CN112865882B - Anti-frequency offset DMR interphone signal rapid identification method - Google Patents
Anti-frequency offset DMR interphone signal rapid identification method Download PDFInfo
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- CN112865882B CN112865882B CN202110067536.5A CN202110067536A CN112865882B CN 112865882 B CN112865882 B CN 112865882B CN 202110067536 A CN202110067536 A CN 202110067536A CN 112865882 B CN112865882 B CN 112865882B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/3827—Portable transceivers
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Abstract
The invention discloses a quick identification method of a DMR interphone signal resisting frequency offset, which comprises the steps of extracting integer times and decimal times of baseband data after monitoring and finding out a suspected signal of the DMR interphone, performing normalization correlation on the baseband data, performing precompensation on frequency offset components of a root raised cosine filter and an FM demodulator and a plurality of locally reserved voice synchronous signals, and finally judging whether the signal is the DMR interphone signal through a threshold. The method enhances the receiving range of the equipment to the signal frequency offset and improves the identification probability of the DMR interphone. The invention solves the problem of DMR detection probability drop when frequency deviation exists, and is suitable for the wireless communication field.
Description
Technical Field
The invention belongs to the technical field of signal detection, and particularly relates to a rapid identification method of a frequency offset-resistant DMR interphone signal.
Background
When the wireless monitoring equipment scans the frequency band of the interphone, if suspicious wireless signals are found, spectrum fine analysis can be carried out to further define the bandwidth and the center frequency point of the signals. Because the frequency deviation often exists in the center frequency point estimation, the performance of the synchronous correlation detection of the DMR signal is seriously reduced after the frequency deviation is more than 1 Khz.
Disclosure of Invention
The invention aims to: aiming at the defects, the invention provides the rapid identification method of the anti-frequency deviation DMR interphone signal, which improves the success rate of the monitoring equipment for identifying the DMR interphone signal.
The technical scheme is as follows: the invention provides a quick identification method of a DMR interphone signal resistant to frequency offset, which is characterized by comprising the following steps:
(1) Acquiring an N times oversampling signal;
(2) According to the oversampling multiple N, the sampled data p (N) passes through an FM demodulator, and the output data is recorded as q (N);
(3) Filtering q (n) by a root raised cosine filter to obtain baseband data g (n) 1;
(4) Adding and subtracting offset numbers according to the data g (n) 1 to obtain three groups of data to be detected, namely demodulation signal negative frequency offset precompensation, demodulation signal positive frequency offset precompensation and demodulation original signal;
(5) Respectively carrying out sliding normalization correlation operation on the three groups of data to be detected obtained in the step (4) and the locally reserved 4 groups of voice synchronous data of the DMR interphone;
(6) And (3) judging whether the correlation data peak value calculated in the step (5) exceeds a threshold, if so, judging that the signal is a DMR interphone signal, and if not, judging that the signal is not the DMR interphone signal.
Further, the specific step of acquiring the N times of oversampling signal in the step (1) is as follows:
(1.1) performing large bandwidth monitoring on a wireless environment;
(1.2) if suspicious signals are found in the frequency band of the DMR interphone, reducing the monitoring bandwidth and improving the spectrum analysis precision;
(1.3) if the bandwidth of the signal accords with the spectrum characteristics of the DMR interphone, obtaining a center frequency point f 0;
(1.4) performing down-conversion processing on the data by taking f 0 as a central frequency point to obtain baseband data { x (n), n=1, 2, … … };
(1.5) by integer and fractional decimation, an N-fold oversampled signal { p (N), n=1, 2,3, … }.
Further, the output data g (n) 1 in the step (3) is specifically
Further, the specific steps for obtaining three groups of data to be detected in the step (4) are as follows: the demodulation data g (n) 1 minus the offset fre2KOffset to { g (n) 2＝g(n)1 -fre2KOffset, n=1, 2, … }, the other group is the demodulation data g (n) 1 plus the offset fre2KOffset to { g (n) 3＝g(n)1 +fre2KOffset, n=1, 2, … }, plus g (n) 1 to form three groups of data to be detected.
Further, the specific steps of performing sliding normalization correlation operation on the three groups of data to be detected in the step (5) and the locally reserved 4 groups of voice synchronization data of the DMR interphone respectively are as follows:
k=0, 2,4, …, W-1; w is the interval of the voice synchronous head, M is the length of the synchronous head
I=1, 2,3; i is the index of the baseband three sets of data g (n) i
J=1, 2,3,4; j is four voice synchronization header indexes
L=0, 1, …, L-1; l is the number of periods of the voice synchronization signal for buffering the baseband data
The invention adopts the technical scheme and has the following beneficial effects: the method can accurately detect the DMR interphone signal with high probability under the condition that the frequency deviation is within +/-3 KHz, simplifies the hardware design of monitoring equipment, reduces the precision requirement on frequency point estimation by a method of adding and subtracting constants from a demodulation signal, does not need carrier synchronization, and reduces the complexity of software.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
fig. 2 is a graph of signal power of the DMR interphone at a sampling rate of 38.4Khz in an embodiment;
Fig. 3 is an accumulated correlation diagram of DMR interphone signals and local matching signals without frequency offset in a specific embodiment;
fig. 4 is a schematic diagram of recognition rates under different frequency offset conditions in an embodiment.
Detailed Description
The present application is further illustrated below in conjunction with specific embodiments, it being understood that these embodiments are meant to be illustrative of the application and not limiting the scope of the application, and that modifications of the application, which are equivalent to those skilled in the art to which the application pertains, fall within the scope of the application defined in the appended claims after reading the application.
As shown in fig. 1-4, the DMR interphone direct mode time slot 1 communication operating at 409.7625MHz is monitored and described as an example:
step 1, monitoring the wireless environment with 500MHz bandwidth;
Step 2, once suspicious signals are found in the frequency band of the DMR interphone, the monitoring bandwidth is reduced to 25MHz, and the signal bandwidth is estimated to be 9.85Khz;
Step 3, the bandwidth of the signal accords with the spectrum characteristics of the DMR interphone, and a center frequency point f 0 = 409.761324MHz is estimated;
step 4, taking f 0 as a central frequency point, performing down-conversion treatment on the data to obtain baseband data { x (n), n=1, 2, … … }, wherein the sampling frequency is 1M;
Step 5, obtaining a 40K sampling signal by 25 integer times extraction and a signal with a 38.4K sampling rate by 40/38.4 fractional times extraction, wherein the signal is an n=8 times oversampling signal { p (N), n=1, 2,3, … }, and fig. 2-4 are signal power spectrums;
Step 6, the FM demodulator demodulates to obtain a demodulation signal { q (n), n=1, 2,3, … };
Step 7, according to the oversampling multiple n=8, the sampled data q (N) is passed through a root raised cosine filter h (N), the oversampling multiple of the root raised cosine filter is 8, 49 tap coefficients are provided across 6 symbols, and the output data is recorded as
Step 8, demodulating data g (n) 1 minus offset fre KOffset =5 to obtain { g (n) 2＝g(n)1 -fre2KOffset, n=1, 2, … }, and the other group is demodulating data g (n) 1 plus offset fre KOffset =5 to obtain { g (n) 3＝g(n)1 +fre2KOffset, n=1, 2, … }, plus g (n) 1 to form three groups of data to be detected;
Step 9, performing sliding normalization correlation operation on data { g (n) 1,g(n)2,g(n)3 } and locally reserved 4 groups of DMR interphone voice synchronization data (base station voice synchronization, hand station voice synchronization, through time slot 1 voice synchronization, through time slot 2 voice synchronization) { dmrSync (n) j, n=1, 2,..: k=0, 2, …
K=0, 2,4, …, W-1; w is the interval of the voice synchronous head, M is the length of the synchronous head
I=1, 2,3; i is the index of the baseband three sets of data g (n) i
J=1, 2,3,4; j is four voice synchronization header indexes
L=0, 1, …, L-1; l is the number of periods of the voice synchronization signal for buffering the baseband data
And overlap-accumulate the correlation results of L=6 cycles, M=192 is the length of the voice synchronous head;
In step 10, as shown in fig. 3-4, the peak value of the synchronization head related data of the through slot1 is normalized, where the normalized correlation value is 0.965 exceeding the threshold threshold=0.65, and the DMR interphone signal is recognized.
Claims (3)
1. A quick identification method of a DMR interphone signal resistant to frequency deviation is characterized by comprising the following steps:
(1) Acquiring an N times oversampling signal;
(2) According to the oversampling multiple N, demodulating the sampling data p (N) by using an FM demodulator, and recording the output data as q (N);
(3) Q (n) is subjected to a root raised cosine filter h (n) to obtain baseband data g (n) 1;
(4) Adding and subtracting offset numbers according to the demodulation data g (n) 1 to obtain three groups of data to be detected, namely demodulation signal negative frequency offset precompensation, demodulation signal positive frequency offset precompensation and demodulation original signal;
(5) Respectively carrying out sliding normalization correlation operation on the three groups of data to be detected obtained in the step (4) and the locally reserved 4 groups of voice synchronous data of the DMR interphone;
(6) Judging whether the correlation data peak value calculated in the step (5) exceeds a threshold, if yes, judging that the signal is a DMR interphone signal, and if not, judging that the signal is not the DMR interphone signal;
The specific steps for acquiring the N times of oversampling signals in the step (1) are as follows:
(1.1) performing large bandwidth monitoring on a wireless environment;
(1.2) if suspicious signals are found in the frequency band of the DMR interphone, reducing the monitoring bandwidth and improving the spectrum analysis precision;
(1.3) if the bandwidth of the signal accords with the spectrum characteristics of the DMR interphone, obtaining a center frequency point f 0;
(1.4) performing down-conversion processing on the data by taking f 0 as a central frequency point to obtain baseband data { x (n), n=1, 2, … … };
(1.5) obtaining an N-times oversampled signal { p (N), n=1, 2,3, … …, M }, by integer multiple extraction and fractional multiple extraction;
the specific steps of performing sliding normalization correlation operation on the three groups of data to be detected and the 4 groups of locally reserved voice synchronous data of the DMR interphone in the step (5) are as follows:
Wherein W is the interval of the voice synchronous head, M is the length of the synchronous head; i=1, 2,3, i is the baseband three sets of data g (n) i index; j=1, 2,3,4, j is four voice synchronization head indexes; l=0, 1, …, L-1, L is the number of voice synchronization signal cycles to buffer baseband data; in dmrSync (n) j, n=1, 2,..m, j=1, 2,3,4, representing a sliding normalization correlation operation.
2. The method for quickly identifying a DMR interphone signal resistant to frequency offset according to claim 1, wherein the output data g (n) 1 in the step (3) is specifically
3. The method for quickly identifying the anti-frequency deviation DMR interphone signal according to claim 1, wherein the specific steps of obtaining three groups of data to be detected in the step (4) are as follows: the demodulation data g (n) 1 minus the offset fre2KOffset to { g (n) 2＝g(n)1 -fre2KOffset, n=1, 2, … }, the other group is the demodulation data g (n) 1 plus the offset fre2KOffset to { g (n) 3＝g(n)1 +fre2KOffset, n=1, 2, … }, plus g (n) 1 to form three groups of data to be detected.
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| CN111083803A (en) * | 2019-12-09 | 2020-04-28 | 深圳市普天宜通技术股份有限公司 | Method and system for realizing communication between public network interphone and DMR interphone |
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| CN101515910A (en) * | 2009-03-30 | 2009-08-26 | 西安电子科技大学 | DMR physical layer four-level modem |
| CN101888253A (en) * | 2010-05-28 | 2010-11-17 | 深圳国微技术有限公司 | Deviation correcting method and system of communication channel baseband frequency |
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