Date post: | 23-Dec-2015 |
Category: |
Documents |
Upload: | leonard-curtis |
View: | 212 times |
Download: | 0 times |
1
O-MAC: A Receiver CentricPower Management Protocol
Hui Cao, *Kenneth W. Parker, Anish Arora
The Ohio State University, *The Samraksh Company
2
Outline
1. Receiver centric design
2. Energy efficiency comparison
3. O-MAC protocol design
3
Part I: Receiver Centric Design
4
Dominant Receiver Power Consumption
Large portion of energy is consumed in receiver radio
One typical surveillance application:
Receiver Radio~2100 J/day
Signal processing ~60 J/day
Everything else ~8 J/day
Receiver Radio
Signal Processing
Other
5
Increasing Rx Power Consumption
Rx becomes higher than Tx!with evolution of Berkeley motes
3.8
9.6
19.7
12
16.5 17
0
5
10
15
20
25
TR1000 (Mica 2001) CC1000 (Mica2 2002) CC2420 (Telos 2004)
mA
Rx Power Tx Power
0
5
10
15
20
25
30
35
40
Freescale MC12192 OKI ML7222 Ember EM250
mA
Rx Power Tx Power
Other popular radio chips also have higher Rx power consumption
6
Receiver Centric vs. Transmitter Centric
Transmitter Centric MAC design:• Transmitter implicitly knows receiver will wakeup during transmission
• Collision avoidance is transmitter driven (i.e., RTS-CTS, CCA)
Receiver Centric MAC design:• Receiver explicitly communicates its wakeup schedule to transmitter
• Collision avoidance is receiver driven (i.e., receivers use TDMA)
TransmitterReceiver
TransmitterReceiver
Transmitter
Receiver
7
Why Receiver Centric Design?
We claim: Receiver Centric approach yields substantially higher Receiver Efficiency
Receiver Efficiency ≈ Total Energy Efficiency ≠ Transmitter Efficiency
Receiver Efficiency = Goodput
Receiver Power Consumption
Transmitter Efficiency = Goodput
Transmitter Power Consumption
Total Energy Efficiency = Goodput
Transmitter + Receiver Power Consumption
Historically, MAC design has focused on Transmitter Efficiency
However, dominant cost of receiver radio has implied that
8
Part II: Energy Efficiency Comparison
9
Assumptions and Notations
Traffic model• Uniform random traffic
Notations:
• E: energy efficiency
)( j
iji
ji
RS
ME
Goodput (Msgs Sent + Receive)
Total (Msgs Sent + Receive)
10
Theoretical Energy Efficiency
We’ll consider:• Synchronous Blinking (S-MAC, T-MAC)
• Long Preamble (B-MAC, WiseMAC)
• Asynchronous Wake-up
• Random Time-Spreading
• Staggered On
• Pseudo-random Staggered On
11
Frame
Slot Slot
Frame
SlotSlotSlot Slot Slot Slot
Listen
Transmit
Sleep
Frame
Slot Slot
Frame
SlotSlotSlot Slot Slot Slot
Sender
Receiver
1) Synchronous Blinking (e.g. S-MAC & T-MAC)
1
74.0
)1(
2max
e
E : number of interfering nodes
12
2) Long Preamble (e.g. B-MAC, WiseMAC)
Case 2: Multiple Repeat Packets
Listen
Transmit
Sleep
Slot Slot
Slot Slot
Sender
Receiver
Slot Slot
Frame
Frame
SlotSlot
Slot
Sender
Slot
Slot Slot
Receiver
Slot Slot
Preamble
Case 1: Single Packet
2max
E : duty cycle
13
3) Asynchronous Wakeup
Sender
Frame
Slot Slot
Receiver
Listening
Transmission
Sleep
SlotSlot Slot Slot Slot
Frame
Slot Slot SlotSlot Slot Slot Slot
2max E : duty cycle
14
4) Random Time Spreading
In each time slot, each node wakes up randomly No time sync
Power efficiency:
2
max E : duty cycle
: number of interfering nodes
15
5) Staggered On
43.0max E
Only one receiver wakes up in the interference region at one time
Scheduled globally to avoid receiver collision
16
6) Pseudo-random Staggered On
Frame
Slot Slot
Frame
SlotSlotSlot Slot Slot Slot
Listen
Transmit
Sleep
Frame
Slot Slot
Frame
SlotSlotSlot Slot Slot Slot
Sender
Receiver
rE *43.0max r is a factor near 1
17
Energy efficiency comparison
10 15 20 25 30 35 40 45 500
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
The average number of nodes that interfere
The
ene
rgy
effic
ienc
y
Staggered On
Pseudo-random Staggered On
Long PreambleSynchronous Blinking
Asynchronous Wake-up
Random Time Spreading
18
Part III: O-MAC Protocol Design
19
O-MAC Protocol Design
Based on: Pseudo-random Staggered On
The Core Protocol• Interfaces
• Neighbor list
• Send
• Receive
• Synchronous ACK
• Pseudo-random Scheduler
20
O-MAC Analysis and Simulation
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
The transmission probability when one neighborhood receiver is on (ptm
)
The
ene
rgy
effic
ienc
y
Energy efficiency-simulation
Energy efficiency-theoretical1. Simulation confirms
theoretical analysis
2. Maximal energy
efficiency for
particular traffic load!
Adaptive duty cycle
21
O-MAC Key Implementation Issues
Time Synchronization• Current technique:
• < 10 PPM
• Every 2 minutes, to guarantee 1ms accuracy
• Cost: 0.001% duty cycle
Adaptive Duty Cycle• A cross layer design issue
Sender Centric
Application
Receiver Centric
Communication
22
Conclusion and Future work
Conclusion:• Receiver Centric has substantial impact on power
management
• Receiver vs. Transmitter Collision Avoidance
• OMAC has been implemented and is being integrated for mobile sensor network experiments on Dec.7 at OSU
Future work:• Receiver Centric higher layer protocol
(Network, Transport, Application)
• Adaptive duty cycle scheme