Cross-layer design has been a hot topic in the last few years in wireless networking research due to the fact that the traditional layering network protocol suite such as TCP/IP for wired networks are no longer efficient in wireless networks, particularly true for multi-hop wireless ad hoc networks. Although there are many papers on cross-layer design, few of them really touch upon the essence of the cross-layer design, most of them still cross physical layer and link layer for one-hop transmissions and do not reveal the real layering coupling of multiple layers. There are indeed a few papers that formulate the cross-layer design as an optimization problem and attempt to optimize all layers. Unfortunately, most optimization problems are either too difficult to solve (often may not have feasible solutions), or too idealistic to come up with practical cross-layer solution. In this talk, the speaker will present a novel approach to cross-layer design: boosting the network performance while keeping the implementation practical. This approach attempt to use the MAC layer as the anchor and extract/abstract the information about the channel environment using certain novel metrics (such as the channel busyness ratio) and then tie these parameters to higher layer performance optimization. He will use a few design examples(distributed flow/congestion control and medium access, the wireless congestion control protocol , and multi-user diversity) to demonstrate the more appropriate way to do cross-layer design.