Dynamic Battery State Aware Approaches for Improving Battery Utilization

1
Dynamic Battery State Aware Approaches for
Improving Battery Utilization

• Sung Park, Mani B. Srivastava
• UCLA
• CASES 2002

2
Introduction

• Ubiquitous environment powered by battery
• The gap between increasing power demand and
  limited battery capacity is one of the critical
  challenge
• Evaluation metric is the total amount of service
  not lifetime
• It demonstrate improved battery utilization by
  adapting system performance based on batterys
  state

3
System Model
Notation p power
consumption fHW, fAPP service curve
function RHW, RAPP service rate SAPP(t) total
amount of service
4
Battery Model

• Battery capacity varies depending on discharge
  rate p
• Battery output voltage decrease during
  discharging. It cause power
• consumption to increase and battery to die
  prematurely

5
Service Model

• Medusa II sensor node based on mote
• Communication protocol similar to 802.11 ad-hoc
  PSM
• Periodically collect sensor data and transmit
  them to receiver
• The goal is to maximize the amount of data
  transferred from
• the sensor node with given limited capacity

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Service Model(Contd)
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Non Battery Aware Approach

• Assume that battery is an ideal energy source. In
  other words, discharge rate doesnt affect
  battery capacity
• Power consumption p is constant during
  discharging
• Battery capacity is 375J

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Static Battery State Aware Approach

• Consider rate capacity effect
• Battery capacity depends on power consumption
• The best SAPP(T) is 9363 bytes at 11.0mW
• 600 increase than non battery aware approach

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Dynamic Battery State Aware Approach

• Periodically recalculate power consumption p
  which will maximize SAPP(T)
• as battery voltage decreases
• Use voltage slope as lifetime computation
• The result of SAPP(T) is 11235 bytes at 11.0mW
• 60 increase than static and 720 increase non
  battery aware approach

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Dynamic Battery State Aware Approach(Contd)

• Impact of factors

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Dynamic Battery State Aware Approach(Contd)
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Conclusion

• Battery utilization depends on discharging
  characteristics
• Approaches with battery state awareness
• The total amount of service is considered as main
  metric instead of just lifetime
• Sufficient improvement than non battery aware
  approach