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Questions and Answers
What is the name of the course lecturer?
What is the name of the course lecturer?
Lenin Joseph (LJ)
What are the two outcomes discussed in this lecture?
What are the two outcomes discussed in this lecture?
Outcome 2 and 3, Design of Digital Communication Systems
Which of the following can be transmitted in digital transmission?
Which of the following can be transmitted in digital transmission?
- A digital message originating from a data source, for example a computer or keyboard.
- An analog signal such as a phone call or video signal, digitized into a bit stream using PCM or advanced source coding.
- Both A and B (correct)
- None of the above
The term "digital-over-digital" transmission refers to the method where analog signals are converted into digital signals and then transmitted.
The term "digital-over-digital" transmission refers to the method where analog signals are converted into digital signals and then transmitted.
Baseband Transmission requires modulation.
Baseband Transmission requires modulation.
Which of the following are examples of line coding schemes used in baseband transmission?
Which of the following are examples of line coding schemes used in baseband transmission?
Passband transmission involves modulation.
Passband transmission involves modulation.
What is the purpose of using a modem in passband transmission?
What is the purpose of using a modem in passband transmission?
Parallel transmission is the simultaneous transmission of signal elements of a character or other entity of data, regardless of the type of transmission (digital or analog).
Parallel transmission is the simultaneous transmission of signal elements of a character or other entity of data, regardless of the type of transmission (digital or analog).
What is the main advantage of parallel transmission compared to serial transmission?
What is the main advantage of parallel transmission compared to serial transmission?
What is the main disadvantage of parallel transmission?
What is the main disadvantage of parallel transmission?
Serial transmission transmits data sequentially over a single path, such as a wire, frequency, or optical path.
Serial transmission transmits data sequentially over a single path, such as a wire, frequency, or optical path.
Serial transmission is ideal for long distances compared to parallel transmission, particularly when using electrical wires.
Serial transmission is ideal for long distances compared to parallel transmission, particularly when using electrical wires.
Asynchronous transmission is sometimes called start-stop transmission because it uses start-stop characters to define the beginning and end of a data block.
Asynchronous transmission is sometimes called start-stop transmission because it uses start-stop characters to define the beginning and end of a data block.
Which of the following statements is NOT true about asynchronous transmission?
Which of the following statements is NOT true about asynchronous transmission?
Synchronous transmission uses start and stop bits to define the beginning and end of each character.
Synchronous transmission uses start and stop bits to define the beginning and end of each character.
What is the purpose of sync bytes in synchronous transmission?
What is the purpose of sync bytes in synchronous transmission?
Synchronous transmission requires the use of SYN characters.
Synchronous transmission requires the use of SYN characters.
What is the main advantage of synchronous transmission over asynchronous transmission?
What is the main advantage of synchronous transmission over asynchronous transmission?
What is the formula to calculate the bandwidth (B) in Hertz?
What is the formula to calculate the bandwidth (B) in Hertz?
What is the bandwidth of a periodic signal consisting of five sine waves with frequencies of 100, 300, 500, 700, and 900 Hz?
What is the bandwidth of a periodic signal consisting of five sine waves with frequencies of 100, 300, 500, 700, and 900 Hz?
If a periodic signal has a bandwidth of 20 Hz and a highest frequency of 60 Hz, what is the lowest frequency?
If a periodic signal has a bandwidth of 20 Hz and a highest frequency of 60 Hz, what is the lowest frequency?
What is the meaning of information capacity in the context of digital transmission?
What is the meaning of information capacity in the context of digital transmission?
What is the most basic digital symbol used to represent information?
What is the most basic digital symbol used to represent information?
Information capacity is directly proportional to bandwidth and transmission time.
Information capacity is directly proportional to bandwidth and transmission time.
The formula for Hartley's Law is I ______ B x t.
The formula for Hartley's Law is I ______ B x t.
Who developed the relationship between bandwidth, transmission time, and information capacity known as Hartley's Law?
Who developed the relationship between bandwidth, transmission time, and information capacity known as Hartley's Law?
What is the Shannon Limit, and what does it relate to?
What is the Shannon Limit, and what does it relate to?
The Shannon Limit is also known as the Shannon-Hartley Theorem.
The Shannon Limit is also known as the Shannon-Hartley Theorem.
A higher signal-to-noise ratio results in higher information capacity.
A higher signal-to-noise ratio results in higher information capacity.
What is the mathematical formula for the Shannon Limit for information capacity?
What is the mathematical formula for the Shannon Limit for information capacity?
The Shannon-Hartley Theorem is applicable only for binary information.
The Shannon-Hartley Theorem is applicable only for binary information.
What is the formula for the information capacity (I) in the Shannon-Hartley Theorem when considering multiple coding levels (M) and ignoring noise?
What is the formula for the information capacity (I) in the Shannon-Hartley Theorem when considering multiple coding levels (M) and ignoring noise?
For binary information with two possible levels (0 and 1), the information capacity is determined by I = 2 * B * log (2) * M.
For binary information with two possible levels (0 and 1), the information capacity is determined by I = 2 * B * log (2) * M.
What is the purpose of M-ary encoding?
What is the purpose of M-ary encoding?
What is the mathematical formula to calculate the number of bits (N) required to generate M levels in M-ary encoding?
What is the mathematical formula to calculate the number of bits (N) required to generate M levels in M-ary encoding?
How can you represent the number of conditions possible with N bits in M-ary encoding?
How can you represent the number of conditions possible with N bits in M-ary encoding?
What is the bit rate in a system where each bit is represented by a pulse of width Tb = 0.1 ms?
What is the bit rate in a system where each bit is represented by a pulse of width Tb = 0.1 ms?
What is the alternative name for baud rate?
What is the alternative name for baud rate?
Baud rate is directly proportional to the bit rate.
Baud rate is directly proportional to the bit rate.
What is the baud rate for a system that transmits binary data with a bit duration of 1 μsec and each symbol is represented by four bits?
What is the baud rate for a system that transmits binary data with a bit duration of 1 μsec and each symbol is represented by four bits?
What is the bit rate for a modulator that transmits symbols with 64 possible states at a rate of 10,000 symbols per second?
What is the bit rate for a modulator that transmits symbols with 64 possible states at a rate of 10,000 symbols per second?
What is the minimum allowable bandwidth to transmit a 2-bit binary signal with a bit rate of 3 Mbps?
What is the minimum allowable bandwidth to transmit a 2-bit binary signal with a bit rate of 3 Mbps?
The error probability (Pb) is calculated as the number of errors divided by the total number of bits received.
The error probability (Pb) is calculated as the number of errors divided by the total number of bits received.
What is the typical range for acceptable error probability in communication systems?
What is the typical range for acceptable error probability in communication systems?
How is the average number of errors calculated in a transmission with m bits and error probability Pb?
How is the average number of errors calculated in a transmission with m bits and error probability Pb?
What does BER stand for?
What does BER stand for?
BER is an exact measure of the bit error probability.
BER is an exact measure of the bit error probability.
Flashcards
Parallel Transmission
Parallel Transmission
The simultaneous transmission of all bits of a data unit, typically a byte, on separate wires.
Serial Transmission
Serial Transmission
The sequential transmission of bits on a single wire or channel.
Synchronous Transmission
Synchronous Transmission
A type of serial transmission which sends data in blocks with special synchronization bytes at the beginning and end of each block.
Asynchronous Transmission
Asynchronous Transmission
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Transmission Bandwidth
Transmission Bandwidth
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Shannon Limit for Information Capacity
Shannon Limit for Information Capacity
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Information Capacity
Information Capacity
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Bit Rate
Bit Rate
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Baud Rate
Baud Rate
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Nyquist Minimum Bandwidth
Nyquist Minimum Bandwidth
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Probability of Error (Pb)
Probability of Error (Pb)
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Bit Error Rate (BER)
Bit Error Rate (BER)
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Energy Per Bit (Eb)
Energy Per Bit (Eb)
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Baseband Transmission
Baseband Transmission
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Passband Transmission
Passband Transmission
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Multilevel Signalling
Multilevel Signalling
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Number of Bits Encoded into a Signaling Element (N)
Number of Bits Encoded into a Signaling Element (N)
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Number of Discrete Signal or Voltage Levels (M)
Number of Discrete Signal or Voltage Levels (M)
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M-ary Encoding
M-ary Encoding
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Digital Transmission
Digital Transmission
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Intersymbol Interference (ISI)
Intersymbol Interference (ISI)
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Pulse Shaping
Pulse Shaping
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Eye Diagram
Eye Diagram
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Signal to Noise Ratio (SNR)
Signal to Noise Ratio (SNR)
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Analog to Digital Conversion (ADC)
Analog to Digital Conversion (ADC)
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Data Compression
Data Compression
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Digital to Analog Conversion (DAC)
Digital to Analog Conversion (DAC)
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Study Notes
Digital Communication and Switching Course Notes
- Course title: Digital Communication and Switching
- Semester: I AY 2024-25
- Class lecture: 2
- Outcome: #2-Design of Digital Communication Systems
- Lecturer: Lenin Joseph (LJ)
- Date: Dec 24, 2024
Outcome #2 & #3
- Explain general constraints and limitations in designing communication systems.
- Understand problems and techniques involved in baseband data transmission (ISI, Pulse Shaping, Eye diagram).
Digital Transmission
- Transmission of digital signals between two or more points in a communication system.
- Physical transfer of digital bit stream over a point-to-point or multipoint communication channel.
- Information transmitted can be:
- Digital messages originating from a data source (e.g., computer, keyboard).
- Analog signals (e.g., phone calls, video signals) digitized into a bit stream using PCM or advanced source coding (Analog-to-Digital Conversion and data compression).
Transmission Schemes for Analog and Digital Signals
- Diagrams illustrating different transmission schemes for analog and digital signals.
- Analog signal with no modulation
- Standard analog modulation system
- Digital transmission on digital scheme
- Digital transmission on analog scheme
- Analog transmission on digital channel
- Digitized analog signal transmission on analog scheme
Types of Digital Data Transmission
- Baseband Transmission:
- "Digital-over-digital" transmission (direct transmission of information signal without modulation).
- Transmission of electrical or light pulses using line coding schemes (RZ, NRZ, Manchester coding).
- Used in serial cables, wired LANs (e.g., Ethernet), and optical communication.
- Passband Transmission:
- "Digital-over-analog" transmission (transmission of a modulated sine wave representing a digital bit stream).
- Utilizes digital modulation schemes (PSK, FSK, QAM).
- Demodulation carried out by modem equipment.
- Used in wireless communication and over telephone network local loop and cable-TV networks.
Digital Transmission Mode - Parallel Transmission
- Simultaneous transmission of signal elements of a character or entity of data.
- Signal elements of related data transmitted over multiple separate paths.
- Uses multiple electrical wires for higher data transfer rates than serial transmission.
- Used internally within computers (e.g., internal buses) and sometimes externally (e.g., printers).
- Disadvantage: Skewing (bits arriving before others) can corrupt the message. Electrical wire parallel data transmission less reliable for long distances.
- Error check bit (parity bit) can help reduce the error.
Digital Transmission Mode - Serial Transmission
- Sequential transmission of signal elements of a group representing a character or entity of data.
- Bits sent over a single wire, frequency, or optical path sequentially.
- Requires eight clock pulses to transmit eight bits of data.
- Less signal processing and fewer error chances compared to parallel transmission.
- Faster transfer rate for individual paths.
- Usable over longer distances with error check bit or parity bit.
Two Types of Serial Transmission
- Asynchronous Transmission:
- One character transmitted at a time.
- Each character (or 8-bit series) marked by a start bit and a stop bit.
- Synchronous Transmission:
- Data sent in blocks (frames or packets) containing hundreds or thousands of characters.
- Frames started and ended by one or more sync bytes.
- Sync bytes synchronize internal clocks in transmitting and receiving devices.
Transmission Bandwidth
- Band of frequencies allowed for signal transmission.
- Set of frequencies for transmitting data.
- Example calculations and illustrations (Example 3, 4 on specific signals).
Parameters in Digital Transmission
- Information Capacity: A measure of how much information can be propagated through a communication system; function of bandwidth and transmission time.
- Hartley's Law: The amount of information transmitted in a given time is directly proportional to bandwidth and transmission time (I = B * t).
- Shannon Limit for Information Capacity: Mathematically expressed, relating the information capacity of a communication channel to bandwidth and signal-to-noise ratio. (I=B * log2(1+S/N)).
- Shannon-Hartley Theorem: Maximum theoretical data rate for a given noise level.
- M-ary Encoding: M represents the number of conditions, levels, or combinations possible for a given number of binary variables. The number of bits necessary is expressed as N=log2M.
Probability of Error (Pb), Bit Error Rate (BER) and Energy per Bit (Eb)
- Errors in digital communication systems result from noise.
- Error probability (Pb) is the number of errors per total number of bits received.
- Acceptable error probability in communication systems.
- Average number of errors = m * Pb.
- BER (Bit Error Rate) is the number of bit errors for a given number of bits transmitted.
- Example calculations.
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