CN102223628A - Frequency domain encryption method and device for random subcarrier weight - Google Patents

Abstract

The invention relates to a frequency domain encryption method and a frequency domain encryption device for random subcarrier weight. An information receiving and transmitting device comprises a transmitter and a receiver; the transmitter comprises a signaling receiving module, a channel estimation module, a random subcarrier weighting coefficient generator, an encoder, a multi-carrier modulator and a transmitting front end; the receiver comprises a signaling transmitting module, a multi-carrier modulator, a decoder and a receiving front end; after being received by the signaling receiving module, channel detection signals transmitted by the signaling transmitting module are transmitted into the channel estimation module, and the output signals of the channel estimation module enter the random subcarrier weighting coefficient generator; a source signal is first encoded to be a signal containing a plurality of subcarriers, the random subcarrier weighting coefficient generator further weighs data of each subcarrier, and modulates and the transmits the signal; and after demodulating and decoding the received signals, the receiver restores a source signal. By the method and the device, the probability of intercepting and capturing the signal by illegal users is greatly reduced under the condition of ensuring that authorized users receive signals normally.

Description

Random sub carrier wave weighted frequency-domain encryption method and device

(1), technical field: the present invention relates to a kind of encryption method and device, particularly relate to a kind of random sub carrier wave weighted frequency-domain encryption method and device.

(2), background technology: growing along with multimedia communication service, people are more and more higher to the rate requirement of radio communication, multi-carrier transmission is by being decomposed into data flow the experimental process bit stream, each sub data flow will have much lower bit rate like this, the low rate multimode symbol that forms with such low bit rate goes to modulate corresponding subcarrier again, thereby constitutes the transmission system that a plurality of low rate symbol parallels send.In single-carrier system, once decline or disturb and just can cause whole link failure, but in multicarrier system, the subchannel that a certain moment only has a small part is subjected to the influence of deep fade, intersymbol interference is eliminated in contrary frequency selectivity decline effectively greatly.

On the other hand, multicarrier system is as a kind of wireless communication system of opening, and more traditional wired system is compared has bigger potential safety hazard.In traditional wired communication system, employing be that the cryptography theory is avoided leakage of information in application layer by the information source cipher mode.Wireless communication system has the different of essence with wired communication system on the process of transmission signals, but what still adopt at present mostly is that information source encryption mechanism in the wire communication ensures communication security, because the opening of wireless channel and the broadcast characteristic of electromagnetic signal propagation, the disabled user is connecting system and then enforcement destruction more easily, threatens the fail safe of communication.

At present, adopt traditional security strategy to have a series of problems in the radio communication.For example during the radio communication key distribution, can't guarantee this safe transmission in wireless channel of key.Therefore fundamentally do not solve the safety problem that the wireless channel opening causes.Adopt spread spectrum, frequency hopping, the signal of special system design such as ultra broadband possesses the characteristic of low probability of intercept, and making can provide certain encryption performance by the correctly signal of demodulation eavesdropping acquisition of listener-in.Yet specific frequency expansion sequence or frequency hopping pattern in the signal system be in case reveal, and information will be by the correct demodulation of listener-in, thereby lost the purpose of safe transmission.

A kind of new thinking is to utilize the spatial domain characteristic of wireless channel to encrypt.Encryption method shown in Figure 1 at the wireless security model relate generally to the three parts, Alice need be transferred to validated user Bob to information security as the base station end, sends and Eve only carries out passive reception as eavesdropping end and do not do any active.Alice, Bob all adopt single antenna, and Eve both can adopt single antenna also can adopt many antennas for guaranteeing the eavesdropping performance.

In the communication process, Bob at first sends the unencrypted solicited message to Alice, and this solicited message comprises training sequence simultaneously; Alice receives solicited message, and estimates that according to the training sequence that receives the channel between them obtains channel information.Because Alice do not send any training sequence, Bob and Eve all do not know the channel information between they and the Alice, therefore are in a kind of total blindness's state.In TDD radio communication system, suppose that channel becomes slowly, according to reciprocity theorem, can think that the transceiver channel between Alice and the Bob is identical.Therefore Alice can encrypt the information that is about to send to Bob according to the multipath channel of estimating.Channel information between Alice and the Bob is the key that Alice uses in this case, finish deciphering automatically behind information via Alice after the encryption and the channel between the Bob, so Bob need not to know how Alice encrypts directly to finish proper communication.And Eve receives is signal after the encryption of a Unknown Channel information, is not knowing to solve the symbol that Alice sends under the situation of key.

At this wireless transmission security model, document " Using antenna array redundancy and channel diversity for secure wireless transmissions " (Journal of Communication, vol.2, pp.24-32, May 2007) a kind of method of carrying out encryption in physical layer based on the array redundancy of proposition.This method is similar to launching beam and forms, and guaranteeing under the constant prerequisite of ideal user end channel, by the weight coefficient of each array element of picked at random, making transmits can directly demodulate the symbol sebolic addressing of being launched through wireless channel stack back at the desired user end.For illegal wiretapping person, the change at random of array element weight coefficient can make signal constellation which that the listener-in receives scramble at random, thereby the method that causes features such as utilizing permanent mould and limited sign indicating number collection to carry out the channel blind equalization can't effectively be implemented final satisfied requirement with low probability of intercept.At transmitting terminal array of designs antenna, the implementation complexity height is not suitable for the system of broadband wireless communication that single antenna is adopted in transmitting-receiving to these class methods at the narrow band signal that sends.

In the broadband wireless system that adopts multi-carrier modulation, the same time is in the space diverse location, and the channel difference of different frequent points is to distinguish the most important characteristic of different user.By extracting and using channel characteristics is the key of carrying out the wireless security transmission.The wireless security transmission will be distinguished the user by distinguishing different channels exactly, and the information that prevents is intercepted and captured in the wireless transmission process.

(3), summary of the invention:

The technical problem to be solved in the present invention is: the defective that overcomes prior art, a kind of random sub carrier wave weighted frequency-domain encryption method and device are provided, this method and device are by utilizing legitimate correspondence both sides and listener-in's differences in spatial location, the different sub carrier data carried by data is carried out the frequency domain precoding reach cipher round results, it is a kind of method of utilizing the essential characteristic solution safe transmission problem of radio communication, this method and device greatly reduce the probability of being intercepted and captured by the disabled user under the situation that guarantees the normal received signal of authorized user.

Technical scheme of the present invention:

A kind of R-T unit, contain transmitter and receiver, transmitter contains signaling receiver module, channel estimation module, random sub carrier wave weight coefficient generator, encoder, multi-carrier modulator, front end of emission and transmitting antenna, and receiver contains signaling transmitter module, multicarrier demodulator, decoder, receiving front-end and reception antenna; Transmitter and receiver is operated under the tdd mode, up-downgoing has reciprocity, the signaling transmitter module of receiver sends out the channel detection signal, this channel detection signal is sent into channel estimation module after the signaling receiver module of transmitter receives, be used to estimate the radio channel information of each subcarrier between the transmitter and receiver, the output signal of channel estimation module enters in the random sub carrier wave weight coefficient generator; Become behind the earlier encoded device coding of source signal and contain a plurality of subcarrier signals, the random sub carrier wave weight coefficient generator produces a complex coefficient at random for each subcarrier again, and to the data weighting on this subcarrier, then, a plurality of subcarrier signals that contain that multi-carrier modulator was handled the random sub carrier wave weight coefficient generator are modulated, send through transmitting antenna by front end of emission then, the signal that transmitting antenna sends is after reception antenna receives, again through restoring source signal behind receiving front-end, multicarrier demodulator, the decoder.

Can when not influencing the validated user demodulation, reduce eavesdropping user demodulation probability of successful through the signal after the processing of random sub carrier wave weight coefficient generator.

The random sub carrier wave weight coefficient generator contains random phase generator, phase calculator and magnitude calculator, the output signal of random phase generator enters in the phase calculator, the output signal of channel estimation module enters in phase calculator and the magnitude calculator, and the output of phase calculator and magnitude calculator is used for handling a plurality of subcarrier signals that contain of encoder output; Contain the serial to parallel conversion module in the encoder, contain the parallel serial conversion module in the multi-carrier modulator; Contain the serial to parallel conversion module in the multicarrier demodulator, contain the parallel serial conversion module in the decoder.

The output of front end of emission is connected with the input of signaling receiver module, and the output of signaling transmitter module is connected with the input of receiving front-end.

A kind of random sub carrier wave weighted frequency-domain encryption method of utilizing described R-T unit to realize contains and has the following steps:

Step 1: at first, receiver is by its signaling transmitter module emission pilot signal or training sequence, and pilot signal or training sequence are the symbol sebolic addressings with same frequency and anchor-frame form of receiving-transmitting sides agreement; Pilot signal or training sequence are used for measuring and the monitoring wireless channel environment, thereby obtain channel characteristics;

Step 2: after transmitter receives pilot signal or training sequence, this pilot signal or training sequence are sent into channel estimation module, be used to calculate k sub-carrier channels state information h _AB(k), and with k sub-carrier channels state information h _AB(k) channel parameter in is sent into the random sub carrier wave weight coefficient generator, and k sub-carrier channels state information note made h _AB(k), the expression formula of k sub-carrier channels state information is:

$h_{\mathrm{AB}}\left(k\right)=\underset{l=0}{\overset{L}{\mathrm{\Σ}}}{a}_B\left(l\right)e^{-j2\mathrm{\πk\Δf}{\mathrm{\τ}}_B\left(l\right)},$

Wherein, L represents multipath number, a _B(l) complex coefficient of expression l footpath amplitude, Δ f represents subcarrier spacing, τ _B(l) time delay in expression l footpath, j represents imaginary unit;

Step 3: in the random sub carrier wave weight coefficient generator, the random sub carrier wave weight coefficient generator is each subcarrier structure weight coefficient, this weight coefficient contain at random amplitude and phase place at random;

Channel estimation module is with the 1st sub-carrier channels state information h _AB(1) input phase calculator and magnitude calculator, random phase generator produce the phase place of the 1st sub-carrier weighting coefficient

Phase calculator is according to the phase place of the 1st sub-carrier weighting coefficient

By formula

Produce the phase place of k sub-carrier weighting coefficient

Wherein,

The phase information of representing k sub-carrier channels,

The phase information of representing the 1st sub-carrier channels.

Magnitude calculator produces the range value of the 1st sub-carrier weighting coefficient at random | w ₁|, produce the amplitude of k sub-carrier weighting coefficient then according to the amplitude constraint formula | w _k|, the amplitude constraint formula is:

|w ₁||h _AB(1)|＝|w _k||h _AB(k)|＝C，

Wherein, C is a constant,

At last, by the amplitude of k sub-carrier weighting coefficient | w _k| and the phase place of k sub-carrier weighting coefficient

Go out the weighted factor w of k subcarrier data according to following formula construction _k:

Wherein, j represents imaginary unit;

Step 4: pilot signal that transmitter receives the signaling receiver module or training sequence add to before the source signal, then the source signal that added pilot signal or training sequence is sent in the string and modular converter of encoder, making the 1st subcarrier upload defeated data is pilot signal or training sequence, transmit information data on all the other subcarriers, then, corresponding the multiplying each other of weighted factor of the data on each subcarrier and corresponding subcarrier data, again after multi-carrier modulator modulation, send at last by sending front end;

Step 5: the receiving front-end of receiver is sent the data of receiving into demodulation in the multicarrier demodulator, contains the pilot data y of the 1st sub-carriers carry in the signal after the demodulation _B1With all the other subcarrier loaded information data y _B2, the pilot data y of the 1st sub-carriers carry _B1With all the other subcarrier loaded information data Y _B2Expression formula as follows:

$y_{B1}=I{w}_1{h}_{\mathrm{AB}}\left(1\right)+n_{B_1}$

$Y_{B2}=X1{W1}_k{H1}_{\mathrm{AB}}\left(k\right)+N_{B_k}$

Wherein, I represents one dimension pilot vector, w ₁The weighted factor of representing the 1st subcarrier data, n _B1Be the 1st noise in the sub-carrier channels,

Be the matrix of the weighted factor of all the other subcarrier datas, H1 _AB(k) be the matrix of all the other sub-carrier channels state informations, Be the noise in all the other sub-carrier channels, X1 represents the information data that sends; Then carry out maximum likelihood decision by following formula:

$\hat{X}=\underset{X}{\arg \min }{\left|\right|Y_{B2}-X{y}_{B1}\left|\right|}_F^2;$

Wherein, X represents the exhaustive value of the information data that sends,

The estimated value of the information data of the transmission under the expression maximum likelihood decision criterion, F represents two norms.

At last, the estimated value of the information data of transmission Parallel serial conversion module in decoder restores data.

In the step 5, the estimated value of the information data of transmission

Meet following formula:

$Y_{B2}=\hat{X}{W1}_k{H1}_{\mathrm{AB}}\left(k\right)+N_{B_k}.$

The signaling transmitter module periodically sends channel detection signal in order to the detection wireless channel characteristics to transmitter according to pre-set receiving and dispatching mechanism.

Encryption method of the present invention and device can be used for comprising OFDM (OFDM), Discrete Multitone modulation (DMT) and multi-carrier modulation multiple multicarrier transmission systems such as (MCM), are used to ensure secure wireless communication.

Beneficial effect of the present invention:

1, the present invention is directed to the communication system of time division duplex multi-carrier modulation, utilize communicating pair wireless channel principle of reciprocity to design a kind of frequency domain encryption method and device.The present invention is according to legitimate correspondence both sides' channel characteristics, at transmitting terminal is the reception that the pre-at random weighted factor of each subcarrier data setting is upset the listener-in, validated user can utilize the channel characteristics of communicating pair, data on each subcarrier of demodulation, and illegally eavesdrop the pre-weighted change at random of each symbol process transmitting terminal that the user receives, therefore can't restoring data information.The present invention is by making wireless signal have low probability of intercept at encryption in physical layer, combines with traditional application layer encryption and can obtain better cipher round results, is with a wide range of applications in digital broadband secure wireless communication field.

2, the present invention only increases by one and sends precoder at random on the communication system of conventional multi-carrier modulation, and transceiver all adopts single antenna, just can realize the safe transmission of information, has reduced the complexity that system realizes.

3, the present invention is directed to the broadband wireless communications characteristics, adopt multi-carrier modulation that frequency-selective channel is divided into a series of flat fading subchannels, intersymbol interference is eliminated in contrary frequency selectivity decline effectively greatly.

(4), description of drawings:

Fig. 1 is the schematic diagram of existing wireless security mode;

Fig. 2 is the structural representation of transmitter;

Fig. 3 is the structural representation of random sub carrier wave weight coefficient generator;

Fig. 4 is the structural representation of receiver.

(5), embodiment:

Referring to Fig. 2～Fig. 4, R-T unit contains transmitter and receiver, transmitter contains signaling receiver module, channel estimation module, random sub carrier wave weight coefficient generator, encoder, multi-carrier modulator, front end of emission and transmitting antenna, and receiver contains signaling transmitter module, multicarrier demodulator, decoder, receiving front-end and reception antenna; Transmitter and receiver is operated under the tdd mode, up-downgoing has reciprocity, the signaling transmitter module of receiver sends out the channel detection signal, this channel detection signal is sent into channel estimation module after the signaling receiver module of transmitter receives, be used to estimate the radio channel information of each subcarrier between the transmitter and receiver, the output signal of channel estimation module enters in the random sub carrier wave weight coefficient generator; Become behind the earlier encoded device coding of source signal and contain a plurality of subcarrier signals, the random sub carrier wave weight coefficient generator produces a complex coefficient at random for each subcarrier again, and to the data weighting on this subcarrier, then, a plurality of subcarrier signals that contain that multi-carrier modulator was handled the random sub carrier wave weight coefficient generator are modulated, send through transmitting antenna by front end of emission then, the signal that transmitting antenna sends is after reception antenna receives, again through restoring source signal behind receiving front-end, multicarrier demodulator, the decoder.

Can when not influencing the validated user demodulation, reduce eavesdropping user demodulation probability of successful through the signal after the processing of random sub carrier wave weight coefficient generator.

The random sub carrier wave weight coefficient generator contains random phase generator, phase calculator and magnitude calculator, the output signal of random phase generator enters in the phase calculator, the output signal of channel estimation module enters in phase calculator and the magnitude calculator, and the output of phase calculator and magnitude calculator is used for handling a plurality of subcarrier signals that contain of encoder output; Contain the serial to parallel conversion module in the encoder, contain the parallel serial conversion module in the multi-carrier modulator; Contain the serial to parallel conversion module in the multicarrier demodulator, contain the parallel serial conversion module in the decoder.

The output of front end of emission is connected with the input of signaling receiver module, and the output of signaling transmitter module is connected with the input of receiving front-end.

The random sub carrier wave weighted frequency-domain encryption method of utilizing described R-T unit to realize contains and has the following steps:

Step 1: at first, receiver is by its signaling transmitter module emission pilot signal or training sequence, and pilot signal or training sequence are the symbol sebolic addressings with same frequency and anchor-frame form of receiving-transmitting sides agreement; Pilot signal or training sequence are used for measuring and the monitoring wireless channel environment, thereby obtain channel characteristics;

Step 2: after transmitter receives pilot signal or training sequence, this pilot signal or training sequence are sent into channel estimation module, be used to calculate k sub-carrier channels state information h _AB(k), and with k sub-carrier channels state information h _AB(k) channel parameter in is sent into the random sub carrier wave weight coefficient generator, and k sub-carrier channels state information note made h _AB(k), the expression formula of k sub-carrier channels state information is:

$h_{\mathrm{AB}}\left(k\right)=\underset{l=0}{\overset{L}{\mathrm{\Σ}}}{a}_B\left(l\right)e^{-j2\mathrm{\πk\Δf}{\mathrm{\τ}}_B\left(l\right)},$

Wherein, L represents multipath number, a _B(l) complex coefficient of expression l footpath amplitude, Δ f represents subcarrier spacing, τ _B(l) time delay in expression l footpath, j represents imaginary unit;

Step 3: in the random sub carrier wave weight coefficient generator, the random sub carrier wave weight coefficient generator is each subcarrier structure weight coefficient, this weight coefficient contain at random amplitude and phase place at random;

Channel estimation module is with the 1st sub-carrier channels state information h _AB(1) input phase calculator and magnitude calculator, random phase generator produce the phase place of the 1st sub-carrier weighting coefficient

Phase calculator is according to the phase place of the 1st sub-carrier weighting coefficient

By formula Produce the phase place of k sub-carrier weighting coefficient

Wherein,

The phase information of representing k sub-carrier channels, The phase information of representing the 1st sub-carrier channels.

Magnitude calculator produces the range value of the 1st sub-carrier weighting coefficient at random | w ₁|, produce the amplitude of k sub-carrier weighting coefficient then according to the amplitude constraint formula | w _k|, the amplitude constraint formula is:

|w ₁||h _AB(1)|＝|w _k||h _AB(k)|＝C，

Wherein, C is a constant,

At last, by the amplitude of k sub-carrier weighting coefficient | w _k| and the phase place of k sub-carrier weighting coefficient

Go out the weighted factor w of k subcarrier data according to following formula construction _k:

Wherein, j represents imaginary unit;

Step 4: pilot signal that transmitter receives the signaling receiver module or training sequence add to before the source signal, then the source signal that added pilot signal or training sequence is sent in the string and modular converter of encoder, making the 1st subcarrier upload defeated data is pilot signal or training sequence, transmit information data on all the other subcarriers, then, corresponding the multiplying each other of weighted factor of the data on each subcarrier and corresponding subcarrier data, again after multi-carrier modulator modulation, send at last by sending front end;

Step 5: the receiving front-end of receiver is sent the data of receiving into demodulation in the multicarrier demodulator, contains the pilot data y of the 1st sub-carriers carry in the signal after the demodulation _B1With all the other subcarrier loaded information data y _B2, the pilot data y of the 1st sub-carriers carry _B1With all the other subcarrier loaded information data y _B2Expression formula as follows:

$y_{B1}=I{w}_1{h}_{\mathrm{AB}}\left(1\right)+n_{B_1}$

$Y_{B2}=X1{W1}_k{H1}_{\mathrm{AB}}\left(k\right)+N_{B_k}$

Wherein, I represents one dimension pilot vector, w ₁The weighted factor of representing the 1st subcarrier data, n _B1Be the 1st noise in the sub-carrier channels,

Be the matrix of the weighted factor of all the other subcarrier datas, H1 _AB(k) be the matrix of all the other sub-carrier channels state informations,

Be the noise in all the other sub-carrier channels, X1 represents the information data that sends; Then carry out maximum likelihood decision by following formula:

$\hat{X}=\underset{X}{\arg \min }{\left|\right|Y_{B2}-X{y}_{B1}\left|\right|}_F^2;$

Wherein, X represents the exhaustive value of the information data that sends,

The estimated value of the information data of the transmission under the expression maximum likelihood decision criterion, F represents two norms.

At last, the estimated value of the information data of transmission

Parallel serial conversion module in decoder restores data.

In the step 5, the estimated value of the information data of transmission

Meet following formula:

$Y_{B2}=\hat{X}{W1}_k{H1}_{\mathrm{AB}}\left(k\right)+N_{B_k}.$

The signaling transmitter module periodically sends channel detection signal in order to the detection wireless channel characteristics to transmitter according to pre-set receiving and dispatching mechanism.

Encryption method of the present invention and device can be used for comprising OFDM (OFDM), Discrete Multitone modulation (DMT) and multi-carrier modulation multiple multicarrier transmission systems such as (MCM), are used to ensure secure wireless communication.

Further specify technical scheme of the present invention at concrete example below, contain tripartite user: Alice (sending the user), Bob (desired user) and Eve (eavesdropping user) in this example.

According to this Alice-Bob model, suppose that the channel impulse response of k subcarrier can be expressed as in the multicarrier modulation system that adopts N subcarrier:

$h_{\mathrm{AB}}\left(k\right)=\underset{l=0}{\overset{L}{\mathrm{\Σ}}}{a}_{\mathrm{AB}}\left(l\right)e^{-j2\mathrm{\πk\Δf}{\mathrm{\τ}}_{\mathrm{AB}}\left(l\right)},(0\≤k\≤N-1),$

Wherein L represents multipath number, a _AB(l) the complex coefficient mould of expression l footpath amplitude, Δ f represents subcarrier spacing, τ _AB(l) time delay in expression l footpath, j represents imaginary unit, N is the sub-carrier number in the multicarrier system.

When the design of Alice end sends signal, the 1st subcarrier in N the subcarrier is used to transmit pilot tone, all the other N-1 subcarrier is used for transmitting data information x (k).The present invention has increased precoding module at random in the emitter of this multicarrier modulation system, by designing pre-coding matrix w at random, the data on each subcarrier are finished encryption by frequency domain weighting.If the channel state matrix between Alice-Bob is H _AB, data send through multi-carrier modulation, and the frequency-domain expression of Bob received signal is:

Y _B＝XWH _AB+N _B (1)

Y wherein _BThe pilot data y that comprises the 1st sub-carriers carry _B1, and the information data Y of N-1 the sub-carriers carry in back _B2, N _BBe the noise in N the sub-carrier channels, X is the data that Alice sends.

When design encryption in physical layer method, need utilize the channel characteristics H of Alice and Bob _ABChannel characteristics H with Alice and Eve _AEDifference construct pre-coding matrix at random.Order:

w ₀h _AB(0)＝w ₁h _AB(1)

.

. (2)

w ₀h _AB(0)＝w _N-1h _AB(N-1)

Can get the symbol that each sub-carrier channels receives

Wherein, N _B1Be the 1st noise in the sub-carrier channels, N _B2Be the noise in N-1 the sub-carrier channels in back, Bob carries out demodulation according to the maximum-likelihood criterion of formula (3) can solve Alice transmission data x (k).

$\hat{X}=\underset{X}{\arg \min }{\left|\right|Y_{B2}-{\mathrm{XY}}_{B1}\left|\right|}_F^2---\left(3\right)$

Because it is H that Bob and Eve are in the space diverse location _AB≠ H _AE, exist so:

w ₀h _AB(0)≠w ₁h _AE(1)

.

. (4)

w ₀h _AB(0)≠w _N-1h _AE(N-1)

Then Eve can't demodulate data x (k) by formula (3) by the pilot frequency information that carries on first subcarrier, thereby Alice sends information data listener-in Eve be played the encryption effect.

Effect by the w of pre-coding matrix at random of formula (2) structure is that randomization sends signal, make the listener-in can't obtain continuously signal stably, the signal constellation which quilt of receiving is scramble at random, thereby the method that causes features such as utilizing permanent mould and limited sign indicating number collection to carry out the channel blind equalization can't effectively be implemented final satisfied requirement with low probability of intercept.Therefore, when the channel status between Alice-Bob and the channel status between Alice-Eve not simultaneity factor finish encryption automatically.

Claims (6)

1. R-T unit, contain transmitter and receiver, it is characterized in that: transmitter contains signaling receiver module, channel estimation module, random sub carrier wave weight coefficient generator, encoder, multi-carrier modulator, front end of emission and transmitting antenna, and receiver contains signaling transmitter module, multicarrier demodulator, decoder, receiving front-end and reception antenna; Transmitter and receiver is operated under the tdd mode, up-downgoing has reciprocity, the signaling transmitter module of receiver sends out the channel detection signal, this channel detection signal is sent into channel estimation module after the signaling receiver module of transmitter receives, be used to estimate the radio channel information of each subcarrier between the transmitter and receiver, the output signal of channel estimation module enters in the random sub carrier wave weight coefficient generator; Become behind the earlier encoded device coding of source signal and contain a plurality of subcarrier signals, the random sub carrier wave weight coefficient generator produces a complex coefficient at random for each subcarrier again, and to the data weighting on this subcarrier, then, a plurality of subcarrier signals that contain that multi-carrier modulator was handled the random sub carrier wave weight coefficient generator are modulated, send through transmitting antenna by front end of emission then, the signal that transmitting antenna sends is after reception antenna receives, again through restoring source signal behind receiving front-end, multicarrier demodulator, the decoder.

2. R-T unit according to claim 1, it is characterized in that: described random sub carrier wave weight coefficient generator contains random phase generator, phase calculator and magnitude calculator, the output signal of random phase generator enters in the phase calculator, the output signal of channel estimation module enters in phase calculator and the magnitude calculator, and the output of phase calculator and magnitude calculator is used for handling a plurality of subcarrier signals that contain of encoder output; Contain the serial to parallel conversion module in the encoder, contain the parallel serial conversion module in the multi-carrier modulator; Contain the serial to parallel conversion module in the multicarrier demodulator, contain the parallel serial conversion module in the decoder.

3. R-T unit according to claim 1 is characterized in that: the output of described front end of emission is connected with the input of signaling receiver module, and the output of signaling transmitter module is connected with the input of receiving front-end.

4. random sub carrier wave weighted frequency-domain encryption method of utilizing the described R-T unit of claim 1 to realize is characterized in that: contain and have the following steps:

Step 1: at first, receiver is by its signaling transmitter module emission pilot signal or training sequence, and pilot signal or training sequence are the symbol sebolic addressings with same frequency and anchor-frame form of receiving-transmitting sides agreement;

Step 2: after transmitter receives pilot signal or training sequence, this pilot signal or training sequence are sent into channel estimation module, be used to calculate k sub-carrier channels state information h _AB(k), and with k sub-carrier channels state information h _AB(k) channel parameter in is sent into the random sub carrier wave weight coefficient generator, and k sub-carrier channels state information note made h _AB(k), the expression formula of k sub-carrier channels state information is:

$h_{\mathrm{AB}}\left(k\right)=\underset{l=0}{\overset{L}{\mathrm{\Σ}}}{a}_B\left(l\right)e^{-j2\mathrm{\πk\Δf}{\mathrm{\τ}}_B\left(l\right)},$

Wherein, L represents multipath number, a _B(l) complex coefficient of expression l footpath amplitude, Δ f represents subcarrier spacing, τ _B(l) time delay in expression l footpath, j represents imaginary unit;

Step 3: in the random sub carrier wave weight coefficient generator, the random sub carrier wave weight coefficient generator is each subcarrier structure weight coefficient, this weight coefficient contain at random amplitude and phase place at random;

Channel estimation module is with the 1st sub-carrier channels state information h _AB(1) input phase calculator and magnitude calculator, random phase generator produce the phase place of the 1st sub-carrier weighting coefficient

Phase calculator is according to the phase place of the 1st sub-carrier weighting coefficient

By formula

Produce the phase place of k sub-carrier weighting coefficient

Wherein,

The phase information of representing k sub-carrier channels,

The phase information of representing the 1st sub-carrier channels;

Magnitude calculator produces the range value of the 1st sub-carrier weighting coefficient at random | w ₁|, produce the amplitude of k sub-carrier weighting coefficient then according to the amplitude constraint formula | w _k|, the amplitude constraint formula is:

|w ₁||h _AB(1)|＝|w _k||h _AB(k)|＝C，

Wherein, C is a constant,

At last, by the amplitude of k sub-carrier weighting coefficient | w _k| and the phase place of k sub-carrier weighting coefficient

Go out the weighted factor w of k subcarrier data according to following formula construction _k:

Wherein, j represents imaginary unit;

Step 4: pilot signal that transmitter receives the signaling receiver module or training sequence add to before the source signal, then the source signal that added pilot signal or training sequence is sent in the string and modular converter of encoder, making the 1st subcarrier upload defeated data is pilot signal or training sequence, transmit information data on all the other subcarriers, then, corresponding the multiplying each other of weighted factor of the data on each subcarrier and corresponding subcarrier data, again after multi-carrier modulator modulation, send at last by sending front end;

Step 5: the receiving front-end of receiver is sent the data of receiving into demodulation in the multicarrier demodulator, contains the pilot data y of the 1st sub-carriers carry in the signal after the demodulation _B1With all the other subcarrier loaded information data y _B2, the pilot data y of the 1st sub-carriers carry _B1With all the other subcarrier loaded information data Y _B2Expression formula as follows:

$y_{B1}=I{w}_1{h}_{\mathrm{AB}}\left(1\right)+n_{B_1}$

$Y_{B2}=X1{W1}_k{H1}_{\mathrm{AB}}\left(k\right)+N_{B_k}$

Wherein, I represents one dimension pilot vector, w ₁The weighted factor of representing the 1st subcarrier data,

Be the 1st noise in the sub-carrier channels,

Be the matrix of the weighted factor of all the other subcarrier datas,

Be the matrix of all the other sub-carrier channels state informations,

Be the noise in all the other sub-carrier channels, X1 represents the information data that sends; Then carry out maximum likelihood decision by following formula:

$\hat{X}=\underset{X}{\arg \min }{\left|\right|Y_{B2}-X{y}_{B1}\left|\right|}_F^2;$

Wherein, X represents the exhaustive value of the information data that sends,

The estimated value of the information data of the transmission under the expression maximum likelihood decision criterion, F represents two norms;

At last, the estimated value of the information data of transmission

Parallel serial conversion module in decoder restores data.

5. random sub carrier wave weighted frequency-domain encryption method according to claim 4 is characterized in that: in the described step 5, and the estimated value of the information data of transmission

Meet following formula:

$Y_{B2}=\hat{X}{W1}_k{H1}_{\mathrm{AB}}\left(k\right)+N_{B_k}.$

6. random sub carrier wave weighted frequency-domain encryption method according to claim 4 is characterized in that: described signaling transmitter module periodically sends channel detection signal in order to the detection wireless channel characteristics to transmitter according to pre-set receiving and dispatching mechanism.

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