DOEACC Society 2006 DOEACC C Level CE7 - Real Time Systems( ) - Question Paper

CE7-R3: REAL TIME SYSTEMS
NOTE:
Time: three Hours Total Marks: 100
1.
a) What do you understand by clock synchronization?
b) elaborate the properties, which should be satisfied by a transaction in a conventional
database?
c) Why do static priority task scheduling algorithms needs less run time overhead
compared to the dynamic priority task scheduling algorithms?
d) provide 2 reasons why deadlock detection is more practical than deadlock avoidance.
e) Why can any interactive application be considered as a kind of real-time system?
f) elaborate the features of Real Time CORBA suitable for distributed real time systems?
g) Can hardware fault-tolerance techniques be easily adapted to give software faulttolerance?
(7x4)
2.
a) elaborate the roles of sensors, actuators and controllers in real-time systems? provide
examples of these from practical systems. Depict the general structure of a real-time
system by using a schematic diagram, clearly showing the controller, actuators and sensors.
b) In providing system-level fault-tolerance, why are hardware failures more predictable and
easier to handle compared to software failures? discuss the N-version scheme to give
software fault-tolerance. elaborate the shortcomings of this scheme?
c) explain the important performance parameters, which you would consider to select
ranging from 2 real-time computers.
(6+6+6)
3.
a) What do you understand by temporal data? provide a few examples of temporal data. Can
any database containing temporal data be called a real-time database? explain.
b) Would you prefer an optimistic concurrency control protocol or a pessimistic concurrency
control protocol for use in real-time database systems? Would your option depend on
the load on the system? discuss your ans.
c) discuss a disk-scheduling algorithm, which can satisfactorily be used in real-time
applications.
(6+6+6)
4.
a) Why is debugging and testing of real-time software more difficult than traditional
software? discuss how real-time software can be efficiently debugged and tested.
b) Consider a 10Mbps token ring network. The walk time is one mSec. The shortest deadline
among various messages is 10mSec. The frame size is 512 bytes. Determine the
maximum time for which a message may undergo priority inversion under IEEE 802.4
and IEEE 802.5 protocols.
c) What issues would you experience if you used a contention-based protocol such as
Ethernet for real-time task communications? define a contention-based real-time
communication protocol and discuss how it overcomes the issues that Ethernet
suffers from.
(6+6+6)
CE7-R3 Page one of two January, 2006
1. ans ques. one and any 4 ques. from two to 7.
2. Parts of the identical ques. should be answered together and in the identical
sequence.
5.
a) Is EDF algorithm used for scheduling real-time tasks a dynamic priority-scheduling
algorithm? Does EDF calculate any priority value of tasks any time? If yes, discuss
when it is calculated and how it is calculated. If no, discuss what is the concept of priority
in EDF then.
b) Determine whether the subsequent set of periodic tasks is schedulable on a uniprocessor
using RMA ignoring situation switch overhead.
Task Processing-time (mSec) Period (mSec)
T1 28 100
T2 70 200
T3 60 400
Now, Suppose situation switch overhead of one milli Seconds is to be taken into account,
determine the schedulability.
c) What do you understand by exception handling? discuss how you can handle
exceptions using a programming language of your option.
(6+8+4)
6.
a) Why are concurrency control protocols required? Identify the reasons why 2PL is not a
suitable protocol for use in real-time databases. How can it be replaced for use in realtime
database?
b) Why is Real-Time Linux more suitable to support real-time applications compared to the
traditional Unix system. discuss your ans with respect to a few of the important
features needed to support running real-time applications. Can Real-Time Linux be
used in embedded applications?
c) Examine the pros and cons of using an object-oriented language for real-time application
development.
(6+8+4)
7.
a) discuss how clock synchronization can be achieved in a distributed real-time system.
Why does presence of Byzantine faults makes clock synchronization issue difficult?
What is the minimum number of clocks necessary to ensure proper synchronization in
the presence of m Byzantine faults?
b) Are supports for pointer data kind and pointer arithmetic desirable for a programming
language used in real-time application development? discuss your ans.
c) What do you understand by the term “delay jitter” in a real-time communication
application? Identify at lowest 2 factors, which contribute to delay jitter in real-time
communications and discuss how they reason jitter.
(8+5+5)
CE7-R3 Page two of two January, 2006

Earning:   Approval pending.