## 4 Integration with Communication Technologies  
### Synergy Between RISs and Current, Future Wireless Communication Systems Including 6G  
Integrating RISs into existing and forthcoming communication systems, including the anticipated 6G, signifies a transformative leap towards more dynamic, efficient, and robust communication networks [103; 104]. The RIS holds immense potential in synergizing with and enhancing current and future communication protocols [105]. This section explores how RISs can be harmoniously integrated with current and future wireless communication systems, mainly focusing on the evolution towards 6G. 1. **Enhancing 5G Networks and Beyond:** As the world gradually transitions from 5G to 6G, RISs are poised to play a crucial role in addressing the limitations of previous generations and enhancing network performance [104]. Fifth-generation networks, characterized by high data rates, low latency, and massive device connectivity, can benefit from RIS's ability to provide surfaces that improve signal propagation and coverage, especially in urban environments where obstacles are prevalent [103]. RISs can mitigate signal degradation and enhance the efficiency of massive MIMO systems, which are integral to 5G technology [106; 107]. 2. **Empowering 6G Vision with RISs:** The envisioned 6G networks aspire to provide ubiquitous wireless intelligence, extreme connectivity, and profound integration with AI. RISs inherently align with these goals, offering adaptive environments that can be optimized for various communication needs. By controlling the propagation of electromagnetic waves, RISs can help 6G to achieve its targets of THz communications, extremely low latencies, and seamless integration of terrestrial, aerial, and space networks [103; 105]. 3. **Synergy with IoT and Machine-Type Communications:** The IoT and Machine-Type Communications (MTCs) are expected to increase under 6G, with billions of devices communicating simultaneously [105]. RISs can enhance these devices' energy efficiency and reliability by optimizing signal paths and reducing interference, thereby extending the battery life and improving the performance of IoT and MTC networks [108; 109]. This is especially crucial in dense networks where traditional methods of ensuring quality of service may fall short. 4. **Facilitating Advanced Beamforming and Spatial Diversity:** Advanced beamforming and exploiting spatial diversity are critical techniques in modern communication systems to improve signal quality and system capacity. RISs can provide a cost-effective means to implement these techniques, offering finer control over the signal propagation environment [110]. By dynamically adjusting the phase shifts of individual elements, RISs can create constructive or destructive interference where needed, significantly enhancing the capabilities of beamforming and MIMO technologies in current and future communication systems [111]. 5. **Integrating with Software-Defined Networks (SDNs) and Network Function Virtualization (NFV):** As networks become more software-driven, integrating RISs with SDNs and NFV can lead to highly flexible and adaptable network architectures. RISs can provide physical-layer adaptability, while SDNs and NFV can dynamically adjust network resources and functions [105]. This synergy optimizes real-time network performance, meeting modern communication systems' diverse and dynamic requirements. 6. **Enabling Energy-Efficient and Sustainable Networks:** As global communication demands surge, so does the energy consumption of communication networks. RISs offer a pathway to more sustainable networks by enhancing signal efficiency and reducing the need for power-intensive transmitters and infrastructure [111]. This aligns with the green communication objectives of 6G, which emphasize sustainability alongside technological advancement. 7. **Security Enhancements:** Security is a paramount concern in modern communication systems.