Decision Feedback Equalization for Underwater Acoustic Channels

Deepthi Chander (05407003)

Pallavi Manohar (05407002)

Features of Underwater Acoustic (UWA) channels

Underwater acoustic channels - severely bandlimited

• High temporal and spatial variability of channel conditions and multipath propagation.

• Digital transmission-severe ISI caused.• Non-Gaussian noise environments.

feedforwardfilter

Input

+ Symboldecision

feedbackfilter

-

Estimated symbol

AdaptiveAlgorithm (RLS)

Training symbol

+

-error

Decision Feedback Equalizer

MSE convergence (AWGN)

MSE convergence (lognormal noise)

Error percent vs SNR (AWGN)

Error percent vs SNR (lognormal noise)

Simulation Set-up

• PROpogation channel SIMulator (PROSIM) - based channel model

(www.saclantc.nato.int/mast/prosim/mainpg/main.html)• PROSIM used for simulations of broad-band (100Hz-10kHz)

sound propagation• Source depth=30 m• Receiver depth = 40 m, Range=1 km• Frequency = 500 Hz • Channel constant for 0.2 minutes and multipath delay spread

=0.685 seconds• Data rate assumed = 1000 bps• Noise: AWGN, coloured• Adaptive algorithm: RLS

Channel response at 0.6 minutes

PROSIM channel model simulations

•AWGN •Number of taps=32•Feedforward filter: 20 taps•Feedback filter: 12 taps•At 20 dB SNR : %of bits in error = 35.

Scatter plots

With Coloured noise (obtained using PROSIM)

THANK YOU