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Mitigate the Bottleneck of Underwater Acoustic Sensor
Networks via Priority SchedulingJunjie Xiong, Michael R. Lyu, Kam-Wing
Ng
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Background
Wireless sensor networks (WSNs) Underwater acoustic sensor networks (UWASNs)
Deployed in oceans Difference from terrestrial wireless sensor networks (TWSNs)
Wireless medium Sound (Electromagnetic waves)
Longer latency Higher cost Sparser deployment
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RegionRegion
Base stationBase station
Sensor nodes
Sensor nodes
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Ocean bottom monitoring by UWASNs
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Outline Motivation Protocol Design Evaluation Conclusions
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Motivation
CTS8ms
CTS8ms
RTS8ms
RTS8ms Propagation time
740msPropagation time
740ms
DATA80ms
DATA80ms
ACK8ms
ACK8ms
CTS8ms
CTS8ms
RTS8ms
RTS8ms
Propagation time 3.7us
Propagation time 3.7us
DATA80ms
DATA80ms
ACK8ms
ACK8ms
SenderSender
ReceiverReceiver TT
A DATA transmission in UWASNs with CSMA/CA
SenderSender
ReceiverReceiver TT
A DATA transmission in TWSNs with CSMA/CA
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Motivation
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DATA1: P->QDATA1: P->Q T
1T1
I1I1
R1R1
DATA2: Q->SDATA2: Q->S
I2I2
R2R2
T2T2
T3T3
R3R3
DATA3: S->QDATA3: S->Q
I3I3
DATA4: P->QDATA4: P->Q T
4T4
I4I4
R4R4
T stands for transmittingR stands for receivingI stands for interference
T stands for transmittingR stands for receivingI stands for interference
Node PNode P
Node QNode Q
Node SNode S
TT
TT
TT
Data transmission between 3 nodes in UWASNs
Data transmission between 3 nodes in UWASNs
DATA4: P->SDATA4: P->S T
4T4
I4I4
R4R4
Collision!
R2
R3
I1
R1
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Motivation
T stands for transmittingR stands for receivingI stands for interference
T stands for transmittingR stands for receivingI stands for interference
Node PNode P
Node QNode Q
Base stationBase station
CycleCycle
CycleCycle
CycleCycle
Data transmission between 3 nodesData transmission between 3 nodes
TPTP
IPIP
RPRP
TPTP
IPIP
RPRP
TPTP
IPIP
RPRP
TPTP
IPIP
RPRP
TPTP
IPIP
RPRP
TPTP
IPIP
RPRP
TPTP
IPIP
RPRP
TPTP
IPIP
RPRP
IQIQ
RQRQ
TQTQ
IQIQ
RQRQ
TQTQ
IQIQ
RQRQ
TQTQ
IQIQ
RQRQ
TQTQ
IQIQ
RQRQ
TQTQ
IQIQ
RQRQ
TQTQ
IQIQ
RQRQ
TQTQ
Utilize the propagation time Maximize the throughput by minimizing working period in a cycle
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Outline Motivation Protocol Design Evaluation Conclusions
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A Routing and Application based Scheduling Protocol (RAS)
DATA1: P->QDATA1: P->Q T
1T1
I1I1
R1R1
T stands for transmittingR stands for receivingI stands for interference
T stands for transmittingR stands for receivingI stands for interference
Node PNode P
Node QNode Q
Node SNode S
TT
TT
TT
Data transmission between 3 nodes in UWASNs
Data transmission between 3 nodes in UWASNs
I1
R1
One time
One time
Three times
Three times
We discover a unique scheduling problem that exists only in UWASNs: different scheduling element.
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A Routing and Application based Scheduling Protocol (RAS)
We design the Routing and Application based Scheduling protocol (RAS) which is composed of : The TDMA based MAC mechanism The static routing calculation Centralized schedule calculation by utilizing application data direction
Calculate the traffic of each node. Schedule the traffic transmission and reception.
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A Routing and Application based Scheduling Protocol (RAS)
Scheduling principles of RAS At a node, guarantee a DR will not overlap any DT. At a node, guarantee a DR will not overlap any IR. At a node, a DT and one or more IR can coexist. No DR from i-th hop node to (i+1)-th hop node. At a node, use DR as the scheduling basis rather than DT or IR.
DR: data receptionIR: interference receptionDT: data transmission
DR: data receptionIR: interference receptionDT: data transmission
DRDT DT Node m
TDATA
Scheduled DT
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To be integrated to the previous slide
DRDT DT Node m
TDATA
DRIR IR Node m
TDATA
Scheduled DT
Scheduled IR
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A Routing and Application based Scheduling Protocol (RAS)
Congestion avoidance algorithm Besides throughput, queue length, fairness are important Step1: Schedule the BS's DR from 1 hop nodes. Step2: Schedule the DR tier by tier: from inner tier to outer tier. Step3: For each node m that is going to receive data packets
from its children, arrange its DR from its children alternatively.
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Outline Motivation Protocol Design Evaluation Conclusions
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Performance Evaluation
Network Throughput
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Performance Evaluation
Average End-to-end Delay
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Performance Evaluation
Average Maximum Queue Length per Node
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Performance Evaluation
Time Slots Required for the RAS Network Working Period
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Outline Motivation Protocol Design Evaluation Conclusions
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Conclusion
We discover a unique scheduling problem that exists only in UWASNs.
A priority scheduling protocol RAS is designed to provide communications for UWASNs. RAS allows parallel transmissions, and thus improve the
throughput and delay performance based on the scheduling principles.
RAS mitigates queue overflow and is scalable in calculating proper schedules.
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Q & AThank you!
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UW-FlASHR
UW-FLASHR (Achieving high channel utilization in a time-based acoustic mac protocol, ACM Mobicom Workshop on UnderWater Networks, 2008) is a distributed TDMA based MAC protocol. utilizes propagation delay to increase throughput. employs no energy-saving mechanism. suffers from collisions.
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A Cross-layer Communications Protocol Design
Advantages of RAS Reduces mutual communications Reduces energy consumption Avoids collision, increases throughput, and reduces delay and
queue overflow probability for each node
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A Cross-layer Communications Protocol Design
Scheduling algorithm formulation Maximize the throughput by minimizing the working period of a cycle
The number of the decision variables equals the number of the packets to be received in a cycle.
Unique scheduling element: the combination of a DR, a DT and a sequence of IR to the other nodes.
The schedule principles.
The time node m receives the Qmjw-th packet from its children node Cmj
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A Cross-layer Communications Protocol Design
Congestion avoidance algorithm
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A Cross-layer Communications Protocol Design
Congestion avoidance algorithm
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