Overlapping OFDMA Communication Cycles for Industrial Control
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Solution Overview
Problem
Current industrial communication systems, particularly for controlling industrial robots, face challenges in increasing the speed of periodic communication while ensuring reliability, especially in wireless networks where transmission errors can occur.
Innovation Solution
The proposed communication system employs an orthogonal frequency division multiple access (OFDMA) method with a constant reference cycle and overlapping communication periods for data transmission and retransmission, allowing for efficient use of bandwidth and centralized control, ensuring high-speed and reliable data transfer between an access point and stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless communication is used for industrial control networks, then freedom of placement and reduced wiring costs are achieved, but communication speed and reliability deteriorate due to transmission errors
Solution Approach 1:
The patent applies preliminary action by pre-planning retransmission periods before data transmission occurs. The access point determines in advance which time periods will be used for retransmission of potentially erroneous data, allowing proactive error handling rather than reactive delays. This is implemented through the establishment of predetermined retransmission time periods in the wireless communication system.
Solution Approach 2:
The patent implements continuity of useful action by overlapping the normal transmission period of one communication cycle with the retransmission period of the previous cycle. This overlapping structure ensures that communication channels remain continuously utilized - while one data set is being retransmitted, the next data set begins transmission, eliminating idle time and maintaining continuous productive communication flow.
2Reliability
If retransmission periods are added to ensure communication reliability, then communication reliability improves, but communication speed deteriorates due to extended cycle times
Solution Approach 1:
The patent merges two communication cycles by overlapping the retransmission period of one cycle with the normal transmission period of the next cycle. This merging allows simultaneous execution of retransmission and new data transmission, effectively combining error correction functionality with continuous data flow without additive time penalties.
Solution Approach 2:
The patent employs periodic action by establishing regular communication cycles with predetermined normal transmission periods and retransmission periods. The access point periodically switches between these modes according to the cyclic structure, creating a rhythm of transmission and error handling that optimizes both reliability and speed through predictable, repeating patterns.
3Reliability
If the communication cycle is extended to include retransmission periods, then communication reliability improves, but productivity deteriorates due to longer control cycles
Solution Approach 1:
The patent applies dynamics by making the communication structure adaptable through overlapping periods. Rather than fixed sequential phases, the system dynamically overlaps retransmission and transmission activities, allowing the effective control cycle to be shorter than the sum of individual periods. This dynamic timing optimization maintains productivity while ensuring reliability through redundant transmission opportunities.
Data Source
AI summary
A communication system is designed to achieve high speed of periodic communication while ensuring reliability of communications. An access point and multiple stations are provided. A beacon cycle is set as a reference cycle and a communication period of N reference cycle is set for transmitting data to perform periodic communication. Successive communication periods are overlapped by an overlapping of M cycle which is shorter than the N cycle. The communication period has a normal transmission period and one or more cycles of retransmission period, and the normal transmission period of the next communication period overlaps the retransmission period of the previous communication period. Orthogonal frequency division multiple access method is used for communication between the access point and stations.