Dual-encrypted time-domain hybrid PAM encoding method, decoding method and system

Abstract

The application discloses a dual-encryption time-domain hybrid PAM encoding method, decoding method and system, relates to the field of optical communication, and the encoding method comprises the following steps: in a sending end, converting a bit stream to be sent into pulse amplitude modulation (PAM) signals of two modulation formats according to a preset proportion, and then mixing the PAM signals into a TDHP signal; performing phase modulation encryption on the TDHP signal stream according to a key; and after digital-to-analog conversion of the TDHP signal after the phase modulation, converting the TDHP signal into signal light through an optical source and emitting the signal light. The application realizes dual encryption while not affecting other performances by using different encoding PAM signal proportions and keys, and the encryption method is simple and flexible; different proportions make the transmission rate variable, and the application can be used in free space optical transmission and short-distance optical interconnection scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication, in particular to a double-encrypted time-domain hybrid PAM encoding method, decoding method and system. BACKGROUND

[0002] Free space optical communication (FSO) as one of the sixth generation wireless communication standards has been widely concerned for its advantage of being able to transmit large capacity. But the FSO communication in the visible light band in free space is difficult to avoid the perception and eavesdropping of the third party, so it needs higher security compared with wired communication. Quantum key distribution (QKD) technology is usually used for high-security FSO communication between two points, and a secret key is securely shared between the two points through QKD. But for high-speed transmission and power supply difficult terminal communication, a simpler algorithm is needed to avoid excessive encryption and decryption calculation. SUMMARY

[0003] The present application provides a double-encrypted time-domain hybrid PAM encoding method, decoding method and system, which is simple in algorithm and small in encryption and decryption calculation.

[0004] In a first aspect, the present application provides a double-encrypted time-domain hybrid PAM encoding method, which comprises:

[0005] At the sending end, the bit stream to be sent is converted into two kinds of pulse amplitude modulation PAM signals of modulation format according to a preset proportion, and then mixed into a TDHP signal;

[0006] The TDHP signal stream is phase-modulated and encrypted according to a key;

[0007] After the phase-modulated TDHP signal is converted into a digital signal, it is converted into signal light by an optical source and emitted.

[0008] In the present embodiment, at the sending end, two kinds of pulse amplitude modulation PAM signals are mixed into a TDHP signal, and the TDHP signal stream is phase-modulated and encrypted according to a key. The proportion of different encoding PAM signals and the key realize double encryption without affecting other performances, and the encryption method is simple and flexible. Different proportions make the transmission rate variable, which can be used in free space optical transmission and short-distance optical interconnection scenarios.

[0009] In combination with the first aspect, in an implementation mode, the TDHP signal stream is phase-modulated and encrypted according to a key, which comprises:

[0010] When the encryption key bit is 1, the polarity of the data symbol is reversed; when the encryption key bit is 0, the polarity of the data symbol remains unchanged.

[0011] Or, when the encryption key bit is 1, the polarity of the data symbol remains unchanged; when the encryption key bit is 0, the polarity of the data symbol is reversed.

[0012] In this embodiment, phase inversion encryption is performed according to the bit of the key, and the encryption is more simple and flexible.

[0013] In combination with the first aspect, in an implementation, the preset ratio is an integer multiple.

[0014] In this embodiment, the preset ratio can be set according to different situations, so that the transmission rate is variable and the use scenarios are extensive.

[0015] In combination with the first aspect, in an implementation, the light source of the signal light is an LED light source or an LD light source, and when the light source is an LD light source, the TDHP signal after digital-to-analog conversion further includes:

[0016] The TDHP signal is added with a direct current bias to generate a TDHP signal with a direct current bias, and then converted into signal light by a light source and emitted.

[0017] In this embodiment, the direct current bias is added to facilitate positive amplitude modulation, and to ensure that the symbol with the lowest amplitude corresponds to a level of 0, thereby generating a TDHP signal with a direct current bias.

[0018] In the second aspect, the embodiments of the present application also provide a decoding method of the time-domain hybrid PAM encoding method based on the double encryption of the first aspect, and the decoding method includes:

[0019] At the receiving end, the signal light is converted into an electrical signal, and after filtering out the direct current component, a symmetrical TDHP signal is formed;

[0020] After the TDHP signal is analog-to-digital converted, time-domain equalization and frequency-domain equalization are performed, and decryption is performed according to the same rules and keys as the sending end;

[0021] According to the preset ratio, the symbol stream is divided, and different modulation format symbols are mapped to a bit stream.

[0022] In this embodiment, at the receiving end, decryption is performed according to the same rules and keys as the sending end, and then the symbol stream is divided according to the same preset ratio as the sending end, so that correct decoding is achieved.

[0023] In combination with the second aspect, in an implementation, the sending end performs phase modulation encryption on the TDHP signal stream according to a key, including:

[0024] When the encryption key bit is 1, the polarity of the data symbol is reversed; when the encryption key bit is 0, the polarity of the data symbol remains unchanged;

[0025] Or, when the encryption key bit is 1, the polarity of the data symbol remains unchanged; when the encryption key bit is 0, the polarity of the data symbol is reversed.

[0026] The receiving end decrypts according to the same rules and keys as the sending end, including:

[0027] According to the bit of the key, the polarity of the data symbol is shifted and flipped.

[0028] In a third aspect, the embodiments of the present application also provide an encoding system of the time-domain hybrid PAM encoding method based on the double encryption of the first aspect, and the encoding system comprises:

[0029] A light source is configured to provide an optical carrier;

[0030] A symbol mapping module is configured to convert a bit stream to be sent into pulse amplitude modulation (PAM) signals of two modulation formats according to a preset ratio, and then mix the PAM signals into a TDHP signal.

[0031] A phase encoding module is configured to perform phase modulation encryption on the TDHP signal stream according to a key.

[0032] A digital-to-analog conversion module is configured to perform digital-to-analog conversion on the TDHP signal after phase modulation, and convert the TDHP signal into signal light through the light source.

[0033] In combination with the third aspect, in an embodiment, the light source is an LED light source or an LD light source, and when the light source is an LD light source, the encoding system further comprises:

[0034] A bias module is configured to add a direct current bias to the TDHP signal after digital-to-analog conversion, to generate a direct current biased TDHP signal.

[0035] In a fourth aspect, the embodiments of the present application also provide a decoding system based on the decoding method of the second aspect, and the decoding system comprises:

[0036] A detector is configured to detect signal light emitted by the sending end and convert the signal light into an electrical signal, and then filter out a direct current component to form a symmetrical TDHP signal.

[0037] An analog-to-digital conversion module is configured to perform analog-to-digital conversion on the TDHP signal.

[0038] A time-domain equalization module is configured to perform time-domain equalization on the TDHP signal after analog-to-digital conversion.

[0039] A frequency-domain equalization module is configured to perform frequency-domain equalization on the TDHP signal after time-domain equalization.

[0040] a decoding module configured to decrypt the frequency domain equalized TDHP signal according to the same rule and key as the sending end;

[0041] a decision module configured to divide the symbol stream according to a preset proportion and map symbols of different modulation formats to a bit stream.

[0042] In combination with the fourth aspect, in an implementation, the detector is a PD detector or an APD detector.

[0043] The technical scheme provided by the embodiments of the present application has the following beneficial effects:

[0044] At the sending end, pulse amplitude modulation (PAM) signals of two modulation formats are mixed into a TDHP signal, the TDHP signal stream is phase-modulated and encrypted according to a key, and the proportion of different encoded PAM signals formed by the two modulation formats can be adjusted according to requirements. The proportion of different encoded PAM signals and the key achieve double encryption while not affecting other performances. The encryption method is simple and flexible, the different proportion makes the transmission rate variable, and the method can be used in free space optical transmission and short-distance optical interconnection scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 a flowchart of a double-encrypted time domain hybrid PAM encoding method according to an embodiment of the present application;

[0046] Figure 2 a flowchart of a double-encrypted time domain hybrid PAM decoding method according to an embodiment of the present application;

[0047] Figure 3 a process diagram of double-encrypted time domain hybrid PAM encoding and decoding according to an embodiment of the present application;

[0048] Figure 4 a schematic diagram of a double-encrypted time domain hybrid PAM encoding system according to an embodiment of the present application;

[0049] Figure 5 a schematic diagram of a double-encrypted time domain hybrid PAM decoding system according to an embodiment of the present application.

[0050] REFERENCE NUMERALS:

[0051] 1, sending end; 11, light source; 12, symbol mapping module; 13, phase encoding module; 14, digital-to-analog conversion module; 15, bias module;

[0052] 2, receiving end; 21, detector; 22, analog-to-digital conversion module; 23, time domain equalization module; 24, frequency domain equalization module; 25, decoding module; 26, decision module. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0054] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0055] In a first aspect, an embodiment of the present application provides a double-encrypted time-domain hybrid PAM encoding method.

[0056] In one embodiment, referring to Figure 1 , Figure 1 This is a flowchart of the time domain hybrid PAM encoding method for double encryption of this application. Figure 1 As shown, the encoding method includes:

[0057] S101: At the transmitting end, a bit stream to be transmitted is converted into pulse amplitude modulation (PAM) signals of two modulation formats according to a preset ratio, and then mixed into a TDHP signal, wherein the preset ratio is an integer multiple ratio.

[0058] S102: Perform phase modulation encryption on the TDHP signal stream according to the key.

[0059] In this embodiment, phase-flip encryption is performed based on the bits of the encryption key. When the encryption key bit is 1, the polarity of the data symbol is reversed; when the encryption key bit is 0, the polarity of the data symbol remains unchanged. In other embodiments, the polarity of the data symbol may remain unchanged when the encryption key bit is 1, and reversed when the encryption key bit is 0.

[0060] S103: Performing digital-to-analog conversion on the phase-modulated TDHP signal, that is, converting the digital signal into an analog signal, and then converting it into signal light through a light source and emitting it.

[0061] In this embodiment, Figure 2 As shown, the ratio of different coded PAM signals formed by two modulation formats can be adjusted according to needs. The ratio of different coded PAM signals and the key realize double encryption. The encryption method is simple and flexible, and the amount of calculation is extremely small compared to QKD encryption. Different ratios make the net rate adjustable at a fixed symbol rate, which is suitable for scenarios such as free space optical transmission and short-distance optical interconnection.

[0062] Further, in an embodiment, the light source used in S103 can be a LED (Light Emitting Diode) light source or a LD (Laser diode) light source. When the light source is a LD light source, in the step S103, after the TDHP signal is converted from digital to analog, the TDHP signal is further added with a direct current bias to facilitate the positive amplitude modulation, to ensure that the symbol with the lowest amplitude corresponds to a level of 0, and the polarity of the data symbol remains unchanged, and the TDHP signal after the direct current bias is converted into a signal light by the light source and emitted. When the light source is a LED light source, the step of adding the direct current bias can be omitted at the sending end.

[0063] In a second aspect, based on the above-mentioned embodiment of the encoding method, an embodiment of a decoding method of a double-encrypted time-domain hybrid PAM encoding method is provided. As shown in Figure 2 The decoding method includes the following steps:

[0064] S201: At the receiving end, the received optical signal is converted into an electrical signal through photoelectric conversion, and after the direct current component is filtered out, a symmetrical TDHP signal is formed.

[0065] S202: After the TDHP signal is converted from analog to digital, the analog signal is converted into a digital signal, and then the converted digital signal is subjected to time-domain equalization and frequency-domain equalization, and then decrypted according to the same rules and keys as the sending end.

[0066] Specifically, since the sending end performs phase shift according to the bit of the key, the decryption includes flipping the polarity of the data symbol according to the bit of the key.

[0067] S203: The symbol stream is divided according to the preset proportion of the sending end, and the symbols of different modulation formats are mapped to the bit stream.

[0068] Time-domain hybrid pulse amplitude modulation (TDHP) can be transmitted based on a single carrier method and the communication capacity is variable, which is achieved by adjusting the proportion of different spectrum efficiency pulse amplitude modulation (PAM) signals. By adjusting the proportion of different encoded PAM signals, data can be encrypted at a fixed symbol rate, and only a fixed equalizer needs to be designed to compensate for the specified frequency characteristics of high-frequency devices. It has been found in existing research that a simple phase shift method for symbol-level encryption is also effective, especially for brute-force key interception. The proportion of different encoded PAM signals and the phase shift key can simultaneously act on the transmitted symbol sequence to achieve encryption without affecting other performance, and therefore this simple encryption method provides the feasibility of implementing simple and flexible encryption in addition to QKD.

[0069] AsFigure 3 As shown, an embodiment of the process of double-encrypted time-domain hybrid PAM encoding and decoding is provided. In this embodiment, at the transmitting end, the two modulation formats are PAM4 and PAM2, respectively. The differently coded PAM signals formed by the two modulation formats are filled with symbols of different formats according to a preset ratio and represented by black dots and white dots. After the phase is flipped according to the key, a DC bias is added to ensure that the level corresponding to the symbol with the lowest amplitude is 0. At the receiving end, a symmetrical TDHP signal is formed after filtering out the DC component, and then the phase is flipped according to the key. Then, the symbols of different formats are restored according to the ratio preset by the transmitting end to complete the decoding process.

[0070] In summary, in the aforementioned encoding and decoding methods, the preset time-domain mixing ratio of the differently coded PAM signals can be set to suit specific needs. The encoding and decoding key lengths are adjustable, and the preset ratio and key content can be mutually agreed upon between the transmitter and receiver. This dual encryption method is simple and flexible, with a variable net transmission rate, and can be used in scenarios such as free-space optical transmission and short-haul optical interconnects.

[0071] In the third aspect, based on the above-mentioned double-encrypted time-domain hybrid PAM coding method embodiment, an embodiment of a coding system is provided. Figure 4 As shown, in this embodiment, the encoding system is arranged at the transmitting end 1, and includes a light source 11, a symbol mapping module 12, a phase encoding module 13 and a digital-to-analog conversion module.

[0072] The light source 11 is used to provide an optical carrier.

[0073] The symbol mapping module 12 is used to convert the bit stream to be transmitted into two modulation formats of pulse amplitude modulation (PAM) signals according to a preset ratio, and then mix them into a TDHP signal. The preset ratio is an integer multiple.

[0074] The phase encoding module 13 is used to perform phase modulation encryption on the TDHP signal stream according to a key.

[0075] Specifically, the phase encoding module 13 performs phase modulation based on the encryption key bits. When the encryption key bit is 1, the polarity of the data symbol is reversed; when the encryption key bit is 0, the polarity of the data symbol remains unchanged. Alternatively, when the encryption key bit is 1, the polarity of the data symbol remains unchanged; when the encryption key bit is 0, the polarity of the data symbol is reversed.

[0076] The digital-to-analog conversion module 14 is used to perform digital-to-analog conversion on the phase-modulated TDHP signal, convert the digital signal into an analog signal, and then convert it into a signal light through the light source 11 and emit it.

[0077] The light source 11 can be an LED light source or an LD light source. Further, in an embodiment, when the light source 11 is an LD light source, the coding system further comprises a biasing module 15 configured to add a direct current bias to the TDHP signal after digital-to-analog conversion to generate a direct current biased TDHP signal. In the embodiment, the biasing module 15 is implemented by a direct current bias voltage and a Bias-T (T-type biasing device), and the analog signal after digital-to-analog conversion passes through the direct current bias voltage and the Bias-T to add a direct current bias to the TDHP signal to facilitate positive amplitude modulation, ensure that the symbol corresponding to the lowest amplitude has a level of 0, and generate a direct current biased TDHP signal.

[0078] In a fourth aspect, based on the above-mentioned dual encryption time domain hybrid PAM decoding method embodiment, an embodiment of a decoding system is provided. As shown in Figure 5 The decoding system in the embodiment is arranged at the receiving end 2 and comprises a detector 21, an analog-to-digital conversion module 22, a time domain equalization module 23, a frequency domain equalization module 24, a decoding module 25, and a decision module 26.

[0079] The detector 21 is configured to detect the signal light emitted by the sending end 1 and convert the signal light into an electrical signal through photoelectric conversion, and form a symmetrical TDHP signal after filtering out the direct current component.

[0080] The analog-to-digital conversion module 22 is configured to perform analog-to-digital conversion on the TDHP signal to convert the analog signal into a digital signal.

[0081] The time domain equalization module 23 is configured to perform time domain equalization on the TDHP signal after analog-to-digital conversion by the analog-to-digital conversion module 22.

[0082] The frequency domain equalization module 24 is configured to perform frequency domain equalization on the TDHP signal after time domain equalization by the time domain equalization module 23.

[0083] The decoding module 25 is configured to decrypt the TDHP signal after frequency domain equalization by the frequency domain equalization module 24 according to the same rules and keys as the sending end 1. Specifically, the decoding module 25 flips the polarity of the data symbol according to the bit position phase shift of the key.

[0084] The decision module 26 is configured to divide the symbol stream after decryption by the decoding module 25 according to a preset proportion and map the symbols of different modulation formats to a bit stream.

[0085] Further, the detector 21 can be a PD detector or an APD detector. The working wavelength can also be distributed from visible light to infrared band according to different applications.

[0086] The functions of the modules of the encoding system and the decoding system correspond to the steps in the encoding method and the decoding method, and the functions and implementation processes will not be described here.

[0087] Through the above-mentioned embodiments of the encoding system and the decoding system, by changing the different preset proportions, the proportions of different encoding symbols in the time domain mixed PAM signal are dynamically adjusted, the symbol sequence to be sent is phase flipped and encrypted according to the key, the double encryption is realized without affecting other performances, the feasibility of realizing simple and flexible encryption outside QKD is provided, and the encryption calculation amount is extremely small compared with QKD, and the net rate is adjustable under the fixed symbol rate.

[0088] It should be noted that the sequence numbers of the embodiments of the present application described above are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0089] The terms "comprising" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device. The terms "first", "second" and "third" and the like descriptions are used to distinguish different objects, and do not represent the order or limit the types of "first", "second" and "third".

[0090] In the description of the embodiments of the present application, "exemplary", "for example" or "for instance" is used to represent as an example, illustration or description. Any embodiment or design scheme described as "exemplary", "for example" or "for instance" in the embodiments of the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. On the contrary, the words "exemplary", "for example" or "for instance" are intended to present the relevant concept in a specific way.

[0091] In the description of the embodiments of the present application, unless otherwise specified, " / " represents or, for example, A / B can represent A or B; "and / or" in the text only describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent: A exists alone, A and B exist together, and B exists alone, in addition, in the description of the embodiments of the present application, "multiple" means two or more than two.

[0092] In some of the processes described in this specification, the order of operations or steps can be modified. Specifically, the serial order of any two consecutive steps carried out according to the processes described in this specification can be changed so that these two steps can be carried out in parallel or simultaneously, or the order of these two steps can be reversed.

[0093] Those skilled in the art can clearly understand the above-mentioned embodiment method from the description of the above embodiments, which can be realized by software and a necessary general hardware platform, of course, it can also be realized by hardware, but in many cases, the former is a better embodiment. Based on this understanding, the technical solutions of the present application can be embodied in the form of a software product, which is stored in a storage medium (such as a ROM / RAM, a magnetic disk, or an optical disc) and includes a plurality of instructions for causing a terminal device to execute the methods described in the various embodiments of the present application.

[0094] The above is only a preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A dual-encrypted time-domain hybrid PAM encoding method, characterized by, The encoding method comprises: At the sending end, a bit stream to be sent is converted into pulse amplitude modulation (PAM) signals of two modulation formats according to a preset ratio, and then mixed into a TDHP signal; The TDHP signal stream is phase-modulated and encrypted according to a key; After digital-to-analog conversion of the phase-modulated TDHP signal, the signal is converted into signal light by an optical source and emitted.

2. The dual-encrypted time-domain hybrid PAM encoding method of claim 1, wherein, The phase-modulated and encrypted TDHP signal stream comprises: When the encryption key bit is 1, the polarity of the data symbol is reversed; when the encryption key bit is 0, the polarity of the data symbol remains unchanged; Or, when the encryption key bit is 1, the polarity of the data symbol remains unchanged; when the encryption key bit is 0, the polarity of the data symbol is reversed.

3. The dual-encrypted time-domain hybrid PAM encoding method of claim 1, wherein, The preset ratio is an integer multiple ratio.

4. The dual-encrypted time-domain hybrid PAM encoding method of claim 1, wherein, The optical source of the signal light is an LED optical source or an LD optical source, and when the optical source is an LD optical source, the TDHP signal after digital-to-analog conversion further comprises: A direct current bias is added to the TDHP signal to generate a direct current biased TDHP signal, which is then converted into signal light by an optical source and emitted.

5. A decoding method based on the double-encrypted time-domain hybrid PAM encoding method of claim 1, characterized in that, The decoding method comprises: At the receiving end, the signal light is converted into an electrical signal, and after filtering out the direct current component, a symmetrical TDHP signal is formed; After analog-to-digital conversion of the TDHP signal, time domain equalization and frequency domain equalization are performed, and decryption is performed according to the same rules and keys as the sending end; The symbol stream is divided according to the preset ratio, and symbols of different modulation formats are mapped to a bit stream.

6. The decoding method of claim 5, wherein, The sending end phase-modulates and encrypts the TDHP signal stream according to a key, comprising: When the encryption key bit is 1, the polarity of the data symbol is reversed; when the encryption key bit is 0, the polarity of the data symbol remains unchanged; Or, when the encryption key bit is 1, the polarity of the data symbol remains unchanged; when the encryption key bit is 0, the polarity of the data symbol is reversed. The receiving end decrypts according to the same rules and keys as the sending end, comprising: The polarity of the data symbol is flipped according to the bit of the key.

7. An encoding system based on the double-encrypted time-domain hybrid PAM encoding method of claim 1, characterized by, The encoding system comprises: An optical source for providing an optical carrier; A symbol mapping module for converting a bit stream to be sent into pulse amplitude modulation (PAM) signals of two modulation formats according to a preset ratio, and then mixing into a TDHP signal; A phase encoding module for phase-modulating and encrypting the TDHP signal stream according to a key; A digital-to-analog conversion module for digital-to-analog conversion of the phase-modulated TDHP signal, which is converted into signal light by an optical source and emitted.

8. The encoding system of claim 7, wherein, The optical source is an LED optical source or an LD optical source, and when the optical source is an LD optical source, the encoding system further comprises: A bias module for adding a direct current bias to the TDHP signal after digital-to-analog conversion to generate a direct current biased TDHP signal.

9. A decoding system based on the decoding method of claim 5, characterized in that, The decoding system comprises: A detector for detecting the signal light emitted by the sending end and converting it into an electrical signal, and after filtering out the direct current component, a symmetrical TDHP signal is formed; An analog-to-digital conversion module for analog-to-digital conversion of the TDHP signal; A time domain equalization module for time domain equalization of the TDHP signal after analog-to-digital conversion; A frequency domain equalization module for frequency domain equalization of the TDHP signal after time domain equalization; A decoding module is configured to decrypt the frequency domain equalized TDHP signal according to the same rule and key as the sending end. A decision module is configured to divide the symbol stream according to a preset proportion, and map symbols of different modulation formats to a bit stream.

10. The decoding system of claim 9, wherein, The detector is a PD detector or an APD detector.

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