Optimizing Sensor Networks in the Energy- Latency-Density Design Space Curt Schurgers, Vlasios Tsiatsi s, Saurabh Ganeriwal, Mani Srivast ava, IEEE TRANSACTIONS ON MOBILE COMPUTING,2002 Speaker : hsiwe i
Dec 30, 2015
Optimizing Sensor Networks in the Energy-Latency-Density
Design Space
Curt Schurgers, Vlasios Tsiatsis,
Saurabh Ganeriwal, Mani Srivastava,
IEEE TRANSACTIONS ON MOBILE COMPUTING,2002
Speaker : hsiwei
Outline
INTRODUCTIONSTEMSIMULATIONCONCLUSIONS
INTRODUCTION
Sensor networks are made up of a large number of tiny devices,call sensor node
Sensor nodes have only a small battery as a power source
To achieve satisfactory network lifetime,energy efficiency is really a problem
Network communications as the radio is the main energy comsumer in a sensor node
INTRODUCTION(con.)
Monitoring state : The network is only sensing its environment.
Transfer state : Once an event happens, data needs to be forwarded to the data sink.
目的 : It reduces the energy consumption in the monitoring state to a bare minimum while ensuring satisfactory latency for transitioning to the transfer state.
INTRODUCTION(con.)
Sleep state:In the monitoring state, where there is no traffic to forward.
Working state: The radio is only turned on if the processor decides that the information needs to be communicated to other nodes.
To forward traffic, nodes on the multihop path need to be awakened, or,equivalently, transition from the monitoring to the transfer state.
INTRODUCTION(con.) Initiator node:The node that wants to communicate. Target node: initiator node polls the node it is trying to w
ake up. Once the link between nodes is activated data is transfer
red using a MAC protocol The reason is that MAC protocols are designed to organi
ze access to the shared medium. STEM offers an alternative by trading energy for latency.
STEM
Each node periodically turns on its radio for a short time to listen if someone wants to communicate with it.
Since this aggressive nature is needed to limit the wakeup latency
STEM
The solution : is to completely separate data transfer from wakeup. transfer stat
e
wakeup band
STEM
STEM-B : As soon as the target receives a beacon, it turns on its data radio in band f1 and also sends back an acknowledgment in band f2.
STEM-T : a target node never sends back an acknowledgment.
contains the MAC address of both the target and initiator node.
STEM
Target node has received the beacon correctly or seen a collided packet and turned on its data radio in either case.
If they do not receive any traffic in band f1 after some time, they time out and return to the monitoring state.
SETUP LATENCY
Fig. 11. Analysis of the setup latency of STEM-B without collisions.
SETUP LATENCY
T
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T
TBTkTP B
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TKBTTBTKTP BRX
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21
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)( 1
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S 2*)1()
21(*
2
2
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K=1….K
SETUP LATENCY
KT
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)( 1
1BTT BRX
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1(*221 T
TTTBT BB
S
RXBS TBBTTT 21*2 NO collision
SETUP LATENCY
21max *)1( BTKT BS
RXBS TBBTTT 21*2
Beacon collision
SETUP LATENCY
Fig. 12. Analysis of the worst-case setup latency of STEM-T.
IRXS TTTT *2Tone -based
SIMULATION
Were written on the Parsec platform, an event-driven parallel simulation language
distribute N nodes in a uniformly random fashion over a field of size L x L
transmission range : R the average number of neighbors of a node:
The node turns its data radio back off if it has not received any traffic for 20 seconds.
20,100 N
22
* RL
N
SIMULATION
Setup latency of a link
ENERGY CONSUMPTION
1
2
P
P
1
2,1,
P
PP sleepsleep
burstwdata tft
t*
power of wakeup radio and data radio
sleep power for the data and wakeup radio
The average time the radio is on during one such data communication phase
The number of such transitions per second the node sets up a link
ENERGY CONSUMPTION
datawakeupnode EEE
setupsetupsetupnodewakeup tPttPE *)(* 2,2,
T
TPTTPP RXlistenRXsleepnode
*)(* 2,2,2,
datadatadatasleepdata tPttPE *)(* 1,1,
tPE originalnode *1
originalnode
node
E
E
E
E
0
tPE originalnode *1there is only one radio that is never in the sleep state,
ENERGY CONSUMPTION
**0
sS TfE
E
SSsetup Tft
t*
*)1(*0 T
T
t
t
t
t
T
T
E
E RXsetupdataRX
1)1( T
TRX
RXT
T
其中Setup frequency
SIMULATION
SIMULATION
SIMULATION existing topology management schemes, such as GAF
and SPAN.
CONCLUSIONS
STEM: A topology management technique that trades power savings for path setup latency in sensor networks.
the combination of STEM and GAF can
reduce the energy to 1 percent or less of that of a network without topology management
Summary
利用兩個不的 channel,達到 sensor node 節省電力 .
透過數學的分析及模擬 ,得到不錯的省電效果