CN103684583A - Detection method of GSM (Global System for Mobile Communications) frequency calibration package - Google Patents
Detection method of GSM (Global System for Mobile Communications) frequency calibration package Download PDFInfo
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- CN103684583A CN103684583A CN201310749374.9A CN201310749374A CN103684583A CN 103684583 A CN103684583 A CN 103684583A CN 201310749374 A CN201310749374 A CN 201310749374A CN 103684583 A CN103684583 A CN 103684583A
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Abstract
The invention relates to the synchronization technology in the technical field of mobile communication, and provides a detection method of a GSM (Global System for Mobile Communications) frequency calibration package. The detection method of the GSM frequency calibration package comprises the following steps: step 1, sampling GSM baseband signals to obtain a sampled data sequence of the GSM baseband signal, wherein the sampling frequency is the data rate of GSM; step 2, calculating phase difference of signals of two adjacent sampling points in the sampled data sequence of the GSM baseband signal; step 3, if the phase differences of continuous N adjacent sampling points in the sampled data sequence are more than 0, determining that the frequency calibration package is detected, wherein N is a positive integer, not less than 140 and not more than 148. The invention further provides a detection device of the GSM frequency calibration package. According to the method and device provided by the invention, the calculation amount, complexity and cost of the system can be reduced.
Description
Technical field
The present invention relates to the simultaneous techniques in mobile communication technology field, relate in particular to a kind of detection method of GSM frequency calibration bag.
Background technology
The empty physical layer of GSM (Global System of Mobile communication, global system for mobile communications) adopts the mode of time division multiplexing and frequency division multiplexing.GSM eats dishes without rice or wine will the time be divided into time slice in each frequency, i.e. time slot, each slot transmission 156.25 Bit data.Several packets below can transmitting in the time slot of GSM: frequency calibration bag, sync packet, normal packet, access package, empty bag etc.Wherein the effect of frequency calibration bag be to provide terminal find base station and calculate self and base station between frequency deviation.Frequency calibration bag is the packet of full 0.Full 0 data are through forming than the sine wave signal of the high 67KHZ of carrier frequency after GSM modulation system GMSK.Due to continuous 0 and continuous 1 data rarely in GSM, so the signal strength signal intensity of frequency calibration packet generation is just a little more than the average signal strength of GSM carrier wave.Thereby this is conducive to terminal detection frequency calibration, bag further carries out frequency deviation estimation and the parsing to sync packet.
A typical example of frequency calibration bag is the FCB of the upper carrying of FCCH in gsm system (Frequency Correction CHannels, frequency correction channel).FCCH transmits the information of proofreading and correct travelling carriage (MS) frequency to user.All 148 bits of FCB are all " 0 ".Gsm system adopts GMSK (Guassian Minimum Shift Keying) GMSK modulation mode, and FCCH, after modulation, is a pure sine wave, the high 67kHz of frequency ratio centre carrier frequency.
Current frequency calibration packet inspection method is generally the method for frequency domain computing aspect or uses the method for computing cross-correlation aspect.
the method of frequency domain computing aspect detects frequency calibration bag and is generally use fast Fourier transform, by the sine wave signal of catching higher than carrier wave average signal strength, frequency calibration bag detected.The algorithm of cross-correlation aspect is generally the GSM carrier signal sampling and preprepared GSM frequency calibration bag signal is carried out to computing cross-correlation, if detect the value of the result of cross-correlation, is greater than thresholding and just thinks and GSM frequency calibration bag detected.
The operand of above-mentioned two kinds of methods is larger, all needs through a fairly large number of multiplying, to having relatively high expectations of processor.If will detect a plurality of carrier waves simultaneously, said method just needs to use more expensive processor.For overcoming the shortcoming that said method detection complexity is high, the invention provides a kind of detection method of GSM frequency calibration bag, operand is little, can fast detecting arrive frequency calibration bag.
Summary of the invention
The detection method that the object of this invention is to provide a kind of GSM frequency calibration bag, can reduce system operand, and mitigation system complexity reduces system cost.
To achieve these goals, the invention provides a kind of detection method of GSM frequency calibration bag, it is characterized in that, comprise the steps:
Step 1. sampling GSM baseband signal, obtains the sampled data sequence of GSM baseband signal, wherein, and the data rate that sample rate is GSM;
The described sampled data sequence of step 2. pair GSM baseband signal is calculated the phase difference of the signal of adjacent two sampled points;
If there are the data that make to occur continuously that N above described neighbouring sample point signal phase difference is greater than 0 in step 3. in described sampled data sequence, definitely frequency calibration bag detected, wherein, N is positive integer, N be more than or equal to 140 and N be less than or equal to 148.
Above-mentioned method, also comprises:
If step 4. sampled data reaches M sampled point, the data that occur that continuously N described neighbouring sample point signal phase difference is greater than 0 also do not detected, judgement can't detect frequency calibration bag or judges that data carrier is not the broadcast carrier of GSM base station, and wherein M is 12500.
Above-mentioned method, wherein, the account form of phase difference is as follows:
S
n=I
n+ Q
n* j is previous sampled point, S
n+1=I
n+1+ Q
n+1* j is a rear sampled point, wherein, and I
n, Q
n, I
n+1, Q
n+1for real number, n is integer;
Phase difference D
n=arctg (S
n+1/ S
n).
Above-mentioned method, wherein, described N is 148;
Describedly occur that continuously the above described neighbouring sample point signal phase difference of N is greater than 0 and is specially:
D
nto D
n+147all be greater than 0.
Above-mentioned method, wherein, described data rate is 270.833Kbps; The effect of described frequency calibration bag be make terminal find base station and calculate self and base station between frequency deviation; The packet that described frequency calibration bag is full 0.
In order better to realize object of the present invention, the present invention also provides a kind of checkout gear of GSM frequency calibration bag, it is characterized in that comprising:
Sampling module, the GSM baseband signal that is configured to sample, obtains the sampled data sequence of GSM baseband signal, wherein, the data rate that sample rate is GSM;
Computing module, is configured to the described sampled data sequence of GSM baseband signal to calculate the phase difference of the signal of adjacent two sampled points;
Determination module, if be configured to existence in described sampled data sequence, make the data that occur that continuously more than N described neighbouring sample point signal phase difference is greater than 0, determine and frequency calibration bag detected, wherein, N is positive integer, N be more than or equal to 140 and N be less than or equal to 148.
Utilize the present invention, can realize the function that detects GSM frequency calibration bag with few operand.If detect the frequency calibration bag of a plurality of GSM carrier waves simultaneously, it is obvious that operation efficiency of the present invention is compared existing method increase rate.The present invention can be applied to GSM mobile handset, GSM base station testing instrument, GSM road measuring device etc.
Accompanying drawing explanation
Fig. 1 is the present invention's GSM frequency calibration packet inspection method flow chart;
Fig. 2 is the present invention's GSM frequency calibration package detection device structure chart.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.
In communication system, receiving terminal need to be consistent with the frequency source signal frequency of transmitting terminal.At transmitting terminal and receiving terminal, adopt high-precision crystal oscillator.After the use of a period of time, crystal oscillator can drift about by occurrence frequency, need to carry out frequency correction.
By transmitting terminal, to receiving terminal, send a frequency reference signal, receiving terminal carries out automatic calibration according to the frequency reference signal receiving to the frequency of local frequency source signal, make the frequency of frequency tracking frequency reference signal in the scope of error permission of local frequency source signal, reach the object of receiving terminal and transmitting terminal Frequency Synchronization.
Frequency reference signal is intermittently to send, and receiving terminal needed first to detect to receive in signal whether have frequency reference signal before carrying out automatic frequency correction, under the prerequisite that frequency reference signal existence detected, can implement automatic frequency correction.
In gsm mobile communication system, between base station and mobile terminal or repeater, carry out frequency correction.Base station is in downlink broadcast channel, every about 46ms or 51ms, send the calibrating frequency burst packets (FCB) that a duration is about 577 μ s, it is frequency reference signal, these FCB are detected in mobile terminal or repeater in receiving signal, and proofread and correct the frequency source signal frequency of oneself according to these FCB.
The effect of frequency calibration bag be to provide terminal find base station and calculate self and base station between frequency deviation.Frequency calibration bag is the packet of full 0.Full 0 data are through forming than the sine wave signal of the high 67KHZ of carrier frequency after GSM modulation system GMSK.Because GSM frequency calibration wraps in after ovennodulation the sine wave signal a little more than its carrier wave with regard to forming frequency, if be therefore baseband signal by the frequency conversion of GSM carrier signal, baseband signal is sampled, the sampled data of GSM frequency calibration bag will have phenomenon like this so again: in adjacent two sampled points, the phase place of a rear sampled point is affirmed the phase place higher than previous sampled point.The present invention is just based on this principle.
Executive agent in the present invention is terminal, comprises mobile phone, travelling carriage, mobile phone, laptop computer, car-mounted terminal etc.
Mobile terminal of the present invention comprises microprocessor, and it is by three kinds of buses---control, address and data/address bus and program storage, data storage and various circuit contact.These circuit comprise clock, its allow identification in time when receiving and send with the synchronizeing of the frequency of the signal frame of base station exchange.Corresponding data are stored in memory.Clock is also for the identification time migration corresponding with near other base station being positioned at mobile terminal, and when mobile terminal likely switches in community and these base stations are set up and contacted.At other circuit, comprise local oscillator and various demodulator circuit, orthogonal demodulation circuit wherein have two frequency mixers and and a phase shifter, also comprise sample circuit and sample circuit, it generates I and Q signal after the demodulation through quantizing.Then these I and Q signal are processed in treatment circuit.
The present invention uses the data of complex signal sampling, and the signal of each sampled point is by a complex representation, as:
S=I+Q*j; Wherein j represents complex signal;
The signal of sampled point S is that the complex signal that I and imaginary part are Q represents by real part.
Accompanying drawing 1 shows the detection method flow process of frequency calibration bag of the present invention, method of the present invention is applied to GSM cellular network, this network itself comprises a plurality of MSC/VLR service areas, and each has Yi Ge mobile switching centre (MSC) and a Visited Location Registor being connected (VLR).MSC communicates by letter with at least one base station controller (BSC), and it is connected with at least one base-station transceiver system (BTS).This BTS is physical equipment, and it provides the radio of be responsible for community is covered.BSC and BTS element are commonly referred to base station system as a whole.
The implementation step of the detection method of GSM frequency calibration bag of the present invention is:
1. first GSM frequency range is divided into n frequency range, frequency range 1, frequency range 2....... frequency range n, scan lock-on signal successively to n frequency range.
Intercept the downstream signal of wireless communication system, can adopt and intercept arbitrarily mode, cell search process that for example can analog wireless communication system terminal, for different wireless communication systems, because the concrete system parameters such as its frequency range, standard, power, channel is different, the detailed process that realization is intercepted is different, but can realize by the cell search process in respective wireless communication system, to the wireless communication system that may exist in monitoring range, may exist the frequency range of community to carry out Cell searching.
Mobile terminal comprises the RF receiver that is coupled to antenna, for receiving RF signal.RF receiver is converted to medium-frequency IF signal based on RF PLL by radio frequency rf signal.In gsm communication system, the common transmission frequency of radio frequency rf signal is 800 MHz, 1800 MHz or 1900 MHz, and medium-frequency IF signal is conventionally in 200MHz left and right.IF demodulator and low-converter are converted to base-band analog signal by IF signal, and described base-band analog signal comprises real part P and imaginary part Q.
Use band-pass filter, remove noise and distorted signals in signal.
The data rate (1625Khz/6) of GSM of take is sample rate sampling GSM baseband signal, obtains the sampled data sequence of GSM baseband signal, store sample data sequence in memory;
Sampled data sequence can be expressed as:
S
n=I
n+j*Q
n=cos(2πf/f
s*n+φ
0)+j*sin(2πf/f
s*n+φ
0)；
This complex signal comprises real part I
nwith imaginary part Q
n.
2. through filtered signal, be input in phase calculator.
The sampled data of GSM baseband signal is calculated to the phase difference of adjacent two sampled points, the account form of phase difference is as follows: establish S
n=I
n+ Q
n* j is previous sampled point, S
n+1=I
n+1+ Q
n+1* j is a rear sampled point;
Phase difference D so
n=arctg (S
n+1/ S
n).
3. usage counter carrys out the number of times that the phase difference of store sample point signal is greater than 0, to judge the burst that whether has desired length in the signal of reception.Described number of times should be enough greatly to guarantee that the frequency of the signal of reception has continued the sufficiently long cycle.Burst packets has than the frequency of the high 67kHz of carrier wave, duration 577 μ s, and in actual applications, described number of times is set to any one value in 140-148.For example, be set to 148, if existed, make to occur continuously the data that more than 148 adjacent signals phase differences is greater than 0, i.e. D in sampled data sequence
nto D
n+147all be greater than 0.So just determine and frequency calibration bag detected.
4. for some scanning frequency, in its signal, do not comprise frequency calibration bag, if the quantity of sampled data reaches certain threshold value, can determine that this frequency can't detect calibration data bag.In the present invention, threshold value setting is 12500, the cycle that FCCH occurs.GSM sampled data reaches 12500, the data that 148 adjacent signals phase differences of continuous appearance are greater than 0 also do not detected, can judge so and can't detect frequency calibration bag, and this carrier wave is not the broadcast carrier of GSM base station.The frequency range that continuation does not scan the next one scans.
According to detected frequency calibration bag, carry out frequency deviation estimation, the frequency departure between computing terminal and base station.
Crystal oscillator is according to the frequency calibration packet generation reference frequency that receives, and RF PLL and IF PLL all adopt this reference frequency as with reference to clock.
5. recording frequency calibration contracts out existing frequency point information, temporal information and power information.
6. complete after aforesaid operations, frequency point information, temporal information and signal strength signal intensity in the time of just can obtaining all signals that comprise frequency calibration bag of whole GSM frequency ranges and occur, and can catch on this basis sync packet SB.
In order more effectively to improve false dismissal and the false-alarm performance of the detection of frequency calibration bag, carry out after primary detection frequency calibration bag, further, can utilize the power spectrum characteristic of conventional burst and noise to be optimized analysis judgement, obtain final testing result.
Object to better implement the present invention, the present invention also provides a kind of checkout gear of GSM frequency calibration bag, and as shown in Figure 2, described checkout gear comprises its structure:
Intercept module, be configured to intercept the downstream signal of wireless communication system, wherein, GSM frequency range is divided into n frequency range, described in intercept module and intercept the signal in frequency range according to frequency range number order.
Filtration module, is configured to remove noise and the distorted signals receiving in signal.
Demodulation module, the signal being configured to after filtration module is processed is converted to baseband signal.
Sampling module, the GSM baseband signal that is configured to sample, obtains the sampled data sequence of GSM baseband signal, wherein, the data rate that sample rate is GSM.
Memory module, is configured to store sample data sequence.
Computing module, is configured to the described sampled data sequence of GSM baseband signal to calculate the phase difference of the signal of adjacent two sampled points.
Determination module, if be configured to existence in described sampled data sequence, make the data that occur that continuously more than N described neighbouring sample point signal phase difference is greater than 0, determine and frequency calibration bag detected, wherein, N is positive integer, N be more than or equal to 140 and N be less than or equal to 148.
Logging modle, is configured to recording frequency calibration and contracts out existing frequency point information, temporal information and power information.
Above modules intercouples, and jointly realizes the function that frequency calibration bag detects.
The function of described frequency calibration package detection device can be used computer program to realize, and described frequency calibration package detection device can be realized at fpga chip, dsp chip or other embedded chips.
Described frequency calibration package detection device can be applied to GSM mobile handset, GSM base station testing instrument, GSM road measuring device etc.
In gsm system, adopt above-mentioned automatic frequency to detect and the descending calibrating frequency signal (being frequency reference signal) of bearing calibration tracking base stations, only need simple algorithm to realize circuit, just can provide high-precision local frequency source for terminal, the relative error of the frequency of terminal and base station is remained in the desired ± 5X10_8 of GSM standard (ETSI EN 300609-4, YD/T 1337-2005).Provide method, frequency domain operation method, the cross correlation algorithm of local frequency source to compare with adopting expensive constant-temperature crystal oscillator, both reduced cost, do not need again regularly to carry out artificial calibrating frequency.
The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (10)
1. a detection method for GSM frequency calibration bag, is characterized in that, comprises the steps:
Step 1. sampling GSM baseband signal, obtains the sampled data sequence of GSM baseband signal, wherein, and the data rate that sample rate is GSM;
The described sampled data sequence of step 2. pair GSM baseband signal is calculated the phase difference of the signal of adjacent two sampled points;
If there are the data that make to occur continuously that N above described neighbouring sample point signal phase difference is greater than 0 in step 3. in described sampled data sequence, definitely frequency calibration bag detected, wherein, N is positive integer, N be more than or equal to 140 and N be less than or equal to 148.
2. method according to claim 1, characterized by further comprising:
If step 4. sampled data reaches M sampled point, the data that occur that continuously N described neighbouring sample point signal phase difference is greater than 0 also do not detected, judgement can't detect frequency calibration bag or judges that data carrier is not the broadcast carrier of GSM base station, and wherein M is 12500.
3. method according to claim 1, is characterized in that, the account form of described phase difference is as follows:
S
n=I
n+ Q
n* j is previous sampled point, S
n+1=I
n+1+ Q
n+1* j is a rear sampled point, wherein, and I
n, Q
n, I
n+1, Q
n+1for real number, n is integer;
Phase difference D
n=arctg (S
n+1/ S
n).
4. method according to claim 1, is characterized in that, described N be more than or equal to 140 and N be less than or equal to 148;
Describedly occur that continuously the above described neighbouring sample point signal phase difference of N is greater than 0 and is specially:
D
nto D
n+N-1all be greater than 0.
5. according to the method described in claim 1-4 any one, it is characterized in that, described data rate is 270.833Kbps; The effect of described frequency calibration bag be make terminal find base station and calculate self and base station between frequency deviation; The packet that described frequency calibration bag is full 0.
6. a checkout gear for GSM frequency calibration bag, is characterized in that comprising:
Sampling module, the GSM baseband signal that is configured to sample, obtains the sampled data sequence of GSM baseband signal, wherein, the data rate that sample rate is GSM;
Computing module, is configured to the described sampled data sequence of GSM baseband signal to calculate the phase difference of the signal of adjacent two sampled points;
Determination module, if be configured to existence in described sampled data sequence, make the data that occur that continuously more than N described neighbouring sample point signal phase difference is greater than 0, determine and frequency calibration bag detected, wherein, N is positive integer, N be more than or equal to 140 and N be less than or equal to 148.
7. device according to claim 6, is characterized in that described determination module is configured to:
If sampled data reaches M sampled point, the data that occur that continuously N described neighbouring sample point signal phase difference is greater than 0 also do not detected, judgement can't detect frequency calibration bag or judges that data carrier is not the broadcast carrier of GSM base station, and wherein M is 12500.
8. device according to claim 6, is characterized in that, the account form of described phase difference is as follows:
S
n=I
n+ Q
n* j is previous sampled point, S
n+1=I
n+1+ Q
n+1* j is a rear sampled point, wherein, and I
n, Q
n, I
n+1, Q
n+1for real number, n is integer;
Phase difference D
n=arctg (S
n+1/ S
n).
9. device according to claim 8, is characterized in that, described N is 148;
Describedly occur that continuously the above described neighbouring sample point signal phase difference of N is greater than 0 and is specially:
Dn is greater than 0 to Dn+147.
10. according to the method described in claim 6-9 any one, it is characterized in that, described data rate is 270.833Kbps; The effect of described frequency calibration bag be make terminal find base station and calculate self and base station between frequency deviation; The packet that described frequency calibration bag is full 0.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104333443A (en) * | 2014-10-27 | 2015-02-04 | 大唐移动通信设备有限公司 | Method and device for acquiring signal channel |
| CN104333443B (en) * | 2014-10-27 | 2017-10-17 | 大唐移动通信设备有限公司 | A kind of method and device of bid |
| CN113630209A (en) * | 2020-05-08 | 2021-11-09 | 中国科学院大学 | WiFi to low-power-consumption Bluetooth (BLE) cross-technology communication method based on narrow-band decoding |
| CN113630209B (en) * | 2020-05-08 | 2023-11-07 | 中国科学院大学 | WiFi-to-Bluetooth Low Energy (BLE) cross-technology communication method based on narrowband decoding |
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