Free-space optical communication through atmospheric turbulence channels
Free-space optical communication through atmospheric turbulence channels
复制标题
DOI：
10.1109/tcomm.2002.800829
复制
发表时间：
2002-08-01
影响因子：
8.3
通讯作者：
Kahn, JM
中科院分区：
文献类型：
--
作者：
Zhu, XM;Kahn, JM
在自由空间光通信链路中，大气湍流导致接收光信号的强度和相位的波动，从而损害链路性能。在本文中，我们描述了几种通信技术，以减轻相干引起的强度波动，即，信号衰落这些技术适用于接收机孔径小于衰落相关长度和观测间隔小于衰落相关时间的情况。我们假设接收机没有瞬时衰落状态的知识。当接收机只知道衰落的边缘统计时，可以使用逐符号的NIL检测器来提高检测性能。如果接收器具有衰落的联合时间统计的知识，则可以采用最大似然序列检测（MLSD），从而产生进一步的性能改进，但是以非常高的复杂度为代价。利用多个接收机的空间分集接收也可以用于克服相干性引起的衰落。我们描述了使用NIL检测在空间分集接收，以减少在不同的接收机衰落之间的相关性所造成的分集增益惩罚。在配套文件中，我们描述了两个降低复杂度的MLSD实现，它利用一个单步马尔可夫链模型的衰落相关性与每幸存者处理。
In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received light signal, impairing link performance. In this paper, we describe several communication techniques to mitigate turbulence-induced intensity fluctuations, i.e., signal fading. These techniques are applicable in the regime in which the receiver aperture is smaller than the correlation length of fading and the observation interval is-shorter than the correlation time of fading. We assume that the receiver has no knowledge of the instantaneous fading state. When the receiver knows only the marginal statistics of the fading, a symbol-by-symbol NIL detector can be used to improve detection performance. If the receiver has knowledge of the joint temporal statistics of the fading, maximum-likelihood sequence detection (MLSD) can be employed, yielding a further performance improvement, but at the cost of very high complexity. Spatial diversity reception with multiple receivers can also be used to overcome turbulence-induced fading. We describe the use of NIL detection in spatial diversity reception to reduce the diversity gain penalty caused by correlation between the fading at different receivers. In a companion paper, we describe two reduced-complexity implementations of the MLSD, which make use of a single-step Markov chain model for the fading correlation in conjunction with per-survivor processing.