Preferred Roaming List
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The Preferred Roaming List (PRL) is a data file for wireless phones (primarily CDMA services) which provides a list of alternate networks to use when the service provider's and/or subscriber's primary wireless network cannot be reached. The PRL indicates which bands, sub bands and service provider identifiers it should accept. Without a PRL, a cellphone may not be able to roam, i.e. obtain service outside of the home area.
[edit] Usage
On many networks, regularly updating the PRL is advised if the subscriber uses the device outside the home area frequently, particularly if they do so in multiple different areas. This allows the phone to choose the best roaming carriers, particularly "roaming partners" that the home carrier has a cost-saving roaming agreement with, rather than using non-affiliated carriers which will incur a premium roaming charge.
[edit] Structure
The PRL structure and coding is defined in TIA/EIA IS-683.
The PRL consists of 3 parts:
1. Header and overhead
2. Acquisition Table
Frequencies and service types to use
3. System Table
Systems to use and ignore System to geographic coverage area mapping
