A Multi-Metric Performance Analysis of STAR-RIS Aided MIMO-NOMA Framework for CIoT-Enabled 6G Wireless Networks

Consumer internet of things (CIoT) devices are increasingly being integrated into various aspects of wireless communication, enhancing the scalability of networks. Along with these, in sixth-generation (6G) wireless networks, reconfigurable intelligent surface (RIS) has emerged as a prominent technology that can dynamically control the wireless environment. As a progression of this technology, recently, simultaneously transmitting and reflecting-RIS (STAR-RIS) has gained significant attention for its ability to achieve full-space coverage by simultaneously transmitting and reflecting signals. On the other hand, multiple input multiple output (MIMO) and non-orthogonal multiple access (NOMA) technologies have already proven their dominance in fifth-generation (5G) wireless communication networks by obtaining massive connectivity and high spectral efficiency. This paper proposes a mode switching-based STAR-RIS aided MIMO-NOMA framework for 6G wireless networks to cover the non-line-of-sight (NLoS) region as a footprint. The proposed framework adopts the selection combining and maximum ratio combining protocols to meet the quality of service requirements of the CIoT devices in NLoS regions. The study also derives mathematical formulations for the proposed framework by analyzing key performance metrics, including achievable data rate (ADR), outage probability, bit error rate (BER), diversity order, and throughput. To evaluate the effectiveness of the proposed system, comparative analyses are conducted against benchmark models such as STAR-RIS assisted single-input single-output (SISO) orthogonal multiple access and STAR-RIS assisted SISO-NOMA schemes. Simulation results affirm the superiority of the proposed framework for both the reflecting and transmitting regions of the STAR-RIS. In the transmitting region, under the maximum ratio combining protocol, the far CIoT device of the proposed STAR-RIS aided MIMO-NOMA framework attains an ADR at least 0.45 times higher than the conventional framework. Further, the BER of the proposed framework is 0.93 times lower than conventional framework.