02 09 16

Pagina 1

Internet of Things, September 2, 2016 Total Available time: 1.45 hours 1 – Exercise (6 points) A Personal Area Network is operated according to the IEEE 802.15.4 standard and is composed of 20 sensor nodes and a PAN Coordinator (only Collision Free Part, nominal data rate, R= 250[kbit/s], packet length, L=128[byte]). 15 sensor nodes (out of 20) require an equivalent rate of r [bit/s], whereas the remaining 5 sensor node require twice that rate (2r [bit/s]). Assuming that the network administrator sets a duty cycle of 1%, find the maximum allowed value for r, and the corresponding Beacon Interval duration (assume to assign one slot in the CFP to each mote requiring a rate of r…). 2 – Exercise (6 points) Sensor node 1 and Sensor node 2 are equipped with cameras and collect images with size I=12.8[kbyte]. The two sensors have to deliver the images to Sensor 3 by using packets whose length is L=128[byte]. Assuming that: the energy required to operate the TX/RX circuitry is Ec=2 [uJ/packet], the energy required to support sufficient transmission output power Etx(d)= k d2 [nJ/packet], being k=120 [nJ/packet/m2], find the total energy consumption (energy consumed by Sensor 1, Sensor 2 and Sensor 3) to deliver one single image each in the following two cases: • Sensor 1 and Sensor 2 send directly the images to Sensor 3 . • Sensor 1 sends the image to Sensor 2, Sensor 2 sends to Sensor 3 its own image and a compressed version of Sensor 1’s image (compression ratio 0.1, that is, the compressed image has size 0.1 I). In this case the energy required by Sensor 2 to compress the image is Ep= 0.1 [uJ] for each packet of the original uncompressed image. 3 – Exercise (5 points) A RFID system based on Dynamic Frame ALOHA is composed of 4 tags. Assuming that the initial frame size is…