The broadcast in a multihop radio network is the process of delivering copies of messages to the entire transmission range of the network. Based on the properties of the node and area coverage communications enabled by the grid structure, optimal broadcast procedures are derived for an arbitrary single source node for each case. These procedures are then applied to determine the length of time slots so that the maximum time until the broadcast completion may be minimized. In order to allow any number of nodes in the network to initiate broadcasting, a hierachical broadcasting protocol based on spanning tree of the network is proposed for node coverage broadcast. Furthermore, three schemes for assigning the collision-free channel to each node are presented. Based on these schemes, an area coverage broadcast protocol which enables each node in the network to initiate a broadcast is derived.