Praxis

8/201454

Battery Life CompetitionNew smart phones usually have increased capabilities over their predecessors. Does this decrease endurance? We deci-ded to find out which phone has a longer battery life - an ol-der model like a Samsung Galaxy S4 or the newer S5 model.

he annoying thing about smartphones is

that each newer generation has less battery life than its predecessor.“ This is the ty-pical opinion of our con-nect readers. And „Now that smartphones can do just about everything, it´s time manufacturers start improving the battery life. Smartphones should last for at least a week before recharging, like in the old days!“

So what is the true situati-on? Is there indeed reduced battery life as phone displays continue to get bigger and include more and more fea-tures and functions? Or are manufacturers actually deve-loping better batteries and/or better power efficiency so that each new phone genera-tion runs longer? With the question of „old versus new“

on the agenda, we were de-lighted to get an offer from mobile device user experi-ence expert Spirent Com-munications (see the box on page 58) to examine and compare the differences in battery life between two

smartphones. What could be more ap-

propriate than to compare the Samsung Galaxy S4 with its successor model, the S5? Both phones are widely ac-claimed, sell very well, offer modern technical features and include leading func-tions. According to connect testing, both phones are well engineered so it is not likely

that one of them has a design failure due to a bad day at the production line.

Sophisticated Measurement MethodsSpirent´s Quantum Battery Life Measurement System was chosen as the basis for analysis (see box on page 57). Quantum can determine the power consumption and hence the battery life under a variety of conditions, ma-king the comparison bet-ween models easier. Three typical scenarios were inves-tigated. In the first case, the Samsung competitors had to stream a YouTube video. This entailed a fairly cons-tant connection with conti-nual data transfer and placed high demands on the proces-sor and graphics card. A se-cond and more dynamic case which challenges the

T

Old versus new - which phone runs longer?

Foto

s: ©

Pet

er F

enyv

esi (

12)

55

The current drain (blue) and power consumption (green) differ markedly bet-ween the Galaxy S4 (lighter-colored curve) and the S5 (darker-colored curve).

Several recordings are necessary to get a reliable estimate of the mean. Differences in coverage (poor, fair and good) are unmistakable.

The differences in battery life (measured in hours) between Galaxy S5 (dark blue) and S4 (light blue) for different user scenarios is higher than expected.

The difference between the Galaxy S5 (dark blue) and its predecessor S4 (light blue) are less apparent in 4G mode than in 3G mode.

„balanced user“ (33% video streaming, 33% surfing, and 33% multi service) or a „soci-al media maven“ (10% video, 80% surfer, 10% multi ser-vice) or perhaps a „business user“ with 5%, 20%, 75% phone usage. With these weighted modes of usage it´s possible to predict battery life for each user type based on a realistic set of assumptions.

Coverage is a cruical factorApart from general operation of a smartphone, there are also several marginal factors which affect power consumption. Most experts agree that the co-verage situation is a crucial factor. At low levels of recepti-on (from -100 to -85 dBm) smartphones have to transmit with full capacity. They will require more time to receive data due to increased coding to

processor involved surfing the web using the phone´s brow-ser.The third case incorporated a multi-service voice and data application. In this scenario, a virtual user initiates a down-load and after 20 seconds ma-

kes a phone call. This test ends with the conclusion of the call and the termination of the download.

From Video Addict to Busi-ness UserStreaming video, web brow-sing and multi-service usage represent three typical usage

scenarios for smartphones. Consisting of varying types of traffic from short bursts to long continuous transmissi-ons, each usage scenario places different demands on the phone´s processor, gra-phics card and audio systems. Moreover it is possible to de-termine battery life for parti-cular user types by applying different weightings to each base usage scenario. For ex-ample, a „video addict“ could be someone who spends a high proportion (85%) of pho-ne time streaming videos. Other user types include a

protect against errors as well as the repetition of lost data

For additional analysis of our video test we use circular and rapidly rota-ting symbols to detect missing, fro-zen or impaired frames.

Surfing the web is the number 1 batte-ry life killer!

Praxis

56 8/2014

The Quantum System simultaneously captures the current flow between the batteries and the supply port for a maximum of two smart phones. Up to 25,000 measurements per second for each device are possible.

Although the individual test scenarios run automatically once started, a specialist is still required to set up and initiate the measurement process.

The Quantum Battery Life Measurement System consists of a two channel measurement probe (below) coupled to desktop software to measure power consumption and control the data transfers with Quantum Cloud acting as a server.

Spirent used its Quantum System for all measurements.metHoD of meaSUrement

The sophistication requi-red to take realistic mea-surements of smartphone power consumption can be seen in the numerous mobile applications and services controlled by the Quantum Mobile Soft-ware. This special soft-ware must first be ins-talled on the smartphone under investigation to enable remote control of the device.

Simulating User ActivityThe Quantum Mobile soft-ware runs in the back-ground emulating the ac-tivity of a normal user. Using this approach, the user scenario being tested can be set to run automa-tically on the smartphone. For example, in the web browsing test the browser window could be opened and a particular web address entered, with ad-ditional defined actions once the web page had loaded. The important point is that the software itself places minimal de-mands on the phone´s re-sources so as not to influ-ence measurement re-sults significantly. Just as important are the stan-dard settings of the smartphone, since options such as display brightness and GPS functions etc. can affect power con-sumption.Besides the smartphone, a notebook with the Quan-tum Desktop Software to

run the test scenarios is used. This software moni-tors and coordinates the measurement process and creates the reports. The Quantum Interface, between the smartphone and notebook, is respon-sible not only for the pow-er supply but also for measuring supply voltage and current drain. It´s im-portant that the Quantum Interface is able to make several thousand readings per second because some smartphone components are capable of shutting off within milliseconds. A pre-cise measurement system must gather this precise information as well as the peak consumption values for short bursts of power.

The Other End in the CloudPart of the service testing set up is the other end of the connection, the Quan-tum Cloud. In order to re-cord power consumption during a phone conversa-tion, it is necessary to ha-ve a connecting number to automatically receive the call. Also uploading and downloading requires a server connection which ideally should not be de-pendent on some arbitrary platform, but should be within the control of the end user. This way it´s possible to avoid false readings due to disrup-tions at the other end of the line.

57

Praxis

58 8/2014

packages, both of which incre-ase power consumption.

The question of whether 3G or 4G reception consumes more power is not clear and this was therefore examined separately. The experts at Spi-rent investigated three user scenarios, using two smart phones with two mobile pho-ne transmission standards un-der three different supply situ-ations. Using received signal measurement analysis, three locations in the vicinity of Munich were selected to pro-vide the different coverage situations. Apart from the ex-ternal factors there were also

internal factors affecting mea-surements such as settings for display brightness. Both pho-nes were set for normal

Spirent Communications is a worldwide acclaimed telecommunication testing enterprise.

Spirent CommUniCationS

Originally founded in 1936 in London as Goodlife Electric Sup-plies and later changing its name to Spirent Communications the company achieved an annual turnover of over 400 million USD with around 1,500 employees by the year 2013. The com-pany generates its turnover from three main business fields. First, accounting for almost 50% of their turnover is the field of Networks and Applications, which concentrates on the areas of Ethernet, central data and cloud computing, applications and security, test optimization and wireless infrastructure. Secondly, Wireless & Service Experience includes everything to do with terminal equipment, channel simulation, navigation and service quality. And finally, there is the field of Service Assurance in which testing of networks, network operations and customer satisfaction are the main focus of attention.

lighting conditions. Also the WLAN adapter was switched on but remained disconnec-ted.

Optimum Chip Components for Better Video StreamingGPS was the only function during testing that was disab-led. This is not normally the case with smartphones but since GPS tracking occurs sporadically and requires lar-ge amounts of power, it would have meant doing several in-volved measurement sets in order to make the effect negli-gible. Fifteen repetitions of each single measurement we-re sufficient to get a 95% sta-tistically acceptable confi-dence interval. The results of the study are therefore quite reliable.

The bottom left bar graph on page 56 points out how the current drain between the two models for different scenarios compares with each other. Although both smartphones have almost identical OLED

displays and batteries (S4: 5 inch and 2600 mAh; S5: 5.1 inch and 2800 mAh) there is a marked difference in current drain between the two. To the satisfaction of those believers

in technological advancement who are eager for noticeable improvements in battery life, here´s evidence that the S5 is better than the S4. Amazingly the graph shows that surfing the web places the highest de-mand on the batteries. The multi-service scenario seems to take advantage of a swit-ched off display during phone conversations while with vi-deo streaming it appears that a large portion of the video co-

Does LTE Really Con-sume More Power? Apparently Not!

Spirent expert Joao Cardoso (left) and Manfred Rösch (right) discuss the measurement results together with connect’s reporter, Bernd Theiss (middle).

59

ding is now performed by specially optimized chip components. That saves a lot of power when compared to the computation task perfor-med by a general purpose processor.

Clear Result: The Galaxy S5 Lasts Longer!The Galaxy S5 has between 37% and 60% better battery life than the S4. The Galaxy S5 has up to 40% less battery life when web browsing as compared to video streaming or voice calling with data transfers running in the back-ground. The same measure-ments made with 3G gave negligible differences com-pared with 4G. Although the S4 lost a little battery life, the S5 gained slightly in two of the three categories. This can be seen from the bottom right bar graph on page 56. Overall the Galaxy S5 not only provi-des longer battery life, but there were noticeably smaller fluctuations between measu-rements which indicate a hig-

her standard of optimization. Should anyone comparing the results wonder why connect´s laboratory testing using a manual method of phone life measurement gave

higher figures than Spirent´s, they should consider the fact that during connect´s tes-ting, short spaces of time were additio-nally taken into ac-counting for users to supposedly read their

displays.Regardless of the method

of phone life measurement, the Galaxy S5 offers roughly 50% better battery life than the S4. This is a clear confir-

mation not only for connect´s test lab but also for our faith in technological advance-ment. BERND ThEiSS

Key Account Manager Rösch (right) showing connect’s reporter, Theiss the server room where various testing is done.

Spirent’s Project Engineer and specialist for the Quantum system, Joao Cardoso, performing a typical application test in office for connect’s investigation.

User-Type Balanced Video-Addict social-Media-Maven Business-User

smartphone samsung Galaxy s4

samsung Galaxy s5

samsung Galaxy s4

samsung Galaxy s5

samsung Galaxy s4

samsung Galaxy s5

samsung Galaxy s4

samsung Galaxy s5

WeiGhTinG

Videostreaming 33,3% 85% 10% 5%

Webbrowsing 33,3% 10% 80% 20%

Multi-Service 33,3% 5% 10% 75%

BATTery perforMAnce 3G

Videostreaming (h) 1:36 2:36 4:00 6:30 0:30 0:48 0:12 0:24

Webbrowsing (h) 1:00 1:18 0:18 0:24 2:18 3:06 0:36 0:48

Multi-Service (h) 1:30 2:42 0:12 0:24 0:30 0:48 3:30 6:00

Total (h) 4:06 6:36 4:30 7:18 3:18 4:42 4:18 7:12

BATTery perforMAnce 4G

Videostreaming (h) 1:42 2:18 4:18 6:00 0:30 0:42 0:18 0:24

Webbrowsing (h) 1:00 1:24 0:18 0:24 2:24 3:18 0:36 0:48

Multi-Service (h) 1:36 2:30 0:12 0:24 0:30 0:48 3:30 5:36

Total (h) 4:18 6:12 4:48 6:48 3:24 4:48 4:24 6:48

Total Battery Performance 4:12 6:24 4:39 7:03 3:21 4:45 4:21 7:00

Advantage s5 52% 52% 42% 61%

MeAsUreMenT resUlTs