Aggregated Data Network

A real-time data collection system built around a wireless sensor network (WSN). Three Arduino-based sensor nodes transmit simulated sensor readings over 433 MHz radio to a single base station, which aggregates, validates, and reports on the incoming data stream in real time.

Built for MREN 178 (Team 04) by Dushyant Saini, Callum Smith, Luka Sijakovski, and Jeffrey Zhao.

Overview

The system emulates the core challenges of a real IoT/monitoring deployment — packet loss, burst traffic, duplicate transmissions, and node dropouts — and demonstrates the data structures and algorithms needed to handle them reliably on constrained hardware.

• 3 sensor nodes (Arduino Uno) each transmit a simulated reading over an HC-12 radio transceiver at a fixed interval (3000 / 3200 / 3400 ms)
• 1 base station (Arduino Uno) receives, buffers, and processes all incoming packets, then outputs live diagnostics and a periodic report over Serial and as CSV

[Sensor Node 1] --\
[Sensor Node 2] ---> HC-12 (433 MHz) ---> [Base Station] ---> Serial Monitor / CSV log
[Sensor Node 3] --/

How it works

Ring buffer queue

Incoming packets at the base station are pushed into a 4-slot fixed-length circular queue, then dequeued and processed one at a time on the main loop. This decouples packet reception from processing, so bursts of traffic from multiple nodes don't cause dropped packets. The queue uses modulo arithmetic to wrap indices, so no shifting or copying is ever needed. Peak queue depth is tracked and reported every 15 seconds as evidence the buffer is absorbing bursts correctly.

Hash table (node state store)

Each node's state (last reading, rolling average, sequence number, packet/anomaly counts, timestamps, connection status) is stored in an array indexed directly by node ID, giving O(1) lookup and update with no search required — important for a real-time system with tight per-packet processing budgets.

Per-packet checks

Every incoming packet is checked for:

• Anomalies — out-of-range values or values that deviate too far from the node's rolling average
• Duplicates — repeated sequence numbers
• Missed packets — gaps in sequence numbers
• Timeouts — a node is flagged MISSING after 10 seconds of silence, and logged as RECONNECT when it resumes

Reporting

Every 15 seconds the base station prints a performance report (uptime, packets processed/dropped, queue peak, average processing time, free RAM) and a CSV block summarizing each node's status, suitable for pasting into a spreadsheet for analysis.

Packet format

NODE:<id>,SEQ:<seq>,TS:<timestamp>,VAL:<value>

Simulated sensor values: 92% normal range (20.0–35.0), 5% out-of-range anomaly (80–120), 3% error code (−99.0).

Example output

====================
WSN Base Station
====================
[N1] V=24.5 Avg=24.5 S=1 OK P=1 us=162
[N2] V=97.0 Avg=97.0 S=1 ANOMALY P=1 us=170
[MISS] N1 x1 (missed packet detected)
[ALERT] N3 MISSING. (node went silent for 10s)
[RECONNECT] N3 back after 14s. (node came back online)
[BURST] 3 packets in 1s — queue buffering active.
====================
[REPORT]
Uptime(s) : 45
Processed : 12
Dropped   : 0
Queue peak: 2
Avg us    : 165
Free RAM  : 1390
[NODE SUMMARY]
N1|OK      |P=5 M=1 A=1 V=24.5 Avg=26.2 Up=45s
N2|ANOMALY |P=4 M=0 A=2 V=97.0 Avg=55.1 Up=42s
N3|MISSING |P=3 M=0 A=0 V=28.1 Avg=27.4 Up=38s
--- CSV ---
Node,Status,Packets,Missed,Anomalies,LastVal,AvgVal,Uptime_s
1,OK,5,1,1,24.5,26.2,45
2,ANOMALY,4,0,2,97.0,55.1,42
3,MISSING,3,0,0,28.1,27.4,38
--- END CSV ---

Repository structure

src/
├── SensorNodeConfigurationCode/     # Sensor node firmware (flash to 3 Arduinos)
├── BaseStationCalibrationCode/      # Base station firmware (flash to 1 Arduino)
└── CalibrationCode/                 # One-time HC-12 module calibration sketch
docs/
└── INSTALL.pdf                      # Full hardware wiring + setup guide

Hardware

Qty	Component	Notes
4	Arduino Uno R3	1 base station, 3 sensor nodes
4	HC-12 wireless transceiver	433 MHz, all set to CH001 @ 9600 baud
20	Jumper wires (M-F)	HC-12 connections
4	USB Type-A to Type-B cable	Upload + monitoring

HC-12 wiring (identical for all 4 Arduinos): VCC → 5V, GND → GND, TXD → Pin 10, RXD → Pin 11, SET → unconnected.

Getting started

Full step-by-step instructions (calibration, upload order, wiring diagram, troubleshooting) are in docs/INSTALL.pdf. Short version:

1. Calibrate every HC-12 module using src/CalibrationCode/CalibrationCode.ino (one Arduino at a time).
2. Flash the sensor nodes: open SensorNodeConfigurationCode.ino, set NODE_ID to 1, 2, or 3 and TX_INTERVAL to 3000, 3200, or 3400 respectively, then upload to each of the 3 node Arduinos.
3. Flash the base station: upload BaseStationCalibrationCode.ino to the 4th Arduino and keep it connected to your laptop.
4. Power the 3 sensor nodes, open the Serial Monitor on the base station at 9600 baud, and reset it — packets should start arriving within seconds.

Requirements: Arduino IDE 1.8+, SoftwareSerial (bundled with the IDE, no extra install needed).

License

MIT — see LICENSE.