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In the conventional CoAP specification, the retransmission timeout (RTO) is statically defined or exponentially backed off after each timeout event.
While this approach guarantees delivery, it fails to adapt to dynamic wireless conditions-leading to either premature retransmissions (when the RTO is too short) or prolonged latency (when the RTO is too long).
To overcome these inefficiencies, our scheme introduces an adaptive RTO adjustment mechanism at the client side, inspired by the TCP-style delay estimator but modified for resource-constrained CoAP endpoints operating in lossy and delay-variable networks.
Each client maintains a temporary mapping table that stores information about ongoing transactions.
When a matching ACK or response is received, the client computes the observed round-trip time (RTT).
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IEEE/ICACT20260196 Slide.21
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