Cyber-Physical Systems

422 Cyber-Physical Systems: From Theory to Practice

In this chapter, we assume that a laser beam is projected to one cell at a time with a cluster forming

time interval, T, for each cell. T should be just long enough to allow the sensors in a cell to form a

cluster, but not so long as to cause unnecessary delay for the operations between cells. In general, T

is a function of sensor density—n (the number of sensor nodes in a cell), radio propagation delay τ

and IEEE 802.11 MAC layer back off delay β in its CMSA/CA protocol with p as a probability of

package collision in the form of

T = n

2

βp + nτ + c (17.1)

where c is a constant for initial delay from sensing the light signal to transmitting the data. With

this assumption, a sensor node can only belong ...