CN113794664B - Anti-interference method based on subcarrier subtraction - Google Patents
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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
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2691—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation involving interference determination or cancellation
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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
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2668—Details of algorithms
- H04L27/2681—Details of algorithms characterised by constraints
- H04L27/2688—Resistance to perturbation, e.g. noise, interference or fading
Abstract
The invention discloses an anti-interference method based on subcarrier deduction, which comprises the steps of transmitting a designated carrier sequence on a time domain symbol in advance, decoding by a receiving end by using the same sequence, carrying out block statistics and demodulation on a signal-to-noise ratio and an error rate on a frequency domain carrier, recording an index indication of a carrier block with a large error rate according to the signal-to-noise ratio, carrying out filtering on the indication for a period of time, transmitting the indication to an transmitting end through signaling, and transmitting the indication on an undisturbed subcarrier block according to the index indication when the transmitting end transmits signaling and data information next time, thereby effectively avoiding adverse influence of an interference carrier on service transmission and improving the error rate performance.
Description
Technical Field
The invention relates to the technical field of narrowband interference resistance, in particular to an anti-interference method based on subcarrier subtraction.
Background
The wireless ad hoc network is a distributed wireless packet autonomous network, has no fixed infrastructure, has peer node positions, can move freely, has the characteristics of flexible networking, multi-hop relay, self-healing resistance and the like, and is widely applied to scenes such as emergency deployment, public service, military communication and the like. In military communications, there is a pattern-rich and statistically characteristic time-varying interference in the channel, where high-power narrowband interference becomes one of the main factors that undermine the stability of the communications system. In order to eliminate the influence of narrowband interference on normal communication service transmission, a narrowband interference identification and deduction scheme based on frequency domain subcarrier blocking is provided so as to improve the narrowband interference resistance of a system.
The OFDM technology has the advantages of high frequency band utilization rate, high transmission rate, interference resistance and the like, but the frequency band of the system is wider, the system is easily interfered by the narrow band of the traditional short-wave radio station, and the performance is deteriorated when the interference is serious. Because of the dynamic change of topology, the ad hoc network cannot introduce a multiple retransmission mechanism to reduce the performance requirement of single transmission error rate like the public network system, and in the service transmission with higher requirement on the error rate, how to eliminate the influence of narrowband interference on the whole broadband service transmission becomes the design of the patent. The prior patent only provides an interference identification method and how to eliminate the influence on AMC modulation order calculation, the information interaction of the AMC of the actual receiving and transmitting end needs to be realized by means of control messages, the control messages carry key parameter information of data service, the requirement on error rate is generally required to be 0, and how to eliminate the influence of narrowband interference on service transmission, especially control messages, becomes the design concern of the patent.
Disclosure of Invention
The invention provides an anti-interference method based on subcarrier subtraction, which aims to solve the problem of how to eliminate the influence of narrowband interference on service transmission, especially control information in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme:
an anti-interference method based on subcarrier deduction divides the whole frequency domain transmission bandwidth into M subcarrier blocks by taking N carriers as subcarrier block units, adopts M bits to represent the occupation condition of an actual transmitted subcarrier block, and indicates that available subcarrier block bits are 1 and interfered subcarrier block bits are 0, comprising the following steps:
step 1, for a control symbol, no interference indication information is transmitted for the first time, fixedly selecting L subcarrier blocks for transmission, transmitting bit indication information FixBitmapInd of the L subcarrier blocks in the first control symbol, and repeatedly transmitting M bit indication information N times on a frequency domain, wherein L < = M;
step 2, the receiving end receives the first control time slot, firstly extracts the first control symbol to carry out hard judgment decoding, and then respectively carries out accumulation and combination of corresponding bits on M bit decoding values of N subcarrier blocks:sequencing M accumulation results from large to small, selecting L maximum accumulation values, wherein the bit indication of the corresponding carrier positions is 1, the bit indication of the rest M-L carrier positions is assigned to 0, the obtained indication bitmap Ind 'of the M-bit subcarrier block corresponds to the subcarrier block indication of the actually transmitted control message symbol, and the receiving end receives the subcarrier block indication bitmap Ind' of the subsequent control symbol output according to the first control symbol, and takes out the corresponding subcarrier block for demodulation and decoding to obtain the control message content;
step 3, the receiving end calculates a demodulation EVM value according to the balanced output result of the obtained subcarrier while demodulating the control symbol, and the calculation process of the demodulation EVM is as follows:
wherein Z represents a transmitting signal actually detected by a receiving end, and R represents an ideal receiving signal; and carrying out accumulation and average according to subcarrier blocks and the number of control symbols in the scheduling time slot to obtain average EVM of each carrier block:
judging the average EVM value EVM_AVG of each subcarrier block, judging whether the minimum working threshold EVMThrshld of the demodulation signal-to-noise ratio corresponding to the control symbol transmission modulation mode is met, if the threshold EVMThrshld is larger than or equal to the threshold EVMThrshld, indicating the bit of the subcarrier block as 1, and if the bit of the subcarrier block is smaller than the threshold EVMThrshld, indicating the bit of the subcarrier block as 0:
simultaneously counting the number NumPassthreshold of available subcarrier blocks which are subjected to threshold, if the number of the available subcarrier blocks is smaller than the minimum subcarrier block number MinBlockNum, selecting the subcarrier blocks of the MinBlockNum blocks according to the sequence from high to low of signal to noise ratio, setting the bit indication of the corresponding subcarrier blocks to 1, and outputting the bit indication bitmap Ind of the subcarrier blocks;
step 4, the receiving end sends the bit indication bitmap Ind of the obtained subcarrier block to the transmitting end through the control time slot, and the step 1 is synchronous, wherein the first control symbol of the control time slot is used for sending the bit indication bitmap Ind of the M bits obtained in the step 3, the frequency domain carrier mapping method indicated by the available subcarrier block bit is the same as the step 1, and the messages of the rest control symbols of the control time slot are mapped on the corresponding subcarrier blocks according to the available subcarrier block indication;
step 5, the transmitting end receives the control time slot of the receiving end, according to step 2, step 3, decodes the first control symbol and judges and output and obtains the subcarrier block instruction used first, then extracts the subcarrier block from the follow-up control symbol according to the subcarrier block instruction and demodulates and decodes and processes and analyzes and obtain the control message content to be used for data time slot analysis, meanwhile, according to the result of equilibrium, according to step 3, recalculate the available subcarrier block instruction, then according to the instruction mapping control symbol time slot and send;
and 6, if the sender needs to send the data service, the sender needs to send a control time slot request available time slot resource to the receiver, the receiver calculates an available subcarrier block indication according to the step 3 after receiving the request, and sends the available subcarrier block indication to the sender in a control message, meanwhile, the receiver stores the available subcarrier block indication information, the sender analyzes the available subcarrier block indication, then sends the available subcarrier block indication according to the indication mapping data message, and the receiver also extracts and demodulates the subcarrier block of the data time slot according to the stored available subcarrier block indication.
Compared with the prior art, the anti-interference method based on subcarrier subtraction has the following remarkable and superior effects:
the invention provides an anti-interference method based on subcarrier subtraction, which is used for comparing EVM demodulation signal to noise ratios of different carrier blocks with a threshold value capable of normally carrying out service transmission to determine an interfered subcarrier block.
The invention provides an anti-interference method based on subcarrier subtraction, which is characterized in that the calculated interference subcarrier block indication is transmitted by using the frequency domain subcarrier of the first symbol of a control time slot, and repeated transmission is carried out on the frequency domain subcarrier block, so that the transmission reliability and the decoding accuracy probability of a receiving end are increased.
Drawings
Fig. 1 is a schematic diagram of frequency domain carrier block of an anti-interference method based on subcarrier subtraction provided by the present invention;
fig. 2 is a schematic diagram of a frequency domain binary transmission sequence of a first control symbol of an anti-interference method based on subcarrier subtraction provided by the present invention;
fig. 3 is a schematic diagram of a transmission flow of a first control slot of an anti-interference method based on subcarrier subtraction according to the present invention;
fig. 4 is a schematic diagram of a control timeslot receiving process flow of an anti-interference method based on subcarrier subtraction provided in the present invention;
fig. 5 is a schematic diagram of a transmitting flow of a receiving end control time slot of an anti-interference method based on subcarrier subtraction provided by the present invention;
fig. 6 is a schematic diagram of a data slot interaction flow of a transceiver end based on an anti-interference method of subcarrier subtraction provided by the present invention;
fig. 7 is a schematic diagram of simulation results of an anti-interference method based on subcarrier subtraction.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is evident that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by a person skilled in the art without any inventive effort, are intended to be within the scope of the present invention, based on the embodiments of the present invention.
As shown in fig. 1 to fig. 7, in the embodiment of the present invention, an anti-interference method based on subcarrier subtraction is provided, where the entire frequency domain transmission bandwidth is divided into M subcarrier blocks by using N carriers as subcarrier block units, and as shown in the following figures, M bits are used to represent the actual occupation situation of the transmitted subcarrier block, the available subcarrier block bit indicates 1, and the interfered subcarrier block bit indicates 0. For example: as shown in fig. 1, the bandwidth of the ad hoc network system is 10M, the total number of available subcarriers in the frequency domain is 320, the number of carriers N in each carrier block is 40, the number of subcarriers M is 8, and if the interfering subcarrier blocks are 0, 2, 6, and 7, the bit indication of the available subcarriers can be expressed as: 01011100.
1) For the control symbol, no interference indication information is transmitted for the first time, fixedly selecting L (L < =m) subcarrier blocks for transmission, and transmitting bit indication information fixbitmap ind of the L subcarrier blocks in the first control symbol, and repeatedly transmitting M bit indication information N times in the frequency domain, for example: as shown in fig. 2, in the ad hoc network 10M system, n=40, m=8, and l=4, and the first transmission selects the 2 nd, 3 rd, 4 th, and 5 th subcarrier blocks for transmission, the subcarrier block indication actually used for transmitting the control message is expressed as: 00111100, the binary bit sequence transmitted on the frequency domain carrier of the first control symbol is shown in the following diagram:
2) As shown in fig. 3, the receiving end receives the first control slot, extracts the first control symbol to perform hard judgment decoding, and then performs accumulation and combination of corresponding bits on M-bit decoding values of N subcarrier blocks respectively:sequencing the M accumulation results from large to small, selecting L maximum accumulation values, wherein the bit indication of the corresponding carrier positions is 1, the bit indication of the rest M-L carrier positions is assigned to 0, the obtained indication bitmap Ind 'of the M-bit subcarrier block corresponds to the subcarrier block indication of the actually transmitted control message symbol, and the receiving end receives the subcarrier block indication bitmap Ind' of the subsequent control symbol output according to the first control symbol, and takes out the corresponding subcarrier block for demodulation and decoding to obtain the control message content.
3) The receiving end demodulates the control symbol and simultaneously calculates the signal-to-noise ratio of the demodulated EVM according to the balanced output result of the obtained subcarrier, and the calculation process of the signal-to-noise ratio of the demodulated EVM is as follows:
wherein Z represents a transmitting signal actually detected by a receiving end, and R represents an ideal receiving signal; and carrying out accumulation and average according to subcarrier blocks and the number of control symbols in the scheduling time slot to obtain average EVM signal-to-noise ratio of each carrier block:
judging the average EVM signal-to-noise ratio EVM_AVG of each subcarrier block, judging whether the minimum working threshold EVMThrshld of the demodulation signal-to-noise ratio corresponding to the control symbol transmission modulation mode is met, if the threshold EVMThrshld is larger than or equal to the threshold EVMThrshld, indicating the bit of the subcarrier block as 1, and if the bit of the subcarrier block is smaller than the threshold EVMThrshld, indicating the bit of the subcarrier block as 0:
and meanwhile, counting the number NumPassthreshold of available subcarrier blocks which are subjected to threshold, if the number of the available subcarrier blocks is smaller than the number MinBlockNum of subcarrier blocks, selecting the subcarrier blocks of the MinBlockNum blocks according to the sequence from high to low of signal to noise ratio, setting the bit indication of the corresponding subcarrier blocks to 1, and outputting the bit indication bitmap Ind of the subcarrier blocks.
4) As shown in fig. 4, the receiving end sends the bit indication bitmap ind of the obtained subcarrier block to the transmitting end through the control time slot, and the (sending process) step 1 is performed, wherein the first control symbol of the control time slot is used to send the bit indication bitmap ind of the M-bit subcarrier block obtained in the step 3, the frequency domain carrier mapping method indicated by the available subcarrier block bit is the same as the 1 (sending process) step 1, and the messages of the rest control symbols of the control time slot are mapped on the corresponding subcarrier blocks according to the available subcarrier block indication.
5) As shown in fig. 5, the transmitting end receives the control time slot of the receiving end, according to the steps of 2) and 3), firstly decodes and decides the first control symbol to output to obtain the used subcarrier block indication, then extracts the useful subcarrier block from the subsequent control symbol according to the subcarrier block indication to perform demodulation and decoding processing, analyzes to obtain the useful control message, and simultaneously recalculates (step 3) the available subcarrier block indication according to the equalizing result, and then maps the control symbol time slot according to the subcarrier block indication to send.
6) As shown in fig. 6, if the sender needs to send a data service, the sender needs to send a control time slot request to the receiver first to use available time slot resources, the receiver calculates (step 3) an available subcarrier block indication after receiving the request, and sends the available subcarrier block indication to the sender in a control message, and meanwhile, the receiver stores the available subcarrier block indication information, and after analyzing the available subcarrier block indication, the sender sends the available subcarrier block indication according to the indication map data message, and the receiver also performs subcarrier block extraction and demodulation decoding processing of the data service according to the stored available subcarrier block indication.
Table 1 simulation parameters
| Parameter type | Parameter setting |
| Channel type | AWGN |
| Modulation order + code rate | QPSK 1/2 |
| Channel coding scheme | RS+CC |
| Controlling the number of OFDM symbols in a slot | 4 |
| Number of emulated slots | 10000 |
| Bandwidth of a communication device | 24MHz |
| Interference bandwidth percentage/% | 12.5 |
| Narrowband interference relative power | 50 |
Further, as can be seen from table 1 and fig. 7, when the system bandwidth is 24M, the ratio of the narrowband interference bandwidth is 12.5%, and the interference intensity is 50dB, if the interference cancellation by the subcarrier subtraction is not performed, the error rate of the system will be very high (> 0.1) and will not be significantly improved along with the increase of the signal-to-noise ratio, so that the OFDM system must perform narrowband interference cancellation in a strong narrowband interference environment, otherwise it is difficult to perform normal service transmission.
In the description of the present specification, a particular feature, structure, material, or characteristic may be combined in any suitable manner in one or more embodiments or examples.
Of course, the present invention is capable of other various embodiments and its several details are capable of modification and variation in light of the present invention by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (1)
1. The anti-interference method based on subcarrier deduction is characterized in that the whole frequency domain transmission bandwidth is divided into M subcarrier blocks by taking N carriers as subcarrier block units, M bits are adopted to represent the occupation condition of an actual transmission subcarrier block, the available subcarrier block bit is indicated as 1, and the interfered subcarrier block bit is indicated as 0, and the method comprises the following steps:
step 1, for a control symbol, no interference indication information is transmitted for the first time, fixedly selecting L subcarrier blocks for transmission, transmitting bit indication information FixBitmapInd of the L subcarrier blocks in the first control symbol, and repeatedly transmitting M bit indication information N times on a frequency domain, wherein L < = M;
step 2, the receiving end receives the first control time slot, firstly extracts the first control symbol to carry out hard judgment decoding, and then respectively carries out accumulation and combination of corresponding bits on M bit decoding values of N subcarrier blocks:sequencing M accumulation results from large to small, selecting L maximum accumulation values, wherein the bit indication of the corresponding carrier positions is 1, the bit indication of the rest M-L carrier positions is assigned to 0, the obtained indication bitmap Ind 'of the M-bit subcarrier block corresponds to the subcarrier block indication of the actually transmitted control message symbol, and the receiving end receives the subcarrier block indication bitmap Ind' of the subsequent control symbol output according to the first control symbol, and takes out the corresponding subcarrier block for demodulation and decoding to obtain the control message content;
step 3, the receiving end calculates a demodulation EVM value according to the balanced output result of the obtained subcarrier while demodulating the control symbol, and the calculation process of the demodulation EVM is as follows:
wherein Z represents a transmitting signal actually detected by a receiving end, and R represents an ideal receiving signal; and carrying out accumulation and average according to the subcarrier blocks and the number of control symbols in the scheduling time slot to obtain average EVM of each carrier block:
judging the average EVM value EVM_AVG of each subcarrier block, judging whether the minimum working threshold EVMThrshld of the demodulation signal-to-noise ratio corresponding to the control symbol transmission modulation mode is met, if the threshold EVMThrshld is larger than or equal to the threshold EVMThrshld, indicating the bit of the subcarrier block as 1, and if the bit of the subcarrier block is smaller than the threshold EVMThrshld, indicating the bit of the subcarrier block as 0:
simultaneously counting the number NumPassthreshold of available subcarrier blocks which are greater than or equal to the threshold EVMThrshld, if the number of the available subcarrier blocks is smaller than the minimum subcarrier block number MinBlockNum, selecting the subcarrier blocks of the MinBlockNum blocks according to the sequence from high to low of the signal to noise ratio, setting the bit indication of the corresponding subcarrier blocks to 1, and outputting the bit indication bitmap Ind of the subcarrier blocks;
step 4, the receiving end sends the bit indication bitmap Ind of the obtained subcarrier block to the transmitting end through the control time slot, and the step 1 is synchronous, wherein the first control symbol of the control time slot is used for sending the bit indication bitmap Ind of the M bits obtained in the step 3, the frequency domain carrier mapping method indicated by the available subcarrier block bit is the same as the step 1, and the messages of the rest control symbols of the control time slot are mapped on the corresponding subcarrier blocks according to the available subcarrier block indication;
step 5, the transmitting end receives the control time slot of the receiving end, according to step 2, step 3, decodes the first control symbol and judges and output and obtains the subcarrier block instruction used first, then extracts the subcarrier block from the follow-up control symbol according to the subcarrier block instruction and demodulates and decodes and processes and analyzes and obtain the control message content to be used for data time slot analysis, meanwhile, according to the result of equilibrium, according to step 3, recalculate the available subcarrier block instruction, then according to the instruction mapping control symbol time slot and send;
and 6, if the sender needs to send the data service, the sender needs to send a control time slot request available time slot resource to the receiver, the receiver calculates an available subcarrier block indication according to the step 3 after receiving the request, and sends the available subcarrier block indication to the sender in a control message, meanwhile, the receiver stores the available subcarrier block indication information, the sender analyzes the available subcarrier block indication, then sends the available subcarrier block indication according to the indication mapping data message, and the receiver also extracts and demodulates the subcarrier block of the data time slot according to the stored available subcarrier block indication.
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