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Internet of Things Prof. M. Cesana Exam– September 10, 2012 Family Name Given Name Student ID Course of studies Total Available time: 2 hours E1 E2 E3 Questions Questions OS 1 – Exercise (8 points) A personal area network (PAN) is operated according to the IEEE 802.15.4 beacon enabled mode. • The Collision Access Part (CAP) of the superframe is composed of 20 slots. • The inactive part of the beacon interval is composed of 2000 slots. • The duty cycle is 2%. • Each slot (of CAP and CFP) carries 127 [byte] packets. • The nominal data rate is 250 [kb/s]. 1. How many slots are available in the CFP? 2. What is the rate of the channel defined as “one slot per beacon interval”? Using the numbers found in 1 and 2, suppose that two motes (Mote 1 and Mote 2) are active in the PAN with the following traffic patterns Ø Mote 1 and Mote 2 have statistical (non-deterministic) traffic towards the PAN coordinator characterized by the following probability distribution: § P(required rate=1200 [bit/s])= 0.3 § P(required rate=600 [bit/s])= 0.3 § P(required rate=200 [bit/s])= 0.4 3. Define a consistent slot assignment in the CFP for the two motes (the motes do not use the CAP). 4. How many additional motes requiring a channel of 120 [bit/s] could be added to the network? 5. Find the average energy consumption of the two motes (assume that the two motes do not overhear the transmissions of each other). The total energy for receiving in a slot is Erx=20 [uJ], the total energy to transmit in a slot is Etx=30[uJ], the energy of being idle in a slot is Eidle = 15 [uJ] and the energy for sleeping in a slot is Esleep = 0.5 [uJ] 6. Assume now that the two motes start transmitting one packet (each) at the same time t=0 in the CAP. What is the average success time (time to the successful…