System identification number
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A System Identification Number (SID) is used to identify a cellular network in a certain area. It is a Global number to identify base stations for AMPS, TDMA or CDMA networks. This number sometimes has conflicts (see IFAST).
SID Codes
These codes are 15/16 bit values and can be listed within a Wireless Device to show preference for one network over another. TIA TR-45.2 assigned ranges to every country in the 1980's and national regulators assigned individual numbers. IFAST took over in 1997. This number space is 90% utilized, however many countries do not use all of their allocated codes.
SIDs are assigned by IFAST to every carrier (e.g., Verizon, Sprint, Alltel). SIDs are programmed into the phone when you purchase them.
How SIDs work
When the phone is turned on, it listens for a signal. If it receives a signal, it looks at the SID (being carried by the signal), and compares it with the one that is stored in the phone. If they match, then you are in your home area. You are roaming if you are in an SID area that is not recognized by your phone.
The Preferred Roaming List (PRL) is mostly responsible for determining which SIDs a phone could roam on.
A typical SID area is about 30 - 60 miles in diameter, but some may be as large as 200 or more miles.
External links
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