Energy Management in Smart Devices.

Engr.Ebeh,C.ObedControl Systems Engineer,Process Computers,Engineering and Technical Service Dept.WRPC

IntroductionSmartphones saw their advent some 16 years ago. Growth of smartphones only started increasing exponentially in recent years. According to Strategy Analytics, total number of smartphones in the world has reached to one billion. It is expected to hit two billion in three years.This shows how much part smartphones are playing, and will play, in our dailylives. Latest smartphones are handy, powerful and are equipped with various functionalities.Smart devices derive the energy required for their operation from batteries. In the case of many consumer electronics devices, especially mobile phones, battery capacity is severely restricted due to constraints on size and weight of the device. This implies that energy efficiency of these devices is very important to their usability. Hence, optimal management of power consumption of these devices is critical.

Power in SmartphonesWith these constraint that come along in the form of power consumption. It is normal to recharge (or replace) smartphone batteries at least once or more times a day. Similarly, smartphone battery appears to drain over night, even when smartphone is partially or fully idle.Smartphone companies are taking this challenge of energy management issue seriously, as we can notice bigger batteries with newer models of Smartphone's with different operational modes included to save energy thus increasing the battery usage hours.

Device Under Test (DUT)The 2 devices considered are SHV-E120S, also known as Samsung Galaxy S2 HD LTE and a Nokia N95 with specifications as shown below.

Operating System SpecficationsAndroid SystemAndroid system performs most of functions of OS, and consumes more power than other components of OS. Android system includes, the following:(a) Service manager :Android runtime uses the ServiceManager to add services, and to end them (b) Sensor managerModern day smartphones have many interesting sensors available to enhance user experience, . Some of the sensors available in our device are:AccelerometerMeasures the acceleration force in m=s2 that is applied to a device on all three physical axes (x, y, and z), including the force of gravity.Gyroscope.Measures a device's rate of rotation in rad=s around each of the three physical axes (x, y, and z).Magnetic field sensorsOrientation sensorsMeasures degrees of rotation that a device makes around all three physical axes (x, y, z).

OS KernelKernel in OS links facilitates the communication between hardware and soft-ware layers. Kernel includes drivers, scripts, Android core appsThey are basically applications which are installed by default with AndroidOS. Email service i.e. Gmail, keyboard, Internet Voice calling, clock, calen-dar and alarm Google Store,Maps, Navigation to name a few.etc. are some of the core apps available in Gingerbread 2.3.Microbes :Microbes is live wallpaper application available in Gingerbread .Mediaserver: Mediaserver in Android accesses gallery, audio and video les available on device and plays them. Goolge sevices frameworkAnti-virus: Anti-virus program may run on smartphone at all times to ensure security.Misc. servicesOther important Android, Google or stand-alone services running on devicesare email synchronization program, message, store, dictionary Facebook, Twitter, Skype and mobile messaging service etc.

Below is a table of obtained results of energy consumption.

Technology Action Power Energy

Technology Action Power Energy

Modes of OperationPower performance of DUT were considered for the following modes under various scenarios. Data NetworksLTE and Wi-Fi data networks are both used during experimentation. We analyze both networks during their normal and sleep mode.Normal OperationDuring normal operation, users use their smartphones in a typical way. Different users utilize their smartphones differently. Though based on average current consumption, some optimized criteria can be set Average of these samples is presented in this work.SleepSleep mode/ passive mode. Flight ModeGenerally Fliight mode in phones disables data connection i.e. no data enters or leaves the phone. Only native applications can be used in this mode.Power Save ModeLatest smartphones include this mode to enhance the battery life by taking steps needed to decrease the current consumption.

Power consumption Analysis for Different ModesFunctions Operating in Different Modes

Power consumption Analysis for Different Modes

Six Top energy consumers

CONCLUSIONIn this work we gave a detailed survey on the energy consumption of smartphones. This focus of this work is bring to light where energy is used and help to design energy aware protocols to reduce the overall energyconsumption. In this work we have shown that the most energy hungry parts of a mobile phone are the wireless technologies and not the display or the CPU as this is the case for laptops.One of the findings is that voice calls should be done by using the 2G network, while data connections should be realized by 3G technology in order to achieve the lowest possible energy consumption. For the short range communication Bluetoothshould be used in case only a few data needs to be exchanged. If more data needs to be transmitted, WiFi should be used. It does not cost much to have BT always on. This creates opportunities for new services which combine the local communication with cellular communications.This study also showed that some modes that are meant for saving power i.e. power-save mode, are not that efficient in saving power. In sleep, putting our smartphones in flight mode can help us in saving most of its energy, and thus extend its battery consumption. LTE, although a new network, performs better in sleep mode. In normal operation, however, it is still expensive for power.

Energy Saving Tips for Smart Devices.

1. Display: Back to black2. Dealing with different types of display (LCD and OLED)3. Display stand-by4. Connectivity.5. Applications: Reduce multi-tasking6. Updates7. Battery Saver Mode8. Phone charging9. Alerts: Bad Vibrations10. Try a third-party power app 11.Keep things cool12. Human logic

Finally, if even all of these tips can't get your phone through the day, buy a second battery as a failsafe.

References:

1.ARROLL, A. AND HEISER, G. An analysis of power consumption in a smart-phone. Proceedings of the 2010 USENIX conference on USENIX annual technical conference (2010), pp. 21-21.2. SAGAHYROON, A. Power consumption in handheld computers. In Proceedings of the International Symposium on Circuits and Systems (Dec. 2006), pp. 17211724.3. SNOWDON, D. C., LE SUEUR, E., PETTERS, S. M., AND HEISER, G. Koala:A platform for OS-level power management. In Proceedings of the 4th EuroSys Conference (Nuremberg, Germany, Apr. 2009).4. BIRCHER, W. L., AND JOHN, L. K. Analysis of dynamic power managementon multi-core processors. In Proceedings of the 22nd International Conference on Supercomputing (Island of Kos, Greece, June 2008), pp. 327338.5. Monsoon Solutions' power monitor, http://msoon.github.com/powermonitor/PowerTool/doc/Power%20Monitor%20Manual.pdf

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