T-MAC Adaptive Duty Cycle Animation

Step through Timeout-MAC active periods, TA resets, early sleep, FRTS protection, and energy savings versus fixed S-MAC scheduling.

animation
tmac
timeout-mac
smac
mac-protocol
duty-cycling
wireless-sensor-networks
architecture
interactive
Interactive T-MAC workbench with synchronized frame timing, adaptive active-period timeout, S-MAC comparison, early-sleep/FRTS scenarios, duty-cycle and average-current formulas, mobile-safe controls, and technical accuracy notes.
T-MAC Synchronized MAC Adaptive active period

T-MAC Adaptive Duty Cycle Animation

Watch one synchronized WSN frame. S-MAC keeps a fixed listen window; T-MAC lets the radio sleep when no activation event resets the TA timer.

-- msT-MAC active time
--%Energy saved vs S-MAC
--%Adaptive duty cycle
--Receiver outcome

What Moves

The cursor travels across one MAC frame. Event markers reset TA while the node remains awake.

What Changes

The T-MAC sleep boundary moves with traffic, TA length, overhearing, and FRTS reservation.

What To Compare

Use the S-MAC row as the fixed baseline and the T-MAC row as the adaptive result.

Common Trap

A shorter TA saves idle listening but can let a receiver sleep before a neighbor sends.

Frame Timeline And Node State

T-MAC sleeps after the last activation event plus TA.

WakeNeighbor schedules align at the start of the frame.
ListenThe radio listens for SYNC, carrier activity, RTS, CTS, DATA, or ACK.
Reset TAEach activation event pushes the sleep decision later.
TimeoutIf no activation occurs before TA expires, T-MAC sleeps.
SleepSaved energy comes from turning off idle listening early.
-- msCursor time in this frame
-- msTA expires after last activation
-- msFixed S-MAC active window
-- mAT-MAC average radio current
Formulas And Units

These simplified frame-level calculations separate active receive/listen time, transmit time, and sleep time.

active_ms = max(min_listen_ms, last_activation_ms + TA_ms)

Currents in this animation use a typical low-power WSN radio scale: receive/listen 18 mA, transmit 23 mA, and sleep 0.015 mA. Real hardware must be measured.

Protocol Accuracy Notes
  • T-MAC is a synchronous duty-cycling MAC: neighbors still need a shared schedule like S-MAC.
  • TA is a timeout after activation. The common teaching rule is roughly 1.5 times the contention interval, but implementations tune it for radio, traffic, and clock drift.
  • Activation events can include receiving data, completing a handshake, sensing channel activity, or overhearing RTS/CTS that implies future traffic.
  • FRTS-style reservation is shown as a mitigation for early sleeping, not as a guarantee that all hidden-terminal losses disappear.
Window Tuning Guide

Short TA

Saves idle listening in quiet frames, but raises early-sleep risk when a neighbor is about to send.

Long TA

Keeps the receiver awake through bursty exchanges, but approaches the S-MAC fixed active cost.

Heavy Traffic

Many activation events keep T-MAC awake for most of the S-MAC active window, reducing its energy advantage.

Design Tradeoffs

Energy

T-MAC removes idle listening when the active window would otherwise be empty.

Latency

Like S-MAC, maximum rendezvous delay is still bounded by the schedule period.

Robustness

Clock drift, overhearing policy, hidden terminals, and TA tuning decide whether the savings are safe.