22 09 15 1

Page 1

Internet of Things, September 22, 2015 Available time: 2h Exercise 1 (4 points) Exercise 2 (6 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 1600 slots and the duty cycle is 2.02%. Each slot (of CAP and CFP) carries 127 [byte] packets. The nominal data rate is 250 [kb/s]. How many slots are available in the CFP? What is the rate of the channel defined as “one slot per beacon interval”? Using the numbers found above, suppose that two motes (Mote 1 and Mote 2) are active in the PAN with the following traffic patterns Ø P(amount of data generated in one BI=508[byte])= 0.3 Ø P(amount of data generated in one BI =0 [byte])= 0.3 Ø P(amount of data generated in one BI=635 [byte])= 0.4 Define a consistent slot assignment in the CFP for the two motes (the motes do not use the CAP). What is the total capacity of the CAP? Exercise 3 (6 points) The three nodes in the figure mount temperature sensors and are set to deliver 1 temperature sample to the sink at a frequency of 2 [Hz] for a total time of 10[s]. 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] Questions (10 points) 1. A SPARE MAC network is characterized by the following parameters: number of slots in the signaling sub frame N=10, number of slots in the data sub frame M=12, slot duration…