Implementation of Underwater Channel Emulator (1804) Aaron DeMaio, - PowerPoint PPT Presentation

Implementation of Underwater Channel Emulator (1804) Aaron DeMaio, Michael Stratton, and Nicholas Gorbenko Advisor: Dr. Peter WIllett Sponsor: The MITRE Corporation

Overview Introduction ● The MITRE Corporation ○ Underwater ACOMMS ○ Background ● Current Technology ○ Drawbacks of current methods ○ Channel Emulation ● What is modeled ○ Main problems ○ Design Plan ● Basic plan ○ Future plans ○ Timeline ● Conclusion ●

Introduction The MITRE Corporation ● Manages Federally funded research and ○ development centers Based in Bedford, Massachusetts ○ Underwater acoustic communications (ACOMMS) ● 71 percent of the earth is covered in water ○ 95 percent unexplored ■ Underwater communication systems have great ○ importance Figure 1: Current Underwater nodal system

Background Current Technology ● Radio wave communication ○ Seawater absorbs radio waves ■ Light communication ○ Attenuation in water is great and the ■ signals are easily lost in underwater channels with poor clarity Cables ○ Impractical ■ Easy to disrupt ■ Acoustic ○ Figure 2: Global underwater fiber optic cable network

Drawbacks of Current Methods Testing on site ● Costly ○ Environment and channel need to be static ○ RF Emulators ● Do not work well underwater ○ Pure Software Simulation ● Cannot test hardware ○

Channel Emulation Software Defined Radio System ● Models time-varying underwater channel and effects in software and ○ hardware Design Platform ○ Based in C++ ■ Uses 3 USRP X310 Software Defined Radios ■ Benefits ○ Cheaper ■ More reliable ■ More closely models underwater channels ■ Modular ■ Figure 3: USRP X310 Software Defined Radio

Main Underwater Effects Four main problems with underwater channel modeling ● Path losses due to spreading and absorption ○ Ambient noise ○ Reverberation due to multipath ○ Doppler spreading ○ Figure 4: Multipath reverberation

Basic Plan Data modulated by BPSK from a laptop and given to the first USRP X310 for ● transmission Transmitter USRP sends a signal with a bandwidth of 4kHz carrying the data ● Second USRP as a transceiver connected to another laptop via. Ethernet ● Receives data wirelessly from transmitter ○ Transmits data wirelessly to receiver ○ Laptop will process the received signals and add channel effects ● Final USRP will receive signal and its attached laptop will demodulate the signal ● and obtain the data

Static Channel Response - SNR = -10

The Setup *CE = Channel emulator

Basic Plan (cont.) Creating the channel ● Code in C++ to model the channel effects ○ Ambient noise modeled with Gaussian Curve ■ Path Losses modeled with spherical spreading ■ Reverberation due to multipath modeled with ■ time-varying response Doppler spreading modeled by adding frequency ■ variations

Time Varying Channel Response ● Autoregressive Function can be used to partially model a time varying system ● Dictates that the current output is linearly dependent on the previous outputs with a coefficient

Checking Data Accuracy How can the validity of the channel simulation be established? ● Test USRPs in a tub of water, hydrophone used to receive ○ signal Send the same message as above using our channel ○ emulator instead of the tub of water and compare the results Check data efficacy using a pool as well to gather data with ○ increased length of channel Compare the second data set with results of channel ○ emulator

Fall Timeline

Spring Timeline

Budget There is nothing necessary for this project that is not provided ● USRPs provided by MITRE ○ Hydrophones provided by MITRE ○ Laptops borrowed from UConn ○ Ethernet cables brought from home ○

Questions?