Transcript Diapositiva 1

Homework # 5
A square room with side 26 m must be equipped with sensor nodes distributed along
its walls. A sink is located in the centre and a star topology is established.
Assume the free space conditions are met (i.e. Pcon is one or zero). 802.15.4 with BE mode
without acknowledgements is used, whose performance chart is attached.
The sink sends a period query by means of the beacon whose length is 30 bytes to all nodes
in order to receive samples. On average, nodes stay in backoff/sensing state for a period
of 6 ms, and then they transmit a data burst whose length is 30 bytes.
They move to sleep state after transmission of their packet, till the end of the superframe.
The sensor nodes data sheets report the following: the power consumed in backoff/sensing ,
transmission, reception or sleep state is 30, 45, 40, 0.001 mW, respectively; transmit power
and receiver sensitivity are 0 dBm and -92 dBm respectively. The node is equipped with
external dipole antennas.
The requested network lifetime is eight months, and nodes are equipped with batteries
having an initial charge of 25 000 J. The average number of samples received by the sink after
each query must be larger than 5.
1) Determine the minimum query interval fulfilling the requirement on network lifetime.
2) Determine the minimum number of sensor nodes to deploy in the room.