CN117834060A - Spectrum sensing method in mobile communication network - Google Patents
Spectrum sensing method in mobile communication network Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 58
- 238000001228 spectrum Methods 0.000 title claims abstract description 46
- 238000010295 mobile communication Methods 0.000 title claims abstract description 25
- 230000005540 biological transmission Effects 0.000 claims abstract description 99
- 238000013507 mapping Methods 0.000 claims abstract description 21
- 230000006854 communication Effects 0.000 claims description 32
- 238000004891 communication Methods 0.000 claims description 31
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- 125000004122 cyclic group Chemical group 0.000 claims description 9
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- 238000005516 engineering process Methods 0.000 abstract description 10
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
- H04B17/345—Interference values
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
- H04B17/336—Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/382—Monitoring; Testing of propagation channels for resource allocation, admission control or handover
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
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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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/14—Spectrum sharing arrangements between different networks
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Abstract
The invention relates to a frequency spectrum sensing method in a mobile communication network, belonging to the technical field of mobile communication. The method adopts OFDM technology to communicate, a transmitting end generates a transmission data block and carries out channel coding on the transmission data block to modulate the transmission data block into data modulation symbols, and then the data modulation symbols are mapped on OFDM wireless subcarriers to form wireless resource blocks, and the wireless resource blocks are subjected to OFDM modulation and transmitted to a wireless channel; the receiving end receives the OFDM signal on the wireless channel and demodulates the OFDM signal to obtain a transmission data block. And under the condition that the transmission data block is verified to be correct, the receiving end carries out channel coding, modulation and resource mapping on the received transmission data block to obtain a reconstructed wireless resource block. The receiving end utilizes the reconstructed wireless resource block and the received wireless resource block to carry out subcarrier channel assessment, the subcarrier information with the signal-to-noise ratio lower than the threshold value is fed back to the sending end, and the sending end receives subcarrier interference information and then transmits the subcarrier interference information in a mode of eliminating the subcarrier when sending data.
Description
Technical Field
The invention belongs to the technical field of mobile communication, in particular to a spectrum interference detection technology in a wireless communication system, and provides a spectrum sensing method in a mobile communication network.
Background
The wireless communication system adopts a wireless transmission medium for signal communication, and because the wireless communication has an open transmission line, the transmission performance of the communication system is greatly affected due to the easy interference problem, and particularly in the application of the internet of things, the wireless communication system usually adopts a shared frequency band mode to work due to the shortage of wireless resources, i.e. the communication system is not distributed with a fixed special frequency band, so that mutual interference exists between different wireless communication systems.
In actual engineering, for the internet of things system, particularly for the shared frequency band communication system, the following methods are mainly adopted to avoid the mutual interference between the systems.
First: before the wireless communication system is deployed, a frequency sweep generator or special equipment is adopted to detect the spectrum use condition of the deployment site, and whether the spectrum occupied by the system of the Internet of things to be used is used by other systems or is interfered by other systems is determined. The method has the biggest characteristics that the working frequency band cannot be modified at will after the application system is installed, and the frequency spectrum conditions occupied by other systems in the working period are difficult to accurately detect, so that the later-period interference is serious, and the maintenance is difficult.
In a general solution, after an application system receives interference, the communication performance is seriously affected, and then the deployed area spectrum needs to be scanned again, and the working frequency band of the system is reconfigured, which clearly increases the difficulty and cost of the post maintenance technology.
Second,: the system needs to additionally add a functional module, namely a frequency spectrum sensing module is adopted to finish real-time detection of the interference condition of the frequency band used by the wireless communication system. The frequency sweep module is needed to be added in the system, and the frequency sweep module is similar to the frequency spectrometer functional module in nature, and the wireless spectrum use and interference condition of the deployment place are detected in real time, so that the wireless communication system can automatically or manually adjust the working frequency band.
In the method, an independent working module is additionally added in the wireless communication system, spectrum use and interference conditions need to be detected in real time, and surrounding usable blank frequency bands are searched for the requirement of the wireless communication system for detecting and adjusting the working frequency bands in real time. In the low-cost internet of things wireless communication system, the additional hardware cost is required to be increased, and the popularization and the use cannot be achieved.
Disclosure of Invention
In view of the above, the present invention is directed to providing a method for spectrum sensing in a mobile communication network, which is capable of completing a spectrum interference detection task without adding additional mapping equipment under the existing OFDM wireless communication framework, for the current internet of things wireless communication system, particularly for a shared frequency band internet of things system using OFDM (Orthogonal frequency-division multiplexing) technology.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the method for sensing the frequency spectrum in the mobile communication network comprises the following steps:
s1, a transmitting end carries out channel processing on a transmission data block to be transmitted to form a data modulation symbol to be transmitted, wherein the channel processing comprises the steps of carrying out channel coding and modulation on the transmission data block;
s2, when transmitting the data modulation symbols, the transmitting end maps the data modulation symbols and the reference signals onto wireless subcarriers in a communication system in a resource mapping mode to form wireless resource blocks, OFDM modulates the wireless resource blocks to form time domain OFDM signals, and then loads the time domain OFDM signals into a wireless transmission channel for transmission;
s3, the receiving end receives the time domain OFDM signals from the wireless transmission channels and demodulates the time domain OFDM signals to obtain data modulation symbols on each wireless subcarrier, and the data modulation symbols are demodulated and channel decoded to obtain transmission data blocks of the receiving end;
s4, the receiving end performs the same compiling operation as the sending end on the received transmission data block under the condition that the transmission data block is checked to be correct so as to obtain a reconstructed wireless resource block of the receiving end;
s5, the receiving end utilizes the reconstructed wireless resource block and the received wireless resource block to carry out subcarrier channel assessment, subcarrier information with the signal-to-noise ratio lower than a threshold value is fed back to the sending end, and the sending end receives subcarrier interference information and then transmits the subcarrier interference information in a mode of eliminating the subcarrier when sending data.
Further, in step S1, the transmission data block to be transmitted includes a check information bit, where the check information bit is used for the receiving end to perform a cyclic check on the received transmission data block to determine whether the received transmission data block is correct. In the transmission data block, firstly, information data which needs to be transmitted is contained, and secondly, check information bits are additionally contained.
Further, in step S2, the resource mapping refers to mapping the data modulation symbols onto the designated OFDM time-frequency resource grid, where the reference signal inserted in the mapping process is a determination signal known in transmit-receive, and the reference signal is used for channel measurement and signal estimation.
Further, in step S3, the receiving end extracts the radio resource block and the reference signal from the time domain OFDM signal in the demodulation process; the receiving end utilizes the extracted reference signal and the local known reference signal to carry out channel characteristic estimation on the frequency band occupied by the wireless resource block; performing equalization processing on the wireless resource block based on the channel estimation result; and carrying out demodulation processing on the data modulation symbols of the wireless resource blocks through channel demodulation decoding to obtain each bit log likelihood ratio value, and then obtaining a transmitting end transmission data block through channel decoding.
Further, in step S4, the receiving end performs a cyclic check on the obtained transmission data block, and performs a reconstruction of the radio resource block if the check is correct; in case of failure of the verification, the information transmission process is immediately ended.
Further, when the receiving end performs the reconstruction of the radio resource block, the receiving end performs channel coding and modulation on the acquired transmission data block to form a data modulation symbol, and maps the data modulation symbol and the reference signal onto the radio resource block to obtain a reconstructed radio resource block.
Further, in step S5, the process of performing subcarrier channel estimation by the receiving end includes counting the signal-to-noise ratio of each subcarrier on the time-frequency resource of the radio resource block; when the radio resource block is formed by a plurality of OFDM symbols, the signal-to-noise ratio of each subcarrier is the average value of the signal-to-noise ratios of the subcarriers corresponding to the plurality of OFDM symbols.
The invention has the beneficial effects that:
first: compared with the existing OFDM system which adopts a frequency sweep generator or other special equipment to detect the spectrum use condition of a deployment site and the deployment scheme of additionally adding a spectrum sensing module in the existing system, the method can complete the spectrum interference detection task without adding additional hardware resources or carrying out additional spectrum scanning treatment, and is beneficial to popularization, deployment and use in practical engineering.
Second,: in an actual wireless communication system, the method can complete real-time detection of the signal-to-noise ratio of each subcarrier, detect the interference condition of each subcarrier and influence actual communication, and the existing method or technology can only measure the whole transmission bandwidth and can not evaluate the interference condition of each subcarrier specifically.
Third,: the invention skillfully completes the subcarrier interference detection work under the condition of not influencing the data transmission by means of the communication characteristics of the OFDM system, is beneficial to the long-term detection of the subcarrier interference of the OFDM system by the receiving end, and is used for counting the subcarrier interference information which is more in line with the actual situation.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.
Drawings
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:
fig. 1 is a simplified block diagram of a spectrum sensing principle in a mobile communication network according to the present invention;
fig. 2 is a flow chart of spectrum sensing in a mobile communication network according to the present invention;
FIG. 3 is a diagram of a received resource grid and reconstructed resource grid generation process of the present invention;
FIG. 4 is a schematic diagram of a single OFDM symbol time-frequency resource in the simulation process of the present invention;
FIG. 5 is a graph of the OFDM signal during simulation of the present invention;
FIG. 6 is a graph of OFDM signal spectrum subject to subcarrier interference in a simulation process of the present invention;
FIG. 7 is a graph of subcarrier channels (graph a) and block error rate and bit error rate statistics (graph b) for different signal-to-noise ratios in the simulation process of the present invention;
fig. 8 is a simplified schematic diagram of the working principle of the subcarrier masking decision module in the simulation process of the present invention;
fig. 9 is a schematic diagram of an interference subcarrier index and an actual detected interference index in a simulation process according to the present invention;
fig. 10 is a schematic diagram of a subcarrier channel after shielding interfering subcarriers (fig. a) and a statistical schematic diagram of block error rate and bit error rate (fig. b) in the simulation process of the present invention;
FIG. 11 is a schematic diagram of analysis of block error rate before and after shielding interfering sub-carriers (FIG. a) and a schematic diagram of comparison analysis of block error rate (FIG. b) in the simulation process of the present invention;
fig. 12 is a schematic diagram of subcarrier channel estimation before and after interference subcarrier shielding under different signal to noise ratios in the simulation process of the present invention;
FIG. 13 is a diagram showing the comparison of the bit error rates before and after the masking interfering subcarriers in the simulation process of the present invention.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.
Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.
Referring to fig. 1 to 13, a method for spectrum sensing in a mobile communication network for completing a spectrum interference detection task without adding additional mapping equipment under the existing OFDM wireless communication frame is provided for a current internet of things wireless communication system, in particular to a shared frequency band internet of things system using an OFDM (Orthogonal frequency-division multiplexing) technology.
Example 1
The invention provides a method for detecting working spectrum interference by utilizing the characteristics of OFDM wireless communication technology aiming at a wireless communication system adopting the OFDM technology.
The transmitting end and the receiving end communicate on a wireless transmission medium by adopting an OFDM technology, the transmitting end generates a transmission data block, carries out channel coding on the data block, modulates the data block into data modulation symbols, then maps the data modulation symbols onto OFDM wireless subcarriers to form a wireless resource block, and carries out OFDM modulation on the wireless resource block and sends the wireless resource block to a wireless channel; the receiving end receives OFDM signals on a wireless channel, performs OFDM signal demodulation to obtain data modulation symbols carried on each subcarrier, and then obtains a received transmission data block through demodulation and channel decoding. If the cyclic check of the received transmission data block is correct, the received transmission data block is identical to the transmitted transmission data block, and the receiving end performs channel coding, modulation and resource mapping on the received transmission data block to obtain a wireless resource block identical to the transmitting end. Each time the system transmits a transmission data block, a radio resource block before the channel and a radio resource block after the channel are transmitted can be obtained, so that the channel quality of each subcarrier on each radio resource block can be estimated.
According to the simplified structure diagram of the spectrum sensing principle in the mobile communication network shown in fig. 1, the method of the present invention is implemented on the basis of four modules, which are respectively: the device comprises a transmitting end module, a receiving end module, a reconstructed transmitting end resource module and a spectrum sensing calculation module.
In the method for spectrum sensing in a mobile communication network of the present invention, the transmitting end module includes a transmission data block containing cyclic check bits for the receiving end module to confirm whether to receive correctly. The transmitting end module also comprises operations such as channel coding modulation, resource mapping and OFDM. The channel coding modulation performs a channel coding function on the transmission data block, and modulates the coded bits to form data modulation symbols. The resource mapping maps the data modulation symbols to the appointed OFDM time-frequency resource grid to form a wireless resource block, wherein the wireless resource block also needs to be inserted with a reference signal; the OFDM modulation module performs OFDM modulation (inverse Fourier transform) on the wireless resource block to form a time domain OFDM signal.
In the method for sensing the frequency spectrum in the mobile communication network, a receiving end module comprises an OFDM demodulation module, and the OFDM demodulation module demodulates (Fourier transforms) the OFDM time domain signal received from a transmission channel to obtain an OFDM time domain resource grid; the resource demapping module takes out the wireless resource block used by the transmitting end and the reference signal from the OFDM resource grid; the reference signal is a determination signal which is known to transmit and receive and is used for channel measurement and channel estimation; the channel estimation module carries out channel characteristic estimation on the frequency band occupied by the wireless resource block by utilizing the received reference signal and the local known reference signal; the channel equalization module performs equalization processing on the wireless resource block by using a channel estimation result; carrying out demodulation processing on data modulation symbols of a wireless resource block by using channel demodulation decoding to obtain each bit log likelihood ratio value, and then obtaining a transmitting end transmission data block by using channel decoding; and the transmission data block detects whether the transmission data block is correctly received according to the cyclic check code carried by the transmission data block.
In the method for sensing the frequency spectrum in the mobile communication network, the resource module of the reconstructed transmitting end comprises a channel coding modulation module which is completely the same as the channel coding modulation module in the transmitting end module, so as to complete the channel coding and modulation functions of the transmission data block in the receiving end and finally form a data modulation symbol; the reference signal is a determination signal known to transmit and receive; the resource mapping module maps the data modulation symbols and the reference signals to radio resource blocks to form the radio resource blocks which are identical to the transmitting end, and the blocks are also called as reconstructed radio resource blocks.
In the method for spectrum sensing in the mobile communication network of the invention, the spectrum sensing calculation module comprises a subcarrier channel evaluation module and a subcarrier shielding module. The subcarrier channel evaluation module utilizes the wireless resource block and the reconstructed wireless resource block obtained by the receiving end to evaluate the channel quality, and adopts a signal-to-noise ratio calculation method to evaluate the channel quality; and the subcarrier shielding module finally determines the interference subcarriers by utilizing the multiple subcarrier channel evaluation results and informs the transmitting end that the interference subcarriers are not started for data transmission.
Example 2
According to the spectrum sensing flow chart in the mobile communication network of the present invention shown in fig. 2, the method for spectrum sensing in the mobile communication network of the present invention comprises the following steps:
s1, a transmitting end carries out channel processing on a transmission data block to be transmitted to form a data modulation symbol to be transmitted, wherein the channel processing comprises channel coding and modulation processes on the transmission data block.
Specifically, in the communication process, the transmitting end transmits a transmission data block, where the data block includes check information bits, and is used by the receiving end to determine whether to correctly receive the transmission data block. And then carrying out channel processing, particularly channel coding and modulation processes, on the transmission data block to form data modulation symbols to be transmitted. As in steps 1 and 2 of fig. 2.
S2, when transmitting the data modulation symbols, the transmitting end maps the data modulation symbols and the reference signals onto wireless subcarriers in a communication system in a resource mapping mode to form wireless resource blocks, OFDM modulates the wireless resource blocks to form time domain OFDM signals, and then loads the time domain OFDM signals to a wireless transmission channel for transmission.
Specifically, according to the requirements of the wireless communication system, the data modulation symbols are mapped onto the wireless resource blocks, namely mapped into specific OFDM time domain lattices, and meanwhile, the mapping system is required to transmit required reference signals. The radio resource block is a subset of time-frequency resource grid of the OFDM system, and is specifically represented by frequency domain as subcarrier and time domain as OFDM symbol. The transmitting end carries out OFDM modulation on the OFDM resource grid to form an OFDM signal of a time domain, and then the OFDM signal is loaded to a wireless transmission channel. As shown in steps 3 and 4 in fig. 2.
S3, the receiving end receives the time domain OFDM signals from the wireless transmission channels and demodulates the time domain OFDM signals to obtain data modulation symbols on each wireless subcarrier, and the data modulation symbols are demodulated and channel decoded to obtain transmission data blocks of the receiving end.
Specifically, the receiving end receives a time domain OFDM signal from a wireless transmission channel, performs OFDM demodulation processing to obtain OFDM time-frequency resource grid data, and takes out a wireless resource block and a reference signal used for transmission from the OFDM time-frequency resource grid. The reference signal is used for channel estimation and equalization, and the data modulation symbols are extracted from the radio resource blocks after equalization. As in steps 5, 6 and 7 of fig. 2.
After demodulating the data modulation symbol, obtaining the log likelihood ratio of each transmission bit, obtaining the transmission data block of the transmitting end by adopting a soft decoding method in channel decoding, and ending the statistics if the verification of the transmission data block fails. As in steps 8, 9 and 10 of fig. 2.
And S4, the receiving end performs the same compiling operation as the sending end on the received transmission data block under the condition that the transmission data block is checked to be correct so as to obtain a reconstructed wireless resource block of the receiving end.
Specifically, if checking that the received transmission data block is correct, performing channel coding and modulation processing on the transmission data block at the transmitting end, wherein the channel coding and modulation processing are identical to those of the transmission data block, and finally mapping the formed data modulation symbol onto the wireless resource block, and simultaneously mapping a reference signal adopted by transmission to generate a reconstructed wireless resource block. As in steps 11 and 12 of fig. 2.
S5, the receiving end utilizes the reconstructed wireless resource block and the received wireless resource block to carry out subcarrier channel assessment, subcarrier information with the signal-to-noise ratio lower than a threshold value is fed back to the sending end, and the sending end receives subcarrier interference information and then transmits the subcarrier interference information in a mode of eliminating the subcarrier when sending data.
Specifically, the receiving end utilizes the local reconstructed wireless resource block and the received wireless resource block to evaluate the subcarrier channel, namely, the signal to noise ratio of each subcarrier is counted on the time-frequency resource of the wireless resource block. If the radio resource block is made up of a plurality of OFDM symbols, the signal-to-noise ratio of each subcarrier is the average of the signal-to-noise ratios of the corresponding subcarriers of the OFDM symbols. As in step 13 of fig. 2.
And the receiving end counts the signal-to-noise ratio of each subcarrier in the used wireless resource block every time when the receiving end correctly receives the transmission data block, judges that the subcarrier is interfered and cannot be used for bearing data modulation symbols if the signal-to-noise ratio is lower than a threshold value, and informs the transmitting end of subcarrier interference information. As in step 14 of fig. 2.
By the method, the subcarrier interference detection method is performed in the wireless communication system adopting the OFDM transmission technology, and has the advantages that the method can finish real-time detection of the signal-to-noise ratio of each subcarrier, detection of the interference condition and detection of the actual communication influence of each subcarrier under the condition that no additional hardware resource is required to be added and no additional frequency spectrum scanning processing is required to be performed on the basis of the conventional OFDM system, finally, the interference subcarriers are determined, and a transmitting end is informed that the interference subcarriers are not started for data transmission so as to ensure that the data transmission is not interfered.
Example 3
In order to clearly illustrate the use of the present invention in a specific scenario, the present embodiment uses MATLAB R2023b to build a link implementation simulation, and the link is built with reference to the spectrum sensing schematic block diagram of fig. 3. The OFDM basic parameter table in this embodiment is shown in table 1.
TABLE 1
At the transmitting end, the transmission data block firstly randomly generates 4328 bits of 0 and 1 as transmission information bit data, adopts a cyclic check code (CRC) with a polynomial of 24a to carry out CRC coding on the data information, and then adds CRC redundant data information to form a complete transmission data block with the length of 4352 bits. And performing Turbo channel coding on the transmission data block to form a coded data block, wherein the encoder adopts a Turbo code rate of 1/3 and a tail bit of 6 bits. Next, the coded data block is modulated, and in this embodiment, a Quadrature Phase Shift Keying (QPSK) modulation scheme is used, that is, a bit sequence is modulated into a complex sequence, so as to form a data modulation symbol. The resource mapping module then maps the data modulation symbols onto the OFDM time-frequency resources to form radio resource blocks.
As shown in fig. 4, the subcarrier usage is on one OFDM symbol, where the subcarrier payload symbols are used to carry data modulation symbols, and the DMRS reference signal symbols are used to carry reference signals. The reference signal is used for channel estimation, estimating the channel characteristics of this subcarrier in the frequency domain, and then used for channel equalization. In the embodiment of the present invention, each OFDM symbol has 504 subcarriers for transmission, and the subcarrier index value of each OFDM symbol, i.e., 1-504, also becomes the subcarrier number. A radio resource block is composed of 14 OFDM symbols and 504 subcarriers, and a 504×14 resource grid is formed, wherein reference signals occupy 1008, data modulation symbols occupy 6048, and finally an IFFT with 1024 points is used to perform OFDM modulation on the radio resource block. The spectrum of the OFDM signal is shown in fig. 5.
This embodiment is further described with respect to specific parameter settings in the simulation process.
Specific parameters of the OFDM signal in this embodiment are shown in table 2 below:
TABLE 2
The transmission channel adopts a 5GNR dedicated channel model TDL, and the specific model is TDL-B. The single antenna transmits and receives the signal, the background noise of the signal channel is AWGN Gaussian white noise, and (-6, +6) db is set in the simulation.
The interfering signal simulates the interference the signal suffers in the channel by adding multitone interference. The subcarrier index is 1-504, 35 index values are randomly selected, which adds interference to the 35 subcarrier channels. The OFDM signal spectrum after the interference signal is added as shown in fig. 6. The locations where peaks occur in the spectrum are locations that are subject to subcarrier interference.
At the receiving end module, the OFDM time domain signal is received from the transmission channel, totaling 14336 points, with a sampling rate of 15.36MHz. Firstly, the timing and channel estimation of the OFDM time domain signal are completed, namely OFDM demodulation is carried out, namely 1024 fast Fourier transform is carried out, the timing and channel estimation is carried out by adopting the reference signal, and the time-frequency resource block is proposed from the OFDM time domain signal, and the specification of the time-frequency resource block is 504x14.
The reference signal channel estimation is taken out from the wireless resource block of 504x14, and in the embodiment of the invention, a zero forcing equalization method is adopted to perform channel equalization on the subcarrier load symbol, so as to obtain the carrier data modulation symbol.
QPSK demodulation is carried out on the data modulation symbols, and a soft demodulation method is adopted to obtain likelihood comparison of transmission data blocks, wherein the total data blocks are 13062 data. And performing Turbo channel decoding on the likelihood logarithmic block to obtain 4352-bit decoding block data, namely receiving a transmission data block, wherein the data block comprises 24-bit cyclic check, and finally performing CRC decoding by adopting 24a to obtain the transmission information bit number. In this embodiment, the bit error rate is obtained by comparing each bit in the transmission data block with each bit in the reception transmission data block.
And a resource block reconstruction module, wherein the received transmission data block is subjected to 1/3Turbo channel coding according to the step of a sending end module, and a new 504x14 wireless resource block is reconstructed after QPSK modulation and resource mapping. The same reference signal needs to be inserted in reconstructing the radio resource block.
In the simulation process, each link uses the same reference channel, and the receiving and transmitting ends know the content of the reference signal and the positions occupied in the wireless resource grid.
Each resource element on the reconstructed resource block and the received resource block is in a one-to-one correspondence, and the subcarrier channel is evaluated by using the reconstructed resource block and the received resource block. The specific method is that the reconstructed resource block and the receiving resource block are correlated, if the subcarrier channel has interference, the correlation module value is necessarily lower than the correlation module value of the non-interference subcarrier channel. The subcarrier channel signal to noise ratio may be evaluated based on the correlation modulus value to thereby evaluate the subcarrier channel.
Assume that: the reconstructed radio resource is denoted as a_reconfiguration_regrid, and its dimension is 504×14, i.e. 504 subcarriers, 14 OFDM symbols. The radio resource block a_rx_regrid is received, and its dimension is 504x14.
The power per resource element can be expressed as
a_subcarrier_re_power＝a_reconstruction_REGrid.*conj(a_rx_REGrid)；
Wherein "..x" represents multiplication of corresponding elements in the array; conj (x) represents conjugating each element in the x array.
The average power per subcarrier is:
a_subcarrier_power＝mean(abs(a_subcarrier_re_power),2)；
the mean (x, 2) expression averages the row vectors in the x array, that is, averages the power of each subcarrier over different OFDM symbols. abs (x) represents modulo computation of each element in the x array.
In this embodiment, the signal-to-noise ratio of each subcarrier is calculated as follows:
a_subcarrier_snr＝a_subcarrier_power./mean((abs(a_rx_REGrid)).^2,2)；
where a_subsubcarrier_snr is an array of 504x1, "(x) & gt" denotes modular computation for each member in the x array
The resource elements of the OFDM radio resource block represent the resources of one OFDM symbol and one subcarrier.
This embodiment verifies the method without loss of generality. In the simulation of this embodiment, (-6, +6) db gaussian white noise is added, and simulation is performed by dividing the white noise into 8 segments, wherein several SNRs are selected for display analysis, as shown in fig. 7, fig. 7 (a) shows SNR cases of each subcarrier under different gaussian white noise, 4 SNR cases are selected and given, the ordinate represents the SNR value of each subcarrier, and the abscissa represents the subcarrier number. It can be seen in detail that the SNR of the interfered sub-carriers is much lower than the SNR of the normal sub-carriers. The first column in fig. 7 (b) is the block error rate at different signal-to-noise ratios. The second column shows the bit error rate at different signal-to-noise ratios. It can be seen from fig. 7 that the signal-to-noise ratio of the subcarrier channel in which interference exists is significantly lower than that of the non-interfering subcarrier channel.
In the present invention, according to different SNR measurement conditions of subcarriers, the subcarriers with interference need to be removed, as shown in fig. 8. The specific method is that the signal to noise ratio of the sub-carriers are subjected to differential operation one by one and absolute values are taken. The differential values are averaged and a 1.9 times average value is taken as a threshold above which interference is determined to exist. The detection results are shown in FIG. 9. Where the icon o represents the detected interfering subcarrier index and the icon x represents the actual interfering subcarrier index.
The result shows that the method can detect the subcarrier positions where all the interferences are located. After detecting the subcarrier where the interference exists, shielding the subcarrier where the interference exists at the transmitting end from transmitting data, and moving the data of the subcarrier where the interference exists to the non-interference subcarrier for transmitting. The transmission process is as described above, and the subcarrier channel signal-to-noise ratio is also evaluated, and the block error rate and the bit error rate are counted for comparison. As shown in fig. 10.
In fig. 10 (a), it can be seen that the SNR of each subcarrier is not subject to an interference mutation under different SNR SNRs, which is a normal condition that the system is not interfered. Fig. 10 (b) shows graphs of block error rate and bit error rate at the receiving end under different signal-to-noise ratios, where the subcarrier where the interference is masked is transmitted.
To clearly see the practical effect of the present invention, the performance after not using the present invention and using the present invention will be compared as shown in fig. 11. The first column initial in fig. 11 (a) is the block error rate when there are different signal to noise ratios in the subcarrier interference scenario. The second column of frequency sensing is the block error rate at different signal to noise ratios under the condition of eliminating subcarrier interference. Fig. 11 (b) compares the block error rates of the two scenes. It is evident that the performance with the present invention is better than the performance without.
For better evaluation and analysis, the present embodiment also gives a comparison of SNR in the presence of interfering subcarriers and in the absence of interfering subcarriers at the same time, as shown in fig. 12. In fig. 12, there are 4 SNR cases in total, the first is snr= -4.2857db, there is no correctly parsed transport block, so the method of the present invention will not start; the second is snr= -0.85714 scene; the third is snr= 2.5714 scene, the fourth is snr=6 scene. Wherein the continuous line represents the case of the interfered sub-carrier and the discontinuous line represents the case of rejecting the interfered sub-carrier.
Fig. 13 shows the bit error rate analysis, i.e. the bit error rate comparison of the presence of interfering sub-carriers and the rejection of interfering sub-carriers under different SNR scenarios. Wherein initial indicates that subcarrier interference exists, and frequency sensing indicates that subcarrier interference is removed. By combining fig. 11, fig. 12, and fig. 13, it can be obtained that the transmission performance of rejecting the subcarrier interference is better than that of the subcarrier interference situation.
Finally, it is noted that the above embodiments are only 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 preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.
Claims (7)
1. A method for spectrum sensing in a mobile communication network, characterized by: the method comprises the following steps:
s1, a transmitting end carries out channel processing on a transmission data block to be transmitted to form a data modulation symbol to be transmitted, wherein the channel processing comprises the steps of carrying out channel coding and modulation on the transmission data block;
s2, when transmitting the data modulation symbols, the transmitting end maps the data modulation symbols and the reference signals onto wireless subcarriers in a communication system in a resource mapping mode to form wireless resource blocks, OFDM modulates the wireless resource blocks to form time domain OFDM signals, and then loads the time domain OFDM signals into a wireless transmission channel for transmission;
s3, the receiving end receives the time domain OFDM signals from the wireless transmission channels and demodulates the time domain OFDM signals to obtain data modulation symbols on each wireless subcarrier, and the data modulation symbols are demodulated and channel decoded to obtain transmission data blocks of the receiving end;
s4, the receiving end performs the same compiling operation as the sending end on the received transmission data block under the condition that the transmission data block is checked to be correct so as to obtain a reconstructed wireless resource block of the receiving end;
s5, the receiving end utilizes the reconstructed wireless resource block and the received wireless resource block to carry out subcarrier channel assessment, subcarrier information with the signal-to-noise ratio lower than a threshold value is fed back to the sending end, and the sending end receives subcarrier interference information and then transmits the subcarrier interference information in a mode of eliminating the subcarrier when sending data.
2. A method of spectrum sensing in a mobile communication network according to claim 1, wherein: in step S1, the transmission data block to be transmitted includes a check information bit, where the check information bit is used for performing a cyclic check on the received transmission data block by the receiving end to determine whether the received transmission data block is correct.
3. A method of spectrum sensing in a mobile communication network according to claim 1, wherein: in step S2, the resource mapping refers to mapping the data modulation symbols onto the designated OFDM time-frequency resource grid, where the reference signals inserted in the mapping process are determination signals known in transmit-receive, and the reference signals are used for channel measurement and signal estimation.
4. A method of spectrum sensing in a mobile communication network according to claim 1, wherein: in step S3, the receiving end extracts the radio resource block and the reference signal from the time domain OFDM signal during demodulation; the receiving end utilizes the extracted reference signal and the local known reference signal to carry out channel characteristic estimation on the frequency band occupied by the wireless resource block; performing equalization processing on the wireless resource block based on the channel estimation result; and carrying out demodulation processing on the data modulation symbols of the wireless resource blocks through channel demodulation decoding to obtain each bit log likelihood ratio value, and then obtaining a transmitting end transmission data block through channel decoding.
5. A method of spectrum sensing in a mobile communication network according to claim 1, wherein: in step S4, the receiving end performs cyclic check on the obtained transmission data block, and performs reconstruction of the radio resource block when the check is correct; in case of failure of the verification, the information transmission process is immediately ended.
6. The method for spectrum sensing in a mobile communication network of claim 5, wherein: when the receiving end reconstructs the wireless resource block, the receiving end carries out channel coding and modulation on the obtained transmission data block to form a data modulation symbol, and maps the data modulation symbol and a reference signal to the wireless resource block so as to obtain the reconstructed wireless resource block.
7. A method of spectrum sensing in a mobile communication network according to claim 1, wherein: in step S5, the process of the receiving terminal for estimating the subcarrier channel includes counting the signal-to-noise ratio of each subcarrier on the time-frequency resource of the radio resource block; when the radio resource block is formed by a plurality of OFDM symbols, the signal-to-noise ratio of each subcarrier is the average value of the signal-to-noise ratios of the subcarriers corresponding to the plurality of OFDM symbols.
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