1-bit feedback-based beamforming scheme for an uplink FSO-NOMA system with SIC errors

Area of Science:

• Optical Communications
• Wireless Communication Systems
• Signal Processing

Background:

• Free-space optical (FSO) communication systems offer high bandwidth but are susceptible to fading.
• Nonorthogonal multiple access (NOMA) enhances spectral efficiency by allowing users to share resources.
• Multiple-input single-output (MISO) systems can improve signal reliability and capacity.

Purpose of the Study:

• To investigate the performance of a novel beamforming scheme for MISO uplink FSO-NOMA systems.
• To analyze the impact of 1-bit channel state information feedback on system performance.
• To evaluate the effectiveness of the proposed scheme in mitigating successive interference cancellation (SIC) errors.

Main Methods:

• Bit error rate (BER) analysis over negative exponential fading channels.
• Derivation of a simplified asymptotic upper bound for BER using order statistics.
• Optimization of the beamforming vector by minimizing the BER upper bound.
• Analytical and simulation-based comparisons with existing FSO-NOMA and SISO FSO systems.

Main Results:

• The proposed beamforming scheme with 1-bit feedback significantly suppresses SIC errors, leading to improved BER performance.
• Optimal performance is achieved by assigning higher weights to channels with greater gain.
• The beamforming vector is independent of average signal-to-noise ratio under specific channel conditions.
• The scheme demonstrates a substantial coding gain advantage over conventional FSO-NOMA and SISO FSO systems.

Conclusions:

• The 1-bit feedback beamforming scheme offers a robust solution for MISO uplink FSO-NOMA systems, enhancing reliability and performance.
• The proposed scheme effectively mitigates the impact of SIC errors, achieving comparable BER for all transmitters.
• System performance degrades with an increasing number of transmitters in MISO FSO-NOMA configurations.