BodyQoS: Adaptive and Radio-Agnostic QoS for Body Sensor Networks
Gang ZhouCollege of William and MaryJian LuUniversity of VirginiaChieh-Yih Wan, Mark D. YarvisIntel ResearchJohn A. StankovicUniversity of VirginiaIEEE INFOCOM 2008
College of William and Mary4
Health Monitoring During Emergency
Manual tracking of patient status, based on papers and phones, is the past;Real-time & continuous monitoring, through body sensor networks, is the future;
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A Typical Body Sensor Network
Heart rate & blood oxygen saturation
Two-Lead EKG
Limb motion & muscle activity
Sweat
Temp.
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BodyQoS GoalsBodyQoS Goals Priority-based admission control Wireless resource scheduling Providing effective bandwidth
Design ConstraintsDesign Constraints Heterogeneous resources Heterogeneous radio platforms
EKG
Light
Sweat
DataControl
Quality of Service for Body Sensor Networks
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BodyQoS Contributios
The first Running QoS System for Body Sensor Networks
Asymmetric Architecture• Most work for the aggregator• Little work for sensor nodes
Virtual MAC• Separate QoS scheduling from underlying real MAC• Easy to port to different radio platforms
Effective BW Allocation• Adaptive resource scheduling, so that statistically the delivered
BW meets QoS requirements, even during interference
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Asymmetric Architecture
TransportTransport
Admission Control
Slave QoS Schduler
V-MACV-MAC
Sensor Motes Aggregator
QoS Scheduler
Slave Admission
Control
AppApp
Real MACReal MAC
Poll
Data
BodyQoS
(1) Schedule wireless resources(2) Calculate effective bandwidth(3) Put radio to sleep
(1) Abstract wireless resource for QoS scheduling
(2) Implemented by calling real MAC’s functions
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
(1) Decide which streams to serve and which not to serve
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Wireless Resource Abstraction
…...packet packet packet packet packet packet
…... …... …...…...
packet packet
…... …... …...
Tinterval Npkt Spkt TPkt TmaxPkt TminSleep
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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Wireless Resource Abstraction
…...packet packet packet packet packet packet
…... …... …...…...
packet packet
…... …... …...
Tinterval
Npkt Spkt TPkt TmaxPkt TminSleep
The length of each interval
Tinterval
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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Wireless Resource Abstraction
…...packet packet packet packet packet packet
…... …... …...…...
packet packet
…... …... …...
Npkt
Tinterval Npkt Spkt TPkt TmaxPkt TminSleep
The maximum number of packets QoS Scheduler can send/receive within each interval, if there is no interference
Npkt
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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Wireless Resource Abstraction
…...packet packet packet packet packet packet
…... …... …...…...
packet packet
…... …... …...
Spkt
Tinterval Npkt Spkt TPkt TmaxPkt TminSleep
The effective data payload size in each packet that can carry application data
Spkt
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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Wireless Resource Abstraction
…...packet packet packet packet packet packet
…... …... …...…...
packet packet
…... …... …...
Tinterval Npkt Spkt TPkt TmaxPkt TminSleep
The minimum time needed to send out a packet, if there is no interference
Tpkt
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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Wireless Resource Abstraction
…...packet packet packet packet packet packet
…... …... …...…...
packet packet
…... …... …...
Tinterval Npkt Spkt TPkt TmaxPkt TminSleep
The maximum time needed to send out a packet or finally report giving up, if it suffers maximum backoffs/retransmissions
TmaxPkt
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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Wireless Resource Abstraction
…...packet packet packet packet packet packet
…... …... …...…...
packet packet
…... …... …...
Tinterval Npkt Spkt TPkt TmaxPkt TminSleep
The minimum time for putting radio to sleep, which includes the sleeping/activation switch time and also considers the energy cost;
TminSleep
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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Virtual MAC Operation
Assigned resource to send D packets within time T
D ≥ 1 andtime left ≥ TmaxPkt?
End
Call real MAC to send the next packet
N
Update time leftD=D-1Y
Wait for real MAC returns: sendDone/failure
Delivered Bytes / Actual TimeBWeffective
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
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If application requests BW bi, BodyQoS allocates BW bi
pkt
intervalii S
T*bD
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
Minimum per packet transmission time
Packet size
Interval length
The ideal case: no Interference
That is, in each interval Tinterval, QoS scheduler requests VMAC to send/receive Di packets within time Ti=Di*Tpkt
The general case: when interference is present
Effective BW Allocation
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18
Interference
Max. MAC Retrans. Time
HInterference
H
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
The general case: when interference is present
Per Packet Trans. Time: *pktTpktT # Requested Packets: *
iDiD
*pktT *
iD
}T,BWBWmin{TT maxPkt
effective
idealpkt
*pkt
pkt*pkt
effectiveideali
*i TT
BWBWDD
Effective BW Allocation
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EKGLocation
Aggregator
Adaptive QoS
Best effort
Explicit Noise
Data Collection
Temperature
RTP-Like QoS
Performance Evaluation Setup
Implemented at Intel with Imote2
Ported to MicaZ at UVA
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Performance
① Adaptive QoS always delivers requested BW
② Delivered BWs for RTP-Like QoS and best-effort reduce when interference increase
③ RTP-like QoS has better performance than best-effort
135s0s 225s 315s 400s
Noise Node Off
Noise Node On 30ms per packet
Noise Node On 25ms per packet
Noise Node On 20ms per packet
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ConclusionsWe designed, implemented, and evaluated the first Running QoS System for Body Sensor Networks Asymmetric Architecture
• Most work for the aggregator• Little work for sensor nodes
Virtual MAC• Separate QoS scheduling from underlying real MAC• Easy to port to different radio platforms
Effective BW Allocation• Adaptive resource scheduling, so that statistically the delivered
BW meets QoS requirements, even during interference
For more information, visit: www.cs.wm.edu/~gzhou
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Interference
Max. MAC Retrans. Time
HInterference
H
① Asymmetric Architecture② Virtual MAC③ Effective BW Allocation
The general case: when interference is present
Per Packet Trans. Time: *pktTpktT # Requested Packets: *
iDiD
*pktT *
iD
effective
idealpkti
*pkt
*i BW
BW)T(DTD effective
idealpkt
*pkt BW
BWTT
}T,BWBWmin{TT maxPkt
effective
idealpkt
*pkt
pkt*pkt
effectiveideali
*i TT
BWBWDD
Effective BW Allocation
College of William and Mary24
Implementation
01234567
ROM (kBytes)
AdmissionControl
QoSScheduler
VMAC
Mote Aggregator
Implemented at Intel with Imote2
Ported to MicaZ at UVA
1:17Most Work Done at the Aggregator
1:4 The sameVMAC <100 lines of codeBodyQoS ~3700 lines of code
Only need to modify VMACEasy to Port to Different Radio Platforms
Ported to Telos at W&M
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Evaluation -- Bandwidth Delivery Ratio
① Adaptive QoS always delivers requested BW
② Delivered BWs for RTP-Like QoS and best-effort reduce when interference increase
③ RTP-like QoS has better performance than best-effort
Aggregator Side
135s0s 225s 315s 400s
Noise Node Off
Noise Node On 30ms per packet
Noise Node On 25ms per packet
Noise Node On 20ms per packet
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Evaluation -- Data Buffer Fetching Speed
① Adaptive QoS always maintains 4Kbps fetching speed
② Fetching speeds of RTP-Like QoS and best-effort reduce when interference is present
③ Fetching speed of RTP-like QoS is higher than that of best-effort
Mote Side
135s0s 225s 315s 400s
Noise Node Off
Noise Node On 30ms per packet
Noise Node On 25ms per packet
Noise Node On 20ms per packet