond-stage timestamp generation method, a mathematical model is built with measured large-ring time delay data, large-ring time delay at any moment can be deduced, and the measurement accuracy and the measurement reliability are improved.

Description

The large ring time-delay measuring method of digital satellite television time dissemination system

Technical field

The invention belongs to communication technical field, be specifically related to the measurement to the large ring time delay of digital satellite TV signal with timestamp.

Background technology

The time service of digital satellite television high accuracy is to utilize existing digital satellite television system to transmit a kind of time service means of split-second precision information.Satellite TV system mainly consists of three parts: up earth station, spaceborne transponder and downlink receiving station.Wherein, forward the geostationary satellite of TV signal apart from ground approximately 3.6 ten thousand kms, TV signal is emitted to satellite from up earth station, then is forwarded back to approximately 250 milliseconds of ground time delays through satellite repeater.

To realizing digital satellite television hundred nanosecond precision time services, need accurately to measure and revise the propagation delay of TV signal.Propagation delay is mainly divided into uplink time delay and descending time delay.Estimation for uplink time delay can obtain by measuring the large ring time-delay calculation of TV signal, and therefore the certainty of measurement of large ring time delay directly affects the precision of TV time service.

Last century, the eighties realized the method for standard time information being inserted to TV signal in simulated television system-based, by the TV signal receiving is carried out to demodulation, the standard time information in the time of can obtaining broadcast.But along with appearance and the Technique Popularizing of standards for digital broadcasting, anolog TV signals are replaced by digital satellite television signal gradually.Because great change has occurred signal system, the time service method of original simulated television can not continue to use, and the time signal carrying in original anolog TV signals also stops thereupon.Under current television transmission standard and system, utilize existing TV signal, and in the situation that not changing existing TV signal structure, how accurately to measure the large ring time delay of TV signal, and while there is data exception in measuring process, how accurately the problem such as the large ring time delay of estimating and forecasting is needed solution badly.It is one of key issue realizing digital satellite television high accuracy time dissemination system.Very few to this Study on Problems both at home and abroad at present, do not find pertinent literature report.

Summary of the invention

Technical problem to be solved by this invention has been to provide that a kind of certainty of measurement is high, accuracy is high, good reliability, the large ring time-delay measuring method of digital satellite television time dissemination system that antijamming capability is strong.

It is comprised of following step to address the above problem adopted technical scheme:

(1) signal is synchronous

In the asynchronous serial interface of the up ground station of digital satellite television system modulator, take out the signal bit stream that speed is 270 MBPSs, signal completed to synchronizing process as follows:

1) by serial digital receiver, carry out clock recovery, completion bit is synchronous.

2) initial data after bit synchronization is put into successively to the shift register of 50, detected that in this 50 bit data, whether to have two continuous special control character K28.5 be 0011111010 or 1100000101; If have, using this coding as the border of numeric data code byte of reception, be about to later data and be classified as a byte every 10 bits, complete byte of sync, enter step 3); If nothing, repeating step 2).

3) each transport stream packets is the regular length of 188 bytes, and the sync byte in packet header is 0x47, and 10 corresponding bits of encoded are " 1110000101 " or " 0001110101 "; First find a 0x47 code word, if the code word of 187 bytes of being separated by is also 0x47, thinks and complete transport stream packets synchronous by a rear sync byte that 0x47 code word is transport stream packets; Otherwise again find 0x47 code word.

(2) nanosecond timestamp production method

1) frequency signal to 200MHz by the 10MHz frequency signal frequency multiplication of atomic clock, each clock cycle was 5 nanoseconds, rolling counters forward value N scope is 0～199999999, Counter Value is started from scratch, each cycle counter value adds 1, is added to 199999999, Counter Value zero setting, the count cycle of counter is 1 second, and resolution was 5 nanoseconds.

2) extract the rising edge of the 7th to the 8th in the sync byte 0x47 of packet header, with the value N of this rising edge recording counter.The corresponding moment t of this transport stream packets _sfor N * 5 nanosecond.This value is deposited in register 1.

3) extract the 5th byte to the 11 bytes after the sync byte 0x47 of packet header, be stored in register 2; Data in register 2 are converted to ASCII character, revert to former transmission data; Four figures in register 2, according to being program clock reference value flag bit, if zero, returns to step 2); If 1, show that this transmission package contains program clock reference, by the t in the 2nd byte to the 7 byte datas and register 1 in register 2 _scoding generates nanosecond timestamp, and front 6 bytes of nanosecond timestamp are program clock reference value, and rear 4 bytes are t _s.

(3) encircle greatly latency measurement and correction

By nanosecond timestamp production method step (2) gained nanosecond timestamp, be denoted as transmitting time stamp, deposit in the memory A of first in first out, the size of memory A is 100 bytes.

1) ground receiving terminal via satellite antenna reception from the downstream signal of satellite, asynchronous serial signal bit stream through demodulation, output 270 MBPSs, carry out that signal is synchronous, nanosecond timestamp produces, obtain timestamp and be denoted as time of reception stamp, the signal synchronizing method of this step is identical with signal synchronizing step (1), and nanosecond timestamp production method is identical with nanosecond timestamp production method (2); The corresponding moment of rising edge of the 7th to the 8th of synchronous head in transport stream packets is denoted as to t _r.

2) by step 1) the program clock reference value in time of reception stamp finds the transmitting time stamp of same program clock reference value in memory A as keyword.If do not mate, abandon this time of reception stamp, wait for next time of reception stamp; If find, transmitting time stamp and time of reception are stabbed to corresponding moment value and subtract each other, obtain encircling greatly latency measurement value:

$\mathrm{\&Delta;t}=\left\{\begin{array}{cc}{t}_r-t_s& t_r>t_s\\ t_r-t_s+{10}^9& t_s<t_r\end{array}\right.$

In formula, Δ t is large ring latency measurement value, takies four bytes, and tr is the moment value in time of reception stamp, and ts is the moment value in transmitting time stamp; Whether Δ t is deposited in to the memory B of first in first out, determine as follows;

Get nearest three measurement data Δ t ₁, Δ t ₂, Δ t ₃, obtain predicted value if record large ring time delay Δ t and predicted value residual error be not more than

$\sqrt{\underset{i=1}{\overset{10}{\mathrm{\&Sigma;}}}{(\mathrm{\&Delta;}{t}_i-\mathrm{\&Delta;}\stackrel{\&OverBar;}{t})}^2}$

Think that this measures Δ t effective, Δ t is deposited in memory B; Otherwise, think that program clock reference time stamp is abnormal or Δ t is abnormal, abandon Δ t, get predicted value large ring time delay as correspondence, deposits in memory B.

The present invention is by the transmitting-receiving time of special identifier position in mark TV signal, the method that generates nanosecond timestamp is measured large ring time delay, adopt the large ring of measurement delay data to set up Mathematical Modeling, the large ring time delay of any time of can deriving, has improved accuracy and the reliability measured.

Accompanying drawing explanation

Fig. 1 is the flow chart of the embodiment of the present invention 1.

Fig. 2 is the flow chart that nanosecond timestamp of the present invention produces.

Embodiment

Below in conjunction with drawings and Examples, the present invention is described in more detail, but the invention is not restricted to these embodiment.

Embodiment 1

In Fig. 1,2, the large ring time-delay measuring method of the digital satellite television time dissemination system of the present embodiment is comprised of following step:

1, signal is synchronous

In Fig. 1, in the asynchronous serial interface of the up ground station of digital satellite television system modulator, take out the signal bit stream that speed is 270 MBPSs, signal completed to synchronizing process as follows:

(1) by serial digital receiver, carry out clock recovery, completion bit is synchronous.

(2) initial data after bit synchronization is put into successively to the shift register of 50, detected that in this 50 bit data, whether to have two continuous special control character K28.5 be 0011111010 or 1100000101.If have, using this coding as the border of numeric data code byte of reception, be about to later data and be classified as a byte every 10 bits, complete byte of sync, enter step (3); If nothing, repeating step (2).

(3) each transport stream packets is the regular length of 188 bytes, and the sync byte in packet header is 0x47, and 10 corresponding bits of encoded are " 1110000101 " or " 0001110101 ".First find a 0x47 code word, if the code word of 187 bytes of being separated by is also 0x47, thinks and complete transport stream packets synchronous by a rear sync byte that 0x47 code word is transport stream packets; Otherwise again find 0x47 code word.

2, nanosecond timestamp production method

In Fig. 2, the production method step of nanosecond timestamp is as follows:

(1) frequency signal to 200MHz by the 10MHz frequency signal frequency multiplication of atomic clock, each clock cycle was 5 nanoseconds, rolling counters forward value N scope is 0～199999999, Counter Value is started from scratch, each cycle counter value adds 1, is added to 199999999, Counter Value zero setting, the count cycle of counter is 1 second, and resolution was 5 nanoseconds.

(2) extract the rising edge of the 7th to the 8th in the sync byte 0x47 of packet header, with the value N of this rising edge recording counter.The corresponding moment t of this transport stream packets _sfor N * 5 nanosecond.This value is deposited in register 1.

(3) extract the 5th byte to the 11 bytes after the sync byte 0x47 of packet header, be stored in register 2.Data in register 2 are converted to ASCII character, revert to former transmission data.Four figures in register 2, according to being program clock reference value flag bit, if zero, returns to step (2); If 1, show that this transmission package contains program clock reference, by the t in the 2nd byte to the 7 byte datas and register 1 in register 2 _scoding generates nanosecond timestamp, and front 6 bytes of nanosecond timestamp are program clock reference value, and rear 4 bytes are t _s.

3, encircle greatly latency measurement and correction

In Fig. 1, by nanosecond timestamp production method step 2 gained nanosecond timestamp, be denoted as transmitting time stamp, deposit in the memory A of first in first out.The size of memory A is 100 bytes.

(1) ground receiving terminal via satellite antenna reception from the downstream signal of satellite, asynchronous serial signal bit stream through demodulation, output 270 MBPSs, carry out that signal is synchronous, nanosecond timestamp produces, obtain timestamp and be denoted as time of reception stamp, the signal synchronizing method of this step is identical with signal synchronizing step 1, and timestamp generative process is identical with nanosecond timestamp production method 2.The corresponding moment of rising edge of the 7th to the 8th of synchronous head in transport stream packets is denoted as to t _r.

(2) by the program clock reference value in step (1) time of reception stamp, as keyword, in memory A, find the transmitting time stamp of same program clock reference value.If do not mate, abandon this time of reception stamp, wait for next time of reception stamp; If find, transmitting time stamp and time of reception are stabbed to corresponding moment value and subtract each other, obtain encircling greatly latency measurement value:

$\mathrm{\&Delta;t}=\left\{\begin{array}{cc}{t}_r-t_s& t_r>t_s\\ t_r-t_s+{10}^9& t_s<t_r\end{array}\right.$

In formula, Δ t is large ring latency measurement value, takies four bytes, t _rfor the moment value in time of reception stamp, t _sfor the moment value in transmitting time stamp.Whether Δ t is deposited in to the memory B of first in first out, determine as follows.

Get nearest three measurement data Δ t ₁, Δ t ₂, Δ t ₃, obtain predicted value if record large ring time delay Δ t and predicted value residual error be not more than

$\sqrt{\underset{i=1}{\overset{10}{\mathrm{\&Sigma;}}}{(\mathrm{\&Delta;}{t}_i-\mathrm{\&Delta;}\stackrel{\&OverBar;}{t})}^2}$

Think that this measures Δ t effective, Δ t is deposited in memory B; Otherwise, think that program clock reference time stamp is abnormal or Δ t is abnormal, abandon Δ t, get predicted value large ring time delay as correspondence, deposits in memory B.

Claims (1)

1. the large ring time-delay measuring method of digital satellite television time dissemination system, is characterized in that it is comprised of following step:

(1) signal is synchronous

In the asynchronous serial interface of the up ground station of digital satellite television system modulator, take out the signal bit stream that speed is 270 MBPSs, signal completed to synchronizing process as follows:

1) by serial digital receiver, carry out clock recovery, completion bit is synchronous;

2) initial data after bit synchronization is put into successively to the shift register of 50, detected that in this 50 bit data, whether to have two continuous special control character K28.5 be 0011111010 or 1100000101; If have, using this coding as the border of numeric data code byte of reception, be about to later data and be classified as a byte every 10 bits, complete byte of sync, enter step 3); If nothing, repeating step 2);

3) each transport stream packets is the regular length of 188 bytes, and the sync byte in packet header is 0x47, and 10 corresponding bits of encoded are " 1110000101 " or " 0001110101 "; First find a 0x47 code word, if the code word of 187 bytes of being separated by is also 0x47, thinks and complete transport stream packets synchronous by a rear sync byte that 0x47 code word is transport stream packets; Otherwise again find 0x47 code word;

(2) nanosecond timestamp production method

1) frequency signal to 200MHz by the 10MHz frequency signal frequency multiplication of atomic clock, each clock cycle was 5 nanoseconds, rolling counters forward value N scope is 0～199999999, Counter Value is started from scratch, each cycle counter value adds 1, is added to 199999999, Counter Value zero setting, the count cycle of counter is 1 second, and resolution was 5 nanoseconds;

2) extract the rising edge of the 7th to the 8th in the sync byte 0x47 of packet header, with the value N of this rising edge recording counter.The corresponding moment t of this transport stream packets _sfor N * 5 nanosecond.This value is deposited in register 1;

3) extract the 5th byte to the 11 bytes after the sync byte 0x47 of packet header, be stored in register 2; Data in register 2 are converted to ASCII character, revert to former transmission data; Four figures in register 2, according to being program clock reference value flag bit, if zero, returns to step 2); If 1, show that this transmission package contains program clock reference, by the t in the 2nd byte to the 7 byte datas and register 1 in register 2 _scoding generates nanosecond timestamp, and front 6 bytes of nanosecond timestamp are program clock reference value, and rear 4 bytes are t _s;

(3) encircle greatly latency measurement and correction

By nanosecond timestamp production method step (2) gained nanosecond timestamp, be denoted as transmitting time stamp, deposit in the memory A of first in first out, the size of memory A is 100 bytes;

1) ground receiving terminal via satellite antenna reception from the downstream signal of satellite, asynchronous serial signal bit stream through demodulation, output 270 MBPSs, carry out that signal is synchronous, nanosecond timestamp produces, obtain timestamp and be denoted as time of reception stamp, signal synchronizing method is identical with signal synchronizing step (1), and nanosecond timestamp production method is identical with nanosecond timestamp production method (2); The corresponding moment of rising edge of the 7th to the 8th of synchronous head in transport stream packets is denoted as to t _r;

2) by step 1) the program clock reference value in time of reception stamp finds the transmitting time stamp of same program clock reference value in memory A as keyword.If do not mate, abandon this time of reception stamp, wait for next time of reception stamp; If find, transmitting time stamp and time of reception are stabbed to corresponding moment value and subtract each other, obtain encircling greatly latency measurement value:

$\mathrm{\&Delta;t}=\left\{\begin{array}{cc}{t}_r-t_s& t_r>t_s\\ t_r-t_s+{10}^9& t_s<t_r\end{array}\right.$

In formula, Δ t is large ring latency measurement value, takies four bytes, and tr is the moment value in time of reception stamp, and ts is the moment value in transmitting time stamp; Whether Δ t is deposited in to the memory B of first in first out, determine as follows;

Get nearest three measurement data Δ t ₁, Δ t ₂, Δ t ₃, obtain predicted value if record large ring time delay Δ t and predicted value residual error be not more than

$\sqrt{\underset{i=1}{\overset{10}{\mathrm{\&Sigma;}}}{(\mathrm{\&Delta;}{t}_i-\mathrm{\&Delta;}\stackrel{\&OverBar;}{t})}^2}$

Think that this measures Δ t effective, Δ t is deposited in memory B; Otherwise, think that program clock reference time stamp is abnormal or Δ t is abnormal, abandon Δ t, get predicted value large ring time delay as correspondence, deposits in memory B.