CN104735649A - Wireless link signature extraction method based on Gnu Radio - Google Patents
Wireless link signature extraction method based on Gnu Radio Download PDFInfo
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- CN104735649A CN104735649A CN201510134852.4A CN201510134852A CN104735649A CN 104735649 A CN104735649 A CN 104735649A CN 201510134852 A CN201510134852 A CN 201510134852A CN 104735649 A CN104735649 A CN 104735649A
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Abstract
The invention provides a wireless link signature extraction method based on a Gnu Radio. The method includes the steps that a sending machine and a receiving machine use the same pseudorandom sequence as sending and receiving information; the pseudorandom sequence is sent by the sending machine after being modulated to generate a time-domain signal; the time-domain signal received by the receiving machine is divided into two paths, one path of time-domain signal is used for conducting frequency domain transformation operation on the received signal, and the other path of time-domain signal is used for conducting conversion operation from the received signal to the sent signal; the received signal is represented to be in a convolution mode of signal sending and channel filtering, and a link signature is converted to be subjected to frequency domain calculation from time-domain calculation; at last, the link signature is obtained through calculation. The wireless link signature extraction method based on the Gnu Radio has the advantages that a large number of extra hardware devices are needless, only a small amount of extra calculation is needed, signal time-domain transformation is converted into frequency domain transformation for calculation so that computation complexity can be lowered, and the method is compatible with an existing protocol and device.
Description
Technical field
The present invention is a kind of wireless link based on Gnu Radio signature extracting method, relates to software and radio technique field.
Background technology
Wireless link signature is the signal characteristic of physical layer between a kind of transmit leg at signal and recipient, its multipath fading feature mainly utilizing wireless signal to have in the middle of transmission.
Wireless signal, in indoor environment and line-of-sight transmission environment, has multipath fading feature, referred to as multipath characteristics.An important feature of multipath characteristics is exactly that Received signal strength also exists multidiameter delay, and this time delay is exactly signal arrives receiving terminal time difference by different transmissions.When an independent pulse signal is by after multipath channel, a pulse train can be become.
Link signature extraction based on radio channel characteristic is the basis of security certification system, and wireless link signature is as the basic material of certification.Using radio channel characteristic as security certification system, do not rely on public safety facilities, there is the features such as quick, reliable, operand is low.
Be directed to the extraction of wireless link signature, need one to be simply easy to realize and reliable algorithm.
Along with software engineering is in the development of the communications field, the radio (Software DefinedRadio, SDR) of software definition is more and more widely used among Wireless Telecom Equipment and wireless communication module.Software radio software operates and replaces " pure hardware circuit " in the past.Compare with hardware circuit, software control radio has, and diverse in function, uses the features such as flexible, with low cost and easy to understand.
Gnu Radio runs on linux system, its principle run is: sent and received RF signal by USRP (general software radio peripheral hardware), with crossing network interface by base band signal transmission to the enterprising row relax of PC, PC running the signal processing module that C++ writes and Digital Signal Processing is carried out for signal.Programmer can pass through flow graph, conveniently builds communication system.
Summary of the invention
The object of the invention is to design a kind of wireless link signature extracting method realized under Gnu Radio radio platforms, wireless link signature can be extracted easily.
According to technical scheme provided by the invention, the described signature of the wireless link based on Gnu Radio extracting method comprises the following steps:
The first step: identical pseudo random sequence is denoted as s as sending and receiving information with receiver both sides by transmitter;
Second step: pseudo random sequence sends through ovennodulation by transmit leg, produce time-domain signal and be denoted as s (t), t represents the time;
3rd step: recipient receives time-domain signal and is denoted as r (t); Signal is divided into two-way, and the frequency domain map function of Received signal strength is carried out on a road, and Received signal strength is carried out fast Fourier transform and is converted to frequency-region signal R (f), f represents frequency; Received signal strength is carried out to the conversion operations sending signal in one tunnel, carries out modulation again obtain transmission signal s (t) by Received signal strength after carrying out demodulation;
4th step: Received signal strength r (t) can be expressed as the convolution form sending signal s (t) and channel filtering: r (t)=s (t) * h
i, j(t), h
i, jt () represents the channel impulse response between transmit leg i and recipient j, namely channel is for the impact sending signal and produce,
Link signature is converted into the calculating of frequency domain by time domain; At frequency domain, above-mentioned formula can be expressed as: R (f)=S (f) H
i, jf (), is multiplied by the conjugation S sending signal simultaneously in both members
*f () then obtains as down conversion: S
*(f) R (f)=| S (f) |
2h
i, j(f), so h
i, jt () can be expressed as h
i,
wherein
represent reverse Fourier transform;
5th step: recipient carries out fast Fourier transform for transmission signal s (t) obtained and is converted to frequency-region signal S (f), is calculated the conjugation S sending signal frequency domain by the conjugate operation of complex function
*(f), then by modulo operation calculate send signal modulus value square | S (f) |
2;
6th step: recipient is by two paths of signals R (f) and and conjugated signal S
*f () is multiplied, then carry out reverse fast Fourier transform, obtains its time-domain signal
7th step: the time-domain signal that the 6th step calculates by recipient, square obtains link signature divided by what send signal modulus value
Advantage of the present invention is: do not need hardware device extra in a large number; Only need computing extra on a small quantity; The conversion of the time domain of signal is transformed into frequency domain calculate, decreases computation complexity; With existing agreement and equipment mutually compatible.
Accompanying drawing explanation
Fig. 1 is the extraction flow chart of wireless link signature.
Fig. 2 is Gnu Radio realization flow figure.
Embodiment
Below introduce content of the present invention in detail with accompanying drawing in conjunction with the embodiments.
As shown in Figure 1, the described signature of the wireless link based on Gnu Radio extracting method, concrete steps are as follows:
The first step: identical pseudo random sequence is denoted as s as sending and receiving information with receiver both sides by transmitter.
Second step: pseudo random sequence sends through ovennodulation by transmit leg, produces time-domain signal and is denoted as s (t).
3rd step: recipient receives time-domain signal and is denoted as r (t).Signal is divided into two-way, and the frequency domain map function of Received signal strength is carried out on a road, Received signal strength is carried out fast Fourier transform and is converted to frequency-region signal R (f); Received signal strength is carried out to the conversion operations sending signal in one tunnel, carries out modulation again obtain transmission signal s (t) by Received signal strength after carrying out demodulation.
4th step: Received signal strength r (t) can be expressed as the convolution form sending signal s (t) and channel filtering: r (t)=s (t) * h
i, j(t).Because inverse convolution is very complicated computational process, so link signature is converted into the calculating of frequency domain by scheme by time domain.At frequency domain, above-mentioned formula can be expressed as: R (f)=S (f) H
i, j(f).Be multiplied by the conjugation S sending signal in both members simultaneously
*f () then can obtain as down conversion: S
*(f) R (f)=| S (f) |
2h
i, j(f).So h
i, jt () can be expressed as
5th step: recipient carries out s (t) for the transmission signal obtained and carries out fast Fourier transform and be converted to frequency-region signal S (f).The conjugation S sending signal frequency domain is calculated by the conjugate operation of complex function
*(f), then by modulo operation calculate send signal modulus value square | S (f) |
2.
6th step: recipient is by two paths of signals R (f) and and conjugated signal S
*f () is multiplied, then carry out reverse fast Fourier transform, obtains its time-domain signal
7th step: the time-domain signal that the 6th step calculates by recipient, square obtains link signature divided by what send signal modulus value
Fig. 2 is the flow chart of the whole leaching process of embodiment, and embodiment uses Gnu Radio Software Radio platform, uses USRP N210 model peripheral hardware as signal transmitting and receiving instrument.Below to wireless link signature leaching process and modules make introductions all round.
The extraction of wireless link signature adopts 2 USRP N210 to be connected with 2 main frames, and every cover system is respectively as transmit leg and recipient.
Under transmit leg and recipient are operated in the frequency of 2.2Ghz, carry out the extraction of link signature with identical pseudo random sequence s.
Transmit leg adopts PSK modulation system, is a transmission cycle with every 10s, pseudo random sequence s is carried out circulation and sends.
Recipient, by the multiple modification signal data of USRP front-end collection, is transferred to the enterprising row relax of main process equipment by USB 2.0.Whole handling procedure adopts Python to write, and each signal processing module called adopts C Plus Plus to write.The signal received is divided into two-way to process by recipient, as shown in Figure 2:
Packet computing is carried out on one tunnel, flow data is one group with 64 units and divides into groups, then carry out the fast Fourier transform of forward, and the window size of conversion is 64, the frequency domain data after conversion is carried out solution division operation, is converted to flow data.
The signal data received is carried out PSK digital modulation and carries out PSK digital demodulation again by another road, and PSK digital modulation and demodulation all adopt QPSK modulation system.Flow data is one group with 64 units divide into groups, then carries out the fast Fourier transform of forward, the window size of conversion is 64, the frequency domain data after conversion is carried out solution division operation, is converted to flow data.Copy a circuit-switched data and carry out magnitude calculation, and modulus value data are carried out square operation.
Two paths of data merged and carry out multiplying, result fluxion is one group with 64 units and divides into groups, then carry out reverse fast Fourier transform, the window size of conversion is 64, the frequency domain data after conversion is carried out solution division operation, is converted to flow data.
By the data after reverse Fourier transform divided by modulus value data square, and by result preserve hereof, store with binary file format .bin file.
Claims (1)
1., based on the wireless link signature extracting method of Gnu Radio, it is characterized in that, comprise the following steps:
The first step: identical pseudo random sequence is denoted as s as sending and receiving information with receiver both sides by transmitter;
Second step: pseudo random sequence sends through ovennodulation by transmit leg, produce time-domain signal and be denoted as s (t), t represents the time;
3rd step: recipient receives time-domain signal and is denoted as r (t); Signal is divided into two-way, and the frequency domain map function of Received signal strength is carried out on a road, and Received signal strength is carried out fast Fourier transform and is converted to frequency-region signal R (f), f represents frequency; Received signal strength is carried out to the conversion operations sending signal in one tunnel, carries out modulation again obtain transmission signal s (t) by Received signal strength after carrying out demodulation;
4th step: Received signal strength r (t) can be expressed as the convolution form sending signal s (t) and channel filtering: r (t)=s (t) * h
i, j(t), h
i, jt () represents the channel impulse response between transmit leg i and recipient j, namely channel is for the impact sending signal and produce,
Link signature is converted into the calculating of frequency domain by time domain; At frequency domain, above-mentioned formula can be expressed as: R (f)=S (f) H
i, jf (), is multiplied by the conjugation S sending signal simultaneously in both members
*f () then obtains as down conversion: S
*(f) R (f)=| s (f) |
2h
i, j(f), so h
i, jt () can be expressed as
wherein
represent reverse Fourier transform;
5th step: recipient carries out fast Fourier transform for transmission signal s (t) obtained and is converted to frequency-region signal S (f), is calculated the conjugation S sending signal frequency domain by the conjugate operation of complex function
*(f), then by modulo operation calculate send signal modulus value square | S (f) |
2;
6th step: recipient is by two paths of signals R (f) and and conjugated signal S
*f () is multiplied, then carry out reverse fast Fourier transform, obtains its time-domain signal
7th step: the time-domain signal that the 6th step calculates by recipient, square obtains link signature divided by what send signal modulus value
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108732592A (en) * | 2018-05-10 | 2018-11-02 | 大连大学 | GPS software receiver based on GNU Radio |
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| CN101243622A (en) * | 2005-10-21 | 2008-08-13 | 中兴通讯股份有限公司 | Uplink signal transmitting method for user device and its method for timing synchronization |
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