Joint Design of Polar Coding and Physical Network Coding for Two-User Downlink Non-Orthogonal Multiple Access

Area of Science:

• Wireless Communications
• Information Theory
• Coding Theory

Background:

• Successive interference cancellation (SIC) in polar decoding is suboptimal for finite blocklength transmissions in NOMA.
• Non-orthogonal multiple access (NOMA) systems require efficient coding and decoding strategies for improved performance.

Purpose of the Study:

• To propose a joint polar coding and physical network coding (PNC) scheme for two-user downlink NOMA (PN-DNOMA) channels.
• To enhance channel polarization and decoding performance for both users in finite blocklength transmissions.

Main Methods:

• Constructing an XORed message of two user messages.
• Superimposing the XORed message with the weak user's message for broadcast.
• Utilizing PNC mapping and polar decoding for direct recovery of the strong user's message.
• Employing an equivalent long-length polar decoder for the weak user's message recovery.
• Optimizing power allocation based on channel conditions, user fairness, and performance.

Main Results:

• Direct recovery of User 1's message using PNC mapping and polar decoding.
• Equivalent long-length polar decoder construction for User 2's message recovery.
• Significant improvements in channel polarization and decoding performance for both users.
• Achieved performance gains of 0.4-0.7 dB over conventional schemes in two-user downlink NOMA systems.

Conclusions:

• The proposed PN-DNOMA scheme effectively addresses the limitations of SIC-aided polar decoding in finite blocklength NOMA.
• The joint coding approach enhances spectral efficiency and overall system performance.
• Optimized power allocation further boosts system efficiency and fairness.