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How to minimize the power consumption of your app

Rick Schwartz, Senior Product Manager Qualcomm Technologies, Inc.

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Mobile trends

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Mobile trends resulting in increased power consumption

High end processor speeds increased from 1.5 GHz to 2.3 GHz over a 16 month period

The number of cores in mobile devices have increased 3 of the past 4 years

Mobile displays are getting larger and higher in resolution − HD (1280x720) > FHD (1920x1080) > QHD (2560x1440)

Some mobile devices now designed to work 24/7 − Tracking location − Listening for voice commands − Integrated step counters track movement

A single mobile processor can replace several discrete chips

Source: Qualcomm Technologies, Inc. data

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Processor speed and number of cores has changed dramatically Processor specs for flagship Android devices by year

Number of Cores

3 8

7

6

5

4

3

2

1

2.5

2

1.5

1

0.5

0

Frequency (GHz)

Cores

Frequency 80% increase in processor speeds

2012 2013 2014

Source: Qualcomm Technologies, Inc. data 2012 – Samsung Galaxy S III - Snapdragon S4 SoC featuring a dual-core 1.5 GHz; 2013 – Samsung Galaxy S4 - Qualcomm Snapdragon 600 APQ8064AB quad-core 1.9 GHz; 2014 – Samsung Galaxy S5 - Qualcomm Snapdragon 801 (8974) 2.5 GHz quad-core

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Battery capacity hasn’t kept up Processor specs for flagship Android devices by year

Number of Cores

3 8

7

6

5

4

3

2

1

2.5

2

1.5

1

0.5

0 2012 2013 2014

Frequency (GHz)

Cores

Frequency 80% increase in processor speeds

33% increase in battery power

Battery

Source: Qualcomm Technologies, Inc. data 2012 – Samsung Galaxy S III - Snapdragon S4 SoC featuring a dual-core 1.5 GHz; 2013 – Samsung Galaxy S4 - Qualcomm Snapdragon 600 APQ8064AB quad-core 1.9 GHz; 2014 – Samsung Galaxy S5 - Qualcomm Snapdragon 801 (8974) 2.5 GHz quad-core

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Mobile displays are getting larger Larger screens with higher pixel densities often require more power

47 46 42 29

48 116

156 193 2

9

51

185

1

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2009 2010 2011 2012

5.0 – 5.9 in

4.0 – 4.9 in

3.0 – 3.9 in

Less than 2.9 in

Number of Smartphone models with given display size1

Smart phones, Worldwide, units (%) by screen size, Q1 2014;

This year 34% of all smartphones have screens that are larger than 5 inches2

1 Source: Yankee Group, 2013 2 Source: Canalsys

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Location services designed to track movement in the background Taking a GPS fix consumes power

Source: Google Location History

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Listening apps are becoming more popular Continuous listening for a phrase that wakes-up the device consumes power

Good morning.

Say help me for a list of commands

Speak now…

Screen images simulated

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Qualcomm® Snapdragon™ processors designed to do many things

Qualcomm® Izat™ GNSS with support for three

GPS constellations

Support for up to 2560x2048 display Miracast 1080p HD support

21MP with dual ISP

Ultra HD Capture and Playback DTS-HD and Dolby Digital Plus audio

Expanded Gestures

Integrated Qualcomm® Gobi™ 4G LTE World Mode

1, 802.11ac

1, USB 3.0 and BT 4.0 offers

broad array of high speed connectivity

Qualcomm® Hexagon™ QDSP6 for ultra low power applications and custom programmability

Qualcomm® Adreno™ 330 for advanced graphics

Krait™ 400 CPU features 28HPm process technology superior 2GHz+ performance

Low-power Snapdragon Sensor Core increases sensor accuracy and

efficiency

1 Available only in select processors

Qualcomm IZat is a product of Qualcomm Atheros, Inc.

Qualcomm Snapdragon, Krait, Qualcomm Adreno, Qualcomm Hexagon, Qualcomm Gobi and Snapdragon Sensor Core are products of Qualcomm Technologies, Inc.

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Processors are getting more efficient, but power demands are increasing Over a two-year period power consumption doubled or tripled in some areas

Source: MICROWAVE JOURNAL - NOVEMBER 2012 – Technical Feature by Matthew Hubbard

Function 2009 2011 % Change

Display 300 mW 900 mW 300%

Peripherals 400 mW 1500 mW 275%

Processor 800 mW 1620 mW 200%

Audio 300 mW 400 mW 30%

RF 1200 mW 1330 mW 11%

Total 3000 mW 5750 mW 92%

Power consumption changes for different functions over two years

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The problem

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Battery life is very important to consumers

Consumers rank phone battery life as the most important factor in their smartphone buying decision. Q: For your next smartphone/mobile phone purchase, which of the following features would drive your decision to select one phone over others?

Importance of Smartphone Features Among Smartphone Buyers1

38%

42%

44%

46%

46%

48%

52%

72%

Display / screen resolution

Memory / storage

4G or LTE connectivity

Screen / display type / quality

Screen / display size

Touchscreen

WiFi speed / quality

Battery life

1 Source: Qualcomm Brand Tracker, Market Research Group. United States, January 2014

Top 10 Smartphone Purchase Drivers2

Android vs. iOS Windows vs.

Battery Life

Ease of Use

Operating System Android, Symbian,

webOS, Windows Mobile

Touch Screen

Screen size

56% 49% 53%

33% 39% 38%

37% 32% 40%

34% 34% 37%

37% 22% 34%

2 Source: IDC's ConsumerScape 360 by IDC Michael DeHart

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“High-risk” apps can waste power and mobile data List of “high risk” apps that drain the battery faster than normal typically highlighted

Over 70% of these apps are chart toppers in Google Play

Some of these apps can cause the battery to drain 2 to 5 times faster than normal

Some of these apps can cause unexpected data usage (up to 2.2GB a month)

Source: Descriptions taken from Verizon’s High-risk App site. April 2014

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Heavy battery usage is a top reason consumers uninstall apps

76%

59%

71%

55% 53%

Freezes Slow responsiveness Crashes Heavy battery usage Too many ads

What causes users to delete and app? What causes users to delete an app?

Source: Fierce Developer Survey – Exploring the reasons users complain about apps (Nov. 2012)

#1 #2

#3 #4 #5

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Does your app consume too much power?

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Measuring power consumption using hardware Monsoon Power Monitor

Displays overall current, voltage and power usage

Can display averages over a specific time period

Off-target - Attaches directly to the battery in a mobile device

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Measuring power consumption using software Option 1: PowerTutor

Displays power usage for CPU, LCD, Wi-Fi, 3G, GPS and Audio Estimates power usage based on system state model

Available on Google Play

Runs on all Android devices

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Measuring power consumption of individual apps Using Trepn™ Profiler - Starter Edition to measure power consumption

Restart your device and make sure nothing is running in the background

Source: Trepn Profiler screenshots | Trepn is a product of Qualcomm Technologies, Inc.

“Profile App” or “Profile System”

Launch Trepn, go to Settings, and select the Battery Power data point

Check “Acquire Wakelock while Profiling” keep your processor awake

1 2 3 4

3.3x more power than idle

5x more power used than idle 53% more than another game

Screen off after 2 min

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Measuring per-rail power consumption Using Trepn Profiler to view per-rail delta power measurements

This software is preinstalled on Snapdragon MDP hardware

The Snapdragon 805 MDP/T has rails for Battery power, CPU, Camera, Digital Core, Graphics, Internal Memory, LCD Backlight, SD Card and WLAN/BT

Power Delta Before Photo Taken Power Delta After Photo Taken

Source: Trepn Profiler Premier Edition screenshots

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Identifying the cause of power spikes in your code Inserting markers in your code can help identify the cause of power spikes

Source: Trepn Profiler screenshots

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Common causes of excessive power consumption

1. Preventing the processor

(or other hardware subsystems) from

going to sleep

3. Inefficient use of the cellular radio

and Wi-Fi network

2. Keeping the display lit too long

4. Taking too many GPS location fixes

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Do your apps have any of these problems?

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Does your app prevent the processor from going to sleep? Using Wakelock Detector (WLD) to identify processor sleep problems (Android 4.3 and earlier)

To test, unplug your device and run it for at least 2-3 hours

A large number of short wakelocks or wakeup triggers can have a negative impact on battery usage because a phone takes time to wake and go back asleep

CPU Wakelocks Wakeup Triggers

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Sometimes there are good reasons to keep the processor awake. How can you tell? Trepn plug-in shows which wake locks are needed by correlating them to other system events

Source: Trepn plug-in screenshot

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Why keeping the screen awake is a problem The display is the single biggest consumer of system power

Full wakelocks – Keep your screen from turning off

Using wakelocks for extended periods will significantly increase battery consumption

Full wakelocks are less of a problem than partial wakelocks because they are much more obvious

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Many apps do not use the network efficiently Multiple apps acting independently can create network signaling congestion

Apps can pull notifications, updates, and message users – even when the phone not actively used

Many news and social networking apps wake up your device at least 4x an hour

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Connected (Idle) 8-15 seconds

Current (m

A)

Connected (Active)

Time (seconds)

<10mA

250-300 mA

~150 mA

Why this is a problem

A dormant cellular radio consumes less than 10 mA

When data is sent or received, the radio comes up and goes into an active state, consuming 250-300mA

When not sending data, the radio drops down to idle, but still consumes about 150mA

After a timeout of 8 to 15 seconds, the radio finally goes back to a dormant state

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How to tell if your app is using the cellular radio efficiently Trepn plug-in shows cellular radio and Wi-Fi network state, amount of data transmitted and the name of apps sending data

See mobile network state and mobile data usage by app

Source: Trepn plug-in

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Does your app use GPS efficiently?

Many apps take GPS fixes when they are not needed

Utilities like AT&T’s ARO and Trepn plug-in show GPS fixes

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One way to tell if your app is CPU bound Trepn Profiler’s real-time overlays show CPU and GPU utilization

Source: Trepn

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How to address excessive power consumption

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How to avoid preventing your device from going to sleep Expert advice how to use wakelocks more efficiently

1. Do not acquire PowerManager.Wakelocks unless you really need them − Device battery life will be significantly affected by the use of this API

2. Use the minimum levels needed

3. Be sure to release wakelocks as soon as possible

4. To keep the screen lit when your app is in the foreground, use FLAG_KEEP_SCREEN_ON instead

Source: http://developer.android.com/reference/android/os/PowerManager.html#PARTIAL_WAKE_LOCK

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How to efficiently use your cellular radio and Wi-Fi network

1. Connect less often – After you transmit data, the radio stays on for an additional 10 to 12 sec

2. Push, don’t poll – Specify how often items are delivered

3. Use analytics wisely − Capture data locally and group transmissions to your server. Extend the time between transmissions

4. Offer ad-free versions of apps – Apps without ads connect to the network much less often

5. Don’t continuously scan − Create timeouts appropriately when scanning for Wi-Fi networks or GPS signals

6. Don’t continuously stream – Download streams in chunks

7. Offload to Wi-Fi – It uses significantly less battery than 3G or 4G

Source: AT&T “Tips to Increase Battery Life Handout”

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Bundling traffic can reduce overhead-to-data ratio

Ta Tb Tc

The amount of overhead to eac data burst is high

Bundling data results in shorter connection time and less overhead

Td

Td

Td < Ta+ Tb + Tc

Bundling or gating reduces the number of times the device connects to the network, which reduces signaling and power consumption

Data from different apps

Overhead (Radio on duration)

Overhead transmission continues (based on dormancy timer) before terminal goes back to idle

Source: The Smartphone Challenge: Signaling Congestion and Power Consumption - Gerardo Giaretta – Qualcomm Technologies Inc.

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The benefit of using your radio more efficiently Bundling data results in significant power savings

~9000mA

~5000mA Nearly half the power!

300

150

10

2 minutes 1 minute 3 minutes

2 minutes 1 minute 3 minutes

300

150

10

Power (m

A)

Power (m

A)

Source: Qualcomm Technologies, Inc. data

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Using WifiLocks more efficiently Here’s what Google says about the use of WifiLocks

1. The Wi-Fi radio will only turn off if no WifiLocks are held by any application

2. Before using a WifiLock, consider if your app requires Wi-Fi access, or could function of the mobile network

3. Large file downloads should hold a WifiLock to ensure the download will complete

Source: http://developer.android.com/reference/android/net/wifi/WifiManager.WifiLock.html

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How to save power when using the GPS

1. Make sure you don’t take a GPS fix when it’s not needed – AT&T’s ARO and Trepn plug-in show when GPS fixes occur

2. Use coarse GPS fixes when possible because they require less power

3. Make the user aware when location tracking is active

4. Make it easy for users to disable location tracking without crippling their device

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Recap of power saving tips

Use wakelocks only when necessary, use the minimum levels possible and release them as soon as possible. Use KEEP_DISPLAY_ON instead

Close TCP sockets when done. Otherwise, you unnecessarily bring up the network just to tear down. This simple fix can reduce network power up to 20%

Group network activity when possible; Be flexible in your ping times

Review Best Practices for detailed solutions to power and performance-related problems

Turn off functions like GPS, camera, accelerometer and other sensors when they are no longer required

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Summary

Long battery life is very important to consumers

There is no excuse for bad power management – Free software is available that makes it easy to locate and fix problems with excessive power consumption

Better battery life can give your app an advantage over the competition, which could result in more positive reviews

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