Low Power MAC for Ad Hoc Wireless Network

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Low Power MAC for Ad Hoc Wireless Network

• EECS
• University of California at Berkeley

2
Outline

• Media Access and Existing Solutions
• MAC for PicoNode Overview
• Multi-Channel MAC and Distributed Algorithm
• Sleeping Mode Based on Ultra Low Power Wakeup
  Radio
• Future Research, Design Methodology and
  Environment, Status and Time Line

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Wireless Media Access Control

• MAC Let multiple radios share the same
  communication media.

• Local Topology Discovery and Management.
• Media Partition By Allocation or Contention.
• Provide Logical Channels to Upper Layers.

Application
Network
MAC
Physical
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Media Access in Multi-hop Networks

• Large number of short range radios in a wide area
  Transmission Locality

Good thing Channel Reuse
Problems
Hidden Terminal, (CSMA is not appropriate) No
Global Synch.
D
C
B
E
A
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Solution 1 Contention Based

• MACA p. Kam, 90
• RTS-CTS-DATA
• MACAW V. Bharghavan, 1994
• add link layer ACK.
• FAMA C.L. Fuller, 95 802.11
• Add carrier sensing
• Optional ACK
• PAMAS S. Singh, 2000
• Power aware MAC
• Separate signaling channel

B
A
C
D
RTS
RTS
CTS
collide
Collision at B

• Collision still exists.
• Too much overhead.

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Solution 2 UCLA Allocation Based

• Localized Central Control Cluster
• Self-elected Cluster Head.
• Neighboring Clusters Use Different Codes
• Same Code, TDMA Inside Cluster
• Virtual Circuit QoS Support

Unstable Cluster Structure Too much Management
Overhead
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PicoMAC ? Why Not Just Pick One?

• Most existing MACs are Targeted for
• One-hop, centralized control network cellular
  network, 802.11, Bluetooth
• Bandwidth hungry application, strict QoS
  requirement.
• Existing MACs are Based on Existing Radios
• More than 90 of power is burned when radio is
  idle.

Low power System Built on Existing MAC is NOT
Low Power
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Opportunities for PicoMAC

• Application Driven, Low Duty-Cycle MAC
• New Radio Architectures
• Vertically-Integrated Interactive Design
  Methodology

Application Network
MAC
PHY
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Outline

• Media Access and Existing Solutions
• MAC for PicoNode Overview
• Multi-Channel MAC and Distributed Algorithm
• Sleeping Mode Based on Ultra Low Power Wakeup
  Radio
• Future Research, Design Methodology and
  Environment, Status and Time Line

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PicoNode ? MultiMedia

• Low-date Rate Radio 10kbps (peak)
• Low Traffic Duty Cycle
• 1, 1200 Bytes/source/s
• Short Packet lt50Bytes
• Loose QoS Requirements, Often not Delay Sensitive

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Design Goal

• Primary Goal energy / useful bit (EPB)
• Scalability both in global sense of network size
  and local sense of nodes density
• Distributed Protocol to achieve a robust and
  self-configuring network.
• Mobility limited number of mobile nodes, with
  limited speed.

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Where Energy Goes?
When idle Channel Monitoring Collision and
Retransmission Signaling overhead (header,
control pkts)
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Low Power MAC for PicoNode

• Spread Spectrum Multi-Channel Scheme
• To Reduce Collision Rate
• To Reduce Signaling Overhead (Shrink Address
  Space)

• Deep-Sleep Mode with Wakeup Radio
• Power Down the Whole Data Radio
• Reduce Monitoring Energy Consumption by 103 Times

Adaptive Mobility Support
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Outline

• Media Access and Existing Solutions
• MAC for PicoNode Overview
• Multi-Channel Scheme and Distributed Algorithm
• Sleeping Mode Based on Ultra Low Power Wakeup
  Radio
• Future Research, Design Methodology and
  Environment, Status and Time Line

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CDMA Multi-Channel Scheme
Idea Nodes use different channels to transmit
data, no collision at receiver.
6
7
2
1
5
8
3
4
Key Locally Unique with Global Reuse

• Parallel Transmission without Synch.
• Implicit Local Address Channel

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Multiple Channel Assignment

• Receiver based CA
• Primary collision

• Sender based CA
• No primary collision

• Receiver only listen to its own channel
• No need signaling channel

• Receiver need switch data channels
• Needs a separate signaling channel

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Find the Solution Graph Coloring
2

• Goal For any node, all its neighbors are with
  different colors
• Or All two-hop neighbors with different colors.
• Number of colors needed
• (NCA) lt min d(d-1)1, v
• Brook and Vizing theorem

3
1
5
4

• Model
• An incomplete graph
• G (V,E)
• d is the maximum degree of nodes

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Performance Analysis

• Model a ?-regular graph
• p traffic density

SC (Share Single Channel ) Bsca p (1-p)
(?-1) (1-p) RCA (Send on Receivers Channel )
Brca p (1-p/?) (?-1) (1-p) TCA (Send on
Senders Channel ) Btca p 1-(1-p/?) ? (1-p)
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CA Performance Analysis
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Outline

• Media Access and Existing Solutions
• MAC for PicoNode Overview
• Multi-Channel MAC and Distributed Algorithm
• Sleeping Mode Based on Ultra Low Power Wakeup
  Radio
• Future Research, Design Methodology and
  Environment, Status and Time Line

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Power Down Data Radio

• Current Radio Sleeping Mode 1050 Power
  Consumption
• For PicoNode Running at 1 Duty Cycle, 9095
  Energy When Radio Is Idle.
• Even Worse As PicoNode Radio Is Shorter Range

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Sleeping mode signaling

• Problem How To Send Data To a Sleeping Node?
• Solution
• Scheduling Wakeup
• Reactive wakeup Sender Send Beacon
• PicoNode chose to do reactive wakeup

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Wake-up Radio

• Always running
• Super low power 10-4 10-3 active mode power
• Data radio shut down when idle, and powered up by
  wake-up radio
• Broadcast and uni-cast mode
• Receiver response time lt10ms

PowerAmplifier
D/A
ED
PPD
Wakeup Tone
Data/control codes
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Wakeup Sequence and Energy Profile
ACK
CTS
Node B
WUP
DATA
Node A
Useful data
Power Profile
Tr
Th
Tw

• E(useful data traffic) E(overhead traffic)
  E(idle)

EPB
L(useful data traffic) 1-p(collision)
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EPB Performance Analysis
Lp 20bits
Lp 60bits
Lp 300bits
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EPB Performance Analysis
Conclusion For duty cycle 110 percent 10
100 times better
Ps 1mW
Ps 100uW
Ps 1uW
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Outline

• Media Access and Existing Solutions
• MAC for PicoNode Overview
• Multi-Channel MAC and Distributed Algorithm
• Sleeping Mode Based on Ultra Low Power Wakeup
  Radio
• Future Research, Design Methodology and
  Environment, Status and Time Line

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Things To Be Addressed

• Topology Control
• Equal Transmission Power, Results in Bad
  Connectivity
• Proposed Solution Link-based Transmission Power
  Management to reach a good network connectivity
• Power, Traffic Aware

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Design Flow Environment
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Conclusion

• Create General-Purpose Tools and Vertical Design
  Methodology for Application Driven Low Power
  Protocol Design
• A Low Power MAC Design Based on DMCA and Wakeup
  Radio
• A Flexible and Clean MAC Interface for Upper
  Layer to Do Aggressive Tradeoff between
  Communication and Computation.
• Motivate More Innovations in Radio Architecture
  for Low Power System

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Thanks !
Q A