Download Code-Division-Multiple-Access - Computer Networks - Old Exam Paper and more Exams Computer Networks in PDF only on Docsity!
Cork Institute of Technology
Bachelor of Science (Honours) in Software Development – Stage 2
(NFQ Level 8)
Summer 2006
Computer Networks
(Time: 3 Hours)
Answer 4 questions, at least ONE from Section 1 and ONE from section 2 All questions carry equal marks.
Examiners: Ms. D. Griffin Dr. J. Twomey Dr. M. O Cinneide Mr. M. Donnelly
Section 1
Q1. (a) Explain with the aid of diagrams the difference between 'Baud Rate and Bit Rate? (5 marks) (b) A PC generates data at a rate of 21kbps. The data is encoded providing symbols each containing 128 binary levels prior to entering a transmission line. What is buad rate on the line and the required bandwidth of the line? (5 marks) (c) Discuss and explain the concept of sampling. A data spectrum has frequency components up to a maximum of 30Khz. Determine the minimum sampling rate required without any loss in information content. (5 marks) (d) What is PSK, use diagrams to illustrate your answer. Show the PSK constellation diagram for a system where the bandwidth required is reduced by a factor of three compared with the base requirement. (5 marks) (e) A telephone line has a bandwidth of 4000Hz and a Signal-To-Noise ratio of 36dB What is the maximum date rate for error free transmission? (Note log 2 X = 3.32xlog 10 X). (5 marks)
Q2. (a) Explain the main features of CDMA (Code-Division-Multiple-Access) Technologies. What are the main advantages and disadvantages of CDMA Technology? (5 marks) (b) Draw a block diagram of a frequency-hopped CDMA system and explain its operation. (6 marks) (c) In a slow binary Frequency -Hopped System FH-SH at one bit per hop the tone separation between '1' from ‘0’s is 60Hz in an FSK system. Determine the transmit frequency bandwidth BH to guarantee adequate separation and also the overall spreading or system bandwidth Bs if the frequency synthesiser has 18 addressing inputs. (6 marks) (d) Outline the basic construction of a fiber distributed data interface(FDDI) frame. Briefly define the functionality of the various components. (4 marks) (e) The latency of an FDDI optical ring consisting of 300 stations is 400 microseconds. Additionally the latency per station is one microsecond. Determine the total or composite latency both in microseconds and also in terms of bits of delay assuming a transfer rate 200Mbps. (4 marks) .
Q3. (a) Explain the differences between hardware addressing, IP addressing and Ports. List one well known port number. (5 marks) (b) Compare and briefly describe the following types of multiplexing namely TDM, FDM and Statistical Multiplexing. (5 marks) (c) A number of low utilisation terminals each operating at 1200bps are to be connected to a leased line operating at 24000bps via a multiplexor. What type of multiplexor would you use and estimate the maximum number of terminals that may be employed? (5 marks) (d) Explain the terms BRI and PRI applicable to the European ISDN standard. What is overhead? (4 marks) (e) What are the essential features of ATM (Asynchronous Transfer Mode)? What are the main components of an ATM cell? Briefly outline some of the advantages of ATM over Frame Relay? (6 marks)
Q5. (a) Host A wishes to send a frame to Host B, but does not know Host B’s Ethernet address. What protocol is used to determine this, and using frame diagrams explain in detail the operation of this protocol.
HOST A IP: 157.191.41. MAC: 04:54:FA:22:AC:
HOST B IP: 157.191.41. MAC: 2C:22:A6:2e:33:
HOST C IP: 157.191.41. MAC: 4D:11:3B:44:1C: (8 marks)
(b) What are the main concerns when using a Link State Routing algorithm? (3 marks) (c) In what way does OSPF solve many of the problems associated with Routing Information Protocol (RIP)? (4 marks) (d) In the context of Routing, what does the term convergence mean? (2 marks) (e) Routing Information Protocol (RIP) suffers from a problem known as Counting to Infinity. What does this means and provide one way that RIP overcomes this problem? (3 marks) (f) What is the Routing Algorithm, and outline in detail its main parts? (5 marks)
Q6. (a) What are the main properties of Ethernet? Explain in detail the operation of the protocol Carrier Sense Multiple Access\Collision Detect (CSMA\CD)? (4 marks) (b) Why is minimum frame size so important in the above protocol? (3 marks) (c) Using a table state the media characteristics of the main types of networking media? (4 marks) (d) With the aid of a diagram outline the structure of fibre optic cable, and state its advantages. (4 marks) (e) What’s the function of the Domain Name Service (DNS)? What does DNS allow and how does it work? (5 marks) (f) In classical cryptography, what is a Polyalphabetic cipher? Using the key and plaintext below, produce the corresponding ciphertext. Key IAMINDCOM Plaintext WEARETHEKEY Ciphertext
(5 marks)
