Performance Enhancement of V2V Communication by QC-LDPC Code and NOMA-UM-MIMO Techniques

This study addresses the critical challenges in Vehicle-to-Vehicle (V2V) communications, particularly the issues of high mobility, dynamic channel conditions, and interference that adversely affect Bit Error Rate (BER) performance and overall system capacity. We propose an innovative integration of NOMA with a specific form of Quasi Cyclic-Low Density Parity Check (QC-LDPC) coding to enhance communication reliability and efficiency in vehicular environments, ensuring effective system operation even without clustering. Analytical and numerical simulations based on the NOMA-MIMO system are conducted to derive BER formulas for both near $\text {(}{Bob}_{1})$ and far $\text {(}{Bob}_{2})$ users. The effectiveness of Successive Interference Cancellation (SIC) techniques in mitigating interference in vehicular environments is also explored. Additionally, mathematical formulations for outage probability in NOMA-MIMO systems indicate that outage probability decreases with increased transmit power as users get closer to the base station. Our research demonstrates that QC-LDPC codes without $Girth_{4}$ cycles significantly enhance error correction capabilities and achieve higher spectral efficiency over Rician fading channels. OFDMA-LDPC and SM-NOMA (Spatial Multiplexing-Non Orthogonal Multiple Access) based vehicular communication systems are also compared, emphasizing the impact of $2\times 2$ and $4\times 4$ MIMO configurations on BER and capacity. The results highlight NOMA’s superiority and the simplified structure of QC-LDPC, resulting in enhanced system performance in dynamic vehicular communication scenarios. Moreover, increasing the antennas at both ends leads to further performance improvements, with results achieved at a code rate 1/3 among the benchmarked schemes. The Sum-Product algorithm is often employed as a preferred decoding method in high-mobility scenarios due to its efficiency and simplicity, which enhance communication reliability and system capacity. This research also addresses the challenges associated with high vehicle velocities and the resulting Doppler shifts, which are significant in highway and urban scenarios. The mentioned effects were particularly pronounced at a frequency of 0.2 THz and a speed of 120 km/h, impacting signal quality and reliability.