This document discusses system architecture and operating systems for wireless sensor networks and embedded devices. It defines system architecture as the structure and organization of a computing system consisting of hardware and software modules that enable data exchange. It then describes several operating systems used for wireless sensor networks and embedded devices, including TinyOS, Contiki, Mantis, Windows CE, eCos, QNX, and XMK. It explains key aspects of each operating system such as scheduling, concurrency, programming models, and dynamic reprogramming capabilities.

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M.Tech[EST]

2.  A System Architecture is a combination of
different hardware & software components or
modules which enable exchange of data
between the client & server (or) sender &
receiver.

4.  The structure and organization of a computing
system, as a set of functional modules and their
interactions.
 Node Intervals
 Interaction of Nodes

5.  It presents the possible abstraction levels in a
single node.
 Operating systems, the simplest approach,
provide basic system functionality including a
uniform way of accessing the hardware.

6.  The two main sets of functionalities, namely
low-level functionalities, including tasks
corresponding to physical, link, routing and
transport layers.
 The high-level functionalities are coordination
and support, clustering, timing and localization,
addressing, lookup, collaboration, failure
detection and security.

7.  In a data-centric approach, the execution is
controlled by the data.
 For example, on the basis of the type of
incoming data, the appropriate function is called
which is able to handle this type.
 Sensor network scenarios are said to be data-
centric.

8.  A service is a well-defined and self-contained
function that does not depend on the context or
the state of other services.
 The service is executed on the explicit request
of a caller, who has to know the interface of the
service. A response is returned after the
completion of the service.

9.  An operating system (OS) is system software that
manages compute
hardware and software resources and provides
common services for computer programs.
 The different operating systems for COs,unlike
general purpose desktop operating systems such
as Windows or Linux, these operating systems run
on devices that are designed for special-purpose
tasks.

10.  The main tasks of these operating systems is to
provide an abstract interface to the underlying
hardware and to schedule system resources.
 The three operating systems used in WSN
namely TinyOS,Contiki, and Mantis.
 TinyOS does not provide any multithreading
 Contiki provides multithreading as a library for
those applications that explicitly require it.
 Mantis is a layered multithreaded operating
system.

11.  Microsoft Windows is the most common
operating system for desktop computers.
 Windows XP Embedded is a modular cut-down
version of XP that allows the designer to choose
the modules to be used.

12.  Since Linux is open source, anyone can
customize Linux to his/her PDA, Palmtop or
other mobile or embedded device.
 RTLinux (Real-time Linux), an extension of the
Linux kernel that provides real-time entities.
 uClinux, a scaled-down Linux version for
system without a memory mapping unit.
 Montavista Linux with Linux distributions for
ARM, MIPS.

13.  The Palm OS is specifically designed for PDAs
featuring a small screen, with less processing
power than desktop PCs and limited memory.
 In Palm OS, the kernel is responsible for thread
scheduling, handling hardware interrupts and
other low-level management tasks.
 Although Palm-applications are single-
threadded, the kernel itself uses multiple
threads.

14.  Symbian OS is a robust multi-tasking operating
system, designed specifically for wireless
environments and the constraints of mobile
phones.
 The core kernel’s size is less than 200 KB. The
OS has support for handling low memory
situations and a power management model.
 Symbian OS runs on fast, low-power, low-cost
CPU cores such as ARM processors.

15.  In contrast to Windows XP Embedded,
Windows CE has a different codebase than
Windows XP. Windows CE is particularly
designed for small hand-held devices.
 Windows CE is a multitasking operating system
allowing multiple applications or processes to
run within the system simultaneously.
 According to Microsoft, the code size is 200 KB
without graphics, but the code size increases
dramatically when graphics and networking are
included.

16.  eCos has extensive configuration possibilities
and can be scaled up from a few hundred bytes
in size to hundreds of KB.
 eCos provides features such as pre-emptable
tasks with multiple priority levels, low latency-
interrupt handling.

17.  It is a Unix-like operating system with real-time
properties, and is the most prominent example
of a successful micro-kernel design.
 The micro-kernel is surrounded by cooperating
processes that provide higher-level services
such as inter-process and low-level networking
communication
 QNX is designed for systems running x86,
MIPS, PowerPC or ARM CPUs.

18.  XMK (eXtreme Minimal Kernel) is an open-
source real-time kernel designed to fit very
small micro-controllers, yet be scalable up to
larger systems.
 A minimal kernel configuration requires only
340 bytes of ROM and 18 bytes of RAM.

19.  TinyOS is an operating system specially
designed for the constraints and requirements
of WSNs.
 It is currently the most widely used system for
academic research in the area of sensor
networks.
 TinyOS is available for several platforms.

20.  Scheduling Hierarchy
 Concurrency
 Programming
 Dynamic Reprogramming

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M.Tech[EST]