This paper presents an algorithm for the complete coverage of
free space by a team of mobile robots. Our approach is based on a
single robot coverage algorithm, which divides the target
two-dimensional space into regions called cells, each of which can be
covered with simple back-and-forth motions; the decomposition of free
space in a collection of such cells is known as the Boustrophedon
decomposition.  Single robot coverage is  achieved by ensuring that
the robot visits every cell.  The new multi-robot coverage algorithm
uses the same planar cell-based decomposition as the single robot
approach, but provides extensions to handle how teams of robots cover
a single cell and how teams are allocated among cells.  This method
allows planning to occur in a two-dimensional configuration space for
a team of $N$ robots. The robots operate under the restriction that
communication between two robots is available only when they are
within line of sight of each other.