29 Notes

On Apple’s statement about iPhone reception strengths

A few people and even some significant blogs have asked me what I think of Apple’s open letter to iPhone 4 owners about the reception problems. I guess I’m famous now? Anyway, the important bits of Apple’s press release are:

We have discovered the cause of this dramatic drop in bars, and it is both simple and surprising.

Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong. Our formula, in many instances, mistakenly displays 2 more bars than it should for a given signal strength. For example, we sometimes display 4 bars when we should be displaying as few as 2 bars. Users observing a drop of several bars when they grip their iPhone in a certain way are most likely in an area with very weak signal strength, but they don’t know it because we are erroneously displaying 4 or 5 bars. Their big drop in bars is because their high bars were never real in the first place.

To fix this, we are adopting AT&T’s recently recommended formula for calculating how many bars to display for a given signal strength. The real signal strength remains the same, but the iPhone’s bars will report it far more accurately, providing users a much better indication of the reception they will get in a given area. We are also making bars 1, 2 and 3 a bit taller so they will be easier to see.

We will issue a free software update within a few weeks that incorporates the corrected formula. Since this mistake has been present since the original iPhone, this software update will also be available for the iPhone 3GS and iPhone 3G.

Having reviewed Anandtech’s excellent research on the issue, I agree with their position:

The drop in signal from holding the phone with your left hand arguably remains a problem. Changing the bars visualization may indeed help mask it, and to be fair the phone works fine all the way down to -113 dBm, but it will persist - software updates can change physics as much as they can change hardware design. At the end of the day, Apple should add an insulative coating to the stainless steel band, or subsidize bumper cases. It’s that simple.

The mapping of signal strength to reported ‘bars’ on the iPhone’s display is oddly out of whack, which causes two problems. For users already in a marginal signal strength area, it makes the drop in reception when they hold the phone look disproportionately — and alarmingly — worse (as the phone can drop from five bars to none). For users in a strong signal area, it masks the issue completely (as the phone’s reception is still inside the five bar range). These are the two positions we’ve seen rage in discussion forums across the Internet over the last eight days (“it sucks!” / “no, it’s fine, you suck!”, etc etc). Basically, it looks like this:

Making the bars more closely represent reality is a step forward, and I believe the perception of the size of the problem has certainly been exaggerated by the miscalibration - with the attendant hysteria from some of the press.

But if there is no design issue at work here, why did Anandtech and my own testing both show significantly different attenuation when holding an iPhone 4 in a bare hand compared to holding it in a case? And why did Apple themselves recommend “using a case” as a possible solution to the problem?

Apple’s position is that the reception strength is so much better on the iPhone 4 that, even with the attenuation factored in, it’s still better than the 3GS. They, of course, would say that; they’ve just sold a couple of million of the things. Maybe they’re right but I remain unconvinced. The problem isn’t as big as some people are saying — but it’s not the non-problem Apple are trying to paint it as either.

I await my free Bumper with bated breath!

(Edited 2010-07-02 to fix incorrectly labelled graph axis.)



  1. penllawen posted this