KiYoung Jang Shuai Hao Anmol Sheth Ramesh Govindan Background 2 Evolution of WiFi Performance vs Energy Usage 8x speedup compared to 80211ag Mbps Background 3 80211n Features and Energy Usage ID: 405963
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Slide1
Snooze: Energy Management in 802.11n WLANs
Ki-Young Jang,
Shuai Hao, Anmol Sheth, Ramesh GovindanSlide2
Background
2
Evolution of Wi-Fi
Performance vs. Energy Usage
8x speedup compared to 802.11a/g
MbpsSlide3
Background
3
802.11n Features and Energy Usage
A
B
Energy management should exploit both
sleep opportunities
and
antenna configuration
.
MIMO
higher data rate
spatial diversity
Additional power states:
10-30% of peak power consumption of the tablet!
#
of
Antenna
1
2
1.99
1.27
1.13
0.10
3
2.10
1.60
1.45
0.10
Intel Wi
-
Fi Link 5300(W)
Tx
Rx
Idle
Sleep
1.28
0.94
0.82
0.10
1.5x and 1.6x
1.3x and 1.7xSlide4
Motivation Design Implementation
Evaluation
Motivation4Micro-sleep Opportunities
A
B
AP
t
Sleep!
Z
Z
Z
Sleep!
Z
Z
Z
t
tSlide5
Micro-sleep
Sleep + Wakeup = ~2ms
Motivation Design Implementation
Evaluation
Motivation
5
Micro-sleep Opportunities
# of STA
Traffic
Sleeping while AP is servicing others
1
Sleeping during inter-frame gaps
2
Depending on the traffic and number of clients, we can get energy savings of 30% ~ 90%.Slide6
Motivation Design Implementation
Evaluation
Motivation6
Internet as bottleneck:
SISO
is best
High bandwidth scenario:
MIMO3 is best
Antenna
Configuration
Antenna configuration should be
adaptive
based
on traffic demand and link quality
.Slide7
Challenges
7
Micro-sleep with minimal impact on delay and throughput-sensitive trafficAdaptive antenna configuration managementJoint design of both mechanisms
Application agnostic
Time (
ms
)
Power(W)
100 200 300
Sleep for 50ms
Sleep for 70msSlide8
Contribution
8
Design and Implementation of Snooze
Joint, application-agnostic
design of
client
micro-sleep
and
antenna
configuration management.
Extensive experiments that demonstrate
30~85% energy-savings over CAM across a wide range of traffic scenarios.Slide9
Motivation Design
Implementation Evaluation
AP-Directed Design9
Snooze AP
Snooze Client
Shapes traffic to create sleep opportunities
M
inimal impact on traffic
Minimizes the number of active clients
Manages antenna configurations
Minimizes antennas needed
Goal: Reduce client
energy consumption
by jointly controlling sleep and antenna
configurationSlide10
Sleep duration: based on measured packet arrival rate
Awake duration: based on average airtime consumption
Motivation
Design
Implementation
Evaluation
Snooze Components
10
Micro-sleep
Scheduling
Antenna
Mgmt.
If measured airtime utilization is
< 0.3: high link quality or more antennas
-> turn off 1 antenna
> 0.7: low
link quality or
less
antennas
->
turn on
1
antenna
Rate Adaptation:
AP uses default rate-control algorithm with restricted search space
Hysteresis and moving averages
A: 1Mbps
B: 20Mbps
Time (Second)Slide11
Motivation Design Implementation
Evaluation
ImplementationAPClient
11
Driver
Kernel
Rate
Table
Airtime
Usage
iwlagn
Airtime Scheduling
Sleep/Wakeup
Computation
mac80211
...
Per client traffic queue
Sleep/
Wakeup
Antenna Configuration
iwlagn
mac80211Slide12
Motivation Design Implementation Evaluation
Evaluation
12Applications used for evaluation
Delay/Jitter Sensitivity
High
Low
Bandwidth Requirement
High
HD video streaming
File downloading
Low
VoIP
Chat
Overview and Setup
Performance comparison
Constantly Awake Mode (CAM)
802.11 Power Save Mode (PSM)
Evaluation metric
Total
energy usage of NIC
Application throughput
and delaySlide13
Motivation Design Implementation Evaluation
Evaluation
13High Definition Video Streaming
More than 25% low-power sleeping
compared
with both CAM and PSM
About 50% energy savings
compared with both CAM and PSM
Average delay
CAM : 2.5ms, PSM : 4ms, Snooze : 8msSlide14
Motivation Design Implementation Evaluation
Evaluation
14Heterogeneous Traffic
Snooze can accommodate multiple concurrent applications.
Client
Mode
One app per client
Both techniques contribute significantly to energy savings, but contribution varies across
traffic.
Energy saving breakdown
File
VoIP
HD
Chat
micro-sleep
antenna
config
.Slide15
Related Work
15
Energy Management Techniques for 802.11
uPM
C-PSM
Catnap
NAPman
Snooze
AP-directed
Traffic types
HB-DS
HB-DI
LB-DS
LB-DI
802.11n
Rate adaptation
Multiple apps per clientSlide16
Conclusion
16
Client micro-sleep and antenna configuration managementApplication
agnostic
30~85% energy saving across a wide range of traffic scenarios
Snooze: Energy Management Scheme for 802.11n
Future Work
Multi-AP setting
Highly
bursty
workloads
Parameter sensitivity