Here is Part 2 in the series of articles (Part 1, 2, 3 & 4) continuing the theme concerning 6G and the challenging situations concerning the impact of the changing characteristics of technology advancement that needs constant assessment if evidence from it placed in legal proceedings is to be understood to be trustworthy and reliable.
Investigators observing Cell ID detection in RIS-aided communications is largely correct, but there are important nuances to consider regarding its forensic implications.
1. Confirmation of Cell ID in RIS-Aided Communications
- Figures 4.2-1 and 4.2-2 in ETSI GR RIS-005 illustrate two scenarios: Tx-RIS-Rx Paths Only: The direct transmission path is blocked (e.g., due to outdoor-to-indoor (O2I) loss), so the signal only reaches the receiver via the RIS reflection.
- Tx-Rx and Tx-RIS-Rx Coexistence: Both direct and RIS-aided paths exist simultaneously.
- Cell ID detection is possible in both cases because the signal still originates from the base station (Tx), meaning the Cell ID remains embedded in the transmission.
2. Where RIS Challenges Traditional CSA Assumptions
Although Cell ID is still detectable, the interpretation of location based on Cell ID alone becomes problematic due to RIS effects:
✅ Multipath Complexity: The receiver might receive multiple reflections with different time delays, making timing-based distance estimations unreliable.
✅ False Location Inference: A forensic analyst might assume the device is in a direct Tx-Rx coverage area, when in reality it is receiving an RIS-reflected signal from another angle.
✅ Time-Varying Signal Paths: RIS elements can dynamically alter their configuration, meaning the same location may receive different paths at different times, complicating historical RF reconstruction.
3. How This Affects CSA and RFPS
- In traditional CSA, Cell ID + Timing Advance (TA) helps estimate a device’s proximity to the tower.
- In RIS environments, TA values can be misleading because the actual signal path is indirect.
- RF Propagation Surveys (RFPS) conducted after an incident may not match conditions at the time of the event, as RIS configurations change dynamically.
4. Interpretation Not Oversimplified, but Partial
- You'll correctly note that Cell ID can still be detected in RIS-assisted communications.
- However, the forensic reliability of CSA based solely on Cell ID is now compromised because the path the signal takes is no longer straightforward.
- Future forensic CSA in RIS environments must integrate additional RIS metadata (e.g., RIS control logs) to determine if a signal was direct or reflected.
This article continues on from the discussions posted:
Forensic Challenges in 6G Cell Site Analysis (CSA) and Radio Frequency Propagation Surveys (RFPS) - https://cellsiteanalysis.blogspot.com/2025/04/forensic-challenges-in-6g-cell-site.html
Reconfigurable Intelligent Surfaces (RIS) and forensic implications in 6G CSA (Part 1) - https://cellsiteanalysis.blogspot.com/2025/04/reconfigurable-intelligent-surfaces-ris.html
