Aggressively Duty-Cycled Platforms: Embedded, Mobile & Multi-Core Some observations from the field Rajesh Gupta UC San Diego mesl . ucsd . edu Nokia Meeting, August 2008 “ Future lies in system architectures built for aggressive duty-cycling”
Multiple radios without base-station modifications to improve energy/bit, idle power, throughput
Use Cellular radios for event notification to WiFi
Mitigate impact of VOIP traffic over WiFi infrastructure
Use network interface smarts to duty-cycle computers
Collaborating Radios can improve efficiency, reliability,…
50% energy reduction with CoolSpots
VOIP with Cell2Notify can reduce power 1.7-6.4x over WiFi and better than Cellular radios!
Switch : Wi-Fi -> BT Bluetooth Wi-Fi
GreenLight: Putting Machines To Sleep Transparently Somniloquy enables servers to enter and exit sleep while maintaining their network and application level presence. Peripheral Laptop Low power domain Network interface Secondary processor Network interface Management software Main processor, RAM, etc
SwitchR: Reducing System Power Consumption in a Multi-Client Multi-Radio Environment - Yuvraj Agarwal, Trevor Pering, Roy Want, Rajesh Gupta, IEEE Symp. On Wearable Computers, 9/8
"A Gateway Node with Duty-Cycled Radio and Processing Subsystems for Wireless Sensor Networks", Zhong Yi Jin, Curt Schurgers, R. Gupta, ACM Trans. Design Automation in Electronic Systems, June 2008.
"Improved Distributed Simulation of Sensor Networks based on Sensor Node Sleep Time", Z. Jin, R. Gupta , 4th IEEE/ACM Intl. Conference on Distributed Computing in Sensor Systems (DCOSS) , June 2008
"Improving the Data Delivery Latency in Sensor Networks with Controlled Mobility", R. Sugihara, R. Gupta , 4th IEEE/ACM Intl. Conference on Distributed Computing in Sensor Systems (DCOSS) , June 2008 (Best paper for Systems track)
"A different approach to sensor networking for SHM: Remote powering and interrogation with unmanned aerial vehicles", Todd, M., et al , 6th Intl. workshop on Structural Health Monitoring , 2007.
"Temperature-Aware Processor Frequency Assignment for MPSOCs Using Convex Optimization," S. Murali, D. Atienza, G. De Micheli, R. Gupta, IEEE/ACM/IFIP CODES+ISSS / ESWeek, September 2007
“ An Embedded Platform with Duty-Cycled Radio and Processing Subsystem for Wireless Sensor Networks”, Z. Jin, C. Schurgers and R. Gupta, Embedded Computer Systems: Architectures, Modeling and Simulation Conference (SAMOS), July 2007
"Wireless Wakeups Revisited: Energy Management for VoIP overWi-Fi Smartphones", Y. Agarwal, R. Chandra, A. Wolman, P. Bahl, K. Chin and R. Gupta, MobySys'07, Puerto Rico, June 2007
"CoolSpots: Reducing Power Consumption Of Wireless Mobile Devices Using Multiple Radio Interfaces", T. Pering, Y. Agarwal, R. Gupta and R. Want, Fourth International Conference on Mobile Systems, Application and Services (MobiSys), Uppsala, Sweden, June 18-22, 2006
CoolSpots Network Architecture Infrastructure Computers CoolSpot Access Point BT WiFi BT WiFi Mobile Device Backbone Network IP address on Backbone Subnet Low-power Bluetooth link (always maintained, when possible) 1 Mobile device monitors channel and implements switching policy 2 WiFi link is dynamically activated based on switching determination 3 Access point changes routing table on “switch” message from mobile device 4 Switching is transparent: applications always use the IP address of the local subnet. 5
Technical Challenge: Design of Switching Policies
Three main components contribute to the behavior of a multi-radio system
Position: Where you are
Need to address the difference in range between Bluetooth and WiFi
A non-intrusive way to tell which interface to use
When: Policies bluetooth-fixed (using sniff mode) wifi CAM (normalization baseline) wifi-fixed (using PSM) bandwidth-X cap-static-X cap-dynamic kbps > X kbps < X kbps < X time > Y time > Y kbps < Z Z = kbps Use WiFi Channel Use Bluetooth Channel
Use the geometric mean to combine benchmarks into an aggregate result
Moved devices around on a cart to vary channel characteristics
Test Machine (TM) Base Station (BS) RM Mobile Device (MD) SP Data Acquisition (DA) ETH BT WiFi mW Distance adjustment ETH = Wired Ethernet mW = Power Measurements BT = Bluetooth WiFi = WiFi Wireless RM = Route Management SP = Switching Policy Benchmark suite
blue-fixed does well in terms of energy but at the cost of increased latency
cap-dynamic does well in terms of both energy and increased latency
CoolSpots Results across various benchmarks w ifi-fixed consumes lowest energy for data transfer, any bluetooth policy for idle Overall, cap-dynamic does well taking into account energy and latency Video benchmarks really highlight problems with wifi-fixed and bandwidth-x
3. VoIP in Enterprise: Cell2Notify Internet IP Phone Soft Phone LAN Access Point SIP Proxy Smart Phone Wi - Fi interface GSM interface Base Station ATA GSM Network PSTN Enterprise Network Register GSM number Incoming VoIP call Disable Wi-Fi Match VoIP to GSM number Call GSM number Enable Wi-Fi Complete call setup over Wi-Fi ATA = Analog Telephony Adapter
Problem: Wi-Fi has to be ON to receive incoming calls.
Wi-Fi power consumption is high even when idle, reduces battery lifetime: Cingular 2125 : GSM (6.25days), Wi-Fi (9Hrs) !
Power Consumption of a Smartphone Cingular 2125
Used to estimate energy savings for the Smartphone
Using real usage patterns from 3 different enterprise users
Lifetime based on the integrated 1150mAH @ 3.7V Li-ion battery
1113.811 Wi-Fi (send/recv) 441.82 Wi-Fi (Connected) 1042.44 Wi-Fi (searching) 27.38 GSM Idle 15.688 All Radios Off (Flight mode) Power (mW) Scenario