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Everyone enjoys the smartphone revolution - users, developers, network operators, device vendors and network equipment vendors such as Ericsson. However, there are challenges since the network systems have not been optimised for smartphones from start. Until recently, the key optimisation objectives for mobile broadband networks have been peakrate and throughput, which are still important properties. The advent of mass-usage of smartphones, and the related traffic, has shown that also other properties of the 3G radio and networks are important. In particular, the high frequency of data activities, sometimes with moderate volumes of data transferred, has lead to both a high battery drain, and increased the signaling load in the system, due to the transitions between the standardised states of the 3G radio.
Citation preview
understandingsmartphone traffic
impact on battery and networks
Per willars, Ericsson
Public | © Ericsson AB 2010 | 2010-10-28 | Page 2
outline
› Challenges with smartphone traffic
› Understanding the 3G radio state machine
› Shaping application traffic
› Conclusion
Public | © Ericsson AB 2010 | 2010-10-28 | Page 3
outline
› Challenges with smartphone traffic
› Managing the radio connection
› Shaping application traffic
› Conclusion
Public | © Ericsson AB 2010 | 2010-10-28 | Page 4
battery
Battery lifetime is a challenge with smartphones
› Typically dominating:
– display, when user is active
– 3G radio modem, when inactive
– (CPU)
› Trend:
– slow increase in battery capacity
– faster increase in components
peak power
› Low duty cycle key for battery lifetime
Exam
ple
, P
ow
ert
uto
r ap
p
Public | © Ericsson AB 2010 | 2010-10-28 | Page 5
3G Traffic load Comparisontraffic per active device
Data traffic
Sig
nalin
g t
raff
ic
Feature
phones
Smart
Phones
PCs
Data: IP packets to/from apps, services, Internet
Signaling: Mobile-specific messages for managing mobility and resources for the Data traffic
Significant signaling
x
Many smartphones =
Impact on some networks
Signaling load increasingly important with smartphones
Public | © Ericsson AB 2010 | 2010-10-28 | Page 6
smartphone challengesoverview
Application server
Internet
MobileNetwork
Trade-off between:- Battery efficiency - Radio resources- Signaling & network resources- User experience (latencies)
Device behavior
New usage patterns
Application behavior
Networkbehavior
Battery Radio resources
Signaling &network resources
Userexperience
Chattytraffic
Application behavior
Public | © Ericsson AB 2010 | 2010-10-28 | Page 7
smartphone challengesfocus areas
Application server
Internet
MobileNetwork
Trade-off between:- Battery efficiency - Radio resources- Signaling & network resources- User experience (latencies)
Device behavior
New usage patterns
Application behavior
Networkbehavior
Battery Radio resources
Signaling &network resources
Userexperience
Chattytraffic
Application behavior
Shaping application traffic
Managing the radio connection
Public | © Ericsson AB 2010 | 2010-10-28 | Page 8
outline
› Challenges with smartphone traffic
› Managing the radio connection
› Shaping application traffic
› Conclusion
Public | © Ericsson AB 2010 | 2010-10-28 | Page 9
Data rate / lower latency / resources
Po
we
r co
nsu
mp
tio
n (
rela
tive
)
1
0.5
0.01-
0.02
HSPA
FACH
“Standby”Idle
3G Radio statesbalancing data transfer, battery and resources
~ 2s inactivity
~ 10-30 s inactivity
~ 10-30 min inactivity
Activity
Activity
~ 256 byte UL~ 512 byte DL
with IP headers
Activity
“High”
“Low”
URAIdle
IDLE CONNECTED
› Signaling needed for state transitions, esp. to/from Idle
› ”Standby” state (URA) deployed in more and more networks
Typical trigger thresholds
Public | © Ericsson AB 2010 | 2010-10-28 | Page 10
Po
we
r
HSPA
FACH
“Standby”Idle
device-triggered fast dormancyToday - aggressive disconnect to save battery
“High”
“Low”
URAIdle
IDLE CONNECTED
› Device trigger: data + display inactivity
› Problems: latency, signaling, shortcuts “Standby” state
~ 3s inactivity
Data rate
Public | © Ericsson AB 2010 | 2010-10-28 | Page 11
HSPA
FACH
“Standby”Idle
device-triggered fast dormancyfuture solution – standardized behaviour
“High”
“Low”
URAIdle
IDLE CONNECTED
› Device-triggered battery efficiency in ”Standby” state
› Short-term recommendation:
– shorter timers in networks, selective Fast Dormancy in device
Po
we
r
Data rate
Public | © Ericsson AB 2010 | 2010-10-28 | Page 12
outline
› Challenges with smartphone traffic
› Managing the radio connection
› Shaping application traffic
› Conclusion
Public | © Ericsson AB 2010 | 2010-10-28 | Page 13
shaping application traffic
› Guiding principles
– Stay in battery-efficient states
–Minimize state transitions
–Minimize intermittent small transactions
–When transmitting – transmit it all
– Small keepalive messages
Reduces battery consumption and network signaling
HSPA
FACH
“Standby”Idle
“High”
“Low”
URA
IDLE CONNECTED
Pow
er
Data rate
Public | © Ericsson AB 2010 | 2010-10-28 | Page 14
shaping application trafficbad application example
Device
Network
3s 5s
50s
3s 5s3s 5s
50s
3s 5s
› Chatty IM application example
– 2% of traffic generated 10% of signalling load
– Lots of signaling due to frequent polling
› Possible improvements:
– Clean close of TCP(avoid TCP RST)
– Keeping TCP connection(to own server)
– Push on one persistent TCP connection
“High”
“Low”
Idle
Public | © Ericsson AB 2010 | 2010-10-28 | Page 15
background polling applications
› Multi-tasking: freedom with responsibility – higher risks screwing up!
› Developer tutorial from Sony Ericsson blog:
– Synchronize polls with other apps
› using alarmManager: setInexactRepeating and/or use RTC rather than RTC_WAKEUP
– Execute polls as short as possible
› single requests, short server responses, multi-queries, gzip
– Manage HTTP connections
› use of Apache httpclient and explicitly shut down the connection when poll is done
– Stop services
› wake up with intents (e.g. alarmManager) when needed
http://blogs.sonyericsson.com/developerworld/2010/08/23/android-tutorial-reducing-power-consumption-of-connected-apps/
Public | © Ericsson AB 2010 | 2010-10-28 | Page 16
synchronize background polling example on synching android apps
HTC Hero, Android 1.5. Trace on WLAN. Showing all TCP activities.
FB app
Contacts FB
POP3 mail
Google port 5228
Google/loc/m/api
Daytime
Snowstorm
weather
Newsrob RSS
google reader
AGPS
Poweron
Manual refreshes
Charging Wake
display
Public | © Ericsson AB 2010 | 2010-10-28 | Page 17
push instead of pollingAndroid 2.2 Cloud-to-device messaging (C2DM) API
CP/SP
CP/SP
Android
App App
API
Internet
1. New event / data
2. Message to ”ID”
Data up to 1 kB
3. Message to ”ID”
4. Message to app. Download more data and/or notify user.
long-lived TLS/TCP (port 5228)also used for GTalk, Gmail,...
› Push more efficient if:
– high immediacy is required
– frequency of data is not too high
› Further optimizations:
– multiple apps share single
connection (c2dm)
=> reduced keepalives
– transmit only delta
=> no need for additional polls
FW/NAT
c2dm
Server
Public | © Ericsson AB 2010 | 2010-10-28 | Page 18
small keepalive signaling
› Minimize size of keepalive messages
– Allows switch from ”Standby” (URA) to stay in ”Low” (FACH) state
– Avoid upswitch by limiting data Typical settings in todays networks: Uplink < 250B, Downlink < 500B, incl IP headers
Esta
blis
hm
ent
Info
tra
nsfe
r
Inactivity
“High”
“Low”
“Standby”
“Low”
“Standby”Po
we
rP
ow
er
Save battery, use small keepalive messages
6 messagesover radio
3 messagesover radio FACH
URA
HSPA
FACH
URA
Public | © Ericsson AB 2010 | 2010-10-28 | Page 19
optimizing video streaming1. Download start at peak rate
2. Serverthrottling
3. Client throttling
› Staying long in ”High” (HSPA) state drains battery
› More efficient: transmit with peak rate, then sleep the radio
– Intervals long enough to use power-saving state,
but not too long since many videos not viewed fully
– Consider adaptive HTTP streaming (upcoming – not yet in Android)
Long Youtube
video on Android
Time [s]
Thro
ug
hp
ut
[Mbps]
Public | © Ericsson AB 2010 | 2010-10-28 | Page 20
conclusions
› Smartphones a success for all involved
› Chatty smartphone traffic– Impacting battery and network signaling
› Measures to manage smartphone traffic– Network dimensioning, tuning and features
– Device behaviour - fast dormancy
– Impact application traffic to be battery- and radio-efficient
› minimize chattiness of traffic
› optimize background traffic
› small & infrequent keepalives
› when transmitting – transmit it all
NW operators/vendors
Terminal vendors
App developers
Public | © Ericsson AB 2010 | 2010-10-28 | Page 21
developer guidelines, some references
› Our blog post on this topic: – https://labs.ericsson.com/developer-community/blog/smartphone-
traffic-impact-battery-and-networks
› Android Application Coding Guidelines, Power Save: – http://developer.sonyericsson.com/cws/download/1/788/263/127192
0135/dw-300012-Android_Power_Save.pdf
› Android tutorial, Reducing power consumption of connected apps:– http://blogs.sonyericsson.com/developerworld/2010/08/23/android-
tutorial-reducing-power-consumption-of-connected-apps/
› Coding for Battery life, Google IO 2009: – http://www.youtube.com/watch?v=OUemfrKe65c
Q & A
Public | © Ericsson AB 2010 | 2010-10-28 | Page 23