In a significant class of sensor-network applications, the identities
of the reporting sensors constitute the bulk of the communicated data,
whereas the message itself can be as small as a single bit---for instance,
in many cases, sensors are used to detect whether and where a certain interesting
condition occurred, or to track incremental environmental changes at fixed locations.
In such scenarios, the traditional network-protocol paradigm of separately
specifying the source identity and the message in distinct fields leads to
inefficient communication.

This work addresses the question of how communication
should happen in such identity-aware sensor networks.
We calculate theoretical performance bounds on the minimum cost required
for communication,
where cost refers to the number of bits employed. We then  develop joint source-identity coding schemes
that are close to the optimal bounds,
simple to implement, and gracefully adaptable to scenarios frequently
encountered in sensor networks---for instance, node failures, or
large numbers of nodes where only few are active during each reporting round.
We also show that our proposed approach outperforms  the traditional source-identity/message  separation schemes.