Acoustic Communication System With Two Branch Diversity

1
Acoustic Communication SystemWith Two Branch
Diversity

• System Designers
• Stefan Allevad
• Tomas Andersén
• Henrik Back
• Jonas Gustafsson
• Mattias Nyström
• Adam Wiå

2E1366 Project Course In Signal Processing And
Digital Communication Royal Institute of
Technology, Stockholm May 2000
2
Acoustic Communication SystemWith Two Branch
Diversity

• Requirements
• Robust against multipath propagation
• Coherent detection
• High data rate, low bit error rate lt1-2
• Real time implementation
• Communication in one direction
• Random placement of speaker and microphones, 3
  meters
• Resulting performance
• 2000 bits/sec
• BER 1

2E1366 Project Course In Signal Processing And
Digital Communication Royal Institute of
Technology, Stockholm May 2000
3
Experimental Setup
2E1366 Project Course In Signal Processing And
Digital Communication Royal Institute of
Technology, Stockholm May 2000
4
Discrete Time Model Of TheCommunication System

• Data symbol
• the filter
• outputs a pulse
• the filter
• outputs a pulse
• Equalizer coefficients
• updated using the NLMS-
• algorithm.
• Decision rule

Receiver
2E1366 Project Course In Signal Processing And
Digital Communication Royal Institute of
Technology, Stockholm May 2000
5
Transmission Protocol
2E1366 Project Course In Signal Processing And
Digital Communication Royal Institute of
Technology, Stockholm May 2000
6
The Decision Variables(The Output From The
Equalizer)
2E1366 Project Course In Signal Processing And
Digital Communication Royal Institute of
Technology, Stockholm May 2000
7
Modulation Methods And The Channel
The impulse response of the acoustic channel

• Binary PSK
• Pulse duration 6 ms
• Severe ISI
• Linear MMSE equalizer

h(n)
Discrete time n ms