What is an embedded system?
Some definitions:
*) Embedded Systems are information processing systems embedded into larger inclosing products
*) The invisible computer; Computers that normally are not directly visible to the user
*) Computers dedicated to specific task(s)
Provide a definition and an example of “cyber physical system”.
Cyber physical systems are engineered systems that are built from and depend upon the synergy of computational and physical components.
-> CPS bring together sensing, computation, communication, control and actuation in order to sustain continous interaction with the physical world
Uses: Smart power-grid, transportation and traffic roads, building of automation systems
Give an example of system that fits the following descriptions and explain why.
1.) Rice cooker: If deadline is not met, rice could still edible but at one point it will be burned
2.) Netflix: real-time streaming, but not embedded into bigger system
3.) Airbag-system of a car: Catastrophic consequences if deadline is not met
-> An embedded system is called reactive if it ca correctly predict and respond to sensor inputs and environmental stimuli.
(meines Erachtens falsch, da es nicht predicted, oder?)
What does Dennard Scaling postulate? Why did it end around 2006? What is the consequence of the end of Dennard scaling?
Dennard: In every technology generation, if the transistor density doubles, the circuit becomes 40% faster and power consumption stays the same.
End of the scale:
What are the properties of an embedded system that distinguish them from general-purouse computers?
-> Reactivity and timing
-> Predicatbilitsy and dependability
-> Efficiency and specialization
What do reactivity and timing of an embedded system mean?
-> The embedded system must react to stimuli from the environment in a timely manner
-> Real-time constraints must be met!
-> Ensuring taht real-time constraints are met requires appropriate scheduling of tasks and analysis of worst-case performance
Which real-time constraints do you know and what happens if the constraint is not met?
-> hard real time: missing the deadline may cause a catastrophic result (e.g. air-bag system)
-> firm real time: missing the deadline renders the result useless but causes no damage (e.g. TO DO)
-> soft real time: missing the deadline degrades the performance but still has some utility
What does it mean for an embedded system to be predictable?
-> The system has to behave as predicted at the design time, despite changes in the environment, sensor inputs, internal states etc.
-> predictability may refer to
-> timing (guarantee real-time constraints)
-> performance (guarantee to operate for a given time)
-> functional proportions (guaranteeing that operations follow a given order)
-> Predictability is achieved by using models and context awareness
What does it mean for an embedded system to be dependable?
-> The embedded system should provide correct functionality that can be relied on by the user
-> Attributes of dependability:
-> availability (readiness for correct service)
-> reliability (continuity of correct service)
->maintainability (easily repair and maintain the system)
-> safety (no catastrophic consequence in case of a failure)
-> integrity (absence of improper system alteration)
-> confidentiality (protection of information and access to the system)
llustrate briefly the difference between errors, faults, and failures.
fault -> error -> failure
-> fault: a defect, can be software or hardware
-> error: system enters an incorrect internal state due to an activation od a fault (unobserved)
-> failures: a system displays behavior that is contray to it specification (observed)
Important: An error not necessarily causes a failure
How can failures be prevented?
-> fault prevention
-> fault removal
-> fault forecasting
-> fault tolerance
What does the efficiency of an embedded system mean?
Embedded system have to be efficient in terms of
-> cost
-> power consumption
-> size
-> weight
etc.
Effieciency does not mean limited resources!
How can the efficiency of embedded systems be improved?
use of:
-> small code size
-> specialized hardware
-> specialized software
-> spezialized communication protocols
-> energy harvesting techniques to achieve long-term autonomous operation
What does the specialization of an embedded system describe?
Embedded system are often designed towards specific tasks.
Used to achieve efficiency, as no resource is used for tasks that are not required by the application domain.
Exploits knowledge about the known behavior and the system environment at design time to minimize resource usage.
What is a distributed architecture?
Systems are built by connecting together nodes that cooperate and provide services for other nodes to use their local components.
What are advantages and challenges of distributed systems?
advantages:
-> thinner cable bundles
-> higher flexability
-> higher performance
-> easier debugging and maintainability
-> scaleability
-> fault-tolerance
-> modularity
challenges:
-> synchronization
-> coordination
-> communication
-> security
What is a networked embedded system?
Embedded systems not only communicate with each other but also with the internet, forming the internet of things (IoT). The IoT enables applications and services that leverage the data and capabilities of embedded devices.
What are challenges with networked embedded systems?
-> Interoperability
-> Scalability
-> Security
-> Privacy
What is cloud computing?
Cloud computing refers to the use of remote servers to store and process data from embedded devices.
It is used to offload heavy computations from embedded devices and provide additional services such as data-analytics and machine learning.
What challenges come with cloud computing?
-> Latency
-> bandwidth consumption
-> security tasks
-> dependancy on network availability
What is edge computing?
Use of local servers or devices to perform computations near the data source.
What are the advantages of edge computing in comparison to cloud computing? What are the drawbacks?
It reduces:
-> Bandwidth consumption
-> security risks
-> network dependancy
Drawbacks:
-> requires more resources on the edge device or servers
->
What is Moore’s law?
The number of transistors on a cost-effective chip doubles every year.
-> The predicted curve has started to slow down
Since around 2016 it is not cost-efficient any more for companies to keep up with Moore’s law.
What is Kryder’s law?
The cost of storage per unit of information decreases more than half every two years.
What is Bell’s law?
Every roughly 10 years a new class of computers emerges
What is Koomey’s law?
For about half a century. the number of computations per joule of energy dissipated doubled every 1.5 years.
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