Module 4/5 · Weeks 10–12 · 27 h

IoT and WMS

UAT 363 Unmanned Aircraft Systems Technology for Transportation and Smart Warehousing

About 90 minDraft, awaiting reviewLast updated 27 September 2026

By the end of this module you will be able to

Design data flow from drones over MQTT with suitable topics and QoS levels
Design JSON scan messages that a warehouse management system (WMS) can use
Reconcile scan results with WMS records and compute record accuracy
Validate product codes with the GS1 check digit

Prerequisites: UAT 363 module 3 · UAT 322 (IoT and MQTT)

Why this matters

Scan results that stay on the drone are useless. The data must flow into the warehouse management system (WMS), be compared with records, and alert staff when discrepancies are found. The ETH report names integration with existing systems as a main challenge for warehouse drones. If messages are lost, duplicated or a product code is misread, the system wrongly concludes that stock is missing or in excess.

MQTT in the warehouse

The knowledge unit on MQTT and Eclipse Mosquitto explains the publish–subscribe architecture. The publisher (the drone) sends messages to a topic on a broker, and subscribers (the WMS, a dashboard) subscribe to that topic. Publishers and subscribers do not need to know each other directly.

The OASIS MQTT 5.0 standard defines three quality of service (QoS) levels:

QoS	Meaning	Effect on scan results
0	At most once; messages may be lost	A correct location may appear “not found”
1	At least once; duplicates may occur	Receivers must handle duplicates, e.g. by message ID
2	Exactly once	Slower because of multi-step acknowledgement

Stock scans usually use QoS 1 with a unique message ID so receivers can drop duplicates. Frequent drone position updates may use QoS 0, since a new message soon replaces a lost one.

Example 1. Scan messages and reconciliation

One JSON message per location, then compared with the WMS records (8 synthetic locations).

import json

scan_msg = {"msg_id": "D1-20260927-0001", "location": "A1-03-2", "item": "4012345000016",
            "qty": 12, "ts": "2026-09-27T09:15:02+07:00", "drone": "D1"}
print("topic warehouse/scan/A1 payload", json.dumps(scan_msg))

wms = {"A1-01-1": ("4012345000016", 10), "A1-02-1": ("4012345000023", 5), "A1-03-2": ("4012345000016", 12),
       "A1-04-3": ("4012345000030", 8), "A1-05-1": ("4012345000047", 20), "A1-06-2": ("4012345000054", 6),
       "A1-07-4": ("4012345000061", 4), "A1-08-5": ("4012345000078", 9)}
scan = {"A1-01-1": ("4012345000016", 10), "A1-02-1": ("4012345000023", 3), "A1-03-2": ("4012345000016", 12),
        "A1-05-1": ("4012345000047", 20), "A1-06-2": ("4012345000054", 6), "A1-07-4": ("4012345000061", 4),
        "A1-08-5": ("4012345000078", 9), "A1-09-1": ("4012345000085", 2)}

result = {"match": [], "qty differs": [], "not found": [], "unexpected": []}
for loc, (item, qty) in wms.items():
    if loc not in scan:
        result["not found"].append(loc)
    elif scan[loc] == (item, qty):
        result["match"].append(loc)
    else:
        result["qty differs"].append(loc)
result["unexpected"] = [loc for loc in scan if loc not in wms]
for k, v in result.items():
    print(f"{k:<12} {len(v)} {v}")
print(f"record accuracy {len(result['match']) / len(wms):.1%} of {len(wms)} WMS locations")

topic warehouse/scan/A1 payload {"msg_id": "D1-20260927-0001", "location": "A1-03-2", "item": "4012345000016", "qty": 12, "ts": "2026-09-27T09:15:02+07:00", "drone": "D1"}
match        6 ['A1-01-1', 'A1-03-2', 'A1-05-1', 'A1-06-2', 'A1-07-4', 'A1-08-5']
qty differs  1 ['A1-02-1']
not found    1 ['A1-04-3']
unexpected   1 ['A1-09-1']
record accuracy 75.0% of 8 WMS locations

“Not found” may mean the stock really is missing, that the drone could not read the label, or that a QoS 0 message was lost. Before adjusting the WMS, staff must confirm the finding and record the cause.

Figure 2. Reconciling scan results with the WMS

Product codes and check digits

Product codes under the GS1 standard (GS1 General Specifications) end with a check digit computed from the other digits. If a camera misreads one digit, the check digit usually no longer matches, so the system rejects the code instead of recording the wrong item.

Example 2. Validating the check digit of a 13-digit code

def gs1_check_digit(digits):                 # without the check digit
    total = sum(int(d) * (3 if i % 2 == 0 else 1) for i, d in enumerate(reversed(digits)))
    return (10 - total % 10) % 10

def is_valid(code):
    return code.isdigit() and gs1_check_digit(code[:-1]) == int(code[-1])

for code in ("4012345000016", "4012348000016", "4012345000023"):
    print(f"{code}: check digit {gs1_check_digit(code[:-1])}, valid {is_valid(code)}")

4012345000016: check digit 6, valid True
4012348000016: check digit 3, valid False
4012345000023: check digit 3, valid True

The second code has one digit misread (5 as 8), so the check digit does not match and the system should ask for a rescan instead of recording it.

Module lab

Lab: sending scan results into a system

Install Mosquitto in the lab and use paho-mqtt to send scan results from the module 3 lab in the message format of Example 1
Write a subscriber that records to a table (standing in for the WMS), drops duplicates by msg_id, and test QoS 0 and 1 while briefly cutting the network
Reconcile scan results with the records and compute record accuracy
Validate the check digit of every code read and count the rejects
Write a staff confirmation procedure before records are adjusted

Common mistakes

Watch out

Using QoS 0 for scan results and concluding stock is missing
No message ID, so QoS 1 duplicates are counted twice
Adjusting WMS records automatically without confirmation
Not validating check digits, recording the wrong item
Leaving the broker unprotected without authentication and encryption (see the MQTT knowledge unit)

Summary

MQTT publish–subscribe carries scan results from drones to the WMS and dashboards
QoS 0 may lose, QoS 1 may duplicate, QoS 2 delivers exactly once; choose by the effect on data
Reconciliation by location gives four outcomes, and findings are confirmed before records change
The GS1 check digit catches misread codes

Check your understanding

Which QoS level may duplicate messages?
50 locations checked and 46 match. What is the record accuracy?
Why should scan results carry a unique message ID?
The first 12 digits are 401234500001. What is the check digit?
What are possible causes of a “not found” result?

Answers

QoS 1
$46/50 = 92%$
So receivers can drop duplicates when QoS 1 is used
6
The stock is really missing, the label could not be read, or the message was lost in transit

Key formulas

Record accuracy	$accuracy = \frac{# matching locations}{# locations checked} \times 100%$
GS1 check digit (mod 10)	$c = (10 - (\sum w_{i} d_{i} mod 10)) mod 10, w = 3, 1, 3, \dots from the right$

Key references

OASIS. (2019). MQTT version 5.0 (OASIS Standard, 7 March 2019). link
Eclipse Foundation. Eclipse Mosquitto: An open source MQTT broker. link
Eclipse Foundation. paho-mqtt: MQTT version 5.0/3.1.1 client class (Python package). link
GS1. (2026). GS1 general specifications (Release 26.0). link
Wawrla, L., Maghazei, O., & Netland, T. (2019). Applications of drones in warehouse operations (White paper). ETH Zurich, D-MTEC, Chair of Production and Operations Management. link
Ma, Y., Selby, N., & Adib, F. (2017). Drone relays for battery-free networks. In Proceedings of ACM SIGCOMM 2017 (pp. 335–347). ACM. link
Kurose, J. F., & Ross, K. W. (2025). Computer networking: A top-down approach (9th ed.). Pearson. link

In class / field

Intensive lab and field practice recorded in a lab notebook

Learning evidence: Lab notebook signed by the instructor

Module quiz

This is a formative self-check, not a graded exam

Knowledge domain: Delivery, indoor operations and warehousing · Communications, networks and IoT · Programming and digital technology

IoT and WMS

By the end of this module you will be able to

Why this matters

MQTT in the warehouse

Product codes and check digits

Module lab

Common mistakes

Summary

Check your understanding

Key formulas

Key references

Further reading

IoT and smart warehouse systems

Deep dive: MQTT and Eclipse Mosquitto for drone and IoT systems

In class / field

Module quiz

IoT and WMS

Lesson

By the end of this module you will be able to

Why this matters

MQTT in the warehouse

Product codes and check digits

Module lab

Common mistakes

Summary

Check your understanding

Key formulas

Key references

Further reading

IoT and smart warehouse systems

Deep dive: MQTT and Eclipse Mosquitto for drone and IoT systems

In class / field

Module quiz