e-mili: energy-minimizing idle listening in wireless networks xinyu zhang and kang g. shin dept. of...
TRANSCRIPT
E-MiLi: Energy-Minimizing Idle Listening in Wireless Networks
Xinyu Zhang and Kang G. ShinDept. of EECS Univ. Michigan
Presented by: Fenggang Wu2011/11/04
2/20
Author
•HIT(01)-> Toronto(05)->U Michigan(08)->(11)Princeton NEC Lab
Name: Xinyu Zhang
Gender: Male
Birthyear: 1984
Place of Birth: Baotou, Inner-Mongolia, China
Nationality: Chinese
4/20
Background
•Scenario:▫WiFi AP-client senario
•Idle listening (IL) in CSMA▫Why listening? (transmit, receive)▫Energy waste
•Problem▫How to reduce the energy consumption in
IL?
5/20
Existing Work•PSM
▫Reducing IL energy cost by reducing IL time
▫Yet IL still dominate clients’ energy consumption even with PSM enabled 80% busy network, 60% idle network
•Another dimension▫Reducing IL energy cost by reducing IL
power
6/20
The E-MiLi Approach
•E-MiLi: Energy-Minimizing idle Listening•Key Idea:
▫Reduce the IL energy cost by downclocking.
•Challenge:▫Nyquist’s Theorem: ▫How to put the radio in a subconscious
mode while it can still respond to incoming packets properly?
8/20
Solutions
•SRID (Sampling Rate Invariant Detection)▫How to perceive arriving packet in low
sampling rate?▫Key: separate detecting and decoding
•Odoc (Opportunistic Downclocking)▫When safe to downclock?▫Key: predict the possibility of coming
packet
9/20
SRID (1/3)•M-preamble
Duplicated Sequence
(Gold Sequence)
Check the self-correlation
Able to be detected arriving packet even when down
sampled
Embedded
Address
Switching Time
10/20
SRID (2/3)Self-correlation of
samples
Energy level of samples
|𝑅 (𝑘 )|≈ {𝐸 (𝑘) , 𝑖𝑓 𝑐𝑜𝑟𝑟𝑒𝑙𝑎𝑡𝑒𝑑0 ,𝑖𝑓 𝑛𝑜𝑡 𝑐𝑜𝑟𝑟𝑒𝑙𝑎𝑡𝑒𝑑
12/20
Address Allocation• as the embedded address
▫Multiple user?▫What if is large?
• Minimum-cost address sharing▫Multiple clients share a limited number of addresses▫Clients tx/rx more frequently share the addr. with
less other clients• Broadcast address
▫ , clients maintain a self-correlator with offset and ▫For carrier sensing purpose, double preamble is
needed.
13/20
Odoc (Opportunistic Downclocking)
•Switching time (~)▫Compared to SIFS()
•Arrival prediction (Outage prediction)▫Key intuition: Burstininess of WiFi▫Deterministic operation
CTS, DATA, ACK are all deterministic operations after RTS
▫Non-deterministic operation recorded if the arriving interval if shorter
than
14/20
Evaluation (1/5)
•Two Questions:▫Packet detecting accuracy▫IL energy saving
•Setups▫E-MiLi implementation on GNURadio▫Network level simulator on real WiFi trace
19/20
Related Work
•Energy-efficient protocols for WiFi▫PSM and its variants (can be integrated with E-MiLi)▫Wakeup on demand approach (second radio needed)
•Packet detection▫Self-correlate (problem when down-sampled)▫Cross-correlate (down-sampled prob and offset-
sensitive)•Dynamic voltage-frequency scaling
▫In multi-processor design▫SampleWidth (tx and rx agree on same clock rate)
20/20
Conclusion
•Goal: reducing the IL energy by downclocking▫Sampling-Rate Invariant packet Detector▫Opportunistic downclocking scheme
•Future works▫ZigBee extension▫Changing working voltage
21/20
Comments•Pros:
▫Novel idea▫Practical use
•Cons:▫Overhead: doesn’t consider the delay
caused by the additional preamble.•Take home message:
▫From simple questions▫Learn from real practice▫Paper writer skill