RIS-assisted near-field localization using practical phase shift model

Area of Science:

• Wireless communication
• Signal processing
• Electromagnetics

Background:

• Accurate localization of user equipment (UE) is crucial for advanced wireless services.
• Reconfigurable intelligent surfaces (RIS) offer potential for enhancing wireless communication environments.
• Existing models often oversimplify RIS behavior, particularly amplitude variations.

Purpose of the Study:

• To analyze user equipment localization performance using RIS-based lenses in the uplink.
• To evaluate the impact of realistic RIS phase-dependent amplitude variations on localization accuracy and data rates.
• To propose a simplified localization algorithm to mitigate computational complexity.

Main Methods:

• Fisher Information Matrix (FIM) analysis for localization performance.
• Modeling of actual RIS phase-dependent amplitude variations.
• Development of an angular expansion-based localization algorithm.
• Near-field region analysis of Position Error Bound (PEB) and Root Mean Square Error (RMSE).

Main Results:

• Superior localization performance is achieved with prior location information.
• Realistic RIS amplitude models reveal increased localization error and degraded data rates for amplitude values less than one in the near-field.
• The widely used unity amplitude assumption for RIS phase shifts is demonstrated to be inaccurate.

Conclusions:

• Realistic modeling of RIS amplitude variations is essential for accurate near-field localization.
• The proposed angular expansion algorithm offers a computationally efficient approach to localization.
• Future research should consider these realistic amplitude effects for optimized RIS-aided wireless systems.