  We consider an energy harvesting transmitter sending status updates regarding
a physical phenomenon it observes to a receiver. Different from the existing
literature, we consider a scenario where the status updates carry information
about an independent message. The transmitter encodes this message into the
timings of the status updates. The receiver needs to extract this encoded
information, as well as update the status of the observed phenomenon. The
timings of the status updates, therefore, determine both the age of information
(AoI) and the message rate (rate). We study the tradeoff between the achievable
message rate and the achievable average AoI. We propose several achievable
schemes and compare their rate-AoI performances.
