Question 1: Network Design
Consider a square area of 100m x 100m. You want to detect the presence of rodents (say rats) in this area using Mica 2 motes equipped with a motion detector whose range is 2m and powered by a 2000 mAh battery. Each mote with its sensor board costs 100 USD. The table below lists the power consumption and other attributes for for various activities for the mica mote.
| Component/Activitiy |
Rate |
Startup Time |
Current Consumption |
| MCU active |
4 MHz |
N/A |
5.5mA |
| MCU idle |
4 MHz |
1 s |
1.6mA |
| MCU suspend |
32 kHz |
4ms |
<20 s |
| Radio transmit |
40 kHz |
30 ms |
12 mA |
| Radio receive |
40 kHz |
30 ms |
1.8 mA |
| Photoresister |
2000 Hz |
10 ms |
1.235 mA |
| Motion detector |
100 Hz |
10 ms |
5 mA |
| Accelerometer |
100 Hz |
10 ms |
5 mA/axis |
| Temperature |
2 Hz |
500 ms |
0.150 mA |
Your monitoring application should run continuously for 6 months. Every time a rat is detected a message should be sent to a server (through gateway(s)).
Describe a solution to this problem: discuss node placement, choice of gateway(s), sensing strategy, routing strategy, duty cycling and the cost of your solution. Also explicitly state all assumptions that you make.
Question 2: Security
Due to the lack of a centralized authority, it is not easy to manage node identity in large-scale networks. One possible attack is for an attacker to capture nodes in the network, duplicate their identities (including secure credentials), and insert them back into the network. The attacker will then be able to launch other attacks using the replicated/fabricated nodes. Propose a solution to detect such node replication attacks. You must clearly outline your protocol in detail and state all assumptions. Including an illustrative example demonstrating your solution is also strongly recommended.
Question 3: Routing
Fig. shows a network topology, where Node S is the source node and Node D is the destination node. A 0 to 1 number beside an arrow shows the link quality Packet Reception Rate (PRR) of an asymmetric wireless link; for example, the PRR from Node a to D is 0.9 (90%). The numbers inside the brackets beside a node is the X, Y co-ordinates of a node; for example, the coordinates of Node c is (1, 2).
(a) If the nodes run Collection Tree Protocol (CTP) that uses expected number of transmissions (ETX) as routing metric. What is the path between Nodes S and D? What is the path ETX?
(b) If the nodes run Greedy Perimeter Stateless Routing (GPSR), assumed the radio range of a node is p2, what is the path between Nodes S and D? Note that GPSR assumes circular link model and does not take link quality into account.
Question 4: Outlier detection
Fig. shows the two-dimension values of 10 sensors. What are the Local Outlier Factor (LOF)1, LOF3, and LOF5 of Nodes 1, 3, 5, 7, 9?
The sensor values of the nodes are:
| Node ID |
X |
Y |
| 1 |
116 |
91 |
| 2 |
91 |
102 |
| 3 |
99 |
136 |
| 4 |
107 |
116 |
| 5 |
75 |
91 |
| 6 |
79 |
87 |
| 7 |
231 |
172 |
| 8 |
255 |
219 |
| 9 |
203 |
206 |
| 10 |
190 |
223 |
