We investigate the technique of the task migration from mobile terminals to computation servers over the wireless network. In the perceived architecture, the mobile terminals are assisted by the network infrastructure in the execution of their computational tasks. Thus, the terminal has two basic options (and combinations of them): \bullet Local Execution, that is execute the tasks locally, or \bullet Remote Execution, which involves (1) sending the tasks to a computation server over the wireless network, (2) executing the tasks at the server, and (3) downloading the computation results back to the terminal. The latter provides energy savings for the terminal (sparing its local processor) and execution speed gains (the server is usually much faster than the terminal), but incurs some overhead as well, resulting from the terminal \leftrightarrow server wireless communication. The net gains, if any, are dependent on (i) the degree of the connectivity between the terminal and the network server, and (ii) the server load. Both these two parameters fluctuate with time; the former due to the varying network load and the volatile wireless channel, and the latter due to the sharing with other clients at the server. To decide optimally on the execution policy, we introduce a Markovian framework. We then study the associated energy vs. delay trade-offs, and assess the performance gains attained in various test cases compared to the conventional paradigms of the exclusively local/remote execution.