## 4 Integration with Communication Technologies
### RIS's Potential in Enhancing Radar and Navigation Systems  
Including RISs in radar and navigation systems represents a significant technological advancement, promising enhanced performance and new functionalities [110; 113; 114]. RIS,essentially a surface with the ability to alter EM waves passing through or reflecting off it, can dramatically improve the efficacy and capabilities of radar and navigation systems in several ways.  
1. **Signal Enhancement and Path Loss Reduction:** RISs can reflect signals toward specific directions, mitigating path loss and enhancing signal strength at the receiver. RISs can provide alternative non-LOS paths in complex urban environments or terrains where LOS is obstructed, significantly improving coverage and reliability [110].
2. **Target Resolution and Detection:** RISs can contribute to a higher resolution and better target detection in radar systems. By controlling the phase and amplitude of the reflected waves, RISs can help to distinguish between closely spaced objects, enhancing the radar's ability to detect and track objects with improved accuracy [110; 115].
3. **Reducing Interference and Clutter:** Unwanted signals can be mitigated when an RIS is set up correctly. It will reduce interference and improve the SNR [113]. This is particularly helpful in crowded frequency bands such as those used by frequency-modulated continuous-wave (FM-CW) radar or navigation signals, which are prone to interference from multiple sources. By focusing the signal in desired directions and avoiding undesired ones, RISs can significantly reduce clutter and enhance the system's performance.
4. **Dynamic Beamforming and Steering:** Traditional radar and navigation systems require mechanical steering of antennas or complex phased array systems for beamforming. RISs can provide a more efficient and faster means to control the wavefront, enabling dynamic beamforming and steering without moving parts or expensive arrays [113]. This can lead to systems that are more responsive, precise, and less prone to wear and tear.
5. **Enhanced Multipath Exploitation:** RISs can be strategically leveraged to harness the dynamic multipath propagation environment; a scenario unequivocally deemed detrimental in conventional systems [110; 116]. By meticulously controlling the properties of the surfaces within the environment, RISs can transform the multipath effects from a formidable challenge into a potent advantage, utilizing these phenomena to reinforce system robustness and glean unparalleled insights about the communication environment.
6. **Improved Security:** The ability of an RIS to control electromagnetic waves can also be leveraged to improve the security of multi-static radar and localization signals [104; 105]. By ensuring that signals are only strong in intended directions and locations, RISs can make it more difficult for adversaries to intercept or jam the signals in an electronic warfare situation, providing a layer of security that is actively adaptable to threats.  
Hence, integrating RISs into radar and navigation systems holds substantial potential, from enhancing signal quality and system performance to opening up new capabilities and improving security. As research intensifies and practical implementations materialize in this field, we may be on the brink of a new era in radar and navigation technology, marked by unprecedented adaptability, enhanced efficiency, and improved robustness. The capabilities of RISs in the beyond 5G (B5G) networks is just beginning to be explored, and the coming years will likely see significant advancements and innovative applications of this promising technology.