A modulation and demodulation method for double-interval pulse position in indoor VLC system
A technology of pulse position modulation and demodulation method, which is applied in the direction of transmission system, digital transmission system, short-distance system, etc. It can solve the problems that synchronization and demodulation have great influence, reduce system anti-interference, etc., and improve bandwidth utilization rate, improve the effect of anti-interference
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Embodiment 1
[0035] The embodiment of the present invention provides a double-interval pulse position modulation and demodulation method for an indoor VLC system, see figure 1 , the method includes the following steps:
[0036] 101: modulation process:
[0037] First map the original signal into a modulated signal, and then transmit the signal synchronously by adding two frame headers (0110 and 0111) to the modulated signal, which can reduce the number of time slots for data bits;
[0038] 102: Demodulation process:
[0039] The receiving end correctly identifies the frame header as the synchronous signal by means of sequence detection. When 0110 and 0111 serial signals are detected, it is also necessary to verify whether the detected 0110 and 0111 are synchronous frame headers or bit errors. If it is verified that 0110 and 0111 are synchronous Frame header, and then demap the modulated signal of data bits into the original signal.
[0040] 103: Both PPM modulation and MPPM modulation a...
Embodiment 2
[0043] In order to ensure that the receiving end can accurately identify the starting position of a frame during communication, PPM modulation and its derivative modulation add a frame header to the starting position of each frame of data bits as a synchronization signal, and the principle of adding a frame header is: Assume The number of connected high-level time slots in the data bits of a frame of information is at most x, then the first time slot added to the frame header is low-level, and the number of high-level time slots that need to be connected after that is x+1, The data bit information in a frame of information can only be read when the receiving end detects the added frame header.
[0044] The data bits of each frame of information modulated by PPM do not have consecutive high-level time slots, and its frame header is 011; the data bits of each frame of information modulated by MPPM have two consecutive high-level time slots, and its frame header is 0111. The data...
Embodiment 3
[0052] Performance analysis:
[0053] 1. Anti-interference analysis
[0054] When the number m of time slots of the original signal is 3, 4, 5 and 6 respectively, the relationship between the total time slot error rate and SNR of the three modulation methods is as follows: Figure 5 shown. It can be seen from the figure that when the signal-to-noise ratio is the same, the slot error rate of PPM modulation is lower, the slot error rate of DIPPM modulation is next, and the slot error rate of MPPM modulation is higher. The anti-interference of DIPPM modulation is between PPM modulation and MPPM modulation. At the same time, the influence of the m value of the three modulations on the slot error rate is analyzed. With the increase of the m value, the slot error rate of the three modulation methods is in a downward trend, and the anti-interference is stronger.
[0055] 2. Bandwidth Utilization Analysis
[0056] The three modulations of PPM, MPPM and DIPPM are compared and analy...
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