Sensor Pipeline Payload Budget Calculation Audit
Sensor Pipeline Payload Budget Calculation Audit
Ada checks payload size, scale, and send rate before trusting a byte-budget decision
ADA · CALCULATION AUDIT
Sensor Pipeline Payload Budget Calculation Audit
A packet is a physics ledger after it becomes a network object: count size, scale, send rule, and wrapper bytes decide whether the receiver gets evidence or just a smaller mystery.
The chapter’s sample payload contract packs temperature_c as an int16 scaled 0.01 C per count alongside a uint16 humidity_pct, a uint8 status_flags, and a uint32 timestamp_s, then lists send rules like “send every 10 minutes” and “send when temperature changes by at least 0.5 degrees C.” This audit asks the question those field widths and rules invite: how many bytes does that payload actually cost per hour, and how many raw counts does a 0.5-degree-C threshold really represent?
Companion to the chapter Processing Readings Into Packets — every number here comes from that chapter.
See the relationship before changing it
The figure reads from left to right. The blue card is scheduled send interval. The middle card applies this page's rule. The green card is scheduled payload volume. Walk the arrows once: set the input, apply the rule, then read the result with its unit.
The retained audit below checks several chapter fixtures. This model keeps those stated values fixed and changes only scheduled send interval, so the numeric fixture does not switch without explanation.
Derive the baseline in four named moves
- 1
Name the input. The chapter baseline is 10 min.
- 2
Name the relationship. payload volume = 9 bytes x 60 min/hour / send interval
- 3
Substitute with units. 9 x 60 / 10 = 54 bytes/hour
- 4
Read the result. Keep the unit beside the value. Use it only inside the technical boundary on this page.
Predict, then change scheduled send interval
Try Predict the direction of payload volume = 9 bytes x 60 min/hour / send interval. Test another scheduled send interval, then compare scheduled payload volume.
Observe A shorter reporting interval sends the nine-byte payload more often before headers and retries are added. Reset scheduled send interval to 10 and compare scheduled payload volume.
Explain A shorter reporting interval sends the nine-byte payload more often before headers and retries are added.
Check yourself
What should you do before trusting a moved-control result?
What does this small model leave out?
Pack int16 temperature, uint16 humidity, uint8 status, and uint32 timestamp, then use a 0.5 C threshold at 0.01 C/count before Check audit.
The payload size reads 9 bytes and threshold reads 50 counts; a 10-minute periodic rule emits 54 payload bytes/hour before wrappers.
The 9-byte field widths set message cost while 0.01 C/count scaling converts the threshold; send policy independently determines how often that cost repeats.
1. The sample contract carries 9 payload bytes before any protocol wrapper
The chapter's example uses a 16-bit temperature field, a 16-bit humidity field, an 8-bit status field, and a 32-bit timestamp:
This is only the application payload. The whole-transaction review still has to add addressing, sequence, acknowledgement, retry, and security behavior from the chosen protocol boundary.
2. The existing 0.01 C/count scale turns a 0.5 C send threshold into 50 counts
The text gives temperature_c: int16, scale 0.01 C per count and a send example of "temperature changes by at least 0.5 degrees C":
That arithmetic is why the payload contract must record units and scale. A receiver that treats the integer as whole degrees would be off by a factor of 100.
3. A 10-minute schedule creates 6 routine sends per hour
The chapter's schedule example is "send every 10 minutes":
| Review item | Arithmetic shown | Audit result |
| Payload only, scheduled | 9 bytes x 6 sends/hour | 54 payload bytes/hour before headers, acknowledgements, retries, and security metadata |
| One-minute aggregation window | 60 minutes / 1 minute | 60 windows/hour, if every window becomes a packet |
| Threshold send rule | 0.5 C / 0.01 C per count | 50 counts must separate two encoded temperature values before this rule fires |
What the audit buys you: payload compression, event suppression, and packet wrappers are different cost levers. Shaving field bytes helps only after the review proves the scale is preserved, the send rule is intentional, and the surrounding transaction does not dominate the cost.
Every number above is taken from this chapter's own worked example and re-derived step by step.
Technical boundaries: The 9-byte field sum excludes alignment, serialization metadata, packet headers, checksums, encryption tags, retransmissions, timestamp compression, event bursts, and CPU or radio energy.