CN110365447B - Air interface encryption safe transmission method based on NI USRP-RIO - Google Patents

Air interface encryption safe transmission method based on NI USRP-RIO Download PDF

Info

Publication number
CN110365447B
CN110365447B CN201910465554.1A CN201910465554A CN110365447B CN 110365447 B CN110365447 B CN 110365447B CN 201910465554 A CN201910465554 A CN 201910465554A CN 110365447 B CN110365447 B CN 110365447B
Authority
CN
China
Prior art keywords
user terminal
channel
relay node
time
frame
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201910465554.1A
Other languages
Chinese (zh)
Other versions
CN110365447A (en
Inventor
徐洪斌
孙黎
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xian Jiaotong University
Original Assignee
Xian Jiaotong University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xian Jiaotong University filed Critical Xian Jiaotong University
Priority to CN201910465554.1A priority Critical patent/CN110365447B/en
Publication of CN110365447A publication Critical patent/CN110365447A/en
Application granted granted Critical
Publication of CN110365447B publication Critical patent/CN110365447B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0071—Use of interleaving
    • 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
    • H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
    • 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
    • H04L27/2673—Details of algorithms characterised by synchronisation parameters
    • H04L27/2675—Pilot or known symbols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/12—Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22—Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/001—Synchronization between nodes

Abstract

The invention discloses an air interface encryption safe transmission method based on NI USRP-RIO, which specifically comprises the following steps: 1) the relay node R, the user terminal A and the user terminal B carry out time synchronization; 2) the user terminal A and the user terminal B firstly alternately send channel estimation frames to the relay node R, and the relay node R firstly estimates a channel h after receiving the channel estimation frames from the user terminal A and the user terminal BARAnd channel hBRFor channel hARAnd hBRThe amplitude and the angle of the received signal are respectively quantized and coded, then pilot frequency is inserted before the coding result and broadcasted to a user terminal A and a user terminal B, and the user terminal A and the user terminal B respectively estimate a channel h after receiving the signal sent by the relay node RRAAnd channel hRBThen obtaining channel information h by coherent detectionARAnd hBR(ii) a 3) The user terminal A and the user terminal B complete bidirectional information interaction under the assistance of the relay node R, and the method can realize safe information transmission.

Description

Air interface encryption safe transmission method based on NI USRP-RIO
Technical Field
The invention belongs to the field of wireless communication physical layer security, and relates to an air interface encryption secure transmission method based on NI USRP-RIO.
Background
The bidirectional relay communication can overcome the limitation of half duplex and remarkably improve the spectrum efficiency, and is considered as one of key technologies of a new generation of wireless networks. To date, a great deal of research work has been conducted in academia and industry around bi-directional relay transmission, and most of them focus on the design of schemes for improving the transmission efficiency and reliability of the system. However, in recent years, as the concerns of society, public and academic circles on the security of wireless networks continue to increase, more and more researchers are beginning to examine the two-way relay network from the perspective of physical layer security, and a series of theoretical analysis and solutions are proposed. Currently, physical layer security technology research for a bidirectional relay system mainly involves artificial noise injection, relay selection strategies, distributed beam forming and the like, most of these schemes assume that an eavesdropper is an independent individual outside a network, however, in some application scenarios, a relay itself may also be a potential eavesdropper, for example, in a military communication system, a relay node may be deployed by an enemy through disguising, or itself is deployed by a self-party but is invaded by an enemy or is implanted with a virus, and such a relay node may attempt to steal important strategic tactical information in a process of assisting communication; furthermore, in an office network of a government or financial institution, different nodes have differentiated information access rights, and those nodes with low information access rights may cause information leakage. In order to solve the problem, a method for realizing signal air interface encryption by combining channel inversion and phase compensation of a terminal node is required to be provided, by utilizing the method, a signal sent by a terminal user reaches a relay node through the same equivalent channel, then constellation overlapping occurs, the relay is forced to reply the signal by randomly guessing, and an error code platform is generated, so that the transmission safety of information is ensured. In order to verify the effectiveness of the air interface encryption scheme based on constellation overlapping in an actual communication environment, research on the influence of channel estimation errors, time synchronization errors, channel quantization errors, multipath propagation and the like on the constellation overlapping effect and the safety performance, and to evaluate the complexity and the feasibility of the scheme in engineering implementation, a test verification system needs to be designed and developed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an air interface encryption secure transmission method based on an NI USRP-RIO, which can realize the secure transmission of information.
In order to achieve the aim, the air interface encryption safe transmission method based on the NI USRP-RIO of the invention is characterized in that a bidirectional relay communication system is arranged and comprises a terminal user A, a terminal user B and a relay node R, the channel quality between the terminal user A and the terminal user B is poor, the relay node R is required to assist in completing bidirectional information interaction, the terminal user A, the terminal user B and the relay node R respectively comprise an upper computer and a USRP-2943R device, the upper computer and the USRP-2943R device are connected by adopting a high-speed PCI-e data line, the USRP-2943R device serves as a radio frequency front end and is responsible for conversion between passband analog waveforms and discrete baseband data, the upper computer is responsible for processing all baseband data, the system works in a time division duplex mode, the relay node R adopts an amplification forwarding protocol, and the method specifically comprises the following steps:
1) the method comprises the steps that an upper computer gives time to each USRP-2943R device, each USRP-2943R device obtains absolute time, a relay node R continuously sends N time synchronization frames, a user terminal A and a user terminal B calibrate the channel trigger time of the user terminal A and the channel trigger time of the user terminal B by means of received signals, and the user terminal A and the user terminal B synchronize the trigger time of the user terminal A and the trigger time of the relay node R, wherein the time synchronization frames comprise frame serial numbers sent by the relay node R, and the user terminal A and the user terminal B judge whether a time synchronization stage is finished or not by means of the frame serial numbers;
2) the bidirectional relay communication system enters an uplink channel estimation and channel state information interaction stage, namely, a user terminal A and a user terminal B alternately send a channel estimation frame to a relay node R at first, the channel estimation frame comprises a pilot frequency sequence for channel estimation, and the relay node R estimates a channel h at first after receiving the channel estimation frame from the user terminal A and the user terminal BA RAnd channel hB RFor channel hA RAnd hB RThe amplitude and the angle of the received signal are respectively quantized and coded, then pilot frequency is inserted before the coding result and broadcasted to a user terminal A and a user terminal B, and the user terminal A and the user terminal B respectively estimate a channel h after receiving the signal sent by the relay node RR AAnd channel hR BThen obtaining channel information h by coherent detectionA RAnd hB R；
3) The user terminal A and the user terminal B complete bidirectional information interaction under the assistance of the relay node R.
The specific operation process of time synchronization in the step 1) is as follows:
11) before entering a time synchronization process, the system acquires time from the internet by using three upper computers, and then respectively carries out time service on USRP-2943R equipment controlled by the system, so that each USRP-2943R equipment obtains absolute time, then the user terminal A, the user terminal B and the relay node R record relative time by using a clock in the USRP-2943R equipment, and appoint to simultaneously start a transmitting channel and a receiving channel at the same time t in the future;
12) when the internal clock of the relay node R reaches the time T, the relay node R opens the radio frequency channel and continuously sends the synchronous data frame with the period of T, and the frame length of the synchronous data frame is TcEach sync data frame comprising a time identical sequence and control data, wherein,the control data comprises the serial number of the synchronous frame and the type and size information of the file to be sent;
13) when the internal clock of the user terminal reaches the time T, the user terminal opens the radio frequency channel and receives the signal sent by the relay node R, wherein the length T of the receiving time windoww＞TcThe user terminal uses the data received in the ith time window to carry out correlation operation with the known short pilot sequence to obtain a correlation peak value so as to judge whether the ith frame receiving data contains the time synchronization frame sent by the relay node, wherein when the correlation peak value is more than or equal to the threshold delta0If so, the receiving time window is considered to contain the time synchronization frame; when the correlation peak value is less than the threshold delta0Then, the receiving time window is considered not to contain the time synchronization frame, and the user terminal A and the user terminal B adjust T according to the position of the correlation peaki+1Until any time N, the whole data frame is contained in the receiving time window and is at the forefront of the receiving time window, so as to realize the accurate synchronization of the relay node R with the time axes of the user terminal a and the user terminal B, the user terminal a and the user terminal B can decode the serial number of the synchronization frame and the type and size information of the file to be sent, and the time synchronization stage is finished.
The amplitude quantization in the step 2) adopts 20-bit uniform quantization, and the angle quantization adopts 8-bit uniform quantization.
The specific operation of the step 3) is as follows:
user terminal a and user terminal B process the transmitted signals according to table 4 and then broadcast to relay node R, table 4
Figure GDA0002186680520000041
And
Figure GDA0002186680520000042
an estimated value representing a channel coefficient on the ith subcarrier;
TABLE 4
Figure GDA0002186680520000043
After receiving the signal, the relay node R firstly amplifies the received signal and then broadcasts the amplified signal to the user terminal A and the user terminal B in the next time slot, wherein the relay node R decodes the received signal according to the table 5;
TABLE 5
Figure GDA0002186680520000051
The user terminal A and the user terminal B receive the signal forwarded by the relay node R and process the received signal according to the table 6 to recover the data file sent by the other party;
TABLE 6
Figure GDA0002186680520000052
The invention has the following beneficial effects:
when the air interface encryption safe transmission method based on the NI USRP-RIO is specifically operated, the user terminal A, the user terminal B and the relay node R are used for automatically realizing time synchronization, the method does not depend on GPS or centralized control, can adapt to relatively complex transmission environments, can support the test verification of other physical layer safe transmission methods designed around bidirectional untrusted relay communication through small-range modification, and has good expansion capability. Meanwhile, the time synchronization of each node enables different nodes to perform receiving and sending switching in a pace-consistent manner, thereby providing a premise for realizing bidirectional relay transmission.
Drawings
FIG. 1 is a diagram illustrating a time synchronization frame structure according to the present invention;
FIG. 2 is a schematic diagram of the time synchronization process of the present invention;
fig. 3 is a diagram illustrating a structure of a channel estimation frame transmitted by a user terminal;
fig. 4 is a schematic diagram of a channel estimation frame structure sent by a relay node;
fig. 5 is a schematic diagram of a signal frame transmitted by a user terminal to a relay node;
FIG. 6 is a diagram of the operation of each node in the present invention;
fig. 7 is a schematic diagram of the operation process of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
referring to fig. 1, the air interface encryption secure transmission method based on the NI USRP-RIO according to the present invention includes the following steps:
the bidirectional relay communication system is arranged to comprise a terminal user A, a terminal user B and a relay node R, the channel quality between the terminal user A and the terminal user B is poor, so that the relay node R is required to assist in completing bidirectional information interaction, the relay node R tests a message sent by a graphic code terminal user in the process of auxiliary information transmission so as to cause information leakage, and in order to ensure reliable and safe transmission of information, the bidirectional relay communication system adopts a constellation-overlapping-based air interface encryption method, each node in the bidirectional relay communication system is composed of an upper computer and a USRP-2943R device, the upper computer is connected with the USRP-2943R device through a high-speed PCI-e data line, wherein the USRP-2943R device is used as a radio frequency front end and is responsible for conversion between passband analog waveforms and discrete baseband data, and the upper computer is responsible for processing all baseband data, the system works in a time division duplex mode (TDD), and the relay node R adopts an amplification forwarding protocol, and the method specifically comprises the following steps:
1) the method comprises the steps that an upper computer gives time to each USRP-2943R device, each USRP-2943R device obtains absolute time, a relay node R continuously sends N time synchronization frames, a user terminal A and a user terminal B calibrate the channel trigger time of the user terminal A and the channel trigger time of the user terminal B by means of received signals, the user terminal A and the user terminal B enable the trigger time of the user terminal A and the trigger time of the relay node R to be synchronous, the time synchronization frames comprise frame numbers sent by the relay node R, and the user terminal A and the user terminal B judge whether a time synchronization stage is finished or not by means of the frame numbers;
the specific operation process of time synchronization is as follows:
11) before entering a time synchronization process, the system acquires time from the internet by using three upper computers, and then respectively carries out time service on USRP-2943R equipment controlled by the system, so that each USRP-2943R equipment obtains absolute time, then the user terminal A, the user terminal B and the relay node R record relative time by using a clock in the USRP-2943R equipment, and appoint to simultaneously start a transmitting channel and a receiving channel at the same time t in the future;
12) when the internal clock of the relay node R reaches the time T, the relay node R opens the radio frequency channel and continuously sends the synchronous data frame with the period of T, and the frame length of the synchronous data frame is TcEach synchronous data frame comprises a time identical sequence and control data, and the control data comprises a serial number of the synchronous frame and information of the type and the size of a file to be sent;
13) when the internal clock of the user terminal reaches the time T, the user terminal opens the radio frequency channel and receives the signal sent by the relay node R, wherein the length of the receiving time window is Tw＞TcThe user terminal uses the data received in the ith time window to carry out correlation operation with the known short pilot sequence to obtain a correlation peak value so as to judge whether the ith frame receiving data contains the time synchronization frame sent by the relay node, wherein when the correlation peak value is more than or equal to the threshold delta0If so, the receiving time window is considered to contain the time synchronization frame; when the correlation peak value is less than the threshold delta0Then, the receiving time window is considered not to contain the time synchronization frame, and the user terminal A and the user terminal B adjust T according to the position of the correlation peaki+1Until any time N, the whole data frame is contained in the receiving time window and is at the forefront of the receiving time window, so as to realize the accurate synchronization of the relay node R with the time axes of the user terminal a and the user terminal B, the user terminal a and the user terminal B can decode the serial number of the synchronization frame and the type and size information of the file to be sent, and the time synchronization stage is finished.
2) After the time synchronization stage is finished, the bidirectional relay communication system enters an uplink channel estimation and Channel State Information (CSI) interaction stage, and a user terminal A and a user terminal B firstly alternate to a relay node RSending a channel estimation frame, wherein the channel estimation frame comprises a pilot frequency sequence for channel estimation, and after receiving the channel estimation frames from a user terminal A and a user terminal B, a relay node R firstly estimates a channel hA RAnd channel hB RThen to channel hA RAnd hB RThe amplitude and the angle of the received signal are quantized and coded respectively, finally, pilot frequency is inserted before the coding result and is broadcasted to a user terminal A and a user terminal B, and the user terminal A and the user terminal B estimate a channel h respectively after receiving the signal sent by the relay node RR AAnd channel hR BThen obtaining channel information h by coherent detectionA RAnd hB R；
The specific operation of the step 2) is as follows:
the uplink channel estimation and Channel State Information (CSI) interaction phase comprises three time slots in total, wherein in the first two time slots, a user terminal A and a user terminal B alternately send channel estimation frames to a relay node R, the frame structure is shown in FIG. 3, the channel estimation frames comprise short pilot sequences and random data, the random data has the function of ensuring that the lengths of the channel estimation frames and time synchronization frames are consistent, the short pilot is composed of m sequences with the length of 63, and the short pilot is repeated for 10 times to form a synchronization sequence sync 1;
the processing procedure of the baseband signals before the user terminal a and the user terminal B transmit signals is shown in table 1, and it should be noted that: since the random data occupies 101 OFDM symbols in total, the system generates 101 £ 63 ═ 6363 bits in total in the first step of random data generation, and the probability of each bit being 0 or 1 is 1/2.
TABLE 1
Figure GDA0002186680520000091
Figure GDA0002186680520000101
After receiving the signal sent by the user terminal a or the user terminal B, the relay node R performs correlation operation with the received data by using the short pilot frequency to obtain a correlation peak value, then searches the initial position of the time synchronization frame by using the correlation peak value, and then processes the received data, wherein the processing process is the inverse process shown in table 1, and after the relay node R performs OFDM demodulation on the received signal, the received signal model of the relay node R is as follows:
Figure GDA0002186680520000102
wherein the content of the first and second substances,
Figure GDA0002186680520000103
for the channel gain on the ith subcarrier,
Figure GDA0002186680520000104
for the relay node R to receive signals on the ith subcarrier,
Figure GDA0002186680520000105
for equivalent noise on the ith subcarrier, the estimated value of the channel coefficient obtained by the relay node R is:
Figure GDA0002186680520000106
similarly, the relay node R can obtain the channel coefficient
Figure GDA0002186680520000107
Is estimated value of
Figure GDA0002186680520000108
After finishing channel estimation, the relay node R performs quantization, coding and baseband data processing on the estimated channel information, and the processing process is as shown in table 2, wherein the quantization process includes amplitude quantization and angle quantization, the amplitude quantization adopts 20-bit uniform quantization, and the angle quantization adopts 8-bit uniform quantization; the quantized data passes through a (7,4) -Hamming code encoder and then outputs 49 bits of information to be sent;
Figure GDA0002186680520000109
and
Figure GDA00021866805200001010
respectively mapping 49 bit information corresponding to the 49 bit information through a QPSK constellation to obtain 49 constellation symbols, respectively mapping the 49 constellation symbols to sub-carriers No. 1-49, and respectively mapping sub-carriers No. 50-63 and sub-carrier No. zero to not send data, and setting all the data to zero; then the relay node R sends the mapped constellation symbols to the OFDM modulator, inserts a time synchronization sequence sync1 at the front end of the output result of the OFDM modulator, and broadcasts the result to the user terminal a and the user terminal B, the frame structure of the signal sent by the relay node R is shown in fig. 4, as can be seen from fig. 4, in 101 OFDM symbols, the first 63 symbols sequentially correspond to the channel coefficients on each subcarrier, and the last 28 symbols are data filled randomly, so as to ensure that the length of the channel estimation frame is consistent with that of the time synchronization frame.
TABLE 2
Figure GDA0002186680520000111
After receiving the signal, user terminal a and user terminal B process the signal as shown in table 3, and perform frame synchronization, then perform OFDM demodulation on the synchronized data, and then perform downlink channel estimation by using sync1 to obtain the downlink channel estimation and the frame synchronization, respectively
Figure GDA0002186680520000112
And
Figure GDA0002186680520000113
to complete channel estimation, wherein, on the ith subcarrier, the received signal model of the user terminal a is:
Figure GDA0002186680520000114
on the ith subcarrier, the received signal model of the user terminal B is:
Figure GDA0002186680520000121
by using
Figure GDA0002186680520000122
And
Figure GDA0002186680520000123
user terminal A and user terminal B respectively carry out coherent detection to obtain channel information
Figure GDA0002186680520000124
And
Figure GDA0002186680520000125
to complete the full channel estimation and CSI interaction.
TABLE 3
Figure GDA0002186680520000126
3) The user terminal A and the user terminal B complete bidirectional information interaction under the assistance of the relay node.
After the channel estimation and CSI interaction phase is finished, the system enters a data transmission phase, and in the phase, the user terminal A and the user terminal B complete bidirectional information interaction under the assistance of the relay node R.
The data frame structure sent by the terminal user a and the terminal user B is shown in fig. 5, the data frame structure includes a short pilot (sync1), a long pilot (sync2) and data, wherein the short pilot is used for frame synchronization, the long pilot is used for real-time downlink channel estimation, the data carries information to be transmitted, and the short pilot is the same as the short pilot of the channel estimation frame and the time synchronization frame; the long pilot frequency adopts the same design parameters as the data segment, that is, each OFDM symbol occupies 2048 sub-carriers, the length of the cyclic prefix is 512, the long pilot frequency is formed by inserting zeros in the middle of m sequences with the length of 1023, the user terminal A and the user terminal B insert respective pilot frequency sequences into the sub-carriers in an orthogonal mode, the user terminal A occupies even sub-carriers, the user terminal B occupies odd sub-carriers, and the zero sub-carriers are set to be zero.
In the data transmission phase, the user terminal a, the user terminal B and the relay node R complete bidirectional information interaction with two time slots as a cycle, wherein in the first time slot, the user terminal a and the user terminal B simultaneously send information to the relay node R, the signal frame structures sent by the user terminal a and the user terminal B are shown in fig. 5, and the baseband data processing process before the user terminal a and the user terminal B form a physical signal frame is shown in table 4;
TABLE 4
Figure GDA0002186680520000131
The received signal model of the relay node R in the first time slot is:
Figure GDA0002186680520000132
wherein the content of the first and second substances,
Figure GDA0002186680520000133
data sent for user terminal a;
Figure GDA0002186680520000134
for the data transmitted by ue B, due to the influence of channel estimation error, quantization error and channel time variation, channel inversion cannot be performed by ue a and ue B, i.e. the data is transmitted by ue B
Figure GDA0002186680520000141
And
Figure GDA0002186680520000142
the equivalent channel coefficients of the relay node R are different, and the receiving channel model of the relay node R is:
Figure GDA0002186680520000143
wherein the content of the first and second substances,
Figure GDA0002186680520000144
in order to consider equivalent channels from the user terminal A, the user terminal B to the relay node R after channel estimation errors and channel fluctuation, the relay node R receives signals
Figure GDA0002186680520000145
Then, trying to decode the information of the user terminal a and the user terminal B, and the signal processing procedure is shown in table 5, it is worth pointing out that the relay node R needs to complete the amplify-and-forward operation in the second time slot except trying to decode the transmission contents of the user terminal a and the user terminal B, and the specific implementation method is as follows: the relay node R performs digital amplification after receiving the signal, and then sends the data directly to the USRP-2943R device.
TABLE 5
Figure GDA0002186680520000146
Because the user terminal A and the user terminal B have symmetry, the invention takes the decoding process of the user terminal A as an example to explain the baseband signal processing process of the user terminal A, and in the second time slot, the receiving signal form of the user terminal A on the t-th subcarrier theoretically is as follows:
Figure GDA0002186680520000151
however, due to the influence of channel estimation error, quantization error, synchronization error between nodes, channel time variation and other factors, the actual received signal model of the user terminal a is:
Figure GDA0002186680520000152
wherein the content of the first and second substances,
Figure GDA0002186680520000153
for equivalent downlink channel coefficients, for obtaining information sent by user terminal B
Figure GDA0002186680520000154
The user terminal A firstly estimates the equivalent channel coefficient by using the long pilot frequency sequence
Figure GDA0002186680520000155
And
Figure GDA0002186680520000156
then obtaining statistic through self-interference elimination;
Figure GDA0002186680520000157
finally, the user terminal a completes signal detection according to the channel model shown in equation (9), the baseband signal processing process of the user terminal a is shown in table 6, and the following explains the first to fourth steps in table 6, in the first step, the user terminal a performs correlation operation on sync1 and the received signal, and the correlation operation is obtained from the rough estimation value of the initial positions of the interference signal and the target signal, and because the self-interference signal and the target signal are mutually influenced, the rough estimation value may have a synchronization error; estimating a time domain channel by using a self-interference signal and synchronizing the self-interference signal, wherein a time domain receiving signal of the user terminal A is as follows:
yA＝hrAxA+hrBxB+nA(10)
wherein x isA、xBFor the transmitted signal vectors, y, of user terminal A and user terminal B in the time domainAFor the time domain received signal vector of user terminal A, hrA、hrBTime domain channel coefficients for links R → A and R → B, nATo take into account the receiver noise of the relay node R and the equivalent noise after the receiver noise of the user terminal a, the above model assumes that the channel can be distinguished as one multipath, and that the channel coefficient remains unchanged for the time of one frame of signal, the channel coefficient hrAThe estimation method comprises the following steps: self-interference signal x in time domainAPerforming correlation operation with the received signal, and normalizing the square of self-interference norm by the correlation peak value to obtain the channel estimation value
Figure GDA0002186680520000161
Namely, it is
Figure GDA0002186680520000162
Due to xAAnd xBIndependent of each other and have a mean value of zero, therefore
Figure GDA0002186680520000163
Approximately zero, and because the noise power is much lower than the signal power, so
Figure GDA0002186680520000164
And thirdly, time domain self-interference elimination is carried out, and the mathematical description is as follows:
Figure GDA0002186680520000165
since the frame synchronization in the first step may have errors, the fourth step utilizes the signal y with the self-interference removedA (rem)And re-synchronizing the target signal to reduce the probability of synchronization failure.
TABLE 6
Figure GDA0002186680520000166
Figure GDA0002186680520000171
The design principle of the long pilot sync2 and the channel estimation method are as follows: in order to perform signal detection smoothly, each terminal must estimate equivalent instantaneous channel information in real time
Figure GDA0002186680520000172
And
Figure GDA0002186680520000173
however, the signals of user terminal a and user terminal B interfere with each other on each subcarrier, so thatThe channel estimation cannot be completed, so the pilot sequences of the user terminal a and the user terminal B need to be inserted into 2048 subcarriers in an orthogonal manner, that is, the pilot of the user terminal a occupies even-numbered subcarriers, and the pilot of the user terminal B occupies odd-numbered subcarriers, by such design, when i ═ 0, 2, 4, 6., 2046, the received signal model of the user terminal a is:
Figure GDA0002186680520000174
when i is 1, 3, 5., 2047, the received signal model of the user terminal a is:
Figure GDA0002186680520000175
user terminal A completes using equation (13)
Figure GDA0002186680520000176
The channel estimation of the even number sub-carriers is completed by the equation (14)
Figure GDA0002186680520000177
The odd number sub-carrier channel estimation is obtained by interpolation
Figure GDA0002186680520000178
And
Figure GDA0002186680520000179
the interpolation method comprises the following steps of channel estimation values on all subcarriers:
Figure GDA00021866805200001710
at this point, an information exchange cycle of the data transmission phase is finished.

Claims (2)

1. An air interface encryption safe transmission method based on NI USRP-RIO is characterized in that a bidirectional relay communication system is arranged to comprise a terminal user A, a terminal user B and a relay node R, the channel quality between the terminal user A and the terminal user B is poor, the relay node R is required to assist in completing bidirectional information interaction, the terminal user A, the terminal user B and the relay node R respectively comprise an upper computer and a USRP-2943R device, and the upper computer is connected with the USRP-2943R device through a high-speed PCI-e data line, wherein the USRP-2943R device is used as a radio frequency front end and is responsible for conversion between passband analog waveforms and discrete baseband data, the upper computer is responsible for processing all baseband data, the system works in a time division duplex mode, and the relay node R adopts an amplification forwarding protocol, and specifically comprises the following steps:
1) the method comprises the steps that an upper computer gives time to each USRP-2943R device, each USRP-2943R device obtains absolute time, a relay node R continuously sends N time synchronization frames, a user terminal A and a user terminal B calibrate the channel trigger time of the user terminal A and the channel trigger time of the user terminal B by means of received signals, and the user terminal A and the user terminal B synchronize the trigger time of the user terminal A and the trigger time of the relay node R, wherein the time synchronization frames comprise frame serial numbers sent by the relay node R, and the user terminal A and the user terminal B judge whether a time synchronization stage is finished or not by means of the frame serial numbers;
2) the bidirectional relay communication system enters an uplink channel estimation and channel state information interaction stage, namely, a user terminal A and a user terminal B alternately send a channel estimation frame to a relay node R at first, the channel estimation frame comprises a pilot frequency sequence for channel estimation, and the relay node R estimates a channel h at first after receiving the channel estimation frame from the user terminal A and the user terminal BARAnd channel hBRWherein the channel hARRepresenting the channel between the user terminal A and the relay node R, channel hBRIndicating the channel between the user terminal B and the relay node R, and then for channel hARAnd hBRThe amplitude and the angle of the received signal are respectively quantized and coded, then pilot frequency is inserted before the coding result and broadcasted to a user terminal A and a user terminal B, and the user terminal A and the user terminal B respectively estimate a channel h after receiving the signal sent by the relay node RRAAnd channel hRBThen obtaining channel information h by coherent detectionARAnd hBR；
3) The user terminal A and the user terminal B finish bidirectional information interaction under the assistance of the relay node R;
the specific operation process of time synchronization in the step 1) is as follows:
11) before entering a time synchronization process, the system acquires time from the internet by using three upper computers, and then respectively carries out time service on USRP-2943R equipment controlled by the system, so that each USRP-2943R equipment obtains absolute time, then the user terminal A, the user terminal B and the relay node R record relative time by using a clock in the USRP-2943R equipment, and appoint to simultaneously start a transmitting channel and a receiving channel at the same time t in the future;
12) when the internal clock of the relay node R reaches the time T, the relay node R opens the radio frequency channel and continuously sends the synchronous data frame with the period of T, and the frame length of the synchronous data frame is TcEach synchronous data frame comprises a time identical sequence and control data, wherein the control data comprises a serial number of the synchronous frame and information of the type and the size of a file to be sent;
13) when the internal clock of the user terminal reaches the time T, the user terminal opens the radio frequency channel and receives the signal sent by the relay node R, wherein the length T of the receiving time windoww＞TcThe user terminal uses the data received in the ith time window to carry out correlation operation with the known short pilot sequence to obtain a correlation peak value so as to judge whether the ith frame receiving data contains the time synchronization frame sent by the relay node, wherein when the correlation peak value is more than or equal to the threshold delta0If so, the receiving time window is considered to contain the time synchronization frame; when the correlation peak value is less than the threshold delta0Then, the receiving time window is considered not to contain the time synchronization frame, and the user terminal A and the user terminal B adjust T according to the position of the correlation peaki+1Until any time N, the whole data frame is contained in the receiving time window and is positioned at the forefront end of the receiving time window so as to realize the accurate synchronization of the relay node R and the time axes of the user terminal A and the user terminal B, the user terminal A and the user terminal B can decode the serial number of the synchronous frame and the type and size information of the file to be sent, and the time synchronization stage is finished;
the specific operation of the step 3) is as follows:
user terminal a and user terminal B process the transmitted signals according to table 4 and then broadcast to relay node R, table 4
Figure FDA0002444598780000031
And
Figure FDA0002444598780000032
an estimated value representing a channel coefficient on the ith subcarrier;
TABLE 4
Figure FDA0002444598780000033
After receiving the signal, the relay node R firstly amplifies the received signal and then broadcasts the amplified signal to the user terminal A and the user terminal B in the next time slot, wherein the relay node R decodes the received signal according to the table 5;
TABLE 5
Figure FDA0002444598780000034
The user terminal A and the user terminal B receive the signal forwarded by the relay node R and process the received signal according to the table 6 to recover the data file sent by the other party;
TABLE 6
Figure FDA0002444598780000035
Figure FDA0002444598780000041
2. The air interface encryption secure transmission method based on the NI USRP-RIO according to claim 1, wherein the amplitude quantization in step 2) is 20-bit uniform quantization, and the angle quantization is 8-bit uniform quantization.
CN201910465554.1A 2019-05-30 2019-05-30 Air interface encryption safe transmission method based on NI USRP-RIO Active CN110365447B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201910465554.1A CN110365447B (en) 2019-05-30 2019-05-30 Air interface encryption safe transmission method based on NI USRP-RIO

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201910465554.1A CN110365447B (en) 2019-05-30 2019-05-30 Air interface encryption safe transmission method based on NI USRP-RIO

Publications (2)

Publication Number Publication Date
CN110365447A CN110365447A (en) 2019-10-22
CN110365447B true CN110365447B (en) 2020-06-19

Family

ID=68214964

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201910465554.1A Active CN110365447B (en) 2019-05-30 2019-05-30 Air interface encryption safe transmission method based on NI USRP-RIO

Country Status (1)

Country Link
CN (1) CN110365447B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112073109A (en) * 2020-08-19 2020-12-11 南京奈思电子科技有限公司 Method and system for reducing system performance influence generated by channel estimation error
CN113573308B (en) * 2021-09-22 2022-01-25 四川创智联恒科技有限公司 Method and module for improving air interface security

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102932083B (en) * 2011-08-11 2016-12-07 中兴通讯股份有限公司 A kind of method and apparatus during microwave synchronization pair
US10169119B1 (en) * 2011-08-28 2019-01-01 Ross Daniel Snyder Method and apparatus for improving reliability of digital communications
CN107005314B (en) * 2014-09-04 2019-07-30 华盛顿大学 From the mode of operation of the user's driving of single sense point detection electronic equipment
CN107204798A (en) * 2017-05-12 2017-09-26 南京邮电大学 A kind of amplification relay forwarding optimization system and its optimization method based on USRP
CN107359929B (en) * 2017-07-27 2021-01-19 西安交通大学 Air interface encryption method based on constellation overlapping in bidirectional relay system

Also Published As

Publication number Publication date
CN110365447A (en) 2019-10-22

Similar Documents

Publication Publication Date Title
US8842601B2 (en) Method and device for detecting primary synchronization signal and generating sequence in long term evolution (LTE) system
JP4529281B2 (en) Transmitting apparatus, receiving apparatus, and communication system
KR100967657B1 (en) Method and apparatus for synchronization of femtocell base station
CN110365447B (en) Air interface encryption safe transmission method based on NI USRP-RIO
CN102172071B (en) User device and cell search method
CN110086560B (en) Synchronous frame structure and synchronous method suitable for short burst communication time-frequency joint synchronization
US20220224463A1 (en) Satellite communication method and related communication device
CN109600222B (en) Key generation method based on channel characteristics
EP3185430A1 (en) Power-line carrier communication method
EP2145443B1 (en) Broadcast channel timing detection
CN111817823B (en) PBCH (physical broadcast channel) receiving method and system
US7738548B2 (en) System and method for communicating at low signal-to-noise ratio using injected training symbols
JP2007502568A (en) Encryption method and decryption method for digital transmission system
CN102843777B (en) Control method for random access signals
CN109714146B (en) Sliding window-based quadratic correlation frame synchronization method
CN101626360A (en) Method and system for transmitting digital signal
CN110808752A (en) Communication method and system of Internet of things
Zhang et al. Synchronization analysis for wireless TWRC operated with physical-layer network coding
CN102571663B (en) Microwave communication data transmission and device
CN115037445A (en) Key generation method and device
Al-Azzawi et al. HaLow Wi-Fi performance in multi-users and channels environment with MATLAB Simulink
CN116208194B (en) Cognitive frequency hopping synchronization method for resisting strong interference
WO2017031759A1 (en) Method and device for indicating synchronous signal period
Ferré et al. A downlink non orthogonal multiple access for chirp spread spectrum communications
CN103973625B (en) A kind of method and apparatus of synchronization decisions

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant