Open AccessPerformance analysis of a LDPC coded OAM-based UCA FSO system exploring linear equalization with channel estimation over atmospheric turbulence
Author(s) -
Yan Zhang,
Ping Wang,
Tao Liu,
Lixin Guo,
Yutao Li,
Wei Wang
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.022182
Subject(s) - low density parity check code , keying , fading , mimo , computer science , equalization (audio) , phase shift keying , bit error rate , minimum mean square error , channel (broadcasting) , algorithm , coding gain , free space optical communication , optical communication , electronic engineering , optics , estimator , decoding methods , physics , telecommunications , mathematics , statistics , engineering
A low-density parity-check (LDPC) coded orbital angular momentum (OAM)-based uniform circular array (UCA) free space optical (FSO) system exploring linear equalization is investigated with channel estimation over the atmospheric turbulence fading channels. On the basis of the proposed system model, the least square (LS) channel estimator is adopted to obtain the channel state information (CSI) of this OAM-FSO system. Then, the average bit error ratio (ABER) expressions with M P -ary phase shift keying (M P PSK) modulation scheme are derived by ensemble average with the aid of the large number theorem. Besides, LDPC codes are applied in the simulation to improve the ABER performance, and subsequently the probability expressions of the estimated signals with zero forcing (ZF) and minimum mean squared error (MMSE) equalizers for LDPC decoder are achieved, respectively. Results show that the ABER performance of the OAM-FSO system degrades with increasing turbulence strengths. With ZF and MMSE equalization algorithms, the ABER performance is significantly enhanced with an increase in the number of receive antennas for considerable diversity gain. Furthermore, a substantial coding gain can be attained by LDPC codes in this OAM-FSO system, especially under strong turbulence condition. This work will benefit the research and development of OAM-FSO system.