Wi-Fi Multi-Link Handover Using Link-Specific PTKs and BA States
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Solution Overview
Problem
Existing Wi-Fi multi-link devices face challenges in maintaining seamless handover (zero handover) during mobility while mitigating issues related to shared pairwise transient keys (PTK) and block acknowledgement (BA) agreements, especially in non-collocated multi-link environments, which are critical for supporting Time-Sensitive Networking (TSN) and Real-Time Applications (RTA) with high reliability and low latency.
Innovation Solution
Implementing different pairwise transient keys (PTKs) and block acknowledgement agreements for non-collocated multi-link devices, where each link has its own PTK or security key, and performing packet reordering among collocated multi-link sets, with a centralized controller managing traffic steering and redundancy to ensure seamless transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a shared PTK is used across multiple links for simplicity, then device complexity is reduced, but reliability deteriorates during handover due to packet loss and security key conflicts
Solution Approach 1:
The patent divides the shared PTK into link-specific PTKs, where each link has its own dedicated security key. This segmentation allows independent key management per link, eliminating conflicts during handover while maintaining security. The source link and target link can operate with different PTKs simultaneously, enabling seamless transitions without packet loss.
Solution Approach 2:
The patent establishes PTKs for both source and target links before handover occurs. The mobile station and target access point pre-share a PTK that is activated only when needed for handover. This preliminary setup ensures that security keys are ready in advance, eliminating delays and packet loss during the actual handover transition.
2Device complexity
If block acknowledgement agreements are shared across links, then implementation complexity is reduced, but productivity deteriorates due to retransmission overhead during mobility
Solution Approach 1:
The patent segments the shared BA agreement into link-specific BA agreements. Each link maintains its own BA state and retransmission buffer, allowing independent acknowledgment and retransmission management. This prevents retransmission conflicts during handover, as the target link can independently acknowledge packets without being constrained by the source link's BA state.
Solution Approach 2:
The patent changes the BA agreement parameters from a shared state to link-specific states. Each link has its own BA version number, window size, and retransmission counter. This parameter differentiation allows the system to optimize BA performance for each link independently, improving overall data transmission efficiency during mobility.
3Reliability
If centralized controller manages traffic steering for seamless handover, then handover reliability is improved, but device complexity increases due to additional control infrastructure
Solution Approach 1:
The patent introduces a centralized controller as an intermediary that coordinates handover between access points. The controller receives handover requests, selects optimal target APs, and manages the activation/deactivation of links. This intermediary simplifies the complexity by centralizing control logic, allowing individual APs and mobile stations to operate with simpler local decision-making while maintaining seamless handover through coordinated control.
Data Source
AI summary
This disclosure describes systems, methods, and devices related to multi-link devices (MLDs). A MLD may identify a first security key received from a first access point MLD (A-MLD); identify a second security key received from the first A-MLD; transmit, from a first physical location, a first packet to the first A-MLD, the first packet including the first security key; identify a first subset of N packets, the first subset received from the first A-MLD; transmit, from a second physical location, a second packet to the second A-MLD, the second packet including the second security key; identify a second subset of the N packets, the second subset received from the second A-MLD; determine that a third packet of the N packets was not received; and transmit, to the first A-MLD or the second A-MLD, an indication that the third packet was not received.