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Apple's iPhone Signal Strength Placebo
As previously noted, users continue to report poor 3G signal strength under iPhone OS 2.1. To be clear, iPhone OS 2.1 does not purport to actually boost signal strength. Instead, it provides "more accurate" signal strength display, which, in most cases, means more bar bars, but not necessarily better reception or ability to make/receive calls. However, it appears that "more accurate" may mean "unreasonably generous."
Noted in our previous report, the most reliable indicator of actual signal strength is the iPhones dB meter, which can be accessed in field test mode. Dial *3001#12345#* then press "Call." A dB reading below 50 generally indicates good strength.
iPhone Atlas reader Michael did some testing, and found that widely varying dB readings resulted in the same five-bar signal indicator on his iPhone. He writes:
"After I upgraded to 2.1, I did indeed notice a consistent indication of '5 bars' of signal strength. Then I learned how to put my iPhone in field test mode so the phone displays an absolute signal strength indication of dBm rather than a relative signal strength indication of 'bars.' You can then tap the signal strength to switch between the two. I have done an informal survey and observed the following:
- -50 dBm = 5 signal bars
- -75 dBm = 5 signal bars
- -80 dBm = 5 signal bars
- -95 dBm = 5 signal bars
- -113 dBm = 5 signal bars
Michael's results beg the question -- does iPhone OS 2.1 really provide more accurate signal strength indication? Or does it simply inflate the signal strength reading?
Feedback? http://www.iphoneatlas.com/contact.
I'd like to start keeping track of my phone's performance, and am not clear if we are in the realm of negative or positive numbers. Thanks in advance for the kind assistance.
The same signal strength and noise level will arrive to any cell phone, so how many bars get displayed is not really helpful. It all depends on what the phone *does* with that signal.
I don't necessarily think this is apple's fault, but more AT&T's crappy 3G network.
-113 dBm = 1 signal bar [bad or no 3G use possible]
-52 dBm = 5 signal bars [best I got so far, 3G works perfectly]
ATT's 3G network sucks. Last year, I bought an ATT 3G air card for my MBP. I returned it because it was useless. The 3G coverage was weak and the card almost always defaulted to Edge. I bought a Sprint EVDO card and it rocks.
One cannot expect an iPhone 3G to be any better than the ATT network.
It's bizarre how much variation there is between phones on many things, (call quality, sync issues, backup speed, lockups and errors, etc...) They all use the same hardware and same OS, why so much variation?
My wife's phone (purchased at exactly the same time as mine) behaves differently even though they are both running the same OS version with no hacks. My phone locks up and needs to be restored upon every OS update, her's updates without issue. Her phone won't fall back to Edge when 3G isn't available, mine falls back perfectly. I can get a 3G signal in places she can't.
With Apple tightly controlling the hardware and software, you would think they would all behave the same.
- by daytexas48 March 16, 2009 2:24 PM PDT
- The nature of digital radio communcation is that the signal level has little to do with the quality of the transmission path until a threshold is reached below which the digital signal is lost altogether. I am not surprised that a -97 (dBm) signal level performs every bit as well as a -26 dBm. (dB below a reference signal of 1 mW). I would not be surprised if say a -113 dBm would be lost althogether. An abrupt cutoff is to be expected from a digital radio system rather than gradual fade out one sees with analog radio. The question of the most appropriate way to assign the vaule to "bars" is another matter; equate the number of bars directly to RF signal strength or to the "useability" of the digital signal? Most users are more interested in the serviceability of a digital radio link and could care less about the actual signal strength which for most of the dynamic range of a digital radio system is essentially flat.
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