NDP Structure for Secure Multiuser Sounding
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Solution Overview
Problem
The existing P-matrix structure in IEEE 802.11n/ac/ax specifications is insecure for multiuser downlink sounding, making users vulnerable to security attacks when an attacker is present, as it fails to provide secure MU downlink sounding.
Innovation Solution
The proposed solution modifies the Null Data Packet (NDP) structure by removing cyclic prefix (CP) and symbol-level repetition, using zero-prefix or padding, and applying masking sequences to generate unique sounding symbols for each user, ensuring that sounding signals are distinct and resistant to replay attacks, and varying the sounding signals over time or frequency to prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing P-matrix structure with cyclic prefix and symbol-level repetition is used for NDP, then the sounding signal structure is simple and backward compatible, but the system becomes vulnerable to CP replay attacks and P-matrix code replay attacks in multiuser downlink sounding
Solution Approach 1:
The patent extracts and removes the cyclic prefix (CP) and symbol-level repetition components from the traditional NDP structure. By taking out these elements that enable replay attacks, the patent eliminates the security vulnerability while maintaining the essential sounding functionality through alternative mechanisms like zero-prefix and unique masking sequences for each user.
Solution Approach 2:
The patent applies local quality by making each user's sounding signal have unique characteristics through user-specific masking sequences. Instead of using a uniform structure for all users, each user's NDP contains locally differentiated elements (unique masking sequences and zero-prefix patterns) that prevent one user's signal from being replayed as another user's signal, thereby providing security at the local user level.
2Reliability
If cyclic prefix and symbol-level repetition are removed from NDP structure, then replay attacks are prevented, but the sounding signal structure becomes more complex requiring zero-prefix and masking sequences
Solution Approach 1:
The patent changes key parameters of the NDP structure: replacing cyclic prefix with zero-prefix, and introducing user-specific masking sequences as new parameters. These parameter changes transform the NDP from a simple repeated structure to a differentiated structure where each user has unique signal characteristics, preventing replay attacks while maintaining structured organization for multiuser support.
Solution Approach 2:
The patent segments the sounding signal generation process into distinct components: zero-prefix addition, user-specific masking sequence application, and structured symbol arrangement. This segmentation allows each component to be independently optimized for security while maintaining overall system organization, making the complexity manageable through modular design.
3Reliability
If unique sounding symbols are generated for each user using masking sequences, then secure MU downlink sounding is achieved, but the signal processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-generating and storing masking sequences for each user before the actual sounding process. These user-specific masking sequences are prepared in advance, allowing the access point to quickly apply them during multiuser downlink sounding without real-time computation overhead, thereby reducing signal processing complexity during critical operations while maintaining security.
Data Source
AI summary
Methods and apparatuses for arranging sounding symbol are provided. An example apparatus comprises memory; and processing circuitry coupled to the memory. The processing circuitry is configured to encode a sounding signal. The sounding signal comprises a plurality of sounding symbols, and the repetition of sounding symbols to be transmitted in sequence is avoided.