Average BER performance of FSO SIM-QAM systems in the presence of atmospheric turbulence and pointing errors
Average BER performance of FSO SIM-QAM systems in the presence of atmospheric turbulence and pointing errors
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DOI：
10.1080/09500340.2015.1093662
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发表时间：
2016-04
影响因子：
1.3
通讯作者：
G. Djordjevic;Milica I. Petkovic
中科院分区：
文献类型：
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作者：
G. Djordjevic;Milica I. Petkovic
本文对采用副载波强度调制（SIM）和格雷码正交幅度调制（QAM）的自由空间光学系统的平均误码率（BER）进行了精确的分析。接收光信号的强度波动是由路径损耗、大气湍流和指向误差引起的。假设SIM-QAM具有任意的星座尺寸，在存在伽玛-伽玛闪烁的情况下，推导出平均误码率的精确封闭形式的解析表达式。给出了简单的平均误码率近似表达式，只考虑有限求和中的主导项。导出的表达式被简化为光信号传输仅受大气湍流影响的特殊情况。数值结果，以说明导出的表达式的有用性，也给洞察不同的调制，信道和接收机参数的平均BER性能的影响。结果表明，发射激光器和接收探测器之间的失调对平均误码率有很大的影响，特别是在平均信噪比较高的范围内。
This paper presents the exact average bit error rate (BER) analysis of the free-space optical system employing subcarrier intensity modulation (SIM) with Gray-coded quadrature amplitude modulation (QAM). The intensity fluctuations of the received optical signal are caused by the path loss, atmospheric turbulence and pointing errors. The exact closed-form analytical expressions for the average BER are derived assuming the SIM-QAM with arbitrary constellation size in the presence of the Gamma–Gamma scintillation. The simple approximate average BER expressions are also provided, considering only the dominant term in the finite summations of obtained expressions. Derived expressions are reduced to the special case when optical signal transmission is affected only by the atmospheric turbulence. Numerical results are presented in order to illustrate usefulness of the derived expressions and also to give insights into the effects of different modulation, channel and receiver parameters on the average BER performance. The results show that the misalignment between the transmitter laser and receiver detector has the strong effect on the average BER value, especially in the range of the high values of the average electrical signal-to-noise ratio.