Communication Systems and Computer Networks PDF

Communication Systems and Computer Networks (1404703) Prepared by: Prof. Shawkat K. Guirguis Professor of Computer Science & Informatics Part 10 2024-12-...

Communication Systems and Computer Networks (1404703) Prepared by: Prof. Shawkat K. Guirguis Professor of Computer Science & Informatics Part 10 2024-12-09 (c) Prof.Shawkat K. Guirguis 1  Analog transmission Analog signaling consists of varying a voltage with time to represent an information stream If transmission medium is perfect the receiver would receive the same signal But, transmission lines suffer from attenuation, delay distortion and noise 2024-12-09 (c) Prof. Shawkat K. Guirguis 2  Analog signals problems Attenuation: is the loss of energy as the signal propagates outward (expressed in decibels per kilometer). The amount of energy lost depends on frequency. Delay: natural phenomena Distortion: due to harmonics traveling in different speeds Noise: Thermal noise, crosstalk, impulse noise, … etc. 2024-12-09 (c) Prof. Shawkat K. Guirguis 3  Modem Uses a sine wave carrier It can work in either: 1. Amplitude modulation 2. Frequency modulation 3. Phase modulation The number of symbols sent per second is called the baud rate 2024-12-09 (c) Prof. Shawkat K. Guirguis 4  Modems 2024-12-09 (c) Prof. Shawkat K. Guirguis 5  Multiplexing Time division multiplexing Frequency division multiplexing Wavelength division multiplexing 2024-12-09 (c) Prof. Shawkat K. Guirguis 6  Time division multiplexing Analog signals (e.g. telephone voice) are digitized through a Codec (Coder – Decoder) Codec makes 8000 samples/sec (125μsec/sample) The technique is called PCM (Pulse Code Modulation) T1 carrier consists of 24 multiplexed voice channels 2024-12-09 (c) Prof. Shawkat K. Guirguis 7  Time Division Multiplexing The T1 carrier (1.544 Mbps). 2024-12-09 (c) Prof. Shawkat K. Guirguis 8  Time Division Multiplexing (2) Delta modulation. 2024-12-09 (c) Prof. Shawkat K. Guirguis 9  Time Division Multiplexing (3) Multiplexing T1 streams into higher carriers. 2024-12-09 (c) Prof. Shawkat K. Guirguis 10  Frequency Division Multiplexing (a) The original bandwidths. (b) The bandwidths raised in frequency. (c) The multiplexed channel. 2024-12-09 (c) Prof. Shawkat K. Guirguis 11  Wavelength Division Multiplexing Wavelength division multiplexing. 2024-12-09 (c) Prof. Shawkat K. Guirguis 12  Switching Circuit switching Message switching Packet switching 2024-12-09 (c) Prof. Shawkat K. Guirguis 13  Circuit vs Packet Switching (a) Circuit switching. (b) Packet switching. 2024-12-09 (c) Prof. Shawkat K. Guirguis 14  Comparison of Switching modes (a) Circuit switching (b) Message switching (c) Packet switching 2024-12-09 (c) Prof. Shawkat K. Guirguis 15  Circuit vs Packet Switching A comparison of circuit switched and packet-switched networks. 2024-12-09 (c) Prof. Shawkat K. Guirguis 16