Optimal Source Codes for Timely Updates

A transmitter observing a sequence of independent and identically distributed random variables seeks to keep a receiver updated about its latest observations. The receiver need not be apprised about each symbol seen by the transmitter, but needs to output a symbol at each time instant $t$ . If at time $t$ the receiver outputs the symbol seen by the transmitter at time $U(t)\leq t$ , the age of...