# Sixth-Generation (6G) Networks for Improved Machine-to-Machine (M2M) Communication in Industry 4.0
## 3 Results of the Review
### Key Issues to Be Addressed
This can be implemented, for example, by optimizing the feedback point of the minimum mean squared error ordered successive elimination constellation (MMSE-OSIC), which provides an approximation of optimal detection. The vector closest to the received signals is selected based on the maximum likelihood criterion, improving the correctness of the decision in subsequent iterations. For fast operation, however, it requires a reasonable selection of initial parameters (such as the relaxation coefficient) and parallel coarse and fine detection [16]. Sixth-generation network security is also important from an economic perspective--identifying business relationships and business-oriented security analysis by qualitatively assessing the impact of individual security breaches under different business conditions. This means that one can model the effects of security attacks in individual scenarios and their impact on the dynamics of a specific type of business (for instance, a product or service market segment; Figure 7) [17]. The capabilities of reconfigurable intelligent surface (RIS) and rate-splitting multiple access (RSMA) technologies extend to 6G and beyond. They provide control of the propagation environment and interference management, as well as the division of a given user's messages into private and shared messages. For further development, progress is needed in optimizing the grouping of RIS elements and power division based on fractional programming (FP) as an alternative to existing spatial division multiple access (SDMA) systems supported by RIS [18]. VLC delivers robust systems that strongly support IIoT connections and throughput, including VLC channel modeling and ray tracing simulation to explore the VLC channel in IIoT scenarios. This makes it possible to analyze large-scale fading and multipath characteristics (channel impulse response--CIR; optical path loss--OPL; delay spread--DS; angular spread--AS) and distance-dependent distribution. The channel characteristics from a single transmitter are proportional to the distance, and the degree of dispersion in the factory floor (temporally, spatially) is higher than in typical office rooms. The density of objects and even the influence of the user's height on the characteristics of the channel are also important. It is necessary to take into account the environment and link adaptation to optimize the multipath interference problem. The signal-to-noise ratio (SNR), RMS DS value, CIR coefficients, and bit error rate (BER) have been proposed as key parameters for the selection of a solution [19]. Wireless sensor networks (WSNs) are increasingly using hybrid RF-VLC cognitive systems, for WSNs with cognitive radio sensor networks (CRSNs) and VLC. This requires a trade-off between performance and complexity, which increases as the number of devices and data rates increase. Further progress requires the development of cognitive radio strategies based on ML and DL while  
Figure 7: Security requirements, assets, and business relationships model [17]. providing large datasets for training the network. This must be reconciled with energy-efficient resource allocation, efficient industrial scenarios, energy harvesting, the effective use of spectrum, and network performance [20]. VLC provides wireless communication in areas where radio frequency (RF)-based technology has limited use, such as in industrial environments due to interference. VLCs offer solutions both inside buildings (including industrial locations) and outdoors, for example for traffic management. Optical noise-tolerant VLC systems based on on-off keying (OOK) modulation and Manchester encoding or binary frequency shift keying (BFSK) and non-return-to-zero (NRZ) modulation can maintain a maximum noise radiation intensity of 3500 \(\upmu W/\)cm\({}^{2}\) and provide a 20-25% improvement in indirect exposure to incandescent light sources [21].