Statistical Analysis of Noise Propagation Effect for Mixed RF/FSO AF Relaying Application in Wireless Sensor Networks

Area of Science:

• Wireless Communication Systems
• Optical Networking
• Signal Processing

Background:

• Wireless sensor networks (WSNs) often use hybrid radio-frequency/free-space optical (RF/FSO) systems for data transmission.
• Limited transmit power in battery-operated sensor nodes exacerbates noise propagation effects.
• Existing studies often overlook the impact of constrained amplifying gain at the relay.

Purpose of the Study:

• To investigate the noise propagation effect in a dual-hop mixed RF/FSO amplifying-and-forwarding (AF) relaying system.
• To derive an exact expression for the cumulative distribution function (CDF) of the end-to-end signal-to-noise power ratio (SNR).
• To evaluate system performance metrics including outage probability, average bit-error rate, and ergodic capacity under realistic power constraints.

Main Methods:

• Derivation of an exact CDF expression for the end-to-end SNR in a dual-hop mixed RF/FSO AF system.
• Modeling of a tightly power-constrained amplifying gain at the relay.
• Application of the derived CDF to analyze outage probability, average bit-error rate, and ergodic capacity.
• Numerical simulations to validate the analytical model.

Main Results:

• An exact CDF expression for the end-to-end SNR was derived, accounting for noise propagation.
• The analysis revealed a significant performance gap (2-12%) due to noise propagation, particularly in medium-to-low SNR regimes (10-20 dB).
• Simulations confirmed the accuracy of the derived analytical model.

Conclusions:

• The noise propagation effect in mixed RF/FSO AF systems is substantial and cannot be ignored, especially with power-limited relays.
• Accurate performance evaluation requires considering the amplifying gain constraints at the relay.
• The derived analytical framework provides a valuable tool for designing robust WSNs utilizing mixed RF/FSO technologies.