L7 Flashcards
Define node clustering in IoT networks
- It aggregates nodes into groups (clusters) to facilitate deployment and operation when base stations are far away
Considerations of node clustering in WSNs
- sensor nodes are densely deployed
- sensor nodes are prone to failure
- Topology of WSN can change frequently
- Sensor nodes mainly use broadcast
- Sensor nodes are limited in power, computation capacity, and memory
- Sensor nodes may not have global ID due to large number of sensors
What is the need of structuring node clusters and two deployment techniques?
- Necessary for maintaining power efficiency among nodes
- Types: regular and random
Explain regular and random deployment techniques
- Regular: follows standard geometric shapes (i.e. triangle). Offers best possible coverage.
- Random: randomly distributed. Nodes need to discover neighbours by themselves.
Draw an schematic of rectangular cluster topology (L7 7)
write on paper
How are nodes distributed in a randomly-distributed scenario?
- Nodes are randomly distributed over an area (A) with a Poisson distribution
Draw schematic of flat homogeneous network topology (L7 10)
write on paper
Draw schematic of hierarchical network topology (L7 11)
write
Draw schematic of heterogeneous network topology (L7 12)
write
Draw schematic of cellular structured cluster (L7 13)
write
Explain how the cluster-head is selected using highest connectivity algorithm and draw schematic (L7 14)
- Node with highest connectivity degree is chosen
Explain idea of mobility-based clustering algorithm
- Adaptative algorithm which keeps track of any mobility events within the network
- Node with higher mobility is not elected as cluster-head
Why is localization crucial for IoT?
- Nodes are mostly mobile, accurate data requires accurate positioning
- nodes need to collaborate and exchange data from time to time
- If a node fails, a backup node is needed
4 Common localization metrics
- Time of arrival (TOA): propagation delay is used to estimate travelled distance
- Time difference of arrival (TDOA): requires two or more receivers to calculate time delay difference and find position
- Angle of arrival (AOA): signal phase used to calculate distance
- Received signal strenght (RSS):
Draw an schematic of 2D localization using three anchors (L7 23)
write
Draw an schematic of TOA-based ranging (L7 24, 27)
write
How can we use TOA when there is no direct path to localize a node?
- use amplitude and propagation delay of non-direct path (NDP)
- requires highly-sensitive receiver
How can we eliminate the effect of multipath fading in the RSS localization metric?
- By averaging the signal over a longer period
- Effect of signal bandwidth is negligible
Draw an schematic of RSS based ranging (L7 32)
write
Compare TOA and RSS techniques (L7 33)
write
Examples of 2D geometric triangularization techniques
- 2D localizations require at least 3 anchors
- Least-square algorithms
2 types of cooperative localization in WSNs
- centralized: processing performed in the cloud
- distributed: processing performed in the same network nodes
