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 Channel Emulation ● Underwater Effects ● Path losses due to spreading and absorption ○ Ambient Noise ○ Multipath Reverberation ○ Doppler Spreading ○ Design ● Basic Design ○ Setup ○ Data Accuracy ● Impulse Response ○ Results so far ● Timeline ●

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 1: 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 2: Multipath reverberation

Path Losses due to spreading and absorption Path losses modeled using Thorp’s equation ● The equation dictates that the attenuation is related to the frequency of the signal ● Mostly used to obtain the transfer function ●

Multipath and Doppler Spreading Multipath is modeled with tapped delay line ● The tapped delay line also models doppler spreading due to the delays ● Input signal is modulated with a delay and coefficient and the output is a sum of ● these signals Each sample is input through this delay line to simulate each signal having many ● copies that arrive at different times

Basic Design One USRP X310 to act as a transmitter ● A second USRP X310 as a transceiver connected to another laptop ● Laptop will process the received signals and add channel effects ● Final USRP X310 will receive signal ●

The Setup *CE = Channel emulator

Basic Design (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

Checking Data Accuracy How can the validity of the channel simulation be established? ● Impulse response ○ Checking against a MATLAB version done by Milica ○ Stojanovic

Impulse Response Found through an impulse train ● Vector [1,0,0,0… inputted into delay line ○ Output signal is measured to be the impulse ● response

Multipath Response Part 1 Channel Response to input data ●

Multipath Response Part 2 Delay Response ●

Noise Response Effects of SNR of channel on signals ●

Spring Timeline

Questions?