One of the few good things to come out of the iPhone 4 "Death Grip" controversy is an increased focus on how smartphones communicate with cell networks. If this hadn’t happened, for example, you might not know that – since phone manufacturers got the bright idea to hide antennas inside cases – most phones will have some signal degradation if you hold them the "wrong" way.

Among the experts recently sounding off is Richard Gaywood, who describes himself as "fractionally more than Just Another Internet Dude on this subject". Gaywood has a Ph.D in wireless network planning and has experience working with software used on cellular networks.

In this fascinating blog post (language alert!), he concludes after testing (he’s got a cell tower atop the building where he works) that, yep, Apple’s got a problem on its hands, and it might be fixable by software – but he thinks it might not.

But that’s not the most interesting part of his entry. What I found compelling was his revelation that the cell signal indicator on most mobile phones are "almost meaningless".

To understand part of what’s going on, it’s necessary to realise what the signal bar indicator on a cell phone does (and doesn’t) mean. Wireless engineers don’t think in terms of bars, they think in terms of signal to noise ratio, which is often called SNR. When you’re not using the phone, a few times a second it checks it can still hear the control channels that the cell tower uses to send messages to the phones — messages like “here’s an incoming call, wake up and deal with it”. Of course, in today’s crowded airwaves, your signal is my noise, and vice versa; usually what happens when the signal suddenly drops away is that something has started up nearby and is interfering with your reception. This is like when a car with faulty shielding drives past and you lose your AM radio to the blaring sound of the car’s coil discharging. So, the phone has this number in its head which represents the SNR and that number is constantly fluctuating up and down as the airwaves around you teem with random signals, reflections, and other interference. This isn’t a particularly nice thing to show end users, so the phone does two things. Firstly, it takes that ever-changing number and does a moving average on it to smooth out those rapid spikes. Then, it applies some sort of magic formula to approximate that complicated number into a 1-to-5 scale, which it then puts on the screen as bars. The magic formula is basically made up by the design engineers as they see fit, and it can vary from phone to phone and even between software releases on the same phone. If someone is kicking it old school and getting five bars at your house with their Motorola RAZR and you’re getting three on your Nokia 8210, that doesn’t mean their phone is better than yours. It might just mean that Motorola’s designers made their bars work differently, or it might not. The tl;dr version of this is: the signal strength bars are almost meaningless and should not be relied on. Incidentally, this also explains what’s going on when you have a strong signal, attempt to make a call, and can’t connect. The bars only indicate how well your phone can listen to the cell tower. They don’t tell you anything about how well the tower can receive your phone, but that’s a pretty important part of making a call. Similarly, the phone doesn’t know anything about what’s going on in the cell provider’s network past the tower; if you’re on a really busy cell it might not have any spare outgoing circuits to direct your call to, so even if the radio is working fine, you might still not be able to get through. If you’re on AT&T it’s probably all of the above at the same time of course.

This is only a small part of the whole piece, which is worth your time to read, particularly if you a.) have an iPhone 4; b.) are interested in buying an iPhone 4; c.) want to know more about mobile phones and signal strength; or c.) like to spend your time leaving trollish comments bashing Apple products on blog posts. Gaywood’s entry has something for everyone!