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What is Acoustic Telemetry?

In its broadest sense, telemetry can be defined as the art and science of conveying information from one location to another. With acoustic telemetry, sound waves are utilized to convey that information.

Conveying the information generally happens in three steps:

  1. Acoustic transmitter emits acoustic signal
  2. Receiver detects the acoustic signals and decodes the transmitter ID and sensor data
  3. ID and other relevant data are appended to a date and time and stored in the receiverís memory

Technical Overview of Acoustic Telemetry Technologies

JSATS

The Juvenile Salmon Acoustic Telemetry System (JSATS) is a technology that was developed to satisfy the research and regulatory requirements for monitoring juvenile salmon in the Columbia River Basin. The transmitterís small size and relatively long life enables tracking of sub-yearlings throughout their natural environment while minimizing impact on them.

JSATS, at its core, uses a digital modulation method called Binary Phase Shift Keying (BPSK). BPSK conveys data by changing, or modulating, the phase of the reference signal to either 0 or 180 Degrees. Each phase, in turn, corresponds to a binary digit (0 or 1).

As shown below, the modulating wave changes from a 0 to a 1 at the instant that it detects a phase change in the modulated result wave and changes back from 1 back to a 0 as the modulated result wave changes phase again.

Carrier Modulationg Wave Modulated Result

JSATS signals are 31-bits in length, 744 microseconds in duration, and are emitted at a programmed interval. BioSonics Telemetry JSATS transmitters are factory programmable at one second intervals.

The process for transmitting and receiving is as follows:

  1. JSATS transmitter emits acoustic signal
  2. JSATS receiver detects the acoustic signal and decodes the transmitter ID
  3. ID is appended to the date and time of the detection and stored in the receiverís memory

Learn more about BioSonics Telemetry JSATS products: L-AMT Series transmitters and the WHS4000 receiver.

MAP

MAP technology enables:

  • Fine-Scale Positioning
  • Very High Detection Rates
  • Very High Collision Immunity
  • High Speed Mobile Tracking

At its core, MAP utilizes Code Division Multiple Access (CDMA) in which digital information is transmitted through discrete frequency changes of a carrier wave. By using a pair of discrete frequencies, binaries (0s and 1s) can be detected.

As shown below, the data changes as the frequency of the modulated signal changes.

Data Carrier Modulated Signal

The total length of a MAP signal is 63-bits and this signal is less than 7 milliseconds in duration at 200kHz and less than 27 milliseconds in duration at 76 kHz.

With a clock that enables 50 microseconds of resolution, fine scale (sub-1-meter accuracy) positioning can be achieved with a minimum of 3 hydrophones.

The process for transmitting and receiving is as follows:

  1. MAP transmitter emits acoustic signal
  2. MAP hydrophone/receiver detects the acoustic signal, decodes the transmitter ID, and detects sensor data (where applicable)
  3. ID and sensor data (where applicable) are appended to the date and time of the detection and stored in the receiverís memory

Learn More about BioSonics Telemetry MAP products: M Series transmitters, WHS3000 Series receivers, LHP Series hydrophones, and the MAP600 Series receivers.

R Code

R Code is a technology that enables unique presence/absence detection of thousands of tagged animals.

At its core, R Code utilizes a modulation method called Pulse Position Modulation (PPM). Pulse Position Modulation is based on shifting the position of a pulse in time.

PPM is illustrated below.

R Code

To detect a unique ID, the receiver determines the sequence of unique time differences between pulses and compares this sequence with the list of valid sequences and assigns the ID that matches, along with the date and time of arrival.

Typical transmission intervals for R Code are 30, 60, or 90 seconds to avoid interference with other transmitters. Longer transmission intervals can also help to save on power, thus increasing transmitter life.

The process for transmitting and receiving is as follows:

  1. R Code transmitter emits acoustic signal
  2. R Code receiver detects the acoustic signal, decodes the transmitter ID, and detects sensor data (where applicable)
  3. ID and sensor data (where applicable) are appended to the date and time of the detection and stored in the receiverís memory

Learn More about BioSonics Telemetry R Series transmitters and the WHS2000 receiver.

Multi-Mode

Multi-Mode technology offers the ability to transmit MAP Code and R Code from the same transmitter. This enables detection by either an R Code or MAP receiver without having to place two different transmitters on the same animal.

In order to transmit both MAP and R Code, the transmissions must happen in shifts. The transmission durations and intervals are factory programmable.

The process for transmitting and receiving is as follows:

  1. Multi-Mode transmitter emits acoustic signal
  2. R Code and/or MAP hydrophone/receiver detects the acoustic signal, decodes the transmitter ID, and detects sensor data (where applicable)
  3. ID and sensor data (where applicable) are appended to the date and time of the detection and stored in the receiverís memory

Learn More about BioSonics Telemetry Multi-Mode products: MM Series transmitters and compatible receivers (WHS2000 receiver, WHS3000 Series receivers, LHP Series hydrophones, and MAP600 Series receivers).

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