PPCGeeks - PRL Confusion and Misconceptions

OK, maybe I'm out of line here, but I have been seeing a lot of talk about updating your PRL on the forum. This is something I have quite a bit of experience in (I've been hacking my own PRL to make it work the way I want for some time), so I'd like to share some thoughts and hopefully clear up any misinformation.

The short version of my post: updating your PRL is not going to have any effect on your signal strength in most cases. It is not a magic fix. Unless you are roaming, it probably won't have any effect at all unless the provider has added new subnets which doesn't happen very often.

The long version (this is kind of oversimplified, but it makes the point):

A PRL (Preferred Roaming List) is not a program. It's not something that will magically increase your signal. As the name implies, what it is is a list of SIDs (System ID, which is a five digit number that indicates which service area the phone is in). This list is specific to each provider and contains information about which SIDs your phone is allowed to roam on, the order of priority, and other tidbits like EvDO capability (hence the "Preferred" and "Roaming" in the name).

So, all it does is group the SIDs into geographical areas and then start at the top and work their way down until they get a usable signal. To wit (example from my Alltel PRL 40023):

(index followed by SID)
0 - 00240
1 - 04153
2 - 04154
3 - 00366

The phone first checks to see if I am in my home SID 240 (not roaming). If I am, that's it. Done. The PRL serves no further function.

If I'm not in SID 240, then my phone moves down the list to look for 4153 (Sprint). If it's available, it connects. If not, then it moves on to checking for 4154 (Verizon), 366 (Cellcom), etc.

Now, you can edit the list if you have a PRL editor (the file is in hex). I did so to move Cellcom down, since Alltel doesn't have a data roaming agreement with them. However, most users would never have a reason to do this.

If you are not in your home area, then the PRL starts looking for preferred roaming partners' SIDs in a certain order. It does not take strength of signal or any other factors into account... either the SID is available or it isn't. In my example above, once I leave SID 240, my phone will attempt to connect to 4153 (Sprint). If it's available, it will "lock on" to it, even if it's a weak signal and 4154 (Verizon) has a stronger signal. (This is an example of where editing the priority index would be helpful).

Hopefully this helps clear things up a bit. I've seen too many posts lately stating that "I updated my PRL and now my signal is way better!". Unless you are roaming, or a *major* network upgrade took place in your area, a PRL update isn't going to make that much difference, if any.