Challenges

Fault tolerance
- Nodes can
  - Get damaged
  - Run out of power
  - Lose comms
- Redundant deployment
Lifetime
- Limited energy supply
- Replacing sometimes not practical
  - Underwater
  - Large/remote field deployments
- Energy efficient a necessity
Scalability
- WSM can have lots of nodes
- Architectures and protocols need to scale
Densities
- Density of network can vary
  - Granularity
  - Coverage
- Different applications warrant different numbers
  - Range of nodes
  - Space and time requirement
- Not necessarily homogenous density throughout
  - Need to handle this
Programmability
- Flexible nodes with changing tasks
- Changeable programs during operation
Maintainability
- WSN and environment can change
- Adaptable system
- Changing operational parameters
  - To increase energy efficiency for example

Node Types

Sensor
- Low power
- Sensing, memory, processor, radio
- Resource-constrained
Sink
- Another sensor node
  - Or different wireless node
- Normally more powerful/better resources
Gateway
- Bridge IoT and internet networks
- More powerful
- Can have
  - Service representation
  - Cache/storage
  - Discovery

Event detection
- Reporting event occurrences
- Reporting abnormalities
- May need collaboration with other nodes
- Defining events and classification difficult
Periodic measurements
- Sense something and report
- Period is application-dependent
Approximation and pattern detection
- Sense messages in space and time
- E.g. combine wind, light, heat to detect forest fires
Tracking
- Source of event is mobile
- Event updates with location information