Frequency Hopping Deviation Authentication for Telecommunications
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Solution Overview
Problem
Existing authentication methods for digital telecommunications systems are inadequate for non-deterministic, unidirectional systems where frequency synchronization is absent, leading to challenges in verifying the identity of terminals due to significant frequency drift and mismatched frequency bands.
Innovation Solution
An authentication method that measures the frequency band of received data packets, extracts the terminal identification code, calculates frequency hopping deviations, and determines the theoretical frequency hopping sequence to verify the authenticity of data packets, even in the absence of synchronization between terminals and stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional authentication methods are used in non-deterministic systems, then authentication can be performed in synchronized systems, but authentication fails in non-synchronized systems with significant frequency drift
Solution Approach 1:
The patent changes the authentication parameter from absolute frequency band matching to frequency hopping deviation calculation. Instead of comparing measured frequency bands against predetermined theoretical bands (which fails when frequency drift exceeds bandwidth), the method calculates the deviation between consecutive frequency hops. This parameter transformation allows authentication to work regardless of the terminal's frequency drift magnitude, as long as the hopping sequence pattern is maintained.
2Measurement precision
If frequency band matching is used for authentication, then authentication works in tuned systems, but frequency mismatch occurs in non-tuned systems
Solution Approach 1:
The patent implements a feedback mechanism by using the previously received data packet's frequency band as a reference for authenticating the current packet. The station calculates the frequency hopping deviation by comparing the current measured frequency band with the previous one, rather than comparing against a predetermined theoretical band. This feedback-based approach compensates for frequency drift, as the deviation between consecutive hops remains predictable even when absolute frequencies drift.
3Reliability
If additional control data is added for authentication, then terminal identity can be verified, but the ratio of useful data to control data decreases
Solution Approach 1:
The patent makes the frequency hopping sequence itself serve the dual purpose of data transmission and authentication. The terminal's predefined frequency hopping sequence acts as an implicit identifier that is already embedded in the transmission process. By measuring and comparing the frequency hopping pattern, the station can authenticate the terminal without adding separate authentication data fields, thus maintaining data transmission efficiency while enabling reliable authentication.
Data Source
Figure 1~2
AI summary
The present invention relates to a method for authenticating data packets transmitted by terminals (10) and received by a station (20), each terminal (10) sequentially transmitting data packets in a plurality of different frequency bands according to a predefined sequence of frequency hops that is specific to said terminal, characterised in that it comprises, for a data packet received by the station (20), the steps of: i) measuring (51) the frequency band in which the data packet in question was received; ii) extracting (52) an identification code from said data packet in question; iii) determining (55) a theoretical frequency hop in accordance with the sequence of frequency hops associated with said identification code extracted from the data packet in question; and iv) calculating (56) a frequency hop deviation in accordance with the theoretical frequency hop and the frequency bands measured for the data packet in question and for the preceding data packet. The authentication method (50) comprises a step (58) of determining whether the data packets received sequentially with a single identification code were transmitted by the terminal (10) associated with said identification code in accordance with at least one frequency hop deviation.