29 Questions
In which mode are system calls executed after interrupting the user processes?
Kernel-mode
What are some situations where system calls are typically made by user level programs?
Manipulating files, managing processes, network connections, accessing hardware devices
What happens once the execution of a system call is completed?
Control returns to the user mode
Which of the following is NOT a typical situation for making system calls by user level programs?
Creating animations on the screen
What purpose do system calls serve in the context of accessing hardware resources?
Allow users to access hardware without worrying about low-level details
What is one of the challenges in Wireless Sensor Networks related to multi-hop communication?
Increased latency
How is power conservation managed in Wireless Sensor Networks?
By switching off radios when not in use
What is one strategy mentioned for Wake-up and demand Duty Cycling in Wireless Sensor Networks?
Node can wakeup whenever needed
Why is centralized management often not feasible in Wireless Sensor Networks?
Energy constraints and large scale of networks
What is a key advantage of decentralized (or distributed) solutions in Wireless Sensor Networks?
Better performance than centralized solutions
How do nodes manage Adaptive Duty Cycling in Wireless Sensor Networks?
A subset of nodes remain active to form a network backbone
What is the purpose of task scheduling in an operating system?
To organize, prioritize, and execute tasks efficiently
Which type of data types in Wireless Sensor Networks (WSN) consume more resources but have strong expressive power?
Complex data types like structs and enums
What distinguishes a single-user operating system from a multi-user operating system?
Ability to allow only one user at a time vs. multiple users concurrently
Which aspect of an operating system focuses on handling interruptions and system calls?
Scheduling
What plays a key role in determining the efficiency of an operating system?
Task Scheduling
Why are simple data types preferred in Wireless Sensor Networks (WSN)?
Because they consume fewer resources and provide limited expressive capability
What is a major concern in resource-constrained processors?
Efficient execution of algorithms
Which architecture employs a single memory space for program instructions and data?
Von Neumann architecture
Why are special-purpose, energy-efficient processors not suitable for tasks requiring frequent updates or remote debugging?
Lack of processing space
What type of processors are considered the best option for dynamic code installation and update in WSNs?
Microcontroller
Which aspect of a processor subsystem involves the transferring of information from and to memory?
Program instructions and data transfer
In the context of processor subsystems, what do program instructions relate to?
Communication, self-organization, data compression, and aggregation algorithms
What is the main reason for needing dynamic reprogramming in wireless sensor networks?
To enhance network performance
Why is manual replacement not considered feasible in the context of wireless sensor networks?
It may introduce bugs and errors
What is a key requirement for an operating system to support dynamic reprogramming effectively?
Clear separation between application and OS
Why is portability important for operating systems in wireless sensor networks?
To accommodate unforeseen requirements
What role does an operating system play in dynamic reprogramming?
Updating software components in the right order
Why should operating systems ideally be portable and extensible?
To accommodate unforeseen requirements
Study Notes
Wireless Sensor Networks (WSN)
- WSNs face challenges in wireless networking, including:
- Multi-hop communication, which increases latency and error probability, and is complicated by power conservation policies.
- Decentralization, as centralized management is often not feasible due to the large scale of the network and energy constraints.
Power Conservation Policies
- Duty Cycling is used to conserve power:
- Wake-up and demand duty cycling: nodes can wake up when needed, using a low-power radio to receive wake-up calls and a high-power radio to respond.
- Adaptive duty cycling: not all nodes sleep at the same time, and a subset of nodes remain active to form a network backbone.
Operating System (OS)
- System Calls:
- Users invoke system calls to access hardware resources, such as sensors, watchdog timers, or radios.
- Steps involved: user mode, system call execution in kernel-mode, and returning to user mode.
Functional Aspects of OS
- Data Types:
- Interactions between subsystems occur through well-formulated protocols and data types.
- Data types include complex types (struct and enum) and simple types (C programming language).
- Scheduling:
- Task scheduling organizes, prioritizes, and executes tasks to determine OS efficiency.
- Two scheduling mechanisms are used.
Node Architecture: Processor Subsystem
- A major concern is efficient execution of algorithms, requiring transfer of information from and to memory.
- Processor subsystem can be designed using one of three basic computer architectures: Von Neumann, Harvard, or Super-Harvard (SHARC).
Non-Functional Aspects of OS
- Portability:
- OS should be able to co-exist and collaborate with other OS.
- Existing OS do not provide this support.
- Dynamic Reprogramming:
- Necessary for unforeseen requirements, including changes in network performance, application requirements, or environment.
- Requires clear separation between application and OS, and OS support for updates and assembly.
Test your knowledge on challenges faced in Wireless Sensor Networks, such as multi-hop communication, increased latency, failure probability, and power conservation policies.
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