Sprint has announced they will be shutting down their IDEN network on 6/30/2013. IDEN is the Push to Talk (PTT) network that some government and public safety uses. Sprint has an upgrade path for those that still use IDEN. This network came to Sprint when they acquired Nextel and lives in the 800-900 mHz. Most likely, Sprint will use this frequency for a future 4G LTE expansion.