Topic '[iPhone] -114 dBm RSSI - How can it even work?' in forum 'All Things Macintosh' - dslreports.com

Re: [iPhone] -114 db RSSI - How can it even work?

Sun, 03 Feb 2013 12:45:41 EDT

Irish Shark posted : We all make typos. That's what I did. I missed the "m" after the "dB" and that is what caused all the hoopla.

The -110dBm was referenced for a 4 and 4s. I also seen that referenced for the 5. Top of my head, I don't remember where I read that. I'll see if I can find it.

Sorry for all the confusion.
--
"You can observe a lot by watching". Yogi Berra

Re: [iPhone] -114 dBm RSSI - How can it even work?

Sun, 03 Feb 2013 06:52:46 EDT

BloodRoses posted : Because you're modulating the attenuator on your pre-amplifier. At -99dB the signal was fully attenuated or 'restricted' if you will. At 0dB the pre-amp is no longer attenuated and is feeding your power amplifier the full signal. The final volume output is going to be based on the impedance load on your power amplifier and the sensitivity of your transducers or "speakers" if you will.
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Fairy Blessings,
Stefanie

Re: [iPhone] -114 dBm RSSI - How can it even work?

Sun, 03 Feb 2013 04:08:46 EDT

Kearnstd posted : silly question, How can db be negative? I had a stereo once that listed the volume as negative db too which made no sense to my mind the numbers should be positive. But the dial was basically full loud if it was 0db and pretty much muted at -99.
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[65 Arcanist]Filan(High Elf) Zone: Broadband Reports

Re: [iPhone] -114 db RSSI - How can it even work?

Sat, 02 Feb 2013 18:52:04 EDT

squircle posted : Sorry, wrong answer.

The signal bar on the top left of your iPhone screen will be replaced by a number, indicating the ~~actual~~ relative signal strength of ~~your device~~ the cellular signal.

You have to understand that dB and dBm are only somewhat related. Yes, RSSI does have units, and yes I did typo my last post, but they're certainly not dB. Quick explanation: it's not an arbitrary ratio (like dB) but a ratio relative to 1 mW. The ISA has a nice explanation.

You also have to consider that signal strength is not the only factor; there's also the signal quality. You can be receiving a very, very weak signal, but as long as it is relatively clean (i.e. free of noise and other interference), you can still have a perfect phone call. On the iPhone's hardware specifically, the minimum value is -121; -110 is not the "minimum". You can make a perfect phone call at -120 (and I personally have).

Think of it like a DSL line. If your line is clean, has minimal interference and crosstalk, as long as your SNR is above 6 dB (yes, this is actually decibels and not dBm), your attenuation won't matter as much.

TL;DR: RSSI is not measured in dB, is relative (not absolute) and signal quality matters more than signal strength

Edit: To answer your original question, your phone is reporting the correct signal level and you should not worry about it.

Edit 2: I remembered the name of the app I used to use from Cydia, it's called "Signal". It costs a few dollars but it's interesting to see how the signal quality compares to signal strength for any given tower.

Re: [iPhone] -114 db RSSI - How can it even work?

Sat, 02 Feb 2013 15:31:48 EDT

Irish Shark posted :

said by squircle:

Just FYI, RSSI is not measured in decibels. Your RSSI is -114, not -114 dB.

Sorry, wrong answer.

The signal bar on top left of your iPhone screen will be replaced by number, indicating the actual signal strength of your device. The reading is in dBm and the higher the number is, the lower its signal strength and anything below -110dBm may experience call failure or drop.

»opengear.org.uk/faq386-Cellular-···gth.html

»www.maximintegrated.com/glossary···/gpk/252

»www.developer.nokia.com/Communit···8RSSI%29
--
"You can observe a lot by watching". Yogi Berra

Re: [iPhone] -114 db RSSI - How can it even work?

Wed, 30 Jan 2013 13:21:12 EDT

squircle posted : Just FYI, RSSI is not measured in decibels. Your RSSI is -114 dBm, not -114 dB.

Edit: noticed my HTML entities were mangled by DSLr.

[iPhone] -114 dBm RSSI - How can it even work?

Wed, 30 Jan 2013 13:09:15 EDT

Irish Shark posted : My iPhone 5 reports the above signal strength. Translated into bars it varies from 1/2 - 1 1/2. According to the specs, the phone should not connect to any signal source.

I have AT&T and all the grid maps show that I am in a solid green area (excellent). The "G" indicator will come on as well as the "LTE" (makes no sense to me).

The signal is the same outside as inside the house. If I drive around and take some signal samples, they get better in some spots, but not so good in other areas.

I am about 1 1/2 miles from the tower and a 1/2 mile from a repeater.

Talking to AT&T, they said the grid maps are wrong and I am in a small "fringe" area with low signals. They also said that I am connecting to a tower that is 3 miles away.

Phone calls seem OK with neither me or the other party having static, fade, or garbled sound.

Is this phone just not reporting the correct signal level or am I missing something and should just go back to sleep?

EDIT: Sorry, but RSSI does have units.

--
"You can observe a lot by watching". Yogi Berra