Underwater Acoustic Networks
Sensors · AUVs · Sonar networks
NetSim's UWAN library lets you design, simulate, and analyse networks that communicate by sound rather than radio. It models the acoustic channel end to end, from propagation and noise to bit errors, across the full five-layer stack, and ships with protocol source code in C.
How NetSim models the acoustic channel
The acoustic channel is one of the hardest communication media in use: low bandwidth, high latency, and frequency-dependent loss. NetSim models each of these effects.
Speed of sound
Sound travels at roughly 1500 m/s, about 200,000 times slower than radio, so propagation delays are large. NetSim computes the speed from water temperature, depth, and salinity, with support for layered temperature zones.
Thorp propagation
Path loss grows with both distance and frequency. NetSim combines Thorp absorption with geometric spreading (cylindrical to spherical), so higher frequencies are attenuated faster, which limits usable bandwidth and range.
Ambient noise
Total noise combines turbulence, distant shipping (a configurable activity factor), wind-driven surface motion, and thermal noise. Each component dominates a different part of the frequency band.
Sonar equation
NetSim uses the passive sonar equation to find the received signal-to-noise ratio from the source level, transmission loss, and noise level. Bit error rate and packet error rate follow from the SNR and the chosen modulation.
A full five-layer stack in every device
The entire TCP/IP stack is modelled in each underwater device, so experiments map to real protocol behaviour.
Underwater traffic
A sensor application with small packets and long inter-arrival times, plus standard NetSim traffic (CBR, voice, video, FTP) adapted to the very low bit rates of acoustic links.
UDP
The transport layer implements UDP, suited to the short, delay-tolerant messages typical of underwater sensing.
IP and routing
IP addresses are assigned automatically. Single-hop links need no routing; multi-hop uses static routing. Buffers are FIFO. Ad hoc routing is on the roadmap.
Slotted Aloha
Slot-synchronised access without carrier sensing, because slow propagation means an idle channel cannot be reliably sensed. Configurable retry count and exponential back-off; slot length is sized to the worst-case propagation delay.
Acoustic PHY
Modulation from BPSK and QPSK to FSK and 16/32/64-QAM, FEC code rates 1/2 to 5/6, and user-set data rate and bandwidth. BER is read from SNR-BER tables; packet capture is modelled with an interference threshold.
Protocol source in C
Every layer ships with C source code. Modify the stack in Visual Studio to build custom protocols, custom SNR-BER tables, or new application models.
Capabilities
Everything you need to set up a scenario, run it, and analyse the results.
Mobility models
Configure underwater sensor movement with Random Waypoint, Random Walk, or file-based trajectories, in all three dimensions, at speeds up to 2000 km/hr.
Energy model
Battery-aware nodes with configurable transmit, receive, and idle currents and operating voltage. NetSim reports per-node energy use and helps estimate network lifetime.
Statistics
Detailed summaries of throughput, delay, and error rates, at both the link level and on a per-application basis.
Trace and logs
Packet and event traces for deep analysis, plus an Acoustic Measurements Log recording distance, transmit power, path loss, total noise, SNR, received power, and BER per transmission.
Source code
Protocol source code in C is provided. Adapt the underlying models in the Visual Studio development environment for specific requirements.
MATLAB integration
Socket-based external interfacing to MATLAB extends the simulation and analysis to custom algorithms and toolboxes.
Typical simulation parameters
Representative ranges configurable in the UWAN PHY layer.
- Source level170–225 dB//1 µPa
- Min receiver sensitivity−120 dB//1 µPa
- Frequency0.01 to 1000 kHz
- Data rateup to 255 kbps
- Bandwidthup to 1000 Hz
- FEC code rates1/2, 2/3, 3/4, 5/6
- Antenna gainconfigurable
- ModulationBPSK, QPSK, FSK, 16/32/64-QAM
Modelled on real underwater modems
The PHY parameters map directly to commercial and research modems, so you can reproduce hardware behaviour in simulation.
| Underwater modem | Tx power (W) | Source level (dB//1 µPa) | Frequency (kHz) | Data rate (kbps) |
|---|---|---|---|---|
| EvoLogics S2CR 18/34 WiSE | 35 | 186.2 | 26 | 13.90 |
| WHOI Micromodem | 48 | 187.6 | 25 | 5 |
| Teledyne Benthos ATM-9xx | 20 | 183.8 | 24.5 | 15.36 |
| LinkQuest UWM4000 | 7 | 179.3 | 17 | 8.50 |
| Aquatech AQUAModem 1000 | 20 | 183.8 | 9.75 | 2 |
| DSPComm AquaComm Marlin | 1.8 | 173.4 | 23 | 0.48 |
Source level computed assuming unit transducer efficiency. Figures from published modem specifications.
Watch it in action
Two walkthroughs of underwater acoustic network simulation in NetSim.
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11:24
Simulation of Underwater Acoustic Networks
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7:12
Simulation of Underwater Acoustic Networks (Thorp Propagation)
Featured project: Depth Based Routing
A worked multi-hop routing project, with full documentation and source code, that implements Depth Based Routing (DBR) on top of the UWAN stack.
- Key concept: DBR uses depth information for forwarding; a node forwards a packet only if it is closer to the surface than the previous node.
- Implementation: code modifications to the DSR protocol in NetSim, with holding-time calculations and packet-queue management.
- Simulation cases: single-hop transmission, void zones, nodes at the same depth, and multi-application scenarios.
- Insights: reveals DBR's limitations, including nodes at similar depths, the impact of horizontal distance on propagation, and behaviour over a Slotted Aloha MAC.
On the roadmap
Active development extends the channel, the receiver, and the waveform set for demanding shallow- and deep-water programmes.
Bellhop multipath propagation
A ray-tracing channel model that captures multipath, surface and bottom reflections, and range-dependent sound speed, driven by sound-speed profile, bathymetry, and sediment inputs. Users will choose Thorp or Bellhop per scenario.
SINR-based receiver model
An effective-SINR receiver that partitions the multipath arrivals into the in-window signal and out-of-window self-interference, capturing delay-spread and equalisation effects, then maps to the per-modulation BER curves.
FH-BFSK (JANUS) waveform
A non-coherent frequency-hopping BFSK modulation aligned with the NATO STANAG 4748 (JANUS) interoperability waveform, alongside the EvoLogics S2C sweep-spread carrier.