Friday 2 July 2010

Apple iPhone 4 signal strength indicator highlights a common problem

It is old knowledge that if progress bars go faster at the end, the user is happy. In other words, if the progress bar is modified so that it doesn't show the perfect progress percentage, you get a better customer satisfaction.

The same principle applies to other indicators, like battery indicators and mobile phone signal strength. Many phones don't seem to lose battery energy until the very last moment, where it drops fast. Apple has now communicated, that their antenna problem actually isn't that bad, but their signal strength indicator is very sensitive at the coverage levels where this problem was demonstrated. Apple will now "adopt AT&T’s recently recommended formula", which should improve on the problem. That doesn't change the fact, that a piece of rubber can improve the iPhone 4 significantly, of course.

The Google Nexus One has a different approach on battery indicator than most: It starts to drop pretty fast after charging to full level, but when the battery indicator is low and red, you actually still have a lot of energy left - 20% in the indicator means about 20% to go.

What is the best solution? There is a commercial side and a usability side of the problem. The commercial side depends on your business model, and I won't get into that here, but the usability side actually doesn't give a clear answer, either. We have several processes that we want to support:

* If the user needs to plan usage of a limited resource for a specific amount of time (e.g. battery energy for one day), the indicator needs to progress during the entire time span.

* If the user normally doesn't care about usage of a limited resource (battery energy), but may end in a situation where the limited resource is sparse (battery almost empty) and then starts to care about it, the progress indicator should progress little during normal use and most when resources run out.

* If the indicator is used to indicate chances for downtime (e.g. signal strength), it should be most sensitive for high downtime probabilities.

* If the indicator is used to indicate rate of energy usage (e.g. signal strength), it should be most sensitive at the rate that is used most frequently. This may be in the upper or lower end, or in the middle.

* If the indicator is used as a provider of a value, on which the user wants to do calculations, the indicator must reflect reality in a way that is easy to interpret. For instance, if you have 5 bars for battery, each could represent 20%. Or if you have 5 bars for signal strength, each could represent a factor (constant amount of dB).

In other words, there is no perfect solution, it will always be a compromise.


stanleyxu (2nd) said...

most people do not care about indicator issue but the potential hardware issue. If calls will be dropped due to holding position, Apple might face a great number of refund. I do not have the new iphone4, but from some youtube videos, I doubt this is true.

Anonymous said...

How about a logarithmic progressbar?

Lars D said...

I have been to USA recently where I used AT&T, and coverage is really bad. In New York, you have absolutely no coverage in the subway, no coverage in the train going out of Penn station, but even inside some buildings like the Rockefeller center, there is no coverage. And if you go to Pennsylvania in the train, you occasionally lose coverage and once you are inside Pennsylvania, it totally disconnected me. A mobile phone in USA is not as dependable as in Europe, even though they tie you up in page-long contracts before you get your SIM card, and require that you use a phone that matches their network.

In an area where coverage is really poor, most phones will lose the signal with certain holding positions, and the iPhone 4 is not a special case. It is special, that the antenna connects with the holder, but they will quickly be able to find a different phone that has worse reception than iPhone 4, which is a great product.

However, Apple uses software as the culprit - my argument is, that there are good usability reasons for many kinds of indicator-to-hardware mappings. The iPhone may be a bit extreme, but Nokia also accelerate their indicators.