Delay-Sensitive NOMA-HARQ for Short Packet Communications

Area of Science:

• Wireless communication systems
• Information theory
• Signal processing

Background:

• Non-orthogonal Multiple Access (NOMA) enables multiple users to share the same time and frequency resources.
• Hybrid Automatic Repeat Request (HARQ) is crucial for reliable data transmission by managing retransmissions.
• Finite blocklength regime considers practical constraints on data packet sizes and associated latency.

Purpose of the Study:

• To investigate the performance of two-user uplink NOMA combined with HARQ in the finite blocklength regime.
• To prioritize and minimize packet delivery delay and queuing for users.
• To propose a novel NOMA-HARQ scheme for enhanced latency performance.

Main Methods:

• Developed a novel NOMA-HARQ approach where retransmissions occur non-orthogonally with new packets in the same time slot.
• Employed a Markov model (MM) to analyze the system dynamics with one retransmission.
• Characterized packet error rate (PER), throughput, and latency.
• Utilized numerical optimization to determine optimal power ratios for users.

Main Results:

• The proposed NOMA-HARQ scheme significantly reduces packet delivery delay compared to standard NOMA-HARQ.
• Performance analysis using the Markov model accurately characterized PER, throughput, and latency.
• Optimal power ratios were identified through numerical optimization, enhancing system efficiency.

Conclusions:

• The novel NOMA-HARQ scheme effectively addresses the challenge of limited latency in finite blocklength systems.
• The proposed approach offers a substantial improvement in packet delivery delay while maintaining a target PER.
• This work provides valuable insights for designing efficient wireless communication systems with strict latency requirements.