Existing routing protocols for mobile ad hoc networks assume that all nodes have the same transmission range. In other words, the mobile ad hoc network has symmetric links, which means that two neighboring nodes A and B are within the transmission range of one another. However, since nodes consume battery power independently according to their computing and communication load, there exist asymmetric links, which means that node A is within node B's transmission range, but not vice versa. In this paper, two approaches are presented to support routing in the existence of asymmetric links: GAHA (GPS-based Hop-by-hop Acknowledgment) and GAPA (GPS-based Passive Acknowledgment) schemes. Both GAHA and GAPA can be applied to any routing protocols by utilizing GPS (Global Positioning System) location information. Simulation results reveal that both GAHA and GAPA protocols cope well in the presence of asymmetric wireless links and nodes' mobility.