1. Network Technology CSE3020 1 Network Technology CSE3020 Week 13

2. Network Technology CSE3020 2 Network Technology  Local Area Networks Ethernet and Token Passing Networks  Wireless Networks Cellular Networks and Wireless LAN  Wide Area Networks ATM and ISDN  Residential Area Networks ADSL, Cable TV  Basic Data Communications Theories Data transmission Coding & Modulation Multiplexing & Switching Transmission Media

3. Network Technology CSE3020 3 Simplified Network Model

4. Network Technology CSE3020 4 OSI Model

5. Network Technology CSE3020 5 OSI Model

6. Network Technology CSE3020 6 TCP/IP Protocol Architecture

7. Network Technology CSE3020 7 OSI and TCP/IP

8. Network Technology CSE3020 8 Computer Networks Token Ring, FDDI Encoding & Modulation Router PCM WLAN Capacity Bridge Ethernet Residential Area Networks ATM Application Presentation Session Transport Network Data link Physical Backbone

9. Network Technology CSE3020 9 Sine Wave  Peak Amplitude (A) - maximum strength of signal, generally in volts.  Frequency (f) - rate of change of signal. - Hertz (Hz) or cycles per second. - Period = time for one repetition (T). - T = 1/f  Phase (  ) - r elative position in time.  Wavelength ( ) - Distance occupied by one cycle. - = vT where v is signal velocity.  General sine wave: s(t)=Asin(2  ft +  ).

10. Network Technology CSE3020 10 Frequency Domain Concepts  Signal are usually made up of many frequencies.   Components are sine waves.  Fourier analysis: Can plot frequency domain functions. Any signal is made up of sine waves.

11. Network Technology CSE3020 11 Transmission Impairments Attenuation Noise Delay Distortion  Signal received may differ from signal transmitted.  Analog - degradation of signal quality.  Digital - bit errors  Impairments: Attenuation, Delay distortion & Noise

12. Network Technology CSE3020 12 Channel Capacity  Maximum rate at which data can be transmitted.  Nyquist Theorem: Maximum bit rate on a noise-free channel.  Shannon Theorem: Maximum bit rate on a noisy channel. C = 2 B log 2 M bits/sec C = B log 2 (1 + S/N) bits/sec channel bandwidth signal-to-noise ratio

13. Network Technology CSE3020 13 Data Encoding  Digital data  digital signal (Encoding/Decoding)  Analog data  digital signal (Digitization/Conversion)  Digital data  analog signal (Modulation/Demodulation)  Analog data  analog signal (Modulation /Demodulation) Data and Signals:

14. Network Technology CSE3020 14 Signaling/Modulation Rate  Signaling/Modulation rate –Rate at which the signal elements are transmitted. –Measured in baud = signal elements per second. –For binary signaling, bit rate = baud rate.  Data rate - Rate of data transmission in bits per second.  Bit rate = Baud rate  Number of bits per signal element.

15. Network Technology CSE3020 15 Interpreting Signals Need to know: Timing of bits/signals and Signal levels. Factors affecting successful interpreting of signals: – Signal to noise ratio, Data rate and Bandwidth An increase in data rate increases bit error rate (BER). An increase in SNR decreases bit error rate. An increase in bandwidth allows an increase in data rate.

16. Network Technology CSE3020 16 Encoding Schemes  Nonreturn to Zero-Level (NRZ-L)  Nonreturn to Zero Inverted (NRZI)  Bipolar-Alternate Mark Inversion (Bipolar-AMI)  Pseudoternary  Manchester  Differential Manchester  Bipolar with 8-zeros substitution (B8ZS)  High-density bipolar-3 zeros (HDB3)  Signal Spectrum.  Clocking.  Error detection.  Signal interference and noise immunity.  Cost and complexity.

17. Network Technology CSE3020 17 Digitization  Analog to digital conversion: PCM & Delta Modulation.  If a signal is sampled at regular intervals at a rate higher than twice the highest signal frequency, the samples contain all the information of the original signal.  Voice data limited to below 4000Hz - Require 8000 sample/second.  Samples are quantized: Quantizing error or noise.  Each sample assigned digital value (4 bit system gives 16 levels).  Equally spaced level: Uniform Quantization.  Non-equally spaced level: Non-uniform Quantization

18. Network Technology CSE3020 18 Pulse Code Modulation(PCM)

19. Network Technology CSE3020 19 Modulation  Analog modulation: - Amplitude Modulation (AM) - Frequency Modulation (FM) - Phase Modulation(PM)  Why modulate analog/digital signals? –Higher frequency can give more efficient transmission. –Permits frequency division multiplexing. –Unguided Transmission needs high frequencies. –For practical antenna size.  Digital modulation: –Amplitude shift keying (ASK) –Phase shift keying (PSK) –Frequency shift keying (FSK)

20. Network Technology CSE3020 20 Spread Spectrum  Spread data over wide bandwidth.  Makes jamming and interception harder.  Frequency hopping: - Signal broadcast over seemingly random series of frequencies. - Receiver hops between frequencies in synchronization with transmitter.  Direct Sequence: - Each bit is represented by multiple bits in transmitted signal by a chipping code. - Chipping code spreads the signal across a wider frequencies.

21. Network Technology CSE3020 21 Transmission Media Guided Transmission: –Twisted Pair - Unshielded Twisted Pair (UTP) - Shielded Twisted Pair (STP) –Coaxial Cable –Optical Fiber Unguided (wireless) Transmission: –Terrestrial Microwave –Satellite Microwave –Broadcast Radio –Infrared

22. Network Technology CSE3020 22 Transmission Media Electromagnetic waves. Characteristics and quality determined by medium and the transmitted signal. Key concerns are data rate and distance. Design Factors: –Bandwidth. –Transmission impairments. –Interference. –Number of receivers. Each transmission media: –Limitations & characteristics. –Pros & Cons. –Applications.

23. Network Technology CSE3020 23 Asynchronous and Synchronous Transmission Transmission requires cooperation and agreement between the two sides. Fundamental requirement is Synchronization: Receiver must know the beginning and end of a bit/rate at which bits are received. –Asynchronous transmission –Synchronous transmission Asynchronous transmission: –Each character treated independently and begins with a start bit. –Not good for long block of data. Synchronous transmission: –Block of data is formatted as a frame with a starting and an ending flag. –Good for block of data.

24. Network Technology CSE3020 24 Multiplexing  Multiplexing.  Demultiplexing.  Different types:  Frequency division multiplexing (FDM).  Time division multiplexing (TDM).  Synchronous TDM  Statistical TDM  Code division multiplexing (CDM).

25. Network Technology CSE3020 25 Switching Circuit switching & Packet switching. Circuit switching: designed for voice. - Dedicated communication path between. - Data rate is fixed. Both ends must operate at the same rate. Packet switching: designed for data networks. –Data transmitted in small packets. –Longer messages split into series of packets. –Each packet contains a portion of user data plus some control information: Routing (addressing). –Packets handled in two ways. –Datagram: No call setup phase and More flexible –Virtual circuit: Sequencing and error control, Fast, Less reliable.

26. Network Technology CSE3020 26 Data Link Control Flow control: Preventing buffer overflow at the receiver. - Stop-and-wait & Sliding window. Error control: Detecting and correcting transmission errors. -Parity check & Cyclic Redundancy Check (CRC). Automatic Repeat Request (ARQ): Error & Flow Control. - Error detection & Retransmission. - ARQ schemes. -Stop-and-Wait. -Go-back-N (retransmission from error frame). -Selective Repeat (selective retransmission). -ARQ efficiency: -Unnecessary waiting and sending unnecessary transmission. High Level Data Link Control (HDLC).

27. Network Technology CSE3020 27 Local Area Network (LAN) LAN applications. LAN Architecture: - Protocol architecture. - Topologies. - Media Access Control. - Logical Link Control. LAN devices: - Repeaters - Bridges - Hubs & Switches.

28. Network Technology CSE3020 28 Local Area Networks (LANs) LAN products fiber twisted pair coax air (wireless) bus star ring tree FDDI Ethernet Token ring Wireless LAN random access token passing polling IEEE ISO, ATM Forum MAC protocols standard bodies topologies transmission media

29. Network Technology CSE3020 29 LAN Types Ethernet: Token ring network. FDDI ATM LANE. Backbone network.

30. Network Technology CSE3020 30 Wireless LAN (WLAN) WLAN advantages. WLAN design considerations. WLAN types/products. WLAN topology/architecture. WLAN MAC protocol (CSMA/CA). Hidden station & exposed station problem.

31. Network Technology CSE3020 31 Asynchronous Transfer Mode (ATM) ATM characteristics. ATM Protocol reference model. ATM logical connections: Virtual paths & circuits. ATM Cell. ATM Service characteristics.

32. Network Technology CSE3020 32 ATM Protocol Reference Model Higher Layer ATM Adaptation Layer (AAL) ATM Layer Physical Layer Management Plane Control PlaneUser Plane Layer Management Plane Management

33. Network Technology CSE3020 33 Residential Area Networks  PSTN:  ISDN:  ADSL:  Cable modem: