Does a 30-Second Report Survive a Ten-Year Deployment?

Ada re-derives this chapter’s own numbers step by step, at full precision

ADA · CALCULATION AUDIT

Does a 30-Second Report Survive a Ten-Year Deployment?

A magnetic parking sensor reports occupancy every 30 seconds over LoRaWAN and is sized for “a typical 10-year deployment,” yet the chapter’s own budget — 2,880 uplinks a day at 40 mA for a second each — drains its 8,000 mAh pack in about 249 days. Those two facts are not at peace. This audit lines the achieved life up against the ten-year goal and asks what reporting interval the target really demands, and whether a bigger battery alone can ever close the gap.

Companion to the chapter Smart Cities — every number here comes from that chapter.

Ada: This section sizes a parking sensor for “a typical 10-year deployment,” then finds an 8,000 mAh pack lasts about 249 days. Those two facts are not at peace. Let me line the achieved life up against the stated goal and read off what the reporting interval would really have to be.

Start from the chapter’s own budget. Each uplink is 40 mA for 1 second, so 40 x 1 / 3600 = 0.0111 mAh, and 2,880 uplinks a day cost 2,880 x 0.0111 = 32.0 mAh. Sleep adds 0.005 x 24 = 0.12 mAh, for 32.0 + 0.12 = 32.12 mAh/day. That gives 8000 / 32.12 = 249 days — the section’s figure, confirmed.

Now invert it for the goal. Ten years is 10 x 365 = 3650 days, so the daily budget is 8000 / 3650 = 2.19 mAh. Take out the fixed 0.12 mAh of sleep and only 2.19 - 0.12 = 2.07 mAh is left for radio, which buys 2.07 / 0.0111 = 186 uplinks a day — an interval of 86400 / 186 = 465 seconds, about one report every 7.7 minutes. Against the design’s 30 seconds that is 2880 / 186 = 15.5x fewer transmissions.

Design meaning: the 30-second interval and the ten-year life are apart by more than an order of magnitude, so no larger battery closes the gap on its own — this node has to report roughly 15x less often, move to event-driven sends, or add energy harvesting, and the arithmetic names which lever and how far.

Every number above is taken from the chapter’s own material and re-derived step by step.