OFDM-Based Optical Spatial Modulation
OFDM-Based Optical Spatial Modulation
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DOI：
10.1109/jstsp.2019.2920577
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发表时间：
2019-06
影响因子：
7.5
通讯作者：
Anil Yesilkaya;R. Bian;Iman Tavakkolnia;H. Haas
中科院分区：
文献类型：
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作者：
Anil Yesilkaya;R. Bian;Iman Tavakkolnia;H. Haas
空间调制（SM）是一种很有前途的多输入多输出（MIMO）技术，具有高能效和降低系统复杂性的优点。在SM中，在任何给定的时间只有一个发射机是活动的，而其余的发射机保持沉默。主动发送器的索引携带信息。这些空间信息是除了星座符号在信号域中所携带的数据之外的。因此，相对于单输入-单输出和空时分组编码(STBC)-MIMO， SM提高了通信系统的传输速率。在信号域数据编码中，正交频分复用（OFDM）被广泛采用。多载波强度调制和直接检测（IM/DD）系统的主要优点是：能够实现高光谱效率，能够有效减轻直流（DC）漂移效应和环境光的影响。然而，目前用作传输实体的现成发光二极管（led）主要是带宽有限的。因此，将SM和OFDM相结合可以在保持低复杂度的同时提高传输速度。本文研究了光无线通信（OWC）中两种最常见的基于ofdm的同步类型，即频域同步（FD-SM）和时域同步（TD-SM）。此外，还提出了概念验证实验结果，以展示两种技术的实际可行性。所得结果与蒙特卡罗模拟结果进行了比较。结果表明，具有最优最大后验概率（MAP）检测器的TD-SM显著优于FD-SM。从结果可以推断，TD-SM是未来光IM/DD无线通信系统中基于ofdm的光SM系统的有力候选者。
Spatial modulation (SM) has proven to be a promising multiple-input-multiple-output (MIMO) technique which provides high energy efficiency and reduces system complexity. In SM, only one transmitter is active at any given time while the rest of them remain silent. The index of the active transmitter carries information. This spatial information is in addition to the data carried by the constellation symbols in the signal domain. Therefore, SM increases the transmission rate of the communication system compared to single-input-single-output and space-time block coding (STBC)-MIMO. For signal domain data encoding, orthogonal frequency division multiplexing (OFDM) has been widely adopted. The key benefits in multicarrier intensity-modulation and direct-detection (IM/DD) systems are: the capability to achieve high spectral efficiency and the ability to effectively mitigate direct-current (DC) wander effects and the impact of ambient light. However, current off-the-shelf light emitting diodes (LEDs) which are used as transmit entities are primarily bandwidth limited. Thus, there are benefits of combining SM and OFDM to enhance transmission speeds while maintaining low complexity. In this paper, the two most common OFDM-based SM types, namely frequency domain SM (FD-SM) and time domain SM (TD-SM), are investigated for optical wireless communications (OWC). Moreover, proof-of-concept experimental results are presented to showcase practical feasibility of both techniques. The obtained results are also compared with Monte Carlo simulations. The results show that TD-SM with an optimal maximum-a-posteriori-probability (MAP) detector significantly outperforms FD-SM. It can be inferred from the results that TD-SM is a strong candidate among OFDM-based optical SM systems for future optical IM/DD wireless communication systems.