Duty-Cycled Platforms for Embedded, Mobile & Multi-Core Systems

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”

New Age Computing & Communications Devices ,[object Object],[object Object],[object Object],Power Supply Battery DC-DC Converter Communication Radio Modem RF Transceiver Processing Programmable  Ps & DSPs (apps, protocols etc.) Memory ASICs Peripherals Disk Display

Much Wider Dynamic Range of Power/Energy Consumption ,[object Object],Stargate – Mobile Research Platform (Device is in “idle” state) packet Transmit Processing Transmit Amplifier d packet Receive Processing 50 nJ/bit 100 pJ/bit/m

Multiple Radios Are Common ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Achieving High Energy Efficiency: Lessons Learnt ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Mult-Core DPM GreenLight Coherent Coprocessing

Algorithmically, there are basically two ways to save power ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Competitive and Adversarial Approaches using Probabilistic Model Checking Machine Learning Techniques Convex Optimization for Thermally Efficient Multi-Cores

Architecturally: ‘Collaborate’ ,[object Object],[object Object]

Collaborating Radios Can ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Our Work ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Collaborating Radios can improve efficiency, reliability,… ,[object Object],[object Object],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

Takeaways ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Recent Publications ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Credits: Projects and Teams ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Typical power distribution Power breakdown for a fully connected mobile device in idle mode, with LCD screen and backlight turned off. ,[object Object],[object Object]

Common Radio Standards Higher throughput radios have a lower energy/bit value … have a higher idle power consumption And they have different ranges.

Consider: BT and WiFi ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],WiFi Active WiFi Active WiFi PSM WiFi Active BT Active WiFi Active BT Sniff Bluetooth Wi-Fi 264 mW 990 mW 81 mW 5.8 mW

1. BT as a paging radio ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Simple paging (with range compensation) ,[object Object],[object Object],Power Savings for 802.11 card only vs PSP : 41% (SS1) to 95% (SS2) Throughput - Same as Awake Mode (CAM) , maximum throughput Latency - Setup latency, amortized across session

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 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

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

Experimental Setup ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],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

Switching Example: MPEG4 streaming ,[object Object],[object Object],Switching is transparent to unmodified applications! Switch : Wi-Fi -> BT Bluetooth Wi-Fi

Results (Intermediate Location) ,[object Object],[object Object]

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 ,[object Object],[object Object]

Power Consumption of a Smartphone Cingular 2125 ,[object Object],[object Object],[object Object],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

Battery Lifetime : Smartphone ,[object Object],[object Object],[object Object],70% 230% 540%

Alternative: VoIP over Cellular Data Network? ,[object Object],[object Object],[object Object],[object Object]

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Duty-Cycled Platforms for Embedded, Mobile & Multi-Core Systems

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Duty-Cycled Platforms for Embedded, Mobile & Multi-Core Systems