Joint Resource Allocation for Multiuser Opportunistic Beamforming Systems with OFDM-NOMA

Area of Science:

• Wireless communication systems
• Signal processing for communications

Background:

• Opportunistic beamforming (OBF) enhances spectrum efficiency (SE) in multiple-input-multiple-output (MIMO) systems.
• Existing OBF multiple-access schemes often yield unsatisfactory SE.
• Low complexity and feedback are key OBF advantages.

Purpose of the Study:

• To propose a novel downlink multiuser OBF system integrating OFDM and NOMA.
• To maximize SE and minimize BER in frequency selective fading channels.
• To address the non-convex optimization problem for resource allocation.

Main Methods:

• Developed a downlink multiuser OBF system combining OFDM and NOMA.
• Derived closed-form expressions for equivalent channels and SE.
• Formulated and solved a non-convex optimization problem using a joint iterative algorithm for subcarrier mapping, user pairing, and power allocation.

Main Results:

• The proposed method achieved approximately 5 dB gain in SE and BER compared to existing OBF techniques.
• Achieved ~2 (bps/Hz) higher SE than sparse code multiple-access (SCMA) under specific conditions.
• Demonstrated high SE and low BER with limited feedback and computation complexity.

Conclusions:

• The proposed OFDM-NOMA OBF scheme effectively improves SE and BER in wireless systems.
• The joint iterative optimization algorithm provides an efficient solution for resource allocation.
• The system offers robust performance with limited feedback and computational load.