1. Short Paper: An Ultrasonic Communication System for Biotelemetry
in Extremely Shallow Waters
Gregory Parsons Shaolin Peng Alexander G. Dean
Motivation
Collecting biotelemetry from underwater fauna such as the Blue Crab
Tight constraints on size, weight, and battery life
Operation in extremely shallow waters
Short-range operation is acceptable
Design History
First Generation
Second Generation
Performance
Field testing was performed in fresh water at Lake Wheeler just south of Raleigh, North Carolina
Floating piers at the site were used as platforms for experimentation
The depth in this area is less than 5 meters
Transducers suspended 1 meter below surface
Test1 was at 30 meters to evaluate throughput
Test2 was at 100 meters to evaluate operational range, and performed at 31 baud for the percentage of packets received error free
Receiver 3.8” x 2.5”
Hardware tone decoders detect carriers
Transmitter 3.8” x 2.5”
DAC and amplifier generate outgoing waveforms
Transmitter 1.1” x 0.7”
Tuned LC circuit efficiently generates waveforms
Solution
The transmitter uses a tuned LC oscillator driven by an MCU timer to generate outgoing waveforms at the requisite 60Vp-p across a ceramic transducer
Very low part count and an inexpensive 8-bit Atmel Atmega168 processor (1K SRAM, 8K Flash, 4 to 14MHz) that is both deployable in large numbers and disposable
Four channel frequency-shift-keying
Allows the processor to sleep while transmitting
The receiver has gone through two revisions:
Hardware tone decoders (NE567) to detect carriers
Software solution utilizing the Goertzel algorithm to detect carriers
Transceiver 2.5” x 1.5”
Tuned LC circuit and software Goertzel algorithm handle both incoming and outgoing waveforms
Energy Consumption
Transceiver Board Current Draw at 2.8V
Transmitter battery life of a 3V CR2450 lithium at 42 baud
MCU
LC Driver
Amplifier
Total
Shutdown
4.6uA
0.10uA
0.70uA
5.4uA
Idle
799.0uA
799.8uA
Receive
3,470uA
724.0uA
4,194uA
Transmit
1,060uA
22,400uA
23,461uA
94%
Viterbi ECC
67%
Without ECC
Next Steps
We will optimize our Viterbi decoder to obtain higher baud rates
Parameterize the software modules for inclusion into the RaPTEX tool chain for ease of future development of underwater networks
NCSU ECE Center for Efficient, Scalable and Reliable Computing
This material is based upon work supported by the National Science Foundation under Grant No Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).