 
Summary: Chapter 1
An Introduction to
Population Protocols
James Aspnes, Yale University
Eric Ruppert, York University
1.1 Introduction
Population protocols are used as a theoretical model for a collection (or pop
ulation) of tiny mobile agents that interact with one another to carry out a
computation. The agents are identically programmed finite state machines.
Input values are initially distributed to the agents, and pairs of agents can ex
change state information with other agents when they are close together. The
movement pattern of the agents is unpredictable, but subject to some fairness
constraints, and computations must eventually converge to the correct out
put value in any schedule that results from that movement. This framework
can be used to model mobile ad hoc networks of tiny devices or collections of
molecules undergoing chemical reactions. This chapter surveys results that
describe what can be computed in various versions of the population protocol
model.
First, consider the basic population protocol model as a starting point. A
formal definition is given in Sect. 1.2. Later sections describe how this model
