Transcript PPT

Realizing the Full Potential of
PSM using Proxying
Ning Ding
Abhinav Pathak
Y. Charlie Hu
Dimitrios Koutsonikolas
Clay Shepard
Lin Zhong
1
Smartphone is Energy Constrained
Battery capacity
only doubles in
last 15 years
3G/4G
GPS
CPU
Screen
WiFi
Camera
2
WiFi Energy Consumption
Data
AP
…
Phone
…
Data
Idle
Even in idle, WNIC
drains out battery
in 6-10 hrs!
Send
WiFi NIC
Power
(mW)
Recv
1000mW
Idle Listen
765mW
650mW
Time (ms)
3
Modes of WiFi NIC
• Constant Awake Mode (CAM)
– Send, Recv, Idle Listen
– High power
• Power Saving Mode (PSM)
– Cannot send/recv/idle listen
– Very little power
4
WiFi: Power Saving Mode
Beacon
Beacon
Beacon
Beacon
AP
100ms
100ms
100ms
Beacon
Phone
WiFi NIC
Power
(mW)
Time (ms)
5
WiFi: Power Saving Mode (cont’d)
Data
Server
PSM Wake-up Delay
PSM does not
come for free!
Beacon
AP
Phone
WiFi NIC
Power
(mW)
WNIC in PSM,
cannot recv
Time (ms)
WNIC switch
to CAM
6
PSM
• Energy - performance
trade off
• Two implementations of
PSM
– Static PSM
– Dynamic PSM
7
Static PSM
Server
Data
SYNACK
Wake-up
Delay
Wake-up
Delay
SYNACK
AP
Wake-up
Delay
ACK
Beacon
Req
SYN
Phone
Static PSM
WiFi NIC
Power
(mW)
Flow Time:
300ms
Energy:
3 μAh
Already
in PSM
Time (ms)
8
Dynamic PSM
Server
Data
SYN
ACK
ACK
AP
Beacon
SYN
Req
Phone
PSM Timeout
WiFi NIC
Power
(mW)
Time (ms)
Static PSM
Dynamic PSM
Flow Time:
300ms
Flow Time:
90ms
Energy:
3 μAh
Energy:
10 μAh
9
Motivation
Performance
Energy
Static PSM
Dynamic PSM
Can we make it
?
10
Understand Dynamic PSM
Server
AP
Phone
RTT
PSM
Timeout
Key: PSM Timeout > RTT
Phone
PSM Timeout
Nokia N900
200ms
HTC Nexus One
200ms
iPhone 4
95ms
11
Percy: Design
1.
AP
2.
AP
Split-TCP
Proxy
PSM Timeout
200ms/95ms
PSM Timeout
30ms
12
Percy: Short Flows
Server
Data
Data
SYN
SYN
ACK
Req
ACK
Req
AP+Proxy
Beacon
SYN
Phone
WiFi NIC
Power
(mW)
Static PSM
Dynamic PSM
Percy
Flow Time:
300ms
Flow Time:
90ms
Flow Time:
110ms
Energy:
3 μAh
Energy:
10 μAh
Energy:
4 μAh
Time (ms)
13
Percy: Long Flows
SYN
Data
Req
SYN
ACK
ACK
SYN
Beacon
Req
Periodical
Flush
WiFi NIC
Power
(mW)
Time (ms)
14
Evaluation
• Trace-driven experiment
– 10-phone 1-week trace
– 38,069 HTTP flows
• PSM configurations
– Percy
– Static PSM
– Dynamic PSM:
Nokia
N900
iPhone 4
HTC Nexus
One
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Result – Energy Consumption
67%
44%
Total energy consumption for different PSM schemes
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Result – Network Performance
Time (ms)
CDF of flow time difference compared to
Android PSM configuration
17
Conclusion
• Existing PSMs have inherent problems
• A simple system: Percy
– improve the energy savings
– maintain good performance
• Percy saves 44-67% energy while incur
minimal flow time elongation
18