The paper proposes a new position-based broadcast algorithm for mobile ad-hoc networks (MANETs) called PBB. It shows how communication methods originally designed for wired multiprocessor interconnection networks can be used in MANETs. PBB is based on a logical 2-dimensional grid view of the geographical region of the MANET. PBB makes use of a known construction of spanning trees in the grid multiprocessor interconnection network. To the best of our knowledge, PBB is the first protocol that uses cell-based spanning trees of the grid to perform broadcasting in MANETs. In this study we derived analytical results for the delivery ratio of PBB protocol and the number of rebroadcast messages per broadcast operation.