A Chaotic Shift Keying Modulation and Demodulation Method Combined with Initial Value Index

Abstract

The present invention relates to a chaotic shift keying modulation and demodulation method combined with initial value index. At the transmitting end, the input bit stream is divided into N bit blocks, each bit block includes bits. The mapping bits are used to select a reference signal with a predefined initial value as the transmission carrier of the mapping bit, and the remaining one bit is a modulation bit. The polarity of the selected reference signal is flipped or maintained according to the transmission bit 0 or 1. The transmitter only transmits reference signals with different initial values ​​at the head of each frame signal, and the remaining N bit blocks share the reference signal with different initial values ​​during modulation. At the receiving end, the system distributes the first signals received in each frame to each demodulation branch, and then performs correlation operations on the remaining N information signals in each demodulation branch, selects the absolute value of the largest correlator output as the basis for judging the mapping bit, and then judges the modulation bit according to the polarity of the correlator output value. Compared with the prior art, the present invention has better bit error performance.

Description

Technical Field

[0001] The invention relates to the technical field of wireless communication, and in particular to a chaotic shift keying modulation and demodulation method combined with an initial value index. Background Art

[0002] Chaotic signals are easy to generate, and have broadband, non-periodicity, initial value sensitivity, noise-like properties, and good correlation characteristics. Chaos-based incoherent communication systems have attracted a lot of attention from academia and industry in the field of short-range wireless communications due to their low hardware complexity, low power consumption, and good anti-multipath performance. Among them, the most widely studied is differential chaotic shift keying (DCSK) based on a reference transmission structure. In DCSK, each transmitted signal contains a reference signal and an information signal. The information signal flips or maintains the polarity of the reference signal according to the transmitted bit 0 or 1. The receiving end only needs to use a simple auto-correlation receiver (AcR) to perform incoherent demodulation on the transmitted bits without any channel estimation. It can be seen that the main disadvantages of DCSK are that the reference signal that does not carry any information wastes transmission energy and the transmission rate is not high.

[0003] Index modulation is considered to be an effective method to improve transmission energy efficiency and spectrum efficiency. Compared with traditional communication technology, index modulation technology can provide freedom from new information transmission dimensions while maintaining a relatively low hardware complexity. Herceg M et al. proposed a differential chaotic shift keying (PI-DCSK) system based on shift index in "Permutation Index DCSK Modulation Technique for Secure Multiuser High-Data-Rate Communication Systems". At the transmitter, the reference signal is sent in the first time slot and the information signal is sent in the second time slot. The input bit stream is transmitted every m c +1 bit is modulated as a group. c The mapping bits are used to select the reference signal arranged in a predefined shift mode as the transmission carrier of the mapping bits for transmission in the second time slot. The remaining bit is the modulation bit, and the polarity of the signal is flipped or maintained according to the transmission bit 0 or 1. The receiving end receives the signal of the first time slot in The demodulation branches perform correlation operations, and the correlator with the largest output absolute value is selected to recover the mapping bit, and the symbol output by the correlator is used to recover the modulation bit.

[0004] In the Permutation Index DCSK Modulation Technique for Secure Multiuser High-Data-Rate Communication Systems, each transmitted signal consists of two time slots. The first time slot is used to transmit a reference signal that does not carry any bit information, and the second time slot is used to transmit an information sequence that carries modulation bits and mapping bits. The information sequence is generated by shifting the reference sequence according to the mapping bits, and the modulation bits flip or maintain the polarity of the shifted copy. The disadvantage is that since the reference signal does not carry any transmission bits, a certain amount of energy is wasted, and the introduction of noise deteriorates the system bit error performance. Summary of the invention

[0005] The object of the present invention is to provide a chaotic shift keying modulation and demodulation method combined with an initial value index, which effectively reduces the bit error rate (BER), shows better bit error performance, and saves transmission energy.

[0006] To achieve the above object, the technical solution of the present invention is: a chaotic shift keying modulation and demodulation method combined with initial value index, at the transmitting end, the input bit stream is divided into N bit blocks, each bit block includes m c +1 bit; where m c The mapping bits are used to select the reference signal with a predefined initial value as the transmission carrier of the mapping bits, and the remaining bit is the modulation bit. The polarity of the selected reference signal is flipped or maintained according to the transmission bit 0 or 1; the transmitter adopts an improved reference transmission frame structure, that is, the transmitter only transmits the reference signal at the head of each frame signal. The remaining N bit blocks share this reference signal during modulation. reference signals with different initial values; at the receiving end, the previous The signals are distributed to each demodulation branch, and then the remaining N information signals are correlated in each demodulation branch, and the absolute value of the largest correlator output is selected as the basis for determining the mapping bit, and then the modulation bit is determined according to the polarity of the largest correlator output value.

[0007] Compared with the prior art, the present invention has the following beneficial effects: the present invention combines the initial value index (IVI) technology with the chaotic shift keying modulation technology, and each time slot of length β can transmit m c +1 information bit. Under the same transmission energy, the present invention adopts an improved reference transmission frame structure, which significantly reduces the waste of energy in transmitting unmodulated reference signals. The present invention is verified by simulation results, and has better bit error performance in both Rayleigh fading channels and ultra-wideband channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a structural block diagram of the IVI-DCSK system transmitter of the present invention.

[0009] Figure 2 This is a frame structure diagram of the IVI-DCSK system of the present invention.

[0010] Figure 3 This is a structural block diagram of the IVI-DCSK system receiver of the present invention.

[0011] Figure 4 The figure is a flow chart of the entire sending-receiving process.

[0012] Figure 5 A technical simulation comparison diagram of the prior art PI-DCSK and the IVI-DCSK system of the present invention under a two-path Rayleigh low-delay channel.

[0013] Figure 6 A technical simulation comparison diagram of the prior art PI-DCSK and the IVI-DCSK system of the present invention under a two-path Rayleigh high-delay channel.

[0014] Figure 7 A technical simulation comparison diagram of the prior art PI-DCSK and the IVI-DCSK system of the present invention under ultra-wideband (UWB) channel. DETAILED DESCRIPTION

[0015] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0016] The present invention discloses a chaotic shift keying modulation and demodulation method combined with an initial value index. At the transmitting end, the input bit stream is divided into N bit blocks, each of which includes m c +1 bit; where m c The mapping bits are used to select the reference signal with a predefined initial value as the transmission carrier of the mapping bits, and the remaining bit is the modulation bit. The polarity of the selected reference signal is flipped or maintained according to the transmission bit 0 or 1; the transmitter adopts an improved reference transmission frame structure, that is, the transmitter only transmits the reference signal at the head of each frame signal. The remaining N bit blocks share this reference signal during modulation. reference signals with different initial values; at the receiving end, the previous The signals are distributed to each demodulation branch, and then the remaining N information signals are correlated in each demodulation branch, and the absolute value of the largest correlator output is selected as the basis for determining the mapping bit, and then the modulation bit is determined according to the polarity of the largest correlator output value.

[0017] like Figure 1 As shown, the following steps need to be completed on the sending end:

[0018] Step 1: Chaotic carrier generator generates A chaotic sequence of length β, and in Figure 2 The transmission frame header shown is sent

[0019]

[0020] in,

[0021] Step 2: The input bit stream is divided into N bit blocks, each of which contains m c +1 bit, m c Represents the mapping bit, and the remaining 1 bit is called the modulation bit;

[0022] Step 3: For the jth bit block, according to the transmitted m c The binary mapping bits are converted to the decimal mapping symbol a j , select the corresponding chaotic carrier from step 1 Used to transmit mapping bits;

[0023] Step 4: According to whether the modulation bit is 0 or 1, the modulation symbol b j are equal to -1 or 1 respectively, and the chaotic carrier selected in step 3 To flip or hold the polarity,

[0024]

[0025] Step 5: The transmitter Figure 2 The frame structure shown in FIG. 1 will carry the information signal D of the j-th bit block information. j Arrange transmission in the corresponding time slot.

[0026] like Figure 3 As shown, the following steps need to be completed on the receiving end:

[0027] Step 1: The received signal is affected by channel fading and noise interference. A β reference signal of length is sent to each demodulation branch;

[0028] Step 2: Send the jth information signal received to A demodulation branch performs related operations;

[0029] Step 3: Take the absolute value of the output value of the correlator in step 2, and the largest value is used to restore the mapping symbol

[0030] Step 4: Perform sign judgment on the original correlation value in the correlator with the largest absolute value in step 3, and judge the positive number. Negative numbers are considered

[0031] Step 5: Use the recovery symbols obtained in steps 3 and 4 and Send to the symbol-bit converter to get the recovered bit

[0032] like Figure 4 Shown is a flow chart of the entire send-receive process.

[0033] Figure 5 A technical simulation comparison diagram of the prior art PI-DCSK and the IVI-DCSK system of the present invention under a two-path Rayleigh low-delay channel. Figure 6 A technical simulation comparison diagram of the prior art PI-DCSK and the IVI-DCSK system of the present invention under a two-path Rayleigh high-delay channel. Figure 7 A comparison chart of the technical simulation of the prior art PI-DCSK and the IVI-DCSK system of the present invention in an ultra-wideband (UWB) channel. It can be seen that compared with the existing PI-DCSK technology, under the same transmission energy, the present invention significantly reduces the waste of energy in transmitting the unmodulated reference signal, and the simulation results also show better bit error performance.

[0034] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A chaotic shift keying modulation and demodulation method combined with an initial value index, characterized in that: At the transmitter, the input bit stream is divided into N bit blocks, each of which consists of m c +1 bit; where m c The mapping bits are used to select the reference signal with a predefined initial value as the transmission carrier of the mapping bits, and the remaining bit is the modulation bit. The polarity of the selected reference signal is flipped or maintained according to the transmission bit 0 or 1; the transmitter adopts an improved reference transmission frame structure, that is, the transmitter only transmits the reference signal at the head of each frame signal. The remaining N bit blocks share this reference signal during modulation. reference signals with different initial values; at the receiving end, the previous The signals are distributed to each demodulation branch, and then the remaining N information signals are correlated in each demodulation branch, and the absolute value of the largest correlator output is selected as the basis for determining the mapping bit, and then the modulation bit is determined according to the polarity of the largest correlator output value; the specific implementation steps of this method are as follows: Sending side: Step 01: Chaotic carrier generator generation A chaotic sequence of length β is sent at the head of the transmission frame. in, Step 02: The input bit stream is divided into N bit blocks, each of which contains m c +1 bit; Step 03: For the jth bit block, according to the transmitted m c The binary mapping bits are converted to the decimal mapping symbol a j , select the corresponding chaotic carrier from step 01 Used to transmit mapping bits; Step 04: According to whether the modulation bit is 0 or 1, the modulation symbol b j are equal to -1 or 1 respectively, and the chaotic carrier selected in step 03 To flip or hold the polarity, Step 05: The transmitter sends the information signal D carrying the j-th bit block information j Arrange transmission in corresponding time slot; Receiver: Step 11: The received signal is affected by channel fading and noise interference. A β reference signal of length is sent to each demodulation branch; Step 12: The jth information signal received is simultaneously sent to A demodulation branch performs related operations; Step 13: Take the absolute value of the output value of the correlator in step 12, and the largest value is used to restore the mapping symbol Step 14: Perform sign judgment on the original correlation value in the correlator with the largest absolute value in step 13, and judge the positive number. Negative numbers are considered Step 15: Use the recovery symbols obtained in steps 13 and 14 and Send to the symbol-bit converter to get the recovered bit

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