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Digital data transmission,line coding and pulse shaping
This document discusses digital data transmission, line coding, and pulse shaping. It covers several key topics: - Digital data transmission involves converting analog signals like voice or images to binary digits for transmission and reconverting them at the receiving end. This allows for clearer, faster transmission using less bandwidth. - There are two main transmission modes: parallel transmits multiple bits at once for higher speed, while serial transmits one bit at a time to reduce costs. Conversion is needed between parallel and serial interfaces. - Line coding converts digital bits to voltage levels for transmission. Common schemes include NRZ, RZ, Manchester, AMI, and pseudoternary. - Pulse shaping filters transmitted pulses to limit
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Introduction to digital data transmission, converting information into binary for clearer communication.
Explains parallel and serial transmission, highlighting their advantages, block diagrams showing data flow.
Describes asynchronous, synchronous, and isochronous transmissions, noting their operational differences.
Introduction to line coding, converting digital data into signal sequences for transmission.
Discusses data rate vs signal rate and the goal of maximizing data transmission efficiency.
Various line coding schemes like Unipolar, Polar, and Bipolar, their characteristics, and implications.
Process of pulse shaping in telecommunications to improve bandwidth efficiency and reduce interference.
Sinc pulse utilization addressing frequency limitations and intersymbol interference in modulated signals.
Closing the presentation with an invitation for questions and expressing gratitude.
Digital data transmission,line coding and pulse shaping
- 1. DIGITAL DATA TRANSMISSION,LINE CODING ANDPULSE SHAPING Made By: AAYUSH KUMAR Roll No.: 1209731002
- 2. What is DigitalData Transmission? • A mode of transmission in which all information to be transferred, such as voice, image or text data, is converted in the digital (mainly binary numbers) before transmission. At the end point, binary code is converted back into original format. • Digital transmission can deliver a signal, free of ghosts, interference, and picture noise. It provides sharper, clearer and faster transmission, using less bandwidth to transmit more information than analog.
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- 5. Parallel Transmission •In Paralleltransmission, by grouping, we can send n data bits at a time instead of 1. •Its advantage over serial transmission is in terms of speed.
- 6. Block diagram ofparallel transmission
- 7. Serial transmission • InSerial transmission, one bit follows another • It advantage over parallel transmission is that it reduces cost of transmission. But communication with device is parallel hence conversion devices are required at the interface between the sender and the line (p to S) and between the line and receiver (S to P)
- 8. Block diagram ofserial transmission
- 9. Asynchronous, synchronous and isochronous •In telecommunications, asynchronous communication is transmission of data, generally without the use of an external clock signal, where data can be transmitted intermittently rather than in a steady stream • The transmission of data in which both stations are synchronized by a clock is known as synchronous transmission of data. Codes are sent from the transmitting station to the receiving station to establish the synchronization, and the data are then transmitted in continuous streams. • Isochronous transmission transmits asynchronous data over a synchronous data link so that individual characters are only separated by a whole number of bit-length intervals
- 10. Line Coding • Convertinga string of 1’s and 0’s (digital data) into a sequence of signals that denote the 1’s and 0’s. • For example a high voltage level (+V) could represent a “1” and a low voltage level (0 or -V) could represent a “0”.
- 11. Line coding anddecoding
- 12. Relationship between datarate and signal rate • The data rate defines the number of bits sent per sec - bps. It is often referred to the bit rate. • The signal rate is the number of signal elements sent in a second and is measured in bauds. It is also referred to as the modulation rate. • Goal is to increase the data rate whilst reducing the baud rate.
- 13. Signal element versusdata element
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- 15. Unipolar NRZ • Allsignal levels are on one side of the time axis - either above or below • NRZ - Non Return to Zero scheme is an example of this code. The signal level does not return to zero during a symbol transmission. • Scheme is prone to baseline wandering and DC components. It has no synchronization or any error detection. It is simple but costly in power consumption.
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- 17. Unipolar RZ • Inunipolar RZ form, the waveform has zero value when symbol ‘0’ is transmitted and waveform has ‘v’ volts when ‘1’ is transmitted. • The ‘v’ volts is present for half time period and for the remaining time period the waveform returns to zero.
- 18. Polar - NRZ •The voltages are on both sides of the time axis. • Polar NRZ scheme can be implemented with two voltages. E.g. +V for 1 and -V for 0. • There are two versions: • NZR - Level (NRZ-L) - positive voltage for one symbol and negative for the other • NRZ - Inversion (NRZ-I) - the change or lack of change in polarity determines the value of a symbol. E.g. a “1” symbol inverts the polarity a “0” does not.
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- 20. Polar - RZ •The Return to Zero (RZ) scheme uses three voltage values. +, 0, -. • Each symbol has a transition in the middle. Either from high to zero or from low to zero. • This scheme has more signal transitions (two per symbol) and therefore requires a wider bandwidth. • No DC components or baseline wandering. • Self synchronization - transition indicates symbol value. • More complex as it uses three voltage level. It has no error detection capability.
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- 22. Split-Phase Manchester • Inmanchestere format,if symbol 1 is to be transmitted,Then a positive half interval pulse is followed by a negative half interval pulse. • If symbol zero is to be transmitted,then a negative half interval pulse is followed by a positive half interval pulse. • Hence for any symbol the pulse takes +ve as weel as –ve values.
- 23. Bipolar - AMIand Pseudoternary • Code uses 3 voltage levels: - +, 0, -, to represent the symbols (note not transitions to zero as in RZ). • Voltage level for one symbol is at “0” and the other alternates between + & -. • Bipolar Alternate Mark Inversion (AMI) - the “0” symbol is represented by zero voltage and the “1” symbol alternates between +V and -V. • Pseudoternary is the reverse of AMI.
- 24. Bipolar schemes: AMIand pseudoternary
- 25. Bipolar Characteristics • Itis a better alternative to NRZ. • Has no DC component or baseline wandering. • Has no self synchronization because long runs of “0”s results in no signal transitions. • No error detection.
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- 27. • In electronicsand telecommunications, pulse shaping is the process of changing the waveform of transmitted pulses. Its purpose is to make the transmitted signal better suited to its purpose or the communication channel, typically by limiting the effective bandwidth of the transmission. • By filtering the transmitted pulses this way, the intersymbol interference caused by the channel can be kept in control. • Typically pulse shaping occurs after line coding and modulation.
- 28. Need for PulseShaping In communications systems, two important requirements of a wireless communications channel demand the use of a pulse shaping filter. 1) generating bandlimited channels 2) reducing inter symbol interference (ISI) from multi-path signal reflections.
- 29. Time vs. FrequencyDomain for a Sinc Pulse The sinc pulse,above , meets both of these requirements because it efficiently utilizes the frequency domain to utilize a smaller portion of the frequency domain, and because of the windowing affect that it has on each symbol period of a modulated signal.
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