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)
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