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Data Communication Network

Data Communication Network. 331: STUDY DATA COMMUNICATIONS AND NETWORKS. 331: STUDY DATA COMMUNICATIONS AND NETWORKS. 1. Discuss computer networks (5 hrs) 2. Discuss data communications (15 hrs). 331.2: Discuss Data Communications. PERFORMANCE STANDARD

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Data Communication Network

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  1. Data Communication Network 331: STUDY DATA COMMUNICATIONS AND NETWORKS

  2. 331: STUDY DATA COMMUNICATIONS AND NETWORKS • 1. Discuss computer networks (5 hrs) • 2. Discuss data communications (15 hrs)

  3. 331.2: Discuss Data Communications • PERFORMANCE STANDARD • Given a network system, identify and illustrate the different data communications components clearly • Objectives: • Define elements of a communication system • Define data communications • Discuss various types of transmission media and their characteristics • Discuss encoding of information for transmission • Discuss types of signal & their characteristics • Relate data capacity of a channel and bandwidth • Classify media based on bandwidth • Discuss channel organization

  4. SKILL AREA 331.2.3 Relate data capacity of a channel and bandwidth

  5. Simplified Data Communications Model

  6. Modulation and Multiplexing • Modulation and Multiplexing are electronic techniques for transmitting information efficiently from one place to another. • Modulation makes the information signal more compatible with the medium. • Multiplexing allows more than one signal to be transmitted concurrently over a single medium.

  7. Data Rate Limit • Channel: The amount of bandwidth that a signal occupies in the radio frequency spectrum. • Channel Capacity: The maximum possible rate information rate that data can be transmitted over a given communication path or channel under given condition.

  8. Data Rate Limit • A very important consideration in data communications is how fast we can send data, in bits per second, over a channel. • The Data rate depends on three factors: • The bandwidth available. • The level of the signals we use. • The quality of the channel (the level of noise).

  9. Data Rate Limit • Two theoretical formulas were developed to calculate the data rate: • Nyquist bit rate for a noiseless channel • BitRate = 2 * bandwidth * log2 L • Shannon Capacity for a noisy channel • Capacity = bandwidth * log2 (1 + SNR)

  10. Data Rate Limit • Bandwidth: The narrow frequency range over which the signal amplitude in a circuit is highest. • The term of Bandwidth can be used in two different measuring value: bandwidth in hertz and bandwidth in bits per second.

  11. Bandwidth • Bandwidth in Hertz: It is the range of frequencies contained in a composite signal or the range of frequencies a can pass. For example: We can say the bandwidth of a subscriber telephone line is 4kHz. • Bandwidth in Bits per Seconds: It refer to the speed of bit transmission in a channel, a link or even a network can transmit. For example: One can say the bandwidth of a Fast Ethernet network is a maximum of 100 Mbps. This means that the network can send 100 Mbps.

  12. Relationship between bandwidth in Hertz and bandwidth in bps • There is an explicit relationship between the bandwidth in hertz and bandwidth in bits per seconds. • Basically, an increase in bandwidth in hertz means an increase in bandwidth in bits per second. • The relationship depends whether we have baseband transmission or broadband transmission.

  13. Baseband transmission • Transmission of digital or analog signal without modulation using a low-pass channel. Low pass channel is a channel with bandwidth starts from zero.

  14. Broadband Transmission • Transmission of signals using modulation of a higher frequency signal. • It means changing the digital signal to analog for transmission and modulation allows us to use a bandpass channel – a channel with a bandwidth that does not start with zero.

  15. Broadband Transmission Modulation of a digital signal for a transmission on a bandpass channel

  16. Digital Channel Capacity • The number of digital values the channel can convey in one second. • A digital communications channel has limitations that determine how often the signal can change states over a period. • These limitations establish the maximum rate at which data can flow through the channel.

  17. Digital Channel Capacity • A variety of baseband signaling techniques are used to convey information or data. • Digital systems may have more than two discrete changes as shown in the Figure. • A binary system has only two discrete energy levels • A digital system can have many discrete energy levels.

  18. Digital system electrical signals

  19. Digital signal distortion and attenuation with distance

  20. Digital signal • Bandwidth versus length characteristics as shown in the previous Figure can be used to determine the length of channel they want to use for specific applications. • high-volume application requires a high bandwidth such as a direct connection between two mainframe computers, a vendor can limit the length of the communications channel to a short distance. • A low-volume application such as the connection between a personal computer and a low speed printer, the vendor can specify a longer channel

  21. Medium bandwidth versus length

  22. Digital Signal Regeneration • Provide devices that regenerate a digital signal. • Repeaters receive the signal and rebuild it to its original strength and shape. • The repeater catches the signal before it degrades to the point that it is unusable. • Digital signal cannot be amplified to increase their distance range in a channel.

  23. Digital Signal Regeneration • If you amplify a digital signal, you also amplify the noise that contaminated the signal. • The amplified noise can become a substantial part of the signal. • A repeater removes the noise from a signal while it is regenerating the signal.

  24. Digital Signal Regeneration

  25. QUESTION?

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