Design and optimization of highly reliable cognitive non-orthogonal multiple access communication systems

Area of Science:

• Wireless Communication Networks
• Signal Processing
• Information Theory

Background:

• Coexisting cellular and device-to-device (D2D) networks face challenges with direct link availability due to shadowing and path loss.
• Relays are crucial for enabling reliable communication in such scenarios.

Purpose of the Study:

• To design and analyze novel transmission schemes for relay-assisted spectrum sharing networks.
• To optimize power allocation for minimizing outage probability (OP) under quality of service (QoS) constraints.
• To evaluate the performance of proposed schemes against benchmarks.

Main Methods:

• Development of multiple access broadcast NOMA (M-NOMA) and time division broadcast NOMA (T-NOMA) schemes.
• Power optimization to minimize D2D OP under cellular QoS constraints.
• Derivation of analytical expressions for outage probabilities and average throughput.
• Proposal of a hybrid M/T-NOMA cognitive communication scheme.

Main Results:

• Optimized power allocation strategies were derived for both M-NOMA and T-NOMA.
• Outage probabilities for cellular and D2D signals were calculated.
• Asymptotic OPs and average throughput were analyzed for performance insights.
• The hybrid M/T-NOMA scheme demonstrated superior system throughput.

Conclusions:

• The proposed M-NOMA and T-NOMA schemes effectively manage relay-assisted spectrum sharing.
• The hybrid M/T-NOMA scheme adaptively selects the optimal transmission strategy.
• Simulation results confirm the analytical findings and highlight performance gains over existing schemes.