阅读说明：本技术 一种基于混合索引的差分混沌相移键控通信方法及系统 (Differential chaotic phase shift keying communication method and system based on mixed index ) 是由 方毅 陶熠威 马焕 韩国军 于 2021-07-16 设计创作，主要内容包括：本发明提出一种基于混合索引的差分混沌相移键控通信方法及系统,解决了现有的差分混沌相移键控通信方案频谱效率和能量效率低下,并且传输数据速率慢的问题,所述方法包括基于混合索引的差分混沌相移键控发送信号调制方法及基于混合索引的差分混沌相移键控接收信号解调方法；其中,混合索引为混合索引比特,包括载波索引比特和载波数目索引比特,将载波索引比特和载波数目索引比特混合,调制发送信号,混合索引下的调制与解调配合,相较于单一的基于载波索引比特的差分混沌相移键控通信方式能量效率和频谱效率高,综合提升了能量效率、频谱效率及误码率性能。(The invention provides a differential chaotic phase shift keying communication method and system based on a mixed index, which solve the problems of low spectrum efficiency and energy efficiency and low transmission data rate of the existing differential chaotic phase shift keying communication scheme; the hybrid index is a hybrid index bit and comprises a carrier index bit and a carrier number index bit, the carrier index bit and the carrier number index bit are mixed, a signal is modulated and sent, modulation and demodulation under the hybrid index are matched, and compared with a single differential chaotic phase shift keying communication mode based on the carrier index bit, the hybrid index is high in energy efficiency and spectral efficiency, and the energy efficiency, the spectral efficiency and the error rate performance are comprehensively improved.)

1. A differential chaotic phase shift keying communication method based on mixed indexes is characterized by comprising the following steps: a differential chaotic phase shift keying transmission signal modulation method based on a mixed index and a differential chaotic phase shift keying receiving signal demodulation method based on the mixed index; the mixed index is a mixed index bit, and comprises a carrier index bit and a carrier number index bit, the carrier index bit and the carrier number index bit are mixed to modulate a transmission signal, and then the signal is demodulated based on the mixing of the carrier index bit and the carrier number index bit.

2. The hybrid index-based differential chaotic phase-shift keying communication method according to claim 1, wherein the hybrid index-based differential chaotic phase-shift keying transmission signal modulation method comprises the following processes:

s1, generating a chaotic signal c_xSetting N subcarriers f of different frequencies₀,f₁，…,f_NTo convert the chaotic signal c_xAs a reference signal, the reference signal is pulse shaped by f₀The sub-carrier of the frequency bears the reference signal after the pulse shaping and sends;

s2, the chaotic signal c generated in the step S1_xIndex selection and Hilbert transform are respectively carried out, wherein a first subcarrier activation chaotic signal c is obtained after Hilbert transform_yActivating the first subcarrier to generate chaotic signal c_yIndex selection is also performed;

s3, segmenting the initial information bit to obtain an index bit a_kAnd modulation bit b_kIndex bit a_kDetermining the selection of reference signal carrying information bits, index bit a_kActivating chaotic signal c acting on subcarrier subjected to index selection_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_k；

S4, chaotic signal c_kAnd modulation bit b_kChaotic modulation is carried out, the chaotic modulated signal is pulse shaped, and f is utilized respectively₁，…,f_NThe sub-carriers of the frequency carry the pulse-shaped signal and transmit.

3. The hybrid-index-based differential chaotic phase-shift keying communication method according to claim 2, wherein the hybrid-index-based differential chaotic phase-shift keying received signal demodulation method comprises the following processes:

setting a receiving signal of a sending signal after channel transmission as r (t), wherein t represents the time of the signal; for middle frequency f of r (t)₀，f₁，…,f_NIs separated to obtain f₀Signal r in a subcarrier of frequency₀(t) and f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t)；

SB. pairs f₀Signal r in a subcarrier of frequency₀(t) performing Hilbert transform to obtain a signal

SC. mixing f₀Signal r in a subcarrier of frequency₀(t) are each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing correlation to obtain a first correlation variable I_jJ 1,2, …, N, will signalAre each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing a correlation to obtain a second correlation variablej＝1,2，…，N；

SD. relating the first variable I_jWith a second dependent variableRespectively subtracting absolute values to obtain a final decision variable xi_j；

SE. based on the final decision variable ξ_jFor index bit a_kRecovering;

SF. according to index bit a_kJudging chaotic signal adopted by activation of subcarrier, and further solving demodulation modulation bit b_kBased on the decision metric, demodulating the modulation bit b_k。

4. The differential chaotic phase-shift keying communication method based on hybrid index according to claim 3,

chaotic signal c generated in step S1_xObtaining a first subcarrier activation chaotic signal c after performing Hilbert transform_yChaotic signal c_xAnd a first subcarrier activation chaotic signal c_ySatisfies the following relationship:

wherein, beta represents the number of sampling points of the signal; i represents the ith sample point order;

let t denote the signal time, index bit a_kActivating chaotic signal c acting on subcarrier subjected to index selection_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_kAt signal time t, the following are satisfied:

wherein, c_x(t) the subcarrier activates the chaotic signal at the time t; c. C_y(t) the first subcarrier activates the chaotic signal at the time t; c. C_kAnd (t) represents a chaotic signal used by the subcarrier at the time t and carrying modulation bits.

The chaotic signal c_kAnd modulation bit b_kPerforming chaotic modulation, wherein at the moment t, the chaotic modulated signals meet the following conditions:

wherein, c_kAnd (t) represents a chaotic signal used by the subcarrier at the time t and carrying modulation bits.

5. The differential chaotic PSK communication method based on hybrid index as claimed in claim 4, wherein t is the signal time, and the signal time f is the signal time t₀The pulse shaped signal carried by the subcarrier of frequencies is represented as:

s₁(t)＝c_x(t)cos(2πf₀)

wherein, c_x(t) the subcarrier activates the chaotic signal at the time t; f. of₀Representing the frequency, s, of the subcarrier₁(t) represents the t signal time f₀A pulse shaped signal carried by a subcarrier of the frequency;

at time t of signal, f₁，…,f_NThe pulse shaped signal carried by the subcarrier of frequencies is represented as:

wherein s is₂(t) represents f₁，…,f_NA pulse shaped signal carried by a subcarrier of the frequency; n represents f₁，…,f_NThe number of subcarriers of a frequency; c. C_k(t) represents a chaotic signal used by a subcarrier at the time t and carrying modulation bits;

the differential chaotic phase shift keying transmission signal based on the mixed index is represented as follows:

where s (t) denotes a differential chaotic phase shift keying transmission signal based on a mixing index.

6. The differential chaotic phase-shift keying communication method based on mixed index as claimed in claim 5, wherein when the chaotic signal used by the jth sub-carrier is c_xIf so, the first correlation variable I in step SC_jThe expression of (a) is:

second related variableThe expression of (a) is:

wherein, the terms A, B, C and D are noise interference terms; j represents the way of the subcarrier; beta denotes a spreading factor, n₀Is additive white gaussian noise of the reference signal,is n₀Hilbert transform of (n)_jAdditive white Gaussian noise of the jth path of sub-carrier;

in the step SD, the first relevant variable and the second relevant variable are subtracted after absolute values are respectively taken to obtain a final decision variable xi_jThe expression of (a) is:

neglecting noise interference, decision variable xi_jExpressed as:

i.e. xi_jGreater than 0; when the chaotic signal used by the jth sub-carrier is c_yTime, decision variable xi_jExpressed as:

based on the final decision variable ξ_jFor index bit a_kThe formula for recovery is:

7. the differential chaotic PSK communication method based on hybrid index as claimed in claim 6, wherein the bit a is the index bit in step SF_kThe process of judging the chaotic signal adopted by the activation of the subcarrier is as follows:

when index bit a_kWhen the value is 0, the chaotic signal used by the subcarrier at the time t and carrying modulation bits is c_y(t) the chaotic signal used for subcarrier activation is c_yDemodulating the modulated bit b_kThe decision metric of (a) is expressed as:

when index bit a_kWhen the value is 1, the chaotic signal used by the subcarrier at the time t and carrying modulation bits is c_x(t) the chaotic signal used for subcarrier activation is c_x(ii) a Demodulating modulated bits b_kThe decision metric of (a) is expressed as:

modulation bit b_kThe demodulation formula is:

8. a hybrid index-based differential chaotic phase shift keying communication system, characterized in that the system comprises a transmitter for implementing the hybrid index-based differential chaotic phase shift keying transmission signal modulation method of claim 1 and a receiver for implementing the hybrid index-based differential chaotic phase shift keying transmission signal modulation method of claim 1.

9. The hybrid-index-based differential chaotic phase-shift keying communication system according to claim 8, wherein the transmitter comprises:

a chaotic signal generator for generating a chaotic signal c_x；

A first Hilbert transformer for the chaotic signal c_xPerforming Hilbert transform to obtain a first subcarrier activation chaotic signal c_y；

An index selector for selecting the chaotic signal c_xAnd a first subcarrier activation chaotic signal c_yCarrying out index selection;

a bit divider for dividing the initial information bits to obtain index bits a_kAnd modulation bit b_k；

Index bit a_kInputting the signal into an index selector, acting on the chaos signal c of the activation of the sub-carrier selected by the index selector_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_k；

A chaotic modulator for modulating the chaotic signal c_kAnd modulation bit b_kPerforming chaotic modulation to obtain N chaotic modulation signals;

n +1 pulse shapers for pulse shaping N chaotic modulation signals and one chaotic signal c_xPerforming pulse shaping;

n +1 carrier multiplicationMethod using N f₁，…,f_NThe subcarriers of the frequency are respectively multiplied by N paths of pulse-shaped chaotic modulation signals; using an f₀Subcarrier of frequency and a chaotic signal c subjected to pulse shaping_xMultiplying;

an adder for aggregating the N +1 carrier multiplier correspondences f₀，f₁，…,f_NAnd transmitting the pulse-shaped signals carried by the subcarriers of the frequency.

10. The hybrid-index-based differential chaotic phase-shift keying (dpsk) communication system according to claim 9, wherein the receiver demodulates the signal transmitted from the transmitter, where r (t) is a signal indicating a time of the signal:

the receiver includes:

n +1 matched filters for separating the received signal into frequencies f₀，f₁，…,f_NTo obtain f₀Signal r in a subcarrier of frequency₀(t) and f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t)

A second Hilbert transformer for pair f₀Signal r in a subcarrier of frequency₀(t) performing Hilbert transform to obtain a signal

A first correlator for converting f₀Signal r in a subcarrier of frequency₀(t) are each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing correlation to obtain a first correlation variable I_j，j＝1,2，…，N；

A second correlator for correlating the signalAre each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing a correlation to obtain a second correlation variablej＝1,2，…，N；

A decision variable calculator for calculating a first correlation variable I_jWith a second dependent variableRespectively subtracting absolute values to obtain a final decision variable xi_j；

A threshold decision device for deciding the final decision variable xi_jFor index bit a_kRecovering to obtain index bit a_k；

A modulation bit demodulator based on the index bit a_kJudging chaotic signal adopted by activation of subcarrier, and further solving demodulation modulation bit b_kBased on the decision metric, demodulating the modulation bit b_k。

Technical Field

The invention relates to the technical field of chaotic communication, in particular to a differential chaotic phase shift keying communication method and system based on mixed indexes.

Background

At present, as various multimedia technologies are more and more commonly applied to life, the number of wireless users is sharply increased, and the shortage of available spectrum resources is caused, so that the spectrum resources are reasonably utilized and the frequency band utilization rate and the code element speed are very important under the conditions that the current frequency band resources are increasingly tense and the requirement of people on the data transmission rate is higher and higher.

Because the chaotic signal has the characteristics of internal broadband, noise-like, long-term unpredictability, good initial value sensitivity and the like, the chaotic broadband communication system can be conveniently constructed, and has wide application prospect in the field of wireless communication. Due to low power consumption and low hardware complexity, the differential chaotic phase shift keying communication system becomes a candidate for wireless communication application, such as a wireless personal area network and a wireless sensor network.

In the traditional differential chaos phase shift keying communication system, the bit transmission time is divided into two time slots. The previous slot transmits a reference signal. The latter time slot transmits a reverse or a same-direction signal carrying information bits. The incoherent chaotic digital modulation technology adopts a Transmitted-Reference (T-R) mode to send all Reference signals and information-carrying signals to a receiving end, so that the problem of decision threshold drift in chaotic shift keying is solved, but half bit time is spent in the transmission mode to transmit the Reference signals without data signals, so that the transmission rate and the energy efficiency of a system are lower. In order to improve the system performance, the index modulation technique proposed recently arouses great interest of researchers, the index modulation transfers information by selecting different index serial numbers, for example, 10/9/2020, chinese patent of invention (publication No. CN111756664A) discloses a short reference carrier index differential chaos shift keying modulation and demodulation method and system, and introduces a repeat signal on the basis of short reference by combining CI-DCSK and short reference signal, so as to reduce the noise received by the system on the basis of improving the system band transmission rate, but the system fixes the number of activated carriers and keeps silent subcarriers, thereby causing the waste of spectrum resources. In addition, there is also a communication system of orthogonal frequency division multiplexing based on the index of the number of carriers, for example, but since the number of activated subcarriers is not fixed, that is, the number of activated subcarriers is unknown to be determined, when the determination of the number of activated subcarriers is wrong, information bits are lost or redundant.

Disclosure of Invention

In order to solve the problems of low spectral efficiency and energy efficiency and low transmission data rate of the existing differential chaotic phase shift keying communication system, the invention provides a differential chaotic phase shift keying communication method and system based on mixed index, which improve the energy efficiency, the spectral efficiency and the data transmission rate and have better bit error rate.

In order to achieve the technical effects, the technical scheme of the invention is as follows:

a differential chaotic phase shift keying communication method based on mixed indexes comprises a differential chaotic phase shift keying sending signal modulation method based on mixed indexes and a differential chaotic phase shift keying receiving signal demodulation method based on mixed indexes; the mixed index is a mixed index bit, and comprises a carrier index bit and a carrier number index bit, the carrier index bit and the carrier number index bit are mixed to modulate a transmission signal, and then the signal is demodulated based on the mixing of the carrier index bit and the carrier number index bit.

Preferably, the process of the differential chaotic phase shift keying transmission signal modulation method based on the mixed index is as follows:

s1, generating a chaotic signal c_xSetting N subcarriers f of different frequencies₀,f₁，…,f_NTo convert the chaotic signal c_xAs a reference signal, the reference signal is pulse shaped by f₀The sub-carrier of the frequency bears the reference signal after the pulse shaping and sends;

s2, the chaotic signal c generated in the step S1_xIndex selection and Hilbert transform are respectively carried out, wherein a first subcarrier activation chaotic signal c is obtained after Hilbert transform_yActivating the first subcarrier to generate chaotic signal c_yIndex selection is also performed;

s3, segmenting the initial information bit to obtain an index bit a_kAnd modulation bit b_kIndex bit a_kDetermining the selection of reference signal carrying information bits, index bit a_kActivating chaotic signal c acting on subcarrier subjected to index selection_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_k；

S4, chaotic signal c_kAnd modulation bit b_kChaotic modulation is carried out, the chaotic modulated signal is pulse shaped, and f is utilized respectively₁，…,f_NThe sub-carriers of the frequency carry the pulse-shaped signal and transmit.

Preferably, the process of the differential chaotic phase shift keying received signal demodulation method based on the mixed index is as follows:

setting a receiving signal of a sending signal after channel transmission as r (t), wherein t represents the time of the signal; for middle frequency f of r (t)₀，f₁，…,f_NIs separated to obtain f₀Signal r in a subcarrier of frequency₀(t) and f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t)；

SB. pairs f₀Signal r in a subcarrier of frequency₀(t) performing Hilbert transform to obtain a signal

SC. mixing f₀Signal r in a subcarrier of frequency₀(t) are each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing correlation to obtain a first correlation variable I_jJ 1,2, …, N, will signalAre each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing a correlation to obtain a second correlationVariables of

SD. relating the first variable I_jWith a second dependent variableRespectively subtracting absolute values to obtain a final decision variable xi_j；

SE. based on the final decision variable ξ_jFor index bit a_kRecovering;

SF. according to index bit a_kJudging chaotic signal adopted by activation of subcarrier, and further solving demodulation modulation bit b_kBased on the decision metric, demodulating the modulation bit b_k。

Preferably, the chaotic signal c generated in step S1_xObtaining a first subcarrier activation chaotic signal c after performing Hilbert transform_yChaotic signal c_xAnd a first subcarrier activation chaotic signal c_ySatisfies the following relationship:

wherein, beta represents the number of sampling points of the signal; i represents the ith sample point order;

let t denote the signal time, index bit a_kActivating chaotic signal c acting on subcarrier subjected to index selection_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_kAt signal time t, the following are satisfied:

wherein, c_x(t) the subcarrier activates the chaotic signal at the time t; c. C_y(t) the first subcarrier activates the chaotic signal at the time t; c. C_kAnd (t) represents a chaotic signal used by the subcarrier at the time t and carrying modulation bits.

The chaotic signal c_kAnd modulation bit b_kPerforming chaotic modulation, wherein at the moment t, the chaotic modulated signals meet the following conditions:

wherein, c_kAnd (t) represents a chaotic signal used by the subcarrier at the time t and carrying modulation bits.

Preferably, let t denote the signal instant at which the signal instant f₀The pulse shaped signal carried by the subcarrier of frequencies is represented as:

s₁(t)＝c_x(t)cos(2πf₀)

wherein, c_x(t) the subcarrier activates the chaotic signal at the time t; f. of₀Representing the frequency, s, of the subcarrier₁(t) represents the t signal time f₀A pulse shaped signal carried by a subcarrier of the frequency;

at time t of signal, f₁，…,f_NThe pulse shaped signal carried by the subcarrier of frequencies is represented as:

wherein s is₂(t) represents f₁，…,f_NA pulse shaped signal carried by a subcarrier of the frequency; n represents f₁，…,f_NThe number of subcarriers of a frequency; c. C_k(t) represents a chaotic signal used by a subcarrier at the time t and carrying modulation bits;

the differential chaotic phase shift keying transmission signal based on the mixed index is represented as follows:

where s (t) denotes a differential chaotic phase shift keying transmission signal based on a mixing index.

Preferably, when the chaotic signal used by the jth subcarrier is c_xIf so, the first correlation variable I in step SC_jThe expression of (a) is:

second related variableThe expression of (a) is:

wherein, the terms A, B, C and D are noise interference terms; j represents the way of the subcarrier; beta denotes a spreading factor, n₀Is additive white gaussian noise of the reference signal,is n₀Hilbert transform of (n)_jAdditive white Gaussian noise of the jth path of sub-carrier;

in the step SD, the first relevant variable and the second relevant variable are subtracted after absolute values are respectively taken to obtain a final decision variable xi_jThe expression of (a) is:

neglecting noise interference, decision variable xi_jExpressed as:

i.e. xi_jGreater than 0; when the chaotic signal used by the jth sub-carrier is c_yTime, decision variable xi_jExpressed as:

based on the final decision variable ξ_jFor index bit a_kThe formula for recovery is:

preferably, step SF is performed according to index bit a_kThe process of judging the chaotic signal adopted by the activation of the subcarrier is as follows:

when index bit a_kWhen the value is 0, the chaotic signal used by the subcarrier at the time t and carrying modulation bits is c_y(t) the chaotic signal used for subcarrier activation is c_yDemodulating the modulated bit b_kThe decision metric of (a) is expressed as:

when index bit a_kWhen the value is 1, the chaotic signal used by the subcarrier at the time t and carrying modulation bits is c_x(t) the chaotic signal used for subcarrier activation is c_x(ii) a Demodulating modulated bits b_kThe decision metric of (a) is expressed as:

modulation bit b_kThe demodulation formula is:

the invention also provides a differential chaotic phase shift monitoring communication system based on the mixed index, which comprises a transmitter for realizing the differential chaotic phase shift keying signal sending modulation method based on the mixed index and a receiver for realizing the differential chaotic phase shift keying signal sending modulation method based on the mixed index.

Preferably, the transmitter includes:

a chaotic signal generator for generating a chaotic signal c_x；

A first Hilbert transformer for the chaotic signal c_xPerforming Hilbert transform to obtain a first subcarrier activation chaotic signal c_y；

An index selector for selecting the chaotic signal c_xAnd a first subcarrier activation chaotic signal c_yCarrying out index selection;

a bit divider for dividing the initial information bits to obtain index bits a_kAnd modulation bit b_k；

Index bit a_kInputting the signal into an index selector, acting on the chaos signal c of the activation of the sub-carrier selected by the index selector_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_k；

A chaotic modulator for modulating the chaotic signal c_kAnd modulation bit b_kPerforming chaotic modulation to obtain N chaotic modulation signals;

n +1 pulse shapers for pulse shaping N chaotic modulation signals and one chaotic signal c_xPerforming pulse shaping;

n +1 carrier multipliers with N f₁，…,f_NThe subcarriers of the frequency are respectively multiplied by N paths of pulse-shaped chaotic modulation signals; using an f₀Subcarrier of frequency and a chaotic signal c subjected to pulse shaping_xMultiplying;

an adder for aggregating the N +1 carrier multiplier correspondences f₀，f₁，…,f_NPulse-shaped signals carried by subcarriers of frequencyAnd then transmitting.

Preferably, the receiver receives and demodulates the signal transmitted by the transmitter, where the signal is r (t), and t represents a time of the signal:

the receiver includes:

n +1 matched filters for separating the received signal into frequencies f₀，f₁，…,f_NTo obtain f₀Signal r in a subcarrier of frequency₀(t) and f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t)

A second Hilbert transformer for pair f₀Signal r in a subcarrier of frequency₀(t) performing Hilbert transform to obtain a signal

A first correlator for converting f₀Signal r in a subcarrier of frequency₀(t) are each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing correlation to obtain a first correlation variable I_j，j＝1,2，…，N；

A second correlator for correlating the signalAre each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing a correlation to obtain a second correlation variable

A decision variable calculator for calculating a first correlation variable I_jWith a second dependent variableRespectively subtracting absolute values to obtain a final decision variable xi_j；

A threshold decision device for deciding the final decision variable xi_jFor index bit a_kRecovering to obtain index bit a_k；

A modulation bit demodulator based on the index bit a_kJudging chaotic signal adopted by activation of subcarrier, and further solving demodulation modulation bit b_kBased on the decision metric, demodulating the modulation bit b_k。

Compared with the prior art, the technical scheme of the invention has the beneficial effects that:

the invention provides a differential chaotic phase shift keying communication method and system based on a mixed index, wherein the mixed index refers to index bits mixed by carrier index bits and carrier number index bits, the differential chaotic phase shift keying communication method based on the mixed index comprises a signal sending modulation method and a signal receiving demodulation method, and modulation and demodulation under the mixed index are matched.

Drawings

Fig. 1 is a schematic diagram of an overall framework of a hybrid-index-based differential chaotic phase-shift keying communication method proposed in an embodiment of the present invention;

fig. 2 is a block diagram illustrating a structure of a transmitter of a hybrid-index-based differential chaotic phase-shift keying communication system according to an embodiment of the present invention;

fig. 3 is a block diagram illustrating a structure of a hybrid-index-based differential chaotic phase-shift keying receiver according to an embodiment of the present invention;

FIG. 4 is a graph showing a comparison between the method of the present invention and the differential chaotic phase shift keying modulation of carrier index and the multi-carrier differential chaotic phase shift keying modulation method in terms of spectral efficiency and energy efficiency;

FIG. 5 is a graph showing the comparison of error rate performance between the method of the present invention and the multi-carrier differential chaotic phase shift keying communication method in the case of Gaussian channel and multi-path Rayleigh fading channel;

fig. 6 shows a comparison graph of error rate performance of the differential chaotic phase shift keying communication method using the method of the present invention and a single carrier index under a gaussian channel and a multipath rayleigh fading channel.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent;

for better illustration of the present embodiment, certain parts of the drawings may be omitted, enlarged or reduced, and do not represent actual dimensions;

it will be understood by those skilled in the art that certain well-known descriptions of the figures may be omitted.

The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent;

the technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

Examples

As shown in fig. 1, the embodiment of the present invention provides a hybrid index-based differential chaotic phase shift keying communication method, which includes a hybrid index-based differential chaotic phase shift keying transmission signal modulation method and a hybrid index-based differential chaotic phase shift keying reception signal demodulation method; the mixed index is a mixed index bit, and comprises a carrier index bit and a carrier number index bit, the carrier index bit and the carrier number index bit are mixed to modulate a transmission signal, and then the signal is demodulated based on the mixing of the carrier index bit and the carrier number index bit.

Specifically, the differential chaotic phase shift keying transmission signal modulation method based on the mixed index comprises the following processes:

s1, generating a chaotic signal c_xSetting N subcarriers f of different frequencies₀,f₁，…,f_NTo convert the chaotic signal c_xAs a reference signal, the reference signal is pulse shaped by f₀The sub-carrier of the frequency bears the reference signal after the pulse shaping and sends;

s2. the result of step S1Chaotic signal c_xIndex selection and Hilbert transform are respectively carried out, wherein a first subcarrier activation chaotic signal c is obtained after Hilbert transform_yActivating the first subcarrier to generate chaotic signal c_yIndex selection is also performed;

s3, segmenting the initial information bit to obtain an index bit a_kAnd modulation bit b_kIndex bit a_kDetermining the selection of reference signal carrying information bits, index bit a_kActivating chaotic signal c acting on subcarrier subjected to index selection_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_k；

S4, chaotic signal c_kAnd modulation bit b_kChaotic modulation is carried out, the chaotic modulated signal is pulse shaped, and f is utilized respectively₁，…,f_NThe sub-carriers of the frequency carry the pulse-shaped signal and transmit.

The differential chaotic phase shift keying received signal demodulation method based on the mixed index comprises the following processes:

setting a receiving signal of a sending signal after channel transmission as r (t), wherein t represents the time of the signal; for middle frequency f of r (t)₀，f₁，…,f_NIs separated to obtain f₀Signal r in a subcarrier of frequency₀(t) and f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t)；

SB. pairs f₀Signal r in a subcarrier of frequency₀(t) performing Hilbert transform to obtain a signal

SC. mixing f₀Signal r in a subcarrier of frequency₀(t) are each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing correlation to obtain a first correlation variable I_jJ 1,2, …, N, will signalAre each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing a correlation to obtain a second correlation variable

SD. relating the first variable I_jWith a second dependent variableRespectively subtracting absolute values to obtain a final decision variable xi_j；

SE. based on the final decision variable ξ_jFor index bit a_kRecovering;

SF. according to index bit a_kJudging chaotic signal adopted by activation of subcarrier, and further solving demodulation modulation bit b_kBased on the decision metric, demodulating the modulation bit b_k。

In the present embodiment, the chaotic signal c generated in step S1_xObtaining a first subcarrier activation chaotic signal c after performing Hilbert transform_yChaotic signal c_xAnd a first subcarrier activation chaotic signal c_ySatisfies the following relationship:

wherein, beta represents the number of sampling points of the signal; i represents the ith sample point order;

let t denote the signal time, index bit a_kActivating chaotic signal c acting on subcarrier subjected to index selection_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_kAt signal time t, the following are satisfied:

wherein, c_x(t) the subcarrier activates the chaotic signal at the time t; c. C_y(t) the first subcarrier activates the chaotic signal at the time t; c. C_kAnd (t) represents a chaotic signal used by the subcarrier at the time t and carrying modulation bits.

The chaotic signal c_kAnd modulation bit b_kPerforming chaotic modulation, wherein at the moment t, the chaotic modulated signals meet the following conditions:

wherein, c_kAnd (t) represents a chaotic signal used by the subcarrier at the time t and carrying modulation bits.

Let t denote the signal time, at t the signal time f₀The pulse shaped signal carried by the subcarrier of frequencies is represented as:

s₁(t)＝c_x(t)cos(2πf₀)

wherein, c_x(t) the subcarrier activates the chaotic signal at the time t; f. of₀Representing the frequency, s, of the subcarrier₁(t) represents the t signal time f₀A pulse shaped signal carried by a subcarrier of the frequency;

at time t of signal, f₁，…,f_NThe pulse shaped signal carried by the subcarrier of frequencies is represented as:

wherein s is₂(t) represents f₁，…,f_NA pulse shaped signal carried by a subcarrier of the frequency; n represents f₁，…,f_NThe number of subcarriers of a frequency; c. C_k(t) represents chaotic signal used by subcarrier at t moment and used for carrying modulation bitNumber;

the differential chaotic phase shift keying transmission signal based on the mixed index is represented as follows:

where s (t) denotes a differential chaotic phase shift keying transmission signal based on a mixing index.

In this embodiment, when the chaotic signal used by the jth subcarrier is c_xIf so, the first correlation variable I in step SC_jThe expression of (a) is:

second related variableThe expression of (a) is:

wherein, the terms A, B, C and D are noise interference terms; j represents the way of the subcarrier; beta denotes a spreading factor, n₀Is additive white gaussian noise of the reference signal,is n₀Hilbert transform of (n)_jAdditive white Gaussian noise of the jth path of sub-carrier;

in the step SD, the first relevant variable and the second relevant variable are subtracted after absolute values are respectively taken to obtain a final decision variable xi_jThe expression of (a) is:

neglecting noise interference, decision variable xi_jExpressed as:

i.e. xi_jGreater than 0; when the chaotic signal used by the jth sub-carrier is c_yTime, decision variable xi_jExpressed as:

based on the final decision variable ξ_jFor index bit a_kThe formula for recovery is:

according to the index bit a as stated in step SF_kThe process of judging the chaotic signal adopted by the activation of the subcarrier is as follows:

when index bit a_kWhen the value is 0, the chaotic signal used by the subcarrier at the time t and carrying modulation bits is c_y(t) the chaotic signal used for subcarrier activation is c_yDemodulating the modulated bit b_kThe decision metric of (a) is expressed as:

when index bit a_kWhen the value is 1, the chaotic signal used by the subcarrier at the time t and carrying modulation bits is c_x(t) the chaotic signal used for subcarrier activation is c_x(ii) a Demodulating modulated bits b_kThe decision metric of (a) is expressed as:

modulation bit b_kThe demodulation formula is:

the embodiment of the invention also provides a differential chaotic phase shift monitoring communication system based on the mixed index, which comprises a transmitter for realizing the differential chaotic phase shift keying transmission signal modulation method based on the mixed index and a receiver for realizing the differential chaotic phase shift keying transmission signal modulation method based on the mixed index.

Referring to fig. 2, the transmitter includes:

a chaotic signal generator for generating a chaotic signal c_x；

A first Hilbert transformer for the chaotic signal c_xPerforming Hilbert transform to obtain a first subcarrier activation chaotic signal c_y；

An index selector for selecting the chaotic signal c_xAnd a first subcarrier activation chaotic signal c_yCarrying out index selection;

a bit divider for dividing the initial information bits to obtain index bits a_kAnd modulation bit b_k；

Index bit a_kInputting the signal into an index selector, acting on the chaos signal c of the activation of the sub-carrier selected by the index selector_xAnd a first subcarrier activation chaotic signal c_yObtaining the chaotic signal c of the carrier used for carrying modulation bit_k；

A chaotic modulator for modulating the chaotic signal c_kAnd modulation bit b_kPerforming chaotic modulation to obtain N chaotic modulation signals;

n +1 pulse shapers for pulse shaping N chaotic modulation signals and one chaotic signal c_xPerforming pulse shaping;

n +1 carrier multipliers with N f₁，…,f_NThe subcarriers of the frequency are respectively multiplied by N paths of pulse-shaped chaotic modulation signals; using an f₀The sub-carrier of the frequency is pulse-shaped with one pathChaotic signal of shape c_xMultiplying;

an adder for aggregating the N +1 carrier multiplier correspondences f₀，f₁，…,f_NAnd transmitting the pulse-shaped signals carried by the subcarriers of the frequency.

The receiver receives and demodulates the signal transmitted by the transmitter, and the signal is set as r (t), wherein t represents the time of the signal: referring to fig. 3, the receiver includes:

n +1 matched filters for separating the received signal into frequencies f₀，f₁，…,f_NTo obtain f₀Signal r in a subcarrier of frequency₀(t) and f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t)

A second Hilbert transformer for pair f₀Signal r in a subcarrier of frequency₀(t) performing Hilbert transform to obtain a signal

A first correlator for converting f₀Signal r in a subcarrier of frequency₀(t) are each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing correlation to obtain a first correlation variable I_j，j＝1,2，…，N；

A second correlator for correlating the signalAre each independently of f₁，…,f_NSignal r in a subcarrier of frequency₁(t),…,r_N(t) performing a correlation to obtain a second correlation variable

A decision variable calculator for calculating a first correlation variable I_jWith a second dependent variableRespectively subtracting absolute values to obtain a final decision variable xi_j；

A threshold decision device for deciding the final decision variable xi_jFor index bit a_kRecovering to obtain index bit a_k；

A modulation bit demodulator based on the index bit a_kJudging chaotic signal adopted by activation of subcarrier, and further solving demodulation modulation bit b_kBased on the decision metric, demodulating the modulation bit b_k。

In order to further verify the effectiveness of the method provided by the invention, the following description is provided with a specific simulation effect diagram, FIG. 4 is a graph showing the comparison between the method of the present invention and the differential chaotic phase shift keying modulation of carrier index and the multi-carrier differential chaotic phase shift keying modulation method in terms of spectral efficiency and energy efficiency, wherein, the smooth line represents the mark of the method provided by the invention, a mark of a differential chaotic phase shift keying modulation method with a carrier index and a mark of a multi-carrier differential chaotic phase shift keying modulation method are shown in figure 4, the method and the system provided by the invention have great advantages in the aspects of spectral efficiency and energy efficiency compared with the differential chaotic phase shift keying modulation and the multi-carrier differential chaotic phase shift keying modulation with the carrier index, when the number of carriers is large, the spectral efficiency and the energy efficiency of the method provided by the invention are about twice as high as those of other methods.

Fig. 5 shows the comparison graphs of the error rate performance under the gaussian channel and the multipath rayleigh fading channel by using the method of the present invention and the multi-carrier differential chaotic phase shift keying method (the "multi-carrier differential chaotic phase shift keying" legend in fig. 5), which respectively shows the case where N is 4, the spreading factor β is 300, the number of paths L is 3 and N is 32, the spreading factor β is 300, and the number of paths L is 3, and has the average power gain E (λ [, ] is₁ ²)＝E(λ₂ ²)＝E(λ₃ ²) 1/3, delay τ₁＝0，τ₂＝2，τ₃4. Under the Gaussian channel, when the number of the carriers N is 4, the error rate is 10^-5In the meantime, the method of the present inventionCompared with a multi-carrier differential chaotic phase shift keying system, the multi-carrier differential chaotic phase shift keying system has 1dB performance gain. Under the multipath Rayleigh fading channel, the differential chaotic phase shift keying scheme of mixing the carrier index and the carrier number index also has better error rate performance.

Fig. 6 is a graph showing the comparison of the error rate performance between the method of the present invention and the differential chaotic phase shift keying communication method with a single carrier index (the legend of "differential chaotic phase shift keying with carrier index" in fig. 6) under gaussian channel and multipath rayleigh fading channel, which shows the cases of N being 4, spreading factor β being 300, path number L being 3 and N being 32, spreading factor β being 300, and path number L being 3, respectively, and having an average power gain E (λ [ # ])₁ ²)＝E(λ₂ ²)＝E(λ₃ ²) 1/3, delay τ₁＝0，τ₂＝2，τ₃4. Referring to fig. 6, in the gaussian channel, the bit error rate is 10 when the number of carriers N is 4^-5Compared with the differential chaotic phase shift keying scheme of carrier index, the scheme provided by the invention has the performance gain of 1-2dB, and the error rate is 10 when the number N of the carriers is 32^-5Compared with a differential chaotic phase shift keying system with carrier indexes, the scheme provided by the invention has the performance gain of 2-3 dB. When the carrier number N is 32, the error rate is 10 under the multipath Rayleigh fading channel^-5The proposed scheme of the present invention has a gain of 3 dB.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.