Energy Management in Ad Hoc Wireless Networks

Energy Management
in Ad Hoc Wireless
Networks
Raj Jain
Washington University in Saint Louis
Saint Louis, MO 63130
Jain@cse.wustl.edu
These slides are available on-line at:
http://www.cse.wustl.edu/~jain/cse574-06/
Washington University in St. Louis
CSE574s
16-1
©2006 Raj JainOverview
Battery Management:
? Datalink and Network layers
? Transmit Power Management:
? Datalink and Network layers
? System Power Management
?
Washington University in St. Louis
CSE574s
16-2
©2006 Raj JainBattery Management Schemes
Key Fact: Batteries recover their charge when idle
? Use some batteries and leave others to idle/recover
? Task scheduling:
1. Round-robin batteries
2. Divide batteries in High-charge and low-charge
class. Select one from high-charge using round-
robin
?
Washington University in St. Louis
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©2006 Raj JainDatalink Layer Battery Management
Lazy Packet Scheduling:
Reduce the power ? Increase the transmission time
? Battery-Aware MAC Protocol:
Packets carry remaining charge.
Lower back off interval for nodes with higher charge
?
Washington University in St. Louis
CSE574s
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©2006 Raj JainNetwork Layer Battery Management
Goal: Increase the lifetime of the network
? Shaping: If battery charge becomes below threshold,
stop next transmission allowing battery to recover
? Battery Energy Efficient (BEE) Routing Protocol:
Minimize energy and use max battery charge
Washington University in St. Louis
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16-5
©2006 Raj JainTransmission Power Management
More transmit power ? Longer reach but lower battery life
Datalink:
1. Dynamic Power Adjustment: Use the min power required for
Low High
the next hop
2. Distributed Topology Control: Find power required and
direction of neighbors. Remove neighbors that have two-hop
paths with less power than direct transmission
3. Distributed Power Control Loop: Find the minimum power
required for successful RTS/CTS, Data/Ack
4. Centralized Topology Control: The power of each node is
reduced until it has single connectivity, i.e., there is one path
between each pair of nodes or bi-connectivity, i.e, there are 2
disjoint paths between each pair of nodes
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©2006 Raj JainTransmission Power Management (Cont)
Network Layer: Minimize computation (compression, idle
listening, routing table)+transmission
1. Common Power Control: Given reachability of each node as a
function of power, find the min power level that provides
network connectivity.
2. Min Power Consumption Routing: Bellman Ford using
Power as the cost metric
3. Min Variance in Node Power Levels: Every node should
relay the same amount of traffic. Select next hop with the
shortest Q.
Washington University in St. Louis
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©2006 Raj JainTransmission Power Management (Cont)
4. Min Battery Cost Routing: Minimize sum of battery cost
(based on charge) along a path ? Does not ensure that lower
charge nodes are not used
4
4
2
1
5
3
5. Min-Max Battery Cost Routing: Select the path which
minimizes the max power required at any node
? Does not give min total power
? Reduced lifetime for the network
6. Conditional Min-Max Battery Cost Routing:
Using only nodes that have battery charge over a threshold,
Find the min total power path.
Washington University in St. Louis
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©2006 Raj JainTransmission Power Management (Cont)
7. Localized Power-Aware Routing: Power =ad ? +c, ? > 2
? Two one mile hops are better than one two mile hop
? n-hops are best, n = round{da(?-1)/c 1/? )}
Find the neighbor with the minimum expected power
8. Charge Based Clustering: Select cluster head that has the
highest charge. Reconfigure when the cluster head is not the
one with highest charge.
Higher layers can also be made energy conscious
? shut down when inactive
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©2006 Raj JainProcessor Power Management Schemes
Logic
Receiver
Standard Receiver/
Transmitter
Remote Access
Switch
Power Status
Device
Electronics
1. Remote Access Switch: System sleeps. Only PHY receiver is
on. On receipt of a particular signal, wakes up the system.
2. Power Aware Multi-Access Signaling (PAMAS): Power-off
if you hear RTS/CTS for another node or if you have nothing to
send.
Washington University in St. Louis
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©2006 Raj JainDevice Power Management Schemes
Turn off individual components: LCD display,
DRAM, CDROM, CPU, Drive
? Run CPU at lower clock rate, lower voltages
? Spin down disks when unused
?
36%
Power
Consumption
Washington University in St. Louis
21%
18%
18%
CPU/ Wireless Hard
Display Memory LAN
Disk
CSE574s
16-11
7%
Others
©2006 Raj JainSummary
?
?
?
Battery Management: idling increases the capacity of the
battery
Transmission Power Management: Distance vs. Power
tradeoff
System Power Management: Put system/components to sleep
whenever possible
Washington University in St. Louis
CSE574s
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©2006 Raj JainReading Assignment
?
Read Chapter 11 of Murthy and Manoj
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©2006 Raj JainHomework
Transmit power = ad ? +c
1. Where should intermediate node A be located between source S
and destination D so that the total power is minimized.
S
A
D
r
s
r+s
2. If the path between source S and destination D consists of n
equal size hops. What should n be so that the total power is
minimized?
S
A
B
C
D
r
r
r
r
d = nr
Washington University in St. Louis
CSE574s
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©2006 Raj Jain