In a wireless mobile computing system such as ad hoc network or sensor network, it is very difficult to manage resources - the precious bandwidth shared by the mobile terminals and the energy in each mobile terminal - in an efficient manner, due to the lack of network infrastructure support. The difficulties are aggravated by the fact that the wireless link is highly unreliable with high-error rate and bursty errors, and thus, is a CSI (channel state information) dependent time-varying function. In this paper, we consider two important issues in mobile computing systems - routing in wireless ad hoc network and energy management in sensor network. We argue that the time-varying property of the wireless link can have a great influence on these two issues, and propose two schemes - channel adaptive routing in ad hoc network and channel adaptive energy management in sensor network under such CSI fluctuating environment. As indicated in our numerical studies, our proposed schemes outperform other algorithms without channel adaptation in that higher network throughput and energy efficiency are achieved in their respective application scenarios.