Double NIC AP Handover in Industrial WiFi Networks
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Solution Overview
Problem
In industrial mobile networks, especially those based on WiFi, the handover process between Access Points (APs) is delayed due to scanning and certification processes, leading to interruptions in data flow, as the 802.11 standard lacks clear specifications for rapid and autonomous handover, resulting in significant delays and packet loss.
Innovation Solution
The implementation of a method using double wireless network interface cards with a pre-learning mechanism and a non-overlaying soft handover channel allocation, which allows for seamless handover by pre-learning AP information and optimizing handover timing and channel allocation, reducing scanning delays and packet loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mobile terminal conducts continuous scanning to ensure timely handover among WiFi nodes, then handover reliability is improved, but handover delay increases significantly
Solution Approach 1:
The patent implements a pre-learning mechanism where the mobile terminal proactively discovers and stores AP information (MAC addresses, locations) before handover is actually needed. This preliminary action allows the terminal to have candidate APs ready in advance, eliminating the need for continuous scanning during critical handover moments, thus reducing handover delay while maintaining reliability
Solution Approach 2:
The patent introduces a controller as an intermediary that receives AP information from multiple APs and provides it to mobile terminals. This intermediary consolidates scanning efforts centrally, allowing terminals to receive pre-processed handover information without conducting their own continuous scans, thereby reducing terminal-side scanning delay while ensuring reliable handover through centralized coordination
2Speed
If the scanning stage is extended to reduce handover delay, then handover speed is improved, but packet loss increases due to sustained interruption
Solution Approach 1:
By performing AP information discovery and evaluation in advance (pre-learning phase), the system prepares handover candidates before data transmission interruptions occur. This allows the terminal to switch to a pre-evaluated AP with minimal interruption, reducing both handover time and packet loss
Solution Approach 2:
The patent implements feedback mechanisms where the controller receives information from APs about their capacity and status, and also receives handover performance feedback from terminals. This feedback loop allows the system to optimize handover decisions dynamically, selecting APs that minimize both delay and packet loss based on real-time conditions
3Adaptability or versatility
If WiFi network connection is hopped frequently to maintain connectivity in mobile environments, then network coverage is improved, but data flow interruption increases due to switch learning delay
Solution Approach 1:
The system performs preliminary learning of AP locations and MAC addresses before handover is needed, storing this information in advance. When handover occurs, the switch already has the new location information or can quickly update it, minimizing data flow interruption while maintaining network coverage adaptability
Solution Approach 2:
The patent implements a mechanism where AP information (including MAC address to location mappings) is copied and stored in advance at multiple locations (terminal, controller, and switches). This copying allows any node to quickly determine the correct switching path without waiting for real-time learning, reducing data flow interruption during handover
Data Source
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AI summary
The present invention provides an AP handover method based on double wireless network interface cards. A mobile terminal actively scans the signal strength of an AP, compares the scanned signal strength with the signal strength of a currently accessed AP, and if the signal strength is greater than the signal strength of the current AP, starts handover; otherwise, continuously scans till the handover succeeds. To reduce the handover delay and in accordance with the characteristic that the moving paths are basically fixed in industrial application scenarios, the present invention provides a pre-learning mechanism, that is, before formal application, information such as the location of the AP and the handover sequence in the application scenario is learned and stored in a terminal node, so that specific scanning and handover can be implemented in formal application. The present invention solves the problem of rapid AP handover in the industrial mobile network scenario, the double wireless network interface cards are used to achieve handover without interruption, and the pre-learning mechanism is used in specific industrial application scenarios, so the scanning delay is further reduced.