Performance tradeoffs in mobile computing: to fetch or not to fetch?

As portable wireless devices have become commonplace today, the popularity and acceptance of a broad range of mobile applications is higher than ever. Acceptable user experience warrants low latency of execution of computational tasks on the mobile terminals, which, owing to their portability requirements, are typically constrained in memory. It is hence important to judiciously fetch new tasks from application servers while background applications are running on the device. In this work we use a dynamic programming (DP) framework to capture the tradeoff between congestion caused due to background tasks running on a mobile device and latency of execution of new tasks fetched from a central server over a time-varying wirelesschannel. Adopting a baseline model for wireless channel variations, rate of task execution, and congestion experienced at a mobile terminal, we establish the optimality of a switchover policy, which makes a decision to fetch or not depending on the number of tasks queued up for the mobile terminal at the central server and at the mobile terminal itself. We use the policy iteration methodology to develop an approximation to the optimal control and leverage it to design a low complexity heuristic algorithm FON (fetch-or-not). We illustrate our approach via numerical examples and also discuss severals modeling extensions to the baseline scenario.