Two messages are generated for every sensor for every
event. It means an XSM detecting an event sends two messages per sensor
per event, for a total of six messages. With our assumption of six events
per hour and a per-hop retransmission factor of 1.43 per event-detection
message, me = 52.
mpp: Number of event-detection messages routed by the heaviest-loaded XSM
every hour.The heaviest-loaded XSM is the one close to the base station.
Every event generates two messages per sensor from every XSM that detects
this event. The number of XSMs that detect an intruder type appears
in Table 3. These numbers depend on the topology of the sensor
network deployed [16] and the assumption that intruders always cross
through the network via least-covered paths. Assuming both the intruder
types are equally likely to occur, every event results in the generation
of 2 ?ยค ((30 + 30 + 5) + (10 + 0 + 0))/2 = 75 messages (using the values
from Table 3). The routing used in the ExScal application [25] balances
the routing load on eight XSMs that are within one hop of the base station.
Therefore, the most energy constrained XSM routes an average of
10 messages for every event. Assuming a retransmission factor of 1.43, it
will transmit an average of 15 messages for every event. Since six events
are assumed to occur every hour, 90 event detection messages are routed
by the most energy constrained XSM every hour. Therefore, in ExScal,
mpp = 90.
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