Design of Repairable Sensor Networks
In this chapter the service and estimation availability and reliability of sensor networks that are subject to corrective maintenance are studied. Finally, a minimum cost model is presented.
As it was discussed in Chapter 10, when repairs are not present, the service availability of a sensor is equal to its service reliability. In addition, the failure rate has been considered constant. However, in the presence of repairs, failure is no longer an event that depends on how many hours the sensor survived from the time it has been put in service. It is also conditioned by the fact that maintenance is made and/or the sensor has been repaired at a certain time after being put in service. These events condition the failure rate. Thus, we distinguish unconditional from conditional events in failure and repair. These concepts are first formally introduced to be later used to determine sensor maintenance cost, which accounts for nearly 20% of all maintenance cost (Masterson, 1999). Its reduction or containment is essential.