Testbed for Wireless Adaptive Signal Processing Systems

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Testbed for Wireless Adaptive Signal Processing
Systems

• György Orosz, László Sujbert, Gábor Péceli
• Department of Measurement and Information Systems
• Budapest University of Technology and Economics,
  Hungary
• Instrumentation and Measurement Technology
  Conference IMTC 2007
• Warsaw, Poland, May 1-3, 2007

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Wireless signal processing

• Advantages of Wireless Sensor Networks (WSNs)
• Easy to install
• Flexible arrangement
• Wireless signal processing
• Difficulties of utilization of WSN
• Data loss
• Undeterministic data transfer
• Limit of the network bandwidth
• Purpose of the testbed
• Considerations in the design
• Hardware structure
• Adequate application
• Realistic demands
• Exploits the resources

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ANC as test application

• Principles of Active Noise Control (ANC)
• Why ANC?
• Inherently MIMO systems plenty of sensors
• Plant acoustic system
• Scalable
• Linear
• Exist everywhere
• Various algorithms
• No HW modification
• Comparability of structures
• Easy to build and cheap
• Identification characterization of signal path

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System configuration

• Plant to be controlled acoustic system
• Noise sensing
• Berkeley
• micaz motes
• Actuators
• active loudspeakers
• Gateway network ? DSP
• Signal processing
• DSP board
• ADSP-21364 32 bit floating point
• 8 analog output channels
• 330 MHz
• motes

microphone
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Research fields related to the testbed

• Signal processing adaptation to WSN
• Synchronization
• Data transmission
• Effective algorithms
• Data compression
• Distributed signal processing

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Results 1.

• Implemented ANC algorithms
• Synchronization algorithm in WSN
• Principles of operation

active loudspeaker
DSP board
gateway mote
sensor mote
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Results 2.

• Deterministic network operation
• Implicit synchronization messages
• Synchronization with continuous data flow
• No extra load for network

Network topology
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Results 3.
Data transmission methods

• Transmission of
• row data
• 1.8 kHz sampling frequency on the motes
• Synchronization of WSN?DSP
• LMS and observer based ANC algorithms
• Bandwidth restriction about 2-3 sensors

• Transformed domain
• data transmission
• 1.8 kHz sampling frequency on the motes
• Transmission of Fourier-coefficients
• Increased number of sensors8 sensors (expansion
  possible)

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Conclusions

• Platform for testing wireless systems
• Application ANC
• Components
• Berkeley micaz motes
• ADSP-21364 floating point DSP
• Main difficulties
• Data transmission
• Synchronization
• Some codes and technical details available at
• http//home.mit.bme.hu/orosz/wireless

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Future work

• Improvement of the website
• http//home.mit.bme.hu/orosz/wireless
• Discover the limits of the system
• Sensor network bandwidth limit
• DSP computational and memory limits

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Synchronization 1

• Mechanism of the synchronization

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Synchronization 2

• Graph of the reception time of synchronization
  messages

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Synchronization 3

• Tdiff  ?tsend  TSend  Tloc2

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Synchronization 4
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Synchronization 5

• Indirect proof for synchronization

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Network timing