Post on 04-Jan-2016
description
Exploring the Energy-Latency Trade-off for Broadcasts in
Energy-Saving Sensor Networks
Matthew J. Miller, Cigdem Sengul, Indranil Gupta
Department of Computer Science University of Illinois Urbana-Champaign
IEEE ICDCS 2005.6
outlines
Introduction Energy-efficient Communication in Wireless
Sensor Networks Probability-Based Broadcast Forwarding
(PBBF) Analytical Results Simulation Results Conclusion Future Work
Introduction
Sensor nodes are inherently resource constrained.
Offer better reliability and performance to a sensor network application
Provide enough flexibility for a designer to choose the appropriate operation point on the resource-performance spectrum.
Introduction
Broadcast is useful to applications for disseminating sensor data, instructions, and code updates.
The goal is to design a broadcast protocol that allows a range of operating points from which an application designer can choose.
PBBF (Probability-Based Broadcast Forwarding), which is a MAC-layer approach and can be integrated into any sleep scheduling protocol
Related Work
Gossip-Based Ad Hoc Routing [5],• site percolation model
• Achieving a given level of reliability requires the probability of forwarding to be beyond a threshold.
• The approach does not allow an energy-latency trade-off.
PBBF protocol• bond percolation model
• Two knobs, p and q, can be tuned to explore the energy-latency trade-off.
Energy-efficient Communication in Wireless Sensor Networks
Efficient Broadcast Protocols Sleep Scheduling Mechanisms
Efficient Broadcast Protocls SPIN protocols [6,MobileCom 1999]
• Incorporate negotiation in order to avoid deficiencies of the class flooding approach.
[15][16]• Virtual infrastructure
[5,Infocom 2002][13]• To forward a message with some probability
(i.e., gossip)
Sleep Scheduling Mechanisms
reduce energy consumption in WSNs• Active-sleep cycle
• IEEE 802.11 PSM, S-MAC, T-MAC
• Additional low-power wake-up radio
problem• Increasing latency
• redundant packets
Probability-Based Broadcast Forwarding (PBBF)
PBBF exploits the redundancy in broadcast communication and forwards packets using a probability-based approach
The goal is to ensure that, with high probability, a node receives at least one copy of each broadcast packet, while reducing the latency due to sleeping.
p=0.5 q=0.5
N1
N2
N3
The two Knobs
p• It is the probability that a node rebroadcasts a packet
immediately without ensuring that any of its neighbors are active
q• It is the probability that for a given node and a given
time instant when it is supposed to be asleep due to its active-sleep schedule, the node instead stays awake in the expectation that it might be a receiver of an immediate broadcast
Probability-Based Broadcast Forwarding (PBBF)
PBBF exploits the redundancy in broadcast communication and forwards packets using a probability-based approach
The goal is to ensure that, with high probability, a node receives at least one copy of each broadcast packet, while reducing the latency due to sleeping.
p=0.5 q=0.5
N1 O O
N2 ♦ X
N3 X O
Probability-Based Broadcast Forwarding (PBBF)
PBBF exploits the redundancy in broadcast communication and forwards packets using a probability-based approach
The goal is to ensure that, with high probability, a node receives at least one copy of each broadcast packet, while reducing the latency due to sleeping.
p=0.5 q=0.5
N1 ♦ O
N2 O O
N3 ♦ ♦
Probability-Based Broadcast Forwarding (PBBF)
PBBF exploits the redundancy in broadcast communication and forwards packets using a probability-based approach
The goal is to ensure that, with high probability, a node receives at least one copy of each broadcast packet, while reducing the latency due to sleeping.
p=0.5 q=0.5
N1 ♦ O
N2 O O
N3 ♦ ♦
Pseudo-code for PBBFSleep-Decision-Handler()1 /* Called at the end of active time */2 /* If stayOn is true, remain on; otherwise sleep*/3 stayOn false4 5 If DataToSend=ture or DataToRecv=true6 then7 stayOn ture8 else if Uniform-Rand(0,1) < q9 then stayOn true---------------------------------------------------------------------------------------Receive-Broadcast(pkt) 1. /* Called when broadcast packet pkt is received */2. If Uniform-Rand(0,1) < p3. then Send(pkt)4. else Enqueue(nextPktQueue,pkt)
Analytical Results
Reliability Energy Latency Energy-Latency Trade-off
Reliability The reliability of PBBF protocol can be
analyzed using percolation model. Percolation model, [3]
• Bond percolation
• Site percolation
Site Percolation Theory
Site Percolation Theory
Bond Percolation Theory
Bond Percolation Theory
Percolation Theory [3]
G(V,E) : an infinite connected graph Co : the set of nodes, which can be reached by
a specific node no
Θbond(Pedge) : the probability of the component Co being of infinite size
so that Θbond(Pedge)=0 if Pedge<Pcbond(G)
xnVxC oo :
0:sup edgebond
edgebondc PPGP
Reliability (PBBF)
The probability of AB is p·q+(1-p)• p·q : A broadcasting the message immediatel
y after reception and that B being awake at the time
• (1-P) : a rebroadcast when B is awake• Each edge in the network is open with this probabili
ty.
Remark 1 (p and q for high reliability):• If Pedge=1-p·(1-q) P≧ c
bond(G), the broadcast is received at infinitely many node.
Reliability (PBBF) - simulator
Fig.4. Threshold behavior for 90% reliability
Fig.5. Threshold behavior for 99% reliability
Reliability (PBBF) - simulator
Fig.6. Pcbond for various grid sizes Fig.7. Relationship between p and q
for a given reliability level in a 30*30 grid network
Energy
sleepactiveframe
frame
activeoriginal
TTT
T
TE
frame
sleepactive
frame
PBBFactivePBBF
sleepPBBFsleep
sleepactivePBBFactive
T
TqT
T
TE
TqT
TqTT
:
:
:
1
active
sleep
active
sleepactive
original
PBBF
T
Tq
T
TqT
E
E
1
Fig.8. Average energy consumption.
Latency
L: the expected time between A sending the broadcast and B receiving it from A
BSlenLL BS ,,
qpp
pLL
pqp
pLLqpLL
1
1
1
121
211
145
,
o
BS dLL ,[4][10]
Latency - simulator
Fig.9. Average hops traveled by an update to reach a node 20 hops from the source
Fig.10. Average hops traveled by an update to reach a node 60 hops from the souce
Latency - simulator
Fig.11. Average per-hop update latency.
Energy-Latency Trade-off
originalactive
sleepPBBF E
T
T
p
pLL
LLLE
11 1
12
Fig.12. Energy-Latency trade-off for 99% reliability.
Simulation Results
Environment parameter• assume perfect
synchronization in the network
• Ns-2
• The values of our parameters are based on Mica2 Mote hardware
• Run time:500 sec
• Each data point is averaged over ten runs
Parameter Value
N 5625(75*75)
PTX 81mW
PI 30mW
PS 3μW
λ 0.01 pakcets/s
L1 ≈1.5s
Tframe 10s
Tactive 1s
q 0.25
∆ (node density) 10.0
Total Packet Size 64bytes
Data Packet Payload 30bytes
The impact of the q parameter
Fig.13. Average energy consumption
The impact of the q,p parameter
Fig.14. 2-hop average update latency Fig.15. 5-hop average update latency
The impact of the q,p parameter
Fig.16. Average updates received
The impact of △ A
NR2
Fig.17. Average update latency Fig.18. Average updates received
Conclusion
PBBF is an efficient broadcast mechanism
PBBF provides an application designer the opportunity to tune the system to an appropriate operating point along the reliability-resource-performance spectrum.
Future Work
Explore how PBBF can be augmented to improve performance
The p and q parameters could be adjusted dynamically by nodes
Compare its performance with other adaptive sleep protocols.
Thank you