ts, a is typically in the range of 2 to 5. SNR SNR, Equivalently, (3.7.2) Therefore, an increase in sensor density by a factor of k Therefore, the power advantage of an N-hop trans- improves the SNR at a sensor by 10 log k db. mission versus a single-hop transmission over the same distance Nr is 3.7.3 Sensor network applications (3.7.1) A sensor network is designed to perform a set of high- level information processing tasks such as detection, tracking, or classification. Measures of performance for Figure 3.7-3 illustrates the power attenuation for the these tasks are well defined, including detection of false multihop and single-hop networks. A larger N gives alarms or misses, classification errors, and track quality. a larger power saving due to the consideration of RF Applications of sensor networks are wide ranging and can energy alone. However, this analysis ignores the power vary significantly in application requirements, modes of usage by other components of an RF circuitry. Using deployment (e.g., ad hoc versus instrumented environ- more nodes increases not only the cost, but also the ment), sensing modality, or means of power supply (e.g., power consumption of these other RF components. In battery versus wall-socket). Sample commercial and practice, an optimal design seeks to balance the two military applications include: conflicting factors for an overall cost and energy effi- Environmental monitoring (e.g., traffic, habitat, ciency. Latency and robustness considerations may also security) argue against an unduly large number of relay nodes. Industrial sensing and diagnostics (e.g., appliances, factory, supply chains) 3.7.2.2 Detection advantage Infrastructure protection (e.g., power grids, water distribution) Each sensor has a finite sensing range, determined by the Battlefield awareness (e.g., multitarget tracking) noise floor at the sensor. A denser sensor field improves Context-aware computing (e.g., intelligent home, the odds of detecting a signal source within the range. responsive environment) O