A High-Speed Modulation and Demodulation System Combining PPM and PI-DCSK for Short-Range Communication

Abstract

The present invention relates to a high-rate modulation and demodulation system combining PPM and PI-DCSK for short-distance communication, adopting a transmission-reference mode. At the transmitting end, the input bit stream is divided into groups of bits. The position-mapping bits are used to select specific pulse positions, the permutation-mapping bits are used to select a predefined permutation pattern, and the last modulation bit is used to select whether to repeat or flip the permutation copy of the reference signal. At the receiving end, the reference segment is first arranged according to a predefined permutation index rule, and all permutation copies are successively correlated with the information segments at different positions. The position-mapping bits and the permutation-mapping bits are simultaneously determined by the index of the correlator with the maximum absolute value, and the last modulation bit is recovered by comparing the value of the correlator with the maximum absolute value with a zero threshold. The present invention significantly improves the data transmission rate and reduces the bit error rate under the same transmission energy.

Description

Technical Field

[0001] The present invention relates to the technical field of short - range wireless communication, and particularly to a high - rate modulation and demodulation system combining PPM and PI - DCSK for short - range communication. Background Art

[0002] In the traditional technology, each data frame is divided into two time slots. In the first time slot, a chaotic signal is transmitted as a reference signal, and in the second time slot, a copy of the reference signal in a predefined arrangement selected by the mapping bits is transmitted, and the copy is flipped or repeated according to the modulation bits. The disadvantage is that since the reference signal does not carry the transmitted bit information, a certain amount of transmission energy is wasted, and at the same time, noise is introduced, resulting in a decline in system performance;

[0003] The modulator at the transmitting end transmits a chaotic signal as a reference sequence, and the pulse position is selected by the mapping bits and DCSK modulation is simultaneously performed as an information - bearing signal. The disadvantage is that under the same transmission energy, the transmission rate is low. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a high - rate modulation and demodulation system combining PPM and PI - DCSK for short - range communication, which significantly improves the data transmission rate and reduces the bit error rate under the same transmission energy.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A high - rate modulation and demodulation system combining PPM and PI - DCSK for short - range communication adopts a transmission - reference mode.

[0007] At the transmitting end, the input bit stream is divided into m a +m b +1 bits. The position - mapping bits m a select specific pulse positions, the permutation - mapping bits m b select a predefined permutation method, and the last modulation bit selects to repeat or flip the permutation copy of the reference signal;

[0008] At the receiving end, the reference segment is first arranged according to a predefined arrangement index rule, and all permutation copies are sequentially correlated with the information segments at different positions. The indexes of the correlators with the largest absolute values are used to simultaneously determine the position - mapping bits m a and the permutation - mapping bits m b , and the value of the correlator with the largest absolute value is compared with a zero threshold to recover the last modulation bit.

[0009] Further, at the transmitting end, specifically as follows:

[0010] (1) The chaotic signal generator generates a chaotic sequence of length β and transmits it as a reference signal in the first time slot;

[0011] (2) The input bit stream is divided into multiple bit blocks with (m a + m b + 1) bits. m a represents the mapped bits corresponding to the pulse position index, m b represents the mapped bits corresponding to the permutation index, and the last one represents the DCSK modulation bit;

[0012] (3) Formulate the pulse position mapping rule to map m a position mapped bits to a PPM position,

[0013]

[0014] where p l is the position index modulation symbol converted by the mapped bits, indicates that the value at the p l -th position of the PPM matrix H is 1 and the rest are 0;

[0015] (4) Formulate the permutation mapping rule to map m b permutation mapped bits to predefined permutation rules, that is, select one of the permutation methods to perform a permutation operation on the reference signal;

[0016] (5) Repeat or invert the selected permutation copy in (4) according to the last modulation bit. If the modulation bit is "1", it is the same, and if it is "0", it is the opposite;

[0017] (6): Transmit the permutation copy modulated in (5) at the position selected in (3), and no information is transmitted at the remaining positions.

[0018] Further, in the PPM-PI-DCSK system, the format of transmitting a data frame is:

[0019]

[0020] C i represents a chaotic signal of length β, placed in the first time slot as a reference signal, H represents the PPM pulse position index modulation matrix, is the Kronecker operator, P j (·) represents the j-th shift operator, b l represents the modulation bit b l ∈{-1, +1}, and DCSK modulation is performed.

[0021] Further, at the receiving end, the specific steps are as follows:

[0022] (1): The receiving end receives the signal from the sending end, arranges the reference signal in the first time slot using the predefined permutation method to obtain

[0023] (2): Calculate the correlation characteristics of each of these permutation copies with the positions in the information-bearing signal respectively, to obtain a correlation value matrix with rows and

[0024] (3): Take the absolute value of the values in (2). The largest absolute value in the correlator is used to estimate the position index and the permutation index, thereby determining the position mapping bit and the permutation mapping bit

[0025] (4): Compare the correlation value in the correlator with the largest absolute value in (3) with a zero threshold to recover the modulation bit That is, if the correlation value is greater than 0, the modulation bit is recovered as "1"; if the correlation value is less than "0", the modulation bit is recovered as "0".

[0026] The present invention has the following beneficial effects compared with the prior art:

[0027] Under the same transmission energy, the present invention significantly improves the data transmission rate and reduces the bit error rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the structural block diagram of the transmitter of the PPM-PI-DCSK system of the present invention;

[0029] Figure 2 is the structural block diagram of the receiver of the PPM-PI-DCSK system of the present invention;

[0030] Figure 3 is the flowchart of a sending-receiving process in an embodiment of the present invention;

[0031] Figure 4 is the technical simulation comparison diagram between the prior art PI-DCSK and the proposed PPM-PI-DCSK system in a two-path Rayleigh low-delay channel;

[0032] Figure 5 is the technical simulation comparison diagram between the prior art PI-DCSK and the proposed PPM-PI-DCSK system in a two-path Rayleigh high-delay channel;

[0033] Figure 6 Technical simulation comparison chart of the prior art PI-DCSK and the proposed PPM-PI-DCSK system under an ultra-wideband (UWB) channel. Detailed implementation manners

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0035] Please refer to Figure 1-6 , the present invention provides a high-rate modulation and demodulation system combining PPM and PI-DCSK for short-range communication, adopting a transmission-reference mode,

[0036] At the transmitting end, specifically as follows:

[0037] (1) A chaos signal generator generates a chaos sequence of length β and transmits it as a reference signal in the first time slot;

[0038] (2) The input bit stream is divided into multiple bit blocks with (m a + m b + 1) bits, where m a represents the mapping bits corresponding to the pulse position index, m b represents the mapping bits corresponding to the permutation index, and the last one represents the DCSK modulation bit;

[0039] (3) Formulate a pulse position mapping rule to map m a position mapping bits to a PPM position,

[0040]

[0041] where p l is the position index modulation symbol converted through the mapping bits, indicates that the value at the p l -th position of the PPM matrix H is 1, and the other values are 0;

[0042] Taking the position mapping bits as 2 (m a = 2, M = 4) as an example, then p l has four possible position indexes, namely:

[0043]

[0044] When p l is "10", select the third pulse position to transmit the information segment, and no information is transmitted at other positions. The other three mapping bit cases are the same. is the Kronecker operator;

[0045] (4) Formulate a permutation mapping rule to map m b permutation mapping bits to on a predefined permutation rule, that is select one of the permutation methods to perform a permutation operation on the reference signal;

[0046] (5) Repeat or invert the selected permutation copy in (4) according to the last modulation bit. If the modulation bit is "1", it remains the same; if it is "0", it is the opposite;

[0047] (6): Transmit the modulated permutation copy in (5) at the position selected in (3), and do not transmit any information at the remaining positions.

[0048] Preferably, in this embodiment, in the PPM-PI-DCSK system, the format of transmitting one data frame is:

[0049]

[0050] C i represents a chaotic signal with a length of β, placed in the first time slot as the reference signal, H represents the PPM pulse position index modulation matrix, is the Kronecker operator, P j (·) represents the j-th shift operator, b l represents the modulation bit b l ∈{-1, +1}, and perform DCSK modulation.

[0051] Taking m a = 2, m b = 2 as an example to specifically illustrate this modulation scheme, that is, every two time slots contain five bits: the position mapping bit is 2, the permutation mapping bit is 2, the modulation bit is 1, and assume a block of bit data is {10010}.

[0052] The first two bits "10" are the position mapping bits. As shown in step (3), select the third position to transmit the chaotic sequence. The next two bits "01" are the permutation mapping bits. As shown in step (4), select the second permutation method to permute the reference signal. The last bit "0" is the modulation bit, and perform an inversion operation on the obtained permutation copy. So the finally modulated signal is sent into the channel for transmission.

[0053] As Figure 3 shown, at the receiving end, specifically as follows:

[0054] (1): The receiving end receives the signal from the sending end, and permutes the reference signal in the first time slot using the predefined permutation methods during modulation to obtain permutation copies;

[0055] (2): This One permutation copy is successively correlated with the positions in the information-bearing signal to obtain a correlation value matrix of M rows and N columns;

[0056] (3): Take the absolute value of the values in (2). The largest absolute value in the correlator is used to estimate the position index and the permutation index, thereby determining the position mapping bit and the permutation mapping bit

[0057] (4): Compare the correlation value in the correlator with the largest absolute value in (3) with a zero threshold to recover the modulation bit That is, if the correlation value is greater than 0, the modulation bit is recovered to "1", and if the correlation value is less than "0", the modulation bit is recovered to "0".

[0058] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A high-rate modulation and demodulation system combining PPM and PI-DCSK for short-range communication, including a transmitter and a receiver, characterized in that, At the sending end, the input bit stream is in the form of m a +m b +1 bit is divided by position mapping bit m a Select pulse position, arrange mapping bit m b Selecting a predefined permutation, the last modulation bit selects to repeat or flip the permuted copy of the reference signal; At the receiving end, the reference segment is first arranged according to a predefined arrangement index rule, and all arranged copies are successively correlated with information segments at different positions. The position mapping bit m is simultaneously determined by the index of the correlator with the largest absolute value. a and the arrangement mapping bit m b , and the last modulation bit is recovered by comparing the value of the correlator with the largest absolute value with a zero threshold; at the transmitter, specifically as follows: (1) A chaos signal generator generates a chaos sequence of length β and transmits it as a reference signal in the first time slot; (2) Divide the input bit stream into multiple bit blocks with (m a + m b + 1) bits. The position mapping bit m a refers to the mapping bit corresponding to the pulse position index, and the permutation mapping bit m b refers to the mapping bit corresponding to the permutation index. The last one represents the DCSK modulation bit; (3) Develop a pulse position mapping rule to map the mapping bits corresponding to m a pulse position indices to a PPM position. where p l is the position-index modulation symbol converted by mapping bits, indicating that the value at the p l -th position of the PPM pulse position index modulation matrix H is 1 and the rest are 0; (4) Develop an arrangement mapping rule to map m b arrangement mapping bits to pre-defined arrangement rules, that is select one of the arrangement methods to perform an arrangement operation on the reference signal; (5) Repeat or invert the selected permutation copy in (4) according to the last modulation bit, the same if the modulation bit is "1", and the opposite if it is "0"; (6): Transmit the modulated permutation copy in (5) at the position selected in (3), and no information is transmitted at the remaining positions; at the receiver, specifically as follows: (1): The receiving end receives the signal from the sending end, and arranges the reference signal in the first time slot using predefined permutation methods to obtain permutation copies; (2): Successively perform calculations of relevant characteristics on each of these permutation copies with the positions in the information-bearing signal respectively, to obtain a row column correlation value matrix; (3): Take the absolute value of the value in (2). The largest absolute value in the correlator is used to estimate the position index and the permutation index, and thus judge and are the position mapping bits after the decision, are the permutation mapping bits after the decision; (4): Compare the correlation value in the correlator with the largest absolute value in (3) with the zero threshold to recover the recovered modulation bit; that is, if the correlation value is greater than 0, the modulation bit is recovered as "1", and if the correlation value is less than "0", the modulation bit is recovered as "0".

2. The high-rate modulation and demodulation system combining PPM and PI-DCSK for short-range communication according to claim 1, characterized in that, the system adopts a transmission-reference mode.

3. The high-rate modulation and demodulation system combining PPM and PI-DCSK for short-range communication according to claim 2, characterized in that, in the PPM-PI-DCSK system, the data frame format for transmitting one frame is: C i represents a chaotic signal of length β, placed in the first time slot as a reference signal, H represents the PPM pulse position index modulation matrix, is the Kronecker operator, P j (·) represents the j-th shift operator, b l represents the modulation bit b l ∈{-1, +1}, and DCSK modulation is performed.

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