bwrc chunlong guo, prof. jan rabaey
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BWRC
Chunlong Guo, Prof. Jan Rabaey
Low Power MAC for Ad Hoc Wireless Network
EECSUniversity of California at Berkeley
BWRC
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
BWRC
Wireless Media Access Control
MAC: Let multiple radios share the same communication media.
Time
Code
Freq
uen
cyPhysical
MACNetwork
Application
• Local Topology Discovery and Management.• Media Partition By Allocation or Contention.• Provide Logical Channels to Upper Layers.
BWRC
Media Access in Multi-hop Networks
• Large number of short range radios in a wide area Transmission Locality
Problems: Good thing: Channel Reuse
Hidden Terminal, (CSMA is not appropriate)No Global Synch.
AB C
ED
BWRC
Solution 1: Contention BasedMACA: [p. Kam, 90]
RTS-CTS-DATAMACAW: [V. Bharghavan, 1994] add link layer ACK.FAMA [C.L. Fuller, 95] 802.11: Add carrier sensing Optional ACKPAMAS: [S. Singh, 2000] Power aware MAC Separate signaling channel
RTS
CTS
RTS
Collision at B
Collision still exists. Too much overhead.
A B C D
collide
BWRC
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 StructureToo much Management Overhead
BWRC
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 Radio’s More than 90% of power is burned when radio is idle.
‘Low power’ System Built on Existing MAC is NOT Low Power
BWRC
Opportunities for PicoMAC
• Application Driven, Low Duty-Cycle MAC
• New Radio Architectures
• Vertically-Integrated Interactive Design Methodology
PHY
MAC
ApplicationNetwork
BWRC
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
BWRC
PicoNode ≠ MultiMedia• Low-date Rate Radio : 10kbps (peak)
• Low Traffic Duty Cycle: ~ 1%, 1~200 Bytes/source/s
• Short Packet: <50Bytes
• Loose QoS Requirements, Often not Delay Sensitive
BWRC
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.
BWRC
Where Energy Goes?
When idle: Channel MonitoringCollision and Retransmission Signaling overhead (header, control pkts)
BWRC
Low Power MAC for PicoNode
Spread Spectrum Multi-Channel SchemeTo Reduce Collision RateTo Reduce Signaling Overhead (Shrink Address Space)
Deep-Sleep Mode with Wakeup RadioPower Down the Whole Data RadioReduce Monitoring Energy Consumption by 103 Times
Adaptive Mobility Support
BWRC
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
BWRC
CDMA Multi-Channel Scheme
• Parallel Transmission without Synch.• Implicit Local Address: Channel
Idea: Nodes use different channels to transmit data, no collision at receiver.
Key: Locally Unique with Global Reuse
1
3
2
4
5
6 7
8
BWRC
Multiple Channel Assignment• Sender based CANo primary collision
Receiver need switch data channels
Needs a separate signaling channel
• Receiver based CAPrimary collision
Receiver only listen to its own channel
No need signaling channel
BWRC
Find the Solution: Graph Coloring
• Goal: For any node, all its neighbors are with different colors
• Or: All two-hop neighbors with different colors.
• Number of colors needed:#(NCA) <= min {d(d-1)+1, |v|}
Brook and Vizing theorem
Model:An incomplete graph
G = (V,E)d is the maximum degree of
nodes
1
2
3
4
5
BWRC
Performance AnalysisModel: a ∆-regular graphp: traffic density
SC (Share Single Channel ): Bsca = p (1-p) (∆-1) (1-p)
RCA (Send on Receiver’s Channel ): Brca = p (1-p/∆) (∆-1) (1-p)
TCA (Send on Sender’s Channel ): Btca = p [1-(1-p/∆) ∆ ](1-p)
BWRC
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
BWRC
Power Down Data Radio• Current Radio Sleeping Mode: 10~50% Power
Consumption• For PicoNode Running at 1% Duty Cycle, 90~95%
Energy When Radio Is Idle.
• Even Worse As PicoNode Radio Is Shorter Range
150mW50mWBWRC TCI
0.18W1.48W3WLucent WaveLAN 23dBm 915MHz
0.18W1.8W1.825WLucent WaveLAN 15dBm 915MHz
0.05W0.6W1.8WDEC Plessey DE 6003 2.4GHz
StandbyReceiveTransmit
BWRC
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
BWRC
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: <10ms
D/APowerAmplifier X
ED PPD
Data/control codesWakeup Tone
BWRC
Wakeup Sequence and Energy Profile
Node B
DATA
ACK
Useful dataPower Profile
WUP
CTS
E(useful data traffic) + E(overhead traffic) + E(idle)EPB =L(useful data traffic) * [1-p(collision)]
TwTr Th
Node A
BWRC0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Traffic Rate (10kbps)
Ene
rgy
Per
Bit
(mJ/
bit)
Lp = 20 Lp = 60 Lp = 100Lp = 140Lp = 180Lp = 220Lp = 260Lp = 300
EPB Performance AnalysisTotal Number of Nodes
N=100Network Dimention
D = 6Number of Channels
M = 32Radio Bit Rate
R=10kbps
Pt =2mw
Pr =3mw
Pm = 2mw
Ps = 1uW
Lp = 20bits
Lp = 60bits
Lp = 300bits
BWRC0 0.05 0.1 0.15 0.2 0.25 0.3
100
101
102
Traffic Density (10kbps)
EP
B (u
W/b
it)
Ps=1uW Ps=100uWPs=1mW
EPB Performance Analysis
Ps = 1uWPs = 100uW
Ps = 1mW
Conclusion:For duty cycle 1~10 percent:
10 ~ 100 times better
BWRC
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
BWRC
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
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 300
5
10
15
BWRC
Design Flow & Environment
AlgorithmExploration/Evaluation
System SimulationPerformance Evaluation
SDLFunctionalVerification
Documentation
Test-BenchPrototyping
Measurements
System DefinitionAbstraction
VCCArchitectureExplorationEvaluation
I II
BWRC
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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