Just How Good Is CDMA?

[fortesquieu]

I have my classes in one of my school's building in the basement with no windows. I have ZERO bars and signal strength of -105 dBm, yet I'm usually able to use 3G and that day, I was able to receive phone call.

So I'm curious just how low can the signal strength be, before it is totally not usable?

I mean GSM in basement, didn't work for me before.

 

[K2e2vin]

I never checked but for the same service(VZW), me and my friend were out in the country and I could make and answer calls with "no service" while his wasn't working at all. Though the phones were different(IIRC he had a Chocolate and I had a Samsung A930)

 

[jasoraso]

There 2 possible reasons why your Verizon phone could make a call while in the basement, where the GSM phone you apparently were using earlier couldn't:
1 - CDMA can increase power as needed - in a weak signal area, the CDMA radio will draw more power to be able to stay connected. This results in shorter battery life, but at least you can make a call. (GSM may do something similar, but I'm not sure).
2 - The other big difference with Verizon is that *most* of Verizon's phone service is on the 800 mhz band, which is better at penetrating walls than the 1900 mhz band that other providers use. Verizon also uses 1900mhz, but in most cases that will be the data portion.

 

[Crashumbc]

Also tower location can have a huge impact.

 

[gruss]

also the dbm reading isn't the end all be all. out in the middle of no where you might be able to make a call at -110 (or said basement), where in a place with alot of radio interference the call might drop at -90. Alot of factors to be considered, might also be that vzw tower is simply closer to where you are allowing you to make a call where your gsm phone couldnt. VZW's voice typically runs in the cellular band, but if you say you had 3g then the pcs band was also connecting as that's where they usually run their 3g data from.
in my experience, vzw's coverage typically trumps gsm carriers, but I don't know if they just planned their build outs better or if its the technology or a combination of both or simply coincidence that that is where i spend my time?