Jeong Dae-Kyo, Park Cheol-Sun, Kim Dongwoo
Department of Electronics and Communication Engineering, Hanyang University, Ansan 15588, Korea.
Agency for Defense Development, Daejeon 34186, Korea.
Sensors (Basel). 2020 Feb 12;20(4):979. doi: 10.3390/s20040979.
In this paper, we investigate the so-called noise propagation effect in a mixed radio-frequency/free-space optical (RF/FSO) amplifying-and-forwarding (AF) relaying system that is applied for data transmission in wireless sensor networks. The noise propagation could be essentially severe when battery-charged sensor nodes have very limited transmit power. We provide an exact expression on the cumulative distribution function (CDF) of end-to-end signal-to-noise power ratio (SNR) for a dual-hop mixed RF/FSO AF relaying system. We assume a tightly power-constrained amplifying gain at the relay, which has been usually ignored in existing performance studies for the mixed RF/FSO AF system. It however should be considered to properly evaluate the noise propagation effect especially if the relaying power is not infinite or the sensor has a poor budget in transmit power. We apply the derived exact CDF to evaluate the system performances such as outage probability, average bit-error rate, and ergodic capacity. Numerical investigation is used to justify that the proposed analysis is exactly matched with the simulation and shows that the performance gap caused by the inclusion of the noise propagation effect is significant (about 2-12%) especially when the SNR per hop is in the medium- or the low-SNR ranges (i.e., at 10-20 dB).
在本文中，我们研究了一种应用于无线传感器网络数据传输的混合射频/自由空间光（RF/FSO）放大转发（AF）中继系统中的所谓噪声传播效应。当电池供电的传感器节点发射功率非常有限时，噪声传播可能会非常严重。我们给出了双跳混合RF/FSO AF中继系统端到端信噪比（SNR）累积分布函数（CDF）的精确表达式。我们假设中继处的放大增益受到严格的功率限制，而在现有的混合RF/FSO AF系统性能研究中，这一点通常被忽略。然而，为了正确评估噪声传播效应，尤其是当中继功率不是无穷大或者传感器发射功率预算较低时，应该考虑这一点。我们应用推导得到的精确CDF来评估系统性能，如中断概率、平均误码率和遍历容量。数值研究表明，所提出的分析与仿真结果完全匹配，并且表明考虑噪声传播效应所导致的性能差距是显著的（约2 - 12%），特别是当每跳SNR处于中低SNR范围时（即10 - 20 dB）。
