[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] flexfulton:
FYI - Network Handoff and Signal Strength

Here is some good information about 4G signal strength and handoffs to 3G. OP is here..... http://rootzwiki.com/topic/36320-app2012-12-20-advanced-signal-status-v113/

And here are some key pieces of information from it that I think are useful. There is also a nice little app called Advanced Signal Status on the last page of that thread that you can download for free. It's also avaliable in the market. Check it out.

RSRP:

Reference signal received power (RSRP), is defined as the linear average over the power contributions in Watts of the resource elements that carry cell-specific reference signals within the considered measurement frequency bandwidth. Used to measure the signal of your LTE (GSM/4g) connection. In short, it's what's used to determine the best cell tower your LTE device can connect to at the given time. Anything below say -80db is considered pretty good and you're pretty close to a tower. -80db to -90db is average what you should expect most of the time. -90db or above and you're probably in an "extended network" area for LTE and getting close to a likely handoff. -105db and above you would be likely to see a handoff to 3G if your signal does not get better.

Throughput for your connection measured with LTE is estimated to decline between 30-50% if your signal goes from -75db to -90db for RSRP. Above -95db and your throughput dramatically drops. At around -108db and worse, your throughput for download drops to nearly 3G rates or worse. Note that this doesn't exactly represent how strong your signal is, just the potential of how efficiently it will send that data.

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"But why can I have a super awesome RSRP signal and still my download/upload speeds are not that good (or why is it still sometimes good when RSRP is low)?"

Because it's only measuring the efficiency between you and the tower, not the rest of the network or the end source (the website). There are many network hops along the way to the destination and some may also handle connections inefficiently. The more hops, the slower the connection generally is.

However, it does also represent the greater likelihood that your connection will drop more packets of data that need to be retransmitted and thus not only slowing your connection but also causing it to have to work harder and draining more battery when it's actively downloading/uploading. That's why having it hand off is for the best than fighting it to stay on LTE. This is most likely why people always complained about the Thunderbolt having such poor battery life as no one ever saw what their RSRP was on it, only their RSSI like all other Gingerbread devices.

You can also consider RSRP the "absolute strength" of your current connection.

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"Why does my Nexus not hand off exactly the same as <insert proprietary android os based phone here>?"

Because it goes back to what I already mentioned in that other OEMs don't measure the LTE signal with the same metrics as they do on the Nexus (it was only added to the Android source with ICS and before then each carrier just "rolled their own" thing probably using the RSSI of the LTE signal to handle when to hand off) so the phone thinks the LTE signal is also better than it actually is and so it's staying on what is really a *worse* LTE signal when it should be handing off to a better CDMA/3g signal. Also see the part about RSRQ above and the graph. It'll be far easier to tell what they're doing when they update to ICS though as we'll have access to more information.