CN106850478A - A kind of data for ship automatic identification system are demodulated and synchronous method - Google Patents
A kind of data for ship automatic identification system are demodulated and synchronous method Download PDFInfo
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- CN106850478A CN106850478A CN201611246744.7A CN201611246744A CN106850478A CN 106850478 A CN106850478 A CN 106850478A CN 201611246744 A CN201611246744 A CN 201611246744A CN 106850478 A CN106850478 A CN 106850478A
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- data
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- identification system
- automatic identification
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0054—Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0061—Error detection codes
Abstract
Synchronous method is demodulated the invention discloses a kind of data for ship automatic identification system, the method realizes data syn-chronization by the way of time domain sequential search phase and verification detection, the short frame signal of burst can be overcome to be difficult to the problem of synchronization and synchronization accuracy difference, improve the short frame signal synchronization accuracy of burst；In addition, simplifying data demodulation process process present invention employs the processing mode that 2bit difference and Viterbi iteration are adjudicated, the performance of data demodulation, complex process and resource requirement The method avoids traditional 1bit differential ference spirals mode are improved.
Description
Technical field
The present invention relates to signal detection demodulation techniques field, more particularly to a kind of data for ship automatic identification system
Demodulation and synchronous method, the method are used to carry out data demodulation synchronization to burst, short frame signal.
Background technology
2 months 2014 International Telecommunication Union ITU-R use that M.1371-5 recommendation proposes in VHF Waterborne movable frequency ranges
The technical characteristic of the automatic recognition system (AIS) of time division multiple acess, and it is special to the communication technology of automatic recognition system (AIS) system
Property has made corresponding regulation, but does not make respective specified to implementation.Particularly synchronous to the short frame signal that happens suddenly and solution
The implementation of tune, does not clearly state implementation.
The content of the invention
It is an object of the invention to overcome the deficiencies in the prior art, there is provided a kind of number for ship automatic identification system
According to demodulation and synchronous method, the method can overcome the short frame signal of burst to be difficult to the problem of synchronization and synchronization accuracy difference, improve
Happen suddenly short frame signal synchronization accuracy；In addition, present invention employs the processing mode simplification that 2bit difference and Viterbi iteration are adjudicated
Data demodulation process processes, improve the performance of data demodulation, The method avoids traditional 1bit differential ference spirals mode
Complex process and resource requirement.
Technical solution of the invention is：
A kind of data for ship automatic identification system are demodulated and synchronous method, are comprised the following steps：
(1), the docking collection of letters number obtains receiving data after carrying out sample quantization treatment；Wherein, sample rate is fs；
(2), to obtaining delayed data after the reception data delay T, then by the delayed data and reception data phase
It is multiplied to mixing data；Wherein,fbIt is the data transfer rate of setting；
(3), the mixing data of step (2) extract and LPF, obtain data xn, wherein：Data pick-up rate
For M is the positive integer and M of setting<N；The filtering bandwidth of LPF is
(4), by the data x in same tdma slotnIt is sequentially stored in memory RAM；
(5) data, are read from memory RAM；Then, reduction of speed treatment is integrated to the reading data, is dropped
Fast data yn, i.e.,：Continuous N data point is carried out cumulative summation as reduction of speed data yn1 data point；
(6), to reduction of speed data ynNoise whitening treatment is carried out, noise whitening data z is obtainedn；
(7), under Viterbi decoding rules, according to reduction of speed data ynWith noise whitening data znCalculate weight αn；
(8), according to weight αnChoose corresponding optimum state transfer path；And the optimum state transfer path is determined
Demodulating data carry out CRC check, wherein：If the demodulating data has passed through CRC check, judge that demodulation result is correct；
If the demodulating data is not over CRC check, the digital independent original position of memory RAM, and return to step are changed
(5)。
The above-mentioned data for ship automatic identification system are demodulated and synchronous method, in step (3), are dropped using integration
The extraction to data and LPF are realized in speed treatment, and concrete methods of realizing is as follows：
(3a), the corresponding N number of sampled point of same data symbol in mixing data is divided into M groups；
(3b), each sampled point in every group is carried out into data accumulation summation, as corresponding data point after data pick-up, i.e.,：
Sampled point in m groups is carried out into accumulative summation, as carrying out the m-th strong point after data pick-up to N number of sampled point；
Wherein, m=1,2 ..., M；
The above-mentioned data for ship automatic identification system are demodulated and synchronous method, and N number of sampled point is divided into M groups, are had
Body group technology is as follows：Every group of data include P sampled point, and P isInteger after rounding up；Wherein, if MP>N,
MP-N data gather together enough M group data before then being extracted from the corresponding N sampled points of next data symbol.
The above-mentioned data for ship automatic identification system are demodulated and synchronous method, in step (6), to reduction of speed data
ynNoise whitening treatment is carried out, specific processing method is as follows：Produce pseudo-random sequence pn；Then by the pseudo-random sequence pnWith
Reduction of speed data ynIt is multiplied, obtains noise whitening data zn。
The above-mentioned data for ship automatic identification system are demodulated and synchronous method, in step (7), according to reduction of speed number
According to ynWith noise whitening data znCalculate weight αn, specific formula for calculation is as follows：
Wherein, L is the front and rear code element memory span of setting.
The beneficial effect brought of the present invention is：
(1) after, the docking collection of letters number of the invention carries out sample quantization, will directly be mixed after reception two symbols of data delay
Frequently, the cost of generation local carrier is saved；
(2), the present invention simplifies data demodulation process process using the processing mode of Viterbi iteration judgement, improves
The performance of data demodulation.
Brief description of the drawings
Fig. 1 is of the invention for the data demodulation of ship automatic identification system and synchronous method realization principle schematic diagram.
Specific embodiment
The present invention is described in further detail with instantiation below in conjunction with the accompanying drawings：
As shown in figure 1, the data demodulation and synchronous method for ship automatic identification system of the invention, specifically include with
Lower step：
(1) obtain receiving data after, carrying out sample quantization treatment using the ADC docking collection of letters number；Wherein, ADC
Sample rate be fs；
(2), to obtaining delayed data after the reception data delay T after ADC, then by the delayed data and reception data
Multiplication obtains being mixed data；Wherein,fbIt is the data transfer rate of setting, being equivalent to will receive two sign bits of data delay
After obtain local carrier signal, can so save generation local carrier cost；
(3), the mixing data of step (2) extract and LPF, obtain data xn, wherein：Data pick-up rate
For M is the positive integer and M of setting<N；The filtering bandwidth of LPF isTwo frequencys multiplication letter can be filtered
Number component.In this step, the extraction to data and LPF, concrete methods of realizing can be realized using integration reduction of speed treatment
It is as follows：
(3a), the corresponding N number of sampled point of same data symbol in mixing data is divided into M groups；
(3b), each sampled point in every group is carried out into data accumulation summation, as corresponding data point after data pick-up, i.e.,：
Sampled point in m groups is carried out into accumulative summation, as carrying out the m-th strong point after data pick-up to N number of sampled point；
Wherein, m=1,2 ..., M.Wherein, N number of sampled point is divided into M groups, specific group technology is as follows：Every group of data include that P is adopted
Sampling point, P isInteger after rounding up；If MP>N, then before being extracted from the corresponding N sampled points of next data symbol
MP-N data gather together enough M group data.
(4), by the data x in same tdma slotnIt is sequentially stored in memory RAM；Can so use higher
Reading rate obtain data in a time slot, and processed simultaneously, and limited without by data transfer rate.
(5) data, are read from memory RAM；Then, reduction of speed treatment is integrated to the reading data, is dropped
Fast data yn, i.e.,：Continuous N data point is carried out cumulative summation as reduction of speed data yn1 data point；
(6), to reduction of speed data ynNoise whitening treatment is carried out, noise whitening data z is obtainedn；Specific noise whitening treatment side
Method is as follows：Produce pseudo-random sequence pn, then by the pseudo-random sequence pnWith reduction of speed data ynIt is multiplied, obtains noise whitening number
According to zn。
(7), under Viterbi decoding rules, according to reduction of speed data ynWith noise whitening data znCalculate weight αn, specifically
Computing formula is as follows：
(8), according to weight αnChoose corresponding optimum state transfer path；And the optimum state transfer path is determined
Demodulating data carry out CRC check, wherein：If the demodulating data has passed through CRC check, judge that demodulation result is correct；
If the demodulating data is not over CRC check, the digital independent original position of memory RAM, and return to step are changed
(5)。
Embodiment：
In the present embodiment, the data rate f of ship automatic identification system (AIS)bIt is 9.6kbps, modulation system is
GMSK, frame length 256bit, coded system NRZ-I, data are initiated with 0X7E, and data terminate as 0X7E, CRC check 16.
Processed using data of the invention demodulation and synchronous method, implemented step as follows：
(1) sample quantization, is carried out using the ADC docking collections of letters number, obtains receiving data.Wherein, ADC in the present embodiment
Sample rate be set as 9.6MHz, therefore the corresponding sampling number N of each data symbol in reception data after sample quantization
=1000.
(2), after by above-mentioned 2000 sampled points of reception data delay, it is multiplied with current reception data and obtains mixing letter
Number.
(3), according to performance requirement, data pick-up is carried out to above-mentioned mixed frequency signal.Wherein, taken out in each data symbol
Take 20 points, i.e. M=20.In this step, the points bigger performances of M are extracted better, but extracting points will bring hardware to provide more
The consumption in source, it is therefore desirable to compromise.
(4), by the data Cun Chudao depth after above-mentioned extraction for 256x20 RAM memory in, according to extract speed essence
Degree control read memory original position, successively by the data read-out in memory, and export reduction of speed module to integration.
(5), integration reduction of speed module integration points arranges value it is consistent with number of sampling points, will continuous N data point carry out
Cumulative summation is used as reduction of speed data yn1 data point.
(6), by reduction of speed data ynThe treatment that is multiplied is carried out with pseudo-random sequence (such as m-sequence), is equivalent to reduction of speed data yn
Noise whitening treatment is carried out, noise whitening data z is obtainedn。
(7) weight α of each symbol, is calculated according to equation belown：
Wherein, L is the front and rear code element memory span of setting.The bigger performance of L values is better, considers resource and performance,
The present embodiment chooses L=4.
(8) and then according to the state-transition table in table 1, judge to be transferred to the path of NextState, until last
Optimal path is selected after symbol, the corresponding bit of each state in optimal path is demodulating data.For example：A upper shape
State is state 1 (- 1, -1, -1, -1), and currently αn=+1, then next state will jump to state 9 (- 1, -1, -1 ,+1)；
Table 1Viterbi adjudicates state-transition table
| Sequence number | Transfering state | |||||||||
| 1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | 1 9 | |
| 2 | +1 | -1 | -1 | -1 | +1 | -1 | -1 | -1 | 1 9 | |
| 3 | -1 | +1 | -1 | -1 | -1 | +1 | -1 | -1 | 2 10 | |
| 4 | +1 | +1 | -1 | -1 | +1 | +1 | -1 | -1 | 2 10 | |
| 5 | -1 | -1 | +1 | -1 | -1 | -1 | +1 | -1 | 3 11 | |
| 6 | +1 | -1 | +1 | -1 | +1 | -1 | +1 | -1 | 3 11 | |
| 7 | -1 | +1 | +1 | -1 | -1 | +1 | +1 | -1 | 4 12 | |
| 8 | +1 | +1 | +1 | -1 | +1 | +1 | +1 | -1 | 4 12 | |
| 9 | -1 | -1 | -1 | +1 | -1 | -1 | -1 | +1 | 5 13 | |
| 10 | +1 | -1 | -1 | +1 | +1 | -1 | -1 | +1 | 5 13 | |
| 11 | -1 | +1 | -1 | +1 | -1 | +1 | -1 | +1 | 6 14 | |
| 12 | +1 | +1 | -1 | +1 | +1 | +1 | -1 | +1 | 6 14 | |
| 13 | -1 | -1 | +1 | +1 | -1 | -1 | +1 | +1 | 7 15 | |
| 14 | +1 | -1 | +1 | +1 | +1 | -1 | +1 | +1 | 7 15 | |
| 15 | -1 | +1 | +1 | +1 | -1 | +1 | +1 | +1 | 8 16 | |
| 16 | +1 | +1 | +1 | +1 | +1 | +1 | +1 | +1 | 8 16 |
(9) CRC check, is carried out to the demodulating data that the optimum state transfer path determines, wherein：If the demodulation
Data have passed through CRC check, then judge that demodulation result is correct；If the demodulating data is deposited not over CRC check, modification
The digital independent original position of reservoir RAM, and return to step (5).
The above, only one specific embodiment of the present invention, but protection scope of the present invention is not limited thereto, and appoints
What those familiar with the art the invention discloses technical scope in, the change or replacement that can be readily occurred in, all
Should be included within the scope of the present invention.
The content not being described in detail in description of the invention belongs to the known technology of professional and technical personnel in the field.
Claims (5)
1. a kind of for the data demodulation of ship automatic identification system and synchronous method, it is characterised in that：Comprise the following steps：
(1), the docking collection of letters number obtains receiving data after carrying out sample quantization treatment；Wherein, sample rate is fs；
(2) it is then that the delayed data is mutually multiplied with reception data, to obtaining delayed data after the reception data delay T
To mixing data；Wherein,fbIt is the data transfer rate of setting；
(3), the mixing data of step (2) extract and LPF, obtain data xn, wherein：Data pick-up rate isM is the positive integer and M of setting<N；The filtering bandwidth of LPF is
(4), by the data x in same tdma slotnIt is sequentially stored in memory RAM；
(5) data, are read from memory RAM；Then, reduction of speed treatment is integrated to the reading data, obtains reduction of speed number
According to yn, i.e.,：Continuous N data point is carried out cumulative summation as reduction of speed data yn1 data point；
(6), to reduction of speed data ynNoise whitening treatment is carried out, noise whitening data z is obtainedn；
(7), under Viterbi decoding rules, according to reduction of speed data ynWith noise whitening data znCalculate weight αn；
(8), according to weight αnChoose corresponding optimum state transfer path；And to the solution of optimum state transfer path determination
Adjusting data carries out CRC check, wherein：If the demodulating data has passed through CRC check, judge that demodulation result is correct；If
The demodulating data then changes the digital independent original position of memory RAM, and return to step (5) not over CRC check.
2. a kind of for the data demodulation of ship automatic identification system and synchronous method according to claim 1, its feature exists
In：In step (3), the extraction to data and LPF are realized using integration reduction of speed treatment, concrete methods of realizing is as follows：
(3a), the corresponding N number of sampled point of same data symbol in mixing data is divided into M groups；
(3b), each sampled point in every group is carried out into data accumulation summation, as corresponding data point after data pick-up, i.e.,：By m
Sampled point in group carries out accumulative summation, used as carrying out the m-th strong point after data pick-up to N number of sampled point；Wherein,
M=1,2 ..., M.
3. a kind of for the data demodulation of ship automatic identification system and synchronous method according to claim 2, its feature exists
In：N number of sampled point is divided into M groups, specific group technology is as follows：Every group of data include P sampled point, and P isRound up
Integer afterwards；Wherein, if MP>N, then MP-N data gather together enough M before being extracted from the corresponding N sampled points of next data symbol
Group data.
4. a kind of for the data demodulation of ship automatic identification system and synchronous method according to claim 1, its feature exists
In：In step (6), to reduction of speed data ynNoise whitening treatment is carried out, specific processing method is as follows：Produce pseudo-random sequence pn；
Then by the pseudo-random sequence pnWith reduction of speed data ynIt is multiplied, obtains noise whitening data zn。
5. a kind of for the data demodulation of ship automatic identification system and synchronous method according to claim 1, its feature exists
In：In step (7), according to reduction of speed data ynWith noise whitening data znCalculate weight αn, specific formula for calculation is as follows：
Wherein, L is the front and rear code element memory span of setting.
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Cited By (2)
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| CN108632185A (en) * | 2018-05-15 | 2018-10-09 | 北京遥测技术研究所 | A kind of the AIS systems demodulation method and demodulating system of ship VDES systems |
| CN110943956A (en) * | 2019-12-03 | 2020-03-31 | 航天恒星科技有限公司 | Signal demodulation method and system of satellite-borne automatic identification system AIS |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108632185A (en) * | 2018-05-15 | 2018-10-09 | 北京遥测技术研究所 | A kind of the AIS systems demodulation method and demodulating system of ship VDES systems |
| CN108632185B (en) * | 2018-05-15 | 2021-02-09 | 北京遥测技术研究所 | AIS system demodulation method and demodulation system of ship VDES system |
| CN110943956A (en) * | 2019-12-03 | 2020-03-31 | 航天恒星科技有限公司 | Signal demodulation method and system of satellite-borne automatic identification system AIS |
| CN110943956B (en) * | 2019-12-03 | 2022-05-24 | 航天恒星科技有限公司 | Signal demodulation method and system for satellite-borne automatic identification system AIS |
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