We present a radio telemetry solution for remote sensor networks that uses rotational actuation of directional antennas. The benefits of this solution over either omnidirectional or fixed directional antennas for intra-nodal communications include greater energy efficiency, sparse node deployment, and robustness to node failure. Four strategies for minimizing link acquisition time are presented. Each strategy uses a search algorithm tailored to a unique combination of radio hardware to provide

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... odes with coordination and/or geolocation capabilities. These strategies are implemented on a two-node testbed and their performance is measured in a realistic field trial. Results show that the use of secondary radios for search coordination and geolocation provide an order of magnitude reduction in search duration. In particular, the strategy using only search coordination yields performance that is independent of node separation while performance of the strategy using only geolocation is strongly dependent on range. I. INTRODUCTION An important class of sensor networks are those that enable the monitoring of time-critical phenomena in remote terrestrial regions. These networks find application in seismology, meteorology, security, and environmental studies [1, 2, 3, 4] . A lack of energy, transportation, and communication infrastructure in these regions requires that a practicable system be energy self-sufficient, convenient to deploy and maintain, and able to establish its own communication network for real-time sensor telemetry. Radio communications between sensor-nodes is an attractive telemetry solution in the context of remote sensor networks because it accommodates ad hoc deployment. Energy conscious link level and network level solutions to radio telemetry design are the topic of growing interest [5, 6, 7, 8] . However, the focus has thus far been on networks whose nodes are equipped with omnidirectional or fixed directional antennas. We propose a link level strategy for radio telemetry that is sensitive to the energy, deployment, and real-time telemetry requirements of remote sensor networks but differs from other approaches by employing rotational actuation of directional antennas. This strategy accommodates greater options for link range and energy efficiency than omnidirectional antennas while maintaining a level of flexibility in network topology not possible with fixed directional antennas. We present a set of field-tested node configurations that evaluate four options for minimizing link acquisition times during the stage immediately following deployment in which the nodes autonomously assemble a fully connected network.