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squircle

join:2009-06-23
Oakville, ON

3 edits
reply to Irish Shark

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

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.


Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
kudos:5
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