CN112187694A - DMRS-based mobile phone terminal signal shielding method and system - Google Patents

DMRS-based mobile phone terminal signal shielding method and system Download PDF

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CN112187694A
CN112187694A CN202011016669.1A CN202011016669A CN112187694A CN 112187694 A CN112187694 A CN 112187694A CN 202011016669 A CN202011016669 A CN 202011016669A CN 112187694 A CN112187694 A CN 112187694A
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pbch dmrs
sequence
dmrs sequence
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CN112187694B (en
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张小飞
魏梅英
王志欣
李晨
李安平
杨旭
马晓莹
李川
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STATE RADIO MONITORING CENTER
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K3/00—Jamming of communication; Counter-measures
    • H04K3/60—Jamming involving special techniques
    • H04K3/68—Jamming involving special techniques using passive jamming, e.g. by shielding or reflection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

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Abstract

The invention provides a mobile phone terminal signal shielding method and system based on DMRS, belonging to the technical field of wireless mobile communication. The system of the invention comprises: the device comprises a signal receiving module, a cell searching module, a PBCH DMRS demodulation module, an interference sequence generating module and an interference signal sending module. The method comprises the following steps: receiving 5G signals in the environment, and calculating the physical cell identifier and the PBCH DMRS sequence of the current cell; generating a mask PBCH DMRS sequence and an adjacent mask PBCH DMRS sequence by utilizing phase rotation; inserting the shielding sequence on the resource units of the synchronous broadcast block in the frequency domain; and after OFDM modulation, transmitting the OFDM modulated signal to the environment at the same frequency point as the base station. The shielding signal sent by the invention can accurately interfere, greatly reduces the transmitting power of the shielding system on the basis of only occupying a small part of system resources, and does not influence the normal work of the 5G base station.

Description

DMRS-based mobile phone terminal signal shielding method and system
Technical Field
The invention relates to the technical field of wireless mobile communication, in particular to a method and a system for shielding mobile phone terminal signals based on Demodulation Reference signals (DMRS) in a specific scene.
Background
Because the 5G mobile communication system adopts the optimized air interface technology and wider system bandwidth, mobile communication users can experience faster transmission rate and lower transmission delay, the communication between the users is more convenient, and the communication forms are more diversified. However, due to the characteristic of openness of the wireless channel, the communication content between users is likely to be intercepted by an illegal receiving device, thereby causing information leakage. Especially in some scenes with privacy requirements, it is important to prevent information leakage.
In the LTE (Long Term Evolution) system, there are some mature mobile Signal shielding schemes, such as Signal shielding schemes for synchronization signals, CRS (Common Reference Signal), PBCH (Physical Broadcast Channel), and the like. However, in the 5G system, the definition of the reference signals is different from that of the LTE system, and the design of each reference signal is more flexible, so that signal shielding for the 5G system is more challenging.
In the 5G system, DMRS is used for demodulation of uplink and downlink data, and when DMRS signals are masked, the result of channel estimation is severely affected, thereby masking transmission of mobile signals. The DMRS sequences are designed differently and the resource mapping positions are different for different physical channels. Among them, DMRSs for PDSCH (Physical Downlink Shared Channel) and PDCCH (Physical Downlink Control Channel) are user-specific, and the position on the time-frequency resource is determined by a high-level signaling, which makes it difficult to shield.
In a mobile communication system, the purpose of shielding mobile signals can be achieved by interfering a network in various ways. Common methods are constant interference, deceptive interference and random interference. Constant interference prevents legitimate nodes from communicating with each other by transmitting consecutive random bits to keep the line busy, as described in references 1 and 2. This type of attack is low in energy and easy to detect, but can disrupt network communications such that anyone under the same network cannot communicate. Spoofing interference misleads the receiver to believe that this is a message from a legitimate source by continuously sending regular packet data, forcing the receiver to wait in a listening state, as described in reference 2. But spoofing interference is energy inefficient due to continuous transmission. Random interference intermittently sends random bits or regular packets to the network that sleep for a period of time, interfering with the network for a period of time, continuously switching between two states, as described in references 1-3. The ratio between sleep time and interference time can be manipulated to adjust the trade-off between efficiency and effectiveness. Although the random interference can save energy and reduce power consumption to a certain extent, the random interference is not efficient. At present, the methods are not ideal for shielding 5G signals and are not suitable for shielding signals in a 5G system.
Reference 1: pelechrinis K, Iliofotou M, Krishhnamuthy S V.Denial of service attributes in wireless networks The case of jammers [ J ]. IEEE Communications summary & tutorials,2010,13(2): 245-.
Reference 2: xu W, trap W, Zhang Y, et al, the ease of proofing and testing of adhesives in wireless networks [ C ]// Proceedings of the 6th ACM international system on Mobile ad networks and computing.2005: 46-57.
Reference 3: grover K, Lim A, Yang Q, Jamming and anti-java technologies in wireless networks a survey [ J ]. International Journal of Ad Hoc and Ubiquitous Computing,2014,17(4): 197-215.
Disclosure of Invention
Aiming at the problems that the signal shielding difficulty in the existing 5G system is high and the existing method is not applicable, the invention discloses a mobile phone terminal signal shielding method and system based on DMRS (demodulation reference signal), aiming at the PBCH DMRS with a relatively fixed resource mapping position, and aiming at illegal receiving equipment, accurately shielding the 5G mobile phone terminal signal under the condition of not influencing the normal work of a 5G base station.
The invention provides a mobile phone terminal signal shielding method based on DMRS, which comprises the following steps:
step 1, receiving 5G signals in an environment, and calculating a physical cell identifier and a PBCH DMRS sequence of a current cell;
step 2, generating a screening PBCH DMRS sequence and an adjacent screening PBCH DMRS sequence;
generating a PBCH DMRS sequence by using a pseudorandom sequence which is the same as the PBCH DMRS sequence of the current cell, carrying out Phase rotation on the sequence after QPSK (Quadrature Phase Shift Keying) modulation to obtain a shielded PBCH DMRS sequence, and carrying out Phase rotation twice on the sequence after QPSK modulation to obtain an adjacent shielded PBCH DMRS sequence;
step 3, obtaining frequency domain offset by the physical cell identifier, and inserting the shielding PBCH DMRS sequence and the adjacent shielding PBCH DMRS sequence on the resource unit of the synchronous broadcast block in the frequency domain to obtain a mapping shielding PBCH DMRS sequence;
and 4, after OFDM modulation is carried out on the PBCH DMRS sequence, the PBCH DMRS sequence is sent to the environment on the same frequency point as the base station.
In the step 1, a main synchronization signal and an auxiliary synchronization signal of the 5G signal in the environment are detected by using a blind detection technology, and a physical cell identifier is calculated and obtained.
In step 1, the method for obtaining the demodulation reference signal PBCH DMRS of the physical broadcast channel of the cell by demodulation includes:
firstly, counting the number of synchronous broadcast blocks in a synchronous broadcast block set acquired from a physical broadcast channel of a current cell, and determining an index value i of the synchronous broadcast blocksSSBIntermediate variables of
Figure BDA0002699292360000021
Figure BDA0002699292360000022
Is a positive integer which is a positive integer,
Figure BDA0002699292360000023
then, utilize
Figure BDA0002699292360000024
Obtaining an initialization parameter c of an m sequence in a pseudo-random sequenceinitA number of suspicion values of; the pseudo-random sequence consists of two m sequences x1(n) and x2(n) constitution x1(n) has an initialization parameter of x1(0)＝1,x1(n) 0, n 1,2, 30, m-sequence x2(n) has an initialization parameter of x2(n)＝cinitN is 0,1, …, 30; generating PBCH DMRS sequences of a plurality of current cells by the pseudo-random sequences; finally, each generated PBCH DMRS sequence is respectively subjected to cross-correlation operation with the received PBCH DMRS sequence, and the PBCH DMRS sequence corresponding to the received PBCH DMRS sequence with the maximum correlation peak is obtained
Figure BDA0002699292360000025
Reuse the same
Figure BDA0002699292360000026
And calculating the physical cell identification of the current cell to generate the PBCH DMRS sequence of the current cell.
When the method is used in the same-frequency multi-cell environment, the shielding PBCH DMRS sequence and the adjacent shielding PBCH DMRS sequence of each cell are obtained according to the steps 1-2, and then the shielding PBCH DMRS sequences or the adjacent shielding PBCH DMRS sequences are overlapped on the frequency domain to obtain the shielding PBCH DMRS sequence and the adjacent shielding PBCH DMRS sequence in the same-frequency multi-cell environment.
The invention provides a mobile phone terminal shielding system based on DMRS, comprising: the device comprises a signal receiving module, a cell searching module, a PBCH DMRS demodulation module, an interference sequence generating module and an interference signal sending module. The signal receiving module is used for receiving base station signals in the environment, preprocessing received data and inputting the processed data into the cell searching module; the cell search module is used for solving the physical cell identification through blind detection of the PSS and the SSS and inputting the physical cell identification into the PBCH DMRS demodulation module; the PBCH DMRS demodulation module obtains a PBCH DMRS sequence used by the base station by carrying out correlation operation with the possible DMRS sequence of the current cell and inputs the PBCH DMRS sequence into the shielding sequence generation module; the shielding sequence generating module is used for generating a PBCH DMRS sequence based on the PBCH DMRS sequence used by the base station and the physical cell identification information and inputting the PBCH DMRS sequence into the shielding signal transmitting module; and the shielding signal sending module is used for mapping the PBCH DMRS signal to a corresponding time frequency resource and sending the PBCH DMRS signal to the environment at the same frequency point as the base station with certain power.
A storage medium having a computer program stored therein, wherein the computer program is arranged to perform the above method when executed.
An electronic device comprising a memory having a computer program stored therein and a processor arranged to run the computer program to perform the above method.
Compared with the prior art, the invention has the following advantages and positive effects:
(1) the DMRS-based 5G signal shielding method and system provided by the invention are an accurate shielding scheme with strong pertinence, the transmitted shielding signal can be interfered accurately, only a small part of system resources are occupied in both time domain and frequency domain, and the transmitting power of the shielding system can be greatly reduced.
(2) The DMRS-based 5G signal shielding method and the DMRS-based 5G signal shielding system only send the shielding signal on the downlink channel and do not influence the normal work of the 5G base station.
(3) The DMRS-based 5G signal shielding method and system provided by the invention are not only suitable for a single-frequency single-cell system, but also suitable for a same-frequency multi-cell system, and when signals of the same-frequency multi-cell communication system are shielded, only the DMRS sequences shielding each cell are required to be superposed on a frequency domain.
Drawings
Fig. 1 is a schematic flow chart illustrating an implementation of a DMRS-based mobile terminal signal shielding method according to the present invention;
fig. 2 is a schematic diagram of mapping of PBCH DMRS resources masked according to the present invention;
fig. 3 is a schematic block diagram of a DMRS-based mobile terminal signal shielding system according to the present invention.
Detailed Description
The present invention will be described in further detail and with reference to the accompanying drawings so that those skilled in the art can understand and practice the invention.
The DMRS-based mobile phone terminal signal shielding method and system provided by the invention are used for a 5G communication system, are realized based on a Physical Broadcast Channel (PBCH), are an efficient and low-power consumption 5G signal shielding technology, and can accurately shield 5G mobile phone terminal signals aiming at illegal receiving equipment under the condition that other wireless communication systems in different frequency bands are not influenced to normally work.
As shown in fig. 1, the method for shielding a mobile terminal signal based on DMRS according to the present invention, which implements 5G signal shielding based on PBCH DMRS, is divided into the following 4 steps, and each implementation step is described below.
Step 1, receiving 5G signals in the environment, and calculating the physical cell identifier and the PBCH DMRS of the current cell.
In the embodiment of the invention, a blind detection technology is used for detecting the primary synchronization signal and the secondary synchronization signal of the 5G signal in the environment. The step 1 comprises the following steps 101-104.
Step 101, detecting a primary synchronization signal of a 5G signal in an environment to obtain a cell identifier 2.
Searching 5G Frequency points in the environment, blindly detecting PSS (Primary Synchronization Signal), completing OFDM (Orthogonal Frequency Division Multiplexing) symbol boundary Synchronization and coarse Frequency Synchronization, and obtaining a cell identifier 2 marked as
Figure BDA0002699292360000041
Wherein, the blind detection is performed by using all existing PSS sequencesAnd performing correlation operation on the array and the received data to find out the PSS sequence currently used by the base station.
102, detecting an auxiliary synchronization signal of the 5G signal in the environment to obtain a cell identifier 1.
Performing initial frequency offset correction on 5G signals in the environment, blindly detecting SSS (Secondary Synchronization Signal), obtaining a cell identifier 1, and marking as
Figure BDA0002699292360000042
Step 103, obtaining a physical cell identifier through the cell identifier 1 and the cell identifier 2
Figure BDA0002699292360000043
And 104, demodulating and acquiring a demodulation reference signal PBCH DMRS of the physical broadcast channel of the current cell. The demodulation process of step 104 includes the following steps a to C.
Step A, setting the PBCH DMRS sequence of the current cell as r (k) and expressing the sequence as follows:
Figure BDA0002699292360000044
wherein c (2k) denotes the 2 k-th value of the pseudorandom sequence c (n); c (2k +1) denotes the 2k +1 th value of the pseudorandom sequence c (n); c (n) is a Gold sequence; j denotes an imaginary unit. k is a positive integer.
Since the PBCH DMRS of the current cell is a sequence generation method well defined in the 3GPP standard, and all base stations generate sequences according to the method, the pseudo-random sequence c (n) is a Gold sequence with a length of 31, and c (n) is composed of two m-sequences x1(n) and x2(n) constitution x1(n) and x2And (n) are m sequences with the length of n. The pseudo-random sequence c (n) and the m sequence are generated as follows:
Figure BDA0002699292360000051
wherein N isCIs the state offset added to ensure non-correlation between different sequences, mod represents the remainder operation. Since all base stations generate sequences according to the sequence generation method specified in the 3GPP standard, N herec＝1600。
m sequence x1(n) has an initialization parameter of x1(0)＝1,x1(n) ═ 0, n ═ 1,2, ·, 30; m sequence x2(n) has an initialization parameter of x2(n)＝cinit，n＝0,1,…,30，cinitIs calculated as follows:
cinitthe following formula is satisfied:
Figure BDA0002699292360000052
wherein x is2(i) Denotes the m sequence x2(n) th number of (n).
Initialization parameter cinitCalculated according to the following formula:
Figure BDA0002699292360000053
wherein the content of the first and second substances,
Figure BDA0002699292360000054
is about the index value i of synchronous broadcast block (SSB)SSBIntermediate variable of (1), with iSSBThe correspondence that exists is illustrated in the following step B,
Figure BDA0002699292360000055
is a positive integer which is a positive integer,
Figure BDA0002699292360000056
step B, mixing a plurality of cinitAnd performing cross-correlation operation on the PBCH DMRS sequences of the current cells corresponding to the suspected values and the received PBCH DMRS sequences to obtain values corresponding to the index values of the synchronous broadcast blocks. Obtaining a plurality of c through the following steps a-cinitIs suspected ofThe value is obtained.
Step a, acquiring a synchronous broadcast block set from a physical broadcast channel of a current cell, and counting the number of synchronous broadcast blocks contained in the synchronous broadcast block set;
step b, when the synchronous broadcast block set contains 4 synchronous broadcast blocks,
Figure BDA0002699292360000057
nhfrepresenting the field information, and taking the value of 0 or 1, wherein 0 corresponds to the first field and 1 corresponds to the second field; when the synchronized broadcast block set contains 8 or 64 synchronized broadcast blocks,
Figure BDA0002699292360000058
it is also a specification in the 3GPP standard that the set of sync broadcast blocks contains 4, 8 or 16 sync broadcast blocks.
Step c, calculating c according to the above formula (4) by the physical cell identification and the value corresponding to the index value of the synchronized broadcast blockinitSeveral suspicion values of.
Step C, according to the calculated CinitAnd obtaining the PBCH DMRS sequence of the current cell by the plurality of suspected values.
Initialization parameter cinitAccording to
Figure BDA0002699292360000059
There are also 8 possible values for the range of values of (a), and an m-sequence x can be obtained from each value2And (n), correspondingly generating a PBCH DMRS sequence of the current cell according to the formulas (1) and (2), wherein the PBCH DMRS sequence of the current cell is also the local PBCH DMRS sequence. Performing cross-correlation operation on each generated local PBCH DMRS sequence and the received PBCH DMRS sequence to acquire the PBCH DMRS sequence with the maximum correlation peak and corresponding to the received PBCH DMRS sequence
Figure BDA00026992923600000510
The received PBCH DMRS sequence is derived from the received 5G signal in the environment. Finally will be
Figure BDA00026992923600000511
And obtained
Figure BDA00026992923600000512
And substituting equations (1) - (4) to obtain the PBCH DMRS sequence used by the current cell.
And 2, generating a shielding PBCH DMRS sequence and an adjacent shielding PBCH DMRS sequence.
And shielding the PBCH DMRS sequence, wherein the following conditions are met:
(1) the screening PBCH DMRS sequence can use a pseudo-random sequence which is the same as a local PBCH DMRS sequence sent by a current cell base station, and can also use a certain fixed pseudo-random sequence which is different from the local PBCH DMRS sequence of the base station;
(2) after the PBCH DMRS sequence is modulated by QPSK and then phase rotation is carried out, the PBCH DMRS sequence is shielded
Figure BDA0002699292360000061
Can be expressed as:
Figure BDA0002699292360000062
wherein, l represents an OFDM (orthogonal frequency division multiplexing) symbol number within one slot; n issIndicating a slot number within a radio frame;
Figure BDA0002699292360000063
indicating the nth in a radio framesAnd the PBCH DMRS sequence corresponding to the l-th OFDM symbol in each time slot, wherein alpha is a rotated phase angle.
Figure BDA0002699292360000064
Indicating the nth in the generated radio framesA masked PBCH DMRS sequence of the l-th OFDM symbol in a slot. k denotes the kth value in the DMRS sequence.
Figure BDA0002699292360000065
Is a PBCH DMRS sequence generated using the same pseudo-random sequence or some fixed pseudo-random sequence as the local PBCH DMRS sequenceAnd finally, obtaining the product after QPSK modulation.
In addition, the angle difference delta alpha of the phase rotation of the adjacent OFDM symbols carrying PBCH DMRS is not 0, so that the adjacent shielding PBCH DMRS sequences
Figure BDA0002699292360000066
Can be expressed as:
Figure BDA0002699292360000067
wherein l ' represents the l ' th OFDM symbol, n 'sDenotes n 'th in radio frame'sA slot, wherein the l 'th OFDM symbol is adjacent to the l' th OFDM symbol;
Figure BDA0002699292360000068
denotes n 'th in generated radio frame'sA masked PBCH DMRS sequence for the l' th OFDM symbol in a slot. Δ α is a phase rotation angle difference between the adjacent l' th OFDM symbol and the l-th OFDM symbol.
Step 3, shielding PBCH DMRS sequence
Figure BDA0002699292360000069
Masked PBCH DMRS sequences adjacent to each other
Figure BDA00026992923600000610
Mapping to Resource Element (RE) of the synchronized broadcast block.
And inserting the shielding PBCH DMRS sequence and the adjacent shielding PBCH DMRS sequence in the resource units of the synchronous broadcast block in the frequency domain according to the frequency domain offset obtained by the physical cell identifier to obtain the mapping shielding PBCH DMRS sequence.
The PBCH DMRS sequence to be mapped is interspersed in PBCH in frequency domain, each RB (Resource Block) of PBCH has 3 DMRS, the DMRS has 4 frequency domain offsets v, the offsets v are related to physical cell identification,
Figure BDA00026992923600000611
mod 4. As shown in fig. 2, a PBCH DMRS resource mapping diagram is shown.
And 4, carrying out OFDM modulation on the PBCH DMRS sequence, and then sending the modulated PBCH DMRS sequence to the environment with a set power on the same frequency point as the base station.
As shown in fig. 3, correspondingly, the DMRS-based 5G signal shielding system provided by the present invention includes: the device comprises a signal receiving module, a cell searching module, a PBCH DMRS demodulation module, an interference sequence generating module and an interference signal sending module.
The signal receiving module is used for receiving base station signals in the environment, preprocessing received 5G signal data and inputting the processed data into the cell searching module. Preprocessing the 5G signal includes removing invalid data and the like.
And the cell searching module is used for solving the physical cell identification through blind detection of the PSS and the SSS and inputting the physical cell identification into the PBCH DMRS demodulation module.
And the PBCH DMRS demodulation module is used for acquiring the PBCH DMRS sequence of the current cell and inputting the PBCH DMRS sequence into the interference sequence generation module. The PBCH DMRS demodulation module obtains the PBCH DMRS sequence used by the current cell base station through performing correlation operation with possible DMRS sequences, and the specific obtaining manner is referred to in step 104.
The interference sequence generating module generates a shielding PBCH DMRS sequence and an adjacent shielding PBCH DMRS sequence based on the PBCH DMRS sequence and the physical cell identification information used by the current base station, and sends the sequences to the interference signal sending module. The generation process of the masked PBCH DMRS sequence and the adjacent masked PBCH DMRS sequence is specifically referred to step 2 above.
The interference signal sending module maps the PBCH-shielding DMRS signal and the adjacent PBCH-shielding DMRS sequence to a resource unit of the synchronous broadcast block, and sends the mapped PBCH-shielding DMRS sequence to the environment at a certain power on the same frequency point as the 5G base station after OFDM modulation is carried out on the mapped PBCH-shielding DMRS sequence.
Further, based on the DMRS based handset terminal shielding method of the present invention, a storage medium may be implemented, in which a computer program is stored, the computer program being configured to perform the method of the present invention when running.
Based on the mobile phone terminal shielding method of the present invention, an electronic device may be realized, comprising a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the method of the present invention.
When the method and the system are applied, the method and the system are arranged on intelligent equipment, such as a smart phone, a notebook computer and the like, of a place needing signal shielding, and then the method or the system is started to realize 5G signal shielding.
The method and the device are not only suitable for single-frequency single-cell application scenes, but also suitable for same-frequency multi-cell scenes. And overlapping the PBCH DMRS sequences of all the cells under the same-frequency multi-cell environment to obtain the PBCH DMRS sequence of the current environment. For example, cell 1 may have a masked PBCH DMRS sequence of
Figure BDA0002699292360000071
Cell 2 masked PBCH DMRS sequence of
Figure BDA0002699292360000072
The finally sent masked PBCH DMRS sequence is
Figure BDA0002699292360000073
The above-mentioned embodiments are merely for better illustrating the objects, principles, technical solutions and advantages of the present invention. It should be understood that the above-mentioned embodiments are only exemplary of the present invention, and are not intended to limit the present invention, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A mobile phone terminal shielding method based on DMRS is characterized by comprising the following steps:
step 1, receiving 5G signals in an environment, and calculating a physical cell identifier and a PBCH DMRS sequence of a current cell; wherein PBCH represents a physical broadcast channel, and DMRS represents a demodulation reference signal;
step 2, generating a screening PBCH DMRS sequence and an adjacent screening PBCH DMRS sequence;
generating a PBCH DMRS sequence by using a pseudo-random sequence which is the same as the PBCH DMRS sequence of the current cell, carrying out phase rotation on the sequence after QPSK modulation to obtain a shielding PBCH DMRS sequence, and carrying out phase rotation twice on the sequence after QPSK modulation to obtain an adjacent shielding PBCH DMRS sequence; wherein QPSK denotes quadrature phase shift keying;
step 3, obtaining frequency domain offset by the physical cell identifier, and inserting the shielding PBCH DMRS sequence and the adjacent shielding PBCH DMRS sequence on the resource unit of the synchronous broadcast block in the frequency domain to obtain a mapping shielding PBCH DMRS sequence;
step 4, after OFDM modulation is carried out on the PBCH DMRS sequence, the PBCH DMRS sequence is sent to the environment on the same frequency point as the 5G base station of the current cell; OFDM denotes an orthogonal frequency division multiplexing technique.
2. The method of claim 1, wherein in step 1, the method for acquiring the PBCH DMRS sequence of the current cell comprises:
(1) firstly, counting the number of synchronous broadcast blocks in a synchronous broadcast block set acquired from a physical broadcast channel of a current cell;
(2) secondly, an index value i of the synchronous broadcast block is determined according to the number of the synchronous broadcast blocksSSBIntermediate variables of
Figure FDA0002699292350000011
Figure FDA0002699292350000012
Is a positive integer which is a positive integer,
Figure FDA0002699292350000013
(3) then, the PBCH DMRS sequence is generated based on a pseudo-random sequence consisting of two m-sequences x1(n) and x2(n) constituent m sequence x1(n) has an initialization parameter of x1(0)＝1,x1(n) 0, n 1,2, 30, m-sequence x2(n) has an initialization parameter of x2(n)＝cinit，n＝0,1,…,30；
According to the physical cell identification of the current cell
Figure FDA0002699292350000014
And
Figure FDA0002699292350000015
calculation of cinitAll the suspicion values of;
(4) finally, according to cinitObtaining an m-sequence x for each suspect value of (c)2(n), further generating a PBCH DMRS sequence of the current cell, performing cross-correlation operation on each generated PBCH DMRS sequence and the received PBCH DMRS sequence respectively, and acquiring the PBCH DMRS sequence corresponding to the received PBCH DMRS sequence with the maximum correlation peak
Figure FDA0002699292350000016
By using
Figure FDA0002699292350000017
And obtained
Figure FDA0002699292350000018
Generating a PBCH DMRS sequence of a current cell.
3. The method according to claim 2, wherein in (2), the intermediate variable is
Figure FDA0002699292350000019
The determination method of (1) is as follows: let the counted number of the synchronized broadcast blocks in the synchronized broadcast block set be K, if K is 4,
Figure FDA00026992923500000110
nhffor field information, take value 0 or1, 0 corresponds to the first half frame, and 1 corresponds to the second half frame; if K is 8 or 64, then,
Figure FDA00026992923500000111
4. the method of claim 1, wherein in the step 2, the screening of the PBCH DMRS sequence can be further generated by using a fixed pseudo-random sequence different from the PBCH DMRS sequence of the current cell.
5. The method of claim 1 or 4, wherein the masked PBCH DMRS sequence generated in step 2 is represented by
Figure FDA00026992923500000112
The following were used:
Figure FDA00026992923500000113
wherein k represents the kth value in the DMRS sequence, l represents the OFDM symbol serial number in a time slot, and nsIndicating a slot number within a radio frame;
Figure FDA0002699292350000021
indicating the nth in a radio framesAnd the PBCH DMRS sequence corresponding to the ith OFDM symbol in each time slot, wherein alpha is a rotated phase angle, and j is an imaginary unit.
6. The method of claim 5, wherein in the step 2, the generated adjacent masked PBCH DMRS sequence is represented as
Figure FDA0002699292350000022
The following were used:
Figure FDA0002699292350000023
wherein the content of the first and second substances,
Figure FDA0002699292350000024
denotes n 'th in generated radio frame'sAnd the shielding PBCH DMRS sequence of the l 'OFDM symbol in each time slot, wherein delta alpha is the phase rotation angle difference between the adjacent l' OFDM symbol and the adjacent l OFDM symbol.
7. The method according to claim 1 or 4, wherein when the method is used in an environment of the same frequency and multiple cells, the masked PBCH DMRS sequence and the adjacent masked PBCH DMRS sequence of each cell are obtained according to the steps 1-2, and then the masked PBCH DMRS sequences or the adjacent masked PBCH DMRS sequences are superimposed on the frequency domain to obtain the masked PBCH DMRS sequence and the adjacent masked PBCH DMRS sequence in the environment of the same frequency and multiple cells.
8. The DMRS-based mobile terminal signal shielding system according to any of claims 1 to 4, comprising: the device comprises a signal receiving module, a cell searching module, a PBCH DMRS demodulation module, an interference sequence generating module and an interference signal sending module;
the signal receiving module is used for receiving 5G signals in the environment, preprocessing the 5G signals and inputting the preprocessed 5G signals into the cell searching module;
the cell search module detects a primary synchronization signal and a secondary synchronization signal of a 5G signal by using a blind detection technology, calculates and acquires a physical cell identifier, and inputs the physical cell identifier into the PBCH DMRS demodulation module;
the PBCH DMRS demodulation module acquires a PBCH DMRS sequence of a current cell and inputs the PBCH DMRS sequence into the interference sequence generation module;
the interference sequence generation module generates a shielding PBCH DMRS sequence and an adjacent shielding PBCH DMRS sequence according to the PBCH DMRS sequence of the current cell and the physical cell identifier; the shielding PBCH DMRS sequence is obtained by generating a pseudo-random sequence which is the same as the PBCH DMRS sequence of the current cell, modulating the pseudo-random sequence by QPSK and then performing phase rotation; the adjacent shielding PBCH DMRS sequences are obtained by generating a pseudo-random sequence which is the same as the PBCH DMRS sequence of the current cell, modulating by QPSK and then performing phase rotation twice;
the interference signal sending module maps the PBCH-shielding DMRS signal and the adjacent PBCH-shielding DMRS sequence to the resource unit of the synchronous broadcast block, and sends the mapped PBCH-shielding DMRS sequence to the environment on the same frequency point as the 5G base station of the current cell after OFDM modulation is carried out on the mapped PBCH-shielding DMRS sequence.
9. A storage medium having a computer program stored thereon, the computer program being arranged to perform the method when executed.
10. An electronic device according to any of the claims 1-4, comprising a memory having a computer program stored therein and a processor arranged to run the computer program to perform the method.
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