CN109412750B - Anti-eavesdrop transmission method based on fountain codes in multimedia communication - Google Patents
Anti-eavesdrop transmission method based on fountain codes in multimedia communication Download PDFInfo
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- 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
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Abstract
The invention discloses an anti-eavesdrop transmission method based on fountain codes in multimedia communication, which comprises the following steps: 1) dividing a source file to be sent into N source data packets by a legal sender Alice; 2) the legal sender Alice sorts the importance of each source data packet based on the service characteristics, and simultaneously divides the channel quality into three channel quality intervals from good to bad; 3) the legal sender Alice utilizes the received source data packet mark fed back by the legal receiver Bob, then dynamically adjusts the fountain coding structure according to the importance of the source data packet to be sent and the current channel information, and then sends the coding packet tnSending the data to a legal receiver Bob; 4) and the legal receiver Bob decodes the received coded packet to obtain a source packet, and then feeds back the mark of the source packet to the legal transmitter Alice.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and relates to an anti-eavesdropping transmission method based on fountain codes in multimedia communication.
Background
Physical layer security has attracted extensive attention from researchers at home and abroad because it can utilize wireless channel characteristics to achieve secure transmission and does not rely on key encryption. However, the conventional physical layer security technology aiming at maximizing the private capacity and minimizing the private outage probability has the limitations of low transmission rate, high decoding delay and the like, which are not matched with the requirements of multimedia broadband service on high-speed transmission and delay constraint.
The fountain code has the following characteristics: the receiving end must accumulate enough code packets to recover the original file. That is, as long as the legal user can accumulate enough encoding packets before the eavesdropper, the information leakage can be avoided, and the secure communication is realized. And when the fountain codes realize safe transmission, the transmission rate of the system is only limited by the Shannon capacity of a legal link, and the decoding time delay is greatly reduced. Meanwhile, the generation of the channel quality self-adaptive adjustment coding packet of the legal link is obtained by utilizing the feedback channel, so that a receiving end can obtain more important information under the time delay constraint condition, and therefore, the research on the fountain code-based multimedia security transmission technology has great significance.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a fountain code-based anti-eavesdropping transmission method in multimedia communication, which can realize fountain-based multimedia secure transmission.
In order to achieve the above purpose, the anti-eavesdropping transmission method based on fountain codes in multimedia communication according to the present invention comprises the following steps:
1) dividing a source file to be sent into N source data packets by a legal sender Alice;
2) the legal sender Alice carries out importance sequencing on each source data packet based on service characteristics, wherein each source data packet is divided into three types of type-I, type-II and type-III in a decreasing mode according to the importance degree, the channel quality is divided into three channel quality intervals from good to poor, the channel quality is determined by the module value of a channel characteristic coefficient h, and the ratio of the probability of | h | belonging to the three channel quality intervals is equal to the ratio of the data quantity of the three types of source data packets;
3) the legal sender Alice utilizes the received source data packet mark fed back by the legal receiver Bob, and then dynamically adjusts the fountain coding structure according to the importance of the source data packet to be sent and the current channel information to obtain a coding packet tnThen encode the packet tnSending the data to a legal receiver Bob;
4) and the legal receiver Bob decodes the received coded packet to obtain a source packet, and then feeds back the mark of the source packet to the legal transmitter Alice.
In step 3), when | h tint>Th1When it is, then there are
Wherein sk1mIndicates the type-I source packet, sk1, that was last solvednRepresenting a source packet randomly selected from type-I source packets that have not been solved;
when Th is1>|h|≥Th2When it is, then there are
Wherein sk2mtype-II source packets representing the most recent solution, sk2nRepresents a source packet randomly selected from type-II source packets that have not yet been solved, Σ sk1iThe method comprises the steps of obtaining the data by carrying out XOR on parts randomly selected from type-I source data packets which are already solved;
when | h |<Th2If so, not sending the coded packet;
and when any source data packet is sent, the delay threshold is not reached yet, and the source data packet is not sent, the step 2) is carried out.
For multimedia service, each frame of video is divided to obtain a series of static images, each static image is regarded as a source file, and the static images are divided into N division images with the same size, namely N source data packets s1,s2…skFor the N source packets s1,s2…skThe specific operations for classification are:
11) calculate the mean significance of each segmentation map
Wherein S isiThe significance value of each pixel point in the segmentation graph is represented, and l represents the number of pixel points contained in each pixel block;
12) obtaining a binary image by edge detection, and calculating the amount of edge information contained in the divided region
SjRepresenting the value of each pixel point in the binary image;
13) calculating importance score S of each source data packetp，
Wherein S ispThe larger the size, the more important the source packet is.
The invention has the following beneficial effects:
when the fountain code-based anti-eavesdropping transmission method in the multimedia communication is specifically operated, the fountain code structure is dynamically adjusted according to the importance of a source data packet to be sent and the current channel information to encode the source data packet to be sent, the channel quality of a legal link is not completely depended on and is better than that of an eavesdropping link, the method still has certain anti-eavesdropping performance when the channel quality of the legal link is worse than that of the eavesdropping link, and meanwhile, the anti-eavesdropping effectiveness is greatly improved when the channel quality of the legal link is better than that of the eavesdropping link, so that the information transmission safety is effectively improved. In addition, the invention carries on the code of the source data packet to be sent on the basis of the fountain code structure, in order to improve the information transmission rate of the system, and the information transmission rate is only limited by Shannon capacity of the legal link, effective reduction decodes the time delay, meet the high-speed transmission requirement of this broadband business of multimedia and strict time delay and limit the requirement. In addition, the invention adaptively selects the source data packet to be sent according to the current channel quality, and ensures the video receiving quality of the legal receiver Bob while expanding the advantages of the legal channel, so that the legal receiver Bob can acquire more important information as far as possible within the limited time delay.
Drawings
FIG. 1 is a diagram of a system model of the present invention;
FIG. 2 is a graph of intercept probability as a function of SNR;
fig. 3 is a graph of QoS violation probability versus number of source packets;
FIG. 4 is a graph of MSE as a function of average signal-to-noise ratio;
FIG. 5 is a graph of PSNR as a function of average signal-to-noise ratio;
fig. 6 is a diagram of the effect of actual video transmission according to the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
the invention discloses a data transmission system, which comprises a legal transmitter Alice and a legal receiver Bob, wherein the legal transmitter Alice and the legal receiver Bob are both provided with a single antenna, the system works in a time division duplex mode, the legal transmitter Alice transmits data according to frames, and the transmission of each frame of data comprises three stages: the first stage, a legal receiver Bob feeds back the current channel quality to a legal transmitter Alice through a feedback channel; in the second stage, the legal transmitter Alice adaptively selects a source data packet which needs to participate in coding according to the channel quality and a source data packet which is already received by the current legal receiver Bob to carry out coding to obtain a coded packet, and then sends the obtained data packet to the legal receiver Bob; in the third stage, the legal receiver Bob feeds back the label of the source packet to the legal transmitter Alice, which specifically includes the following steps:
1) dividing a source file to be sent into N source data packets by a legal sender Alice;
2) the legal sender Alice carries out importance sequencing on each source data packet based on service characteristics, wherein each source data packet is divided into three types of type-I, type-II and type-III in a decreasing mode according to the importance degree, the channel quality is divided into three channel quality intervals from good to poor, the channel quality is determined by the module value of a channel characteristic coefficient h, and the ratio of the probability of | h | belonging to the three channel quality intervals is equal to the ratio of the data quantity of the three types of source data packets;
for multimedia service, each frame of video is divided to obtain a series of static images, each static image is regarded as a source file, and the static images are divided into N division graphs with the same size, namely N source data packets s1,s2…skFor the N source packets s1,s2…skThe specific operations for classification are:
11) meterCalculate the mean significance of each segmentation map
Wherein S isiThe significance value of each pixel point in the segmentation graph is represented, and l represents the number of pixel points contained in each pixel block;
12) using FT algorithm to carry out edge detection to obtain binary image, and then calculating edge information content contained in the divided region
SjRepresenting the value of each pixel point in the binary image;
13) calculating importance score S of each source data packetp，
Wherein S ispThe larger the size, the more important the source packet is.
3) The legal sender Alice dynamically adjusts the fountain coding structure according to the importance of the data packet to be transmitted and the current channel information to encode the source data packet to be transmitted to obtain an encoded packet tnThen encode the packet tnSending the data to a legal receiver Bob;
4) and the legal receiver Bob decodes the received coded packet to obtain a source packet, and then feeds back the mark of the source packet to the legal transmitter Alice.
In step 3), when | h tint>Th1When it is, then there are
Wherein sk1mIndicates the type-I source packet, sk1, that was last solvednRepresenting a source packet randomly selected from type-I source packets that have not been solved;
when Th is1>|h|≥Th2When it is, then there are
Wherein sk2mtype-II source packets representing the most recent solution, sk2nRepresents a source packet randomly selected from type-II source packets that have not yet been solved, Σ sk1iThe method comprises the steps of obtaining the data by carrying out XOR on parts randomly selected from type-I source data packets which are already solved;
when | h |<Th2If so, not sending the coded packet;
and when any source data packet is sent, the delay threshold is not reached yet, and the source data packet is not sent, the step 2) is carried out.
The specific operation of dividing the channel quality into three channel quality intervals from good to bad in the step 2) is as follows: let P be the ratio of good channel quality interval1The ratio of the general channel quality interval is P2，Th1And Th2Represents a channel gain threshold, where Th1＝(1/λln(1-P1)-1)1/2，Th2＝(1/λln(1-P1-P2)-1)1/2When | h |>Th1The channel quality is good; when Th is1≥|h|>Th2The channel quality is normal; when | h | ≦ Th2The channel quality is poor.
In step 4), the legal receiver Bob demodulates by using the maximum likelihood criterion, and then the source data packet is obtained by using a BP iterative decoding algorithm.
Simulation experiment
For convenience of description, firstly, introducing several definitions, wherein the interception probability 1 is defined as the probability that an eavesdropper Eve receives the whole file under the condition that a legal receiver Bob decodes all K source data packets; the interception probability 2 is defined as the probability that an eavesdropper Eve solves K-1 source data packets under the condition that a legal receiver Bob solves all K source data packets, and the QoS violation probability is defined as:
wherein, TreqIndicating the number of allowed coded packets, Ttot,BAnd Ttot,EThe number of coding packets needed by a legal receiver and an eavesdropper to recover all source data packets respectively represents, a first item in a formula defines the delay violation probability, and a second item calculates the information interception probability of the eavesdropper Eve.
The effectiveness of the invention mainly depends on the difference of the two link channels, and the channel quality advantage of the legal link is enlarged by adjusting the coding strategy according to the channel quality of the legal link through the feedback of the legal receiver Bob, so that when the channel condition is poor, namely the SNR is low, the gain obtained by adjusting the coding structure is not large, and the interception probability is relatively high. With the increase of SNR, the advantages of the invention begin to play, and the interception probability is reduced to a certain extent; when the SNR is increased to a certain degree, the optimization gain of the channel quality of a legal user is not large relative to the quality of the channel, the anti-eavesdropping effectiveness is deteriorated to a certain extent, and the interception probability is increased again. However, the interception probability is generally low and the anti-interception performance is better, as shown in fig. 2, the interception probability is first decreased and then increased with the increase of SNR.
For the QoS violation probability, when the SNR is extremely low, the delay violation probability is extremely high, and the QoS violation probability is larger; as the SNR increases, the probability of delay violation decreases and the present invention advantageously provides that the probability of information interception decreases, so the QoS violation probability decreases. When the SNR continues to increase, the delay violation probability of the legitimate receiver Bob is low and remains substantially unchanged due to good channel conditions, and the information interception probability increases and the QoS violation probability increases due to the reduced advantages of the present invention, as shown in fig. 3, the QoS violation probability first decreases rapidly and then increases with increasing SNR.
Fig. 4 and 5 show the applicability of the present invention to the anti-eavesdropping performance in multimedia applications, and referring to fig. 6a, 6b, and 6c, the video recovery quality of the legal receiver Bob is better, and although there is also local distortion, the pixels in the important area can be recovered well without affecting the subjective feeling; and the recovery video of the eavesdropper Eve has a large amount of mosaics, so that the video content is difficult to understand, and the applicability of the invention to multimedia transmission is fully shown.
Claims (2)
1. An anti-eavesdrop transmission method based on fountain codes in multimedia communication is characterized by comprising the following steps:
1) dividing a source file to be sent into N source data packets by a legal sender Alice;
2) the legal sender Alice carries out importance sequencing on each source data packet based on service characteristics, wherein each source data packet is divided into three types of type-I, type-II and type-III in a decreasing mode according to the importance degree, the channel quality is divided into three channel quality intervals from good to bad, the channel quality is determined by the module value of a channel characteristic coefficient h, and the ratio of the probability of | h | belonging to the three channel quality intervals is equal to the ratio of the data quantity of the three types of source data packets;
3) the legal sender Alice utilizes the mark of the received source data packet fed back by the legal receiver Bob, and then dynamically adjusts the fountain coding structure according to the importance of the source data packet to be sent and the current channel information to obtain a coding packet tnThen encode the packet tnSending the data to a legal receiver Bob;
4) the legal receiver Bob decodes the received coded packet to obtain a source packet, and then the mark of the source packet is fed back to the legal transmitter Alice;
in step 3), when | h tint>Th1When it is, then there are
Wherein sk1mIndicates the type-I source packet, sk1, that was last solvednRepresenting a source packet randomly selected from type-I source packets which are not solved;
when Th is1>|h|≥Th2When it is, then there are
Wherein sk2mtype-II source packets representing the most recent solution, sk2nRepresents a source packet randomly selected from type-II source packets that have not yet been solved, Σ sk1iThe method comprises the steps that XOR is carried out on parts randomly selected from type-I source data packets which are already solved;
when | h |<Th2If so, not sending the coded packet;
and when any source data packet is sent, the delay threshold is not reached yet, and the source data packet is not sent, the step 2) is carried out.
2. The method as claimed in claim 1, wherein for the multimedia service, each frame of the video is divided into a series of still images, each still image is regarded as a source file, and the still images are divided into N division maps with the same size, i.e. N source packets s1,s2…skFor the N source packets s1,s2…skThe specific operations for classification are:
11) calculate the mean significance of each segmentation map
Wherein S isiThe significance value of each pixel point in the segmentation graph is represented, and l represents the number of pixel points contained in each pixel block;
12) obtaining a binary image by edge detection, and calculating the amount of edge information contained in the divided region
SjRepresenting the value of each pixel point in the binary image;
13) calculating importance score S of each source data packetp，
Wherein S ispThe larger the size, the more important the source packet is.
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