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A contention-based geographic routing (CGR) protocol for mobile ad hoc networks is proposed, which operates in two schemes: greedy-forwarding scheme and void-handling scheme. The greedy-forwarding scheme consists of basic mode and optional mode. In the basic mode, when receiving a data packet from upstream node, intermediate nodes within its forwarding area contend to relay it by waiting for a dynamic forwarding delay (DFD), which is computed based on its own position relative to the upstream node and destination node. The intermediate node with minimum DFD transmits the data packet first and other nodes cancel their scheduled transmission for the same data packet by overhearing its packet forwarding. In the optional mode, upstream node can send data packets to its specified downstream node as long as the communication link between them is valid. An accurate link forecast scheme is used to compute the valid time based on location and mobility information of upstream and downstream nodes. In the void- handling scheme, a one-hop flooding method is introduced to overcome communication void problem. Finally, simulation results show that CGR outperforms LAR1 and BLR protocols in terms of end-to-end delay and packet delivery ratio.