Light-space-time trellis code encoding method suitable for intensity modulation/direction detection

Abstract

The invention discloses alight-space-time trellis code encoding method suitable for intensity modulation / direction detection. The method comprises the following steps: I, encoding a binary bit stream to generate a QAM / PSK signal; II, implementing serial-to-parallel conversion on the output encoded signal; III, performing vector mapping on a signal output by a serial-to-parallel convertor, so that the mapped signal meets Hermitian symmetry; IV, performing fast Fourier transform of 2N points on the mapped signal, and adding a direct-current component; V, eliminating a negative signal; VI, converting a received optical signal into an electric signal by a photoelectric detector at a receiving end, and removing the direct-current component; VII, performing analog / digital conversion and 2N-point series-to-parallel conversion to obtain a parallel bipolar signal, and converting the parallel bipolar signal into a plural / negative signal through the fast Fourier transform; VIII, feeding an inversely-mapped signal into a space-time trellis code decoder through inverse mapping and parallel-to-series conversion to finish decoding.

Description

technical field [0001] The invention relates to a design method of space-time grid coding in a wireless optical communication multiple-input multiple-output (MIMO) system, a method for realizing quadrature amplitude modulation (QAM) or phase keying (PSK) by using light intensity modulation, belonging to wireless optical communication ( FSO) technical field. Background technique [0002] Wireless optical communication has the advantages of high bandwidth, large capacity, low cost, and no need for frequency licenses. It is an effective means to build triple play, solve the "last mile" bottleneck, and achieve global high-speed and real-time communication. Optical signals are subject to various interferences such as loss, attenuation, background radiation and atmospheric turbulence when transmitted in the atmosphere. Among them, atmospheric turbulence has the most serious impact on optical signals, especially in the case of strong turbulence, which can achieve a fading greater ...

AI Technical Summary

Problems solved by technology

[0006] The present invention is an optical space-time trellis code encoding method suitable for intensity modulation / direct detection, and its goal is to convert the PSK or QAM output by the space-time trellis code encoder into a positive real number signal, thereby solving the problem of the original space-time The problem that the complex signal output by the trellis code encoder cannot be directly transmitted in the optical communication link; the receiving end adopts the opposite process, through real / complex conversion, to obtain the signal input to the space-time trellis code decoder, and finally Complete the decoding; the steps are:

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