MAC Control Unit Retransmission Waiting Time Determination
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Solution Overview
Problem
In wireless communication environments where urgent messages, such as alarm notifications, are transmitted, the likelihood of initial transmission failure due to collisions is high, leading to prolonged retransmission delays and potential failure to meet time requirements.
Innovation Solution
A communication apparatus that determines a shorter retransmission waiting time using a random number, ensuring prompt retransmission even if the initial transmission fails, thereby reducing the time required for successful data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If waiting time for retransmission is set according to conventional methods (IEEE 802.15.4 or BEB), then collision avoidance probability is improved, but retransmission delay increases and data transmission cannot be completed within required time
Solution Approach 1:
The patent changes the parameter of waiting time for retransmission from conventional fixed or exponentially increasing values to a shortened random value. Specifically, the waiting time for retransmission is set to a random value within a shortened period (shorter than the initial waiting time period), which reduces the expected waiting time while still providing randomization to avoid collisions. This parameter change directly resolves the contradiction by reducing retransmission delay while maintaining adequate collision avoidance through randomization.
2Speed
If waiting time before first transmission is shortened to enable urgent message transmission, then transmission speed is improved, but collision likelihood increases in densely disposed node environments
Solution Approach 1:
The patent applies preliminary action by setting the waiting time for retransmission in advance to be shorter than the initial waiting time. This preliminary determination of a shortened retransmission waiting period ensures that if the first transmission fails, the system is already prepared to retry quickly without needing to calculate or decide on shorter timing during the retransmission process. This preliminary preparation enables fast retransmission while the randomization component maintains collision avoidance.
Data Source
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AI summary
A MAC control unit (404) determines first transmission waiting time which is waiting time before performing first transmission of data, from a first time width, using a random number. Then, the MAC control unit (404) determines, when the first transmission fails, retransmission waiting time which is waiting time before performing retransmission of the data, from a second time width which is shorter than the first time width, using the random number.