Method and apparatus for acquisition of reliable time in a wireless network
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Solution Overview
Problem
Wireless communication networks face challenges in providing accurate and reliable time acquisition, especially when Global Navigation Satellite System (GNSS) signals are unavailable due to spoofing or jamming, and existing methods lack robustness in verifying the authenticity of time signals.
Innovation Solution
A method where a base station broadcasts ciphered current time, and user equipment (UE) determines a propagation delay to correct the time, using techniques like timing advance or round trip propagation time, while also verifying the authenticity of the signal using digital signatures to detect spoofing attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station broadcasts current time without ciphering, then the time acquisition process is simple and fast, but the reliability and security of the time signal is compromised making it vulnerable to spoofing attacks
Solution Approach 1:
The base station performs ciphering of the current time signal before broadcasting it to UEs. This preliminary encryption action ensures that only authenticated UEs with the correct decryption key can access the time signal, preventing spoofing attacks while maintaining a streamlined acquisition process for legitimate users.
Solution Approach 2:
A digital signature mechanism is introduced as an intermediary between the base station and UEs for time signal verification. The base station signs the time signal with its private key, and UEs verify the signature using the base station's public key, providing cryptographic authentication without complicating the overall time acquisition flow.
2Measurement precision
If the UE uses unciphered current time from the base station, then the time acquisition is straightforward, but the time accuracy is insufficient for applications requiring microsecond or nanosecond precision
Solution Approach 1:
The base station pre-calculates and includes timing advance compensation values in the broadcast time signal. This preliminary compensation action accounts for propagation delays before the signal reaches the UE, enabling the UE to achieve microsecond or nanosecond precision without performing complex real-time calculations.
Solution Approach 2:
The system implements a feedback mechanism where the UE measures the actual reception time of the time signal, compares it with the expected time based on propagation delay calculations, and reports any discrepancies to the base station. The base station uses this feedback to refine timing advance compensation values, progressively improving time accuracy.
3Reliability
If the UE accepts time signals from any source, then the time acquisition is easy and fast, but the system becomes vulnerable to spoofing attacks by malicious devices
Solution Approach 1:
The system applies preliminary anti-action by implementing cryptographic authentication mechanisms before the UE accepts any time signal. The base station signs each time signal with its private key, and the UE verifies the digital signature using the base station's public key before processing the time value, fundamentally preventing spoofing attacks at the authentication stage.
Solution Approach 2:
A digital signature verification mechanism serves as an intermediary layer between the time signal source and the UE's time processing. This cryptographic intermediary automatically detects spoofing attempts by verifying the digital signature, making spoofing detection transparent and integrated into the normal time acquisition process rather than a separate complex measurement task.
4Measurement precision
If the base station provides time correction based on propagation delay, then the time accuracy is improved, but the complexity of time synchronization increases
Solution Approach 1:
The base station performs preliminary propagation delay calculation and compensation by including timing advance values in the broadcast time signal. This preliminary correction action accounts for the time required for the signal to travel from the base station to the UE, enabling accurate time synchronization without requiring complex real-time delay measurement and correction mechanisms at the UE.
Data Source
AI summary
Accurate and reliable time is acquired by a user equipment (UE) from a base station in a wireless network. The base station may obtain the time, e.g., UTC time or a GNSS time, and ciphers at least a portion of the time before broadcasting the time. The UE determines a propagation delay between the UE and the base station based on a timing advance, known locations of the UE and the base station, or a measured round trip propagation time (RTT) between the UE and the base station. A corrected time can be determined based on the time received from the base station and the propagation delay. A digital signature included with the time broadcast by the base station increases reliability. Spoofing of the broadcast time by an attacking device may be detected by the UE based on the propagation delay being outside an expected range.