You can freely build on How Phones Automatically Find and Update Network Lists Using CDPD
This patent expired in 2015. Every claim — 0 independent, 1 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Bell Atlantic Network Services Inc
Patent granted
1999
Expired
2015
Forward citations
179
What this patent covers
The patent describes a method for mobile phones to stay updated on which cellular networks they should use without manual input. It uses a specific data channel called CDPD to broadcast a version number for a list of preferred service providers. The phone compares this broadcasted version number to the one it already has stored. If the numbers do not match, the phone automatically downloads the updated list over the CDPD channel, ensuring it always knows which local networks are available and preferred for roaming.
What is now free to use
All 1 claims of US 5920821 are in the public domain. Specifically:
The 1 dependent claim add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
Does not cover updates delivered over standard voice channels or SMS.
Does not cover modern 4G/LTE or 5G network selection protocols.
Does not cover methods for updating firmware or OS software, only network identification lists.
Does not cover manual network selection by the user via a settings menu.
Who is building on this today
The core logic of using a dedicated data stream to manage device configuration is now standard practice for all major cellular carriers and device manufacturers like Apple and Samsung. While the specific CDPD technology is obsolete, the concept of 'over-the-air' (OTA) provisioning for network settings remains fundamental.
Products built on expired version of this technology
Early analog cellular roaming
Automated network provider list updates
How to cite this patent in your documentation
Bell Atlantic Network Services Inc. US Patent 5920821. Use of cellular digital packet data (CDPD) communications to convey system identification list data to roaming cellular subscriber stations. Granted 1999, expired 2015. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.