distortion minimization via adaptive digital and … · distortion minimization via adaptive...
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DISTORTION MINIMIZATION VIA ADAPTIVE DIGITAL AND ANALOG
TRANSMISSION FOR ENERGY HARVESTING-BASED WIRELESS SENSOR
NETWORKS
Yong Xiao, and Zhu Han, University of Houston
Zixiang Xiong, Texas A&M University
Dusit Niyato, Nanyang Technological University of Singapore
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OUTLINE
• Introduction
• System Model and Problem Formulation
• Adaptive Digital and Analog Transmission
• Numerical Results
• Conclusions
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INTRODUCTION: ENERGY HARVESTING
• Extracting energy from external source in natural environment such as solar power, wind energy, radio frequency energy, vibration power, etc.
• Main Challenges:
• Environment is unstable, unpredictable and unreliable,
• To achieve reliability guaranteed energy supply.
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INTRODUCTION: ENERGY HARVESTING-BASED WIRELESS SENSOR NETWORKS
• Physical sources observed by wireless sensor networks are analog in natural and can have infinite number of possible values,
• It is known that the digital and analog transmission are energy efficient in the high or low power regime,
• Main challenge: How to dynamically optimize the wireless energy use to achieve the highest accuracy of the observed source signal with harvested energy.2
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OUTLINE
• Introduction
• System Model and Problem Formulation
• Adaptive Digital and Analog Transmission
• Numerical Results
• Conclusions
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SYSTEM MODEL
Transmitter can process and transmit its observed signals using two methods:
• Digital Transmission,
• Analog Transmission (also called uncodedtransmission).
Energy harvested from the environment
source
+
+
+
1,tN
2,tN
,K tN
sensor 1
sensor 2
sensor K
... transmitter...
+tZ
receiverh
te
Observation noise for each sensor
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PROBLEM FORMULATION
• Observation signal at sensor k
• Combined observation signal sent by the transmitter
• Signal received by the fusion center
• Causality constraints:Battery capacity
Harvested energy
Energy for data transmission
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PROBLEM FORMULATION
• We consider reconstruction distortion with the mean squared error criterion
• We seek a policy to minimize the long-term discounted distortion for energy harvesting-based wireless sensor networks
4 Discount factor
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OUTLINE
• Introduction
• System Model and Problem Formulation
• Adaptive Digital and Analog Transmission
• Numerical Results
• Conclusions
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DISTORTION ANALYSIS
• The minimum distortion that can be achieved by the digital transmission method is given by
• If the transmitter uses the analog transmission method, the optimal distortion that can be achieved is given by
Observation noise
5
Additive noise of sensor
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ADAPTIVE DIGITAL AND ANALOG TRANSMISSION
• We model adaptive digital and analog transmission problem as a Markov decision process (MDP) consisting of
• State: battery level
• Action: Transmission method (digital or analog) and transmit power
• State transition function calculated by
where6
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AN OPTIMAL POLICY
• We can prove that the optimal policy 𝜋𝜋 that decides the optimal action of transmitter is given by
where State transition function
Long-term expected distortion
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Distortion in the current time
Discounted expected distortion in the future
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OUTLINE
• Introduction
• System Model and Problem Formulation
• Adaptive Digital and Analog Transmission
• Numerical Results
• Conclusions
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NUMERICAL RESULTS
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Distortions of adaptive, digital and analog transmission methods under different iterations
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NUMERICAL RESULTS
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Distortions of adaptive, digital and analog transmissions under different amounts of energy that can be harvested by the transmitter.
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OUTLINE
• Introduction
• System Model and Problem Formulation
• Adaptive Digital and Analog Transmission
• Numerical Results
• Conclusions
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CONCLUSIONS
• We study optimal strategy that can minimize the distortion between the signal observed by the sensors and that recovered by a fusion center,
• A novel adaptive transmission method in which the transmitter can adapt its transmission method and transmit power according to the dynamics of the energy harvesting process.
• A MDP was formulated to derive the optimal policy to minimize the long-term discounted distortion
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Any further question, please contact:
Dr. Yong Xiao
E-mail: [email protected]
Homepage: https://sites.google.com/site/xyong2007/