MPPM modulation soft demodulation algorithm and symbol error rate performance estimation method

Abstract

The invention discloses a MPPM modulation soft demodulation algorithm and a symbol error rate performance estimation method. The soft demodulation algorithm is characterized in that a random 0,1 sequence is generated, and (N,M) MPPM signal modulation is carried out; index Weber channel fading and white Gaussian noise are generated, and the MPPM signal blocks affected by the white Gaussian noise and the channel fading are acquired, and then M maximum values are found after a sampling process, and then a demodulation process is carried out, and at last, the symbol error rate is acquired after carrying out enough times of simulation. The complexity of the algorithm is low, and the symbol error rate performance thereof is better than that of the hard demodulation algorithm. The symbol error rate estimation method is characterized in that a mathematical model of an atmospheric channel is established, and cumulative distribution functions of signal and non-signal time slot sampled values are calculated, and probability density functions of M and N-M non-signal time slot random variable minimum values and maximum values are respectively calculated, and then the probability density functions of the difference value delta Y are respectively calculated, and the integral of the probability density functions of the difference value delta Y can be calculated, and therefore the result is the symbol error rate of the (N,M)MPPM. The problem of the inability of the Monte Carlo simulation algorithm of directly carrying out the theoretical analysis of the symbol error rate of the (N,M)MPPM is solved.

Description

technical field [0001] The invention relates to a soft demodulation calculation method of an (N, M) MPPM modulation mode under an exponential Weber channel in a wireless optical communication system, and belongs to the technical field of wireless optical communication. Background technique [0002] Wireless optical communication is also known as free-space optical communication (free-space optical, FSO), which uses atmospheric channels as the transmission medium, and the random fluctuation of the optical refractive index caused by atmospheric turbulence will cause light intensity flickering and light beams during the transmission of optical signals. Effects such as drift and beam expansion. The channel fading caused by these effects will lead to the degradation of the transmitted beam quality and the degradation of the bit error rate, thereby affecting the stability and reliability of the system. [0003] In order to study the influence of atmospheric turbulence on FSO comm...

AI Technical Summary

Problems solved by technology

[0006] The current problem is that due to the complexity of MPPM, there are few reports on its soft demodulation characteristics

At present, most of the known soft demodulation system algorithms are based on calculations under conditional channels, that is, only the existence of additive Gaussian white noise is considered, and the fading caused by the atmosphere is not considered

This algorithm cannot be used to guide the actual FSO communication system receiver design

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