Telecommunication Network

1. TelecommunicationNetwork Course Details Semester 1, 2006

2. Prof. Madya Dr Mahamod Ismail • Lecturer in UKM since 1987. • Diploma - UTM (Electrical Communication), 1981 • BSc. – Univ of Strathclyde (Electronics & Electrical) ,UK, 1985 • MSc – UMIST, Manchester (Communication Eng. & Digital Electronics), 1987 • PhD – Univ of Bradford, Mobile Communication, 1996 • Research Area – Mobile Communication & Wireless Networking • Team Engineer, Tiungsat, 1997-98, Uni. of Surrey, U.K. • Guest Professor, University Duisburg Essen, Germany , 2002 • Currently: Coordinator UKM Mercator Office, Fac. of Eng. UKM • Email: mahamod@eng.ukm.my, dr_mbi@yahoo.com • Telephone: 019-3275425, 03-89216191/6322 KT6123

3. Syllabus – Program Booklet KT6123 – TELECOMMUNICATION NETWORK Switching system engineering: Types of public switched network. Switching system: circuit, store and forward, packet. Numbering, routing system and charging. Subscriber function. Telephone system basic requirement. Telephone equipment characteristics. Local circuit and hybrid transformation. Dialing system: decadic and DTMF. Subscriber and group switching. Analog and digital switching. Switching: Strowger, cross-bar and time and space. Digital analysis. Controlling sections. Stored Programmable Controlled exchange. Signaling: subscriber, line and register. Transmission system: FDM and PCM 30/32 channel. CCITT, CCIR function in switching planning. Digital Network: ISDN, SDH. Teletraffic Engineering: telephone traffic performance. Teletraffic and queuing theory. Delay and loss system, Grade of service. Erlang and Bernoulli distribution. Broadband network: ATM and B-ISDN. Intelligent network. KT6123

4. Course Outline • Introduction • Transmission • Multiplexing and Hierarchy • Switching • Telecommunication Traffics • Switching Network • Signaling • Services KT6123

5. References 1. J.E.Flood, Telecommunications Switching, Traffic and Networks, Prentice Hall, 1994 2. E.H. Jolley, Introduction to Telephony and Teleplay, Pittman Publication. 3. Schwartz, M., Telecommunication Networks Protocols, Modelling & Analysis, Addison-Wesley 4. Clarke, M.P., Network & Telecommunications: Design & Operation, Wiley KT6123

6. Evaluation • 2 Assignments 30% • Midterm exam 20% • Quiz 10% • Final exam 40% KT6123

7. Assignment 1 • Report • Format 1 • Content 5 • Discussion/Conclusion 2 • References 2 • Presentation 5 KT6123

8. TelecommunicationNetwork Introduction Semester 1, 2006

9. Introduction • Tele/communications • The process of transmitting a message between two remote locations. • Message - could be Voice, Music, Textual, Pictorial (graph, diagram, image, etc.) or moving image (video). • Recently we have a better proportion of data communications links and speech is being converted into digital forms as well as “data” will eventually be conveyed more naturally in these digital forms. • The purpose of telecommunications is to convey information from one location to another. • Data : Precise communication • Voice : More convenient to convey information, that’s why voice communication has predominated for over a century • The telephone network, until the last decade, was almost entirely analog KT6123

10. Communication Telecommunication Introduction KT6123

11. Introduction • Broadband : • is a technique where the data to be transmitted is sent using a carrier signal, such as a sinusoidal wave. Many different frequency carrier signal can be transmitted simultaneously, more than one signal can be sent on the same wire. • Baseband : • a single data signal is transmitted directly on a wire. The data is transmitted directly on the wire using positive and negative voltages. RS-232 interface is an example of baseband transmission. • A baseband signal • is an information signal that has not undergone the modulation process. • represents voice, data, or video information signal. • must be band-limited before being used to modulate a carrier signal. KT6123

12. Introduction • When data (or any other signal) is to be conveyed outside one’s place, this involves the modulation of the broadband signal onto a carrier frequency, either by • Amplitude Shift Keying (ASK) • Frequency Shift Keying (FSK) • Phase Shift Keying (PSK) • or Combination of the ASK and PSK (QPSK, /4-PSK, DQPSK) • In baseband signal recently, speech is being conveyed by Pulse Code Modulation (PCM) • The standard digital voice channel that available in today has a capacity of 64 Kbps, or a multiplexed of 1.544Mbps [T1], 2.048Mbps [E1] KT6123

13. Transmitter Receiver Transmission Channel Telecommunication System Input Transducer Encoder Modulator Amplifier Air, Free Space Copper Cable Optical Fiber Output Transducer Decoder Demodulator Amplifier KT6123

14. Telecommunication System Information signal output Information signal input Encoder Modulator/ Transmitter Transmission Channel Demodulator/ Receiver Decoder Free-space loss Reflection Refraction scattering Multipath Diffraction Shadowing Noise Interference KT6123

15. Telecommunication System • Transducer : transform one form of Energy into another • eg. Sound Electrical • Transmitter : amplifies and processes the electrical replica of message for transmission • Receiver : amplifies and processes the received elctrical signal in reverse manner to recover the original message • Transmission Channel : a path connecting Transmitter [Tx] to Receiver [Rx], which is characterized by attenuation • Factors involve in a communication system: • Type of information (data, text, graphic, voice, music, multimedia, etc.) • Information format (analog, discrete, digital, random, deterministic, periodic etc.) • Transmission speed (low, medium, high, etc.) • Transmission medium (wired, wireless) • Transmission distance (short, medium, long) • Modulation techniques (AM, PM, ASK, PSK, GMSK, PCM, OFDM, etc.) • Error control (BCD, Gray, Morse, ASCII, FEC, cyclic, etc.) KT6123

16. Telecommunication System KT6123

17. Transmission Mode • Simplex transmission • Only one way communication • Half duplex transmission • Two ways communication, but one at a time; not simultaneously • Full duplex transmission • Simultaneously in both directions • Unicast, Multicast, Anycast, Broadcast KT6123

18. Half Duplex versus Full-Duplex KT6123

19. Modes of transmission • Asynchronous • Each character is considered a unit of information • All timing and error checking is included within it • Synchronous • Information is sent as a block of data • Control and error checking information is added to each block KT6123

20. Asynchronous transmission 1 0 0 0 0 1 1 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0 1 0 1 0 0 modem modem Stop bit Start bit Characteristics: Efficiency (1000 character transmission) Data is sent one character at a time Control / overhead bits: 1 start and stop bits per Each character has a start and 1, 1.5, or 2 stop bits character Synchronization is reestablished for each character 2 control bits per character x 1000 characters = 2000 Time between character is unsynchronized and of control bits random length 7000 data bits / 9000 total bits = 77.7% efficient Synchronous transmission 1 0 0 0 0 1 1 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0 1 0 1 0 0 modem modem Synchronization character Characteristics: Efficiency (1000 character transmission) Data is sent as a block of uninterrupted characters Control / overhead bits: 48 total control bits per block Synchronization characters precede and follow the using HDLC data block 48 control bits per block x 1 block = 48 control bits The data block may be 1000 uninterrupted characters 7000 data bits / 7048 total bits = 99.3% efficient Synchronization is maintained whether data is actually being sent and detected or not Modems remain synchronized during idle time Asynchronous versus Synchronous KT6123

21. Asynchronous Transmission • Each character is sent independent of the next (or previous character sent) • Before each character is a START bit • Time between each character is not constant • Requires control bits for each character sent (for error checking) • At the end of each character is a STOP bit • At least 3 of 9 bits (for a 7 bit code) sent are not information but overhead. Hence this is inefficient KT6123

22. Synchronous Transmission • Information is transmitted in a block of bits • Each block is preceded by a sequence of bits called a preamble • Each block ends with a sequence of bits called a postamble • Control bits are added to allow error checking • The data plus preamble plus postamble plus control information is called a Frame. • Much more efficient as compared to Asynchronous transmission • More complex and expensive to implement than Asynchronous KT6123

23. Receiver |0|1|0|1|1|0|1|1| |0|1|0|1|1|0|1|1| Sender Receiver Sender Serial versus Parallel Transmission • Serial mode • Message is sent one bit at a time • Parallel mode • Each character is sent over a different wire, simultaneously • The size of messages depends on its context • Credit card authorization = 1000 bits • One page typed memo = 15000 bits • One second of digital voice = 56000 bits • One second of Full motion video = 100 million bits KT6123

24. Transmission Topology KT6123

25. Transmission Topology KT6123

26. Transmission Topology As the area covered by a star network and the number of stations served by it grow, line costs increase and it then economic to divide the network into several smaller network served by its own exchange KT6123

27. PSTN Topology KT6123

28. PSTN • Transmission links/nodes • Customer nodes • Switching nodes • Transmission nodes • Service nodes • Subsystem • Transmission systems • Switching systems • Signalling system KT6123

29. Telecommunication Standard KT6123

30. Telecommunication Network • Bearer Service provides a "transport system" for exchanging information • Tele-services complete… includes functions for connection, and a uniform "language" for communication and for shaping the messages conveyed Example: two telephones talk to each other via telephone network Also, Voice/Data/Text/Image etc KT6123

31. Typical Network Services • PSTN(Public Switched Telephone Network) • PLMN(Public Land Mobile Network) • PSPDN(Packet Switched Public Data Network) • ISDN(Integrated Services Digital Network) • Frame Relay • Signaling Network(CAS/CCS) • Internet • IN(Intelligence Network) KT6123

32. Network Services Teleservices – depend on particular terminal apparatus e.g. telephone, teleprinter Bearer Services – transmission capacity that can be used for any desired function e.g. private circuit KT6123

33. Network Services KT6123

34. More About WANs • Virtual private networks (VPNs): • A private network configured within a public network • Can be built on top of the Internet • Service offered by the telephone companies and ISPs KT6123

35. Value added networks (VANs): • Public data networks that “add value” by transmitting data and by providing access to commercial databases and software • Use packet switching • Subscription based • Often used in electronic data interchange (EDI) systems KT6123

36. Public switched data network technologies (PSDN) • Data flows through a public network managed by a telecommunications carrier • Most common technologies: • ISDN (integrated service digital network) • X.25 • Frame relay • Asynchronous transfer mode (ATM) KT6123

37. (example of Frequency Modulation) KT6123

38. ASK/FSK/PSK KT6123

39. Sending Multiple Bits Simultaneously Each of the three modulation techniques can be refined to send more than one bit at a time. It is possible to send two bits on one wave by defining four different amplitudes. This technique could be further refined to send three bits at the same time by defining 8 different amplitude levels or four bits by defining 16, etc. The same approach can be used for frequency and phase modulation. KT6123

40. Sending Multiple Bits Simultaneously KT6123

41. Hybrid Amplitude and Phase modulation • QAM : Quadrature Amplitude Modulation • represents 4 bits per baud (I.e. V = 16) 90o 8 phase changes 2 different amplitude levels Therefore V = 16 135o 45o 0o 180o 315o 225o Used in ITU V.32 modems 270o KT6123

42. Digital Encoding of Analog Signals (PCM) • Concept: • Take samples of analog signal. To each sample - assign a code. Then transmit that code (digital signal). • If we sample at the rate of twice the bandwidth of the channel then the resulting digital signal contains all the information in the original analog signal - Nyquist’s theorem (1924) KT6123

43. PCM - Pulse Code Modulation Samples time Each is assigned a n bit binary code KT6123

44. PCM • Transmitting an analog signal over a digital network (eg. Voice on telephone n/w) • Each signal is sampled 8000 times per second • Each sample is converted to a 7 bit code • 1 bit is added for control information • there are 128 different such codes (27) • The digital signal is then transmitted at 64,000 = 64 Kbps = 8*8000 KT6123

45. Differential PCM • Voice signals do not change extremely rapidly • Changes of more than +/- 16 levels between samples is very rare • Hence use just 5 bits instead of 7 to represent each sample • If signal jumps very widely then several samples are needed to “catch up” KT6123

46. Delta Modulation • Voice signals do not change very rapidly • Transmit only one bit at each sample (indicating a +1 or -1) to indicate whether the signal is increasing or decreasing. • Amplitude of next sample differs from previous one by 1 unit (either +1 or -1). • If very rapid changes take place then the coding takes a while to “catch up” KT6123

47. Problems (Delta Modulation) Samples cannot keep up with rapidly changing signal time KT6123

48. Predictive Encoding • Both sender and receiver extrapolate from the last few values received to predict what the next value would be. • The transmitter sends a value only if it were different from what is predicted KT6123

49. Data transfer in the presence of noise • Shannons Law: C = B * log2 (1 + S/N) where: • C = achievable channel capacity • B= Bandwidth of line (in Hz) • S = Average signal power • N = Average Noise power • S/N = Signal to Noise Ratio • this is usually measured in decibels (dB) • where dB = 10 * log10 (S/N) KT6123

50. Telephone Channel Capacity Voice Channel 0-4,000 Hz Voice Bandwidth 300-3,300 Hz Voltage Guard Band Guard Band 0 300 3,300 4,000 Frequency (Hertz) KT6123