Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Standby power wikipedia , lookup
Surge protector wikipedia , lookup
Radio transmitter design wikipedia , lookup
Audio power wikipedia , lookup
Power electronics wikipedia , lookup
Rectiverter wikipedia , lookup
Mobile operating system wikipedia , lookup
Wireless power transfer wikipedia , lookup
Energy Management: Part I Uichin Lee KAIST KSE Mobile Processing Power – Changing the Mobile Device From http://www.ieee-infocom.org/2010/docs/Infocom2010_keynote.pdf Chipset Business Evolving to System Business Integration is key to driving advanced functionality to mass market From http://www.ieee-infocom.org/2010/docs/Infocom2010_keynote.pdf Creating New Mobile, Computing and CE Device Categories From http://www.ieee-infocom.org/2010/docs/Infocom2010_keynote.pdf But Major Gaps Exist Battery Technology is Falling Behind How do we balance battery life with performance and cost? Energy Management on Handheld Devices Marc A. Viredaz, Lawrence S. Brakmo, William R. Hamburgen HP Labs ACM Queue Oct. 2003 Itsy Platform • Itsy goals (YR 2000): – Small, powerful, flexible h/w platform – Flexible, extensible, advanced s/w environment • Base system – StrongArm SA-1100 microprocessor – 32MB DRAM & Flash Drive – LCD display and touch screen • Passive matrix gray scale – – – – – Li-ion battery (charges from USB) 2-axis accelerometer Microphone Jacks (headset, docking) Daughtercard connecter • Software – Linux 2.0.30 w/ modified memory/flash-based file systems – Power management capability Ohm’s law, Power, Energy • Ohm’s law: V=IR (=current*resistance) I=V/R? 9v 2.2Ω Voltage drop = 16v 2kΩ I=V/R? • Power: watt (W) = 1 joule/second (J/s) – Power (W) = VI= I2R • Energy: (Ws, or Joule) – Energy (Ws) = power (w) * time (s) Power Measurement • Voltages are directly measured. • Currents are calculated from the corresponding sense-resistor voltage drop. • Elementary power domains are delimited by dashed lines. Power Consumption Energy Saving Techniques • Simple approach: if a unit is not used, turn off or put into sleep mode • But requires well structured h/w and s/w design • Inter-connected building blocks must independently function and be independently powered on/off • Operating systems (or applications) utilize measured power values to balance performance and battery life • Major power draws: processor, memory, display, audio system, wireless networking Processor StrongARM SA-1100 Processor • Frequency or/and voltage scaling: Power ∝ f·v2 – f: operating frequency, v: voltage Voltage Scaling in Strong Arm SA-1100 59Mhz at 0.79v 251Mhz at 1.65v J.Pouwelse, K.Langendoen, and H. Sips, “Dynamic Voltage Scaling on a Low-Power Microprocessor”, MOBICOM2001 Processor: How to Scale? • How to scale voltage/frequency? power Low frequency ? High frequency ... time Watts Watts Eactive Eactive Eidle t t Critical Power Slope: Understanding the Runtime Effects of Frequency Scaling, ICS2002 Processor: Critical Power Slope m mcritical mcritical P f min Power f : energy efficient to run at lower freq Pidle min mcritical Pf min m mcritical : energy efficient to run at higher freq Pidle f min Frequency fmin: min operating frequency Pfmin: power consumption at freq fmin Pidle: idle power consumption Critical Power Slope: Understanding the Runtime Effects of Frequency Scaling, ICS2002 Memory • DRAM typically has four states: – Activate/pre-charge: read/write happen (most energy consuming) – Fast lower-power: short-term sleeping (w/ fast wake-up time: ~10ns, and consumes only half of the active power) – Self-refresh: only refreshing is happening (much less power consumption, requires several 100 cycles) – Deep power-down: refreshing stopped (lost data) Figure from: http://research.microsoft.com/pubs/102932/flicker-tr-2009.pdf Display • LCD itself consumes minimal energy, yet display front- and back-light dominates.. – Possible to dim lights of “light” pixels (for energy saving) • Organic light-emitting diode (OLED) – Better quality than LCD (fast response), but it’s emissive and can’t make use of ambient light (energy consuming..) Wireless Networking • Technologies – WiFi, Bluetooth – 2G/3G/4G cellular communications • Power consumption: BT < WiFi < 2/3/4G • Caveats: – bit/joule must be considered – bit/joule varies with data rate Cool-Tether: Energy Efficient On-the-fly WiFi Hot-spots using Mobile Phones, CoNext 2009 Decomposing power measurements for mobile devices Andrew Rice and Simon Hay Percom 2010 We want to know how much energy a particular action will consume Example: joining the wireless network consumes 6 Joules HTC G1 (or Magic), Android 1.1, 194 trials We measure energy consumption by intercepting the power supply Both voltages are sampled at 250 kHz V1 0.02Ω V2 Power ∝ V1 x V2 Trace of the G1 boot process HTC G1 (or Magic), Android 1.1 Joining a wireless network: DHCP • Dynamic Host Configuration Protocol (DHCP) – Provides automatic configuration of the host connected to network – Provides hosts with initial configuration information upon bootup: • IP address with subnet mask, default gateway, IP address of the DNS server server A server B client (not selected) DHCP discover (selected) DHCP discover determine configuration determine configuration DHCP offer DHCP offer select configuration DHCP request DHCP request DHCP ack Initialization completes using the allocated configuration graceful shutdown DHCP release discard lease Joining a wireless network: ARP • Address Resolution Protocol (ARP) and Reverse ARP (RARP): translation between IP and MAC addresses TCP IP address (32 bit) ARP RARP Ethernet MAC address (48 bit) UDP ICMP IP IGMP ARP Network Access RARP Media Transport Layer Network Layer Link Layer Joining a wireless network: ARP Argon 128.143.137.144 00:a0:24:71:e4:44 Router137 128.143.137.1 00:e0:f9:23:a8:20 ARP Request: What is the MAC address of 128.143.71.1? Argon 128.143.137.144 00:a0:24:71:e4:44 Router137 128.143.137.1 00:e0:f9:23:a8:20 ARP Reply: The MAC address of 128.143.71.1 is 00:e0:f9:23:a8:20 Access point beacons correlate with spikes in the power trace HTC G1 (or Magic), Android 1.1 Timestamped events from the phone must be aligned with the appropriate sample points The synchronization information is embedded in power trace Bright screen Dimmed screen HTC G1 (or Magic), Android 1.1 Hypothesis matching pulses g(t) HTC G1 (or Magic), Android 1.1 Find alignment from autocorrelation with a hypothesized signal autocorrelation (f*f)(t) – cross-correlation (f*g)(t) f(t) Cross-correlation: a measure of similarity of two waveforms as a function of a time-lag applied to one of them. Autocorrelation: cross-correlation of a signal with itself; there will always be a peak at a lag of zero, unless the signal is a trivial zero signal. HTC G1 (or Magic), Android 1.1 HTC G1 (or Magic), Android 1.1 Remove the DHCP overhead by using static addressing HTC G1 (or Magic), Android 1.1 Static addressing reduces the connection cost to 1.5 Joules Static Addressing Dynamic Addressing HTC G1 (or Magic), Android 1.1, Static = 143 trials, Dynamic = 194 trials We could remove the ARP probes from our client implementation • “ARP probe”: ARP probe is broadcast to see if the address is already in use • RFC2131 “...the client SHOULD probe the newly received address, e.g., with ARP.” • RFC2119 – SHOULD “...there may exist valid reasons in particular circumstances to ignore a particular item” Enter the Android 2.1 doesn't ARP probe in our tests Dynamic addressing now costs 1.5J Dynamic Addressing N1 Dynamic Addressing G1 Google N1, Android 2.1, 100 trials / HTC G1 (or Magic), Android 1.1, 194 trials Joules consumed The G1 histogram peaks are due to discontinuities in connection time Time to connect (seconds) HTC G1 (or Magic), Android 1.1, Dynamic HTC G1 (or Magic), Android 1.1, Dynamic DHCP Finish DHCP Finish DHCP Start DHCP Start Power (Watts) Power (Watts) Caused by power control in radio? This power control is evident when sending data too Send 7K of data over TCP HTC G1 (or Magic), Android 1.1 Send 8K of data over TCP This effect has a big impact on energy cost HTC G1 (or Magic), Android 1.1, 1120 Trials (HTC Hero, Android 1.5 is the same) N1 energy performance Best case: same Google N1, Android 2.1, 900 Trials Worst case: much better