The notation for the parameters used in lifetime analysis appears in Table
4. In the following, we derive the values or expressions for those parameters
whose values are not straightforward to calculate or whose values are variable
(in the context of the ExScal application).
tlpl
slp: Sleep period of the radio in the LPL mode. It can take a value of 0.01,
0.02, 0.05, 0.1, 0.2, 0.4, 0.8, or 1.6 seconds [20].We do not use sleep periods
of 0.8 seconds and 1.6 seconds in our analysis because the notification
latency requirement of 2 seconds can not be satisfied with these sleep
periods.
7 The per-hop reliability was close to 1 in the absence of interference but was 0.7
in the presence of interference (as is the case in an operating sensor network).
8 The value of 1.43 is an approximation. The actual value will be lower than 1.43
because the maximum times a packet was transmitted was 3, whereas in geometric
distribution the maximum number of trials is assumed to be infinite (trials are
made until there is a success).
272
Table 4. Notations for parameters used in the lifetime analysis and their values in
ExScal. The values of the parameters that are variable are derived in Section 4.2.
Identifier Meaning Value
ebattery Usable capacity of the batteries 1800
mA-hr
iproc
act Current drawn by the processor in active mode 8 mA
irad
act Current drawn by the radio in active mode 8 mA
irad
tx Current drawn by the radio in transmit mode 16 mA
tpkt
tx Time to transmit a packet 0.
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