Indirect Time Synchronization

In indirect time synchronization, both the sender and the receivers synchronize their time with a time reference and hence the sender and the receiver can reach implicit time synchronization. This approach is favorable especially in cases where the application needs time synchronization with a time reference anyhow. Let $\Delta$_SC + |ε_SC| denote the measured upper bound of the difference of the sender's time and the time reference's time with $|\epsilon$_SC| as the maximum error, and let $\Delta$_CR + |ε_CR| denote the measured upper bound of the difference of the time reference's time and the receiver's time with $|\epsilon$_CR| as the maximum error. Thus the receiver could reach an implicit time synchronization with the sender as $\Delta \; =\; \Delta$_SC + Δ_CR + |ε_SC| + |ε_CR| with $\epsilon \; =\; |\epsilon$_SC| + |ε_CR| as the maximum error.

In settings where the receiver is already time synchronized with the time reference, the receiver does not need to send any information to the sender. The sender just needs to periodically broadcast digitally signed packets that contain its time synchronization with the time reference, the time interval and key chain information outlined in section 2.2, along with the sender's maximum synchronization error $\epsilon$_SC. A new receiver can start authenticating the data stream right after it receives one of the signed advertisements. This is particularly useful in the case of satellite broadcast.