Pre-deployment tests of sensor networks in indoor testbeds can only
deliver a very approximate view of the correctness and performance of a deployed
sensor network and it is therefore common that after deployment problems and
failures occur that could not be observed during pre-deployment tests. Finding
and fixing such problems requires visibility of the system state, such that an en-
gineer can identify causes of misbehavior. Unfortunately, exposing the internal
state of sensor nodes requires resources such as communication bandwidth and
energy: the better visibility of system state is required, the more resources are
needed to extract that state from the sensor network. In this paper we propose a
concept and tool that give the user explicit control over this tradeoff. Essentially,
the user can specify a resource budget and our tool strives to provide best possible
visibility while not exceeding the resource budget. We present the design of our
vLevels framework and report the results of a case study demonstrating that the
overhead of our approach is small and that visibility is automatically adjusted to
meet the specified resource budget.