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Internet of Things, Exam– February 18, 2015 Available time: 1h 45m 1 – Exercise (6 points) A wireless sensor network is composed of three nodes and a sink. The three nodes mount temperature sensors and are set to deliver 1 temperature sample to the sink at a frequency of 2 [Hz]. The temperature sample is carried by packets with size L=128[byte]. Assuming that: the energy for acquiring one temperature sample is Es=40[uJ], the energy required to operate the TX/RX circuitry is Ec=50 [nJ/bit], the energy required to support sufficient transmission output power Etx(d)= k d2 [nJ/bit], being k=1 [nJ/bit/m2], the energy for processing one temperature sample Ep=20[uJ], d=5[m] and r=5[m] 2- Exercise (6 points) A sensor network runs the IEEE 802.15.4 protocol and is composed by 5 sensor nodes directly connected to the PAN Coordinator. The Beacon Interval is composed of CFP slots only and each slot can carry a packet of size L=127[byte] and the nominal rate is R=250[kbit/s]. The sensor nodes have the following traffic requirements: • Sensor 1, Sensor 2: need a channel of 100[bit/s] with probability 0.5, and a channel of 25 [bit/s] with probability 0.5 • Sensor 3 and 4 need a channel of 500[bit/s] • Sensor 5 needs a channel of 50 [bit/s] Find out a feasible structure for the BI indicating the CFP duration, the slot duration, the duty cycle and the number of slots assigned to each terminal. Assuming that the energy consumed in a slot for receiving/transmitting is E=40[uJ], the energy for overhearing other nodes’ transmission is Eov= 30[uJ], the energy for being idle is Ei=10[uJ], and the energy for sleeping is Es=1[nJ], find out the energy consumption for the sensor nodes assuming that sensors 1, 3 and 5 are in range (and viceversa) and sensor 2 is in range of sensor 4 (and…