CN118764153B

CN118764153B - Multiframe synchronization method, device, equipment and storage medium of GSM system

Info

Publication number: CN118764153B
Application number: CN202411255020.3A
Authority: CN
Inventors: 周建红; 赖远萱; 陈亮; 黄晓光
Original assignee: Nexwise Intelligence China Ltd
Current assignee: Nexwise Intelligence China Ltd
Priority date: 2024-09-09
Filing date: 2024-09-09
Publication date: 2025-01-14
Anticipated expiration: 2044-09-09
Also published as: CN118764153A

Abstract

The invention relates to the technical field of communication and provides a multiframe synchronization method, a device, equipment and a storage medium of a GSM (Global System for Mobile communications) system, wherein the method comprises the steps of receiving a communication signal sent by a base station and acquiring a baseband signal of the communication signal; the method comprises the steps of carrying out rough synchronization search on a baseband signal based on a peak value ratio algorithm, detecting the position of a frequency correction burst to determine a rough synchronization point, carrying out fine synchronization search on the baseband signal based on an energy ratio algorithm and the rough synchronization point, detecting the position of a synchronization burst to determine a fine synchronization point, and carrying out multiframe synchronization on the baseband signal according to the fine synchronization point. Based on the structural characteristics of the GSM frame, the detection accuracy of the frequency correction burst is improved through a peak value ratio algorithm, the detection accuracy of the synchronous burst is improved through an energy ratio algorithm, the fine synchronous search is carried out on the basis of the coarse synchronous search, the synchronous position of the multi-frame is determined, and the accuracy of the multi-frame synchronization is ensured.

Description

Multiframe synchronization method, device, equipment and storage medium of GSM system

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method, an apparatus, a device, and a storage medium for synchronizing multiple frames in a GSM system.

Background

GSM (Global System for Mobile Communications ) belongs to the second generation of mobile communications, and is widely used for communication of global mobile terminals. The GSM system adopts a modulation mode of GMSK (Gaussian Filtered Minimum SHIFT KEYING, gaussian minimum frequency shift keying), and the frame structure comprises five layers, namely an ultra-high frame, a super frame, a multi-frame, a TDMA (Time Division Multiple Access ) frame and a time slot. The TDMA frame is a basic unit in communication technology, and is composed of a plurality of time slots, where each time slot is allocated to a user for communication. This frame structure ensures that the data of different users do not overlap in time, thus avoiding signal interference, while TDMA frame design takes into account the synchronization and timing of the GSM system to ensure that each user transmits data in a designated time slot.

At present, for synchronization of a GSM system, idle data of a nearby base station is monitored, a time slot synchronization point is obtained through capturing FB and SB sequences or demodulation processing, and time slot synchronization is performed, so that multiframe synchronization of the GSM system cannot be realized.

Disclosure of Invention

The invention provides a method, a device, equipment and a storage medium for synchronizing a multiframe of a GSM system, which are used for solving the defect that the prior art can not realize the multiframe synchronization of the GSM system and realizing the multiframe synchronization of the GSM system.

The invention provides a multiframe synchronization method of a GSM system, which comprises the following steps:

receiving a communication signal sent by a base station and acquiring a baseband signal of the communication signal;

performing coarse synchronization search on the baseband signal based on a peak ratio algorithm, and detecting the position of a frequency correction burst to determine a coarse synchronization point;

Based on an energy ratio algorithm and the coarse synchronization point, performing fine synchronization search on the baseband signal, and detecting the position of a synchronization burst to determine a fine synchronization point;

and carrying out multi-frame synchronization on the baseband signal according to the fine synchronization point.

According to the multiframe synchronization method of the GSM system provided by the present invention, the peak ratio algorithm-based coarse synchronization search is performed on the baseband signal, and the position of the frequency correction burst is detected to determine a coarse synchronization point, which includes:

Acquiring the sampling rate of the baseband signal, and determining a first window size according to the sampling rate, wherein the first window size corresponds to a first number of sampling points;

Performing sliding window processing on the baseband signal based on the first window size, and performing fast Fourier transform processing on a first target sampling point in a current window based on a peak ratio algorithm to calculate peak energy of the first target sampling point;

Calculating the ratio of the peak energy to the total energy of the baseband signal to obtain the peak ratio of the first target sampling point;

determining whether a first signal segment corresponding to the first target sampling point contains a frequency correction burst or not according to the peak value ratio;

and if the first signal segment corresponding to the first target sampling point does not contain the frequency correction burst, sliding the current window based on a preset first sliding step length to perform coarse synchronization search on the baseband signal, returning to and executing the fast Fourier transform processing on the first target sampling point in the current window based on the peak ratio algorithm to calculate the peak energy of the first target sampling point until the first signal segment corresponding to the first target sampling point contains the frequency correction burst, and determining a coarse synchronization point according to the position of the frequency correction burst.

According to the multiframe synchronization method of the GSM system provided by the present invention, the determining whether the first signal segment corresponding to the first target sampling point includes a frequency correction burst according to the peak ratio includes:

Comparing the peak value ratio with a preset first threshold value;

Determining whether a first signal segment corresponding to the first target sampling point contains a frequency correction burst or not according to a comparison result;

And if the peak value ratio is smaller than or equal to the first threshold value, the first signal segment corresponding to the first target sampling point does not contain the frequency correction burst.

According to the multiframe synchronization method of the GSM system provided by the invention, the fine synchronization search is carried out on the baseband signal based on the energy ratio algorithm and the coarse synchronization point, and the position of the synchronization burst is detected to determine the fine synchronization point, which comprises the following steps:

determining a second window size according to the sampling rate, wherein the second window size corresponds to a second number of sampling points;

taking the coarse synchronization point as a starting point of the fine synchronization search, and carrying out sliding window processing on the baseband signal based on the second window size so as to carry out the fine synchronization search on the baseband signal;

In the sliding window processing process, performing correlation operation on a second target sampling point in a current window based on an energy ratio algorithm to calculate a correlation energy value of the second target sampling point;

Calculating the ratio of the correlation energy value to the total energy value of the baseband signal to obtain the energy ratio of the second target sampling point;

And detecting the position of the synchronization burst according to the energy ratio to determine a fine synchronization point.

According to the multiframe synchronization method of the GSM system provided by the invention, the position of the synchronization burst is detected according to the energy ratio so as to determine a precise synchronization point, and the multiframe synchronization method comprises the following steps:

comparing the energy ratio with a preset second threshold value;

Determining whether a second signal segment corresponding to the second target sampling point contains a synchronization burst or not according to a comparison result;

If the second signal segment does not contain a synchronization burst, returning to and executing the step of carrying out sliding window processing on the baseband signal based on the second window size to carry out fine synchronization searching on the baseband signal until the second signal segment contains the synchronization burst, and determining a fine synchronization point according to the position of the synchronization burst;

Wherein if the energy ratio is greater than a preset second threshold value, the second signal segment corresponding to the second target sampling point comprises a synchronization burst, and if the energy ratio is smaller than or equal to a preset second threshold value, the second signal segment corresponding to the second target sampling point does not contain the synchronization burst.

According to the multiframe synchronization method of the GSM system provided by the invention, the determining of the precise synchronization point according to the position of the synchronization burst comprises the following steps:

Determining a first candidate synchronization point according to the position of the synchronization burst, wherein the synchronization burst comprises a plurality of synchronization bursts, and the position of any synchronization burst corresponds to a candidate synchronization point;

calculating the position difference between the first candidate synchronous point and a second candidate synchronous point, wherein the second candidate synchronous point is a candidate synchronous point adjacent to and before the first candidate synchronous point, and the position difference corresponds to a first preset number of time division multiple access frames or a second preset number of time division multiple access frames;

and if the position difference corresponds to a first preset number of time division multiple access frames, returning to and executing the step of carrying out sliding window processing on the baseband signal based on the second window size so as to carry out fine synchronization searching on the baseband signal until the position difference corresponds to a second preset number of time division multiple access frames, and determining a fine synchronization point according to the position of the first candidate synchronization point.

According to the multiframe synchronization method of the GSM system provided by the present invention, the obtaining the baseband signal of the communication signal includes:

The communication signal is subjected to digital processing to obtain a digital intermediate frequency signal, wherein the digital processing comprises filtering, mixing and intermediate frequency analog signals;

Carrying out digital mixing processing on the digital intermediate frequency signals to obtain zero intermediate frequency digital signals;

and based on a preset sampling rate, sampling the zero intermediate frequency digital signal to obtain a baseband signal.

The invention also provides a multiframe synchronization device of the GSM system, which comprises:

The signal acquisition module is used for receiving a communication signal sent by a base station and acquiring a baseband signal of the communication signal;

the coarse synchronization searching module is used for carrying out coarse synchronization searching on the baseband signal based on a peak value ratio algorithm, detecting the position of the frequency correction burst and determining a coarse synchronization point;

The fine synchronization searching module is used for carrying out fine synchronization searching on the baseband signal based on an energy ratio algorithm and the coarse synchronization point, and detecting the position of a synchronization burst so as to determine a fine synchronization point;

and the multi-frame synchronization module is used for carrying out multi-frame synchronization on the baseband signal according to the fine synchronization point.

The invention also provides an electronic device comprising a memory, a processor and a computer program stored on the memory and operable on the processor, the processor implementing the steps of the multiframe synchronization method of the GSM system as described in any one of the above when executing the computer program.

The invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the multiframe synchronization method of the GSM system as described in any of the above.

The invention also provides a computer program product comprising a computer program which, when executed by a processor, implements the steps of the multiframe synchronization method of the GSM system as described in any one of the above.

The invention provides a multi-frame synchronization method, a device, equipment and a storage medium of a GSM system, which are characterized in that the position of a frequency correction burst is detected through a peak ratio algorithm, a coarse synchronization search is carried out on a baseband signal, a coarse synchronization point is determined, the synchronization burst position is detected based on an energy ratio algorithm on the basis, a fine synchronization point is determined through a fine synchronization search, the position of the multi-frame synchronization point is obtained, and multi-frame synchronization is realized. Based on the structural characteristics of the GSM frame, the detection accuracy of the frequency correction burst is improved through a peak value ratio algorithm, the detection accuracy of the synchronous burst is improved through an energy ratio algorithm, the fine synchronous search is carried out on the basis of the coarse synchronous search, the synchronous position of the multi-frame is determined, and the accuracy of the multi-frame synchronization is ensured.

Drawings

In order to more clearly illustrate the invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic flow chart of a multiframe synchronization method of a GSM system provided by the present invention.

Fig. 2 is a schematic diagram of a synchronization burst sequence provided in the present invention.

Fig. 3 is a schematic diagram of a coarse synchronization search process provided by the present invention.

Fig. 4 is a schematic diagram of a fine synchronization search process according to the present invention.

FIG. 5 is a diagram of a second embodiment of the fine synchronization search process according to the present invention.

Fig. 6 is a schematic structural diagram of a multiframe synchronization device of the GSM system provided by the present invention.

Fig. 7 is a schematic structural diagram of an electronic device provided by the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that in the five-level frame structure of the GSM system, each super-high frame is composed of 2715648 consecutive TDMA frames. Meanwhile, each super-high frame is composed of 2048 continuous superframes, each superframe is composed of 51 continuous 26 multiframes or 26 continuous 51 multiframes, and the two multiframes are set to meet the information transmission requirements of different rates. The 26 multi-frames consist of 26 continuous TDMA frames with a time interval of 120ms and are mainly used for TCH (TRAFFIC CHANNEL ), SACCH (Slow Associated Control Channel slow associated control channel), FACCH (Fast Associated Control Channel ) and the like, the common 51 multi-frames consist of 51 TDMA frames with a time interval of 235.385ms and are mainly used for BCCH (Broadcast Control Channel ), CCCH (Common Control Channel, common control channel) and the like. 120ms is 26 TDMA frames, one TDMA frame is 4.616ms, and there are 8 time slots TS0 to TS7, each time slot is 0.577ms, each time slot corresponds to 156.25 bits, the code rate is 156.25/(120/26/8) =270.8333 KB, and one TDMA frame is 156.25 when there is no over-sampling8=1250 Points.

Further, in the GSM system, the FCCH (Frequency Correction Channel ) is a FB (Frequency Correction Burst, frequency correction Burst) sequence for synchronizing frequencies, the SCH (Synchronization Channel ) is a SB (Synchronization Burst, synchronization Burst) sequence for resolving TDMA frame numbers and BSIC (Base Station Identity Code, base station identification code) codes, the BCCH and CCCH are NB (Normal Burst) sequences for resolving cell general information and receiving paging and access, and the IDLE is an IDLE frame that does not contain useful information and is a DB (Dummy Burst) sequence.

Based on the above frame structure of the GSM system, the embodiment of the present invention provides a multiframe synchronization method of the GSM system, which is based on FPGA (Field Programmable GATE ARRAY ) architecture, to realize multiframe synchronization of the GSM system. Specifically, fig. 1 is a flow chart of a multiframe synchronization method of a GSM system provided by the present invention, as shown in fig. 1, the method includes the following steps:

step 100, receiving a communication signal sent by a base station, and obtaining a baseband signal of the communication signal;

Step 200, performing coarse synchronization search on the baseband signal based on a peak ratio algorithm, and detecting the position of a frequency correction burst to determine a coarse synchronization point;

Step 300, based on the energy ratio algorithm and the coarse synchronization point, performing a fine synchronization search on the baseband signal, and detecting the position of the synchronization burst to determine a fine synchronization point;

step 400, performing multiframe synchronization on the baseband signal according to the fine synchronization point.

And receiving a communication signal transmitted by the base station, namely a GSM signal, and acquiring a baseband signal of the GSM signal. Optionally, the baseband signal of the GSM signal is obtained by filtering, frequency conversion, and the like.

The baseband signal is subjected to a coarse synchronization search based on a peak ratio algorithm, and the position of the frequency correction burst (pulse sequence of FCCH frames) is detected to determine a coarse synchronization point, which characterizes the approximate position of the multiframe synchronization.

On the basis of the rough synchronization search, the base band signal is subjected to the fine synchronization search based on an energy ratio algorithm, and the position of a synchronization burst (pulse sequence of an SCH frame) is detected to determine a fine synchronization point, wherein the fine synchronization point is a multi-frame synchronization point, namely a multi-frame synchronization position.

According to the position of the fine synchronization point, the baseband signal is subjected to multi-frame synchronization, and in the embodiment, the multi-frame synchronization is mainly used for 51-frame synchronization, and the multi-frame synchronization point is 51-frame synchronization point. Alternatively, the multi-frame synchronization is aimed at solving the problem of misrouting of the signaling of each landmark, ‌ by ensuring that each landmark signaling in the associated signaling has a respective determined position on the TS16 of one multi-frame. If the multiframes are not synchronized, the flag signaling may be misrouted, resulting in communication failure. The multi-frame synchronization effectively avoids communication interruption by ensuring that each sign signaling is at a specific position in the multi-frame, ensures the continuity and reliability of communication, and ensures that a receiving end can accurately identify and split digital signals, thereby maintaining the quality and efficiency of communication.

Alternatively, the FCCH frame is an all-zero sequence, the GMSK modulated signal is a standard sine wave at a specific frequency, and the spectrum of the standard sine wave has sharp single peak characteristics, so that the coarse synchronization search based on the peak ratio algorithm detects the burst sequence of the FCCH frame by detecting the single peak, thereby determining the coarse synchronization point.

Optionally, the burst sequence of the SCH frame carries the information of the SCH channel and is used for synchronizing the terminal and the base station, the SCH burst sequence contains 64-bit training sequences, the training sequences of all the SCH burst sequences are identical, namely {1011100101100010000001000000111100101101010001010111011000011011}, the composition of the burst sequence of the SCH frame is shown in figure 2, and the burst sequence comprises two 3 tail bits, two 39 information bits, one 64-bit training sequence and one 8.25 guard bit. The two 39 information bits include information such as TDMA frame number, which is the basis of terminal synchronization, so that the first burst sequence to be demodulated after the terminal starts up and works, and the characteristic that the training sequence in the SCH channel has good correlation is utilized to determine the fine synchronization point.

In this embodiment, the position of the frequency correction burst is detected by the peak ratio algorithm, coarse synchronization search is performed on the baseband signal, a coarse synchronization point is determined, on the basis, the synchronization burst position is detected based on the energy ratio algorithm, the fine synchronization point is determined by the fine synchronization search, and the position of the multi-frame synchronization point is obtained, so that multi-frame synchronization is realized. Based on the structural characteristics of the GSM frame, the detection accuracy of the frequency correction burst is improved through a peak value ratio algorithm, the detection accuracy of the synchronous burst is improved through an energy ratio algorithm, the fine synchronous search is carried out on the basis of the coarse synchronous search, the synchronous position of the multi-frame is determined, and the accuracy of the multi-frame synchronization is ensured.

In one embodiment, the baseband signal of the GSM signal is obtained through a digitizing process and a mixing process, specifically, in step 100, the baseband signal of the communication signal is obtained, including:

Step 110, performing digital processing on the communication signal to obtain a digital intermediate frequency signal, wherein the digital processing comprises filtering, mixing and intermediate frequency analog signal;

step 120, performing digital mixing processing on the digital intermediate frequency signal to obtain a zero intermediate frequency digital signal;

and 130, based on a preset sampling rate, sampling the zero intermediate frequency digital signal to obtain a baseband signal.

And carrying out digital processing on the received GSM signal, and converting the communication signal of the GSM system into a digital intermediate frequency signal, wherein the digital processing at least comprises filtering, mixing and intermediate frequency analog signal processing. And then further carrying out digital mixing processing on the digital intermediate frequency signal to obtain a zero intermediate frequency digital signal, and finally, carrying out sampling processing on the zero intermediate frequency digital signal based on a preset sampling rate to obtain a baseband signal.

In one embodiment, both the coarse and fine synchronization searches are implemented based on a sliding window process on the baseband signal. Specifically, in step 200, performing a coarse synchronization search on the baseband signal based on a peak ratio algorithm, detecting a position of a frequency correction burst to determine a coarse synchronization point, including:

step 210, obtaining the sampling rate of the baseband signal, and determining a first window size according to the sampling rate, wherein the first window size corresponds to a first number of sampling points;

step 220, performing sliding window processing on the baseband signal based on the first window size, and performing fast fourier transform processing on a first target sampling point in a current window based on a peak ratio algorithm to calculate peak energy of the first target sampling point;

step 230, calculating the ratio of the peak energy to the total energy of the baseband signal to obtain the peak ratio of the first target sampling point;

Step 240, determining whether the first signal segment corresponding to the first target sampling point includes a frequency correction burst according to the peak ratio;

And 250, if not, performing sliding processing on the current window based on a preset first sliding step length to perform coarse synchronization searching on the baseband signal, returning to and executing fast Fourier transform processing on a first target sampling point in the current window based on a peak ratio algorithm to calculate peak energy of the first target sampling point until a frequency correction burst is included in a first signal segment corresponding to the first target sampling point, and determining a coarse synchronization point according to the position of the frequency correction burst.

First, a sampling rate of a baseband signal is obtained, and a first window size is determined according to the sampling rate, wherein the first window size corresponds to a first number of sampling points. The baseband signal is windowed based on a first window size, and a fast fourier transform FFT (Fast Fourier transform ) process is performed on a plurality of first target sample points within a current window based on a peak ratio algorithm, thereby calculating peak energy of the first target sample points within the window.

Further, according to the calculated peak energy, the ratio of the peak energy to the total energy of the baseband signal is further calculated to obtain the peak ratio of the first target sampling point, so as to determine whether the first signal segment corresponding to the first target sampling point contains a frequency correction burst, namely an FCCH burst, according to the calculated peak ratio. If the first signal segment does not contain the frequency correction burst, sliding the current window based on a preset first sliding compensation, so as to perform coarse synchronization search on the baseband signal, and recalculate the peak energy of a first target sampling point in the current window until the first signal segment corresponding to the first target sampling point is determined to contain the FCCH burst according to the calculated peak ratio, and determining a coarse synchronization point according to the detected position of the FCCH burst.

Further, when determining whether the first signal segment includes the FCCH burst according to the peak ratio, specifically, comparing the calculated peak ratio with a preset first threshold value, and determining according to the comparison result. Thus, step 240 further comprises:

step 241, comparing the peak ratio with a preset first threshold value;

step 242, determining whether the first signal segment corresponding to the first target sampling point includes a frequency correction burst according to the comparison result;

Comparing the calculated peak value ratio with a preset first threshold value, and determining whether the first signal segment corresponding to the first target sampling point contains the FCCH burst or not according to the comparison result. And if the calculated peak value ratio is smaller than or equal to the preset first threshold value, the first signal section corresponding to the first target sampling point does not contain the FCCH burst.

In one embodiment, referring to the coarse synchronization search procedure described in fig. 3, the FCCH frame is an all-zero pulse burst sequence, and the GMSK modulated signal is a standard sine wave of a specific frequency, whose spectrum has sharp unimodal characteristics. Thus, the presence of the FCCH burst sequence can be detected by detecting a single peak and determining the location of the coarse synchronization point. Illustratively, if the baseband signal of the received GSM signal is 4 times oversampled, the sampling rate is 1.0833MHz, the FCCH signal length is 625 (4156.25 During the sliding window processing, FFT processing is performed on 512 sampling points within the window. As can be seen, the single peak corresponding to the FCCH frequency domain generally appears near the (n=33) th sampling point, and 10 sampling points (21 sampling points in total) are taken as the range for calculating the peak ratio around the (33) th sampling point (i.e., peak point). And comparing the peak value ratio with a preset first threshold value G0, if the peak value ratio is larger than G0, determining that the FCCH burst sequence is detected in a window processed by the current sliding window, otherwise, continuing to detect the sampling point in the next sliding window until the FCCH burst sequence is detected.

Optionally, in the FPGA architecture, the first sliding step size of the coarse synchronization search stage is set to 256 samples, the first threshold G0 is configured to be set to 0.75, if the number of sampling points corresponding to the first window size is 512, FFT processing is performed on 512 sampling points in the window each time, the frequency resolution is approximately 2115Hz, and the actual device generally does not have such a large frequency offset, so that the value of the 33 th sampling point is taken as a peak value, the coarse synchronization point can be searched theoretically by using 12 frames of data, and the window can be slid for 234 times at most according to the sliding step size of 256 sampling points.

As shown in fig. 3, in the coarse synchronization search phase, the sliding window process is provided with a window maximum number of slides, which is a preset value, for example 234. And when the calculated peak value ratio is smaller than or equal to a preset first threshold value G0, acquiring window sliding times N, and if N is smaller than or equal to a first preset value corresponding to the maximum sliding times, sliding the window, and acquiring the next 512 sampling points to perform FFT operation. And when the sliding times of the window are larger than a first preset value corresponding to the maximum sliding times, completing the coarse synchronization search, or when the calculated peak value ratio is larger than a preset first threshold value G0, determining the position of a coarse synchronization point according to the position of the detected FCCH burst sequence, and completing the coarse synchronization search.

In one embodiment, the fine synchronization search is performed based on the search result of the coarse synchronization search, where the fine synchronization search is performed by using a sliding window processing method, specifically, step 300 may further include:

Step 310, determining a second window size according to the sampling rate, wherein the second window size corresponds to a second number of sampling points;

Step 320, taking the coarse synchronization point as a start point of the fine synchronization search, and performing sliding window processing on the baseband signal based on the second window size to perform the fine synchronization search on the baseband signal;

step 330, in the process of sliding window processing, performing a correlation operation on a second target sampling point in the current window based on an energy ratio algorithm, so as to calculate a correlation energy value of the second target sampling point;

step 340, calculating the ratio of the correlation energy value to the total energy value of the baseband signal, so as to obtain the energy ratio of the second target sampling point;

step 350, detecting the position of the synchronization burst according to the energy ratio to determine a fine synchronization point.

And similarly, determining a second window size according to the sampling rate of the baseband signal, wherein the second window size corresponds to a second number of sampling points, and performing sliding window processing on the baseband signal based on the second window size by using the starting point of the coarse synchronization point fine synchronization search obtained by the coarse synchronization search, so as to perform fine synchronization search on the baseband signal. In the process of sliding window processing, based on an energy ratio algorithm, carrying out correlation operation on a plurality of second target sampling points in a current window to calculate correlation energy values of the second target sampling points, further calculating the ratio of the correlation energy values to the total energy value of a baseband signal according to the calculated correlation energy values to obtain the energy ratio of the second target sampling points, and detecting the position of a synchronous burst sequence according to the energy ratio to determine a precise synchronization point.

Further, when detecting the position of the synchronization burst sequence according to the calculated energy ratio, the calculated energy ratio is specifically compared with a preset second threshold value. Thus, step 350 may further comprise:

step 351, comparing the energy ratio with a preset second threshold value;

Step 352, determining whether the second signal segment corresponding to the second target sampling point includes a synchronization burst according to the comparison result, and returning to and executing the step of performing sliding window processing on the baseband signal based on the second window size to perform fine synchronization search on the baseband signal;

step 353, if the second signal segment includes a synchronization burst, determining a fine synchronization point according to a position of the synchronization burst;

After the energy ratio is calculated, comparing the energy ratio with a preset second threshold value, and determining whether a second signal segment corresponding to a second target sampling point in the current window contains a synchronous burst sequence or not according to a comparison result. And if the calculated energy ratio is larger than a preset second threshold value, the second signal segment corresponding to the second target sampling point in the current window contains the synchronous burst sequence, otherwise, if the calculated energy ratio is smaller than or equal to the preset second threshold value, the second signal segment corresponding to the second target sampling point in the current window does not contain the synchronous burst sequence.

Further, if the second signal segment includes a synchronization burst, a fine synchronization point is determined according to a position of the synchronization burst.

After determining whether a second signal segment corresponding to a second target sampling point contains a synchronization burst or not, sliding the current window based on a preset second sliding step length, so as to perform fine synchronization search on the baseband signal.

In one embodiment, during the fine synchronization search, a plurality of synchronization burst sequences may be detected through a sliding window process, and a fine synchronization point needs to be determined according to the positions of the plurality of synchronization burst sequences, so step 353 may further include:

Step 3531, determining a first candidate synchronization point according to the position of the synchronization burst, wherein the synchronization burst comprises a plurality of synchronization bursts, and the position of any synchronization burst corresponds to a candidate synchronization point;

step 3532, calculating a position difference between the first candidate synchronization point and a second candidate synchronization point, wherein the second candidate synchronization point is a candidate synchronization point adjacent to and before the first candidate synchronization point, and the position difference corresponds to a first preset number of time division multiple access frames or the position difference corresponds to a second preset number of time division multiple access frames;

and step 3533, returning and executing the step of performing sliding window processing on the baseband signal based on the second window size to perform fine synchronization search on the baseband signal if the position difference corresponds to a first preset number of tdma frames, until the position difference corresponds to a second preset number of tdma frames, and determining a fine synchronization point according to the position of the first candidate synchronization point.

By means of fine synchronization search, the position of one or more synchronization burst sequences can be detected, and when a synchronization burst is detected in the current window, whether the position of the synchronization burst is a fine synchronization point or not is determined. Specifically, when the fine synchronization point is determined according to the position of the synchronization burst, the first candidate synchronization point is determined according to the position of the synchronization burst in the current window, and when the synchronization burst includes a plurality of synchronization bursts, the position of any synchronization burst corresponds to a candidate synchronization point, that is, the position of each synchronization burst is taken as a candidate of the fine synchronization point.

Further, a position difference between a first candidate synchronization point and a second candidate synchronization point is calculated, wherein the second candidate synchronization point is a candidate synchronization point adjacent to and before the first candidate synchronization point, and the position difference between the first candidate synchronization point and the second candidate synchronization point corresponds to a first preset number of TDMA frames of time division multiple access, or corresponds to a second preset number of TDMA frames.

If the position difference between the first candidate synchronization point and the second candidate synchronization point corresponds to the first preset number of TDMA frames, returning to and executing step 320, performing sliding window processing on the baseband signal based on the second window size, so as to perform fine synchronization searching on the baseband signal, thereby continuing searching for the next candidate synchronization point until the position difference between the searched first candidate synchronization point and the previous second candidate synchronization point corresponds to the second preset number of TDMA frames.

If the position difference between the first candidate synchronization point and the second candidate synchronization point corresponds to a second preset number of TDMA frames, determining a fine synchronization point according to the position of the first candidate synchronization point, where the position of the first candidate synchronization point is the fine synchronization point.

Alternatively, one or more fine synchronization searches may be performed on the baseband signal based on a sliding window process on the baseband signal. Optionally, a fine synchronization search detects a synchronization burst position, i.e. a candidate synchronization point is obtained. Optionally, a fine synchronization search detects the positions of a plurality of synchronization bursts, and a plurality of candidate synchronization points are obtained.

In one embodiment, referring to the fine synchronization search flow shown in fig. 4, in the fine synchronization search process, a sliding window process is performed on the baseband signal, and a correlation operation is performed on the sampling points in the current window, so as to calculate the correlation energy values of the sampling points in the window. And then calculating the ratio of the correlation energy value to the total energy of the baseband signal to obtain the energy ratio of sampling points in a window, and detecting whether a synchronous burst sequence exists in the current window according to the energy ratio.

Further, comparing the calculated energy ratio with a preset second threshold value G1, if the calculated energy ratio is larger than the preset second threshold value G1, the synchronization burst sequence exists in the current window, otherwise, if the calculated energy ratio is smaller than the preset second threshold value G1, the synchronization burst sequence does not exist in the current window.

Further, if the synchronization burst exists in the current window, determining the position of the fine synchronization point, otherwise, if the synchronization burst does not exist in the current window, acquiring the sliding times M of the current window, if the sliding times M of the current window are larger than a second preset value, finishing the fine synchronization search, and if the sliding times of the current window are smaller than or equal to the second preset value, sliding the window, and continuing the fine synchronization search on the baseband signal. The second preset value is the maximum number of sliding windows of the sliding window processing of the fine synchronization search, and may be the same as or different from the first preset value of the sliding window processing of the coarse synchronization search stage.

When determining the fine synchronization point according to the position of the synchronization burst in the current window, specifically, the position of the synchronization burst is taken as a candidate synchronization point, the position difference between the candidate synchronization point and the previous candidate synchronization point is calculated, and if the position difference corresponds to a specific frame number of the TDMA, the position of the synchronization burst in the current window is the position of the fine synchronization point.

Taking the 4 times of oversampled baseband signal as an example, according to the structural characteristics of the GSM frame, the position of the SCH burst sequence differs from that of the FCCH burst sequence by 1 TDMA frame, so after the coarse synchronization point is obtained, the approximate position of the fine synchronization can be determined according to the coarse synchronization point, and then 256+336 sampling point data are taken out as the searching range of the fine synchronization. The second window size corresponds to 256 sampling points, 256 sampling points are sequentially selected to carry out correlation operation in the sliding window processing process, and the ratio of the correlation energy value to the total energy value of the input baseband signal is calculated to obtain the energy ratio of the sampling points in the window. And comparing the calculated energy ratio with a preset second threshold value G1, if the energy ratio is larger than G1, then the SCH sequence exists in the current window, otherwise, sliding the window, and continuing to detect the sampling point in the next window until the SCH sequence is detected. In particular, if there are a plurality of energy ratios that are all greater than G1, the sampling point corresponding to the maximum correlation energy value is used as a candidate position for the fine synchronization point.

Under the FPGA architecture, the sliding step length of the correlation operation on 256 sampling points can be 1 sampling point, the second threshold value G1 is configured and set to be 0.3, and the candidate position of the precise synchronization point can be searched theoretically by using 256+336 sampling points, and the sliding step length of the sampling points is at most 337 times according to the sliding step length of the sampling points.

In another embodiment, referring to the fine synchronization search flow shown in fig. 5, the fine synchronization search is set to a maximum number of searches, and in each fine synchronization search, a sliding window processing manner is adopted to detect whether the second signal segment corresponding to the sampling point in the window includes a synchronization burst sequence. When the existence of the synchronous burst is detected, specifically, based on an energy ratio algorithm, calculating the correlation energy value of the sampling points in the window, then calculating the ratio of the correlation energy value to the total energy of the baseband signal, obtaining the energy ratio of the sampling points in the window, and detecting whether the synchronous burst exists in the window according to the energy ratio. Further, if the calculated energy ratio is greater than a preset second threshold value G1, the synchronization burst sequence exists in the window, otherwise, if the calculated energy ratio is less than the preset second threshold value G1, the synchronization burst sequence does not exist in the window.

Further, according to the structure characteristics of the GSM frame, except for 11 TDMA frames, which are the positions of the SCH synchronization burst sequence of the IDLE frame and the next SCH synchronization burst sequence, the positions between the rest adjacent SCH synchronization burst sequences are different by 10 TDMA frames. Based on this, as long as the candidate synchronization points of 2 fine synchronization points are detected, and the positions of the next candidate synchronization point and the first 1 candidate synchronization point differ by 11 TDMA frames, the last 1 of the two candidate synchronization points can be determined to be the fine synchronization point, that is, the 51 multiframe synchronization point.

Therefore, if the synchronization burst is detected, the position of the corresponding candidate synchronization point is determined, one fine synchronization search is completed, the position difference between the current candidate synchronization point and the previous candidate synchronization point is calculated, and if the position difference is 11 TDMA frames, the currently detected candidate synchronization point is the fine synchronization point, so that the position of the fine synchronization point is determined. Otherwise, if the position difference between the current candidate synchronization point and the previous candidate synchronization point is 10 TDMA frames, the current fine synchronization search frequency K is obtained, if K is smaller than or equal to the preset maximum search frequency, the sliding window processing is continuously performed on the baseband signal, and the next fine synchronization search is performed until the detected candidate synchronization point is the fine synchronization point, or the current fine synchronization search frequency K is greater than the preset maximum search frequency, so that the fine synchronization search is completed.

In some embodiments, the multiframe synchronization method of the GSM system provided by the embodiments of the present invention is applied to a GSM multiframe synchronization system, where the system includes a radio frequency subsystem, a down-conversion subsystem, a coarse synchronization subsystem, a fine synchronization subsystem, a multiframe synchronization subsystem, and a configuration management subsystem. The down-conversion subsystem, the coarse synchronization subsystem, the fine synchronization subsystem and the multi-frame synchronization subsystem are all realized based on an FPGA architecture, and the configuration management subsystem can be realized based on an ARM (Acorn RISC (Reduced Instruction Set Computer, reduced instruction set computer) Machine architecture.

During multi-frame synchronization, the radio frequency subsystem receives the GSM signal sent by the base station through the antenna, completes the filtering, mixing and the digital processing of the intermediate frequency analog signal of the GSM frequency point signal, and finally transmits the obtained digital intermediate frequency signal to the down-conversion subsystem. The down-conversion subsystem realized based on the FPGA architecture firstly carries out digital mixing processing on the digital intermediate frequency signals according to GSM frequency point information preset by the configuration management subsystem to obtain zero intermediate frequency digital signals, and secondly completes the digital down-conversion function according to the pre-planned GSM baseband signal sampling rate (the GSM baseband sampling rate is 1.0833M under the assumption of 4 times of oversampling) to finally obtain the GSM baseband signals with given sampling rate.

The coarse synchronization subsystem realized based on the FPGA architecture is used for performing coarse synchronization search on the baseband signals and determining coarse synchronization points. Specifically, since the burst sequence of FCCH frames is an all-zero sequence, the GMSK modulated signal is a standard sine wave with a frequency of 67.708KHz, and the spectrum of the standard sine wave has sharp single peak characteristics, the coarse synchronization subsystem detects the existence of the burst of FCCH frames by detecting the single peak, and determines a coarse synchronization point.

The fine synchronization subsystem realized based on the FPGA performs fine synchronization search on the basis of the coarse synchronization point determined by the coarse synchronization subsystem, and determines a fine synchronization point. Because the SCH sequence carries the SCH channel message, the SCH sequence is used for synchronization of the terminal and the base station. The fine synchronization subsystem utilizes the characteristic that training sequences in the SCH channel have good correlation to determine candidate synchronization points of the fine synchronization points. The multi-frame synchronous subsystem is characterized by that according to GSM frame structure, except that the position between the SCH burst sequence with IDLE frame and the next SCH burst sequence is different by 11 TDMA frames, the positions of the rest adjacent SCH burst sequences are different by 10 TDMA frames. Based on the above, as long as 2 candidate synchronization points of fine synchronization are detected, and the position of the next candidate synchronization point differs from the position of the previous 1 candidate synchronization point by 11 TDMA frames, the next 1 candidate synchronization point can be determined to be a multi-frame synchronization point, so that the multi-frame synchronization subsystem finds the fine synchronization point of the multi-frame synchronization based on the candidate synchronization point searched by the fine synchronization subsystem in combination with the GSM frame structure characteristics.

The configuration management subsystem realized based on ARM architecture is used as a control center for managing and controlling the whole GSM multiframe synchronization system, including but not limited to issuing GSM frequency point information, monitoring the synchronization completion state of each subsystem and the like.

In the embodiment, the position of the rough synchronization point is determined based on the peak value ratio, the detection accuracy of the FCCH burst sequence is improved, the position of the fine synchronization point is determined based on the energy ratio, the detection accuracy of the SCH burst sequence is improved, the position of the multi-frame synchronization point is determined according to the position difference between two candidate synchronization points by combining the GSM frame structure characteristics during fine synchronization search, and the accuracy of multi-frame synchronization is ensured.

Furthermore, the multi-frame synchronization is realized based on the FPGA, the speed is high, the energy consumption is low, the occupied hardware resources are small, and the efficiency of the multi-frame synchronization is improved.

The following describes the multiframe synchronization device of the GSM system provided by the present invention, and the multiframe synchronization device of the GSM system described below and the multiframe synchronization method of the GSM system described above can be referred to correspondingly.

Referring to fig. 6, a multiframe synchronization device of a GSM system provided by an embodiment of the present invention includes:

A signal acquisition module 10, configured to receive a communication signal sent by a base station, and acquire a baseband signal of the communication signal;

A coarse synchronization search module 20, configured to perform coarse synchronization search on the baseband signal based on a peak ratio algorithm, and detect a position of a frequency correction burst to determine a coarse synchronization point;

A fine synchronization search module 30, configured to perform fine synchronization search on the baseband signal based on an energy ratio algorithm and the coarse synchronization point, and detect a position of a synchronization burst to determine a fine synchronization point;

and the multiframe synchronization module 40 is configured to multiframe synchronize the baseband signal according to the fine synchronization point.

In one embodiment, the coarse synchronization search module 20 is further configured to:

Comparing the peak value ratio with a preset first threshold value;

In one embodiment, the fine synchronization search module 30 is further configured to:

comparing the energy ratio with a preset second threshold value;

In one embodiment, the signal acquisition module 10 is further configured to:

Fig. 7 illustrates a physical schematic diagram of an electronic device, which may include a processor (processor) 710, a communication interface (Communications Interface) 720, a memory (memory) 730, and a communication bus 740, where the processor 710, the communication interface 720, and the memory 730 communicate with each other via the communication bus 740, as shown in fig. 7. Processor 710 may invoke logic instructions in memory 730 to perform steps of a multiframe synchronization method of a GSM system, including, for example:

Further, the logic instructions in the memory 730 described above may be implemented in the form of software functional units and may be stored in a computer readable storage medium when sold or used as a stand alone product. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. The storage medium includes a U disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, an optical disk, or other various media capable of storing program codes.

In another aspect, the present invention also provides a computer program product, where the computer program product includes a computer program, where the computer program can be stored on a non-transitory computer readable storage medium, where the computer program when executed by a processor can perform the steps of the multiframe synchronization method of the GSM system provided in the foregoing embodiments, for example, including:

In yet another aspect, the present invention further provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, is implemented to perform the steps of the multiframe synchronization method of the GSM system provided in the above embodiments, for example, including:

The apparatus embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.

From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on this understanding, the foregoing technical solution may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method described in the respective embodiments or some parts of the embodiments.

It should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the technical solution described in the above-mentioned embodiments may be modified or some technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiments of the present invention.

Claims

1. A method for synchronizing multiple frames of a GSM system, comprising:

carrying out multi-frame synchronization on the baseband signal according to the fine synchronization point;

the energy ratio algorithm and the coarse synchronization point are based on, the baseband signal is subjected to fine synchronization search, and the position of a synchronization burst is detected to determine a fine synchronization point, which comprises:

Acquiring the sampling rate of the baseband signal, and determining a second window size according to the sampling rate, wherein the second window size corresponds to a second number of sampling points;

Detecting the position of the synchronization burst according to the energy ratio to determine a fine synchronization point;

The detecting the position of the synchronization burst according to the energy ratio to determine a fine synchronization point includes:

comparing the energy ratio with a preset second threshold value;

If the energy ratio is greater than a preset second threshold value, the second signal segment corresponding to the second target sampling point contains a synchronization burst, and if the energy ratio is less than or equal to the preset second threshold value, the second signal segment corresponding to the second target sampling point does not contain the synchronization burst;

The determining a fine synchronization point according to the position of the synchronization burst includes:

2. The method of claim 1, wherein the performing a coarse synchronization search on the baseband signal based on a peak ratio algorithm, detecting a location of a frequency correction burst to determine a coarse synchronization point, comprises:

Determining a first window size according to the sampling rate, wherein the first window size corresponds to a first number of sampling points;

3. The method for synchronizing multiple frames of a GSM system according to claim 2, wherein said determining whether the first signal segment corresponding to the first target sampling point includes a frequency correction burst according to the peak ratio comprises:

Comparing the peak value ratio with a preset first threshold value;

4. The method for multiframe synchronization of a GSM system according to claim 1, wherein said obtaining a baseband signal of said communication signal comprises:

5. A multiframe synchronization device for a GSM system, comprising:

The multi-frame synchronization module is used for carrying out multi-frame synchronization on the baseband signals according to the fine synchronization point;

The fine synchronization search module is further configured to:

comparing the energy ratio with a preset second threshold value;

The fine synchronization search module is further configured to:

6. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the steps of the multiframe synchronization method of the GSM system as claimed in any one of claims 1 to 4 when the computer program is executed by the processor.

7. A non-transitory computer readable storage medium having stored thereon a computer program, which when executed by a processor, implements the steps of the multiframe synchronization method of the GSM system of any one of claims 1 to 4.