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In the distributed operations of route discovery and maintenance, strong interaction occurs across mobile ad hoc
network (MANET) protocol layers. Quality of service (QoS) requirements of multimedia service classes must be
satisfied by the cross-layer protocol, along with minimization of the distributed power consumption at nodes and along
routes to battery-limited energy constraints. In previous work by the author, cross-layer interactions in the MANET
protocol are modeled in terms of a set of concatenated design parameters and associated resource levels by multivariate
point processes (MVPPs). Determination of the "best" cross-layer design is carried out using the optimal control of
martingale representations of the MVPPs.
In contrast to the competitive interaction among nodes in a MANET for multimedia services using limited resources,
the interaction among the nodes of a wireless sensor network (WSN) is distributed and collaborative, based on the
processing of data from a variety of sensors at nodes to satisfy common mission objectives. Sensor data originates at the
nodes at the periphery of the WSN, is successively transported to other nodes for aggregation based on information-theoretic
measures of correlation and ultimately sent as information to one or more destination (decision) nodes. The
"multimedia services" in the MANET model are replaced by multiple types of sensors, e.g., audio, seismic, imaging,
thermal, etc., at the nodes; the QoS metrics associated with MANETs become those associated with the quality of fused
information flow, i.e., throughput, delay, packet error rate, data correlation, etc. Significantly, the essential analytical
approach to MANET cross-layer optimization, now based on the MVPPs for discrete random events occurring in the
WSN, can be applied to develop the stochastic characteristics and optimality conditions for cross-layer designs of sensor
network protocols. Functional dependencies of WSN performance metrics are described in terms of the concatenated
protocol parameters. New source-to-destination routes are sought that optimize cross-layer interdependencies to achieve
the "best available" performance in the WSN. The protocol design, modified from a known reactive protocol, adapts the
achievable performance to the transient network conditions and resource levels. Control of network behavior is realized
through the conditional rates of the MVPPs. Optimal cross-layer protocol parameters are determined by stochastic
dynamic programming conditions derived from models of transient packetized sensor data flows. Moreover, the
defining conditions for WSN configurations, grouping sensor nodes into clusters and establishing data aggregation at
processing nodes within those clusters, lead to computationally tractable solutions to the stochastic differential
equations that describe network dynamics. Closed-form solution characteristics provide an alternative to the "directed
diffusion" methods for resource-efficient WSN protocols published previously by other researchers. Performance
verification of the resulting cross-layer designs is found by embedding the optimality conditions for the protocols in
actual WSN scenarios replicated in a wireless network simulation environment. Performance tradeoffs among protocol
parameters remain for a sequel to the paper.
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