By now everyone in the world has heard that Apple’s shiny new iPhone 4 allegedly has a fatal flaw worse than the Death Star. Consumer Reports claims that their “engineers have confirmed that iPhone 4 has an antenna problem…” and that it “…really is only with the iPhone 4.”
Oh really? Just watch this video I recorded this evening with the original iPhone 2G, on T-Mobile USA’s network:
Anand Lal Shimpi over at AnandTech did quite a rigorous investigation into iPhone 4’s reception and observed that:
“squeezing it really tightly, you can drop as much as 24 dB. Holding it naturally, I measured an average drop of 20 dB.”
Interesting! I measured an average drop of 20 dB when holding my iPhone 2G naturally, as seen in my video above. But here’s the kicker from Anand’s research:
“From my day of testing, I’ve determined that the iPhone 4 performs much better than the 3GS in situations where signal is very low, at -113 dBm (1 bar)…I can honestly say that I’ve never held onto so many calls and data simultaneously on 1 bar at -113 dBm as I have with the iPhone 4, so it’s readily apparent that the new baseband hardware is much more sensitive compared to what was in the 3GS. The difference is that reception is massively better on the iPhone 4 in actual use.”
In my opinion–and I happen to be an RF communications engineer at one of the largest cellphone designers in the world–the only thing Consumer Reports really can say with certainty is that signal strength depends on a variety of factors, one of which is dependent on how a phone is held. Any smartphone, or really any radio for that matter, will have it’s performance affected by how the antenna is placed, held, etc. It’s irresponsible and dishonest for them to claim anything otherwise.
But wait a minute! Consumer Reports said that they tested the iPhone 4 in a “signal proof room” that simulates “real life conditions”! Before addressing that, some background:
Your smartphone, and the cellular tower (or “base station”) both are really just digital radios. When you make phone calls, you’re talking on a walkie talkie that digitizes your voice and sends it to the base station using radio waves. Once there, the base station relays that voice data through the carrier’s network to the phone on the other end of the call, and vice versa.
For this whole system to work, you need to have a certain amount of Signal-to-Noise ratio, or SNR, at both the smartphone, and at the base station. SNR is measured in dBm, or decibels referenced to one milliwatt (mW), which is the standard unit of measure for RF engineers. If your SNR drops below the level of sensitivity of either radio, packets (small chunks of data, i.e. your voice or network synchronization traffic data) start getting dropped. If SNR is too low for too long, too many packets are dropped (this is where your voice starts “breaking up”) and then the call is dropped by the tower if SNR doesn’t recover to a level above sensitivity so that you don’t end up consuming precious bandwidth and preventing others from making calls.
What can cause SNR to drop? A whole slew of things:
- Distance from the cell tower
- Interference from other radio waves
- Attenuation from buildings, trees, trucks passing by, and how you hold the phone 😉
- Multipath distortion (a phenomenon in radio communications where multiple copies of the signal sent bounce off of buildings, etc. and arrive at slightly delayed times, causing inter-symbol interference (ISI). Think of it as the radio confusing 0’s and 1’s, causing corruption in packets sent. Though 2G, 3G, and 4G technologies do have equalization circuits and forward-error-correction (FEC) circuits that can help combat this, it does require a stronger SNR that otherwise to help decode the bits sent over the air.
So, back to the “real life condtions” in Consumer Report’s “signal proof room.” The room they’re referring to is what’s known as a screen room. In their video, they claim that this environment simulates “real life conditions”. No it doesn’t! Screen rooms are designed to test radio performance while ignoring real-life issues, such as multipath, deep fades, interference, etc.
Does shorting the two antennas together cause a degradation in the performance of iPhone 4’s antenna? Sure. Does holding any phone change the performance of the antenna? Absolutely. Is the iPhone 4’s antenna a flawed design? Absolutely not. Could it be better? Definitely…but so can anything. Anand does suggest that Apple should “add an insulative coating…or subsidize bumper cases”. I’m not sure I agree, at least not yet. Depending on how Apple designed their antenna and radio front end, they could improve radio performance with a software update–I’ve implemented algorithms that did precisely this.
All in all, it seems clear that Consumer Reports didn’t prove anything is “flawed” with the iPhone 4, and acted irresponsibly in making the claims they did. The evidence they gave doesn’t support their claims, and was more smoke and mirrors than concrete information. It’s going to be difficult for me to trust their reviews of products in the future. As for what Apple does next, stay tuned for their invitation only press conference, scheduled for this Friday.