Themes in Broadcast Calculi

Broadcast communication between computers became common with the Ethernet, which inspired the first, "wired", broadcast calculi. Here, senders choose what to send and when, reception is instantaneous to everyone connected to the (local) Ethernet, and contention among senders is arbitrarily resolved. These calculi were easily embedded into programming languages to express concurrent and parallel programs, and into proof checkers to give correct executable concurrent programs. They also easily accommodated priorities and time. The last wired calculi added mobility and asynchronous connections between locally synchronous nets. But such algebraic scoping matters less in the recent wireless calculi to describe MANETS and sensor networks, which note network topology separately from process structure. Wireless calculi model the hardware more closely and at different levels, so their concerns include limited and overlapping ranges of broadcasts, or collisions between them. Despite these fundamental differences, several ideas have survived from the wired into the wireless era.