1. Prepared By: Dr. Abdulrahman Awadhi
T209-A Review Session
Prepared By: Dr. Abdulrahman Awadhi
B.Sc., Ph.D.

2. A bridge divides a LAN into separate collision domains.
Part 1: Answer the following True/False statements (put T or F answers in the brackets):
2.5G is an intermediate status between the second generation and the third generation mobile phone systems.
Answer [T]
A bridge divides a LAN into separate collision domains.

3. 8-bit binary equivalent of denary 68 is 01111111.
Answer [F]
3G cellular phone systems use FDMA technology.
The RAD Action object is equivalent to the I/O symbol in the flowchart.

4. The term knowledge can be defined as information coded for subsequent processing, generally by a computer.
Answer [F]

5. Part 2: Answer the following questions in the space given below each question.
Compression is a process that is often used when files are transferred across the Internet (and sometimes when they are stored, as well). What is compression and what is meant by lossless compression and lossy compression methods. Give an example on each method.
Lossless compression is a process which compresses the original binary data in such a way that it can be reconstructed exactly later on (e.g. ZIP compression). Lossy compression is a process which compresses the original binary data in such a way that it cannot be reconstructed exactly later on (e.g. MP3 coding)

6. In each country there are several companies all offering a mobile telephone system in the same physical region. Each of these companies uses radio signals to connect its subscribers’ mobile phones to its base stations. Explain how do these companies distinguish between the calls being made by their users and those being made by other users?
The radio spectrum available for GSM telephony has been divided up into various bands, and each company has been allocated just some of these bands. Thus the companies distinguish between their subscribers and those of other companies by using different sets of frequencies for the calls.

7. In the context of computers, what are (a) a bit, (b) a byte, and (c) an octet and how are they related to each other?
A bit is a binary digit. That is, it is either 1 or 0. A byte is a group of 8 bits. An octet is another name for a byte.

8. What is meant by error detection and error correction in the context of manipulating and transmitting binary data?
Error detection is a process whereby pieces of binary data are checked while they are being manipulated or transmitted, in order to discover whether an error has occurred. If an error is detected, a special action usually follows: for example a request for retransmission of the binary data, or the display of an error message.
Error correction is a process whereby pieces of binary data are checked while they are being manipulated or transmitted, in order to discover whether an error has occurred. If an error is detected, it is corrected.

9. Briefly explain the beauty or usefulness of spectrogram for speech recognition.
The power of spectrogram for speech recognition lies in the fact that it helps in tracking the shift of the formant frequencies with time – that is, the variation in the resonant frequency of the vocal tract during an utterance of speech. Since each utterance has its own distinct set of formant contours, hence this provides another acoustical characteristic to help recognize individual phonemes, and hence words.

10. What are the main duties of the TCP and IP layers in the TCP/IP protocol stack?
In OSI terms, TCP is the transport layer protocol and is concerned with end-to-end issues rather than routing messages. It provides a reliable service in the sense that it guarantees error-free transportation of messages between source and destination.
In OSI terms, IP is the network layer protocol and is concerned with routing messages across the network. It provides no guarantee that it will succeed, although it tries its best i.e. it provides a "best-effort" service.

11. Briefly discuss 2 main features of the air interface of the 2G GSM phone system. What does GPRS stand for? How does GPRS make GSM a 2.5G system?
The air interface of the GSM phone system uses the TDMA technology. It uses 8 time slots instead of 6 as used by the North American TDMA system.
GPRS stands for General Packet Radio System. It makes GSM a 2.5G system by providing it limited Data Communication capability such as the SMS data feature.

12. Radio signals are modulated onto carriers
Radio signals are modulated onto carriers. Explain the terms ‘carrier’ and ‘modulation’ in this context.
In the context of this question, the carrier will be a radio wave. Modulation is the variation of some characteristic of this radio wave (such as its amplitude, or its frequency) in accordance with the value at each instant of another signal (called the message signal) in order to make the message signal more suitable for transmission. For example, the message signal may have only component frequencies which are much lower than radio frequencies, but may need to be sent as a radio signal. Modulation makes this possible.

13. Part 3: Answer 2 out of 3 of the following questions in the space given below each question.
Consider the following diagram:
Idealized frequency spectrum of an analogue signal with cut-off frequencies f1 and f2
Let f1=10KHz and f2=5KHz.
What is the bandwidth of the above signal?
Bandwidth= f1 – f2 =10KHz-5KHz=5KHz
What is the minimum sampling frequency in order to convert the above signal into digtail form?
minimum sampling frequency=2*Bandwidth=2*5KHz=10KHz;

14. Given a propagation velocity of 1. 77x108 m/s and a delay of 3
Given a propagation velocity of 1.77x108 m/s and a delay of 3.5 µS introduced by each repeater, what is the round trip delay for two computers at either end of a 2500 m link that includes three repeaters?
The time travel between two computers is equal to the sum of the time required to travel along the cable and the delay introduced by the three repeaters. This is given by:
One-way time (t)= (d/v) + (number of repeaters x delay)
= (2500/1.77x108) + (3x3.5x10-6)=24.6 µS
The round trip delay is twice this value: 49.2 µ S.

15. Consider a sinusoidal signal
Consider a sinusoidal signal. Answer the following questions in this regard:
What is the general equation for a sinusoidal and a cosinusoidal signal?
X(t)=A sin(wt) is a sinusoidal signal
Z(t)=B cos(wt) is a cosinusoidal signal
Write the general equation for a sinusoidal signal with 0.75 the amplitude of the signal in part a).
Y(t)=0.75A sin(wt).
Write the general equation for a sinusoidal signal with half the angular frequency of the signal in part a).
Y(t)=A sin(ω/2t).
Write the general equation for a sinusoidal signal with an advance of π/4 radians.
Y(t)=A sin(wt + π/4)

16. Quiz 2: Part 1: Read all the answers and circle the most correct statement:
The ______ attempts to explore the physical aspect of ICT system to enable users to manipulate them in ways that are more similar to the ways in which we interact with one another and with the objects in the real world
virtual reality
augmented reality
visual reality
physical reality
none of the above
Answer B

17. the CSLU Toolkit is classed as a ___________ recognition system
continuous-speech
speaker-dependent
speaker-enrolment
speaker-independent
none of the above
Answer D

18. suppose that we have a signal with amplitude = 2
suppose that we have a signal with amplitude = 2.5 and the frequency = 30 Hz. Then the sinewave expression of this signal is :
x = 5 sin (20 л t)
x = 2.5 sin (30 л t)
x = 2.5 sin (60 л t)
x = 5 sin (40 л t)
none of the above
Answer C

19. __________ RAD object provides a means to execute program code directly
generic
action
media
start
none of the above
Answer B

20. The maximum Ethernet frame size is:
1518 bytes
1518 bits
64 bytes
512 bytes
None of the above
Answer A

21. The minimum Ethernet frame size is:
1518 bytes
64 bits
64 bytes
512 bytes
None of the above
Answer C

22. The repeater is related to ___________ layer
physical
data link
network
transport
None of the above
Answer A

23. The bridge is related to ______________ layer
physical
data link
Network
transport
None of the above
Answer B

24. The Gateway is related to _________________ layer
physical
data link
network
transport
None of the above
Answer C

25. The SNMP protocol is related to _____________________ layer
physical
data link
application
transport
None of the above
Answer C

26. Part 2: Fill the spaces that related to the following questions:
(1)
Line spectrum
(2)
Flow chart
(3)
Speech-based
(4)
speaker-independent
(5)
Spectrogram
(6)
Speaker-enrolment
(7)
Frames
(8)
HTD
(9)
Multimodal
(10)
Formants
interfacing is a type of human interface architecture that uses more than one modaloty of communication between user and system .
recognition system recognizes larger vocabulary than ______ recognition system .
3- the time-domain and frequency-domain representation can be combined into a
4- the black ( or dark grey) bands in the spectrogram are called
5- the diagrams convey the sequential relationship between tasks.
Answer 1(9), 2(6)&(4), 3(5), 4(10), 5(2)

27. connection less service connection oriented service
(1)
TCP
(2)
slot time
(3)
bits
(4)
connection less service
(5)
(6) IP
(7)
best effort service
(8)
bit-rates
(9)
(10)
Time
(11)
(12)
connection oriented service
(13)
(14)
CSMA/CD
(15)
UDP
1- The (2) is defined in (3) , rather than (10) , because Ethernet can operate at different (8) .
2- (6) provides a (9) .
3- (11) not provides a (7)
4- (14) provides a (13)
5- Whereas (1) provides (12) , the (15) , provides (4)
6- Whereas (5) provides reliable service, the 15) , provides (13) .

28. Part 3: Answer the following questions:
what are the main conditions that yield problems in automatic speech recognition?
Speech style
Extraneous noise
list two of the HTI system ?
GUI
Virtual reality

29. what is an ultimate goal of HTC?
The primary goal of HTC is to design and develop interfaces that enable natural and straightforward ways of communication between users and machines such as speech-based interfacing

30. Briefly show the three main stages of the isolated-word recognition system?
Stage 1 consist of capturing a digital representation of the spoken word , this representation is referred to as the waveform.
Stage 2 (spectrogram) converts the waveform into a series of elemental sound units, referred to as phonemes . so as to classify the words prior to recognition
Stage 3 (time-aligned phoneme categorization graph) uses various forms of mathematical analysis to estimate the most likely word consistent with the series of recognized phonemes

31. What are the advantages to organizations of using computer networks?
A- More efficient use of resources through sharing network elements such as printers and scanners
B- Purchasing networked application software, which may be more economical than buying individual software packages
C- Access to multiple sources of information
D- Ability to transfer information across the network
E- Opportunity for collaborative work using and conferencing facilities and to keep employees informed of the organization’s business through an intranet
F- Remote access to the organization by customers, suppliers and field workers through an extranet

32. Briefly discuss the round trip delay??
The worst case scenario occurs when a frame transmitted at one end of a collision domain collides with another frame at the farthest end
This is the worst case because this is the longest period of time for a collision to be detected by the transmitting computer, which has to wait for notice of the collision to propagate back. This time period is called the round trip delay, because it is the time it takes for a frame to take a ‘round trip’ to the furthest limit of the network

33. Why is it that, once a computer has monitored for the slot time, and detected no collisions, it can transmit the rest of its frame without risk of collision?
If no collision has been detected in the slot time, then no other computer, even the one at the furthest limits of the collision domain, has tried to transmit. Once this point is reached, then all other computers will detected the transmitting computer’s frame through the carrier-sense (CS) part of the protocol, as by this time the frame will have reached all nodes within the same collision domain

34. Why does separating the attempts to transmit, of two computers, by at least one slot time ensure they do not collide?
The slot time is chosen to allow a frame to propagate across the extremes of a collision domain and back again; called the round trip delay.
Therefore, if one computer waits for one slot time before beginning to transmit, it is certain to detect if another computer had started to transmit one slot time earlier

35. Briefly discuss the SNMP protocol?
Simple Network Management Protocol (SNMP), a standard protocol that specifies how information is carried between the agent and the network management software.

36. mention the two functions that related to RAD generic object?
First they can generate spoken prompts using either a text-to-speech synthesizer or by playing pre-recorded speech waveforms
Second they can be used to recognize spoken words …

37. Part 4: Answer the following problems: (you should show all the steps required to solve the questions)
suppose that we have an analogue signal covers the frequency range from 3 kHz to 11.5 kHz
what is the bandwidth of the signal ?
bandwidth = 11.5 – 3 = 8.5 kHz = 8500 Hz
what is the minimum sampling rate required for a signal ?
sampling rate = 2 x bandwidth = 2 x 8500 = Hz = 17 kHz

38. What is the maximum round trip delay for an Ethernet frame operating at 10 Mbit/s?
Delay = number of bits sent / bit rate = 512 / 10 × 106 seconds = 1.2 µs

39. an analogue-to-digital converter has an input voltage range of V . if the resolution of the converter is 5 bits. What is the quantization interval?
quantization interval = 11 / 25 = 11 / 32 = 0.34 volt
What is the peak level of quantization noise produced by the converter defined above?
peak quantization noise = 0.34 / 2 = 0.17

40. suppose that we have hotels reservation system
suppose that we have hotels reservation system. this system deals with four famous hotels . the different types of hotels the client wishes to be available (with the price of single room per night ) are:
Meridian 55 KD
Sheraton 50 KD
Safir International 45 KD
Crown Plaza 40 KD
Whereas the Safir Iternational and Crown Plaza hotels have only a single room , Meridian and Sheraton hotels can have both single room or suite. The suites prices are as following:
Meridian 70 KD
Sheraton 65 KD
The voice recognition interface of this hotels reservation system will provide the following functions:
Be friendly and welcoming
Ask the user to enter the hotel type
Check if they want a single room or suite in case if they choose Meridian or Sheraton hotels
Confirm that the hotel reservation is correct
Tell the user the price of this hotel
If the user agree , then the system print the reservation voucher of this hotel and finish this transaction in a friendly manner
Now you should do the following :
Clearly draw the flowchart of this hotels reservation system ?
Clearly label the symbols of this flowchart ?
Shows how errors are handled