Underwater Acoustic Networks
Sensors · AUVs · Sonar networks
The NetSim UWAN library lets you design, simulate and analyse networks that communicate by sound, not radio. It models the acoustic channel end to end, from propagation and noise to bit errors, across the full five-layer stack. It ships with protocol source code in C.
How NetSim models the acoustic channel
The acoustic channel is one of the most difficult communication media in use: low bandwidth, high latency and frequency-dependent loss. NetSim models each of these effects.
Speed of sound
Sound travels at about 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, and supports layered temperature zones.
Thorp propagation
Path loss increases with distance and with frequency. NetSim combines Thorp absorption with geometric spreading (cylindrical to spherical). Higher frequencies therefore attenuate faster, and this limits the 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. The SNR and the selected modulation give the bit error rate and packet error rate.
A full five-layer stack in every device
NetSim models the full TCP/IP stack in each underwater device, so experiments show real protocol behaviour.
Underwater traffic
A sensor application with small packets and long inter-arrival times, plus standard NetSim traffic (CBR, voice, video, FTP) for the very low bit rates of acoustic links.
UDP
The transport layer implements UDP, which suits the short, delay-tolerant messages of underwater sensing.
IP and routing
NetSim assigns IP addresses automatically. Single-hop links need no routing, and multi-hop links use static routing. Buffers are FIFO. Ad hoc routing is on the roadmap.
Slotted Aloha
Slot-synchronised access without carrier sensing, because with slow propagation a node cannot reliably sense an idle channel. The retry count and exponential back-off are configurable. The slot length matches 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. NetSim reads the BER from SNR-BER tables, and models packet capture with an interference threshold.
Protocol source in C
Each 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
These features let you 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 have configurable transmit, receive and idle currents and operating voltage. NetSim reports the energy use of each node, so you can estimate network lifetime.
Statistics
Detailed summaries of throughput, delay and error rates, for each link and each application.
Trace and logs
Packet and event traces for detailed analysis. An Acoustic Measurements Log records the distance, transmit power, path loss, total noise, SNR, received power and BER of each transmission.
Source code
NetSim provides the protocol source code in C. Adapt the 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
These are typical ranges that you can configure 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 |
The source level assumes unit transducer efficiency. The figures come 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
This multi-hop routing project, with full documentation and source code, 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
Development continues on the channel, the receiver and the waveform set, for shallow-water and deep-water programmes.
Bellhop multipath propagation
A ray-tracing channel model captures multipath, surface and bottom reflections, and range-dependent sound speed. Its inputs are the sound-speed profile, bathymetry and sediment. Users will choose Thorp or Bellhop for each scenario.
SINR-based receiver model
An effective-SINR receiver divides the multipath arrivals into the in-window signal and out-of-window self-interference. It captures delay-spread and equalisation effects, then maps the result to the BER curve of each modulation.
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.